Dew and Frost Points Measurements and Estimation for Residual Gases in High-Pressure Hydrogen

Dew and frost points estimation procedure for phase equilibrium systems with solid phases as condensed phases was developed utilizing Peng-Robinson equation of state (PR-EOS), and estimation for H₂+H₂O systems corresponding to actual hydrogen stations of pressure up to 70 MPa were carried out. It became clear that condensable components in hydrogen stations were only water. Dew and frost point measurement system with high pressure test cell utilizing cooled mirror technique with original visible image analysis were designed and produced. The system was designed available for frost point temperature below −50 °C, and total pressure of system up to 10 MPa. Pressure tight test cell with view port was installed separately from the optics, and had extensible design available for higher pressure experiments up to 40 MPa. Dew and frost points measurements with several compositions of H₂+H₂O standard gases were carried out. Frost point data obtained by the present measurement system with pressure tight test cell had good repeatability, and obtained binary interaction parameter k_ij was small value with the negative sign for about 5 MPa, 50 ppm conditions.