Prediction of Novel Humified Gas Turbine Cycle Parameters for Ammonia/Hydrogen Fuels

Abstract

Carbon emissions reduction via the increase of sustainable energy sources in need of storage defines chemicals such as ammonia as one of the promising solutions for reliable power decarbonisation. However, the implementation of ammonia for fuelling purposes in gas turbines for industry and energy production is challenging when compared to current gas turbines fuelled with methane. One major concern is the efficiency of such systems, as this has direct implications in the profitability of these power schemes. Previous works performed around parameters prediction of standard gas turbine cycles showed that the implementation of ammonia/hydrogen as a fuel for gas turbines presents very limited overall efficiencies. Therefore, this paper covers a new approach of parameters prediction consisting of series of analytical and numerical studies used to determine emissions and efficiencies of a redesigned Brayton cycle fuelled with humidified ammonia/hydrogen blends. The combustion analysis was done using CHEMKIN‐PRO (ANSYS, Canonsburg, PA, USA), and the results were used for determination of the combustion efficiency. Chemical kinetic results denote the production of very low NOx as a consequence of the recombination of species in a post combustion zone, thus delivering atmospheres with 99.2% vol. clean products. Further corrections to the cycle (i.e., compressor and turbine size) followed, indicating that the use of humidified ammonia-hydrogen blends with a total the amount of fuel added of 10.45 MW can produce total plant efficiencies ~34%. Values of the gas turbine cycle inlet parameters were varied and tested in order to determine sensibilities to these modifications, allowing changes of the analysed outlet parameters below 5%. The best results were used as inputs to determine the final efficiency of an improved Brayton cycle fuelled with humidified ammonia/hydrogen, reaching values up to 43.3% efficiency. It was notorious that humidification at the injector was irrelevant due to the high water production (up to 39.9%) at the combustion chamber, whilst further research is recommended to employ the unburned ammonia (0.6% vol. concentration) for the reduction of NOx left in the system (~10 ppm).

Performance Analysis of an Ammonia-Fueled Micro Gas Turbine

“…The goal is to maximize the electric efficiency of the system, while maintaining low NO concentration. With the same aim, an improved Brayton cycle fed by humidified ammonia/hydrogen was conceived theoretically by Božo and Valera-Medina [28], through a sensitivity analysis on Brayton cycle pressure ratio and compressor/turbine polytropic efficiency. The maximum cycle efficiency is up to 43.4%; hence, comparable to that of fossil-based systems.…”

“…None of the cited modeling studies ( [27][28][29]) accounted for part-load behavior of an ammonia-fueled MGT, which is instead particularly relevant for a prime mover in combined-heat and power (CHP) mode. More generally, the lack of tools predicting the off-design characteristics of an MGT-when integrated with on-site renewable technologies such as solar photovoltaics, wind turbines, as well as battery energy storage, to meet the power demand-was pointed out by Hampel and Braun [30].…”

Prospects for Using Hydrogen in Various Branches of the World Economy as One of the Directions of Its Decarbonization

“…Studies performed in various countries since the 1960s demonstrated in principle the possibility of using ammonia as a motor fuel without essential upgrade of internal combustion engines both when ammonia is added to standard motor fuel and when it is used as a mixture with methane, hydrogen, and organic solvents [36,[39][40][41]. In addition, ammonia, both in the pure form and in a mixture with methane and hydrogen, is considered as a fuel for gas turbines [42][43][44][45]. Recently there has been active progress in studies concerning the possibility of using the existing and developing new fuel cells allowing conversion of ammonia to electric power [42].…”

Evaluating ammonia as green fuel for power generation: A thermo-chemical perspective

“…These results are consistent with respect to previous analysis. Božo and Valera-Medina (2020) studied the operation of a humidified gas turbine alone excluding the combined cycle, the preparation of raw materials and the gas-clean up section. The maximum efficiency of this system was 43.4%.…”