水泥窑协同处置过程低温段铅和镉的吸附/冷凝动力学研究

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

对铅、镉两种重金属的氯化物(Pb Cl2、Cd Cl2)开展了吸附/冷凝实验研究。利用管式回转炉和控温立式炉联用装置研究了铅、镉在水泥生料上的吸附冷凝特性。结果表明:在水泥窑共处置的低温段水泥生料对重金属铅、镉的吸附冷凝作用主要以冷凝为主。进入吸附冷凝炉的重金属可以分为三部分,第一部分冷凝在管壁上,该部分Pb含量占进炉总铅的60%左右,Cd占进炉总镉的60%;第二部分吸附/冷凝在生料上,该部分Pb含量占总铅比例低于30%,Cd为20%~30%;第三部分随烟气释放到空气中,该部分Pb比例低于20%,Cd占10%左右。水泥生料对Pb、Cd的吸附冷凝量随时间的增加而增加,随温度的升高而降低。水泥生料对Pb、Cd的吸附冷凝特性可用双常数速率方程拟合,拟合效果较好,得到Pb的活化能为5.013 k J/mol,Cd的活化能为5.07 k J/mol。

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 k J / mol,and Cd was 5. 071 k J / mol.