CONDENSATION AND ABSORPTION KINETICS OF THE CEMENT RAW MEAL ON LEAD AND CADMIUM AT LOW-TEMPERATURES DURING CO-PROCESSING IN CEMENT KILNS

This paper studied the condensation and absorption characteristic of the cement raw meal for Pb and Cd in lead and cadmium chloride through a coupling device of a rotary tube furnace and a vertical furnace with automatic temperature control． Ｒesults showed that heavy metal vapor in the flue gas mainly condensated on the surface of cement raw meal at lowtemperatures during co-processing in cement kilns． Heavy metals ( Pb、Cd) into the experimental furnace could be divided into three parts: Condensation on the wall of the vertical furnace，occupying approximately 60% for Pb，and 60% for Cd; condensation and absorption on the cement raw meal，occupying lower than 30% for Pb，and 20% ～ 30% for Cd; releasing into the atmosphere，which occupies less than 20% for Pb，and approximately 10% for Cd． The condensation and absorption of the cement raw meal for Pb and Cd both increased with time，but decreased as the temperature increase． The condensation and absorption kinetics could be well described by the double constant rate equation，and the apparent activation energy of Pb was 5. 013 kJ /mol，and Cd was 5. 071 kJ /mol．