Study On Characteristics Of Air Gasification Tar Of Fluidized Bed Sewage Sludge

The gasification tars of S1-650#?S1-750#?S1-850#were obtained by the.air gasification of indigested sludge S1 from A2/O process at 650??750? and 850 ? in a fluidized bed;and the gasification tars of S2-650#?S3-650#and S4-650#were obtained by the air gasification of digested sludge S2 from A2/O process,indigested sludge S3 and digested sludge S4 from activated sludge process at the gasification temperature of 650 ?.The influence of the gasification temperature and sludge nature on the yield,chemical compositions andcombustioncharacteristicof gasification tar were studied by GC-MS andthermogravimetricAnalysis.The yields of sludge gasification tars decrease with gasification temperature increasing,and the yields of the tars from the gasification of anaerobic digestion sludge are lower than that from indigested sludge.The chemical compositions in sludge gasification tar can be divided into five categories:aliphatic compounds,alicyclic compounds,aromatic hydrocarbons,aromatic hydrocarbon derivatives andheterocyclic compounds.When the gasification temperature of the indigestion sludge from A2/O process are increased,the yields of aliphatic and alicyclic compounds decrease,and aromatic hydrocarbon derivatives increase,while the yields of aromatic hydrocarbons and heterocyclic compounds increase firstly and then decrease.At the gasification temperature of 650?,the yields of the five kinds oforganiccompoundsin the tar from the digestion sludge from activated sludge process are lower than that from the indigestion sludge from the same process,and the yields of aliphatic compounds,alicyclic compounds,aromatic hydrocarbon derivatives and heterocyclic compounds in the tar from the the digestion sludge from A2/O process are lower than that from the indigestion sludge from the same process,while the yields of aromatic hydrocarbons are higher that from the indigestion sludge.The results of combustion thermogravimetric analysis show that the combustion processes of the six kinds of gasification tars all can be divided into three stages:the first stage is the volatilization and combustion of light organic matter with the highest weight loss;the second stage is decomposition and combustion of heavy organic matter with a smaller weight loss;the third stage is combustion of a small amount ofcarbonresiduewith the smallest weight loss.The results of combustion kinetics of the gasification tars show that the reaction order of the first and second stages of the gasification tar were different,but all are between 1 and 2.5.The activation energy ofthe first stage of six kinds of gasification tars are all lower than that of the second stage.The values of activation energy of the first stage of the combustion process of the six gasification tars are all less than 30 kJ·mol-1,which shows that all of them have good combustion performance.