Sulfur trioxide removal performance of alkaline sorbents injection in the temperature range 400–705 °C: a pilot‐scale study

Abstract

AbstractBACKGROUNDSulfur trioxide (SO3) in coal combustion flue gas can adversely affect power plant equipment and the environment. In this work, the removal of SO3 with typical sodium (Na), magnesium (Mg) and calcium (Ca)‐based sorbents was investigated at a pilot‐scale facility in the temperature range 400–705 °C.RESULTSThe injection of sodium bicarbonate (NaHCO3) showed the highest SO3 removal efficiency, which was ∼85% at the sorbent/SO3 molar ratio of 2 with the gas residence time of 1 s. This is much higher than that of calcium hydroxide (Ca(OH)2) (∼25%) and magnesium hydroxide (Mg(OH)2) (∼30%). The removal efficiency of Mg(OH)2 and Ca(OH)2 increased with increasing the reaction temperature from 400 to 705 °C. With the addition of 800 ppm sulfur dioxide (SO2), the adsorption of SO3 on alkaline sorbents was inhibited due to the competitive adsorption, which caused SO3 removal efficiency to decrease by 5–12.5%. When injecting the sorbents in slurry form, the removal efficiency was found to be two times higher than that in powder form.CONCLUSIONNaHCO3 is the most effective sorbent comparing to Mg(OH)2 and Ca(OH)2. To increase the SO3 removal efficiency, the alkaline sorbents should be injected in the high temperature zone in flue gas. It is recommended to inject the sorbents in slurry form instead of injecting powders directly to achieve high removal efficiency. © 2019 Society of Chemical Industry