Q&A

Question 3: Carbonate stress corrosion cracking (CSCC) has been identified as a cause of failure in FCC main fractionator overhead systems. What changes in feed quality, unit operation, or configuration would lead to increased risk of CSCC? What parameters do you monitor to determine whether a system is susceptible to CSCC? Has the problem been significant enough to warrant either comprehensive PWHT in potentially affected areas or localized PWHT when problem areas are identified?

Carbonate stress corrosion cracking, CSCC, is characterized by inter-granular, sometimes branchy, scale-filled cracks. It is believed that ammonium carbonate is the main contributor to the cracking mechanism.

Question 4: Does your refinery/company adopt a time-based rather than inspection-based replacement strategy for FCC reactor and regenerator hardware such as feed nozzles, air distributor, cyclones, cyclone support systems, and flue gas expansion joint bellows? If so, what is the planned service life for this equipment?

Service life of each component is highly dependent on the application and varies from unit to unit. We have generally found that inspection-based replacement frequency is used as opposed to time-based. We use the results of the last unit inspection, coupled with a run history, to determine whether we need to replace a particular component.

Question 5: What is the shortest possible time between oil out and entry for maintenance on large inventory, high capacity FCC units? How is this achieved?

With FCCs at 27,000 bpd and 9,000 bpd capacity, neither of our units really qualifies for high throughput or large capacity. However, in discussions amongst the members of the panel, we found that throughput and inventory are not necessarily good indicators of how quickly you can move oil-out to maintenance-in.

Question 6: Some CO and waste heat boilers operate with bypass stacks separated by seal pots or isolation valves. Maintenance of these seal systems can be expensive and these seal systems can be sources of poor reliability. What design upgrades and operating practices have enabled you to eliminate these bypass systems?

Holly Refining continues to use bypass stacks with diversion valves at both of our refineries. Those stacks and diversion valves are allowed by permit and we use them during startup/shutdown manning upset conditions. Both our Operations and Maintenance groups are assigned weekly preventative maintenance tasks to ensure operability when we do have to throw these valves.

Question 7: Is your company either considering, or actually implementing, FCC projects that include reduced CO2 emissions (greenhouse gas reduction-GHGR) as an offset/credit?

We do not have any current FCC projects that plan on utilizing some form of CO2 offset or credit in the emissions analysis. ConocoPhillips has performed a limited modeling study to evaluate the effect of operational changes on CO2 emissions from the FCC. Also, the study indicated that there is very little you can do to reduce overall emissions without also overall significantly reducing unit throughput or conversion.

Question 8: What level of PM2.5 particulate removal do you expect (or have achieved) with flue gas fines separation and removal equipment such as third-stage separators, fourth-stage separators, electrostatic precipitators, or wet gas scrubbers?

We have not benchmarked particulate removal technologies within our system for PM 2.5 removal. This data is difficult to obtain because many stack tests do not analyze the captured particulate matter for particle size distribution or PSD.

Question 9: Are there specific lab studies or commercial examples regarding the effect of regenerator temperature on catalyst deactivation and particle integrity, specifically attrition properties, apparent bulk density, and morphology?

There is a very definite correlation between activity degradation and regenerative temperature. Some catalysts are more susceptible to thermal deactivation depending on the technology and the poor architecture used.

Question 10: What is your recent experience regarding the maximum level of equilibrium catalyst metals (Ni, V, Na, Fe, Ca) in FCC units processing residual feedstocks? Have there been any recent improvements in vanadium passivation technologies? At nickel levels approaching 10,000 ppm, have you experienced increased catalyst deactivation as evidenced by lower equilibrium zeolite surface area?

Here we see data regarding one of our FCCUs that operates at e-cat nickel levels exceeding 10,000 ppm. We observe that the MAT generally remains within the same range until high e-cat nickel concentrations are approached.

(2008) Is your company planning to install modified HF acid capability (usage of the volatility suppressing additive)? What are the incentives for doing this? What alternatives have you considered?

In March 2006, in our continuing effort to support safe, reliable, and environmentally sound operation, we announced our plans to apply for a permit to independently initiate an alkylation process improvement project in our Philadelphia HF alkylation unit.

(2008) Question 70: How frequently do you have fires on reformer reactor flanges? What bolting techniques and gasket types do you use to prevent leaks? What other fixes, such as flange resurfacing, have you employed? Do you use steam ri

GRUBB (Chevron USA, Inc.) Chevron has had some experience with flange fires in the past, so I’ve consulted with Dave Reeves, our corporate expert and also our Best Practice that we’ve developed for this. I know that I said temporary fixes up on the slide, but it’s not really a temporary fix.

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