The Cleaning of Heat Exchangers and Evaporators After Processing Milk or Whey

The composition of the deposit and the cleaning rate were studied in heat exchangers and evaporators of a semi-industrial scale, after processing of milk, whey or concentrated whey. Milk deposit is represented as a matrix Of protein to which minerals are associated and in which fat is embedded. Under good cleaning conditions, milk deposit in a heat exchanger or evaporator can be removed readily by an alkaline cleaning followed by an acid cleaning. If during the cleaning of an evaporator, the flow rate is too low or the alkali concentration too high, or both, then the cleaning will be slow and incomplete. By optimizing the cleaning procedure, a reduction in energy costs during cleaning of 50% can be achieved. Whey deposit is represented as a complex of protein together with calcium salts, containing mainly calcium phosphate, but in the case of concentrated whey, calcium citrate is also found. Since whey deposit contains considerably more mineral compounds than milk deposit, it is recommended to start with an acid cleaning followed by an alkaline cleaning after processing (concentrated) whey. As with milk deposit, whey deposit in a heat exchanger or evaporator is removed quickly. Using a model heat exchanger and evaporator with outer walls of glass, it was possible to follow the cleaning process visually. Based on these observations, together with the analysis of the cleaning solutions, a schematic view of the removal of deposit is presented for both milk and whey.