Evaporators are thermal
concentrators. Evaporators are for concentrating dilute liquids, for
increasing solids content & for reducing volume by evaporating
water.
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 vapour 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.
Selection of evaporator depends on the various properties of feed &
product such as crystallization, foaming, corrosion, salting &
scaling.
Types of Evaporators
Falling Film Evaporators
Rising Film Evaporators
Forced Circulation Evaporators
Short Tube Evaporators
Falling Film
Evaporators
The feed gets distributed and thin film is formed
Hold up and residence time is short hence liquid does not get
overheated
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
Rising Film
Evaporators
Useful for moderately heat sensitive product
Compact and simple design
Most suitable for corrosive liquids
In rising film feed, solution forms a rising film in the tubes. These
are unsuited to salting or severely scaling liquids. These evaporators
are compact, simple in construction. They are suitable for corrosive
liquids.
Forced Circulation
Evaporators
Can handle salting, scaling and fouling liquids
Best suitable for crystalline products, corrosive viscous
solutions
Forced circulation evaporators can handle salting, scaling &
fouling liquids. They are best suitable for crystalline products,
corrosive & viscous solutions.
These 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.
Short Tube
Vertical Evaporators
Reclusively less expensive
Facilitate easy de-scaling
Can be widely used in sugar industry
Short tube evaporators are the oldest but still widely used. They are
most widely used in Sugar Industry in evaporation of cane-sugar juice
They are relatively inexpensive & 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.
We offer single effect or multi-effect evaporators according to product
properties & /or clients requirement with or without thermal
compression to lower temperatures & reduce residence time of
product.