DEHALOGENATION OF PYROLYSIS PRODUCTS

During pyrolysis of chlorine-containing materials, it is necessary to trap the HCl formed to avoid re-formation of organochlorine compounds and to prevent corrosion in the plant. This is usually done using limestone, but the resulting mass streams cause many difficulties. These mass streams, which increase with the amount of organochlorine compounds, were the main reason for the shut down of the technical pilot plant in Ebenhausen. When ammonia is added to the fluidizing gas during pyrolysis NH3.HCl is formed, passes the cyclone at temperature above 450 degrees C and is collected behind the cyclone. In contrast to dechlorination with limestone, this procedure causes only small mass streams. The chlorine content remaining is less than 1000 p.p.m. To reduce it to less than 10 p.p.m. sodium is added to the product gases at temperatures of about 500 degrees C behind the cyclone. Educts containing small amounts of PCB, and polychlorinated dioxines and furanes were also pyrolyzed. The economy of pyrolysis depends on the costs of plastics disposal and of plastics incineration, compared with the cost of pyrolysis, which is believed to be 250 DM/t.