Safety Based on Emergency Relief Systems

The identification and characterization of the worst case upset conditions has been discussed above. It should be recognized that the rate of an exothermic reaction at a particular relief pressure, which determines the vent area required, can vary by up to two orders of magnitude depending on the upset conditions assumed. 

Relief and disposal systems are difficult to modify once installed. Therefore, the characteristics of future processes should be considered, as far as possible, in the case of multi-product plants or development units. 

1 CLASSIFICATION AS VAPOUR-PRESSURE, GASSY OR HYBRID SYSTEM 

In order to decide which method should be used to calculate the vent area required, it is necessary to classify the reaction system as one of three types  

A vapour pressure system is one in which the pressure generated by the runaway reaction is solely due to the increasing vapour pressure of the reactants, products and/or solvents as the temperature rises. 

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