The influence of oxygen on the steam gasification of PVC

A promising option for PVC-recycling is hydrothermal recycling, where PVC is thermally converted in a steam atmosphere into hydrogen chloride, hydrogen, carbon dioxide, carbon monoxide and some gaseous and liquid hydrocarbons. Hydrogen chloride gas can be recovered for reuse and the product gas will be used for energy recovery. Gasification with only steam is an endothermic reaction. Partial combustion of PVC by addition of small amounts of air enables autothermic operation of the process. This work deals with the effects of addition of air on the gasification products, comparing endothermic operation with autothermic and exothermic operation. Partial combustion decreases the caloric value of the product gas. Oxidation with air results in a higher yield of carbon dioxide in the product gas and consequently in a lower yield of carbon monoxide and also hydrogen. Oxygen is mainly involved in gas reactions, converting hydrogen to water and carbon monoxide to carbon dioxide. Emission of PCDDs and PCDFs are very low, with and without addition of air. No increase in the emissions of these highly toxic compounds is observed upon the addition of air.