Abstract:The coal gas sudden leakage from the storage tank to air can be disastrous. The diffusion law of coal gas (as light gas) must be carefully studied to prevent the damaging consequence to the workers. This paper presents a simulation of the leakage and diffusing process of coal gas using a simplified two-dimensional plane model combined with LES turbulence model, from which the law of CO concentration versus time and space is obtained. The simulation results show that (1) at the initial stage, the CO concentration near the mouth of leak is more concentrated during disclosure process; (2) when the leak is stopped, the concentration of CO is not immediately reduced and it is followed by a gentle process of development, due to bulky tanks up the wind, which induce the wind turbulence. With the leakage, its leaked CO around the mouth of pressure and velocity disturbance, a disturbance will spread. In the horizontal direction of leakage mouth upward, the CO concentration is significantly higher than that in windward direction. In the natural and ventilated conditions, when leakage stops, the concentrations of CO are not quickly reduced, but take a gentle development process. The results of the study may help to establish the emergency gas leak alarm and preventive measures.