The sulfur block is a very mature technology. There have been few new developments to optimize operations. Optimizing operations of a sulfur plant can indicate an increase of sulfur production while reducing all related sulfur emissions. Some of the new developments in a sulfur plant consist of catalyst-burner design, dip leg improvement, upgrade of ferrule types, oxygen enhancement, oxygen enrichment, TGU developments, and increase in safety stewardship.

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.

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. 

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. 

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?

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.

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.

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.

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. 

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.