Pyrolysis Of Solid Wastes Based On Fluidized Bed And Characterization,Research Of Solid,Liquid And Gas Products

The main research content of this subject is to use fluidized bed to carry out the basic research of sewage sludge(SS)and corn stalk(CS)single and mixed pyrolysis.The effects of temperature,blending ratios and additives on the distribution and composition of pyrolysis products such as biochar,condensate and non-condensable gas were mainly investigated.A variety of detection and characterization methods were used to detect and analyze pyrolysis products,and the distribution,migration and transformation rules of nitrogen(N),sulfur(S)and chlorine(Cl)elements in pyrolysis products were studied.The main results are as follows:(1)With temperature increasing,biochar yield decreases.Biochar yield reaches a minimum of 28.82 wt%and non-condensable gas yield reaches the maximum value of 37.61 wt%at 850? while the maximum condensate yield(35.38 wt%)was observed at 650? when the sample is CS.ZSM-5 reduced biochar yield of SS and CS.Both CaO and ZSM-5 decreased condensate yield and increased non-condensable gas yield.When sample is SS and mixtures of SS and CS,as the temperature and CS content in mixtures increased,the content of C,H and N elements in biochar continuously decreased.The addition of CaO and ZSM-5 both reduced the content of C,H and N elements in SS and CS derived biochar.In addition,CaO increased the S content in biochar while ZSM-5 decreased the S content in biochar.(2)FTIR results showed that the increase of temperature promoted the decomposition and conversion of organic macromolecules in samples to alcohols,phenols,carboxylic acids,amides,amines,saturated aliphatic and aromatic compounds.XRD results showed that there are few types of crystalline phases in biochar.Temperature and additives promoted the decomposition and release of volatiles in the material and changed the surface morphology of biochar.As temperature increased,the non-condensable gas production rate increased.The main components of non-condensable gas are CO2,CO,CH4 and H2.The results showed that,the yield of CO2 maintained at a relatively high level comparing with the yield of CO,CH4 and H2,and increased with temperature increasing.Meanwhile,the H2 yield is very low.The maximum yield of CO2 is 24.16 w.t%and CaO reduced the yield of CO2 while increased the yield of CH4 and H2.The addition of ZSM-5 increased the yield of CO2,CO,CH4 and H2.(3)The density of condensate is slightly bigger than that of water,With high water content,and the pH value is between 4-9.The maximum yield of SS-derived bio-oil is 1.57 wt%,while the maximum yield of CS-derived bio-oil is 3.40 wt%.At the same temperature,the more CS mixed into the sample,the higher the yield of bio-oil.The addition of CaO and ZSM-5 reduced the yield of SS and CS-derived bio-oil.GC-MS results show that the organic substances contained in bio-oil mainly are nitrogen-containing compounds,aromatic compounds,aliphatic compounds,ketones and some compounds containing S and Cl atoms.(4)With temperature increasing,the N and Cl element RP values of biochar gradually decreased,while the S element RP value in SS biochar did not change much and is at a high level,and the S element RP in CS biochar gradually decreased,which may be caused by the fact that the S element in SS exists mostly in the form of inorganic substances,while in the form of organic S in CS.CaO reduced the RP value of N element in biochar while ZSM-5 increased the RP value of N element in biochar.Additives showed almost no effect on the S element RP in SS-derived biochar.CaO increased the RP value of S element in the CS-derived biochar,indicating the S retention of CaO on CS.Meanwhile,additives increased the RP value of Cl element in biochar,indicating the Cl retention capacity of additives.The nitrogen-containing aliphatic ring will produce methylamine during pyrolysis process,and then produce HCN.The secondary pyrolysis of intermediate products(such as stable amine N,nitrile N and heterocyclic N)is the key factor for the formation of NH3 and HCN;The thermal decomposition of aliphatic S,aromatic S and thiophene S compounds plays an important role in the formation of H2S.There may be two reasons for the formation of HCl,one is the reaction of potassium chloride with hydrated protons generated by pyrolysis,and the other is the thermal decomposition and release of organic chlorine in the material.