水泥窑共处置过程中砷挥发特性及动力学研究

针对不同形态的含As化合物开展了热重实验、熟料煅烧以及熟料消解实验,研究了水泥窑共处置过程中砷在等温条件下随时间的挥发特性和可能的化学反应.结果表明,不同化学形态的砷挥发规律不尽相同,砷酸钠在水泥生产涉及的温度区间基本不挥发;硫化亚砷在水泥窑共处置的过程中,砷的挥发率随时间逐渐增大,25min以后基本不再挥发,低于1000℃时,砷的挥发率随温度的升高而增大,但高于1000℃时,挥发率随温度的增大而减小;亚砷酸钠在1000℃以上的挥发规律与硫化亚砷类似,挥发率随温度的升高而减小,25min以后基本不再挥发.硫化亚砷在1000℃以下煅烧时,挥发率随时间和温度变化的动力学方程为a =1-exp[-1.77exp(-3158/T)t],可以根据此方程计算不同温度和停留时间工况下砷挥发的理论值,进而控制含砷废物的投加量,避免对环境造成危害.

Volatilization characteristics and dynamics research on arsenic during co-processing in cement kilns

Arsenic compounds in different chemical forms were added to cement raw materials to produce clinkers. Thermogravimetric analysis, clinker sintering and clinker digestion were conducted to investigate the volatilization characteristics of arsenic related to time under isothermal conditions and possible reactions during co-processing of hazardous wastes in cement kilns. The results indicate that the volatile law varies with different chemical forms. The volatility of arsenic in sodium arsenate is small within the temperature range producing clinker. The volatilization proportion of arsenic in orpiment during co-processing increases with time, and after 25min, it does nearly not increase. And the volatilization proportion of arsenic in orpiment increases as temperature increases at temperatures below 1000℃, but decreases as temperature increases at temperatures above 1000℃. The volatile law of arsenic in sodium arsenite at temperatures above 1000℃ is similar to orpiment, that is the volatilization proportion decreases with the increase of temperature, and after 25min it does nearly not increase. The volatilization kinetics equation of arsenic in orpiment which indicates the relation between the volatilization proportion and temperature and time was obtained: α=1-exp[-1.77exp (-3158/T)t]. Through the calculation of theoretical values of arsenic volatilization at different temperatures over different time periods, the feeding quantities of arsenic wastes can be controlled to avoid environmental pollutions.