Document 0L4bXn9E8E6B8p5BJpmKYEm7R

and Combustion 299 > The heat of combustion of the several fuel elements and compounds in their pure state is given in Table 1: The reaction of the carbon in the'fuel with oxygen may result in the' formation of carbon monoxide or carbon dioxide. In burning-to carbon monoxide, the carbon is not completely oxidized and, as shown by the data, the heat produced is considerably less than if it were completely oxidized. This fact is of greatest importance in considering the efficiency , of combustion. The calorific value of a fuel is determined by direct measurement of the heat evolved during combustion in a calorimeter. Although the ash and moisture content of coal from a given mine or locality may vary widely, the heating value of the coal, on a moisture and ash free basis, remains relatively constant. ' It is therefore possible to approximate the heating value of a shipment of coal as received if its moisture and ash content are determined, and if the heating value of similar coal on a moisture and ash free basis is known. This may be calculated by Equation 1. Heating value, as received = Heating value, moisture and ashfree X [100 -- (Moisture + Ash)] 100 ,,, UJ where, moisture and ash are expressed in per cent. Typical analyses.of the coals of the United States are given in U. S. Bureau of Mines Bulletin HQ. As practically all fuels, including coal, oil,, and gas, contain hydrogen, water vapor is one of the products of combustion. The amount of water vapor produced is proportional to the hydrogen content of the fuel. When the heating value of a fuel is determined in a.calorimeter the water vapor is condensed and the latent heat of vaporization is included in the heating value of the fuel. The heating value so determined is termed the gross or higher heating value and this is what is ordinarily meant when the heating value of a fuel is specified. In burning the fuel,' however, the products of-combustion are not cooled to the dew-point and the higher heating value cannot be. obtained. oValue from National Bureau of Standards. FLAME The appearance of the flame or products of combustion may serve as an approximate measure of the temperatures developed in the combustion process. The luminosity of a flame is caused by the heating to incan descence of unconsumed particles of combustible matter in the gases, and the higher the temperature of these particles the whiter the flame. Table 2 gives some approximate flame temperature data. Table 2. Approximate Flame Temperature Data Red, visible in Orange-yellow. Appearance of Flame' Temperature F Dbg 1000 . 1800 2000 2200 2400 2600