Exergy and Exergoeconomic Assessment of an Acid Gas Removal Unit in a Gas Refinery Plant

Energy, exergy, economic, environment, exergo-environment based assessment of amine-based hybrid solvents for natural gas sweetening

Natural gas is the cleanest form of fossil fuel that needs to be purified from CO₂ and H₂S to diminish harmful emissions and provide feasible processing. The conventional chemical and physical solvents used for this purpose have many drawbacks, including corrosion, solvent loss, high energy requirement, and the formation of toxic compounds, which ultimately disrupt the process and affect the environment. Hybrid solvents have lately been researched to cater to these liabilities and enhance process economics. This study screened eight solvents based on CO₂ selectivity viscosity, absorption enthalpy, corrosivity, working capacity, specific heat, and vapor pressure. From the screened solvents, ten cases of hybrid solvents are simulated and optimized on Aspen HYSYS®. Furthermore, 5Es (Energy, Exergy, Economic, Environmental, and Exergy-environmental) analyses were performed on optimized cases, and results were compared with the base case, MEA (30 wt%). The hybrid blend of Sulfolane and MDEA with weight percentages of 6% and 24%, respectively, showed the highest energy savings of 20% concerning the base case. In addition, it offered 93% savings in exergy destruction and 17.26% in the total operating cost of the process. It is also promising to the environment due to reduced entropy sent to the ecosystem and controlled CO₂ emissions. Therefore, the blend of Sulfolane and MDEA is proposed to Supersede the conventional solvent MEA for the natural gas sweetening process.

Exergy, advance exergy, and exergo-environmental based assessment of alkanol amine- and piperazine-based solvents for natural gas purification

Purification of Natural gas is vital for utilizing it as a source of energy harvesting for the world. Amine-based chemical absorption technique is the most utilized in the gas field for the purification of gas that ensures the purity of the sweet gas stream with the elimination of carbon dioxide. However, it is considered an energy-intensive process to deal with considerable energy loss and environmental damage to the ecosystem. Five cases have been developed in this study based on various blends comprising mono and tertiary amines in combination with piperazine with a focus on the use of Aqueous Monodiethanolamine (Aq. MDEA), Aqueous Monoethanolamine (Aq. MEA) and piperazine (Pz) for the CO₂ sequestration from the sour natural gas extracted from the remote location located in the province of Baluchistan in Pakistan. The use of exergy, advanced exergy, and exergo environment for optimizing and selecting a suitable solvent combination that may result in an effective separation process has been proposed. Five cases have been developed based on various blends such as mono and tertiary amines combined with piperazine. From the results of all the studied scenarios, Case IV, based on the combination of Aqueous monoethanolamine and piperazine, provides reduced exergy destruction of 2551.7 KW. It was observed that the maximum removal of CO₂ around 99.87 wt% is achieved in case IV. In addition, advance exergy analysis also highlights that case-IV has a venue of 25% exergy destruction avoidable, which would further enhance its performance. Nevertheless, still, case-IV has 75% exergy destruction unavoidable. The environmental factors show that Case-IV has a reduced exergy destruction factor of 0.96, a highly environmentally benign choice as a solvent with a high value of 1.03, and case-IV has the higher operational stability and higher exergy efficiency with an exergy stability value of 0.40. Therefore, monoethanolamine combined with piperazine to be an effective and efficient solvent blend that could be an energy-effective approach for sweetening the natural gas.

The Feasibility Study, Exergy, and Exergoeconomic Analyses of a Novel Flare Gas Recovery System

One of the challenging issues that has always attracted the attention of the experts is how to control and reduce greenhouse gas emissions because of their overwhelming negative environmental impacts. Although burning the hazardous gaseous products in the flare systems boosts the safety of gas and oil fields and diminishes the internal pressure of the extraction systems, it has a catastrophic impact on the surrounding environment. In this study, a new system was designed to recover flare gas. In this system, ejectors and compressors are used in parallel to compress flare gas. One of the aims of this system is to minimize environmental disadvantages and prevent the waste of national capital. The described system is firstly simulated using the HYSYS software based on Peng–Robinson state equations. The efficiency and exergy destruction can be calculated through exergy analysis, which is the second step in the process. Finally, by considering investment and fuel cost to each exergy flow, exergoeconomic analysis was evaluated. From the exergy analysis results, it can be concluded that the ejectors have the highest exergy efficiency (99.87%) compared with other devices in the process, and their total exergy destruction rate is 8458.35 kW. Findings from exergoeconomic analysis suggest that the highest exergy destruction cost for flare system is associated with EJ-3 ejector which is 89.01 USD/h. Furthermore, a sensitivity analysis was applied to specify the dependency of the exergy and exergoeconomic results of this process on the flow rate of recovered gas and flare gas pressure as important input plant feed parameters. By this study, we aim to evaluate the feasibility of the implementation of this system in an industrial plant.