Furnaces spacing

For steam boilers, fuels are natural gas and blast furnace gas. A large number of small burners (about 30 hp. each) is used for the former. Burners are thoroughly distributed. As with fuel oil, they may be directed either slightly downward toward the rear or may face from the bridge wall toward the front. The combustion space should be large. The air supply is drawn in around the gas jet. High eflSciency is easily possible. For blast furnace gas, use a furnace space of 2 cu. ft. per rated horsepower, 0.8 sq. in. of gas passage area per horsepower and 2 in. blast (based on 6 to 8 in. pressure in main). Provision must be made for removal of dust. With all gas burners, the gas and air supply should be separately controllable. 

A schematic drawing of the effusion cell is shown in Figure 7.1. The cell opening shape is a capillary with radius r and length 1. The cell is suspended inside the furnace at temperature T. The inert gas is denoted by subscript 1 and the vapor by subscript 2 , while subscript f denotes the furnace space and the subscript i denotes the interior of the cell. The symbol c denotes concentration, x molar fraction, and P pressure. 

All the mechanical part of the balance, with the beam, set of weights, beam position sensor and compensation electromagnet, is enclosed in a thick-walled metallic chamber, which allows evacuation of the balance and beam cavity (of total volume of about 40 L) to a pressure of 4 x 10 bar with a mechanical rotary pump and to 4 x 10 bar with an additional diffusion pump. The evacuation can be performed either before starting the heating or during the course of the measurements. The gas distribution system allows the furnace space to be filled with various gases. Both static and dynamic atmospheres can be provided in the furnace, and two gases can be introduced in a preset ratio. 

Using many small burners to utilize the whole wall area is a way to achieve good temperature uniformity. (See figs. 3.4 and 3.5, and sec. 7.4.) There are large burners that can hold the burner wall as hot as the point of conventional maximum heat release. These adjustable thermal profile burners (fig. 6.1) can automatically hold a desired temperature profile by controlling the spin of the products of combustion. Optimum use of furnace space and overall refractory wall radiation usually favors the hottest possible burner wall (maximum flame spin, minimum flame length). In... 

TABLE 6.5 Comparisons of heating curves for 6 in. (0.152 m) square steel blooms in a continuous reheat furnace, spacing = 1.6 1, with or without enhanced heating... 

Fig. 3.18 Furnace space of the Derivatograph modified for determination of ignition temperature A furnace, B quartz beaker, C crucible for the sample, D crucible for reference material, E thermocouples, F spark gap, G air conduit coil. Dimensions in mm Reprinted from Ref. 20 by permission of the author... 

Group A1 represents the materials which do not ignite in the course of this test and for which the temperature of the furnace space does not rise more than 50 ""C. 

An excess pressure of 10 5 Pa is applied to the furnace space during the whole heating period of the test. 

In which the quenching medium is introduced into the furnace space containing a fixed sample. 

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