SO_xMitigation Technologies for Combustion Systems

Abstract

SO x emissions from coal‐fired plants cause harmful impacts on the environment and human being health. To limit SO x emissions, air pollution control regulations have been established on international and national levels, and industrially relevant SO x mitigation technologies have been rapidly developed and applied over the past few decades. In this article, fluidized bed combustion ( FBC ) for in‐furnace DeSO x , dry sorbent injection ( DSI ), spray drier absorber, circulating dry scrubber ( CDS ), and wet scrubber processes are comprehensively discussed. The wet scrubber process is the most widespread SO 2 mitigation technology around the world and is reviewed in detail. The chemistry of wet scrubber processes is analyzed. Four typical wet scrubber configurations are presented. Wet scrubber operational challenges are shortly discussed. The DSI process is comprehensively discussed as well. In this process, fine and dry sorbents are directly injected into flue gas to capture SO x and other acid gases. In the CDS process, flue gas flows upward through a fluidized bed of sorbents to create a long contact time and have good mass transfer conditions. The spray drier process uses an atomizer to generate fine droplets to contact and react with SO 2 . The regenerable processes are presented, in which sorbents are regenerated. The absorbed SO 2 is further processed to sealable elemental sulfur or sulfuric acid products. Finally, an outlook of recent and future developments and challenges for SO x mitigation technologies is given. Even though different effective SO x mitigation technologies are available, the economics of their application are dominated by many factors, such as emission limits, fuel quality, sulfur content, size of plant, firing system, availability of sorbents, and utilization of by‐products. Therefore, a case‐by‐case evaluation is recommended to find the most suitable flue gas desulfurization ( FGD ) process for a particular application.