Q&A

(2014) Question 22: What is your method to clean a "Texas Tower" type of combined feed/effluent exchanger? Comment on the differences between cleaning in-place, extraction and reinsertion, and online cleaning.

Pulling the VCFE tube bundle can be very difficult. Removing and re-installing the bellows is also a difficult task. Care should be taken not to damage the exchanger when pulling or installing the tube bundle. In addition, setting the bundle in the horizontal will, in most instances, cause damage such as tube to tube sheet leaks.

(2014) Question 23: What are the sources of platinum loss in precious metals catalysts? What role can your refinery engineers play in minimizing this loss?

Typical operating conditions in a reformer do not result in platinum volitization. However, it is possible for Platinum to become volatile and come off the catalyst at very high temperatures. One place this can occur is in the Chlorination zone of the CCR Regeneration Tower, where slipping coked catalyst into an oxygen rich atmosphere can result in very high temperatures.

(2014) Question 24: What is the maximum oxygen content you allow for the platinum redistribution step in a fixed bed reformer? What sets the maximum oxygen concentration?

Directionally the higher O2 level is better for metal dispersion during oxidization. UOP recommends aminimum of 5% with typical maximum O2 content of 8-10 mol% based on the seal oil combustion limits. Dry seals or nitrogen purge seals allow higher O2 content without explosive conditions.

(2014) Question 25: What factors contribute to your decision to place the regeneration section of a CCR in standby mode when the unit is operating in a low-coke mode? Discuss the advantages and disadvantages of the different standby modes (black-catalyst circulation, hot-shutdown, cold-shutdown, etc.).

If the coke content is very low in comparison with the coke burn capacity of the CCR unit, the operation can be limited in one of a few ways. A minimum gas flow is required to ensure the catalyst is properly dried before leaving the regenerator and returning for reduction.

(2014) Question 26: What are options for disposition of the caustic regeneration outgas stream associated with an LPG or gasoline caustic treater? What measures have you successfully used to prevent fouling, pluggage, and corrosion in this line?

The caustic treating off gas stream is primarily air that has been partially depleted of oxygen during the oxidation of mercaptides to disulfides in the caustic regeneration step.

(2014) Question 27: What impacts are you seeing in naphtha processing units from contaminants suspected to come from shale crudes (e.g. tramp amines, chlorides, fouling)? What are you doing to mitigate these impacts?

Tramp amines, chlorides, and fouling related to processing of Shale Crudes (or more specifically, Tight Oils) are issues that are of concern on the Crude Unit. I am not aware of issues specific to the gasoline pool and blending downstream of the crude unit.

(2017) Question 33: What conditions are tied to fired-heater shutdown interlocks? Do these cause an immediate shutdown, or are there any time delays built into the logic? If so, how long of a time delay do you use? Are there any operating conditions that would allow interlocks on fired heaters to be bypassed?

Marathon Petroleum Corporation (MPC) standard practices rely heavily on the guidance recommended by API 556. Most of our heater shutdown interlocks are derived from this API Recommended Practice. Our internal practices are intended to prevent a heater explosion due to uncombusted fuel in the firebox or a tube rupture that can lead to an explosion or uncontrolled fire.

(2010) Question 49: What testing procedures do you use for emergency shutdown valves? What are the parameters you measure and what are acceptable values?

The appropriate required testing of emergency shutdown valves is included in each Marathon refinery’s Mechanical Integrity (MI) program, complying with OSHA’s Process Safety Management regulation and EPA’s Risk Management Plan regulation.

(2010) Question 50: Chemical cleaning of towers and vessels prior to entry is being used to reduce time to entry. What practices are you employing and how much time is saved?

Our chemical cleaning practices for Crude/Vacuum and Coking units have evolved over many years. The starting point in most cases, after feed is out and the unit has circulated down, cooled and pumped out, is a flush with diesel or LCO followed by a good steamout.

(2010) Question 52: What areas of a delayed coker are susceptible to naphthenic acid corrosion? How do you determine the maximum allowable TAN for these areas?

The primary areas of concern include: •Coker feed circuit above 450 °F •Bottom section of the fractionator, including internals •Heater charge pumps and associated piping •Heater tubes.

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