(29d) Comparison of Distillation Packing Efficiency Through HETP or Mass-Transfer Coefficients Obtained by Profile-Method

Cyclohexane/n-heptane mixture serves as one of standard distillation test systems. Introduction of standard systems should ideally enable comparison of packing performance determined at various sites. This data comparison is conditioned, however, by identification of all relevant process parameters and by keeping them constant at all facilities.

This contribution presents hydraulic and HETP data measured with Mellapak 250Y under atmospheric pressure with various fractions of C₆ in the batch. It is revealed that HETP, pressure drop and capacity of tested packing significantly depend on the composition of the batch. This implies, that local hydraulic and efficiency output of the packing is dependent on the local composition of the mixture and overall results are dependent on the achieved separation – composition range over the packed bed.

To remedy the problem pure n-heptane is used by our workplace for hydraulic measurements, while separation efficiency measurements are performed with composition of the mixture within narrow range in the bottom of the column.