Analisador de Óleo em Água – OIW-100

In various industries, complying with environmentalagencies often boils down to verifying specified limits for oil content ineffluent water. For refineries and plants to validate their investments inwastewater processing, they require highly accurate online monitoring ofdissolved and un-dissolved hydrocarbon concentrations in runoff. Aside frompotential environmental code violations, higher-than-specification oil contentin post-processing water can indicate faulty equipment such as leaky heatexchangers. Also, since a portion of the water is often recycled into theprocess as cooling fluid or otherwise, oil contamination in wastewater can endup causing maintenance problems upstream.

The OIW-100 continuously monitors oilconcentrations in water ranging down to the low parts per million (ppm). Oilcontains a significant amount of aromatic hydrocarbons; crude carries around15% wt aromatics. These molecules show strong absorbance in the 250-320nmwavelength range. The nova-II spectrometer driving the OIW-100 is configured tomonitor aromatics’ absorbance in this region, correlating the data to the totaloil concentration in water; to perfect the correlation, the instrument iscalibrated for the typical composition of trace oil in the process (using acustomer sample).

Whereas basic photometric analyzers for oil inwater will measure at a single, discrete wavelength-254nm, a benzene absorbancepeak-the OIW-100 uses diode array technology, where 1,024 photodiodes monitor acontinuous absorbance range (250-320nm). This range comprises unique absorbancefeatures of light aromatics (including the benzene 254nm peak) as well asheavier aromatics. The diode array advantage is significant: monitoring thecomplete structure of the aromatic absorbance region allows for internalreferencing and produces a far more accurate measurement of total aromatics’concentration-and thus correlating more accurately to total oil-than a lone measurementat a benzene absorbance peak, a value which is susceptible tocross-interference or misattribution.

A traditional difficulty in this application is theimmiscibility of water and oil. The OIW-100 uses an ultrasonic homogenizer toforce the oil into mixture so that, for spectroscopic purposes, thehydrocarbons appear to be in aqueous solution. (For more about the homogenizer,see the sampling system tab.)

Applications for online oil-in-water analysis areoften found in:

• Oil pollution prevention for refineries, oil fields, offshore drilling platforms, chemical and petrochemical plants, airports, steel mills, automobile manufacturing and other industries that tend to produce oily runoff
• Treatment of wastewater, effluent streams, and rainwater
• Deballasting
• Any process stream sensitive to concentrations of aromatics like benzene, toluene, styrene, or xylene in water