Efficiency improvement for a utility steam generator with a regenerative air preheater

Abstract

A steam generator system comprising a coal-fired steam generator in fluid communication with a regenerative air preheater. The steam generator being adapted to receive a flow of heated combustion air exiting from the regenerative air preheater and to discharge a flow of hot flue gas to the regenerative air preheater. The regenerative air preheater adapted to receive a flow of cool air in counter flow to the flow of hot flue gas and to provide a heat exchange between the cool air and the hot flue gas to convert the cool air into the heated combustion air exiting to the steam generator. The steam generator system further comprising a first flow of heated air, diverted from the flow of heated combustion air, and routed through a source of pulverized coal to form a mixture comprising heated air and pulverized coal. The mixture being directed, by means of a fan positioned downstream of the source of pulverized coal, to the steam generator for combustion therein. A recycle fluid flow of heated air, diverted from the flow of heated combustion air and directed by means of a fan to re-enter the regenerative air preheater at a location substantially separate from where the flow of cool air is received in the regenerative air preheater to be further heated therein and exit as the flow of heated combustion air.