| American Fuel & Petrochemical Manufacturers

Question 91: In a catalytic reformer with a given pressure, severity, and feed quality (N+2A), what are the major factors that determine the C5+ yield? How do you optimize yield? Have you quantified the impact of pentane and/or hexane content in the feed?

Question 91: In a catalytic reformer with a given pressure, severity, and feed quality (N+2A), what are the major factors that determine the C5+ yield? How do you optimize yield? Have you quantified the impact of pentane and/or hexane content in the feed? Michael Newton (Roddey Engineering) Setting pressure, severity, and feed quality limits you on any significant “knobs to turn” in determining the C5+ yield. If you assume that LHSV is also fixed, there are two factors that can impact C5+ yield. Reactor Inlet Temperature Profile – typically running a “downhill” profile will give you a slightly higher C5+ yield and will lower overall coke make in the unit. Water Chloride balance – having an over-chlorided catalyst will result in more cracking and lower C5+ yields. Under-chlorided – higher deactivation, higher yield, higher temp required.

Question 90: What determines the minimum feedrate for a fixed bed reformer? What process indicators would tell you that the feedrate is too low?

Question 90: What determines the minimum feedrate for a fixed bed reformer? What process indicators would tell you that the feedrate is too low? Rick Grubb (Chevron USA) Besides mechanical limitations, such as pump capacities, flowmeter ranges, control valve sizes, etc., the process factors that determine the minimum feed rate of a fixed-bed reformer are: •Flow distribution in the reactors •Heat of reaction dissipation in reactors •Flow distribution in furnaces •Phase separation in exchangers

Question 7: What are your typical precious metal recoveries from reforming catalysts? What factors impact this?

BILL KOSTKA (AXENS NORTH AMERICA)
Reported platinum recoveries from reforming catalyst following commercial utilization have typically ranged between 90 and 100 wt% and have rarely been less than 80 wt%. The magnitude of this range is both frustrating and at least somewhat explainable.

Question 6: What is your main blending limit for gasoline for both summer and winter specs?

ABIGAIL SLATER (HollyFrontier)
Gasoline blending specifications are vast and different in various geographical areas. The common blending limit that taxes both summer and winter specifications are volatility specifications. Depending on the gasoline blend, Reid Vapor Pressure (RVP), Total vapor over liquid (TV/L), and distillation (typically T10 and T50) can be limiting in both seasons.

Question 5: How will Tier 3 rules impact gasoline-producing units at your facility?

ABIGAIL SLATER (HollyFrontier)
The Tier 3 gasoline regulation partially took effect in 2017 and will be fully implemented in 2020. The Tier 3 gasoline regulation has impacted the refining industry in a myriad of ways as refiners reduce sulfur further. These impacts will be similar to most refineries, but will have varying severities based on refinery configuration, company compliance strategy, and market factors.

Question 4: What are your best practices for controlling caustic strength in an isomerization unit scrubber? How frequently is the caustic refreshed?

It is quite important to optimize PERC injection in feed as guided by technology supplier as otherwise the HCl concentration in off gas can go too high (normal range 1500 - 2500 ppm). This will lead to rapid depletion of caustic strength due to neutralization effect, thereby requiring frequent fresh caustic make-up.

Question 3: What is your experience with ball valves in feed and make-up gas drier circuits in ISOM Units? What strategies have you adopted for monitoring leaks, regular maintenance and achieving longer run length?

DAVINDER MITTAL (HPCL Mittal Energy)

The gas and liquid dryers perform important task of safeguarding the ISOM catalyst from water vapor and other impurities in the make-up hydrogen and hydrocarbon feed.
The dryer switching valves play an important role of directing the inlet/outlet gas streams into the adsorption beds, switching the dryers from adsorption phase to regeneration phase (and cooling phase) and vice versa in a pre-set sequence.

Question 2: We have a Selective Hydrogeneration Units (SHU) unit that removes butadiene from the olefin feed to the alkylation unit. What is the typical concentration of hydrogen and light ends in the olefin product leaving the SHU? How do hydrogen and light ends affect alky operations?

THOMAS PORRITT (Chevron U.S.A)
A selective hydrogenation unit or SHU converts diolefins to olefins in a stream before it feeds an alkylation unit.

Below is a basic flow scheme.

Figure Q2 - 1 Selective Hydrogenation Unit Flow Scheme

Question 89: What are the typical problem areas for CCR catalyst circulation loops? What are the most reliable valve types? How frequently do you conduct fines surveys and what is a reasonable range for fines make?

GRUBB (Chevron U.S.A., Inc.) My experience here is with the design of a new unit in Pascagoula. So we went to the other CCRs within the Chevron system and asked this question already on how to increase our reliability with that project. This is a roundabout answer arranged from all the different operating ones. On the valve types, I’ll just state that all of Chevron’s experience is with the UOP designs and what we do is we specify soft seat on the “V” notch ball valve wherever the catalyst flow must be stopped. We use a double-seated plug and globe “G” valves on the vents and spring loaded “B” ball valves for the gas tight seal on the catalyst transfer line.

Question 88: What is your experience with feed-side fouling on combined feed/effluent (CFE) exchangers? What is the foulant? How often do you clean them and what cleaning techniques do you use? On Texas Towers (vertical shell & tube exchangers), how do you extract the bundle from the shell if it gets stuck?

NEWTON (Roddey Engineering Services, Inc. Engineering) I’m just going to deal with Roddey Engineering’s experience. I know some people on the panel have different experiences. But as far as feed effluent exchangers go, and especially Texas Towers, we have seen significant fouling on all that we’ve dealt with. Pretty much every refinery that has one, they do not clean the tower.

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