Combustion Characteristics And Numerical Simulation Of Blended Sludge In Power Plant Boilers

With the rapid development of urbanization in China,the output of municipal sludge is increasing day by day.How to deal with municipal sludge has gradually become a growing concern.Sludge,as one of the main pollutants in sewage treatment,has a high content of water and organic matter.Organic matter is generally perishable,and it contains environmental pollutants such as pathogenic bacteria,parasites and pathogenic microorganisms.If not properly treated,it will easily cause secondary pollution to the environment.At present,the common treatment methods are:direct discharge of the sea,land landfill,land use,heat drying and combustion.Among the various sludge treatment methods,the direct combustion method of sludge has the advantages of fast processing speed,short storage time,no need for long distance transportation,obvious capacity reduction effect,and can be used for power generation and heating.On the basis of experimental research,this paper uses numerical simulation method to study sludge blending under different mixing ratio and water content,and determines the optimal mixing ratio and water content of sludge blended in power plant.This paper studies the pyrolysis combustion characteristics of sludge and its mixture with pulverized coal through thermogravimetric analysis and other experimental methods.The pyrolysis combustion characteristics of sludge at different heating rates were investigated.At the same time,the combustion characteristics of the mixture of sludge and pulverized coal were studied.The results show that:when the sludge is pyrolyzed in N₂ atmosphere,there are three obvious peaks of weight loss,which correspond to the stages of water precipitation,volatilization analysis and the decomposition of remaining organic matter.When the sludge is burned in the air atmosphere,there are mainly two obvious weightlessness peaks,which respectively correspond to the precipitation and combustion of the first type of volatiles in the sludge,and the combustion and fixed carbon combustion of the second type of volatiles.When the mixed samples of sludge and pulverized coal were burned in the air atmosphere,the shoulder peak of the original single pulverized coal was gradually divided into two peaks with the increase of the mixture ratio of sludge and pulverized coal.In this paper,the ignition point and volatilization temperature of sludge were calculated by TG-DTG curve,providing boundary conditions for subsequent numerical simulation.Then,on the basis of the experimental study,using the method of numerical simulation,the study on the sludge combustion of Xuzhou China resources power co.,LTD.330MW boiler was carried out under the conditions of different combustion ratios and varying water content.The content of CO and CO₂ decreased,the content of O₂ increased,the content of thermal NOx decreased,and the content of fuel NOx increased.When the combustion ratio reaches 40%,the furnace can no longer maintain the normal combustion,so it is recommended that the power plant combustion sludge can not exceed 30%.The content of CO and CO₂ increases,the content of O₂ decreases,the content of thermal NOx increases,and the content of fuel NOx does not change much.When the moisture content is reduced to 40%,the temperature in the furnace increases obviously,which is beneficial to improve the combustion effect.Therefore,it is suggested that when mixing and burning sludge in power plants,proper drying treatment should be carried out in advance before the sludge is sent into the furnace through the belt.The moisture content of sludge should be controlled within 40%.In this paper,experimental study and numerical simulation of sludge blending in power plant boilers are carried out to provide suggestions and suggestions on sludge blending ratio and water content for future power plant boilers.