Distillation process and multi-column heat-integrated distillation system

A process for separating a multi-component feed mixture in a distillation system comprising a first distillation column having a first fired reboiler, and a second distillation column having a second heat-exchange reboiler, comprising:

• a) introducing the feed mixture into the first distillation column, and separating into at least a first top and a first bottom product;
• b) adjusting pressure of the first bottom product and heating in the first fired reboiler and returning part thereof to the first distillation column as a first circulating reboiler stream;
• c) taking another part of heated stream from the first fired reboiler for providing heat to the second heat-exchange reboiler as a utility stream,
• d) feeding part of said utility stream after heat-exchange as main feed to the second distillation column for further separation;
• and
• e) heating another part of said utility stream after heat-exchange with the first bottom product in step b);
• wherein temperature and pressure of said part of said utility stream are adiabatically adjusted before feeding to the second column.