Mass nonsteady state method

Which experimental method should be used depends on the type of reactor and how it will be operated, and if clean or process water is to be used for the measurement. Nonsteady state methods are generally simpler and faster to perform if kLa is to be determined in clean water without reaction. For processes that are operated at steady state with a reaction, determination of kLa using steady state methods are preferred, since continuous-flow processes need not be interrupted and operating conditions similar to the normal process conditions can be used. This is especially important for systems with reactions because the reaction rate is usually dependent on the concentration of the reactants present. They are thus often applied for investigations of the mass transfer coefficient under real process conditions with chemical reactions kLa(02) or biological activity kLa(02), e. g. in waste water treatment systems. 

Nonsteady State Methods without Mass Transfer Enhancement... 

The nonsteady state methods described in this section are all based on no or negligible reactions taking place in the system. If reactions are present, the treatment of the mass balances becomes more complicated since... 

Common Problems Inherent to the Determination of Mass Transfer Coefficients with the Nonsteady State Method... 

A variety of problems encountered with the measurement of oxygen mass transfer coefficients by using the nonsteady state method are well known and well understood. Libra (1993) gives a comprehensive discussion based on oxygen mass transfer measurements. The most important problems are found in the following table. 

Table 3-4 Problems inherent to the determination of mass transfer coefficients with the nonsteady state method.

Derive steady-state and nonsteady-state mass and energy balances for a catalyst monolith channel in which several chemical reactions take place simultaneously. External and internal mass transfer limitations are assumed to prevail. The flow in the chaimel is laminar, but radial diffusion might play a role. Axial heat conduction in the solid material must be accounted for. For the sake of simplicity, use cylindrical geometry. Which numerical methods do you recommend for the solution of the model ... 

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