Q&A

(2019) Question 26: What do you do to predict Silicon breakthrough in a naphtha hydrotreater? What are the consequences to the downstream units if breakthrough occurs?

AMIT KELKAR (Shell Catalysts & Technologies)
The primary source of Silicon is the anti-foam injection at the coker. Silicon is also present in a wide variety of crudes including Maya, Canadian syncrudes and Venezuelan. It may show up in straight run naphtha due to use of Silicon based additives in

(2019) Question 26A: What is important for feedstock selection for a hydroprocessing unit regarding incompatibility? What related concerns are there in a heavy gasoil resid unit? What feedstock quality parameters are used to predict and /or prevent these issues?

GRANT YOKOMIZO and JOHN PETRI (Honeywell UOP)
A hydroprocessing unit can be designed to handle all potential feedstocks when there is a detailed understanding of the feedstocks’ characteristics. Specifically feedstock selection regarding incompatibility limits needs to be considered as a broad and

(2019) Question 26B: What concerns should be addressed before applying dewaxing catalyst in diesel service? What changes can be expected in unit operation with dewaxing?

AMIT KELKAR (Shell Catalysts & Technologies)
Dewaxing involves isomerization or / and cracking of linear paraffinic molecules to improve cold flow properties such as cloud and pour point. It may be required in winter season in cold climates to maintain flow properties of diesel. Economic benefits of

(2019) Question 27: What do you do to predict Silicon breakthrough in a naphtha hydrotreater? What are the consequences to the downstream units if breakthrough occurs?

JOE RYDBERG (CITGO)
CITGO refineries basically operate in the full coking mode which means that on our usual crude blends we do no net VTB for outside sales nor we are a player in the Bunker fuels supply market. Having said that, we have to be watchful of the demand shift that will follow with the

(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

(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.

Question 1: Historically, instrument air was used to purge FCC reactor instruments. More recently, dry gas or nitrogen is typically used for this service. Please explain the reasons for moving away from air and provide examples of operating upsets that have occurred when using air to purge instruments.

Gas purge streams for instrumentation in FCCU reactor-regenerator service are required to ensure their functionality. For example, the reliability of level- and pressure-measuring devices relies on clear impulse lines. The utilization of a continuous-purge gas stream ensures that catalyst particles are prevented from entering or are swept from impulse lines to keep them clear and reliable.

Question 2: Which type of valve technology or design is typically utilized in units with high catalyst withdrawal rates? Do you continuously withdraw catalyst? From a reliability and safety perspective, what type of hardware are you using for control? What is the best withdrawal line design?

Valve selection for FCC catalyst withdrawal services is dictated by temperature and erosion considerations.

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