Emission characteristics of condensable particulate matter and sulfur trioxide from coal-fired power plants

Abstract

Non-criteria air pollutants, namely, sulfur trioxide (SO3) and condensable particulate matter (CPM), are attracted more attention due to the non-negligible emission. In this work, the migration and emission characteristics of SO3 and CPM were investigated in two typical coal-fired power plants using the isopropanol absorption method and the dry impinger method, respectively. One of the power plants was equipped with two-stage wet flue gas desulfurization (WFGD) and the other one was self-generation power plant using Zhundong coal equipped with one-stage WFGD. The mass concentrations of SO3 and CPM were measured at the inlet and outlet of the air pollution control devices. To further understand the removal characteristics, the chemical compositions in organic and inorganic fractions of CPM were analyzed. Based on the measurement data, the emission factors of CPM and SO3 were calculated. The final emissions of SO3 range from 2.16 to 2.29 mg•Nm−3 and the emission factor is 0.024–0.040 kg/(t of coal). The stack emissions of filterable particulate matter all meet the ultra-low emission standard and are less than 5 mg•Nm−3. However, CPM emissions all exceed 10 mg•Nm−3 and account for more than 85% in total particulate matter. CPM concentrations are notable and the emissions should not be ignored. In both power plants, WFGD and wet electrostatic precipitator can reduce the emission of organic fraction in CPM; while one-stage WFGD has negative effect on the mitigation of inorganic fraction in CPM with the concentrations of water-soluble ions NH4+, SO42- and Cl− increasing by 41.37%, 52.22% and 91.73%, respectively.