Modeling of arsenic migration and emission characteristics in coal-fired power plants

Abstract

After coal combustion, the minerals present in fly ash can adsorb arsenic (As) during flue gas cooling and reduce As emissions. However, a quantitative description of this adsorption behavior is lacking. Herein, the As adsorption characteristics of minerals (Al/Ca/Fe/K/Mg/Na/Si) were investigated, and a model was developed to predict As content in fly ash. Lab-scale experiments and density functional theory calculations were performed to obtain mineral As adsorption potential. Then, the model was established using lab-scale experimental data for 11 individual coals. The model was validated using lab-scale data from ten blended coals and demonstrated acceptable performance, with prediction errors of 2.83–11.45 %. The model was applied to a 350 MW coal-fired power plant (CFPP) with five blended coals, and As concentration in the flue gas was predicted from a mass balance perspective. The experimental and predicted As contents in fly ash were 11.92–16.15 and 9.61–12.55 μg/g, respectively, with a prediction error of 17.39–22.29 %, and those in flue gas were 11.52–16.58 and 5.37–34.04 μg/Nm3. Finally, As distribution in the CFPP was explored: 0.74–1.51 % in bottom ash, 74.05–82.70 % in electrostatic precipitator ash, 0.53–1.19 % in wet flue gas desulfurization liquid, and 0.13–0.73 % in flue gas at the stack inlet.