A new technology to control H2O concentration at desiccant dryer outlets for optimum plant performance.
Molecular Sieves, Activated Alumina and Silica Gel desiccants are the most common drying techniques for Natural Gas Processing plants. Typically, two desiccant vessels are operated in series, using a piping system that allows either bed to be the first bed in line, and allows either to be removed from the process for regeneration. As the first bed in the line is exhausted, it is put into the regeneration circuit where hot, dry gas drives the absorbed moisture out. The freshly regenerated bed becomes the second bed in the series.
CRITICAL CONTROL OF MOISTURE
Normally, when the inlet gas moisture concentration is constant or can be measured, the desiccant dryers have a predictable operational period between regenerations. But as the desiccant ages, or from overheating, or from contamination in the process or regeneration circuit, the desiccant can lose capacity. Desiccant beds can also channel, allowing small concentrations of wet gas to flow through the bed without being dried. In any case, as the gas will subsequently be cooled for cryogenic separations downstream, the gas must be dry.
TRADITIONAL MEASUREMENT SOLUTIONS
Electrochemical and vibrating quartz crystal moisture analyzers have been the traditional method for monitoring the levels of H2O in Desiccant Dryer Outlets. Unfortunately, trace hydrocarbons and other contaminants present in the stream contaminate the electrochemical probes, resulting in high maintenance costs due to the need to be constantly replaced. It’s not uncommon for moisture probes to be replaced multiple times a year. Quartz crystal moisture meters have slow wet-up and dry-down times that allow water downstream and prolong regeneration times.
SpectraSensors SS2100 is the ideal solution for this challenging application. Its non-contact laser and detector is impervious to damage from contaminants. Tunable Diode Laser technology means that measurement interferences from other infrared absorbing compounds are avoided. There are no wet-up or dry-down delays, resulting in fast updates even when the concentration changes dramatically. Only SpectraSensors employs Differential Spectroscopy, which incorporates a dryer using metal getter technology to subtract the spectrum of the dry gas from the wet spectrum. This allows the SS2100 to measure streams whose background gas compositions changes.
Validation of low level (<10 ppm) water measurements is essential, but also extremely difficult, as certified blends at such low levels are not readily available. Some have attempted to put permeation devises, but these require regular maintenance to prevent drying out, and there is no independent way to verify the accuracy of the permeation device. SpectraSensors employs a dilution system that dilutes a relatively high concentration certified standard of H2O in Methane using dried sample gas. Thus the validation is accurate and traceable.
Fast- No wet-up or dry down times- Responds to changes in H2O concentration in as little as 1 sec. Virtually maintenance free- No frequent change- out of sensor. Avoids damage to sensor from contaminants. Tunable Diode Laser and Detector are isolate from the process Gas. No interference from other compounds- uses high resolution TDL technology
Want more information on the SS2100 and how it can make a difference in your plants performance? Call our sales team today at 918-446-1611 or e-mail us at firstname.lastname@example.org.