A New Solution to Eliminate Centrifuge for Sulfur in Crude Oil Analysis

BACKGROUND

Test methods for measuring sulfur content, like ASTM D4294 and ISO 8754, have become critical for assessing the value of crude oil. These methods utilize X-ray Fluorescence (XRF) analysis, and with any method, it is important to consider the interferences inherent within the analysis technique. The ASTM D4294 standard test method references matrix effects as a known interference, which may influence the sulfur measurement in crude oil and produce biased results. 

CHALLENGE

Crude oil presents unique challenges for ASTM D4294 analysis. While sulfur containing compounds in crude oil are primarily comprised of organosulfur compounds that remain homogeneous in hydrocarbons, interferences like Si, Ca, Cl, Fe and water are commonly present and will settle to the bottom of a sample over time. These interferences can absorb the X-ray signal and reduce the concentration of sulfur reported. While many D4294 instruments (traditional XRF) can correct for interfering elements, interferences that settle in crude oil can create challenging scenarios. Diagram A demonstrates settling over a period of 60 minutes.