Protection of synthetic ammonia catalysts

If the nitrogen pressure can be ensured and the purity is satisfactory, then such protection should be problem-free. Before starting the machine, the compressor cylinder should be thoroughly purged to ensure that no liquid remains in the drain lines. Before driving, ensure the process gas is tightly controlled, and your problem should be resolved. Wish you a safe drive! If it turns out to be helpful, please give me feedback sooner! :) :) :)

These are common problems in manufacturing enterprises; generally, after entering shutdown protection mode, it takes 1–2 shifts for a factory to return to normal operation. It is likely caused by the partial oxidation of the catalyst surface.

No, it won’t happen. It only takes 5 to 7 hours for us to get the synthesis and driving process up and running properly; the temperature is raised from 200 degrees to over 460 degrees, and by continuously increasing the pressure, we boost the power of the electric furnace. We use the H/N system from other systems to raise the temperature. If the previous stage functions properly, then the synthesis process will also work fine. I’m not sure what’s going on with you guys. This post was last edited by yunanshu on 2008-1-25 at 13:30.]

It takes 1-2 shifts driving to return to normal. If such problems are not resolved in a timely manner, how much damage will it cause! You should also look carefully for the reason, just like the original poster did. :) :) :) This post was last edited by yunanshu on 2008-1-26 08:32 ]

It is best not to use nitrogen for pressure maintenance; although its purity is high, its main impurity is oxygen. If a large amount of gas is used for this purpose, it has a significant impact on the catalyst’s activity. It is preferable to use an ammonia tank to supply the gas for pressure maintenance, but care must be taken not to use too much gas from the ammonia tank, as this can affect the process of ammonia injection during operation. So as long as there is a sound of air flowing in during pressure holding, that’s fine.

In my opinion, the reasons should be sought from the following aspects: 1. Whether the purity of the nitrogen meets the standards and whether the analysis instruments are accurate; 2. Whether the pressure used for nitrogen protection is low enough, and whether a pressure gauge with appropriate accuracy range is being used to measure it; 3. Whether the synthesis circuit has been properly purged after shutdown; 4. Whether the purified gas supplied is of satisfactory quality and whether there are any excessive trace elements present; 5. What model of catalyst are you using? What is its activity level, and how many years has it been in use? Our factory uses the Nanhua A110-1 model, which has been in use for over 4 years now. It’s in good condition, and there are no issues of the kind you mentioned; the only problem is that the electric heater has low power, resulting in a slower rate of temperature increase. This post was last edited by binghua2008 on 2008-2-1 at 20:32

1\ It is recommended that the nitrogen shielding pressure not be too high; in fact, maintaining a slight positive pressure is the best approach. 2\ Do not continuously supply nitrogen – therefore, it is necessary to ensure that other vent points are closed. 3\ Check the purity of the nitrogen; do not be misled by false indications.

A few more points: 1. A purity of 99.5 is too low; our company requires >99.9%. 2. Slightly positive pressure protection is sufficient; close all vent valves and supply air intermittently, as long as no air is drawn in. 3. If an increase in temperature is observed during nitrogen filling, the nitrogen filling must be stopped immediately, and the cause must be thoroughly investigated. A lesson in blood!

I think there shouldn’t be any problem. The situation you described is a case of catalyst poisoning, but it is necessary to determine where the source of contamination lies: Could it be that the pressure was not maintained, allowing air to enter the tower? Well, the nitrogen content you mentioned is on a dry basis; there is water present, and it is the water that causes the problem. A detailed analysis is needed, but using nitrogen for protection is absolutely no issue.

The simplest form of protection (if the synthesis tower does not need maintenance): simply use syngas and effectively isolate the synthesis tower; the pressure can be kept lower!

What was said on floor 12 is correct; for short-term parking, it’s sufficient to use syngas to seal the tower and reduce the pressure accordingly. For long-term parking, the pressure needs to be reduced, and nitrogen displacement is used for pressure protection. Our factory requires a very high purity for nitrogen, with an oxygen content of less than 50PPM. The 99.8% purity level of the nitrogen supplied by the owner is far too low, and this is the main cause of catalyst poisoning! Catalyst poisoning, reactivation – it causes serious economic losses!

Maintain pressure with high-purity nitrogen; during operation, turn on the make-up gas supply and perform appropriate venting at the front and rear of the tower to prevent air from entering the tower during maintenance.

1. The purity of nitrogen must be at least 99.9% (which is generally achievable through air separation). A high oxygen content reduces the surface oxidation activity of the ammonia synthesis catalyst; therefore, it takes some time to restore the catalyst’s activity once operation resumes. 2. When using nitrogen protection, it is best to keep the pressure as low as possible; a slight positive pressure is sufficient. The higher the pressure, the greater the partial pressure of oxygen in the nitrogen, which in turn leads to greater catalyst deactivation. 3. When shutting down the system, the temperature of the catalyst layer is crucial; it should be reduced to below 60 degrees during shutdown, after which nitrogen should be used for purging.

During the startup process, the purification of the cryogenic system must be thorough; especially in those sections that require major repairs. It is generally easy to use nitrogen for purification, but it is much more difficult to use ammonia, particularly in the cryogenic system. It is essential to enhance the removal of nitrogen and condensates. During startup, attention should also be paid to draining water and inert gases behind the synthesis tower as well as between the various cryogenic sections.

One more thing to add； Nitrogen needs to be analyzed for CO and CO2.

1. If the synthesis tower is not to be overhauled, it is best to maintain pressure with syngas； 2. If there are no valves at the inlet and outlet of the synthesis tower, pressure cannot be maintained; it is best to reduce the temperature of the catalyst layer to below 60°C ； 3. High-purity nitrogen must be used to protect the catalyst; ordinary nitrogen cannot be used. Before using high-purity nitrogen, its oxygen content and other properties must be analyzed ； 4. When driving, ensure that the purity of the refined gas meets the required standards before sending it for synthesis; do not rush and send it without waiting for those standards to be met ；

Protection measures for synthetic catalysts: 1. The loading and reduction of synthetic catalysts must be carried out strictly in accordance with the procedures specified by the production department; normal startup and shutdown operations must also be conducted in compliance with relevant regulations. 2. It is necessary to adhere strictly to the process parameters set by the production department, keeping the fluctuations in furnace temperature within a range of plus or minus 5°C. Additionally, as the catalyst is used over time, if an increase in temperature is required, approval from the production department must be obtained before such an action can be taken; otherwise, a fine of 30 yuan will be imposed on the person who attempts to increase the temperature, with the rate of temperature change limited to ≤60°C per hour； 3. Maintain stable production conditions; pressure should not rise or fall suddenly, with the rate of pressure change being ≤0.5 Mpa/min. If a sudden increase in pressure is detected during normal operation, the cause must be identified immediately, appropriate action taken, and a detailed report submitted to the shift supervisor. A fine of 10 yuan will be imposed on the main operator each time this happens, to ensure that such incidents do not occur again. 4. The addition of machines or the increase in dosage should be carried out at staggered times; the interval between adding smaller machines must be 15 minutes, and that between adding larger machines must be 20 minutes. This helps to maintain stable synthesis conditions, thereby extending the service life of the contact coal and protecting the internal components. 5. The control of the circulation volume should be kept stable; valves should be adjusted gradually, frequently, and in a steady manner, with predictive adjustments made. Rapid opening and closing should be avoided, as otherwise the operator is responsible for any leakage incidents caused by the thermal effects of the gas. 6. Control the gas composition carefully, strictly adhere to the process specifications, maintain a stable hydrogen-to-nitrogen ratio, and promptly contact the relevant personnel in case any abnormal signs are detected so that they can address the issue. 7. Keep the level of the cold exchange liquid under control; it is strictly prohibited to allow liquid ammonia to enter the synthesis tower. Any incident resulting from the presence of liquid in the tower that leads to a drop in furnace temperature will result in a fine of 50 yuan for the operator each time such an incident occurs. 8. Strengthen the discharge of oil residues – at least one discharge per shift (to be carried out during the handover), and the frequency of discharges should be increased depending on the situation. Failure to carry out a discharge at any given time will result in a fine of 10 yuan for the main operator. 9. Ensure proper refinement to prevent copper liquid from entering the synthesis tower; avoid any increase in carbon monoxide and carbon dioxide levels. In case of any abnormalities, take immediate action to maintain the integrity of the catalyst, thereby extending its service life and increasing ammonia production. If catalyst poisoning occurs due to trace amounts of harmful substances, causing the furnace temperature to drop by more than 100°C, the pressure in the synthesis tower should be reduced to 5 MPa, and the temperature of the catalyst layer raised to 20°C above the normal operating temperature (but not above 525°C). This condition should be maintained for three hours before returning to normal operating conditions and resuming normal production. 10. The furnace temperature is checked daily; any attempt at fraud will result in a fine of 50 yuan for the person in charge of operations. For each deviation of 1–5°C from the set temperature, 5 points are deducted; for each deviation of 5–10°C, 10 points are deducted; for each deviation of 10–15°C, 20 points are deducted. Deviations of more than 20°C are treated as accidents.

Hehe~ The person upstairs must be a manager, huh~~~~ They really like to deduct money~~`

Use N2 for protection, but ensure that the concentration of N2 is ≥99.9%, and the pressure inside the tower should be between 100–200 water columns; remember to close all vents, including the sampling cocks. In this way, even if catalyst deactivation occurs, it is only in the upper part of the bed, without affecting the heating time.

It mainly comes down to the nitrogen content; generally, nitrogen with a purity of four nines is used for inflation. As for pressure, a differential water column is more than sufficient – ensuring a slight positive pressure is enough. However, it is necessary to have responsible personnel who carry out inspections and handle the pressurization process. Of course, the temperature should be very low