The typical hydrocracking–base oils line-up.
Figure 1: The typical hydrocracking–base oils line-up.

Although middle distillates often provide a higher-value product stream, the economics in some regions are better for lubricant base oils, and many refiners have been able to exploit this. What is driving this trend and how can a refinery be reconfigured to prioritise feed for lubricant base oils?

The lubricant base oil business is in a state of transition: production is rapidly moving away from solvent-based plants towards catalytic hydroprocessing. This is chiefly because the base oil’s quality and yields are much higher, there is less dependence on a specific crude source and it is easier to make the high-quality Group III base oils the current market demands.

A significant drop in demand for Group I products is expected, especially in Europe and North America. There has already been several closures in Group I capacity in those regions. All the new base oil capacity and additional projects that have been announced are exclusively for Group II and Group III base oils produced using catalytic technology.

This is pertinent to refiners because Group II and Group III base oils are typically derived from hydrocracker bottoms. Certainly, Group III base oils require the higher conversion that only a hydrocracker can provide to deliver the necessary very high viscosity indices of 120–130. In short, the hydrocracker will provide the feedstock for all future base oils.

However, producing lubricant base oil feedstock requires an in-depth understanding of what drives the properties of the unconverted material that comes off the bottom of the fractionator, especially the viscosity index and aromatics, sulphur and nitrogen contents. The hydrocracker process configuration and the application of the right catalyst system are important to maximising both the yield and the quality of the final base oil products.

Figure 1 shows a typical line-up. In the high-vacuum unit (HVU), deep-flash technology can be used to maximise feed heaviness. The hydrocracker’s conversion can be fine-tuned to balance product qualities and yields, and the catalytic dewaxing/ hydrofinishing (CDW/HF) unit can generate the base oils for Group II or Group III products, as appropriate.

If there is sufficient demand for heavier (500N) base oils, deasphalted oil can also be added. The processing route using C3 deasphalted oil will also enable the production of Group II bright stock, a product that currently does not exist in the market but will be in demand as more Group I plants close and the traditional supply of bright stock disappears.

In recent years, Shell Global Solutions has supported several refiners as they have reconfigured their hydrocrackers to generate a high-quality feed for a new base oils plant. One of these projects, at Hyundai Oilbank in South Korea, is described by the customer here below.

Figure 2: Hyundai’s HVU and hydrocracker were revamped and configured to work with the new base oil plant as a value chain.
Figure 2: Hyundai’s HVU and hydrocracker were revamped and configured to work with the new base oil plant as a value chain.

Customer Case Study

Hyundai’s HVU–hydrocracker–base oils value chain

When Hyundai Oilbank identified a strategic opportunity to build a 20,000-bbl/d Group II lubricant base oil manufacturing plant adjacent to its Daesan refinery in South Korea because demand for Group II products was robust in the region, revamps to the HVU and the hydrocracker were critical to the project’s economic viability, writes Dal-Ho Kang, Executive Vice President and Refinery Manager, Hyundai Oilbank Daesan refinery.

“To integrate the new base oils plant with our existing line-up, it was necessary to revamp the hydrocracker, which would provide the feed for the new facility. To get the right amount of feed (hydrowax) at the right quality, we had to find a way to increase the hydrocracker’s throughput by 15%, decrease its conversion from 68 to 50%, increase its viscosity index to 125, and increase the cycle length from three to four years to align with the new base oil plant.

“We were able to achieve this by making several relatively inexpensive changes. In the reactor section, for example, we installed new reactor internals and catalysts, and added a new high-pressure effluent exchanger. In the fractionator, we upgraded the hydrowax rundown hydraulic system.

“To get sufficient and suitable feed for the hydrocracker, it was also necessary to go further back into the processing stream and revamp the HVU.

“Figure 2 shows how the project changed the refinery configuration. It increased the unit’s capacity and enhanced the potential for making heavy base oils as opposed to light ones. A hydrocracker on a diet of conventional vacuum gas oil (VGO) typically makes very light base oils, mostly in the 2–6-cSt range and some in the 6–8-cSt range. In contrast, we are producing a substantial amount of base oil in the 10–12-cSt range. This is only possible because the HVU can lift very heavy VGO and closely control the levels of asphaltene, Conradson carbon residue (CCR) and metals.

VGO Quality Parameter Before Revamp After Revamp
D1160 T95%, °C 540 562
Nickel + vanadium, wppm 0.3 0.5
CCR, %wt 0.4 0.5

“As a result, the VGO yield increased and its quality specifications were met. The improvement in quality parameters is shown in Table 1.

“Through these changes, the HVU is delivering the VGO feed to the hydrocracker at the right yield and heaviness: the profile is exactly as per design. The hydrocracker is operating at target conversion to deliver the hydrowax quantity and quality that the base oil plant needs. In addition, all this is helping the base oil plant to deliver the right product quality.”

Key Takeaways

  • There is a global trend away from Group I products, based on solvent technology, towards Group II and Group III lubricant base oils produced using catalytic dewaxing technology and hydrofinishing technology.
  • In some regions, lubricant base oil feed can command a higher margin than middle distillates, so many refiners are revamping their hydrocrackers to enable the right quality of feed.
  • The hydrocracker’s catalyst system and configuration are key, as they have a major influence on the yield and quality of the final base oil products.

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