The Impact of Flue‐gas Desulphurization on the Water Environment

Abstract

ABSTRACTElectricity generation in the UK is dominated by fossil fuels, principally coal. In order to reduce emissions of sulphur dioxide to the atmosphere new fossil fuel‐fired power stations will be equipped with flue‐gas desulphurization (FGD) facilities, and in the short term the Central Electricity Generating Board proposes to retrofit FGD systems to 6000 MW of its coal‐fired generation capacity, including the 4000‐MW station at Drax. The first generation of these plants will be based on the limestone‐gypsum process.In addition to the product gypsum the process generates a liquid effluent as a result of the need to remove chloride from the process inter alia to protect gypsum quality. This effluent also contains other contaminants such as metals, fluoride and nitrate, and a mathematical model has been developed to predict effluent volumes and composition as a function of different coal, limestone and process water combinations. The model also calculates the effect of the discharge of this effluent on a receiving watercourse, both untreated and following treatment based on neutralization and precipitation/sedimentation.The paper discusses the development of the mathematical model and the impact of treated FGD effluent on power station cooling‐water discharges, via which the effluent would normally be discharged, for both once‐through and recirculating cooling systems used at coastal and inland stations respectively.