Experimental evaluation and analysis of methane fire and explosion mitigation using isolation valves integrated with a vent system

• Published in: Journal of hazardous materials 2017-10, Vol.339, p.301-309
• Main Authors: Ajrash, Mohammed J., Zanganeh, Jafar, Moghtaderi, Behdad
• Format: Article
• Language: English
• Subjects: Detonation tube; Explosion isolation; Explosion vent; Fire mitigation; Flame deflagration
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2017.06.012

•Applying the passive isolation valve reduces the downstream peak pressure to approximately 0.42bar.•The passive mitigation valve stopped the flame but generated an oscillating pressure wave downstream.•The active mitigation valve effectively isolates the flame without pressure detecting downstream.•A reflected pressure wave significantly participates in deflagration mitigation upstream. There has been a surge of interest from the extractive industries in the application of mechanical means to the mitigation of flame deflagration. To verify the implementation and performance of passive and active mitigation protection, a comprehensive experimental investigation has been conducted on a large scale detonation tube, 30m long and 0.5m in diameter, with two mitigation valves (passive and active) and a burst panel venting system. The valves were used alternately to mitigate the flame deflagration of methane in concentrations ranging from 1.25% to 7.5%. The experimental work revealed that locating the passive mitigation valve at 22m distance from the ignition source mitigates the flame by fully isolating the tube. However, closing the valve structure in the axial direction generated another pressure wave upstream, which was approximately the same value as for the original pressure wave upstream. In the case of the active mitigation system, the system perfectly isolated upstream from downstream with no further pressure wave generation. When the vent was located at 6.5m from the ignition source, the total pressure was reduced by 0.48bar. Due to the counter flow of the reflected pressure wave the flame was extinguished at 12.5m from the ignition source.