
195Refining Processes for Used Oil Recycling to Base Oils or Fuels
proposed for the distillate coming from the TFE or WFE as shown in Figure 7.12
when the sludge content, as measured as toluene insoluble constituents, was higher
than approximately 100 to 300 ppm. It was found that the rst heat soak resulted
in a distillate from the WFE that still contained approximately 150 to 400 ppm of
residual sludge at 310°C (590°F). This sludge was made up of 100 to 300 ppm of
toluene insoluble constituents at room temperature, and approximately 50 to 100
ppm of sludge that can form at the high temperatures of 300°C to 310°C (570°F to
590°F) from the sl ...