Hydrogen is expected to play an important role in renewable power storage and the decarbonization of the power sector. In order to clarify the environmental impacts of power regenerated through hydrogen-fueled gas turbines, this work details a life cycle model of the greenhouse gas (GHG) and NOx emissions of the power regenerated by power-to-H₂-to-power (PHP) technology integrated with a combined cycle gas turbine (CCGT). This work evaluates the influences of several variables on the life cycle of GHG and NOx emissions, including renewable power sources, hydrogen production efficiency, net CCGT efficiency, equivalent operating hours (EOH), and plant scale. The results show that renewable power sources, net CCGT efficiency, and hydrogen production efficiency are the dominant variables, while EOH and plant scale are the minor factors. The results point out the direction for performance improvement in the future. This work also quantifies the life cycle of GHG and NOx emissions of power regenerated under current and future scenarios. For hydro, photovoltaic (PV) and wind power, the life cycle of the GHG emissions of regenerated power varies from 8.8 to 366.1 g_CO2e/kWh and that of NOx emissions varies from 0.06 to 2.29 g/kWh. The power regenerated from hydro and wind power always has significant advantages over coal and gas power in terms of GHG and NOx emissions. The power regenerated from PV power has a small advantage over gas power in terms of GHG emissions, but does not have advantages regarding NOx emissions. Preference should be given to storing hydro and wind power, followed by PV power. For biomass power with or without CO₂ capture and storage (CCS), the life cycle of the GHG emissions of regenerated power ranges from 555.2 to 653.5 and from −2385.0 to −1814.4, respectively, in g_CO2e/kWh; meanwhile, the life cycle of NOx emissions ranges from 1.61 to 4.65 g/kWh, being greater than that of coal and gas power. Biomass power with CCS is the only power resource that can achieve a negative life cycle for GHG emissions. This work reveals that hydrogen-fueled gas turbines are an important, environmentally friendly technology. It also helps in decision making for grid operation and management.

CO₂ sequestration by flue gas desulfurization gypsum (FGDG) has become a promising FGDG disposal technology due to simultaneous CO₂ emission reduction and FGDG conversion into calcium carbonate. In this paper, another merit of the novel technology, i.e., the removal of toxic elements (e.g., Hg and As) in FGDG, will be addressed for the first time. In three different aqueous ammonia (or amines) media, removal efficiencies of Hg and As in FGDG samples were evaluated during CO₂ sequestration. Higher than 90% and 20% removal efficiencies, respectively, for Hg and As are achieved at 40°C in aqueous ammonia media, but they decrease at elevated temperatures. Ammonia loss takes place at 80°C and pH varies greatly with temperatures in aqueous ammonia. This is disadvantageous for the formation of Hg–ammonia complexes and for the yield of carbonates, which are responsible for Hg or As re-adsorption. The sequential chemical extraction method suggests that the speciation changes of Hg are induced by FGDG carbonation, and that unstable Hg speciation in triethanolamine increases at elevated temperatures.

The emission of nitric oxide from the combustion process of fossil fuels causes air pollution problems. In addition to traditional removal methods, nitric oxide can be removed by the electrochemical reduction method. In this study, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ powders were synthesized using a solid-state reaction method. Symmetrical cells, with Sm_0.2Ce_0.8O_1.9 as the electrolyte and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ as the electrodes, were prepared as the electrochemical reactor for nitric oxide reduction. In the process of electrochemical reduction, nitric oxide reduction occurs at the cathode and oxygen evolution occurs at the anode. To study the nitric oxide reduction performance of the electrode, impedances of the symmetrical cell in different atmospheres were analyzed. For the nitric oxide conversion in symmetric cells, two different modes, dual chamber and single chamber, were applied. Results demonstrated that the denitrification performance of the double chamber was better but the single chamber mode had other advantages in its simple structure. Presliminary stability results of the single chamber symmetric cell show that the electrochemical reduction of nitric oxide in symmetric cells with BSCF performed most reliably.