Incineration plant

Description Your team works for a company that provides electricity to the grid through the incineration of household waste. Establish the likely aspects and impacts of the plant and carry out an analysis of these considering the likely risks to the environment. In the light of the information critically appraise the overall environmental position of such processing of waste. The company is investigating the prospect of widening the scope of the types of waste that can be processed at the plant and is looking at new fluidised bed technology. A local University has been studying the impact of such technology on emissions of N2O and NOx. Their findings are shown after carrying out a study at a partner incineration plant in Austria. Examining the figures provided for the trials, indicate what the ideal conditions might be for minimum N2O production in terms of operating temperature and free O2 levels. The Austrian plant, for cost reasons, runs at an operating temperature of 850 oC. The university has calculated that predicted N2O levels will be that due to temperature plus that due to the level of free O2 present during combustion. In other words:- Total N2O = N2O due to Temperature + N2O due to free O2 Incineration Plant Background Information On average, the company produces 550 to 750 kilowatt-hours of electricity per ton of waste, by the incineration of waste from the locality. This waste is termed municipal solid waste or MSW. Combustion of MSW is the complete oxidation of the combustible materials contained in the solid waste fuel, and the process is highly exothermic. During combustion of solid waste, several complex processes happen simultaneously. The chamber containing the waste is heated to evaporate moisture and volatise the components of the waste mixture. Combustion then begins once the gases given off by the waste are ignited in the presence of air. This is highly exothermic. The process leads to the conversion of waste fuel into flue gas, ash and heat. The heat released is used to produce a high-pressure superheated steam from water, which is sent to the steam turbine that is coupled with a generator to produce electricity. Leftover ash, now a cement-like product, is then taken off to line landfill.