| The energy crisis and environmental pollution are double pressures that human societies are facing. As the only renewable energy that can be converted into liquid fuels directly, it’s very important for energy security and CO2 emission reduction to develop techniques for obtaining liquid fuels from biomass. An analysis and evaluation work with consideration of energy, economics and environment was performed to the biomass fast pyrolysis to liquid fuels system in the thesis.Firstly, the biomass fast pyrolysis and bio-oil upgrading in supercritical ethanol to liquid fuels system(PY-USE) and the biomass fast pyrolysis and bio-oil catalytic hydrotreating to liquid fuels system(PY-CH) were structured. Process simulation models of PY-USE and PY-CH based on Aspen Plus were developed. The thermodynamic parameters from simulation(mass flow rate, heat flow rate, power consumption, chemical composition and concentration, enthalpy, entropy, and so on) are the basis for the following research work.Secondly, an exergy analysis was conducted to PY-USE and PY-CH. Physical exergy and chemical exergy of each stream were calculated based on the thermodynamic parameters from simulation. In the analysis, PY-USE and PY-CH were both divided into four subsystems: pre-treatment, biomass fast pyrolysis, bio-oil upgrading and energy recovery. In addition, the exergy loss and exergy efficiency calculations were also carried out. The results show that the key to reduce the exergy loss in pre-treatment subsystem is decreasing heat consumption during the process of biomass drying. The exergy loss in biomass fast pyrolysis subsystem is mainly caused by the pyrolysis reactor and the process of coke and non condesable gas combustion. The exergy efficiency of biomass fast pyrolysis subsystem is 69.12%. PY-USE has a much larger exergy loss in bio-oil upgrading subsytem than PY-CH, because bio-oil upgrading in supercritical ethanol requires more heat than bio-oil catalytic hydrotreating. The exergy efficiencies of bio-oil upgrading subsystem for PY-USE and PY-CH are respectively 88.37% and 89.94% and can be improved by optimizing heat exchanger networks. For energy recovery subsystem, the exergy efficiencies is 43.91% and the exergy loss is mainly casued by combustion in the furnace. From the aspect of the whole system, the exergy efficiencies of PY-USE and PY-CH are 48.69% and 38.14%, respectively. The exergy losses of both systems occur mainly in biomass fast pyrolysis subsystem and energy recovery subsystem.To understand the economic performance of biomass fast pyrolysis to liquid fuels system, a techno-economic evaluation study was performed on PY-USE, PY-CH, the non cogeneration biomass fast pyrolysis and bio-oil upgrading in supercritical ethanol to liquid fuels system(NCPY-USE) and the non cogeneration biomass fast pyrolysis and bio-oil catalytic hydrotreating to liquid fuels system(NCPY-CH). The capital costs for these systems are Y810 million, ￥525 million, ￥625 million, ￥375 million. Fuel product value estimates are ￥6052, ￥5108, ￥7741, ￥5752 per ton, respectively. The sensitivity analysis results suggest that ethanol price, bio-oil yield and catalyst consumption have significant impacts on the cost of fuel for PY-USE and NCPY-USE. Furthermore, bio-oil yield, fuel yield and biomass price have strong impacts on the cost of fuel for PY-CH and NCPY-CH.Finally combining the results of exergy analysis and techno-economic evaluation, thermoeconomic model of PY-USE was established based on the structure theory of thermoeconomics. In addition, the exergy cost and the thermoeconomic cost were decomposed to analyze their composition. Exergy value and environmental damage cost of emissions from PY-USE were respectively used to quantify the environmental impact of the system. Then, the environmental thermoeconomics model was also established by introducing the environmental cost to the thermoeconomic model. The results show that both exergy cost and thermoeconomic cost gradually increase along the process of production. The unit exergy costs of liquid fuel, hydrogen and electricity are 1.6119 kJ/kJ,2.8566 kJ/kJ and 5.4214 kJ/kJ, respectively. The unit thermoeconomic costs of liquid fuel, hydrogen and electricity are 147.4 ￥/kJ,180.0 ￥/kJ and 370.0 ￥/kJ, respectively. The exergy cost is divided into fuel part and exergy destruction part. The thermoeconomic cost is divided into fuel part, exergy destruction part and capital part. Value of the fuel part reflects the exergy efficiency of the subsystem for both exergy cost and thermoeconomic cost, while value of the capital part reflects the economic investment of the subsystem for thermoeconomic cost. After introducing the environmental cost, the calculated exergy cost and thermoeconomic cost from the environmental thermoeconomics model increase. In the environmental thernoeconomic model, the unit exergy costs of liquid fule, hydrogen and electricity increase by 0.39%,0.77% and 1.17%, respectively. The unit thermoeconomic costs of liquid fule, hydrogen and electricity increase by 0.20%,0.67% and 1%, respectively. |
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