Furnaces lining design

Holding furnaces usually operate with a relatively constant metal level. Included in this category are furnaces that supply metal to various casting processes and large pots that hold metal for continuous coating lines. Multiple inductor furnaces are designed so that individual inductors can be replaced... 

Mass burn Refractory furnace lining Various grate or stationary hearth designs Old or small facilities... 

Combustion Test Facility. The 500-lb/hr combustion test facility is shown schematically in Figure 1. The furnace was designed to simulate the performance of an industrial steam generator. The unit is 7 feet wide, 5 feet deep, and 12 feet high, and has a volumetric heat liberation rate of about 16,000 Btu/hr ft3 at a thermal input of 6.5 million Btu/hr. The furnace walls are refractory-lined and water-cooled. 

The combustion roar associated with flares typically peaks at a frequency of approximately 63 Hz while combustion roar associated with burners can vary in the 200-500 Hz range. Burner noise can have a spectrum shape and amplitude that can vary with many factors. Several of these factors include the internal shape of the furnace, the design of the burner muffler, plenum and tile, the acoustic properties of the furnace lining, the transmission of the noise into the fuel supply piping, and the transmissive and reflective characteristics of the furnace walls and stack. 

Furnace construction with monolithic refractories is determined by the method(s) to be used in installing the furnace lining, which may be dictated by furnace configuration, time limitations, or other local site conditions. The furnace designer must determine the minimum refractory thickness required. (See table 9.3.) Thicker-than-minimum linings are usually mandated by fundamental economic considerations such as fuel conservation (less heat loss), extended lining life, and reduced maintenance. Additional lining thickness also may be required because of workplace environmental considerations (e.g., external shell temperature or interal atmosphere). 

Furnace shell temperature there is more heat loss to the surroundings when the furnace shell temperature is high and this adversely affects the heat recovery by the waste heat boiler. Hence, modem furnaces are designed with optimum thicknesses of insulating and fire brick linings. 

In all cases, it is necessary to use a special furnace designed to withstand highly corrosive conditions, usually at temperatures of 700°C to 1000°C. Paradoxically, the materials of construction which have been found most useful for furnace linings of this type are graphite or silica despite the fact that graphite is often a suitable form of carbon for use as a reactant, and silica is a common constituent of ores processed by this technique, which reacts readily to give silicon tetrachloride. Their success as materials of construction is due to their use in separate massive form rather than as an intimate mixture with one another. They are slowly attacked even under these conditions and must be regarded as expendable. The corrosion products, however, produced by the reaction ... 

Refractory Linings. The refractory linings (2,3) for the hearth and lower wads of furnaces designed for melting ferrous materials may be acidic, basic, or neutral (see Refractories). Sdica has been widely used in the past, and is stid being used in a number of iron and steel foundries. Alumina, a neutral refractory, is normally used for furnace roofs and in the wads for iron foundries, but basic brick can also be used in roofs (4). 

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. 

Furnace Design. Modem carbide furnaces have capacities ranging from 45,000 t/yr (20 MW) to 180,000 t/yr (70 MW). A cross-section of a 40 MW furnace, constmcted in 1981, having a 300 t/d capacity is shown in Figure 2. The shell consists of reinforced steel side walls and bottom. Shell diameter is about 9 m and the height to diameter ratio is shallow at 0.25 1.0. The walls have a refractory lining of 0.7 m and the bottom has a 1-m layer of brick topped by a 1.5-m layer of prebaked carbon blocks. The steel shell is supported on concrete piers and cooling air is blown across the shell bottom. A taphole to withdraw the Hquid carbide is located at the top of the carbon blocks. 

C. R. T. Tarley, E. C. Figueiredo and G. D. Matos, Thermospray flame furnace-AAS determination of copper after on-line sorbent preconcentration using a system optimised by experimental designs. Anal. Sci., 21(11), 2005, 1337-1342. 

One of the drawbacks of this CAVERN device is the occurrence of a nonuniform distribution of reactant on catalysts because adsorption occurs on a deep bed of catalyst packed in a MAS rotor. To overcome this problem, we developed several shallow-bed CAVERN devices (95), and Fig. 10 shows a version of one such design. A thin layer of catalyst is supported on a glass trapdoor, and the device is evacuated. A furnace is clamped in place so that the catalyst can be activated if necessary. The catalyst is cooled with a cryogen bath, and a controlled amount of adsorbate is introduced from the vacuum line. The trapdoor is raised, the loaded catalyst falls into the MAS rotor, and the seal is driven into place. Finally the cold, sealed rotor is manually transferred into the cold MAS probe. The added advantages of the shallow-bed CAVERN is that all manipulations can be carried out without using a glovebox in any step. 

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