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  • What are the latest advances in FCC SOx reduction, and what levels can be achieved?

    Mar-2021

Answers


  • Tom Ventham, Johnson Matthey - Intercat, Tom.ventham@matthey.com

    FCC SOx additives have been used in the industry for decades. However, it is felt that further development stalled once it proved possible to control FCC SOx emissions using catalyst additives in the majority of cases. G. W. Aru, LLC and Unicat have entered the FCC additives market with a fresh approach and commitment to critical thinking as a way to push the boundaries in understanding and provide effective, non-hazardous SOx reduction additives that give benefits back to the end-user. It is by taking an approach of integrity, innovation and value, that the range of Ultra SOxBuster® additives are now available to refiners. All patents covering core FCC SOx reduction additive technologies are expired. Working with global manufacturing partners, we have the ability to produce high quality SOx additives. Improvements in safety and performance have been implemented and additional work is in progress. Specifically, understanding health and safety aspects of SOx additives has been our primary focus. FCC SOx additives contain a vanadium component to improve SOx removal efficiency. Some SOx reduction additives report compositions which contain hazardous forms of vanadium. The safety datasheet can be used to identify presence of human health hazards related to vanadium species present. Extensive work at Argonne National Laboratories showed Ultra SOxBuster® additives, whether they are hydrotalcite based or spinel based, contain vanadium in the form of a non-hazardous reference compound.

    Further, once differences to other SOx reduction additives were observed, it was possible to relate this to disparities and improvements with in-unit results. Superior performance to the current top-selling SOx reduction additive has been seen in all commercial trials thus far. Closer inspection showed an interesting relationship between performance and retention of the additive. It is the belief of G. W. Aru, LLC and Unicat that retention characteristics are key in achieving optimum SOx control performance and minimising costs. High SOx reduction levels, up to 95-99% in full burn FCCs, can be achieved with a minimal amount of additive when using well retained additive, as have been proven with Ultra SOxBuster®. Refiners have observed SOx stack values below 5 ppm for significant periods. High-quality, non-hazardous SOx additives with superior retention properties, and a wider range of technology platforms available, means the Ultra SOxBuster® series provides refiners the best option for controlling FCC emissions.

    Apr-2021

  • Carl Keeley, Johnson Matthey, Carl.Keeley@matthey.com

    Fluid catalytic cracker (FCC) feed contains sulphur compounds. In the riser, the feed is converted to products and coke. Part of the feed sulphur deposits in the coke on the catalyst. The catalyst is regenerated in the regenerator. In a full burn regenerator, the sulphur is oxidised to sulphur oxides (SOx). In a partial burn regenerator, where oxygen availability is limited, part of the sulphur is converted to reduced sulphur species (carbonyl sulphide, for instance). Dedicated SOx additives are needed for each situation. Johnson Matthey’s R&D has developed SOx additives specifically tailored for each application.

    In full burn operation, a high concentration of sorbent is needed to capture sulphur trioxide. Johnson Matthey’s latest development has the highest concentration of sorbent available.

    In partial burn, where oxygen availability is limited, a specific oxidation package is needed to maximise the conversion of sulphur to sulphur trioxide – without disturbing the CO/CO2 balance.

    To control SOx emissions, refineries can reduce feed sulphur, use SOx additives, use a scrubber, or employ a combination of these. Refineries that have scrubbers can take advantage of SOx additives to reduce operating costs and reduce caustic consumption and waste handling problems.

    Based on the experience of our customer base, a SOx reduction level of >90% can be achieved in full burn operation. However, in partial burn operation, where oxygen availability is limited, SOx reduction is less. SOx reduction depends on the depth of partial burn (see Figure 1). The SOx reduction shown in the plot is based on SOx concentration in the CO boiler flue gas, not the regenerator flue gas.

    In addition to different regenerator types, some FCC units target maximum distillate production and operate with a low riser top temperature, for instance <950°F (<510°C). Consequently, sulphur release in the stripper is more challenging. Sulphur release is also more challenging in units with poor stripper design or performance. Johnson Matthey has optimised SOx additive release functionality to improve sulphur release in these units.

    Johnson Matthey has dedicated products for each situation and continues to develop improved products for unique FCC challenges.

    Mar-2021



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