Study On Optimization Of Co-Hydrothermal Liquefaction Process Of Plastics And Biomass

With the gradual depletion of traditional fossil energy,it is urgent to seek sustainable alternative energy for social development.Biomass energy has attracted much attention because of its carbon neutral character and sustainability.The properties of bio-oil obtained by hydrothermal liquefaction of biomass are similar to petroleum derived products,and its subsequent refining process is relatively mature,and it has broad application prospects in the field of transportation,so it has become a research hotspot of academic research.Biomass hydrothermal liquefaction oil production has some problems,such as low oil yield and poor oil quality.And there are many kinds of biomass and complex components.In this thesis,the co-hydrothermal liquefaction experiment of biomass and hydrogen-rich raw material-plastic was carried out to explore the process of biomass hydrothermal liquefaction oil yield and quality improvement.The main research contents and conclusions are as follows:(1)Firstly,the distribution characteristics of hydrothermal liquefaction products of different biomass and PP were studied.Based on the characteristics analysis of biomass and PP raw materials,it is clear that biomass and PP have significant differences in co-liquefaction behavior and product characteristics.The lignin content of biomass chemical components is positively correlated with the co-liquefaction oil yield.For example,the co-liquefaction oil yield of poplar and pine groups of high wood quality is 45% and 40%.It was higher than that of low lignin biomass(rice straw 35%,wheat straw 34%,corn straw 23%).According to the distribution characteristics of three-phase products with biomass species,a synergistic effect analysis method was established,and the synergistic effect of biomass and PP co-liquefaction three-phase products was further compared and analyzed.The results showed that biomass and PP co-hydrothermal liquefaction has advantages in promoting the generation of target product oil and improving the quality of oil.The triggering mechanism of PP depolymerization caused by the difference of ash and lignin content and structure in different biomass was revealed.(2)Furthermore,the oil quality characteristics of hydrothermal liquefied oil phase products using TGA and GC-MS were studied.The analysis results showed that,compared with the hydrothermal liquefaction oil of biomass alone,the ketones and phenols in the co-liquefaction oil decreased,while the alcohols and hydrocarbons increased to a certain extent.Compared with the hydrothermal liquefaction of poplar and PP alone,the alcohols and hydrocarbons in the hydrothermal liquefaction oil increased from 10.33% and 6.97% to 28.05% and 36.98%,respectively.Ketones and phenolic compounds decreased from 23.48% and 33.36% to 4.80% and 0.91%respectively.The content of target hydrocarbons in co-hydrothermal liquefaction oil is significantly higher than that of biomass liquefaction alone,which further verifies the significant advantage of co-hydrothermal liquefaction to produce high quality liquefied oil.(3)In order to maximize oil yield and oil quality,an optimization model of coliquefaction oil yield was established by response surface design experiment,and the variation law of oil yield and quality under the action of multiple factors was studied.The results showed that under the optimal conditions,the reaction temperature was324 °C,the holding time was 23 min,and the ratio of poplar was 31 wt.%,the predicted oil yield could reach 54.91±2.75 wt.%.At the same time,the optimal range for obtaining high yield and high quality liquefied oil is 320～350 °C temperature,15～25min time and 30～50 wt.% poplar,which significantly reduces the energy input-tooutput ratio of co-liquefaction process and improves the economic feasibility of the process.