What Is Thin Film Evaporation?

Evaporation of a liquid into a thin film is called thin film evaporation. The principle that thin film evaporation can accelerate evaporation is that under reduced pressure, the liquid forms a thin film with a large vaporized surface area, and the heat spreads quickly and uniformly without the influence of liquid co-pressure, which can better prevent the material from overheating. It has the advantages of low heating temperature, short time, fast evaporation speed, continuous operation and shortened production cycle of the extraction liquid. There are two ways to perform thin film evaporation: one is to make the thick liquid film quickly flow over the heating surface to evaporate; the other is to make the extraction solution boil violently to generate a large amount of foam, and use the inner and outer surfaces of the foam as the evaporation surface to perform evaporation. The latter method is more common. ^[1-2]

Evaporation of a liquid into a thin film is called thin film evaporation. The principle that thin film evaporation can accelerate evaporation is that under reduced pressure, the liquid forms a thin film with a large vaporized surface area, and the heat spreads quickly and uniformly without the influence of liquid co-pressure, which can better prevent the material from overheating. It has the advantages of low heating temperature, short time, fast evaporation speed, continuous operation and shortened production cycle of the extraction liquid. There are two ways to perform thin film evaporation: one is to make the thick liquid film quickly flow over the heating surface to evaporate; the other is to make the extraction solution boil violently to generate a large amount of foam, and use the inner and outer surfaces of the foam as the evaporation surface to perform evaporation. The latter method is more common. ^[1-2]

The extract to be evaporated passes the infusion tube. After entering the preheater through the flowmeter for preheating, it flows out from the upper part of the preheater and enters the tube evaporator from the bottom. When heated by steam, it boils violently and forms a large foam; In the gas-liquid separation bridge, the vapor-liquid is separated into concentrated liquid and steam; the concentrated liquid flows into the concentrated liquid storage tank through the lower outlet valve of the separator, and water vapor enters the interlayer of the preheater through the secondary steam pipe for preheating and extraction The excess exhaust gas is condensed in the mixed condenser, the condensed water is discharged from the outlet, and the uncondensed exhaust gas is discharged into the atmosphere from the top of the condenser. If the heating tube is too long and the evaporation tray is too large to operate improperly, some dry wall phenomena may occur, which will reduce the heat transfer effect after scaling. ^[1]

Thin film evaporation principle and equipment

The centrifugal force formed by high-speed rotation is used to disperse the liquid into a uniform film and is called centrifugal thin film evaporation. Centrifugal thin film evaporator is a new type of efficient evaporation equipment. It uses two principles of centrifugal separation and thin film evaporation under the action of centrifugal force. It has a thin liquid film thickness (0.1 mm), a heat transfer coefficient of up to 4 000 kCa / mz · h · , small equipment volume, large evaporation strength, high concentration ratio (15-20 times), and short material heating time () Is only 1 s), it is not easy to foam when concentrated, and the evaporation chamber is easy to disassemble and clean after scaling. It is suitable for the concentration of water extract of edible and medicinal fungus materials, and it has a good concentration effect on the water extract of heat sensitive objects. The equipment is mainly composed of dilute liquid tank, pipeline filter, balance tank, centrifugal film evaporator, concentrated liquid tank, hydraulic jet vacuum pump and other components.

Thin film evaporation operation process

Operation process: The leaching solution is filtered by the pipeline filter and then enters the equilibrium capture. There are two floating valves in the balance tank, and one valve is connected to Laos for liquid extraction. It can keep the flow entering the evaporation bitter and stable: the next valve is a safety device. Once the liquid is interrupted, the liquid level in the tank drops and the valve opens automatically. Tap water will flow into the essence. Ensure that the evaporator host will not cause evaporation and coking due to the material cut-off. The feed liquid flow entering the evaporation host is adjusted by the feeding whale rod pump, and the flow rate is displayed by the flowmeter. After the preheating zone is preheated, it enters the centrifugal film evaporator to perform the point. The repulsive force or feed rate meets the predetermined process concentration requirements. The concentrated material solution flows to the concentrated solution by centrifugal force, and the concentrated solution is sent to the subsequent process by a discharge screw pump. ^[1]