Selection of air pollution control technologies for power plants, gasification and refining processes

Abstract

Air quality legislation in South Africa is entering a transformation phase, shifting the concept of atmospheric emission control towards pollution prevention and emission minimisation through a more integrated approach. This transformation, along with public pressure and increased foreign trade, is providing industries with incentives to consider their effect on the environment and to take action where required. To assist South African industries in determining what air pollution control technologies are best suited to power plants, gasification and refining processes in South Africa; an assessment of air pollution control technologies used in other countries was carried out. This assessment concluded that the best available technologies for power plants to control air emissions are electrostatic precipitators, low-NOx burners, selective catalytic reduction systems and wet flue gas desulphurisation (limestone) systems. For gasification processes it was found that the main air pollution contributor is the gas handling and treatment process. Releases from this process are controlled through dust collection, wet scrubbing, conversion of sulphide compounds, sulphur recovery and the incineration of final vent gases before release to the atmosphere. For refining processes the catalytic cracking unit is normally the largest single air emission source and controlling emissions from this unit avoids controlling multiple minor sources. Emissions from this unit are controlled via wet scrubbing, selective catalytic reduction systems and carbon monoxide boilers. An assessment of the financial effects associated with air pollution control at power plants was conducted by completing a cost analysis. This analysis demonstrated that by increasing capital expenditure on control technologies by R 1,7 billion, the external costs associated with producing electricity can be reduced by almost R 3,4 billion. Formulation of external cost factors for South African conditions, and the development of a software database for the information obtained from the different countries, will promote future technology selections.