Q&A

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(2016) Question 63: What are your current methods used for regenerator cyclone temperature control? Do you use water sprays or steam injection?

In the early days of FCC, the normal bed and dilute-phase operating temperatures –being less than 1100°F –did not support CO combustion. These units operated with high levels of carbon on catalyst and about 10 vol% CO in the flue gas with almost no excess oxygen in the flue gas.

(2016) Question 64: What are your typical operating guidelines to prevent compressor surge episodes? How closely do your FCCU operators approach the actual surge line of a compressor before adjusting operation?

[United Refining Company (URC)] The unit engineer/compressor manufacturer should be able to provide guidelines to prevent surge episodes. These guidelines may include safe windows of operation for air rates, discharge pressures, and discharge temperatures.

(2016) Question 65: Please comment on which FCC feed types you are currently processing and what chemicals you are using for gas plant corrosion prevention. Is waterwashing sufficient to sustain adequate unit reliability?

Our refinery typically runs Western Canadian Crudes, SYN, and some conventional heavy crudes.

(2016) Question 66: In your experience, how does changing the feed cutpoints impact FCC conversion and product yields? How does the LP (liquefied petroleum) determine where to make these cutpoints?

Deeper cuts will not have as high a conversion as will lighter cuts. For example, an FCC charge API gravity of 22 may have a conversion of 83%, while a lighter gravity of 23 will show conversion one point higher at 84%.

(2010) Question 43: In both Extractive Distillation and Liquid-Liquid Extraction units, foaming in the Extractive Stripper column leads to solvent carryover and unit upsets. What are the determinants of foaming, and how do you determine foaming risk? Is continuous antifoam injection necessary? What are the countermeasures do you take to minimize this risk?

Marathon has two liquid-liquid extraction units. Both are fed from reformers. We continuously inject anti-foam into the stripper feed. The only foaming events we have observed have been after the loss of anti-foam injection.

(2010) Question 44: Contaminants in aromatics extraction unit feeds such as chlorides and oxygen are difficult to measure, and can lead to operational issues (such as fouling / corrosion / erosion, etc) in the extraction unit. In your experience, what are the primary effects of these contaminants, and how can one manage these impacts?

Most of Marathon’s experiences with contaminants that affect solvent quality are with oxygen. Oxygen can enter the unit from solvent storage, feed, and re-run tanks. Any vessel operating under a vacuum can also be source of oxygen. Most of our issues with corrosion have occurred in the stripper and recovery column reboilers.

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Q&A

(2016) Question 63: What are your current methods used for regenerator cyclone temperature control? Do you use water sprays or steam injection?

(2016) Question 64: What are your typical operating guidelines to prevent compressor surge episodes? How closely do your FCCU operators approach the actual surge line of a compressor before adjusting operation?

(2016) Question 65: Please comment on which FCC feed types you are currently processing and what chemicals you are using for gas plant corrosion prevention. Is waterwashing sufficient to sustain adequate unit reliability?

(2016) Question 66: In your experience, how does changing the feed cutpoints impact FCC conversion and product yields? How does the LP (liquefied petroleum) determine where to make these cutpoints?