Renewable energy sources such as offshore wind power will be vigorously developed, but the delivery of offshore wind power is a great challenge. Chemical energy storage via fuel synthesis using renewable electricity is a new type of energy storage technology to consume renewable energy including offshore wind power. At present, the most mature technology in this field is hydrogen production by electrolysis of water, but the storage and transportation of hydrogen face challenges, and ammonia synthesis powered by renewable electricity is a potential technology to store hydrogen. The traditional Haber-Bosch ammonia synthesis, which has been developed for more than 100 years, is mature, but the harsh conditions and high cost of plant construction make it difficult to adapt to the current scenario. Therefore, developing efficient and mild ammonia synthesis technology is urgent. This report reviews the low-pressure thermal-catalytic, electrochemical catalytic, and plasma-catalytic ammonia synthesis technologies that may be applied to the distributed ammonia synthesis powered by renewable electricity. Low-pressure thermal-catalytic ammonia synthesis can reduce pressure conditions to around 1 MPa, but the process is highly dependent on novel catalysts, whose long-lasting operation has not been fully demonstrated; electrochemical catalytic ammonia synthesis operating at atmospheric pressure can synthesize ammonia directly from nitrogen and water but faces challenges in terms of Faraday efficiency and ammonia yield; and ammonia yields of plasma-catalytic ammonia synthesis without heating under ambient pressure conditions can be comparable to those of thermal catalytic ammonia synthesis at 1 MPa, but its energy consumption needs to be further reduced. Finally, this report presents our latest research progress in plasma-catalytic ammonia synthesis in terms of catalyst supports screening, catalyst design, and the interaction between catalyst and plasma discharge.

Green NH₃ production using H₂ obtained from renewable energies offers a sustainable alternative that can significantly reduce CO₂ emissions compared to traditional NH₃ production. However, the mere integration of water electrolysis unit and NH₃ synthesis loop requires more energy than the conventional Haber-Bosch process. Achieving energy-efficient and environmentally friendly NH₃ production necessitates reducing energy consumption by shifting the reaction conditions to milder temperatures and pressures, but this is a formidable challenge due to the limitations imposed by reaction kinetics. Overcoming these challenges requires the development of novel catalysts capable of high activity under low temperature and low pressure conditions. Here, we introduce the progress made by the Korea Institute of Energy Research (KIER) in developing advanced heterogeneous catalysts for NH₃ synthesis. Our investigations first focus on how the catalytic components synergistically work with each other to show high activity. Based on these identifications, an optimal catalyst synthesis recipe was rationally derived. We then proceeded to scale-up and shape the invented catalyst to make it practical to use. KIER’s catalyst shows high activity and long-term stability in a bench-scale ammonia production process (> 1 kg NH₃ per day). Finally, we discuss the prospects and challenges of developing new technical catalysts for NH₃ synthesis.

The worldwide ammonia infrastructure is increasingly recognised as being the backbone of the global future hydrogen economy. In today’s hydrogen economy, which is dominated by oil refining and ammonia production, hydrogen is a transient molecule, in both time and place. Ammonia is the pragmatic choice to be the carbon- free chemical fuel that will over the coming decades displace fossil fuels. With green ammonia produced from air and water using renewable energy, hydrogen, in contrast, will continue to be a transient in its future eponymous economy.

This talk begins with a brief comparison of global hydrogen and ammonia infrastructures followed by a short outline of green ammonia production. The remainder of the talk with focus on turning carbon-free energy (in the form of ammonia) to carbon-free power (in the form of partially cracked ammonia). Our recent results will be presented which successfully show stable combustion of an ammonia/hydrogen/nitrogen blend rated at 56kW. Our current focus, the scaling-up of our ammonia cracking catalysts, will be presented and future opportunities discussed.

Green ammonia is increasingly recognized for its potential as a hydrogen carrier and carbon-neutral fuel. Aligned with Korea's Hydrogen Economy Roadmap, which aims to scale up hydrogen production and utilization by 2040, including significant hydrogen imports, the Korea Institute of Energy Research (KIER) is leading in developing cost-effective methods for both ammonia synthesis and ammonia cracking.

KIER is pioneering advancements in green NH3 production using H2 from renewable energies, significantly reducing CO2 emissions compared to traditional methods. Integrating a water electrolysis unit with an NH3 synthesis loop requires more energy than the conventional Haber-Bosch process. To address this, KIER focuses on reducing energy consumption by shifting reaction conditions to milder temperatures and pressures—a challenge constrained by reaction kinetics. KIER has developed advanced heterogeneous catalysts demonstrating high activity under low temperature and pressure conditions. By understanding the synergistic effects of catalytic components, an optimal catalyst synthesis recipe was derived, scaled up, and shaped for practical use, producing over 1 kg of NH3 per day in a bench-scale process.

Simultaneously, KIER advances ammonia cracking technology for clean hydrogen production. Notably, they developed an 1,000 Nm³/h class clean hydrogen production pilot plant via ammonia cracking. This plant utilizes an innovative single pressure swing adsorption (PSA) process, enhancing efficiency and achieving a high recovery rate while using tail gas as fuel for an integrated burner.

These initiatives by KIER represent significant strides towards low-cost, energy-efficient, and environmentally friendly ammonia synthesis and cracking technologies, essential for South Korea’s hydrogen economy and carbon-neutral goals.

Hydrocarbon fuels remain the primary energy sources for the economy and daily life presently. T o minimize carbon-based fuels consumptions have become more prominent than ever because the fact that the emission of greenhouse gases like carbon dioxide has cause the sea level rise globally. T o find an attractive alternative fuel for decarbonization movement has contracted many  attentions and efforts worldwide. Hydrogen is considered one of the ideal clean energy resources due to its high calorific value, having only H2O as a combustion product, fast flame propagation, and high energy density. However, whether it is liquid hydrogen storage at low temperature (−253 °C) or gaseous hydrogen storage at high pressure (~70 MPa), there are stringent requirements for the pressure or temperature resistance of storage vessel. Ammonia (NH3) is an important chemical product and has important applications in agriculture and industry. As  a promising ideal hydrogen storage sourc e,   a mmonia is also a new zero-carbon fuel with high octane number, high hydrogen storage density, and high energy density. Pure ammonia fuel requires high ignition energy when burning, and its flame propagation speed (~10 cm/s) and combustion temperature are much lower than that of methane and hydrogen. A mmonia offers a practical alternative for sustainable power generation by internal combustion engine, i.e. the engine and gas turbine. Because of the high-energy electrons and large number of active substances that promote the chemical process of ammonia ,  plasma technology is a promising instantaneous (<μs) ammonia decomposition and combustion technology to overcome the shortcomings of ammonia as fuels for internal combustion engines. I n this report we are going to present the fundamental research of plasma assisted ammonia decomposition and combustion, and the attempts to industry application in engines and gas turbines.

The properties of ammonia necessitate different strategies to enhance ignition, combustion development, and the range of operating conditions (such as low load and varying engine speeds). These strategies also aim to reduce unburnt ammonia in the exhaust of internal combustion engines. One attractive approach is the injection of more reactive molecules, as it can allow for the retrofit of existing engines.

In most studies, hydrogen is the most frequently considered molecule. It is a carbon-free molecule that can be produced on board by a reformer. However, hydrogen introduces safety concerns and potentially increases NOx emissions. Another approach is to inject reactive molecules found in conventional engine fuels (e.g., diesel or HVO) or bio-fuels (e.g., ethanol, DME). Although this method is gaining traction, the energy fraction share of these reactive molecules remains around 5%.

Additionally, other molecules that can improve ignition, such as NOx, ozone, and others, should also be considered to evaluate their potential.

Under the background of carbon neutrality, how to solve the power problem of heavy commercial vehicles? What kind of power system can fully meet the needs of heavy commercial vehicles for load, mileage, efficient transportation and TCO?

The future automotive power system will be diversified, electric, fuel cell and zero-carbon internal combustion engine are the three main technical routes.The zero-carbon internal combustion engine mainly includes hydrogen internal combustion engine and ammonia internal combustion engine. The load of electric vehicles is limited, the fuel cell durability and environmental adaptability need to be improved, the hydrogen engine mileage is limited, and they can not fully meet the power requirements of the above heavy commercial vehicles. Can the ammonia internal combustion engine meet the requirements? Because of the inertness of ammonia combustion, it is very difficult to develop ammonia internal combustion engine. However, if the combustion problem can be solved and its  thermal efficiency is improved, it will be a power system  that can fully meet the above requirements of heavy commercial vehicles.

Ammonia-hydrogen combined internal combustion engine is proposed: liquid ammonia in cylinder direct injection , hydrogen injection active pre-chamber jet ignition, high compression ratio, high pressure ratio and intelligent cooling, etc. Through a large number of CAE analysis and engine bench test, it is proved that the combustion system can achieve stable and efficient combustion, and the engine power and economy is comparable to that of diesel engine.

An on-board ammonia cracking and hydrogen production system was developed to realize the convenience of only carrying one ammonia fuel on the vehicle.

Ammonia-hydrogen combined internal combustion engine has achieved the multiple goals of "high power, high efficiency, whole life cycle economy and environmental protection".The engine is a competitive new energy power worthy of promotion and application in the field of heavy commercial vehicles.

In recent years, interest in green ammonia as potential alternative fuel for maritime applications has increased enormously. The marine internal combustion engine industry seems keen to develop diesel-ammonia DF engines, applying either the Conventional Dual Fuel concept (CDF) in which gaseous ammonia enters the engine cylinders via Port Fuel Injection (PFI) or a DFDI concept in which both diesel and ammonia are directly injected into the engine cylinders. In these concepts ammonia is used as an energy carrier only.

AmmoniaDrive seeks to develop power plant concepts that utilize ammonia both as energy and as hydrogen carrier. The intention is to “free” some of the hydrogen that is stored in ammonia and use it as a second fuel on board of ships. Either to improve the combustion of ammonia in large ICE’s for propulsion or use hydrogen directly in smaller ICE’s / Fuel Cells for electric power generation. An integrated concept in which hydrogen in the anode off gas of a high-temperature Fuel Cell is used as second fuel in one or more main propulsion engines is at the center of the research project.

The A+I invited lecture titled “Ammonia Energy for ship power and propulsion” will introduce the AmmoniaDrive concept as well as the research project. The collaboration between academia and industry within the project is emphasized by introducing the 20+ partners in the consortium as well as their interaction during General Assembly meetings.

In the context of fuel-flexible operation of gas turbines, providing on-demand large-scale electric power without incurring in emissions of CO2, a convenient feature of Ansaldo Energia’s Constant Pressure Sequential Combustion (CPSC) system is the possibility of controlling the amount of fuel independently fed to the two combustion stages depending on the reactivity and combustion characteristics of the fuel itself. Crucially, in the case of ammonia-based fuels, this includes the capability of switching the CPSC operating mode from a conventional Lean Pre-Mixed (LPM) combustion to a Rich-Dilute-Lean (RDL) staging strategy that mitigates undesired emissions of atmospheric pollutants (NOx) and greenhouse gases (N2O) emerging from the oxidation of fuel-bound nitrogen.

Building upon an earlier numerical-modelling assessment of the CPSC system capability to operate in RDL mode, the present work extends the scope of the initial preliminary study with a comprehensive set of additional calculations based on Large Eddy Simulations performed in conjunction with detailed chemical kinetics. Firstly, it is reported that, according to the numerical modelling predictions, a transition to stable, low-emission combustion of pure (non-decomposed) ammonia in the Multi-Burner First Stage (MBFS) can be achieved following an initial ignition and flame stabilization of a more reactive, partially decomposed ammonia blend. Secondly, it is shown that, at the equivalence ratio investigated, the unburnt fuel fractions emerging from the fuel-rich MBFS flames are completely oxidated by secondary air injected within the Dilution-Air Mixer (DAM) section of the CPSC. Furthermore, it is found that this burnout process occurring in the DAM section of the CPSC does not lead to significant increase of NOx and N2O emissions, thereby confirming the potential of the CPSC to operate cleanly and efficiently with ammonia-based fuels. The numerical simulations and the data analysis were conducted at SINTEF in collaboration with Ansaldo Energia and supported by the NCCS Research Centre.

Ammonia is a carbon free fuel with the potential to solve the issues related to the transport and storage of hydrogen. It is however a novel fuel with specific challenges that has rightfully triggered intense research on combustion fundamentals and generic configurations. Industrial burners and combustors are hardware that operate at varying loads and changing conditions, where flow dynamics and chemistry interact in complex manners. In this presentation we present results from downscaled models of industrial burners under relevant conditions of pressure and power, and investigated the effect of switching fuels from methane to mixtures with ammonia or decomposed ammonia mixtures.

The kingdom of Saudi Arabia (KSA) is blessed with an excellent combined solar and wind potential. Therefore, KSA is well positioned to become a leader in the production and export of green hydrogen (H₂) and its carriers, such as ammonia (NH₃) or methanol (MeOH). For this reason, KSA is highly motivated to promote R&D on technologies for green fuel production and utilization. As an example of such efforts, ENOWA is pioneering green fuel production, such NH₃, H₂, and MeOH in NEOM. In the first half of this talk, Prof. S. Mani Sarathy, former Senior Manager of Technology and Innovation at ENOWA will share his views on the production and export of green fuels in KSA, including key technology-based cost drivers.  

Through funding from Saudi Aramco and, more recently, NEOM, the King Abdullah University of Science and Technology (KAUST) in KSA has been working on the retrofitting of a current commercial micro gas turbine (mGT) to enable its operation with NH₃-H₂-MeOH blends. The target mGT is the Ansaldo AE-T100, which was originally developed for natural gas and outputs up to 100 kW_elec. This work will be detailed in the second part of this talk by Dr. Thibault F. Guiberti.

The prediction of combustion characteristics for ammonia and its blends with other fuels using CFD models presents a significant challenge, particularly in accurately quantifying NOx emissions. The results of recent collaborative research projects between Sapienza University of Rome and Baker Hughes will be presented, focusing on the application of CFD methodologies for the evaluation of NOx emissions in gas turbine burners. This research has been carried out using experimental data provided by Baker Hughes and Cardiff University with the aim of facilitating the integration of alternative fuels, such as ammonia and hydrogen, while contributing to the decarbonisation of the gas turbine sector. An initial investigation was carried out using kinetic analysis and low order models (0D-1D or RANS based) to gain a fundamental understanding of the combustion process. Subsequently, comprehensive and detailed numerical simulations were conducted using LES. Finally, a LES-CRN (Chemical Reactor Network) methodology was employed to enable comprehensive analysis of key combustion parameters. This approach has facilitated a deeper understanding of the mechanisms underlying NOx formation. The results of this collaboration highlight the importance of numerical investigations in advancing the development of sustainable energy solutions and support the ongoing efforts to reduce CO2 emissions from gas turbine systems.

Ammonia cofiring is a promising approach to reduce the CO₂ emissions from coal-fired boilers. However, the potential drastic increase of NO_x emissions may hinder its wide application. To explore the NO_x control strategies, systematic studies on the NO_x emission characteristics of ammonia cofiring were conducted in a laboratory 20 kW furnace, a 40 MW boiler, and a 630 MW boiler.

The laboratory furnace was designed to allow for ammonia injection with coal stream or downstream of coal injection to flexibly control the combustion environment of ammonia. A variety of trends of NO_x emissions with the increase of ammonia cofiring ratio (R_NH3) were observed under different ammonia injection conditions. It was found that all these trends are governed by the same mechanism – the competition between the NO formation and reduction reactions of ammonia in the varying O₂ environment in the furnace.

Then, industrial testing was conducted in a 40 MW boiler with R_NH3 in the range of 0% ~ 25%. The NO_x emissions showed similar trends to the laboratory experiments. The burnout of coal were also improved under ammonia cofiring conditions. Recently, ammonia cofiring was implemented on a 630 MW coal-fired boiler under 500 MW and 300 MW boiler loads with R_NH3 in the range of 0% ~ 10%. Under all conditions, the NO_x emissions showed only small changes within 50 mg/Nm³ comparing to the coal combustion case and the ammonia slip were very low. The thermal efficiency of boiler was slightly reduced mainly due to the increase of gas temperature at the outlet of air preheater.

The above results on different scales of systems showed that the NO_x emissions of ammonia cofiring could be well under control and demonstrated the technical feasibility of ammonia cofiring in coal-fired boilers.

As a carbon-free fuel, ammonia (NH₃) can contribute to reducing carbon emission by being combusted with pulverized coal particles. However, as the co-firing rate, X_NH3, of NH₃ increases, the flame instability due to the low burning velocity of NH₃ also increases, raising concerns about the formation of nitrogen compounds, including NOx. Therefore, it is essential to concurrently measure flame behavior and emission characteristics in order to conduct a comprehensive study. In this presentation, the flame radical chemiluminescence and flue gas species characteristics according to the increase in the NH₃ co-firing ratio, which are 20% and 50%, were experimentally measured in-situ in a scaled-down model of a burner used in an actual coal-fired boiler. Primarily, based on the same calorific value as that of 100% pulverized coal combustion, it was directly observed through imaging that the flame length increases as the co-firing rate of NH₃ rises. Furthermore, the occurrence of ignition delay in pulverized coal particles has been substantiated through spontaneous emission measurements of CH^* and OH^* radicals in the flames. Upon staging NH₃ individually into each burner, as opposed to co-injecting it with pulverized coal particles and primary air, a reduction in NOx emissions has been verified. This reduction is attributed to the combined effects of flame stabilization and selective non-catalytic reduction (SNCR). The NOx emissions during 100% coal combustion were recorded at approximately 200 ppmv level, whereas staging NH₃ demonstrated the capability to reduce these emissions to a minimum of 30-50 ppmv level. Nevertheless, the injection of NH₃ into the burner unit farthest from the flame center resulted in a reduction of NOx emissions. However, unreacted NH₃, not engaging in the SNCR reaction, was detected as slip.

Coal fired power generation is the largest source of CO₂ emissions in China, and reducing carbon emissions from coal-fired power plants is of great significance for achieving the Carbon Neutrality. The ammonia and coal co-firing can aid in achieving carbon dioxide reduction.

Based on the experimental platform of 50kW/4MW, the combustion behavior and pollutants characteristics such as NOx during coal ammonia blending combustion were systematically investigated. Increasing the co-firing ratio of ammonia can promote the ignition of pulverized coal in advance, and adopting a low co-firing ratio can significantly shorten the ignition time of the co-firing flame, and then increasing the co-firing ratio has no obvious promoting effect on the ignition of pulverized coal. The flame length of coal ammonia blending combustion is dominated by the combustion of pulverized coal. Ammonia co-firing will affect the formation characteristics of particulate matter, especially sub-micron particulate matter, which was higher than that without ammonia co-firing. The generation of NOx is mainly affected by the competition between the generation of NO and the reduction reaction of NH₃ by the change of oxygen. The generation of NOx can be effectively controlled by controlling the relative concentration of oxygen-fuel in the combustion environment in the early and middle stage of combustion.

An experimental research on ammonia co-combustion at Wanneng Tongling 300-MW coal-fired power plant was carried out. Eight direct-flow type ammonia burners were developed with the maximum 21 tons/hr pure ammonia flow. The highest ammonia-coal cofiring ratio is around 35% at 100-MW electricity power. The results show that, in the 300-MW coal-fired power plant, ammonia burners located in the middle of main combustion zone has better high-temperature reduction performance than those located in the upper part of main combustion zone. NH₃ concentration at the outlet remained below 1 ppm. the thermal efficiency of the boiler slightly decreased.

Combating CO2 emissions is part of initiatives towards net zero carbon emission target globally in addition to mitigate climate change challenges. Burning fossil fuels contributes to increase CO2 composition in the atmosphere. Power industries faced the challenge when generating electricity using coal. Further, carbon emissions are also derived from burning natural gas, gas flaring and in manufacture of cement. Malaysia is among the countries that gives key priorities in reducing National GHG emissions. National Energy Transition Roadmap highlighted the nation strategies with specific target to reduce the GHG emissions and accelerating the country’s green and sustainable agenda. Ammonia potentially can be utilized as future fuel to generate electricity through co-firing with coal upon overcoming its cost limitations. From technology exploration perspective, co-firing of ammonia with coal was explored at testing facility in TNBR through collaborative efforts and the findings are highlighted in the lecture.