| The rapid development of civil aviation is accompanied by a rapid increase in the demand for jet fuel,and the excessive use of fossil energy will lead to very severe environmental problems.Therefore,it is imminent to develop renewable energy.In many renewable energy sources,biomass is the only renewable energy that can be transformed into solid,gas and liquid fuels.At present,the technology of using the oligomerization of light-olefins(ethylene,propylene and butene)to prepare hydrocarbon fuels is very mature,and the process of preparing light olefins from biomass catalyzed pyrolysis is seldom discussed.Therefore,this paper will mainly focus on the optimization of the process of preparing light-olefins from biomass.Firstly,the experiment of biomass one-step process of preparing light-olefins(biomass direct catalytic pyrolysis to produce light-olefins)is studied.Using cellulose as biomass feedstock,HZSM-5 zeolite catalysts with phosphorus content of lwt.%,3wt.%and 5wt.%were used to conduct catalytic pyrolysis experiments.It is shown from the experimental results that the mole yield of light-olefins in the catalytic pyrolysis products can be greatly increased by the catalyst and the carbon content of the zeolite catalyst after used is slowed down.The carbon mole yield of light-olefins reaches the maximum value of 4.6C-mol%when the amount of phosphorus is lwt.%.On the basis of this experiment,Aspen Plus simulation of the process is carried out in this paper.Secondly,on the basis of the existing literature,the process of biomass two-steps preparing light-olefins system(prepare light-olefins through biomass-oil catalyzed by biomass pyrolysis)was simulated.The analysis and comparison of mass flow and energy flow were carried out on the process of one-step and two-steps preparation of light-olefins by biomass.The yield of light-olefins with one-step method is 5.06%and the energy efficiency is 13.94%.The yield of light-olefins with two-steps method is 12.07%and energy efficiency is 32.03%.According to the simulation,the process of biomass two-steps preparing light-olefins system is complex,but the yield of light-olefins is better than the process of biomass one-step preparing light-olefins system.Finally,the exergy of the two processes is analyzed seperatly.In order to obtain the chemical exergy of the biomass accurately,the fitting formula obtained by combining PCA pretreatment with ridge regression is used to predict the high calorific value of the biomass based on the biomass industry analysis.The simulation results show that the exergy efficiency of one-step preparation of light-olefins system is 11.7%,and the exergy efficiency of two-steps preparation of light-olefins system is 27.11%.The two-steps preparation of light-olefins system is optimized.After optimization,the total exergy loss of the system is reduced by 12.86%. |
