BTEX OMA-300 Measuring Aromatic Hydrocarbons

The composition of pipeline natural gas varies widely by source but typically reflects a mixture of simple hydrocarbons, some inert gases, and often trace amounts of aromatic hydrocarbons. Benzene, toluene, ethylbenzene, and xylene(s) are common aromatics, collectively known at “BTEX” components, whose concentrations may be measured independently (speciation) or in total. The measurement of these aromatics may be necessary to meet compliance, safety, or tariff limits.

Fortunately, aromatic hydrocarbons have strong absorbance in the ultraviolet range and can be easily measured through spectroscopic methods. The laboratory standard ASTM method D1017-51 uses UV spectroscopy for aromatic hydrocarbon analysis. The OMA-300 system takes the same principle and brings it to the field for continuous, fast-response analysis on site. Using a dispersive UVVis spectrophotometer, the OMA continuously measures absorbance at each integer wavelength in the 200-300 nm range — the spectral region in which common aromatic hydrocarbons have very prominent, distinct absorbance curves. This allows the OMA-300 to easily differentiate the absorbance of each compound from the total sample absorbance.