In the juice concentration industry, plate evaporator has the following advantages and is widely used:
1. Good accessibility: Plate heat exchanger consists of a set of heat exchanger plates fixed on a frame, with plates separated from each other by a gasket, or two plates brazed to form a kind of box-type component, with a vapour channel in the middle. The plates are easily removed and the entire heat transfer surface can be easily inspected visually. If problems such as clogged runners and scaling occur, the plates can be removed and the heat exchange surface can be cleaned manually. Individual plates can be replaced if they are damaged. The number of plates can be easily increased or decreased.
2. When the product changes or process adjustment, if necessary, the number of plates can be increased or decreased to adjust the processing capacity of the equipment, so as to get more ideal processing results. It can be reduced to 40% of the original production capacity.
3. In the same heat exchange area, the height of plate heat exchanger is much smaller than tube heat exchanger, plate heat exchanger for the height of the room is very low, even for the large-scale evaporator, can be made to the overall height of the equipment in the 5 metres or less, which means that the structure of the plant is more simple, the cost is also lower. Due to the volume reduction, the whole set of equipment installation is more easy, no need to machine weight or other special equipment, equipment installation cost is reduced accordingly.
4. The product stays in the evaporator for a short time, many products to be evaporated are heat-sensitive, and staying for a period of time at a higher temperature will make part of the ingredients destroyed, and the product's flavour will be reduced and its colour will be darkened. Plate heat exchanger heat transfer coefficient is tube heat exchanger 2-4 times, at the same time, because of the occupation of space volume is small, you can design a larger area of heat transfer, so that the liquid to be evaporated in the heat exchanger residence time can be shortened to 1 / 3 ~ 1/4, greatly improving product quality.
5. Due to the high heat transfer coefficient, the liquid can pass through the heat exchanger faster, and the volume of the retained liquid in the heat exchanger is reduced to 1/2~1/4, so that the whole evaporator can reach the equilibrium state in a shorter time at the beginning of the evaporation process.
6. For high viscosity liquid, plate heat exchanger is more suitable, because of the high heat transfer coefficient, the liquid can pass through the plate heat exchanger with a very fast speed, and under the action of the pattern on the surface of the plate, a strong turbulence will be formed, so that it is not easy to be adhered to on the surface of the heat exchanger, on the other hand, even for the high viscosity liquid, it is still possible to achieve a high heat transfer coefficient. The plate heat exchanger type evaporator has certain advantages in dealing with liquids of higher viscosity.
7. The high degree of turbulence caused by the pattern of the plates not only favours heat transfer, but also makes in-situ cleaning faster and more effective. The plates can also be replaced in the event of severe scaling that cannot be cleaned.
8. The temperature difference between each effect is smaller than that of shell and tube type. When doing multi-effect evaporator, the temperature of the first effect can be lower, and the number of effects can be increased or the product can be treated more gently.
In the following cases, plate heat exchanger is not applicable, but should use tube heat exchanger.
1. when the working pressure is higher than 2 bar.
2. sealing rings are required between the plates of the plate heat exchanger, when the working medium is thus restricted.
3. for the liquid to be concentrated in the case of large solid suspended particles (particle size of 2mm and above), need to use tube heat exchanger.
4. for extra-large evaporator, large plate processing is more difficult, often used tube heat exchanger, but with the improvement of plate processing capacity, now there are 100 tonnes / hour evaporation capacity of the plate evaporation unit implementation success.
