Polytropic reaction control

Thus, the lower starting temperature controls the reaction temperature in a smooth way. The polytropic reaction control is often used to this purpose. In addition, it detects the initiation of the reaction, proved by the temperature increase during the adiabatic phase. 

Ideal batch stirred tank with polytropic reaction control... 

A polytropic reaction means the reactor is neither designed to work under isothermal conditions, nor under adiabatic conditions. The reactor control strategy comprises different periods of time, where different modes of temperature control are applied. These different temperature control strategies may include heating to... 

Figu re 6.7 Polytropic reaction Temperature course and heat release rate of the reaction corresponding to the example substitution reaction. The reactor is initially heated to 35°C, then left heating adiabatically to 44°C (period a), where maximum cooling is switched on (period b). Finally controlled cooling is applied, once the final temperature of 100°C is reached (period c). 

In most cases non-isothermal processes are used. A part of the energy of the reaction is used to heat the reactor to the desired process temperature in the so-called polytropic reaction mode. A typical temperature control strategy is to use an adiabatic phase, during which there is no cooling, so that the correct initiation of the reaction can be checked. Then, in a second stage, after reaching a specified temperature, the cooling system is switched. The correct choice of the initial temperature... 

In polytropic operation, the choice of the initial temperature and the temperature at which the cooling system is switched on are important for proper control of the reaction. If the cooling system is switched on too late, the temperature may overshoot the allowed maximum temperature. On the other hand, if it is switched on too early, the reaction will be too slow or may not mn to completion in a reasonable time. 

In order to ensure smooth control of the reaction, it must be started at a lower temperature, perhaps under adiabatic conditions, followed by a period with maximal cooling when the desired temperature level is reached. Therefore, batch reactions are often performed in the so-called polytropic mode of operation. 

The polytropic mode this is a combination of different types of control. As an example, the polytropic mode can be used to reduce the initial heat release rate by starting the feed and the reaction, at a lower temperature. The heat of reaction can then be used to heat up the reactor to the desired temperature. During the heating period, different strategies of temperature control can be applied adiabatic heating until a certain temperature level is reached, constant cooling medium temperature (isoperibolic control), or ramped to the desired reaction temperature in the reactor temperature controlled mode. Almost after the... 

The technical design is largely determined by the extent of heat generated or consumed by the reaction and by the type of temperature control used. We have to distinguish between the rare case of isothermal operation, polytropic operated cooled or heated reactors, and adiabatic operation (ideal insulated reactor, no heat exchange with the surrounding). For isothermal and adiabatic operation, no radial profiles of temperature will develop inside the reactor. 

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