Features of liquid mixtures separation in large-scale distillation columns with structured packing. New ideas and approaches

Abstract

Negative vapor stratification along the height of distillation column caused by different density of vapor mixture components and higher temperature at the column bottom, leads to formation of large-scale maldistribution of temperature and mixture composition over the column cross-section even at uniform irrigation of the structured packing. Experimental results concerning the dynamic effect of packing irrigation on separation efficiency of the two-component mixture of R-21 and R-114 are presented in this paper. The structured packing Zulser 350Y was installed in the distillation column with the diameter of 0.9 m. Experiments were carried out on the 10- and 19-layer packing with an overall height of 2.1 and 4 m, respectively. The liquid distributor with independently controlled 126 valves for each irrigation point, developed by the authors, was used for packing irrigation. The experiments showed that the periodic impact of the irrigation system on the large-scale non-uniformity of mixture composition, formed in the packing, could significantly affect the distribution of flow parameters over the cross-section and height of the mass transfer unit. Essentially nonuniform periodic irrigation of the packing can improve the separation efficiency of the column within 20%, if the switching periods are comparable with the times of formation of large-scale non-uniformity.