Film Evaporator

Film Evaporator

Detailed Description
Steam produced in the heating chamber carries a large amount of droplets. Upon entering the larger evaporation chamber, these liquids are separated from the steam due to their own condensation or by the action of defoamers. Typically, defoamers are installed at the top of the evaporation chamber.
Evaporators are classified into three types based on operating pressure: atmospheric, pressurized, and vacuum. They are also categorized according to the movement of the solution within the evaporator principle: ① Recirculating type. The boiling solution passes through the heating surface multiple times in the heating chamber, such as in recirculating tube, suspended basket, external heat, Lenntech, and forced circulation types. ② Single-pass type. The boiling solution passes through the heating surface once in the heating chamber, does not recirculate, and is then discharged as a concentrated liquid, like in ascending film, descending film, stirred film, and centrifugal film types. ③ Direct contact type. Heat transfer occurs through direct contact between the heating medium and the solution, such as in immersed combustion evaporators. During operation, evaporators consume a large amount of heating steam, so to save steam, multi-effect evaporators and steam recompression evaporators can be used. Evaporators are widely used in chemical, light industry, and other departments.

The tubular evaporator, also known as the standard evaporator, consists of a heating chamber made up of vertical tube bundles. It features a large diameter recirculation tube in the middle, with the remaining smaller diameter heating tubes referred to as boiling tubes. Due to the larger size of the recirculation tube, the heat transfer surface area per unit volume of solution it occupies is smaller than that in the boiling tubes. This results in different levels of heating for the solution in the recirculation tube and the other heating tubes, leading to a lower density of vapor-liquid in the boiling tubes compared to the solution density in the recirculation tube. Additionally, the upward suction effect of the rising steam causes the solution in the evaporator to form a circulation flow, descending from the recirculation tube and ascending through the boiling tubes. This circulation, primarily driven by the density difference of the solution, is called natural circulation. This mechanism is beneficial for enhancing the heat transfer efficiency within the evaporator.

Heating tube height is generally 1~2 meters; the diameter ranges between 25~75 mm. This evaporator is widely used due to its compact structure, ease of manufacturing, good heat transfer, and reliable operation. However, due to the structural limitations of the evaporator, the circulation speed is not high. Additionally, the continuous circulation of the solution in the heating chamber keeps its concentration close to that of the finished liquid, resulting in a high boiling point and a reduced effective temperature difference. This is a common drawback of circulation evaporators. Moreover, the cleaning and maintenance of the equipment are not convenient, making it difficult for this type of evaporator to fully meet production requirements.

Evaporation is a unit operation that involves heating a solution containing non-volatile solutes to the boiling point, causing a portion of the solvent to vaporize and be removed, thereby increasing the concentration of the solute in the solvent. The application of evaporation in industrial production includes the following scenarios:

1. Directly produce products from concentrated dilute solutions or further process concentrated solutions (such as cooling crystallization) to obtain solid products.

2. Simultaneously concentrate solutions and recover solvents, such as the concentration and de-benzene of organic phosphorus pesticide benzene solutions, the evaporation of alcohol extraction in traditional Chinese medicine production, etc.

3. To obtain pure solvents, such as desalinated seawater;

In summary, the evaporation process is widely used in industries such as the chemical and food industries.

Evaporator Principle

1. A metal round bowl with an internal diameter of φ200mm and a height of approximately 100mm.

2. The evaporator is a metallic circular structure with a smooth inner wall. The edges of the evaporator must not have burrs or scratches, etc.

3. All parts in contact with water should be smooth, and the seams of their mating or connecting parts should be tight and strong, with no leakage or seepage.

4. The assembly of all components of the evaporator should be correct, with no loose parts, deformation, or other defects affecting operation.

5. The protective layer applied to each part and component of the evaporator should be firm, even, and smooth, without any delamination or rusting defects.

6. The evaporator and mounting frame should be easy to install, and ensure that the evaporator does not become dislodged during normal operation due to wind influence.

7. Accessories: One measuring cup with etched lines, one water storage unit, one installation frame, and one metal wire mesh cover (for bird-proof drinking water, user selectable).