Case study - Whey milk: recovery of proteic substances
A Portoguese cheese factory producing a wide range of dairy products for the National market.
According to the type of dairy production, the curdling process produces an amount of whey equivalent to about 85-90% of the volume of transformed milk. The whey characteristics, which also determine its economic value, are strictly connected to the chemical composition.
The polluting charge of whey is very high, with a BOD5 (biochemical oxygen demand) and a COD (chemical oxygen demand) respectively of about 35000 mg/l and 70000 mg/l, so that it cannot be discharged directly on the ground or into the sewer, but it needs a depurative treatment.
Besides the whey is an instable product from the microbiological point of view, because of the fermentation phenomenon caused by the milk bacteria. The use of whey in zootechnics is not practicable, as its characteristics make it a non-exploitable product.
On the other hand the whey is a source of food substances and an economic source as well, despite it is a problem for cheese factories in environmental matters.
The solution provided
The whey, as soon as it is separated, is stored in a tank.
The unit used to treat it is an EVALED E 24000, a heat pump vacuum evaporator with external shell and tube heat exchanger: the heat pump supplies both the calories to evaporate the liquid and the frigories to condense its vapours; the high vacuum (5,3 kPa) allows to lower the boiling temperature to only 30°C/86°F approximately.
The boiling produces about 90% of distilled water, which is directly discharged, and a fluid concentrate enriched in proteins and salts.
Results & benefits
EVALED evaporators allow to remove residual water from the concentrate avoiding clogging phenomena, typical of alternative techniques, such as membrane filtration, and achieve higher concentration grades. They also allow to recover whey components and, at the same time, to avoid the pasteurization process, which would cause the alteration of proteins and glucides structure. Low temperature and anaerobic environment, due to the vacuum in the boiling chamber, grant stability to the whey giving the opportunity to sell it as ingredient for feedstuff.
A further economical benefit is given by the fact that the client does not need any refrigerant storage tank, saving the electric energy necessary to keep the whey at a low temperature to avoid the fermentative process.
Main benefits of treatment by vacuum evaporation are:
- High energy efficiency: less than 150 watth\kg of water distilled
- Good quality of the concentrate
- No corrosion phenomena due to high quality of the materials used and low operation temperature of the distillation (30°C/86°F).
- Opportunity for a new income and energy consumption savings.