20,000 Time(h)



Figure 2. Elapsed time changes in surface area of Cu on CO shift catalyst

Performance evaluation of the process

The CO shift reaction (CO + H2O CO2 + Ha) is an exothermic reaction and low temperature is advantageous in chemical equilibrium. On the other hand, high temperature is advantageous in reaction rate. Consequently, a trade-off relation must be considered between reaction rate constant and chemical equilibrium in regard to the reaction temperature in CO shift reaction.

Cooling coils are equipped with our CO shift reactor and cooling water flows inside the coils. This cooling water removes the reaction heat of the CO shift reaction and also decreases the reaction temperature towards the exit, which is favorable for the point of chemical equilibrium. As the result, a temperature distribution is determined by a delicate affair between reaction heat and cooling in the CO shift reactor.

Because of the above mentioned reason, it is difficult to make a simple estimate of the performance of the CO shift process and also difficult to reproduce this temperature distribution by a labo-scale experiment. The help of a reactor simulation is necessary to evaluate the process performance.

Reactor simulation

There exist complex radial and axial temperature distributions by reaction heat and cooling water in the CO shift reactor. Moreover, radial and axial concentration distributions of gas components occur. Therefore, we need two-dimensional simulation model taking radial and axial distributions into account.

A calculation of the amount of the reacted CO can be expressed in the form of an equation

k(T); reaction rate constant, catv ; catalyst volume Kp ; equilibrium constant As regards a calculation of heat balance, the following conditions are assumed.

• Flow direction of fluid is only axial direction.

• Flow rate is uniform in the whole reactor.

• Heat conductivity of axial direction can be ignored.

• Heat of reaction exists.

On the assumption, the calculation of heat balance can be expressed in the form of an equation

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