Q&A

(2010) Question 78: In your experience, how effective and reliable are hydrocyclones, electrostatic separator, additives, and filters in reducing the ash content of the slurry?

There are basically 3 types of ways to reduce the ash content in slurry oil. They are electrostatic separators, additives with settling and filters. They all have their advantages and disadvantages, and they all do a reasonable job in reducing ash in slurry.

Question 42: What are your best practices to minimize catalyst carry over to the main column on start up?

Catalyst loss events experienced while bringing the FCC online after a shutdown are troublesome as they can add significant cost and delay to the startup. Because the main air blower is run close to design conditions throughout the startup, losses are more frequently observed from the reactor side.

(2019) Question 45: What are your options to maximize light cycle oil from the FCCU (e.g. operating conditions, feedstock, recycle, equipment, catalyst, etc.)?  What are the typical unit constraints?  What projects have been considered at your facility to capture the increased value of diesel?

There are multiple ways to maximize light cycle oil from the FCC including reducing conversion, reformulating the fresh catalyst, utilizing additives, and adjusting fractionation.

(2019) Question 46: How often do you perform steam optimization in the FCC reactor? What process response and benefits do you typically see from performing "step tests" to feed nozzle, lift, and stripping steam flow rates?

How often do you perform steam optimization in the FCC reactor? What process response and benefits do you typically see from performing "step tests" to feed nozzle, lift, and stripping steam flow rates?

(2019) Question 47: For units not challenged by standpipe fluidization, are there benefits to reducing fresh catalyst 0-40 um particle content?

There are multiple benefits to reducing fresh catalyst 0–40-micron particle content for FCCs not challenged by fluidization. A significant portion of the 0-40 content cannot be retained in the FCC.

(2019) Question 48: What is your experience with carbon on regenerated catalyst levels in partial burn operations?  How do you confirm an optimal level of carbon to ensure desired product yields?  How do metal amounts or feedstock play a role in controlling carbon on regenerated catalyst?

The optimal level of carbon on regenerated catalyst (CRC) is often a balance between conversion and feed rate. Lowering CRC can be achieved by increasing air rate. In FCCs that are air blower or regenerator temperature limited, this can result in a feed rate reduction or residue processing reduction.

(2019) Question 50: What methods or operating parameters do you use to monitor/diagnose FCCU regenerator air and catalyst maldistribution?  What can be done operationally to mitigate air and catalyst maldistribution?  What mechanical changes have been successful at improving air and catalyst distribution?

Localized regenerator afterburn is a common symptom of non-optimal air and/or spent catalyst distribution. Regional CO bed breakthrough will combust and afterburn in the regenerator dilute phase and cyclones indicating a stochiometric imbalance of air and coke. In a partial combustion operation, localized afterburn confirms confined oxygen breakthrough from the bed resulting in CO combustion in the dilute phase and cyclones.

(2010) Question 38: What measurements and criteria do you use to decide when to change your gas and liquid chloride absorber material? How do you determine the selection of absorber material?

For both gas and liquid service, Chevron monitors the inlet HCL/Total Chloride and replaces the adsorbent/molecular sieve based on material balance loading of chloride on the adsorber media. Chevron does monitor adsorbent outlet HCL/Total Chlorides, but as a best practice will change the adsorbent material before vendor maximum loading if breakthrough has not occurred.

(2010) Question 39: With lower severity requirements due to ethanol blending and corresponding reduced coke make in the reformer, what changes are you making in regards to reformer operation? What opportunities does this evolution present for both CCR and semi-regen units?

Increased ethanol blending has reduced the severity of the reformers on average 2 octane numbers. This has increased reformate yield and decreased hydrogen production. Although the octane boost realized by ethanol blending reduces overall pool octane requirements, minimum reformer severity may be dictated by octane requirements of premium gasoline grades, or by refinery hydrogen requirements.

(2010) Question 40: Has anyone experienced high chloride levels in off gases from the lock hopper of a pressurized regenerator? What are the consequences of the high levels (i.e. fouled burner tips)? What are ways to mitigate the problem?

Marathon has not experienced any high hydrogen chloride concentrations in Lock Hopper off gases from the two CycleMax regenerators that we operate. We have also not experienced problems with fouled burner tips due to high hydrogen chloride in the fuel gas to a heater.

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