Abstract:
Objective Doping hydrogen into natural gas pipelines is an effective way to transport hydrogen on a large scale and long distances. However, during the venting process, high-pressure hydrogen-doped natural gas poses a risk of spontaneous combustion due to various factors such as pressure, temperature, chemical reactions, and electrostatic friction. Therefore, the conditions leading to spontaneous combustion during the venting process of hydrogen-doped natural gas were analyzed.
Methods Based on fluid mechanics, chemical reactions, and electric field theory, a coupled model of the flow field, temperature field, chemical reaction field, and electric field for venting hydrogen-doped natural gas was established, and the model decoupling solution algorithm was studied. Then, taking the venting system of a valve chamber in the West-East Gas Pipeline as an example, this study analyzed the effects of hydrogen doping ratio, inner diameter of vent pipe, height of vent riser, and vent pressure on spontaneous combustion.
Results The increase in hydrogen doping ratio, inner diameter of the vent pipe, height of the vent riser, and vent pressure not only leads to the rising of maximum temperature but also promotes the increase of OH− mass fraction, while the length of the horizontal pipe has no significant effect on gas temperature and OH− mass fraction. In addition, even under the most prone conditions to spontaneous combustion, the gas temperature and OH− mass fraction have not reached the spontaneous combustion criterion.
Conclusion Under the existing design and operation conditions of the valve chamber venting system mentioned above, hydrogen-doped natural gas venting does not have the conditions for spontaneous combustion to form stable combustion flames.
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