| As the urbanization process increases,the rate of urban sewage treatment increases year after year and the production of sewage sludge increases dramatically.Using the existing municipal waste incineration system,sludge can be blended and burned as a low-quality fuel in waste-to-energy plants to achieve efficient and low-pollution co-disposal.However,the sludge blending ratio has a significant impact on the combustion stability and pollutant emissions in the furnace,thus limiting the sludge blending ratio.In addition,the blending of sludge causes the SNCR system in the incinerator to deviate from the design operating conditions,so the optimization of the SNCR based on the sludge characteristics and blending ratio is important to improve the denitrification efficiency in the furnace.Therefore,in this thesis,the Flic bed combustion control software is coupled with Fluent numerical simulation software to carry out numerical simulation and SNCR optimization adjustment of municipal domestic waste and municipal sludge blending incineration with three different capacity waste incinerators commonly used in Guangdong Province,with the objective of efficient and low pollution utilization of municipal domestic waste and municipal sludge.The study aims to determine the optimum sludge blending ratio for different capacity incinerators and the optimal SNCR operating parameters under blending conditions.The main research elements of the thesis include:(1)Analyze the flue gas composition of sludge blending combustion based on gas chromatography experiments;the combustion characteristics,and pollutant emission characteristics under different sludge blending ratios(3%,5%,7%,10%,13%,17%)are investigated by tube furnace experiments and flue gas testing.(2)Simulate the combustion characteristics of waste and sludge blending in an incinerator and its adaptation to three different capacities(350t/d,750t/d and 900t/d)of incinerators.Simulation models of the three mainstream incinerators are developed and validated in terms of accuracy and validity in conjunction with field operation data.On this basis,the adaptability of each incinerator to waste blending with sludge fuel and the effect of sludge blending on the incinerator ignition point location,chamber temperature distribution characteristics,NOx generation,and emission patterns are analyzed.(3)Simulation of SNCR analysis and optimal adjustment for different sludge blending conditions in three different capacity incinerators Based on the adaptability of the incinerator to sludge blending and the characteristics of the chamber temperature,turbulence and residence time in the high temperature zone,SNCR analysis is carried out for each operating condition and the SNCR lance structure arrangement,number,ammonia to nitrogen ratio and reductant particle size are optimized to improve SNCR denitrification efficiency while reducing ammonia escape.Research has found that:(1)when the incinerator body remains unchanged,the removal of the front wall bending flames and rear arch bending angles improves the flow field distribution,temperature field distribution,and combustion product generation in the chamber while improving the fuel adaptability of the incinerator and increasing steam production.(2)Sludge blending is effective in reducing the ignition point temperature of the fuel and regulating the location of the ignition point on the grate.The adaptability of different capacity incinerators to the same fuel varies and requires a combination of incinerator construction,temperature,flow field,and pollutant emission distribution to be matched and there is an optimum fuel configuration.Optimizing the configuration of the secondary air can help diversify the fuels to meet the incinerator in the "3T principle" of combustion.(3)Taking into account the emission control of pollutants from large capacity incinerators,the corrosion of high-temperature heated surfaces of flue equipment,and the distribution of components and temperatures within the furnace,it is recommended that the maximum sludge blending ratio for 750t/d incinerators should not exceed 13% and for 900t/d incinerators should not be higher than 10%.(4)A certain amount of sludge blending is beneficial to reduce the emission of NOx pollutants,and the number of SNCR lances and layers arranged for sludge blending combustion is positively correlated with the capacity of the incinerator under the "3T principle".The number of lances and the arrangement of multiple layers are both effective measures to improve the de-combustion efficiency,taking into account the temperature and flow field distribution of the sludge blending combustion.The results of the study provide theoretical guidance and data reference for the design of series incinerators with efficient combustion and low pollution emissions. |
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