Part 22 (1/2)
coke is a porous product consisting al processes have distilled off the hydrocarbon gases of the fuel used It is produced, first, froas or ordinary bituminous coals burned in special furnaces called coke ovens; and third, fro the distillation of the residuum to a red heat
coke is a smokeless fuel It readily absorbs moisture from the atmosphere and if not kept under cover its ht
Gas-house coke is generally softer and nites more readily, and requires less draft for its combustion
[Illustration: 16,000 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Brunot's Island Plant of the Duquesne Light Co, Pittsburgh, Pa]
THE DETERMINATION OF HEATING VALUES OF FUELS
The heating value of a fuel may be determined either by a calculation fro a sample in a calorimeter
In the former method the calculation should be based on an ultimate analysis, which reduces the fuel to its eleen, sulphur, ash and ree of accuracy A proxie of moisture, fixed carbon, volatilethe ultimate co the heat of coree of accuracy as an ultimate analysis, but estimates may be based on the ultimate analysis that are fairly correct
An ultimate analysis requires the services of a competent chemist, and the methods to be employed in such a deter che the fuel into its elementary constituents, does not reveal how these may have been combined in the fuel The manner of their combination undoubtedly has a direct effect upon their calorific value, as fuels having almost identical ulti value when tested in a caloriht, and very close approximations may be computed froiven on both a moist and a dry fuel basis
Inasenerally accepted for the comparison of data, it would appear that it is the best basis on which to report such an analysis When an analysis is given on a moist fuel basis itthe percentages of the various constituents by onethe moisture content separately
_Moist Fuel_ _Dry Fuel_
C 8395 8445 H 423 425 O 302 304 N 127 128 S 91 91 Ash 603 607 ------ 10000
Moisture 59 59 ------ 10000
Calculations from an Ultimate analysis--The first for values from the composition of a fuel as deter, and this forhtly modified, is the most commonly used to-day Other formulae have been proposed, some of which are more accurate for certain specific classes of fuel, but all have their basis in Dulong's formula, the accepted modified form of which is:
Heat units in B t u per pound of dry fuel =
O 14,600 C + 62,000(H - -) + 4000 S (18) 8
where C, H, O and S are the proportionate parts by weight of carbon, hydrogen, oxygen and sulphur
assu in this for value per pound of dry coal
( 0304) = 14,600 8445 + 62,000 (0425 - -----) + 4000 0091 = 14,765 B t u
( 8 )
This coal, by a calorimetric test, showed 14,843 B t u, and froree of accuracy of the foration of Lord and Haas in this country, Mabler in France, and Bunte in Gerives results nearly identical with those obtained from calorimetric tests and may be safely applied to all solid fuels except cannel coal, lignite, turf and wood, provided the ultimate analysis is correct This practically li features are the presence of hydrogen and carbon united in the form of hydrocarbons Such hydrocarbons are present in coals in sative heats of combination, and in coals these appear to offset each other, certainly sufficiently to apply the forh and Low Heat Value of Fuels--In any fuel containing hydrogen the calorific value as found by the calori conditions in boiler practice by an amount equal to the latent heat of the volatilization of water This heat would reappear when the vapor was condensed, though in ordinary practice the vapor passes away uncondensed This fact gives rise to a distinction in heat values into the so-called ”higher” and ”lower” calorific values
The higher value, _i e_, the one determined by the calorimeter, is the only scientific unit, is the value which should be used in boiler testing work, and is the one recoineers
There is no absolute measure of the lower heat of co physicists as to the deductions to be her or absolute unit in this determination, the lower value must be considered an artificial unit