Study On Synergetic Pyrolysis And Gasification Of Sludge And Biomass

Rapid resource utilization,harmlessness,reduction,and stabilization of municipal sludge are prerequisites for maintaining sustainable human development.The composition of sludge is very complicated.It contains a lot of hard-to-degrade organic matter,heavy metals,pathogenic bacteria,pathogenic microorganisms,and parasite eggs,and is accompanied by foul odor.These complex substances will bring great harm to human health.In addition,sludge also has the characteristics of high water content,high ash content and low heating value.It is not easy to recycle,and the cost of pretreatment of pyrolytic sludge is huge,and its pyrolysis Technology needs further improvement.Biomass is a renewable energy source with low water content,low ash content,and high heating value.Mixing with sludge can directly reduce the water content of the mixture,greatly reducing the energy consumed during drying,and can increase gas production Calorific value,improve gas quality.There are a variety of inorganic metal compounds in the sludge,which will have a significant effect on the pyrolysis of the sludge,but there have been few reports in this area.This paper focuses on the synergistic pyrolysis characteristics of municipal sludge and wood powder,and investigates in depth the effects and mechanisms of additives on the co-catalytic pyrolysis of sludge and wood flour.The main research contents are as follows:(1)Thermogravimetric analysis and fixed-bed reactors were used to study the pyrolysis characteristics of sludge,wood powder and mixtures with different mixing ratios.The results showed that pyrolysis of wood flour and sludge can produce a synergistic effect,wood powder can make up for the shortcomings of low volatile matter content in the sludge,significantly increased the thermal mass loss rate of the mixture,promoted the pyrolysis of sludge at low temperatures.At the same time,the addition of wood powder promoted the catalytic cracking of tar,and the content of macromolecular oxygen-containing heterocyclic compounds were significantly reduced,resulting in more oxygen-containing aliphatic compounds,mainly acid,aldehyde and ketone compounds.These compounds are then deacidified and decarbonylated at higher temperatures to form CO2 and CO gas;The gas yield also increased with the addition of wood powder,especially at 900?,when the wood powder addition ratio is 20%,the combustible gas volume percentage is significantly improved,which is 20.47%higher than the theoretical calculation value,and the gas calorific value increased by 47.02%;Elemental analysis and FTIR analysis of the collected coke found that the organic compounds present in the sludge were more easily decomposed than wood powder,and the ash contained a variety of nutrients,which could improve soil fertility.After adding wood powder,the pyrolysis coke has higher aromaticity,and the content of nitrogen compounds are reduced,which is beneficial to improve the stability of the pyrolysis coke in the soil environment.The above results further prove the synergistic effect of co-pyrolysis of sludge and wood powder.(2)Using thermogravimetric analysis to study the effects of three different additives,K2CO3,CaO and Fe2O3,on the catalytic pyrolysis characteristics of biomass and sludge.The results showed that K2CO3,CaO,and Fe2O3 can all promote the pyrolysis of MSWP.Among them,K2CO3 mainly shifted the mass loss peak to the low temperature section and reduced the pyrolysis temperature.CaO effectively increased the rate of mass loss and improved the yield of volatile substances.In the fixed-bed thermal experiments,additives will increase the content of gas components.K2CO3 mainly promoted the production of H2,CaO played the dual role of CO2 capture and tar catalytic cracking,and Fe2O3 promoted CO reforming.GC-MS analysis of tar components showed that K2CO3,CaO,and Fe2O3 can effectively increase the content of aromatic compounds through deoxygenation reactions,promoted the depolymerization,cyclization,and aromatization of macromolecular oxygen-containing aromatics,thereby releasing more small molecule hydrocarbons and gases.XRD characterization analysis of char showed that the three additives exhibit different mechanisms for MSWP catalysis.K2CO3 reacts with C during pyrolysis to release gas and change the tar cracking path;CaO drove tar cracking and steam reforming by capturing CO2 Reaction;Fe2O3 has reduced by reducing gas to release more CO2.