水泥窑共处置含Cr废物中Cr在不同温度下的形态转化

将Na₂CrO₄加入生料中模拟含Cr入窑物料〔掺加比例为0.048%(以w计)〕,以探索水泥窑共处置含Cr废物过程中Cr的形态转化. 将含Cr入窑物料在不同温度条件下进行煅烧,消解煅烧样品以分析Cr在不同温度下的残留率并利用XANES(X射线吸收近边结构光谱)技术分析煅烧样品中Cr的存在形态. 结果表明:对应900、1000、1100、1200、1300和1450℃煅烧条件下,熟料中Cr的残留率分别为88.2%、70.7%、73.7%、67.2%、69.5%和67.8%. 由于窑尾温度为1050～1100℃,并且Cr的残留率在1100℃较高,因此从窑尾添加含Cr废物可以减少水泥窑共处置含Cr废物过程中的Cr逸放. 在900～1450℃煅烧条件下,所有样品中的Cr主要以CrO₃、Cr₂O₃和CaCrO₄的形式存在. 1000℃煅烧温度下存在K₂Cr₂O₇,但不存在K₂CrO₄；900℃和1100～1300℃煅烧温度下有K₂CrO₄存在,但不存在K₂Cr₂O₇. 1100～1450℃煅烧温度下,Cr元素进入到水泥熟料的主要矿物中,并主要以CrO₃和Cr₂O₃的形式与其他物质结合生成了较为复杂的Ca₄A₁₆O₁₂CrO₄、Ca₆Al₄Cr₂O₁₅等. 

Form Transformation of Cr during Co-Processing Waste Contained Cr in Cement Kiln at Different Temperatures

In orde to discover the form migration of Cr during co-processing hazardous wastes contained Cr,Na₂CrO_4was added to the raw material simulation Cr-containing material into the kiln (the mixing ratio is 0.048%(w)). The raw material mixing with Na₂CrO_4was calcined at different temperatures. The residual rate of Cr was studied by digestion of samples calcined. The chemical forms of Cr were obtained by X-ray absorption near edge structure (XANES). The results showed that, the conditions of Cr clinker residual rates were 88.2%, 70.7%, 73.7%, 67.2%, 69.5% and 67.8% at temperatures of 900-1450℃. The kiln tail of temperature was 1050-1100℃ and was closed to 1100℃, at the temperature of 1100℃. Therefore, it reduced the disposal of Cr during co-processing waste in the cement kiln adding waste at the kiln tail. Cr mainly existed in the forms of CrO₃,Cr₂O_3and CaCrO_4under the conditions of 900-1450℃. In addition, K₂Cr₂O_7was produced under the condition of 1000℃ and K₂CrO₄was produced under the conditions of 900,0,1200and 1300℃. Cr entered into the main cement mineral combined with other substances to generate more complex Cr-containing substances such as Ca₄Al₆O₁₂CrO_4and this material was mainly in the form of CrO_3and Cr₂O₃under the ranges from 1100℃ to 1450℃.