Numerical Calculation Of The Cement Kilns System’s Temperature Field For Co-processing Hazardous Waste Under Oxy-combustion Atmosphere

With the increasing pressure of hazardous waste disposal,the cement kiln plays an increasingly important role in the collaborative disposal of hazardous waste due to its advantages.For the disposal system,the temperature field distribution is an important parameter.According to the principle of material balance and energy balance,the temperature field distribution of the collaborative disposal system under the atmosphere of the total oxygen and air combustion is analyzed by numerical simulation,and its thermodynamic efficiency is evaluated.Firstly,the model is established,the calculation strategy is selected and the calculation parameters are set.Then,the main influencing factors of the temperature distribution of the cascade and bypass cooperative disposal system are calculated and analyzed.Finally,the thermal efficiency and exergy efficiency are calculated after selecting a set of comparative parameters for the bypass and cascade systems under air and full oxygen combustion atmosphere respectively.From the analysis of the cooling machine subsystem,it is found that the secondary and tertiary air in the whole oxygen combustion atmosphere can not be designed simply according to the theoretical combustion needs,and the abundance needs to be provided.When the factors other than the secondary and tertiary winds remain constant,increasing the amount of gas passing through the cooler,that is,increasing the amount of the secondary and tertiary winds,will reduce the gas temperature in all parts of the whole disposal system.When,for example,the gas volume of the over-cooler increased from 2.05 to 2.13 kg /(kg ×cl),the gas temperature at the outlet of the rotary kiln decreased from 1515℃ to 1318℃.From the analysis of combustion-supporting atmosphere and system flow,it is found that when the gas quantity of the whole disposal system is equal or similar to that of the two combustion-supporting atmosphere,the temperature distribution of the system under the full oxygen and air combustion-supporting atmosphere is not different,especially at the outlet of the C1 and C2 preheater and the outlet of the decomposition furnace.When the combustion-supporting atmosphere is the same,the temperature distribution of bypass and serial disposal systems is quite different only at the outlet of hazardous waste disposal furnace.For example,in this example,the gas temperature at the outlet of the waste disposal furnace of bypass and serial disposal system is 1417.7 and 963.3℃,respectively.The difference also indicates that the tandem system is superior to the bypass system in terms of temperature control and reducing heat load in rotary kilns.After analyzing the influence of the separation efficiency,carbonate decomposition rate distribution and equipment surface heat dissipation on the system temperature distribution,it is found that when the heat income and expenditure of the cooling machine system remain constant,the temperature of the preheater,disposal furnace,decomposition furnace and rotary kiln will increase and the temperature of the secondary and secondary air will decrease as the calorific value of hazardous waste and pulverized coal continues to increase,the quantity or amount of disposal will increase and the water content of hazardous waste will gradually decrease.As the separation efficiency of the cyclone preheater continues to increase,the temperature of the preheater,disposal furnace,decomposition furnace,and rotary kiln will also gradually increase,and the temperature of the second and third winds will not be affected.When the net decomposition rate of carbonate in a certain part is increased and the net decomposition rate of the downstream part of the part is reduced based on the gas flow direction,the temperature of the part gradually decreases.The temperature of other parts is not affected,and the temperature of the second and third wind is not affected.As the heat dissipation on the surface of the equipment continues to increase,the temperature of the entire disposal system will continue to decreaseAfter calculating the thermal efficiency and thermal efficiency of the system,it is found that the thermodynamic efficiency of the two types of disposal system is relatively close when the auxiliary gas is the same,the thermodynamic efficiency of the system is relatively close when the total oxygen is used as the combustion supporting atmosphere,and the thermodynamic efficiency of the system will be significantly improved if the type of disposal system using total oxygen as the combustion supporting atmosphere is changed to the circulating disposal system.