410t/h煤粉锅炉的汞排放及其NID系统除汞特性研究

Characteristics of mercury emission and demercurization property of NID system of a 410t/h pulverized coal fired boiler

对配备有NID系统的410t／h燃煤电站锅炉的煤、底渣、飞灰进行取样，测定了样品中汞的含量。采用Ontario-Hydro方法测定了NID前和ESP后烟气中汞的形态。实验结果表明，汞主要以飞灰形式排放，占总汞量的90％，烟气汞占10％。NID前和ESP后的烟气中，汞的浓度分别为21．3μg/m^3～22．4μg/m^3和1．93μg/m^3～3．67μg/m^3，说明该NID系统对烟气中汞具有相当高的脱除效率，达到83．6％-90．9％。对汞的化学形态研究表明，NID前烟气汞主要以Hg^2＋形式存在，占气态汞量的67％；ESP后烟气中Hg^2＋占气态汞量的71．8％-85．1％，Hg^0的含量为零，说明烟气中Hg^0在NID系统中经历一系列的氧化还原反应后．被氧化成Hg^2＋并吸附脱除。

Coal, slag, and fly ashes were sampled from a 410 t/h utility boiler with the equipment of NID （ Novel Integrated Desulfurization） system and mercury concentrations of these samples were determined. Ontario-Hydro method was applied to determine mercury speciation in flue gas before NID and after ESP. The experimental data indicate that the majority of mercury goes into fly ash. The ratio of mercury quantity in fly ash to total combustion product is about 90% , while that in flue gas is about 10%. The results also show that before NID and after ESP, the gaseous mercury concentration in the flue gas is about 21.3 μg/m^3 - 22. 4 μg/m^3 and 1. 93μg/m^3 -3.67 μg/m^3 respectively, indicating that the NID system has quite high mercury removal efficiency up to 83.6% - 90.9%. The percentage of Hg^2＋ which is the main mercury speciation in flue gas before NID is about 67%. The percentage of Hg^2＋ in flue gas after ESP is about 71.8% -85.1%, while the content of Hg^0 is zero, indicating that some chemical reactions have been happened to Hg^0 when it passes by NID system. Hg^0 becomes Hg^2＋ and is then adsorbed and removed.