Design and optimization of heat integrated dividing wall columns for improved debutanizing and deisobutanizing fractionation of NGL

Abstract

Dividing wall columns, capable of reducing the energy required for the separation of ternary mixtures, were explored for the energy-efficient integration of debutanization and deisobutanization. A new practical approach to the design and optimization of dividing wall columns was used to optimize dividing wall columns. A conventional dividing wall column and a multi-effect prefractionator arrangement were shown to reduce total annual cost considerably compared with conventional distillation sequence. Various configurations incorporating a heat pump in a bottom diving wall columns were also proposed to enhance energy efficiency further. The result showed that operating cost could be reduced most significantly through novel combinations of internal and external heat integration: bottom dividing wall columns employing either a top vapor recompression heat pump or a partial bottom flashing heat pump.