Worldwide Inline Process Control Solutions

Naphtha Quality in Crude Distillation Unit


The quality of fractions from the crude distillation unit (CDU) need to be continuously monitored. By installing an optek inline photometer, the refinery maintains peak performance from the column and controls product quality downstream.

Color Scales

Flameproof housing EX d for optek C4000 converter

Naphtha, gasoline, kerosene and jet fuels are the lightest and highest quality hydrocarbons drawn off the top of the distillation column. Because of their low levels of impurities, they normally have a clear visual appearance. Their color is measured using the Saybolt color scale, ranging from brightest +30 to darkest -16, where acceptable product quality typically measures between +27 to +30. Heating oils, gas oils and lubricating oils are heavier hydrocarbons that are darker in appearance and drawn from the middle of the distillation column. Their color is measured using the ASTM color scale, ranging from brightest 0 to darkest 8, where acceptable product quality typically measures between 3 to 4. Using an optek AF26 sensor in conjunction with the C4000 converter, the refinery operator can continuously monitor the color of any refined hydrocarbon in any color scale. This allows for real-time determination of process upsets, eliminating poor quality products while maximizing process efficiency.

Contamination Detection

Increased color intensity typically indicates the presence of undesirable contamination resulting from a process upset or a reduction in process efficiency. Upsets generally occur when the heavier hydrocarbon fractions, such as crude, are carried upward with the lighter fractions, resulting in the contamination of the naphtha stream. If not detected immediately, the contaminated naphtha will feed downstream, damaging plant equipment and reducing product quality.

Continuous Monitoring

By installing an optek inline color sensor, the naphtha stream will be continuously monitored in real-time. The AF26 explosion proof sensor will immediately detect color changes caused by upsets or gradual reduction in process efficiency. Even at high pressures and temperatures, these important color measurements are made without the need for sample conditioning.