AlfaVap™ system A cassette evaporator for high viscosity products Applications AlfaVap cassette evaporators are designed for concentrating process liquids that contain dissolved and finely dispersed proteins of animal or fish origin, such as: • stickwater from fishmeal plants • glue water from meat by-product plants • fish extracts and bouillon products • canning cooking water • meat extracts and bouillon products • fish or meat-based hydrolysate products • fish silage products • gelatin products AlfaVap cassette evaporators are also supplied in food-grade quality, which means that all inner parts can be effectively cleaned by a CIP (Cleaning-in-Place) cycle. This is available as an automatic program integrated into the controls of the AlfaVap system. Cassette evaporator design AlfaVap cassette evaporators combine the state-of-the-art thermal technology and know-how available from Alfa Laval into very compact evaporator units, which come in standardized models or can be customized to meet individual requirements. The AlfaVap system is available as a single-stage, two-stage or three-stage evaporator – depending on the heating medium, throughput or specific concentration demands of the end product. The modular AlfaVap skid concept includes all the main components of the evaporator, such as one or more cassette evaporator stages with circulation pumps, vapour condenser, vacuum pump station and concentration monitoring equipment. Each cassette stage is arranged within a frame, which can accommodate different numbers of cassettes. This means that any moderate increase of throughput is possible without additional installation work. The electrical control and monitoring panel can be placed alongside the evaporator or more centrally in a general control room. Cassette evaporator operation principle The AlfaVap cassette evaporator works on the basis of the so-called rising film principle, partly enabled by forced circulation. However, unlike other evaporators based on this technology, the AlfaVap system conducts practically all of the evaporation within the cassettes. These thus serve almost as foam-filled boiling chambers, with very high velocities of the evaporating medium. The cassettes are equipped with special corrugated surfaces that create a high rate of turbulence throughout the entire product chamber, which results in high heat transfer coefficients. This high turbulence and the rising foam film also eliminate wetting problems and dead spots, which again substantially reduces any tendencies to fouling. This means longer operation periods between cleaning cycles. Evaporation step by step The following step-by-step description is based on a twostage evaporator, but the basic principles also apply to threestage evaporators, or can be transferred to single-stage evaporators.

The cassette evaporator stage I is heated by steam, which circulates in the closed welded compartments of the cassettes. Pumps evacuate the condensate, as the steam pressure in the cassette may become less than 1 bar abs. The product is circulated through the detachable compartments of the cassette stack, and is led into these compartments in stage I via a regulation valve, controlled by the level monitor in the cyclone separator I. This controlling loop ensures that fresh product is led to the evaporator at the same pace as the evaporation removes water from stage I. The product is optimally...