Humidified ammonia/hydrogen RQL combustion in a trigeneration gas turbine cycle

Abstract

Ammonia is an example of a zero-carbon fuel of high interest for implementation in gas turbine technologies. Preliminary analyses showed that a basic humidified ammonia-hydrogen Brayton cycle can produce total plant efficiencies of ~34%. However, further improvements are required to make these units competitive to current fossil-based plants whose efficiencies are above 80%. Thus, this work seeks to numerically and analytically demonstrate the implementation of a complex cycle that will increase final efficiencies whilst using the full potential of ammonia as a cooling fluid, power fuel and heating gas (i.e. trigeneration cycle) with heat district distribution. Therefore, a basic gas turbine cycle was inserted into a two-shaft, reverse Brayton gas turbine plant facility. In order to improve combustion and reduce emissions, a Rich-Quench-Lean system was integrated into the analysis by resolving the combustion performance via CHEMKIN-PRO. Detailed sensitivity analyses were also conducted throughout the burner to identify the key reactions responsible for both flame stability and NO formation/reburn pathways, which are vital for future safe and efficient operation of these types of cycles. The study shows that the total efficiency has significantly increased when compared to the basic turbine facility, with a value ~59%. Moreover, low emissions were accomplished below current European NOx thresholds. The obtained values show a significant potential for the utilisation of ammoni-based blends with steam injection in gas turbine facilities through employment of novel cycles that consider lower dilution in the combustion sector in combination with novel ammonia combustion systems and trigeneration concepts.