Issue with catalyst replacement – urgent

A cobalt-molybdenum catalyst is used, with a pressure of 6 Mpa. . . . . . . . .

We haven’t replaced it either; I only have my own slight understanding of it. Should it be passivated before replacement? It needs to be vulcanized after replacement! The rest should be handled according to the normal catalyst filling procedure.

Before replacement, it is generally necessary to fully passivate the surface. When carrying out passivation, care must be taken to control the heating rate when introducing air, in order to prevent accidents caused by sintering of the catalyst. Of course, it needs to be vulcanized after the replacement is complete. Passivation involves oxidizing cobalt and molybdenum in their sulfide state to their oxide states, thereby preventing oxidation reactions when in contact with air, which would otherwise release large amounts of heat and lead to sintering. After replacement, both the new catalyst and the original catalyst need to be sulfided to their sulfided state in order to exhibit catalytic activity. Is the conversion rate not increasing because the catalyst at the top has worn away? Looking forward to the original poster coming back to provide an answer after making the changes, thank you!

I agree with haiyangqh’s view; however, poor control of the passivation process can damage the catalyst’s activity, so caution is necessary. It is best to work together with experts from the catalyst manufacturers to develop a comprehensive plan.

The passivation method cannot be used for replacing some catalysts, as passivation results in a 20%-30% loss of the catalyst’s activity after sulfidation. Cool the catalyst to below 40 degrees, ensure proper nitrogen purging, and isolate the shift reactor from the system by installing blind flanges; at this point, some of the catalyst can be removed. It is important to keep nitrogen flowing through the shift reactor while removing the catalyst to prevent air from entering. It goes without saying that re-sulfurization is required after replacing the catalyst!

Agree with the comment above! No passivation is needed. First, the lifespan is reduced; second, it’s too troublesome! It is best to introduce nitrogen; when removing some of the catalyst, water can be sprayed to prevent burns!

Thank you all. In other words, nitrogen is introduced into the furnace during extraction to maintain a positive pressure, right? What worries me now is that since the air separation unit will be shut down, I’m afraid there won’t be enough nitrogen.

Nitrogen from cylinders can be used; the key is that during catalyst removal, the shift converter must not experience air convection.

1 Throughout the entire process of catalyst removal, strict precautions must be taken to prevent oxygen from entering the furnace. 2 The catalyst should preferably be unloaded at night, and the unloaded catalyst must be properly sealed to prevent any exposure to oxygen. 3 It is necessary to take strict care to prevent air convection from occurring during the demolition process. 4 Assign a dedicated person to monitor and record the temperature changes in the catalyst bed, to prevent the catalyst from coming into contact with air and reacting spontaneously. 5 When removing the catalyst, be sure to prevent personal injury and pay attention to safety precautions. 6 When using a long-tube respirator, be careful not to bend the tube or damage the mask. 7 Avoid scraping pipelines, thermocouples, etc. during the loading and unloading of refractory porcelain balls

Placing it in a passivation state will result in a loss of activity; this has not been explored yet. I’ve heard of removing the catalyst under nitrogen protection, but it’s very dangerous – any carelessness can lead to serious consequences