In-Situ Desulfurization of Coal Gas with CaO-Based Sorbents

Abstract

Calcium-based sorbents, such as limestone and dolomite, are viable candidates as sulfur-capturing agents in an in-situ coal asification/desulfurization process. The effect of limestone addition on the hydrodynamics of a fluidized-bed gasifier and desulfurization of the product gas have been studied. The hydrodynamic characteristics of coal char/limestone mixtures, such as solid mixing and fines retention, have been studied in a 0.2-m diameter fluidization column. The results indicate that a superficial gas velocity of 0.6 cm/s is sufficient to produce a well-mixed bed of limestone/char mixture in the gasifier. The presence of limestone does not appear to affect the fines retention while the bed height has a significant effect on the fines elutriation from the fluidized bed gasifier. Reaction rate data pertaining to the reaction between calcium-based sorbents and hydrogen sulfide have been obtained by a thermogravimetric technique in the temperature range of 650° to 1050°C. The results indicate that calcium-based sorbents can be used effectively for capturing sulfur during the gasification of high sulfur coals.