(58p) Design and Optimization of Hydrogen-Blended Natural Gas Pipeline and Separation Systems

Important energy challenges that the world is facing now include the security of supply, environmental pollution, greenhouse gas emissions and the consequent issue of climate change. As a relatively clean fuel that can be produced from a range of sustainable sources and gasification of coal, hydrogen is expected to become an alternative energy carrier capable of addressing these challenges. Apart from decarbonizing potential, the use of hydrogen as fuel substitutes in heat and power applications improves the overall energy supply security and reduces current fossil fuel source-dependency. To promote hydrogen utilization, establishing economically feasible delivery infrastructure represents a key issue that must be addressed¹.

Given that hydrogen has not been massively applied as fuel, it is more commonly used as raw material in traditional chemical industries or to be directly converted into heat and electricity. Blending hydrogen into existing natural gas pipeline is the best option for long-distance and large-scale hydrogen transportation for the early market of hydrogen economy, rather than constructing specialized pure hydrogen pipeline².

Therefore, we propose a MINLP model of delivering hydrogen to markets by blending hydrogen into natural gas pipeline networks in certain proportions, and using separation and purification technologies downstream to extract hydrogen close to the point of end use. Moreover, several adjustments are applied to the original natural gas pipeline network to ensure that our design scheme can satisfy the stability and safety requirements of gas transportation, such as introducing new compressor stations that are compatible with hydrogen environment and reconsidering operation pressure of pipeline to avoid the adverse effects of hydrogen-induced material failure.

For the separation part, we will consider the combination of hydrogen-selective membranes and pressure swing adsorption (PSA) for the recovery of hydrogen from the natural gas/hydrogen blend of various hydrogen concentrations (5-50% (v/v)). An optional membrane unit will be used for hydrogen enrichment. A single or double PSA unit will further purify the permeate to the required product quality. At the same time, all the residual gas, including membrane retentate stream and PSA off-gas, will be recompressed and returned to the network. All these separation requirements will be considered together with the pipeline network design to ensure that the important decisions, such as the hydrogen blending ratio, are optimized.

We will show the quantitative estimation and analysis of the hydrogen contents that are most cost-effective in the transported gas passing through the existing infrastructures of the natural gas transmission. In addition, the location of new compressor stations, pressure ratio, maximum operation pressure of pipeline can be obtained by this model. It is seen that this work can be used as a decision-support tool for the design of reformation schemes of natural gas pipeline networks with hydrogen injection.

Reference：

(1) Pu L.; Yu H.; Dai M.; He Y.; Sun R.; Yan T. Research progress and application of high-pressure hydrogen and liquid hydrogen in storage and transportation. Chin. Sci. Bull. 2022, 67 (19), 2172–2191. https://doi.org/10.1360/TB-2022-0063.

(2) Ogden, J.; Jaffe, A. M.; Scheitrum, D.; McDonald, Z.; Miller, M. Natural Gas as a Bridge to Hydrogen Transportation Fuel: Insights from the Literature. Energy Policy 2018, 115, 317–329. https://doi.org/10.1016/j.enpol.2017.12.049.