Solid fuels, flames from

Solid Fuel Flames. The flames from the combustion of solids such as coal and wood arc the result of a combination of processes including the burning of gases that have been released from the heated solid (devolatization) that burn in the gas phase as diffusion... 

Other seemingly solid fuel flames such as those from the burning of plastics are actually more like liquid pool flames because the plastic melts and vola-tizes ahead of the advancing flame front. 

The flaming results extend to = 4 in Figures 2.3 and 2.4, at which point gas phase combustion appears to cease. However, combustion must continue since the heat of combustion remains nonzero. This is due to oxidation of the remaining solid fuel. If we consider wood, it would be the oxidation of the surface char composed primarily of carbon. From Example 2.3, we obtain the heat of combustion for carbon (going to CO2) as 32.8 kJ/g carbon. From Figure 2.4, we see a significant production of carbon monoxide at < > 4, and therefore it is understandable that Figure 2.3 yields a lower... 

The most interesting feature of the decomposition flames is their analogy to flames of the solid monopropellants. In fact, many of these substances, which are ordinarily liquids, may support a flame directly from the liquid phase without auxiliary vaporization of the liquid. In this case, the flame supplies the necessary heat of vaporization or decomposition in exact analogy to the solid propellant flame.8 The principal usefulness of a decomposition flame is found in the simplicity of design and control of a rocket powered by such a flame, even though more powerful fuels are readily available. A recent example, which has been featured in the news, is the hydrogen peroxide attitude-control rocket used in the artificial earth satellites of the U.S.A. 

Liquid or pulverized solid fuels are blown into the kiln through a nozzle with primary air. Additional secondary air is drawn into the kiln through the clinker cooler. The flame in the rotary kiln must meet several requirements. The clinker must be correctly burned, so as to minimize its content of free lime, with the least expenditure of fuel. The ash from a solid fuel must be uniformly absorbed by the clinker. For normal Portland cements, the conditions must be sufficiently oxidizing that the iron is present as Fe however, for white cements, mildly reducing conditions may be preferable. Proper flame control also extends the life of the refractory lining of the kiln. Computer-aided or fully automated control of kiln operating conditions is increasingly used. 

The boundary conditions that will be adopted at y = 0 (where conditions will be identified by the subscript 0) are = 0,(Xp = (Xp q = constant (a measure of the sublimation or boiling temperature), and u = 0. The first of these conditions would follow from a flame-sheet hypothesis and is accurate for many liquid fuels (see Section 3.3.4 or [21]). The validity of the second condition is discussed in Section 3.3.4 this condition will be most accurate for a volatile liquid fuel. The third condition is rigorously true only for a solid fuel but is an excellent approximation for liquid fuels if longitudinal flow of the liquid is surpressed (for example, by extruding the liquid through a porous solid material). ... 

In studying the combustion of liquid and solid fuels in air at pressures from 0.3 to 4 atmospheres, Franldand00 found that the candle power of wax candle flames varied almost linearly with pressure, falling off 5.1 per... 

The feed, consisting of a blend of fine ore and solid fuel (coal), is first placed as uniformly as possible onto an endless perforated belt, made-up of connected and hinged cast iron or steel sections, and then passes through an ignition furnace, which is a short hood with burners inside. The flames impinge on the surface of the bed and ignite solid fuel that is close to the hot interface. From that point on, air is pulled through the completely open bed, in a downdraft fashion combustion of the solid... 

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