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Jul-2019

Generating value in the FCC

New catalyst technologies and technical service support helped a refiner overcome difficulties with VGO conversion.

DICHO STRATIEV IVAN CHAVDAROV and ALEXANDR IVANOV, Neftochim Burgas JSC
ALEKSEY POPOV and RAFAEL GONZÁLEZ, W. R. Grace & Co.
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Article Summary
Lukoil Neftochim Burgas Refinery JSC (Neftochim) commissioned an H-Oil vacuum residue ebullating bed hydrocracker in 2015 that led to a significant deterioration of the FCC unit’s vacuum gasoil (VGO) feedstock quality. Consequently, a significant drop in conversion was observed that negatively affected FCC unit profitability. Grace and Neftochim went through the challenge successfully by means of a collaboration that included implementation of state of the art catalyst technology together with a variety of tailored services, resulting in a gain of +1.6 wt% conversion and 0.86 wt% gasoline in the more challenging scenario. In this article, Neftochim and Grace explain how a strong technology partnership can deliver value far beyond simply the supply of FCC products.

Located on the Balkan Peninsula at 15km from Burgas in Bulgaria, Lukoil Neftochim is the largest oil refinery in the Balkans and the largest industrial enterprise in Bulgaria. It started operations in 1963 and became part of the Lukoil group in 1999. With a refining capacity of 7 million t/y, Neftochim refinery produces a wide range of products that include LPG, gasoline, diesel, jet fuel, and polymers. Neftochim refinery has a Nelson complexity index of 13 with a crude conversion rate of 87%.

The FCC is a primary conversion unit that plays a crucial role in the Neftochim refinery profitability. It uses heat and catalyst to convert a low cost, high molecular weight feed type like VGO into lighter, more valuable products such as gasoline, LPG and fuel oil. Commissioned in 1982, Neftochim FCC is a Groznii Project institute side-by-side design with a feedstock processing capacity of 250 t/h. Several major revamps to the unit have been conducted through the years, including air distribution, feed nozzles, riser termination device, and cyclones, and ancillary equipment in the FCC complex has also been upgraded/debottlenecked, including the wet gas compressor, steam production system, and depropaniser unit. The FCC complex also has a VGO hydrodesulphurisation unit for feedstock pretreatment.

The H-Oil VGO challenge
The Neftochim FCC unit typically processed desulphurised VGO as its main feedstock contributor. The FCC unit’s objectives are typically:
• Maximise FCC unit conversion.
• Maximise gasoline yields and gasoline octane
• Optimise C3= and C4 cut
• Increase FCC feed throughput.

Feedstock properties are the dominating factor determining FCC conversion levels and yields of high margin key products like naphtha, C3=, C4 cut or light cycle oil (LCO). In 2015, Neftochim commissioned an H-Oil vacuum residue ebullating bed hydrocracker and, since then, the Neftochim FCC unit has processed an approximately 20-30% range of a blend of HVGO and LVGO from the H-Oil unit. As this VGO feedstock is already cracked, its nature is very aromatic and heavy – it can exhibit  densities as high as 973 kg/m3. Its introduction into Neftochim’s FCC feedstock blend had a huge impact on feed crackability, as shown in Table 1.

Given the expected negative impact of processing H-Oil VGO, with losses of conversion between 2-6 wt% FF, the Neftochim refinery asked Grace to provide technology solutions to cope with this new, very challenging scenario. To provide the highest increase in unit profitability to Neftochim, Grace proposed to engage both parties in a collaboration to find the optimum catalyst technology and services, with a focus on the following value generators:
• Continuous state-of-the-art FCC catalyst and additives technologies implementation
• FCC unit operations optimisation and debottlenecking
• FCC unit reliability monitoring and improvement.

Nadius 4G technology platform
In the current challenging and ever changing refining market, it is vital to build long term strategies to maintain the highest levels of competitiveness. Neftochim and Grace have been collaborating closely over the last decade to achieve increases in FCC unit performance throughout the period. Indeed, continuous implementation of newly developed catalyst technologies has delivered consistent unit conversion growth and additional value to FCC operations (see Figure 1).

Grace has been continuously delivering value through different technologies to the site since 2012. Due to rare earth hyperinflation in 2011, Grace introduced its rare earth-free REsolution technology to help Neftochim alleviate its operating costs with no debit in catalyst performance. Indeed, Grace’s Z-21 rare earth-free zeolite stabilisation delivered a 1 wt% FF conversion increase compared to the incumbent competitor catalyst at the time. Once this price inflation period ended, Grace introduced the Nadius 4G Technology Platform with Nadius 545, which provided further benefits in unit conversion by additional 1 wt% FF conversion.

Nadius 4G catalyst technology is the latest generation of Grace’s Nadius catalyst family for hydrotreated and straight-run VGO feed applications. Nadius 4G incorporates new technologies that were developed during the R&D programme that was initiated as a result of the tight oil boom in North America and the new challenges faced by European refineries. This R&D programme resulted in advances to key catalytic functionalities; Nadius 4G features higher zeolitic activity with a tailored hydrogen transfer specific for this particular application (see Figure 2).

The new catalyst technologies resulted in successive improvements in FCC unit operating profitability, as expected. Nevertheless, Neftochim challenged the status quo and trialled an alternative FCC catalyst supplier in 2015 together with the commissioning of the H-Oil unit. The resulting conversion levels were about 2 wt% FF lower than the base level of 2011. This massive drop of conversion was at the time partly attributed to the change in FCC feedstock quality due to its lower crackability.

Meanwhile, Neftochim encouraged Grace to find new technology solutions to maximise conversion in the new scenario. Grace conducted extensive research to develop Nadius 865 ZP catalyst technology. Subsequent ACE pilot plant testing with representative feedstock for the new scenario (see Table 2) against the base catalyst Nadius 983 catalyst confirmed the performance according to Neftochim’s objectives (see Figures 3-5).

Following the promising performance benefits identified in the ACE pilot plant for Nadius 865 ZP, Neftochim conducted a commercial FCC unit trial employing the technology. FCC unit results shown in Table 3 revealed that Nadius 865 ZP provided superior performance, achieving +1.6 wt% FF conversion and 0.86 wt% FF gasoline at 25 wt% H-Oil VGO level versus the base case.

Ecat testing results
A change of FCC catalyst represents a significant step for refiners. Grace provides a risk mitigation plan and performs a range of activities to support refineries, both before and during the catalyst change-out, with the express purpose of minimising those risks and ensuring a smooth and successful transition. A key part of this reinforced technical support is the close monitoring of the circulating inventory change-out coupled with an ACE pilot plant Ecat performance evaluation using Ecat samples received on a weekly basis. It is generally accepted that most of the impact on yield shifts from a new catalyst can be observed when circulating inventory reaches ≥60% change-out level of the new catalyst. As ACE pilot plant operating conditions and feedstock are constant, the ACE  unit allows a selectivity assessment without the influence of the ever changing operating variables of the FCC commercial unit.
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