Simulation and optimization of a liquified petroleum gas sweetening process using Aspen HYSYS

Abstract

Liquefied petroleum gas (LPG) is one of the common fossil fuels that can be derived from natural gas or crude oil. In either case, it contains impurities such as H2S and CO2, which should be removed to obtain sweet liquified petroleum gas with a pure concentration of hydrocarbons such as ethane, propane, and butane. The most common method of gas sweetening process is by using amine compounds, which come in various types, each designed for specific and selective removal of acidic gases. In this study, methyldiethanolamine (42 wt.%) was used as a solvent to extract approximately 0.8% of H2S from sour LPG at a temperature of 400C. The objective of this study focuses on simulating and optimizing the LPG sweetening unit using Aspen HYSYS V11 to investigate the different parameters that affect the separation of acidic gases and to achieve high profitability. The number of trays, circulation rates, temperature, mass and molar flow rates, and other parameters were studied to reduce the H2S concentration to 0% in the treated LPG stream. The sweetening process was proposed to produce LPG with high levels of specific preferred specifications such as calorific value and purity, in addition to being environmentally friendly.