Conradson Carbon Residue

The Conradson Carbon Residue (CCR) test is a method used to determine the amount of carbon residue left behind when a sample of crude oil is distilled at high temperatures. The test provides an indication of the coke-forming capacity of petroleum fraction or crude oil. In general, the test is applicable to petroleum products that are relatively non-volatile, and which decompose on distillation at atmospheric pressure.

The Conradson Carbon Residue is also an indicator of the relative “heaviness” or “lightness” of crude oil, with higher values indicating a heavier crude oil with a higher proportion of heavy, high-boiling point hydrocarbons. Heavy crude oils typically have a higher Conradson Carbon Residue value than light crude oils.

A quantity of sample is weighed, placed in a crucible, and subjected to destructive distillation at a high temperature ~ 525 °C and at atmospheric pressure. During a fixed period of severe heating, the residue undergoes cracking and coking reactions. At the end of the heating period, the crucible containing the carbonaceous residue is cooled in a desiccator and weighed. The residue remaining is calculated as a percentage of the original sample and reported as Conradson carbon residue.

Conradson Carbon Residue is an important quality parameter of furnace oil, showing the tendency of deposits on the burner tips.

  • Diesel fuel deposits on the combustion chamber of diesel engine.
  • For delayed cokers, the Conradson Carbon Residue estimation of coke production
  • CCR depicts the coke formation on the catalysts of  Fluid Catalytic Cracking Units and other catalytic units in petroleum refineries.
  • CCR (Conradson Carbon Residue) values of arab crudes are; Arab Extra Light 3.65 %, Arab Light 3.83%, Arab Medium 5.71%, and Arab Heavy 7.86 %.


  1. www,
  2. Petroleum Economics and Engineering by Hussein K. Abdel-Aal Mohammed A. Alsahlawi
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