Analysis of chlorine behavior in the high temperature waste treatment process and the reduction of the chloride compounds

焙烧法是处理含重金属和氯化物的飞灰的一种技术。随着有毒阳离子（汞，镉，铅，铬，镍，和钴）的存在下，这些元素的高排放水平是由与Cl自由基的重组诱导。由于环境污染和腐蚀性问题，近年来HCl的排放一直是人们关注的问题。目前的研究内容主要集中在通过改善燃烧条件和添加添加剂来控制HCl的排放，而对Cl_2的行为研究相对较少。主要目的是研究氯和氯化合物的行为。此外，还建立了该反应体系的详细动力学模型，并用流动反应器的实验结果进行了验证，Cl自由基是由HCl和O_2的碰撞反应产生的，它是整个反应过程的起始反应。在相对有限的O_2浓度范围内，Cl_2浓度随O_2浓度的增加而增加，反应HCl +O_2→Cl+HO_2是引发该体系链式反应的Cl自由基的主要来源。高温下产生的Cl自由基在冷却过程中最终形成HCl和Cl_2。增加HCl和不加H_2O两种实验结果表明，在不同的氯含量下，重金属的蒸发与分配比HCl更容易发生。在由SiO_2、Al_2O_3、PbCl_2、ZnO、CuO、CaCl_2和Fe_2O_3组成的实验样品中，氯浓度由CaCl_2的比例控制。结果表明，在此条件下，较高的Cl含量有利于Pb的挥发，Pb化合物的适宜回收温度为973K以下。

As one of the cleanup technologies of fly ash including some heavy metals and chloride compounds, a roasting method is being developed. With the presence of toxic cations (Hg, Cd, Pb, Cr, Ni, and Co), high emissions level of these elements is induced by the recombination with Cl radical. Due to the environment pollution and corrosive problem, the emission of HCl has been a subject of concern in recent years. Most of research contents focus on controlling the emissions of HCl by improving combustion conditions and adding additives, however, a relative little attention is paid on the behavior of Cl_2. The main purpose is to investigate the behaviors of chlorine and chloride compounds. In addition, a detailed kinetic model of this reaction system is developed and validated against experimental results obtained from a flow reactor.Cl radicals are originally produced from the collision reaction of HCl and O_2, which initiates the overall reaction process. Within a relative limited range of O_2 concentration, Cl2 concentration is increasing with O_2 concentration.The reaction HC1+O_2→Cl+HO_2 is the main source of Cl radicals which initiate the chain reaction of this system. The Cl radicals generated at high temperature finally form HCl and Cl_2 during the cooling process. The two experimental results, increasing HCl and without H_2O, indicate that the formation of Cl_2 is more likely to proceed than the formation of HCl.The experiments on heavy metals vaporization and partition with different chlorine content were performed in a drop tube furnace (DTF) with air condition. The chlorine concentration was controlled by the proportion of CaCl_2 in the experimental samples which were composed by SiO_2, Al_2O_3, PbCl_2, ZnO, CuO, CaCl_2 and Fe_2O_3. According to this result, more fraction of Cl makes Pb to vaporize easily and the suitable recovery temperature for Pb compounds is below 973K in this case.