Study On Characteristics Of Steam Liquefied Tar Of Sewage Sludge Fluidized Bed

The generation characteristics of sludge gasification tar was studied by the sludge fluidized bed steam gasification experiment.The chemical compositions and pyrolysis characteristics of tar was studied by Gas Chromatography-Mass Spectrometer(GC-MS)analysis and TG-DTG-DSC thermoanalysis respectively.According to the organic carbon skeleton,the organic compounds in tar are classified as alicyclic hydrocarbons,aromatic hydrocarbon compounds(1-ring aromatic hydrocarbons and polycyclic aromatic hydrocarbons),aromatic hydrocarbon derivatives(aromatic-N and aromatic-O)and heterocyclic compounds(heterocyclic-N,heterocyclic-O and heterocyclic-S),and the influence of gasification temperature and S/B(steam to biomass ratio)on the yield and chemical compositions of tar was also studied.The results show that the yields of tar increase with S/B value and gasification temperature(S/B=1.1?1.5)improving.The yields of polycyclic aromatic hydrocarbon in the tar present increase with the increase of gasification temperature and increase with the increase of S/B value at 800 ? and 850 ?.At 800 ?and 850 ?,the main compositions of aromatic hydrocarbon derivatives and heterocyclic compounds in the tar are aromatic-N and heterocyclic-N and the yields of them are decreased with the increase of gasification temperature at S/B value 1.5.In view of the same parent compound or chemical groups of organic compound with similar field of application,the aromatic hydrocarbon compounds,aromatic hydrocarbon derivatives and heterocyclic compounds in tar are classified as aromatic hydrocarbon compounds(Indenes etc.),nitrogen-containing compounds(Pyridines etc.),oxygen-containing compounds(Phenols etc.)and sulfur-containing compounds by the same parent compound and chemical groups,and the influence of gasification temperature and S/B on the distribution characteristics of chemical compositions of tar was also studied.The results show that the chemical compositions of aromatic hydrocarbon compounds of tar include phenanthrenes and naphthalenes etc,among them the yield of phenanthrenes and naphthalenes reach maximum at 850 ? when the S/B value is 1.1,1.5 and 1.9.Indoles compounds is the main chemical compositions of nitrogen-containing compounds,which yield present decrease with the increase of gasification temperature at S/B value 1.5 and 1.9;the major compositions of oxygen-containing compounds is phenols compounds,which yield increase with the increase of S/B value at 750 ?;the major compositions of sulfur-containing compounds is 4,4'-bis(tetrahydrothiopyran)and naphtho[1,2-b]thiophene only be detected under the gasification condition of 850 ? and S/B value 1.9.The aromatic hydrocarbon compounds of tar are majorly consisted of two and three rings of aromatic hydrocarbon compounds and the yield of two and three rings of aromatic hydrocarbon compounds present increase with the increase of gasification temperature at S/B value 1.1.The formation mechanism of aromatic hydrocarbon compounds in gasification tar are mainly include the discharge of polycyclic aromatic hydrocarbons in the sludge,cracking of primary tar,Diels-Alder reaction,C4 path,C3 path,hydrogen abstraction carbon addition,cyclodehydrogenation,phenyl addition/cyclization and methyl addition/cyclization.The results of TG-DTG-DSC pyrolysis of sludge gasification tar show that the pyrolysis processes of the five kinds of gasification tars all can be divided into two stages:the first stage is volatilization and decomposition of light organic matter;the second stage is decomposition of heavy and decomposable organic matter.The reaction series of 5 kinds of tar in the first stage is 3 and the activation energy of pyrolysis in the second stage is between 13?33 kJ·mol-1.