CHARACTERIZATION OF TAR FROM A FLUIDIZED BED STEAM

REFORMER OF BLACK LIQUOR

by

Carolina Rubiano

A thesis submitted to the faculty of The University of Utah

in partial fulfillment of the requirements for the degree of

Master of Science

Department of Chemical Engineering

The University of Utah

December 2006

Copyright © Carolina Rubiano 2006

All Right Reserved

ABSTRACT

Black liquor is a big energy source and a crucial component for the economy of the

pulp and paper industry. Black liquor is conventionally burned in the Tomlinson recovery

boiler. However, black liquor gasification combined cycle (BLGCC) has some

advantages over the conventional technology, like superior energy efficiency, that makes

this technology suitable to replace the traditional boiler.

Low-temperature steam gasification converts the black liquor to a quality synthesis

gas. This gas contains H2 and CO and, in addition, some gaseous impurities and inert

gases such as CO2, H2O and N2. These gaseous impurities, like tar, might condensate and

cause downstream problems such as plugging and corrosion, among others. Especially

when gasifying at low temperatures, these impurities are a big drawback for the

commercialization of this technology.

The steam reformer of black liquor at the University of Utah was operated at different

operating conditions to evaluate tar production and some tar characteristics. Two sample

collecting systems were tested: an impinger sampling train and a so-called Petersen

column. Total tar concentration for different gasification conditions was satisfactorily

obtained using the impinger train. Increasing the reformer temperature, decreasing the

liquor feed rate, increasing the fluidizing steam temperature and co-injecting air in to the

system all decreased tar production. On the other hand, changing the superficial gas

velocity did not seem to affect tar concentration for the range of

velocities considered. Tar concentrations varied from 36.2 g/m3 to 140.2 g/m3of dry gas.

Tar characterization was performed using different techniques that would provide a

better understanding of its physical and chemical properties. A series of analyses were

performed at the University of Utah; gas chromatography-flame ionization detection

(GC-FID) analysis, gas chromatography-mass spectrometry (GC-MS) analysis and,

thermogravimetric analysis (TGA). In addition, selected samples were sent to Huffman

Laboratories, Inc. for elemental analysis. These analyses suggested that the chemical

composition of the tar samples were very similar for all the experimental conditions

tested. Tar samples mainly showed the presence of phenolics and both substituted and

unsubstituted multi-ring structures with high concentrations of single-ring aromatics and

phenolic compounds.

It was concluded from this study that tar produced in a fluidized bed black liquor

steam reformer is a very complex and broad mixture of hydrocarbons, and that the

product gases would require strict temperature control to avoid tar condensation

downstream. Gasification temperature seemed to be the parameter that most affected tar

production, followed by black liquor flow rate.

v

Mis sueños siempre han sido viables a tu lado. Tú y la pequeña personita que viene en camino son la alegría y la fuerza de mi vida.

CONTENT

ABSTRACT iv ACKNOWLEDGMENTS viii 1 INTRODUCTION 1

1.1 Paper industry and black liquor 1 1.2 Black liquor recovery 3 1.3 Gasification processes 6 1.4 Black liquor conversion 10 1.5 Tar definition and impact on low temperature steam gasification 13 1.6 Research Objectives 14

2 LITERATURE REVIEW 15

2.1 Tar formation 15 2.2 Characterization and collection of tar 18 2.3 Factors affecting tar production and composition 20 2.4 Tar removal systems 21

3 EXPERIMENTAL 23

3.1 Introduction 23 3.2 Equipment 24

3.2.1 University of Utah steam reformer 24 3.2.2 Tar sampling systems 28 3.2.3 Tar isolation system 33 3.2.4 Analysis equipment 33

3.3 Procedures 36 3.3.1 Tar sampling 36 3.3.2 Tar isolation and gravimetric determination of tar concentration 40 3.3.3 Analytical procedures 40

4 RESULTS AND DISCUSSION 52

4.1 Reproducibility of the tar isolation method 52 4.2 Influence of operating conditions on production of tar 54

4.2.1 Reformer temperature 54

4.2.2 Liquor feed rate 57 4.2.3 Superficial gas velocity 60 4.2.4 Fluidizing steam temperature 63 4.2.5 Air addition 63 4.2.6 Petersen column 65

4.3 Characterization of tar 75 4.3.1 Speciation comparison at different operating conditions 75 4.3.2 Speciation – University of Utah system and commercial system 80 4.3.3 Volatility of the tar samples 101 4.3.4 Elemental analysis 111

5 CONCLUSIONS 118

5.3 Tar concentration and composition at different gasification conditions 118 5.4 Recommendations for future work 121

Appendices A. DATA BASE OF TAR COMPOUNDS 123

B. RAW CHROMATOGRAMS OF TAR SAMPLES

TAKEN AT DIFFERENT OPERATING CONDITIONS 133 C. MAJOR AND MINOR COMPOUNDS FOUND IN STANDARD SAMPLE FROM RUN 1 145 REFERENCES 149

vii

ACKNOWLEDGMENTS

I want to thank Dr. Kevin Whitty for his direction, guidance and exceptional support

in this challenging project.

I would like to thank Dr. Eric Eddings who gave me an opportunity that has changed

my life.

Special thanks to Mr. Dana Overacker, Mike Siddoway, Mauricio Naranjo and the

technical staff of ICES for their help and ideas that facilitated this experimental work.

This research wouldn’t have been possible without the financial support provided by

the DOE cooperative agreement DE-FC26-02NT41490.

The technical contribution of Georgia-Pacific Corporation, Norampac Corporation

and ThermoChem Recovery International is also acknowledged.

CHAPTER 1

INTRODUCTION

1.1 Paper industry and black liquor

Paper was invented around 105 A.D. by Ts’ai Lun, but it was not until 1690 that the

United States built its first mill. Of the total world’s paper production, the U.S. produced

about 60% in 1950 while in 1990, due to the strong competition from Europe, Asia and

South America, the U.S. did not reach 30% of the total paper production in the world.1

The invention of the paper machine forced paper companies to develop a technology

for converting wood into pulp, during the 19th century. Depending on the kind of paper or

the type of wood stock, pulp is made by physical and/or chemical processes that break

down wood or other lignocellulosic materials to form fibers.

In the U.S. almost 80% of the pulp for papermaking is produced by Kraft pulping

process.2 This chemical process can be used with all type of woods and produces a high

strength pulp by cooking wood chips with Na2S and NaOH. A simplified diagram of the

Kraft pulping and chemical recovery process is shown in Figure 1.

The pulp (wood fibers) is send to the paper mill after being separated from the spent

chemical (weak black liquor) by washing. Weak black liquor, with a solid content of 14-

17% wt, mainly consists of lignin, extractives, dissolved wood, water, and pulping

chemicals. This liquor is concentrated to yield strong black liquor (with a solid content of

2

Causticizing

Wood chips Pulp

digester

Evaporator Gasifier (or Boiler)

Pulp

White liquor

Black liquor

Green liquor Water

Gas (or steam)

Figure 1. Simplified figure of the Kraft pulping and chemical recovery process (Adapted from reference 3).

3

60-80% wt.) which is the principal supply of energy for the pulping process,3 with a

higher heating value (HHV) of 12-16 MJ/kg on the basis of solids in the liquor.4 The

concentrated black liquor contains roughly 1/3 water, 1/3 organics and 1/3 inorganic

salts. The typical composition of black liquor from North American woods is presented in

Table 1.

1.2 Black liquor recovery

Besides being a big energy resource in the paper process because of its organic

content, black liquor recovery is crucial for the economy of the process since it also

recycles the pulping chemicals and reduces the amount of waste released to the

environment. Black liquor is conventionally burned to release energy and to recover the

inorganic content as a molten slag (smelt), composed essentially of Na2S and Na2CO3.

The smelt is dissolved in water forming green liquor that is further mixed with Ca(OH)2

so that Na2CO3 reacts and produces NaOH. White liquor (NaOH and Na2S) is recycled to

the pulping process. Finally by burning the CaCO3 produced in the causticizing process,

Ca(OH)2 is regenerated after the dissolution of CaO in water.

Black liquor is traditionally burned in a Tomlinson recovery boiler. A schematic

diagram of the boiler can be seen in Figure 2. This process has been used for many years

to burn the organics from black liquor and to recover the heat of combustion in the form

of steam, by heating circulating water or steam in the walls and heat exchange tubes of

the furnace.

The recovery boiler can be divided in three zones: (1) the oxidizing zone where

complete combustion is achieved by injecting excess air, (2) the drying zone where black

liquor is injected and water and organics are released, and (3) the reducing zone where

4

Table 1. Typical composition of black liquor in dry bases from

North American woods (Adapted from reference 5).

Softwood composition

(%wt.)

Hardwood composition

(%wt.) Element

Typical Range Typical Range Carbon 35 32-37.5 34 31-36.5 Hydrogen 3.5 3.4-4.3 3.4 2.9-3.8 Nitrogen 0.1 0.06-0.12 0.2 0.14-0.2 Oxygen 35.4 32-38 35 33-39 Sodium 19.4 17.3-22.4 20 18-23 Potassium 1.6 0.3-3.7 2 1-4.7 Sulfur 4.2 2.9-5.2 4.3 3.2-5.2 Chlorine 0.6 0.1-3.3 0.6 0.1-3.3 Inert 0.2 0.1-2.0 0.5 0.1-2.0

5

Reduction zone

Drying zone

Oxidation zone

Molten smelt

Figure 2. Tomlinson recovery boiler (Adapted from reference 6).

6

the sulfate in the liquor is reduced to sulfide via reaction with unconverted carbon.

The recovery boiler (recovery furnace) developed in 1930 by Tomlinson, Babcock

and Wilcox is, in many kraft mills, the piece of equipment that limits the maximum

production. Despite its size and price, which is over US$ 100 million,1 it has many

weaknesses such as low efficiency, an odor problem caused by the release of reduced

forms of sulfur (TRS), high capital cost, elevated cost of maintenance and operation,

and a risk of smelt-water explosion.7 Consequently, other technologies that convert the

liquor to fuel gases and char have been developed or are currently under development.

These technologies are centered on gasification of the black liquor.

1.3 Gasification processes

Black liquor gasification is currently being studied as a possible technology to replace

the conventional recovery boiler. The product gas (synthesis gas) from gasification could

be used to produce electricity in a combined-cycle configuration, or it could be used as

feedstock for production of transportation fuels or chemicals. Some of the advantages of

black liquor gasification combined cycle (BLGCC) are an increase of at least 10% in the

overall energy conversion,8 the increase in capital effectiveness, the improvement in

safety, a decrease in the environmental impact by lowering CO2 emissions and by

decreasing the wastewater discharges, the possibility of causticizing the liquor in a more

directly way and, the increase in flexibility when preparing the pulping and the bleaching

chemicals.9

The process in which feedstocks are transformed into combustible gases (CO, H2, and

CH4) by thermochemical conversion of carbonaceous materials in the presence of an

oxidizing gas is known as gasification.10 Some of the reactions that occur in this process

7

are listed in Table 2. Generally, gasification reactions are favored by the increase of

temperature and the decrease of pressure, excluding the methane production.7

Because of recent increases in energy prices, there is a growing interest in gasification

technologies. Gasification is an old technology, initially used for processing coal and

fossil residues in the 1790s.11 Gasification can use different oxidizing agents such as air,

oxygen, steam, or mixtures of these. Using this technology a big range of fuels can be

gasified: liquid, gaseous or solids, like coal, petroleum and refinery residues, coke oven

gas, biomass, solid waste, among others. There are basically three types of reactors:

moving bed gasifiers, entrained flow gasifiers and fluidized bed gasifiers. Some

characteristics that differentiate each process are shown in Table 3.

Fluidized bed gasifiers promote heat and mass transfer due to the very good mixing

between the feed and the oxidant, almost simulating a continuously stirred reactor.3

However, carbon conversion in this kind of gasifiers is lower (97% compared to 99%

achieved in entrained flow gasifiers 3) due to the nonselective removal of unreacted and

fully reacted particles when the bed is dumped and their lower operation temperatures,

which is generally restricted to the melting temperature of the ash.

Biomass gasification in a fluidized bed produces a gas with a heating value of 4-7

MJ/m3 and a hydrogen content of 8-14 vol.% when using air as the gasification agent.12, 13

Abatzoglou et al. 14 recommended a rough approximation for the volume of gas produced

when gasifying biomass; 1 kg of fuel produces about 2.3 m3 of gases.

When biomass is thermally converted through gasification, gaseous fuels like H2 and

CO are generated and, in addition, some gaseous impurities and inert gases such as CO2,

H2O and N2. The gaseous impurities cause corrosion problems, furthermore, if the

8

Table 2. Fundamental gasification reactions.

Reaction Heat of reaction (MJ/kmol)

C + ½ O2 = CO (combustion)

-111

CO + ½ O2 = CO2 (combustion)

-283

H2 + ½ O2 = H2O (combustion)

-243

C + H2O ↔ CO + H2 (water gas reaction)

+131

C + 2H2 ↔ CH4 (Methanation)

-75

CH4 + H2O ↔ CO + 3H2 (steam reforming)

+206

CH4 + 2O2 → CO2 + H2O -803 CO + H2O ↔ CO2 + H2 (water-gas shift reaction)

-41

C + CO2 ↔ 2CO (Boudouard reaction)

+172

9

Table 3. Some characteristics that differentiate the type of gasifier (Adapted from reference 3).

Category Moving-Bed Fluid-Bed Entrained-Flow

Ash condition Dry ash Slagging Dry ash Aglomerating Slagging

Typical

process

Lurgi BGL HTW, CFB KRW, U-Gas Shell, Texaco

Feed size 6-50 mm 6-50 mm 6-10 mm 6-10 mm <100 μm

Acceptability

of fines

Limited Beter than dry

ash

Possibly low Yes any Yes any

Outlet gas

temperature

Low

(425-650 ºC)

Low

(425-650 ºC)

Moderate

(900-1050 ºC)

Moderate

(900-1050 ºC)

High

(1250-1600 ºC)

Oxidant

demand

Low Low Moderate Moderate High

Other

characteristics

Hydrocarbons

in gas

Hydrocarbons

in gas

Lower carbon

conversion

Lower carbon

conversion

Pure gas, high

carbon

conversion

10

temperature decreases downstream, other problems such as plugging and abrasion can

happen. These impurities depend highly on the nature of the biomass feedstock and can

be grouped in the categories shown in Table 4.

1.4 Black liquor conversion

Black liquor gasification is a promising process due to its high energy efficiency,

particularly in countries with a strong pulping sector, such as Sweden, where black liquor

represents about 6% of the national gross energy consumption.3 About 1000 air-dried

tons of pulp per day are produced by an average-size mill, which corresponds to 1800

tons of dry solids per day of black liquor, about 300 MW on a high heating value basis.3

The thermoplastic behavior of black liquor is one of the most important

characteristics of this substance. When a black liquor particle is heated, it swells,

reaching even 30 times its original volume.15 This behavior is attributed to the lignin and

the inorganic molecules that compose the liquor. Concentrated black liquor typically has

a density of 1400 kg/m3.3

The black liquor thermal conversion stages are shown in Figure 3. The stages are:

drying, where the remaining water content is evaporated; devolatilization, where H2O,

CO2, CO, H2, light hydrocarbons, tar, and light sulfur containing gases are produced and

released; char burning, where the carbon still present in the char is oxidized forming CO

and CO2 and inorganic residue reactions, where the inorganic residue may react to release

reduced sulfur.

11

Table 4. Contaminants from the thermal conversion of biomass (Adapted from reference 16).

Contaminants Examples

Particles Char, ash

Low and high molecular weight organic compounds (tars)

Naphthalene, Phenols, etc

Nitrogen containing impurities NH3, HCN

Sulfur containing compounds H2S, COS

Others HCl, alkali metals, etc

12

Smelt Reactions

CO2 O2

O2

CO Fume

Char Burning

O2

CO

Luminous Flame

Pyrolysis

Tar & HC’s

TRS’s

H2O

CO2 H2S

Drying

External Heat External Heat

External Heat

H2O

H2O

H2O

H2O

H2O

H2O H2O

H2O

Figure 3. Burning stages of a black liquor droplet (Adapted from reference 7).

13

1.5 Tar definition and impact on low temperature steam gasification

Low-temperature gasification advantages over high temperature include superior

energy efficiency, improved sodium and sulfur separation, lower restriction on the

materials used for the construction of the equipment and, since the molten smelt is not

formed at low temperatures, enhanced safety.7 A key disadvantage is, however, that the

product gases may have a large concentration of tar that may condense and subsequently

plug downstream lines.

Steam gasification greatly improves the produced gases, resulting in superior carbon

conversion efficiency when compared to the traditional recovery boiler. Furthermore, a

gas with 30-60 vol.% of hydrogen and a higher heating value (HHV) of 10-16 MJ/m3 can

be produced. However, in order to achieve such results, additional energy is required to

produce steam at elevated temperatures (about 600 ºC), otherwise, the quality of the

produced gas can be degraded, decreasing carbon conversion and increasing tar

concentrations, as the steam reduces the overall reaction temperature.17

Tar has traditionally been defined in different ways by many authors; according to

their specific boiling point,18, 19 or the temperature used to trap the tar components in a

specific experiment.20, 21 For the purpose of this research, “Tar” will be defined as: all the

organic compounds, excluding nonaromatic gaseous hydrocarbons (C1 through C6),

present in the producer gas, obtained under thermal or partial oxidation regimes

(gasification) of any organic material.

Many studies have been conducted on tar formation, conversion and gas cleaning.

However, there is a lack of information on tar concentration and composition from steam

14

gasification of black liquor in a fluidized bed gasifier. The majority of previous studies

have been focused on coal and biomass gasification.11, 22-25

1.6 Research objectives

The principal objective of the project described in this thesis was to obtain a detailed

analysis, qualitative and quantitative, of the tar resulting from the gasification of black

liquor in a fluidized bed steam reformer, using a variety of operating conditions. This

research was divided into five objectives:

1. Collect and trap the condensable hydrocarbons using an impinger sampling

train and a Petersen column.

2. Determine the total tar content and its relation to the operating conditions of

the gasifier.

3. Analyze the concentrated tar samples using GC-FID and GC-MS to identify

major tar components.

4. Determine the volatility of the tar samples.

5. Obtain the elemental composition (CHO) of the tar samples.

15

CHAPTER 2

LITERATURE REVIEW

2.1 Tar formation

The amount of tar as well as its chemical composition depends on many factors such

as the type of reactor and its geometry, the black liquor injection point, the oxidizer used,

the black liquor droplet size distribution, and the method for tar collection, extraction and

characterization. In fluidized bed gasifiers, tar production and composition additionally

depend on the temperature and time history of the particles and gas and the mixing of the

solids in the bed.

Tar formation reactions involve the dissociation of the larger organic molecules

produced during the primary devolatilization.26 Tar compounds have shown similarity

with the lignin substructure.26 During gasification, the organics from the black liquor, like

lignin and carboxylic acids, undergo many reactions such as decarboxylation,

decarbonylation, dealkylation and the rupture of aromatic rings to form light and heavy

gases. Sricharoenchaikul et al. 26 suggested that the formation of heavy multiring tar is

due to the thermal condensation of broken aromatic groups. Elliot 27 proposed a sequence

of tar maturation from a primary pyrolysis process using oil as a fuel, this sequence is

shown in Figure 4.

Milne et al. 11 suggested that tar concentration and composition may be used in the

future as an indication of the overall equipment design and performance. Gasification of

16

Larger PAH

900 ºC

Polycyclic Aromatic

Hydrocarbons (PAH) 800 ºC

Heterocyclic Ethers 700 ºC

Alkyl Phenolics

600 ºC

Phenolic Ethers 500 ºC

Mixed oxygenates

400 ºC

Figure 4. Sequence of tar maturation from a primary pyrolysis process using oil as a fuel (Adapted from reference 27).

17

biomass in fluidized beds generally produces a gas mixture with a total tar concentration

between 2–10 g/m3.28 Some components can also serve as markers, suggesting the overall

tar composition. For example, the gasification of pine sawdust yielded high-molecular-

weight polyaromatic compounds (molar mass > 200).29 Coda et al. 30 concluded that tar

formed in updraft gasifiers consists mainly of polar components, whereas tar formed in

downdraft and fluidized bed gasifiers consists mostly of nonpolar components.

Tar production has been studied in different types of gasifiers such as laminar

entrained-flow reactors,10, 26 pressurized fluidized-beds,24, 31 downdraft gasifiers,32 and

updraft gasifiers,12 using different types of fuels: black liquor,10, 26 biomass,24, 31, 32 coal, 24

and wood chips 12 and, a variety of oxidizers: air,31, 32 oxygen 24 and steam.13

Some researchers have listed individual tar species they have identified in biomass 11,

33, 34 and black liquor 26 producer gases. These compounds as well as their molecular

weight (M.W.), their simplified chemical formula, their chemical abstract service (CAS)

register number and, their melting and boiling temperatures can be found in the database

of tar compounds (Appendix A).

Simell et al. 35 reported that downdraft and fluidized-bed gasification of biomass

produces about 20 g/m3 of tar. Of this, about 15% wt. is heavy tar. On the other hand,

Milne et al. 11 recognized the wide range of tar levels that have been reported for biomass

gasification; however, they gave a generalization of the total tar production. They

concluded that updraft biomass gasification is the highest tar production process, with

100 g/m3, followed by fluidized bed, with 10 g/m3, and being downdraft gasification the

process that produces the least tar concentration, of 1 g/m3.

18

Brage et al. 24 found that the type of feedstock and the gasification temperature used

principally affected tar yield. When gasifying coal and biomass in a pressurized fluidized

bed gasifier, they also concluded that tar concentration decreased with increasing

residence time, suggesting that tar evolution was catalytically affected by char.

Tar yield also decreased by increasing bed or freeboard temperature 18, 23 and by

increasing air to fuel ratio.18, 22, 23 Finally, Teislev 12 suggested the importance of

feedstock injection point. He noted that the total tar concentration decreased when the

biomass was feed near bottom of the reactor.

2.2 Characterization and collection of tars

One of the problems when collecting tar is the formation of aerosols, from

polyaromatic hydrocarbons (PAH’s) and phenol compounds, which usually cannot be

trapped on filters even at low temperatures.36

Many of the gas sampling methods used today originated from different versions of

the Environmental Protection Agency (EPA); EPA Method 5.28 However, a standard

method for sampling and analysis of tar has not been established yet, and different

methods have been used to collect and further analyze tar: the solid phase adsorption

(SPA) method,24, 37 the impinger train (from the IEA Tar Guideline),32, 35, 38 the Petersen

column,33 among others.39-41 This lack of a general consensus makes it difficult to

compare results from different researchers.

The “Guideline for Sampling and Analysis of Tar and Particles in Biomass Producer

Gases” 33, 38, was a combined effort of the European Commission, the Netherlands

Agency for Energy and the Environment, the Swiss Federal Office of Education and

Science, the Danish Energy Agency, the US Department of Energy, and the National

19

Resources Canada to standardize tar and particle collection and analysis. This guideline

presents a way to collect and analyze organic contaminants and particles produced during

biomass gasification. It was designed to sample gases with tar concentrations between 1

to 300 g/m3 produced in updraft, downdraft, fixed bed and fluidized bed gasifiers. It

covers a wide range of gasification conditions; temperatures up to 900 °C and pressures

between 0.6–60 bars, using air or oxygen as gasifying agents.33, 38

The solvent used to adsorb tar from the product gas is a very crucial choice. The

guideline recommends isopropanol because of health concerns; however, the use of

dichloromethane (DCM) facilitates the subsequent separation steps and it has also yielded

very good results.14, 26, 41 Solvent evaporation and water or ice condensation and

accumulation during sampling were some of the main concerns stated by Abatzoglou et

al.14 Avoiding repolymerization and secondary reactions after sampling are other crucial

considerations in tar analysis.11 Moreover, the choice of temperature at which the sample

is collected and the subsequent solvent-water separation complicate further the tar

collecting process.

For tar characterization, a wide variety of methods and techniques have been used.

Gas chromatography–mass spectroscopy (GC-MS) 32, 39, 42 is an effective combination to

analyze chemicals present in a tar sample. However, methods such as gas

chromatography–flame ionization detector (GC-FID),32 gravimetric analysis,32

thermogravimetric analysis,39 size exclusion chromatography (SEC),39 ultra violet

fluorescence spectroscopy (UV-F),39 high performance liquid chromatography (HPLC),31,

42 Fourier transform infrared spectrometry 10 and the EPA method 8310 42 have also

contributed to improve tar description.

20

GC-MS is one of the best methods available for analyzing PAHs.42 A crucial factor

when analyzing a sample using a GC, however, is to obtain a reliable result by running a

standard sample with an identical composition to the sample of interest.43 Generally,

components larger than coronene (C24H12) cannot be evaluated by standard GC

analysis.30 Fetzer et al. 44 identified large polycyclic aromatic hydrocarbons of up to 10

rings, in a diesel particulate, by HPLC analysis.

2.3 Factors affecting tar production and composition

Some studies have been conducted to determine the influence of the fuel composition

and the reactor’s operating conditions on tar production and/or composition. Depending

on the residence time and the temperature of the reactor, the formation and destruction of

tar species can be enhanced by the oxidation of gases. 24, 31, 32

Paasen et al. 31 studied some fuel (woody biomass) properties such as the

char/biomass ratio, the moisture content and the lignocellulose composition. In a

fluidized bed gasifier, they found that the ash content (char/biomass ratio tested of 0-17%

wt.) had a negligible effect on the total tar concentration. On the other hand, an increase

in the moisture content of the fuel, from 10 to 45% wt., diminished the total tar

concentration from 14 to 8 g/m3 (dry basis). Finally, the lignocellulose composition did

not show a significant effect on tar composition, however, the total tar concentration was

notably influenced.

Paasen et al. 31 also reported a decrease by a factor of five in tar concentration when

increasing the gasification temperature from 750 to 950 °C. As temperature increases the

tar molecular weight also increases, leading to a higher tar dewpoint, thus aggravating tar

condensation and promoting aerosol formation. Moreover, Teislev 12 gasified wood chips

21

in an updraft gasifier. He noted the complex tar structures that can be obtained at high

temperatures and the greater difficulty of cracking these components.

Yamazaki et al. 32 studied biomass gasification. They reported an increase in tar yield

that could not be analyzed by chromatography, using GC-MS, by increasing the

superficial velocity and by increasing the particle yield in a downdraft gasifier. This study

also concluded that this nonchromatographable material was composed of ash particles,

fragments of char (carbon that did not react) and soot, which is formed by the surface

growth and agglomeration of PAH’s.

2.4 Tar removal systems

Tar concentration at the exit of the gasifier can vary from 1 to 180 g/m3 for different

gasification processes. However, depending on the final gas application, this

concentration needs to be lowered to 0.05-0.5 g/m3.13 For example, for internal

combustion engines, it has been reported that the gases need to have less than 0.05 g/m3

of particles and a tar concentration below 0.1 g/m3.36

Due to the disposable condition and the relatively low price, the most commonly used

catalyst for tar conversion in biomass gasification processes is calcined dolomites.

However, the tar conversion efficiency of the dolomites is high only when working with

steam at high temperatures (900 °C) and since dolomites are not robust, attrition becomes

a problem in fluidized bed reactors.45 Dayton 45 gave a summary of the nonmetallic

catalysts, the novel catalyst and the commercial nickel reforming catalysts used for

biomass tar destruction.

A number of physical and chemical methods for cleaning and conditioning gases,

removing dust and/or tar, have been studied. These include: wet electrostatic precipitator

22

(ESP),12, 37 oil based gas washer (OLGA),46, 47 separate catalytic reactor filled with

dolomites from different origins,10, 13, 48 secondary bed of pure calcite,13 secondary bed of

pure magnesite,13 nickel catalyst,49 and olvine,45 among others.11, 13, 45

23

CHAPTER 3

EXPERIMENTAL

3.1 Introduction This chapter describes the University of Utah fluidized bed black liquor steam

reformer system as well as the methods and equipment used for tar collection. The steam

reformer was operated at different operating conditions to evaluate tar production and tar

characteristics. Two sample collecting systems were used: an impinger sampling train

and a so-called Petersen column.

Total tar concentration was obtained gravimetrically and reproducibility tests were

performed to determine the consistency and reliability of the tests. Characterization of tar

was performed using different techniques that would provide a better understanding of its

physical and chemical properties. A series of analysis were performed at the University

of Utah. In addition, selected samples were sent to an outside laboratory for analysis.

Analyses performed include gas chromatography-flame ionization detection (GC-FID)

analysis, gas chromatography-mass spectrometry (GC-MS) analysis, thermogravimetric

analysis (TGA) and elemental analysis.

24

3.2 Equipment

3.2.1 University of Utah steam reformer

The University of Utah has built a pressurized fluidized bed steam reformer,

completely automated, capable of working at elevated pressures and able to handle a

variety of fuels (see Figure 5). This reactor is about 5.2 m height and 0.75 m diameter,

and consists of a gas distributor at the bottom of the bed, a bed section (0.25 m diameter

and 1.4 m height) and a freeboard located at the top of the bed (0.25 m diameter and 3 m

height), which has an internal cyclone that returns entrained solids to the bed.

The black liquor used in this research project had a solid content between 36–58%

wt., and it was obtained from Georgia-Pacific Corporation’s Big Island mill. Its elemental

composition on a dry basis is shown in Table 5. Black liquor is injected directly into the

bed of the gasifier and superheated steam is injected through the gas distributor to

produce a hydrogen-rich synthesis gas in an endothermic reaction. The fluidized bed is

heated with 80 cartridge heaters configured in four perpendicular banks of 20 heaters

each.

A pressurized and automatic lock hopper system at the bottom of the bed permits the

bed solids removal at any time, facilitating the control of the bed height by dumping

inorganic material that makes up the bed during the steam reforming of black liquor.

The normal operating conditions of the reactor are listed in Table 6: the average bed

temperature, the feed rate and temperature of the black liquor, the bed height and the

fluidizing velocity, the steam’s temperature and flow rate, and the temperature of the exit

gases. At these conditions three standard tests were run and tar was collected to determine

the reproducibility of the impinger train procedure and the tar isolation method.

25

Figure 5. The University of Utah black liquor steam reformer system.

26

Table 5. Black liquor composition, dry basis.

Element Concentration (mass %)

Carbon 34.43

Hydrogen 3.00

Oxygen 41.45

Sulfur 0.10

Sodium 18.70

Potassium 2.02

Chlorine 0.09

Nitrogen 0.21

27

Table 6. Normal operating condition of the reactor.

Variable Units Condition

Average bed Temperature °C 605

Liquor feed rate (dry solids) kg/h 8.91

Bed height m 1.47

Fluidizing velocity m/s 0.276

Steam temperature °C 601

Steam flow rate kg/h 14.4

Black liquor feed temperature °C 100

Exit gases °C 389

28

Some of the normal operating conditions were changed later and tar samples collected

to evaluate the impact of some operating conditions on tar formation and in some cases

the tar’s chemical and/or physical properties. The injection of air, through the black

liquor injector and through the bed grid, was also evaluated. The operating conditions of

the gasifier for all the analyzed samples are listed in Table 7.

3.2.2 Tar sampling systems

3.2.2.1 Impinger train

A schematic diagram of the experimental set up used to collect tar samples is shown

in Figure 6. Basically, the sampling train can be divided in three main modules: the

particle collection module, the tar and volatile organic compounds (VOCs) collection

module and the volume measurement module.

Module 1 is the particle collection section, which consists of a heated transfer line, a

furnace and a thimble filter (30 x 100 mm) located inside the furnace. The temperatures

of the transfer line and the furnace are controlled with a temperature controller box and

maintained above 350 °C to prevent tar condensation in this section.

Module 2 is the tar collection section per se. This section can be subdivided in three

submodules. Submodule 1 is the moisture collection section, which consists of three

impingers, one filled with water and glass beads, another with just water and the third one

with DCM. These three impingers are cooled in a water bath that remains at about 30 °C.

Submodule 2 is where tar and VOCs are adsorbed into DCM in three impinger bottles.

The first two bottles are filled with DCM and a third one filled with DCM and glass

29

Table 7. Matrix of operating conditions of the reactor used for tar sampling.

Run Test Average bed temperature

(°C)

Liquor feed rate

(kg/h)

Bed height

(m)

Fluidizing velocity (cm/s)

Steam temperature

(°C)

Steam flow rate

(kg/h)

1 Standard 604 10.43 1.52 28.8 589 14.9

2 Air added through grid 604 10.68 1.52 23.6 525 12.2

3 Air added through black liquor injector

604 11.47 1.56 28.8 590 15

4 Petersen column 604 11.29 1.57 28.6 590 14.9

5 High black liquor flow rate 604 16.82 1.52 28.3 601 14.5

6 Standard 604 11.77 1.5 29.4 601 15

7 Medium black liquor flow rate 604 9.05 1.5 32.4 601 16.7

8 High bed temperature 643 6.03 1.45 Not

recorded 591 15.2

9 Standard 604 6.65 1.48 Not recorded 601 15.2

10 Low bed temperature 564 6.79 1.46 Not

recorded 591 15.2

11 Low black liquor flow rate 607 2.63 1.47 44.8 603 15

12 Standard 607 8.23 1.46 44.6 604 14.5

13 Fluidizing velocity 607 8.41 1.51 57.1 614 29.3

15 Low steam temperature 604 10.34 1.51 28.6 479 14.4

16 Standard 604 8.57 1.47 28.3 604 14.3

17 Reproducibility test 1 605 8.93 1.47 27.4 601 14.4

18 Reproducibility test 2 605 8.93 1.47 27.4 601 14.4

19 Reproducibility test 3 605 8.93 1.47 27.4 601 14.4

30

Figure 6. Schematic diagram of the impinger train used to collect tar samples.

Thimble filter

Backup Filter

Flow Totalizer

Water at 20°C Ethylene Glycol at –20°C

1 2 4 5 6 3

Pump

Furnace

Pressure gauge and critical orifice

Heated transfer line

Tar collection section (module 2)

Sampling section(module 3)

Particle collection section (module 1)

31

beads. Theses three impingers are cooled in an ethylene glycol bath at approximately -20

°C. Finally, Submodule 3 is a back up filter that collects residual VOC’s and tar aerosols

that might penetrate the impinger train. This back up filter is located before the pump and

after the impinger train to prevent pump damage from solvent condensation.

Module 3, the sampling section, helps to control the flow rate while measuring the

volume sampled. This module consists of a critical orifice, a vacuum pump, a pressure

gauge and a dry gas flow meter.

3.2.2.2 Petersen column

A Petersen column was also used to collect a tar sample, it was thought that the whole

impinger train could be replaced with this column, however, due to the high steam

content of the gas, it was necessary to use two impingers before the column to collect

most of the water; these two impingers were in a water bath at the same conditions as

impinger 1 and 2 from the impinger train, but, instead of water, the impinger 2 contained

230 ml of DCM. The rest of the set up used when sampling with the impinger train was

kept the same.

A picture of the Petersen column is shown in Figure 7. The column has two stages, in

the first stage (at approximately 27 °C) the gases bubble through DCM and leave to the

second stage which has a glass frit that improves the solvent gas contact by the

generating small gas bubbles. The Petersen column has two cooling jackets that were

filled with ethylene glycol at -17 °C.

32

Glass frit

Gas entrance

Thermocouple

Second stage cooling jacket

Gas exit

First stage cooling jacket

Figure 7. The Petersen column.

33

3.2.3 Tar isolation system

After sampling, there was about 2 liters of a mixture of water, DCM and tar. In order

to get the total tar amount present in all of the collected samples, separation of the two-

phase sample was carried out in a 1 liter separatory funnel (see Figure 8). Most of the

organic material was dissolved in the DCM (heavy phase), facilitating tar separation.

A Blue M water bath and a BÜCHI MSB 1122A-1 rotary evaporator where used to

concentrate the tar samples by evaporating the solvent as shown in Figure 9. Finally, the

concentrated tar samples were weighed in a balance with accuracy of 0.1g. The carbon

and bed material present in the raw gas was tracked by weighing the thimble filter before

and after every test in a balance with accuracy of 1 mg.

3.2.4 Analysis equipment

A series of analysis was performed at the University of Utah to find the impact on tar

composition and tar relative volatility after changing the gasifier operation conditions.

Initially, GC-FID analysis was used with the dilute tar samples (2.7 % in volume of tar)

to have an idea of the chemical composition of the tar samples. The chromatograph used

was a Hewlett Packard 5890A gas chromatograph. Later, in order to identify some of the

components present in one of the dilute mixtures, tar sample from run 1 was

characterized by GC-MS analysis in a Hewlett Packard 5890 series II gas chromatograph

and a Hewlett Packard 5971A mass spectrometer, with a mass selective detector (MSD).

Finally, the relative volatility of the concentrated tar samples was determined by TGA

analysis in a Hi_Res modulated TGA 2950 thermogravimetric analyzer from TA

instruments.

34

Figure 8. Two-phase sample in a separatory funnel.

35

Figure 9. The rotary evaporator.

36

3.3 Procedures

3.3.1 Tar sampling

Hot gases, at temperatures above 350 °C, exiting the reactor were sucked through the

transfer line using the vacuum pump, at approximately 7 l/min. During the sampling time,

of about 30 min, 200 liters of dry gas were sampled as shown in Figures 10 and 11. These

gases passed through the thimble filter to separate bed fines and carbon (coming from the

reactor) from the raw gases.

Subsequently, the hot gases passed through the six impingers as shown in Figure 12.

The first impinger was filled with approximately 250 g of glass beads (6 mm in

diameter), the second impinger was filled with about 200 ml of water, the third, fourth

and fifth impingers were filled with approximately 300 ml, 170 ml and 220 ml of DCM,

respectively. The sixth impinger was filled with about 150 ml of DCM and 50 g of glass

beads. These glass beads helped promote mass transfer between the cold gases and the

solvent, facilitating aerosol collection.

Before and after each test, the impingers were weighed so that water content and

solvent evaporation could be estimated. At the end of the sampling, the glass pieces were

washed with DCM, which was mixed with the collected sample and stored in a 2 liter

amber bottle for further analysis.

Most of the tar samples were collected with the impinger train. However, there was

one sample at standard conditions that was taken using the Petersen column (run 4). In

this test, the additional restriction to the gas flow was evident. The dry gas flow was

approximately 3 l/min and a total volume of 150 liters was measured.

37

Dry flow meter

Furnacee

Temperature controller box

Cooling bath

Transfer line

Dry flow meter

Furnacee

Temperature controller box

Cooling bath

Transfer line

Figure 10. The front side of the impinger sampling train.

38

Figure 11. The left side of the impinger sampling train.

Back up filter

Vacuum pump

Water bath

Pressure gauge

Glass elbow

connector

39

Figure 12. The impinger sampling train.

1 2 3

6 5 4

40

3.3.2 Tar isolation and gravimetric determination of tar concentration

To obtain the total tar amount present in all of the collected samples, separation of the

two-phase sample was carried out in the separatory funnel. Most of the organics were

mixed in DCM (heavy phase). However, some of the organics were still dissolved in the

water phase (light phase) after the first extraction; thus, about three liquid-liquid

extractions were required per sample to collect most of the organic material present in the

water.

After the DCM phase was separated from the water phase, the DCM-tar mixture was

submerged in the water bath at 40 °C and the DCM was boiled in the rotary evaporator.

The solvent was condensed, collected, and added back to the separatory funnel so that the

DCM could be washed and used to capture some of the organic material still present in

the water phase. After this complete process was carried out about three times and the tar

sample was almost solvent free (when the DCM drops were condensing at rate of less

than one drop per minute) as shown in Figure 13, the flask was weighed so that the tar

concentration could be determined.

From the concentrated tar samples, dilute samples were prepared for further analysis

by mixing 150 ml of DCM with 3 ml of the concentrated tar samples. All the samples

were stored in amber bottles at 4 °C to prevent further reaction.

3.3.3 Analytical procedures

3.3.3.1 Characterization of tar components (GC-FID)

The dilute tar samples (2.7 % in volume of tar) were injected into the GC-FID to see

if the chemical composition changed as the operating conditions changed. The GC-FID

temperature profile used, the column characteristics, the injection volume, among other

41

Figure 13. The concentrated tar sample.

42

analysis parameters can be found in Table 8.

The solvent collected in the evaporation process was also injected in the GC-FID to

prove that a significant concentration of hydrocarbons were not lost during the tar

concentration process.

Finally, a standard sample from Restek Co., a phenols mixture dissolved in DCM (see

Table 9 for sample composition), was analyzed at the same conditions shown in Table 8

to obtain a number of residence times for some hydrocarbons and use them as markers.

Unfortunately due to the chemical complexity of the tar samples, a standard mixture with

comparable composition with the tar samples was not found.

3.3.3.2 Characterization of tar components (GC-MS)

Sample 1 (taken at standard conditions) was analyzed in the GC-MS to characterize

some of the main components of the tar mixture. It was not necessary to analyze all of the

collected tar samples since the chromatograms resulting from the GC-FID analysis

showed no substantial differences between samples. The temperature profile used, the

column characteristics, the injection volume, among other analysis parameters used for

this analysis can be found in Table 10.

In order to estimate the concentrations of some of the more representative

components that were present in the tar sample (Run 1), two standard samples from

Restek Co. were also injected in the GC-MS at the same conditions shown in Table 10,

one calibration sample dissolved in DCM and composed mainly of two to six ring

aromatic hydrocarbons (see Table 11 for sample composition) and the phenols mixture

described before.

The species concentration was obtained with a relationship established to acquire the

43

Table 8. GC-FID conditions and temperature profile.

Initial Temperature 40 °C Initial Time 3 min Heating Rate 4 °C /min Final Temperature 300 °C Final time 15 min Detector Temperature 300 °C Run Time 83 min Carrier Gas Helium Carrier Gas Velocity 35 cm/s Head Pressure 21 kPa Split Ratio Splitless Column HP-5 Column Length 30 m Column Diameter 0.53 mm Injection Temperature 300 °C Injection volume 1 µl

44

Table 9. Standard phenols mixture composition.

Compound Concentration (μg/ml)

4-chloro-3-methylphenon 2000 2-chlorophenol 2000 2,4-dichlorophenol 2000 2,4-dimethylphenol 2000 2-fluorophenol 2000 2-methylphenol 2000 4-methylphenol 2000 2-nitrophenol 2000 Phenol 2000 Phenol-d6 (surrogate) 2000 2,4,6-trichlorophenol 2000

45

Table 10. GC-MS conditions and temperature profile.

Initial Temperature 40 °C Initial Time 3 min Heating Rate 4 °C /min Final Temperature 300 °C Final time 15 min Detector Temperature 300 °C Run Time 83 min Carrier Gas Helium Carrier Gas Velocity 35 cm/s Head Pressure 21 kPa Split Ratio Splitless Column DB-5 Column Length 30 m Column Diameter 0.53 mm Injection Temperature 300 °C Injection volume 1 µl

46

Table 11. Composition of the calibration mixture of 2-6 ring

aromatic hydrocarbons.

Compound Concentration (μg/ml)

Naphthalene 2000 Acenaphthylene 2000 Acenahthene 2000 Fluorene 2000 Phenanthrene 2000 Anthracene 2000 Fluoranthene 2000 Pyrene 2000 Benz(a)anthracene 2000 Chrysene 2000 Benz(b)fluoranthene 2000 Benz(k)fluoranthene 2000 Benz(a)pyrene 2000 Indeno(1,2,3-cd)pyrene 2000 Dibenz(a,h)anthracene 2000 Benzo(g,h,i)perylene 2000

47

milligrams of total tar per milliliter of tar solution. This approximation was done by

comparison between the integrated peak area obtained, at the same GC-MS conditions,

for a specific compound in the calibration mixture with the area obtained for a similar

compound, based on the molecular structure, in the tar sample. In addition, some

analyses were performed on a number of samples from the commercial steam reformer at

Georgia-Pacific’s Big Island mill. The objectives of these analyses were to get familiar

with sample preparation and tar analysis while collaborating with Georgia-Pacific. The

commercial gasifier operates similarly to the University of Utah’s unit. The date when the

samples were collected and the collection points are shown in Table 12. These samples

were collected when gasifying 4100-4800 kg/h of black liquor, with a solid content of

59%, a bed temperature between 606 and 610 ºC and a fluidizing velocity of 0.213-0.215

m/s.

3.3.3.3 Volatility of the tar samples

The concentrated tar samples were analyzed in the TGA to obtain the volatility of

each sample and, in addition, sample 1 was analyzed 2 more times in order to establish

the reproducibility of the analysis and the reliability of the equipment. The temperature

profile and conditions used for these analyses can be found in Table 13.

3.3.3.4 Elemental analysis of tar samples

All the concentrated tar samples were sent to Huffman laboratories, Inc. to be

analyzed for chorine content. The chlorine still present in the concentrated tar samples

would give a relationship to determine the DCM (CH2Cl2) that was not removed in the

vaporization process and was still present in the samples, affecting the gravimetric tar

48

Table 12. Samples from Georgia-Pacific’s commercial gasifier, analyzed by GC-MS.

Date of collection Point where the samples were collected

April/2005 Gas cooler April/2005 Solid sample

June/2005 From the tubing coming out of the heated sample line to the sample conditioner

June/2005 Venturi June/2005 Venturi June/2005 Venturi May/2005 Venturi October/2005 Gas cooler October/2006 Flare low point boot drain

49

Table 13. TGA conditions and temperature profile.

Initial Temperature 40 °C Heating Rate 15 °C /min Final Temperature 1000 °C Run Time 64 min Gas Nitrogen Pan material Platinum Sample Volume 0.15 ml

50

determination. In addition, concentrated tar sample from run 6 was analyzed for carbon,

hydrogen, oxygen and once again, chlorine. These values would allow the determination

of the percentage of the organic carbon present in the black liquor injected that ended up

as tar.

The solids captured in the thimble filter used in run 1 (see Figure 14) were also

analyzed for elemental composition (CHO). It is believed that due to the high

temperatures used in the filter holder (350 °C), no tar would condense in the filter and

just carbon particles and soot would be collected. A Soxhlet extraction of the filter

material with DCM was also done to confirm that no tar was captured or condensed in the

thimble filter.

51

Figure 14. The thimble filter and the solids captured in run 1.

52

CHAPTER 4

RESULTS AND DISCUSSION

4.1 Reproducibility of the tar isolation method

After tar mixtures were collected, separated, concentrated, and weighed as described

in the experimental chapter, the gravimetric tar concentration was obtained. It is

important to emphasize that these values are overestimated since high concentrations of

DCM were still present in the concentrated tar samples. To obtain the corrected tar

concentrations, tar samples were sent to Huffman laboratories, Inc. to be analyzed for

chlorine content. However, any attempt to quantify sample composition is a very

complex process because tar samples contain some extremely volatile components.

Furthermore, Huffman laboratories, Inc. cautioned that both weight and chlorine

containing compounds were lost during analysis.

Nevertheless, it is believed that the concentration of DCM in all the samples was very

similar since the procedure used to concentrate the tar samples was performed until

samples reached the same DCM evaporation level. Therefore, the following results are

considered valuable, even though approximately half of the weight obtained for each

sample is DCM.

The fractions of organic carbon in the feed ending up as tar, for the reproducibility

tests (runs 17-19), are shown in Figure 15. This figure shows good reproducibility,

suggesting that the method used for collection and further separation to obtain

53

5

10

15

20

25

30

35

Frac

tion

of o

rgan

ic c

arbo

n in

the

feed

endi

ng u

p as

tar (

appr

ox. %

wt.)

Run 17 Run 18 Run 19

Figure 15. Fractions of organic carbon in the feed ending up as tar for the reproducibility test (runs 17-19). The error bars in the figure represent one

standard deviation.

54

concentrated tar samples was appropriate.

The average tar content determined gravimetrically was approximately 73.8 g/m3 of

dry gas and 20.3 g/m3 for the wet gas. See Figure 16. This means that about 33% of the

total organic carbon that entered the gasifier as black liquor ended up as tar. However, it

is important to note here that all this mass is not expected to condense and cause

downstream troubles. The magnitude of the tar problem depends on the final gas

application and the tar composition.

Finally, from this reproducibility analyses the error that would represent a 90%

confidence interval was determined for the rest of the result. These are indicated in the

following section.

4.2 Influence of operating conditions on production of tar

4.2.1 Reformer temperature

As expected, tar production is clearly affected by temperature. It has been reported

previously that the lower the tar concentration, the higher molecular complexity of tar

mixtures, when gasifying at high temperatures.12, 31 High temperature promotes most of

the gasification reactions; however, heavy multiring tar formation is also aggravated from

the repolymerization of broken aromatic rings.

Tar samples were collected when the system was operating at three different bed

temperatures; from 560 to 650 ºC (runs 8-10). Results are shown in Figure 17. When

comparing the highest with the lowest temperature, tar concentration decreased by a

factor of 3.5 on a dry basis and by almost 2 on a “wet” basis (when H2O in the product

gas was taken into concentration) which means that the fraction of organics ending up as

tar decreased by approximately 43%.

55

Run 17

Run 18

Run 19

0 15 30 45 60 75

Tar concentration (g/m3)

Dry basisWet basis

Figure 16. Tar concentrations obtained in the reproducibility test (runs 17-

19). The error bars in the figure represent the standard deviation.

56

0

20

40

60

80

100

120

140

160

560 580 600 620 640 660

Bed temperature (ºC)

Tar p

rodu

ctio

n (g

/m3 )

0

5

10

15

20

25

30

35

40

45

50

Frac

tion

of o

rgan

ic c

arbo

n in

the

feed

endi

ng u

p as

tar (

appr

ox. %

wt.)

Wet basis Dry basis

Figure 17. Relationships between tar concentrations (in dry and wet bases) and fraction of organic carbon in the feed ending up as tar and the bed temperature (runs 8-10). The error bars in the figure represent a 90% confidence interval.

57

Finally, it is important to mention that the fluidizing solids of the bed did not show

signs of agglomeration, even at the highest temperature tested. This particle mechanism is

one of the main drawbacks of working at high temperatures,2 causing, in some cases, the

immediate shut down of the gasifier.

4.2.2 Liquor feed rate

Black liquor feed rates from 2.6 to 16.8 kg/h (about 1.4 to 9.7 kg of black liquor

solids per hour) were tested during two campaigns, performed on two different days (runs

5-7 and 11-12). The results obtained are shown in Figures 18 and 19, respectively.

Tar production was highly influenced by the black liquor solids feed rate on both a

dry and a wet basis, decreasing tar production by decreasing the solids feed rate. In both

campaigns, a reduction of about 40% was achieved when comparing the highest with the

lowest black liquor flow rate. However, the results obtained for the fraction of organic

carbon ending up as tar were very contradictory for both campaigns, since the data did

not follow any obvious trend, and instead, all the values seemed to level off.

Given the good mixing condition that fluidized beds have, it was believed that it was

not necessary to wait for long time periods between experiments, and thus, after changing

the black liquor flow rates, just about an hour was given to the system to stabilize itself

and begin sampling.

What was not considered was that the solids production rate also changed as the black

liquor solids feed rate was varied. Indeed, the carbon content of these solids might have

changed as well. Therefore, when the black liquor flow rate was increased, part of the

organic carbon that entered the reactor did not end up as tar, and instead, it became part

58

0

20

40

60

80

100

120

140

160

180

2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

Black liquor solids feed rate (kg/h)

Tar p

rodu

ctio

n (g

/m3 )

10

15

20

25

30

35

40

Frac

tion

of o

rgan

ic c

arbo

n in

the

feed

endi

ng u

p as

tar (

appr

ox. %

wt.)

Wet basis Dry basis

Figure 18. Relationships between tar concentrations (in dry and wet bases) and fraction of organic carbon in the feed ending up as tar and the black liquor solids feed rate (runs 5-

7). The error bars in the figure represent a 90% confidence interval.

59

0

20

40

60

80

100

120

140

160

180

2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

Black liquor solids feed rate (kg/h)

Tar p

rodu

ctio

n (g

/m3 )

10

15

20

25

30

35

40

Frac

tion

of o

rgan

ic c

arbo

n in

the

feed

endi

ng u

p as

tar (

appr

ox. %

wt.)

Wet basis Dry basis

Figure 19. Relationships between tar concentrations (in dry and wet bases) and fraction of organic carbon in the feed ending up as tar and the black liquor solids feed rate (runs 11

and 12). The error bars in the figure represent a 90% confidence interval.

60

of the bed itself, increasing the production of bed solids. That was perceived because the

height of the bed increased by increasing the liquor flow, thus, increasing the amount of

times that the solids had to be dumped. Assuming a constant carbon content in the

dumped bed solids, the estimated organic carbon production rate, as a result of the black

liquor solids feed rate, can be seen in Figure 20.

Consequently, it is recommended that in future tests the bed be allowed to stabilize

and reach the organic carbon production rate expected before tar sampling starts. In this

way, the influence of the black liquor solids feed rate on both tar production rate and the

fraction of feed ending up as tar would give satisfactory results.

4.2.3 Superficial gas velocity

Two tar samples were obtained to compare the effect that the fluidizing velocity has

on tar formation. Initially, one tar sample was collected when the fluidizing velocity was

44 cm/s and later it was increased by about 30% to reach 57 cm/s (runs 12 and 13). The

results are depicted in Figure 21. No conclusion can be drawn here since there was no

statistically significant influence.

Brage et al. 24 had suggested the catalytic effect that char had on tar evolution,

decreasing tar concentration with increasing residence time (by decreasing the fluidizing

velocity), when gasifying coal and biomass for about an hour in a pressurized fluidized

bed. However, they also suggested that the effect of fluidizing velocity was more

pronounced for coal than for biomass gasification, since the char produced in biomass

gasification is easily oxidized, generating only small steady-state amounts capable to

catalyze tar cracking reactions.

61

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

2.4 3.4 4.4 5.4 6.4 7.4 8.4 9.4 10.4

Black liquor solids feed rate (kg/h)

Org

anic

car

bon

prod

uctio

n ra

te

(k

g/h)

Figure 20. Relationship between the estimated carbon production rate that ended up

unreacted in the bed solids and the black liquor solids feed rate.

62

0

20

40

60

80

100

120

40 45 50 55 60

Fluidizing velocity (cm/s)

Tar p

rodu

ctio

n (g

/m3 )

30

35

40

45

50

Frac

tion

of o

rgan

ic c

arbo

n in

the

feed

endi

ng u

p as

tar (

appr

ox. %

wt.)

Wet basis Dry basis

Figure 21. Relationships between tar concentrations (in dry and wet bases) and fraction of organic carbon in the feed ending up as tar and the fluidizing velocity (runs 12 and 13).

The error bars in the figure represent a 90% confidence interval.

63

Yamazaki et al. 32 also found a decrease in tar concentration and, at the same time, an

increase in the GC-detectable tar yield when gasifying at low superficial gas velocities.

However, they also found that the main composition did not show extreme change. They

investigated the effect that fluidizing velocities (from 30 to 70 cm/s) had, on tar yield

concentration and composition, when gasifying biomass with air in a downdraft gasifier.

4.2.4 Fluidizing steam temperature

To determine the influence that steam temperature has on tar formation, two tests

were accomplished: one injecting steam at 479 ºC and the other at 604 ºC (runs 15-16).

The results obtained are shown in Figure 22.

When steam was injected at the lower temperature, tar concentration increased by

about 18% in dry basis, while the organic carbon ended up as tar increased by

approximately 5%. Still, these values fall at the edge of confidence interval, particularly

the value of organic tar ending up as tar. Thus, it is recommended to gather more data, in

order to satisfactorily identify the effect that steam temperature has on tar formation.

It was thought that perhaps tar concentration would be affected by the steam

temperature, since the low temperature might have ended up decreasing the bed

temperature locally, affecting the quality of the produced gas. However, the bed

temperature was kept at 604 oC for both cases by controlling the temperature of the in-

bed heaters.

4.2.5 Air addition

The influence of air addition on tar production was studied for two different cases.

Initially air was preheated to 538 ºC, and then, 18% by volume of air was injected though

64

0

10

20

30

40

50

60

70

80

90

450 500 550 600 650

Steam temperature (ºC)

Tar p

rodu

ctio

n (g

/m3 )

20.0

30.0

40.0

50.0

Frac

tion

of o

rgan

ic c

arbo

n in

the

feed

endi

ng u

p as

tar (

appr

ox. %

wt.)

Wet basis Dry basis

Figure 22. Relationships between tar concentrations (in dry and wet bases) and fraction of organic carbon in the feed ending up as tar and the steam temperature (runs 15 and 16).

The error bars in the figure represent a 90% confidence interval.

65

the fluidizing grid with the fluidizing steam (run 2). Later, the same amount of air, this

time preheated to 121 ºC, was added though the black liquor injector (run 3).

The influence of air addition on the fraction of organic carbon in the feed ending up

as tar, for the two different cases, is shown in Figure 23. The results show that the

fraction of organic carbon in the feed ending up as tar decreased by about 20% for both

cases. This might be the result of the presence of oxygen and the enhanced oxidation

associated.

The effect that air addition had on tar concentration (dry and wet basis), for the two

injection points studied, is shown in Figure 24. The results show that tar concentration

significantly decreased by more than 20% when air is injected.

Although tar production can be reduced by the presence of air in the oxidizing media,

it is important to emphasize that the hydrogen concentration drops because the oxygen

from the air can react with hydrogen. Therefore, the heating value of the product gas

decreases as well.

4.2.6 Petersen column

In order to test the advantages that the Petersen column could have over the impinger

train in term of user friendliness, an additional tar sample was collected (run 4). The

sampling was not improved by the use of the Petersen column, since it was necessary to

install two impingers before the column, in order to collect the high load of water in the

raw product gas.

Also, due to the additional restriction to the gas flow, the sampling time increased

from 30 min, necessary time to sample about 200 liters of dry gas with the impinger train,

to 50 min, necessary time to sample only 150 liters of dry gas.

66

5

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35

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ic c

arbo

n in

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ing

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as t

ar (a

ppro

x. %

wt.)

Standard Air thru. grid Air thru. injector

Figure 23. Fractions of organic carbon in the feed ending up as tar for the air addition

tests (runs 1-3). The error bars in the figure represent a 90% confidence interval.

67

Air thru. injector

Air thru. grid

Standard

0 15 30 45 60 75 90 105 120

Tar concentration (g/m3)

Dry basisWet basis

Figure 24. Tar concentrations obtained for the air addition tests (runs 1-3).

The error bars in the figure represent a 90% confidence interval.

68

The results obtained suggest that the ability of the Petersen column to collect tar

samples is limited. See Figures 25 and 26. Even though these results fell at the edge of

the confidence interval, when sampling was taking place the temperature of the first stage

of the Petersen column was about 27 °C even when the glycol bath was kept at -20 °C,

which might be the reason for the lower tar content. On the other hand, the achieved

trapping temperature was significantly lower inside the last impinger of the impinger

train, about -5 °C.

It is important to mention that aerosols were observed leaving the last impinger when

using the impinger train, as shown in Figure 27. On the other hand, no aerosols were

observed leaving the Petersen column, probably because the final temperature was not

low enough, or because of the glass frit that the Petersen column has between the first

and second stage.

It is essential to clarify that all the quantitative results here are estimates. After every

sample was collected, there was a small tar deposition in the elbow connecting the first

impinger and the heated furnace. See Figure 28. This deposition was not taken into

consideration in any analysis since its removal was not possible without affecting the

quality of the samples. Thus the values for tar concentrations are in some cases

overestimated, as was explained before, due to the DCM still present in the samples after

the concentration process, and tar concentration can also be underestimated due to both

the escape of tar aerosols and tar deposition on the elbow glass connector.

Finally, even though the influence on tar production was studied at different operating

conditions, there is not much information about the cleaned product gas. The steam

reformer has one continuous emission monitor for hydrogen, carbon monoxide, carbon

69

510

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tion

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rgan

ic c

arbo

n in

the

feed

end

ing

up

as t

ar (a

ppro

x. %

wt.)

Impinger train Petersen column

Figure 25. Comparison of the fractions of organic carbon in the feed ending up as tar obtained with the Petersen column and with the impinger train at standard conditions

(Runs 1 and 4). The error bars in the figure represent a 90% confidence interval, based on the reproducibility experiment with the impinger train.

70

Petersen column

Impinger train

0 20 40 60 80 100

Tar concentration (g/m3)

Dry basisWet basis

Figure 26. Comparison of the tar concentrations obtained with the Petersen column and with the impinger train at standard conditions (Runs 1 and 4). The error bars in the figure represent a 90% confidence interval, based on

the reproducibility experiment with the impinger train.

71

Figure 27. The tar aerosols exiting the sixth impinger of the impinger train.

Tar aerosols

Tar aerosols

72

Figure 28. The tar deposition in the glass elbow connector.

Tar deposition

Tar deposition

73

dioxide and methane, and in future experiments an on-line micro-GC will provide a more

detailed analysis of the cleaned product gas.

The hydrogen content of the cleaned product gas, when changing black liquor flow

rate, bed temperature and when adding preheated air, is shown in Figure 29. There was

no significant change when changing fluidizing velocity or steam temperature.

It was expected that the hydrogen content would change when adding air because the

nitrogen would dilute the product gas. However, the hydrogen content was even lower

than the expected value. That could be the result of replacing part of the incoming steam

to the reactor by air and the oxygen in the air reacting with the hydrogen from the gas.

The increase in bed temperature clearly enhanced the hydrogen production, as could

be expected, since gasification reactions are generally favored by increasing

temperature.7 The difference in hydrogen concentrations between the highest and the

lowest temperatures tested was more than 30%.

The behavior of hydrogen production by changing black liquor flow rate seems to

depend on the liquor feed rate per se. At relatively high black liquor rates (first

experimental campaign), it seems that decreasing the liquor feed rate decreases the

hydrogen production. However, at low black liquor feed rates (second experimental

campaign) the hydrogen production was enhanced by increasing the flow. Therefore, it is

suggested to reevaluate the hydrogen concentration of the cleaned product gas,

especially, since it was emphasized before the importance of allowing the solid bed to

stabilize and reach the organic carbon production rate expected before sampling.

74

32

1

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54

7

8

9

1110

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

Air additionBlack liquor flow rate (first campaign)Bed temperatureBlack liquor flow rate (second campaign)

Figure 29. Hydrogen concentration of the cleaned product gas for different operating condition: (1) standard conditions; (2) air injected through grid; (3) air injected through

black liquor injector; (4) black liquor flow rate of 9.05 kg/h; (5) black liquor flow rate of 11.77 kg/h; (6) black liquor flow rate of 18.82 kg/h; (7) bed temperature of 564 °C; (8)

bed temperature of 604 °C; (9) bed temperature of 643 °C; (10) black liquor flow rate of 2.63 kg/h; (11) black liquor flow rate of 11.77 kg/h.

75

4.3 Characterization of tar

4.3.1 Speciation comparison at different operating conditions

Initially, the standard phenol sample from Restek Co. was analyzed to obtain a

number of residence times for some hydrocarbons and use them as markers when

analyzing tar samples. The raw chromatogram is shown in Figure 30, and the

corresponding peaks are described in Table 14.

The chemical composition of the tar samples seems to be very similar for all the

experimental conditions tested. A chromatogram of the tar sample taken at standard

conditions (run 1) can be seen in Figure 31. The chromatograms of the tar samples taken

at different operating conditions can be seen in Appendix B.

All the chromatograms follow a similar trend, with high concentrations of 1-ring

aromatics as would be expected from gasification at low temperatures, like Teislev 12

suggested. Complex tar structures could be expected when gasifying at high temperatures

while at low temperatures higher total tar concentrations are obtained. However, it seems

that not very heavy and complicated molecules were formed in either test.

Miège et al. 42 reported that in an evaporation process to concentrate a PAH sample

diluted in toluene, about 13% of fluoranthene and 72% of naphthalene is lost. A

chromatogram of the DCM condensed after having been boiled off in the tar

concentration process is shown in Figure 32. This figure suggests that just little

concentrations of light and heavy hydrocarbons were evaporated from the tar sample,

concentrations that were not even detected in the GC-FID analysis (the GC detection

limit for a compound in solution is 10 ppm).

It is important to clarify that light organic components (e.g. benzene) were possibly

76

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Figure 30. Raw chromatogram of the Restek’s standard phenol mixture.

77

Table 14. Labeled peaks description of the raw chromatogram of the standard phenols mixture.

Compound Peak number 2-fluorophenol 1 Phenol-d6 (surrogate) 2 Phenol 3 2-chlorophenol 4 2-methylphenol 5 4-methylphenol 6 2-nitrophenol 7 2,4-dimethylphenol 8 2,4-dichlorophenol 9 4-chloro-3-methylphenon 10 2,4,6-trichlorophenol 11

78

0500

10001500200025003000350040004500

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 31. Raw chromatogram of a tar sample taken when gasifying at standard conditions (run 1).

79

0100200300400500600700800900

1000

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Time (min)

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-FID

det

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r sig

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Figure 32. Raw chromatogram of the extracted DCM.

80

overlapped by the solvent during the GC-FID analyses. However, these compounds are

expected not to cause fouling and subsequent plugging problems, in the gasification

process, since they would remain in the cooled product gas.

4.3.2 Speciation – University of Utah system and commercial system

After being diluted in DCM (2.7 % in volume of tar), tar sample 1 (run at standard

conditions) was analyzed by GC-MS, so that some of the most significant components

could be determined. The raw chromatogram obtained is shown in Figure 33, with peaks

of the more concentrated components labeled. These labeled compounds as well as the

time when they were eluted, the identification quality achieved, the approximate

concentration of each compound in the concentrated tar mixture and, an estimation of the

compound concentration in the sampled gas are listed in Table 15. The concentration

values were obtained from a relationship established between the integrated peak area of

the compound of interest and the integrated peak area obtained from a similar

standardized compound, both acquired using the same GC-MS conditions and analytical

procedures.

A list that contains most of the components that were present in this tar sample as

well as their retention time, relative concentration, and identification quality is included

in Appendix C. It is important to mention that this relative concentration is an

approximation that only considers the sum of the detectable species. This approximation

was done by comparison between the integrated peak area and the percentage area only,

and some of the compounds present in the mixture were not detected and instead some

peaks of column material (CM) were considered.

The identification quality shown in Table 15 is an indication of the match between the

81

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Figure 33. GC-MS result from the standard sample No. 1, University of Utah system.

82

Table 15. Major components of standard sample from run 1.

Peak Retention Time

Component name

Concentration (mg/l of dry

gas)

Concentration (mg/mg of

concentrated tar)

Identif. quality

1 6.856 1,2-dimethyl-Benzene 4.906 0.056 91

2 7.601 Bicyclo[4.2.0]octa-1,3,5-triene 4.087 0.047 89

3 8.167 2-methyl-2-

Cyclopenten -1-one

3.045 0.035 96

4 11.549 Ethenylmethyl-Benzene 4.501 0.052 58

5 13.424 1-propynyl-Benzene 5.065 0.058 93

6 14.249 2-methyl-Phenol 5.422 0.062 76

7 15.206 3-meyhyl-Phenol 3.035 0.035 94

8 15.373 2-meyhyl-Phenol 5.399 0.062 83

9 17.89 2,5-dimethyl-Phenol 3.366 0.039 87

10 17.959 2,6-dimethyl-Phenol 3.257 0.037 83

11 18.786 2,3-dimethyl-Phenol 4.009 0.046 90

12 18.959

Azulene overlapped with 2,6-dimethyl-

phenol

Not obtained Not obtained --

83

observed spectrum and the compound spectrum. Due to the complexity of the mixture, a

number of peaks were superimposed, making identification very difficult and resulting in

poor identification quality in some cases. In other cases, the identification quality

obtained was so low that, instead of specifying the name of the suspected compound, the

molecular mass was given in atomic mass units (amu).

The total ion chromatogram showed the presence of phenolics and both substituted

and unsubstituted multi-ring structures. Compounds with molecular structures higher than

five rings were either at concentrations below the detection limit of the equipment (about

10 ppm) or these compounds were not eluted from the GC column. Thus, they were not

shown in the chromatogram. The lightest compounds, that might be present in the tar

sample, were not detected by this method either, because their peaks are covered by that

of the solvent (DCM). However, as mentioned earlier, these light compounds are not

expected to cause fouling problems downstream of the steam reformer because they will

exit the system in the gaseous phase.

From the tables it can be concluded that the tar sample, taken at standard conditions,

is composed mostly of single-ring aromatics and phenolic compounds (about 32 and 24

% respectively). About 18% of the detectable molecules present in this sample were

substituted and unsubstituted two-ring aromatic and less than 3% were heavier molecules

of three rings up to five rings. The condensation and fusion temperatures of the

components identified in this tar sample are well spread. Thus, it would be difficult to

control tar condensation if the gas temperature is reduced. However, certain

concentration of each component would remain in the vapor phase, even though, the

84

temperature of the gas stream gets well below the boiling point. This quantity is

determined by the vapor pressure of each constituent.

A number of tar samples from Georgia-Pacific were analyzed by GC-MS to identify

various compounds present in high concentrations. The dates when some of the analyzed

samples were collected and a few samples characteristics are listed in Table 16. It is

important to mention here, that there is no relationship between samples, but they were

collected on random days.

The raw chromatogram obtained for sample A is shown in Figure 34, and the

corresponding labeled compounds, as well as the retention time and the identification

quality are listed in Table 17. It is interesting to notice that this tar mixture seems to be a

mixture of very heavy hydrocarbons. Actually, the first peak detected was naphthalene

(M.W. = 128.17 amu, B.P. = 217.9 ˚C and M.P. = 80.2 ˚C) between 19–20 min, and the

list of identified compounds goes all the way up to benzo[a]pyrene (M.W. = 252.31 amu,

B.P. = 495 ˚C and M.P. = 177 ˚C). That composition might explain the solid state of this

tar sample.

The raw chromatogram obtained for sample B is shown in Figure 35, and the

corresponding labeled compounds, as well as the retention time and the identification

quality are listed in Table 18. From this table, it can be concluded that about 24% of the

detectable molecules present in this sample were naphthalene compounds, with

condensation and fusion temperatures in the range of 217-269 °C and 80-105 °C,

respectively. Another compound that was found in this sample and had an important

relevance due to its very high percentage (approximate 31%) was N-butyl-

benzenesulfonamide; used as plasticizer to soft plastics. It was concluded that this

85

Table 16. Samples collected by Georgia-Pacific and analyzed by GC-MS.

Date of collection Sample Some sample characteristics

April/2005 A Solid sample with a non soluble content of 28.08%

June/2005 B Liquid sample contaminated with Benzenesulfonamide, N-butyl-

June/2005 C Liquid sample June/2005 D Liquid sample June/2005 E Liquid sample Octuber/2005 F Sticky solid with a non soluble content of 14% Octuber/2006 G High viscous liquid with an approximate solid content of 39%

86

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Figure 34. Raw chromatograph of sample A from Georgia-Pacific’s commercial system.

87

Table 17. Some of the major components of sample A from Georgia-Pacific’s commercial system.

Ret. time (min)

Peak No.

Compound name Identif. quality

19.73 1 Naphthalene 87 23.86 2 2-Methyl-Naphthalene 91 24.39 3 1-Methyl-Naphthalene 91 28.12 4 1,5-Dimethyl-Naphthalene 97 29.1 5 Acenaphthylene 72

32.831 6 1H-Phenalene 72 33.42 7 9H-Fluorene 90 34.77 8 3-Methyl-1-Naphthalenol 90 39.19 9 9-Methylene-9H-Fluorene 90 42.426 10 2-Methyl-Anthracene 68 42.73 11 1-Methyl-Anthracene 64 46.462 12 Fluoranthene 93 47.555 13 Pyrene 95 49.75 14 11H-Benzo[b]fluorine 80 51.087 15 4-Methyl-Pyrene 91 55.142 16 Benzo[a]anthracene 76 55.482 17 Crysene 81 61.52 18 Benzo[a]Pyrene 76

88

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Figure 35. Raw chromatograph of sample B from Georgia-Pacific’s commercial system.

89

Table 18. Some of the major components of sample B from Georgia-Pacific’s commercial system.

Ret. time (min)

Peak No

Compound name Identif. quality

18.31 1 Phenol, Indene and Benzene derivatives 19.10 2 Phenol and 2,3-dimethyl- 91 19.52 3 Naphthalene 90 23.20 4 1H-Cyclopropa[b]naphthalene,

1a,2,7,7a-t, 1H-Inden-1-one and 2,3-dihydro- Benzene-1-cyclopenten-1-yl-

23.68 5 2-methyl-Napthalene 91 24.22 6 1-methyl-Napthalene 91 27.11 7 2-ethyl-Napthalene 93 27.48 8 Naphthalene, 1,5-dimethyl- 97 27.94 9 2,3 Dimethyl-Naphthalene 97 28.93 10 Acenaphthylene 90 39.51 11 Benzenesulfonamide, N-butyl- 91

90

compound leached out the plastic tubing that Georgia-Pacific uses.

Raw chromatograms obtained for samples C, D and E are shown in Figures 36 to 38,

and the corresponding labeled compounds, as well as an estimation of the compound

concentration are listed in Tables 19 to 21. These three samples were collected during the

same day at different times (16:00, 20:00 and 23:50, respectively), which explains the

similarity between chromatograms. From these tables, it can be concluded that about 24

and 22% of the detectable molecules present in these samples were phenol and

naphthalene compounds with condensation temperatures in the range of 94-180 °C.

The raw chromatogram obtained for sample F is shown in Figure 39, and the

corresponding labeled compounds are listed in Table 22. This sample showed a total

concentration of naphthalene compounds of about 17% only, while more than 76 % of

the detected components were very heavy hydrocarbons of more than three rings. That

might explain the consistency of this sample (solid at room temperature).

The raw chromatogram obtained for sample G is shown in Figure 40, and the

corresponding labeled compounds are listed in Table 23. From this table, it can be seen

that about 40% of the detectable molecules were naphthalene compounds and that lighter

and heavier material ranging from benzene to benz[e]acephenanthrylene was also

present.

All the analyzed samples not only help to increase the knowledge on tar

characterization, but also, the detected components contributed to enlarge the tar data

base (Appendix A), that contains more than 200 molecules identified in tar samples from

biomass gasification and was later complemented from reference.50

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Figure 36. Raw chromatograph of sample C from Georgia-Pacific’s commercial system.

92

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Figure 37. Raw chromatograph of sample D from Georgia-Pacific’s commercial system.

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Figure 38. Raw chromatograph of sample E from Georgia-Pacific’s commercial system.

94

Table 19. Some of the major components of sample C from Georgia-Pacific’s commercial system.

Compound name Peak No. concentration (mg/l)

Phenol 1 332.19 2-methyl phenol 2 716.60 2,4 dimethyl phenol 3 285.32 Naphthalene 4 1445.42 Acenaphthylene 5 1122.54 Acenaphthene 6 634.14 fluorene/9H-fluorene 7 438.42 Anthracene 8 976.92 Phenanthrene 9 478.20 Fluoranthene 10 573.70 Pyrene 11 680.17 Benz(a)anthracene 12 124.59 Chrysene 13 197.05

95

Table 20. Some of the major components of sample D from Georgia-Pacific’s commercial system.

Compound name Peak No. concentration (mg/l)

Phenol 1 349.38 2-methyl phenol 2 1432.94 2,4 dimethyl phenol 3 1078.55 Naphthalene 4 828.24 Acenaphthylene 5 585.71 Acenaphthene 6 328.27 fluorene/9H-fluorene 7 199.39 Phenanthrene 8 484.00 Fluoranthene 9 270.57 Pyrene 10 265.82 Benz(a)anthracene 11 64.32 Chrysene 12 95.09

96

Table 21. Some of the major components of sample E from Georgia-Pacific’s

commercial system.

Compound name Peak No. concentration (mg/l)

Phenol 1 640.61 2-methyl phenol 2 2009.09 4-Methyl phenol 3 4710.39 2,4 dimethyl phenol 4 2749.73 Naphthalene 5 939.85 Acenaphthylene 6 655.04 Acenaphthene 7 217.12 fluorene/9H-fluorene 8 404.98 Phenanthrene 9 301.93 Anthracene 10 131.98 Fluoranthene 11 191.17 Pyrene 12 160.43 Chrysene 13 63.32

97

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Figure 39. Raw chromatograph of sample F from Georgia-Pacific’s commercial system.

98

Table 22. Some of the major components of sample F from Georgia-Pacific’s commercial

system.

Compound name Peak No.

Naphthalene,1-methyl 1 Naphthalene,2-methyl 2 Naphthalene,1,8-dimethyl 3 Acenaphthylene 4 Naphthalene,1,2-dimethyl 5 1H-Phenalene 6 Fluorene-9-methanol 7 9H-Fluorene 8 166 amu 9 9H-Fluorene,1-methyl- 10 9H-Fluorene,2-methyl- 11 9H-Fluorene,3-methyl- 12 9H-Fluorene,9-methyl- 13 9H-Fluorene,9-methylene- 14 Naphthalene,1-phenyl/204 amu 15 Phenanthrene,9-methyl- 16 192 amu 17 Anthracene,1-methyl- 18 204/206 amu 19 Fluoranthene 20 Pyrene 21 CM 22

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Figure 40. Raw chromatograph of sample G from Georgia-Pacific’s commercial system.

100

Table 23. Some of the major components of sample G from Georgia-Pacific’s commercial system.

Compound name Peak No.

Benzene, 1,2-propadienyl- 1 Benzene, (1methyl-2-cyclopropen-1-yl)- 2 1H-Indene, 1-methyl 3 130 amu 4 Naphthalene 5 Naphthalene,2-methyl 6 Naphthalene,1-methyl 7 Naphthalene,1-ethyl- 8 Naphthalene,1,2-dimethyl- 9 Naphthalene,2,3-dimethyl- 10 Acenaphthylene 11 Naphthalene,1,8-dimethyl- 12 Acenaphthene 13 1H-Phenalene 14 9H-Fluorene 15 166 amu 16 9H-Fluorene,4-methyl- 17 Anthracene 18 Fluoranthene 19 Pyrene 20 202 amu 21

101

4.3.3 Volatility of the tar samples

The volatility of the standard sample from run 1 was determined three times in a

thermogravimetric apparatus (TGA) to determine the reproducibility of this analytical

procedure, as shown in Figure 41. The volatility of all the concentrated tar samples,

collected at different operating conditions, was also determined and the results are shown

in Figures 42-47. Very similar mass loss curves were obtained for all the samples. The

differences between curves are within the error obtained in the reproducibility tests that

was completed with the standard sample.

For the tar samples analyzed, the average temperature to lose over 85% of the total

mass was between 225 and 660 °C, while, over 60% of the mass was lost within the

temperature window of 135-285 °C. This indicates that most of the gravimetric tar will

condense in the cooler downstream lines unless the gas is properly treated.

It is important to emphasize here the high volatility of the concentrated tar samples, in

part because of the high DCM present. Therefore, the temperatures obtained could be

shifted even to higher values, aggravating tar condensation.

The temperatures at which 60% of the tar weight was lost for the tar samples

collected when changing the black liquor flow rate and the bed temperature are shown in

Figures 48 and 49, respectively. Even though the temperatures are at the edge of the

confidence interval, in both cases, these results suggest a trend. Instead, the other set of

experiments did not show any evident trend. This confidence interval was determined

from the data collected in the reproducibility test, comparing the temperatures at which

60 % of the mass was lost for the standard sample from run 1.

The results suggest that by increasing the black liquor flow rate, the molecular

102

0102030405060708090

100

0 200 400 600 800 1000Temperature (°C )

Wei

ght

( % ) Run 1

Run 2Run 3

Figure 41. Reproducibility test for the thermogravimetric analyzer, standard sample from run 1.

103

0102030405060708090

100

0 200 400 600 800 1000

Temperature (°C )

Rem

aini

ng m

ass (

% ) Standard

Air through gridAir through BL injectorPetersen column

Figure 42. Remaining mass versus temperature for samples collected with the impinger train and with the Petersen column, with and without the addition of air.

104

0102030405060708090

100

0 200 400 600 800 1000

Temperature (°C )

Rem

aini

ng m

ass (

% ) 16.82 kg/h

11.77 kg/h9.05 kg/h

Figure 43. Remaining mass versus temperature for tar samples collected for different black liquor feed rates.

105

0102030405060708090

100

0 200 400 600 800 1000

Temperature (°C )

Rem

aini

ng m

ass (

% ) 643 °C

604 °C564 °C

Figure 44. Remaining mass versus temperature for tar samples collected for different gasifier temperatures.

106

0102030405060708090

100

0 200 400 600 800 1000

Temperature (°C )

Rem

aini

ng m

ass (

% )

57.1 cm/s29.4 cm/s

Figure 45. Remaining mass versus temperature for tar samples collected for different fluidizing velocities.

107

0102030405060708090

100

0 200 400 600 800 1000

Temperature (°C )

Rem

aini

ng m

ass

( % ) 11.77 kg/h

2.63 kg/h

Figure 46. Remaining mass versus temperature for tar samples collected for different black liquor flow rates.

108

0102030405060708090

100

0 200 400 600 800 1000

Temperature (°C )

Rem

aini

ng m

ass (

% ) 604 °C

479 °C

Figure 47. Remaining mass versus temperature for tar samples collected for different steam temperatures.

109

0

50

100

150

200

250

300

350

Tem

pera

ture

(°C

)

Liquor feed rate 9.05 kg/h

Liquor feed rate 11.77 kg/h

Liquor feed rate 16.82 kg/h

Figure 48. Temperatures at which 60% of the tar weight was lost for the samples collected at different black liquor feed rates. The error bars in the

figure represent a 90% confidence interval.

110

0

50

100

150

200

250

300

350

Tem

pera

ture

(°C

)

Bed temperature 564 °C

Bed temperature 604 °C

Bed temperature 643 °C

Figure 49. Temperatures at which 60% of the tar weight was lost for the samples collected at different bed temperatures. The error bars in the

figure represent a 90% confidence interval.

111

complexity of the components in the tar sample is also increased, leading to high

evaporation temperatures. One of the black liquor components is lignin, which is a large

and complex three dimensional polymer containing thousands of phenyl-propane units,51

thus, increasing the back liquor flow rate without changing any other operational

condition seems to affect the overall conversion and hence heavier and more complex

molecules can be found in the product gas.

On the other hand, increasing the bed temperature seems to decrease the evaporation

temperatures, suggesting that the components in the tar mixture are less complex. High

temperatures promote most of the gasification reactions. However, heavy multi-ring tar

formation is also aggravated from the repolymerization of broken aromatic rings. The

results obtained suggest that even at the highest temperature tested these

repolymerization reactions did not increase the molecular complexity of the tar mixture,

implying that repolymerization reactions were not fast enough at these temperatures.

4.3.4 Elemental analysis

Initially, the tar sample from run 6 was analyzed by Huffman laboratories, Inc. for

carbon, oxygen, hydrogen and chlorine content, the results can be seen in Table 24. It

was suspected that some DCM would remain still in the concentrated samples increasing

the results obtained for tar concentrations, even though the boiling temperature of DCM

at Salt Lake City’s altitude is 36 °C and the samples were evaporated in a rotary

evaporator, with a water bath at 40°C, until no further condensation was observed.

Surprisingly, the sample from run 6 had 39.5% chlorine by weight, which

corresponds to 47.2% DCM by weight. Thus, nearly half the weight of this sample was

DCM, suggesting that the actual amount of tar produced was much less than originally

112

Table 24. Elemental composition of concentrated tar sample from run 6.

Results from Huffman laboratories, Inc.

Element Concentration (% wt.)

Hydrogen (H) 5.63 Oxygen (O) 5.36 Carbon (C) 49.55 Chlorine (Cl) 39.45

113

reported. After subtracting the amount of DCM from this sample the elemental

composition of the tar sample from run 6 was recalculated and it is listed in Table 25. The

high molar concentration of hydrogen, compared to carbon, suggests that tar consists

mainly of substituted ring structures.

It was decided to send all tar samples for chlorine analysis so that the actual amount

of tar could be back-calculated. However, because of the very volatile characteristic of

the concentrated tar samples, the original sample was sent back again to confirm the

reproducibility of the chlorine analysis. The results obtained are listed in Table 26.

The new results showed that the tar sample from run 6 had only 21.6% chlorine by

weight, even though, the first analysis showed a concentration of 39.5%. This suggests

that some of DCM was lost by evaporation, and hence, the light tar components were lost

too. Furthermore, the analytical lab had cautioned that the samples were very volatile and

that accurately measuring chlorine would be difficult for this reason.

The chlorine contents for the 19 samples analyzed ranged from 8.6 to 39.6% by

weight, and showed no systematic variation. An attempt to correct the tar concentrations,

by subtracting the DCM content, was conducted. However, when each of the tar analysis

was re-evaluated the results became very scattered and the trends seen above, e.g.

temperature and liquor flow rate, ceased to exist.

Thus, it was concluded that reliably backing out the fraction of DCM in the tar

sample would not be possible, because of the variation in chlorine content observed for

the one sample that had duplicate chlorine analyses. However, the results shown above

are considered valuable, since the methodology used to concentrate tar samples was

reproduced as close as possible for all the samples. Thus, it is believed that the amount of

114

Table 25. Corrected elemental composition of concentrated tar sample from run 6.

Element Concentration (% wt.)

Molar composition

Carbon (C) 81.28 6.77 Hydrogen (H) 8.54 8.46 Oxygen (O) 10.16 0.64

115

Table 26. Chlorine content for all the tar samples collected.

Test Run Chlorine content (%wt.)

Standard 1 27.34 Air added through grid 2 28.07 Air added through black liquor injector

3 23.16

Petersen column 4 17.89 High black liquor flow rate 5 19.18 Standard 6 21.55 Medium black liquor flow rate 7 14.62 High bed temperature 8 8.46 Standard 9 22.23 Low bed temperature 10 20.58 Low black liquor flow rate 11 23.35 Standard 12 32.73 Fluidizing velocity 13 22.29 KOH addition to black liquor 14 28.01 Low steam temperature 15 39.62 Standard 16 18.33 Reproducibility test 1 17 29.64 Reproducibility test 2 18 22.2 Reproducibility test 3 19 34.85

116

DCM still present in the concentrated tar samples should be roughly the same for all

these samples. Furthermore, the good reproducibility obtained in the gravimetric tar

determination and the correspondence between results and expected trends for variation,

e.g., bed temperature, also validate the data.

However, it is recommended to modify the analytical method to ensure that either all

the DCM is removed without affecting light tar concentration, or the DCM content just

after the sample has been concentrated is reliably determined.

The material captured in the thimble filter from run 6 was also analyzed by Huffman

laboratories, Inc. for carbon, hydrogen and oxygen. It is believed that due to the high

temperatures used in the filter holder (350 °C), no tar would condensate in the filter and

just carbon particles, bed material (Na2CO3) and soot would be collected. In addition, a

Soxhlet extraction with DCM to the material captured in the filter was done to confirm

that no tar (soluble in DCM) was captured or condensed in the thimble filter.

The results obtained are shown in Table 27. They suggest that more than 26% of the

collected material in the filter is inorganic material, which could be fine particles of

Na2CO3 that were elutriated or it also can be filter material (SiO2). Thus, it is

recommended to analyze the collected matter for sodium to clarify this hypothesis.

Finally, after subtracting the inorganic (assumed to be quartz) portion from the

collected material, a high concentration of carbon (95%) was observed. See Table 28,

suggesting that some unreacted carbon might be elutriated from the reactor. Also, the low

hydrogen concentration suggests the presence of soot or nondissolvable tar (in DCM).

Not much can be said about oxygen, since the composition of the inorganic matter was

not determined.

117

Table 27. Elemental composition of the solids collected in the thimble filter from run 6. Results from Huffman laboratories, Inc.

Element Concentration (% wt.)

Hydrogen (H) 1.36 Oxygen (O) 31.09 Carbon (C) 41.07 Other 26.48

Table 28. Elemental composition of the solids collected in the thimble filter from run 6, after subtraction of nonanalyzed material.

Element Concentration (% wt.)

Carbon (C) 94.73 Hydrogen (H) 3.13 Oxygen (O) 2.13

118

CHAPTER 5

CONCLUSIONS

5.1 Tar concentration and composition at different gasification conditions

This research project described qualitatively and quantitatively the tar resulting from

the gasification of black liquor in a fluidized bed steam reformer. Tar samples were

collected, using a variety of operation conditions, and compared. Tar samples were

satisfactorily collected in the impinger train arrangement. On the other hand, the results

suggested that the ability of the Petersen column to collect tar samples was limited and

did not facilitate the sampling process. The reformer temperature, the liquor feed rate, the

fluidizing steam temperature and the addition of air through the grid and through the

black liquor injector seemed to have an effect on tar production. On the other hand,

changing the superficial gas velocity did not seem to affect tar concentration over the

range of velocities considered.

Even though the quantitative results presented here are estimations, it is believed that

all the samples had similar deviations to the actual value. Therefore, the presented results

are considered valuable, although, approximately half of the weight obtained for each

sample was DCM. Tar concentrations varied from 36.2 g/m3 to 140.2 g/m3of dry gas. At

standard conditions, the average tar content was approximately 73.8 g/m3 of dry gas and

20.3 g/m3 for the wet gas.

119

Tar production was mainly affected by the gasification temperature. Tar

concentration decreased by a factor of 3.5 on a dry basis and by almost 2 on a wet basis,

when the gasification temperature increased from 565 °C to 643 °C. In the same way, the

fraction of organics ending up as tar decreased by approximately 43%. In addition,

increasing the bed temperature seemed to enhance the hydrogen production by more than

30%. Finally, the volatility of the tar mixtures apparently decreased by increasing the bed

temperature, suggesting that the components are less complex and that even at the highest

temperature tested repolymerization reactions did not increase the molecular complexity

of the tar mixtures.

Black liquor solids feed rate also influenced significantly tar production in both, dry

and wet basis, decreasing tar production by about 40% when decreasing the solids feed

rate from 9.65 kg/h to 3.22 kg/h. Also, the results suggested that by increasing the black

liquor flow rate, the molecular complexity of the components in the tar sample is also

increased, leading to high evaporation temperatures.

The location at which air was injected appeared not to have much effect on tar

production. On the other hand, tar concentration in wet and dry basis and the fraction of

organic carbon in the feed ending up as tar decreased by about 20% when about 18% in

volume of preheated air was injected. However, the hydrogen concentration of the

cleaned gas also dropped by about 20% because of the air injection.

Finally, the temperature at which the steam was injected seemed to have a small

effect on tar concentration. When the fluidizing steam temperature increased from 479 °C

to 604 °C tar concentration decreased by about 18% in dry basis, giving a decrease in the

organic carbon ending up as tar increased of approximately 5%.

120

The chemical composition of the tar samples seemed to be very similar for all the

experimental conditions tested. A tar sample, taken at standard condition, showed the

presence of phenolics and both substituted and unsubstituted multiring structures with

high concentrations of 1 ring aromatics and phenolic compounds (about 32 and 24 %

respectively). It seemed that not very heavy and complicated molecules were formed in

either test. Only about 18% of the detectable molecules present in the standard tar sample

were substituted and unsubstituted two-ring aromatic and less than 3% were heavier

molecules of three to five rings.

The volatilities of all the tar samples seemed to be very similar. The average

temperature to lose over 85% of the total mass was between 225 °C and 660 °C, while,

over 60% of the mass was lost within the temperature window of 135-285 °C. That

indicates that most of the tar would condense in the cooler downstream lines unless the

gas is properly treated. This problem could be further aggravated if consider the high

concentration of DCM in the analyzed tar samples; thus, the just mentioned temperatures

could be shifted even to higher values.

Based on these experimental results, it is concluded that tar produced in a fluidized

bed black liquor steam reformer is a very complex and broad mixture of hydrocarbons

that can affect the overall gasification efficiency and deteriorate the quality of the gas.

Tar concentration in the product gas as well as some of its chemical and physical

properties seemed to be most affected by the gasification temperature, followed by the

black liquor flow rate. Thus, depending on the final use of the product gas, these

parameters could offer a solution to one of the main drawbacks of low temperature

gasification.

121

5.2 Recommendations for future work

Black liquor gasification in a fluidized bed steam reformer is a promising technology

that can bring many advantages for the pulp and paper industry. Thus, it is recommended

to continue the experimental work on tar related problem, from its formation and

composition to its removal. Sampling campaigns to collect tar samples should increase

and corroborate the work presented in this thesis.

Even though the impinger train seemed to collect tar samples in a very accurate and

reproducible way, it is recommended to modify the tar isolation method to ensure that

either all the DCM present in the concentrated tar samples is removed without affecting

light tar concentration, or the DCM content just after the sample has been concentrated is

reliably determined. Furthermore, light organic components (e.g., benzene) should be

also targeted since these components were possibly overlapped by the solvent during the

GC-FID and the GC-MS analyses when using the method described in this thesis.

For future tests, it is recommended that the bed be allowed to stabilize and reach the

organic carbon production rate expected before tar sampling starts. In addition, the

organic carbon in the dumped solids should be estimated to facilitate the overall carbon

balance. Also, it is recommended to gather more tar samples in a wider window of

superficial gas velocities to reevaluate the effect of this parameter on tar production.

In addition, it is important to gather more information about the cleaned product gas.

That can be facilitated by the on-line micro-GC that the University of Utah steam

reformer will have available for analysis in the future.

Finally, there is no information about the composition of the inorganic material

collected in the filter thimble. This information can be valuable in the future when

122

installing a cleaning system for the product gas. Thus, it is recommended to analyze the

collected matter for sodium content to determine whether fine bed particles are being

elutriated or the collected inorganic material is just filter particles.

123

APPENDIX A

DATA BASE OF TAR COMPOUNDS

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

66.10 C5H6 Cyclopentadiene 542-92-7 -88 41

67.09 C4H5N 1H-Pyrrole 109-97-7 -23 131

68.07 C4H4O Furane 110-00-9 -86 31

78.11 C6H6 Benzene 71-43-2 5.64 80

79.10 C5H5N Pyridine 110-86-1 -41 115.2

82.14 C6H10 1-Methyl-3-cyclopentene 1759-81-5 -127 75

82.14 C6H10 3-Methylcyclopentene 1120-62-3 66

82.14 C6H10 1-Methylcyclopentene 693-89-0 -126 76

84.14 C4H4S Thiophene 110-02-1 62 84

92.14 C7H8 Toluene 108-88-3 -94.4 110.6

93.13 C6H7N 2 Picoline 109-06-8 -67 129

93.13 C6H7N 3 Picoline 108-99-6 -18 144

93.13 C6H7N 4 Picoline 108-89-4 3 145

94.11 C6H6O Phenol 108-95-2 41 181.8

96.13 C5H8N2 2-ethyl-1H-imidazole 1072-62-4 268

96.13 C6H8O 2-Cyclopenten-1-one, 2-methyl- 1120-73-6 159.7

98.14 C6H10O 2-Methyl-Cyclopentanone 1120-72-5 -75 140

98.14 C6H10O 3-Methyl-Cyclopentanone 1757-42-2 -58 145

102.13 C8H6 Ethynylbenzene 536-74-3 -44.65 143

104.2 C8H8 1,3,5,7-Cyclooctatetraene 629-20-9 -8 142

104.15 C8H8 Styrene 100-42-5 -32 145

124

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

104.15 C8H8 Bicyclo[4,2,0]octa-1,3,5-triene 694-87-1 50.5 - 51

(0.027 atm)

106.12 C7H6O Benzaldehyde 100-52-7 -14 179.7

106.17 C8H10 O Xylene 95-47-6 -25 144

106.17 C8H10 M Xylene 108-38-3 -48 139.3

106.17 C8H10 P Xylene 106-42-3 13.4 138.3

106.17 C8H10 Ethylbenzene 100-41-4 -94 136.3

107.15 C7H9N Pyridine, 2,6-dimethyl- 108-48-5 -5 144

107.15 C7H9N Pyridine, 3,4-dimethyl- 583-58-4 -13 163

107.15 C7H9N Pyridine, 2,3-dimethyl- 583-61-9 -15 163

107.15 C7H9N Pyridine, 3,5-dimethyl- 591-22-0 -6.2 169.7

107.15 C7H9N Pyridine, 3,5-dimethyl- 589-93-5 -14 158

107.15 C7H9N o-Ethylpyridine 100-71-0 -63 149

107.15 C7H9N m-Ethylpyridine 536-78-7 -76.7 165.2

107.15 C7H9N p-Ethylpyridine 536-75-4 -90.35 168

107.15 C7H9N 2,4-Lutidine 108-47-4 -64 158

108.14 C7H8O p-Cresol 106-44-5 34 201.9

108.14 C7H8O o-Cresol 95-48-7 31 191

108.14 C7H8O m-Cresol 108-39-4 11 202.2

110.11 C6H6O2 Dihydroxybenzene 12385-08-9 172 285

110.11 C6H6O2 1,2-benzenediol 120-80-9 104 245

116.2 C9H8 Methylphenylacetylene 673-32-5 185

116.2 C9H8 1-Ethynyl-4-methyl-Benzene 766-97-2 169

116.16 C9H8 Indene 95-13-6 -2 182

116.16 C9H8 Phenylpropadiene 2327-99-3

117.15 C8H7N Indole 120-72-9 52 254

118.18 C9H10 Methylstyrene 98-83-9 -24 165

118.18 C9H10 Indan 496-11-7 -52 177

125

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

118.2 C9H10 Cyclopropyl-Benzene 873-49-4 171

118.13 C8H6O Benzofuran 271-89-6 -41/-28 174

118.18 C9H10 1-Propenylbenzene 637-50-3 174

120.15 C8H8O 4-Hydroxystyrene 2628-17-3 70

120.15 C8H8O 2-Ethenyl-Phenol 695-84-1 29.4

120.15 C8H8O 2-Phenylethenol 4365-04-2

120.15 C8H8O 1-Phenylethenol 4383-15-7

120.2 C8H8O 1-phenyl-Ethanone 98-86-2 20 202

120.2 C9H12 1-ethyl-3-methyl-Benzene 620-14-4 -97 161

120.2 C9H12 Propylbenzene 103-65-1 -100 159

120.2 C9H12 1,2,4-Trimethyl-Benzene 95-63-6 -46 169.4

120.2 C9H12 1,3,5-Trimethyl-Benzene 108-67-8 -48 164.8

120.2 C9H12 1-Ethyl-4-methyl-Benzene 622-96-8 -63 162

120.2 C9H12 1-ethyl-2-methyl-Benzene 611-14-3 -83 165

120.2 C9H12 1,2,3-trimethyl-Benzene 526-73-8 -26 176

121.18 C8H11N 2,4,6-trimethyl-pyridine 108-75-8 -45 171

122.16 C8H10O Dimethylphenol 576-26-1 47 201

122.16 C8H10O 3-Ethyl-Phenol 620-17-7 -3.9 216

122.16 C8H10O 2,3-Dimethyl-Phenol 526-75-0 74 217

122.16 C8H10O 2,4-Dimethyl-Phenol 105-67-9 25 211

122.16 C8H10O 2-Ethyl-Phenol 90-00-6 7 205

122.16 C8H10O 2,5-Dimethyl-Phenol 95-87-4 74 211

122.16 C8H10O 3,4-Dimethyl-Phenol 95-65-8 64 227

124.14 C7H8O2 3-Methoxy-Phenol 150-19-6 144

124.14 C7H8O2 4-Methoxy-Phenol 150-76-5 53 243

124.14 C7H8O2 3,5 Dihydroxytoluene 504-15-4 105-109 289

128.17 C10H8 Naphthalene 91-20-3 80.2 217.9

126

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

128.17 C10H8 Azulene 275-51-4 30 / 100 242

129.16 C9H7N Isoquinoline 119-65-3 24 243.2

129.16 C9H7N Quinoline 91-22-5 -17 237.1

130.15 C8H6N2 Quinazoline 253-82-7 48 243

130.19 C10H10 3-Methyl-1H-Indene 767-60-2

130.2 C10H10 (1-Methyl-2-cyclopropen-1-

yl)-Benzene 65051-83-4

130.2 C10H10 1-Methyl-1HIndene 767-59-9

130.2 C10H10 1,2-dihydro-Naphthalene 447-53-0 89

131.2 C9H9N 4-methyl-1H-Indole 16096-32-5 267

131.2 C9H9N 2-methyl-1H-Indole 95-20-5 272

132.16 C9H8O 3-Methylbenzofuran 21535-97-7 190.5-198

132.16 C9H8O 2-Methylbenzofuran 4265-25-2 197

132.16 C9H8O 1-Indanone 83-33-0 40 244.2

134.18 C9H10O 2-Propenylphenol 6380-21-8 230

134.19 C8H6S Benzo[b]thiophene 95-15-8 32 221

134.2 C10H14 1-Ethyl-3,5-dimethyl-Benzene 934-74-7 -85 183

136.19 C9H12O 2,3,5-Trimethyl-Phenol 679-82-5 95 234

136.19 C9H12O 4-Ethyl-3-Methyl-Phenol 1123-94-0 26-45 229

136.2 C9H12O 1-ethyl-4-methoxy-Benzene 1515-95-3 195

136.19 C9H12O 3-Ethyl-5-methyl-Phenol 698-71-5 53 234

136.19 C9H12O 2,4,6-Trimethyl-Phenol 527-60-6 71 220

136.19 C9H12O 4-Ethyl-2-Methyl-Phenol 2219-73-0 225

136.19 C9H12O 2-Ethyl-5-Methyl-Phenol 1687-61-2 43 224

136.19 C9H12O 3,4,5-Trimethyl-Phenol 527-54-8 108 250

136.19 C9H12O 2,4,5-Trimethyl-Phenol 496-78-6 71 232

136.19 C9H12O 2,3,6-Trimethyl-Phenol 2416-94-6 81

136.2 C9H12O 2-Ethyl-6-methyl-Phenol 1687-64-5 213

127

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

136.19 C9H12O Propoxybenzene 622-85-5 -28 189-190

136.19 C9H12O 1-Methylethyl-Phenol 25168-06-3

138.16 C8H10O2 Creosole 93-51-6 221

140.18 C11H8 1H-

Cyclopropa[b]naphthalene 286-85-1

142.20 C11H10 2-Methylnaphthalene 91-57-6 34 241.1

142.20 C11H11 1-Methylnaphthalene 90-12-0 -29 242

142.00 C11H12 1,1-Dimethyl-1H-indene 18636-55-0

143.19 C10H9N Quinaldine 91-63-4 -2.7 247

144.00 C11H12 1,2-Dihydro-3-

methylnaphthalene 2717-44-4

146.00 C10H10O Methyl-1-indanone 87259-53-8

146.19 C10H10O 3,5-Dimethylbenzofuran 10410-35-2 224.7

146.19 C10H10O 2,3-Dimethylbenzofuran 3782-00-1 73-102 (0.07 atm)

146.2 C11H14 (3-methyl-2-butenyl)-

Benzene 4489-84-3 100 (0.027atm)

146.2 C11H14 (1-Ethyl-2-Propenyl)-

Benzene 19947-22-9

150.22 C10H14O 2-ethyl-4,5-dimethyl-Phenol 2219-78-5 51.65 250.15

150.22 C10H14O 3-ethyl-2,4-dimethyl-Phenol 62126-74-3 70.65

150.22 C10H14O 4-ethyl-3,5-dimethyl-Phenol 62126-77-6 90.65 259.75

150.22 C10H14O 3-ethyl-4,5-dimethyl-Phenol 62126-75-4 80.15 242.65

150.22 C10H14O 5-ethyl-2,4-dimethyl-Phenol 62115-48-4 39.65 243.15

150.22 C10H14O Dimethylethylphenol 66/42-77-6, etc

152.19 C12H8 Acenaphthalene 208-96-8 92 264.9-280.1

154.2 C8H10O3 2,6-Dimethoxy-Phenol 91-10-1 261.2

154.21 C12H10 Acenaphthene 83-32-9 94 279

154.21 C12H10 2-Vinylnaphthalene 827-54-3 65 135

(0.024 atm)

154.21 C12H10 1-Vinylnaphthalene 826-74-4 124

128

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

136.19 C9H12O Propoxybenzene 622-85-5 -28 189-190

136.19 C9H12O 1-Methylethyl-Phenol 25168-06-3

138.16 C8H10O2 Creosole 93-51-6 221

140.18 C11H8 1H-

Cyclopropa[b]naphthalene 286-85-1

142.20 C11H10 2-Methylnaphthalene 91-57-6 34 241.1

142.20 C11H11 1-Methylnaphthalene 90-12-0 -29 242

142.00 C11H12 1,1-Dimethyl-1H-indene 18636-55-0

143.19 C10H9N Quinaldine 91-63-4 -2.7 247

144.00 C11H12 1,2-Dihydro-3-

methylnaphthalene 2717-44-4

146.00 C10H10O Methyl-1-indanone 87259-53-8

146.19 C10H10O 3,5-Dimethylbenzofuran 10410-35-2 224.7

146.19 C10H10O 2,3-Dimethylbenzofuran 3782-00-1 73-102 (0.07 atm)

146.2 C11H14 (3-methyl-2-butenyl)-

Benzene 4489-84-3 100 (0.027atm)

146.2 C11H14 (1-Ethyl-2-Propenyl)-

Benzene 19947-22-9

150.22 C10H14O 2-ethyl-4,5-dimethyl-Phenol 2219-78-5 51.65 250.15

150.22 C10H14O 3-ethyl-2,4-dimethyl-Phenol 62126-74-3 70.65

150.22 C10H14O 4-ethyl-3,5-dimethyl-Phenol 62126-77-6 90.65 259.75

150.22 C10H14O 3-ethyl-4,5-dimethyl-Phenol 62126-75-4 80.15 242.65

150.22 C10H14O 5-ethyl-2,4-dimethyl-Phenol 62115-48-4 39.65 243.15

150.22 C10H14O Dimethylethylphenol 66/42-77-6, etc

152.19 C12H8 Acenaphthalene 208-96-8 92 264.9-280.1

154.2 C8H10O3 2,6-Dimethoxy-Phenol 91-10-1 261.2

154.21 C12H10 Acenaphthene 83-32-9 94 279

154.21 C12H10 2-Vinylnaphthalene 827-54-3 65 135

(0.024 atm)

154.21 C12H10 1-Vinylnaphthalene 826-74-4 124

129

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

154.21 C12H10 Biphenyl 92-52-4 70 254

156.2 C12H12 2,7-dimethyl-Naphthalene 582-16-1 97 263

156.22 C12H12 1,6 Dimethylnaphthalene 575-43-9 263

156.22 C12H12 1,2 Dimethylnaphthalene 573-98-8 -3 266

156.22 C12H12 1,3 Dimethylnaphthalene 575-41-7 265

156.22 C12H12 1,4 Dimethylnaphthalene 571-58-4 6 265

156.22 C12H12 1,5 Dimethylnaphthalene 571-61-9 81 265

156.22 C12H12 2,3 Dimethylnaphthalene 581-40-8 105 269

156.2 C12H12 1-Ethyl-Naphthalene 1127-76-0 -14 267

156.2 C12H12 1,8-Dimethyl-Naphthalene 569-41-5 62 140 (0.024atm)

156.2 C12H12 1,7-Dimethyl-Naphthalene 575-37-1 263

156.22 C12H12 2,6 Dimethylnaphthalene 581-42-0 110 263

156.22 C12H12 2-Ethylnaphthalene 939-27-5 35 252

160.3 C12H16 6-ethyl-1,2,3,4-tetrahydro-

Naphthalene 22531-20-0

160.3 C12H16 1,4-Dimethyl-1,2,3,4-tetrahydronaphthalene 4175-54-6

166.22 C13H10 Fluorene 86-73-7 115 295

166.22 C13H10 1H-Phenalene 203-80-5

168.00 C13H12 Methylbiphenyl 28652-72-4 168.24-261

168.19 C12H8O Dibenzofuran 132-64-9 82 287

168.22 C12H8O Naphtho[2,1-b]furan 232-95-1

168.2 C13H12 1-[2-propenyl]-Naphthalene 2489-86-3 266

168.23 C13H12 4-Methyl-1,1'-Biphenyl 644-08-6 48 268

168.2 C13H12 2-Methyl-1,1'Biphenyl 643-58-3 -1 259

168.2 C13H12 3-Methyl-1,1'-Biphenyl 643-93-6 4 271

168.23 C13H12 Diphenylmethane 101-81-5 26 264.5

170.3 C13H14 2-(1-methyl-ethyl)-

Naphthalene 2027-17-0 11 267

130

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

170.3 C13H14 1,6,7-trimethyl-Naphthalene 2245-38-7 25.65 285 (1.02 atm)

170.3 C13H14 1,4,6-Trimethylnaphthalene 2131-42-2

170.25 C13H14 1-Propyl-Naphthalene 2765-18-6 -8.45 273

170.25 C13H14 2-Propyl-Naphthalene 2027-19-2 -3.4 275

170.25 C13H14 1,4,5-Trimethyl-Naphthalene 2131-41-1 64

170.3 C13H14 2,3,6-Trimethyl-Naphthalene 829-26-5 97 263

178.23 C14H10 Anthracene 120-12-7 217 339.9

178.23 C14H10 Phenanthrene 85-01-8 99 340

179.22 C13H9N Benzoquinoline 85-02-9 94 338-350

180.3 C14H12 3-methylfluorene 2523-39-9

180.3 C14H12 4-methyl-9H-Fluorene 1556-99-6

180.3 C14H12 4-ethenyl-1,1'-Biphenyl 2350-89-2 119

180.25 C14H12 1-Methylfluorene 1730-37-6

180.25 C14H12 2-Methylfluorene 1430-97-3 318.2

180.25 C14H12 9-Methylfluorene 2523-37-7 46.2 154-156 (0.02 atm)

180.25 C14H12 Methylfluorene 26914-17-0 154-156 (0.02 atm)

182.22 C13H10O Phenylbenzaldehyde (4-phenyl carboxaldehyde) 3218-36-8 320

182.2 C13H10O 4-methyl-Dibenzofuran 7320-53-8

182.26 C14H14 4,4'-Dimethylbiphenyl 613-33-2 121 295.2

182.26 C14H14 2,2'-Dimethylbiphenyl 605-39-0 47 258

182.26 C14H14 3,3'-Dimethylbiphenyl 612-75-9 5 287

182.26 C14H14 3,4'-Dimethyl-1,1'-Biphenyl 7383-90-6 10 296

182.26 C14H14 2,4'-Dimethyl-1,1'-Biphenyl 611-61-0 274.7

182.26 C14H14 2,3'-Dimethyl-1,1'Biphenyl 611-43-8 273

182.26 C14H14 2,6-Dimethyl-1,1'Biphenyl 3976-34-9 -5 263

182.26 C14H14 2,4-Dimethyl-1,1'-Biphenyl 4433-10-7 265

131

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

182.26 C14H14 3,5-Dimethylbiphenyl 17057-88-4 22.7 279

182.26 C14H14 3,4-Dimethylbiphenyl 4433-11-8 29.6 282

190.24 C15H10 Methylenephenanthrene 203-64-5 116 353

192.26 C15H12 4-Methyl-Phenanthrene 832-64-4

192.26 C15H12 2-Methyl-Phenanthrene 2531-84-2 57

192.26 C15H12 1-Methyl-Phenanthrene 832-69-9

192.26 C15H12 3-Methyl-Phenanthrene 832-71-3

192.26 C15H12 9-Methyl-Phenanthrene 883-20-5 350

192.26 C15H12 1-Methyl-Anthracene 610-48-0 363

192.3 C15H12 2-Methyl-Anthracene 613-12-7

194.2 C14H10O Anthrone 90-44-8 155

194.2 C14H10O 9-Phenanthrenol 484-17-3

194.3 C15H14 9H-Fluorene, 2,3-Dimethyl- 4612-63-9

194.3 C15H14 Fluorene, 2-ethyl- 1207-20-1

202.25 C16H10 Pyrene 129-00-0 151 404

202.25 C16H10 Fluoranthene 206-44-0 112 384

202.00 C16H10 Benzacenaphthalene 76774-50-0

202.25 C16H10 Acephenanthrylene 201-06-9

204.27 C16H12 2-Phenyl-Napthalene 612-94-2 102.2 345.7

204.27 C16H12 1-Phenyl-Napthalene 605-02-7 324.7

206.28 C16H14 2,3-Dimethyl-Phenanthrene 3674-65-5

206.28 C16H14 2,7-Dimethyl-Phenanthrene 1576-69-8

206.3 C16H14 3,6-dimethyl-Phenanthrene 1576-67-6 362

206.3 C16H14 2,5-Dimethyl-Phenanthrene 3674-66-6 204

216.28 C17H12 1-Methylpyrene 2381-21-7 74.65

216.28 C17H12 4-Methyl-Pyrene 3353-12-6 143 410

216.3 C17H12 2-methyl-Pyrene 3442-78-2

132

M.W. Formula Name CAS register number

Melting point (ºC)

Boiling point (ºC)

216.28 C17H12 1,2-Benzofluorene 238-84-6 189 412

216.28 C17H12 2,3-Benzofluorene 243-17-4 209 401.2

216.28 C17H12 Benzo [a,b,c] fluorene 30777-18-5 398-410

226.27 C18H10 Benzo [g,h,i] flouranthene 203-12-3 151.4 422

228.29 C18H12 Benzo [c] phenanthrene 195-19-7 61 430

228.29 C18H12 Chrysene 218-01-9 256 448.2

228.29 C18H12 Triphenylene 217-59-4 200 438

228.29 C18H12 Benzoanthracene 56-55-3 159 437

228.29 C18H12 Naphthacene 92-24-0 340.15 440

230.00 C18H14 2H-Benzo [d] phenathrene 68238-65-3

240.00 C19H12 Methylbenzo [ghi]

fluoranthene 51001-44-6

252.31 C20H12 Benzo [b] fluoranthene 205-99-2 163-165 480

252.31 C20H12 Benzo [a] pyrene 50-32-8 177 495

252.31 C20H12 Benzo [k] fluoranthene 207-08-9 217 480

252.31 C20H12 Perylene 198-55-0 270 497

253.31 C20H13 Benzo [j] fluoranthene 205-82-3

253.3 C20H12 Benzo[e]pyrene 192-97-2 179 310-312

276.33 C22H12 Anthanthrene 191-26-4 257.9 547

276.33 C22H12 Benzo [ghi] perylene 191-24-2 280 542

276.33 C22H12 Indeno [1,2,3-cd] pyrene 193-39-5 262 536

278.35 C22H14 Dibenzo [a,h] anthracene 53-70-3 267 524.2

278.35 C22H14 Benzo [b] triphenylene 215-58-7 205 518

278.35 C22H14 Dibenz [a,j] anthracene 224-41-9

300.35 C24H12 Coronene 191-07-1 437.5 525.2

133

0500

100015002000250030003500400045005000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

APPENDIX B

RAW CHROMATOGRAMS OF TAR SAMPLES TAKEN AT DIFFERENT

OPERATING CONDITIONS

Figure 50. Raw chromatogram of tar sample obtained when air was injected through the

bed grid (run 2).

134

0500

100015002000

25003000

35004000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 51. Raw chromatogram of tar sample taken when air was injected through the

black liquor injector (run 3).

135

0500

10001500200025003000350040004500

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 52. Raw chromatogram of a tar sample collected by using the Petersen column at standard conditions (run 4).

136

0500

100015002000250030003500400045005000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 53. Raw chromatogram of a tar sample taken during gasification at a black liquor

flow rate of 18.82 kg/h (run 5).

137

0500

10001500200025003000350040004500

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 54. Raw chromatogram of a tar sample taken during gasification at a black liquor

flow rate of 11.77 kg/h (run 6).

138

0500

100015002000250030003500400045005000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 55. Raw chromatogram of a tar sample taken during gasification at a black liquor flow rate of 9.05 kg/h (run 7).

139

0500

100015002000250030003500400045005000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 56. Raw chromatogram of a tar sample taken during gasification at a bed

temperature of 643 °C (run 8).

140

0

500

1000

1500

2000

2500

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 57. Raw chromatogram of a tar sample taken during gasification at a bed

temperature of 604 °C (run 9).

141

0500

10001500200025003000350040004500

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 58. Raw chromatogram of a tar sample taken during gasification at a bed

temperature of 564 °C (run 10).

142

0100020003000400050006000700080009000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 59. Raw chromatogram of a tar sample taken during gasification at a black liquor flow rate of 2.63 kg/h (run 11).

143

0100020003000400050006000700080009000

0 10 20 30 40 50 60 70 80 90

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 60. Raw chromatogram of a tar sample taken during gasification at a fluidizing

velocity of 57 cm/s (run 13).

144

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70

Time (min)

GC

-FID

det

ecto

r sig

nal

Figure 61. Raw chromatogram of a tar sample taken during gasification with steam at a

temperature of 479 °C (run 15).

145

APPENDIX C

MAJOR AND MINOR COMPOUNDS FOUND IN STANDARD SAMPLE FROM

RUN 1

Retention Time Name of component

Relative concentration

(mg/l of dry gas) Quality

6.02 2-methyl-Cyclopentanone 1.760 72 6.281 3-methyl-Cyclopentanone 1.094 91 6.539 ethyl-Benzene 1.852 86 6.856 1,2-dimethyl-Benzene 4.803 91 7.601 Bicyclo[4.2.0]octa-1,3,5-triene 4.002 89 8.167 2-methyl-2-Cyclopenten-1-one 2.982 96 9.666 methyl-Cyclopentene 0.747 74 9.89 propyl-Benzene 0.487 80

10.193 1-ethyl-2-methyl-Benzene 1.594 95 10.297 1-ethyl-3-methyl-Benzene 0.847 64 10.523 3-ethyl-2-Cyclopenten-1-one 1.769 76 10.842 1-ethyl-4-methyl-Benzene 1.009 91 11.473 Phenol 2.507 81 11.549 ethenylmethyl-Benzene 4.408 58

11.856 Tetramethylmethylene-Cyclopropane 2.235 86

13.02 1-propemyl-Benzene 0.901 50 13.353 4-methyl-Cyclopentene 1.679 60 13.424 1-propynyl-Benzene 4.959 93 14.249 2-methyl-Phenol 5.309 76

14.489 2,3,4-trimethyl-Cyclooent-2-ene-1-one 1.460 91

15.068 3-ethyl-1-methenyl-Benzene 0.578 50 15.206 3-meyhyl-Phenol 2.971 94 15.373 4-meyhyl-Phenol 5.285 83

146

Retention Time Name of component

Relative concentration

(mg/l of dry gas) Quality

15.642 2,3,4-trimethyl-2-Cyclopenten-1-one 1.969 60

15.964 2,4,4-trimethyl-2-Cyclopenten-1-one 1.681 52

16.168 2,6-dimethyl-Phenol 1.448 94 16.298 Bicyclo[3.2.1]oct-6-en-3-one 0.800 50 17.088 2-methyl-4-Octyne 1.953 49 17.546 1-methyl-1H-Indene 2.372 89 17.641 3-methyl-1H-Indene 1.681 93

17.774 (1-methyl-2-cyclopropen-1-yl)-Benzene 0.917 89

17.89 2,5-dimethyl-Phenol 3.569 87 17.959 2,6-dimethyl-Phenol 3.453 83 18.786 2,3-dimethyl-Phenol 4.251 90

18.959 Azulene overlaped with 2,6-dimethyl-phenol 4.395

19.139 2-ethyl-6-methyl-Phenol 1.045 72 19.709 3,4-dimethyl-Phenol 1.527 90 19.909 2,3,5-trimethyl-Phenol 1.634 87 20.912 2,3,6-trimethyl-Phenol 1.321 95 21.086 2-ethyl-6-methyl-Phenol 0.545 70 21.245 2-ethyl-5-methyl-Phenol 1.199 91 21.444 3-ethyl-5-methyl-Phenol 0.661 87 21.758 1,1-dimethyl-1H-Indene 1.531 91 22.007 1,2-dihydro-3-methyl-Naphthalene 1.350 90 22.088 1,2-dihydro-2-methyl-Naphthalene 2.231 72 22.314 2,4,5-trimethyl-Phenol 1.459 81 22.465 136 amu 2.646 91 22.724 2,3-dihydro-1H-Inden 1.989 94 22.922 1,2-dihydro-6-methyl-Naphthalene 0.682 70 23.107 1-methyl-Naphthalene 1.738 91 23.289 1H-Indole 0.717 72 23.424 CM 1.184 23.628 2-methyl-Naphthalene 2.442 90 24.01 ethyl(1-methylethenyl)-Benzene 0.888 83 24.139 2,4,6-trimethyl-Phenol 0.695 68

147

Retention Time Name of component

Relative concentration

(mg/l of dry gas) Quality

24.214 CM 0.745

24.886 1,2,3,4-tetrahydro-1,4-dimethyl-Naphthalene 0.632 76

25.109 1-pentenyl-Benzene 0.977 53 25.396 158 amu 0.677 25.591 158 amu 0.578 25.821 1,4-bis(1-methylethenyl)-Benzene 1.079 87 26.51 1-ethyl-Naphthalene 1.388 76 26.648 146 amu 0.912 26.777 1,8-dimethyl-Naphthalene 0.549 76 26.942 1,6-dimethyl-Naphthalene(1,3,5,7) 0.561 81 27.002 2,6-dimethyl-Naphthalene 0.484 91 27.216 146 amu 0.713 27.366 1,4-dimethyl-Naphthalene 0.791 93 27.509 1,5-dimethyl-Naphthalene 1.312 95 27.833 160 amu 1.224 28.132 3-(4-methylphenyl)-2-Propyn-1-ol 2.215 91 28.362 Acenaphthylene 0.798 72 28.5 2,3-dimethyl-Naphthalene 1.446 87

29.052 CM 2.193 29.204 160 amu 0.753 30.188 (1-methylethyl)-Naphthalene 0.596 58 30.418 170 amu 0.756 30.844 170 amu 1.027 31.341 ovelaped 145 and 160 amu 1.027 31.444 1,6,7-trimethyl-Naphthalene 0.662 72 31.629 2,3,6-trimethyl-Naphthalene 0.592 80

31.843 1-(2-butenyl)-2,3-dimethyl-Benzene 1.776 81

32.06 1H-Phenalene 0.691 64 32.435 166 amu 1.164 32.646 9H-Fluorene 1.442 90 33.99 3-methyl-1-Naphthalenol 0.794 86 36.989 5,7-dimethyl-1-Naphthol 0.583 86 37.136 172 amu 0.706

148

Retention Time Name of component

Relative concentration

(mg/l of dry gas) Quality

37.404 overlaped 172 and 180 amu 0.834 38.432 Phenanthrene 0.875 70 45.013 overlaped 190 and 196 amu 0.892 47.016 Fluoranthene 0.392 89 52.435 1,3-dimethyl-Pyrene Not determined 76 52.844 5,6-Dihydrochrysene Not determined 76 65.169 CM 0.542 65.985 Benzo[e]pyrene 0.489 81 62.733 Benz[e]acephenanthrylene Not determined 81

149

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