Reclamation of used lubricating oil.

摘要

Used lubricating oil comprising organometallic cpds. including zinc dithiophosphate (A) is reclaimed by (a) heating the oil to an additive decomp. temp. of 400-1000 deg.F; and (b) maintaining the temp. for 10-120 min. Concn. of (A) is reduced to 0.001 wt.% or less, in absence of chemical demetallising. Pref. steps (a) and (b) are followed by (c) vacuum distilling at 500-1050 deg.F, 20-500 mm Hg, esp. 500-750 deg.F, 50-150 mm Hg; and (d) recovering a distillate product containing 0.001 wt.% or less (A), and an asphaltic bottoms product comprising zinc and degradation products. Step (a) is carried out by direct heat exchange by admixing used oil, e.g. at 32-120 deg.F, with a heated product oil. After step (b), the product is heated to additive decomposition temp. by indirect heat exchange. Vol. ratio used oil to heated product oil in step (a) is 1:1 to 1:120. The process may be carried out continuously.