Below is an excerpt from some of the submissions by Becht in the recent PTQ Q&A.
Participants from Becht were: Mel Larson, Jeff Johns, Jeff Kaufman, Stephen DeLude, Gene Roundtree
In building the petrochemical value chain, how much further can we see the FCCU being used to increase olefins production with the wide range of feedstocks currently available, including waste plastics derived pyrolysis oil? Mel Larson
The answer is less about “how much further” rather shifting the fuels plants only, where the location allows, to more sustainable Petrochemical feed stock provider. Today the FCC plays a dual role of both fuels and petrochemical provider. As the transportation fuel demand declines, both the reformer and FCC operating modes will shift directionally to BTX, Styrene, Olefin market demands. The next step which is already in deep R&D analysis is how to adjust the FCC to more of a “crude to chemical” engine in a “single” unit as compared to other technologies. The FCC operation of the future may include more recycling of product back through additional catalytic / thermal processing steps than is currently practiced. Additionally if the rules change the FCC will be the location where Synthetic oils can be cracked with the potential addition of partial burn and hydrogen for further circular value of the unit. This last point may be decades off, however the system and infrastructure is already present with selected additions to move in this direction.
Considering the range of petrochemicals used crosswise for preparing a wide range of marketable products, including textiles, detergents, adhesives, antifreeze, solvents, pharmaceuticals, etc., what state-of-the-art catalysts are emerging for production of petrochemicals such as styrene, polymers, aromatics, etc.? Mel Larson
Both the Petrochemical catalyst vendors as well as traditional oil catalyst vendors are actively investing catalyst types to improve the selectivity for the specialty market. However, in the Petchem market its not a catalyst only issue, it’s the processing configuration. In the petrochemical systems the feed stocks are in general purified prior to the reaction steps to optimize size and maximize yield value. In the refinery systems the yields are not pure and span a wider array of reaction products mixed within a given yield stream. Therefore, though yield selectivity may, on the margin, improve for example olefin yield, this shift will not change the need for the purification steps necessary for the final product demand.
Maximizing cycle duration of hydroprocessing units has always been important to refiners, but what other step-out gains can we see from catalyst developments in terms of volume swell, PNA saturation, and HDN activity while achieving high HDS performance? Steve DeLude/Jeff Johns/Jeff Kaufman
Catalyst activity improvements over the years have allowed operators to pursue various options to improve profitability and operating flexibility. While increasing cycle length and reducing the annualized shutdown cost can be significant, most refiners find that increasing throughput (debottlenecking), processing more difficult feedstocks, changing feed fraction cutpoints (yield optimization), modifying operation to improve blending flexibility (improved product quality through higher hydrogenation), and/or higher volume yields offer better overall value than simply pursuing a long cycle length strategy.
Catalyst vendors have pursued multi-catalyst systems and new modeling techniques to be able to tailor catalyst loads to specific refinery objectives. This situation makes it very important for the refiner to discuss in detail with potential catalyst suppliers their preferred operating strategy, feed options, and product quality improvement opportunities when considering their next reactor catalyst load.
Besides improved catalyst systems, what advances in reactor internals are improving efficiency and throughput while also mitigating the effect of fouling, catalyst poisons, etc.? Jeff Johns/Jeff Kaufman / Stephen DeLude/Gene Roundtree
Improved understanding of feed quality, improved reactor, and improved modeling of flows through reactor systems (CFD modeling) have allowed licensors and catalyst vendors to improve their internals and tailor their catalyst systems.
Improved feed filtration systems reduce particulate and fouling on top catalyst beds.
Improved distribution trays / internals and improved quench mixing allows better utilization of loaded catalysts and reduces the risk of partial bed bypassing and/or hot spot formation. These increase the potential operating range for the reactor.
In addition, the best new internals designs are taking up less space (allowing more room for active catalyst) and they are designed for easy assembly and disassembly reducing unit downtime during a turnaround and catalyst replacement.
We also note that when new internals are installed in existing reactors, the upgrade should also strongly consider new bed Tis for better temperature control and reactor monitoring.
Finally, graded / tailored catalyst loads including specifically designed materials for fine particulate and/or maximum metals trapping allows sustained operation with high catalyst activity and reduced fouling/pressure drop.
What hydrocracking reactor catalysts are demonstrating optimal middle distillate selectivity, better yield structures, and more efficient use of hydrogen? In combination, which of these catalyst systems seem to be the most flexible in adjusting to feed quality variations and heavy feeds such as DAO and HVGO molecules? Stephen DeLude / Jeff Kaufman
Becht’s SMEs are aware that many catalyst suppliers are developing catalysts that are focused on reduced gas make, higher selectivity to middle distillates, improved final product properties (such as cold flow and cetane), and/or improved hydrogen use efficiency. Catalyst optimization becomes a greater challenge when also combined with processing more difficult heavier feedstocks such as DAOs and HVGO streams. With these heavy streams, the ability to maintain high catalyst activity for HDS, cold flow improvement, and/or cetane boost may be compromised by catalyst poisoning / coke deposit formation / pore mouth plugging.
The refiner must work closely with the catalyst supplier to identify the best catalyst option (including multi-catalyst systems) for their unit and specific objectives while recognizing feed variations and/or quality constraints.
What are some of the optimal strategies for processing (or co-processing) 2nd and 3rd generation renewable feedstocks? Steve Delude
The optimal strategy is dependent on each site’s specific configuration, level of exposure to GHG emission related costs (penalties) and/or biofuel production incentives, the logistical considerations related to the available biomass feedstocks, the cost of the feedstock, and corporate capital availability/investment hurdle rates.
The mandates of the Paris accord established requirements for carbon intensity and greenhouse gas emission reductions that impact energy firms, regional / national governments, and investors. As part of the transition to lower emissions, traditional fossil fuel-based transportation fuels will be substituted by a combination of electric vehicles and bio-derived and renewable fuel sources. Existing refining and petrochemical assets are seen as key infrastructure in the energy transition equation, as much of the existing processing and distribution infrastructure can be repurposed for this new reality. This change in the marketplace will drive traditional refiners to examine processing and configuration options to align to the new feedstock and product profile as well as energy input options. Those entities that are able to meet the changes in this dynamic market, while remaining profitable, will continue as long term viable enterprises.
Biofuel related strategies seen in the industry range from:
- Full biofuel integration with dedicated biofuel units providing fully fungible final product blend components
- Partial integration and co-processing approach with biofeeds brought on-site and pretreated adequately to match with the site’s existing units.
- 3rd party pretreatment arrangement or dedicated own facility with feed specifications strictly monitored to ensure meeting co-processing/blending requirements
- Purchase of biofuel blend components via open market
- Purchase of GHG offsets from other entities
Finding an optimal strategy requires fully analyzing each specific situation and identifying the range of options that could achieve the desired business goals.
The progression of biofuel processing technologies from the current level to those in development are more catalyst related than process. The steady progression of catalyst advancements have improved hydrogen selectivity and isomerization to final products. As catalyst technologies further improve, the opportunities exist for processing more challenging feedstocks and moving from biofeeds that are in competition with food sources to those which are non-edible. Europe’s Annex IX describes some of these biofeeds with consideration being given to the use of nonedible cover crops using nonfood producing lands. The changing feedstock quality imposes increasing levels of contaminants and lower carbon contents. Processing these feeds requires consideration of how to remove the contaminants (including water) and capture the maximum amount of hydrocarbon products.
The future transition to these new feeds requires consideration of thermal pretreatment processes linked with refinery post treatment to make fungible fuels. (See Sayles and Ohmes, Conversion to a green refinery,” Decarbonization, Q4, 2022 for additional details). Refinery configuration and biofeed considerations determine the ease of integration. In general, more complex refineries offer greater opportunities for biofeed integration.
In conclusion, the consideration of co-processing is dependent on the refinery configuration, feedstock selection, catalyst application, and location. Optimized process designs are just one aspect of the overall solution with biofeed supply logistics very often as the overall controlling factor determining the most attractive co-processing opportunity.