M.S. Thesis: Gasification: An Alternative Disposal and Energy Recovery Process for MSW
By Alexander Klein
Advisor: Professor Nickolas Themelis
Department of Earth and Environmental Engineering
Fu Foundation School of Engineering & Applied Science
Columbia University
May 2002
The two gasification plants compared in this study utilize unique gas cleaning and gasification technologies to produce a synthesis gas suitable as fuel in a combined cycle turbine. The first plant assessed was designed by TPS Termiska. This process uses partial combustion with air at atmospheric pressure in a bubbling fluidized bed, followed by a circulating fluidized bed vessel containing dolomite that catalytically “cracks” the tars. The TPS system has been operating using 200 tonnes of “refuse-derived fuel” per day (RDF) since 1993 in Italy, sending its product gas to a closely coupled boiler. Battelle-Columbus Laboratories designed the second plant examined in this study. This system is an indirectly heated atmospheric pressure gasifier that avoids nitrogen in the fuel stream and produces a medium BTU gas. The Battelle plant has been licensed by the Future Energy Resources Company and is near the commercial stage for biomass gasification with a capacity of 200 tons/day.
Finally, this paper speculates on the viability of two processes in which gasification takes place in a hydrogen rich environment, known as hydrogasification. The first process generates a 3 methane rich gas that can be transported to a utility and combusted in a gas turbine. The second process reforms the synthesis gas on-site into a relatively pure hydrogen stream that is then fed to a fuel cell stack. This system utilizes the formation of calcium carbonate to provide heat for reforming while capturing carbon dioxide emissions. Both of these processes result in zero emissions to the atmosphere at the plant site.