超低排放燃煤电站三氧化硫的迁移和排放特征

采用美国环保署(USEPA)method 8推荐的方法,对典型超低排放燃煤电站满负荷工况下的燃煤、烟气、飞灰、渣进行三氧化硫监测.实验结果表明:燃煤电站超低排放环保设备对三氧化硫的总脱除率为71.86%,大气三氧化硫排放浓度为1.5 mg·m~(-3)(气体体积为标准大气压下的体积,下同).选择性脱硝催化剂(SCR)前烟气中三氧化硫生成量为二氧化硫的0.46%,在SCR催化剂SO_2/SO_3的转化率为0.58%,空气预热器内气态三氧化硫浓度显著降低.低温电除尘(LLT-ESP)内三氧化硫与飞灰结合得到脱除,LLT-ESP细灰中三氧化硫含量为粗灰的1.38倍.湿法脱硫系统(WFGD)对三氧化硫的脱除率为48.45%.超低排放燃煤电站大气三氧化硫排放因子EF_煤、EF_电分别为17.13 mg·kg~(-1)、4.41 mg·kW~(-1)·h~(-1).估算2018年我国燃煤电站三氧化硫大气排放总量约为3.99万t·a~(-1).

Migration and emission of sulfur trioxide in ultra-low emission coal-fired power plant

To investigate the emission and migration of sulfur trioxide in an ultra-low (ULE) coal-fired power plant operating with full load, the method 8 released by U.S. Environmental Protection Agency (USEPA) was used for sampling and measuring the sulfur trioxide concentrations in coal, flue gas, fly ash and bottom ash. It is found that the removal rate of sulfur trioxide by the air pollution control devices (APCDs) is 71.86%. The clean flue gas emitted to the atmosphere has a sulfur trioxide concentration of 1.5 mg·Nm^-3. Sulfur trioxide accounted for 0.46% of total sulfur dioxide (SO₂) in the flue gas before selective catalytic reduction (SCR) and the SO₂-to-SO₃ conversion rate in the SCR is 0.58%. The concentration of gaseous sulfur trioxide decreased significantly in the air preheater. In the Low-low temperature electrostatic precipitator (LLT-ESP), the sulfur trioxide was removed by attaching to the fly ash. The content of sulfur trioxide in fine ash is 1.38 times of that in coarse ash. The removal rate of sulfur trioxide in wet flue gas desulfurization (WFGD) is 48.45%. The coal-specific emission factor is 17.13 mg·kg^-1 and the electricity-specific emission factor is 4.41 mg·kW^-1·h^-1 in the ULE power plant. In China, the total sulfur trioxide emitted to the atmospheric from coal-fired power stations was estimated to be 39900 tons in 2018.