Fluidized Bed Pyrolysis Of Solid Wastes And Analysis Of Products

Waste tires（WT）and spent bleaching clay（SBC）are generated from wear and tear of tires and the refining of edible crude oil,respectively,their serious environmental pollution and effective resource disposal have always been the attention of enterprises and governments.In the study,the effects of different temperatures on the properties of WT and SBC pyrolysis products were investigated in a fluidized bed coupled screw-feeder benchtop pyrolyzer,the transfer paths of polymers and N-and S-containing organics in WT during pyrolysis were proposed combined with on-line analysis technology,the regeneration and pyrolysis mechanism of SBC and the recovery of residual oil in it were explored,and the transformation pathway of inorganic matters in SBC with pyrolysis temperature was proposed for the first time.（1）WT pyrolysis could be divided into four stages,the small molecule compounds were mainly released in the second and third stages（230～250°C,total weight loss ratio of them≥52 wt.%）according to the TG-MS analysis.The yield of condensate（41.10%）and the degree of carbonation or aromatization（H/C=0.061）of pyrolysis carbon blacks（p CBs）reached the maximum at 650°C.The conversion of Zn O to Zn S and sulfur fixation effect of p CBs were promoted at high temperature.p CBs could be used as stable and ordered carbon materials（I_D/I_G<1）.D-Limonene was the most abundant compound in tire pyrolysis oils with the maximum of 41.55%（550°C）,the content of hydrocarbons（alkenes,aromatic hydrocarbons,and alkanes）reached the maximum of 87.42%at 750°C,fluidized bed pyrolyser（FBP）inhibited the formation of N-,S-,and O-containing compounds at high pyrolysis temperature.Flammable gases（CO,CH₄,and H₂）increased from1.29 to 6.21 wt.%（750°C）with the increase of temperature.Isoprene and D-Limonene were the main organic compounds after depolymerization of natural rubber（NR）,could be interconverted by Diels-Alder and scission reaction,respectively.Monomers or dimers produced by styrene-butadiene rubber（SBR）,NR,and butyl rubber（BR）and polymer N,S-containing compounds produced in the vulcanization process generated aromatic hydrocarbons（AHs）,ploymerized aromatic hydrocarbons（PAHs）,and small-molecule N-and S-containing compounds through scission,cyclization,isomerization,dehydrogenation and hydrogenation reaction.（2）TGA revealed that the residual oil in SBC was～31.9 wt.%.The condensate yield（19.2%）,the oil recovery ratio（ORR,60.2%）,and the methylene blue adsorption value（213.6 mg/g）of pyrolysis char reached the maximum at 600°C,and the content of hydrocarbon in pyrolysis oil up to73.9%at this temperature.The decolorization ability of SBC（96.3%）was significantly improved by FBP,close to that of virgin bleaching clay（VBC）.The ontents of heavy metals in PCs complies with the national standards of VBC（GB 25571-2011）.During the pyrolysis of SBC,the fatty acids produced alkanes,alkenes,short-chain fatty acids,and ketons through scission and dimerization,C-C bonds of unsaturated fatty acids and esters were prone to form olefins throughβ-scission reaction,then the olefins underwent Diels-Alder reaction with other dienes or endo cyclization reaction and then dehydrogenation to generate aromatics.The large amount of inorganic substances in SBCs prompted PAHs to generate AHs through cracking and isomerization at 700°C,and further converted to alkanes and alkenes by ring-opening.Oxygen atoms were eliminated in the form of CO₂,CO,and H₂O during pyrolysis.