Carbon capture on micro gas turbine cycles: Assessment of the performance on dry and wet operations

Abstract

The large employment of renewable energies requires flexible, efficient and low-carbon production from fossil fuels. From all non-renewable power production routes, the electricity produced with micro Gas Turbines (mGTs) running on natural gas has a very high load flexibility and the lowest CO2 emissions. However, if we want to move towards full carbon clean power production, then CO2 in the exhaust must be captured. In this scenario, mGTs coupled with a Carbon Capture (CC) plant could be a suitable option, but only a few numerical and experimental analyses are available which assess their real potential.The low concentration of CO2 in the mGT exhaust gas is disadvantageous from a CC point of view, however the concentration can be increased by performing Exhaust Gas Recirculation (EGR). Furthermore, the efficiency loss introduced by the CC plant can also be reduced by using the concept of micro Humid Air Turbine (mHAT).In this study, both the dry and the wet operations of the Turbec T100 coupled with a chemical-absorption plant are simulated and compared using the software Aspen Plus®. The goal of these simulations was to investigate state-of-the-art measures which could be applied to small-scale generation to assess what the energy impact of a carbon clean production would be.Simulation results show that applying EGR to a mGT or mHAT can reduce the exhaust gas mass flow rate by 50% and it can increase the concentration of CO2 by three times the traditional cycle. The humidification of the mGT can entirely compensate for the efficiency losses of the EGR application. Both cycle performances are strongly affected by the thermal input from the stripping process, decreasing the global electric efficiency by around 7.9 absolute percentage points in the mGT case and by 8.3 absolute percentage points in the mHAT case in full load conditions. The results of this paper can be used as a starting point for new cycle concepts between the mGT and CC plant.