Leungs method for gassy systems

The peak gas evolution rate, QGmax) can be obtained from calorimetric measurements (see Annex 2 and equations (A2.3) and (A2.4)). It is important that such calorimetric tests are performed so as to minimise the amount of dissolved gas in the test. Open tests are therefore preferred to closed tests1141. 

2 Worked example using Leung s method for gassy systems 

The same example problem as used in Chapter 7 and A5.9.2 above will be used. A reactor of volume 3.5 m3 has a design pressure of 14 barg (maximum accumulated pressure 16.41 bara). A worst case relief scenario has been identified in which a gassy decomposition reaction occurs. The mass of reactants in the reactor would be 2500 kg. An open cell test has been performed in a DIERS bench-scale apparatus, in which the volume of the gas space in the apparatus was 3800 ml, and the mass of the sample was 44.8 g. The peak rate of pressure rise was 2263 N/m2s at a temperature of 246°C, and the corresponding rate of temperature rise was 144°C/minute. These have been corrected for thermal inertia. The pressure in the containment vessel corresponding to the peak rate was 20.2 bara. The liquid density at 246°C is estimated as 820 kg/m3. The gas generated by the runaway has a Cp/Cv value of 1.3. The problem is to evaluate the relief size required. 

Peak gas generation rate, QGmax = 0.374 m3/s Void fraction, a = 0.129 

Two-phase mass flow rate per unit area, G = 19,620 kg/m2s 

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