Deaeration system: For the removal of undesirable gasses.
Evaporating plant: Multiple effects forced recirculation/Falling film/Combination of both evaporating plant to concentrate the effluent upto 30 % TS which can be used as Biocomposting.
Advantages of Forced recirculation evaporator over Falling film evaporator
Forced recirculation evaporator is best suitable evaporator in comparison to falling film evaporator. Following are the features of Forced recirculation evaporator in comparison to falling film evaporator:
Forced recirculation evaporator is most suitable evaporator to concentrate the product up to 55-65% total solids, whereas falling film evaporator is suitable to concentrate only 45-48% Total solids.
Forced recirculation evaporator can be run for 30-40 days without any scaling, whereas falling film evaporator can only be run for 20 hrs only. 4 hours are required to clean the falling film evaporator daily.
Cleaning shall be required after 30 to 40 days of continuous running of the forced recirculation plant, so there is saving of chemicals, steam and power consumption used for cleaning. Where as cleaning of falling film is required on daily basis for 4 hours, so there will be extra cost for chemicals, steam and power.
In forced recirculation evaporator, capacity of the plant is designed at lower side with respect to falling film evaporator.
Despite of having high power consumption in forced recirculation evaporator, processing cost per lit of distillery effluent is less than falling film evaporator.
Falling film evaporators are designed by FBE with special care to meet a wide variety of specifications and duties of the final products. Having installed number of units worldwide during the last decade, FBE has acquired substantial experience and knowhow to comply with customer requirements
Salient Features of Falling Film Evaporator
Liquid distribution is through distributor plates placed at top of calandria.
The film is going with gravity.
Thinner film formation throughout the tubes.
Shorter product contact time.
Concentration of highly-sensitive materials.
Can be operated at much lower del T.
The lower del T is favorable to vapor recompression and consequently the energy consumption is low.
Concentration level can be achieved upto 45% TS.
Useful for the concentration of milk, fuit juice, malt etc.
FBE designed falling film evaporators, especially for dairy industry feature items such as:
Adjustable and controllable direct contact heat treatment units.
Shortest possible residence time
Special design to prevent bacteriological growth including thermophiles.
Special design of liquid distribution systems to ensure correct tube coverage
Multiple Effect Operation Evaporator combine two or more evaporator bodies to conserve steam, which is condensed in the first-effect heat exchanger only. Water evaporated in the first-effect vapor body is condensed in the second effect heat exchanger, which provides energy for evaporation in the second-effect vapor body (and so on for additional effects). Vapor from the last effect flows to a condenser. The last-effect vapor body is maintained at a high vacuum with a steam-jet air ejector or mechanical vacuum pump.
A rough “rule of thumb” for comparison purposes is that 1/N kg of steam is required for 1 kg of Water evaporation, where N is number of effects. e.g In 4 effects evaporator 0.25 Kg (1/4) steam is required for 1 kg of water evaporation.
High steam economy is obtained by recompression of the vapor generated from the boiling product. This is done by adding energy to the vapor by a steam jet. Part of vapor separated to be used together with boiler steam, to the thermo compressor. Boiler steam (usually at a pressure of 3.5-10 bar) is introduced through a nozzle creating a steam jet in the mixing chamber whereby vapor from the evaporator is sucked into the mixing chamber. The thermo compressor uses the high pressure steam to increase the kinetic energy and the steam ejects at high speed through the nozzle. The velocity of the mixture of boiler steam and vapor is reduced in diffuser and consequently, the pressure and temperature are increased, making the mixture suitable as a heating medium in the calandria.
FBE provides Evaporators using the most advanced and reliable resources in the industry. FBE evaporation technology is dedicated to meet a wide range of industrial application needs. This gives us a unique data base for today’s applications.
FBE concentration plants are used in the food, dairy, chemical, fermentation, and pharmaceutical industries. They are also used for wastewater treatments like Spent Wash concentration in Alcohol industries. We manufacture tubular type evaporators with energy saving options such as thermal vapor recompression (TVR) and Mechanical Vapor Recompression (MVR).
We have delivered systems for Milk, Fruit juices pulp concentrates, Herbal extracts, Malt mix slurry, Starch and derivatives, Spent wash concentration, and Aroma recovery for many different kinds of products.
Forced Recirculation Evaporators are ideally suited for highly viscous liquids or liquids containing suspended solids. The liquid to be evaporated is heated in tubular heater at large circulation volumes to obtain high liquid velocities. Evaporation takes place in a separator as the product is flashed down to its operating pressure.
The forced circulation evaporator sometimes used as a finishing stage of multiple effect evaporators, or for products with high boiling point elevations. Because of the high velocities in the finisher, scaling is kept to a minimum, therefore it can be used as a crystallizing evaporator.
Salient Features of Forced Recirculation evaporator
Liquid circulated at high rate through the calandria.
Higher coefficients are obtained.
Boiling being prevented within the unit by virtue of a hydrostatic head maintained above the top tube plate. As the liquid enters the separator where the absolute pressure is slightly less than in the tube bundle, the liquid flashes to form a vapor.
Since the velocity of flashing is very high, impingement deflector/ baffles are important to minimize entrainment.
Liquid returns to the pump inlet from Vapor separator and meets incoming feed, vapor leave the top of evaporator body to a condenser, part of the liquid leaving the separator is continuously withdrawn as concentrate.
Require large circulating pumps.
The concentration level can be achieved upto 65 % TS.
Useful for concentration of inversely soluble material or for material which is susceptible to scaling or crystallizing like distillery effluent, mango/tomato juice, Malt concentrate (70% TS).
Mechanical Vapor Recompression (MVR) is used to raise the pressure and temperature of vapor. The vapor is drawn out of the evaporator and compressed before being returned to the evaporator and compressed before being returned to the evaporator when mechanical compression is used. The pressure increase takes place by means of mechanical energy, used to drive the compressor. No thermal energy is supplied to the evaporator (except steam for heating in the 1st effect). There is no excess steam which has to be condensed. Apart from the steam used for start up, a MVR evaporator requires no steam and no cooling water. However, if high concentration to be achieved, it is advantageous to use a steam heated finisher for the last concentration. In this way, it will be easier to control the evaporator. An MVR evaporator may also be coupled with TVR and/or multiple effect evaporation stages.
The high initial capital cost of an MVR unit must be weighed against the operating cost savings.
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