Study On The Simulation Exergy Analysis And Life Cycle Comprehensive Assessment Of Fuel Ethanol System From Cellulose Biomass

Preparation of fuel ethanol by cellulose biomass fermentation has good development prospects because of its energy and environmental advantages.This paper took two different pretreatment cellulose ethanol process systems as the research object,comprehensively performed the quality,energy,life cycle assessment and exergoenvironment analysis of the process system.Suggestions for optimization and improvement were pointed out.First,this paper established two process routes of liquid hot water pretreatment cellulose ethanol process(LWH-CE)and steam explosion-diluted acid pretreatment cellulose ethanol process(SE-DS-CE)with the help of Aspen simulation.In the process simulation model,the biomass raw materials of the two process routes were corn stalks,and the biomass input was 2000t/d.The simulation calculation results show: LWH-CE and SE-DS-CE two processes of fuel ethanol output reached18638.7kg/h and 20681.8kg/h,raw material utilization rate reached 22.37% and24.82%.In addition to meeting the power consumption of their own systems,the two processes could supply external power up to 475 kW and 455.86 kW,power consumption losses were mainly concentrated in logistics transportation pumps.Secondly,this paper used the second law of thermodynamics to calculate the system flow results based on the energy flow data in Aspen calculations,and obtained the exergy data of all logistics lines,the exergy loss and efficiency of all units in the two routes of LWH-CE and SE-DS-CE two processes.The total efficiency of LWH-CE and SE-DS-CE two processes reached 21.67% and 27.11%.The efficiency of the LWH-CE boiler combustion subsystem is lower than that of the SE-DS-CE process by nearly 10%.The subsystems with the largest exergy loss in both routes are distillation purification subsystems,the exergy losses of the crude distillation column in the distillation purification subsystem of the two routes accounted for 57.15% and 49.60% of the overall loss of the subsystem,the exergy losses came from the large change in flow rate of the unit and the large number of trays.Therefore,how to choose the appropriate pretreatment process,optimize the pretreatment reaction conditions,and optimize the distillation purification reaction conditions are very important to improve the overall exergy efficiency.Then,this paper analyzed the environmental impact and resource consumption of the cellulose ethanol process system at every stages with the help of the Danish EDIP evaluation model and seven different types of potential environmental impact potentials.The results showed that the discharge of pollutants was mainly concentrated in the agricultural process.Because of the large amount of gypsum emissions in the SE-DS-CE process,the discharge of solid waste pollutants was much higher than that of the LWH-CE process.In summary,the environmental friendliness of the LWH-CE process was superior to the SE-DS-CE process.The potential impact value distribution of the two processes was similar.The potential value of solid waste(SW)was mainly distributed in the production stage,the potential value of fossil resource consumption(FDP)was mainly distributed in the use stage,and the other potential values were mainly distributed in the agricultural stage.Finally,this paper introduced the exergoenvironment analysis model that combines exergy analysis and environmental analysis proposed by Meyer et al to conduct a comprehensive evaluation from the composite perspective of energy and environment.The exergy environmental cost of biomass raw materials reached7.25E-04,6.53E-04Pt/k J,the exergy environmental cost of fuel ethanol reached32.21E-04,22.96E-04Pt/k J,it could be seen that the exergy environmental cost contribution value in the production stage is much higher than that in the agricultural stage.In the distillation purification stage of LWH-CE and SE-DS-CE processes,the exergy environmental cost value rised the most,because the loss in this stage was the highest in the process system,and the exergy environmental cost of the SE-DS-CE process is better than the LWH-CE process.