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(2013) Question 31: What is the threshold concentration of arsenic and phosphorus requiring a dedicated trap system? How are the arsenic and phosphorus trap systems specified,and what are the controlling mechanisms?

Arsenic is a big concern because it is a permanent poison that causes fairly significant activity. We generally see around a 60° Floss per weight percent pickup; so, you will want to pay attention to it. As a side note, it is also common in most fractions of hydrotreating: so anything from naphtha to heavy gas oil.
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(2013) Question 32: What is a typical range of HDM (hydrodemetallization; metals removal) in a gas oil hydrotreater? Can HDM decline rapidly when metals in the feed become excessive relative to catalyst system design? Is there a point when metals in the feed are so high that they “overwhelm” the demet (demetallization) and main bed catalyst, resulting in lower percent of HDM?

Nickel and vanadium contamination generally come in heavy gas oils and resid hydrotreating. It is obviously not very common in diesels and light feeds. We see that it is about a 5°F to 9°F loss per weight percent combined pickup. The reason you will want to pay attention to these metals is because of their ability to actually diffuse onto the catalyst, so you will need a space to deposit them.
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(2013) Question 33: What is the philosophy or criteria for optimizing catalyst bed grading material to prevent high reactor pressure drop from feed containing significant amounts of Fe (iron)?

Certainly, identifying the sources of the iron coming in – whether organic, iron oxides, iron sulfides, or just scale from tanks – is very critical to understanding your best strategy for mitigating pressure drop. Ultimately, when you form iron sulfide, it creates deposits on the bed and coke deposition, and certainly leads to reduced catalyst life.
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(2013) Question 34: When processing cracked naphtha, what is done to ensure that polymerization of the diolefins/olefins will not result in pressure drop problems in a reactor or upstream equipment?

Again, we are trying to prevent the polymerization of the olefin/diolefin. The primary concern is trying to prevent contact with oxygen because that will ultimately lead to gum formation. So, the preference would be, if possible, to feed this hot to all the downstream units and avoid intermediate storage.
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(2013) Question 36: Has the increased use of tight oil crudes and western Canadian crude been correlated with increased metals and solids in diesel, gas oil or vacuum resid?

The FHR CC (Corpus Christi) refinery has not seen an increase in raw crude filterable solids. With the increased domestic crude rates, we typically run about 20 to 50 pounds per thousand barrels with these occasional spikes to 100. We have recently started monitoring the filtrate from the 0.45-micron test with 0.1-micron paper.
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(2013) Question 37: How does the increased processing of tight oil (Eagle Ford, Bakken, etc.) affect hydroprocessing operations? With lighter feeds and less sulfur, how can the hydroprocessing reactors and catalyst systems be tailored to optimize performance? What other factors in economics replace volume gain when processing these lighter feeds (i.e., impact on FCC yields, gasoline blending, minimizing cetane giveaway, etc.)?

Tight oil crudes have impacted our hydrotreater operations in several ways. Catalyst lifecycles are extending due to the low severity required for treating low-sulfur feed. Low reactor severities have caused emulsion problems due to our not hydrogenating our surface-active compounds in the feed.
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(2013) Question 38: Elaborate on the relative value of the various distillate feed streams in a refinery (i.e., straight-run diesel, light atmospheric gas oil, light vacuum gas oil, light cycle oil, coker distillate, kerosene, coker naphtha, heavy cat naphtha, and other) when considering maximum saturation and volume swell in high-pressure ULSD service.

The question asks specifically about high-pressure ULSD service. ‘High pressure’ means the reactor has to operate around 1,000 pounds without any problem supplying hydrogen to these units. The relative value of the volume swell depends on how much you can saturate aromatics. This aromatic saturation is an equilibrium reaction, so you need high hydrogen partial pressure on the lower temperature side.
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(2013) Question 39: There is a drive to target the highest endpoint possible on all distillate feed streams when maximizing overall diesel production. Are there feed streams that should be targeted first, considering operational impacts of such optimization, impacts to catalyst performance and life cycle, as well as cutpoint optimization between distillate units and the FCC?

For maximum diesel, in general, we prefer getting the distillate out of the FCC. I think we had a discussion last year in the FCC forum during which we said that keeping some distillate in the FCC feed is a benefit. We still say that if you want to maximize the diesel, heavy-out the straight-run distillate of virgin gas oil because it will be the easiest to treat compared to the other two, which are coker distillate and LCO.
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