Thermal Plasma Waste Treatment

Thermal plasma treatment of wastes exhibits specific performance characteristics. The energy delivered by plasma is used for melting and vitrification of inorganic materials and for gasification of organic substances. The principal goal of gasification is the production of fuel gases, principally the mixture of carbon monoxide and hydrogen, called syngas. Alternatively, the production of hydrogen together with solid carbon (carbon black, nanoparticles) is produced if oxygen is not present in input substances. The main role of plasma is the transport of energy needed for the endothermic process of material decomposition, control of reaction temperature, and supply of chemical components needed for reactions. The governing mechanisms in a plasma reactor are heat transfer from plasma to material, decomposition of material and dissociation of molecules, and chemical reactions between all components at controlled temperature. Three processes—pyrolysis, gasification, and plasma-aided combustion, which differ by the relative concentrations of carbon and oxygen atoms, are described. The energy balance of a plasma treatment process is discussed. The model of heat transfer from plasma to treated material is presented and the effect of heat transfer on the process rate is discussed. Examples of gasification of several organic wastes in steam plasma are presented.