溴元素对烟气中汞的形态和分布的影响

Effect of Bromine on Speciation and Distribution of Mercury in Flue Gases

采用化学热力平衡分析方法研究了煤燃烧过程中溴对烟气中痕量元素汞的形态及分布的影响.在一个大气压下,25～825℃温度范围内,研究了汞-煤-溴系统中高氯煤和低氯煤在添加溴前后汞化学形态和分布的变化,着重探讨了溴对汞在烟气中的形态和分布的影响.对于高氯煤,当烟气中加入溴后,氯化汞的分布区域明显受到了抑制;而对于低氯煤,氯化汞和单质汞的分布区域均明显受到抑制,且溴化汞的最大生成量所对应的温度有所下降.随着烟气中O2(g)含量的增加,HgBr2(g)的生成量显著减少;烟气中的SO2(g)体积分数变化对汞形态分布的影响不明显.化学热力平衡分析结果表明,溴化汞的生成主要取决于烟气中Br2(g)的含量.

An equilibrium analysis has been carried out to determine in detail the speciation and distribution of mer-cury in flue gases during coal combustion.Calculations are done for the Hg-coal-Br system.The effect of bromine on the speciation of mercury was studied under the condition of one stand air pressure and within the temperature range of 25—825 ℃.The results show that,with the addition of bromine,the formation of HgCl2（g）is inhibited for high Cl coal,and the formation of both HgCl2（g）and Hg（g）is inhibited for low Cl coal.The temperature for the maximal HgBr2（g）formation in case of low Cl coal is lower than that in case of high Cl coal.As the O2（g）content increases,HgBr2（g）observably decreases.SO2（g）hardly changes the speciation of mercury.The chemical thermal equilibrium analysis results show that the formation of HgBr2（g）is mainly dependent on the Br2（g）content.