Page 135 - Chemical process engineering design and economics

Process Circuit Analysis 119

Methanot Air

Coolant

Products

Figure 3.4.1 Packed-bed, catalytic reactor.

Table 3.4.1 lists the component balances, the energy balance, and thermo-
dynamic property relations. Because moles are generally not conserved in a
chemical reaction, we must include a source term in the component balances to
account for the depletion or generation of moles. The balances are given in Table
3.4.1 by Equations 3.4.4 to 3.4.8. In this case, the conversion is an experimental
value. If the conversion is unknown and the reaction is at equilibrium, then we
can write an equilibrium relation for the reaction to calculate the conversion. Be-
sides the general list of relationships, discussed earlier, there is a specification rela-
tionship. Equation 3.4.11 specifies that the moles of oxygen should be 80% of the
stoichiometric amount to minimize the risk of the methanol and formaldehyde
igniting and burning.

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