Evaporators

An evaporator is a device used to turn the liquid form of a chemical into its gaseous form. The liquid is evaporated, or vaporized, into a gas.

An evaporator is used in an air-conditioning system to allow a compressed cooling chemical, such as R-22 (Freon) or R-410A, to evaporate from liquid to gas while absorbing heat in the process. It can also be used to remove water or other liquids from mixtures. The process of evaporation is widely used to concentrate foods and chemicals as well as salvage solvents. In the concentration process, the goal of evaporation is to vaporize most of the water from a solution which contains the desired product. In the case of desalination of sea water or in Zero Liquid Discharge plants, the reverse purpose applies; evaporation removes the desirable drinking water from the undesired product, salt.

One of the most important applications of evaporation is in the food and beverage industry. Foods or beverages that need to last for a considerable amount of time or need to have certain consistency, like coffee, go through an evaporation step during processing.

In the pharmaceutical industry, the evaporation process is used to eliminate excess moisture, providing an easily handled product and improving product stability. Preservation of long-term activity or stabilization of enzymes in laboratories are greatly assisted by the evaporation process.

Another example of evaporation is in the recovery of sodium hydroxide in kraft pulping. Cutting down waste-handling cost is another major reason for large companies to use evaporation applications. Legally, all producers of waste must dispose of waste using methods compatible with environmental guidelines; these methods are costly. By removing moisture through vaporization, industry can greatly reduce the amount of waste product that must be processed.

Water can be removed from solutions in ways other than evaporation, including membrane processes, liquid-liquid extractions, crystallization, and precipitation. Evaporation can be distinguished from some other drying methods in that the final product of evaporation is a concentrated liquid, not a solid. It is also relatively simple to use and understand since it has been widely used on a large scale, and many techniques are generally well known. In order to concentrate a product by water removal, an auxiliary phase is used which allows for easy transport of the solvent (water) rather than the solute. Water vapor is used as the auxiliary phase when concentrating non-volatile components, such as proteins and sugars. Heat is added to the solution, and part of the solvent is converted into vapor. Heat is the main tool in evaporation, and the process occurs more readily at high temperature and low pressures.

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