April 2025

Process Optimization

Synergize FCCUs and hydrocracking processing units to maximize refining margins—Part 2

Part 1 of this article appeared in the February issue. Part 2 here will explore the role of FCC and hydrocracking in crude-to-chemicals and the challenge of cracked feeds, among other topics. 

IP: 3.133.100.195

The capacity to add value to bottom-of-the-barrel streams represents a significant competitive advantage among refiners, especially considering strict regulations like the International Maritime Organization’s (IMO’s) 2020 regulation that has imposed a significant reduction in the sulfur content of marine fuel oils (bunker).^2,3 This requires even more capacity to treat bottom-of-the-barrel streams—especially for refiners processing heavier crude oils—and puts refining margins under pressure that are still in recovery in the post pandemic scenario. 

Under this scenario, process units that can improve the quality of crude oil residue streams (vacuum residue, gasoils, etc.) or convert them to higher added-value products gain strategic importance, mainly in countries with large heavy crude oil reserves. These process units are fundamental for compliance with environmental and quality regulations and ensure the profitability and competitiveness of refiners by increasing refining margins. Recently, the reduction in transportation fuels demand is impelling refiners to seek closer integration with petrochemical assets and maximize the yield of petrochemicals in the refinery. The use of residue upgrading technologies to produce petrochemicals against transportation fuels can be an attractive route in some markets. 

Part 1 of this article appeared in the February issue. Part 2 here will explore the role of FCC and hydrocracking in crude-to-chemicals and the challenge of cracked feeds, among other topics. 

Crude oil-to-chemicals: What is the role of FCC and hydrocracking? Due to the increasing market, higher added-value and the trending reduction in transportation fuels demand, some refiners and technology developers have dedicated their efforts to develop crude-to-chemicals refining assets.⁴ One of the big players invested in this alternative is Saudi Aramco: the company’s concept is based on the direct conversion of crude oil to petrochemical intermediates (FIG. 9). 

FIG. 9. A basic schematic of the Saudi Aramco crude oil-to-chemicals concept. Source: IHS Markit. 

The process presented in FIG. 9 is based on the quality of the crude oil and deep conversion technologies like high-severity or petrochemical FCCUs and deep hydrocracking technologies. The processed crude oil is light with low residual carbon, which is a common characteristic in Middle Eastern crude oils, and the processing scheme involves a deep catalytic conversion process to reach maximum conversion to light olefins. In this refining configuration, the combination of hydrocracking and petrochemical FCC is applied to ensure maximum added-value to the processed crude oil through near-zero production of transportation fuels. FIG. 10 shows a comparison of the petrochemicals yields of traditional refineries, a benchmark integrated refinery and crude-to-chemicals complexes. The dark green represents the chemicals yield variation. 

FIG. 10. Petrochemicals yield comparison. Source: Wood Company. 

Analyzing FIG. 10, it is possible to note the higher added-value reached in crude-to-chemicals refineries when compared even with highly integrated refineries.⁵ 

Synergies between hydrocracking and FCCUs: A high bottom-barrel conversion refining equipment. As mentioned, hydrocracking and FCC technologies face competition due to the similarities of the feed streams processed in these units. In some refining schemes, mild hydrocracking units can be applied as a pretreatment step to FCCUs, especially to bottom-barrel streams with high metals content that can poison FCC catalysts. Furthermore, the mild hydrocracking process can reduce the residual carbon to the FCC feed, improving the performance of the FCCU and the yield of light products like naphtha, liquefied petroleum gas (LPG) and olefins.⁶ 

The integrated refining scheme that relies on deep residue upgrading technologies like hydrocracking and FCC can achieve the production of high-quality petrochemicals, according to market trends. In some refining configurations, mild hydrocracking technologies are applied upstream of FCCUs to improve the quality of FCC products, mainly by reducing the sulfur content.  

Considering the flexibility of deep hydrocracking technologies that can convert feed streams that vary from gasoil to residue, an attractive alternative to improve the bottom barrel conversion capacity is to process the uncracked residue in an FCCU in hydrocracking units—this will improve the yield of high added-value derivatives in the refining equipment, mainly middle distillates like diesel and kerosene. This configuration can be especially attractive for gasoline Tier 3 production (with a maximum 10-ppm sulfur) for refiners processing high-sulfur crudes.⁷ 

The combination of FCC and hydrocracking processing units can help refiners maximize the added value of processed crude through the production of high added-value molecules (e.g., petrochemicals). The growing demand for petrochemical intermediates like ethylene and propylene should be considered compared to the forecasted long-term decline in gasoline demand. FIG. 11 shows another refining configuration based on the crude-to-chemicals concept; again, the refining scheme relies on FCC and hydrocracking synergies.⁵ 

FIG. 11. A typical crude-to-chemicals refinery configuration. Source: Wood Company.  

The side effect of cracked feeds: A special challenge to hydrocracking units. The most common cracked feeds directed to hydrocracking units are residual streams like light cycle oil (LCO) and decanted oil (DO) from FCC, and heavy coker gasoil (HCGO) from delayed coking units. Another less common feed is residue from visbreaking units.  

The main characteristics that influence hydrocracking performance for each feedstock include: 

• FCC cycle oils—Present high aromaticity that are normally refractory to cracking reactions, as well as refractory sulfur components, raising the sulfur content in the final products and reducing the diesel cetane number. Conversely, they normally present low basic nitrogen content that is poisonous to hydrocracking catalysts. 

• Thermal cracking feeds—Normally present low aromatics content but concentrate refractory sulfur components. 

HCGO is an interesting case study as a feed to a hydrocracking unit. Refiners with highly complex refining equipment can rely on the synergies between delayed coking and hydrocracking technologies to ensure added value to bottom-barrel streams.⁸ 

The quality of the HCGO relies on the quality of the feed to the delayed coking unit as well as the operating mode of the unit, mainly the recycle ratio. Higher recycle ratios produces better quality HCGO, which reduces the Conradson carbon residue (CCR) and contaminants like metals, sulfur and nitrogen.⁹ 

Despite this advantage, delayed coking operators normally minimize the recycle ratio to as low as possible to raise the fresh feed processing capacity, and the quality of HCGO is not an optimization focus of the refinery. For this reason, HCGO is normally a hard feed for hydrocracking units due to the high content of refractory sulfur components, and high CCR and nitrogen content, and aromatics concentration.¹⁰ 

The sulfur and nitrogen content raises the heat release in the first bed (higher exothermal profile), which can damage the catalysts, and the nitrogen tends to inhibit the cracking reaction leading to lower conversion in the unit. Hydrocrackers processing feeds with high nitrogen content usually apply a processing configuration with intermediate gas separation to control catalyst activity. The increased production of hydrogen sulfide (H2S) and ammonia (NH3) due to the higher concentration of sulfur and nitrogen reduces the hydrogen (H2) partial pressure, increasing the necessity of wash water to the units and the corrosion rate in the processing unit.^8,10 

Aromatics compounds tend to raise the H2 consumption and the heat release in the catalyst bed and are precursors of coking deposition that deactivates the catalyst. Other side effects of the cracked feeds to hydrocracking units are the impact over the quality of the final products, such as a lower diesel cetane number, a higher smoke point of kerosene, a lower viscosity index in the lubricating oils and higher sulfur content.¹¹ 

As described above, processing cracked feeds in hydrocracking units presents additional challenges to refiners related to H2 consumption, better quench design of the catalyst bed due to the higher exothermic profile of the reactions, and lower activity of the catalyst due to the higher poison content.¹² These characteristics lead refiners processing cracked feeds in hydrocracking units to invest more capital in feed treating systems like filtering and guard beds. Despite this apparent disadvantage, refiners able to add value to bottom-barrel streams can enjoy competitive advantage considering the downstream market post IMO 2020. For refiners processing extra-heavy bottom-barrel streams, deep hydrocracking technologies like slurry-phase hydrocracking can be an interesting option, despite the high capital and operating costs.^13,14 

Significant growth in global hydrocracking capacity is expected over the next several years. As expected, Asian refiners will lead this growth (FIG. 12). 

FIG. 12. Global growth of hydrocracking capacity by region. Source: GlobalData. 

Asian operators have effective integration between refining and petrochemical assets—requiring high bottom barrel conversion capacity to maximize the yield of petrochemicals—which provides them a competitive advantage, operational flexibility and increased profitability.¹⁵ 

FCCUs can ensure operational flexibility and higher refining margins for downstream players during challenging times for the fossil fuels industry: this will lead to further FCCU installations over the next several years. Based on an industry study,¹⁵ global installed FCC capacity will increase from 14.4 MMbpd in 2022 to 15.8 MMbpd in 2026, a growth of 9.3% during that 4-yr period (FIG. 13). 

FIG. 13. Newbuild and expansion refinery FCC capacity additions by key regions, 2022–2026. Mpd = thousands of barrels per day. Source: GlobalData. 

As expected, the growth of FCC capacity will be lead by Asian operators, which boast the highest integration capacity among downstream players and which have been investing heavily to maximize petrochemicals yield in their refining assets, including crude-to-chemicals refineries. Asian operators will add ~900,000 bpd of FCC processing capacity by 2027. They are followed by African operators, which have been investing in FCC as part of their strategy to reduce external dependence on high-quality gasoline. The addition of global FCC capacity produced by African refiners tends to be related to conventional and low-severity FCCUs. In particular, the Dangote refinery in Nigeria is leading gasoline production. African operators will add ~570,000 bpd of FCC processing capacity by 2027.¹⁵  

Takeaways. Refiners capable of maximizing their yield of petrochemicals will achieve a competitive advantage in today’s market, ensuring higher added-value to processed crude oils. An effective synergy between refining technologies is a basic concept in the downstream sector and one of the first steps to define an adequate refining configuration. The synergies between residue upgrading technologies is increasingly relevant for refiners aiming to maintain and improve their economic sustainability, especially considering the downstream market post IMO 2020. Considering the limitations of FCC technology to treat heavier feedstocks, the synergy with hydrocracking and mild hydrocracking units can allow a higher level of bottom-barrel conversion and maximum production of high added-value derivatives.  

Despite the relatively high capital costs, the synergies between hydrocracking and FCCUs are economically attractive for refiners in markets with a higher demand for lighter derivatives, especially petrochemicals and middle distillates. In addition to the benefits of petrochemical integration, it is necessary to achieve a circular economy in the downstream industry: to achieve this goal, the chemical recycling of plastics is essential. As presented above, promising technologies are available that can help close the sustainability cycle of the petrochemical industry. 

LITERATURE CITED 

1 Becarri, M. and U. Romano, Encyclopaedia of hydrocarbons: Refining and petrochemicals, Vol. 2, ENI, 2006.  

2 Silva, M. W., “More petrochemicals with less capital spending,” PTQ Magazine, 2020. 

3 Singh, V. P., “KBR olefins technology solutions—The key is flexibility,” KBR Company, 2018. 

4 Chang, R. J., “Crude oil to chemicals—Industry developments and strategic implications,” IHS Markit, Global Refining & Petrochemicals Congress, Houston, Texas (U.S.), 2018.   

5 Zhang, Z., “Crude oil to chemicals: Challenges and opportunities in a sustainable world,” Wood Co., METECH 2024, 2024. 

6 Vu, T. and J. Ritchie, “Naphtha complex optimization for petrochemical production,” UOP Co., 2019. 

7 Zhu, F., R Hoehn, V. Thakkar and E. Yuh, Hydroprocessing for clean energy—Design, operation and optimization, 1st Ed., Wiley Press, 2017. 

8 Robinson, P. R. and C. S. Hsu, Handbook of petroleum technology, 1st Ed., Springer, 2017. 

9 Speight, J. G., Heavy and extra-heavy oil upgrading technologies, 1st Ed., Elsevier Press, 2013. 

10 Sarin, A. K., “Integrating refinery with petrochemicals: Advanced technological solutions for synergy and improved profitability,” Global Refining & Petrochemicals Congress, Mumbai, India, 2017. 

11 Gary, J. H. and G. E. Handwerk, Petroleum refining: Technology and economics,” 4th Ed. Marcel Dekker Inc., 2001. 

12 Maller, A. and E. Gbordoze, “High severity fluidized catalytic cracking (HS-FCC™): From concept to commercialization,” Technip Stone & Webster, REFCOMM™, 2016. 

13 “Advances in catalysis for plastic conversion to hydrocarbons,” The Catalyst Group, (TCGR), 2021. 

14 Beccari, M. and U. Romano, Encyclopedia of Hydrocarbons: Refining and Petrochemicals, Vol. 2, ENI, 2006. 

15 “Refining industry capacity and capital expenditure forecast by region, countries and all operating and planned refineries to 2027,” GlobalData, 2027. 

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