Energetic valorisation of PVC-containing waste

Abstract

Wastes are increasingly regarded as important sources of energy, particularly their polymeric component. However, most of these wastes contain polyvinyl chloride (PVC) in their composition, constraining the use of a thermal valorization process in their treatment [1]. This work aims the development of a process for the material and energetic valorization of the PVC-containing wastes. A two-step process was firstly defined and tested at a laboratory scale and subsequently its feasibility evaluated by a factorial plan of tests performed in a pilot plant designed and built in the aim of the Project PVC4GAS. The pilot plant consists of a reactor, with a stainless steel body heated by electrical resistances, a column to clean the produced gas and three sequential columns to fixed the released chlorine before the gas burn. Initially, a slight vacuum is created in the reactor to remove most of the oxygen trapped inside the reactor, and subsequently the test is performed in two stages. The first stage consists of a low-temperature pyrolysis (400±10 ºC) or carbonization, for the de-chlorination of the PVC-containing waste. The resulting carbonaceous residue is energetically valorized at temperatures above 550ºC, in a second stage of the process. The results from these tests showed that the temperature of 800 ºC leads to a gas with better powerful properties. The main process product is a synthesis gas with fuel power, which might after treatment by low temperature pyrolysis, be used in different types of equipments as substitute of traditional fuels. Hydrochloric acid and a coke with carbon content higher than 37% are also generated during the developed process.