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How can the FCC unit be upgraded to benefit petrochemical integration?

Feb-2025

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Fu-Ming Lee, Shin Chuang Technology Co Ltd, fmlee@shinchuang.com

To further upgrade the FCC unit for enhanced petrochemical integration, refiners can leverage a variety of advanced catalysts and technologies, including Magnetic Advanced Filtration System (MagAFS) and drop-in FCC catalyst additive solutions. The following case summary focuses on a technology aimed at slurry oil (SO) upgrading. SO is one of the major FCC unit products, but with low quality and very limited applications, mainly due to its significant content of small catalyst fines (3,000-6,000 µg/g).

Worldwide SO production from FCC units is huge in quantity. For example, even 25 years ago, FCC units in China alone generated 5 million tons of SO annually. Therefore, the potential benefits of upgrading SO for petrochemical and fuel applications are substantial.

Small catalyst fines, mostly smaller than 20 µm (10-6m), in SO are extremely difficult to remove. Conventional methods, such as gravity sedimentation, centrifugal separation, filtration, and electrostatic precipitation, are ineffective for fines removal, especially nanometer size (nm, 10-9m) particles. The development of an effective process for removing catalyst fines from SO to upgrade its quality to transportation fuels and improved petrochemical applications is not only profitable but also environmentally preferred.

MagAFS technology has been developed to remove particles larger than 50 nm. The tests were conducted in a lab UMF unit consisting of two magnetic filtration chambers connected in series. Typical compositions of the tested SO are listed in Table 2.

SO was fed through the lab unit at a controlled flow rate. Treated SO samples at the exit of the first and second chambers were collected for particle size distribution (PSD) analysis. Samples of solid particles removed by the first and second chambers were also collected for PSD analysis. Focusing on the nm size particles, PSD of the original SO (SO-O), treated SO (SO-1), and duplicate treated SO (SO-1A) are given in Figure 1. It shows that with original SO (SO-O), more than 64% of the solid particles were larger than 6,000 nm (or 6 µm). Only particles smaller than 44.3 nm were left in treated SO (SO-1). The result was confirmed by PSD in the duplicate treated SO (SO-1A).

Further details of the operation are revealed in Figure 2, where SO exiting the first chamber contained mainly 6-500 nm particles, but still had 20% 6,000+ nm particles. SO exiting second chamber contained only 9-44 nm particles (no 6,000+ nm particles). Most larger particles (2,600-6,000+ nm [63.3%]) were removed by the first chamber. Smaller particles (800-6,000+ nm [33.4%]) were removed by the second chamber. Figure 3 compares the PSD of the original (SO-O), treated (SO-1), and duplicate treated (SO-1A) slurry oil, based on the analysis of all samples collected from the experiments.

The result confirmed that any solid particles having a size larger than 50 nm (44.3 nm) were successfully removed from the slurry oil by MagAFS process technology. It is also possible to provide low-cost and convenient on-site testing by installing a small portable MagAFS unit through a slip-stream connection without disruption to normal FCC unit operations.

Jan-2025
Carel Pouwels, Ketjen, carel.pouwels@ketjen.com

For petrochemical integration, the maximisation of light olefins by the FCC unit is essential. Within a given unit configuration, the first choice is to enhance process conditions that maximise unit severity. Maximising reactor outlet temperature is one of the first independent process variables to consider; preferably, the temperature is enhanced to the range of 545-550°C. More extreme process conditions can be applied when the FCC unit is upgraded to so-called ‘high-severity’ FCC units, whereby reactor temperatures up to 600°C are possible.

Depending on the metallurgy, a revamp might be needed. Due to the increased dry gas and LPG production, the refinery needs to address the wet gas compressor handling too. If not yet present in the current downstream configuration, the refinery needs to expand with deC2, deC3, and deC4 recovery units while also building a C₃ splitter to make chemical-grade propylene.

Next to the enhanced severity by a higher reactor temperature, conversion can also be enhanced by increased catalytic cracking reactions through more catalyst circulation (or cat-to-oil ratio). Consequently, more gasoline molecules are generated, which can be cracked to light olefins. Note, however, that hydrogen transfer reactions will also increase and can negatively impact C3=/LPG. The key to a high olefins yield is control of the various competing reactions. Hence, the reduction of hydrocarbon partial pressure through enhanced dispersion and lift steam is also of importance. This way, light olefins are preserved, and reactions to paraffins by unwanted hydrogen transfer are minimised.

While dedicated unit hardware and process conditions for high-severity operations are needed, the third element of importance is the FCC catalyst that is optimised for such application. While every FCC unit with its specific feed is unique, it thus requires a unique catalyst solution, preferably from a repository of expertise with a wealth of industrial experience in high-severity FCC applications, ranging from the lightest to the heaviest feedstocks. With decades of supply to various FCC units of all licensors, Ketjen’s max propylene catalysts AFX and Denali AFX with optional usage of its DuraZOOM-MA additive, have achieved record olefins yields. Ketjen’s new ZSM-5 investment at its Bayport site will support the industry in this move to petrochemical integration.

Jan-2025
Mark Schmalfeld, BASF Refinery Catalysts, mark.schmalfeld@basf.com

Upgrading the FCC unit can significantly enhance the integration of petrochemical processes within refineries. The unit primarily converts heavy petroleum feedstocks into lighter, more valuable products like gasoline and diesel. However, by implementing specific upgrades, refineries can optimise the FCC unit to produce higher yields of petrochemical feedstocks, thus improving overall operational efficiency and profitability.

Choosing advanced catalysts that are more selective towards lighter olefins, such as propylene and ethylene, can significantly increase the output of petrochemical precursors. Some modern catalysts also have enhanced stability and longer lifetimes, reducing the frequency of catalyst replacement and downtime.

Modifying the FCC unit’s riser section allows for better catalyst distribution and contact time with the feedstock. A design that promotes turbulent flow can enhance catalyst effectiveness by improving the distribution of catalyst within the unit. Special bed riser terminations can also increase residence time to increase reaction severity. The implementation of a secondary or dedicated riser to crack recycled light naphtha also can play a fundamental role in maximising light olefins yield, especially in the range of ethylene and propylene under severe reaction conditions. Additionally, upgrading to advanced catalyst injection systems ensures uniform dispersion and optimal contact between feed and catalyst. Upgrades to injection systems can also be beneficial when using new advanced catalysts.

Adjusting operating conditions such as temperature, pressure, and feedstock composition can help in maximising desired olefins production. Increasing the severity of the cracking process can lead to higher yields of lighter products but requires careful balancing to avoid excessive coke formation and catalyst deactivation. High-temperature equipment such as reactors and advanced separators may need to be changed to handle the desired operational conditions. One particular feature that allows high light olefins yield is the reduction of the hydrocarbons partial pressure by increasing steam streams to the reaction environment. This facilitates the equilibrium conditions to increase the conversion of heavy hydrocarbons to light olefin molecules. In this regard, some units maximising light olefins operate within the range of 10-20% steam-to-feed ratio.

Installing high-temperature reactors or modifying existing reactors to handle elevated temperatures safely can improve the cracking of heavier feedstocks. Utilising high-efficiency separators can better recover lighter products, minimising the loss of valuable olefins.
Petrochemical integration

Refineries can install downstream units such as olefin conversion units (OCUs), fractionators or propane dehydrogenation (PDH) units that utilise the lighter products generated from the FCC. Another interesting integration is with steam cracking units (SCU) since ethylene produced by FCC can be recovered, while ethane can be further converted to ethylene in the SCU. Modifications to piping and the addition of heat exchangers may also be necessary to connect these units effectively to the existing FCC unit. This integration allows for a more seamless transition from refining to petrochemical production, effectively creating a more versatile and adaptable processing facility.

Coprocessing biofeedstocks or lighter hydrocarbons alongside conventional feeds in the FCC unit can diversify the product slate. This method not only helps in meeting regulatory requirements for renewable content but also allows for the production of unique petrochemical intermediates. Alternative feeds often require dedicated storage systems. Additional equipment modifications could include enhancing feedstock pretreatment systems to accommodate biofeedstocks or lighter hydrocarbons. This might involve upgrading pumps and heat exchangers to handle different viscosities and properties of the new feedstocks. Additionally, FCC licensors have unique equipment modifications they can recommend for co-processing, particularly around how the alternative feedstocks are injected into the FCC.

Implementing advanced process control systems can optimise the FCC unit’s performance in real-time. These systems can adjust parameters dynamically based on feedstock variations and desired product specifications, maximising yield and minimising waste. Many advance control systems are already available today in most refiners, such as real-time monitoring tools and automated control systems. This includes the installation of advanced sensors for temperature, pressure, and composition analysis to enable real-time adjustments and optimisation of the cracking process.

Upgrades
Advanced distributed control systems (DCS) upgrades can dynamically adjust operational parameters based on feedstock characteristics and desired product yields, while upgrading heat exchangers and integrating heat recovery systems can improve FCC unit energy efficiency. By capturing and reusing heat generated during the cracking process, refineries can reduce overall energy consumption and enhance the economic viability of producing petrochemical products.

Continuous investment in R&D can lead to the discovery of new catalysts, processes, and technologies that can further enhance FCC performance and its integration with petrochemical production. Investments in new pilot plant equipment, testing equipment or modifications to existing designs are often needed to support new R&D innovations.

By focusing on these upgrade strategies, refineries cannot only boost their FCC unit’s efficiency but also enhance their capability to produce a broader range of valuable petrochemical products, aligning with market demands and economic trends.

Jan-2025
Delphine Le-Bars, Axens, bars@axensgroup.com

The FCC unit can be upgraded to benefit petrochemical integration through strategies ranging from some that can be easily applied to the existing FCC units to modifications involving the implementation of new satellite units. An example of easy and quick implementation could be increasing severity and/or using specific catalyst formulations and additives (like ZSM-5 zeolite) with high selectivity to olefins. Other possibilities when evaluating unit modifications to maximise olefins production include:
• Incorporation of a separated riser (Petroriser) for light naphtha cracking recycling at a higher temperature (operating under more severe conditions) than the main riser to maximise propylene production.
• Integration of FlexEne technology, an innovative combination of FCC and oligomerisation technologies, to expand the capabilities of the FCC process towards maximising olefins production. This flexibility is achieved by the oligomerisation of light FCC alkenes (olefins) and recycling oligomerate for selective cracking in the FCC unit. The FlexEne concept can be easily implemented in existing FCC units.

Investment in new FCC technologies, such as HS-FCC (high severity fluid catalytic cracking) technology, is an excellent prospect for olefins maximisation. The HS-FCC unit is an evolution of the well-known FCC process to reach a considerably higher level of light olefins production, in particular propylene, to bridge the gap between refining and petrochemicals industries.

Petroriser, FlexEne, and HS-FCC are marks of Axens.

Jan-2025