Loss in B. t. u. per pound = (T - t) × .24 × W.
Where T and t have values as in ([33]),
.24 = specific heat of chimney gases,
W = weight of dry chimney gas per pound of coal.
(D) Loss due to incomplete combustion of the carbon content of the fuel, that is, the burning of the carbon to CO instead of CO2.
| Loss in B. t. u. per pound | = | C | × | | 10,150 CO | | –––––––––––––––––– | | CO2 + CO |
| (35) |
|
C = per cent of carbon in coal by ultimate analysis,
CO and CO2 = per cent of CO and CO2 by volume from flue gas analysis,
10,150 = the number of heat units generated by burning to CO2 one pound of carbon contained in carbon monoxide.
(E) Loss due to unconsumed carbon in the ash (it being usually assumed that all the combustible in the ash is carbon).
| Loss in B. t. u. per pound | = | per cent C | × | per cent ash | × | B. t. u. per pound of combustible in the ash
(usually taken as 14,600 B. t. u.) | (36) |
|
[TABLE 57]
DATA FROM WHICH HEAT BALANCE
([TABLE 58]) IS COMPUTED| Steam Pressure by Gauge, Pounds | 192 | | Temperature of Feed, Degrees Fahrenheit | 180 | | Degrees of Superheat, Degrees Fahrenheit | 115.2 | | Temperature of Boiler Room, Degrees Fahrenheit | 81 | | Temperature of Exit Gases, Degrees Fahrenheit | 480 | | Weight of Coal Used per Hour, Pounds | 5714 | | Moisture, Per Cent | 1.83 | | Dry Coal Per Hour, Pounds | 5609 | | Ash and Refuse per Hour, Pounds | 561 | | Ash and Refuse (of Dry Coal), Per Cent | 10.00 | | Actual Evaporation per Hour, Pounds | 57036 | | Ultimate Analysis Dry Coal | { | C, Per Cent | 78.57 | | H, Per Cent | 5.60 | | O, Per Cent | 7.02 | | N, Per Cent | 1.11 | | Ash, Per Cent | 6.52 | | Sulphur, Per Cent | 1.18 | | Heat Value per Pound Dry Coal, B. t. u. | 14225 | | Heat Value per Pound Combustible, B. t. u. | 15217 | | Combustible in Ash by Analysis, Per Cent | 17.9 | | Flue Gas Analysis | { | CO2, Per Cent | 14.33 | | O, Per Cent | 4.54 | | CO, Per Cent | 0.11 | | N, Per Cent | 81.02 | |
The loss incurred in this way is, directly, the carbon in the ash in percentage terms of the total dry coal fired, multiplied by the heat value of carbon.
To compute this item, which is of great importance in comparing the relative performances of different designs of grates, an analysis of the ash must be available.