Post-combustion Carbon Capture for Combined Cycle Gas Turbines

The Intergovernmental Panel on Climate Change (IPCC) have conveyed in their fifth assessment report that anthropogenic emissions and endeavours are responsible for approximately 100 % of global warming since 1950 [1] and electricity and heat generation account for 41 % of the 32.8 billion tons of global CO2 emission from fossil fuel combustion in 2017 [2]. There is thus a sense of urgency to capture CO2 from large point sources of fossil fuel combustion to limit global temperature rise. Natural gas combustion is envisaged to play a fundamental role towards a zero-carbon economy as opposed to coal and oil due to its low carbon content. However, capturing CO2 from natural gas combustion, which emits about 6.7 billion tonnes of CO2 in 2017 is challenging as it, bestows a parasitic energy penalty on Natural Gas Combined Cycle (NGCC) power plants. This is due to the low partial pressure of CO2 in the flue gas of gas turbines, which necessitate that substantial reboiler heat duty is employed for solvent regeneration. To address the aforementioned impasse, pertinent experimental campaigns at the UKCCSRC- PACT National Core Facility were carried out to simulate Selective-Exhaust Gas Recirculation (S- EGR) under the influence of 40 wt(%) of Monoethanolamine (MEA). This was to enhance the driving force behind CO2 capture and to reduce the Specific Reboiler Duty (SRD), consequently counterweigh against the forfeit on the power plant’s productivity. Furthermore, the impact of varying Pressurized Hot Water (PHW) temperature at the inlet of reboiler was studied. The influence of oxidative degradation of the amine solvent at 15 vol(%) of O2 and 5 vol(%) of CO2 has been experimentally investigated. Results from these studies have demonstrated that Selective Exhaust Gas Recirculation (S-EGR) is favourable in reducing the solvent regeneration energy requirement by about 25 % at CO2 concentration of 6.6 vol(%) prior to flue gas introduction in the Post-combustion Carbon Capture (PCC) system. PHW temperature at 125 °C was identified to give the lowest SRD by 6 % against the baseline SRD. Detection of Dissolved Oxygen (DO) peaks was observed as water from the water-wash column was transferred to the absorber column which may have a possible impact on the oxidative degradation of the amine solvent in the PCC system. The concentration of the Iron in the amine solvent, which is a key indicator of the solvent decay increased by approximately 10 times from 3.68 to 36.20 mg/l over a course of 545 hours of experimental operation. Results and recommendations from these studies will potentially reduce the solvent regeneration energy requirement of the next generation PCC technologies and facilitate the global deployment of such technologies towards decarbonisation of the fossil fuel combustion industries and strengthening the efforts of limiting global temperature increase.