In all cases the product gas from gasifier after a

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: duced gas have, therefore, been left out of consideration. Modelling work 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 Biomass Oxygen-blown 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)[20], 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[21]. 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 system. 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...
View Full Document

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.

Ask a homework question - tutors are online