Advances in Hydrogen Blending and Injection in Natural Gas Networks: A Review

With growing concerns about carbon emissions and the need for decarbonization, hydrogen is a promising hy pothesis for the replacement of fossil fuels. Blending hydrogen with natural gas and using existing natural gas transmission networks is a strategy that could reduce carbon emissions. However, a significant challenge with using hydrogen in transmission networks is its potential to cause embrittlement, compromising the structural integrity of pipelines. This paper provides an overview of the complexities involved in blending and injecting hydrogen into natural gas transmission pipelines and discusses methods to enhance system performance and mitigate these challenges by reviewing studies focused on these topics. The paper highlights the multidisciplinary nature of hydrogen injection into natural gas pipelines and discusses ongoing research efforts to address this issue. The study shows significant progress in the technological development of injection strategies, mixing solutions, sensors, and materials. Still, challenges remain regarding experimental work, sensors capable of operating in high-pressure transmission pipelines, and material solutions such as coatings that can inhibit embrittlement and be applied in-situ in operating pipelines. Although numerous numerical studies exist, experimental research on mixing and injection systems remains limited. While real-time measurement tech nology is advancing, more innovation is needed for high-pressure environments. New coatings and linings have been developed to mitigate embrittlement, but their application in operating pipelines requires further investigation.