CCR Naphtha Reforming Regenerator Side Turnaround Atmospheric Regenerator Part 1 of 2

CCR Naphtha Reforming Regenerator Side Turnaround Atmospheric Regenerator Part 1 of 2

This article focuses on the turnaround (TA) of a UOP CCR PlatformingTM regenerator and covers activities related to the atmospheric regenerator, although, much of what’s written here can be applied to UOP CycleMaxTM, as well.  We’ll focus on the preparation and removal of disengaging hopper and regenerator inner screen. A separate article(s) will follow to capture what’s not covered here.

A note to inspectors, these TA articles are not intended to cover the scope of work and accountability that you have, they are intended to target operations personnel that rarely see this side of the larger picture. The intent is to improve one’s ability to identify equipment problems and better associate them with unit performance and operability.

An old saying… Turnaround is where you really learn the most about your unit, and it’s true.

Catalyst Handling (Rx and Regenerator)

Catalyst unloading and handling are integral to readying the unit for TA. Below are key points to remember prior to TA but not all inclusive.

  • Don’t forget to add make-up catalyst to your TA activities list. It’s best to order 4 ~ 6 months in advance and depending on unit design, make-up catalyst requirements can vary from 5 ~ 15 wt% of the entire catalyst load. Work with your service representative to determine typical catalyst make-up requirements for your specific unit.
  • Do not underestimate your catalyst needs. The consequences can leave you short to fill the RZ. This is rare but has happened. Service will work with you to ensure you order enough catalyst and you should solicit their opinion.
  • Customers should feel comfortable requesting that any unneeded catalyst be sent back to the vendor. Historically, there have been fees associated with this request, but if the drums are still sealed and you don’t need that much make-up catalyst on-site, you should request to only pay for the shipping and handling costs to return it.
  • Always stage drums of catalyst you unload by coke content whether you’re reloading it or completely changing it out with a new load of catalyst.
  • Reloaded catalyst must go back in with the intent of recreating the same coke profile you had before you shutdown.
  • Establish a staging area large enough to manage the drums or bins that you’re working with so you can keep them organized and separated as needed.
  • Safety: It should be anticipated that the catalyst unloaded (particularly from the Rx side) contains iron sulfides making the catalyst potentially air pyrophoric. Follow all applicable site safety practices and prevent air ingress into all spent catalyst containers. Fire suppression equipment should be accessible.
  • Any catalyst ≥ 9 wt% coke is considered heel catalyst and should not be reloaded. Drums of heel catalyst must be clearly marked “heel catalyst” and isolated from catalyst that is ≤ 9 wt% coke and will be reloaded.
  • If you mix high coke or heel catalyst with catalyst that you’re reloading, the consequences on the regenerator side are obvious.
  • If you mix high coke or heel catalyst with catalyst that you’re sending out for Pt reclamation, the vendor will charge you more for their services.
  • Use waterproof markers to identify the drums and bins. I’ve seen cases where this wasn’t done and the catalyst reload was somewhat random.
  • Request a detailed copy of unloading and loading procedures from your vendor. If you’ve already reloaded catalyst in past, these procedures and a final loading tally are likely part of a final report to you, provided your vendor had a representative on site.

Spare Parts (Rx and Regenerator)

“Do you have a list of spare parts needed for a TA?” The answer is always the same, there’s no way to know what you may find during inspection. UOP has a general list of spare parts that’s not all-inclusive but provides solid guidance on how to be “best prepared” for your upcoming TA.  This list of spare parts is available to all licensees of UOP CCR Platforming technology.  Just reach out to your service contact and request a copy.

As mentioned in a previous article, it’s best practice to save scrap scallop and centerpipe material from the Rx side left over from previous TA’s. This material can be reused to make repairs on both sides of the unit where patches need to be fabricated.  Any scrap materials you decide to keep may be extremely useful down the road.

Disengaging Hopper

Prior to starting any work, ready the vessel for safe line-breaking and eventual vessel entry.

This should include isolation of the nuclear source used for level indication by closing the shutter and padlocking it shut. This is also a good time to check the data on the source housing to determine the isotope being used and its half-life.  As these nuclear sources approach their half-life, they begin to weaken and become less reliable. Keep in mind that purchasing and shipping these nuclear sources is highly regulated, and with that, should be considered a long-lead item.  Field Note: Do not permit anyone to lean tools, ladders, scaffolding, etc. up against the source or detector.  This happens a lot during TA and is not good for either.

Matchmark each CTP with its corresponding flange on the DH and top head to make reinstallation less confusing.  Remove the CTP’s, thoroughly clean each one to ensure there are no obstructions and then set them aside with gasket seating surfaces protected and both ends covered to prevent moisture ingress.

It’s optional to pull the elutriation tube at the top of the DH but it is recommended.  During normal operation, catalyst is zipping through this section of pipe at a high velocity and inspecting both the lift line and elutriator tube for erosion and thinning is highly recommended. Obviously, look for anything that creates an interior ledge or that can generate catalyst fines. All interior surfaces (including welds) should be smooth.

Note: Prior to any internal vessel inspection be sure to have working copies of all the drawings you’ll need. This includes standard drawings, specifications, and anything else noted at the bottom of all vessel drawings.

Once inside the DH you’ll likely see a coating of catalyst dust stuck to the interior walls.  At times this dust can be > 1” thick and needs to be removed. Whether you remove the DH and bring it to grade or not, if that catalyst dust is still present while you’re repositioning the DH above the regenerator, it may fall off in sheets into the bottom of the DH or regenerator just after you’ve cleaned it.

Upon entry into the DH you may see a screen near the bottom tangent line that’s assembled in sections. This screen is sometimes referred to as a trash catcher. Any foreign debris (larger than catalyst) should have landed on it and should be removed. Retain this material for review with others to help determine its origin.  As needed, disassemble the screen sections to create good access to the bottom of the DH, and clean out any residual catalyst and dust lying in the bottom for Pt reclamation.  Reassemble the trash catcher and inspect it to make sure that it’s securely anchored and the wire is in good shape.  Note: Some early units (Atmo’s and pressurized) may not have these trash catchers. Or, they may have been added later.

There is also a baffle (deflector) where the elutriation gas comes into the side of the DH. It’s welded in place but inspect it the best you can while you have access.

Where to Stage the Inner Screen for Cleaning

There are a couple of options on where to clean the inner screen.  One is to bring it to grade and stand it upright in a staging area set up for that purpose.  This is ideal for CO2 blasting which is an effective alternative to cleaning the inner screen with wire brushes. This method does a very good job cleaning chips and fines out from between the profile wire. Note: The screen is not designed to bear any weight and should always remain suspended by the top head.

Alternatively, some customers clean the inner screen over the hole. In my experience, this is done more frequently for a routine inner-screen cleaning and not a full TA. This method seems to reduce the scope of work and speeds up the turnaround time to get the regenerator back into service.  That said, the outer screen still needs to be cleaned and all catalyst chips and fines that fall to the bottom need to be cleaned out.

Lifting the Regenerator Top Head and Inner Screen

Disconnect all thermocouple (TC) wires from the TC head itself. Mark them clearly so there is no confusion while reconnecting them later. Also, many TC installations are referred to as a “duplex” design. This means that two thermocouples are inserted into one thermowell to create a spare, but only one is connected. Clearly identify the one you’ve been using and continue to use it unless it’s bad. If you have a bad TC and need to switch to the spare, this would be a good time to replace it so you have a spare you can switch to on the fly.

With everything disconnected and bolts removed from the top head it can now be lifted by crane or an appropriately rated hoist.  Note: Regardless of how you decide to stage the top head and inner-screen for cleaning, this is where the importance of match marking flanges becomes obvious.  As soon as the weight of the top head is off the body flange it typically starts to rotate a bit. It’s best practice to keep it in alignment with the match marks as you hoist it up.

This allows you to photograph the inner screen while maintaining its relative position to the outer screen and any nozzles that come in from the side. This can be important later while trying to determine the root cause for significant fouling or any inner screen damage. In my opinion this is when someone from operations should be present to learn from what is now available to see.  Note: Don’t delay protecting the gasket seating surfaces from unintentional damage.

When cleaning the inner screen over the hole, the top head is raised ~ 6’ and those cleaning the screen work from the top /down. Sometimes the refiner will have enough contractors (3 ~ 4) to encircle the screen and clean it in parallel to speed up the work. Note: Do not use portable grinders with wire wheels to clean the inner or outer screens. This can contribute to wire thinning or breakage. Moreover, use stainless steel brushes. Carbon steel brushes leave behind wire fragments that contain iron.  Whether this results in a serious problem or not, the basis for using SS brushes is to avoid introducing iron into equipment that is a catalyst for MCC formation.

Inside the bolt hole pattern of the body flange there’s a 3 ~4” strand of woven wire that runs the circumference of the entire flange. This is where seal gas flows into the annulus of the regenerator to help prevent catalyst from fluidization.  Be sure to keep this area protected from debris falling inside and repair any visible damage. This woven wire is easy to work with, it’s accessible and robust.

The following is important regarding inner screen fouling and determination of a root cause. Here are some examples:

 

 

As the inner screen is hoisted, the patterns on the inner screen can tell you a lot. Sometimes you’ll see the blank-off zone polished like chrome. This is caused by fluidized catalyst essentially polishing the steel and generating catalyst fines in the process. How does that happen?

One common way is for one or more of the CTP’s to become plugged during operation. When any of the CTP’s are obstructed, the catalyst level below that scoop drops. Figures 1 illustrates the drop in catalyst level from one CTP being plugged. Figure 2 shows two adjacent CTP’s plugged, creating an even greater drop in catalyst level. Figure 3 depicts an area called the “blank off zone”. This is an area where there is no open path for the regen gas to flow through. The height of static catalyst in this zone creates what is referred to as a “catalyst seal” or “seal catalyst” and designed to create enough head pressure to prevent catalyst at the top of the bed from fluidizing.  If one of the CTP’s plugs, then the catalyst level below the scoop drops and the catalyst seal height is no longer adequate to prevent fluidization.  If two adjacent CTP’s plug, the level drops even more.

This is when mapping the screen fouling and markings becomes useful and many times conclusive to a root cause. Another reason not to have contractors start cleaning the screen before someone with experience on that unit has had a chance to examine and photograph the screen.

Another way catalyst fluidization can occur in the regenerator is when sections of the inner screen become fouled with catalyst chips and fines. When this happens, the reduced open area causes the screen dP and gas flow velocity to increase, and that can pin catalyst against the screen and prevent it from flowing down the regenerator.  This can result in catalyst fluidization below the top of the bed and will greatly accelerate catalyst fines generation.

In a previous article, we pointed out the importance of the regen gas flow indication.  This high value instrument provides an indication of screen fouling and needs to be in service and reliable. Rule of thumb is when the regen gas flow drops to 90%, the inner screen is 30 ~ 40% plugged and needs to be cleaned. Note: This instrument calibration should only be done after an inner screen cleaning.

Topics  plan on covering are inner and outer screen checks, annular gap measurements, IZ baffle pressure taps. Chloride injection nozzles, and more

 

We welcome your feedback and questions.

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About The Author

Contact:
Michael (Mike) Crocker spent the last 30 years of his career with UOP working predominantly in Field Operating Services, UOP R&D Pilot Plant Testing and Technology Services Gasoline. He spent 12 years prior to UOP working in various Oil Refinery Operations roles that made him intimately familiar with multiple mainstream refinery process technologies. Mike retired from UOP as a Principal Technology Specialist providing technical support to customers who licensed UOP NHT/CCR Platforming Units and catalysts. His technical support included troubleshooting unit operation, evaluating catalyst performance, and working through equipment problems for UOP customers worldwide. Mike completed yield estimates to facilitate the best catalyst selection for his customers based on unit configuration and design feed composition. He also participated in engineering review meetings i.e., Design Basis, PFD, P&ID reviews, and HAZOP. Mike has prepared and presented > 30 UOP (5-day) CCR/Platforming Process Technology and Simulator training courses to his customers both foreign and domestic, and still finds training a passion.

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CCR Naphtha Reforming Regenerator Side Turnaround Atmospheric Regenerator Part 1 of 2

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