How to handle catalyst “bridging”
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Some time ago, catalyst bridging often occurred in our catalytic units. It’s the issue of poor fluidization in the regenerator riser; the inventory in the settler and the gas lift section increases, and in several instances the catalyst had to be removed before fluidization improved in those two units. I would like to ask everyone what the causes of catalyst “bridging” are and how it can be addressed. This is my first post, so please forgive any mistakes. Thank you.
This is rarely encountered; from what you’ve described, it seems to be caused by the excessive particle size of the catalyst.
Reasons for catalyst bridging in catalytic cracking regeneration inclined tube catalysts http://bbs.hcbbs.com/thread-60446-1-1.html
The circulation rate is too high, and the pressure difference across the two units is small. During operation, the opening degree of the regeneration plug valve (sliding valve) is too large, resulting in no throttling effect; moreover, there is not enough pressure drop after the regeneration inclined tubes, which leads to a low linear velocity of the catalyst within those tubes and a longer residence time. This, in turn, causes degassing and deposition that ultimately result in clogging. Haha, not necessarily. The situation is often complex, and only an on-site inspection can allow for an accurate assessment. During operation, the valve pressure drop must be maintained at a reasonable level in order to control the circulation rate.
(1) Pressure pulses in both units (2) Excessive amount of loose air or steam, containing water (3) Low temperature of the stripping steam, resulting in severe water contamination (4) Reduced fluidity of the catalyst (5) Obstructions in the system due to foreign objects (coking blocks, accumulation in the raw material risers) (6) Malfunctioning check valves with insufficient opening degree
The reasons for the formation of inclined tube bridges are generally: 1. Pulsative changes in pressure in the reactors; 2. Excessive loose air or steam, severe water contamination, and imbalance at the loose points; 3. Excessive circulation volume; 4. Low opening degree of the slide valve, as well as changes in the density distribution of the carbon bed or catalyst particles.