Page 44 - Handbook of Energy Engineering Calculations

460). The total weight of N is the sum of the N in the combustion air and
2
2
the fuel.

5. Compute the CO content of the flue gas
2
The CO , wet basis = 31.5/233.2 = 0.135, or 13.5 percent. The CO , dry basis
2
2
= 31.5/(233.2 − 28.6 − 35.9) = 0.187, or 18.7 percent.

6. Compute the air required with the stated excess flow
With 20 percent excess air, (1.20)(6.527) = 7.832 lb (3.524 kg) of air per lb
(kg) of wood burned.

7. Compute the weight of the products of combustion
The weight of the products of combustion = product weight for perfect

combustion, lb + (percent excess air)(air for perfect combustion, lb) = 8.280
+ (0.20)(6.527) = 9.585 lb (4.313 kg) of flue gas per lb (kg) of wood burned
with 20 percent excess air.

8. Compute the volume of the combustion products and the percent CO 2

The volume of the excess air in the products of combustion is found by
converting from the weight to the volumetric analysis and correcting for
temperature as in step 4, using the air weight from step 2 for perfect

combustion and the excess-air percentage, or (6.527)(0.20)(359/28.95)(2.15)
3
3
= 34.8 ft (0.985 m ). Add this to the volume of the products of combustion
3
3
found in step 4, or 233.2 + 34.8 = 268.0 ft (7.587 m ).
By using the procedure in step 5, the percent CO , wet basis = 31.5/268 =
2
0.1174, or 11.74 percent. The percent CO , dry basis = 31.5/(268 − 28.6 −
2
35.9 − 0.20 × 0.837) = 0.155, or 15.5 percent. In the dry-basis calculation, the
factor (0.20)(0.837) is the outside moisture in the excess air.

Related Calculations. Use the method given here when making combustion
calculations for any type of wood or woodlike fuel—spruce, cypress, maple,
oak, sawdust, wood shavings, tanbark, bagesse, peat, charcoal, redwood,
hemlock, fir, ash, birch, cottonwood, elm, hickory, walnut, chopped
trimmings, hogged fuel, straw, corn, cottonseed hulls, city refuse—in any

type of furnace—boiler, heating, process, or waste-heat. Most of these fuels