Preparation Of High Quality Bio-oil By Microwave Co-pyrolysis Of Torrefied Straw And Waste Plastics

With the increased difficulty of finding new sources of shortage of fossil fuel energy,renewable energy from biomass sources has gained plenty of attention.Due to its extensive source and reproducibility,many researchers have studied it in recent years.Biomass microwave pyrolysis is explained as the conversion of biomass using microwave heating to produce solid,liquid and gas products.The bio-oil that is produced normally has a large amount of water and high oxygen content,which in turn affects the quality of the bio-oil.To rectify this problem this investigation adopted microwave torrefaction pretreatment to improve the quality of the bio-oil.The quality of the bio-oil was improved through the addition of H2 and H+with the use of plastics.In addition to the investigation of improved bio-oil quality,a kinetic study was also conducted on microwave pyrolysis and co-pyrolysis to create a reaction mechanism in order to provide a theoretical basis for the application of microwave heating in co-pyrolysis.The main conclusions obtained in this paper are as follows:(1)The optimum mixing ratio of two kinds of raw materials was studied by microwave co-pyrolysis with low density polyethylene(LDPE)which is the model compound used in place of waste plastic,non torrefied rice straw was the biomass source.The results showed that with the increase of LDPE content,the volatile components also increased.The highest yield of bio-oil was 29.83%with the addition of 30%LDPE.When LDPE content was 30%,the highest content of hydrocarbons in bio oil was about 30.80%,while the acid content was the lowest.(2)The use of microwave heating method to pretreat rice straw and mixing 30%ratio of LDPE,it was found out that the optimal conditions are:a torrefaction temperature of 240°C and a time of 10 min.The bio-oil yield obtained under these conditions was relatively high,while the moisture content in bio-oil was relatively low.The GC/MS results showed that the content of hydrocarbons in bio-oil obtained under these conditions was the largest,exceeding 35%of the total material content.This improved the quality of bio-oil.(3)A self-designed microwave reactor with an external catalytic fixed bed for catalytic co-pyrolysis was used for the experiments.The effect of temperature and catalyst on microwave co-pyrolysis was studied.Based on these parameters,the response surface map between experimental parameters and products was established using Design-Expert software to obtain the best condition for optimization of the results.The results showed that when the reaction conditions were 550°C and the amount of catalyst was 5%;the bio-oil yield was relatively high,and the content of hydrocarbons in the bio-oil was highest;the resulting content of phenol and guaicol were also higher.(4)Microwave-catalyzed co-pyrolysis kinetics and reaction mechanism were studied using lignin and cellulose as model compounds for rice straw.The result of catalytic co-pyrolysis showed that the phenolic substances in bio-oil mainly came from the pyrolysis of lignin,while the furan substances mainly came from the pyrolysis of cellulose.The kinetic analysis showed that the temperature range of lignin and LDPE in co-pyrolysis was wide,while the temperature range of cellulose and torrefied rice straw was small.The pyrolysis of the raw materials compared,it was observed that the reaction orders of the kinetic parameters changed while the activation energy decreased during the co-pyrolysis process.It is revealed that the main synergistic mechanism is the pyrolysis of cellulose to produce furan compounds while the olefins were produced by the pyrolysis of LDPE and furan compounds,then the formation of multiolefins and cyclic hydrocarbons under the action of catalysts.The combination of H~+in plastics and lignin produced to form phenolic compounds.A multi-olefin and a cyclic hydrocarbon are formed by a series of reactions under the action of a catalyst.This showed that the addition of waste plastics(LDPE)would be able to improve the yield and quality of bio-oil obtained from pyrolysis of rice straw.