Moving-Bed Gasification of Low Rank American Coal

This paper presents process simulation of moving-bed coal reactor using bituminous coal. The system of differential equations for the mass and energy balances is solved by using a numerical method and it is optimized by shooting method in computer program. This Simulation is used to predict profile of temperature and concentration along of reactor. The results obtained from the simulation were compared with experimental data. The simulation results were compared with experimental data relevant to Westfield plant in Scotland successfully. Also, the effect of operating parameters such as coal-to-oxygen molar ratio, steam-to-oxygen molar ratio, oxygen mole fraction in air stream as feed, inlet gas temperature and solid particle diameter on composition of product gas and conversion of carbon was investigated. Carbon conversion decreased with increasing of solid capacity, but also it increased with reducing of steam-to-oxygen molar ratio, inlet gas temperature or oxygen mole fraction in air stream. The Westfield plant reactor with Pittsburgh coal as feed has a conversion value of 0.99 and capacity of 1 kg per hour of coal. The reactor capacity was increased to 1.2 kg per hour of coal by reducing steam-to-oxygen ratio with maintaining conversion value of 0.99 and maximum temperature above the ash melting point. Results indicate that the value of steam-to-oxygen molar ratio around 6.688 in the oxidizer stream can provide optimum performance in oxygen-based gasification systems with low rank american coal as feed.

Keywords:

Moving-Bed Reactor , Coal Gasification , Combustion , Low Rank Coal , Reactor Capacity