PTQ Q1 2025 Issue

Amine treater

Dryer

Corrosion in OVHD due to HCN and NHCl formation – nitrogen & halides

LSO

Various fractionation units

Reactor euent

Sponge abs.

C3= C4 iC4 nC4

RSO

∆PC

Flue gas

Primary abs.

HCN

LCN

Feed impact on product slate Catalyst performance Deoxygenation pathways Metals tolerance

LCO

Gaso. splitter

Steam

∆PC

HCO

HCN

Debutaniser

Steam

Emulsion and foaming (amine carryover) in downstream gas treatment Acid / base reactions pH impact on scrubbers Possible further reaction of light oxygenates (gums and acids) Light oxygenates in gas separations

MCB

Air

∆PC

Steam

Feed

Injection and stability of b io- oils Free-water expansion Storage

Corrosion issues Metals/halide contaminants

Figure 2 FCC coprocessing – process and catalyst challenges

and piping and potential phase separation due to high water content. It is recommended that this feedstock be sent to an isolated feed nozzle. The licensor should be consulted regarding the need for any special modifications to the existing nozzle or the introduction of entirely new designs (see Figure 1 ). When considering bio-oils, a specially designed nozzle is necessary due to the high water content and miscibil- ity issues. The feed nozzle design and operation should account for the water-to-steam volume expansion and low temperature mixing with the dispersion steam. Bio-oils have poor thermal stability due to the high oxygen content, particularly of pyrolytic sugars present in the oils. Removing

smoke point of the FOG. Elevated temperatures above the smoke point can result in elevated total acid number (TAN), increasing corrosion concerns and dehydration reactions and resulting in biogenic carbon losses as gums and car- bon deposits in feed lines, heat exchangers, and injectors. Considerations must be made for any process component in contact with these high-TAN renewable feedstocks, with improved corrosion-resistant properties where required. One of the main objectives for coprocessing is to incorporate biogenic carbon into fuels to maximise biogenic hydrocar - bon products; switching to a catalyst system that maximises hydrodeoxygenation would be preferred. However, maxi - mising hydrodeoxygenation results in lowering the H/C ratio of the final product slate and results in higher coke and lower product value. To minimise the impact on the product slate and/or improve overall hydrocarbon yields, catalysts favour - ing decarboxylation will result in maximising deoxygenation while maintaining higher H/C ratios of the final products at the expense of lower biogenic carbon in the final hydrocar - bon product compared to hydrodeoxygenation. Dehydration and decarbonylation will result in increased biogenic carbon rejection as coke and CO (see Figure 3 ). In the product recovery section, changes in the water and process/chemical chemistry are necessary. The increased chlorides, CO and CO₂, oxygen-containing hydrocarbons, and lower pH will result in increased corrosion, emulsion, and foaming in the downstream units. This negative impact must be addressed in cooperation with the water process chemical provider. HPC When introducing renewable feedstocks to the hydrotreater, there are several factors to consider that might require some hardware modifications. First of all, the H₂ availability must be evaluated: biofeed processing requires additional

One of the main objectives for coprocessing is to incorporate biogenic carbon into fuels to maximise biogenic hydrocarbon products

water through thermal pretreatment is not feasible due to hydrolysis and decomposition of the pyrolytic sugars at temperatures above approximately 50°C. Decomposition of sugars present results in severe coking and gumming of process lines, heat exchangers, and feed nozzles. Without pretreatment operations for the stabilisation of the bio-oils by removing these sugars, the bio-oil will require separate feed nozzles to directly inject bio-oil into the FCC riser while minimising any preheating (see Figure 2 ). FOG feeds are particularly susceptible to thermal degra- dation at typical FCC preheat conditions, which is above the

PTQ Q1 2025