Evaporators for Pharmaceutical Industry, Food Industry & Chemical Industry

Evaporators

Evaporation is a major energy intensive operation in any processing plant like Chemical, Pharmaceutical, Food and dairy. Evaporators are thermal concentrators. Evaporators are used for concentrating dilute liquids, for reducing volume by evaporating water & for increasing solids content.

Evaporators are based on steam economy i.e. Kg of solvent evaporated per Kg of steam used. Reusing evaporated solvent as heating medium, higher steam economies are achieved. This method of increasing utilization of steam is used in multi-effect evaporator. In multi-effect evaporator vapor from the first effect is passed over to the next effect in which boiling takes place at lower temperature & pressure.

Thermo-compression evaporator is another alternative to increase steam economy. Vapor of solvent evaporated is compressed & is used as heating medium in the same evaporator.

Types of Evaporators

• Falling Film Evaporators
• Rising Film Evaporators
• Forced Circulation Evaporators
• Short Tube Evaporators

Falling Film Evaporators

In Falling film evaporators, feed solution forms a film in the evaporator tubes & gets evaporated. These are best suited for heat sensitive materials such as fruit juices. The hold up time is short & liquid doesn't get overheated. Falling film evaporators are not suitable for crystallizing liquids. They are not suitable for salting & severely scaling liquids or solutions.

Falling Film Evaporators can be particularly useful when the temperature difference between the liquid to be evaporated and the heating media is low.

Application Area:

Dairy Industry

Food Industry

Pharmaceutical Industry

Chemical Industry

Rising Film Evaporators

RISING FILM EVEPORATORS are Useful for heat sensitive product. These are unsuitable to salting or severely scaling liquids. They are suitable for corrosive liquids.

Feed enters the bottom of the heating tubes and as it heats, vaporizes. The ascending force of this vapor produced during the boiling causes liquid and vapors to flow upwards in parallel flow. At the same time the production of vapor increases and the product is pressed as a thin film on the walls of the tubes, and the liquid rises upwards. This co-current upward movement against gravity has the beneficial effect of creating a high degree of turbulence in the liquid. This is advantageous during evaporation of highly viscous products and products that have a tendency to foul the heating surfaces.

The temperature difference in the rising film evaporators should be high between the heating chest and boiling chamber to ensure the circulation and formation of a climbing film.Rising Film evaporators are flexible enough to be converted to Forced Circulation Evaporators.

Application Area:

Chemical Industry

Effluent Treatment Plants

Forced Circulation Evaporators

Forced Circulation Evaporators Can handle salting, scaling and fouling liquids. These are suitable for crystalline products, corrosive viscous solutions.

Forced Circulation Evaporators are short tube evaporators and are ideally used when the boiling of feed liquid on the heating surfaces is to be avoided due to the salting and fouling characteristics of the liquid. Hence in these evaporators the flow velocity in the tubes is kept very high. Forced Circulation Evaporator can be configured in single or multiple effects for steam economy.

Forced Circulation Evaporators have relatively high hold up or residence time thus not suitable for heat sensitive liquids. They suffer frequently from plugging of tubes, salting in tubes & poor circulation.

Application Area:

Effluent Treatments Plants

Chemical Industry

Salt Solutions

Short Tube Vertical Evaporators

Short Tube Vertical Evaporators are most widely used in Sugar Industry in evaporation of cane-sugar juice.

Short Tube Vertical Evaporators are less expensive & easy de-scaling. This type is seldom used as a crystallizing evaporator. By installing a propeller, propeller calendria type evaporator can be used for crystalline products. They suffer from mild scaling but can be cleaned mechanically.

These evaporators can be used with scaling liquids, since evaporation takes place inside the tubes, which are accessible for cleaning. Fairly high heat-transfer coefficients are obtained with thin liquors (i.e., water or dilute solutions of 1-5 cP).

Applications Area:

Suitable for noncorrosive (e.g., cane sugar)
clear and noncrystallizing liquors.