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Feb-2005

Adding value to FCC operations

Case studies show how a distributed matrix structure-based additive enables the conversion of low-valued heavy-cycle oil and slurry into gasoline and LPG

Solly Ismail & Eugenio Macaluso, BASF Catalysts

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Article Summary

Refiners continue to face challenges due to increasing market demands, varying crude quality and stricter environmental regulations. Within these constraints, they still have to optimise their operations and maximise profitability with minimal capital expenditure. One way to improve profitability is with the use of a conversion enhancement additive.

In 2002, Engelhard’s proprietary Converter additive was introduced and is based on the company’s distributed matrix structure (DMS) platform. Implementation of this additive allows the refiner to better upgrade lower-value oils such as heavy-cycle and clarified slurry oils into higher-value products like gasoline and LPG. This additive solution provides an economical, low-risk approach to increase refining profitability and can be readily implemented in almost any FCC unit.

DMS platform
Well-developed pore structures are evident in SEM micrographs of the interior of catalyst particles based on the DMS platform. The entire exposed pore surface is essentially covered with zeolite crystallites. The external surfaces of these crystallites are exposed and accessible to the hydrocarbon feed molecules, which diffuse readily through the controlled pore structure. While other catalyst technologies may feature similar or even higher total pore volumes, they do not have the same morphology and resulting zeolite-based cracking pattern imparted by the DMS structure.1 Converter makes use of this technology to impart performance features such as:
λ Optimised porosity to enhance the diffusion of heavy feed molecules for pre-cracking
λ Reactive pre-cracking selective external zeolite surfaces rather than non-selective amorphous matrix
λ Short diffusional distance from the external surface to the active sites within the 
zeolite provides high activity and low coke selectivity.

Economic evaluation
As heavy-cycle oil and clarified slurry typically have low commercial value, an economic incentive exists to upgrade these lower-valued oils to gasoline. The four-quadrant model shown in Figure 1 gives refiners a quick method of assessing when additional value can be created from upgrading these oil stocks.

When operating with FCC bottoms (heavy-cycle oil plus clarified slurry oil) in excess of 10 wt% and specific gravity below 1.08 (Quadrant I), a refinery will benefit substantially by converting additional FCC bottoms into gasoline and LPG. On the opposite side, when a refinery’s FCC heavy-cycle oil plus clarified slurry oil is below 10 wt% and its specific 
gravity is greater than 1.08, the benefits would be more modest (Quadrant IV).

The profitability of the other two quadrants (II and III) is usually significant and well worth investigating, as the annual incremental value to the refiner may be considerable. By working closely with the actual objectives of the refiner, quantitative incremental profitability can be established, which can then be used as a benchmark to evaluate relative success.

Commercial experience
The Converter additive has been successfully used in more than 15 refineries worldwide. In all cases, the economic benefits were gained without negative offsets in selectivity. Some of the benefits leading to an increase in profitability were:
λ Maximising throughput at a given conversion level
λ Increasing conversion at given throughputs
λ Processing cheaper opportunistic feedstocks.

Case study 1
An Asian refinery with a 40 000 barrel per day FCC unit processes heavy feedstock with an 
average Conradson carbon of 2.87 wt%. The total metals, measured as nickel plus vanadium, averaged 7000ppm. The refinery’s goal was to increase gasoline yield, and the unit constraint was the molecular weight of gas to the wet gas compressor. This FCC unit also uses ZSM-5 to increase propylene production (Engelhard does not supply the base catalyst).

The value created for this refinery was a net incremental increase in profitability of $1.02 per barrel of FCC feed. This value creation translates into an added benefit in excess of $13 million per year (Note: The net increase is based on additional gasoline and LPG produced at the following New York spot market prices [in $/bbl]: gasoline = 58, LCO =53, CSO = 33, LPG = 37, and FCC online time of 330 days per year). A summary of the results is shown in Table 1.

In addition, the refinery noted another benefit with respect to the usage of ZSM-5. When ZSM-5 is used in conjunction with DMS-based products, a synergistic effect is observed. The practical implication of this synergy is that a smaller amount of ZSM-5 is needed to accomplish the same production levels of propylene and LPG in the absence of the additive. This is best seen in Figure 2.

Case study 2
The BP refinery in Kwinana, Australia has a 35 000 bpd FCC and processes varying feedstocks. The feed had an average Conradson carbon of 2.5 wt%, and metals (nickel plus vanadium) during this period averaged 7200 ppm. The refiner’s goals were to increase gasoline, decrease FCC bottoms and to maintain coke selectivity. The value created for this refinery was a net incremental increase in profitability of $0.53 per barrel of FCC feed. This value creation translates into an added benefit in excess of $6 million per year. A summary of the results is shown in
Table 2.


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