about gasification

1. Indirect vs. Direct
Gasification
A. van der Drift
G. Aranda Almansa
B.J. Vreugdenhil
H.J.M. Visser
C.F. Mourao Vilela
C.M. van der Meijden
September 2013
ECN-L--13-063

2. www.ecn.nl
INDIRECT vs. DIRECT
GASIFICATION
Bram van der Drift, Guadalupe Aranda, Berend Vreugdenhil,
Rian Visser, Carlos Vilela, Christiaan van der Meijden
4 September 2013

3. GASIFICATION
matching energy consumption and production
2
+
25%
75%
energy production:
fuel + air (l > 1)  flue gas + heat
energy consumption:
fuel + heat  gas
gasification:
fuel + air (l~0.3)  gas + char/coke
+ char/coke

4. SECOND GENERATION
also called: indirect gasification
3
+
25%
75%
energy production:
fuel + air (l > 1)  flue gas + heat
energy consumption:
fuel + heat  gas
gasification:
fuel + air (l~0.3)  gas + char/coke
+ char/coke

5. GASIFICATION
generations
First generation (=direct)
• One reactor, one gas
• N2-free gas requires ASU
• Incomplete carbon conversion
• High temperature, high steam,
small fuel size, large residence time
needed for acceptable conversion
Second generation (=indirect)
• Two coupled reactors, two gases
• N2-free gas without ASU
• Complete carbon conversion
• Additional degree of freedom:
temperature, steam, fuel size,
residence time
gasifier
fuel air
gas
ash+char
gasifier
fuel air
gas
ash
combustion
fuel
energy
flue gas
gasifier
fuel air
gas
ash+char
gasifier
fuel air
gas
ash
combustion
fuel
energy
flue gas

6. IN OTHER WORDS
lower temperature, better efficiency, higher conversion
0% 100%
Fuel Conversion
Gasification
Temperature
direct gasification
indirect gasification
100-200°C
Carbon energy loss
Carbon energy source
for gasification

7. MILENA TECHNOLOGY
indirect gasification technology by ECN
• Highly efficient
• Complete conversion
• Fuel flexible
• Compact
www.milenatechnology.com 6
raw
producer
gas
flue gas
air
biomass
pyrolysis
combustion
steam or CO2 or …

8. INDIRECT GASIFICATION
• Energy transport between the two reactors
• Bed material takes carbon from gasifier to
combustor
– Char flows with bed material
– Tars adsorb on (porous) bed material
– CO2 transport through carbonates
• Bed material can take oxygen from
combustor to gasifier
gasifier
fuel air
gas
ash+char
gasifier
fuel air
gas
ash
combustion
fuel
energy
flue gas
oxygen

9. OXYGEN TRANSPORT
description of the tests
• Bubbling Fluidized Bed
• Olivine bed material (containing Fe)
• Clean wood fuel, 0.25 kg/h
• 880°C, 1 kg bed
• Two tests:
– Test 1: only gasification
– Test 2: intermittent gasification/combustion,
100 minutes cycle

10. OXYGEN TRANSPORT
description of the tests
oxidation
reduction
Steam
Fuel
N2
oxidation
reduction
Steam
Fuel
N2
Steam
Fuel
N2
Air Air
time
time
Test 1
Test 2
100 minutes

11. OXYGEN TRANSPORT
gas composition
10
Cycle 1 Cycle 2
Oxidation 1 Oxidation 2
Devolatilization 1 Devolatilization 2
Test 2

12. OXYGEN TRANSPORT
tars (by SPA method)
Iron becomes better catalyst due to reduction
Char accumulation
Instant effect of O-release

13. OXYGEN TRANSPORT
oxygen quantity
• Mass balance O mass flow for 1-minute intervals
• Relate to fuel mass flow ER
• Relate to iron phase change  20-25% of iron acts as O-pump

14. COMPARED TO MILENA
13
MILENA operating conditions are equivalent to the initial point of
maximum CO2: olivine is kept at high oxygen transport capacity
Test 2, first few minutes Test 2, after a while

15. OXYGEN TRANSPORT
compared to MILENA

16. CONCLUSIONS
• Indirect gasification offers degree of freedom compared to direct
gasification, since unconverted carbon is not a loss: temperature
• Freedom to operate at low temperature means fuel flexibility
• Bed material in indirect gasification can transport oxygen through chemical
looping
• This may add up to an ER of 0.2-0.3 during first few minutes of reduction
• This theoretically can supply all the required energy for gasification
• This also reduces tar:
– By direct combustion of adsorbed tars on surface where iron reduces (O donor)
– By increased gas phase reforming because of increased CO2 and H2O concentration
• MILENA is operated with fast reduction/short residence time: maximum
oxygen transport

17. THANKS FOR THE ATTENTION
publications: www.ecn.nl/publications
fuel composition database: www.phyllis.nl
tar dew point calculator: www.thersites.nl
IEA bioenergy/gasification: www.ieatask33.org
Milena indirect gasifier: www.milenatechnology.com
OLGA: www.olgatechnology.com / www.renewableenergy.nl
SNG: www.bioSNG.com /www.bioCNG.com
Bram van der Drift
ECN
Westerduinweg 3 P.O. Box 1
1755 LE Petten 1755 ZG Petten
The Netherlands The Netherlands
T +31 224 56 45 15 vanderdrift@ecn.nl
M +31 610 909 927 www.ecn.nl
16

18. 8
ECN
Westerduinweg 3 P.O. Box 1
1755 LE Petten 1755 LG Petten
The Netherlands The Netherlands
T +31 88 515 4949
F +31 88 515 8338
info@ ecn.nl
www.ecn.nl