Kinetic study of thermal de-chlorination of PVC containing waste

With the increasing of plastics content in solid waste, both municipal and industrial, also increases the interest in its use as an energy source. Some of these wastes are an important potential source of energy and might be valorized using the pyrolysis or gasification processes. However, the presence of high chlorine contents in its composition prevents its management by a thermal process, as consequence of toxic compounds production and their release to the atmosphere. The present work asses a possible process for treating PVC-containing wastes in an environmentally friendly way. It is based on the effective de-chlorination of PVC-containing wastes through a pyrolysis process at low temperature before the carbonaceous residue from PVC-containing wastes being subject to a subsequent thermal treatment for energetic valorization.QREN (NORTE-01-0202-FEDER-011447

Energetic valorisation of PVC-containing waste

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