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High efficiency SNG production from biomass
L.P.L.M. Rabou
ECN-L--10-069 JULY 2010
2 ECN-L--10-069
Preface This report contains the extended abstract submitted to and the presentation given at the Novel Gas Conversion Symposium (NGCS 9), held from the 30th of May to the 3rd of June 2010 in Lyon.
Abstract The Energy research Centre of the Netherlands (ECN) is developing technology for the produc-tion of Substitute Natural Gas (SNG) from biomass. The technology involves indirect gasifica-tion, tar removal, further gas cleaning, methanation and upgrading of the product to natural gas standards. The aim is to reach an energy efficiency of at least 70% from biomass to SNG. Re-sults are presented of tests performed with various catalysts and biomass producer gas at lab-scale (about 1 Nm3/hr).
Contents
Extended Abstract 3
Presentation 5
ECN-L--10-069 3
Extended Abstract
Abstract The Energy research Centre of the Netherlands (ECN) is developing technology for the production of Substitute Natural Gas (SNG) from biomass. The technology involves indirect gasification, tar removal, further gas cleaning, methanation and upgrading of the product to natural gas standards. The aim is to reach an energy efficiency of at least 70% from biomass to SNG. Results are presented of tests performed with various catalysts and biomass producer gas at lab-scale (about 1 Nm3/hr). Introduction The production of SNG from biomass starts with the conversion of biomass into syngas or producer gas. The main difference between the two is the presence of methane and other hydrocarbons in producer gas. These allow to reach a higher efficiency from biomass to SNG, as reactions to methane are less exothermal than the reaction CO + 3H2 => CH4 + H2O. However, unsaturated and (poly)aromatic hydrocarbons (= tar) in producer gas make the required gas cleaning more complicated. This paper describes the ECN approach to reach at least 70% efficiency from biomass to SNG and presents results obtained in laboratory tests. Research at ECN ECN is developing the Milena technology for indirect gasification of biomass. Biomass is heated by contact with hot bed material to produce gas and char. Char and bed material are separated from the gas and transported to a combustion zone. There, char is burned with air and the bed material reheated before it is returned to the gasification zone. Steam is supplied to the gasification zone to aid in fluidization of the bed material. The Milena technology is designed to run almost without steam. That increases the thermal efficiency at the expense of a higher tar load. Previously, ECN has developed the Olga tar removal technology which can take care of that problem. Further steps required for SNG production are the removal of gaseous compounds of Cl and S, hydrogenation and reforming of unsaturated and aromatic hydrocarbons, adjustment of the H2/CO ratio, methanation, removal of CO2 and water and final upgrading to a product that is indistinguishable from natural gas. Figure 1 shows an example of the order in which the steps may be performed. Not shown in the figure are heat exchangers and the addition of steam to prevent carbon formation in some of the catalytic reactors. In order to reach the goal of at least 70% efficiency from biomass to SNG, each of the steps has to be optimized separately and in conjunction with other steps. The latter may involve changing the order in which steps are performed or the use of sub-optimum conditions in one step to obtain more favourable conditions in another. In our laboratory, all steps in the process are performed near atmospheric pressure with a gas flow of about 1 Nm3/hr (where Nm3 stands for the volume at 273 K and 1 bar). In the near future, steps downstream Olga will operate at increased pressure. The Milena gasifier and Olga tar removal can be designed for operation at increased pressure, but that will become economic only at commercial scale. The first SNG demonstration unit, scheduled for 2015, will use atmospheric Milena and Olga technology at about 50 MW scale.
4 ECN-L--10-069
Cyclone OLGAChlorine
removal
HDS Absorber Reformer
Multi stage
fixed bed
methanation
Amine
scrubber
Dryer
Milena
SNG
Biomass
steamair ash chlorine
sulphur carbon
dioxide
water
heavy & light tars
dust
Figure 1 Flow scheme of biomass to SNG process using the ECN Milena gasifier. ECN focuses its effort on optimization of the gasification and tar removal technology and intends to use commercially available techniques for gas cleaning and catalytic processes. As the latter are usually developed for different gas and reactor conditions, laboratory tests are needed to select materials and conditions which fit the biomass to SNG process as depicted in figure 1. Figure 2 shows some of the test results which will be presented.
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Test duration [hrs]
Con
cent
ratio
n [%
]
H2 CO CO2 CH4
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Test duration [hrs]
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H2 CO2 CH4 CO
Figure 2 Gas composition downstream the HDS reactor (left) and downstream the multi-stage
methanation (right).
ECN-L--10-069 5
Presentation
www.ecn.nl
High efficiency SNG production from biomass
Luc Rabou
2
SNG = Substitute Natural Gas ≈ CH4
Natural gas ~ 50% of energy use in the Netherlands
SNG from biomass = renewable energy
Biomass => syngas/producergas CH4=>
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SNG advantages
SNG plant
cheap production at large scale
efficient and cheap distribution of gas
easy application
existing gas grid
easy to meet emission limits
high social acceptance
natural gas back-up
distributed use for transport, heat,
electricity
biomass
SNG (Substitute Natural Gas)
CO2 available for storage, EOR, ...
gas storage enables whole year operation
biomass
L. Rabou 2-6-2010
4
10
0
IN(biomass)
OUT(SNG)
NG
€/GJ
5
ECONOMY (for mature technology)
6 €/GJ or 60 €/ton CO2
similar tooff-shore wind,much cheaper than biodiesel
ECN report C-06-019: FT >15 €/GJ
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ECN-L--10-069 7
5
ECN Key technology: MILENA gasifier
• Indirect gasification using little steam => high efficiency
25 kW
800 kW
• Technology in development
• 10 MW planned to start operating in 2012
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Composition of MILENA producer gas
Energy %38
25
17
13
7
-
-
Volume %CO+H2 37
CH4 8
C2H4+C2H2+C2H6 3
C6H6+C7H8+C3Hx+C4Hx 0.8
Tar 0.35
H2O 31
CO2+N2 20
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ECN SNG strategy (downstream MILENA)
• Remove tar by ECN OLGA technology(tar can be used as fuel in gasifier)
Keep other hydrocarbons for conversion to CH4
• Treat producergas at low pressure(~1 - 7 bar)
• Convert to methane at high pressure(~20 - 30 bar)
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SNG system lay-out
-------
---------------
---------1 bar
2006
---------
---------------
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& Cl
ECN-L--10-069 9
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SNG lay-out
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SNG test results 2006
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0 12 24 36 48 60 72 84
Time [hours]
Pre
ssur
e [h
Pa] Pressure drop
SNG reactorsReactors blockedby C-deposition
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Changes since 2006
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• Steam addition
• Hydrogenation of C2H4 (3% db)
• Removal of organic S-compounds (15 ppm db)
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SNG system lay-out
-------
---------------
2009---------
steam
1 bar
---------------
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& Cl
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Thiophene conversion at 1 bar
400
450
500
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600
0 2 4 6 8 10 12
Measurement position
Tem
pera
ture
[°C
]
GHSV 65, 98%
GHSV 40, 99.5%
GHSV 70, 93%
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HDS (side) effects
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• Conversion of thiophene(s), mercaptanes
• Conversion of HCN, pyridine(s)
• Hydrogenation/reforming of CxHy (x = 2 - 4)
• Watergas shift
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SNG test 2009: HDS (1)
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Test duration [hours]
Con
cent
ratio
n [%
]
H2 CO CO2 CH4
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Test duration [hours]
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cent
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n [%
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H2 CO CO2 CH4
HDS in HDS out
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SNG test 2009: HDS (2)
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HDS in HDS out
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Test duration [hours]
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C2H2 C2H4 C2H6
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Test duration [hours]
Con
cent
ratio
n [%
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C2H2 C2H4 C2H6
ECN-L--10-069 13
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SNG test 2009: performance of methanation
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Test duration [hours]
Con
cent
ratio
n [%
]
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H2 CO2 CH4 CO
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SNG test 2009: performance of reformer
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Time in operation [hrs]
Con
cent
ratio
n C
6H6
[ppm
]
0.0
0.5
1.0
1.5
Con
cent
ratio
n C
2H6
[%]C6H6
C2H6
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Conclusions
L. Rabou 2-6-2010
• HDS works at low GHSV and high T
• HDS stable (200 hrs)
• Reformer deactivates quickly
• Methanation stable (200 hrs)
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Future research
L. Rabou 2-6-2010
• Higher pressure
• Better reformer
• Larger scale
• Longer duration
ECN-L--10-069 15
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SNG system lay-out
2015
steam
1 bar
7 bar
20 bar
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HVCtowards BioSNG
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SNG system lay-out
-------
2020steam
7 bar
7 bar
20 bar
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MORE INFORMATION
Luc Rabou [email protected]
Bram van der Drift [email protected]
MILENA indirect gasifier: www.milenatechnology.comOLGA tar removal: www.olgatechnology.comPublications: www.ecn.nl/publications
L. Rabou 2-6-2010
