Energy and exergy analysis of a five-column methanol distillation scheme

In the present paper, a five-column heat integrated methanol distillation scheme is proposed with the aid of process simulation and pinch analysis. Unlike the popular four-column (or 3 + 1 column) scheme, a medium-pressure column is added after the light ends column in this novel scheme. The overhead vapor of the medium-pressure column integrates with the light ends column, and an inter-reboiler is attached to the atmospheric column. Another highlight is that the water column produces fusel oil instead of the methanol product at the top. Analyses show that the energy consumption of the five-column scheme can be reduced by 15.23%, and that the total exergy loss can be decreased 21.5% in comparison to the popular improved four-column scheme, which is taken as the control flowsheet in this paper, and producing the same product methanol purity and yield.

► A novel five-column multi-effect methanol distillation scheme is proposed.
► Process simulation and pinch analysis are employed to design new scheme.
► The energy consumption of the five-column scheme can be reduced by 15.23% and total exergy loss is decreased.
► The maximum gas flow rate in each column of five-column scheme is smaller than that of the four-column scheme.
► The water column in four column scheme can be used as the medium-pressure column in five column scheme.