Experimental Studies On Vapor-Liquid Mass Transfer And Mixing Properties In Structured Packing Under Elevated Pressure

The performance of gauze corrugated structure packing in distillation applications at pressures ranging from 0.7 to 1.9MPa had been analyzed .These data were obtained in a 19mm diameter distillation column operated with n-butane/i-butane system at total reflux. The results indicated that with the increase of operating pressure, the separating efficiency increased also. Under the same operating pressure, the HETP (height equivalent to a theoretical plate) values decreased slightly with the increase of F-factor in the loading area but increased before flooding point. The HETP values varied from 0.05m to 0.12m with pressured and F-factor changed. By compared with early experimental data of Tianjin University and F.R.I. (Fractionation Research Inc.), it could be found that the experimental results differed with data from some of literatures.It was believed that these differences were brought about by discrepancy of pilot plant scale and packing column internals between them.After mechanics and reasons of efficiency hump were analyzed, it could be found that the main reasons were maldistribution induced by various factors as well as back mixing of vapor and liquid.The effects of physical property of system on mass transfer process were investigated; it could be concluded that some factors were benefited to mass transfer process, such as lower surface tension, minor viscosity and density of liquid, less gas viscosity and higher gas density and so on.With the actually measured concentration profile of the gas during distillation, the axial back-mixing coefficient of gas phase was measured by the 1D axial diffusion models. The results revealed that the axial back-mixing coefficient of gas phase increased with the velocity of the gas and liquid phase, and that the pressure had little impact on it. Finally the correlation equation of the axial back-mixing coefficient of gas phase was given in these experimental conditions. The calculated values were compared with the experiment values and the average deviation between them was less than 15%.