Hydrocarbon mixture fractionation direct sequence retrofitting and feed condition sensitivity analysis

Abstract

The objective of this paper is to present the retrofit analysis for the hydrocarbon mixture (HM) direct sequence fractionation process and to analyse the process sensitivity with respect to feed conditions. To perform the study and analysis, the energy efficient HM separation process methodology has been developed. The methodology consists of four hierarchical steps. In the Step 1, a simple and reliable short-cut method of process simulator (Aspen HYSYS) is used to simulate a direct HM sequence. The energy used to recover individual fractions in the base sequence is analysed and taken as a reference. In the Step 2, an optimal HM sequence is determined using driving force method. All individual driving force curves for all adjacent components are plotted and the optimal sequence is determined based on the plotted driving force curves. Once the optimal HM sequence has been determined, the new optimal sequence is then simulated in Step 3 using a simple and reliable short-cut method (using Aspen HYSYS), where the process sensitivity and energy used in the optimal HM sequence are analysed, the process sensitivity of optimal HM sequence is compared with the other three different sequences by changing their feed conditions. Better sensitivity sequence was achieved when compared optimal sequence with the other three sequences in Step 4, the sequence determined by the driving force method has better sensitivity compared to the three other sequences as well as less energy requirement. All of these findings show that the methodology is able to design better sensitivity and minimum energy distillation column sequence for HM fractionation process in an easy, practical and systematic manner.