Abstract: Waste heat is extracted in two stages from the exhaust (20) of a biomass dryer (14) in a grain alcohol plant (10). A boiler circuit (56) provides high pressure steam to a balance of the plant (54). A first energy recovery circuit (36) extracts heat from the exhaust via a non-contact heat exchanger (24) and provides a first relatively lower pressure steam (78) to the balance of the plant, thereby bypassing a portion of the boiler circuit. Working fluids in the boiler and first energy recovery circuits are maintained within boiler water quality specifications and are intermixed to allow the production of the first relatively lower pressure steam without a pressure reduction device. A second energy recovery circuit (44) extracts heat from the exhaust downstream of the first energy recovery circuit using a direct contact heat exchanger (38) and provides a non-boiler quality heated fluid (52) to the balance of the plant.

Abstract: Waste heat is extracted from the exhaust (20) of a biomass dryer (14) in a grain alcohol plant (10). A boiler circuit (74) provides high pressure steam to a balance of the plant (64). A recovered energy circuit (76) extracts heat from the exhaust via a dryer exhaust condensing economizer (24) and provides a steam mixture (60) to satisfy an intermediate pressure steam demand of the balance of the plant, thereby bypassing a portion of the boiler circuit. Working fluids in the boiler and recovered energy circuits are intermixed in a boiler feed vessel (72). Dryer exhaust condensate (30) may be used in an exhaust gas scrubber (22) upstream of the dryer exhaust condensing economizer to remove pollutants and to saturate (26) the exhaust gas for improved heat transfer. Heat transfer may be further improved by operating the dryer exhaust condensing economizer at an elevated pressure.