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Process and Operations

Rerunning slurry to FCCU as feed

What are the advantages and disadvantages for rerunning slurry to FCCU as feed. I realize that slurry would likely not crack due to high aromatic content. Would increased coke be a concern?  Response: The biggest negatives from recycling slurry to the reactor are increased coke, which is reduced air availability from the main air blower (MAB; this also translates into higher regenerator temperatures, which decreases conversion) and increased dry gas, which translates into reduced wet-gas compressor (WGC) availability, (which can reduce unit conversion or throughput if the unit is WGC; limited). The expected yield... more

Overcoming butylene deficits

Refining investment in alkylation expansions and gasoline octane improvement include production of additional feedstock for the alkylation unit. The primary source of olefin feedstock for the alkylation unit is the FCC unit. Operating conditions in the FCC unit can be adjusted to favor increased propylene and butylene (or butene) production. BASF recently announced the availability of a new FCCU additive designed for butylenes selectivity. According to BASF, its proprietary Evolve FCC additive provides measurable improvements in butylene yields while preserving unit conversion and valuable fuels yields. With alkylate becoming a... more

Antimony passivation of E-cat nickel

Issue When should we consider the use of Antimony for Nickel passivation? Background Please see comment below from latest service report. The antimony chemical remains off. The E-cat nickel level has stabilized and even come down some (955 ppm on 8/19/09 vs. 858 ppm on 8/28/09). The E-cat vanadium level has also come down a little (1534 ppm on 8/19/09 vs. 1488 ppm on 8/28/09). Question Do you have a guideline on a H2/CH4 ratio or ECAT metals level in which you think we should absolutely put the antimony back... more

Does your FCC have “Sticking” Slide Valves?

All FCC units are designed with slide valves on catalyst transfer lines. In some units these are used continuously for controlling catalyst flow, while in others they are used only in Startup, Shutdown, or Emergency situations. Whatever their application, these valves must operate reliably in the service for which they are intended. In control applications, it is obviously important that slide valves operate with good response characteristics. In emergency applications, it is usually critical that the slide valve(s) close when required to do so, to permit discontinuing feed charge to... more

Avoiding Octane Deficits in Tier 3 Markets

BASF’s Melissa Clough noted in her presentation during the RefComm® refining conference FCC session on Wednesday that 90% of sulfur in gasoline is derived from FCC gasoline. This condition has been dealt with by refiners for at least the past five years. Clough added to this narrative that in 2011, only about two countries were meeting 10 ppm sulfur limits in their gasoline pool. Now most countries are close to achieving the 10 ppm sulfur limit, but that milestone comes at a heavy price. Not only has sulfur been significantly... more

Ni Passivator

Ni, as a dehydrogenation element, generates Hydrogen and coke. There are several types of Ni passivators. The first are ultra-fine particle metals added to the feed injection system, employing a fluid such as diesel or LCCO as the carrier medium. These ultra-fine particle metals are Antimony (Sb) and Bismuth (Bi). These metals work by permanently attaching to the Ni. The Sb or Bi that have formed this attachment reduces the surface area of the Ni exposed to the process, reducing the H2/coke forming tendencies. In other words, the Sb or... more

CatCracking Process

The FCCU is widely used to convert the high-boiling hydrocarbon fractions of petroleum crude oils to more valuable gasoline, olefinic gases and other products. At the Citizendium you can learn more about reactor and regenerator, distillation column, ergnerator flue gas, chemistry, catalysts and history. These are the major FCC designers and licensors: CB&I Lummus ExxonMobil Research and Engineering (EMRE) Shell Global Solutions International Stone & Webster Engineering Corporation (SWECO) / Institut Francais du Petrole (IFP) Universal Oil Products (UOP) Kellogg Brown & Root (KBR)... more

Why do I have Afterburning in My Regenerator?

“Afterburning” is a term that is used to describe abnormally high temperatures that occur in the dilute phase, cyclones, or overhead line of an FCC regenerator. This phenomenon is also referred to as “post-combustion”. Basically, afterburning is the result of combustion in the flue gas leaving the dense bed, of CO that is leaving the bed unburned, with excess O2. Ideally, in a full-burn regenerator, all the carbon in coke is burned essentially completely to CO2, with only a trace of CO remaining in the flue gas. However, many regenerators... more

Implications of using “Torch Oil”

“Torch oil” is a term which is usually applied to a gas oil that is burned in FCC regenerators, to supply necessary heat requirements during startup, shutdown, or feed-outage conditions, when coke is not being produced in the reactor. It is injected usually through special nozzles which discharge into the dense catalyst bed of a regenerator. Requirements for Torch Oil Lightoff Almost any gas oil can be utilized as torch oil to an FCC unit. However, it is essential to ensure that the oil lights off properly when injected. Torch... more