چكيده به لاتين
One of the most important problems of urbanization is growing trend of waste generation. Therefor reduction of waste production and proper disposal procedures are essential. Combustion in moving grate incinerators occurs in two regions of bed and freeboard zone which the required air enters in two stages, primary air in bed and secondary air in freeboard zone. In this thesis, a developed fixed bed gasifier model is used for modeling the bed region and for freeboard region a thermodynamical combustion model is used while effects of secondary air distribution and fluid dynamics are not considered. Continuity, energy, pressure drop and state equations are solved for bed region. After designing the furnace by semi-empirical corelations, a multiobjective optimization is done to minimize two objective functions, grate surface area and furnace volume with a constant range of flue gas temperature to reduce the production costs and required installation place. Optimum grate surface area and furnace volume for a 3000 kg/hr incinerator with equivalence ratio 0.4, fuel heating value 18 MJ/kg and air temperature 300 K are 22 m2 and 74 m3 respectively. The effects of fuel nitrogen on composition of produced gases are studied and it was found that for fuels with high content of nitrogen, it is better to consider its effect. The effects of performance parameters such as equivalence ratio of primary and secondary air, primary air temperature, air inlet pressure and velocity, length of reduction zone, flue gas recirculation on exhaust gas temperature and furnace efficiency are studied. Also the effect of radiation from frreboard zone and fuenace walls on gas composition and temperature is investigated. Results show that with increasing the radiation intensity, the temperature of bed gases will increase and it causes gas composition change which leads to an increase of H2 and CO and decrease in N2 and CO2 production.
