Trends in the control of NOx and SOx combustion emissions: Implications to the design of fluidised bed combustion operations

This paper attempts to review the implications of the sulphur oxides (SOx), nitrogen oxides (NOx) and nitrous oxide (N₂O) emissions to the design of fluidised bed combustion (FBC) operations. The review focuses on how the knowledge of SOx and NOx emissions trends can be applied to influence the design of FBC operations. The effects of the emission trends of these noxious gases on the design operations for FBC such as temperature control, nozzle designs, sorbent selection design, air supply and control designs were reviewed. The implications of SOx, N₂O and NOx emissions on the design of FBC systems rest primarily on the need to design the operational conditions of the system. The design for the precise location of the fuel feeding ports, secondary air feeding ports, limestone feeding ports and a prescribed size and quantity of sorbents to feed into the system was found to be crucial for reduction of these emissions. The emissions also have an impact on the design of the distributor plate of the system; reduction of the emissions necessitates good fluidisation and well-regulated temperature within the system. The review therefore concludes that there is a close nexus between the design and operation of FBC systems with NOx, N₂O and SOx emissions.