Modelling and Simulation of a Fixed-Bed Reactor for the Production of Liquid Fuel from Synthesis Gas /

Abstract

Producing transportation and energy generation fuels and chemicals from abundant resources of coal and natural gas has been steadily gaining popularity as the age of conventional crude oil is nearing its end. Over the past decade oil prices have skyrocketed and the involvement of international politics is becoming increasingly problematic due to oil not being globally available including countries like Pakistan as it majorly relies on imported crude for its major energy and transportation needs. The use of this indirect coal liquefaction process of syngas conversion and Fischer Tropsch synthesis can greatly benefit the country in terms of low cost, cleaner fuel production and research in this area in Pakistan must be started on an urgent basis. In this study the effect of some of the reaction parameters were investigated with a two-dimensional pseudo homogeneous tubular fixed bed reactor model for fischer tropsch synthesis of syngas using cobalt/titania catalyst. The model was applied using suitable kinetics and the initial operating conditions were taken from experimental data. At first, the model was used to predict the general effects of variation in catalyst activity, tube temperature and diameter. A hotspot problem for all the three cases was noted as well as an increase in conversion and reduction in C5+ selectivity so an optimized approach was considered. The reactor length was divided into fifteen sections and the tube wall temperature of each section was adjusted according to the axial temperature profile. As a result, nearly isothermal condition was achieved axially while radial-wise, the temperature declined to close to the set tube temperature of that section. Therefore the selectivity of methane reduced and of C5+ increased significantly.