Integrated Performance Evaluation Of Liquid Fuel Production From Biomass Pyrolysis And Bio-oil Upgrading Based On Energy-Exergy-Emergy Thermodynamic System Analysis

Fast pyrolysis of biomass and upgrading techniques for high chemical value bio-oil production have been investigated widely in recent decades,due to the non-renewability and serious pollution of the fossil energy.The integrated evaluation on thermodynamic performance of two processes,i.e.,the biomass fast pyrolysis and bio-oil upgrading in supercritical ethanol to liquid fuels system and the biomass fast pyrolysis and bio-oil catalytic hydrotreating to liquid fuels system were carried out based on several evaluation methods,such as energy analysis,exergy analysis,and emergy analysis.Theoretical foundations on improving the integrated performance of fast pyrolysis of biomass and upgrading techniques for the bio-oil production are achieved in this paper.Firstly,process simulation models based on Aspen plus were established.The results show that the input energy and energy efficiency of the PY-USE are more than the PY-CH.The energy efficiency of PY-CH is 34.57%,which is less than the energy efficiency of the PY-USE 39.06%.However,the PY-USE needs extra alcohol,the optimization is to reduce alcohol..Energy analysis was conducted over the two schemes,the results were calculated based on the thermodynamic parameters obtained from simulation..Secondly,exergy analysis were conducted over the two schemes,the results were calculated based on the thermodynamic parameters obtained from simulation.In the analysis,PY-USE and PY-CH were divided into three subsystems:biomass fast pyrolysis,bio-oil reforming and bio-oil upgrading.The results show that the two schemes have the same exergy efficiency for the fast pyrolysis subsystem,however,the PY-USE have a higher exergy efficiency for the bio-oil reforming subsystem and upgrading subsystem.For the aspect of the whole system,the exergy efficiencies of PY-USE and PY-CH are 36.05%and 30.74%.The exergy loss for biomass fast pyrolysis subsystem,bio-oil reforming subsystem,bio-oil upgrading subsystem,is mainly caused by the chemical reaction,but the biomass fast pyrolysis subsystem accounts for the largest percents.The exergy efficiency is able to achieve the maximum level of 64.32%respectively at reforming temperature 700 ?,reforming pressure 13.9MPa,S/C of 10.Based on the input-output framework and emergy indices,with the consideration of environment elements,emergy analysis method was applied to comprehensively evaluate two schemes in this paper,achieving upgraded bio-oil from pinus sylvestris by fast pyrolysis and catalytic hydrogenation(Scheme I)and supercritical ethanol upgrading technique(Scheme II),respectively.As the results indicated,Scheme ? consumed less solar energy and enjoyed higher efficiency when the same amount of fuel was produced.External support,especially industrial water and fertilizer,is dominant for both Scheme ? and Scheme II.Ethanol occupies a large proportion for Scheme ?.The optimal direction for Scheme ? is to adjust the process to produce ethanol.Scheme ? consumed less solar energy and enjoyed higher efficiency when the same amount of fuel was produced.For the renewable ratio,Scheme ? was 48.73 while Scheme II was 36.74,which showed that renewable emergy input occupied higher percent of the total emergy input in Scheme ?.Scheme ? and Scheme ? have larger renewable ratio than the other schemes.For the environment sustainable index,Scheme ? was 0.96 while Scheme II was 0.59,other schemes are under 0.5,which showed that Scheme ? and Scheme ? had less stress on the environment and got more support from it.In brief,Scheme ? has the best competitiveness,while Scheme ? is a little weaker.Finally,a new coupling scheme(Scheme ?)was built by combing the thermo-chemical biomass-to-ethanol technology with the Scheme ?.Emergy analysis was conducted to the new coupling scheme.As the results indicate,the Scheme ??? have a close emergy yield ratio,but a higher renewable ratio,a lower environmental load ratio and a better sustainability.For the three Schemes,Scheme I has the best competitiveness,while Scheme? is a little weaker and Scheme ? is the weakest,which means that combing the thermo-chemical biomass-to-ethanol technology with the Scheme ? improves the competitiveness.