Linkage control of air compressor and freeze dryer

The linkage control between air compressor and freeze dryer is a key link in the compressed air system to ensure gas quality. Its principle, implementation method and advantages are as follows:

1. Linkage control principle

The core goal of linkage control is to achieve the coordinated operation of the air compressor and the cold dryer to ensure that the compressed air is produced efficiently while meeting the dryness requirements. The principle is based on the following two points:

1. Cold dryer function: Cooling the compressed air to 2-10℃ through refrigerant circulation (compression → condensation → expansion → evaporation), condensing water vapor into liquid water, which is discharged through the gas-water separator, thereby reducing the dew point of the compressed air.
2. linkage logic: Automatically control the start and stop of the cold dryer according to the operating status (start/stop) of the air compressor to avoid idling or frequent start and stop of the cold dryer after the air compressor is shut down, and extend the life of the equipment.

2. Implementation method of linkage control

1. Electrical signal linkage

• self-retaining contact: After the air compressor is started, the closing signal will continue to output, and the cold drying machine will run accordingly; when the air compressor is stopped, the signal will be disconnected, and the cold drying machine will stop.
• impulse contact: When the air compressor is started/stopped, it sends an instantaneous closing/opening signal respectively, and the cold dryer responds to the corresponding action.

2. System process linkage

• Pre-open cooling water valve: Open the cooling water valve of the cold dryer 20 seconds before the air compressor is started to prevent system pressure drop and causing failure.
• Pressure and temperature joint control: When the outlet pressure of the air compressor reaches a preset threshold (such as 0.6MPa) and the temperature is higher than the ambient temperature +55℃, the cold drying machine automatically starts.

3. Advantages of linkage control

1. energy efficiency improvement

• Avoid waste of energy consumption when the cold dryer is running alone (energy consumption is reduced by about 15%-20% after linkage).
• Use the residual heat of the air compressor to pre-cool the evaporator of the cold dryer to improve refrigeration efficiency.

2. equipment protection

• Prevent the evaporator from freezing due to low pressure operation after the air compressor is shut down.
• Reduce the risk of air compressors emulsifying lubricating oil due to moisture and extend the life of the main engine.

3. quality assurance

• The linkage system stabilizes the compressed air dew point below-40℃ (compliant with ISO 8573-1 Class 1 standard).
• Avoid problems such as pipeline corrosion and stuck pneumatic components caused by moisture.

4. Typical application scenarios

1. pharmaceutical industry: Ensure that the oil content of compressed air is ≤0.1mg/m³ and the dew point is ≤-20℃, meeting GMP certification requirements.
2. electronics industry: Provide oil-free dry air for chip packaging and spraying processes to prevent electrostatic damage.
3. food packaging: Avoid moisture in compressed air causing moisture and deformation of packaging materials.

5. Market technology trends

1. integrated design: Integrate air compressor, cold dryer, and air storage tank to reduce the floor area (such as integrated screw air compressor).
2. Intelligent control upgrade：

• PID algorithm is used to adjust the refrigerating capacity of the chiller dynamically to match the load variation of the air compressor.
• Internet of Things monitoring: real-time transmission of dew point and pressure data, support remote operation and maintenance.

3. green technology：

• Environmentally friendly refrigerants such as R410a are used to reduce carbon emissions.
• Waste heat recovery: Use the cold dryer to heat the workshop or preheat the compressed air.

summary: The linkage control of the air compressor and the cold dryer not only improves the overall efficiency of the compressed air system, but also is the key to ensuring production quality. Enterprises can choose pulse-type or self-sustaining linkage solutions according to their own needs, and combine intelligent monitoring technology to achieve predictive maintenance, further reducing operation and maintenance costs.