The dust explosion characteristics of commercial rice flour towards different concentration were analysed. Experiments were performed in 20 L spherical explosion chamber to obtain maximum explosion overpressure (Pmax), rate of pressure rise (dP/dT), and minimum explosibility concentration (MEC) of undried and dried commercial rice flour. The dust samples and air mixtures were ignited by two chemical ignitors at ignition time of 100 ms. The Kistler Piezoelectric pressure sensors were used to quantify the propagation of pressure wave during the explosion process. The moisture content of the samples were measured by using proximate analysis. The Pmax was obtained at the highest pressure over the range of concentrations. Pmax for undried rice flour and dried flour are 10.0 bar and 10.4 bar respectively at 1000 kg/m3. Both of the Pmax were attained at the highest level of concentration. The highest value of dP/dT of undried was 70 bar/s at 1000 kg/m3 but for dried rice flour, the highest value obtained was 63.5 bar/s at 750 kg/m3. MEC for both dried and undried was 500 kg/m3. This study concluded that as the concentration increases, the severity of dust explosion would also increase and the presence of moisture decrease the severity of the rice flour explosion but not too significant at ignition time of 100 ms.

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This article presents a dust explosion characteristics of commercial rice flour at different concentration and ignition time. The rice flour with a moisture content of 7.79% (undried) and a mean diameter of D50 = 28.77 μm was used in this work. The moisture in the rice flour was further reduced by oven drying to 2.47% (dried) and both samples were tested for comparison. Experiments were performed in a 20 L spherical explosion chamber to obtain the maximum explosion overpressure (Pmax), rate of pressure rise (dP/dT), minimum explosibility concentration (MEC), and deflagration index (Kst) of undried and dried commercial rice flour. The dust samples and air mixtures were ignited by two chemical ignitors at the ignition time (tv) of 60 and 100 ms. The propagation of pressure wave during the explosion process was measured by the piezoelectric pressure sensor. The Pmax for undried and dried rice flour at tv of 60 ms were found at 11.25 bar and 8.6 bar, respectively. The Pmax was obtained at the highest concentration of dust (1000 kg/m3). The highest pressure rise of undried sample was obtained at 81 bar/s whereas for dried sample the highest value was obtained at 98 bar/s. MEC of undried sample was found at 600 kg/m3 and the dried sample at 500 kg/m3. The Kst of dried rice flour at ignition time 60 ms was found to be the highest at 26.6 bar m/s. It was found that the severity of the dust explosion increases proportionally with the dust concentration. Rice flour with higher moisture content has a lower explosion severity, than that of dried sample. Findings from this work provide a useful safety information about the severity and explosibility of rice flour, for which unsafe handling and operation may be minimized.

In spite of extensive research and development to prevent and mitigate dust explosions in the process industries, this phenomenon continues to represent a constant hazard to industries including manufacturing, using and handling of combustible dust material. Lack of fundamental methods in predicting the explosion severity characteristics and real dust cloud structure are recognized as a major obstacle in predicting the course and consequences of dust explosion in practice. This present paper discusses the influent factors affecting the explosion severity of the dust clouds in order to promote the advanced development for dust explosion. In addition, the impact of inerting on dust properties by using nitrogen or carbon dioxide to a level which the dust cloud can no longer propagate a self–sustained flame would also be explored. Key words: Dust explosion protection and mitigation; explosion severity; inerting