Issues related to catalyst switching during the commissioning of catalytic cracking units
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During the startup and catalyst replacement process in a coaxial catalytic cracking unit, the catalyst fails to circulate properly, and the steam flow rates in the two stages of the settler are not adjusted, just as they are during normal startup. So, to ensure the proper circulation of the catalyst, what should be taken into account when starting up? What are the key points in several aspects? Does an excessively open raw material stop valve have an impact on the rotating agent?
As the original poster said, poor fluidization of the feed line does indeed occur when coaxial catalytic cracking is put into operation. It should be noted: 1. During conversion, the regeneration temperature should be kept at least at 650 degrees. 2. The pressure in the settler should be maintained as stable as possible; it can be set slightly higher than usual. 3. If the regenerator riser and the cone section of the settler’s stripping zone become loose, the orifice plate bypass can be opened slightly depending on the situation, but it is better to keep it closed. 4. The regeneration slide valve and the regenerator plug valve should not be adjusted frequently or significantly. 5. Most importantly, once the reaction temperature reaches the condition for injecting fuel, fuel should be injected as soon as possible, as a coked catalyst ensures much smoother flow in the regenerator circuit compared to a regeneration agent. These are just my personal experiences for reference only.
Determine where the blockage is in the feed line and the regeneration line Are all the loose points in the rising pipe clear? Is there a reserve in the stripping section?
1. When starting up a coaxial catalytic cracker, if there is poor fluidization in the feed line, check whether the backflow system for loosening the components in that line is functioning properly, and whether there are any blockages or missing orifice plates； 2. During the catalyst transfer, the stripping steam in the settler must be used properly to ensure that the catalyst inside the settler remains loose ； 3. When opening the raw material stop valve, do so slowly to prevent clogging of the catalyst due to excessive opening ； 4. When switching catalysts, the reaction pressure can be kept slightly higher to increase the driving force in the raw catalyst line.
Be careful to do the transfer slowly, so that the reactor’s temperature does not rise too rapidly