Planar temperature difference of ammonia synthesis catalyst
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The plane temperature difference of our company’s ammonia synthesis catalyst during heating and reduction is less than 5 degrees. After going into production, points 3 and 4 are on the same plane, yet the temperature difference reaches around 20 degrees. May I ask: What causes this? How should it be handled?
This may be related to the load; we have the same issue. It is a 70% load of the 2-axis 2-diameter percentage of Anchol. What type of tower do you have?
The first reason is inaccurate temperature measurement points, and the second is gas deflection.
This issue generally arises during the startup phase of the synthesis tower; the main cause is an overly rapid heating rate of the furnace used for startup, followed by insufficient flow rate in the main pipeline. It is also necessary to maintain stable pressure, as too rapid pressure increase can easily lead to flow disturbances. When operating normally, there are no major issues as long as the pressure difference in the synthesis tower is well controlled.
Temperatures below 15°C are acceptable; if it’s too high, it will have an impact on production! There are many reasons for this to happen; the main cause is likely an excessive offset in gas flow. Additionally, instrument failures cannot be ruled out (such as incorrect insertion depth of the temperature sensing thermocouple, or the use of inconsistent wiring)!
We can observe for a while; I estimate that the possible reasons are 1) excessive production load, resulting in some flow imbalances inside the tower, and 2) uneven distribution of gas by the diamond-shaped mixers and collectors, which also causes flow imbalances. Observe the temperature during load reduction to see if there are any changes
Reasons: 1. The internal components are not installed properly; the catalyst is not filled evenly, with varying degrees of tightness, which causes the gas to flow in a biased manner. It can easily cause localized overheating of the catalyst, leading to its damage, or incomplete reduction of the catalyst in certain areas. 2. Damage to the internal components causes internal leakage, resulting in a lower temperature in the catalyst bed on the side where leakage occurs, and thus a large temperature difference within the same plane. 3. The insertion depth of the thermocouple is incorrect, or the material of the temperature wire is not uniform. 4. The outer tube of the thermocouple is leaking air. Treatment method 1: Approve the insertion depth of the thermocouple and standardize the material of the temperature wire. 2. Lower the temperature and pressure, then raise them again to reduce the temperature difference within the same plane. 3. Strive for stability in operation, use fewer side streams, control the space velocity appropriately, and minimize fluctuations in temperature and pressure. 4. If the adjustment is ineffective and this phenomenon continues to worsen, it is necessary to stop the machine for maintenance or replace the internal components.
It is unknown what the relative temperature increases are for points 3 and 4 compared to points 1, 2, 5, and 6. If there is a temperature increase at point 3 relative to point 1 (coaxial temperature), while there is no increase – or even a decrease – at point 4 relative to point 2 (coaxial temperature), and if the temperature difference between points 3 and 4 within the same plane is 20 degrees, with points 5 and 6 having normal temperatures, it can be concluded that the temperature testing was inaccurate.
The catalyst is not properly loaded, resulting in uneven gas distribution; in other words, there is the issue of flow deviation mentioned earlier. There are also instrument failures. At the factory where I am currently undergoing training, the temperature difference is over 40 degrees, yet production continues.
The most likely cause is poor catalyst packing; moreover, during the heating and reduction process, proper reduction could not be achieved due to the packing issues
This post was last edited by Grandiose fabrication on 2009-10-31 at 20:52. It is agreed that a poor catalyst loading is the most likely cause, along with leaks in the cold shock tube. The synthetic ammonia catalyst in our plant was replaced in 2008, with a plane temperature difference of 15–20 degrees. Previously, the replacement range was basically between 1 and 5 degrees.