Q&A

(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.

(2011) Question 25: How do you manage process hazard analysis (PHA) scenarios related to corrosion?

First, ConocoPhillips has developed generic PHA scenarios for each major technology to determine what scenarios are applicable to a particular unit. These tables contain initiating categories (such as Corrosion), potential causes and consequences, possible safeguards and suggested consequence rankings.

(2011) Question 32: What are your best practices for minimizing corrosion in aromatics extraction process from oxygen in the feed? Is the strategy to reduce oxygen ingress or treat the feed? Is the situation different for glycol, Sulfolane, Morpholine, or other solvents?

Udex unit uses Tetra Ethylene Glycol as solvent. The Udex performance w.r.t. corrosion was not so high initially after revamp, but we started experiencing severe corrosion from 2008 onwards in stripper reboiler, severe thinning of stripper bottom tray panels and unit had to be shut down repeatedly in 4-5 months interval for attending reboiler leaky tubes till M&I shut down was taken up.

(2011) Question 40: Are there instances where mercaptan treatment of refinery gasoline or naphtha streams is necessary? What are the applicable treatment methods?

As mercaptans are sulfur-bearing compounds, they are one among numerous target species for sulfur removal from naphtha or gasoline streams to meet reactor feed or finished product sulfur specifications.

(2011) Question 45: What tools are you using to predict the yields of Xylene, Benzene, Toluene and other aromatics in a catalytic reformer? What methods do you use and how often do you test the feedstock for these variables? Other than feedstock quality, what factors are you accounting for in the individual yields (unit pressure, RON, etc)? Do you have any rules of thumb for conversion of certain species of aromatics?

Dedicated simulators are run for prediction, either using correlations or kinetic models. To be able to perform accurate predictions, feed analyses shall be performed every time the feedstock quality is changed: the most important one is detailed hydrocarbon analysis by gas chromatography (for instance Carburane).

(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.

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