What Is a Thin-Film Evaporator?
A thin-film evaporator is a device for separating and refining mixtures by forming a thin film to concentrate and evaporate low-boiling-point components (solvents).
Low-boiling point solvents can be evaporated in a short time. Since the heating time can be shortened, it is especially effective for separation and purification of heat-sensitive compounds. It can also be used to process high-boiling point liquids by creating a high vacuum.
Applications of Thin-Film Evaporators
Thin-film evaporators are used to concentrate, dry, and powder solutes (samples) by removing solvents, and to recover reusable solvents and water from spent solvents, waste liquids, and process liquids.
1. Chemistry
In the chemical industry, it is used to separate and purify organic compounds in general, such as amines, esters and other aromatic substances, latex, and monomers. It is also used to recover acetic acid, and to purify monoglycerides, fatty acid amides, various fatty acids and fatty acid derivatives, methacrylic acid derivatives, acetylene derivatives, and compounds with high boiling points.
2. Pharmaceuticals
Major applications in the pharmaceutical industry include the distillation and processing of vitamins, fats and oils such as DHA, EPA, and squalene, as well as the concentration and purification of common organic compounds.
3. Food
Thin-film evaporators are also commonly used in the food industry. Specific applications include the concentration and purification of proteins and sugars, as well as the concentration treatment of various juices, milk, etc.
4. Machinery & Electronics
Thin-film evaporators are also used in the refining of vacuum pump oil, refrigerator oil, and transformer oil, as well as in the vacuum heating treatment of sealing and molding materials used in electronic and semiconductor components.
5. Waste Liquid Treatment
Thin-film evaporators are used for concentration, water recovery, solvent recovery, and volume reduction of process liquids and waste liquids in general industrial production. They are used in various fields such as cutting oil waste in the metal industry, metal surface treatment industry, chemical industry, textile industry, leather industry, and dye industry.
Principles of Thin Film Evaporators
Thin-film evaporators concentrate and dry solutes based on the principle of evaporating solvents by forming a thin film in an evaporation tube equipped with a heating mechanism. Wipers and other devices are built into the evaporation tube to efficiently form a uniform thin film. Since the inside of the evaporation tube is usually designed to be depressurized, the solvent can be removed at low temperatures and in a short time by lowering the boiling point of the solvent through depressurization.
The solute precipitated as a solid is scraped off with a wiper or similar device and sent to a collection vessel. The evaporated solvent is passed through a tube as a gas, trapped in a cooling tube, and re-cooled to be recovered as a liquid. Usually, the evaporation tubes and liquid and gas channels of lab-scale equipment are made of transparent materials such as borosilicate glass, which are resistant to corrosion and chemicals and allow for internal observation.
Types of Thin-Film Evaporation Devices
Thin-film evaporators come in a variety of sizes, ranging from laboratory-size to large, industrial-use ones. Laboratory-size ones are usually made of glass, while industrial-scale ones are made of stainless steel or other materials.
In a normal thin-film evaporator, the evaporation tube is vertical so that the distillate flows down, enabling efficient separation and purification. For this reason, most equipment feeds the mixture to be separated from the top, but there are also rising thin-film evaporators that introduce the mixture from the bottom and heat it to rise. Other shapes include horizontal thin-film evaporators used for industrial applications.
4. Centrifugal Thin-Film Evaporators
Centrifugal thin-film evaporators are a type of thin-film evaporators for industrial use. Centrifugal thin-film evaporators are equipped with rotating blades and use centrifugal force to thin-film the processing liquid on the inner surface of the body. Solvent is evaporated by heat transfer from the jacket and vacuum decompression. Generally, these are large devices for industrial use and are available in a variety of types, including horizontal, vertical, scraping, and sanitary types. They have high separation efficiency and are especially suitable for distillation of high-boiling point solvents.
5. Short-Path Evaporators
Short-path evaporators are similar to thin-film evaporators. Short-path evaporators are capable of creating a higher vacuum in glassware than thin-film evaporators. The short-path evaporator is more suitable when operation in a high vacuum is required, such as for distillation and separation of high-boiling-point components. It is also more suitable for thermally sensitive separations because it can lower the operating temperature and shorten the time required.