EVAPORATORS AND ITS TYPES

What is an Evaporator??

An evaporator is a device used for the process of turning the form of a substance from liquid to gaseous form or vapor and the process is known as evaporation.

Types of Evaporators:-

Falling Film Evaporators:-

The falling film evaporator is a type of evaporator which is used for heat exchanger. It consists of a vertical shell and a tube heat exchanger. The concentrated liquid is fed at the top of the tube and then flows down to the surface tube as a thin film. As it gets heated further, the vapors get generated. It increases the heat transfer and the vapor and liquid get separated further.

Rising Film, LTV (Long Tube Vertical) Evaporators:-

The rising film evaporator is very similar to the falling film evaporator. It’s just the opposite of falling film. It also consists of a vertical shell and a tube heat exchanger and it is also used for heat exchanging. The concentrated liquid is fed at the bottom of the tube. As the heat increases further the vapors get generated and lift the liquid upward. As a result the vapor and liquid get separated further.

Forced Circulation Evaporators:-

Force circulation evaporator is a type of evaporator which is used to separate mixture which is not possible by normal evaporating unit. In normal circular evaporator the velocity of liquid flow is 0.3 to 1m/s but forced circular evaporator increases the velocity of liquid flow to 2 to 6m/s. It contains a circulation pump and because of this it is used for both heat exchanger and flash separation. It separates the mixture without using normal conventional boiling. It consists of a vertical shell and heat exchanger tube with a centrifugal pump.

Plate Evaporators:-

Plane evaporators consist of a plate and frame heat exchanger and are mainly used in food and beverage industry. Plate evaporator is a type of evaporator in which a thin film of liquid is passed and flows between the plates for the process of evaporation. It is typically used for fruit juices, fruit puree, syrup, coffee, milk.

Thermal Vapor Recompression(TVR):-

Thermal vapor recompression evaporator is a type of evaporator which is used as a thermo compressor to reduce the steam required for the process of evaporation. A vapor steam is compressed to a higher temperature and pressure by a steam jet pump.

Mechanical Vapor Recompression (MVR):-

Mechanical vapor recompression is a type of evaporator in which the water vapor is compressed which results in rise of temperature and pressure. The rise in temperature makes the temperature difference between the vapor and the fluid. The further heat transfer results in heat exchanger. The compressed vapor is again fed back to generate more steam. This is energy efficient and energy recovery process.

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How Falling Film Evaporators Are Rendered Tasks At Distillery Stillage Industrial Unit?

Before filling inside knowledge about film evaporators, let’s intellect what is evaporator? An evaporator means the equipment which is employed under vacuum in order to let the water evaporate present in the solution through the inlet feed point. Evaporators have got their exercise in food, dairy, chemical, or other industries. In the plant of the distillery, decreasing the volume of liquid effluents and recovering the water is essential for generating the final product. Falling film evaporators is one of the sorts, pushed in exploitation for distillery stillage. This evaporator is put in use for purposes like bio methanation spent wash and RO reject water concentration.

How does the cycle within falling film evaporators conduct?  

●    Product

●    Concentrate

●    Condensate

●    Vapor

●    Deaeration

●    Steam

●    Falling Film Calandria

●    Vapor Separator

What is the working direction of falling film evaporators?

In such evaporators, the liquid product makes its entry from the head and is equally distributed into the heating tubes placed inboard. A thin film then gets in the heating tubes of falling film evaporators and flows down at boiling temperature & is evaporated to a partial extent. To heat the evaporator, steam is usually used. Further, product and vapor flow downward, maintaining the parallel format. That the downward movement is hereafter augmented by the current of flowing vapor. When the concentrated product separates, a vapor is formed and undergo the bottom section of the separator and heat exchanger devices assembled with the falling film evaporators.

How much in numbers are the limitations of the falling film evaporators?

·        If great precautions and monitoring is put into action, 30% concentration might be accomplished.

·        The smell of fowl causes pollution in the atmosphere as well as bed environment.

·        High foaming and entrainment are the limits for obtaining the effective capacity of such an evaporator.

·        Scale formation in the evaporator can be cleaned after 8 to 10 days by making the selection of the correct combination of MEE with efficient feed treatment methods.

·        Extra effluent generation occurs because of chemical cleaning and special treatment prior to discharging to the main ETP set up.

·        It could seem highly risky to live when bio digester overflow and falling film evaporator is approached as an Integrated Evaporation Arrangement.

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Does remedial measures can be adopted in the case of falling film evaporators?

·        Auto feed control and monitoring system can be installed for the process supervision.

·        Auto steam/temperature control can be made a component of the evaporation frame.

·        Operating cooling water temperature monitoring system for the correct observance.

·        Deploying the Stand by Calandria with extra valves.

·        For the factor to avoid scale formation, pretreatment is an important step.

Is there any problem materialize in bio methanation spent wash plying falling film evaporators?

·        Excessive foaming concludes at polluted condensate.

Solution:

A new design gas removing system can be brought into play which involves rotary clarifier, DSI, gas separator Calandra, anti-foaming mechanism, compressed air injection with filter cartridge for micronizing the air to eliminate the solids that are in suspended stage & also induced draft type gas removal unit with fines ( SS ) removal and sludge scraper.