The process of evaporation concentrates the solution of a solvent. The solvent is usually water. The solvent further vaporizes to yield a concentrated solution. Evaporation is very much different from distillation because evaporation doesn’t involve the separation of vapors into components. An evaporators consists of a heat exchanger, valves, manifolds, controls, pumps, and a condenser.
Evaporators Various industries use evaporators in processes such as pharmaceuticals, foods and beverages, pulp and paper, chemicals, polymers and resins, inorganic salts, acids, bases, and many other applications. In this article, we will discuss the various types of evaporators, their advantages and disadvantages, and their applications.
1. Falling Film Evaporator:
Falling Film Evaporator inverts to optimize heat exchange, placing the exchanger at the top for efficient operation. The evaporator receives the feed at its top, and subsequently distributes it further to the tubes.It consists of a vertical shell and a tube heat exchanger. Solvent introduced atop tube flows downward, forming a thin film on the surface tube. As it gets heated further, the vapors get generated. It increases the heat transfer for the process.
Applications of Falling Film Evaporator-
Falling film evaporator concentrate dairy products, including whey, milk protein, skim milk, cream, and hydrolyzed milk. Sugar solutions, urea, phosphoric acid, and black liquor.
2. Forced Circulation Evaporators:
A forced Circulation Evaporator is a type of evaporator that requires the addition of a pump and additional controls. It is mostly used in cases where the feed contains solids or crystallization is present. And also used to separate mixtures that are not possible by normal evaporating units.Forced circular evaporator boosts liquid flow to 2-6m/s using a circulation pump, serving dual roles in heat exchange and flash separation. Therefore, it separates the mixture without using normal conventional boiling. So, it consists of a vertical shell and a heat exchanger tube with a centrifugal pump. Forced Circulation Evaporator offer high efficiency and reduced fouling but entail drawbacks like higher costs, increased power usage, and time-intensive processes.
Applications of Forced Circulation Evaporators-
The typical applications of Forced Circulation evaporators are sodium sulfate, urea, sodium chloride, ammonium sulfate, magnesium chloride, citric acid, and caustic potash.
3. LTV Evaporators:
Long tube vertical (LTV) refers to a type of evaporator, also recognized as rising film evaporators. Hence, LTV Evaporators are one of the most used evaporators. A liquid separator is attached to a shell and tube heat exchanger. The rising film evaporator is very similar to the falling film evaporators. It’s just the opposite of a falling film. It also consists of a vertical shell and a tube heat exchanger for heat exchanging. The solvent is fed at the bottom of the tube. As the heat increases further, it generates vapors that lift the liquid upward. Moreover, the process completes as a result. The advantages of LTV Evaporator are less floor space requirements, high heat transfer efficiency, and the ability to handle foamy liquids. The common disadvantages of LTV Evaporators are they require high headroom, and higher pressure required.
Applications of LTV Evaporators-
Some of the common uses of Long Tube Vertical Evaporators are the concentration of cane sugar syrups, black liquor in paper plants, nitrates, and electrolytic tinning liquors.
4. Plate Evaporators:
In the process of evaporation, a Plate Evaporator facilitates the flow of a thin liquid film between its plates. Also referred to as gasketed plate and frame evaporator, Plate Evaporators are constructed by arranging multiple plates with corner openings between a top and bottom bar. Therefore, the Plate Evaporator, a type of plate and frame heat exchanger, finds extensive use in the food and beverage industry.
Plate Evaporators offer several advantages, including adaptability to various materials, low required headroom, ease of cleaning, and modification. However, a significant drawback of Plate Evaporator is the presence of a large gasketed area, which may lead to potential leakage if the gasket is not appropriately selected.
Applications of Plate Evaporators-
Typical applications of gasketed plate evaporator are stripping applications, removing monomers from polymers, and deodorization. Typically, people use it for fruit juices, fruit puree, syrup, coffee, and milk.
5. Mechanical Vapor Recompression (MVR):
Mechanical Vapor Recompression (MVR) compresses water vapor, causing an increase in temperature and pressure in this type of evaporator.The rise in temperature makes the temperature difference between the vapor and the fluid. The further heat transfer results in the heat exchanger. Hence, the compressed vapor is again fed back to generate more steam. This is an energy-efficient and energy-recovery process.
Applications of MVR-
The dairy industry, the brewing industry, sugar industry, saline industry, pulp industry, chemical industry, alcohol industry, etc.