Air Cooling Options for Flash Plants
By Kevin Wallace, William Harvey – POWER Engineers
and Roubaix Louw – Reykjavik University, Iceland
Flash steam power plants commonly use evaporative cooling with wet cooling towers, with cooling tower makeup provided by the condensed steam. These units are often preferred over binary units for high temperature resources for thermodynamic and economic reasons. However, at locations where near 100% reinjection of the produced geofluid is required, binary or combined cycle units with air-cooled condensers are generally applied. There are certain limitations in applying air-cooled condensers for flash units, and we discuss these considerations.
The purpose of this paper is to explore the opportunities and challenges of coupling a flash cycle, for harnessing high temperature resources, with air cooling to allow complete reinjection. The performances of air cooled flash plants are investigated and compared to a conventional water cooled flash plant configuration, as well as to an air cooled binary plant. The plants are compared in terms of gross, parasitic, and net power consumption. A number of heat exchanger configuration options for an air-cooled flash steam plant are investigated and described in terms of capital cost, material selections and non-condensible gas handling capability. A configuration with a steam turbine, surface condenser, and air-cooled heat exchanger, circulating water in a closed loop, is presented as a viable air-cooled flash alternative, with modest performance and capital cost penalties compared to a plant equipped with a wet cooling tower or air-cooled binary unit. Avenues for future improvements of the various cycles are presented.
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