Slot furnaces

Slot furnaces are in general use throughout the steel industry to heat steel for forging and are usually fired with light oil. Because many such furnaces are located in small businesses, it is difficult to obtain an accurate estimate of their total energy use. The best approximation available is that about 0.2 quad is consumed in slot forge furnaces annually. 

Figure 24.1 Dual fiber slot furnace combining LT and HT operations. Source Courtesy Harper International...

The desired air—fuel volume ratio is usually seven or more, depending on the stoichiometry. Burners of this general type with many multiple ports are common for domestic furnaces, heaters, stoves, and for industrial use. The dame stabilizing ports in such burners are often round but may be slots of various shapes to conform to the heating task. 

High-Temperature Coke (1173 to 1423 K or 1652 to 2102°F.) This type is most commonly used in the United States nearly 20 percent of the total bituminous coal consumed is used to make high-temperature coke for metallurgical applications. About 99 percent of this type of coke is made in slot-type recovery ovens. Blast furnaces use about 90 percent of the production, the rest going mainly to foundries and gas plants. 

Out of the 900 million tons of coal produced in the United States for domestic purposes in 1992, about 34 million tons were used for coking [10]. The overw helmmg majority of coal is consumed by the electric utilities. Nevertheless, in 1990, the United States steel industry required about 23 million tons of coke which was produced by the byproduct recovery slot oven [15] For a typical blast furnace, this translates to 0 5 tons of coke per ton of iron metal. 

The air curtain design equations are outlined in Chapter 7. The plume data for furnace charging are used in this calculation step. Note that the plume volume flow impinging on the width of the slot should be used rather than the whole plume flow. 

Various hollow-cone simplex atomizers (Fig. 2.1) have been developed for combustion applications, differing from each other mainly in the way that swirl is imparted to the issuing liquid jet. In these atomizers, swirl chambers may have conical slots, helical slots (or vanes), or tangential slots (or drilled holes). Using thin, removable swirl plates to cut or stamp the swirl chamber entry ports leads to economies of the atomization systems if spray uniformity is not a primary concern. Large simplex atomizers have found applications in utility boilers and industrial furnaces. Oil flow rates can be as high as 67 kg/min. 

Several types of atomization cell are available flame, graphite furnace, hydride generation and cold vapour. Flame is the most common. In the premixed laminar flame, the fuel and oxidant gases are mixed before they enter the burner (the ignition site) in an expansion chamber. The more commonly used flame in FAAS is the air-acetylene flame (temperature, 2500 K), while the nitrous oxide-acetylene flame (temperature, 3150K) is used for refractory elements, e.g. Al. Both are formed in a slot burner positioned in the light path of the HCL (Fig. 27.4). 

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