By Todd Foshee, FCC Licensing Technology Manager on Apr 19, 2022
In regions like the Asia Pacific, refiners are increasingly operating their fluidised catalytic cracking (FCC) units at higher conversion for higher propylene yields. Many refiners are seeking to have more propylene product to feed to chemical plants for making more plastics. This differs from the past when FCC units were primarily used for producing mainly gasoline along with other transportation fuels. As a result, refiners are seeking the best and most cost-efficient ways to increase propylene make in their refiners, either by revamping existing FCC units or by building new FCC units. In many cases, refiners are looking to convert the heaviest resid feeds into propylene.
In this interview, Todd Foshee, FCC Licensing Technology Manager, shares insights behind Shell Catalysts & Technologies’ (SC&T) R&D that drove advancements in feed nozzle technology. He discusses Shell’s integrated approach when looking at pre-treat and FCC units to provide holistic strategies on how to increase performance and improve margins.
On Thursday, 21 April 2022, Todd Foshee will be joined by moderator Daniel Shiosaki, Market Specialist Refining, to discuss this new feed nozzle design and answer questions.
1. Why is this advancement in feed nozzle design significant for current customer challenges?
Todd Foshee: The typical refiner already operates against a number of constraints, which can include air blower, wet gas compressor, regenerator temperature, or catalyst circulation limits, to name a few. The refiner is usually operating against more than one constraint, so there is little or no room for the refiner to move to higher conversion or a higher propylene yield without changes to the unit.
By upgrading the feed nozzles technology to Shell max atomisation feed nozzles, refiners can gain flexibility in their FCC unit operations where they previously were constrained. The additional unit flexibility can then be utilised to reach a higher conversion, go to a higher severity, increase feed throughput or some combination of these. This is possible because Shell’s feed nozzles atomise the feed more completely, drastically reducing the liquid volume in the spray that forms liquid strands and globules. As a result, Shell’s feed nozzles reduce the amount of feed that goes directly to coke and increase the yield of desired products from the feed. Shell has implemented their latest feed nozzle design in a number of Shell, joint venture and third-party sites, and the improvement in unit performance has been dramatic, while the capital cost to implement the new feed nozzles has been relatively low.
Shell also builds reliability into their feed nozzle design through the use of a protective shroud which shields the feed nozzles from the highly erosive environment of the riser. Because of this, Shell feed nozzles are able to have high performance, with little to no decline in yields, through the entire run of the FCC unit, which for most units is around five years.
2. Could you share some insight into the R&D?
Todd: Shell Catalysts & Technologies is one of the few licensors that still has an active and robust R&D program, pilot plant and other test facilities, which includes a feed nozzle testing area. In addition, Shell regularly upgrades the analytical capabilities in our R&D facilities to facilitate our ability to improve Shell FCC technology. In the early- to mid-2010s, Shell upgraded the feed nozzle testing analytical equipment to include shadowgraph particle image velocimetry (PIV), and shortly thereafter, was able to use this new analytical capability to find areas for improvement that resulted in the Shell latest advancement in feed nozzle technology.
In the past, we used techniques like phase doppler or laser diffraction to identify droplet sizes within spray, but these methods only identified spherical droplets and left other liquid shapes unidentified and hidden from analysis. By contrast, shadowgraph PIV takes high speed pictures of the spray and is able to identify non-spherical liquid shapes, which resulted in the discovery of whole regions of the spray that were previously unidentified. These unatomised pieces of liquid come in the form of big globules and strands. After using PIV, we noticed that the globules and strands could make up a significant portion of the spray. Once identified, we made improvements to our feed nozzle design to reduce the amount of unatomised liquid in the spray by about 50%. The result is not just better spray atomisation, but a more complete atomisation of the spray.
3. Why should a refiner consider Shell feed nozzles?
Todd: Many other licensors will promote their feed nozzles’ great atomisation capability and reference the Sauder mean diameter of the spray produced as a representation of the atomisation capability of their feed nozzle design. What we found through our R&D efforts is that just looking at the Sauder mean diameter through older techniques like phase doppler and laser diffraction does not provide the complete picture because the non-spherical liquid content gets ignored. At Shell, we’ve focused our feed nozzle improvement efforts on reducing the unatomised liquid content of the spray, and by doing so, have created a feed nozzle design with significant improvement in performance.
In addition, Shell is the only FCC licensor that not only has R&D capabilities, but also operates FCC units with their own technology. This allows Shell to design FCC technology, implement and operate that technology, then accumulate data and provide feedback to our design and R&D teams for continuous improvement.
Finally, because Shell has expertise and technology for a wide range of operating units, Shell is able to draw upon this diverse knowledge base for integrated solutions that can maximise margins and reliability across units. An example of Shell’s integrated approach is highlighted by Shell’s ability to provide an optimised technology offering for both the FCC pre-treat and FCC units together, by working across Shell technology teams and with the refiner, to deliver fit-for-purpose technology for both units that maximises the benefit to the refiner.
Whereas many licensors offer technology to the FCC pre-treat or FCC units individually, Shell has found that you have to look at both units together for the best result. Otherwise, technology can be implemented in either the FCC pre-treat unit or FCC unit that may improve operations for the individual units, but not deliver the best overall result across both units and to the refinery as a whole. For the FCC side, Shell’s max atomisation feed nozzles are a key piece of technology for the integrated solution of the FCC pre-treat and FCC units. As previously mentioned, Shell’s feed nozzle technology provides flexibility in the operation of the FCC unit, through better and more complete atomisation of the feed, that can be taken advantage of in different ways – either directly paired with FCC pre-treat technology for even better FCC conversion and yields, or utilised to reduce FCC pre-treat severity at a similar FCC conversion for longer FCC pre-treat cycle length.