Characteristics Of Catalytic Co-pyrolysis Of Rural Solid Waste And Microalgae

The surge in energy consumption is accompanied by the urgency of primary energy shortage and the increase in carbon emissions and other environmental pollution caused by the process of fossil fuel use.Switching to waste or biomass to obtain renewable energy instead of traditional fossil fuels has broad prospects for achieving low-carbon development.Rural solid waste has the characteristics of large amount and is full of resources.As a third-generation biomass energy source,microalgae has many utilization values thus has been extensively studied by scholars.Based on the research status home and abroad,this article focuses on the co-pyrolysis of microalgae and rural solid waste to obtain high-quality pyrolysis oil and explores the properties of fast,slow,in-situ,and ex-situ catalytic pyrolysis of the two so as to provide technical means for efficient and comprehensive utilization of microalgae and rural solid waste.Characteristics of sole rural solid waste and chlorella vulgaris pyrolysis were studied.The thermal weight loss results show that the pyrolysis of chlorella vulgaris and rural solid waste has three weight loss stages,which are internal water and volatile matter loss stage,main pyrolysis stage and residual carbon decomposition stage.Chlorella vulgaris has a significant weight loss rate peak,and rural domestic waste includes two.The pyrolysis residue quality of rural domestic waste is lower(21.38%,28.67%of microalgae).Under slow pyrolysis alone,the pyrolysis oil of rural domestic garbage contains higher content of alkanes(38.05%)and olefins(44.07%),while microalgae oil contains higher nitrogen-containing compounds(28.72%)and carboxylates.Acid(30.85%)content.For fast pyrolysis,the products obtained are in the same broad categories,but the products of rural solid waste contain higher oxygencontaining compounds(37.97%)and carboxylic acids(20.58%).The characteristics of co-pyrolysis under different mixing ratios of microalgae and rural domestic waste were studied.The results of thermal weight loss show that copyrolysis hinders the pyrolysis in the main stage,and the hindering effect weakens as the temperature rises;mixed pyrolysis reduces the temperature corresponding to the first pyrolysis weight loss rate peak.The apparent activation energy of co-pyrolysis is lower in the period of low conversion rate,and maintained at a higher level when the conversion rate is high.For slow pyrolysis products:the co-pyrolysis of the two suppresses the liquid yield and increases the solid and gas yields.When the mixing ratio is 1:1,co-pyrolysis reduces the acid content to 0;significantly reduces the nitrogencontaining compound content(from 28.72%to 2.85%);increases the relative content of aliphatic hydrocarbons(19.46%to 76.53%);Increases higher heating value(23.73MJ/kg to 32.86MJ/kg).Under fast pyrolysis,co-pyrolysis cannot significantly reduce the content of organic acids and nitrogen-containing compounds.The pyrolysis characteristics of CaO,MgO and HZSM-5 under in-situ and ex-situ catalysis were studied.The thermogravimetric results show that the three catalysts all delay the mass loss and reduce the residual mass(respectively reduced by 5.21%,1.57%and 4.89%).CaO increases the average activation energy(282.56 kJ/mol by FWO),and HZSM-5 and MgO significantly reduce the average activation energy(221.49 kJ/mol and 225.45 kJ/mol by FWO,respectively).CaO reduces the gas yield and increases the solid phase yield.MgO increases the yield of the gas phase and reduces the yield of the solid phase.HZSM-5 increases the gas yield greatly,and reduces both the solid phase and liquid phase yields.CaO significantly reduces the nitrogen-containing compounds(from 28.72%to 11.46%)and organic acids(30.85%to 0)in the microalgae pyrolysis oil;it reduces the proportion of heavy hydrocarbons(C>20)in the pyrolysis oil(The proportion of heavy hydrocarbons in the pyrolysis oil of RSW,4RSW1CV and 1RSW1CV decreases by 5.94%,7.19%and 11.98%respectively).HZSM-5 significantly increases the yield of aromatic hydrocarbons under co-pyrolysis(from 2.32%to 17.62%).The three-phase yield and the chemical composition of the pyrolysis oil obtained by ex-situ catalytic pyrolysis are generally consistent with the in-situ trend.For fast pyrolysis,the product distribution and ratio of ex-situ fast catalytic pyrolysis and in-situ fast catalytic pyrolysis are relatively similar,but the ex-situ catalytic effect is not as significant as in-situ catalysis.In summary,the slow catalytic co-pyrolysis of rural domestic waste and microalgae can realize the high efficiency utilization of biomass resources,increase the relative yields of alkanes and olefins,increase the higher heating value,and increase the energy value of pyrolysis oil thus has the potential to be upgraded to high-quality bio-oil.