Process Simulation And Life Cycle Assessment Of Bio-oil And Heavy Oil Co-catalytic Cracking

Fossil energy is non-renewable,and the shortage of petroleum resources increasingly becomes serious due to the low reserves and high consumption of petroleum.Biomass as the only renewable carbon source is considered as a clean renewable energy.Through rapid pyrolysis,the biomass with low energy density can be converted into bio-oil with high energy density,realizing the maximum utilization of bio-material resources and making storage and transportation more convenient.The co-catalytic cracking of bio-oil and heavy oil can efficiently utilize bio-oil,provide a reasonable way for the treatment of biomass,and alleviate the problem of shortage of raw materials for catalytic cracking of petroleum,which has good economic and environmental benefits.In this paper,CFD simulations were conducted for the fast pyrolysis process of biomass in fluidized bed,and the CFD simulation results were compared with experimental data to validate the developed CFD model.Then,the product yields at nine pyrolysis temperatures of673 K,723 K,773 K,823 K,873K,923 K,973 K,1023 K and 1073 K were investigated.The simulation results showed that the bio-oil yield was the highest at 823 K,so the pyrolysis reaction model in Aspen Plus was built based on this data.The process simulation of biomass fast pyrolysis was performed in Aspen Plus including the biomass pretreatment,fluidized bed fast pyrolysis reactor,reaction product separation and condensation module.The CFD simulation results at 823 K was used in the fluidized bed fast pyrolysis reactor.The product yields of Aspen Plus were consistent with the CFD simulation results,which verify the accuracy of Aspen Plus pyrolysis model.The bio-oil from fast pyrolysis was co-processed with heavy oil in fluid catalytic cracking unit at 10/90 and 20/80 blending ratio.The simulation results were compared with pure heavy oil catalytic cracking results.The results of different blending ratio indicated that:when 90%10%bio-oil and crude oil blending,the product yield is almost the same as those of pure heavy oil catalytic cracking with no significant differences;For mixing of 20%bio-oil and 80%heavy oil,except the significant increase of the yield of slurry oil,all the yields of other products decreased.Finally,the full life cycle model of biomass fast pyrolysis and co-catalytic cracking of bio-oil and heavy oil was established on the GREET software platform to obtain non-renewable net energy consumption and net emissions of greenhouse gas CO₂.