Research progress on "ammonia-hydrogen" green energy roadmap and storage & transportation technology of liquid ammonia

As a high-efficiency hydrogen energy carrier, ammonia has the significant advantages such as high energy density, low storage and transportation cost, high safety and carbon-free energy storage. It can effectively solve the problems of high-pressure storage and transportation of hydrogen energy, which is of great significance to open up a featured storage and transportation roadmap for hydrogen energy correponding to the characteristics of energy structure in China and achieve the goals of carbon peaking and carbon neutrality. Based on the fact that ammonia is easier to store and transport than hydrogen, the development status of ammonia-hydrogen green energy roadmap and the research progress of the transportation process system, safety technology and design standard of liquid ammonia pipeline relying on the roadmap were reviewed. In view of the problems that the safe pipeline transportation technology of liquid ammonia needs further research and the design experience of liquid ammonia pipeline is immature in China, the following 4 suggestions were proposed: (1) Studies should be conducted on the basic physical properties of liquid ammonia containing impurities and the phase change characteristics, as well as the thermo-hydraulic behaviors, of different pipeline transportation technologies through the combination of experiments and simulation methods. (2) The mature experience of oil and gas pipelines can be referred to liquid ammonia pipelines, but comprehensive fitness-for-service evaluation should be performed before transferring in-service oil and gas pipelines to liquid ammonia transportation ones, if any. (3) The leakage monitoring system should be improved based on the leakage and diffusion characteristics of liquid ammonia pipeline, and the effect of protection technologies should be verified and optimized. (4) The construction, operation and management standards of liquid ammonia pipelines should be improved from the perspectives of pipeline materials, equipment, safety and corrosion prevention, etc.