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.