Techno-Economic and Environmental Evaluation of Expansion Turbines for Gas Field Improvement (Case study)

Regarding the increased energy consumption of the processes at the operational units in the National Iranian Oil Company, the present study analyzed energy consumption at one of the gas refineries. In this refinery, which is the main supplier of Fajr Jam refinery for the national gas network, as well as an injection into the oil fields of the Iranian South oil company, the pressure of gas after passing through a Joule Thomson valvefrom120 to 70 barg reduced. This pressure drop results in the loss of gas temperature, as a result, temperature decrease to -15 °c. Due to the sudden drop in gas pressure, considerable energy, it will be lost. Replacing the Joule Thomson valve with an expansion turbine to use its recoverable energy was also studied. Based on the results from HYSYS software as well as the refinery’s operational conditions, three solutions were discussed. These solutions include (1) using an expansion turbine for power generation, (2) using an expansion turbine to generate electricity and gas condensates, and (3) using an expansion turbine to produce condensates. Based on the technical and economic analysis of the solutions, as well as the results from environmental flow diagram (EFD), which is designed to compare the rates and the sources of the environmental pollutants, the second solution with an internal rate of return (IRR) of 74.53% and a payback period (PBP) of 1.3 years is regarded as the most suitable scenario. Results from EFD indicate that using the second scenario will decrease CO, CO2, and NOX by 57% in this refinery.