Q&A

(2013) Question 7: Given challenges in gasoline Reid vapor pressure (RVP), benzene, low-carbon fuels, and other requirements, are refiners considering expansion or other changes to make more alkylate? Has increased catalytic polymerization become a consideration?

UOP has not observed a big uptake in project activity related to this issue. However, we have observed more interest in revamping existing alkylation units rather than new projects.

(2013) Question 8: What is the industry experience with de-isobutanizer (DIB) feed pre-heatexchanger or reboiler fouling? What are the typical causes of the fouling? How do you mitigate this problem? Comment on both HF and sulfuric technologies.

I am going to talk about HF alkylation units only. The feed pre-heaters for the isostripper or main fractionator have experienced corrosion and fouling. There are several possible causes. One is getting the metallurgy, which is typically carbon steel, too hot. If you go over 160°F in the presence of HF, it gets very corrosive; so, you can lose metal that way.

(2013) Question 9: What are the latest strategies for feed dispersion and mixing in HF and sulfuric acid alkylation? How does mixing affect alkylate endpoint? Does better mixing allow for operations at reduced I/O ratios via increased olefin charge rate or operating against isobutane constraints?

I am going to address the HF units again. For the first question, it is more of an issue of, “If it ain’t broke,” we are not going to fix it. The types of mixers are simple in the HF unit. An orifice-type mixer is used for mixing the olefin and the isobutane recycle, and then a spray nozzle is used to mix the isobutane in the olefin into the acid.

(2013) Question 10: What is the industry experience with continuous online acid strength analyzers in HF and sulfuric acid services? Please comment on accuracy and reliability.

Again, I will address the HF units. UOP is aware of two vendors who are marketing online analyzers for percent HF and percent water. The experience of their customers has been generally positive. These analyzers give continuous readings, so you can detect issues much faster.

(2013) Question 11: What changes have refiners made in metallurgy from design specifications? What recommendations have the licensors incorporated into new specifications based on experience and user feedback? Comment on both HF and sulfuric acid alkylation.

The short answer is that there are not very many deviations from the design metallurgy in HF units. Any changes that have been made are based on observed corrosion rates within the unit.

(2013) Question 12: Gasoline blending is becoming more difficult due to the increases in quality specifications; lower sulfur and benzene, for example. What changes are being made to blending facilities and operations to accommodate these changes? Please discuss tankage allocations, working inventories, online analyzer needs, procedural changes, in-line blending, etc.

Blending has indeed become more difficult with the lower product specifications, but our blend methods have only experienced small evolutionary changes in response to the new specs. Most of the changes involved recertification of established methods to demonstrate compliance with the new standards.

(2013) Question 13: What are the typical causes for failing JFTOT and aviation turbine (AVTUR) specifications?

Assuming the jet fuel is on-spec with regard to other quality parameters, with the exception of perhaps copper strip corrosion and mercaptan sulfur, we have found that instability reaction precursors and catalysts are typically the root causes of JFTOT failures.

(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.

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