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Closed-loop cooling water (CLCW) systems are utilized in areas where cooling is critical. In such areas, a high level of chemical treatment is required to maintain good corrosion and scale control. This article discusses various treatment methods and the frequently encountered chemistry problems of such systems, as experienced at the Tüpraş İzmit refinery.
CLCW systems are frequently used in the cooling of reciprocating compressors, which handle light hydrocarbons or hydrogen-specifically, the jackets where the tube metal temperature (TMT) exceeds 100°C. High TMT eliminates open-loop (evaporative) cooling water as a cooling medium due to its high scaleforming potential.
A series of CLCW system failures induced by poorly handled water chemistry is presented in this article. It also discusses the actions taken to diagnose the root cause and address the chemistry problem to ensure that all CLCW systems are stable.
Closed-loop cooling system design. Closed-loop circulation cooling systems are specifically developed for engine applications, and use high-quality water. These engines may include diesel or other internal combustion machines, or jacket cooling systems for compressors.
Closed-cooling systems are used instead of open systems for several reasons. Among these, most cases include hot processes where scale formation on heat transfer surfaces must be eliminated. The products to be cooled impose a limit on the film temperature in the coolers; therefore, cooling water must be kept above a certain temperature. If this temperature is high, then the closed system must be filled with treated water or condensate to prevent solids precipitation.
High-quality water is often used, and the heat absorbed by the cooling water is removed in a heat exchanger without direct contact. Heat absorbed by cooling water in a closed-system exchanger is transferred to atmosphere via a cooling tower, thereby accommodating the evaporation process. Temperatures in these systems vary from 0°C-116°C, and system volumes range from 0.04 m3-26,500 m3, according to literature.
Typical cooling console skids comprise a centrifugal water circulation pump with an outlet pressure of 4 kg/cm2g-5 kg/cm2g, a reservoir or expansion water tank with a level indicator, a filling connection to this tank, a vent nozzle to ambient, an electric heater stab into the tank, a circulating water cooler, and a shell-and-tube exchanger with compressor connection lines and cooling water at the tube side. FIG. 1...