Does the cold dryer work 24 hours a day?

Whether the cold dryer (freeze dryer) needs to work continuously for 24 hours depends on the operation mode of its supporting equipment (such as air compressor), the stability of gas demand and the requirements of the process on the quality of compressed air. Combined with the operation characteristics of oil-free water lubrication air compressor or water lubrication air compressor, the following analysis is carried out from the working principle, operation scenario and optimization suggestions:

working Principle and Continuous Operation Requirements of 1. Cold Dryer

the cold dryer cools the compressed air below the dew point temperature through the refrigeration system, so that the water vapor is condensed into liquid water and discharged, thereby reducing the water content of the compressed air. Its operation shall meet the following conditions:

1. synchronization of supporting equipment: The cold dryer shall be operated in linkage with the air compressor. If the air compressor produces gas for 24 hours, the cold dryer shall be opened synchronously to avoid the compressed air carrying water; if the air compressor runs intermittently (such as shutdown at night), the cold dryer can be shut down with the shutdown.
2. Continuity of gas demand if the downstream gas equipment (such as pneumatic tools and spraying lines) needs 24-hour uninterrupted gas supply and is sensitive to humidity (such as the production of electronic components to prevent short circuit of condensed water), the cold dryer shall be continuously operated.
3. Process requirements for air quality some industries (such as pharmaceuticals, food packaging) require compressed air dew point ≤-40 ℃ (that is, very low water content), cold dryer need long-term operation to maintain a stable water removal effect.

Influence of 2. Water Lubricated Air Compressor on Operation of Cold Dryer

water lubricated air compressor realizes sealing and cooling by replacing lubricating oil with water film, and its exhaust characteristics directly affect the selection and operation of the air dryer:

1. low exhaust temperature: The exhaust temperature of the water lubricated air compressor is usually 60-80 ℃, which is lower than that of the micro-oil air compressor (80-100 ℃), which can reduce the load of the cold dryer, but the cold dryer is still needed to further cool down and remove water.
2. Very low oil content: The exhaust oil content of the water-lubricated air compressor is ≤ 0.01ppm, and no additional oil filter is required, but the cold dryer still needs to process water vapor (the exhaust water content of the water-lubricated air compressor is equivalent to that of the micro-oil compressor).
3. Continuous operation stability the water lubricated air compressor has no risk of oil pollution and low failure rate. If the matching cold dryer is a high reliability model (such as frequency conversion control and intelligent defrosting technology), it can support 24-hour continuous operation.

Application Scenarios and Optimization Suggestions for 24-hour Operation of 3. Cold Dryer

applicable Scenarios

1. continuous gas industry:
   • chemical production: The reaction kettle and pneumatic valve need 24 hours of air supply, and the compressed air containing water may cause pipeline corrosion or reaction out of control.
   • electric power industry: The air intake of the gas turbine needs dry air to prevent the blade from scaling, and the cold dryer needs to run with the air compressor for a long time.
   • Water lubricated air compressor matching scene for example, in semiconductor manufacturing, the water-lubricated air compressor provides a clean air source, and the cold dryer needs to operate continuously to ensure stable dew point (such as ≤-70 ℃).
2. High humidity environment:
   in coastal or humid areas, the air itself has a high water content, and the cold dryer needs to operate for 24 hours to prevent the compressed air from condensing in the pipeline.

Optimization recommendations

1. type selection matching:
   • select the processing capacity of the air dryer according to the air compressor displacement (e. g. air compressor gas production 10m & sup3;/min, need to configure the processing capacity ≥ 10m & sup3;/min of the cold dryer).
   • If the air compressor is of variable frequency type, the cold dryer shall support variable frequency linkage (such as automatic adjustment of cooling capacity by pressure signal).
2. energy saving design:
   • frequency conversion cold dryer: Dynamically adjust the power according to the gas consumption to avoid wasting energy when running at full load (for example, when the gas consumption decreases at night, the cooling capacity decreases simultaneously).
   • Intelligent defrosting: Adopt hot gas bypass defrosting technology to shorten defrosting time (from traditional 10 minutes/time to 3 minutes/time) and reduce downtime.
3. Maintenance Management:
   • regularly clean the condenser: Clean up dust every 3 months to prevent poor heat dissipation from reducing cooling efficiency.
   • Check the drain valve: Ensure the normal operation of the automatic drain valve to avoid the accumulation of liquid water affecting the water removal effect.
   • Water lubricated air compressor supporting maintenance if the cold dryer is linked with the water lubricated air compressor, the water circulation system (such as water quality and flow rate) shall be checked regularly to prevent the failure of the cold dryer due to scale or insufficient flow rate.

Alternatives to 4. non -24-hour operation

if there is a significant intermittent demand for gas (e. g. only daytime production), the following options can be used to reduce energy consumption:

1. gas tank buffer: Equipped with large-capacity air storage tank (such as air compressor with gas production of 10m & sup3;/min, air storage tank volume ≥ 10m & sup3;), supply air from the air storage tank during shutdown to prolong the shutdown time of the air dryer.
2. timing control: PLC or timer is used to control the start and stop of the cold dryer, which is synchronized with the production shift (for example, it runs from 8: 00 a.m. to 6: 00 p.m. and closes the rest of the time).
3. Adsorption dryer linkage after the cold dryer is connected in series with an adsorption dryer (such as a micro-thermal regeneration type), the adsorbent is used to remove water in depth and reduce the running time of the cold dryer (the adsorption dryer can run intermittently and be controlled by the regeneration cycle).

Summary

whether the cold dryer needs 24-hour operation shall be comprehensively evaluated for the air compressor mode, gas demand and process requirements. In the matching scenario of water-lubricated air compressor, if clean and dry air (such as semiconductor and pharmaceutical industries) needs to be continuously provided, the cold dryer should operate 24 hours a day. If there is an interval in gas consumption, the running time can be optimized through the linkage of air storage tank, timing control or adsorption dryer to balance the quality of gas supply and energy consumption.