Investigation of the Suppression of Methane Explosions by N/CO Mixtures in Different Proportions.

To characterize the inerting effect of N/CO mixtures containing various proportions on methane-air explosions, a series of experiments were conducted in a 20 L spherical vessel under the normal temperature (25 °C) and normal pressure (101 kPa). Six concentrations (10, 12, 14, 16, 18, and 20%) of N/CO mixtures were selected to analyze the suppression of methane explosion by N/CO mixtures. The results indicated that the maximum explosion pressure ( ) of methane explosions was 0.501 MPa (17% N + 3% CO), 0.487 MPa (14% N + 6% CO), 0.477 MPa (10% N + 10% CO), 0.461 MPa (6% N + 14% CO), and 0.442 MPa (3% N + 17% CO) in the presence of the same N/CO concentration, and similar decreases in the rate of pressure rise, flame propagation velocity, and production of free radicals were observed. Therefore, with the increase of CO concentration in the gas mixture, the inerting effect of N/CO was enhanced. Meanwhile, the whole process of the methane combustion reaction was affected by N/CO inerting, which was mainly attributed to heat absorption and dilution of the N/CO mixture. N/CO with a greater inerting effect leads to lower production of free radicals under the same explosion energy and a lower combustion reaction rate at the same flame propagation velocity. The findings of the current research provide references for the design of safe and reliable industrial processes and the mitigation of methane explosions.