Q&A

(2017) Question 30: What are common mechanical defects that occur to the weld overlay material in hydroprocessing reactors? What are the most common locations for defects, and does the location play a factor in the mechanical integrity of the equipment? How do you detect and repair the defects? How often do you conduct Remaining Life Analysis (RLA) and/or Fit For Service (FFS) Assessment on critical equipment?

The common mechanical defects that occur are disbonding and cracking. Non-vanadium-modified 2¼ Cr-1 Mo material is more susceptible to disbonding than vanadium-modified 2¼ Cr-1 Mo-V material. V-modified 2¼ Cr-1 Mo has a much higher solubility of hydrogen compared to conventional 2¼ Cr -1 Mo.

(2017) Question 31: What are the potential impacts to hydrocracking units [i.e., deactivation rate, HPNA (heavy polynuclear aromatics) formation, etc.] as heavy coker gasoil (HCGO) rate/endpoint are increased?

Processing heavier and cracked feedstocks poses many challenges to the hydrocracking unit. Thermally-cracked feedstock such as HCGO, apart from being unsaturated, has relatively lower API, higher sulfur, and nitrogen content, higher proportion of C7 insoluble, and Conradson carbon residue (CCR). An increase in the HCGO distillation endpoint results in a significant increase in the proportion of polynuclear aromatics (PNA) and asphaltenes, both of which are coke precursors, which results in an exponential increase in catalyst deactivation rates.

(2017) Question 32: A) What are the variations of target efficiency that can be achieved in hydrogen plant operation? B) What are the operational factors that impact efficiency?

When discussing efficiencies, it is important to define the plant efficiency term. In most cases, hydrogen plant efficiency is measured by calculating the energy [BTU/scf (British thermal unit/standard cubic foot)] required to generate product hydrogen.

(2010) Question 89: In shifting from partial burn to full burn in a side by side unit, what has been your observed impact on the NOx emissions? What is necessary to achieve 20 ppm NOx?

Several Grace customers successfully operate with NOx emissions less than 20 ppm in full combustion without the use of NOx removal hardware in the flue gas circuit.

(2010) Question 90: Does any refiner use an on-line particulate emissions (PM) analyzer to measure PM concentration and/or particle size distribution in the flue gas? Are any of these analyzers using continuous emission monitoring systems (CEMS)? How reliable and accurate have these systems been?

Sunoco currently has a particulate matter (PM) analyzer in one location on the stack of a Wet Gas Scrubber. It is there to measure Filterable PM only, not particle size distribution. This was installed as a requirement of a local environmental permit.

(2010) Question 91: Assuming the FCCU already has a third stage separator, what are the various options you consider for further reduction of particulate emissions (PM) and what is the expected level of PM to be achieved?

The first thing to consider is the fourth stage collector. For designs that re-introduce the collected fines downstream of the expander, a fourth stage collector with fines removal and filter on the TSS underflow gas will aid in reducing PM.

(2019) Question 52: What strategies have you employed to profitably manage Tier III regulations (i.e. crude purchasing strategy, pre/post treating, FCC operational changes, sulfur reducing additives, etc.)?

Question 52: What strategies have you employed to profitably manage Tier III regulations (i.e., crude purchasing strategy, pre/post treating, FCC operational changes, sulfur reducing additives, etc.)?

(2018) Question 11: What constitutes adequate quench reserve when you process cracked feedstocks in hydrotreating units? In hydrocracking units? What if a mixture of both gas and liquid quench is used?

Maintaining control means that the dog walker – needs to be able to hang on to the dog – even if it starts to walk or run away. This takes adequate reserve strength - and an early detection and response when the dog just begins to become distracted or when we begin to feel the pull on the leash.

(2018) Question 12: Discuss impacts of hydrotreating operations required to meet Tier III regulations. Highlight the benefits and concerns of pretreat versus post treat operations including; impacts on cycle length, FCC yields, octane from post treating options, and gasoline blending.

Regulatory specifications for the gasoline and diesel pool, which are constantly evolving, have been in the forefront of refiners’ challenges in the last 15 plus years. In particular, the gasoline sulfur regulations have been a main driver for the remodeling of many refineries’ configurations.

(2018) Question 13: What factors do you consider when co-processing jet fuel in a distillate hydrotreater versus processing the jet separately (including feedstock and unit consideration)?

There are several considerations when deciding if jet fuel and diesel should be co-processed or hydrotreated separately. The most important consideration is if the jet fuel will be blended into the diesel product or if separate products are desired. The decision may depend on if you are looking at constructing new facilities or making the best use of existing equipment.

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