Q&A

(2011) Question 19: With limited hydrogen availability for desulfurization of diesel, what criteria influence the optimization of hydrogen consumption between the FCC Pretreat and ULSD units? What catalytic options exist to achieve the desired balance of consumption?

Hydrogen supply and compression constraints are becoming more common for refineries in the US as more and more bitumen-based crude is brought in from Canada.

(2011) Question 20: Pre-hydrotreated feeds and crudes look easy to process on paper. Why is it more difficult than expected to process pre-hydrotreated feeds in a hydroprocessing unit?

Pre-hydrotreated feeds are often the most difficult feeds to process in hydrotreaters primarily because the remaining molecules to be treated are the most refractory. Low sulfur feeds are not automatically the easiest to process; the sulfur species determines the difficulty of processing, not the total sulfur.

(2011) Question 21: What needs to be considered when processing LCO or increasing the amount of cracked feed in a hydrocracker?

It is important to ensure that sufficient H2 is available to satisfy the minimum required H2/oil ratio because hydrogen consumption will increase significantly.

(2011) Question 22: Which is the impact of feed asphaltenes content on hydrocracker cycle length?

The asphaltenes are high boiling, high molecular weight and hydrogen deficient materials that are the least reactive in a hydrocracking environment.

(2011) Question 23: What is the impact of HPNA (Heavy PolyNuclear Aromatics) on hydrocracking catalyst activity, stability. and yield selectivity?

The impact on hydrocracking catalyst deactivation and yield selectivity due to precipitation of Heavy PolyNuclear Aromatics (HPNA) is typically based on several criteria.

(2012) Question 1: For refiners using Layers of Protection Analysis (LOPA) in their OSHA (Occupational Safety and Health Administration) PHA (Process Hazard Analysis) studies, how do you quantify the frequency and consequences of initiating events?

I have a lengthy description of LOPA itself to help address this question. Layers of Protection Analysis is the structured process used to determine the appropriate layers of protection required to provide adequate safeguards for adverse and sometimes catastrophic events in process units.

(2012) Question 3: How can lubricity be improved in ultra-low sulfur jet fuel?

The increased desulfurization of distillate fuels removes sulfur nitrogen and aromatics, which are components favorable for lubricity properties. The recent market conditions have led most refiners to not only produce ULSD, but also ULSK (ultra-low sulfur kerosene), in order to maximize distillate production.

(2012) Question 4: What are the hydrotreating operating issues when processing shale-derived light, sweet, and highly paraffinic crudes such as Bakken, Eagle Ford, and Utica? What hydrotreating/catalyst strategies can offset any negative effects? What options are available to optimize the distillate hydrotreater(s) with these light, sweet crudes?

The shale crudes in question are highly paraffinic, low sulfur, low nitrogen, and low in conventional contaminants. However, we do see some trace contaminants coming in from some of the fracking and completion chemicals. These crudes have a low resid content, which impacts the bottom of the barrel.

(2017) Question 45: What are your typical consequences and probable sources of fuel gas fouling? What are your respective solutions?

Fuel gas fouling in refineries is an ongoing problem and is typically the result of many years of corrosion due to moisture in the fuel gas system. These systems are typically saturated with water vapor due to the amine scrubbing that is used to remove H2S, and water may drop out as a liquid in low velocity areas or in areas with inadequate insulation.

(2016) Question 27: What methods do you use to reduce particulate loading on or debottleneck of existing filtration equipment in a HPU unit without reducing catalyst cycle life?

The use of feed filters is highly recommended, but it is important to choose a filter size that will be manageable; meaning that if a 5-micron filter is used, it will most likely have to be replaced or backflushed several times per day, which is not practical. However, if a too-large filter size is used, it will not be effective. The only way to reduce the particulate loading on a feed filter is to increase the filter size, thus allowing more material to slip through.

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