Transportation of Mixed Hydrogen Gas in Buried Pipelines in Permafrost Areas

The application of existing gas transmission pipelines to deliver hydrogen-blended natural gas is the most operable method among many delivery methods. Hydrogen-blended natural gas with different hydrogen-blending ratios after passing through the throttling element is not the same. Using FLUENT to analyze the temperature variation after the Joule–Thomson effect for 0%, 5%, 10%, 20%, and 30% hydrogen mixing ratios. Workbench is used to analyze the soil temperature field around the pipeline and the stress displacement of the buried pipeline in the permafrost zone under different hydrogen mixing ratios. The analysis revealed that as the hydrogen mixing ratio increases, the temperature of the same point gradually increases after the Joule–Thomson effect, the low-temperature area around the buried pipe is gradually replaced by the high-temperature area, and the stress of the buried straight pipe also gradually decreases; while the maximum stress of the pipe initially decreases and then increases, and the displacement has no obvious change.

Buried pipelines, which are generally accepted worldwide as one of the many forms of natural gas transmission, pass through permafrost areas during their laying, thus triggering freeze-ups and posing a potential hazard to the safe transportation of natural gas. Most of the existing methods to solve the frozen rise of buried pipelines in the permafrost zone have problems of high energy consumption and construction difficulties. Therefore, this paper, combined with the current trend of vigorous development of hydrogen-blending natural gas projects around the world, proposes a method to alleviate the purpose of freeze-ups by inputting a reasonable hydrogen-blending ratio before the regulator through the negative Joule–Thomson effect of hydrogen and using the phenomenon of temperature rise along the pipeline after the hydrogen passes through the regulator to neutralize the temperature drop of pure natural gas. In this paper, we applied finite element analysis software to simulate the effect of five mixing ratios of hydrogen gas, such as 0%, 5%, 10%, 20%, and 30%, on buried pipelines and also selected 0%–5% as the best mixing ratio to relieve freezing under the working conditions of the simulation environment. The feasibility of delivering hydrogen-blended natural gas at appropriate blending ratios to mitigate freeze-ups in buried pipelines in permafrost areas is demonstrated. It provides a new method for freeze-rise mitigation measures at gas transmission sites.