Q&A

(2013) Question 14: What is industry experience of using tri-metal (platinum-rhenium with promoter) catalysts?

Promoted or multi-metallic reformer catalysts have been a topic of research since at least the early 1970s. They have been tried commercially in various forms over the years, all with the objective of improving yields by suppressing the demetallization reactions.

(2013) Question 15: What is the Best Practice process for sampling, handling, and measuring research octane (RONC) and naphthene content in reformer feed and product? Are refiners considering online RONC and/or other property monitoring?

If you have a poor octane result, the Best Practice is to blame the lab. Isn’t that what we do? The reality is that there are at least four key components of a sample system that all need some attention: sample conditioning, container contamination, sample degradation between collection and analysis, and the analysis method.

(2013) Question 16: What is the typical carbon monoxide (CO) concentration in the reformer net gas? How is the CO content measured? What are the potential effects to downstream units from the CO?

Carbon monoxide can form in reformer units as the hydrocarbon reacts with moisture under very low-unit pressure conditions. Typically, semi-regeneration reformer net gas would have nil CO and only a minimal amount in a CCR-type unit. I expect it to probably be on the order of 5 ppm (parts per million), though some units report routine measurements of 10 to 20 ppm CO in their net hydrogen off gas.

(2013) Question 17: How many continuous reforming operators have completed a catalyst change while the unit continues to operate? What variables should be taken into account when planning such a change?

HollyFrontier has two CCRs: one at Tulsa that was converted from a semi-regeneration reformer and one at Artesia. We have not done a catalyst change at the Tulsa refinery CCR, but we have done an online catalyst change at Artesia.

(2013) Question 18: What are some typical causes for high pressure drop across regenerator dust collectors in continuous reforming units? Is anyone using continuous blowback on the bags?

The obvious answer to the high-pressure drop would seem to be that you have too many fines on the bags. But realistically, why do you get too many fines? The causes could be that you waited too long to do the reverse jet blowing or, a less common cause, that you are getting hydrocarbon carryover which is causing the fines to clump together on the bags.

(2013) Question 19: How are refiners managing low-coke operations in continuous reforming?

There are two ways to address the issue: 1) try to increase the coke that you are making and 2) adjust the regenerator. It would be great if you could just adjust how much coke you are making. However, most of the time you are restricted in what you can do with the unit, given your octane targets and the feed flows and qualities are fixed.

(2013) Question 20: What investment, operational, or processing options are available to upgrade or convert gasoline streams to higher value products?

First, there are not a lot of innovative solutions here on this list. For the most part, everyone is doing many of these things already. They are fairly straightforward. First, just maximize the amount of gasoline you are dropping in the distillate.

(2013) Question 21: What is the maximum olefin content allowed in isomerization unit feed? Are levels encountered different between C4 and C5/C6 units? What are the major concerns and limiting factors? What is the effect of olefins on the mole sieve used for drying the feed?

The typical olefin limit in a C5/C6 isomerization unit is 2 to 3%. The olefin content of the feed is constrained by the high heat release that the olefins cause across the reactor. Olefins can polymerize and cause coking on the catalyst in an isomerization unit.

(2013) Question 22: What considerations in caustic scrubber operation or design are available to mitigate caustic carryover and corrosion? Discuss differences between various services.

Let’s quickly review some concepts for good caustic scrubbing, caustic strength (not just pH, but also the weight percent sodium hydroxide), contacting of the treat stream with the caustic using pre-mixing or submerged inlets, packing within the scrubber, and caustic circulation to keep the caustic uniform in concentration.

(2013) Question 23: What are the operating strategies for C5/C6 isomerization units with current fuels regulations? Are units being run primarily for benzene saturation withchanges in operating parameters, feed sources, and treating being made to account for seasonal differences in gasoline pool RVP?

The answer is basically ‘yes.’ We are looking at isomerization units as benzene polishers for the light straight-run. Sometimes the light straight-run has too much benzene in it and a BenSat™ unit would be more appropriate for benzene conversion. The isomerization unit is an economic unit in the refinery.

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