Falling film evaporators from GEA Niro
Falling film evaporators from GEA Niro

In processing plants for the Food & Dairy industry for powder production, there will often be an evaporator. The evaporator is used to remove water from the product before further processing - typically spray drying or for transport purpose to another plant site.

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The evaporation process
The evaporation of water from a product is typically done in falling film multi-effect evaporators with either thermal (TVR) or mechanical (MVR) recompression of the vapours to a higher energy level for re-using it to save energy. As a general rule, as much water as possible is removed in the evaporator, as it is ten-fold cheaper here compared to spray drying.

The maximum solids content in the concentrate from the evaporator is given by the product composition which is responsible for the viscosity in the concentrate. Besides the evaporation of the milk, the preheating/pasteurizing is very important to be able to produce powders with exact specifications and low content of thermophile and mesophile bacteria.

Evaporators for infant milk formula
Evaporators for infant milk formula are typically high concentrators as they operate in the range from 30 % TS to 56 % TS. High-heat treatment of the concentrate, either before or after the evaporation, is today a requirement from the industry to ensure a product with minimal bacteria content. To comply with this requirement, we have developed the SaniHeat technology which, depending on solids content and composition of the concentrate, will bring the temperature up to 140° C for a split second before the product is flashed down to 80° C and then spray dried.

Evaporation of fruit juices

Evaporation of fruit juices is an integrated part of the process to make fruit juice concentrate, be it citrus or apple juices, which are concentrated up to 50 % Brix or more. The design and engineering of this falling film evaporator is done by GEA Wiegand GmbH.

Evaporation of coffee extracts
Evaporation of coffee extracts is likewise done in a falling film evaporator. When the coffee extract leaves the extractor, it is passed t hrough an aroma recovery flash unit to separate the coffee aroma, as that will otherwise disappear during the subsequent evaporation. This aroma fraction is mixed with the concentrate.

The evaporation is typically done in a 2-3 effect falling film evaporator, where the coffee extract is evaporated from 6-7 % solids to 43-47 % solids, if the concentrate is to be freeze dried. If the concentrate is to be spray dried, then the concentrate is further evaporated in a high concentrator to 55 % solids, before the aroma fractions is mixed back again. The high solids content (sugar) will encapsulate the aroma and only a small portion is lost during the spray drying.

Freeze concentration
Freeze concentration is applied where fo cus is on aroma reten tion and high quality products. It is specially suited for heat sensitive products. Freeze concentration is used for coffee extracts, juices and beer and wine. Freeze concentration has been practiced for centuries. In its earliest form it was as simple as leaving a barrel of liquid outside in the cold winter night.

Water would crystallize and grow as a thick layer of ice along the inside walls of the barrel. The next day they would simply cut a hole through the ice shell and drain the now concentrated product. The water (now ice) was simply discarded.

Modern freeze concentration processes consist of a crystallization section, where part of the water is converted into solid ice crystals using a refrigeration system. The ice crystals are then separated by filters, centrifuges or using the GEA Niro PT technology - wash columns. This patented technology is a specific form of suspension melt crystallization and has made freeze concentration economically feasible for a wide range of applications.