K factor (crude oil refining)

The K factor, also known as the UOP K factor or Watson K factor, is an empirical characterization factor used in the petroleum industry to indicate the paraffinicity of petroleum fractions and crude oils. It is a numerical value that correlates various physical properties of a hydrocarbon mixture, primarily its boiling point and specific gravity (or API gravity), to provide an indication of its chemical composition. A higher K factor suggests a more paraffinic (alkane-rich) character, while a lower K factor indicates a more aromatic-rich or naphthenic (cyclic alkane-rich) character.

The K factor is often used in crude oil characterization, refinery process design, and product quality control. It can assist in predicting the behavior of crude oils during processing, estimating yields of different products, and assessing the suitability of a crude oil for a specific refining scheme. It is also used to estimate other properties that may be difficult or time-consuming to measure directly.

While the K factor provides a useful indication of the overall paraffinicity of a crude oil or fraction, it is important to remember that it is an empirical correlation and does not provide a complete compositional analysis. More detailed analytical techniques are often necessary for a comprehensive understanding of the hydrocarbon composition. Factors like sulfur content, nitrogen content, and metal content are not accounted for in the K factor calculation.

Different correlations for the K factor exist, but they generally relate the mean average boiling point (MABP, usually in degrees Rankine) and the specific gravity (at 60°F/15.6°C). The specific formula may vary depending on the source. Typical values for the K factor range from about 10.5 for highly aromatic oils to about 13 or higher for highly paraffinic oils.