High pressure drop in the regenerated inclined tube
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In the coaxial catalytic cracking unit, the pressure drop across the regeneration slide valve was 25 kPa before maintenance； During this startup, the pressure difference between the two devices was 25–30 kPa, while the pressure drop across the slide valve was around 35 kPa ； When the pressure difference exceeds 30 kPa, the pressure drop across the slide valve rises rapidly to over 60 kPa, causing fluidization to cease; increasing the opening of the slide valve to reduce the pressure difference helps to resolve this issue. I’m not sure why this happens During maintenance, the regeneration inclined tube was tested for smooth flow using iron balls. I would like to know what other factors could have such a significant impact.
We have encountered similar problems before; the main cause is catalyst poisoning, which leads to a deterioration in the catalyst’s fluidization properties. As a result, fluidization does not occur properly in the regeneration riser, and the pressure drop across the regeneration slide valve fluctuates significantly. Increasing the opening of the slide valve may provide temporary relief, but in such cases it is recommended to replace the catalyst as soon as possible.
Fluidization is not working properly; we need to analyze the reasons: 1. The suggestions from the second floor can be tried out to see if there is any poisoning of the catalyst. If so, it is necessary to replenish and replace the catalyst in a timely manner. 2. Based on the phenomena you described, there appears to be some air resistance or bridging in the regenerative inclined tubes. Has the airflow used for fluidizing these tubes been adjusted? Special attention should be paid to the area where the diameter changes, as improper handling of the airflow there can easily lead to bridging.
Check whether the loosening air flow is too high; when the valve opening is small, poor fluidization may occur. You can inspect and adjust the manual valve for the loosening air – this might help
It seems we can no longer consider the inclined tube option. How was the centrifuge inspected during maintenance? Is there any issue with the lift pipe? Furthermore, improve the medium changes and the conveying medium, and carefully check the process.
I think we still need to consider the loosening wind. Let’s analyze the screening of catalysts further.
This is how I view the situation described by the original poster: when the pressure difference is less than 30 kPa, the pressure drop across the regeneration inclined tube remains within normal ranges; it is only when the pressure difference exceeds 30 kPa that the situation mentioned by the original poster occurs. Can it be assumed, under the condition that the pressure drop is less than 30 kPa and the valve opening remains constant, that the fluidization is in a normal state? ； When the pressure drop exceeds 30 kPa, this equilibrium is disrupted; due to the constant opening degree of the slide valve, a reverse resistance is generated above the slide valve, affecting normal fluidization ； After the slide valve opens, the balance is disrupted again, the reverse resistance decreases or disappears, and the fluidization above the slide valve returns to normal.
The loose steam is all used in accordance with the designed orifice plates
Check whether there have been any changes in the particle size distribution of your catalysts, the differential pressure between the two units, and the amount available for regeneration compared to the last operation, especially regarding the particle size distribution