Compressed air is also used for water removal; what are the differences between cold dryers and adsorption dryers?

Thread Content

In most ordinary industries, both cold dryers and desiccant dryers are used for water removal. Although both serve the same purpose, they differ from each other in terms of their functioning and efficiency. The main differences between cold dryers and desiccant dryers lie in the following aspects: 1. Difference in working principle: Cold dryers operate on the principle of freeze-drying; they cool the saturated compressed air coming from upstream by exchanging heat with a refrigerant, thereby reducing its temperature to a certain dew point at which large amounts of liquid water are condensed. This liquid water is then separated from the gas using a gas-liquid separator and discharged outside the machine, thus achieving water removal and drying. A desiccant dryer operates on the principle of pressure swing adsorption: saturated compressed air from the upstream is passed at a certain pressure through contact with a desiccant, whereby the majority of the moisture is absorbed by the desiccant. The dried air then proceeds to the downstream processes, thereby achieving deep drying. 2. Differences in water removal efficiency (difference in dew point values): Due to the limitations of its working principle, adsorption chillers experience freezing when the temperature is too low; therefore, their dew point temperature is usually between 2 and 10°C. Dryers do not require temperature changes to function, and since the desiccant (alumina) enables deep drying, the dew point temperature at their outlet can typically drop below -20°C, meaning deep drying is achieved. 3. Differences in energy consumption: For cold dryers, cooling is achieved through the work done by compressing the refrigerant, which results in higher power requirements. As for the dryer, since it only requires control of the valves through an electrical control box, its power consumption is usually only in the range of a few dozen watts; in other words, there is no significant loss of electricity. 4. Different gas volume loss: Since the cold dryer achieves water removal through temperature variation, and the water is removed from the device via an automatic drain, there is no loss of gas volume. On the other hand, desiccant dryers require regeneration once the desiccant becomes saturated with water, which results in a loss of about 12-15% of the regeneration gas. 5. Difference in failure rate: Since the refrigerant system and air system of a cold dryer, along with its electrical components, are relatively complex, while a desiccant dryer only has valves that may fail due to frequent operation, its failure rate is generally lower than that of a cold dryer. Generally speaking, desiccant dryers are superior to cold dryers in terms of both stability and performance; however, since a certain amount of regenerative gas is consumed, customers are usually required to weigh the pros and cons before making a choice. However, more and more manufacturers are now choosing desiccators, and it can be said that this is gradually becoming a trend. However, in the pharmaceutical industry, both cold dryers and vacuum dryers are used, as their processing effects are different.