Development of a novel thermoacoustic flue-gas analyzer

Flue gas analyzers, such as those based on electrochemical cells and infrared sensors, are commonly used to determine the molar concentrations of the different species of flue-gas mixtures and provide information about the associated air-fuel ratio and the resulting combustion efficiency. Here, a new methodology for quaternary-gas analysis that relies on thermoacoustic technology is described for the determination of the composition of typical mixtures of flue gases [A. I. Abd El-Rahman et al., “Thermoacoustic flue-gas analyzer,” EG Patent: International Application No. PCT/EG2020/0000029 (September 23, 2020)]. The hot flue-gas mixtures resulting from the combustion of high-carbon bituminous coal and low-carbon natural gas are allowed to fill in the resonator of an optimized half-wavelength thermoacoustic engine at TH = 900 °C. Under controlled cooling, spontaneous gas–particle oscillations appear at distinct values of resonance frequencies and onset temperature gradients that particularly depend on the molar concentrations of the quaternary-gas components (CO2, CO, O2, and N2) of the introduced samples. Operational ternary diagrams along with respective sensitivity profiles are discussed in detail.