Refining Community Logo

Reply To: FCCU Severity

Home Forums CatCracking FCC Process FCCU Severity Reply To: FCCU Severity

#27753

Paul R Orlowski
Keymaster

Solly Ismail
Salvatore, While you make an excellent point, UOP K also has its limitations. The 90% point is very important. It only shows up indirectly in the UOP K factor. In fact most heavy feed stocks do not vaporise and that s why all the Ni is deposited on the outside edge of the catalyst.

Catalyst companies use smoke and mirrors techniques by telling refineries they have large pore which allows the heavy portion to diffuse into the interior. Then why is all the nickel deposit on the outside edges. The liquid portion of heavy is drawn into only a short distance into the catalyst by capillary action.

I agree the UOP is important but so is the 90% point.

The ultimate driver of catalytic cracking in FCC is the hydrogen content in the feed. High UOP K means higher higher hydrogen. Higher hydrogen is found in paraffinic stocks. These are easily crackable. The worst is aromatics. Aromatics stocks are very stable and do not crack under FCC conditions. They need high H2 partial pressure.

———————-
Salvatore Mannello
For straight run Vacuum Gasoil or HDT feed, density and UOP K tell just enough for the first approach to a FCC feed quality. If in the feed mix there is also some Residue, the simulated distillation is more suitable for the VABP (and CABP) calculation in the UOP K: refineries now have this approach, being D-86 and D-1160 distillation not always applicable, as Solly said. Aniline point analysis is good, fast and reliable, for feed characterization, but for dark feeds, sample needs dilution and operator high attention; nowadays some refineries don’t run any more. Refractive index is among the most used for FCC feed characterizations: needs four decimal digits. There are also other indirect indications: hydrogen content is one, and it is excellent; it is very good to trend in an every single refinery, unless we are in agreement on the calculation method (Total?).
Talking about FCC unit optimization first we need at least this information: feed quality, objectives and unit type hardware.

———————–
Solly Ismail
Excellent Salvatore! You have nailed it. The most important by far for optimizing the FCC unit is unit is the Feed Quality. Then comes operation conditions and lastly catalyst selection.

While catalyst selection is important, make no mistake, it is more important what is going into the unit, than from whom it is supplied. Catalyst quality supplied to refineries varies greatly and quality supplied is not always what was initially agreed on. For example, there was long standing anecdote, that FCC catalyst supplied by the Chinese was inferior. Then during the Rare Earth Crises during 2010 to 2012 , several refineries bought catalyst from the Chinese. When we analyzed the FCC catalyst from the Chinese was excellent! It had low attrition, comparable selectivity, and much lower cost.

Catalyst suppliers often say each FCC is unique and then go on to say how good their catalyst in other refineries, meaning that it will just as well (FCC unique!) in yours.

Does anyone know of objective technical analysis provided by catalyst company A which states that FCC catalyst from company B is better suited for the given unique operation?

————————
Paul Orlowski
Hoekstra Trading offers independent catalyst testing according to this presentation: https://refiningcommunity.com/presentation/pushing-the-limits-of-fcc-gasoline-desulfurization/. For more FCCU presentations on catalyst go here https://refiningcommunity.com/past-presentations/ and type in catalyst

Refining Community