Preliminary Studies on Methane-Hydrogen Blends in Natural Gas (NG) Pipelines -A Case History for Technical Evaluation in an Existing Distribution Network to Identify Barriers and Enablers

Low-carbon/carbon-free fuels are shaping how will be the future of energy utilization in hard-to-abate sectors such as transport, heavy industries, power generation, building sector, and seasonal energy storage. This is projected to contribute to a 10% CO2 emission reduction by 2050. Storage and transportation are key elements in a hydrogen economy value chain which, will connect production facilities to end users. Transporting hydrogen in liquid form, via trucks and ships, has more techno-economic challenges than transport through pipelines. Therefore, the transportation and distribution of hydrogen purely through new pipelines and/or blending hydrogen with natural gas by repurposing existing Natural Gas (NG) pipelines are seen as more promising. Refurbishing pipelines is estimated to be about 33% of the cost of new infrastructure. Existing NG Transmission System Operators (TSOs) and Distribution System Operators (DSOs) are evaluating the technical readiness of their infrastructures. In this paper, the preliminary studies focus on the feasibility of extending the usage of current pipelines for the distribution of H2-NG blends. The study evaluates the H2-readiness of pipelines in a distribution network in Sicily for its technical adaptability, regulations, and legislation in this local zone. The study provides a review of the different steel types, microstructures, cathodic over-protection, and their impact on Hydrogen Embrittlement (HE). The effect of the interaction of HE gaseous inhibitors such as O2, CO, and SO2 is presented together with the counter-reactive effect of water vapor in the presence of SO2. Based on the case history, the barriers and enablers are critically evaluated for different H2-NG blends until a 10% maximum value which is a threshold in many EU countries.