GREEN ENERGY: PRODUCTION OF
ALCOHOLS FROM SWITCHGRASS
Group Alpha
Greg Dicosola
Tim O’Brien
Tim Bannon
Hasseb Quadri
Catalina Mogollon
OUTLINE






PFD
Gasification
Gas Clean Up
Alcohol Synthesis
Waste Streams
Basic Cost Estimation
PFD
19
TO WASTE
PFD 2
HEAT RECOVERY
17
5
13
16
CYCLONE 4
10
CYCLONE 3
11
4
TCCB-TAR
CATALYTIC
CRACKER B
TCCA-TAR
CATALYTIC
CRACKER A
CYCLONE 1
30
DRIED
FROM PFD 2
BIOMASS
CYCLONE 2
8
6
GASIFIER
12
9
SHREDDER/
HOPPER
3
COMBUSTER
15
TO BIOMASS
ASH
TO PFD 2
DRYER
14
AIR
HEAT
EXCHANGER/
SUPERHEATER 1
OSBL
FLOW VALVE
TO PFD 4
FIC
7
FIC
2
1
STEAM FROM
FROM PFD 3
SUPERHEATER
Page 1 PFD: Gasifier, Combuster, and Tar removal
PIC
23
STEAM
TO PFD 4
SYN GAS FROM
19
FROM PFD 1
TAR REMOVAL
24
25
DI WATER
OSBL
29
WASTE HEAT
BOILER
TO CO2/H2S
TO PFD 3
ABSORBER
28
CWS
PIC
20
FIC
21
INITIAL
COMPRESSOR
WATER
QUENCH
27
GAS /WATER
SEPARATOR
22
LIC
26
MOISTURE
31
WASTE WATER
OSBL
WET BIOMASS
OSBL
30
DRIED BIOMASS
TO PFD 1
TO FEEDER
CONVEYER/
DRYER
PIC
TO FLARE
OSBL
FLUE GAS
FROM PFD 1
15
32
Page 2 PFD: Waste heat recovery and Biomass Drying
42
METHANOL RECYCLE
FROM PFD 4
PIC
50
STEAM
TO PFD 4
43
LIC
41
MIXED ALCOHOL
REACTOR
(boiling water
reactor)
CWS
49
BOILER
OSBL
FEED WATER
EXCHANGE TO
FROM PFD 4
TIC
REACTOR EFFLUENT
47
40
44
PIC
48
HEAT
EXCHANGER 2/
STEAM
SUPERHEATER
45
39
COMPRESSOR
EXCHANGE FROM
TO PFD 4
REACTOR EFFLUENT
33
PIC
46
51
55
GAS TO VENT
OSBL
CO2 /H2S
ABSORBER
HP GAS/
LIQUID
SEPARATOR
38
PIC
LIC
29
PIC
FROM
FROM PFD 2
CO2 TO
VENT
LIC
COMPRESSOR
56
CWS
53
LIC
WATER
34
52
LP GAS/
LIQUID
SEPARATOR
OSBL
35
36
LIC
AMINE HEAT
EXCHANGER
MIXED ALCOHOL
TO PFD 4
54
AMINE
STRIPPER
37
RESET
FIC
XY/XV
SOLVENT
STEAM
LIC
OSBL
MAKE-UP
Page 3 PFD: CO2, H2S removal and Alcohol synthesis
TO FRACTIONATION
47
EXCHANGE FROM
FROM PFD 3
REACTOR EFFLUENT
POWER TO RELAY FOR
PLANT OPERATION
61
OSBL
(ADDITIONAL POWER
TO BE SOLD)
STEAM FROM
REACTOR
50
57
58
59
FROM PFD 3
HEAT
EXCHANGER 2/
STEAM
SUPERHEATER
STEAM FROM
23
FROM PFD 2
WASTE HEAT BOILER
48
EXCHANGE TO
TO PFD 3
REACTOR EFFLUENT
60
WATER TO
OSBL
FLOW
WASTE HEAT BOILER
AND/OR REACTOR
CWS
FROM PFD 1
CONTROLLER
PIC
1
STEAM TO GASIFIER
64
METHANOL TO
TO PFD 1
TO PFD 3
REACTOR
62
LP GAS/
LIQUID
SEPARATOR
LIC
65
WATER TO CLEAN-UP
OSBL
WATER/METHANOL
FRACTIONATION FROM
MIXED ALCOHOL STREAM
MIXED ALCOHOL
FROM PFD 3
FROM SEPARATOR
53
FIC
63
MIXED ALCOHOL
OSBL
PRODUCT
Page 4 PFD: Steam superheating, Power generation, and Product fractionation
GASIFICATION
THE SILVAGAS PROCESS1
• Twin Fluidized Bed Process
• Steam Gasification
• Endothermic gasification
in the gasifier (Left)
• Exothermic combustion
in the combustor (Right)
• Sand recycled to transfer
heat
ADVANTAGES OF THE SILVAGAS PROCESS
• Designed for biomass gasification (adaptable to forest waste,
MSW, agricultural waste, and energy crops).
• High throughput—up to 3000 lb/hr-ft2 (compared to
100 lb/hr-ft2 of comparable gasification processes).
• Syngas composition remains same regardless of changes in
feedstock moisture levels (proven within 10-50%3)
• No pure oxygen required – steam gasification.2
• Short residence times of a few minutes.3
GASIFIER MATERIAL BALANCE
• Choose Basis—used 133,333 acres/year at 11.5 tons/acre in
Alabama4 = 3.07 x 109 dry lb/year
• Assume 10% moisture by weight1
• Switchgrass composition to elemental balance.
Switchgrass Feed
Mass %5
lb/yr
lbmol/yr
C
48.8% 1.50E+09 1.25E+08
H
6.4% 1.97E+08 1.95E+08
O
36.3% 1.11E+09 6.95E+07
N
0.7% 2.21E+07 1.58E+06
S
0.0% 6.13E+05 1.91E+04
Ash
7.8% 2.39E+08
Moisture
11.0% 3.41E+08 1.89E+07
Total
1.1 3.41E+09 4.10E+08
GASIFIER MATERIAL BALANCE
(cont.)
• Assume a percent carbon conversion of 60%3
• Assume 40% moisture by vol. in the syngas6
• Balance carbon with syngas composition
• Assuming 16g/m3 tars in the syngas1, model as ideal gas at 1500oF
• Model tar as C10H8 for lbmol/yr calculation6
SynGas
CO2
CO
H2
CH4
C2H4
C2H6
H2O
Tar
Total
Mol %
lbmol/yr lb/yr
12.2% 1.09E+07 4.79E+08
44.4% 3.96E+07 1.11E+09
22.0% 1.96E+07 3.96E+07
15.6% 1.39E+07 2.23E+08
5.1% 4.55E+06 1.28E+08
0.7% 6.24E+05 1.88E+07
6.31E+07 1.14E+09
1.07E+06 1.38E+08
100.0% 1.53E+08 3.27E+09
GASIFIER MATERIAL BALANCE
(cont.)
Other Assumptions
• No SOx or NOx formed in gasifier2
• 8.3% of S parsed to char; rest is 90% H2S and 10% COS6
• 6.6% of N parsed to char; rest is 25% NH3, 10% HCN, and 65% N2 6
• All chlorine becomes HCl2
Other
Compounds lbmol/yr
lb/yr
H2S
1.58E+04
5.38E+05
COS
1.75E+03
2.11E+04
NH3
3.68E+05
6.27E+06
HCN
1.47E+05
3.98E+06
N2
4.79E+05
1.34E+07
HCl
3.36E+04
1.23E+06
Total
1.04E+06
2.54E+07
GASIFIER MATERIAL BALANCE
(cont.)
Final Balance to Char
• A steam feed of 0.4 lb/lb dry
biomass is assumed6
= 1.23 x 109 lb/yr
= 6.81 x 107 lbmol/yr
• Remaining hydrogen and
oxygen
outside of syngas are
parsed to the char.6
• Ash from the switchgrass is
inert and
is parsed to the char.6
Ash
SiO2
Al2O3
Fe2O3
MgO
CaO
Na2O
K2O
P2O5
Other
lb/year
1.36E+08
1.91E+06
8.83E+05
1.14E+07
2.64E+07
7.16E+05
2.16E+07
1.31E+07
2.56E+07
COMBUSTOR MATERIAL BALANCE
• The H, C, and S in the char are combusted with 20% excess air1
to heat the circulating SiO2.
• The combustion products make up the flue gas while the inert ash
is collected
• All carbon forms CO2, H forms H2O, S forms SO2 and N forms N2
and NO2 in a 6:69 molar ratio7
Combustion Products
lbmol/year
CO2
N2
NO2
H2O
SO2
Total
3.89E+07
4.79E+04
8.32E+03
5.82E+07
1.59E+03
9.72E+07
GASIFIER/COMBUSTOR ENERGY BALANCE
• (heat of formation + sensible heat) products =
(heat of formation + sensible heat) feeds
• Heat of formation of switchgrass—subtract HHV of elements from
HHV of fuel1 (7689 Btu/lb)5 s
• Heat capacity of switchgrass is assumed to be 0.358 Btu/lboF8
• Other streams—Heats of formation are found along with Antoine
Coefficients for calculation of heat capacities.
• Beginning temperatures for calculation:
~500oF for the feed steam10,1
~220oF for the switchgrass feed10
~500oF for the air feed10
~1900oF for the flue gas1
~1500oF for the syn gas1
GASIFIER/COMBUSTOR ENERGY BALANCE
Flue Gas lbmol/year ΔHf
Total
o
11
ΔHf
o
Btu/lbmol Btu/year
Cp/R =
A+BT+DT-2
A
B
11
D
Cp
Sensible
H
Btu/lb F
Btu/year
N2
2.32E+08 0.00E+00
0.00E+00
3.28
0.593
0.04 2.66E-01 2.93E+12
O2
1.04E+07 0.00E+00
0.00E+00
3.639
0.506
-0.227 2.48E-01 1.40E+11
H2O
5.82E+07 -1.04E+05
-6.06E+12
3.47
1.45
CO2
3.89E+07 -1.69E+05
-6.59E+12
5.457
1.045
-1.157 2.75E-01 7.98E+11
NO2
7.86E+03 5.96E+04
4.68E+08
4.982
1.195
-0.792 2.50E-01 9.99E+07
SO2
1.59E+03 -5.34E+05
-8.48E+08
5.699
0.801
-1.015 1.91E-01 3.29E+07
• Total
0.121
enthalpy out in flue gas = 7.88 x 1012 Btu/year
5.11E-01 9.07E+11
COMPLETION OF ENERGY BALANCE
• Assume 1% heat loss7
• Manipulate carbon conversion %, moisture of switchgrass,
steam feed rate, air feed rate, and temperatures of all streams.
• Balance until HIN = HOUT
• Using ΔHrxn for the combustion of C, H, and S, and SiO2 heat
capacity of 0.378 Btu/lb-oF:
The sand is circulated at a rate of 1.13 x 1011 lb/yr
or 37 lb/lb dry biomass
SUMMARY OF GASIFIER STREAMS
Syngas Out
Switchgrass In
T (oF)
1454
T (oF)
220
lb/yr
3.30E+09
lb/yr
3.41E+09
Btu/yr
-9.13E+12
Btu/yr
-1.13E+13
Flue Gas
Steam In
T (oF)
1770
T (oF)
700
lb/yr
9.60E+09
IN
lb/yr
1.23E+09
-7.88E+12
1.31E+10 Btu/yr
Btu/yr
-6.73E+12 lb/yr
Btu/yr
-1.72E+13 Ash
Air In
T (oF)
1770
T (oF)
500
OUT
lb/yr
2.37E+08
(-1% Heat Loss)
lb/yr
8.50E+09
1.31E+10 Btu/yr
-1.50E+10
Btu/yr
8.62E+11 lb/yr
Btu/yr
•All at 23 psia
-1.72E+13
GAS CLEAN UP
Examples of biomass tars
C10 H 8  10 H 2 O  14 H 2  10CO
C10 H 8  10CO  20CO  4 H 2
C10 H 8  10C  4 H 2
Chemical reactions for destruction of napthalene
Component
Mole flow
CO2
1,360.29
CO
4,950.55
H2
2,452.98
CH4
1,739.38
C2H4
568.64
C2H6
78.05
Tars (C10H8)
135.55
H2O
7,889.32
TCCA-TAR CATALYTIC
CRACKER A
TCCB-TAR CATALYTIC
CRACKER B
Type: Fluidized bed
with cyclone filters
Type: Fixed bed with
guard bed
Catalyst: Calcined,
nickel treated
olivine
Catalyst: Calcined
dolomite
Ash: 104.23 lb/hr
Component
Mole flow
CO2
2,322.09
CO
6,373.06
H2
7,435.18
CH4
1,739.38
C2H4
0.00
C2H6
78.05
Tars (C10H8)
4.61
H2O
4,543.21
ALCOHOL SYNTHESIS
- CATALYST
SYNTHESIS OF ETHANOL FROM SYNGAS
 CATALYST: modified Fischer-Tropsch catalyst
 Molybdenum disulfied based promoted with alkali metal salts and
cobalt
 Co/MoS2
 High ethanol selectivity
 Catalytic activity: 13.5% conversion of CO (adding
methanol recycle)
 ethanol yield: 25,900 lb/hr
 Product: mixture of linear alcohols
 Resistant to sulfur (up to 100ppm)
 H2S inlet stream to maintain catalyst activity
 Methanol decomposition functionality
 Methanol in feed is not detrimental to the reaction
SYNTHESIS OF n-BUTANOL FROM BIOMOLECULAR
CONDENSATION OF ETHANOL
 CATALYST: γ-alumina supported nickel
 8%Ni/γ-Al2O3
 γ-Al2O3 and solution of Ni(NO3)2·6H2O
 Dried at 150°C
 Pretreated under hydrogen flow at 500°C for 4 h
 n-butanol selectivity: 64.3%
 High catalytic activity: 19.1% conversion of ethanol
 n-butanol yield: 12.3%
 Low reaction temperature: 200°C
 Table: Catalytic performance over ethanol
condensation reaction
Catalyts
AD
Sel. (%)
BD
Sel. (%)
8%Ni/γAl2O3
5.8
3.8
EA
BO
Sel. (%) Sel. (%)
3.1
64.3
Others
Sel. (%)
23.0
a) AD: Acetaldehyde; BD: Butaldehyde; EA: Ethanyl acetate; BO: nbutanol
c) Others: 2-Ethylbutanol, n-hexanol, ethyl ether, n-butyl ether etc.
ALCOHOL SYNTHESIS
molybdenum-disulfide-based (MoS2)
Langmuir-Hinshelwood kinetic approach
Methanol Recycle
Making Butanol is
Difficult!
 Methanol recycle makes more Ethanol!
 Rh catalyst cost $5000/ounce
Ethanol for Now
• Make as much as possible
• Look into options for Hydrogenation of
Ethanol to make Butanol
Ethanol Targets
 NREL Model Target 60% CO Conversion
Alcohol
Methanol
Ethanol
Propanol
Butanol
Pentanol
Others
Water
Total
NREL Model
(wt%)
5.01
70.66
10.07
1.25
0.17
10.98
1.86
100
Langmuir-Hinshelwood
kinetics
System of Reactions for Mixed Alcohol
Synthesis
Rate Equations
Water Gas Shift Reaction
Parameters found Experimentally
Parameter
Methanol
Ethanol
Hydrocabo
Propanol
ns
Units
mol/hr/kg
cat
KJ/mol
Am, Ae, Ap, Ah
14.6233
3.0518
0.2148
9.3856
Em, Ee, Ep, Eh
143.472
24.986
89.3328
95.416
nm, ne, np, nh
3
1
1
1
K1
7.64E-09
K2
0.6785
K3
0.9987
Ke
0.7367
Kp
0.6086
Kh
1.2472
Kz
0.8359
Tcp
598
Kelvin
Pcpi
46.7*(xi) 46.7*(xi) 46.7*(xi)
46.7*(xi)
atm
Tcp and Pcpi are the temperature and partial pressure at the center point
experiment. The center point experiment describes the basis for calculation of
the above Parameters.
Differential Equations input
to Polymath
With initial
conditions
Into Reactor
Kmol/hr
lb/hr
Out of Reactor
Kmol/hr
lb/hr
CO
2245.532 4950.551
766.3169
47321.2
CO2
6.170226
13.60302
38.7946
3764.064
H2
2601.05
5734.333
964.8306
4287.953
N2
27.13115 59.81394
H2O
3578.64 7889.552
27.13115 59.81394
1.258634
49.98825
CH3OH
~0
0
5.480634
387.1307
C2H5OH
~0
0
17.7324
1800.948
C3H7OH
~0
0
2.660657
352.5019
394.4755
869.6697
498.6421
17636.35
CH4
In H2/CO = 1.16
In CO2/CO = 0.0027
CO conversion ~65%
Out H2/CO = 0.0906
Out CO2/CO = 0.080
Without Recycle
52100 barrels/yr
BASIC COST ESTIMATION
Rough Cost Scale-up
Base Year
Installed cost in 2005 ($)
Installed cost in 2009 ($)
2002
$ 137,228,869
$ 222,999,612
Chemical Engineering Cost
Index :
Cost is scaled up from a
ethanol production plant.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
Higman, C., van der Burgt, M., “Gasification.” 2003, Elsevier
Science
Silvagas Corporation, www.silvagas.com
Paisley, M.A., Overend, R.P., “The Silvagas Process from
Future Energy Resources—A Commercialization
Success.” 2002.
Bioenergy Feedstock Development Program. “Biofuels from
Switchgrass: Greener Energy Pastures.” Oak Ridge
National Laboratory.
Laser, M., “Switchgrass Composition Methods.” Memo: 2004
Philips, S., Aden, A., Jechura, J., Dayton, D.,
“Thermochemical
Ethanol via Indirect Gasification
and Mixed Alcohol Synthesis of Lignocellulosic Biomass.”
NREL: 2007
Basu, P., “Combustion and Gasification in Fluidized Beds.”
Taylor and
Francis Group: 2006
Kaliyan, Morey, “Strategies to Improve the Durability of
Switchgrass Briquettes.” ASAE: 2007
REFERENCES (cont.)
10. Bain, R.L., “Material and Energy Balances for
Methanol from Biomass Using Biomass Gasifiers.”
NREL: 1992
11. Smith, J.M., Van Ness, H.C., Abbott, M.M.,
“Introduction to
Chemical Engineering
Thermodynamics.” 7th Ed. McGrawHill: 2005
12. Yang, K.W., Jiang, X. Z., Zhang, W. C. , “One-step
Synthesis of n-Butanol from Ethanol Condensation
over Alumina-supported Metal Catalysts.” Chinise
Chemical Letters, 2004