Operation Optimization Of Municipal Solid Waste Incinerator Based On CFD And Emission Characteristics Study By Experiment

Incineration, due to its advantages of volume reduction, harmlessness and resources,gradually becomes the mainstream way for harmless disposal of Municipal solid waste（MSW）. In recent years, MSW incineration is popularized and applied rapidly in China. Thenew MSW incineration power plants show two major characteristics of large scale of handlingcapacity and strictness of pollution control. Rapid development of MSW incineration needsthe corresponding support of theory and technology. The combustion and heat transfercharacteristics of the MSW incinerator, the optimization of operation and design, and thecharacteristics of flue gas emissions are all helpful to provide guidance and help, and it is ofgreat significance for the localization of MSW incineration equipments.CFD technique, with low cost, efficient, time-saving and free of building the bench, iswidely used in engineering for prediction, equipment design and troubleshooting. In this paper,the characteristics of combustion and heat transfer of a large scale MSW incinerator wasstudied by CFD technique. Combined with the simulation results in MCR conditions, theoperation optimization and structural optimization to the MSW incinerator was carried out byadjusting the part of the operating parameters and changing some local structure of incinerator.Secondly, the feasibility of co-incineration sewage sludge in a MSW incinerator was studied,and the effect of co-incineration to the operation stability of incinerator was analyzed. Finally,the emission characteristics of combustion synthetic MSW under different temperatures andatmospheres were studied using an electrically heated tubular furnace.Bed calculation software FLIC and commercial CFD software Fluent were combined forthe numerical simulation on the combustion and heat transfer of the MSW incinerator. Theresults well predicted the temperature, velocity, flue gas concentration fields of the MSWincinerator, and the residence time of flue gas. The results of the operation optimization showthat, compared to the parameter setting of MCR conditions, appropriately reduce the air ratioof PA:（SA+OFA）, or slightly enhance the air ratio of OFA-1: OFA-2, or slightly reduce thetotal excess air ratio, can improve the effect of combustion heat transfer, and keep the originaldesign values of the air ratio of four primary air chambers, SA: OFA and SA-1: SA-2canachieve the best effect. The results of the structural optimization show that when two layers ofdual-rotating arrangement of OFA nozzles are adopt, and the OFA spray angles are α₁=40°and α₂=35°, can achieve comprehensive optimization of the organization of flue gas in thefirst flue. And compared to resetting the SA nozzles position or changing the SA nozzlesdiameter, the case maintaining the original SA nozzles arrangement, can achieve the best mixing and combustion effect.The study on co-incineration sludge verified the feasibility of co-incineration sewagesludge with MSW in a MSW incinerator. This study indicates that co-incineration wet sludgeresults in significantly delay in the combustion process, so the co-incineration ratio is low.Co-incineration semi-dried sludge which has lower moisture content, only slightly delays theignition point and the pyrolysis starting point, shortens the pyrolysis stage and advances thechar combustion stage, so a larger proportion of semi-dried sludge can be co-incinerated.Fuel NO_xfrom the oxidation of volatile-N and char-N are the main sources of NO_xemission during the combustion of MSW. As the furnace temperature increases, the startingtime of pyrolysis stage shifts forward, the combustible gases concentration in the flue gasdecreases with the rapid increase of combustion rate, and the NO_xemission increases first andthen decreases. Due to the absent of prompt NO_xand thermal NO_x, and intensification of NO_xdestruction reaction, CO₂/O₂atmosphere is more suitable than N₂/O₂atmosphere forcontrolling NO_xemission around the operation temperature of MSW incineration equipments.