Fuel-flexible gas turbine combustion technology for clean and efficient ammonia firing

Expected Outcome:The use of hydrogen in gas turbines holds significant promise as an enabler for a low-carbon economy and may serve as a pivotal tool in achieving the objectives of the European Green Deal. Nevertheless, the challenges associated with hydrogen storage and distribution remain major obstacles for its widespread adoption. Ammonia emerges as a complementary enabler of the hydrogen economy, functioning as a carbon-free energy carrier with properties well-suited for long-term storage and long-distance transport. Compared to hydrogen, liquefied ammonia storage is significantly less expensive and complex, and it exhibits a much narrower explosive range, enhancing its safety profile. Furthermore, a single mole of ammonia contains more hydrogen atoms than a mole of pure molecular hydrogen and it is entirely carbon-free if it is produced from renewable hydrogen. These characteristics make ammonia not only a practical medium for hydrogen transport but also a viable fuel option for direct use in gas turbines, supporting efforts to decarbonise the existing power generation infrastructure.However, the direct use of ammonia as gas-turbine fuel presents several significant challenges. Firstly, its narrow flammability limits, low reactivity, and slow burning rate introduce serious issues with flame stabilisation. Recent research suggests that partially decomposing ammonia into a mixture of ammonia, hydrogen, and nitrogen — achieved by utilising waste heat from the gas turbine — can help overcome these combustion challenges while also enhancing cycle performance. Secondly, a more challenging issue arises from the fuel-bound nitrogen in the ammonia molecule. Under the fuel-lean conditions typical of modern, clean and efficient natural gas-fired gas turbines, this nitrogen is readily oxidised in the presence of excess oxygen, leading to unacceptable emissions of nitrogen oxides (NOx), which are strictly regulated atmospheric pollutants, as well as nitrous oxide (N2O), a