Filters

(2016) Question 18: The increased production of light straight-run (LSR) from crude units is likely to have an impact on refiners’plans for Tier 3 compliance. What strategies do you employ in order to manage this issue?

Tier 3 drives hydrotreating of essentially all light naphtha streams. Since most United States refineries have FCCs, it is usually desirable to hydrotreat other gasoline streams more completely to minimize the FCC naphtha olefin saturation and the associated octane loss
Read more

(2016) Question 20: When is it appropriate to neutralize austenitic stainless-steel equipment to protect against stress corrosion cracking (SCC)? What neutralization procedures and methodologies do you recommend?

Austenitic stainless steels (200-and 300-series steel) are the most common type of stainless steels. Austenite refers specifically to the geometry of the steel (face-centered cubic crystal). These types of steel are most typically recognized as non-magnetic. Austenitic steels are widely used in the industry because they have very desirable mechanical properties. Their austenitic structure is very tough and ductile down to absolute zero. They also do not lose their strength at elevated temperatures as rapidly as ferritic iron base alloys.
Read more

(2016) Question 21: What programs or systems do you employ to monitor hydrotreater furnaces and prevent tube failures and loss of containment? Can you share your experiences using technologies to implement online temperature monitoring of tube skin temperatures?

In nearly all hydroprocessing heaters, MPC has installed tubeskin thermocouples in order to provide continuous monitoring of tube metal temperatures to the DCS (distributed control system) operator. These thermocouples are strategically located in the heater at the areas with the highest estimated maximum heat flux.
Read more

(2016) Question 22: Describe your strategies for optimizing the pretreat and cracking catalyst cycles. How does this strategy vary when operating between maximum naphtha and maximum distillate modes? How does this impact catalyst selection for the next cycle?

Marathon Petroleum Company has adopted the philosophy of optimizing the hydrotreater and hydrocracking catalyst together as one unit. We do not measure nitrogen slip from the hydrotreater section, but rather allow the hydrocracker apparent conversion dictate adjustments to the pretreat section.
Read more

(2016) Question 23: How do you operate mid-distillate selective recycle hydrocracking units to generate more naphtha while minimizing fuel gas/liquefied petroleum gas without catalyst replacement?

Maintaining flexibility to make gasoline versus ULSD (ultra-low sulfur diesel) is very important to most refiners today due to the volatile nature of the market. Understanding the economic goals of your process unit and building in the flexibility through your catalyst selection process is the best way to set up your process for flexibility in the coming run.
Read more

(2016) Question 24: How do you manage reactor maldistribution once identified?

Reactor maldistribution is a phenomenon that is typically caused by inadequately designed or installed reactor internals, improperly/unevenly loaded catalyst bed, catalyst migration from an upstream bed, or process fouling. The main problems generated by flow maldistribution are the overuse of part of a catalyst inventory and the formation of hot spots, which can create a process safety risk, as well as limit the performance of the cycle.
Read more

(2016) Question 25: For refinery complexes considering grassroots or brownfield expansion of gas oil conversion capacity, what are your typical capital expenditure (capex) costs and relative refinery margin improvement between FCC (fluid catalytic cracking) and hydrocracking? What are the key technology features that impact your economic decision? What are the crucial considerations that, if they include both technologies, to allow for future integration, especially around the changing gasoline/diese

In general, Marathon’s economic viewpoint is that hydrocrackers have better projected margins going forward than FCCUs, as they maximize higher valued ULSD over gasoline and have higher volume expansion (see Figure 1). This is driven by many factors mentioned in the primary response and is particularly attractive when ULSD is strong relative to gasoline and when natural gas or hydrogen) is inexpensive. Each company has a different viewpoint on this topic, so the opinion will vary somewhat across the industry.
Read more

(2016) Question 26: We are interested in minimizing our black oil production from the FCC by recycling heavy cycle oil and/or slurry to our FCC feed hydrotreater for aromatic saturation and further cracking. Do you have any experience with this operating mode or recommendations for reduced slurry make via optimization of an FCC pretreat unit?

Limiting the discussion to HCO, if phenanthrene or anthracene are hydrotreated, one ring readily saturates and a second ring is relatively easy to saturate. A three-ring aromatic with one terminal ring saturated readily opens the saturated ring in an FCC riser, which makes a diesel boiling range diaromatic. If two rings are saturated, gasoline can be produced from this ring opening. As long as the molecule is linear (not Poly condensed), the saturated ring can enter the zeolite cage.
Read more

(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.
Read more