There are significant differences between the cold dryer and the suction dryer in terms of working principle, water removal effect, energy loss, gas loss and failure rate, as follows:
1. working principle
- cold dryer: Based on the principle of freezing and dehumidification, the temperature of the compressed air is reduced through the refrigeration system, so that the water vapor is condensed into liquid water and discharged, so as to achieve the purpose of drying. The specific process is as follows: compressed air first enters the precooler to exchange heat with low-temperature dry air, then enters the evaporator after lowering the temperature, and further exchanges heat with the refrigerant, so that the air is cooled below the dew point temperature, and the water vapor condenses into liquid water. The separator is separated and discharged, and the dry air is output after heating up through the reheater.
- suction dryer the use of adsorbents (such as activated alumina, molecular sieve, etc.) to achieve the adsorption of water vapor drying. After the compressed air enters the adsorption tower, the moisture is adsorbed by the adsorbent, and the dry air enters the downstream work. When the adsorbent is saturated with water, it is decompressed and expanded to atmospheric pressure by regeneration gas (usually dried compressed air), flows through the desiccant layer to be regenerated, absorbs water and takes it out of the dryer to realize dehumidification. Two tower cycle work, no heat source, continuous supply of dry compressed air.
2. water removal effect
- cold dryer: Limited by the principle, if the temperature is too low, icing will occur, so the dew point temperature is usually 2-10 ℃, and the water removal effect is limited.
- suction dryer: Without relying on temperature changes, deep drying can be carried out with the help of desiccant, and the outlet dew point temperature can reach below -20 ℃, or even lower, meeting the industry demand for extremely high air dryness requirements.
3. energy loss
- cold dryer: It is necessary to use refrigerant compression to achieve cooling and water removal. The power supply requires high power and relatively large energy consumption.
- suction dryer: Only the valve needs to be controlled by the electric control box, and the electric power is usually only about tens of watts, and the energy consumption is low. However, the heating regenerative suction dryer needs additional heating in the regeneration stage, and the energy consumption will increase.
4. gas loss
- cold dryer: Water is removed by variable temperature, and the water is discharged by the automatic drain without gas loss.
- suction dryer: The regeneration of desiccant after water absorption saturation needs to consume a certain amount of regeneration gas, usually 12%-15% of the treated gas, and there is gas loss.
5. failure rate
- cold dryer: It is composed of multiple systems such as refrigerant, air and electricity. The system is complex, with many parts and relatively high failure rate.
- suction dryer: Usually only the valve may fail due to frequent actions, the overall structure is relatively simple, and the failure rate is low.
