A Direct Measurement of the C₂H₂ Concentration from the C₂H₂–Oil Mixed Solution Using the Photoacoustic Spectroscopy Method

Abstract

The photoacoustic (PA) method is commonly used in the measurement of trace gas concentration owing to its high accuracy and reliability. However, the conventional PA method is usually used in the gas-phase environment, which leads to a long measurement time and a large equipment volume for the degassing process. In this paper, we report a scheme to measure the acetylene (C2H2) concentration from the acetylene–dielectric oil (C2H2–Oil) mixed solution without the degassing process. The frequency and intensity distribution of the PA signal in the C2H2–Oil mixed liquid is investigated using the finite element method (FEM). Simulation results reveal that the incident light modulation frequency and the geometry size of the PA cell are two core factors to determine the PA signal. Furthermore, a PA sensor system is constructed to measure the concentration of C2H2 from the C2H2–Oil mixed solution. The measurement results demonstrate that the intensity of the PA signal in the C2H2–Oil mixed solution rises mostly linearly with the concentration of C2H2 from 0 to 100 mL/L. The Allan variance results from the continuous tests indicate that the measurement limit of the PA sensor system is about 0.2 mL/L. This work points to a novel method for the measurement of the C2H2 concentration from the C2H2–Oil mixed solution.

Keywords

• photoacoustic spectroscopy
• gas–liquid mixed solution
• direct measurement
• acetylene concentration