Q&A

(2018) Question 21: What are your important considerations for water washing with respect to: 1) Intermittent injection a. Process temperature of injection b. Duration of injection c. Frequency - triggers to begin d. How frequently before making it continuously? 2) Water Quality: a. pH range b. Oxygen c. Total Suspended solids d. Total dissolved solids e. Recirculation vs. make-up f. Other

Hotter temperatures typically will increase in the need for better designed injection systems. The injection mix point needs to be designed to contact and scrub the vapor well, with adequate dilution of water, with metallurgy at the injection point selected to handle the lower pH of the droplets.

(2018) Question 22: Can you elaborate on the benefits, drawbacks, and trade-offs of liquid phase vs. gas phase catalyst activation in a hydrocracking unit? Is there an activity or yield difference of liquid phase or gas phase activation of 2nd stage catalyst in a 2-stage hydrocracking unit? Consider both catalyst formulation and operational factors (MPT, excursion risk, etc.)

Activation (or sulfiding) of hydrotreating and hydrocracking catalysts can be done either ex-situ or in-situ. In both methods, the objective is to convert all the catalyst’s metal oxide sites to active metal sulfides.

(2018) Question 23: What are the sources of silicon that can impact a hydrotreater? How does silicon affect hydrotreater operations? What are your best practices for managing / mitigating silicon poisoning?

One source of silicon is antifoam chemistries. These may be introduced into HDS feeds via use in the Coker process within the refinery or via use in production upstream of the refinery.

(2018) Question 24: How many refiners import and/or purchase gasoil feed for a hydroprocessing unit? What are common issues associated with imported or purchased gasoil feeds? Are there specific characteristics to target and / or avoid? Are there best practices for minimizing negative impacts to unit operations / reliability? How are supply limitations managed?

Key characteristics of imported feed like end point, sulfur, nitrogen, chlorides and carbon residue can be controlled by establishing allowed specifications. But other characteristics may be hard to control.

(2018) Question 25: Coke drum integrity can be compromised due to the use of feed side entry devices. What is your experience with drum roundness upon inspection?

Coke drum integrity is typically dominated by low cycle fatigue. Imposed stresses due to thermal gradients during drum warming, water quenching and the contraction of the drum while full of coke can result in stresses higher than the yield stress of the coke drum metal.

(2018) Question 26: How do you monitor furnace convection section fouling? What mitigation steps do you implement?

Monitoring the flue gas temperature leaving the process convection section is a simple method of tracking the heat transfer in the convection section. The excess air needs to be taken into consideration as a higher O2 concentration will shift heat transfer into the convection section and causes the total quantity of flue gas to increase.

(2018) Question 27: What is your experience with chemical treatment to reduce furnace coking?

For conventional fouling, which is the result of asphaltene destabilization due to temperature, chemical treatment programs have not been effective for Coker heaters. For premature asphaltene precipitation due to resid compatibility concerns, chemical treatment programs have been effective in reducing or eliminating fouling.

(2018) Question 28: What are your best practices around initial crude oil qualifications? Upon receipt, what are your best practices for continuous inspection/receiving crude oil at a plant?

Once they have located these crudes, our economic/planning group will utilize the assay of the crude to evaluate this crude using our linear program (LP). This will generate the possible net back for processing the crude.

Question 29: How are crudes with high filterable solids crude managed to mitigate their impact on the operation? What levels of solids do you see and how are they measured?

Several major refiners have begun to use a water wash step at the end of the D4807 test to determine the actual non-water-soluble filterable solids. This method is more reflective of actual solids contained in the crude.

(2018) Question 30: When injecting wash water upstream of the cold train in a 2-stage system, do you use fresh wash water or brine water from the 2nd stage desalter?

For two stage desalting, injecting all the fresh wash water upstream of the second stage desalter provides the opportunity to use the lowest salt water on partially desalted crude which should result in the lowest level of salt in the desalted crude oil. Water from the second stage desalter is then used to provide wash water for the first stage. This water is typically split between being injected upstream of the exchanger train and upstream of the mix valve for the first stage desalter.

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