FIELD OF THE INVENTION:

The present invention relates to an evaporation system.

BACKGROUND OF THE INVENTION:
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. It is the process by which molecules in a liquid state spontaneously become gaseous.

Types of evaporators
Natural/forced circulation evaporator
Natural circulation evaporators are based on the natural circulation of the product
caused by the density differences that arise from heating. In an evaporator using tubing, after the water begins to boil, bubbles will rise and cause circulation which facilitates the separation of the liquid and the vapor at the top of the heating tubes. The amount of evaporation that takes place depends on the temperature difference between the steam and the solution. Problem in this system arises if the tubes are not well-immersed in the solution which in turn results in drying of the system. In order to avoid this, forced circulation can be used by inserting a pump to increase pressure and circulation. Other problems associated with this system are that the residing time is undefined and the consumption of steam is very high.

Falling film evaporator
This type of evaporator is generally made of long tubes (4-8 meters in length) which are surrounded by steam jackets. The uniform distribution of the solution is important when using this type of evaporator. The solution enters and gains velocity as it flows downward. This gain in velocity is attributed to the vapor being evolved against the heating medium, which flows downward as well. This evaporator is usually applied to highly viscous solutions and is frequently used in the chemical, food and fermentation industry.

Rising film (Long Tube Vertical) evaporator
In this type of evaporator, boiling takes place inside the tubes, due to heating made (usually by steam) outside the same. Submergence is therefore not desired; the creation of water vapor bubbles inside the tube creates an ascensional flow which enhances the heat transfer coefficient. This type of evaporator is therefore quite efficient. The disadvantage of this type of system is that it is prone to quick scaling of the internal surface of the tubes. This design is usually used for clear, non-salting solutions. Sizing this type of evaporator is usually a delicate task, since it requires a precise evaluation of the actual level of the process liquor inside the tubes. Recent applications tend to favor the falling film pattern rather than this one.

Plate evaporator
Plate evaporators have a relatively large surface area. The plates are usually corrugated and are supported by frame. During evaporation, steam flows through the channels formed by the free spaces between the plates. The steam alternately climbs and falls parallel to the concentrated liquid. The steam follows a co-current, counter-current path in relation to the liquid. The concentrate and the vapor are both fed into the separation stage where the vapor is sent to a condenser. Plate evaporators are frequently used in the dairy and fermentation industries since they have spatial flexibility. A negative point of this type of evaporator is that it is limited in its ability to treat viscous or solid-containing products.

Multiple-effect evaporators
Unlike single-stage evaporators, these evaporators can be made of up to seven evaporator stages or effects. The energy consumption for single-effect evaporators is very high and makes up most of the cost for an evaporation system. Putting together evaporators saves heat and thus requires less energy. Adding one evaporator to the original decreases the energy consumption to 50% of the original amount. Adding another effect reduces it to 33% and so on. A heat saving % equation can be used to estimate how much one will save by adding a certain amount of effects. The number of effects in a multiple-effect evaporator is usually restricted to seven because after that, the equipment cost starts catching up to the money saved from the energy requirement drop.

Evaporation system has importance in the distillery process as the pollution part is concerned. The major role of this system is to reduce the stillage generation in the plant itself. Generally many industries utilize evaporating systems such as rising film evaporators, batch type evaporators and falling film evaporators.

United States Patent 4217176 discloses an evaporator which includes vertically oriented vessel having a longitudinal axis, heat exchange means disposed within said vessel and intermediate the ends thereof and including a plurality of generally horizontally extending heat exchange tubes and a pair of tube sheet means arranged in spaced relation for supporting said heat exchange tubes, a plurality of partition means disposed adjacent said heat exchange tubes and engaging with said tube sheet means for defining an evaporating space.

United States Patent 4132587 discloses apparatus for evaporating liquids which comprises a chamber having an inlet for hot vapors, an outlet adjacent the bottom of said chamber for discharge of condensed vapors, a plurality of cylindrical vertical tubes of relatively small diameter occupying said chamber so that said vapors contact the outside surface thereof, means for passing liquid through said vertical tubes, said liquid being heated and at least partially vaporized by heat transfer from said vapors which are condensed as a film which flows down the outside of said vertical tubes, means for receiving said heated liquid and its vapors, and horizontal plate means perpendicular to said vertical tubes, said horizontal plate having holes therein receiving and contacting said vertical tubes in liquid-tight manner so as to prevent any condensed vapors from continuing to flow beyond said horizontal plate means.

United States Patent application 20070051612 discloses heat exchanger and stillage evaporator for the treatment of stillage generated by the tequila industry during distillation and mashing. The stillage evaporator comprising an elbow, which is located at the top to connect to the evaporator with a cyclone, and a vapor lock lid to avoid internal pressure and accumulation of solid material on the walls of the evaporator, the vapor lock lid having an inlet on top on the right-hand side so that the cleaning operation can be performed and on the left-hand side a safety valve to release pressure during the evaporation operation. This lid is connected to a cylinder which has inside it a duct or tangential inlet which is where the steam passes through that was previously generated in the exchanger, on its way to the evaporator.

United States Patent 6793770 discloses an evaporator useful in the sugar industry which comprises at least a first heat exchanger and a second heat exchanger for top loading of a medium to be concentrated; means for heating each of said heat exchangers heat in cross stream by vapors having different compositions and different pressures; means for separately discharging said medium concentrated and exhaust vapors generated after escaping from said heat exchangers; a medium distributor common for all of said heat exchangers for feeding said medium to be concentrated; means for feeding the medium escaping from said first heat exchanger directly to the second heat exchanger; means for discharging the medium from the second heat exchanger thereby separating said medium from said exhaust vapors; a first common dividing wall for separating a space for said exhaust vapors from steam spaces of the heat exchangers; and a second dividing wall between said heat exchangers separating said steam spaces and/or turning chambers of the heat exchangers from each other.

The disadvantage associated with known evaporation systems is that these systems
requires external heat source to carry out the evaporation process. Further, these
known evaporation systems require high water input. Still further, the energy
consumption is very high.
Accordingly, it is desirable to develop an evaporation system which do not require
external heat source to carry out the evaporation process and which is less energy
consuming.

OBJECTS OF THE INVENTION:
It is an object of the present invention to provide an evaporator system.
It is another object of the present invention is to provide an evaporator system which does not employ external heat.
It is still another object of the present invention is to provide an evaporator system in which minimum spent wash is generated.
It is yet another object of the present invention is to provide an evaporator system which requires low water input.
It is a further object of the present invention is to provide an evaporator system which energy saving.

SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an evaporation system comprising a plurality of evaporators arranged in series, each evaporator comprising:
• a shell side and a tube side; the shell side being connected to a source of hot vapors, the tube side being adapted to receive stillage;

• a steam outlet connected to a vapor separating vessel for releasing evaporator steam as stillage boils in response to the heat from the hot vapor; and
• a stillage outlet for releasing stillage;
said evaporation system adapted to utilize the hot vapors as the only source of heat.

In accordance with the present invention the evaporator comprises distribution plates for facilitating thin film formation along the tube side.

Typically, the evaporation system of the present invention comprises at least three evaporators.

Typically, the evaporators and vapor separating vessels are arranged altemately.

Typically, the evaporation system of the present invention comprises at least three vapor separating vessels.

In accordance with another embodiment of the present invention the evaporation system further comprises a condenser unit being connected to the vapor separating vessel of the terminal evaporator.

Brief description of the accompanying drawings
The invention will now be described with reference to the accompanying drawing in which:

FIG. 1 illustrates evaporation system in accordance with the present invention

DETAILED DESCRIPTION
In accordance with the present invention there is provided an evaporation system. The evaporation system in accordance with the present invention is adapted to utilize the hot vapors as the only source of heat. Referring to figure 1, an evaporation system 100 is depicted. The system includes a plurality of serially arranged evaporators (4, 6, 8) having a shell side and a tube side.

The shell side of first evaporator (4) is connected to a source of hot vapors (2) and the tube side of the first evaporator (4) is provided with an inlet for receiving the stillage. The stillage circulated through the tube side of the first evaporator (4) gets heat from the source of vapors connected to shell side.

A stillage left in the first evaporator (4) is transferred to the tube side of second evaporator (6) having a stillage inlet in communication with the stillage outlet of the first evaporator (4). A steam outlet releases first evaporator steam as stillage boils in response to the heat from the hot vapor. The released first evaporator steam is collected in first vapor separating vessel (10). The stillage in the second evaporator (6) gets heated from the vapors obtained from first vapor separating vessel (10).
The stillage left in the second evaporator (6) is then transferred to the tube side of third evaporator (8) having a stillage inlet in communication with the stillage outlet of the second evaporator (6). A steam outlet releases second evaporator steam as stillage boils in response to the heat from the hot vapor obtained from first vapor separating vessel (10). The released second evaporator steam is collected in second vapor separating vessel (12). The steam outlet of third evaporator releases third evaporator steam as stillage boils in response to the heat from the hot vapor obtained from second vapor separating vessel (12). The released third evaporator steam is collected in third vapor separating vessel (14) which is then transferred to a condenser (16).

The evaporator in accordance with the present invention comprises distribution plates that facilitate the formation of thin film along the tube side of the evaporator when stillage falls through the tube side. The thin film creation results in easy heat transfer and maximum evaporation rate.

Typically, the evaporator system of the present invention comprises at least three evaporators arranged in series.

In accordance with the present invention the evaporators and vapor separating vessels are arranged alternately.

Typically, the evaporator system of the present invention comprises the at least three separating vessels arranged in series.

As the stillage passes through each of the serially connected evaporators, its solid contents goes on increasing because of evaporation. The evaporation of stillage in turn increases the vapor recovery.

The amount of dissolved solids and vapor recovery in each evaporator is provided in the following table.
Table No. 1

Evaporator Dissolved solids (%) % recovery of vapor
I 18-19 18-19
II 21-22 22-24
II 28-30 25

Technical advancement;
The evaporation system in accordance with the present invention has several advantages such as:
• The stillage obtained is re-circulated through evaporation system of the present invention without using any external heat.
• Low water input and the low energy cost
• Minimum spent wash generation
• Less scaling problem
• Easy to start and stop, as and when required
• Less operating manpower required
• Ease of operation and no daily cleaning required
• Consistency in plant operation and the performance is very high
• Easy to control and trouble shoot

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:

1. An evaporation system comprising a plurality of evaporators arranged in
series, each evaporator comprising:

• a shell side and a tube side; the shell side being connected to a source of hot vapors, the tube side being adapted to receive stillage;

• a steam outlet connected to a vapor separating vessel for releasing evaporator steam as stillage boils in response to the heat from the hot vapor; and

• a stillage outlet for releasing stillage;
said evaporation system adapted to utilize the hot vapors as the only source of heat.

2. The evaporation system as claimed in claim 1, wherein said evaporator comprises distribution plates for facilitating thin film formation along the tube side.

3. The evaporation system as claimed in claim 1, which comprises at least three evaporators.

4. The evaporation system as claimed in claim 1, wherein the evaporators and vapor separating vessels are arranged alternately.

5. The evaporation system as claimed in claim 1, which comprises at least three vapor separating vessels.

6. The evaporation system as claimed in claim 1, further comprises a condenser unit being connected to the vapor separating vessel of the terminal evaporator.