The refrigeration dryers and suction dryers we often say are all equipment for compressed air drying. They are widely used in industry, but there is no drying equipment suitable for all working conditions. We mainly consider the degree of drying and the cost of use. Which equipment or combination of equipment to meet the needs of users?
Freeze drying
Freeze-drying method is to use refrigerant to cool compressed air to a certain dew point, precipitate over-saturated water, and separate liquid water through a steam-water separator, so as to achieve the purpose of drying, but the equipment outlet pressure dew point value cannot reach water The temperature below freezing. Notable features: it can work continuously, does not require regeneration, and has low energy consumption.
Adsorption drying method
The adsorption drying method uses various adsorbents, such as silica gel, activated alumina, and molecular sieves to absorb moisture in compressed air to achieve the purpose of drying. This method can easily treat the pressure dew point of compressed air to a temperature below the freezing point of water. However, due to the limited adsorption capacity of the adsorbent itself, it is necessary to use a double-tower or multi-tower alternate adsorption method to make the compressed air dry continuously. There are many types of suction dryers on the market, but they all use the principle of adsorbent dehydration, and the difference lies in the way of regeneration.
how to choose
From the perspective of performance requirements
The first and most important point when selecting a model: it should be selected according to user needs.
Refrigerated dryers have lower energy consumption and operating costs than adsorption dryers, but they cannot provide deep dry compressed air like adsorption dryers. The pressure dew point of refrigerated dryers is usually above 3℃td. For general For the manufacturing process, it is sufficient to choose a freeze dryer; for some more demanding and drier compressed gas, you should choose an adsorption dryer.
From the perspective of the installation environment
The adaptability of refrigerated dryers to the environment is weak. Too high or low ambient temperature is not conducive to the operation of the equipment: too high ambient temperature will increase the refrigerant condensation pressure of air-cooled dryers, which will reduce the cooling capacity and increase The pressure dew point at the outlet of the equipment; when the ambient temperature is too low, especially below 0°C, ice blockage is likely to occur when the condensate is drained from the dryer.
Adsorption dryers have relatively strong adaptability to ambient temperature, but the factors affecting the high dew point of compressed air caused by the high air compressor outlet temperature at the highest ambient temperature must be taken into consideration when selecting equipment.
From the perspective of maintenance costs
The refrigeration dryer uses a sealed refrigeration system, the refrigerant is not exposed to the atmosphere, so the system maintenance cost is low.
The adsorption dryer involves frequent valve switching between the adsorption towers, and the adsorption dryer with thermal regeneration also has high and low temperature switching, so the maintenance cost of the valve is relatively high. In addition, most adsorption dryers are equipped with oil-containing lubricated compressors at the front end. Compressor lubricating oil is very easy to cause "oil poisoning" of the adsorbent, which requires regular replacement of the adsorbent, resulting in higher maintenance costs.
From the perspective of acquisition cost
Judging from the current sales prices on the market, among the products of the same brand, the price of adsorption dryers with the same processing gas volume will be higher than that of refrigerated dryers.
From the perspective of operating costs
Due to the difference in the dew point value of the compressed air processed by the two devices, they cannot be simply replaced, so the operating costs are not comparable. Their difference is more in the comparison between the same type of equipment, such as the comparison between different types of heat exchangers, different refrigerants, and different vapor-liquid separation methods of refrigeration dryers; or the adsorption of different regeneration forms Comparison between type dryers.
our suggestion
If the temperature of the pipeline layout area is lower than 2°C for a long time, and the required value of the compressed air pressure dew point is lower than the annual extremely low temperature value by more than 5°C, it is recommended to configure only a suction dryer.
Clarify the user's demand for the actual dew point value when compressed air is used, and compare it with the first point and take the lower value. When selecting equipment, it is necessary to meet the dew point, and then consider different energy-saving configurations among similar equipment, otherwise the gains are not worth the loss.
It is recommended to install a cold dryer before the suction dryer. The cold dryer can remove most of the water and oil in the compressed air, reduce the water removal load of the suction dryer, ensure its drying effect, and reduce the selection of the suction dryer. At the same time, it reduces the pollution of oil impurities to the adsorbent, so that the drying effect can be maintained longer, and the adsorbent replacement time is prolonged.