60057 - Experimental Study on High Pressure Combustion of Decomposed Ammonia 

Hydrogen can be a carbon-free fuel for both existing and future gas turbines. However, it is a challenging gas to transport and store due to its physical properties, and to burn due to its combustion properties favouring NOx formation and hindering the application of DLN technology. One solution is to produce ammonia from hydrogen and transport it as a liquid, which is already distributed worldwide at very large scale by pipeline, rail, road, or ship. Ideally, ammonia would be used directly on site as a fuel, but it has many combustion shortcomings, with a very low reactivity making flame stability challenging and a high propensity to generate NO_x far beyond current regulation limits. Alternatively, ammonia can be decomposed back to a hydrogen – nitrogen mixture (75/25 % by volume) which has better combustion properties, but at the expense of an endothermal reaction. Between these two options, a trade off could be a partial decomposition where the fuel is a mixture of ammonia - hydrogen – nitrogen.

The experimental research study presented aims at optimizing NH₃-H₂-N₂ blends to be used as a step-in fuel for natural gas and provide GT-manufacturers with guidelines for optimal operation for retrofit and new combustion systems. The gas turbine burner considered in this study is a down-scaled version of the latest Siemens burner technology used in the SGT-750 industrial gas turbine, tested in the SINTEF high pressure combustion facility HIPROX.

The overall behaviour of the burner in terms of stability and emissions have been characterized as a function of fuel mixtures representatives of full and partial decomposition of ammonia. It was found that when ammonia is present in the fuel, the NO_x emissions although high can be limited if the primary flame zone is operated fuel rich. Increasing pressure in these conditions has shown to have a strong and favourable effect by decreasing the NO_x formation, both when keeping the power constant or when increasing power linearly with pressure. When ammonia is fully decomposed to 75% H₂ and 25% N₂, the opposite behaviour is observed.