Energy-efficient distillation process with variation of inflow

A process for distilling a raffinate 2 stream as feed stream in a separation unit comprising a first distillation column DK1 and a second distillation column DK2, wherein the first distillation column DK1 and the second distillation column DK2 each comprise a top at an upper end of a column and a bottom at a lower end of the column, the process comprising:

• obtaining a vapour stream at the top of the first distillation column DK1 and at the top of the second distillation column DK2 and a bottom stream at the bottom of the first distillation column DK1 and at the bottom of the second distillation column DK2,
• feeding, to the second distillation column DK2, a portion of the vapour stream from the second distillation column DK2;
• at least partly condensing the vapour streams from the first distillation column DK1 and the second distillation column DK2, and
• heating, with a condensation energy obtained from at least one of the vapour streams from the first distillation column DK1 or the second distillation column DK2, by vapour compression or by a heat pump, the first distillation column DK1 and/or the second distillation column DK2;
• wherein at least the first distillation column DK1 has at least two different inlets for the feed stream, where the at least two different inlets, viewed from the top of the first distillation column DK1, are arranged one below another;
• wherein the feed stream is analysed for its composition before being introduced;
• and
• wherein one of the at least two different inlets for a supply of the feed stream is chosen depending on a composition of the feed stream.