Realization of the optimum reaction temperature curve

In order to conduct the reactions along the optimum reactive temperature curve, the heat of reaction must be removed from the catalyst bed, and to reduce the reaction temperature (to recover the extracted heat). 

Regardless of the configuration of ammonia converters and their diameters, there are only two modes of heat extraction from the catalyst bed in situ heat-exchange or external heat-exchange. The former is called fixed bed with continuous heat exchange the reactor has only one bed housing all the catalysts, and is called a cold-type reactor (Fig. 8.6). The latter is called an adiabatic fixed bed reactor the reactor consists of two or more beds of catalyst, with heat exchange between the beds (Fig. 8.7). 

Heat exchange in multi-bed direct heat exchange reactor is by directly adding a cold gas to the reaction gas to lower the reaction temperature this is the so-called cold-quench . If the quenching gas is the feed gas, it is called feedgas quench , such as the Topspe S-100 type ammonia converter, and ICI cold-quencher ammonia synthesis converter. If the quenching gas is not the feed gas, it is called non-feedgas quench , such as the steam cold-quench carbon monoxide shift reactor. 

The reaction rate of the whole process in some reversible exothermic reactions, such as the carbon monoxide shift reaction, can be considerable. The heat needed to be extracted from unit volume of catalyst at the beginning and the ending stages of the reaction may vary by 10 times or more. These reactions require multi-stage heat exchange reactors. Other reactions, such as the ammonia synthesis 

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