entech. WKP Magazine Explosion Simulation – Gas Dispersal Study P a g e | 11 4.2 GAS VOLUME Gas volume produced by the explosion is determined using gas yields (L/kg) provided by Orica Australia (Table 4-2) combined with the toxic gas default yields provided by the Ventsim™ simulation. Table 4-2 – Gas mix for bulk store ANFO explosion provided by Orica Australia, along with the gas volume equation. NOTE: Table 4-2 reflects the substances produced from the explosion of ANFO in ideal conditions2, however, Entech considers that it is counter intuitive to exclude the toxic gases usually experienced under normal mining applications. Combining all elements, the gas volume is estimated to be 1,007 mᶟ. The Ventsim™ simulation’s default yield for NH3 was used instead of the Orica yield to be conservative. 4.3 PEAK CONTAMINANT CONCENTRATIONS Table 4-3 indicates the peak contaminant concentrations at each surface connection during primary fan operation and when mains power is off. Seasonal variation between summer and winter was compared during power failure. Note that scenario 2 was only present in summer. T&T requested that gas concentrations be referenced in grams per second (g/s), along with exiting velocities, and temperatures. 2 Ideal conditions reflect a well-balanced mixture of ammonium nitrate and diesel, with no water contamination. The more conditions are less than ideal the greater the prevalence of toxic gases.
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