Page 333 - Wastewater Solids Incineration Systems

294 Wastewater Solids Incineration Systems

cific heat ( 0.22 Btu/lb°F) over a wide range. The enthalpy of ash, referenced to 60°F,
may be computed as follows:
h 0.22 (T T ) 0.22 (T 60) (0.22 T 13.2) Btu/lb
(ash) a b a a
The following heat and material balance calculates the availability of methane at
1400°F and 25% XS air. In this example, the air is bone dry at a temperature of 60°F,
hence provides neither sensible heat nor heat of vaporization into the system. The
calculations are shown in the general format of an accounting balance sheet to make
the calculation steps easy to follow and understand by inspection. Tables A.15 and
A.16 provide material and heat balances, respectively, for the combustion of natural
gas (CH ) at an exhaust temperature of 1400°F and 25% XS air.
4
The next set of calculations represents fuel oil at 40% XS air and 1600°F. In this
example, the air temperature is 125°F and has an absolute humidity of 0.01 lb H O/lb
2
bone dry air. These are presented in Tables A.17 and A.18.

TABLE A.15 Material balance for combustion of 100 lb/hr of natural gas (CH ) at 60°F inlet and
4
1400°F exhaust temperature, 25% XS air .
Carbon Hydrogen Oxygen Nitrogen Sulfur Total
Inputs, lb/hr a
Fuel 75.00 25.00 0.00 0.00 0.00 100.00
Stoichiometric air 400.00 1327.86 1727.86
XS air 100.00 331.97 431.97
Air moisture 0.00 0.00 0.00
Totals 75.00 25.00 500.00 1659.83 0.00 2259.83
Outputs, lb/hr
CO 75.00 200.00 275.00
2
O 100.00 100.00
2
N 1659.83 1659.83
2
H O 25.00 200.00 225.00
2
SO 0.00 0.00 0.00
2
Totals 75.00 25.00 500.00 1659.83 0.00 2259.83
Outputs, lb-mole/hrb CO O N H O SO Total
2 2 2 2 2
lb-mole/hr 6.25 3.13 59.28 12.50 0.00 81.16
Volume % (wet) 7.70% 3.86% 73.04% 15.40% 0.00% 100.00%
Volume % (dry) 9.10% 4.56% 86.34% 0.00% 100.00%
a lb/hr 0.453 6 kg/h.
b lb-mole/hr 0.4536 kg-mol/h.