Decarbonisation Technology - November 2024 Issue

Side-red cracker

Pre-cracking

Separation

Liquid ammonia

Hydrogen

Purication

Flue gas to stack

SCR

Option for external fuel

Figure 1 Ammonia cracking process

large to mega-scale, with hydrogen transported to the end-use through extended hydrogen grids, as planned in Europe. It can also be decentralised on a large-scale and co-located with large hydrogen off-takers, possibly via local hydrogen grids. Finally, it can be done on a small-scale and decentralised, for example, at hydrogen filling stations. Solid transportation method for hydrogen Ammonia is considered an important transportation method for hydrogen for several reasons. First, it is energy-dense, with a higher energy density than compressed hydrogen gas. This means that a larger amount of energy can be stored and transported in the form of ammonia compared to compressed hydrogen, making it more efficient for long-distance transportation. Ammonia is also free of carbon, making it the highest energy-density, non- carbon medium. Crucially, ammonia can be stored and transported as a liquid at -33°C, so it does not require high-pressure or cryogenic storage. It is also easier to handle and has well-established safety protocols and regulations. The second reason is that the infrastructure for ammonia is mature, and safety best practices already exist. Ammonia has an extensive infrastructure for production, storage, and transportation. It is already produced in large quantities for various industrial applications, such as fertiliser production. Leveraging this existing infrastructure can help facilitate hydrogen

transportation without needing significant new infrastructure development. Finally, the process of converting ammonia back into hydrogen through ammonia cracking is simple and has been successfully demonstrated on a large scale. This means that hydrogen can be extracted from ammonia at the point of use, enabling the utilisation of ammonia as an ideal and flexible hydrogen carrier. Using ammonia to transport hydrogen Hydrogen needs to be transported to different regions for several reasons. Regions with high energy demand may not have sufficient local hydrogen production capabilities, while other regions may have access to cheaper or more reliable feedstock. Regions rich in renewable energy sources, such as wind or solar, can produce green hydrogen through electrolysis. Transporting this green hydrogen to other areas supports the integration of renewable energy into the broader energy system. By using ammonia as a carrier, end-point users can take advantage of cheaper or more readily available feedstocks and production processes elsewhere on the globe. Additionally, ammonia’s ability to be liquefied allows it to be transported at a lower cost than hydrogen. These benefits help offset the costs of conversion and make the process economically efficient. There are three main stages in transporting hydrogen using ammonia as a carrier:  Conversion of hydrogen to ammonia: H 2 is first converted to NH3 through a process called