Procedure for calculation

I am not sure that I understand your question nor do I know what you mean by "separation Index between two draw in multicomponent distillation column".

The degree of separation between two adjacent side-draws (or sidecuts) in a multicomponent column like an atmospheric crude oil distillation column or an FCC main distillation column will depend upon:

(1) The number of trays in the distillation column between the two sidecuts.
(2) The number of trays and the amount of steam used in the sidecut strippers.

Those two items are part of the complete process design calculation procedure for the distillation column.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

I think you should tune this separation index parameter untill you match the model with current product yields and qualities - whether it is Shell RefSim or Spiral ATS software that you use.

If one of my friends is reading this post, maybe he will be able to give you more detailed procedure.

Regards,