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 dewaxing include ability to upgrade heavier or renewable feeds which have higher cloud and pour points without use of cold flow additives (cost) or kero blending (high value in many places). The main items to be considered when applying dewax catalysts are:
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)
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 upstream crude production and pipeline operations.
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), especially when unit rates are changed quickly.
Question 23: When do you recommend a static mixer upstream of a Reactor Effluent Air Cooler (REAC)?
ROBERT STEINBERG (Motiva Enterprises)
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)
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: