Energy-efficient design and optimization of a demethanizer column

Abstract

Complex column arrangement for a demethanizer used in natural gas processing is required to improve energy efficiency for the recovery of natural gas liquids, as a simplecolumn configuration is not flexible enough to achieve high ethane recovery without a largeamount of energy.As the demethanizer is operated in sub-ambient conditions, the column is typicallyinterconnected with heat exchangers and pressure-changing units. Also, for achieving energyefficient demethanizer, more than one streams to be reboilered are required, while multiplefeeding is necessary to create well-balanced reflux of liquid stream flowing down to thecolumn. Hence, in this study, systematic investigation is made to determine the mostappropriate configuration for the demethanizer and to design the column in a cost-effectiveand energy-efficient manner.Process Integration method is applied to assess energy and power recovery between acolumn and other units interconnected with the columns, with which inefficient features areidentified, and design guidance for improving separation performance without compromisingenergy consumption can be obtained. Case study is presented to demonstrate the importance of system-wide approach for determining configuration of the demethanizer column in practice.