Product technical performance characteristics
The shell-and-tube heat exchangers produced by our company have gone a long way from selecting the performance of the heat exchange tubes, the size of the diameter, the structure, the arrangement, to determining the combination of tube boxes, and adopting new sealing materials and methods In terms of optimized design, comprehensive technical performance is at the domestic advanced level.
1. After accurate matching check, heat exchange calculation, comprehensive optimization design, high heat exchange efficiency.
2. Adopt dense packing and strengthening technology, small size, large heat exchange area and good heat exchange performance.
3. The heat exchange tube is made of high-quality and high-efficiency reinforced copper tube. The connection between the heat exchange tube and the tube sheet is purely mechanically expanded, and the quality is reliable.
4. Adopting high-performance, long-life sealing material and high-strength sealing structure, good sealing performance.
The main characteristics of this type of evaporator are that the solution passes through the heating chamber only once in the evaporator, and is discharged as a concentrated liquid without circulating flow. When the solution passes through the heating chamber, it flows in a film shape on the tube wall, so it is also known as a liquid film evaporator. According to the flow direction of the materials in the evaporator, the single-pass evaporator is divided into the following types.
1. The heating chamber of the rising film evaporator consists of many vertical long tubes. The diameter of the commonly used heating tube is 25-50mm, and the ratio of the tube length to the tube diameter is about 100-150. The feed liquid is introduced from the bottom of the evaporator after preheating. It is boiled in the heating tube and rapidly vaporizes. The generated steam rises at a high speed in the heating tube. Generally, the suitable outlet steam speed is 20-50m / s when operating at normal pressure. The steam speed can reach 100 to 160m / s or more during down operation. The solution is driven by the rising steam, which rises into a film along the tube wall and continues to evaporate. The vapor-liquid mixture is separated in the separator 2, the completed liquid is discharged from the bottom of the separator, and the secondary steam is led out at the top. It should be noted that if the amount of water evaporated from the material liquid is not large, it will be difficult to achieve the above-mentioned steam speed, that is, the rising film evaporator is not suitable for the evaporation of thicker solutions; it has a large viscosity, is easy to crystallize, or easily Scaled materials are also unsuitable.
2. The difference between a falling film evaporator and a rising film evaporator is that the feed liquid is added from the top of the evaporator, and it forms a film along the tube wall under the action of gravity, and evaporates and thickens in the process At the bottom, a concentrated solution was obtained. Because the film-forming mechanism is different from the rising film evaporator, the falling film evaporator can evaporate materials with high concentration, high viscosity (for example, in the range of 0.05 to 0.45 Ns / m2), and heat-sensitive materials. However, because the liquid film is not easily distributed in the tube, the heat transfer coefficient is smaller than that of the rising film evaporator, so it is still not suitable for materials that are easy to crystallize or scale.
Because the solution flows in a film in the single-pass evaporator, the convective heat transfer coefficient is greatly improved, so that the solution can pass through the heating chamber in one pass without recirculation to reach the required concentration, so it has a greater capacity than the circulating evaporator. advantage. The benefits of non-circulation of the solution are: (1) the residence time of the solution in the evaporator is very short, so it is particularly suitable for the evaporation of heat-sensitive materials; (2) the concentration of the entire solution is not always close to the completion liquid like the circulation type Concentration, so the effective temperature difference of this evaporator is large. The main disadvantage is that it is very sensitive to the fluctuation of the feed load, and it is not easy to form a film when the design or operation is not appropriate. At this time, the convective heat transfer coefficient will be significantly reduced.