Co-pyrolysis Of Municipal Solid Waste With Agricultural And Forest Residues And Separation And Upgrading Of Pyrolysis Liquids

With the development of economy and urbanization of our country,the rapid increase of municipal solid waste has brought serious challenges to the urban safety and health.Traditional landfill and compost have a lot of problems,such as a large number of land occupied,a longer treatment cycle and serious pollution.Municipal solid waste produces dioxins and other harmful substances in incineration process.The pyrolysis of municipal solid waste not only has volume and mass reduction but also obtained gas,liquid and coke.When municipal solid waste pyrolysis,due to high moisture and ash content,low carbon and hydrogen content,the yield of the pyrolytic product is relatively low and quality is poor.It is difficult to effective use.It is an effective way to achieve high quality and value added pyrolysis product by municipal solid waste and other waste co-pyrolysis.As an important agricultural and forestry country,we produce a great deal of agricultural and forestry waste every year.Agriculture and forestry waste are high volatile and low ash content relatively,the production rate of pyrolysis gas and liquid is higher.The co-pyrolysis of municipal solid waste and agriculture and forestry waste can not only achieve the goal of volume and mass reduction but also make up for poor quality of municipal solid waste pyrolysis.Due to the complex composition of municipal solid waste and agricultural and forestry waste,the composition and properties of the co-pyrolysis liquid are different,the water content is high,and the traditional oil-water separation methods have poor effect.To achieve efficient use of pyrolysis liquid and realize the oil-water separation,it is necessary to investigate the oil-water separation and upgrading of pyrolysis liquid.This paper is based on Shanxi province science and technology research project Research on the technology of municipal solid waste and forestry waste coordination disposal and efficient resource utilization.Taking municipal solid waste and part of agricultural and forestry waste as a research case,composition analysis and characterizasition were studied by thermogravimetry,fixed bed reacter,gas chromatography,infrared analyzer and scanning electron microscope.The characteristic of pyrolysis and co-pyrolysis,pyrolysis product yield and composition changes were researched.The effects of distillation,extraction and demulsification on pyrolysis liquid oil-water separation and the changes of composition and properties in different conditions of esterification were also investigated.The main conclusions of this paper are as follows:1.The analysis of the municipal solid waste in Taiyuan city shows that the main components are food waste,paper and glass dust.The contents of organic food waste and plastic are high in summer,and the contents of glass dust are high in winter.The industrial analysis shows that municipal solid waste in summer is high volatile and low ash content,it is opposite in winter.The ultimate analysis shows that the content of C,H and O is high in summer and low in winter.The calorific value of municipal solid waste is the highest in summer and the lowest in winter.Industrial analysis of agricultural and forestry waste indicates that the order of content of volatilization is pine branch,cassava stalk,corn stalk and rice husk from high to low.2.Municipal solid waste pyrolysis can be divided into three stages including dry and degassing,active pyrolysis and thermal polycondensation.In the second phase with temperature between 450⁶50?,the weight loss rate of pyrolysis is 57%.According to the thermogravimetry curve,calculation of dynamic parameters shows the correlation coefficient is 0.966,the frequency factor is 0.2460min^-1 and the activation energy is 50.72 kJ/mol.Fixed bed pyrolysis experiments show that maximum yield of pyrolysis liquid is 39.81% at 600? between 450? to 650?.The pyrolysis liquid yield of compression molding material is 8.24% higher than that of the powder one.Adding calcined limestone can improve yield of gas in different level.When calcination temperature is 950?,the improvement of waste pyrolysis gas is most obvious.3.Municipal solid waste pyrolysis liquid moisture content is higher,ranging from 20% to 30% at different temperature range.Acid value is greater than 30 mg/g?KOH?.The oxygen content of pyrolysis liquid is 20.28% and calorific value is 31.42 MJ/kg at 600?.The calorific value of pyrolysis char is lower than 20MJ/kg.The pyrolysis gas H₂,CO,CH₄ and CO₂ are 0.35,17.75,2.10,33.67 mL/g at 600?.4.There are also three stages in the process of agricultural and forestry waste pyrolysis including dry and degassing,active pyrolysis and thermal polycondensation.With the pyrolysis temperature rising,pyrolysis gas yield of cassava stem is increasing,pyrolysis tar yield is declining,pyrolysis liquid yield reach a maximum of 45.6% at 600?.In the second phase,weight loss was obviously.When temperature is 317?,weight loss rate was a maximum of 60%.The dynamic analysis of rice hull shows that the pyrolysis activation energy is 66.55⁷0.92 kJ/mol.Increasing the heating rate of rice husk,the activation energy of pyrolysis decreased.As the heating rate increases,the maximum pyrolysis weight loss rate of rice husk increases.Thermogravimetric analysis of pine boughs shows that the maximum weight loss rate is 67% at 358?.Increasing the pyrolysis temperature,pyrolysis activation energy of pine branch increase at first and then decrease.5.The infrared analysis of cassava stalk pyrolysis liquid shows that the pyrolysis liquid of cassava stalk is complex and contains many organic compounds such as phenol,alcohol and carboxylic acid.The pH,oxygen content,moisture content and calorific value of pyrolysis are 2.7³.1,56.70%,31% and 15.3 MJ/kg respectively.The industrial analysis shows that the fixed carbon,ash,water and volatilization in pyrolysis coke are 75.42%,13.67%,0.05% and 10.86% respectively.The production rate of CH₄ in cassava stalk pyrolysis gas is lagest.6.The co-pyrolysis of cassava stalk and municipal solid waste can provide the atmosphere of hydropyrolysis and promote municipal solid waste pyrolysis.Dynamics analysis shows that the pyrolysis activation energy of mixture of municipal solid waste and cassava stalk is 43.36 kJ/mol,below municipal solid waste pyrolysis activation energy of 50.60 kJ/mol,adding cassava stalk can reduce the apparent activation energy of municipal solid waste pyrolysis and benefit municipal solid waste pyrolysis.The energy analysis of municipal solid waste and cassava stalk co-pyrolysis process shows that with the proportion of cassava stalk increasing,output energy gradually increases.When adding 44.14% cassava stalk,the output energy is equal to the needed energy of 3.64 MJ/kg.Adding cassava stalk can increase the pyrolysis liquid production rate and reduce the pyrolysis production rate of municipal solid waste.When the proportion is 60%,the yield of pyrolysis liquid is a maximum of 47.52%.7.The corn stalk reduces the pyrolysis activation energy of municipal solid waste,and there are some synergistic effects on co-pyrolysis.The energy analysis of municipal solid waste and corn stalk co-pyrolysis found output energy increases gradually with corn stalk percentage increasing.When adding percentage was 37.34%,output energy is equal to the needed energy 3.53 MJ/kg.The addition of corn stalk increases the rate of pyrolysis liquid and reduces the pyrolysis coke of municipal solid waste and enhances the rate of H₂ in pyrolysis gas.When the ratio of corn stalk is 60%,the H₂ in pyrolysis gas is a maximum of 0.20ml/g.8.After the addition of pine branches,the apparent activation energy of municipal solid waste pyrolysis reaction can be reduced.It indicates that the pyrolysis of municipal solid waste is significantly promoted by the addition of pine branches.When the mixing ratio of municipal solid waste and pine branches is 3 to 1,it can promote the production rate of pyrolysis liquid.Adding the quantity of the pine branches,the output energy of the mixture increases and the pyrolysis energy gradually decreased.When the adding proportion is more than 65.28%,the output energy is greater than the required energy.The output energy of municipal solid waste and pine branches co-pyrolysis products can meet their pyrolysis needs.9.The distillation method is used to separate oil and water from the municipal solid waste pyrolysis liquid.As the temperature of pyrolysis liquid increases,the content of the low temperature distillate in pyrolysis liquid is gradually reduced.The addition of Fe₂O₃ and CaO in pyrolysis materials increases the dehydration rate of pyrolysis liquid and decreases the content of low boiling point in pyrolysis liquid.Through changing the extraction agent type and extraction sequence in pyrolysis liquid,the results show the extraction rate of methylene chloride on cassava stalk pyrolysis liquid is higher than that of ethyl acetate.The extraction efficiency of fractional extraction with two extraction agents is higher than that of single extraction.The total extraction rate of ethyl acetate with dichloromethane is 41.03% and the extraction rate is 39.04% after changing the sequence.10.Studying the effects of polyoxyethylene polyoxypropylene copolymer?J?,fatty alcohol polyoxyethylene ether 7.9?Z?,nonylphenol polyoxyethylene ether?R?,Triton X-100?Q?on pyrolysis liquid dehydration rate,the pyrolysis liquid dehydration rate rang from 90.6% to 91.3%.When Triton-X 100?Q?dosage is 100mg/L,pyrolysis liquid dehydration rate is a maximum of 90.87%.Using different kinds of flocculant,the dehydration efficiency of pyrolysis liquid is 90%⁹1.3%.When the amount of flocculant PAM is 150 mg/L,pyrolysis liquid dehydration rate is 90.7%.When above surfactant is mixed with poly aluminum chloride?PAC?and polyacrylamide?PAM?,the dehydration rate of the pyrolysis liquid is above 89.6%.When PAM+J are added to the pyrolysis liquid and raised the demulsification temperature at the same time,the dehydration rate of the pyrolysis liquid is increased.The result of adding PAM+Q is opposite.11.Using the esterification process in pyrolysis liquid for qualitative research with CaO/?-Al₂O₃ as catalyst,when the esterification reaction time,alcohol and cassava stalk ratio,catalyst dosage and reaction temperature for 6 h,3:1,5% and 60? respectively,the reaction effect is best.The acid value of pyrolysis is 2.75 and the oxygen content decreases to 50%.The calorific value is increased from 13.4MJ/kg to 27.5 MJ/kg,and the acidity of organic components decreases from 18.5% to 0.8%.Other organic components such as phenols,ketones,alcohols,alkanes,esters,aromatic substances improved in varying degrees after demulsification,which phenols is still the most,accounting for 37.9%,followed by alcohol,accounting for 21.4%.