In recent years there has been a rapid rise in the costs of water and effluent disposal. There is now an awareness to conserve water as a scarce resource. More problems of the sustainability of industry and public concern about the impact of industrial activity on the nvironment have come to the fore. All these factors mean that there is a growing realisation that there is a need to introduce some form of water recycling - Salt Recovery System / Salt Recovery Plant

Every industry be it textile, tannery, pharmaceutical, distilleries etc generates effluent . These effluents pose a serious problem if disposed into water courses or on land. These effluents contain a wide variety of both organic or inorganic salts which are usually discharged with or without treatment into surface waters or lands resulting in contamination of environment. Hence various pollution control boards have passed stringent laws to monitor the surface water quality by limiting COD, BOD, Ph, suspended solids, temperature, heavy metals etc. In various parts of world it is absolutely necessary to have a Zero Effluent Discharge policy to be able to run the industry. Under Salt Recovery System / Salt Recovery Plant these effluents are hence treated by various methods and passed through a series of membranes where substantial permeate ( water ) is removed from the treated effluent. The high TDS reject from the membranes are then taken to an Evaporator to further concentrate it and the slurry then dried by various other methods.


Under Salt Recovery System / Salt Recovery Plant the feed to Effluent Evaporator initially passes through a series of preheaters which preheat the wash liquor with the help of flash vapors from the condensate flashes. This ensures minimum steam loss in heating the Wash liquor to its boiling point. The liquor comes in contact with the steam in the shell side of heater 1 and the liquor starts boiling. The vapor liquor mixture enters the flash vessel through a tangential entry and the vapors get separated and enter the shell of the 2nd stage. The concentrated liquor enters the 2nd heater due to the pressure difference and comes in indirect contact with the generated vapors and the same procedure is repeated.The concentrated product is removed from the last stage by a product pump. This later is then transferred to a solar pond or to a dryer or a thickener or a crystalliser. The characteristics of the effluent are seldom known to the client or even if known keep changing as per the product mix. Due to this non standard feed quality there are very high chances of tube fouling and maintenance operations. In order to avoid breakdowns and maintenance issues UNITOP has developed multiple effect evaporation plant ( Salt Recovery System / Salt Recovery Plant) with all stages in FORCED CIRCULATION. The axial flow pump maintains sufficient velocity and volume so as to reduce the tendency to scale substantially. Though it may appear to have a higher power consumption but considering the savings in cleaning frequency and the chemical costs Design for flow of liquor is decided based on the nature of the effluent.


Salt Recovery System / Salt Recovery Plant - BACKWARD FEED / COUNTERFLOW

In cases where the concentrated product becomes viscous at low temperature the feed flow is designed in counter flow fashion. The feed enters the stage in vacuum and the product is taken from the 1st stage which is the entry point of steam. Hence the product is at high temperatures. However in case where the product is not desirable at high temperature, choice should be of forward feed plant. The feed and steam travel in co-current fashion.

Salt Recovery System / Salt Recovery Plant - FORWARD FEED / COCURRENT

These are the most common type of evaporators where the feed and the steam travel in the same direction Here the concentrate achieved is at low temperature.
Since the feed is moving in direction of pressure to vacuum it can be transferred from one effect to another without a transfer pump. Hence lower power consumption and lower maintenance points.