(582ct) Integration of Random Pore Model & Langmuir-Hinshelwood Kinetics to Study High Temperature Coal Gasification

Random pore model (Bhatia and Perlmutter, 1980; 1981; 1983) has been applied extensively to both char oxidation systems (Su and Perlmutter, 1985) and char gasification systems with CO₂ (Bhatia, 1981) and H₂O (Chi and Perlmutter, 1989). The model solutions developed in these works assume the reaction to be first order with respect to the reactant gas. But it is well known that coal char systems are highly porous and the gasification reactions follow the Langmuir-Hinshelwood (LH) kinetics (Ergun, 1955).

There have been attempts to combine random pore model with LH kinetics for competing CO₂ and H₂O gasification reactions (Umemoto et. al., 2013). But these efforts are restricted to the low temperature kinetically controlled regime. There is a need to extend the combined model to systems at higher temperature that are pore diffusion controlled to better understand the industrial systems of coal gasification.

In this study, we extend the random pore model with transport and diffusion effects to incorporate LH kinetics first to CO₂ gasification systems with varying amounts of CO using multi-species reaction diffusion modeling. We then study the H2O gasification systems in presence of H₂O, CO and H₂. Finally we combine both these efforts to study the complete industrial gasification systems that involve both CO₂ and H₂O in the presence of all four gases: CO₂, CO, H₂O and H2. Using this model we gain important insights into optimizing the feed compositions to obtain the final product: syngas, with the desired specifications.

References

Bhatia, S. K., and D. D. Perlmutter, “A Random Pore Model for Fluid-Solid Reactions: I. Isothermal, Kinetic Control,”AlChEJ., 26, 379 (1980).

Bhatia, S. K., and D. D. Perlmutter, “A Random Pore Model for Fluid-Solid Reactions: II., Diffusion & Transport Effects,”AlChEJ., 27, 247 (1981).

Bhatia, S. K., and D. D. Perlmutter, “Unified Structural Effects in Fluid-Solid Reactions,”AlChEJ., 29, 281 (1983).

Bhatia, S. K., “The Effect of Pore Structure on the Kinetics of Fluid-Solid Reactions,” PhD Thesis, University of Pennsylvania (1981).

Su, J. L., and D. D. Perlmutter, “The Effect of Pore Structure on Char Oxidation Kinetics,”AlChEJ., 31, 973 (1985).

Chi, W. K., and D. D. Perlmutter, “The Effect of Pore Structure on the Char-Steam Reaction,”AlChEJ., 35, 1791 (1989).

Umemoto, S., S. Kajitani and S. Hara, “Modeling of Coal Char Gasification in Coexistence of CO2 and H2O Considering Sharing of Active Sites” Fuel., 103, 14 (2013).

Ergun, S., “Kinetics of the Reaction of Carbon Dioxide with Carbon,”J. of Phys. Chem., 60, 480 (1955).