Discharge of cooling water

Zero Discharge of Cooling Water by Sidestream Softening Matson, Jack V. Harris, Teaue G. Ill... 

Water consumption total wastewater volume has remained relatively stable since 1990 at about 2.3 millionm3 per day. During the same period the discharge of cooling water/process water per sales volume fell 26%. 

Industrial cooling water discharge simulations in the Arabian Gulf are frequently carried out with tools such as Cormix [1], GEMSS [2], Mike 21 [3], and 3D SMART [4]. Discharges of cooling water into receiving water bodies are an environmental concern... 

Thermal pollution. Degradation of water quality by the introduction of a heated effluent. It is primarily a result of the discharge of cooling waters from industrial processes, particularly from electrical power generation. Even small deviations from normal water temperatures can affect aquatic life. Thermal pollution usually can be controlled by cooling towers. 

Figure 8-3 Three basic types of cooling water systems. Top the once-through system where the cooling water is used once and then discharged. Middle the open recirculation system where the water is cooled and recycled through a system in which it comes in direct contact with air. Bottom a closed recirculation system where the water is cooled and recycled without coming in direct contact with the atmosphere.

Co-location is not be suitable for all desalination plants. This process only becomes feasible if the volume of cooling water discharged from the power plant is at least three to four times greater than the capacity of the desalination plant (Voutchkov 2004). Furthermore, corrosion from power plant heat exchangers may elevate the levels of metal in the feed to the desalination plant, which may then damage the reverse osmosis membrane units (Voutchkov 2004). 

It makes sense therefore to periodically (once per year or so) resurvey all cooling water systems from a point prior to the source of makeup water to a point beyond the discharge of bleed water in order to be aware of cooling system changing needs and to highlight any potential bottlenecks that will ultimately interfere with the users seamless cooling process. 

Oil-water emulsions are widely used in metal machining operations to provide lubrication and cooling. Although recycling of the fluids is widely practiced, spent waste streams are produced. Using ultrafiltration to recover the oil component and allow safe discharge of the water makes good economic sense, and... 

Liquid-liner compressors produce an oil-free discharge of up to 125 psig. The efficiency is relatively low, 50% or so, but Wgh enough to make them superior to steam jet ejectors for vacuum service. The liquid absorbs the considerable heat of compression and must be circulated and cooled a 200 HP compressor requires 100 gpm of cooling water with a 10°F rise. When water vapor is objectionable in the compressed gas, other sealing liquids are used for example, sulfuric acid for the compression of chlorine. Figure 7.19(e) shows the principle and Table 7.10 gives specifications of some commercial units. 

Note that the cooling water flowrate is independent of the temperatures of the process units. The sizes of the heat exchangers depend on all the temperatures, but the flowrate of cooling water does not. The heat discharge temperatures must, of course, all be higher than the cooling water temperature. Otherwise the cooling water would heat, not cool, the process. 

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