Drying of Whey

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Thermal Drying

In the thermal drying, volatile substances, especially moisture (water) is removed from a solid, semi-solid or liquid product by the application of heat to achieve a solid product stream. The drying or removal of water from the product is carried out on the one hand to improve the durability and storage stability and, secondly, to facilitate handling and to reduce transport costs. Often the drying of the product is necessary to achieve the desired quality.

In the thermal drying, two processes run simultaneously. On the one hand, the transition heat to the product to be dried in order to evaporate the water on the surface can take place. The heat transfer from the environment to the product by means of convection, conduction or radiation or a combination of several. On the other hand, the water from the interior of the product must be transported to the surface (diffusion) in order to also be able to evaporate subsequently. By heat conduction, the heat transferred to the surface is brought into the interior of the product. The transport of the water to the surface is carried out either by diffusion in the liquid (by a concentration gradient), or in the vapor state (when the water begins to evaporate already in the interior or by a hydrostatic pressure difference when the rate of evaporation inside is higher than the transport rate of the steam to the surface or into the environment of the product). But can also both mechanisms may be responsible for the transport of moisture. The drying rate is certainly dependent upon both the rate of evaporation at the surface as well as the transport speed of the water from the interior to the surface.

Conventional Drying

The whey powder preparation is effected by spray drying. Whey is dried at 25 ° C a whey concentrate with a solids concentration of 58%, a mass flow rate of 1900 kg / h and an inlet temperature. The whey product comes in powdered form from the spray dryer from having a solid concentration of 97.5 to 98.5%, a temperature of about 85 ° C and an amount of 1176 kg / h. The dryer exhaust air first enters a cyclone and then into a filter for dust removal. The temperature of the exhaust air before it enters the filter is about 85 ° C. The dedusted exhaust air is cleaned or after the filter in a WT, where the heat of the exhaust air for preheating of the supply air of room temperature is used at about 72 ° C. The preheated air is then heated above a WT in the combustion chamber at ~ 184 ° C and reaches this temperature in the spray tower.8.64 Nm ³ natural gas consumed per 100 kg of product.


Figure 1: Conventional Drying of whey

Emerging Technologies in Drying of whey

Drying et1.png Drying et2.png Drying et3.png

Figure 2 :emerging technologies used for drying of whey

Source: Ulrike Herzog (2012)Möglichkeiten des Einsatzes von „Emerging Technologies“ in der Lebensmittelindustrie zur thermischen Energieverbrauchs-senkung und zur Einbindung von Solarthermie