The principle and characteristics of adsorption dryer

The principle of adsorption dryer:
Adsorption drying is a common method for preparing compressed air with a dew point below zero. Its principle is to use certain materials with the ability to adsorb moisture-called adsorbents (such as molecular sieves, activated alumina and silica gel) to adsorb moisture in compressed air. To reduce the water content of compressed air to reduce the dew point.
In the adsorption dryer, when the adsorbent absorbs a certain amount of moisture, it will reach the saturation state of water content (called adsorption equilibrium). In order to continue working, the adsorbent must be dewatered-called adsorbent analysis (or Desorption) to restore its adsorption capacity to its original state-this process is called adsorbent regeneration.
Once the water vapor in the compressed air is in contact with the surface of the adsorbent, the adsorption process can take place immediately without the need for external energy, so the adsorption process is completely spontaneous. However, the analysis process cannot be carried out spontaneously, and it must be completed with the full intervention of external energy. The regeneration method of the adsorbent and the regeneration energy consumption are the main factors affecting the operation of the adsorption dryer.
The dew point of compressed air treated by the adsorption dryer can be very low. Therefore, the adsorption dryer has been widely used where extremely dry compressed air is required.
Product features of adsorption dryer:
1. The most significant advantage of the adsorption drying method is that the dew point of the compressed air can reach -40℃～-70℃ (atmospheric pressure), which is a low level that can not be reached by other drying methods except for cryogenic air separation. Dew point air
2. The limitation of the adsorption dryer is that its regeneration energy consumption is very high, so that before choosing the adsorption dryer (suction dryer), you should first evaluate whether its operating cost is compatible with the process needs. Generally speaking, when the refrigeration dryer can meet the requirements, it is a waste of resources to choose an adsorption dryer.
3. The flow rate of the adsorption dryer is limited by the volume of the drying tower. Especially for the heating regeneration dryer, the continuous adsorption for several hours needs to be supported by filling a large amount of adsorbent, which makes the whole machine very bulky. A large drying tower will produce a large dead angle of airflow, and it is also prone to tunnel effect, which is not conducive to the reduction of the dew point of the finished product. At present, most adsorption dryers produced by foreign manufacturers are below 100m3/min, which is much larger than refrigerated dryers.
4. The working life of the adsorption dryer mainly depends on the time of adsorption deterioration. Generally, after 2-3 years of operation, the adsorbent is required to be replaced; the vulnerable parts in operation include valves, heaters and mufflers, etc.;
5. Adsorption dryers need to pre-process the intake air to remove liquid water droplets and oil in the air as much as possible to prevent the adsorbent from prematurely degrading; in addition, the exhaust of the adsorption dryer contains a large amount of dust generated by the adsorbent during operation. Need to be removed by post-filtering;
6. In order to ensure the exhaust dew point, the contact time between the compressed air flow and the adsorbent in the adsorption tower should generally not be less than 5s, which requires that the air flow rate in the tower should not be too fast, generally controlled at about 0.2-0.4s, so ensure The adsorption tower has an appropriate aspect ratio.