北京市燃煤锅炉烟气中水溶性离子排放特征

Emission Characteristics of Water-Soluble Ions in Fumes of Coal Fired Boilers in Beijing

选择北京市典型烟气脱硫除尘净化工艺的燃煤锅炉,分析和评估了其烟气中水溶性离子的排放水平、排放特征及其影响因素.北京市燃煤锅炉水溶性离子平均基准排放质量浓度最高51.240 mg·m-3,最低7.186 mg·m-3,且水溶性离子排放水平与烟气含湿量无关.SO2-4作为脱硫反应的特征产物是北京市燃煤锅炉烟气排放共有的主要特征离子,其排放量占离子排放总量的63.8%~81.0%;F-是燃煤电厂烟气排放的又一特征离子,其排放量占离子排放总量的22.2%~32.5%.烟气净化工艺对水溶性离子的排放水平和特征有显著影响,Na+是添加脱硫剂Na OH的特征离子;NH+4和NO-3是脱硫剂NH4HCO3的特征离子,Mg2+是作为Mg O脱硫剂的特征离子,但脱硫剂Ca O/Ca CO3未增加Ca2+的排放.燃煤电厂锅炉烟气中排放的NH+4和NO-3显著低于其他工业与供暖锅炉.烟温对水溶性离子的形态分布有显著影响,水溶性离子在烟温高时以超细模态存在而不易被滤膜捕集.

Selecting coal fired boilers with typical flue gas desulfurization and dust extraction systems in Beijing as the study objects,the issues and characteristics of the water-soluble ions in fumes of coal fired boilers and theirs influence factors were analyzed and evaluated. The maximum mass concentration of total water-soluble ions in fumes of coal fired boilers in Beijing was 51. 240 mg·m- 3in the benchmark fume oxygen content,the minimum was 7. 186 mg·m- 3,and the issues of the water-soluble ions were uncorrelated with the fume moisture content. SO2-4was the primary characteristic water-soluble ion for desulfurization reaction, and the rate of contribution of SO2-4in total water-soluble ions ranged from 63. 8% to 81. 0%. F-was another characteristic water-soluble ion in fumes of thermal power plant,and the rate of contribution of F-in total water-soluble ions ranged from 22. 2% to 32. 5%. The fume purification technologies significantly influenced the issues and the emission characteristics of water-soluble ions in fumes of coal fired boilers. Na+was a characteristic water-soluble ion for the desulfurizer Na OH,NH+4and NO-3were characteristic for the desulfurizer NH4HCO3,and Mg2 +was characteristic for the desulfurizer Mg O,but the Ca2 +emission was not increased by addition of the desulfurizer Ca O or Ca CO3.The concentrations of NH+4and NO-3in fumes of thermal power plant were lower than those in fumes of industrial or heating coal fired boilers. The form of water-soluble ions was significantly correlated with fume temperature. The most water-soluble ions were in superfine state at higher fume temperature and were not easily captured by the filter membrane.