Air separation oxygen production area: [Weekly Topic] Week 20 of 2011 – Nitrogen blockage in the argon system: How to deal with it?

This is a quite complex issue; I’ll try to learn about it. 1. Check the temperature difference in the condenser. 2. Examine the argon fraction. As for the other factors, the experts don’t recognize them. a. Resistance b. Pressure c. Liquid level in the condenser

Phenomenon: The argon fraction decreases, its amount falls; the liquid level in the condensers of the crude argon tower and the refined argon tower rises, and the pressure inside the towers increases. Treatment: Remove nitrogen and adjust the argon fraction to normal levels

Under normal operating conditions, the set value for the oxygen content in the argon fraction from the crude argon column is 91.1%. If the oxygen content in this fraction falls below 90.5%, a mild nitrogen blockage occurs in the crude argon column; if it drops below 90%, a severe nitrogen blockage occurs. The main reasons for nitrogen plugging are as follows: (1) Large fluctuations in the oxygen production of the product ； (2) Switching of the molecular sieve purification system ； (3) Variable condition adjustment.

The equipment upstairs is really terrible; the operators must be exhausted from using it. Switching operations can also cause nitrogen blockages. In 90.5% of cases, the problem lies either with the gauge or with the equipment itself. Operating under varying conditions slowly will prevent such blockages, haha. I feel sorry for you guys

Brother on the fourth floor, please tell me more about the situation there; I think your equipment is quite typical. .

The nitrogen level indicates that as the argon fraction at the top of the main tower moves downward, the amount of argon drawn off remains unchanged; consequently, the nitrogen content is high. It is necessary to adjust the operating conditions of the main tower. Such as a slight reduction in oxygen production. Or adjust the argon fraction.

Phenomenon of nitrogen entrapment: 1. Decrease in oxygen analysis at the exit of the crude argon column； 2. Decline in the argon fraction ； 3. The volume of the argon fraction gas decreases ； 4. The temperature difference in the crude argon condenser decreases ； 5. Rising liquid level in the night sky ； 6. Drop in resistance of the crude argon column ； 7. Drop in the bottom liquid level of crude argon ； 8. A very mild nitrogen plug is indicated earliest by unstable pressure in the argon purification tower, with fluctuations occurring ； Treatment: 1. Open the vent valve of the crude argon tower to vent, and discharge the nitrogen accumulated in the crude argon condenser ； 2. Improve the purity of the argon fraction ； 3. Ensure stable liquid level at the bottom of the crude argon ； 4. Increase the cooling capacity of the expander as appropriate to prevent a situation where the nitrogen plugs have been dealt with properly but there is still insufficient cooling capacity ； 5. Appropriately reduce the purity of the night sky and artificially increase the temperature difference in the crude argon condenser; this is mainly aimed at users with a high level of night sky purity

What was said on the 8th floor is correct; in fact, nitrogen blockages mainly occur when the crude argon column is used improperly. During normal operation, a small amount of venting takes place, so blockages are less likely to occur. When starting up the crude argon column, it’s important to keep the argon fraction at a low level, generally between 7% and 9%. At the same time, the flow rate of crude argon gas, as well as the liquid levels in the argon column and the columns above it, need to be adjusted carefully, and the entire process should be carried out slowly. This not only helps maintain stability in the main tower’s operating conditions but also reduces the risk of nitrogen plugging.

We are the largest air separation plant in Asia. I have encountered two severe nitrogen blockages; such severe blockages cannot be resolved. The initial symptoms were a decrease in the temperature of the main tower, a sharp drop in the oxygen content of the feed gas, an increase in valve openings, and fluctuations in flow rate. The main cause was a fault with the compressor vanes, which resulted in no air reaching the tower. Fortunately, the vanes recovered automatically. In the end, the argon tower was shut down to protect the main tower and ensure an ongoing supply of oxygen, after which the argon tower was restarted

The explanation on floor 8 was excellent. An addition: \"7. Decrease in the liquid level at the bottom of the crude argon\" – this occurs during the argon injection phase; after normal operation, due to the automatic control of the liquid level at the bottom of the crude argon, mild nitrogen blockage is not noticeable. To address this issue, \"2. Increase the purity of the argon fraction\"； "--I feel it’s the reduction in the purity of the argon fraction ；