Effect of Pressure on Gasification of Petroleum Coke with Carbon Dioxide.

摘要

As refiners are pushed toward producing cleaner transportation fuels from poorer quality crudes, the production of petroleum coke (petcoke) is increasing as a by-product of heavy oil upgrading units. The majority of petcoke produced in Canada is currently stockpiled on the site of the plant. Gasification, however, can be an effective way to utilize petcoke to produce syngas. The gasification process generally involves several steps, including pyrolysis of the feed material to produce a char, heterogeneous reactions of the produced char with the surrounding gases, as well as homogeneous gas phase reactions. Understanding the kinetics of the heterogeneous reactions, as the slowest gasification step, is essential to design and analyze the gasification processes. Because many industrial gasification processes operate at elevated pressures, understanding the effect of pressure on the gasification kinetics is required. The main objective of this study was to investigate the effect of pressure on the gasification of petcoke with CO2.;The kinetics of non-catalytic and potassium catalyzed CO2 gasification of petcoke were determined using a high pressure thermogravimetric analyzer at pressures between 0.1 and 2.4 MPa, and temperatures between 1173 and 1248 K for non-catalytic, and between 998 and 1098 K for catalytic gasification. A model was developed to evaluate the mass transfer limitations in this apparatus. The calculated effectiveness factors, determined by the model, showed that the mass transfer limitations were not significant for CO2 gasification of petcoke under the conditions studied. The intrinsic kinetic analysis of non-catalytic gasification showed a continuous rate increase with increasing pressure, with reaction order of 0.5 with respect to CO2. The surface characterization of petcoke during gasification at different pressures showed that the surface area increased with pressure, accounting for most but not all, of the increase in the reaction rate. The reaction rate of potassium catalyzed CO2 gasification of petcoke also increased with increasing the pressure, with lower reaction order (0.2 with respect to CO2) in comparison with the non-catalytic gasification. The higher reaction rate of potassium loaded petcoke than that of potassium loaded char indicated the importance of the feedstock properties on the catalytic activity.