What are the effects of high flue gas dust concentration on CaCO3 desulfurization?

When the dust concentration at the inlet is below 200 mg/Nm3, the dust has no impact on desulfurization; however, if the dust concentration exceeds 250 mg/Nm3, it will affect the desulfurization system. The reason is as follows: a. If the dust concentration is too high, it will affect the activity of the desulfurization agent, which is manifested in two aspects: first, dust is alkaline, and if its concentration is too high, it will hinder the dissolution of limestone, thereby being unfavorable for desulfurization ； Secondly, some metal ion elements in the dust react with hydrogen fluoride, hydrogen chloride, etc. to form complexes that adhere to the surface of limestone, preventing the limestone from reacting with SOX and thus increasing the consumption of calcium carbonate. b. Excessively high dust concentrations can also affect subsequent dewatering and the quality of gypsum. Since the main function of a desulfurization tower is to remove SOX, the dust removal function is incidental; it mainly occurs in two areas: one is at the bottom of the desulfurization tower, where dust is absorbed by the circulating slurry ； The other is at the top of the desulfurization tower, where the dust is removed by a secondary demister. Although these two dust removal steps are employed, the final dust removal efficiency of wet flue gas desulfurization is only 75%; therefore, for flue gas with a dust content of over 250 mg/Nm3, the emission standards cannot be met even after passing through the desulfurization tower. Therefore, it is essential to control the dust content in the flue gas entering the desulfurization tower. For flue gas whose dust concentration remains high (>250 mg/Nm3) even after passing through the electrostatic precipitator, the electrostatic precipitator must be modified. Installing a sulfur trioxide flue gas conditioning system is the best option, as it can reduce the specific resistance of dust, improve dust collection efficiency, and lower the dust content in the exhaust gas, which is highly beneficial for the subsequent desulfurization system.