WASTE TYPES MUNICIPAL SOLID WASTE
Plasma pyrolysis or plasma gasification is a waste treatment technology that gasifies matter in an oxygen-starved environment to decompose waste material into its basic molecular structure. It uses high electrical energy and high temperature created by an electrical arc gasifier and does not combust the waste as incinerators do. This arc breaks down waste primarily into elemental gas and solid waste (slag), in a device called a plasma converter. The process has been intended to be a net , depending upon composition input wastes, and to reduce the volumes of waste being sent to landfill sites. Relatively high voltage, high current electricity is passed between two electrodes, spaced apart, creating an electrical arc where temperatures as high as 13,871°C are reached. The temperature one meter from the arc can reach ~4000°C. At these temperatures most types of waste are broken into basic elemental components in a gaseous form, and complex molecules are atomized - separated into individual atoms. The reactor operates at a slightly negative pressure, meaning that the feed system is complemented by a gaseous removal system, and later a solid removal system. Depending on the input waste (plastics tend to be high in hydrogen and carbon), gas from the plasma containment can be removed as Syngas, and may be refined into various fuels at a later stage. Dioxin emissions are possible from plasma arcs when chlorine is present although the extremely high temperature at which plasma gasification operates minimizes the possibility. Process gas cleanup can be necessary when gasifying waste streams such as municipal waste streams known to contain heavy metals, chlorine/fluorine, sulfur, etc. The basic thermodynamics indicates that the electricity costs will be unavoidably high when processing wet wastes such as municipal wastes, using plasma power alone. Plasma is considered a 4th state. It may be noted that at this stage, they pose a considerable technological and budgetary challenge to construct a municipal-waste disposal sized plasma arc facility. An issue regarding plasma systems that rely on high temperatures for processing is in the life of their liners. The liner is an important aspect of separating the high interior temperatures of the plasma system from the [metal] shell of the plasma container. Liners are highly susceptible to both chlorine attack and to local variability in [high] temperatures, both of which would be found with typical municipal waste systems, and are not likely to last than a year in service.
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