The Optimal Selection And Numerical Simulation On Optimal Design Of De-NO_x Technologies For MSW Incineration Flue Gas

With the expansion of the city and rapid development of urbanization process, municipal solid waste (MSW) treatment has became a problem can not be ignored. Scince the refuse could be reduced,became harmless and changed into recources under Municipal solid waste incineration, it has became one of the important technologies on waste disposal.But at the same time, the large number secondary pollutants, which were produced from MSW incineration flue gas, would cause serious environmental problems.NOx was one of the main air pollutants in MSW incinerantion flue gas, which was also the main precursor of forming photochemistry fog. It had been a hot research in the international environmental field to control and treat NOx pollution.The optimal selection of flue gas de-NOx technology which was suitable for a MSW Incinerator of 750t/d was studied.The method of numerical simulation had been adopted to simulate the optimal design of de-NOx technologies.The major researech aspects were outlined as the following:1. At first, multi-level comprehensive fuzzy evaluation model which affected by a number of factors was established based on fuzzy mathematics. The model was applied to evaluate the de-NOx technology, which commonly used in foreign waste incineration power plant, from three respects: environmental performance, economic parameters and technical performance. According to the rule of Maximum Membership Value, SNCR was the optimal selection.2. Numerical simulation of gas combustion in the MSW incinerator performed using CFD method. Calculated the distribution of furnace temperature, gas residence time and flue gas composition.The results of calculation could provide the basis for the design of SNCR. Results showed that the operation condition of combustion effieiency was not good without secondary air. Through the optimum arrangement of secondary air nozzles, the combustion of flue gas was in good condition, residence time and temperature of flue gas could meet the demand on the control of dioxin. The conditions in the exhaust heat boiler could meet the requirement on the process of selective non-catalytic reduction.3. Thermal NOx was simulated by using post-processing method. The typical concentration of NOx discharged from wasted incinerators, which used as boundary codition of fule NOx, was provided by Danish company Volund.The concentration distribution of NOx in the waste heat boiler, which was suitable for the design of SNCR, was analysised.4. The last but not the least, selected the waste heat boiler with the elevation of 12m to 25m as SNCR simulation region.The injection of SNCR reducing agent through a single nozzle was simulated by discrete phase model,and the right nozzle which was suitable for SNCR was selected.Multi-nozzle arrangement and jet simulation were finished. According to the simulation results of MSW incinerator combustion and NOx emissions, the impacts of temperature, residence time and distribution of gas component on SNCR were analysised.