Principle, Construction, Working, Uses, Merits and Demerits of Forced Circulation Evaporator

Forced Circulation Evaporator

Principle

Pumps circulate high pressure liquid through tubes in forced circulation evaporators. The elevated boiling point prevents boiling from taking place. It also causes some form of agitation to be created by forcing the liquids to circulate. When the liquid leaves the tubes, the pressure in the vapor head drops abruptly. This causes superheated liquor to flash, which in turn causes feed to evaporate.

Construction

Pumps are attached to these types of evaporators in order to circulate heat from its contents. Figure below illustrates the forced circulation evaporator as two tube sheets held together by steam jackets. Tubes measure 0.1 meters in diameter and 2.5 meters in length. Several parts of the tubes extend into the deflector of the vapor head. A return pipe from the vapor head runs downward and enters the pump's inlet. A pump circulates liquid throughout the system. As the tube is placed under pressure (but there is no boiling), the boiling point of the liquid is raised, and it enters the evaporator body.

Working

The calendria introduces steam. A positive velocity is applied to the liquid as it enters the tube. During the process of moving up the tube, the liquid gets heated and begins to boil. Consequently, vapor and liquid mixtures rush out of the tubes at a high speed. Liquid and vapor are effectively separated when this mixture strikes the deflector. In cyclone separators, the vapour enters and leaves the equipment. During evaporation, liquids are circulated through pumps. The collected product seeps down into an outlet on the bottom.

Uses

• Solutions containing thermolabile substances are concentrated using forced circulation evaporators.
• Hepatic extracts and insulin are concentrated with it.
• In crystallization operations, it can be used to suspend crystals at all times without causing abrasion.
• These minerals are also used for producing salt, corn steep water, and calcium carbonate.
• The effluent from pharmaceutical industries is treated using this technology.
• By stacking multiple forced circulation chambers, a tower that can be utilized for increasing sugar and syrup concentration can be formed.

Merits

• A high heat transfer coefficient results in rapid movement of liquid.
• Therefore, minimal fouling can be achieved by bringing the liquid entering the circulation evaporator to a boil in the separator, rather than on a heating surface.
• Because of forced circulation, it is impossible to accumulate salt, scale, and fouling.
• The rapid evaporation makes them an ideal evaporator for thermolabile substances.
• Pumping mechanism makes it ideal for viscous preparations.
• Solid-containing liquids can also be evaporated using these evaporators.
• It is relatively easy to clean and handle circulation evaporators.

Demerits

• Liquids hold up for a long time.
• Both the equipment and the power requirements are expensive.
• The maintenance costs are high.
• In addition to the higher corrosion rate, the increased velocity causes the equipment to corrode quicker, raising the total cost of maintenance.

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