Q&A

Question 44: How is coke on catalyst in fixed-bed and moving-bed reforming units tracked? How is this data used to adjust the reactor inlet temperatures in order to maintain constant product octane?

In our cyclic units, just based on the air consumption, we can measure the coke each time a reactor comes out for a regen. We are not grabbing samples. Our experience with the cyclics is that if you get up around 8% coke on catalyst, the unit will be pushed a little too hard. You will then need to think about backing it down on feed rate octane, finding a better-quality feed, or possibly increasing the hydrogen/oil ratio.

(2012) Question 45: What is the maximum allowable limit for the iron content of a reforming catalyst? Is this limit the same for semi-regenerative and continuously-regenerative catalysts?

We have seen that the maximum allowable iron on catalyst cannot be reduced to a simple number. Historically, about 3,000 wppm is the level at which we see yield start to suffer, but not every wppm of iron has the same impact on the unit. Iron deposited on the surface of the catalyst, usually from corrosion-related byproducts, tends to have less of an impact on the overall performance.

(2012) Question 46: Are refiners modifying the operating conditions in reforming units, for example, chloride on catalyst, in order to capture margin differences between natural gas, used as fuel, and liquid products?

I will start with a bit of review of some reactions, and then I will get into a couple of examples of what we have done at HollyFrontier. Of course, the downside to reforming is that the liquid product has less volume than the feed to the unit due to physical laws inherent to the chemical reactions. First, the high-octane product will have a higher density than the feed; and second, some portion of the feed will be cracked to LPGs and fuel gas in the process.

(2012) Question 47: How often do you replace your reformer catalyst? What is monitored, and what triggers the replacement? How has the increased spread between natural gas prices and liquid product prices impacted these decisions?

HollyFrontier operates five semi-regen reformers and two CCRs. There has not been a specific effort to replace catalyst in order to take advantage of the higher liquid product yield that is possible with newer catalyst. However, the spread between natural gas and liquids certainly impacts the decision when looking to upgrade. For two of the semi-regen units, the most recent catalyst replacements were installed after approximately 20 regen cycles, which included multiple dumping and screening events.

(2012) Question 48: Discuss recent advances in reforming catalyst technology. What performance improvements are being researched?

The most current catalysts on the market are multi-promoted using a number of different promoters beyond the base platinum-rhenium or platinum-tin. It is not a one-size-fits-all market, so there are tailored designs for different needs. For CCRs, the current drive is for improved yields. Units are often octane-long. The goal is now to maximize barrels as best as we can.

Question 49: Does the panel have any experience using flexible thermocouples in the regeneration section of a moving-bed reforming unit? What considerations should be given to revamping units that do not have these installed?

Flexible thermocouples, as I understand, are now a part of the standard design for regenerators of moving-bed units. At a refinery in which I worked; we replaced the original slider thermocouples with multipoint thermocouples.

(2012) Question 50: How do you monitor the integrity of internals, and how do you determine when to replace reforming unit reactor center screens? What is the typical life of the center screens, and when are repairs considered excessive?

Typically, we have seen internals last between 15 and 20 years, if not longer. At any point, it becomes a value judgment between the number of repairs you have made, if any, and the potential outcome if the internals do fail.

(2012) Question 51: What is the panel’s experience with recycle gas moisture analyzers?

Phillips 66 has had experience with the Ametek and Panametrics moisture analyzers. Weare talking about moisture in the reformer recycle hydrogen, so we are looking for 10 ppm to 50 ppm with varying success. I do not think we could say that one is a lot better than the other. The Ametek 5000 was designed for that application.

(2012) Question 52: What is your recommended method for mitigating fouling in reforming unit recycle compressors? Has any technique proven successful? Is anyone using reformate to clean the compressor online?

The best method for reducing fouling in the compressor is to take the nitrogen out of the feed. In Valero, we have recently reviewed our naphtha hydrotreater performance. In a lot of cases, we found that the naphtha hydrotreaters can actually be pressure drop-limited versus activity-limited.

(2012) Question 53: What is the panel’s experience with addressing reforming unit stabilizer salting?

I actually have three examples that all apply to a reformer stabilizer. The first slide shows what we call our hot wash. By that, I mean we do not lower the temperatures. We will keep the bottoms re-boil temp in the 440°F to 480°F range. We then have two options on this hot wash. If we just see a high differential pressure on the overhead cooler, then we will put the water in front of that air cooler.

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