PTQ Q4 2025 Issue

Q How can FCC-focused refiners adapt to changing mar - ket conditions in the middle of a four-year run? A Melvin Berrios-Soto, Product Marketing Manager, Emerson’s Aspen Technology business, melvin.berrios- soto@aspentech.com FCC-focused refiners encounter shifts in market conditions, including changes in product demand, feedstock availabil- ity, regulatory requirements, and broader economic factors. Adapting to these changes may require a combination of operational flexibility and the use of industrial AI technolo - gies to support more responsive decision-making. One approach is to improve process agility through dynamic production optimisation. Technologies such as GDOT can support refiners by enabling closed-loop adjust - ments to FCC operations on a minute-by-minute basis. While traditional control systems maintain performance at the unit level, GDOT facilitates broader coordination across the FCC and adjacent units. It aligns production targets with economic drivers while respecting process constraints. For example, GDOT can optimise the production of light cycle oil (LCO) for the diesel pool by determining ideal targets for riser temperatures, feed distribution, and LCO cut points in the fractionation towers. These adjustments are made while maintaining constraints such as preheating duties and feed sulphur levels. By leveraging existing APC models, inferential variables, planning models, and reconciled process informa- tion, GDOT identifies the optimal operating point as market or process conditions evolve, enhancing responsiveness and supporting profitability. FCC units often exhibit nonlinear process behaviour, which adds complexity to model development. For instance, a small change in reactor temperature may significantly impact product yields, depending on catalyst condition and feed quality. Inaccurate or overly simplified models can limit operational agility and reduce performance under changing conditions. To address this, GDOT offers pre-trained hybrid tem- plates specifically designed for FCC applications (see Figure 1 below). These templates combine first-principles knowl - edge with machine learning to capture nonlinear dynam- ics more accurately. They help accelerate deployment and maintain robust optimisation across a wide range of operat- ing conditions, supporting consistent performance even as market conditions shift. By adopting dynamic optimisation and robust modelling strategies, FCC-focused refiners can improve responsiveness to market shifts and maintain per- formance mid-run. This approach supports more informed decision-making and helps sustain profitability in changing conditions.

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Renewable diesel

Light ends

the thumb on the scales to favour SAF. Add to that pending EU SAF subsidy schemes, and renewable diesel will likely be a secondary valuable side product. Production to maxi- mise SAF results in larger amounts of renewable propane and renewable naphtha, but their value pales in comparison to that of renewable diesel. It is conceivable that renewable propane may see a growth in value in the future. Alcohol-to-jet (ATJ) technologies are commercially emerg- ing. On-purpose SAF ATJ production units are slated to produce some 75% SAF, 7% renewable diesel, and the remainder naphtha and light ends, as shown in Figure 1 above. However, the various stages in ATJ, alcohol produc- tion, conversion to olefins, and oligomerisation, offer valu - able side stream options for green chemical production if incorporated into a process site design. Both of the main alcohols of interest, ethanol and isobuta- nol, yield butenes, including isobutene. These olefins can be converted into butadiene, a component in SB rubbers, and tri- isobutenes, which can be used as premium solvents. Whether the economics for such green chemical building blocks ever manifests in an ATJ design for SAF is highly speculative at this point. Despite a long history of more than a century, the Fischer-Tropsch (FT) process also emerges as a technology for SAF production via syngas produced from gasification of low carbon intensity forest, agricultural, and other residues. With an appropriate tandem catalyst system, the poor selectivity of the FT Anderson-Schulz-Flory product distribution can be tailored to SAF to yield about 50% jet and 25%+ diesel, with the remainder naphtha and light ends (20%+) arising from the required cracking of C 22 + hydrocarbons. Relaxing the crack- ing component can yield FT waxes, which can be hydroisom- erised to premium bio base oil lube stocks. The economics of such a scheme has yet to be demonstrated. Another valuable side product is bio-electricity generation, which capitalises upon the large exothermicity of the FT reaction, with promise showing for woody biomass feeds basis paper studies. Figure 1 Comparion of product slates across fuel con- verion pathways ( Source: International Council On Clean Transportation, 2019, Working Paper 2019-05 )

AI templates in unied GDOT

Hybrid models

Machine learning Neutral networks, Data analytics

First principles Domain expertise in Aspen HYSYS®/ Aspen Plus®

Figure 1 FCC hybrid templates are ready for use in the Unified GDOT Builder flowsheet environment

PTQ Q4 2025