experimental study and simulation on dimethyl ether
TRANSCRIPT
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 [email protected]
Oct 5-7, 2009,Syracuse, USAInternational Biorefinery Conference
Headline
1. Background2. Experimental3. Results and Discussion4. 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
• 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
• Odourless gas, water soluble• High oxygen content (35%)
DME Production
Yesterday:
By-product of high temperature methanol synthesis
Today:
Dehydration of methanol
Tomorrow:
Direct approach Syngas to DME
DME Production Evolution:
DME from syngas
Fixed bed Slurry bed
Natural gas Coal Biomass
Synthesis gas production
DME synthesis
Renewable
Carbon neutral
Clean
Abundance
Power generation LPG
Transportation
fuel
Dimethyl ether (DME) CH3OCH3
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
Energy plants, Dry agro-residue,
Forest residue3 billion T
wet agro-residue, Organic trash,
manure, sewage4 billion T
Biomass
Gasification
Anaerobic
Digestion
fertilizer
DME
Methanol
Co-reforming
Wang, Chang, et al, Synthesis Gas Production via Biomass Catalytic Gasification withAddition of Biogas , Energy & Fuels. 2005
A catalyst preparation method for one-step dimethyl ether synthesis from biomass derived syngas, ZL200410052571.6
Preparation method for methanol synthesis catalysts, ZL200410077468.7
R eform er
F ilte r
D ehydra tion
D eoxygen iza tion
S yngas com pressor
C yclone
B iom ass feeder
S yngas conta iner
A ir pum pS team bo ile r
Therm ocoup le
Therm ocoup le
Biogas
CH4 68mol%CO2 32mol.% Avoiding extra
CO2 removal
Zhang, Chang, et al, Effect of Adjusting Methods on the Performance of Methanol Synthesis from Biomass Syngas, The Chinese Journal of Process Engineering 2005
Chang et al, Dimethyl ether production from biomass, Biomass Asia Workshop 2, 2005
Fixed bed
DME
synthesis
Moisture content (wt% wet basis) 9.1Higher heating value (kJ/kg) 20540
Proximate analysis (wt% dry basis)Volatile matter 82.29Fixed carbon 17.16
Ash 0.55Ultimate analysis (wt% dry basis)
C 50.54H 7.08O 41.11N 0.15S 0.57
Proximate and ultimate analysis of feed
air/methane
air-steam/methane
air-steam/biogas
Biomass flow rate (Kg/h)Biomass moisture (wt.%)ERS/BGasification temperature (℃)Reforming temperature (℃)Catalyst loading (g)Methane flow rate (m3/Kg biomass)Biogas flow rate (m3/Kg biomass)
2.129.10.2208007805000.170
2.129.10.220.728007805000.360
2.129.10.220.7280078050000.54
Synthesis gas composition (vol.%, dry basis)H2COCO2CH4C2N2H2/CO
20.125.34.72.80.247.30.83
36.824.04.23.20.3311.53
37.626.04.83.30.4261.45
LHV (MJ/m3)Yield of synthesis gas (m3/Kg biomass)
Carbon conversion (%)
6.502.33
73
8.352.88
74
8.793.40
83
0 50 100 150 200 250 3000
5
10
15
20
25
30
35
40
45
50
55
NiO-MgO Catalyst
Gas
Com
posi
tion
(mol
%)
Time on Stream (h)
200 400 600 800 1000
98.6
98.8
99.0
99.2
99.4
99.6
99.8
100.0
100.2
Rem
aini
ng w
eigh
t / %
Temperature / K
TG
Syngas composition with time (reforming temperature: 750℃; GHSV: 2325h-
1; Catalyst: NiO-MgO; □ H2, ○ CO, △ CO2, ▽CH4, ┼ N2, ◇ C2)
Ultra-stable solid solution catalyst for reforming
DME synthesis from biomass-derived 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
1000 1500 2000 2500 3000 3500 40000.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
30
40
50
60
70
80
biomass syngas conventional syngas
Con
vers
ion
of C
O (m
ol%
)
Yiel
d of
DM
E (g
/ml-c
at.h
)
GHSV (h-1)
conventional syngas biomass syngas
553K3MPa
500 510 520 530 540 550 560 570 5800.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
Con
vers
ion
of C
O
T (K)
Cat1 Cat2 Cat3 Cat4 Cat5 Cat6 Cat7
P:3MPaGHSV:3000h-1
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
Catalysts
Gasoline
diesel
Fuel cell
power
Biomass
AcknowledgmentFinancial support received from NSFC (Project no. 50811120044 and 90610035) is gratefully appreciated.
Contact information:
[email protected] China University of Technology, Guangzhou