The switch of the slurry pump resulted in a significant increase in fine powder at the inlet and outlet of the three spinners

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Incident of increased fine powder due to slurry pump switch-over. Recently, during the switch-over of the slurry pump in our facility, we observed a significant increase in the level of fine powder in the regenerator. The details are as follows: On 2024-06-11 at 9:30, the slurry circulation pump P2209A was switched to pump B; the switch-over was completed at 10:30； 2. At 9:55, it was observed that the particle size of the flue gas at the inlets and outlets of the three-spinner, as well as at the inlets and outlets of the desulfurization scrubber, increased simultaneously. Specifically, the particle size at the inlet of the three-spinner rose from 460 mg/m3 to 1066 mg/m3, while at its outlet it increased from 83 mg/m3 to 163 mg/m3. At the inlet of the desulfurization unit, the particle size increased from 74 mg/m3 to 142 mg/m3, and at its outlet it rose from 2 mg/m3 to 22 mg/m3. By 19:00, these values began to decrease gradually ； On June 12, 2024, the data at various points returned to normal levels. At 11:00, due to excessive gas-phase load on the backside, adjustments were made: the processing volume was reduced from 130 to 118 t/h, while the amount of slurry fed back for reprocessing increased from 14 to 22 t/h ； 4. The slurry taken from the desulfurization unit appeared quite turbid; there was a layer of catalyst at the bottom of the sediment, with a higher catalyst content than in normal slurry ； 5. Increase the amount of slurry discharged outside; at 16:00, a sample of the slurry was analyzed, showing a concentration of 4.4 mg/l, which is within the normal range ； During this period, no large-scale dosing or dosing removal operations were carried out, and the pressure drop in the regenerator and the pressure drop in the three spinners changed synchronously on multiple occasions ； The density at the regenerator cyclone inlet remains essentially unchanged ； It is certain that a large amount of fine powder was indeed carried to the three spinners ； Analysis: It is preliminarily inferred that due to the switching of the slurry pump, the catalyst deposited in the pipelines may have entered the two reactors along with the recycled oil slurry, resulting in a significant increase in fine powder; this was clearly evident at the inlets and outlets of the three spinners as well as in the desulfurization unit ； Question: My unit experienced a similar phenomenon in 2023 due to the switching of the slurry pump; the particle size of the flue gas increased significantly, but it returned to normal by the next day ； But this phenomenon does not occur every time the slurry pump is switched ； It has occurred occasionally in recent years; for example, it happened once in my device in 2023, and once on June 11, 2024. Under normal conditions, the warm-up line of the slurry pump is unobstructed, there is little catalyst accumulated in the pipelines, and any accumulated catalyst can only enter the regenerator through slurry reprocessing. The solid content in the slurry is not high, so it is impossible to generate large amounts of fine powder; this situation persists for a while, and normal operation is generally not restored until the second day ； What could be the reason for this?