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Zero Discharge Systems
Multiple Effect Evaporators - Overview

Carrying an enormous experience of over a decade in designing and manufacturing of Multiple Effect Evaporators, Shail Vac has emerged as a reliable and trustworthy name in the national and international market. Our modern production facilities, engineering excellence and highly experienced and dedicated team of engineers and technicians have made us capable of supplying wide range of Multiple Effect Evaporators in the markets.

Being a client centric firm, we understand the value of our customers’ hard efforts in procuring the various accessories for a MULTIPLE EFFECT EVAPORATOR project. Understanding such concerns and value of our customers’ efforts, we have been taking complete turnkey projects also, so that our customers have a total solution for their MULTIPLE EFFECT EVAPORATOR Projects and they enjoy a single and reliable source of supply.

As a part of Forced Circulation Evaporator, we have been manufacturing and supplying AXIAL FLOW PUMPS in SS 304, SS 316, SS 2205, Titanium etc like materials also, which are being regularly tested on our test benches and then dispatched to our customers. Cutting edge technology and innovative design skills helps us to serve our clients efficiently. Our systems also come with complete instrumentation and automation package which reduces the man power and efforts in running the system, thus making the system more User-Friendly.

In the evaporation process, concentration of a product is accomplished by boiling out a solvent, generally water. The recovered end product should have optimum solids content consistent with desired product quality and operating economics.

A multiple-effect evaporator is an apparatus for efficiently using the heat from steam to evaporate water. In a multiple-effect evaporator, water is boiled in a sequence of vessels, each held at a lower pressure than the last. Because the boiling point of water decreases as pressure decreases, the vapor boiled off in one vessel can be used to heat the next, and only the first vessel (at the highest pressure) requires an external source of heat.

In most of the cases it becomes essential that during evaporation, product undergoes minimum thermal degradation. So accordingly temperature and the time exposure must be minimized. A large number of evaporator types have been introduced for such special requirements.

Increasing demands for energy efficiency and minimum environmental hazards have driven Shail Vac towards very innovative plant configurations and equipment design.

Theory :
Falling Film Evaporator   Forced Circulation Evaporator
Falling Film Evaporator

In falling film evaporators, the liquid product enters from the top of the calendria where it gets evenly distributed into the heating tubes. Steam is usually used as the heating medium and a thin film of product which flows downwards in the tubes is partially evaporated at its boiling temperature.

Due to gravity, the product and the vapor both flow downwards in a parallel flow. This gravity-induced downward movement is increasingly augmented by the co-current vapor flow.
At the bottom of the calendria, vapor is separated from the concentrated product. Vapor is then used as heating medium in the next calendria.

As film is flowing in the direction of gravity, a thinner and faster moving film flows through the tubes. With a shorter product contact time, Heat transfer coefficient improves further. Uniform distribution of the product takes place in all the tubes with help of distribution plates placed in the top of calendria.

A temperature difference of about 14°C is required as a driving force between the heating surfaces in rising film evaporators. But in the falling film evaporator, there is no driving force limitation, which permits a greater number of evaporator effects to be used within the same overall operating conditions.

Falling film evaporators can be operated with small temperature differences and with low liquid holding volume in this type of unit, starting up and cleaning process can be made easy and simple.

Forced Circulation Evaporator:

In a Forced Circulation Evaporator, product is fed from bottom of the calendria at a high rate and usually steam is used as the heating medium. The boiling of the product is prevented within the calendria by virtue of a hydrostatic head maintained above the calendria. The absolute pressure is slightly less in vapour separator than in tube bundles in calendria. So as the product enters the vapour separator, it flashes to form a vapour.

Forced circulation evaporators are used for crystallization, concentrating inversely soluble materials and thermally degradable materials which result in the deposition of solids.

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