Biomass Torrefaction – A Promising P t t t M th d f Th Ch i l Pretreatment Method for Thermo-Chemical Conversion Technologies Sudhagar Mani, Jim , Jim Kaster Kaster, , & KC Das & KC Das Faculty of Engineering, University of Georgia, Athens, GA Faculty of Engineering, University of Georgia, Athens, GA Email: Email: [email protected][email protected]IEA Bioenergy Conference Biofuels & Bioenergy: A Changing Climate Biofuels & Bioenergy: A Changing Climate Vancouver, BC Canada Aug 23-26, 2009
36
Embed
Biomass Torrefaction – A Promising Pt t M fhdtht ... 2009.pdf · Biomass Torrefaction – A Promising Pt t M fhdtht TPretreatment Method for Thermo-Ch i l Chemical ... Torrefaction
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Biomass Torrefaction – A Promising P t t t M th d f Th Ch i l Pretreatment Method for Thermo-Chemical
Conversion Technologies
Sudhagar Mani, Jim , Jim KasterKaster, , & KC Das& KC DasFaculty of Engineering, University of Georgia, Athens, GAFaculty of Engineering, University of Georgia, Athens, GA
IEA Bioenergy ConferenceBiofuels & Bioenergy: A Changing ClimateBiofuels & Bioenergy: A Changing Climate
Vancouver, BC CanadaAug 23-26, 2009
IntroductionIntroductionIntroductionIntroductionIssues with biomass feedstockIssues with biomass feedstock•• Wide range of moisture content (60Wide range of moisture content (60--15% 15% wbwb))
•• Low bulk density (4 Low bulk density (4 –– 8 lbs/ft8 lbs/ft33))
•• Low energy density (4,500Low energy density (4,500--7,500 Btu/lb)7,500 Btu/lb)
•• Uneven particle sizes (no flow)Uneven particle sizes (no flow)
Difficult to handle store and transportDifficult to handle store and transport•• Difficult to handle, store and transportDifficult to handle, store and transport
•• High transport and storage costHigh transport and storage cost
•• Self heating and emission of off gases during Self heating and emission of off gases during Self heating and emission of off gases during Self heating and emission of off gases during storagestorage
IntroductionIntroductionIssues with thermoIssues with thermo--chemical conversion chemical conversion technologiestechnologies•• Combustion:Combustion:
Difficult to coDifficult to co--fire with coalfire with coal
Low energy densityLow energy density
High energy demand for grinding biomassHigh energy demand for grinding biomass
Low energy density & self heatingLow energy density & self heating
Biomass Biomass PyrolysisPyrolysis to Liquid Fuelsto Liquid Fuels
PyrolysisUnit
Bio-oil
Critical ProblemsCritical Problems•• LongLong--term storage and stability of biomassterm storage and stability of biomass•• High energy input for grinding to defined particle sizeHigh energy input for grinding to defined particle size•• Formation of high molecular weight compoundsFormation of high molecular weight compounds•• BioBio--oil is unstableoil is unstable
Vi it i ith ti d t tVi it i ith ti d t tViscosity increases with time and temperatureViscosity increases with time and temperatureLow pH, corrosive Low pH, corrosive
•• Catalytic upgrading difficultCatalytic upgrading difficulty pg gy pg gHigh oxygen contentHigh oxygen contentCatalytic deactivation due to coke formationCatalytic deactivation due to coke formation
What is Torrefaction? What is Torrefaction? Solid-state thermal hydrolysis of biomass in an inert of biomass in an inert atmosphere (e.g.,Natmosphere (e.g.,N22))T t T t 180 t 300180 t 300ooCCTemperature range Temperature range –– 180 to 300180 to 300ooCCHemicelluloseHemicellulose is hydrolyzed is hydrolyzed via release of acetic acid via release of acetic acid and subsequent hydrolysis reactionand subsequent hydrolysis reactionand subsequent hydrolysis reactionand subsequent hydrolysis reactionMoisture reduction, oxygen content reducedMoisture reduction, oxygen content reducedSome extractives volatilized, but 70Some extractives volatilized, but 70--80% solids 80% solids recoveredrecoveredMost familiar example Most familiar example –– roasting coffeeroasting coffee
Green chip Torrefied chip
Torrefaction HistoryTorrefaction HistoryTorrefaction HistoryTorrefaction History1930’s 1930’s –– heat treatment of wood for high heat treatment of wood for high ggdurability, structural stability & fungal resistance (wood durability, structural stability & fungal resistance (wood roasting), provides aesthetic valueroasting), provides aesthetic value
1939 1939 US Patent (Be gst om et al) on the mal heating of US Patent (Be gst om et al) on the mal heating of 1939 1939 –– US Patent (Bergstrom et al) on thermal heating of US Patent (Bergstrom et al) on thermal heating of wood >220wood >220ooCC
1976 1976 –– Pyrochar process for solid biomass into Pyrochar process for solid biomass into fuelsfuelsy py p
1980’s 1980’s –– heat treatment of wood logs (180heat treatment of wood logs (180--220220ooC), retifaction/torrefaction process C), retifaction/torrefaction process (Yvan 1985 Bourgeois et al 1988) Torrefaction process (Yvan 1985 Bourgeois et al 1988) Torrefaction process (Yvan, 1985, Bourgeois et al, 1988), Torrefaction process (Yvan, 1985, Bourgeois et al, 1988), Torrefaction process development & reactor design (four patents)development & reactor design (four patents)
2000 2000 -- Significant research & development on biomass Significant research & development on biomass torrefaction processtorrefaction process
Mass & Energy BalancegyCondensable:WaterNon-condensable:
Temp: 180-280oCHeating rate: <50oC/minResidence time: > mins
Research Objectives Research Objectives Bi T f ti ki ti Bi T f ti ki ti Biomass Torrefaction kinetics Biomass Torrefaction kinetics •• Does it improve biomass storability and Does it improve biomass storability and
t t bilit ?t t bilit ?transportability?transportability?
•• Does it improve biomass Does it improve biomass grindabilitygrindability and reduce and reduce i t? i t?energy input?energy input?
•• Effect of torrefaction on, Effect of torrefaction on,
bi il t bilitbio-oil stability
Eliminate or reduce coke forming precursors and improve catalytic upgrading of bio-oil to fuelsimprove catalytic upgrading of bio-oil to fuels
Syngas quality and tar concentration during gasificationg
Pellet quality
Combustion behavior
Mass loss with time for a range of torrefaction conditions – TG-MStorrefaction conditions TG MS
90
100
70
80
90
nin
g
200
50
60
70
s re
main
215
230
245
20
30
40
% m
ass
245
260
275
0
10
20% pyr. @ 700
00 2000 4000 6000 8000
time / s
Proposed Torrefaction Kinetics Proposed Torrefaction Kinetics M d lM d lModelModel
pinenepinene, camphene, , camphene, phellandrenephellandrene observed at low observed at low temperatures (220C)temperatures (220C)
•• Acetaldehyde evolution increased with timeAcetaldehyde evolution increased with time•• Acetaldehyde evolution increased with timeAcetaldehyde evolution increased with time•• PinenesPinenes decreased with holding timedecreased with holding time•• As temperature increased, acetic acid, As temperature increased, acetic acid, methylestermethylesterp , ,p , , yy
and furans appeared (220 to 250C and above)and furans appeared (220 to 250C and above)Furan, 2Furan, 2--methylfuran, 250Cmethylfuran, 250C2 32 3 dihydrofuran and 2 5dihydrofuran and 2 5 dimethylfuran 280Cdimethylfuran 280C2,32,3--dihydrofuran and 2,5dihydrofuran and 2,5--dimethylfuran, 280Cdimethylfuran, 280C
Results Results –– NonNon--condensable at 280condensable at 280ooCC
9
Non-Condensables vs. Time; Torrefaction at 280oC
Methane
6
7
8
%)
Carbon dioxide
Methyl acetylene
Propylene
4
5
6
mou
nt (m
ole
%
n-Butane
Ethylene
Ethane
2
3
Am
0
1
0 10 20 30 40 50 60
Time (min)
Results Results –– Condensable at 280Condensable at 280ooCC
35000000
Condensables vs. Time; Torrefaction - 280oC
α-pinene
25000000
30000000
ance
α pinene
camphene
β-pinene
β phellandrene
20000000
25000000
elat
ive
Abu
nda β-phellandrene
10000000
15000000Re
0
50000000
0 10 20 30 40 50 600 10 20 30 40 50 60
Time (min)
Results Results –– Compositional changesCompositional changesF t id C ll l H i ll l Li i H ti lForest residue chips
Cellulose(% wt)
Hemi-cellulose(% wt)
Lignin (% wt)
Heating value(Btu/lb)
Non-torrefied(10% m c )
43.1 18.4 20.9 7,774(10% m.c.)
Torrefied at 220oC 40.7 12.0 25.1 8,474
Torrefied at 250oC 37.3 5.0 31.8 9,376,
Torrefied at 280oC 20.6 2.9 47.3 10,167
F t id C H O N S A h (% t)Forest residue chips
C H O N S Ash (% wt)
Non-torrefied(10% m c )
45.3 5.9 48.5 0.3 0.1 0.6(10% m.c.)
Torrefied at 220oC 49.4 5.5 44.1 0.3 0.0 1.1
Torrefied at 250oC 50.5 5.4 41.8 0.4 0.0 1.2
Torrefied at 280oC 56.4 5.4 36.1 0.9 0.1 1.4
Results Results –– Compositional changesCompositional changesF t id M i t V l til C Fi d C A h (%)Forest residue chips
Moisture (%)
Volatile C(% wt)
Fixed C(% wt)
Ash (%)
Non-torrefied(10% m c )
10 75.3 16.3 0.4(10% m.c.)
Torrefied at 220oC 3.2 76.8 19.1 1.1
Torrefied at 250oC 2.3 74.9 20.6 1.2
Torrefied at 280oC 2.1 70.8 25.6 1.4
Change in bulk density during Change in bulk density during T f tiT f tiTorrefactionTorrefaction
TorrefactionTorrefaction-- Pellet Production CostPellet Production Cost
50
/t Packing cost $40
30
40
cost
, $
/
Land use & building
Personnel cost$27 $24 $30
20
30
uct
ion
c
Miscellaneous equipmentScreening
100.00
6.45et
Pro
du
Pellet cooler
Pellet mill
0 0.00 0
Pelle
Hammer mill
Torrefaction
2424Drying operation
Torrefaction PyrolysisTorrefaction - Pyrolysis
TG/MS Analysis of Torrefied BiomassBiomass
TGA/MS (TGA/MS (MettlerMettler Toledo)Toledo)P f d d P f d d l til ti diti diti NN AAPerformed under Performed under pyrolyticpyrolytic conditions conditions –– NN22 or or ArArcarrier gascarrier gas10mg sample, 50 ml/min, 3010mg sample, 50 ml/min, 30--900900°°C at 10C at 10°°C/minC/minMonitored Off Gas in Selective Ion Mode (SIM)Monitored Off Gas in Selective Ion Mode (SIM)
Higher temperature torrefaction Higher temperature torrefaction
2
46
810
Mas
s (m
g)
0 2
0.4
0.6
0.8
X, m
ass
2
46
810
Mas
s (m
g)
0 2
0.4
0.6
0.8
X, m
ass
g e e pe a u e o e ac og e e pe a u e o e ac o(> 300(> 300°°C) appears to reduce C) appears to reduce biomass thermal decomposition biomass thermal decomposition and alter and alter pyrolysispyrolysis kineticskinetics
More research needed to More research needed to 02
0 500 1000Tem perature, C
0
0.2
02
0 500 1000Tem perature, C
0
0.2More research needed to More research needed to confirm effectconfirm effect
Comparison of combustion of torrefied biomass, untreated biomass and coalbiomass, untreated biomass and coal
1
1.2
0.8
1
ctio
n
t225
t235
0.6
nin
g f
rac t235
t250
t260
t275
0.4
rem
ain t275
t285
t300
0
0.2 raw pine
coal
0
0 1000 2000 3000 4000
Time
ConclusionsConclusionsCondensable compounds are mainly released from extractives in the biomass as α, β-pinene, camphene t Th d b di t d t l etc. These compounds can be redirected to supply
heat energy during torrefaction
D i t f ti h i ll l i l t d During torrefaction, hemi-cellulose is almost removed and results in higher energy density product with a heating value of 10 000 Btu/lb Torrefaction heating value of 10,000 Btu/lb. Torrefaction temperature plays a major role in defining the energy density of biomass and can be optimized for any y p yspecific applications.
Torrefaction followed by pelleting costs about $30/t of y p g $pellets. Torrefaction process alone costs about $6.5/t.
ConclusionsConclusionsBiomass torrefaction process can produce high energy Biomass torrefaction process can produce high energy density and consistent feedstock for thermal conversion density and consistent feedstock for thermal conversion density and consistent feedstock for thermal conversion density and consistent feedstock for thermal conversion technologies (gasification, cotechnologies (gasification, co--firing & firing & pyrolysispyrolysis))
PelletingPelleting of Torrefaction of biomass may be difficult due of Torrefaction of biomass may be difficult due PelletingPelleting of Torrefaction of biomass may be difficult due of Torrefaction of biomass may be difficult due to hydrophobic nature of the material and require to hydrophobic nature of the material and require additional binders to increase the bulk densityadditional binders to increase the bulk densityadditional binders to increase the bulk densityadditional binders to increase the bulk density
Future research at UGA is focused on optimizing the best reactor configuration for a torrefaction process g pand promote its application to co-firing, gasification and pyrolysis processes
AcknowledgementAcknowledgement
Financial support from Financial support from • University of Georgia Research
FoundationFoundation• State of Georgia – Traditional Industries