Wet vacuum distillation was used to separate oil and residue from one kind of rolling oil sludge. The effects of the three main factors (temperature

vacuum degree and steam flowrate) on the oil yield were studied by using the quadratic general spinning design. The results showed that the wet vacuum distillation could significantly mitigate the oil destruction and promote the oil recovery rate comparing with simple distillation. Within the range of the experimental condition

the optimal conditions were 321.4℃ in temperature

90 kPa in vacuum degree and 1 ml·min−1 in steam flowrate

at which the oil recovery rate of 57.2% could be reached. Both the excessive temperature and steam flowrate could cause the oil decomposition. If the temperature was too high

it promoted the conversion of oil from resin to aromatics and saturates because of pyrolysis. If the steam partial pressure was too high

oil transformed to aromatics from resin due to the ester-type bonds hydrolysis and the oxidation of heavy oil with co-effect of Fe2O3. As for the heavy organic matters

such as asphaltene

which were difficult to be removed from the distillation residuals. By raising the temperature and steam flowrate

especially raising temperature

they can be effectively decomposed and carbonized to achieve a low oil content in the residues

and thus benefitting to their recovery.