The Recuperative Auto Thermal Reforming and Recuperative Reforming Gas Turbine Power Cycles With CO_2 Removal―Part Ⅱ: The Recuperative Reforming Cycle

摘要

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 CO_2 removal by the natural gas fuel reforming. The second part of the paper is dedicated to the R-REF cycle: the power unit is a gas turbine (GT), fuelled with reformed and CO_2 cleaned gas, obtained by the addition of several sections to the simple GT cycle, mainly: · reformer section (REF), where the reforming reactions of methane fuel with steam are accomplished: the necessary heat is supplied partially by the exhausts cooling and, partially, with a post-combustion, · water gas shift reactor (WGSR), where the reformed fuel is, shifted into CO_2 and H_2 with the addition of water, and · CO_2 removal unit for the CO_2 capture from the reformed and shifted fuel. No water condensing section is adopted for the R-REF configuration. Between the main components, several heat recovery units are applied, together with GT cycle recuperator, compressor intercooler, and steam injection into the combustion chamber. The CO_2 removal potential is close to 90% with chemical absorption by an accurate choice of amine solution blend: the heat demand for amine regeneration is completely self-sustained by the power cycle. The possibility of applying steam blade cooling (the steam is externally added) has been investigated: in these conditions, the R-REF has shown efficiency levels close to 43-44%. High values of specific work have been observed as well (around 450-500 kJ/kg). The efficiency is slightly lower than that found for the R-ATR solution, and 2-3% lower than CRGTs with CO_2 removal and steam bottoming cycle, not internally recuperated. If compared with these, the R-REF offers higher simplicity due to absence of the steam cycle, and can be regarded as an improvement to the simple GT. In this way, at least 5-6 points efficiency can be gained, together with high levels of CO_2 removal. The effects of the reformed fuel gas composition, temperature, and pressure on the amine absorption system for the CO_2 removal have been investigated, showing the beneficial effects of increasing pressure (i.e., pressure ratio) on the specific heat demand.