Premixed ammonia/hydrogen swirl combustion under rich fuel conditions for gas turbines operation

Energy storage is one of the highest priority challenges in transitioning to a low-carbon economy. Fluctuating, intermittent primary renewable sources such as wind and solar require low-carbon storage options to enable effective load matching, ensuring security of supply. Chemical storage is one such option, with low or zero carbon fuels such as hydrogen, alcohols and ammonia having been proposed. Ammonia provides zero-carbon hydrogen storage whilst offering liquefaction at relatively low pressures and atmospheric temperatures, enabling ease of transportation in a pre-existing infrastructure. Ammonia can also be used directly as a fuel in power plants such as gas turbines to avoid complete conversion back to hydrogen. It is a relatively unreactive fuel, and so it is of interest to explore the potential utilisation of ammonia/hydrogen mixtures. Hence, the goal of this paper is to provide a first assessment of the suitability of a chosen 70%NH330%H2 (%vol) blend for utilisation within a gas turbine environment, based on primary combustion diagnostics including combustion stability – via OH chemiluminescence - and emissions (NOx and NH3). An established optical generic swirl-burner enabled studies of the influence of equivalence ratio (φ > 1), ambient temperature (<484 ± 10 K) and bypass air, with a focus on NOx reduction, one of the main challenges for ammonia combustion. A numerical GT cycle model is developed alongside the experimental investigation. The results demonstrate that the blend has considerable potential as a fuel substitute with reasonable combustion stability and significant reduction of emissions for the cases without bypass air, due to increased chemical reactivity of unburned ammonia. However, emissions are still above those recommended for gas turbine cycles, with a theoretical cycle that still produces low efficiencies compared to DLN methane, highlighting the requirement for new injection techniques to reduce NOx/unburned NH3 in the flue gases whilst ensuring increased power outputs

CO2-argon-steam oxy-fuel (CARSOXY) combustion for CCS inert gas atmospheres in gas turbines

CO2 emitted from gas turbines in power plants is considered a major contributor to the global environmental damage. Carbon Capture and Storage (CCS) integrated with oxy-fuel (OF) combustion is an advanced and innovative approach that may be used in turbines to reduce these emissions. This method is based on CO2 recycling, however the obstacle to using this recirculation approach in gas turbines is reduction in their performance and reliability. This paper attempts to address the problem in a novel way by investigating theoretically a number of blends that can overcome the performance and reliability issues of pure CO2. These blends, comprising of argon, H2O and CO2, can be used as a working fluid with oxygen and methane as reactants. Additionally, a numerical model for an industrial gas turbine is employed. The aim is to find the optimum blend for complete NOx elimination with a recirculation of products. This study uses 0-D chemical kinetic software (Gaseq), an empirical selection approach with design of experiments and, 1-D chemical kinetic software (CHEMKIN-PRO). Results identify the optimum blend which is numerically assessed in an industrial gas turbine that has been experimentally correlated. The efficiency of this turbine running the selected blend is 1.75–13.93% higher than when running with natural gas/air conditions. This shows the promising use of this blend for a future high efficiency CCS-Oxyfuel approach in gas turbine combustors