A comparative study of traditional and novel humidity sensing technologies in natural gas

Abstract

This thesis was carried out inside of the temperature and humidity laboratory (LabTH) of the Instituto Nacional de Técnica Aeroespacial (INTA), which is the Spanish Designated Institute (DI) for the field of humidity and, therefore, holder of the national standards in such quantity. Among many other duties of a DI are to promote and participate in national and international R&D projects whose goals set were in line with those scored in the last European Roadmaps for the hygrometry field, for this particular case. For these reasons, and as a part of such participation in research projects, it is essential to emphasize that part of this thesis was developed inside of the framework of the joint research project “ENG01-Gas. Characterization of Energy Gases” which running under the European Metrology Research Program (EMRP), with the main target of supporting the natural gas industry to overcome its current big challenges. Moisture content is a key factor inside the natural gas (NG) industry. Not only does decrease the efficiency of the final product when the water content is high, but it can also trigger potentially dangerous conditions due to the formation of hydrates, that can block pipelines and damage pumping devices and produce other negative effects. For these reasons, accurate measurement and control of humidity is essential in all processing step of natural gas. However, current practice for such moisture measurements is for the devices to be calibrated at atmospheric pressure and in nitrogen or air as the matrix gas, conditions that vary significantly from those present in the actual industrial process, so their performance in real industrial conditions could be much smaller than expected and even insufficient. Besides, technologies traditionally used by NG industry, such us, condensation hygrometers and metal oxide capacitive probes, have some drawbacks that not always allow to measure and control humidity of NG with the accuracy and reliability desired.