Optimization of bio-oil yields by Optimization of bio-oil yields by demineralization of low quality demineralization of low quality

biomassbiomass

International Congress and Expo on Biofuels & International Congress and Expo on Biofuels & Bioenergy Bioenergy

August 25-27, 2015 Valencia, SpainAugust 25-27, 2015 Valencia, Spain

Dr. Angelos A. LappasDr. Angelos A. LappasResearch Director CPERI/CERTHResearch Director CPERI/CERTH

570 01 Thermi Thessaloniki, Greece570 01 Thermi Thessaloniki, Greece

Chemical Process & Energy Resources Institute Chemical Process & Energy Resources Institute (CPERI)(CPERI)

Centre for Research and Technology Hellas Centre for Research and Technology Hellas (CERTH)(CERTH)

OUTLINEOUTLINE

Introduction Materials and Methods

o Biomass samples and characterization

o Biomass pretreatment methods

o Pyrolysis tests

Results and Discussiono Characterization of biomass samples

o Preliminary demineralization results

o Demineralization of different biomass types

o Pyrolysis tests results

o Chemical composition of the bio-oil

Conclusions

Fast pyrolysis is an important thermochemical process for the conversion of biomass to a high added value liquid products (fuels & chemicals)

Minerals (ash) in biomass: act catalytically during fast pyrolysis reducing biooil yield

catalyze chemical reactions during storage of biooil affecting biooil quality

deactivate the catalysts in biomass catalytic pyrolysis and/or in downstream biooil catalytic upgrading processes

Use of low cost-high ash feedstocks (agricultural residues and energy grasses) is important for the pyrolysis process economics

A strategy for process optimization is to remove the inorganics prior to pyrolysis

Inorganics can be removed by water washing, acid washing and size reduction

Objectives of this study :

i) to investigate the water and acid washing as biomass pre-treatment techniques for the removal of inorganics from 6

different biomass types

ii) to examine how inorganics removal affects pyrolysis product yields

INTRODUCTIONINTRODUCTION

EXPERIMENTALEXPERIMENTAL

Biomass samples:Biomass samples:

a reference commercial lignocellulosic biomass from beech wood

two forestry residues (oak and pine wood)

two agricultural residues (wheat and barley straw) and

two energy crops (miscanthus and eucalyptus)

Pre-treatment:Pre-treatment:

Particle size: 90-500 μm.

4 g of biomass dissolved in 80 ml water/acid under stirring

Parameters investigated: T (ambient, 50°C), residence time (2, 4, 8 and 24 h), type of acid (acetic vs nitric), acid concentration

Pyrolysis:Pyrolysis:

Pyrolysis experiments were carried out on a bench-scale, fixed-bed reactor

Mass balances and product characterization were carried out for all tests

RESULTS AND DISCUSSIONRESULTS AND DISCUSSION

CHARACTERIZATION OF BIOMASS SAMPLESCHARACTERIZATION OF BIOMASS SAMPLES

Elemental analysis (wt.%, dry basis)Ash content (wt.

%, dry basis)

Moisture content

(wt.%)

Calorific value

(MJ/kg)C H O S

Beech 48.11 6.24 44.95 0.02 0.68 10.18 19.0

Pine 52.60 5.94 40.55 0.05 0.86 5.89 19.5

Oak 50.05 6.13 43.00 0.08 0.74 11.14 18.7

Wheat straw 45.06 5.64 40.10 0.12 9.08 8.19 16.6

Barley straw 44.93 5.58 40.64 0.08 8.77 8.60 17.3

Eucalyptus 51.32 5.80 40.25 0.16 2.47 10.28 19.1

Miscanthus 49.91 5.96 40.96 0.03 3.14 6.42 18.4

Na K Al Mg Fe Ca Cu P Total

Beech 130 452 - 365 120 1620 - - 2687

Pine 36 1049 167 425 287 1732 3 151 3850

Oak 47 1190 27 423 66 1485 3 242 3483

Wheat straw 786 11826 41 575 36 2383 6 314 15967

Barley straw 2039 17562 153 1298 87 4879 5 931 26954

Eucalyptus 242 1007 80 550 158 8734 2 684 11457

Miscanthus 101 2670 230 371 178 2361 4 151 6066

Inorganics by ICP analysis (ppm, dry basis)

• K, Ca, Na and Mg are the most abundant inorganic elements.K, Ca, Na and Mg are the most abundant inorganic elements.

• Comparing a low ash (pine), with a high ash content feedstock (barley), a ten-fold Comparing a low ash (pine), with a high ash content feedstock (barley), a ten-fold increase in alkali concentration may be noted.increase in alkali concentration may be noted.

Ash removal with H2O 25% (20°C), 43% (50°C)

Much higher de-ashing with acids

Water is adequate for removal of water-soluble metal salts but not for the cations

Nitric is better than acetic acid while higher acid concentrations are preferable

Effect of treatment time not very pronounced

Higher temperatures favor when acid concentration is low

PRELIMINARY DEMINERALIZATION RESULTS PRELIMINARY DEMINERALIZATION RESULTS WITH REFERENCE FEEDWITH REFERENCE FEED

Optimum Conditions Acid concentration = 1 wt% Residence time = 2 h (acid), 4 h

(H2O) Washing temperature = 50°C Acids (Nitric, Acetic)

DEMINERALIZATION OF ALL BIOMASS TYPESDEMINERALIZATION OF ALL BIOMASS TYPES

Washing with acids more efficient compared with water (90% vs. 17-43%)

Nitric more effective than acetic acid

Ash removal from forestry residues higher than with the other biomass samples

The agricultural residues exhibited relatively high ash content, even after treatment with nitric acid

Satisfactory ash removal was achieved for eucalyptus (up to 70%) while miscanthus was much harder to treat (up to 40% ash removal)

The loss of biomass depends more on the biomass type, rather on pre-treatment conditions. Agricultural residues demonstrated the highest weight loss

ASH REMOVAL FOR EACH ELEMENT ASH REMOVAL FOR EACH ELEMENT

Alkali metals, K and Na easily removed (>80% with all pre-treatment methods

Removal of Mg, Fe and Al was lower, following the order Mg > Fe > Al

Ca most affected by the treatment method and its removal increased in the order nitric acid > acetic acid > water treatment

Treatment with nitric acid the most efficient for all inorganics and all biomass types

EFFECT OF DE-ASHING (1% HNO3) ON EFFECT OF DE-ASHING (1% HNO3) ON PYROLYSIS PERFORMANCEPYROLYSIS PERFORMANCE

Bio-oil yield increases on all de-ashed samples, The effect being higher ~17% for agricultural residues

For the demineralized samples, gas yield is about 4-8 wt% lower

Most of this reduction was attributed to the reduction of the CO2 yield

Char formation also decreased, especially in the case of wheat straw, barley straw, eucalyptus and miscanthus

Scission of the o-glucosidic bonds

Levoglucosan

Thermal decomposition of cellulose in the absence of inorganics

C.-Y. Yang, X.-S. Lu, W.G. Lin, X.-M. Yang, J.Z. Yao, Chem Res Chinese U 22 (2006) 524–532

Thermal decomposition of cellulose in the presence of inorganics

Δ

Levoglucosan

Cellulose

Metal cations act as catalystsHomolysis of the pyranose rings

Formation of CO2, carbonyls and acids

Cellulose

CATALYTIC MECHANISMS CATALYTIC MECHANISMS

GCxGC-ToFMS ANALYSIS OF BIO-OILGCxGC-ToFMS ANALYSIS OF BIO-OIL

Bio-oil from treated biomasses contains anhydrosugars and more specifically, levoglucosan

In the bio-oil from the untreated biomasses anhydrosugars are very low and furans, ketones and ethers increase.

Phenolics decrease in bio-oils after demineralization

This indicates that inorganics catalyze cracking of the lignin structure and oligomers, resulted in the formation phenolic monomers

Removal of ash from forestry residues, agricultural residues and energy crops was studied in this work:

Washing with water removed up to 42% of the inorganics whereas washing with acidic solutions achieved higher than 90% removal

Higher washing temperatures were more effective for the removal of the inorganics.

Nitric acid proved to be more effective than acetic acid.

K, Na can easily be removed by all pre-treatment methods

Mg, Fe and Al are more refractory

Ca is affected by the pretreatment conditions and mainly is removed by nitric acid solution

Biomass demineralization affects strongly yields and composition of the pyrolysis products

demineralized biomass yielded less gas products and solid residue while the selectivity towards the liquid product was substantially increased

Biooil from de-ashed biomass contains more levoglucosan levels and is less deoxygenated

CONCLUSIONSCONCLUSIONS

The work was conducted with support from the EU under the frame of the FP7 funded “CAScade deoxygenation process using tailored nanoCATalysts for the production of BiofuELs from

lignocellullosic biomass – CASCATBEL” project (Grant agreement No. 604307).