氧化钙添加剂对烟气中汞分布的影响

在一个大气压下，273．15～l273．15K温度范围里，采用化学热力平衡分析方法研究了煤燃烧过程中CaO和HCl对痕量元素汞的形态及分布的影响。化学热力平衡分析结果表明，在煤燃烧的最高温度区域里，单质汞是汞的主要形式。随着在烟气中温度的降低，单质汞将发生化学反应而生成二价汞的化合物，其中主要是HgCl2(g)；预测结果还表明氯元素的增加可以增强汞元素的蒸发、排放，而CaO(s)对汞元素在烟气中的行为特性的影响不大。尽管化学热力平衡分析结果与实验结果之间存在较大差异，但是通过与实验结果的比较，仍可以推断CaO(s)主要是通过减少灰粒表面积或改变飞灰矿物学和形态学特性影响烟气中汞元素分布特性。

The Impact of CaO Additive on Mercury Distribution in Flue Gases

Under the condition of one atmospheric pressure and within a temperature range of 273.15-1 273.15 K the impact of CaO and HCl formed during a combustion process on the morphology and distribution of trace element mercury was investigated through the use of an analytical method based on chemical thermodynamic-equilibrium. The results of the analysis indicate that elemental mercury is the main form of the mercury in the maximum temperature zone of coal combustion. With the reduction of temperature in flue gases the elemental mercury will undergo a chemical reaction, resulting in the formation of a bivalent mercury compound, which mainly assumes the form of HgCl_2(g). The results being forecast also show that an increase in chlorine elements can lead to an increased evaporation and emission of the mercury element. On the other hand, CaO(s) does not exercise a great influence on the behavior characteristics of mercury in the flue gases. There exists a relatively great difference between the results of chemical thermodynamic-equilibrium analysis and those of experiments. In spite of this, a comparison of the two sets of results still allows one to conclude that the CaO(s) has influenced the distribution characteristics of mercury element in the flue gases. This has been brought about mainly through a decrease in ash-particle surface area and or a change in fly ash mineralogical and morphological features.