Igniter-induced hybrids in the 20-l sphere

The current paper presents new experimental evidence that the energy provided by pyrotechnical igniters may, in some instances, physically alter the dust being tested in the 20-l sphere. KSt values can be several times greater in the small vessel compared to those measured in the 1-m3 chamber. Further visual evidence is provided to show that high energy ignition can produce a turbulent flame region, possibly consisting of a hybrid mixture of flammable gas (or vapor) and dust, which can propagate faster than the corresponding pure dust. The experiments suggest that KSt values measured in the 20-l sphere may no longer be representative of a dust deflagration in a real process environment. We recommend additional tests in a 1-m3 chamber when a dust exhibits a low flash point, or when it's KSt is above 300 bar m/s in the 20-l sphere.