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Overview of thermal pre-treatment processesfor large-scale biomass application
Jaap Kiel
Workshop IEA Bioenergy ExCo 66, York UK, 12 October 2010
2 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Presentation overview
• Thermal pre-treatment / upgrading options
• Pyrolysis (bio-oil)
• Torrefaction (biocoal)
• Gasification (bioSNG)
• Conclusions
3 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Biomass – a difficult energy source ….
• … in view of:
− Logistics (handling, transport and feeding)
− End-use (combustion, gasification, chemical processing)
• Difficult properties are:
− Low energy density (LHVar = 10-17 MJ/kg)
− Hydrophilic
− Vulnerable to biodegradation
− Tenacious and fibrous (grinding difficult)
− Poor “flowability”
− Heterogeneous
4 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Biomass pre-treatment into bioenergy carriers
• Convert biomass into high-energy density biomass fuels (bioenergy carriers) with favourable logistic and end-use properties
• Deal with the difficult biomass properties at the source
• Allow de-coupling availability and end-use in scale, time and place
• Relate to existing logistic infrastructures (coal, oil, gas)
• Allow conventional trading schemes –commodity fuels
Bioenergy carriers play a key role in the bioenergy value chain approach of the EU SET-
plan instruments EERA and EIBI
0
5
10
15
20
25
0 20 40 60
Moisture content (%wb)
En
erg
y d
ensi
ty (
GJ/
m3 )
Biomass
Coal
Lignite
BO2 = ECN torrefied pellets
5 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Biomass pre-treatment options (1)• Dry biomass (< 50% moisture)
− Densification (pellets/briquettes)
− Torrefaction + densification (biocoal pellets/briquettes)
− Carbonisation (charcoal)
− Pyrolysis (bio-oil)
− Gasification (bioSNG) Typical product distribution for wood (dry wood basis). Source: www.pyne.co.uk
6 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Biomass pre-treatment options (2)
• Wet biomass (> 50% moisture)
− Digestion
− Hydrothermal processing
− TORWASH (biocoal)
− Hydrothermal Carbonisation (charcoal-like product)
− HydroThermal Upgrading – HTU (bio-oil)
− Hydrothermal Gasification (bioSNG)
7 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Bioenergy carriers – increasingly popular ….
• Scenarios for European pellets consumption
0,0
20,0
40,0
60,0
80,0
100,0
120,0
140,0
1980
1983
1986
1989
1992
1995
1998
2001
2004
2007
2010
2013
2016
2019
Mill
ion
ton
s 18% growth p.a.
25% growth after 2010
Other projections (2020):• Essent 142 mio tpa• Rotterdam Port 130 mio tpa• AEBIOM 150 mio tpa 2008p
9,2 mio tons
Source: ProPellets analysis 2008 + presentations by Essent, Rotterdam Port & AEBIOM
8 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Bioenergy carriers – … but what is the preferred option?
• Often no direct competition, different bioenergy carriers may serve different markets
• If direct competition, then supply chain studies show that overall supply chain efficiency is an important cost factor (given high biomass feedstock price)
• Most technologies still in development stage – substantial uncertainties
9 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Pyrolysis
• Emphasis on fast pyrolysis – maximum liquids production (bio-oil)
• Options:
• Renewable fuel for boilers, engines and gasifiers
• Feedstock for the secondary conversion into transport fuels or chemicals
• Upgrading of lignin fractions in biorefineryconcepts
10 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Fast pyrolysis – different reactor concepts considered
Source:D. Meier, 2004
11 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Pyrolysis – development in demonstration stage
Source: IEA Task 34 brochure, 2007
BTG 50 t/d rotating cone fast pyrolysis plant, Malaysia
PyTec50 t/d ablative
pyrolysis plant, Germany
Dynamotive100 t/d fluid bed
fast pyrolysisplant, Canada
12 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Typical properties and characteristics of wood derived crude bio-oil
Physical property Typical value Moisture content 20-30%pH 2.5Specific gravity 1.20Elemental analysis C 55-58%
H 5.5-7.0%O 35-40%N 0-0.2%Ash 0-0.2%
HHV as produced 16-19 MJ/kgViscosity (40 oC and 25% water) 40-100 cpSolids (char) 0.1-0.5%Vacuum distillation residue up to 50%
CharacteristicsLiquid fuelReady substitution for conventional fuels in many stationery applicationHeating value of 17 MJ/kg at 25% wt. water, is about 40% that of fuel oil/dieselDoes not mix with hydrocarbon fuelsNot as stable as fossil fuelsQuality needs definition for each application
Crude bio-oil – as bioenergy carrier still some drawbacks
Source: www.pyne.co.uk
13 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Bio-oil upgrading
• Co-refining in standard refineries (“drop-in fuels”)
• Joint effort in EU FP6-project BioCoup
14 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction for upgrading biomass
Gas
Torrefaction200-300°C
mass energy
Dry biomass
Torrifiedbiomass
1 0.7
0.3
1 0.9
0.1
0.7
0.9= 1.31Energy densification (MJ/kg)
Process parameters
− Temperature: 200-300°C
− Residence time: 10-30 minutes
− Particle size: < 4 cm
− Absence of oxygen
− Pressure: near atmospheric
15 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Friable and less fibrous 19 - 22 MJ/kg (LHV, ar)
HydrophobicPreserved
Homogeneous
Torrefaction and pulverisation
Fuel powder
Why torrefaction: from biomass/waste to commodity fuel
Superior fuel properties:− Transport, handling, storage− Milling, feeding− Gasification, combustion− Broad feedstock range− Commodity fuel
Tenacious and fibrous10 - 17 MJ/kg (LHV, ar)
Hydrophilic Vulnerable to biodegradation
Heterogeneous
Agricultural residues
Mixed waste
Woody biomass
Pelletisation
Fuel pelletsBulk density 650-750 kg/m3
Bulk energy density 13-17 GJ/m3
16 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
10
20
30
40
50
60
70
80
90
0.5 1.0 1.5
Average particle size (mm, volume based)
Powe
r con
sum
ptio
n (
)
C(270,21)
C(280,18)
C(290,12)
W(290,24)
W(260,24)
Willow (MC=10 -13%)
Willow (dried)
Cutter wood
AU bituminous coal
Borssele run
demolition wood
D(300,11)
10
20
30
40
50
60
70
80
90
0.5 1.0 1.5
Powe
r con
sum
ptio
n (
kWe/M
Wth
)
C(270,21)
C(280,18)
C(290,12)
W(290,24)
W(260,24)
Willow (MC=10 -13%)
Willow (dried)
Cutter wood
AU bituminous coal
Borssele run
demolition wood
D(300,11)
C(270,21)
C(280,18)
C(290,12)
W(290,24)
W(260,24)
Willow (MC=10 -13%)
Willow (dried)
Cutter wood
AU bituminous coal
Borssele run
demolition wood
D(300,11)
0.0
0
40
80
120
160
200
240
280
320
360
0.2 0.4 0.6 0.8 1.0
Average particle size (mm, volume based)
Mill
capa
city
(kW
th)
Grindability of (torrefied) woody biomass
Torrefaction leads to a dramatic decrease in required milling power and increase in milling capacity
0.00
17 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction of agro residues and mixed wastes
• Agro residues: torrefaction behaviour comparable to woody biomass, determining factor is hemicellulose content
• Good prospects for mixed wastes as well (e.g., RDF, SRF): plastic fractions may become brittle and easily grindable
60
70
80
90
100
220 240 260 280 300 320
Temperature (°C)
Mas
s yi
eld
(wt%
)
PineBagasseWillow
Larch
StrawSpruceRDF
Grass seed hayTrockenstabilatRoad grassBeech
18 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
• Torrefied material from pilot-plant subjected to semi-industrial-scale pelletisation tests at CPM:
− Good quality pellets can be produced without additional binder, despite heterogeneous nature of the biomass
− But case-by-case tuning of the pelletisationconditions (e.g. die type) required
− Good control of torrefaction conditions essential for proper pelletisation performance
ECN pelletisation testing
19 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction pellets in perspective
GoodGoodNormalNormalHandling properties
SlowFastSlowFastBiological degradation
HydrophobicHydrophilicHydrophobicHydrophilicHygroscopic nature
Very goodGoodPellet strength
14.910.14.75.0GJ/m3Energy density (bulk)
750650230475kg/m3Mass density (bulk)
19.915.620.410.5MJ/kgAs received
20.417.720.417.7MJ/kgDry
Calorific value (LHV)
310035wt.%Moisture content
Torrefaction pelletsWood pellets Torrefied Wood Woodunit
Properties (willow, typical values)
1 min 2 min 3 min 4 min 5 min
20 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction ….. how difficult can it be?
21 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Design challenges for torrefaction plants
• Torrefaction process control – condensables, exothermicity, product quality control (in view of subsequent densification and end-use)
• Cost – CAPEX, OPEX, availability
• Energy efficiency (also in view of CO2 footprint) à heat integration àuse energy content torrefaction gas
• Feedstock flexibility
• Environmental impact (avoid waste streams)
• Plant capacity (5-15 tonne/h dry input)
• Energy densification: torrefaction + pelletisation
22 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Features:• Conventional drying and
pelletisation• Compact dedicated moving
bed technology with direct heating (no moving parts)
• Heat integration• High energy efficiency (> 90%)• Cost effective• IP is patent protected
Drying Torrefaction Cooling
Heat exchange
Biomass BO2pellets
Air
Utillity fuel
Flue gas
Combustion
DP
Torrefactiongas
Flue gas
Flue gas
Gasrecycle
Pelletisation
15-20% moisture
Technology example – ECN BO2-technology
23 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction reactor concepts – many considered
• Rotating drum (different heating concepts)
• Moving bed
• Belt reactor
• Torbed reactor
• Multiple hearth furnace
• Screw reactor (Auger reactor)
• ……
24 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction reactor concepts – many limitations
• Derived from drying or pyrolysis technology (e.g. other thermo-chemical regimes)
• Difficult/limited process control (e.g., temperature, residence time distribution)
• Limited efficiency
• Limited fuel flexibility / robustness
• Limited scale-up
• Other observations:
− Often limited bench-/pilot-scale testing; directly to demo
− Often limited attention to energy efficiency through heat integration
− Process control / product quality control underestimated
25 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Torrefaction – a Dutch technology?
• Pioneering role ECN (although building on earlier French experience)
• Several Dutch technology developers, several demo-plants under construction / starting up (ECN, Stramproy Green, Foxcoal, Torrcoal, Topell)
• Dutch Torrefaction Association established
26 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
biomass SNG plant
cheap production at large scale
no local biomass transport
efficient and cheap distribution of gas
easy application
existing gas grid
easy to meet emission limits
high social acceptance
natural gas back-up
distributed use for transport, heat,
electricity
biomass
SNG (Substitute Natural Gas)
CO2 available for storage, EOR, ...
gas storage enables whole year operation
Substitute Natural Gas(bioSNG)
27 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Production of bioSNG – different gasification options
operated at elevated pressure ?no tars in product gas ?
operated at slightly elevated pressure ?methane in product gas ?
methane in product gas ?no oxygen plant required ?
no methane in product gas ?complicated feeding ?
tars and organic sulphur in gas ?“limited” char conversion ?
tars and organic sulphur in gas ?atmospheric, compression required ?
• Oxygen-blownentrained-flow:
• Oxygen-blown CFB:
• Indirect/allothermal:
28 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Production of bioSNG – overall conversion efficiency
53%
70%
64%
50%
55%
60%
65%
70%
75%
Entrained Flow CFB Indirect
effic
ienc
y
BioSNG
C. M
. van
der
Mei
jden
et.a
l., B
iom
ass
and
Bio
ener
gy 3
4, p
p 30
2-31
1, 2
010.
29 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Güssing (A)
Oberwart (A)
OLGA (F) OLGA (P)
Two indirect-gasification based bioSNG technologies
• Austria (TUW) / Switzerland (PSI)
− based on the success of “Güssing”
• Netherlands (ECN)
− based on the success of OLGA tar removal
30 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Two different indirect gasification technologies
producer gas
flue gas
combustion air
biomass
pyrolysis/ gasification
combustion
carrier gas (e.g. steam)
producer gas flue gas
biomass
combustion air
steam
pyrolysis/ gasification
combustion
FICFB MILENA
ECNTUW
31 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Production of bioSNG
32 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Production of SNGDakotagas (USA): Lurgi coal gasification
Large scale coal based SNG production:• The gasifier is not suitable for conversion of biomass and/or tars• The gas cleaning and conditioning applied is operating at pressure levels
and sulphur loads being (for the moment) not realistic for biomass based systems
• The Rectisol unit removes to many high-value gas components
33 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
R&D needs bioSNG via indirect gasificationUpscaling gasification and tar removal
(Indirect) biomass gasification has still not yet matured:• Commercial G?ssing gasifier has a capacity of 8 MW th
• Pilot MILENA gasifier has a capacity of 1 MW th
• Goteborg Energi wants 20-100 MW th
• HVC starts with 50 MW th
• E.ON wants 200+ MW th
34 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Demonstrating the critical gas cleaning steps
Cleaning was developed for fossil-fuel based systems:• The critical gas cleaning systems did not have to handle unsaturated
hydrocarbons, tars, organic sulphur, nor were optimised for being able to handle these components
• Demonstration of the critical gas cleaning steps up till now has been limited to lab and pilot scale testing for a limited period of time
R&D needs bioSNG via indirect gasification
35 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Adjusting the methanation catalyst
There is only 1 commercial methanation unit in operation:• The methanation catalyst was optimised for this specific coal based
application and has over the last 25 years hardly been improved• Optimisation of the catalyst, either in order to be able to handle specific
biomass related contaminants in the product gas or in order to produce CH4more efficiently will require realistic long-term testing
R&D needs bioSNG via indirect gasification
36 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
In conclusion• General trend towards conversion of biomass into bioenergy carriers to
facilitate logistics, trading and end-use
• Rapid growth in application of 1st generation bioenergy carriers (e.g. wood pellets, SNG via digestion)
• Many 2nd generation technologies for biomass upgrading into bioenergycarriers under development, most of them linking to existing infrastructures for coal, oil and gas
• Development of 2nd generation technologies in pilot-to-demo phase with torrefaction maybe closest to large-scale market introduction
37 Overview of thermal pre-treatment processes for large-scale biomass application – Jaap Kiel
Thank you for your attention………
For more information, please contact:
Jaap Kiel
phone +31 224 56 4590e-mail [email protected] www.ecn.nl