Migration and agglomeration of chlorine in dechlorination of coal-fired flue gas

Dechlorination of coal-fired flue gas is a novel approach for realizing zero discharge of desulfurization wastewater. The core principle is to convert the HCl in the flue gas into chloride salt, which will migrate into the fly ash. Pilot-scale experiments were conducted to research the migration and agglomeration of chlorine in actual coal-fired flue gas in a power plant. The results indicate that the HCl removal efficiency in flue gas can rise to 70% at a Na/Cl molar ratio of 7.58 when using NaOH solution with clean water or a ratio of 8.93 when using NaOH solution with desulfurization wastewater. XPS shows that the characteristic peak of chloride in the dechlorinated ash is much more pronounced than that in the original ash. The content of inorganic chloride increases significantly with increasing Na/Cl or the utilization of desulfurization wastewater. SEM–EDS indicates that the various salts agglomerated on the fly ash surface notably increase after dechlorination. The contents of Na, Ca, Mg, Fe and S in the ash increase remarkably, especially with desulfurization wastewater. The chloride salts generated by flue gas dechlorination and the pollutants in the desulfurization wastewater are effectively agglomerated with the fly ash.