水泥窑协同处置过程中重金属挥发流向规律模拟

SIMULATION EXPERIMENT STUDY OF HEAVY METALS’ VOLATILIZATION AND FLOW RULES DURING CO-PROCESSING OF CEMENT KILN

采用自主研发的静态实验设备和小型水泥回转窑模拟装置,分别模拟静态和动态条件下生料中不同类型重金属在不同温度、反应时间下的挥发特性及流向规律。重金属Pb、Zn、Cd的挥发率均随着温度升高而逐渐升高,同温度下窑煅烧气氛下生料中Pb、Zn、Cd及As的挥发率均低于空气气氛下的挥发率;As挥发率随温度升高先逐渐升高后逐渐减少,重金属氯化物挥发率较高。添加重金属的生料粉在800℃以下的温度煅烧后,物料中主要的晶相为CaCO_3、SiO_2及金属氧化物,CaMg(CO_3)_2的衍射峰主要存在600℃以下。由800℃开始,CaCO_3发生分解,并出现CaO衍射峰;从1 000～1 400℃下,生料粉在重金属作用下逐渐生成较为复杂的化合物。在动态模拟条件下,熟料中As、Cd、Pb及Zn的平均固化率分别为85.48%、83.19%、84.49%、85.20%。绝大部分重金属均存在于熟料中,而挥发到大气中的重金属仅为0.002%～0.2%。

Volatile characteristics and flow rules of different heavy metals in raw meals under different temperatures and response time in static and dynamic status were simulated respectively,by the independently-developed static experimental equipment and small simulator of rotary cement kiln.The volatilization rates of Pb,Zn and Cd all increased with the increase of temperature,and the volatilization rates of Pb,Zn,and Cd and As at the same temperature in kiln calcination atmosphere were all below the corresponding rates in air atmosphere ;the volatilization rate of As increased with the "increase of temperature and then decreased gradually,and the heavy metal chlorides had a high volatilization rate.The main crystalline phases in raw meals doped with tleavy metals after calcination below 800℃ were CaCO3,SiO2and metallic oxides,and the diffraction peak of CaMg(CO3)2mainly appeared in the raw meals after calcination'below 600℃.At 800℃ ,decomposition of CaCO3began and was accompanied by diffraction peak of CaO ;during 1000-1400℃ ,more complex compounds were gradually generated in the raw meals under the action of heavy metals.Under the dynamic simulation condition,the average solidification rates of As,Cd,Pb and Zn in the clinker were 85.48%,83.19%,84.49%and 85.20%,respectively.Most of the heavy metals existed in the clinker,while only 0.002%-0.2%were volatilized into the air.