Study of kinetics of carbon gasification reactions

Abstract

The rates of carbon-steam (C-H20) and carbon-carbon dioxide (C-C02) reactions were studied in a laboratory fluidized bed with coke breeze over a temperature range of 920 to 1040 °C at 1013 kPa. Rate equations suggested by a simplification of the Langmuir-Hinshelwood rate expression and also Ergun's model for a fully back-mixed fluidized bed were developed for both reactions, with rate as a function of temperature and gas composition. The success of these equations in fitting gasification results affords some support for Ergun's model but not In all details, and no attempt is made to prove the detailed mechanisms for the reactions In the present study. The reaction rate was found to be independent of the particle size and the inert gas concentration. The variation of the reaction rate with carbon conversion was also studied. This study forms a basis for interpreting char reactivities to be used in projecting plant performance within the range of experimental conditions studied here.

Modeling biomass char gasification kinetics for improving prediction of carbon conversion in a fluidized bed gasifier

“…where T is the temperature at which the conversion occurs and netic model [7], the Langmuir-Hinshelwood model has been…”

Gasification of Coal Chars With Carbon Dioxide and Oxygen

“…Reaction schemes proposed by previous investigators (i.e. Ergun, 1962, Walker and Strange, 1976, Katta and Keairns, 1981 will provide the necessary theoretical basis for correlating the experimental measurements presented here.…”

“…Differences in the temperature dependence of kinetic coefficients for various chars have also been reported in the literature. For example, Walker and Strange (1976) reported a decrease in k3 with increasing reaction temperature for graphite, whereas Katta and Keairns (1981) reported the opposite behavior for pulverized coke particles. Figure 7 compares the reactivities of the lignite, Illinois # 6 and Pittsburgh # 8 chars when they are gasified with C 0 2 at OSatm partial pressure.…”

Influence of changing particle structure on the rate of gas-solid gasification reactions. Final report, July 1981-March 1984

“…Various global rate models, which take into account conversion-dependent 6 eff~ctive diffusivity and specific area, have been proposed (1,25,62,67) (71, 96,126). but, due to lack of experimental data, have not been extensively tested.…”

“…The global rate models are useful only if the specific area and the effective diffusivity can be related to conversion. In the case of spetifi~ area, correlation has been achieved either empirically (8,48,71) or with the aid of theoretical models (78,38,62 17, 25, 37, 38, 40, 41, 54, 60, 62,.69, 87, 90, 98}. The most convenient of these equations express a relationship between reaction rate and the fraction of coal char.ga~ified •.…”