Associated gas with oil extraction is usually burning through the flaring process. This process destroys a valuable natural resource that should be either recovered or stored. The process also pollutes the environment by emitting greenhouse gasses. The current study presents a novel external firing gas turbine cycle to recover the associated gas. The external firing prevents corrosion within gas turbine components due to the corrosive nature of the associated gas. To find an optimal design of the cycle, the comprehensive 4E analysis including Energy, Exergy, Environment and Economic analysis is carried out. The sensitivity analysis is employed to investigate the in- fluence of the key parameters such as the compressor pressure ratio and fuel cost on the evaluation criteria of the system i.e., energy efficiency, exergy efficiency, total cost and environmental impact. Moreover, the net present value and payback period criteria are applied to analyze the whole system economically. The results of the proposed system modeling show that at the base condition for fixed output electricity of 1200 kW, values of the principal parameters are as the 27.6%, 35.8%, 6553 $/kW, 269020 kg/kW, 12.3e7 $, 3.8 year for energy effi- ciency, exergy efficiency, total cost, environmental impact, net present value and payback period, respectively. As another activity, Multi-objective optimization using the NSGAII method is performed to achieve the optimal value of three selective objective functions as well as decision variables. Results reveal that there is a conflict between objective functions (total cost and environmental impact) and the other one i.e., exergy efficiency. It indicates that any effort to increase the system efficiency causes relatively higher costs and environmental issues. The final optimum values of the objective functions i.e. total cost, environmental impact and exergy efficiency are found to be 5864.6 $/kW, 241374.5 kg/kW and 33.4%, respectively.

Keywords