How to Successfully Get Through the Winter for PSA Air Separation Systems

In the blink of an eye, it's time for the beginning of winter, marked by the solar term "Beginning of Winter" among the twenty-four solar terms. This signals the start of the cold season, meaning the weather will gradually turn colder.

For PSA (Pressure Swing Adsorption) air separation systems, this is a special period because low temperatures can negatively affect multiple devices within the system. It may also lead to issues that are not typically encountered during normal operations. If operations or maintenance are not performed carefully, it can result in equipment failure and economic losses.

Generally, there are six parts of the entire PSA air separation system that are affected by low temperatures: the air compressor, refrigeration dryer, molecular sieve, drain valve and piping system, air storage tank, and filter.

Among these, the molecular sieve, drain valve and piping system, air storage tank, and filter encounter the following problems in low-temperature environments:

Molecular Sieve:

Low-temperature conditions may degrade the performance of the molecular sieve in PSA oxygen or nitrogen generators, directly affecting the system's oxygen or nitrogen production performance indicators.

Drain Valve and Piping System:

When cold air enters the air compressor and meets the high temperature inside the system, a large amount of water vapor is generated. When this moisture passes through the drain valve, it may freeze in the pipes or other parts due to the external low temperature. Therefore, it is essential to protect the drain valve and piping system from the cold. When shutting down, it is recommended to fully open the drain valve to drain any condensate before closing the valve.

Air Storage Tank:

The air storage tank may also accumulate excessive condensation water in low-temperature environments, leading to ice formation inside the tank that affects drainage. Regular drainage and maintenance are required. When shutting down, it is advisable to fully open the drain valve of the air storage tank to drain any condensate before closing the valve.

Filter:

When the system needs to be shut down, it is recommended to fully open the drain valve of the filter to drain any condensate before closing the valve.

The aforementioned issues can be addressed by closing the exhaust vent of the machine room, ensuring the ambient temperature of the machine room, wrapping the drain valve and pipes with insulating materials, or installing heating devices to maintain the pipe temperature.

Next, let's focus on the problems faced by the air compressor and refrigeration dryer during winter and their maintenance methods:

Air Compressor:

The air compressor is crucial for the entire PSA air separation system as it provides the air source and system pressure. However, it is not suitable for working under low temperatures and requires extra care to ensure stable and efficient operation of the system during winter.

Air Compressor Winter Management:

⚫ Impact of Low Temperature on Air Compressor:When cold air enters the air compressor and meets the high temperature, a large amount of water vapor is generated, increasing the burden on the air compressor's subsequent water vapor filtration. Therefore, it is necessary to frequently discharge the water from the post-processing equipment.

The oil circuit system is an important part of the air compressor's circulation system. Low temperatures are beneficial for the oil circuit system that needs cooling. However, for standby equipment or air compressors that do not operate continuously, when restarting at low temperatures, the oil circuit may be in an abnormal state due to lubricating oil condensation. Therefore, it is necessary to inspect the oil circuit system to check if the lubricating oil is normal.

⚫ Air Compressor Cold Protection:Heating or heating equipment can be added to ensure that the indoor temperature of the air compressor room is above 0°C. Alternatively, a lubricating oil heating device can be configured separately to heat the lubricating oil circuit before startup, ensuring the air compressor can start normally.

⚫ Air Compressor Shutdown Management:In case of shutdown, the power supply to the air compressor unit and other post-processing equipment should be cut off; the water and contaminants in the air storage tank, refrigeration dryer, and filter should be drained; the air pressure in the air compressor unit and other post-processing equipment should be released, and the air compressor unit exhaust port and other air supply ports should be closed after the gas pressure drops to 0.0MPa. The interior of the unit should be blown out and wiped clean. All cabinet doors should be closed to prevent dust from entering the cabinet.

⚫ Air Compressor Maintenance:When the air compressor needs to be shut down for a long time, it should be started once a week. After running for 3 hours, repeat the above shutdown management steps.

Refrigeration Dryer (referred to as Cold Dryer):

The cold dryer can reduce the moisture content for the PSA air separation system, preventing erosion of the core component—the molecular sieve—and ensuring the purity of the product gas and the service life of the equipment. In the face of low-temperature environments, it needs to take the following precautions:

⚫ Cold Dryer Winter Management:Temperature Management: Ensure that the ambient temperature where the cold dryer is located is between 2°C and 38°C. If the ambient temperature is too low, consider adding heating equipment to increase the ambient temperature.

⚫ Cooling Water Management: The condenser of the cold dryer needs cooling water to dissipate the heat generated to maintain the condensation effect. During winter management, attention should be paid to the supply and discharge of cooling water for the condenser to prevent freezing due to low temperatures. Therefore, in low-temperature environments, it is necessary to ensure proper supply of cooling water for the cold dryer and consider adding heating equipment to control the cooling water temperature and prevent freezing.

⚫ Maintenance: During winter, it is easy for the cold dryer to have internal condensation and freezing of refrigeration components. To ensure normal operation of the equipment, key components such as condensers and evaporators need to be cleaned and inspected regularly. Additionally, the quality and level of compressor lubricating oil should be checked regularly to ensure normal operation of the compressor.

⚫ Load Control: Special attention should be given to the load of the cold dryer for compressed air during winter. When the load is too high, the water content in the compressed air cannot be properly processed. Therefore, when using the equipment during winter, it is necessary to pay attention to the actual load and keep the cold dryer within a reasonable load range to ensure stable and reliable drying effects.

Successfully taking cold protection measures for PSA air separation equipment during winter ensures normal operation of the equipment, which is of great significance for improving production efficiency and extending equipment life. Therefore, enterprises and relevant operators should attach great importance to the cold protection work of system equipment during winter and take effective measures to ensure the safe and stable operation of the equipment.