Pressurized CO2-enhanced gasification of coal
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Carbon dioxide was considered as a co-gasifying agent in a coal gasification reactor. The work presented herein describes the simulation results for the process and the experimental data on coal char gasification with CO2 addition as the rate-controlling step for the entire process. To study the potentially beneficial effect of the introduction of CO2 into the gasification system, several simulations were conducted using the commercial process simulation software ChemCAD 6.3®. The results of a Gibbs equilibrium reactor were evaluated. The Boudouard reaction is a critical path for the development of this process, and the kinetics were studied experimentally. Four chars derived from the pyrolysis of Polish coals of different origins were selected for the experiments. The kinetic characteristics of this system were examined using a custom-designed pressurized fixed-bed reactor. To determine the effect of pressure on the gasification rate, several preliminary studies on the gasification of coal chars were performed isothermally at the temperature of 950 °C and pressures of 1, 10, and 20 bars. In contrast to the thermodynamic calculations, the experimental data revealed that increasing the CO2 pressure leads to a higher reaction rate for medium-rank coal chars and low-rank lignite coal char, resulting in higher efficiency for carbon monoxide production. The pressure influences the reactivity more strongly when varied from 1 to 10 bars; a further increase in pressure affects the rate almost insignificantly. The observed behavior representing the changes in carbon conversion degree during gasification is satisfactorily described by the grain model.
KeywordsCO2 removal Syngas efficiency Char gasification Pressure Reactivity Kinetics
The research results presented herein were obtained during the course of the project “Development of coal gasification technology for high-efficiency production of fuels and energy,” Task No. 3 of the Strategic Program for Research and Development: “Advanced energy generation technologies” funded by the Polish National Center for Research and Development.
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