Waste-Heat Vertical Tube Foam Evaporation for Cooling Tower Blowdown Renovation/Recycle

摘要

A prototype waste-heat vertical tube foam evaporation (WH-VTFE) plant was designed, constructed, and field-tested for reducing power plant cooling tower blowdown to a small residual volume of solids slurried in brine, while producing distilled water for reuse. Facility design was based on previously-developed pilot plant test data. The WH-VTFE facility was constructed for initial parametric testing in upflow/downflow evaporation modes with boiler steam. The field test/demonstration phase was conducted at a power plant site using turbine exhaust steam for the up to 50-fold cooling tower blowdown concentration in a foamy-flow seed-slurried mode of downflow vertical tube evaporation. The VTFE heat transfer coefficient ranged between 5600-9000 W/sq m/degree, over 4-fold the level considered as acceptable in another study. Further, a sufficient temperature difference is available within a typical power plant heat rejection system to operate a WH-VTFE when the plant load is above 50% of its design capacity. Scale formed from inadequate brine recycle rates was readily removed by recycling fresh water through the evaporator to restore the high heat transfer performance of the WH-VTFE. It was concluded that WH-VTFE was demonstrated as feasible and commercially viable.