The Effect Of Reusing Wastewater And Co-liquefaction On Hydrothermal Process For Bio-fuel Production

Hydrothermal liquefaction（HTL）is a promising energy production process with huge potential.This process usually utilizes water as reaction solvent,thereby omits the drying pretreatment of feedstock.The high-moisture biomass would be Converted into bio-crude,hydrochar,and cracked gas under the process Condition of high temperature and pressure.Co-liquefaction and aqueous（AP）phase recirculation,as the process that can decrease the operating cost,have never been combined by previous research.Co-liquefaction means using multiple kinds of biomass as feedstock for HTL,which can decrease the transportation cost and obtain a higher yield of products.The AP recirculation process means using AP produced from previous HTL as reaction solvent for subsequent HTL.The amount of wastewater can be decreased significantly by this process,meanwhile the yield of products can also be increased.More importantly,co-liquefaction can balance the moisture Content of feedstock,thereby improve the feasibility of AP recirculation process.Therefore,these two processes is combined in this study,the feasibility of this process combination and effect on products are evaluated.The 3^rd bio-fuel biomass Chlorella powder（CL）,2^nd bio-fuel soybean straw（SS）,and their mixture（CS）with ratio 1:1 were processed at 300°C for 20 min,and the AP was recirculated four times.The yield of CS bio-crude was increased（from 24.28%to31.83%）by co-liquefaction,but remained stable during AP recirculation.By Contrast,the yields were increased for CL bio-crude（from 32.40%to 41.19%）,SS hydrochar（from 19.55%to 30.88%）,and CS hydrochar（from 9.42%to 14.76%）by recirculation.The multiple analysis method（including GC-MS,XPS,FT-IR,and thermogravimetric analysis,etc.）,comparison group,and verification group are used for the analysis of relevant mechanism.The N-Containing compounds（e.g.,amines）in AP were Converted into amides（acylation）for CL bio-crude,into N-heterocycles（Maillard reactions）for CS hydrochar,and into N-heterocycles（Maillard reactions）and Mannich bases（Mannich reaction）for SS hydrochar,which Contributed to the increased yield and N Content.Furthermore,the O Content of CS bio-crude was decreased（from 15.31%to 12.52%）by recirculation,resulted from the Conversion of N-heterocyclic ketones into pyrazine derivates.The unique decreased O Content and comprehensive combustibility index（from 0.306 to 0.177）of CS bio-crude indicate the great potential of this craft combination.