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.