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Comparative Assessment of Steam Processed pellets produced from wood, straw and switchgrass
S M HASSAN SHAHRUKH, ADETOYESE OYEDUN, AMIT KUMAR1, LINOJ KUMAR, BAHMAN GHIASI, SHAHAB
SOKHANSANJ2
1Department of Mechanical Engineering, University of AlbertaEdmonton, AB, Canada
2Department of Chemical and Biological Engineering, Vancouver, BC, Canada
ADVANCED BIOFUELS SYMPOSIUM July 22 - 24, 2015, Montreal, Canada
Presentation Outline Background and Objective Pellet Production Supply Chain Model Development and Validation Mass and Heat Balance of Steam
Pretreatment Techno-Economic Result Summary of Result
Presentation at BFN, 22-24 July, 2015
Background
Presentation at BFN, 22-24 July, 2015
• Pretreatment helps producing high quality pellets
• Energy density of regular pellets is 1/8th of coal
• High transportation cost of regular biomass and pellets
• Need for higher utilization of Biomass
Low Utilization Cost Issues
Pretreatment
Low Bulk and Energy density of
regular pellets
Objectives
Conduct Techno-Economic Assessment
Cost curves Sensitivity & uncertainty
Conduct Energy Analysis Net energy ratio (NER)
Sensitivity & uncertainty
Develop process model for steam pretreatment of wood, straw and switchgrassHeat and mass
balanceData intensive
modeling
Presentation at BFN, 22-24 July, 2015
Pellet Supply Chain
Biomass collectio
n
Bale formatio
n/ chipping
Transportation to
pellet plant
Pellet producti
on
Transportation of
pellet to biorefinery
Used in biorefinery
Supply chain of pellet to a biorefinery (Conventional method)
Used in biorefinery
Biomass
collection
Transportation to
pellet plant
Pellet Producti
on
Transportation of
pellet to biorefinery
Steam pretreatm
ent
Bale formation/chip
ping
Steam Pretreatm
ent
Supply chain of pellet (produced from pretreated biomass) to a biorefinery
Presentation at BFN, 22-24 July, 2015
Experimental Material and Method
Material
Wood, Straw ,Switchgrass
Moisture content ~ 10%-50%
Method
Pretreatment carried in 2.6L StakeTech
Steam gun with 400g of biomass treated at different temperature
and time
Steam treated biomass pelletized
Presentation at BFN, 22-24 July, 2015
Model Input and Validation
1. Boiler unit: Supply of steam at different time and
temperature2. Time: 10 min
3. Temperature: 180-210⁰C
2. Steam Pretreatment Unit: Biomass
is treated with high pressure steam in batch
reactor (Yield reactor considered)
logR = logනexp(T− 10014.75 )dt Governing Equation:
Source: Lam et al. 2013
Presentation at BFN, 22-24 July, 2015
Model Input and Validation
3. Pellet mill: produces pellet of
20-30 mm long, 6 mm in diameter, has a heating element
operating at 70-100 C.
2. Grinder: Kicks energy constant 100KJ/kg, solid recovery 95%
1. Dryer: operating temperature at
80 C.
Presentation at ASABE, 26-29 July,2015
No grinder is required for pellet production of straw and switchgrass
Model Validation Result
Operation
Experimental Energy Consumption (kJ)
ASPEN model Predicted Energy Consumption (kJ)
Wood Straw SG Wood Straw SG
Steam Pretreatment 2097 749 678 2095 760 710
Drying 6162 6731 8979 6156 6951 9045
Size reduction 15 0 0 17 0 0
Pelletization 492 330 318 500 352 325
Presentation at BFN, 22-24 July,2015
Comparative Heat and Mass Balance
Presentation at BFN, 22-24 July,2015
Wood
A. Regular Pellet
B. Steam Pretreated Pellet
Dryer Hammer
Mill Pellet
Mill
2.4 kg
0.63 kg
0.58 kg
0.54 kg
19.6 MJ
1 kg
2.1 MJ
6.2 MJ
0.01 MJ
0.45 MJ
Dryer Hammer Mill
Pellet Mill
1 kg
0.7 kg
0.65 kg
0.61 kg
18 MJ
1.3 MJ
0.2 MJ
0.5 MJ
Comparative Heat and Mass Balance (Cont’d)
Presentation at BFN, 22-24 July,2015
Dryer Hammer Mill
Pellet Mill
1kg
0.95 kg
0.92kg
0.85 kg
17 MJ
0 MJ
0.3MJ
0.8 MJ
Dryer Hammer Mill
Pellet Mill
1kg
0.95 kg
0.92kg
0.88 kg
17 MJ
0 MJ
0.3MJ
0.8 MJ
Straw Switchgrass
A. Regular Pellet A. Regular Pellet
B. Steam Pretreated Pellet B. Steam Pretreated Pellet
Dryer Hammer
Mill Pellet
Mill
3.0 kg
0.8 kg
0.8kg
0.72 kg
19 MJ
1kg
0.8MJ
6.7 MJ
0 MJ
0.42 MJ
Dryer Hammer
Mill Pellet
Mill
3.4 kg
0.8 kg
0.8kg
0.71 kg
19.1 MJ
1kg
0.7MJ
8.9 MJ
0 MJ
0.4 MJ
Variation of NER with Pretreatment Temperature and Level
Presentation at BFN, 22-24 July,2015
0
0.5
1
1.5
2
2.5
3
140 160 180
NER
Steam Pretreatment Temperature
Straw Switchgrass
-
1.00
2.00
3.00
4.00
5.00
6.00
7.00
25% 50% 75%
NER
Pretreatment level
Wood Straw SG
Uncertainty Analysis
Presentation at BFN, 22-24 July,2015
Straw Switchgrass
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
0.055
Pro
bab
ility
1.1 1.2 1.3 1.4 1.5 1.6 1.7NER
5% 90% 5%
5%(x = 1.21) 95%(x = 1.49)
Wood
Techno-Economic Snapshot
Presentation at BFN 22-24 July,2015
Straw Forest residue SwitchgrassRegular Steam
pretreatedRegular Steam
pretreatedRegular Steam
pretreated
Optimum size
(t year-1)
190,000 250,000 190,000 290,000 190,000 230,000
Pellet cost ($ t-1) 122.04 188.34 116.01 183.14 116.20 192.41
-Capital recovery 9.56 15.31 10.83 20.34 13.74 21.53- Maintenance cost 2.64 3.68 2.34 3.59 2.58 3.76-Field cost 52.34 58.75 28.19 32.08 25.57 29.39-Transportation cost 33.89 42.99 37.04 50.24 45.38 57.68-Premium 0.00 0.00 6.39 5.50 5.34 6.13-Employee cost 7.27 7.85 6.58 6.76 7.27 8.53-Energy cost 5.41 48.91 14.74 53.79 5.41 54.50-Consumable item cost
10.93 10.86 9.90 10.84 10.93 10.88
Pellet transportation 6.30 5.50 6.20 5.45 6.80 6.10Total pellet delivery cost
128.34 193.84 122.21 188.59 123.00 198.51
Variation of Transportation Cost
Presentation at BFN, 22-24 July, 2015
Variation of Capital Cost
Presentation at BFN, 22-24 July, 2015
Variation in Production Cost
Presentation at BFN, 22-24 July,2015
Sensitivity Analysis - Wood
Presentation at BFN, 22-24 July,2015
-20.00% -10.00% 0.00% 10.00% 20.00%
174.00
179.00
184.00
189.00
194.00
199.00
capital cost employee cost
Energy cost Transportation cost
Field cost consumable cost
% change
Pro
duct
ion
Cos
t, $
\ t
-20.00% -10.00% 0.00% 10.00% 20.00%
180.00
182.00
184.00
186.00
188.00
190.00
192.00
194.00
Moisture content Feed stock material loss
Inflation IRR
% area
Pro
du
ctio
n C
os
t, $
\t
Sensitivity Analysis - Straw
Presentation at BFN, 22-24 July,2015
-20.00% -10.00% 0.00% 10.00% 20.00%
180.00
185.00
190.00
195.00
200.00
205.00
capital cost employee costEnergy cost Transportation costField cost consumable cost
% change
Tot
al c
ost o
f pel
let (
$(t)
-1)
-20.00% -10.00% 0.00% 10.00% 20.00%
188.00
190.00
192.00
194.00
196.00
198.00
200.00
Moisture content Feed stock material loss Inflation IRR% area
% change
To
tal c
os
t o
f p
elle
t p
rod
uc
tion
($(t
)-1
)
Sensitivity Analysis - Switchgrass
Presentation at BFN, 22-24 July,2015
-20.00% -10.00% 0.00% 10.00% 20.00%
186.00
191.00
196.00
201.00
206.00
capital cost employee costEnergy cost Transportation costField cost consumable cost
% change
Tot
al c
ost o
f pel
let (
$(t)
-1)
-20.00% -10.00% 0.00% 10.00% 20.00%
193.00
194.00
195.00
196.00
197.00
198.00
199.00
200.00
201.00
202.00
203.00
Moisture content Feed stock material loss
Inflation IRR
% area
% change
To
tal c
os
t o
f p
elle
t p
rod
uc
tion
($(t
)-1
)
Uncertainty Analysis
Presentation at BFN, 22-24 July,2015
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
0.055
Prob
abilit
y
230 235 240 245 250 255 260 265 270 275Pellet Cost ($/tonne)
5% 90% 5%
5%(x = 236.39) 95%(x = 261.8)
Straw
0.00
0.01
0.02
0.03
0.04
0.05
0.06
Prob
abili
ty
230 235 240 245 250 255 260 265 270 275Pellet Cost ($/tonne)
5% 90.005% 4.995%
5%(x = 237.93) 95.005%(x = 258.65)
Switchgrass
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
Pro
babi
lity
220 225 230 235 240 245 250 255Pellet Cost ($/tonne)
4.995% 90.00999% 4.995%
4.995%(x = 228.37) 95.005%(x = 247.11)
Wood
Summary of Result
Energy
• Energy ratio of regular pelletization process is higher than steam pretreated pellet due to addition of steam as energy source
• Calorific value of pellet increases by 21% due to steam pretreatment
• Grinding energy input is zero for straw and switchgrass
Cost
• $/tonne cost of production for steam pretreated pellet is higher than regular pellet due to increased capital cost
• $/GJ cost production of pellet for both steam treated pellet and regular pellet is similar with approximately 30 cents difference
Scaling
• Steam pretreatment is more effective over a plant size of 270,000 tonnes/yr plant capacity due to economy of scale benefits based on $/GJ
Presentation at BFN 22-24 July, 2015
AcknowledgementBio Fuel Net
University of Alberta
Dr. Shahab Sokhansanj, Dr. Linoj Kumar and Bahman Ghiasi, Department of Chemical Engineering, University of British Columbia
Presentation at BFN 22-24 July,2015
THANKS
Contact Information:
Dr. AMIT KUMAR
Professor
NSERC/Cenovus/Alberta Innovates Associate Industrial Research Chair in Energy and
Environmental Systems Engineering
Cenovus Energy Endowed Chair in Environmental Engineering
Department of Mechanical Engineering, University of Alberta
www.energysystems.ualberta.ca
+1 780 492 77972015 CSBE | SCGAB Annual General Conference
July 5 – 8, 2015, Edmonton, AB, Canada