Q&A

(2010) Question 30: What process parameters can affect alkylate T90? What are the critical variables you monitor in both sulfuric and HF units? Discuss processing schemes, feed impacts and operating variables.

The type of feed is very significant for T90. Amylenes make alkylate with higher T90 in both sulfuric and HF units. Propylene generally makes lower T90 than butylene in HF units. However, with sulfuric-catalyzed technologies, propylene can increase T90 as discussed below.

(2010) Question 31: In your experience, when sampling the HF Alky iso-recycle stream, how and where is the sample neutralized prior to analysis? Can this approach be used for online GC analysis as well?

The isobutane recycle sample can be neutralized at the sample location using a chamber filled with alumina or KOH pellets. If using a KOH chamber, it is best to add a filter downstream to filter out any fines.

(2010) Question 32: In your experience, what contributes to Monel denickelification in the HF Acid Regenerator circuit? What are the potential problems associated with this?

Oxygen is a major cause of monel denickelfication. Oxygen can enter the circuit during loading operations. Care should be taken to avoid pressuring air contained within loading pipes/hoses into the unit.

(2010) Question 33: How do refiners avoid De-isobutanizer (DIB) column/reboiler fouling in sulfuric acid alkylation? What process conditions on the column do you use to detect this fouling? What process modifications do you take to minimize the impact of this fouling?

Fouling in the DIB column is almost always caused by salt deposits. These salts are typically sodium sulfate and sodium sulfite but can also contain calcium or magnesium if the effluent treating water is not demineralized. If these water-soluble salts are present in the DIB feed, the water will evaporate once inside the column leaving the solids behind.

(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 30: What progress have you made in crude analysis in a timely manner, establishing stability criteria, scheduling blends, and mitigating processing constraints when blending multiple crude unit feedstocks?

XIOMARA PRICE (SUEZ Water Technologies & Solutions)
Crude blending is still largely based on the economics of the blends and less on the processing constraints that may exist. Real time analytic and predictive tools are available to the industry to help quickly determine the blends relative

(2019) Question 31: Is intermittent or continuous mud washing considered your best practice and why?

STEVE WILLIAMS (Marathon Petroleum Corporation)
• Mud wash is utilized to help keep the bottoms of a desalter vessel relative free of solids build up.
• Utilizes a distribution header with nozzles located near the bottom of the desalter to create a liquid disturbance at the bottom to preclude

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