VACUUM DISTILLATION FOLLOWED BY CLAY TREATMENT 

Vacuum Distillation/Clay Process: To recover the oil base-stock from used oil, vacuum distillation is implemented. Varying grades of oil may be produced through this process giving the re-refiner an added flexibility in blending to meet different product specifications.

Distillation is a common processing technology, used not only in petroleum refining, but also to produce grain ethanol-not to mention whiskey and rum. The main idea is that different compounds have different boiling points, and if you boil a liquid you can get different components to separate based on these boiling points. As this is applied to used oil recycling, the lube oil is boiled away from some of the heavier compounds, leaving behind an asphalt residue that is marketed for paving applications. At atmospheric pressure, lube oil has such a high boiling point that it would tend to break down before it vaporized – but if you boil it under a powerful vacuum (similar to the vacuum that astronauts experience in outer space), the boiling point is reached at a lower temperature, preserving the integrity of the lube oil molecules.

In this process, after distillation we use the clay treatment for the decolourisation. Clay treatment is often used as a finishing step for the distilled lube from vacuum distillation. The clay needs to be activated by heating so that it can effectively treat the oil. The clay can be regenerated through a controlled combustion cycle and can be used multiple times before being disposed of. The clay treatment removes color, odor and some sulfur. The finished product meets API Group I base oil specifications but does not remove the unsaturated compounds to meet API Group II specifications. Clay treatment may be better suited for smaller plant capacities due to lower capital investment.