The Recuperative-Auto Thermal Reforming and the Recuperative-Reforming Gas Turbine Power Cycles With CO2 Removal—Part I: The Recuperative-Auto Thermal Reforming Cycle

Abstract

The relatively innovative gas turbine based power cycles R-ATR and R-REF (Recuperative–Auto Thermal Reforming GT cycle and Recuperative–Reforming GT cycle) here proposed are mainly aimed to allow the upstream CO2 removal by the way of natural gas fuel reforming. The power unit is a gas turbine (GT), fueled with reformed and CO2 cleaned syngas produced by adding some basic sections to the simple GT cycle: • auto thermal reforming (ATR) for the R-ATR solution, where the natural gas is reformed into CO, H2,CO2,H2O, and CH4; this endothermic process is completely sustained by the heat released from the reactions between the primary fuel (CH4), exhausts and steam. • water gas shift reactor (WGSR), where the reformed fuel is, as far as possible, shifted into CO2 and H2 by the addition of water. • water condensation, in order to remove a great part of the fuel gas humidity content (this water is totally reintegrated into the WGSR). • CO2 removal unit for the CO2 capture from the reformed fuel. Among these main components, several heat recovery units are inserted, together with GT cycle recuperator, compressor intercooler, and steam injection in combustion chamber. The CO2 removal potential is close to 90% with chemical scrubbing using an accurate choice of amine solution blend: the heat demand is completely provided by the power cycle itself. The possibility of applying steam blade cooling by partially using the water released from the dehumidifier downstream the WGSR has been investigated: in these conditions, the R-ATR has shown an efficiency range of 44–46%. High specific work levels have also been observed (around 450–550 kJ/kg). These efficiency values are satisfactory, especially if compared with ATR combined cycles with CO2 removal, more complex due to the steam power section. If regarded as an improvement to the simple GT cycle, R-ATR shows an interesting potential if directly applied to a current GT model; however, partial redesign with respect to the commercially available version is required. Finally, the effects of the reformed fuel gas composition and conditions on the amine CO2 absorption system have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the thermal load per kg of removed CO2.