Method of rerefining used lubricating oil

摘要

Used oil is refined by distillation to remove a volatile forecut followed by further distillation with recirculation provisions to obtain the desired fractions of lubricating oil products while reducing the vaporization temperature of the oil. The recycle effect tends to reduce coking and cracking while providing a greater recovery of lubricating oil products through the carrier effect of the light ends. In one embodiment of the invention, a waste oil feedstock has water, gasoline and other similarly volatile components removed in a first stage evaporator (16). Heavier fuel, such as fuel oil is then removed in a second stage evaporator (28). A light lube oil fraction is then obtained by distillation with a third stage wiped-film evaporator (40). Finally, a heavy lube oil fraction is obtained by distillation of the bottoms from the evaporator (40) with a fourth-stage evaporator (64).