Stoichiometric balances constant volume

In Table 3.3, the concentration expressions of the key components are given for some common types of reaction kinetics. The concentration expressions in Table 3.3 are valid for isothermal conditions, for systems in which the volumetric flow rate and the reaction volume are kept constant. In practice, this implies isothermal liquid-phase reactions in a BR, PFR, and CSTR, isothermal gas-phase reactions in a BR with a constant volume, and isothermal gas-phase reactions with a constant molar amount (J2 ij = O) in a PFR or CSTR. The equations in Table 3.3 were developed from balance equations introduced in Sections 3.2 through 3.4 as well as from the stoichiometric relationships that were presented in Sections 3.5 and 3.6. The equations are written in such a way that the concentrations of key components are expressed explicitly for simple reactions, the corresponding design expressions are obtained by solving the space time (t) or the reaction time (t) in the equations. 

This equation balances the available aluminium reservoir, described by the difference between the initial (Q) and the critieal ( Cg) aluminium eontent as well as the volume (F) of the sample with the eonsumption of aluminium by oxidation. The consumption is represented by the growth constant k), the corresponding exponent (1/n) and, of coimse, the total surface area (A) of the sample. The alloy density (p) and the stoichiometric factor (v) cormect the two parts. In [5] this approach has been successfully applied to construct so-called oxidation diagrams from which the lifetime can easily be read, if the temperature and the thickness of the sample are known. 

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