Thermo-economic analysis of natural gas treatment process using triethanolamine (TEA) and diethanolamine (DEA) as gas sweeteners

The concept of thermo-economics was used to analyse natural gas process in a quest to find the most efficient process route to process natural gas from exergetic-economic performance view. This work was carried out to identify the most thermo-economic efficient absorbent in natural gas process using Aspen Hysys® as process simulator. Two different process configurations for natural gas processing (Diethanolamine (DEA) and Triethanolamine (TEA) amine solvent process) were assessed on the basis of exergetic and economic efficiency using similar feed rate and product specifications. The two processes were simulated using feed flow of 1245 kmol/h to produce a clean and treated natural gas with purity of 99% in the final product exit stream. The results of the simulation obtained were data generated for stream properties, heat duties, power requirement and equipment sizes required to carry out exergy and economic evaluation. Energy analysis showed that the two processes satisfied the principles of energy conservation but differs in the amount of energy required and produced. The overall exergetic efficiency and irreversibility of the two selected processes configurations using DEA (97.97%, 49.82 GJ/h) and TEA (98.91%, 21.26 GJ/h) absorbent were determined respectively. Exergy analysis of equipment reveals that amine contactor and regenerator are the major areas of exergy destruction and least efficient among all equipment. The economic analysis result shows that the two processes (DEA and TEA process) have similar payback period and rate of return on investment of 4 years and 26% respectively. The DEA process is favoured by higher net profit after tax of $ 2,927,993. Thermodynamic and economic analysis of both configurations shows TEA and DEA to have close or similar performance in many respect. Therefore, comparison and the use of thermo-economic performances as a discriminating factor between the two selected processes favours the selection of TEA process as the best alternative route to treat natural gas despite fast kinetics, low investment capital and high enthalpies of absorption that favours DEA process in achieving higher purity natural gas.