Coking Kinetics And Process Evaluation Of Bio-Oil Hydrodeoxygenation

Biomass fast pyrolysis is considered to be one of the most efficient thermal conversion pathway of biomass energy.The bio-oil from fast pyrolysis can be upgraded to bio-fuel with low water content,viscosity and acidity,and high calorific value through hydrodeoxygenation(HDO)processes,including a mild stage and a deep stage.However,in the mild HDO process of bio-oil,catalyst coking is recognized as the major factor that affects catalyst life time and causes catalyst deactivation.In the first part of thesis,a series of mild HDO experiments of rice husk bio-oil with nickel-based commercial catalyst(HTB-45)were conducted at different reaction temperatures(250 ℃,280 ℃,300 ℃).Based on the proposed mechanisms of bio-oil hydrogenation reaction and catalyst coking deactivstion,a mathematical model consists of ordinary differential equations(ODEs)with time-on-stream(TOS)was developed to validate the experimental results.Reaction kinetic parameters were obtained by fitting the experimental results with the mathematical model outputs.According to results of the coke deposition morphology study and the activation energy of the coking reactions,it was found that high temperature(300 ℃)favors formation of graphite like insoluble coke deposits,which is the main reason of irrevirsible catalyst deactivation.In the second part of the thesis,a process model of two-stage bio-oil hydrogenation plant was developed Aspen Plus.The key feature of the developed model is the effect of catalyst coking has been embeded into the bio-oil HDO process,as the mild stage hydrogenation is modeled by kinetic reactior,and the catalyst deactivation caused by coke deposition was implemented by the user defined Fortran subroutine.The highest yield of simulated bio-fuel was 45%.An economic analysis has been made for the proposed for a demonstration plant with annual throughput of 100 thousand tons,it was found that the total fixed capital cost of the plant is $1.52 million,and the unit production costs are $1024 per ton of upgraded bio-fuel.In this thesis,the establishment of coke kinetic model and economic feasibility analysis provide parameter support for the industrialization of the HDO process.