Balances on Reactive Processes

7 BALANCES ON REACTIVE PROCESSES 4.7a Balances on Molecnlar and Atomic Species 

One hundred kmol/min of ethane is fed to the reactor. The molar flow rate of H2 in the product stream is 40 kmol/min. 

A number of different balances could be written on this process, including balances on total mass. C.Hs, C2H4, and H2. Of these, only the first has the simple form input = output since the three given species all participate in the reaction, the balance equation for each of them must include a generation terra (for C2H4 and H2) or a consumption term (for C2Hj). 

Notice, however, that balance equations may also be written for atomic carbon and atomic hydrogen, regardless of the molecular species in which the carbon and hydrogen atoms happen to be found. Balances on atomic species can be written input = output, since atoms can neither be created (generation = 0) nor destroyed (consumption = 0) in a chemical reaction. 

Before illustrating these balances, let us resolve an ambiguity. When we speak of a hydrogen balance, it could mean two completely different things a balance on molecular 

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You may analyze reactive processes using (a) molecular species balances (the only method used for nonreactive processes), (b) atomic species balances, or (c) extents of reaction. Molecular species balances on reactive processes are often cumbersome they must include generation and consumption terms for each species, and one degree of freedom must be added for each independent reaction. Atomic species balances have the simple form input = output and are usually more straightforward than either of the other two methods. Extents of reaction are particularly convenient for reaction equilibrium calculations. 

An energy balance on a reactor tells the process engineer how much heating or cooling the reactor requires in order to operate at the desired conditions. In this chapter we show how enthalpy changes that accompany chemical reactions are determined from tabulated physical properties of the reactants and products and how calculated enthalpies of reaction are incorporated in energy balances on reactive processes. 

ENERGY BALANCES ON REACTIVE PROCESSES 9.5a General Procedures... 

Chapter 9 Balances on Reactive Processes given by the expression... 

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