Issues related to the extremely low level of material in the reduction section of continuous reforming
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One of the conditions for hot shutdown is that the catalyst isolation system must be shut down (excluding valve closures caused by the level in the reduction section dropping to the very low level at the point source). How should this statement be understood? What problems can arise as a result of valve closures caused by a low level in the reduction section? Cold shutdown? Hot shutdown? Or an emergency stop?
Low-level isolation mode: It remains in this state until a certain material level is reached in the recovery section, after which it is activated. There is a broad sense and a narrow sense of this concept
The first condition for a thermal stop is that the alarm recorder for regenerative stopping indicates to the operator which conditions have caused the regenerative stop! As for what you mentioned (that I’ve encountered it a few times), generally the catalyst is still flowing when the isolation valve assembly is in the closed position. (Which case applies) It’s not an emergency stop! As for whether it’s hot shutdown or cold shutdown, it depends on the conditions for hot or cold shutdown!
When the material level in the reformation reduction zone is below 10%, the triggering logic simply causes the solenoid valve controlling the secondary gas to be de-energized and closed; the regenerated catalyst continues to be fed upward, and the regeneration unit does not shut down due to overheating； Once the material level in the reduction zone exceeds 30%, power is supplied to the solenoid valve for lifting the deactivated catalyst, and normal operation can be resumed. It should be noted, however, that the oxygen content in the regenerator must be well controlled; if the deactivated catalyst is not regenerated for an extended period, the high oxygen level in the regenerator can easily trigger an automatic thermal shutdown.
It is indeed the quarantine for new arrivals that is closed; thank you for the explanation.
The golden one explains it very clearly. If it is merely a valve caused by the reduction of the level of the reduced material to a very low level at the point source of radiation, then it is neither a hot shutdown nor a cold shutdown; generally, \"neither hot shutdown nor cold shutdown\" refers to the regeneration unit.
May I ask why failing to lift the catalyst that is still in the reactive state for an extended period results in a high oxygen content in the regenerator?
There are two level sensors for the reduced material level: 1 point source and 1 line source. When the level of the linear source material is below 10%, the solenoid valve of the secondary air control valve for lifting the raw material closes, causing the amount of secondary air to drop to 0. As a result, the lifting of the raw material stops, thereby preventing the material level in the reduction section from dropping to zero and preventing oil and gas in the reactor from reaching the reduction section. Although this action does not directly cause a thermal shutdown, once the amount of secondary air drops to 0, the differential pressure for isolating the raw material also falls to a level that meets the interlock conditions, leading to isolation and thus a thermal shutdown. The parking caused by a low level at the point source will result in the closure of the solenoid valve controlling the secondary air flow, thereby reducing the secondary air volume to 0 and stopping the upward movement of the feedstock. At the same time, the feedstock isolation valve is forced to close, as the point source alarm indicates that the level of material in the reduction section is very low, which is extremely dangerous; closing the feedstock isolation valve is necessary to prevent the reduction section from running out of material. If the point source is indeed empty at this time, the standby isolation cannot be activated. And when the standby isolation is turned off, the conditions for a hot shutdown are in effect; without resolving this interlock, the catalyst cannot be circulated, the regeneration process cannot proceed, and the material level in the reduction section cannot be adjusted, which prevents the isolation from being opened – resulting in a dead loop. To address this issue, UOP established a condition whereby the isolation shutdown triggered by a low-low level at the point source is lifted after one minute, thereby removing this thermal shutdown condition. In this way, a catalyst cycle can be established; once the level in the reduction section rises, the isolation can be removed and normal operation can be resumed.