HDS Catalyst Changeout On-line 1

[sshep]

This is a more specific inquiry for which thread124-92856 provides background. Our Ni-Mo catalyst beds are currently held in two seperate vessels, and a third is being considered. One suggested mitigation of loss of catalyst activity is to be able to isolate beds, replace, and activate catalyst on-line.

Of greatest concern to me is the practicality of activating new catalyst with the process running. With our current activation procedure, dimethyl sulfide is dosed into the feed kerosene. This is not a problem when catalyst is replaced during a plant shutdown, but is not practical for an on-line changeout where production is not to be interrupted.

I will take any advice on if a side activation is practical, or other suggestions. I am assuming I can use H2/H2S alone to activate. Is this true? We have spare H2 compressors to create a completely independent loop if needed, and can install isolation, bypass and recycle piping. We can also install additional heat transfer equipment, etc, but this service requires expensive construction so any clever ideas to avoid unneccesary equipment is appreciated.

I have also heard of using preactivated/sulfided catalyst. Can anyone tell me about that?

 

[sshep]

This is my progress so far:

1. Discussions with the sufiding agent supplier (by the way we have been using DMSO not DMS) indicate that side sulfiding of off-line beds is common.
2. A vapor phase (H2/H2S) only sulfiding process is possible. It was estimated that 25% of companies do it like that, however, a vapor-liquid process is probably better. The reason is that the high heat capacity and heat transfer rates of liquid provide better temperature management, and liquid can better quench a runaway situation.
3. I got information from several sources on pre-sulfided catalyst. My finding is that pre-sulfided does not mean pre-reduced. Rather the sulfur is simply coating the catalyst waiting for the H2 and heat to be applied to do the actual reduction.
4. The best measure of the reducing progress is the amount of water coming off. This is something we have not been watching. A more general finding is our unit start-up sulfiding procedures need an overhaul.

I know there are engineers out there with far more hydrotreating unit experience than I have. Any advice on how to set-up a side catalyst replacement and activation process is appreciated.

 

[RogerH]

sshep
You are correct, that when most cat companies talk about pre sulfided is only that they provide the cat with sulphur deposited onto the cat. The reduction step is done in-situ.
There is however one (Tricat in Germany) that is actually sulfiding the cat and delviers it with a coating layer (I guess some kind of waxy paraffine). They their sulfiding step Xpress.
In this case it is only to start up (as normal) and the catalyst will be ready for use without any activation/sulfidation step.
Dont know if there are cat companies on your side of the atlantic that can provide you with the same service. If not I guess it is only a matter of time (& money).
You can read more about it on

http://www.tricatgroup.com/Tricat PTQ article.pdf

 

[epoisses]

Sshep,

Eurecat can provide presulfided/preactivated catalyst and can advise on your changeout and startup. Please visit our websites

http://www.eurecat.com

(for US) or

http://www.eurecat.fr

(rest of world) and/or contact us at sales@eurecat.fr for further information. Discover for yourself whether we are better than Tricat... :=)

 

[sshep]

Thanks to all for your replies. As I have decided to design on the basis of using preactivated catalyst, I will take any additional info/suppliers/etc that I can get.

I can't really go wrong with this basis since the economics of installing a side sulfiding system are not favorable vs a 10 day outage every 3 years. If preactivated catalyst works so that no outage at all is required (reduced rates probably) then even better.

It is my understanding that the only thing needed to bring a preactivated bed on-line is to warm it up. Is this correct? Are any other ancillaries needed?

 

[epoisses]

Correct. You don't need any other ancillaries, neither in terms of hardware, nor in terms of chemicals. Just oil it in and heat it up.
And yes, with preactivated catalyst (Totsucat as Eurecat calls it) you will be able to keep running the other bed on reduced rates in the meantime.
Besides the fact you reduce lost production, there is also a safety benefit: no hassling with smelly DMDS and no H2S formation.
There are many more advantages, but I won't bother everyone with a sales pitch - please contact Eurecat if you want to discuss things further.
Good luck!