Q&A

(2017) Question 17: What is the importance of water content in reformer feed and recycle gas on the performance of the catalyst? What are your desired water concentrations in each of these streams?

Managing the water content in the reactive environment is critical for the overall performance of the reformer unit and catalyst. The content of water (H2O) must be controlled to allow for a sufficient quantity of hydroxyl [AlOH (aluminum hydroxide)] sites while simultaneously controlling the hydrogen chloride (HCl) levels to have the right balance of H2O/HCl to set the catalyst HCl content (Al-Cl).

(2017) Question 18: In a fixed-bed reformer regeneration, caustic is used to neutralize the combustion and chlorination gasses. How do you dispose of caustic after the regeneration is complete?

During the regeneration step of fixed-bed reformers, caustic is typically used to neutralize the regeneration effluent. Additional use of sodium bicarbonate to maintain the pH of the neutralization solution has also been utilized and is included for disposal.

(2017) Question 19: What are your Best Practices for recovering from high coke on spent catalyst in continuously regenerating reforming units?

The Honeywell UOP Platforming™ CCR regenerator is designed to burn 5 wt% (weight percent) carbon off catalyst circulating at 100% of the design rate. Most units can successfully burn off significantly more coke than design at normal operating conditions when the screens are clean and regeneration gas flow is uniform. Note that if there is screen fouling or some other condition leading to non-uniform or reduced flow, the coke-burning capacity would be reduced.

(2017) Question 20: What is your Best Practice for handling temperature excursions for hydrocrackers? Is a manual or automatic control system best?

Automatic depressuring on a “defined” temperature excursion is the procedure considered to be Best Practice and can be used to prevent the potential failure of the reactor outlet elbow or line. Automatic depressuring retrofits to existing units continues in industry.

(2017) Question 21: What are some of your typical examples of integrity operating window (IOW) types which are specific to hydroprocessing? What technique do you use to determine severity level of IOW alarms? How do you coordinate operator response to IOW alarms?

Hydroprocessing is an area that is somewhat unique in refining in the sense that it has everything that you do not want for mechanical integrity: high temperature, high pressure, and a process that can run away at both, as well as high concentrations of hydrogen sulfide and hydrogen; and just to make things fun, injection of water into the process.

(2017) Question 22: A) What has been your experience with hydrogen leaks to cooling water systems and the resulting impacts? B) What are your findings and recommendations from major associated incidents?

I have seen an instance where hydrogen leaking to a cooling water system was detected by a local VOC monitor at the cooling tower. The source was isolated as a pinhole leak at the hydrocracker unit’s makeup hydrogen cooler.

(2017) Question 23: When shutting down a reactor, what is your current Best Practice for measuring CO (carbon monoxide) in a mostly hydrogen/nitrogen atmosphere to assess the carbonyl concentration? Is the steel a potential source of zero-valence metal necessary for carbonyl formation? If so, does that cause a corrosion concern for equipment that normally operates in the temperature range favorable for carbonyl formation?

When shutting down a reactor, what is your current Best Practice for measuring CO (carbon monoxide) in a mostly hydrogen/nitrogen atmosphere to assess the carbonyl concentration? Is the steel a potential source of zero-valence metal necessary for carbonyl formation? If so, does that cause a corrosion concern for equipment that normally operates in the temperature range favorable for carbonyl formation?

(2017) Question 24: What are you doing to meet the Euro VI/BS VI/China VI fuel quality specifications for gasoline and diesel product streams?

This is a global question, so I will try to give you a broad answer. Looking at the specifications, you will notice that whether it is Euro VI, a Bharat stage VI, or a China VI, the specifications are similar with minor variations. All of them are attempting to get to the 10 ppm (parts per million) level for the sulfur while trying to reduce aromatics and olefins in the fuel. This is the general intent of all the specifications and changes happening globally.

(2017) Question 25: What is the optimum role for hydrocrackers in refineries that do not utilize or are eliminating their bottom-of-the-barrel processes due to lighter crude blends?

There have been many refiners who have either been fortunate enough to have existing assets that have allowed them to capitalize on the U.S. shale boom or who have re-tooled to take advantage of availability of shale crudes. I will go through a few case studies to show where the hydrocracking unit fits in.

(2017) Question 26: How are developments in hydroprocessing catalyst adjusting to changes in feedstock quality? Are the new developments able to cope with and provide high activity with varying feedstock severity? 

Catalyst development has focused on this very issue in its development of several of the highest activity hydrotreating catalysts in the Unity™ hydrotreating catalyst portfolio. The catalyst support is engineered to facilitate less diffusion resistance in the same extrudate size/shape class relative to its peers, but with improved interaction between the active phase and the support, leading to greater relative effectiveness for HDN/HDS/HDA and for uptake of metals like vanadium and nickel.

Find the answer to your technical question in AFPM's extensive Q&A database.

Q&A