Plasma gasification uses an external electric source for heat and this results in the conversion of feedstock to fuel gas and the elimination of all tars, chars, and dioxins due to high temperatures. Unlike the reactors described above, plasma reactors are applied more to MSW and as shown in an earlier section they can be easily adapted to process a mixed feedstock including other types of waste such as rubber tires, polymer and plastic waste, and coal waste. The amount of electricity and temperature in the plasma reactor depends on the reactor configuration, energy content of the feedstock, and amount of air (or oxygen) allowed in the reactor. A plasma reactor can pro­duce a variety of products by careful control of reaction conditions.

Westinghouse Plasma manufactures and supplies plasma torches to the industry. The Westinghouse Plasma gasifier is essentially a classic downflow moving bed system operating at 1 atm and about 2,300°F. Various types of plasma reactors described in the previous chapters can also be used for pro­cessing the mixed feedstock.

In addition to Westinghouse, the Solena group uses the Solena gasifier which locates the torch at the bottom of the gasifier to vitrify inorganics in the feed, forming glass aggregate. This reactor uses less energy, and it also uses a carbon-based catalyst to enhance gasification. This group is planning to develop a 10 MWe plant in Malaysia using Padi husks and a number of 130 MWe integrated plasma gasification combined cycle plants in the east­ern United States to use waste coal and coal fines in partnership with Stone and Webster [107, 108]. Startech Environmental Corporation (SEC) is also developing a plasma gasification unit that feeds shredded materials using a pump, screw, or ram, depending on the consistency of the feed. In this reac­tor, the plasma torch is located at the top of the reactor and is then directed to dissociate organics and to melt inorganics in the feed, forming clean gas and glass aggregate. Acid gases, volatile metals, and particulate matter are removed from the cooled gasifier effluent. Starcell™ technology can also pro­duce hydrogen. SEC is also planning a 200 T/D MSW plant in Panama jointly with Hydro-Chem (a division of Linde) and a 10T/D plant in China [6].