experimental study and simulation on dimethyl ether

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 Technologychangjie@scut.edu.cn

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:

changjie@scut.edu.cnSouth China University of Technology, Guangzhou