Design Of Emergency Relief Systems

The majority of chemical processes is performed in pressure vessels. As has been outlined in Section 4.4 in detail, the heat release due to a chemical reaction may lead to a strong temperature increase if it is not adequately controlled. In the case of volatile substances this rise in temperature results in a significant vapour pressure increase. In some cases a higher permanent gas generation rate due to a decomposition reaction may additionally occur. One or both will cause a strong pressure rise if the process is performed in a closed system. Therefore the pressure vessel must be protected against 

The design of emergency relief systems for chemical reactors has been investigated by expert for many years now. Two relief scenarios are generally distinguished, which differ in the character of the relief stream  

Other multi-phase systems, like they can occur due to the additional presence of solids, are not covered by any broad and widely accepted theory so far, but must be treated and assessed individually. 

For the emergency relief design case of single phase venting all necessary design rules are published in technical regulations [91,92,93,94]. In tire case of incompressible fluids the necessary vent area is determined with the help of the following equation, which includes the assiunption of one-dimensional, isentropic flow without phase transition  

In the case of compressible fluids the necessary vent area is determined using the same assumptions described for incompressible fluids, except that the resulting equation includes an additional flow function /  

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Promote the development of new techniques thatw ill improve the design of emergency relief systems. 

In design of emergency relief systems the intrinsic fluid properties can often make a difference. 

It was the aim of this section to present and deduce the main procedures which allow a responsible design of emergency relief systems. The concept is based on the definition of a "credible worst case and the utilization of reaction engineering principles in a suitable combination. 

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