Reclamation of used lubricating oil by supercritical extn. - with partial recycle of extract to improve prod. quality

摘要

Process for reclaiming used oil (mainly spindle and neutral oils) comprises: (i) removing water by distn.; (ii) supercritically extracting the residue with a suitable inert gas, at a temp. above the gas's critical temp. and a pressure between its critical pressure and 350 bar; (iii) progressively releasing the pressure and/or varying the temp. of the extract to deposit at least two oil fractions; and (iv) recycling the first-deposited fraction to stage (ii), and using the remaining fractions in lubricating oils. Extracting gases include CO2 and methane. The average quality of the extract is improved by rejecting the first fraction. Recycle of the latter to extn. reduces losses.