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
