1.4 million tons of catalytic cracking operation: fluidization in the two reactors is established, but catalyst fluidization in the stripping section prior to feed is poor
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In the 1.4 million-ton catalytic cracking unit, fluidization in the two reactors is established. Before feeding begins, fluidization of the catalyst in the stripping section is poor; it is necessary to increase the pressure in the settler and reduce the pressure difference between the two reactors, or even create a reverse pressure difference, in order to get the catalyst from the stripping section to flow downward. After injecting fuel into the riser, the fluidization in the stripping section improved gradually, the plug valve was switched to automatic mode, and the differential pressure returned to normal operating levels. Do any of the experts on Haichuan have the same situation? Explain the reason, where the problem lies, and how to make adjustments.
Actually, this question is quite difficult to answer, as there is a great deal of variation among devices, and many factors come into play! But the principle is basically the same! As for your feeling regarding this operation, I have experienced it as well; in my understanding, before fuel injection the catalyst is in a dry-milling state, resulting in relatively poor fluidity. After fuel injection, the addition of oil and gas as well as carbon acts like a lubricant, thereby **improving the fluidity** of the catalyst. Therefore, generally, the time taken for the three devices to reach a state suitable for fuel injection is kept relatively short.
What was said upstairs is more or less correct. First, during the operation period, a large amount of fine powder is lost when additives are added, and this fine powder helps to facilitate the fluidization of the catalyst to some extent； 2. Flowization of the two reactors became poor upon startup; spraying a little oil improved the situation, as the catalyst was covered with carbon, and carbon has a certain \"lubricating\" effect, which thus greatly improved flowization.
The bed density in the settler should be comparable to or even lower than that during feeding; the steam supply to the stripping section should be increased appropriately, the fluidization medium in the feed leg should also be increased appropriately, and the valve controlling the raw catalyst plug should be opened sufficiently.
In actual operation, this process is very fast; it entirely depends on the operator’s familiarity with the parameters and their skill in operating them. Here, the fuel injection process usually involves two people working together: one monitors the fuel level and pressure, while the other watches the temperature and the conditions in the pressure pump area.
We are of the coaxial type; this issue did not occur with the previous 800,000-ton catalytic system. It shows up every time this catalytic system is put into operation
The larger the device, the higher the requirements for fluidization, and the greater the operational difficulty; it then depends on the skills of the operators!
Is there any blockage or obstruction in the loose medium of the leg? How does the pressure drop across the two sets of material legs compare? Is the reserve of the sedimentators calibrated, and what is the density comparison between the two sets of sedimentators? Was a ball-passing inspection performed on the leg before starting operation? Has the flap angle been checked? If this situation occurs every time work starts, a systematic inspection should be carried out.
Many devices exhibit this phenomenon; it’s just a matter of severity. During startup and during normal operation, the parameters vary greatly, so it’s normal for some problems to occur.