It’s well known that evaporation is a process by which a liquid turns into a gas or vapor below its boiling point occurring on the surface of the liquid. The equipment used for evaporation is known as evaporators. An evaporator usually consists of a heat exchanger, a vacuum pump, a vapor separator and a condenser.
Equipment Uesd for Evaporation
There are a great variety of types of evaporators, and four types of them will be mainly introduced, which are rotary evaporators, falling film evaporators, single-effect external circulation evaporators and thin film evaporators.
1. Rotary Evaporators
A rotary evaporator, known as rotovap as well, is an essential evaporation equipment widely used in many fields such as industrial field, chemical laboratories and other fields. A rotary evaporator usually consists of several parts, including a motor unit, a vacuum system, a water or oil bath for heating, a rotating flask, a receiving flask, condenser pipes and other components. The rotating flask is heated thermostatically and can rotate at a constant speed. Then the material forms a large area of thin film on the inner surface of the flask, which has a higher evaporation efficiency. The receiving flask can collect the distilling solvent after it recondenses. In conclusion, a rotary evaporator serves as an essential evaporation equipment, which can remove a volatile solvent from a liquid mixture through evaporation and condensation.
2. Falling Film Evaporators
A falling film evaporator is an essential evaporation equipment, which is applicable for the evaporation and concentration of the foaming material. A falling film evaporator system mainly consists of several parts. The first part is the evaporator (the heat exchanger), which is used to heat and evaporate liquid materials. The second part is the separator, mainly used to separate the concentrated liquid and the secondary steam generated after heating. The third part is the preheater, which is used to preheat liquid materials entering the steam and cool the secondary steam in order to recycle and utilize it. The fourth part is the condenser, whose function is to condense the secondary steam so that it can be recycled and utilized. The fifth part is the condensate tank, which is connected to the pump at the outlet and capable of discharging condensate liquid automatically.
3. Single-Effect External Circulation Evaporators
As an efficient evaporation equipment, single-effect external circulation evaporator adopts both the natural circulation of external heating method and the vacuum negative pressure evaporation method, possessing a fast evaporation speed. It’s widely used for the recovery of ethanol and the concentration of various liquids.
It boils the feed liquid, removes the vaporized part, and concentrates the feed liquid through heating the materials under negative pressure. In the heating chamber, the heating energy required for evaporation is provided to the liquid, and the material liquid is evaporated to form a density difference. The density of the material liquid in the circulation pipe is higher than that in the heating chamber, so that the natural circulation is formed by the density difference of the material liquid. The steam generated in the heating chamber carries a large amount of liquid foam. After passing through the larger space evaporation chamber, the liquid foam is separated by means of its own condensation and foam trapping device. The steam is recovered after cooling and condensation.