| A substantial amount of bio-waste is produced in agriculture and rural communities.Bioenergy production using bio-waste as a feedstock is an important path way to solve environmental pollution and energy need.Bio-waste can be efficiently converted to bio-crude oil and high value products through hydrothermal liquefaction(HTL).In this paper,HTL of two typical agricultural bio-wastes,cornstalk with high content of carbonhydrate and human feces with high content of protein,was studied.Specific work of this thesis includes:1)investigation of the effect of HTL hydrothermal treatment severity on cornstalk products conversion and products distribution;2)exploration of key parameters of HTL of human feces on the products distribution and characteristics;3)effect of co-liquefaction of cornstalk and human feces on biocrude yield and the analysis of synergistic effect during the process;and 4)set up the continuous HTL reactor.The hydrothermal treatment severity heavily influenced the HTL of cornstalk.The biocrude oil yield improved with the increase of the hydrothermal treatment severity(4.17?7.60)with the highest biocrude yield of 24.99%.The biocrude oil produced in the hydrothermal treatment severity range 5.16 to 7.60 showed similar characteristics.The cornstalk structure was degraded more thorouly with the increase of temperature severirty.Hemicellulose and cellulose were completely degraded at a severity of 5.70 and 7.60,respectively.The lignin could not be significantly degraded until the hydrothermal treatment severity increased to 6.96.The aqueous phase of HTL contained a high concentration of reducing sugars and acids,which constituted 58.9%-92.4%of the total organic compounds.The highest biocrude oil yield and higher heating value for the HTL of human feces was 34.4%and 40.3 MJ/kg,respectively.The results showed that more than 50%carbon and 40%hydrogen in the human feces were migrated to the biocrude oil.It is worth noting that the metals in the human feces migrated to different product phases per its characteristics after HTL.At least 89%of K and 73%of Na were transferred to the aqueous phase,while more than 70%of the heavy metals and alkaline earth metals were accumulated in the solid residue.The highest increase of biocrude yield was 5%when the loading mass ratio of cornstalk and human feces and the hydrothermal treatment severity were 1:4 and 7.67,respectively.The results indicated that significant synergistic effects occurred between cornstalk and human feces,which enhanced the biocrude yield.The analysis showed that the biocrude yield from co-liquefacton of cornstalk and human feces increased from 23.09%(6.41)to 32.22%(8.34),However,the impact of these factors on the organic compounds present in the biocrude was relatively small.The denitrification was enhanced as the hydrothermal treatment severity increased to 8.34.A continuous HTL reaction platform was built.The reaction system was composed of four parts:a hydraulic feed system with a twin cylinder,a plug-flow preheating and reaction system,a product collection system,and an online monitoring system.Water was first used for the performance test of the system,and the experiments were performed continuously at temperatures of 260?300?,and the feeding rate was adjusted to 0.5?1 mL/s.The steady-stage system temperature and the pressure fluctuations were less than 1.5? and 0.2 MPa,respectively.The relative standard deviations were less than 0.5%and 3%,respectively.When the protein powder with TS contents of 2%,10%and 15%were utilized as the feedstock,the relative standard deviations of temperature and pressure were less than 0.5%and 2.5%,respectively.When the raw material was switched to simulated human feces and spirulina,the biocrude yields were 34%and 28%,respectively.The relative standard deviations of temperature and pressure were less than 0.7%and 2.5%,respectively.The products content and property from the same feedstock at different collection time were consistent.The results illustrated that this continuous HTL reaction platform could provide stable operation of raw materials with high loading rate. |
PDF Full Text Request