Composition-sensitive energy saving in distillation column sequences for natural gas liquids (NGL) separation

Distillation is the energy-intensive separation process that recorded approximately 40% of the energy usage in the chemical and petrochemical industries. Natural gas liquids (NGL) is a product of distillation process which characterised by the multicolumn setup that leads to high heating and cooling requirements. Therefore, the main purpose of this study is to investigate the application of driving force method (DFM) with the support of the thermal pinch analysis (TPA) to enhance the energy saving of the NGL distillation process under various feed composition scenarios. The NGL distillation process in this case study comprising three types of feed composition of propane, i-butane, n-butane, i-pentane, and n-pentane, were simulated using Aspen HYSYS. Then the TPM was carried out by utilising the Aspen Energy Analyzer to produce grand composite curves (GCC) and to propose the heat exchanger network (HEN) design. From the results, Composition 2 with lighter feed recorded the highest total energy saving of 33.42%, followed by balanced feed (Composition 1) with 32.42% and lastly Composition 1 (heavier feed) with 29.09% energy saving. The analysis from GCC and HEN further explained on the dynamics of the energy requirement based on the feed composition and reaffirm that the combination of DFM and TPM successfully enhanced the energy saving across various composition scenarios.