Simulation And Control Of Multi Pollutant Formation Process Of Cement Kiln Mixed Sludge

With the continuous progress of urbanization,the waste from industrial production and daily life gradually causes pollution problems.As a product of urbanization process,improper disposal of municipal sludge is very likely to cause secondary pollution,endangering the environment and human health.Synergistic treatment of municipal sludge by cement kiln is one of the effective ways to realize sludge resource utilization,reduction and harmless.Therefore,it is of great significance for industrial production and environmental protection to study the emission characteristics of flue gas from cement kiln after mixing municipal sludge in the production process.Based on the formation process of multi pollutants in the flue gas of cement kiln,this paper systematically analyzes the calcination process of cement kiln burning municipal sludge and the reaction mechanism of flue gas treatment process.Utilize Aspen Plus establishes a simulation model for the generation and treatment process of multi-pollutants in cement kiln mixed with municipal sludge;based on the simulation model,the effects of different combustion conditions,temperatures and combustion atmosphere on the concentration of multi-pollutants are compared;meanwhile,in order to carry out in-depth research on the actual cement kiln flue gas pollutant treatment system,the field test method is adopted.By changing the amount of ammonia injection into the kiln and the amount of sludge burning,the data of SO₂concentration,NO_xconcentration and ammonia escape concentration are obtained,and the partial correlation analysis method is used to analyze the data.Conclusions are as follows:（1）Through the test data,it is verified that the simulation model of the generation and treatment process of multi pollutants from municipal sludge in cement kiln is reliable.The results show that:the relative error of combustor/calciner and rotary kiln model with the actual results is less than 8.5%,the simulation results of five stage cyclone preheating system and flue gas treatment system are in good agreement with the actual measured values,and the error value is less than 5%,which can better reflect the actual situation of the real cement kiln burning municipal sludge.（2）Burning municipal sludge will reduce the temperature and NO_xconcentration in the calciner of cement kiln,increase the concentration of SO₂and NH₃,and increase the moisture content of sludge will reduce the concentration of SO₂and increase the concentration of NO_x.Burning sludge in cement kiln can reduce the temperature from 968℃to 920℃;at the same time,municipal sludge burning in decomposing furnace can decompose ammonia nitrogen compounds and sulfides contained in sludge;and with the increase of sludge burning amount,the concentration of SO₂and NH₃in flue gas will increase,while the concentration of NO_xwill decrease.（3）The oxygen concentration of the decomposition furnace affects the formation of NO_xand SO₂in flue gas,while the formation of CO reducing atmosphere will inhibit the formation of NO.The excess air coefficient changes from 1.05 to1.25,NO_xconcentration increases from 200mg/m³to 448mg/m³,SO₂concentration decreases from 425mg/m³to 230mg/m³,CO concentration changes from 26mg/m³to 990mg/m³,NO_xconcentration decreases from 585mg/m³to 154mg/m³.（4）In the kiln calcination of 6000t cement per day,the concentration of NO_x,SO₂and NH₃can be effectively controlled by controlling the amount of sludge mixed with 12 t/h,limiting the excess air coefficient in the furnace to 1.15 and forming a strong reducing atmosphere in the furnace.（5）The NO_xemission concentration can be effectively reduced by controlling the amount of combustion and ammonia injection in SNCR system.The desulfurization system can effectively reduce the ammonia escape and remove SO₂.Bag filter has a strong effect on removing dust particles.The dynamic change of SNCR system has the greatest influence on NO_xconcentration,the correlation between them is-0.595,the influence on SO₂concentration is small,and the correlation between them is 0.145;the change of sludge system for collaborative treatment has the largest influence on NO_xconcentration,and the correlation between them is-0.742;the dynamic change of wet desulfurization system has the greatest influence on SO₂concentration,and the correlation between them is-0.33.The above research methods and conclusions have certain reference and guiding significance for multi pollutant control of cement kiln industry mixed with municipal sludge.