| Fluidized bed combustion has the advantages of wide fuel adaptability and low pollutants emission.Co-combustion of waste and coal in existing fluidized bed boilers on one hand can apply widely existing combustion experience to waste management,on the other hand can reduce the cost of construction.Tannery sludge(TS)is a kind of hazardous waste posing threats to environment,thus its disposal has drawn common concern of society.Co-combustion of TS in fluidized bed boiler can improve the disposal capacity effectively and economically.Several researches on co-combustion of TS and coal in fluidized bed combustor(FBC)were carried out in this work.(1)Co-combustion characteristics of TS and coal were studied.(2)Mechanism of chromium(Cr)oxidation and its inhibition methods during combustion were studied.(3)Emission characteristics and fate of Cr during co-combustion of TS and coal in FBC were studied.(1)In Chapter 2 and Chapter 3,the co-combustion and co-pyrolysis characteristics were investigated using TG-FTIR.The influence of mixing ratio of TS were studied.Kinetic parameters were obtained according to Coats-Redfern method.Emissions changes of gaseous products with temperature were investigated.(2)In Chapter 4 and Chapter 5,mechanism of chromium(Cr)oxidation and its inhibition methods during combustion were studied.In Chapter 4,influence of different factors(temperature,duration,oxygen concentration and mole ratio of Ca and Cr)on extent of Cr oxidation during combustion were compared.The oxidation extent of Cr at different temperatures together with influence of CaO and three additives(kaolinite,NH4H2PO4,Mg2Si3O8)were investigated.In Chapter 5,X-Ray Diffraction analysis and thermodynamic equilibrium calculation are used to interpret Cr oxidation behaviors and reveal its possible reaction routes.Furthermore,microscopic Mechanism of Cr oxidation is explained from the view of crystal defects and oxygen activation.(3)In Chapter 6,co-combustion experiments were conducted in a 35Kwfluidized bed combustor.The combustion behavior and emission characteristics of the fuels were investigated on a bubbling fluidized bed(BFB)and a circulating fluidized bed(CFB).The Cr speciation and distribution among different ash types were extensively investigated in four co-combustion tests.The influence of(NH4)2HP04 addition at different mixing ratio on Cr oxidation were studied.(4)In Chapter 7,co-combustion experiments were conducted at a 220t/hfluidized bed commercial boiler.Mono-combustion of bituminous coal were compared with those of co-combustion with tannery sludge in terms of operation parameters:,pollutants emissions,heavy metal distribution and the leachability of ash. |
PDF Full Text Request