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It is possible for a single component to achieve multifuel-processing.

Most hydrocarbon fuels warrant a fuel reformer or a cracker prior to feeding it to the SOFC stack. When designing and developing a multi-fuel system, it is of utmost importance to have single component or unit which is capable of processing and reforming different fuels.

The hypothesis here is that it is indeed possible to have a single component which can process and reform multi-fuels by:

• Selecting appropriate materials for the component itself;
• Selecting catalysts which can assist in reforming reactions of more than one fuel;
• Carefully optimizing the operating conditions in a manner that ensures high efficiency, durability, and lifetime of the stack. The schematic of such a multi-fuel processor is shown in Figure 1.

Figure 1. Functioning principle of Multifuel processing unit

SOFC operation under Ammonia and Methanol fuel feed requires identification of suitable operation window.

Although SOFC has been demonstrated to be capable of operating with fuels other than hydrogen, it is of paramount importance to ensure that the electrochemical reactions taking place at the anode side (fuel electrode) of the cell do not degrade the performances of the cell and the overall stack. As an example, methane containing fuel mixtures can be directly fed into the stack where internal reforming occurs, thus increasing the H2 content of the fuel. However, depending on the stack operating conditions, fuel composition and materials employed in the cell, the extent to which this process can be safely performed within the stack can change.

It is therefore necessary to characterize and investigate in detail the electrochemical reactions that each fuel will potentially undergo within the stack, which ultimately affect its performances in terms of efficiency, degradation, and lifetime.

Adjusting the fuel feed composition, pre-treatment processes, degree of pre-processing, and SOFC operating parameters is key in enabling the use of these green fuels in sustainable power generation.

SOFC degradation mechanisms can be fuel dependent and require in depth investigation.

The electrochemical reactions, which consume the fuel, lead to changes in reactant concentration (from inlet to outlet of the cell/stack) and also determine the thermal gradients experienced by the cell and the surrounding materials depending on the nature of the reactions (endothermic or exothermic). During stack operation, the voltage output of the cells, the measured temperature and other gas related parameters are returned as indicative measurable parameters but there is a superimposition of these effects. Decoupling this information is crucial to fully understand how the performances of the SOFC stack can be improved. In the case of ammonia, literature reports highlight how this fuel can cause changes in the mechanical properties of the steel parts of the stack as a result of nitriding process [1].

Similarly, Ni particles present in the anode material can be affected, decreasing the electrochemical efficiency of the cell [2]. Sealing materials, which ensure gas tightness of the anode and cathode compartments, are a vital element in determining SOFC stack degradation, thus calling for dedicated attention in assessing their stability.

Methanol decomposition in the SOFC stack can induce soot or carbon formation in case the steam content is too low. Suitable steam-to-carbon rations should be calculated based on thermodynamic equilibrium for the desired operating temperature. It is also reported that the ohmic and polarization resistance of the cell increase with methanol fuel, possibly due to complex reaction pathways, which eventually negatively affects the stack performance [3].

Figure 2. From system design to system testing.

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[1] M. Kishimoto et al, (2020) Development of 1 kW-class Ammonia-fueled Solid Oxide Fuel Cell Stack, Fuel cells, 20 (1) p. 80-88.

[2] J. Yang et al, (2015) A stability study of Ni/Yttria-stabilized zirconia anode for direct ammonia solid oxide fuel cells, ACS Appl Mater Interfaces 7, 28701.

[3] Y. Ru et al, Durability of direct internal reforming of methanol as fuel for solid oxide fuel cell with double-sided cathodes, International Journal of Hydrogen Energy, Volume 45, Issue 11, 28 February 2020, Pages 7069-707

It is possible for a multifuel SOFC system to achieve Continuous operation of the SOFC system for 500 hours when fed with multi-fuels.

Based on recent advances made in SOFC technology and the developments that will be made in this project, it is envisaged or predicted that the SOFC system that will be built in this project will be able to operate successfully and continuously for 500 hours when fed with ammonia and methanol as fuels.

To verify the above hypothesis, the following research questions will be delved into and answered in the project:

• Will its performance be comparable to operation on hydrogen and methane?
• How the electro-chemical oxidation of the different fuels at the stack level (considered in this project) affects the system? And how the system controller should respond to take preventive action to not damage the stack?
• Will the required number of hours be suitable for use in hard to decarbonize sectors or applications?
• Can a common set of BoP be designed to make the SOFC system truly multi-fuel compatible?

It is possible to define and ensure optimal fuel quality requirements

Fuels used in a SOFC especially methanol or ammonia place high demands on the gas quality. Pollutants in the fuels, such as chlorine and sulphur, can cause lasting damage to fuel cells. The special requirements of an SOFC with regard to the fuel quality of ammonia or methanol are still largely unexplored. It may turn out that pre-conditioning or pre-processing steps are necessary to meet the requirements of the SOFC. Depending on the types of pollutants as well as on the requirements of the SOFC suitable purification installations for ammonia and methanol should be employed.

These should meet both, purity as well as economic requirements.

It is possible to model and build an optimal, possibly green, multi-fuel supply for a port.

The aim is to show that a fuel supply of ports, possibly with green fuels such as green hydrogen, ammonia, and methanol, is possible and how a multi-fuel supply backbone could look like and be optimally designed in the future.

Maritime terminals with multimodal transport links, conversion and other facilities will play a crucial role in connecting production and demand centres. The competitiveness of the various fuel options for maritime applications such as H2, NH3 or methanol depends largely on the way in which they are generated, on the distance over which the respective fuel has to be transported and in what form (gaseous, liquid, pressurized, hydrogen carrier) and manner (ship transport, truck transport, rail, Pipeline etc.) has to be transported from the production site to the port.

In addition, it will be necessary to create new infrastructure such as pipelines, fuelling and storage systems in ports and/or to adapt existing fuel infrastructure. It is necessary to identify corresponding production capacities in the vicinity of ports as well as supra-regionally, to find industrial processes and technologies for fuel production/generation with a focus on green fuels, and to locate and evaluate them locally.

With the aim of increasing the share of sustainable fuels in shipping, it is also necessary to identify waste streams as potential fuel sources, find optimal integration points in industrial applications and evaluate the respective potentials. Depending on the type of fuel and the distance to the port, fuel transport and distribution systems are differently suited. A multi-fuel supply chain for a port should ideally be designed and optimised for the specific location.

This and other parameters must be considered when designing a multi-fuel supply backbone.