EXPERIMENTAL-DETERMINATION OF CHANGES IN METHANOL MODIFIER CONCENTRATION IN PREMIXED CARBON-DIOXIDE CYLINDERS

Experiments were conducted to determine whether a modified Peng-Robins on equation of state (EOS) correctly predicted concentration shifts in premixed methanol-modified carbon dioxide during cylinder depletion. Calibration plots of supercritical fluid chromatography (SFC) retentio n time versus percent methanol modifier were prepared via dynamic mixi ng of methanol and pure CO2. These plots were then used to determine t he concentration of methanol in the premixed cylinder at various stage s of drawdown. The concentration of methanol modifier in the SFC grade CO2 was found to more than double during what would be considered the normal usage life of the cylinder. These results confirmed the validi ty of the EOS model for vapor-liquid equilibrium inside the premixed c ylinder.