Experiments and Kinetic Modeling for CO₂ Gasification of Indian Coal Chars in the Context of Underground Coal Gasification

Abstract

Gasification of four Indian coals is carried out in a CO2 atmosphere, using a thermogravimetric analyzer (TGA) to determine the intrinsic kinetics over a temperature range of 800–1050 °C with different partial pressures of CO2. The applicability of three models, viz., the volumetric reaction model, the shrinking core model and the random pore model, is evaluated. Of these three models, the random pore model is found to be the most suitable for all the coals considered in the current study. The dependence of the reaction rate on the gas-phase partial pressures is explained by the Langmuir–Hinshelwood model, and the parameters for the inhibition due to CO and CO2 are determined by performing experiments at different partial pressures. In underground coal gasification, the reaction takes place on reasonably large sized coal particles, wherein diffusion effects are significant. A one-dimensional reaction diffusion model is therefore developed in order to determine the diffusional resistance in the coal particle, and values of diffusivity are estimated.

Carbon cycle in advanced coal chemical engineering

“…39,43,[45][46][47][48] Overall, reaction rates increase with temperature and vary among different feedstocks. 51 The gasification rate, however, generally decreases as the pressure increases under high pressures, due to the inhibition by CO. 49 CO 2 gasification generally has lower reaction rates than steam gasification due to more endothermic character of the CO 2 reactions.…”

Deployment of Underground Coal Gasification in India

“…GAIL has been one of the major components in the pursuit of commercial scale UCG since 2005 when it initiated work on UCG at Barmer in Rajasthan in collaboration with Ergo Exergy of Canada 37,38 . Kinetic modelling of heterogeneous reactions is carried out using thermogravimetric analysis (TGA) 39 . TGA yields the loss of weight with time under different conditions of temperature and pressure when the particles are stationary.…”

Experimental Analysis and Kinetic Modelling for Steam Gasification of the Turkish Lignites

“…Various mathematical models have been developed in order to express gasification processes [13]. Levenspiel developed a volumetric pore model, in which it was assumed that the reaction occurred at all pore volumes, and also he developed shrinking pore model, in which the reaction occurred from the outside to the inside of pore and was assumed that the structure shrank during the reaction [13][14][15].…”

“…Various mathematical models have been developed in order to express gasification processes [13]. Levenspiel developed a volumetric pore model, in which it was assumed that the reaction occurred at all pore volumes, and also he developed shrinking pore model, in which the reaction occurred from the outside to the inside of pore and was assumed that the structure shrank during the reaction [13][14][15]. Bhatia et al developed random pore model which varied depending on the structural parameters, ensuring suitability for lignite with low reactivity in terms of getting into the impact of structural features of coal, and these reactions were basically classified as assuming the occurrence from outside to inside and from inside to outside [16][17][18][19][20].…”