Evaluating regime diagrams for closed volume hybrid explosions. (September 2017)

• Record Type: Journal Article
• Authors: Cloney, Chris T.; Ripley, Robert C.; Pegg, Michael J.; Amyotte, Paul R.
• Is Part Of: Journal of loss prevention in the process industries. Volume 49:Part B(2017)
• Page Start: 912
• Page End: 918
• Publication Date: 2017-09
• Subjects: Dust explosion -- Hybrid explosion -- Closed volume explosion -- 20-L chamber -- Explosion regime diagram; Chemical industries -- Safety measures -- Periodicals; 660.2804
• DOI: 10.1016/j.jlp.2017.03.004
• Languages: English
• ISSNs: 0950-4230

Abstract

Abstract: Hybrid mixtures of combustible dust and flammable gas represent an enhanced industry hazard due to increased explosion severity over that for the constituent fuels at their given concentrations. The current investigation extends the understanding of hybrid explosion dynamics by identifying and evaluating new explosion regimes on the dust/gas concentration plane. This work builds on previous studies that identified five regimes: gas-driven explosion, dual-fuel explosion, dust-driven explosion, synergic/synergistic explosion, and no explosion. For low ignition energy (e.g., spark ignition) the gas-driven and dual-fuel regimes are extended to include: gas-only explosion, two-stage explosion, single-stage explosion, and dust-only explosion. For high ignition energy (e.g., 10-kJ ignitors) the hybrid behaviour in the dust-driven regime depends on the dust reaction mechanism. For heterogeneous combustion, addition of flammable gas has a minor impact on explosion parameters. For homogeneously reacting dust, two new regimes are proposed: isolated particle combustion close to the dust flammability limit and group combustion further away. It is hypothesized that flammable gas addition has a larger impact in the isolated regime, as the gas acts to bridge individual diffusion flames during flame propagation and explosion. Ongoing research is investigating this hypothesis and reviewing the use of Computational Fluid Dynamics to close the gaps in understanding for hybrid explosion systems. Highlights: Literature data is reviewed to evaluate explosion regimes for hybrid mixtures. Gas-only, two-step, single-step, and dust-only regimes are identified on the gas/dust plane for low ignition energy. Isolated particle combustion and group combustion are proposed for high ignition energy below the gas flammability limit. It is proposed that hybrid explosion effects are larger for isolated particle combustion than group combustion.