Study On Sludge Drying And Combustion Emission Characteristics

China's economic development is gradually accelerating under the influence of the global environment.The rapid growth of the economic volume accompanied by the dense urban population has gradually highlighted the problem of environmental pollution,which has received extensive attention from the government and all sectors of society.The increasing sewage discharge brings great burden to the work of the sewage treatment plant.Sludge is an extremely complex heterogeneous body,which is mainly composed of organic residues,inorganic particles,colloids and a large number of bacterial populations.Because the sludge contains a large amount of water and very rich organic substances,it provides an ideal living environment for bacteria,parasites and bacteria that are not conducive to human health,leading to their concentration in the sludge.At the same time,highly toxic organic and heavy metal pollutants and other harmful substances are also concentrated in the sludge.For these substances,if not properly handled,it will cause very serious secondary pollution to the environment.Therefore,it is particularly important to provide a reasonable and effective sewage treatment system for sewage treatment plants through research.At the same time,a large number of scholars and experts have carried out a series of studies on how to rationally use sludge as a new resource.This paper focuses on sludge in cities and towns.A series of analytical methods,such as thermogravimetric analyzer and thermostatic oven,are used to systematically study the pyrolysis characteristics and drying characteristics of sludge,the product of sewage treatment.The thermostatic drying model of sludge was scientifically put forward by constructing kinetic parameters.In addition,the changes of each component before and after sludge drying were analyzed,and the flue gas emission during sludge combustion was detected by horizontal tubular furnace and flue gas analyzer.And the static heat and mass transfer process of sludge drying is simulated by the mathematical model of thermal,wet and gas-coupled transfer of layered sludge.The pyrolysis characteristics of sludge were analyzed and studied by means of thermal analysis technology.The results show that there are two significant weightlessness peaks in the pyrolysis process.In 200?-400?range,the first stage of weightlessness.Then in400?-600?range,the second phase of weightlessness.However,under N₂atmosphere,the sludge pyrolysis process has three obvious weightlessness peaks.Compared with air atmosphere,the temperature corresponding to the weight loss peak of pyrolysis in N2 atmosphere is higher.The drying temperature at 140?,CO and SO2 emission in the process of drying were rising in the beginning,there was significant increase,to keep time to 10 min to stability.Drying at 160?and 180?temperature,SO2 and CO have been near the maximum fluctuation;Compared with the sludge elemental analysis before and after drying,the mass content of all elements decreased,the mass content of C fluctuated the most,the mass content of O was reduced compared with that before drying,and the mass content of N,S and H was not significantly reduced compared with that before drying.The difference in temperature of the drying temperature is 10?,the drying temperature increased from 160?to170?high calorific value of the loss is far lower than the drying temperature from170?to 180?high calorific value loss;The CO emission peak of sludge was on the right side of the CH4 peak,in line with the sequence of combustion reaction.In the later stage of combustion,with the increase of temperature,the CO release gradually decreases,which is due to the increase of temperature,and the sludge begins to burn completely.Meanwhile,the dynamic process of sludge drying was simulated by introducing a drying model.The change of sludge drying characteristic with temperature is obtained by a whole set of sludge drying experiments,and the Logarithmic kinetic models of three sludge drying properties are compared.The results showed that the drying rate of sludge increased with the increase of temperature,and the drying stage of sludge in this experiment was mainly completed in the deceleration stage.At the same time,by comparing the simulation results,it is Logarithmic model that most fits the sludge drying process.Using the expression of Arrhenius relation and FICK diffusion law,the diffusion coefficient and activation energy of sludge can be calculated accurately.The static heat and mass transfer process of sludge drying was simulated by the mathematical model of thermal,wet and gas-coupled transfer of layered sludge.With the increase of drying temperature,drying temperature of the drying time and decreases the adjacent,sludge,the best drying temperature should be between 160?to 170?.At the same time,the heat loss of sludge should be reduced as much as possible.The purpose of this paper is to provide reference and guidance for the influence of sludge pretreatment and combustion in xuzhou municipal sludge burning project.