Multicomponent leakage and diffusion simulation of natural gas/hydrogen mixtures in compressor plants

Abstract

Mixing hydrogen into the natural gas pipeline network is the most effective and economical way to transport a large amount of hydrogen while resulting in more danger when gas mixtures leak in the confined compressor plant space. Existing studies on the diffusion behavior of CH4/H2/air mixtures ignore the physical property difference between the natural gas and hydrogen, resulting in a bias in evaluating the explosions regions in compressor plants. In this paper, an improved Fick diffusion matrix for CH4/H2/air mixtures is proposed which considers the interaction between CH4 and H2 components. After that, a 2D gas mixture diffusion model is built to research the effect of the gas pressures, leakage hole diameters, and ambient wind speeds on the diffusion range of the CH4/H2 mixtures in air. The method is subsequently extended to a 3D confined compressor plant space with different leak positions, leakage lasting time, and H2 volume concentrations. Results demonstrate that the leakage hole diameter is the main factor influencing the diffusion behavior of CH4/H2/air mixtures in the compressor plant among three factors (the H2 mole fraction, leakage hole diameter, and leakage point). The CH4/H2/air mixtures easily accumulate both on the roof and at the corner of the confined plant. Particularly, the hydrogen concentration may fall within its explosion limit scope and induces an explosion at the position close to the leakage hole, where the natural gas does not easily cause the explosion because the natural gas concentration often exceeds its explosion up-limit. Finally, some suggestions for gas detector installation in compressor plants are proposed according to simulation results, which can give guidance for the safety management of compressor plants.