Discussion on the riser pressure drop of FCC-III gasoline in catalytic cracking, pressure drop in the secondary settler, and pressure drop in the secondary fractionator.

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Recently, the pressure difference between the two vessels connected to the gasoline lift pipe has been changing significantly. The automatic control of the regenerator pressure remains unchanged; it is only the pressure in the gasoline settler that varies. This change affects the downstream auxiliary oil and gas pipeline, the auxiliary fractionation tower, as well as the auxiliary oil and gas butterfly valve, which is used to control the pressure in the settler. At the beginning of operation, an opening degree of 20% for the auxiliary oil and gas butterfly valve was sufficient, but now that it is almost fully open, the pressure in the secondary settler remains high while the pressure difference between the two vessels is very low. Sometimes the pressure in the settler decreases slightly, and the pressure drop from the settler to the bottom of the auxiliary fractionation tower varies greatly, ranging from a maximum of 18 kPa to a minimum of 12 kPa. The pressure drops in the coarse spinner and single spinner also change accordingly, by about 1 kPa each. The pressure drop in the auxiliary fractionation tower does not change much. I suspect there might be a problem with the settler. I have checked the oil and gas butterfly valve and the feed valve, and they seem to be functioning normally. Experts, could it be that there is a problem with the settler? Since the pressure drops of the rough spin and the single spin change simultaneously, where is it most likely to occur a problem? Sometimes it changes every four or five hours, and sometimes every few days