10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Pollutant Emissions from Steelworks Equipped with Various Flue Gas Desulfurization Systems
QING LI, Di Wu, Xiang Ding, Xianmang Xu, JianMin Chen, Fudan University
Abstract Number: 232 Working Group: Control and Mitigation
Abstract China has been the largest steel producer since 1997, and has accounted for about a half of the total world steel production since 2013. Pollutant emissions from sintering machines of steelworks is one of the largest contributor to China’s PM2.5 pollution. Compared to the great efforts made to limit emissions from coal-fired power plants, the percentage of air pollution control devices installed in steelworks is much lower, e.g. flue gas desulphurization systems (FGD) are used in less than 40% of the steelworks. This is due to less public concern and very complex flue gas composition, which has challenged the current FGD technologies.
This study compares removal efficiencies of various pollutants by using active coke, ammonia, and limestone FGD systems based on field measurements. The three FGD systems were installed to clean flue gases for three typical sintering machines, all of which used the same combustion technologies and fuels. The capacity of sintering machine equipped with the dry FGD system (active coke) is 600 m2, while that of the other two wet FGD system (ammonia and limestone) are both 360 m2. Wet electrostatic precipitators were installed for both wet FGD systems. It was found that the efficiency to remove SO2 was sufficient for all the three FGD technologies (>98%). However, compared to the other systems the ammonia FGD is less efficient in removing SO3, which may contribute to primary particulate matter in the flue plumes. Moreover high concentrations of ammonia (2021 mg/ m3) were observed in the flue plume after the ammonia FGD. These high ammonia concentrations are probably caused by carryover from the ammonia FGD system, and should be addressed in the future. Furthermore, compared to the other systems a higher concentration of soluble ions after ammonia FGD was detected owing to the lower removal efficiency of SO3 and slip of ammonia from the FGD system. Comparing dust concentrations at FGD inlets and outlets, the dust concentration in ammonia and limestone FGD outlets were decreased by 61% and 50%, respectively, while that at the active coke FGD outlet was increased by 5%.
To conclude, although all three FGD technologies are effective in removing SO2, the high rate of ammonia slip from ammonia FGD system should be considered, as well as its low efficiency in removing SO2. According to our results we recommend the limestone FGD technology for cleaning flue gases from sintering machines in steelworks.