Q&A

(2016) Question 21: What programs or systems do you employ to monitor hydrotreater furnaces and prevent tube failures and loss of containment? Can you share your experiences using technologies to implement online temperature monitoring of tube skin temperatures?

In nearly all hydroprocessing heaters, MPC has installed tubeskin thermocouples in order to provide continuous monitoring of tube metal temperatures to the DCS (distributed control system) operator. These thermocouples are strategically located in the heater at the areas with the highest estimated maximum heat flux.

(2016) Question 22: Describe your strategies for optimizing the pretreat and cracking catalyst cycles. How does this strategy vary when operating between maximum naphtha and maximum distillate modes? How does this impact catalyst selection for the next cycle?

Marathon Petroleum Company has adopted the philosophy of optimizing the hydrotreater and hydrocracking catalyst together as one unit. We do not measure nitrogen slip from the hydrotreater section, but rather allow the hydrocracker apparent conversion dictate adjustments to the pretreat section.

(2016) Question 23: How do you operate mid-distillate selective recycle hydrocracking units to generate more naphtha while minimizing fuel gas/liquefied petroleum gas without catalyst replacement?

Maintaining flexibility to make gasoline versus ULSD (ultra-low sulfur diesel) is very important to most refiners today due to the volatile nature of the market. Understanding the economic goals of your process unit and building in the flexibility through your catalyst selection process is the best way to set up your process for flexibility in the coming run.

(2016) Question 1: Do you have experience isolating air coolers to water-wash the process side while the unit continues to operate? What safety concerns do you consider beforeremoving this equipment from operation?

Safe isolation with block valves can also be an issue, especially in high pressure units with two-phase flow. We have had experience with water-washing exchangers and air coolers offline.

(2016) Question 2: What procedures do you use to test alkylation unit rapid deinventory systems? Do you perform a functional test using acid?

High level guidelines and philosophy of testing of the valves (as well as all other components) of HF alky safety systems –including rapid acid deinventory or “Dump” systems -is covered in API RP 751 section 2.3.6. The bits of that section that are directly applicable to dump valve testing suggest that the testing procedure should include valve stroking and testing of primary elements and controls. It also says that in addition to individual component tests, each active mitigation system as a whole should be tested to confirm that the system will work as designed. It also says that a service history should be maintained to assist in identifying and correcting problem areas.

(2016) Question 3: What process safety PSM) factors do you consider when contemplating a reformer unit rate increase?

Any change should be handled through the MOC (management of change) process, according to OSHA 1910.119: Process Safety Management of Highly Hazardous Chemicals. This standard includes requirements for preventing or minimizing the consequences of catastrophic releases that may result in toxic, fire, or explosion hazards.

(2016) Question 4: The economic benefit for propylene and amylene alkylation is improving. What considerations do you use in the feed pretreatment and alkylation unit operations before increasing these feeds?

Increased processing of propylene and amylene feedstocks in alkylation (alky) units does bring challenges, but most will depend on the configuration of the existing unit and whether any of these feedstocks have been processed before.

(2016) Question 38: What do you see for the future of ebullated bed technology considering changes in crude quality and availability?

With the worldwide requirement for higher conversion of residue into lighter, more valuable transportation fuels such as diesel remaining firmly in place, we very much see ebullated-bed (EB) residue hydrocracking building on its current trend as a bottom-of-the-barrel upgrading technology of choice going forward. Investment in this commercially proven, well-established technology is a way to increase complexity and ensure long-term survival in an increasingly volatile marketplace.

(2016) Question 39: Please summarize the current status of slurry hydrocracking technology commercialization.

Slurry hydrocracking technology has been commercialized in China (VCC) and Italy (EST) in the past two to three years. Both facilities have demonstrated expected performance, including conversion and selectivity. The reliability of slurry hydrocracking is still an open question as these units have only been in operation for a short time. Additional VCC commercial units are scheduled for startup in the next 12 months.

(2016) Question 41: What are the considerations you use for extending hydrogen plant catalyst life cycles (i.e., lower production rates, furnace tube failure, etc.)?

There are many parameters affecting the hydrogen plant catalyst life cycles, such as lower production rates, furnace tube failure, unplanned plant shutdowns, larger catalyst volumes, elevated energy consumption, and finite ZnO/S (zinc oxide/sulfur) capacity. Lower Production Rates will obviously result in longer catalyst lifetime due to a lower gas velocity over the catalyst.

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