Gas Composition Sensor for Natural Gas and Biogas

The calorific value of energetic gasses is an important parameter in the quality assessment of gas steams, and can be calculated from the chemical composition of the gas. An array of capacitive sensor electrodes was developed, each functionalized with a gas responsive coating to measure the concentration of methane, ethane, propane, carbon dioxide, water and nitrogen in various gas mixtures. Using the data from six functionalized chips, the calorific value could be measured with 5% accuracy. Part of this error is caused by the noise in the electronics, another part by the non-linearity of the responsive coatings. Future developments aim at improving the response of the coatings and a higher integration of electrodes and will lead to a higher sensitivity and an expected accuracy of 0.5%. The sensor should be implemented in flow equipment, restricting the size to several cubic centimeters.