Q&A

(2019) Question 35: What is the importance of sodium to reliability in the coker? What are some of the potential sources of the sodium in coker feed? In light of IMO how should sodium be managed in purchased coker feed?

Sodium in the coker feed can be introduced via sodium content of the salts in crude, caustic addition at the crude unit for corrosion control purposes, as a contaminant in recovered oil material in the refinery, sodium content of other purchased feedstocks (as mentioned in the question) among others.

(2010) Question 34: What has been the experience of refiners operating selective hydrotreating of FCC naphtha regarding gum formation potential of the low sulfur gasoline? Is gum inhibitor addition a recommended practice?

Gum potential exists with unsaturated hydrocarbons (olefins or diolefins) stored in refinery operations with oxygen as a free radical. Organic sulfur and nitrogen compounds remaining in FCC gasoline product can form gums in the presence of olefins and oxygen.

(2010) Question 47: What are the best practices for corrosion probe selection, installation and reliability, especially in high temperature and/or high H2S environments?

Some things to consider when selecting and installing corrosion probes are to match the metallurgy of the probe to the pipe.

(2010) Question 48: In your experience, what is the preferred online (non-destructive) method to identify risk of HIC (hydrogen induced cracking) in gasoline processing units?

The preferred method of identifying the risk of hydrogen induced cracking is to measure the permeation or flux of hydrogen on the outside surface of the equipment and correlate this to the corrosion rate on the inside of the pipe.

(2019) Question 28: In light of IMO (International Maritime Organization) 2020 and the potential for shipping intermediate streams from refinery to refinery, what are your plans to ensure H2S specification in the vapor space is met, either at the shipping or receiving point?

STEVE WILLIAMS (Marathon Petroleum Corporation)

• Movement of intermediate streams from refinery to refinery has been a common practice, including movement of heavy oils. This activity is expected to increase following implementation of the IMO 2020 rules reducing the sulfur content in maritime

(2019) Question 32: Where are ammonium chloride and amine hydrochloride salt found in your crude unit? What is your best practice to monitor and mitigate the resulting corrosion and fouling?

Ammonium chloride and amine hydrochloride salts can form in the top section of the Atmospheric and Vacuum Towers, and the overhead exchangers of the tower. The formation of these salts is a function of partial pressures which dictated by the concentrations of ammonia, amines, chlorides in addition to operating conditions such as overhead temperature, pressure, steam flow rate and hydrocarbon flow rate.

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