Stationary furnaces

Hearth. The hearth of a channel induction furnace must be designed to satisfy restraints that are imposed by the operating inductor, ie, the inductor channels must be full of metal when power is required, and it is also necessary to provide a sufficient level of metal above the channels to overcome the inward electromagnetic pressure on the metal in the channel when power is appHed. Once these requirements are satisfied, the hearth can then be tailored to the specific appHcation (13). Sizes range from stationary furnaces hoi ding a few hundred kilograms of aluminum to rotating dmm furnaces with a useful capacity of 1500 t of Hquid iron. 

The stationary furnace used for reduction has three temperature zones through which the boats loaded with tungsten tri oxide move before the oxide is converted to the metal. The loaded boats pass into the furnace countercurrent to the movement of hydrogen gas. Thus the gas in the highest temperature zone has the minimum moisture content, and the moisture content becomes maximum when the gas passes through the lowest temperature zone. This arrangement ensures the highest possible reduction efficiency. 

Batch sintering in stationary furnaces of different kinds is used primarily for the posttreatment of agglomerated products to gain final strength and properties but also for laboratory work in connection with the development of continuous sintering technologies and for pilot plants [B.12c, B.16, B.25]. 

Doors should be checked often and repaired promptly because hot gas leaks can lead to mnaway ruin quickly. Seals around doors and car hearths need frequent repair or replacement. Doors should be checked for warpage and loss of refractory. Doors that are not used should be bricked up, but with addition of an observation port (with closure on a chain) and closure for monitoring furnace conditions during firing. If there are any gaps between doors and stationary furnace elements exceeding in. (3 mm), they should be adjusted for less leak. 

Medium-sized loads are often processed ia a beU furnace, as shown ia Figure 2. The operation of this furnace is opposite to that of an elevator furnace the work load is placed on a stationary hearth and the furnace is lowered over the hearth. BeU furnaces are often arranged with two or more bases (hearths) which permit more efficient use of the furnace because one base can be unloaded/loaded as the furnace carries out a heating cycle on another base. 

Furnaces of this type, such as the steam locomotive furnace—boHet design, had the obvious disadvantage that pressure was limited to ca 1 MPa (150 psi). The development of seamless, thick-waH tubing for stationary power plants (ie, water-tube furnaces) and other engines for motive power, such as diesel—electric, has in many cases ecHpsed the fire-tube boHet. For appHcations calling for moderate amounts of lower pressure steam, however, the modern fire-tube boHet continues to be the indicated choice (5). 

The first of these reactions takes place at temperatures of about 150°C, the second reaction proceeds at about 550—660°C. Typical furnaces used to carry out the reaction include cast-iron retorts the Mannheim mechanical furnace, which consists of an enclosed stationary circular muffle having a concave bottom pan and a domed cover and the Laury furnace, which employs a horizontal two-chambered rotating cylinder for the reaction vessel. The most recent design is the Cannon fluid-bed reactor in which the sulfuric acid vapor is injected with the combustion gases into a fluidized bed of salts. The Mannaheim furnace has also been used with potassium chloride as the feed. 

Most of the magnesium is cast iato iagots or billets. The refining of the molten metal extracted from the electrolysis is performed continuously ia large, stationary brick-lined furnaces of proprietary design (25). Such iastaHations have a metal yield better than 99.5% and negligible flux consumption. 

Equipment. The standard equipment in magnesium foundries consists of large stationary brick-lined reverbatory furnaces which can hold up to 10—15 t of molten magnesium. Reverbatory furnaces are furnaces in which heat is suppHed by burning a fuel in a space between the reactants and the... 

Multiple-Hea.rth Roasters. The circular types consist of a series of hearths arranged vertically in such a way that the ore entering the top is rabbled and dropped down from hearth to hearth, until it is completely oxidized. The hearths are usually stationary and the plows revolve, such as in the Wedge, Herreshoff, Ord, Skinner, and other roasters (21). In other furnaces, the hearths revolve and the rabbles are fixed, eg, the deSpirlet and its modification, the Barrier. 

Mechanical Properties Mechanical properties of wide interest include creep, rupture, short-time strengths, and various forms of ductihty, as well as resistance to impact and fatigue stresses. Creep strength and stress rupture are usually of greatest interest to designers of stationary equipment such as vessels and furnaces. 

The predominant air pollution problem of the nineteenth century was smoke and ash from fhe burning of coal or oil in the boiler furnaces of stationary power plants, locomotives, and marine vessels, and in home heating fireplaces and furnaces. Great Britain took the lead in addressing this problem, and, in the words of Sir Hugh Beaver (3) ... 

The United States generates about 20 million metric tons of nitrogen oxides per year, about 40% of which is emitted from mobile sources. Of the 11 million to 12 million metric tons of nitrogen oxides that originate from stationary sources, about 30% is the result of fuel combustion in large industrial furnaces and 70% is from electric utility furnaces. 

Figure 12-95. Axial compressor Type AV100-16, during erection. Note stationary and rotating blades. Two identical steam turbine-driven machines supply air to blast furnace at steel works. Suction volume = 560,000 NmVh discharge pressure = 6.2 bar power input = 52,000 kW each. (Used by permission Bui. 26.13.10.40-Bhj. Sulzer Turbo Ltd.)...

Scotch marine boilers (SM boilers) derive their name from the Scottish shipyards that built marine vessels for the British Navy. They were the first design of FT boiler to incorporate both furnace tubes and fire tubes inside the shell and replaced the brick-set boilers that used to burn through the bottoms of ships. The SM boiler was a particularly versatile design and quickly became the boiler of choice for many stationary (land) applications as well as for marine duty. Land-based SM boilers (now commonly called Scotch boilers) were not simply marine boilers adapted for stationary duty but incorporated specific design modifications to meet the requirements of land-based industry. 

Figure 1. Stationary Extraction Furnace Assembly for Plutonium Reduction and Americium Extraction.

Stationary extraction furnace assembly for Pu reduction and americium extraction. 348/... 

Improved furnace designs and combustion techniques could reduce NOx emissions from stationary sources by 40-70%. These methods are not in widespread use now. The processes for removing NOx from flue gases are in an early stage of development. 

Lamb et al studied the conversion concept of a crosscurrent moving bed. The PBC system consisted of a trolley filled with a fuel bed of bagasse. The trolley rolled horizontally over a vertical air duct to simulate the moving bed (Figure 3). The speed of the trolley was controlled to keep the flame in a stationary position over the duct. An electrically heated platen, 30x15 cm, was placed horizontally 12 cm above the base of the bed, simulating radiation from furnace walls. 

This completely automated spectrum analysis procedure represents the final element in our effort to reduce to routine practice the quantitative analysis of similarly constituted gaseous samples by FTIR. It has seen wide and successful application within our laboratory, having been the principle analytic method for two extensive hydrocarbon species-specific auto exhaust catalyst efficiency studies, a comprehensive study of the gases emitted by passive-restraint air bag inflators, several controlled furnace atmosphere analyses, several stationary source stack emission checks and several health-related ambient atmosphere checks. 

Solid fuels such as wood, charcoal, coal, and biomass have been used occasionally for motor vehicles at times of scarcity. They are more suitable for large-scale stationary power plants under the watchful eyes of competent engineers, as they are too difficult to feed into the furnaces, and the fuels are too full of sulfur and ash that would corrode and foul the light engines. 

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