Plant, Equipment and Utilities: Evaporators

Abstract

With a considerable amount of milk and dairy ingredients being sold in powdered form, large volumes of liquid dairy materials are evaporated prior to spray-drying. Furthermore, concentrated milk products such as evaporated milk and sweetened condensed milk also require evaporation of milk. While various evaporation techniques are applied in other sectors, falling film evaporators are used almost exclusively in the dairy sector. In these falling film evaporators, product is distributed evenly on the wall of so-called boiling tubes and flow downward. Due to the combination of temperature and reduce pressure, the product reaches its boiling temperature and evaporation can occur. Steam is used as the heating medium for indirect heating of the product. Through use of multiple effects (each operating at a higher vacuum than the previous), and mechanical and thermal vapor recompression, considerable reductions in steam consumption for evaporation of milk and dairy products can be achieved. Control of product temperatures and residence time is essential for preventing undesirable changes in products during evaporation. This article provides a basic description of the evaporation as applied in the dairy sector.