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(2015) Question 46: What are the mechanical integrity implications for reactor effluent air REAC) after experiencing high-temperature exposure during emergency shutdowns or trips?

During emergency feed removal or partial feed loss of a hydroprocessing unit, the loss of feed oil as a heat sink through the feed/effluent exchangers can elevate temperatures downstream. Expected temperatures can be estimated through process modelling of normal maximum reactor effluent flow continuing at maximum reactor outlet temperature without feed flow through the reactor effluent cooling train.
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(2015) Question 48: What is your experience bringing hydrocracking catalyst online without ammonia attenuation? Are there alternative methods or technologies to temper catalyst activity without adding ammonia?

Hydrocracking catalyst needs to be passivated during sulfiding to avoid potential temperature runaway as temperatures are increased to complete the sulfiding process. In our experience, there are four different ways that we attenuate the catalyst activity. The first is to inject ammonia prior to the high temperature sulfiding to passivate the catalyst.
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(2015) Question 49: Each hydroprocessing unit has an optimum strategy for full load-catalyst replacement: oxidized versus presulfided. How does the strategy change for a partial reload (e.g., top-bed skim or replacement)? Are there other situations when pre-activation is justified?

Use of either oxidized or presulfided catalysts can work fine. It depends on safety approach, cost allowance, time goals, and handling the processing preference. The main point is safely carrying out this skimming operation, whether or not it is oxidized catalyst or presulfided catalyst.
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(2015) Question 51: What is your best method for monitoring salt level in a diesel salt dryer? What are your current guidelines for salt usage and capacity? What are your best practices for loading and monitoring salt dryer performance?

We prefer not to use salt dryers in new ULSD designs. In recent ULSD designs, we will put in a vacuum dryer, or we will re-boil the stripper to meet the low water specs. If there are less stringent water specs, using a coalescer can be sufficient. One of our most recent new units will have a coalescer followed by a vacuum dryer.
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(2015) Question 52: What approaches are effective for you to reduce aromatic levels in the ULSD product streams?

To reduce aromatic levels, we definitely need to assess the unit’s capabilities. Is it a high hydrogen partial pressure unit with psig greater than 800, and does it have a higher than 4.0 hydrogen availability ratio (HAR)? If both answers are greater than those reference points, then full loading of NiMo catalyst can be employed to give higher hydrogenation and very good aromatic saturation results.
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(2015) Question 54: What are your options and Best Practices for routing liquids in a desalter pressure relief scenario if routed to crude fractionator? If routed to crude fractionator, how should one avoid damage caused by water?

The discussion of where to route the discharge of relief valves is always a great conversation, and we are going to talk a lot about what happens in the crude preheat train; and specifically, with desalter PSVs (pressure safety valves). We want to minimize the amount of liquids (especially water) sent to the fractionator whenever possible.
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(2015) Question 55: What strategies do you employ to purge solids from recovered oil at the wastewater treatment plant (WWTP) to avoid recycling solids back to the crude unit?

The crude unit wants them out of the crude oil, and the wastewater treatment plant would prefer not to have them. So essentially, we are talking about wastewater treatment solids. Some people call it recovered oil; some people call it slop oil; and some people call it skimmed oil. So, if I interchange these definitions, what I mean is recovered oil from the wastewater treatment plant. 
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