Hydrocarbon Dew-Point Analyzers: The Best is Now Even Better

New sensor technology boosts the performance of hydrocarbon dew-point detection 

Chilled mirror optical measurement systems using the Dark Spot detection principle have become the accepted standard around the world for measuring Hydrocarbon Dew Point (HCDP).  First developed by Shell Research in 1986 and subsequently pioneered in our range of Condumax analyzers, the technique today plays a vital role in maintaining the quality, safety and efficiency of natural gas production, processing, distribution and combustion systems. 

Although the basic design of chilled mirror instruments has remained largely unchanged since the late 1980s, sensor and detection technologies have evolved, leading to improvements in accuracy, reliability and repeatability.

Now, with the most recent developments, we are poised for a significant move forward in the performance and potential use of a new generation of HCDP analyzers.  This coincides with the growing interest in hydrogen’s role in the global movement towards Net Zero. In addition, there is the potential to simplify and improve the monitoring of both hydrocarbon and water dew point, especially in applications where there is currently a lack of skilled or experienced staff. 

How do current hydrocarbon dew-point analyzers work? 

Existing chilled or cooled mirror HCDP analyzers, such as the Condumax II, are generally designed for continuous on-line use.  At the heart of each instrument is an etched stainless-steel optical surface – the mirror – which has a central conical depression; under normal conditions, this scatters light unevenly.  The system also incorporates a collimated visible red LED light source, focused into the conical depression; a photo-detector is then positioned to gather the reflected light.  Under dry conditions, the incident light beam is dispersed by the matt surface, providing a base signal to the optical detector.

Beneath the optical surface is a thermoelectric Peltier heat pump.  This cools the mirrored surface until condensates from a gas sample begin to appear.  These alter the reflective properties, with the low surface tension of the condensate making the optical surface increasingly reflective.  In turn, an annular ring of light forms around the detector, with a dramatic reduction in the intensity of the light scattered from the center of the ring – the so-called ‘Dark Spot’. The precise temperature at which the dark spot forms corresponds to the dew point. 

What are the latest developments in HCDP measurement? 

The new generation of HCDP analyzers, represented by the CD603 Condumax Dew-Point Analyzer, builds on proven chilled mirror principles, with the addition of new sensor technology and advanced analysis and control software.   

The new instrument incorporates an enhanced sensor cell design.  This features a planar metallic mirror surface with specially modified optical properties that allow detection of the lowest possible levels of hydrocarbon iridescence.  The sensor cell is mated with a PT1000 temperature element, fitted directly to a thermo-electric Peltier heat pump, providing accurate heating and cooling of the mirror surface. 

The innovative new sensor cell design applies a dual opto-electronic system aligned to the mirror surface, which operate simultaneously to both detect the earliest formation of condensation and positively identify dew-point type. A visible red source and photodetector sense the earliest form of condensation on the cooling mirror surface to precisely determine the measured dew-point temperature. Simultaneously, an infrared source and matched photodiode exhibit enhanced signal change to any aqueous formations, be that dew droplets or deposition of frost crystals. This innovation in cooled-mirror method for natural gas thereby accurately measures dew-point temperature and identifies the form of condensation or deposition for every completed measurement cycle, to provide critical information to process and pipeline operators.

The new system offers fully automatic operation and analysis, together with an intuitive user interface that includes logging and charting capabilities, which can be inspected in real time on site or be downloaded for later off-site assessment by experienced staff. 

Supporting the move to Net Zero

This new generation of HCDP analyzers represents a significant step forward in technology.  By combining proven and reliable operating principles with the latest sensing electronics, we have been able to create instruments that will help transform our use of natural gas and, increasingly, hydrogen as we move towards Net Zero. 

We are the world’s leading experts in moisture monitoring and dew-point measurement.  We have eight different technologies covering all moisture applications, backed by unrivalled technical and customer support.  To learn more, talk to one of our application specialists today. 