Unsteady-state mass balance method

Unsteady-State Mass Balance Method One widely used technique for determining Kj a in bubbling gas-liquid contactors is the physical absorption of oxygen or COj into water or aqueous solutions, or the desorption of such a gas from a solution into a sparging inert gas such as air or nitrogen. The time-dependent concentration of dissolved gas is followed by using a sensor (e.g., for O2 or CO2) with a sufficiently fast response to changes in concentration. 

Unsteady-State Mass Balance Method One widely used technique for determining KLa in bubbling gas-liquid contactors is the physical absorption of oxygen or C02... 

The parameters n and X(T) which characterize the rate law are evaluated via the differential method of reaction-rate data analysis based on the unsteady-state mass balance ... 

Chapter 11 deals with dynamic (unsteady-state) mass balancing of a technological system involving inventories. A straightforward method of reconciliation is presented avoiding accumulation of small systematic errors in the time series of measurements. The method has proved successful in practice and can also be supported by theoretical arguments. 

In conclusion to this section, research in the RTD area is always active and the initial concepts of Danckwerts are gradually being completed and extended. The population balance approach provides a theoretical framework for this generalization. However, in spite of the efforts of several authors, simple procedures, easy to use by practitioners, would still be welcome in the field of unsteady state systems (variable volumes and flow rates), multiple inlet/outlet reactors, variable density mixtures, systems in which the mass-flowrate is not conserved, etc... On the other hand, the promising "generalized reaction time distribution" approach could be developed if suitable experimental methods were available for its determination. 

Multiphase reactors can be batch, fed batch, or continuous. Most of the design equations derived in this chapter are general and apply to any of these operating modes. They will be derived for unsteady operation. The unsteady material balances include the inventories in both phases and mass transfer between the phases so that steady-state solutions fonnd by the method of false transients will be true transients if the initial conditions are correct. Compare Section 10.6. 

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