Gasification of municipal solid waste in the Plasma Gasification Melting process

A new waste-disposal technology named Plasma Gasification Melting (PGM) was developed. A pilot PGM reactor was constructed in northern Israel. The reactor is an updraft moving-bed gasifier, with plasma torches placed next to air nozzles to heat the incoming air to 6000 degrees C. The inorganic substances of the feedstock are melted by the high-temperature air to form a vitrified slag in which undesirable materials such as heavy metals are trapped. The residual heat in the air supplies additional heat for the gasification process. A series of tests were conducted to study the performance of PGM gasification. The plasma power was varied from 2.88 to 3.12 MJ/kg of municipal solid waste (MSW), and the equivalence ratio (ER) was varied from 0.08 to 0.12. For air and steam gasification, the maximum steam/MSW mass ratio reached 0.33. The composition of the syngas product was analyzed in all tests; the lower heating value (LHV) of the syngas varied from 6 to 7 MJ/Nm(3). For air gasification, the syngas LHV decreased with increasing ER, whereas the gas yield and energy efficiency increased with ER. When high-temperature steam was fed into the reactor, the overall gas yield was increased significantly, and the syngas LHV also increased slightly. The positive effect may be attributed to the steam reforming of tar. In air and steam gasification, the influence of increased ER on syngas LHV was negative, while the effect of increased plasma power was positive. The maximum energy efficiency of the tests reached 58%. The main energy loss was due to the formation of tar. (C) 2011 Elsevier Ltd. All rights reserved.