The Onus on many FCC units operations is to increase propylene yield, while others are tasked to deal with vacuum gas oil deficits. It’s no secret that FCC units are getting bigger. A historical trend can be seen over the past 10 years indicating average unit capacity has increased from about 60,000 bpd to 120,000 bpd, due to economies of scale. In the process industry, the higher the processing capacity, the more economical it becomes to operate the processing unit, which in this instance is the FCC unit. More importantly, the FCC unit built today is expected to provide more monetization capability than previous generations of cat crackers.
About half of the FCC units built over the past 10 years are actually resid FCC units that can produce a minimum of 9.0 wt% propylene, and can be effectively upgraded to yield 19 wt% propylene, which is what a lot of refiners are currently trying to achieve with their units, as they link up with downstream petrochemical infrastructure. For example, Technip Stone & Webster has licensed close to 12 deep catalytic cracking (DCC) units with one of the objectives being to maximize propylene production in the form of refinery grade proplylene, chemical grade propylene and polymer grade propylene (PGP).
“Older” FCC units can also be cost effectively upgraded to increase propylene yields from (let’s say) 4.0 wt% to 8.0 wt%, with new catalyst formulations and some modest equipment upgrades. However, there’s another compelling reason for the re-emergence of cat cracking at a time when other high conversion technology is taking center stage, such as hydrocracking (for increasing distillate yields) — that is the monetization of fuel oil.
New regulations will no longer allow the use of fuel oil and resid in most marine transportation markets, so cat crackers have to be there to add value to these displaced heavy fuels. To meet stringent emissions requirements, merchant marine vessels are transitioning to diesel, so the heavy fuels (e.g., high-sulfur fuel oil, resid, etc.), after some hydrotreating, will be upgraded in an FCC unit or perhaps a coker. Actually, Exxon Mobil is building a $1.0 billion delayed coker in Europe to process resid, with the heavy coker gas oil then fed to either a hydrocracker or an FCC unit.
To be sure, it will also be interesting over the next year or so to ascertain how FCC units in the US are going to balance the overflow of light domestic sourced feeds at the expense of vacuum gas oil (VGO) feedstock. For some refiners, access to waxy paraffinic shale feedstocks provide an effective substitute for VGO feed deficits. For other FCC based refiners, the VGO deficit conundrum will be an interesting story to follow going forward.