Page 140 - Chemical process engineering design and economics

124 Chapters

Table 3.4.3 Calculation Procedure for Calculating Heat Transfer to a
Reactor___________________________________

1. Solve Equations 3.4.9, 3.4.11 and 3.4.23 to 3.4.25 simultaneously to
obtain m 2, m 3, y 3i1, y 3i2 and y 3, 5.

2. Solve Equations 3.4.4 to 3.4.8 in terms of m 4. Substitute these derived
equations into Equation 3.4.10 and solve for m 4
3. Solve for y4,i, y4,2, y4,3, y4,4, and y4|5 using Equations 3.4.4 to 3.4.8.

4. Calculate the pure component enthalpies from Equations 3.4.15 to
3.4.22.

5. Calculate the mixture enthalpies from Equations 3.4.13 and 3.4.14.

6. Calculate Q from Equation 3.4.12.

the results of a calculation for later reference and for checking the solution. Table
3.4.4 lists the steam properties - temperature, pressure, flow rate and composition.
From experience we specify a 0.81 bar (0.8 atm) pressure drop across the reactor.
Now, calculate the enthalpy for each component by using an average heat
capacity from the inlet temperature to the base temperature of 25 °C and from the
base temperature to the outlet temperature. Thus, Equations 3.4.15 to 3.4.22 for
each component reduce to

Ah = c PAT (3.4.26)

Next, calculate the enthalpy change for each component and then add them
to obtain the enthalpies of streams 3 and 4. Table 3.4.5 summarizes the results of
these calculations.

From Equation 3.4.12 in Table 3.4.1

7
6
6
Q = -13.341xl0 + 800 (-37420) + 16.96 x 10 = -2.63xl0 kcal/h
7
(-10.4xl0 Btu/h). (3.4.27)
Because heat added to the system is defined as positive, the minus sign
means that we must remove heat.

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