Measurement and Modeling of Vapor-Phase Sodium Chloride Formed During Pulverized Coal Combustion

Abstract

The existence of Nacl in the vapour phase of post-combustion guess was confirmed in a laboralory study utilizing size-classified samples of six coals with varying chlorine concentralions. Laser induced photodissociation and fluorescence was used to successfully detect molecular sodium chloride vapor levels in coal combustion gases at 1200 K. Results obtained from combustion of a high chlorine Loy Yang coal yielded a linearly increasing fluorescence signal with increasing coal particle feed rate. Under comparable combustion conditions, relative measurements obtained upon combustion of five U.S. coals with differing chlorine contents yielded normalized NaCI signal intensities strongly dependent on coal lype. Results were found to increase with increasing total chlorine content of the parent coals: for the U.S. coals. results directly scaled with chlorine level within the bounds of experimental error. This dependence on chlorine level was confirmed by equilibrium calculations at both the dilute conditions of the experiments and at realistic post-flame oxygen concentrations. Kinetic calculations for the sodium/ chlorine/oxygcn/ hydrogen system indicated that steady state would be achieved rapidly under the conditions of these experiments.

Key words:

• Alkali
• coal combustion
• laser diagnostics