Theoretical Study and Experimental Test-Rig Implementation for Investigating Water-Gas Shift Conversion Processes for Coal-to-Hydrogen Energy Systems

Downstream of the mixing manifold, where the initial dry gas mixture has been just formed, the first valuation of the gas composition occurs. Fig. 104 shows the three points of gas sampling for composition analysis in the test-rig: the first measurement point is that indicated with “C1”. A dry gas sample is taken and sent to the gas analyser, where the CO and CO2 contents are measured, by means of the Non-Dispersive InfraRed (NDIR) absorption analysis method. Among the various gas analysers available, the gas analyser by Horiba, model VA-3000 (Fig. 105, upper side), has been chosen. The VA-3000 consists of a multi-gas analyser which uses as measurement principles the NDIR absorption spectroscopy (measurement of CO, CO2, CH4, N2O, SO2), chemiluminescent assay (CLA) system (measurement of NOx), paramagnetism, galvanic cell, zirconium oxide methods (measurement of O2), and allows through module systems the analysis of up to three different gases or same gases in different ranges. The gas sample is drawn with a minimum flow rate of 0.5 l/min and minimum pressure of 0.7 barg, and it is directly sent to the analyser through a proper electric valve without any previous conditioning, being the gas at ambient temperature and zero moisture content.

Each measurement module of the gas analyser permits to record up to 4 different measure ranges, with maximum higher-lower range ratio of 10. In the specific case, the analyser has been calibrated in two measurement ranges for each of the two modules: 0÷50% and 0÷100% for CO content analysis, and 0÷10% and 0÷50% for CO2 content analysis. The device provides an analog output signal of 4–20 mA, which therefore has to be compared with the particular measurement range in use. The signal is acquired by means of a data acquisition board connected to a personal computer, which will be described in Par. 4.5 (cf. Tab. 37 and Fig. 118). The analyser is powered at 240 Vac, with a maximum input of 200 VA. The instrument is placed in a rack cabinet (which will be discussed in Par. 4.5, “Rack cabinet”), together with a further electric valve and gas sample flow regulation system, the interface.
In particular the layout scheme of the system is shown in Fig. 106 (upper line). In the same scheme the lines for the other two gas sample analysis are present (second and third line), which compared with the first line have a sample conditioning system.