Production of Syngas by Pressurised Fluidised Bed ...

Production of Syngas by Pressurised

Fluidised Bed Gasification of German

Lignite in a H2O/CO2 Atmosphere

Xiangyi Long*, Vicky Skoulou, Nigel Paterson, Marcos Millan Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK.

*E-mail: [email protected]

10th ECCRIA, Hull, Sep. 2014

Outline

• Background

• Project objectives

• Experimental

• Results

• Conclusions

2

Background – Energy Sector

3

• Prediction of world total primary energy supply by fuels (Source: IEA, 2007)

Primary energy increase more than half between 2015 and 2050, with a

very high reliance on solid fuels.

Background – Promising Technologies

• Gasification is a promising technology for processing solid

fuels, including coal and biomass.

• Depending on the composition, the produced syngas

derived from solid fuels can potentially be used on various

chemical synthesis or hydrogen production processes.

• Fluidised bed gasifier is versatile in terms of fuel.

4

Background – Gasification

Reaction type Reaction ∆H, MJ kmol-1

Combustion reactions

C + 0.5 O2 = CO -111

CO + 0.5 O2 = CO2 -283

H2 + 0.5 O2 = H2O -242

Boudouard reaction C + CO2 ↔ 2 CO +172

Water gas reaction C + H2O ↔ CO + H2 +131

Methanation reaction C + 2 H2 ↔ CH4 -75

CO shift reaction CO + H2O ↔ CO2 + H2 -41

Steam methane reforming

reaction CH4 + H2O ↔ CO + 3 H2 +206

• Principal gasification reactions

5

Background – CO2 Gasification

• Oxy-fuel integrated gasification combined cycle (IGCC)

with CO2 recycling

6

H2O

Project Objectives

• The effect of H2O/CO2 ratio on the carbon conversion, syngas

yield and concentration

• The effect of pressure on the carbon conversion, syngas yield

and concentration

• Evaluation of the suitability of the combined process for

chemical synthesis and hydrogen production, and its potential

scalability

7

CO2 gasification

100% CO2

Steam gasification

100% H2O

pressure

Experimental – Setup

e. Gas cleaning system

d. Fluidised

bed reactor

c. Steam

generator

b. Feeding

system

f. On-line gas analysers

g. Burner

a. Gas supply

8

Experimental – Fluidised Bed Reactor

Syngas exit

Counter weight

Electrodes

Quartz liner Reactor

Heat resistance, pressure vessel

1 2

3 4

Gasification medium

1 2

3 4

9

Experimental conditions

• Solid feed stock: German lignite (coal)

Proven more reactive than other kinds of coals under conventional and

oxy-fuel gasification

Especially when mixed with biomass could promote positive synergies

• Fuel gas production from H2O/CO2 gasification

Temperature at 850 ˚C

Gas (CO2+H2O) to carbon mole ratio 2

Pressure from 1 to 10 bar

Steam concentration from 0 to 40%

10

Typical reaction profile

• Fuel gas composition during continuous CO2 gasification

of German lignite at 850°C and atmospheric pressure

11

Fuel gas production

• H2 yield increased with H2O partial pressure.

• Syngas yield was relatively stable with increased H2O partial pressure.

• Syngas yield slightly reduced by increase of total pressure. 12

CO2/H2O

Fuel gas concentration

• H2 concentration increased by increase of H2O partial pressure.

• Syngas concentration decreased with increase of total pressure.

13

Dry gas heating value

• Heating value can be increased by increase of H2O partial pressure.

• Heating value slightly varied with the change of total pressure.

14

CO/H2 ratio in fuel gas

15

• CO/H2 ratio can be adjusted by inlet CO2/H2O ratio.

Carbon conversion

16

• C conversion increased with increase of inlet steam concentration.

• C conversion decreased with increase of total pressure. (Suppression of coal

devolatilisation, reduction of char reactivity)

Conclusions

• Effect of increasing H2O partial pressure

Both production and concentration of hydrogen in syngas increased.

CO/H2 ratio can be easily adjusted.

Heating value increased.

Carbon conversion increased.

• Effect of increasing total pressure

Both production and concentration of syngas decreased.

Heating value fairly constant.

Carbon conversion decreased significantly (Potential mechanism is

working in progress). 17

• Characterization of the feedstock

* By difference

Feedstock German Lignite (GL)

Proximate analysis (%wt., a.r.)

Moisture, (M) 13.2

Total Volatiles, (VT) 44

Fixed Carbon, (FC) 38.7

Ash, (A) 4.1

Ultimate analysis (%wt., a.r.)

Carbon, ( C) 57.39

Hydrogen, ( H ) 4.03

Oxygen, (O)* 37.72

Nitrogen, (N) 0.61

Chlorine, (Cl) 0.02

Sulphur, (S) 0.23

Calorific Values (MJ/kg, d.a.f)

HHV 23.1

LHV 21.9