[dblewis]

This somehow came to me. I worked on a FCC that had structured packing. It needed to be changed every T/A for us. Where we dealt with cat / coke fines from reactor, the Coker deals with coke fines only. Unfortunately, coke is the problem when dealing with packing. We could not clean out the coke which then had to kept wet. Easier to just replace. I witnessed 2 fires when packing was first introduced and was “cleaned”. As far as the 316L and 410, you should use a metallurgist to answer that question.

[dblewis]

Just contact Intercat

[dblewis]

There is a long list of items that will need to be addressed. The main question should be if you are going to bring it back on line in the fairly near future. A big issue are your pump seals including dry gas seals on compressors. I would revise the shut down and start up procedures to safely document everything that you are doing to preserve the unit.

[dblewis]

I do not know who the new players are. We used an Intercat loading system.

[dblewis]

If your unit SIS system is set up right, that should never happen.

[dblewis]

There are some other options with one being the use of multiple pilot operated relief valves that are set at increasing pressures and having an emergency dump valve as a last resort. The FCC I was on, had 4 pilot operated relief valves and one flare dump valve. The flare dump valve failed open on loss of air pressure or electrical failure.

[dblewis]

I do not know your exact compressor line up so I will try to answer some of your questions. I imagine that the wet gas compressor takes suction off a Main Column OH Accumulator and there are suction flare lines to PSV’s going to a flare system. Some compressors have anti surge lines coming from the discharge back to the OH accumulator / suction after cooling the discharge gas. Are these the 2 valves (stationary to flare/ & anti-surge valve?)you are talking about?

[dblewis]

Even though I have had my experience with the FCC Main Tower, we were careful not to allow the temperature in our naphtha section carefully as salts could form, lead to corrosion, and possibly plug up the packing.

[dblewis]

Are you wanting to depressure the entire gas recovery area @ one time? We had the capabilities to float / depressure individual towers on the plant fuel system or the low pressure system. We were limited on how fast we could depressure by how much gas the downstream systems could handle. Line size is also an issue along with auto refrigeration when depressuring propolyenes.

[dblewis]

You generally cannot change the sulphur content by changing process variables. The sulphur needs to be reduced either upfront with treated feed or processing the gasoline to remove the sulphur.

[dblewis]

This scenario revolves around Unit start up. If the cat losses are coming from the Reactor to the Main Fractionator, the decision to bypass and stop cat circulation should happen very quickly. A series of pressure bumps should be performed as part of your start up procedure.

[dblewis]

I have not seen an interlock on vent flows. We piped the seal flows to a more constant pressure system (low line max pressure 3# to 5 #). While WGC was recycling, did the temperature increase on the discharge? We do have a S/D on temperature to prevent damage to the seals.

[dblewis]

I agree with Chris about the catalyst damage. In our situation, we would rather tear up the catalyst than shut down and de-inventory. Our air line burner is not reliable enough to hope it will perform properly for startup without actually pulling it and performing maintenance on it. Generally during a utility outage, catalyst would back up to the check valve of the Main Air Blower and wreak havoc on the air line burner as it was not designed to see Regenerator catalyst. We also have 2 1st stage compressors and a 2nd stage compressor which also plays into our decision to keep the Regenerator, Reactor, & Main Fractionator hot. We have kept our Regenerator hot for a week or so with obvious catalyst damage but rather easy to re-start the unit.

[dblewis]

We had a similar problem. The CO2 is probably coming from the Reactor as it gets entrained in the vapors. You can look at the absorber / stripper operation and see if you can minimize the CO2 by increasing lean oil and / or stripper bottoms temperature. You could ask your catalyst supplier if other refiners have had this issue when the catalyst was changed to increase LPG production. You mentioned that you increased the stripping steam to the Regen. I am not aware of any stripping steam to a Regen but to the Reactor stripper. I would try cutting the steam rather than increasing the steam.

[dblewis]

What is the temperature of this portion of the tower? If it is too cold, steam will start to condense and cause corrosion. It is also possible that salts can form and actually plug the bed.

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