Page 118 - Chemical engineering design

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CHEMICAL ENGINEERING
Procedure
1. Set up the specific heat coefficients as a matrix.
2. Use equation 3.11a to calculate the enthalpy of each component. Tabulate the results.
Sum the columns to find the total stream sensible enthalpy.
3. Repeat for all the inlet and exit streams.
4. Calculate and add the enthalpy from any reaction or phase change and add to the
stream enthalpies.
5. Subtract the total enthalpy of the outlet streams from the inlet to find the change
in enthalpy.

Example 13.14b
Repeat the calculations for the solution of Example 13.4a using a spreadsheet.

Solution
The spreadsheet used for this example is Microsoft Works. A copy of the example using
Microsoft Excel can be found on the companion web site: http://books.elsevier.com/
companions.

Example 3.14b

Data
Fuel oil %C D 87.5 %H2 D 8 %N2 D 1
%oO2 D 3.5
Cp kJ/kg, K 1.6 CV kJ/kg 39540 lat. heat kJ/kg 350
Specific heats gases

comp. A B C D
CO2 19.763 0.0733 5.52E-05 1.713E-08
H2O 32.19 0.0019207 1.054E-05 3.59E-09
O2 28.06 3.67E-06 1.743E-05 1.06E-08
N2 31.099 0.01354 2.675E-05 1.17E-08
Tin fuel, K 323 Tin air, K 288 Tout, K 1500
Basis 100 kg, as analysis is by weight.
MATERIAL BALANCE

Reactions C C O2 D CO2 H2 C 1/2O2 D H2O
element kg kmol stoichiometric O2, kmol products, kmol
C 87.5 7.29 7.29 7.29 CO2
H2 8 4.00 2.00 4.00 H2O
O2 3.5 0.11 0.11
N2 1 0.04 0.04
Totals 100 11.44 9.29 11.44
O2 with 20% excess, kmol D 11.15 unreacted O2, kmol D 1.86
N2 with combustion air, kmol D 41.95