Catalysis 2026 Issue

Processing extreme feeds in FCC units Using catalyst technology while evaluating combined feeds and optimising process conditions to maximise benefits within unit hardware and operational constraints

Hernando Salgado, Amitkumar Shah, and Myrlla Galdino R S S Machado BASF

F luid catalytic cracking (FCC) units are character- ised by their capability to process a variety of feeds within the refinery, as well as feeds with varied chemical composition, which is highly dependent on the crude slate processed by the upstream crude units. Thus, refineries with FCC units have a great degree of flexibility to process diverse crudes, especially so-called opportunity crudes. These can originate internally from upstream crude units or be procured externally from the market to maximise refining margins. In addition to increasing margins, a con - stantly shifting global landscape has made this ability to quickly adapt to new crude sources particularly important in recent years. Figure 1 shows the range of feeds that FCC units typi- cally process. These feeds range from various gas oils and resids to internally recycled streams, and even the more recent practice of co-processing pyrolysis oils from sources such as plastic, municipal waste, and biomass. FCC units have often been called the refinery ‘garbage bin’ because they even handle slop streams. This article will focus on processing extreme hydrocarbon feeds originating from typical refinery configurations. What is an extreme FCC unit feed? Any feed to an FCC unit can be called an ‘extreme feed’ when the processing of such feed poses immediate and severe challenges to normal FCC operation by adversely impact- ing product yields/quality, catalyst quality, unit operability,

feeds, normal FCC feed can turn into extreme feed due to a sudden deterioration in its quality. However, the amount of a specific feed an FCC unit can process depends on several factors, such as feed properties, unit design/hardware, cat - alyst used, operating conditions, product yield, and quality objectives. The quantity of extreme feed processed in an FCC unit is restricted by the severity of its impact on normal unit operation and unit constraints. Examples of the most com - monly seen unit responses and constraints are a sudden drop or increase in conversion, increases in bottoms or dry gas yields, a drop in gasoline Research Octane Number (RON), increases in equilibrium catalyst (Ecat) metals impacting activity, regenerator temperature swings, air availability limits, catalyst circulation swings, wet gas com - pressor capacity limits, main fractionator pressure drops, and intense fouling. Hence, it is extremely important to characterise the FCC feeds to provide engineers and planners with sufficient information to predict and assess feed impact on product yields and quality. They can then adjust FCC unit operation accordingly to maximise its economic benefit. In addition, well-planned characterisation allows for an understand- ing of the impact on catalyst quality and helps determine whether the current catalyst is optimal for such an opera- tion or needs to be reformulated. Some of the most impor- tant feed properties to consider include: • API or specific gravity.

reliability, or hardware issues within the FCC unit itself and across downstream units such as the alkylation unit and gas recovery system. Feeds with very high levels of contami- nant metals, Conradson car - bon residue (CCR), sulphur, nitrogen, aromatics, and/or a very high distillation end point can be considered extreme feeds, depending on the specific impact they have on an FCC unit, leading to con - strained operation. When a refinery processes low-cost but low-quality opportunity crudes or exter - nally purchased supplementary

Atmospheric distillation

ATB VGO CGO DAO

Cat feed hydrotreter

Crude

AGO

LSVGO

ATB or AR

UCO

Hydro- cracker

CGO

VGO Resid

Coker

Vacuum distillation

VGO

Purchased feed

DAO

Slurry HCO/LCO

Recycle streams

VTB or VR

DAU

Slops

Co-processing

Figure 1 Typical streams processed in FCC units

Catalysis 2026