Chemical and Thermal Methods for Removing Ammonia from Fly Ashes

The presence of ammonia in ashes (i.e. ammonia slip) is a direct consequence of the methods used for denitrification – selective catalytic and non-catalytic reduction (SCR, SNCR). The excess unreacted ammonia used in both of these methods passes as a constituent to ash, impairing its properties, and thus affects the quality of the commercial product. The summary of the available methods for removing NH₃ from fly ashes is presented. Both chemical and thermal methods of removing NH₃are described. The results of the chemical methods depend on the kind of additional reagents used and composition of fly ashes. Thermal methods seem to be simpler and easier to use, but they are used mainly on the smaller scale.