Calibration of a gas mixing system with analytical equipment and improvements for flow mixtures with large differences

The first step to reduce greenhouse gas (GHG) emissions is to detect and track the emissions sources as well as measuring how efficient are the mitigation actions implemented. Thus, GHGs need to be monitored. This can be done either with large instruments that are very accurate and precise, but expensive and stationary, or it can be done with small sensors of lower cost and easier to carry and use for in situ measurements. The drawback of these small sensors is that they are less accurate and need periodic calibrations. For the latter, reference equipment such as gas mixing systems (GMSs) are used. In this thesis a brand new GMS was calibrated using a gas chromatograph as a reference. This GMS will in turn be used to calibrate low-cost sensors used at TEMA M in research projects related to detect, monitor, and reduce GHG emissions. The original research questions were: (i) can the GMS deliver mixtures with less than 2 % error in concentration?; and (ii) can the GMS deliver mixtures with a relative standard deviation of less than 5 %? It was found that the system could rarely deliver mixtures with less than 2 % error (which is the inherent error of its main components), but the relative standard deviation was found to be below 5 % for introduced concentrations higher than 12 ppm. Because of the higher errors found when mixing flows with large differences, a third research question appeared during the work: (iii) can higher accuracy results be achieved by exchanging t-connections for a turbulent mixer? The reason for this was that the t-connection, where the two gases get mixed, was thought to discriminate against the gas with significantly lower flow. This resulted in the fabrication and testing of what is commonly called a static mixer. The results of this thesis help to understand the capabilities of the GMS and show a possible path on how to further improve the GMS.