EFFECTS OF SODIUM-CHLORIDE ON LIMESTONE CALCINATION AND SULFATION IN FLUIDIZED-BED COMBUSTION

A laboratory investigation of the interaction of sodium chloride with natural limestones during calcination and sulfation has been performed. Reactions were carried out at 850 °C in a synthetic flue gas consisting of 0.3% SO2, 5% O2, 20% CO2, and the balance nitrogen. Results show that the presence of salt induces structural rearrangement in the stones that can lead to an optimum pore distribution for reaction with SO2/O2 mixtures. The salt effect involves the presence of a liquid phase that increases the ionic diffusion and mobility of the system, enhancing calcination, enhancing crystallization Of CaO, and creating a pore structure permeable to reactant gas diffusion. Application of NaCl addition to fluidized-bed coal combustion would increase the sulfur capacity of unreactive limestone and would reduce the quantity of limestone needed and the amount of solid waste produced in meeting SO2 emission standards. © 1979, American Chemical Society. All rights reserved.