Coal Char-CO sub(2) Gasification Measurements and Modeling in a Pressurized Flat-Flame Burner

A pressurized flat-flame burner (PFFB) was used to conduct coal gasification studies. The PFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of 10 super(5) K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Char gasification studies by CO sub(2) were conducted on a subbituminous coal and 4 bituminous coals in the PFFB. Pressures of 5, 10, and 15 atm were used with gas compositions of 20, 40, and 90 mol % CO sub(2). Gas conditions with peak temperatures of 1700 to 2000 K were used, which resulted in char particle temperatures of 1000 to 1800 K. Three gasification models were developed to fit and analyze the gasification data. A simple first-order model was used to show that the measured gasification rates were far below the film-diffusion limit. The other two models, designated CCK and CCK super(N), were based on three versions of the CBK models. CCK super(N) used an n super(th)-order kinetic mechanism, and CCK used a semiglobal Langmuir-Hinshelwood kinetic mechanism. The two CCK models fit the PFFB gasification data better than the first-order model. The fits of the gasification data with CCK and CCK super(N) were comparable to each other. The fit of the data in CCK suggests that Knudsen diffusion may have influenced the gasification rates in the PFFB experiments. The gasification rate parameters in each of the three models were correlated with coal rank. super(13)C NMR parameters were used to estimate a structural parameter of the coal char. Char-CO sub(2) gasification rate coefficients correlated better with this NMR-based char structure index than it did with the carbon and oxygen content of the parent coal.