Laser-Based Moisture Analyzer protects catalysts while reducing Downtime And Maintenance

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In petrochemical gas applications, conventional analyzers are often erratic and susceptible to high moisture transients that trigger extensive dry-down times. The result can be seen as unexpected corrosion, premature loss of expensive reactor catalysts, and unscheduled downtime. The new technology, a laser-based analyzer eliminates such problems.

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News stories such as unexpected pipe corrosion attributed to high moisture levels have made headlines recently. Just as costly to the oil refinery or chemical plant is high moisture which is "poison" to process catalysts. Undetected and untreated moisture slugs can result in the premature loss of catalysts, requiring replacement of an exceedingly expensive material as well as costly unscheduled process downtime, due to inaccurate moisture analyzer readings.

Frequently, colleagues discuss potentially disastrous problems, such as when slugs of moisture rendered electrochemical sensors useless for a period. This is often a result of a phenomenon referred to as dry-down time. During those events operations are "flying blind" for hours, at a time when the moisture sensors are needed most. For refineries, the ultimate danger is that there could be not only damage to the reactor catalyst, but also that of production of "off spec" materials -- both of which could cost a company hundreds of thousands of dollars or more.

When a California refinery experienced slug problems with a conventional moisture sensor, they decided to test a new technology, the laser-based sensor. This device is designed to be extremely fast and accurate, is not affected by moisture slugs and has zero dry down times. Moreover, it is virtually maintenance-free because the laser-based sensor is not exposed directly to the moisture or corrosive contaminants in the stream, like conventional sensor probes. This technology utilizes absorption spectrometry that safely measures moisture from behind the non-wetted side of an optical window.

There are no moving parts in the spectrometer so maintenance is minimal. The tunable-diode laser (TDL) moisture analyzer is preset at the factory (SpectraSensors, San Dimas, CA), so it is truly "plug and play." Maintenance is typically not required even after several years of operation.

In increasing numbers, companies report being highly impressed with this laser-based moisture analyzer design, in part because it is completely unaffected by moisture slugs. The timely removal of excess water from feed streams, for instance, enables refiners to lengthen the intervals between catalyst recharges -- in some cases from months to years. Lengthening the useful lifetime of catalyst represents a savings of hundreds of thousands of dollars or more, depending on specific plant requirements.

Moisture problems are detected with extremely high accuracy and measurement intervals as frequent as within a second, enabling practically instantaneous response, eliminating the chance that moisture will "get through reading time gaps."

The SpectraSensors technology also eliminates the costs and downtime incurred by having to either return an analyzer to the manufacturer for reconditioning or calibration, or having to inventory spare sensors as back-up units.

The SpectraSensors TDL moisture analyzer is a microprocessor-based tool that is also in wide use by natural gas producers and pipeline operators. It enables them to get precision measurements of moisture content in their product so quickly and easily that it is completely revolutionizing natural gas sensor standards.

By Charles Smith, PhD

Charles Smith has earned his BS in Chemistry, and MS and PhD in Biophysics through the University of Texas System, and has several decades of experience working at Shell Westhollow Research Center as well as several analytical instrument companies.

For more information contact: Sam Miller, Director of Marketing -- Energy Tel: (909) 542-0394 x228 Fax: 909-542-0402; SpectraSensors, Inc. 972 North Amelia Avenue, San Dimas, CA 91773


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