International Biorefinery Conference
Oct 5-7, 2009,Syracuse, USA
Experimental study and simulation on dimethyl ether
production from biomass gasification
Jie CHANG, Yan FU, Zhongyang LUO
School of Chemistry and Chemical Engineering
South China University of Technology
changjie@scut.edu.cn
Headline
1.
2.
3.
4.
Background
Experimental
Results and Discussion
Simulation and conclusion
Properties of DME
properties
DME
Diesel Fuel
Molar mass, g/mol
46
170
Liquid density, kg/m3
667
831
Carbon content, mass%
52.2
85
Hydrogen content, mass%
13
14
Oxygen content, mass%
34.8
0.4
Critical temperature, K
400
708
Critical pressure, MPa
5.37
-
Auto-ignition temperature, K
508
523
Cetane number
>55
40–50
Stoichiometric air/fuel mass ratio
9.0
14.6
Lower heating value, MJ/kg
27.6
42.5
Kinematic viscosity of liquid, ×104Pa/S
0.15
5.35-6.28
Ignition Limits, Vol% in air
3.4/18.6
0.6/6.5
• Odourless gas, water soluble
• High oxygen content (35%)
• Cetane number (ignition quality) = 55-60
Accelerated mixing & combustion;
Reduced ignition delay– start-up of engine at any T;
Improved ecological characteristics of emission gases:
no smog, low soot, NOx, zero SOx, >Euro-4 standard.
Promising diesel substitute
DME Production
DME Production Evolution:
„
Yesterday:
By-product of high temperature methanol synthesis
„
Today:
Dehydration of methanol
„
Tomorrow:
Direct approach
Syngas to DME
DME from syngas
Fixed bed
Slurry bed
Dimethyl ether (DME) CH3OCH3
Natural
gas
Coal
Biomass
Renewable
Carbon neutral
Clean
Synthesis gas production
Abundance
DME synthesis
Power
generation
Transportation
LPG
fuel
Annually production of
biomass in China
„
„
Total: 5 billion tones in dry weight that is
equal to 1700 MTOE (million tons of oil
equivalent).
Available: mainly come from crop residues,
firewood, forest wood residues and organic
refuses, about 540 MTOE, which is more than
half of the country’s annually primary energy
consumption.
Raw fuel gas produced by
biomass gasification
Low H2/CO ratio (0.20 - 0.80)
High CO2 content (>20mol.%)
High content of tar (10-50 g/m3)
Other light hydrocarbons (CH4,C2+…)
Ideal synthesis gas:
H2/CO = 2.0
CO2 content = 5 mol.%
No tar and hydrocarbons
Integrated DME/Methanol production process
based on co-reforming of biomass-derived syngas
Co-reforming
Energy plants,
Dry agro-residue,
Forest residue
3 billion T
Gasification
Preparation method
for methanol
synthesis catalysts,
ZL200410077468.7
DME
Methanol
Biomass
wet agro-residue,
Organic trash,
manure, sewage
4 billion T
Anaerobic
Digestion
fertilizer
A catalyst
preparation method
for one-step
dimethyl ether
synthesis from
biomass derived
syngas,
ZL200410052571.6
Wang, Chang, et al, Synthesis Gas Production via Biomass Catalytic Gasification with
Addition of Biogas , Energy & Fuels. 2005
Zhang, Chang, et al, Effect of Adjusting Methods on the Performance of Methanol
Synthesis from Biomass Syngas, The Chinese Journal of Process Engineering 2005
T h e rm o c o u p le
F ilte r
CH4 68mol%
CO2 32mol.%
R e fo rm e r
D e h y d ra tio n
T h e rm o c o u p le
Biogas
Avoiding extra
CO2 removal
D e o x y g e n iz a tio n
S y n g a s c o m p re s s o r
Fixed
bed
C y c lo n e
B io m a s s fe e d e r
DME
A ir p u m p
S te a m
b o ile r
S yngas
c o n ta in e r
synthesis
Chang et al, Dimethyl ether production from biomass, Biomass Asia Workshop 2, 2005
Proximate and ultimate analysis of feed
Moisture content (wt% wet basis)
Higher heating value (kJ/kg)
Proximate analysis (wt% dry basis)
Volatile matter
Fixed carbon
Ash
Ultimate analysis (wt% dry basis)
C
H
O
N
S
9.1
20540
82.29
17.16
0.55
50.54
7.08
41.11
0.15
0.57
air/
methane
air-steam/
methane
air-steam/
biogas
2.12
9.1
0.22
0.72
800
780
500
0.36
0
2.12
9.1
0.22
0.72
800
780
500
0
0.54
20.1
25.3
4.7
2.8
0.2
47.3
0.83
36.8
24.0
4.2
3.2
0.3
31
1.53
37.6
26.0
4.8
3.3
0.4
26
1.45
LHV (MJ/m3)
Yield of synthesis gas (m3/Kg biomass)
6.50
2.33
8.35
2.88
8.79
3.40
Carbon conversion (%)
73
74
83
Biomass flow rate (Kg/h)
Biomass moisture (wt.%)
ER
S/B
Gasification temperature (℃)
Reforming temperature (℃)
Catalyst loading (g)
Methane flow rate (m3/Kg biomass)
Biogas flow rate (m3/Kg biomass)
2.12
9.1
0.22
0
800
780
500
0.17
0
Synthesis gas composition (vol.%, dry basis)
H2
CO
CO2
CH4
C2
N2
H2/CO
Ultra-stable solid solution catalyst for reforming
55
100.2
50
NiO-MgO Catalyst
100.0
Remaining weight / %
Gas Composition (mol%)
45
40
35
30
25
TG
99.8
99.6
99.4
99.2
99.0
20
98.8
15
98.6
200
10
400
600
Temperature / K
5
0
0
50
100
150
200
250
300
Time on Stream (h)
Syngas composition with time
(reforming temperature: 750℃; GHSV: 2325h1; Catalyst: NiO-MgO; □ H , ○ CO, △ CO , ▽
2
2
CH4, ┼ N2, ◇ C2)
800
1000
DME synthesis from biomassderived syngas
The direct synthesis of DME from syngas involves
three reactions,
CO + 2H2 = CH3OH, △H = -90.7KJ/mol
CO + H2O = CO2 + H2, △H = -40.9KJ/mol
2 CH3OH = CH3OCH3 + H2O, △H = -23.4KJ/mol
The overall reaction :
3CO + 3H2 = CH3OCH3 + CO2, △H = -245.7KJ/mol
0.55
conventional syngas
biomass syngas
553K
3MPa
0.45
Yield of DME (g/ml-cat.h)
80
70
0.40
0.35
60
0.30
50
0.25
0.20
40
biomass syngas
conventional syngas
0.15
30
0.10
1000
1500
2000
2500
3000
-1
GHSV (h )
3500
4000
Conversion of CO (mol%)
0.50
0.75
0.70
0.65
Conversion of CO
0.60
0.55
0.50
0.45
Cat1
Cat2
Cat3
Cat4
Cat5
Cat6
Cat7
0.40
0.35
0.30
P:3MPa
-1
GHSV:3000h
0.25
0.20
0.15
0.10
500
510
520
530
540
550
560
570
580
T (K)
Performance of one step DME synthesis catalysts
Cu-Zn-Al(Li)/HZSM5 in different preparation methods
150h lifetime test
Gasification conditions:
1073K, ER of 0.24, S/B of 0.72
Reforming conditions:
1023K with the addition of 0.54Nm3 biogas/Kg biomass
(dry basis)
The CO conversion and DME selectivity were kept 75% and
66.7% respectively during the period of 150 h.
DME Yield: 244g DME/Kg biomass (dry basis)
Experiment
„
CO2 reforming of Biomass
Run
1
2
3
4
5
6
7
8
9
10
CO2/
Biomass
(kg/kg)
0
0
0
0
0
0.327
0.327
0.327
0.327
0.327
Steam/
biomass
(kg/kg)
0
0.754
1.058
1.454
1.667
0
0.754
1.058
1.454
1.667
Gas yields
(Nm3/kg
biomass)
1.03
1.40
1.45
1.54
1.40
1.40
1.62
1.59
1.37
1.25
Gas composition (mol %) before reforming
H2
26.45
28.79
27.91
27.70
28.43
25.03
27.20
28.56
28.85
29.32
CO
41.68
33.75
34.57
35.49
34.47
45.73
43.94
39.15
38.92
37.77
CO2
20.82
25.38
25.02
23.81
24.63
12.07
15.14
19.27
20.11
20.71
CH4
7.94
8.65
8.76
9.06
8.71
12.22
9.64
9.15
8.45
8.48
C2
3.09
3.44
3.73
3.93
3.75
4.96
4.08
3.86
3.68
3.72
Gas yields (g/kg biomass) before reforming
H2
24.27
35.78
35.99
38.02
35.45
27.48
35.40
36.21
30.77
28.15
CO
537.33
591.55
625.86
684.09
603.582
705.26
803.21
697.04
583.15
509.30
CO2
421.00
693.73
710.41
719.58
676.53
291.89
433.91
537.87
472.42
437.85
CH4
58.50
86.48
90.61
99.71
87.24
107.60
100.65
93.08
72.35
65.29
C2
40.06
60.31
67.76
76.10
65.94
76.71
75.06
69.06
55.34
50.43
LHV
(kJ/m3)
6695.56
7487.39
7745.95
8135.21
7667.34
8360.37
8199.87
7672.36
6908.13
6534.50
With the biogas addition of 0.54m3 per kg
of biomass, the raw gas in run 6 was
reformed at temperature of 1023K to the
following typical composition (in volume):
43.5% H2, 36.9% CO, 13.7% CO2, 5.0%
CH4 and 0.9% C2. The yield of syngas was
2.5 Nm3/kg biomass. The H2/CO ratio was
adjusted to 1.18 from 0.55.
Kinetic equations and parameters
Simulation on DME production
„
Under 553K, 4MPa, and GSHV of 1800h-1,
78.5% of CO conversion could be obtained,
and the corresponding DME yield was
379g/kg biomass. Compared with air/steam
gasification, which got 224g DME/kg biomass,
the yield of DME in this novel process
increased about 65%. This showed great
potential of DME production from biomass via
gasification with CO2 and co-reforming with
biogas.
Conclusion
„
„
„
A novel route for DME production from
biomass was proposed and test in a bench
scale experimental system.
Gasification of biomass and reforming of
produced gas are the key steps in the DME
production system.
Gasification of biomass with CO2 as agent
has benefit for increasing syngas yield and
saving energy comparing to air/steam agents.
Biorefinery R&D in our group: syngas platform
Biomass resources-energy Cycle
Biomass
Catalysts
Fuel cell
power
Gasoline
diesel
Acknowledgment
„
Financial support received from NSFC (Project no.
50811120044 and 90610035) is gratefully
appreciated.
Contact information:
South China University of
Technology, Guangzhou
changjie@scut.edu.cn