Q&A

(2019) Question 17: What testing frequency and additional feed characterization (apart from bulk properties) should be used to accurately monitor catalyst performance on heavy feeds?

FERNANDO MALDONADO (Shell Catalysts & Technologies)
The type and frequency of tests performed are unit and refinery specific. When creating or modifying a unit’s laboratory test schedule some factors to be considered include:

1.   Unit objectives
2.   Past and/or current operational issues
3.

(2019) Question 18: What are your methods to mitigate bed 1 pressure drop without a unit skim? How would your approach be different if the pressure drop developed in a different bed, say bed 3?

JOE RYDBERG (CITGO)
Mitigation of elevated pressure drop first begins with identification the nature of the pressure drop. Is the DP a result of a more gradual buildup or a step change from a unit event or upset? Was an event related to hydrogen starving of the unit or loss of recycle compressor?

(2019) Question 19: In a hydrocracking unit, what methods do you use to determine the pretreat reactor operating temperature for optimum nitrogen slip to cracking catalyst?

AMIT KELKAR (Shell Catalysts & Technologies)
Nitrogen slip is a key variable in balancing the performance of the pretreat and cracking catalysts for cycle optimization. The optimum nitrogen slip depends on the specific unit objectives and constraints. In general, the pretreat temperature is adjusted

(2019) Question 20: What are the allowable limits/guidelines for water in feed to hydroprocessing units? Does the guidance change for activation vs normal operation? If so, how? What effective test methods do you use to measure water in feed? Do the limits change for different hydroprocessing units?

SUNHEIL ABDO and MICHAEL PEDERSEN (Honeywell UOP)
Tolerance for water is dependent on catalyst type and state. Prior to and during sulfiding and start of run cycle conditioning, hydrotreating catalysts can be quite vulnerable to water. Moisture will promote mobility of catalyst metals resulting in

(2019) Question 20A: What are the recommended guidelines for operating temperature and temperature rise in reactor beds during the initial month of operation? What determines these limits?

Recommended guidelines for operating temperature and temperature rise in reactor beds during the initial month of operation

(2019) Question 21: We are observing fouling of our feed/effluent exchangers that has impacted heat transfer and restricted feed. What are potential contributing causes and how can we mitigate?

ROBERT STEINBERG (Motiva Enterprises)
There are many things that can contribute to fouling of feed/effluent exchangers. Fouling can occur on either the feed or product side of the exchangers.

Possibilities sources of fouling on the feed side include:

• Dissolved O2. Oxygen can get into feeds

(2019) Question 22: What sets the endpoint limit for feed to an Ultra-Low Sulfur Diesel unit? Should 90%, 95%, 98% or Final Boiling Point be monitored and what is an acceptable tail for amount of feed greater than the cutpoint spec? Is the answer different for straight-run diesel vs coker diesel vs Light Cycle Oil feed components?

AMIT KELKAR (Shell Catalysts & Technologies)
There is limited boiling point shift from feed to product in a typical diesel hydrotreater. The boiling point shift correlates strongly with H2 consumption which is dependent on feed properties and unit conditions. In our experience, boiling point shift

(2019) Question 23: When do you recommend a static mixer upstream of a Reactor Effluent Air Cooler (REAC)?

ROBERT STEINBERG (Motiva Enterprises)
Wash water is injected to hydrotreating and hydrocracking reactor effluent upstream of the Reactor Effluent Air Cooler (REAC) to wash out ammonium salts (NH4Cl and NH4HS) that would otherwise deposit. Such salts foul and plug up exchangers. If the salts are wet

(2019) Question 24: What is your engineering design practice for selecting metallurgy for hydroprocessing unit’s amine systems? How does chloride level impact the metallurgy selection?

JOE RYDBERG (CITGO)
At CITGO Lemont Refinery, the base practice is to install post weld heat treated carbon steel piping for the main run of the pipe upon initial fabrication. For a set length downstream of control valves, 304 stainless steel is installed to try and mitigate the corrosive effects of

(2019) Question 25: What are your key factors around amine contactor operation in hydrotreating units?

JOE RYDBERG (CITGO)
The biggest key factor in amine contactor operation in hydroprocessing units is controlling the lean amine flow and the lean and rich amine loading. We have seen corrosion in rich amine piping likely due to elevated H2S loadings and higher velocities (both lean and rich)

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