Safe Normal Operation Of The Cooled CSTR

When all start-up effects v diich are discussed in the following section have leveled off, the cooled CSTR operates in a steady state. The safety assessment has to check whether the cooling capacity is adequate to ensure the removal of all heat produced in such a way that the desired process temperature is not exceeded, as well to evaluate 

The easiest way to obtain such plots is to use the so-called coupling equation and the stationary mass balance of the CSTR given in Equ. (4-29). The coupling equation is derived by first transforming the imsteady heat balance of the cooled CSTR into the stationary balance  

This point is called ignition point. A small increase of the reference temperature will lead to a rapid stabilization in a new operating point at a very high stationary process temperature. If, on the other hand, the reference temperature is slowly decreased, another operating point is reached at which condition Equ.(4-96) is again valid. This is the so-called extinction point. A further decrease in reference temperature will lead to a rapid stabilization, but this time in an operating point at a very low steady state process temperature. To make the understanding of this phenomenon somewhat easier it is 

It follows that the safety assessment has to focus the evaluation on the sensitivity with which the reactor responds to small deviations in its operating conditions. In this consideration the variability of the reference temperature and its consequences is of somewhat greater significance than that of the residence time. Temperature control of feed tanks and streams is usually less extensively installed than comparable installations for the reactor itself. This can lead to significantly varying feed temperatures. Changes of 2 to 3 K are not uncommon in elderly plants, which are not operated with a uniform heating medium. 

This sensitivity of the steady state process temperature in response to changes of the reference temperature is mathematically expressed in a differential quotient  

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