Bottom relief dumping

As for gassy systems, relief from the bottom of the reactor (dumping) may be a better option than relief from the top, for untempered hybrids. This is discussed in 

If top relief is to be used, DIERS proposed the following simple sizing method. This method has the same assumptions and conditions of applicability as the equation proposed for gassy systems (see section 7.3). The version for untempered hybrids 

An open system calorimetric test will tend to measure QGmax, rather than the sum of QGmax and Qvmax, because the vapour produced will tend to condense in the relatively cold containment vessel. A closed system test will also underestimate Qvmax because the high pressure will suppress vaporisation. Qvmax could also be calculated from  

The required relief flow area, A, can be calculated using equation (5.1). The two-phase mass flow capacity per unit cross-sectional area, G, can be calculated using a suitable method for hybrid-systems (see Chapter 9). In order to minimise the relief size obtained, G.should befevaluated at the maximum pressure permitted in the reactor during relief, irrespective of the relief pressure.  

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SIZING METHODS FOR BOTTOM RELIEF (DUMPING) OF GASSY REACTIONS... 

Yesl is bottom relief (dumping) a viable option 7... 

For untempered systems, it is/worthwhile considering the use of bottom venting (dumping), rather than relief from the top of the reactor, since this is likely, to require a smaller system. In either case, the safe disposal of,the vented material should be considered (see Chapter 11). Relief from the bottom of the reactor may be a poor option if a relief system is also-required at the topjof the reactor for other process reasons. Operation of the relief system at the top of the vessel would reduce the pressure available to remove ihe contents of the reactor via the bottom relief system. This is discussed further below. t f. . ... 

Many computer simulation codes (see Annex 4 and 7.4.2) allow the option of specifying a bottom relief system. This can be particularly useful if the effects of simultaneous venting from the top of the reactor needs to be assessed, provided that the code selected contains this option. Again, it will usually be safe to assume liquid only flow if dumping occurs well before the maximum rate.. 

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