STOICHIOMETRY IN MASS BALANCES

If a reduction in the number of molar balances is desired for the calculations, the stoichiometric relationships developed in the previous section must be utilized. We can thus reduce the number of necessary balance equations from N to S one should keep in mind that the number of chemical reactions is usually much lower than the number of components in a system. The molar flows, /, can be replaced by expressions containing reaction extent, specific reaction extent, and reaction extent with concentration dimension or conversion (, I, I , or tia) in a system containing a single chemical reaction. For systems with multiple chemical reactions, h is replaced by an expression containing or i).  

In the following, different kinds of transformations of molar balances are introduced. These transformations are obtained using the extent of reaction, conversion, concentrations of the key components, or their molar flows. The treatment is directly applied to systems 

The molar balances of the three ideal reactor types, tube reactor, BR, and CSTR, Equations 3.8,3.18, and 3.25, can be written in the following form—provided that only the molar balances of the key components are taken into account  

The relationships between the extent of reaction and molar flows, as well as the molar amounts, of the key components are given by 

The above-mentioned equations provide us with the derivatives dhk/dx and dnj /df for tube reactors and BRs, respectively. 

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