
230 Refining Used Lubricating Oils
heat exchanger heated with thermal uid at 275°C (525°F) to a temperature of 225°C
(435°F). The atmospheric ash evaporation produced 30 kilograms (66 pounds) of
light fractions per hour from the top of the separator and 1760 kilograms per h (3881
pounds per h) from the bottom, 900 kilograms per h (1985 pounds per h) of the lat-
ter stream were recirculated to the feed stream. The remaining 860 kilograms perh
(1896 pounds per h) of bottoms from the ash separator were mixed with 3500 kilo-
grams per h (7718 pounds per h) of bottoms from the vacuum column and heated in
the second heat exchanger with a thermal oil ...