Extraction of used lubricating oils with supercritical carbon dioxide

Abstract EN

Recognizing the importance of recycling used lubricating oils in the conservation of material, and the limitations on its use as a fuel under environmental protection, alternative methods for re-refining used oils are necessary.

The use of C02 at supercritical conditions is one such method, due to the relatively high solubility of hydrocarbons in C02, and its non-toxic nature, which does not leave behind any harmful effluent.

In this study, extraction of used oil using C02 was carried out dynamically in a packed column extractor at 313K for pressures from 9.0 MPa to 12.0 MPa.

The used oil extracted at 313 K and 9.0 MPa was found to be similar to the virgin lubricating oil, though the yield was lower than that at higher pressures.

In order to optimize the yield and to study the influence of C02 flow rate, extraction, at 313 K and 9.0 MPa, was carried out with C02 gas flow rates varying from 7.325xlO-6 to 15.18xl0"6m3/s.

The yield increased with increase in flow rate, reached a maximum at a gas flow rate of 9.11 lx 10~6 m3/s and decreased with further increase in flow rate.

The behavior of extraction yield with flow rate was explained as a trade-off between the equilibrium state and mass transfer kinetics.