Ammonia removal from fly ash in an acoustically enhanced fluidized bed

Abstract

A process for removing ammonia from fly ash during processing on an inclined fluidized bed. The process begins by introducing a mixture of particulates having ammonia adsorbed therein into an inclined fluidized bed. Concurrently, a fluidizing gas is pre-heated and is also introduced into the fluidized bed. The mixture is then processed along the fluidized bed with the pre-heated fluidizing gas to achieve bubbling fluidization of the particles. This causes segregation by which a dense fraction settles downward and a light fraction rises upward in the bed. Ammonia in the particles is desorbed by the pre-heated fluidizing gas. The fluidizing gas is then scrubbed after the processing step to remove the desorbed ammonia. The process may also include the use of acoustic enhancement whereby an acoustic field is imposed on the fluidized bed to improve fluidization and segregation of the particles and to increase the efficacy of ammonia removal. In addition, a heat exchanger or electric heating elements immersed in the fluidized bed can be used to heat the ash to the temperatures needed to desorb ammonia from the ash. Furthermore, the energy efficiency of the process can be improved by recovering heat from the hot ash discharged from the fluidized bed and/or from the exhaust stream of hot fluidizing gas, for reuse during preheating steps. The improved process removes ammonia in a simple and efficient manner by preheating the fluidizing gas of the inclined bed to temperatures of 300 to 500° F., and using this preheated gas to drive off any adsorbed ammonia.

Dependencies are inferred from the claim text.