Forced Circulation Evaporator
In forced circulation evaporators the product is recirculated through the tubes with a high flow rate pump ensuring an intense contact with the heating surface and a controlled speed of the product.
This type of evaporators have a heat exchanger in which the product is recirculated and heated but not concentrated until it reaches a flash chamber at the end of each effect in which the pressure drop due to the high vacuum in the chamber forces the evaporation of the product.
In forced circulation evaporators very high heat transfer coefficients are achieved even with difficult products, reducing fouling and extending continuous operating periods without cleaning the equipment. Due to the recirculation of the product, these type of evaporators can operate with minimum inlet flow rates without fouling by excessive heating of the product.
Another advantage of these evaporators is that the evaporator effects can be placed either vertically or horizontally because the product flows by pumping and not by gravity or thermo-shipon like in falling film and rising film evaporators
Nevertheless, forced circulation evaporators have high power consumption because of its large recirculation pumps and longer residence times than falling or rising film evaporators.
These evaporators are used for products which show precipitation, being that in crystal or other solid forms. They are usually used in combination with other evaporators, forming a mixed evaporation system where forced circulation effects are used for the more concentrated stages of the product to increase heat transfer coefficients and reduce equipment size.
- Product and recirculation pumps required
- Optimal for high viscosity products
- Vertical or horizontal evaporators