Study On Drying Characteristics And Catalytic Pyrolysis Characteristics Of Municipal Sludge

As a by-product of urban domestic sewage treatment,municipal sludge has increased with the rapid development of the sewage treatment industry.How to properly handle municipal sludge has become an urgent environmental problem in China.Sludge drying can not only meet the sludge treatment process requirements for sludge moisture content,but also facilitate the storage and transportation of sludge,and it is also a prerequisite for sludge reduction and resource utilization.As a kind of solid fuel utilization method with low pollution and high energy utilization efficiency,sludge pyrolysis can realize sludge reduction and resource utilization.Therefore,this paper carried out the drying and pyrolysis experiments of municipal sludge.The effects of additives(dry sludge,CaO)on the drying characteristics of municipal sludge were analyzed.The variation of carbon and oxygen functional groups and the catalytic effect of CaO in the pyrolysis process of municipal sludge were studied.Firstly,the isothermal drying experiment of municipal sludge was carried out,and the effects of additives(dry sludge,CaO)and blending ratio on sludge drying characteristics were studied.The results show that with the increase of dry sludge blending ratio,the sludge drying rate increases first and then decreases.When the CaO blending ratio is less than 10%,the sludge drying rate increases with the increase of CaO addition amount;when the CaO blending ratio is 10?30%,the sludge drying rate has a significant inhibition point,and this inhibition point changes as the drying temperature increases.Then,the effects of heating rate and CaO blending ratio on the pyrolysis characteristics and pyrolysis activation energy of the sludge were investigated by thermogravimetric analyzer(TG).The experimental results show that the addition of CaO inhibits the release of CO2,reduces the activation energy required for the sludge volatilization analysis stage,and promotes the addition of a weight loss peak in the pyrolysis range of 400?600?,and increases the rate of pyrolysis weight loss in the high temperature range(600?800?).Finally,the rapid pyrolysis experiment of sludge was carried out by thermal cracking-gas chromatography-mass spectrometry(PY-GC/MS).The influence of CaO on sludge pyrolysis products and the changes of carbon and oxygen functional groups during sludge pyrolysis were analyzed.The results show that as the pyrolysis temperature increases,the percentage of the peak area of the carbon-carbon double bond in the pyrolysis product gradually decreases,while the aromatic ring has the opposite tendency;the peak area percentage of the aldehyde group,the carboxyl group,and the hydroxyl group increases in the pyrolysis temperature range of 450 to 650?.The addition of CaO not only promotes the cyclization of aliphatic hydrocarbons to form aromatic hydrocarbons,but also decarboxylation of carboxylic acids to form aliphatic hydrocarbons,and also promotes the decomposition of proteins and increases the yield of nitrogen-containing compounds.