The difference between refrigerated dryer and adsorption dryer

In compressed air systems, adsorption dryers and refrigerated dryer are two common types of dehumidification equipment. They have significant differences in working principles, performance characteristics, applicable scenarios, and maintenance. Below is a detailed comparison of these two types of dryers to fully explain their differences.

1. Working principle

Freeze dryer

Freeze dryers work on the principle of refrigeration dehumidification. Its core is to use heat exchange equipment to transfer heat between the moist compressed gas and the refrigerant, thereby greatly reducing the temperature of the compressed gas. As the temperature continues to decrease, the water vapor in the compressed gas will condense into water droplets, and then the condensed water will be separated and discharged through the gas-water separator. In order to avoid freezing caused by too low temperature of the compressed gas, the processed compressed air will enter the heat exchanger again for temperature recovery, so that its temperature is higher than the pressure dew point, and finally the dry compressed air will be discharged.

Adsorption dryer

Adsorption dryers achieve drying effects through “pressure changes” (pressure swing adsorption principle). The compressed gas flows into the absorber, and the moisture in it is absorbed by the adsorbent material (such as activated alumina, silica gel, etc.). In order to restore the adsorption capacity of the adsorbent material, a small part of the dried compressed gas passes through the throttle valve or directly enters the heater, and is introduced into another adsorber as a regeneration gas flow to regenerate the adsorbent material. The two adsorbers operate in turn according to preset conditions, alternately performing adsorption and regeneration processes, thereby continuously providing dry compressed air to users.

2. Performance characteristics

Freeze dryer

Processing efficiency: Limited by the freezing point, refrigeration heat exchange efficiency and gas-water separator separation efficiency, the pressure dew point that the refrigerated dryer can achieve is relatively high, usually 2°C~10°C.

Inlet air requirements: It can tolerate higher inlet air temperatures and pressures, but its drying effect will be significantly weakened in high temperature environments.

Energy consumption: No additional regenerative energy is required, but the refrigeration system itself will consume a certain amount of electricity.

Failure rate: Since the system components are relatively complex, including refrigerant, air and electrical systems, the probability of failure is high.

Noise: Operating noise is relatively low and is usually not noticeable inside the air compressor room.

Adsorption dryer

Processing efficiency: The achievable pressure dew point is relatively low, usually -20°C~-70°C, and is suitable for occasions with high requirements for compressed air dew point.

Air intake requirements: There are more stringent requirements for the cleanliness of compressed air. It is necessary to ensure that the compressed air does not contain oil molecules to avoid clogging the adsorbent.

Energy consumption: During the regeneration process, part of the compressed air will be consumed as the regeneration air flow, but some high-efficiency models (such as blast-heated regeneration adsorption dryers) can effectively reduce regeneration air consumption.

Failure rate: Compared with refrigeration dryers, adsorption dryers have a lower failure rate, mainly when the valve is frequently activated.

Noise: Due to the pressure release noise from the adsorption tower, the operating noise is relatively high, about 65 decibels.

3. Applicable scenarios

Freeze dryer

It is suitable for occasions where the dew point requirements of compressed air are not high.

It is suitable for environments with large fluctuations in inlet air temperature and pressure.

Suitable for occasions where energy costs need to be saved.

Adsorption dryer

It is suitable for occasions with extremely high requirements on the dew point of compressed air, such as electronics, medicine, food and other industries.

Suitable for situations where high-quality dry compressed air needs to be continuously supplied.

It is suitable for occasions with high ambient humidity or where a large amount of compressed air needs to be processed.

4. Maintenance

Freeze dryer

The automatic drain filter needs to be cleaned regularly to prevent clogging.

Check whether the refrigeration system is operating normally, including the amount of refrigerant, working status of the compressor, etc.

Clean the heat exchanger regularly to improve heat exchange efficiency.

Adsorption dryer

The saturation degree of the adsorbent needs to be checked regularly and failed adsorbents should be replaced in a timely manner.

Inspect and maintain valve components to ensure they open and close properly.

Perform regular maintenance on the muffler to remove impurities attached to the surface.

Refrigeration dryers and adsorption dryers each have their own unique advantages and application scenarios in compressed air systems. Users should comprehensively consider factors such as actual needs, air intake conditions, processing efficiency, energy cost, and maintenance convenience when making selections. Through reasonable selection and correct use and maintenance, the stable operation and efficient dehumidification effect of the compressed air system can be ensured.