SO2 Absorption by Multiple Biomass Ash Types.

Abstract

As the severity of environmental pollution continues to increase and ultralow emission standards are proposed, biomass power plants must implement additional processes to control SO2 emission. Biomass ash can be utilized as a sorbent for flue gas desulfurization because of its strong alkalinity. In this study, the characteristics of SO2 absorption in simulated flue gas using four types of typical biomass ashes were studied in fixed bed experiments. The results showed that the addition of water, the increase in water vapor, and the lower temperature were beneficial for SO2 absorption. The main components of wheat straw ash are KCl and SiO2, cotton stalk ash is rich in K2O and calcium compounds, poplar bark ash has a considerable content of calcium compounds, and corncob ash contains large amounts of KCl and K2O. Alkali substances, such as oxides or carbonates of potassium and calcium, play a crucial role in SO2 absorption. The SO2 removal effect of corncob ash was the best owing to the abundance of potassium oxides. Meanwhile, wheat straw ash performed worst in SO2 removal due to the small amount of K2O and Ca. The desulfurization products were mainly potassium and calcium sulfate.