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Refractoiy

Lr = dimensionless refractoiy-wall loss. m = mass flow rate. n = refractive index. [Pg.570]

Most refractoiy materials have an of 0.8 to 1.0 at wavelengths beyond 2 to 4 Im decreases rapidly toward shorter wavelengths for materials that are white in the visible but retains its high v ue for black materials such as FeO and CrgO. Small concentrarions of FeO... [Pg.572]

Refractoiy materials generally have a total emittance which is high (0.7 to 1.0) at ambient temperatures and decreases with increase in temperature a change from 1000 to 1570°C (1850 to 2850°F) may cause a decrease in of one-fourth to one-third. [Pg.573]

For opaque materials, the reflectance p is the complement of the absorptance. The directional distribution of the reflected radiation depends on the material, its degree of roughness or grain size, and, if a metal, its state of oxidation. Polished surfaces of homogeneous materials reflect speciilarly. In contrast, the intensity of the radiation reflected from a perfectly diffuse, or Lambert, surface is independent of direction. The directional distribution of reflectance of many oxidized metals, refractoiy materials, and natural products approximates that of a perfectly diffuse reflector. A better model, adequate for many calculational purposes, is achieved by assuming that the total reflectance p is the sum of diffuse and specular components p i and p. ... [Pg.573]

If an enclosure may be divided into several radiant-heat sources or sinks Ai, A2, etc, and the rest of the enclosure (reradiating refractoiy surface) may be lumped together as A at a uniform temperature Tr, then the total interchange area for zone pairs in the black system is given by... [Pg.577]

Note that the emissivity and reflectance of the refractoiy are without... [Pg.586]

Description A tray or compartment diyer is an enclosed, insulated housing in which solids are placed upon tiers of trays in the case of particulate solids or stacked in piles or upon shelves in the case of large objects. Heat transfer may be direct from gas to sohds by circulation of large volumes of hot gas or indirect by use of heated shelves, radiator coils, or refractoiy walls inside the housing. In indirec t-heat units, excepting vacuum-shelf equipment, circulation of a small quantity of gas is usually necessary to sweep moisture vapor from the compartment and prevent gas saturation and condensation. Compartment units are employed for the heating and diying of lumber, ceramics, sheet materi s (supported on poles), painted and metal objects, and all forms of particulate solids. [Pg.1190]

In counterflow movement, heat from the outgoing sohds is transferred directly to cold incoming solids, reducing heat losses and fuel requirements. Continuous conveyor ovens are employed also for diy-ing refractoiy shapes and for drying and baking enameled pieces. In many of these latter, the parts are suspended from overhead chain conveyors. [Pg.1199]

Cost Data for Kilns Purchase prices, weights, and horsepower requirements of typical units are given in Table 12-21. Installed costs will run to from 300 to 500 percent of purchase cost. Maintenance will average 5 to 10 percent of the total installed cost per year but is dependent largely on the hfe of the refractoiy lining. [Pg.1208]

For estimating purposes refractoiy lining for a 2.7- to 3.4-m-diameter Idln costs 6000 to 15,000 per meter of Idln length installed (50 percent material, 50 percent labor). [Pg.1208]

In many cases, cold spots on the reactor shell will result in condensation and high corrosion rates. Sufficient insulation to maintain the shell and appurtenances above the dew point of the reaction gases is necessary. Hot spots can occur where refractory cracks allow heat to permeate to the shell. These can sometimes be repaired by pumping castable refractoiy into the hot area from the outside. [Pg.1563]

The violent motion of a fluidized bed requires ample foundations and sturdy supporting struc ture for the reactor. Even a relatively small differential movement of the reactor shell with the lining will materially shorten refractoiy life. The lining and shell must be designed as a unit. Struc tural steel should not be supported from a vessel that is sub-jec t to severe vibration. [Pg.1563]

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. [Pg.1594]

Planetary Ball Milling This is a method of increasing the gravitational force acting on balls in a ball mill. For example, refractoiy metals and carbides can be ground to 1 to 2.6 [Lm in 5 to 20 min in an apparatus capable of applying a centrifugal force of 10 to 50 G. [Dobrovol sldi, Poroshk. MetalL, 7(6), 1-7 (1967)]. [Pg.1857]

Sixty percent of refractoiy magnesite is made synthetically from Michigan brines. When calcined, this material is one of the hardest refractories to grind. Gyratoiy crushers, jaw crushers, pan mills, and ball mills are used. [Pg.1869]

Hepatopulmo- diuretics, volume resuscitation, liver transplantation Paracentesis, 02 therapy Dyspnea, presence of ing other nephrotoxins Liver transplantation tor refractoiy hepatorenal syndrome Acute relief of dyspnea... [Pg.261]

Pancreas powder, penicillin, pharmaceuticals, phosphate ores, plastics, polyvinylchloride (PVC), potash, potassium compounds, protein pigments, pyrites, pyrocatechol Raisin seeds, reduced ores, refractoiy materials, rice starch, rock salt... [Pg.363]

Cardonne, S.M. etal. "Refractoiy Metals Forum I Tantalum and Its Alloys, Advanced Materials Processes, 16 (September, 1992). [Pg.58]

Use of low-temperature molten systems for electrolytic processes related with tantalum and niobium and other rare refractoiy metals seems to hold a promise for future industrial use, and is currently of great concern to researchers. The electrochemical behavior of tantalum, niobium and titanium in low-temperature carbamide-hilide melts has been investigated by Tumanova et al. [572], Electrodeposition of tantalum and niobium from room/ambient temperature chloroaluminate molten systems has been studied by Cheek et al. [573],... [Pg.326]

The temperatures shown are those recorded at the si of the tubes, supports and refractoiy. [Pg.144]

In the case of the CaO-MgO phase diagram shown in Figure 16.41, the MgO refractoiy phase will dissolve in tiie near eutectic liquid. Upon... [Pg.854]

Because of the high operating temperatures, the unit must be constructed of metals capable of withstanding this condition. Combustion devices are usually constructed with an outer steel shell that is lined with refractory material. Refractoiy-wall thickness is usually in the... [Pg.1946]

Tunnel Dryers In tunnel equipment, the solids are usually heated by direct contact with hot gases. In high-temperature operations, radiation from walls and refractoiy lining may be significant also. The air in a direct heat unit may be heated directly or indirectly by combustion or, at temperature below 475 K, by finned steam coils. [Pg.1384]

Figure 9. Plot of apparent temperature recorded between a mineral with slow oxygen diffusion (pyroxene) and a mineral with fast diffusion (plagioclase) vs. the modal percentage of plagioclase in a bi-mineral rock. Cooling is at 5°C/m.y. after peak equilibration at 750°C. In feldspar dominated rocks, Ta may preserve peak temperature, but for a rock dominated by pyroxene, Ta can be hundreds of degrees below peak T approaching 250°C, Tc(plag). The mode effect is modeled by the Fast Grain Boundary diffusion model and predicts that refractoiy accessory mineral (RAM) thermometers are most rehable (from Eiler et al. 1993). Figure 9. Plot of apparent temperature recorded between a mineral with slow oxygen diffusion (pyroxene) and a mineral with fast diffusion (plagioclase) vs. the modal percentage of plagioclase in a bi-mineral rock. Cooling is at 5°C/m.y. after peak equilibration at 750°C. In feldspar dominated rocks, Ta may preserve peak temperature, but for a rock dominated by pyroxene, Ta can be hundreds of degrees below peak T approaching 250°C, Tc(plag). The mode effect is modeled by the Fast Grain Boundary diffusion model and predicts that refractoiy accessory mineral (RAM) thermometers are most rehable (from Eiler et al. 1993).

See other pages where Refractoiy is mentioned: [Pg.570]    [Pg.576]    [Pg.577]    [Pg.577]    [Pg.582]    [Pg.1060]    [Pg.1563]    [Pg.1563]    [Pg.2210]    [Pg.2400]    [Pg.2400]    [Pg.83]    [Pg.369]    [Pg.36]    [Pg.104]    [Pg.146]    [Pg.101]    [Pg.430]    [Pg.2712]    [Pg.408]    [Pg.90]    [Pg.102]    [Pg.179]    [Pg.59]   
See also in sourсe #XX -- [ Pg.2 , Pg.9 , Pg.158 ]




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