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Unformatted text preview: duced gas have, therefore, been left out of consideration.
A block scheme of the stand-alone SNG production systems is presented in figure 6. In
all cases the product gas from gasifier, after a low-temperature cleanup, and passing
through a methanation step, is used for the production of SNG as main product. Heat / steam Indirect
gasification O2 / steam
gasification Pre-treatment Hydrogen Gas cleanup Methanation Gas
conditioning SNG Hydrogasification Fig. 6 SNG production by biomass (hydro)gasification / methanation processes.
In order to determine the mass and energy balances of these processes, three
Aspen Plus models were developed. The operating temperature of the gasifiers is
850°C. The gasifier pressure is respectively 1 bar for indirect gasification, 15 bar for
oxygen- blown gasification, and 30 bar for hydrogasification. In case of indirect
gasification, the product gas after cleanup is compressed to 15 bar, before entering the
methanation section. In case of pressurised options a CO2 stream is used as
pressurisation gas. The cleanup step consists of a dust filter, deep tar removal with the
ECN oil-based gas washer (the OLGA unit), water scrubbing for removal of NH3
and halides, and guard beds for final protection of methanation catalyst. The
methanation process is based on the inter-cooled methanation process, used within the
Lurgi coal-to-SNG process. The conditioning step consists of gas cooling and ECN-RX--04-085 10 drying, followed by partial removal of CO2 (if necessary), in order to bring the Wobbeindex of the gas within the Dutch natural gas specification (i.e. between 43.46 and
44.41 MJ/Nm3). The heat generated at various points in each process is used for steam
and electricity generation in a steam cycle, in order to satisfy the demand within the
Some of the modelling results are presented in table 1 and table 2. The results
show that the upstream atmospheric steam-blown indirect gasification and pressuris...
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This essay was uploaded on 03/18/2014 for the course ENG 316K taught by Professor Kruppa during the Spring '08 term at University of Texas at Austin.
- Spring '08
- Chemical Engineering