Continuous-contact operations water cooling

The purpose of the final cooler is to remove the heat of compression added by the exhauster and to cool the gas to its final temperature so that downstream absorbers will operate more efficiently. Final cooling is typically achieved by direct contact with the cooling medium, either water or oil. An important function of final cooling is removal of naphthalene. In final coolers using wash oil, the naphthalene dissolves in the oil, and a side stream is steam stripped to remove the naphthalene. If water cooling is used, the condensed naphthalene must be absorbed by contacting the water with tar. The tar is continuously exchanged with fresh tar to prevent naphthalene buildup. 

Sodium hydroxide and potassium hydroxide should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C. In particular, splash goggles and impermeable gloves should be worn at all times when handling these substances to prevent eye and skin contact. Operations with metal hydroxide solutions that have the potential to create aerosols should be conducted in a fume hood to prevent exposure by inhalation. NaOH and KOH generate considerable heat when dissolved in water when mixing with water, always add caustics slowly to the water and stir continuously. Never add water in limited quantities to solid hydroxides. Containers of hydroxides should be stored in a cool, dry location, separated from acids and incompatible substances. 

In entrainer sublimation, an entrainer gas is blown into the vaporisation chamber of a sublimer in order to increase the vapour flowrate to the condensing equipment, thereby increasing the yield. Air is the most commonly used entrainer, though superheated steam can be employed for substances such as anthracene that are relatively insoluble in water. If steam is used, the vapour may be cooled and condensed by direct contact with a spray of cold water. Although the recovery of the sublimate is efficient, the product is wet. The use of an entrainer gas in a sublimation process also provides the heat needed for sublimation and an efficient means of temperature control. If necessary, it may also provide dilution for the fractional condensation at the desublimation stage. Entrainer sublimation, whether by gas flow over a static bed of solid particles or through a fluidised bed, is ideally suited to continuous operation. 

Conductivity measurement with contact electrodes is used in many different process analytical applications. In all of them the main interest is to detect the presence of ionic species in the sample. The effectiveness of distillation and demineralization units is normally controlled by continuous measurement of the conductivity of the outgoing stream. Any defect in the operation of the unit can immediately be seen in the increase in conductivity. The feeding water to steam turbines has to be as clean as possible in order to avoid corrosion in the system that operates under high pressure and at elevated temperatures. The conductivities of feeding water as well as the condensed steam are also continuously monitored by conductivity measurement. Increased conductivity is an immediate indication of corrosion in the system or leakage in the cooling system. This is of extreme importance in nuclear power plants where among other risks corrosion products may also become activated. 

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