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(2014) Question 43: How has the increased processing of synthetic and other opportunity crudes in a refinery impacted the buildup of HPNA's (Heavy Poly Nuclear Aromatics) in the hydrocracker and affected conversion? What are your strategies to address this?

PCA (Poly Cyclic Aromatics) formation is not a function of processing synthetic or opportunity crudes. Some opportunity crudes can be much easier to process by a HCU due to much lighter EPs thus providing extended run lengths. Feed type, quality, severity of the operation, unit configuration and catalyst choice in the HCU are determining factors for PCA formation.
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(2014) Question 45: Has bromide been reported in your hydroprocessing unit feeds or discovered as ammonium bromide in the reactor effluent exchangers? If bromide is present, do you use the same wash water practices for ammonium chloride deposition sufficient to avoid exchanger fouling? What are the possible sources of bromides

Bromine is in group 17 of the periodic table commonly known as Halogens. Halogen means “salt former”. It is this salt forming nature of the halogen group that makes them key in natural compounds. Halogen anions of Fluoride, Chloride, Bromide, and Iodide are present in living organisms. Further Bromide is present in all organisms, and organobromine is the most common organohalide.
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(2014) Question 46: Silicon uptake on hydrotreating catalysts is an increasing problem. (1) What operating conditions favor maximum silicon pickup by the catalyst? (2) Are there differences between silicon from coker antifoamsand other sources? (3) Does the presence of other contaminants such as nickel and vanadium affect the silicon pick-up by the catalyst? (4) What best practices are you using to monitoring silicon pick-up by the catalyst?

Silicon in feed streams to Hydroprocessing units can pose a threat to catalyst performance and must be properly managed. Silicon acts as a poison to the catalyst by depositing on the surface of catalyst particles blocking active sites and reducing critical HDS and HDN activity. Silicon can be found in a wide range of feed streams and is a concern for all hydrotreaters processing naphtha, distillates, and vacuum gas oils.
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(2014) Question 51: What is your minimum Cloud Point Improvement that makes economic sense to apply catalytic dewaxing vs. traditional (i.e. additives and kero blending) Cold Flow Improvement methods?

At low temperatures, products with “waxy” components start to crystallize and affect the flow characteristics of the product. To avoid problems of fuel supply to an engine or lubricating problems under low temperature conditions, diesel fuels and lube oils often have stringent specifications on flow properties at low temperature.
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