Theglovebox closed-loop circulation system is essentially a precision closed-loop system integrating gas purification, circulation power, and pressure control. Its core purpose is not simply to “remove the air,” but to keep the inert gas inside the chamber continuously circulating and self-purifying, so that water and oxygen levels can remain at an extremely low level of <1 ppm over the long term. The Mikrouna glovebox closed-loop circulation system consists of five operating stages: circulation power and gas delivery, impurity purification, pressure and valve logic control, purification-column regeneration, and monitoring-feedback regulation.
Step 1: Circulation Power and Gas Delivery
The closed-loop circulation is a completely enclosed circuit. The working gas is high-purity argon or nitrogen, and a variable-frequency circulation fan serves as the power source for the entire system. Mikrouna's fan has a flow rate of 90 m³/h, while different models can provide higher flow rates, such as 145 or 180 m³/h, as required. The fan draws inert gas from inside the glovebox chamber and transports it through stainless-steel piping to the purification-column unit. After purification, clean inert gas is returned to the glovebox chamber, forming a closed circuit. The gas circulates only within the system rather than being discharged directly to the outside, maximizing the conservation of high-purity inert gas.
The glovebox circulation piping can extend to connected process chambers, allowing the gas inside those chambers to participate in the circulation simultaneously and ensuring water and oxygen removal. The circulation loop is equipped with pneumatic angle valves and integrated solenoid valves. The PLC automatically switches the valves on and off according to operating conditions, isolating the purification column during regeneration while ensuring that the main glovebox circulation continues uninterrupted.
Step 2: Water and Oxygen Removal Inside the Purification Column
The mixed gas pushed by the fan enters the purification-column vessel, which is filled with 5 kg of copper catalyst and 5 kg of molecular sieve. The gas first passes through the molecular-sieve layer, where the microporous structure physically adsorbs water molecules from the gas stream, completing dehydration. The gas then flows through the copper-catalyst layer, where elemental copper reacts chemically with oxygen in the gas stream to remove oxygen. The purified high-purity inert gas then flows back through the piping into the glovebox chamber, reducing the water and oxygen concentration inside the chamber.
After repeated circulation, water and oxygen inside the chamber are continuously captured by the filling materials, and the water-and-oxygen level gradually decreases to the 1-ppm range. At the same time, a 0.3-μm filter inside the glovebox can filter powder and dust from the circulating gas, preventing filler powder from being carried back into the chamber and contaminating samples.
Step 3: Coordinated Pressure and Valve Control
The closed-loop circulation system is not completely rigidly sealed. The system continuously monitors chamber pressure and maintains a slightly positive pressure. Operation of the circulation fan causes pressure fluctuations, so the system automatically supplies a small amount of inert gas to compensate for pressure loss. When the pressure is too high, the system automatically opens the vent for pressure relief; when the pressure is too low, an alarm is triggered to indicate a possible sealing problem.
Step 4: Purification Column Regeneration to Restore Purification Capacity
After continuous circulation, the molecular sieve becomes saturated with adsorbed water, while the copper catalyst is largely converted into copper oxide, reducing purification capacity. The system disconnects the purification column to be regenerated from the main circulation loop and introduces a 5–10% hydrogen/inert-gas mixture. The purification column is heated, and the hydrogen reduces copper oxide back to active elemental copper. The molecular sieve releases the adsorbed moisture at high temperature, and the moisture is discharged from the system with the regeneration exhaust gas.
After reduction and desorption are completed, heating stops and inert gas is used to purge and cool the purification column. The filling materials recover their ability to remove water and oxygen, and the valves switch to reconnect the column to the closed-loop circulation. The entire regeneration process is automatically controlled by the PLC and requires no manual operation.
Step 5: Monitoring, Feedback, and Closed-Loop Regulation
Sampling interfaces are installed in the closed-loop piping. A water-and-oxygen analyzer continuously samples the circulating gas and provides real-time water-and-oxygen data to the PLC. If water and oxygen levels rise because materials release impurities or because of sealing leakage, the system keeps the fan at a high speed and increases circulation flow to accelerate impurity removal. When the indicators remain stable and within specification for a prolonged period, the variable-frequency fan reduces its speed to lower energy consumption.
The Mikrouna glovebox closed-loop circulation system relies on inert gas repeatedly flowing through a closed circuit, purification media continuously capturing impurities, regeneration restoring the media after saturation, and sensor-based feedback regulation. Together, these functions ensure that the glovebox chamber—and connected process chambers integrated with the glovebox—can maintain a high-purity, anhydrous, oxygen-free inert atmosphere over the long term.
