Alumina refractories

WulffProcess. The regenerative technique is best exemplified by the Wulff process, Hcensed by Union Carbide Corp. The furnace consists basically of two masses of high purity alumina refractory tile having cylindrical channels for gas flow and separated by a central combustion space as shown in Figure 10. Its cychc operation has four distinct steps, each of approximately 1 min in duration, the sequence being pyrolysis and heat in one direction followed by pyrolysis and heat in the other direction. Continuity of output is achieved by paired installations. 

G. MacZura, "Production Processes, Properties, and Appbcafions for Tabular Alumina Refractory Aggregates," in L. D. Hart, ed.. Alumina Chemicals Science and Technology Handbook, The American Ceramic Society, Columbus, Ohio, 1990. 

High Alumina Refractories. The desired alumina content, from 100% to just above 45%, is obtained by adding bauxites, synthetic aluminosihcates, and synthetic aluminas to clay and other bonding agents. These refractories are used in kilns, ladles, and furnaces that operate at temperatures or under conditions for which fireclay refractories are not suited. Phosphate-bonded alumina bricks have exceptionally high strength at low to intermediate temperatures and are employed in aluminum furnaces. High alumina and mullite are used in furnace roofs and petrochemical apphcations. 

Aluminum chlorite, (Al,Fe)4(Si,Al)402Q(0H)g, in which a gibbsitelike interlayer proxies in part for the bmcitelike interlayer, is being discovered in increasing occurrences and abundance (11,141). Chloritelike stmctures have been synthesi2ed by precipitation of Mg and Al between montmorillonite sheets (143). Cookite [1302-92-7], an aluminous chlorite containing lithium, has been found in high alumina refractory clays and bauxite [1318-16-7] (139). 

Alumina refractory brick, physical properties of, 21 495t... 

Carbon-alumina refractories, 12 794 Carbon arcs, cerium application, 5 688 Carbonatation, in cane sugar refining, 23 452. See also Carbonation Carbonatation plant, in sugarcane processing, 23 450... 

High alumina brick, ASTM classifications and specifications for, 21 508 High alumina catalysts, 11 724 High alumina refractories, 21 515, 518 High analysis fertilizers, 11 123, 124 High aspect ratio micromachining... 

As mentioned earlier, fluid cracking catalyst are presently comprised of three principal ingredients, an amorphous silica-alumina refractory binder, a generally inert filler and the zeolite. 

The laboratory furnace, illustrated in Figure 1, has been described in detail elsewhere (19). The combustion chamber design is similar to that of Pershing and Wendt (20). It consists of a vertical cylinder 1.0 m long and 0.2 m inside diameter cast from alumina refractory cement. A series of convective heat exchangers, also 1.0 m long and 0.2 m inside diameter, are mounted directly below the combustor. The combustor is fired at a rate of 8 to 12 Kw, providing a residence time of 1 to 2 seconds in the combustion chamber. 

Reason number one The 90 percent alumina refractory was rated for 3000°F service. 

MgO-spinel clinker is obtained by the same procedure, but with a substantial proportion of free MgO (75-85%). MgO-spinel is produced by sintering at temperatures of 1600-1800°C and a dense product is obtained. MgO-spinel refractory has better high temperature mechanical properties in arc furnace roof application compared to magnesia-chrome refractories, but it has lower strength than a high-alumina refractory. 

Semler, C.E., Hawisher, T.H. and Bradt, R.C., Thermal shock of alumina refractories damage-resistance parameters and the ribbon test , Am. Ceram. Soc. Bull., 1981 60(7) 724-9. 

W.V. Ballard and D.E. Day, Stability of the refractory-bond phases in high alumina refractories in steam-CO atmospheres, Ceram. Bull., 57 [7] (1978) 660-666. 

Table 18-1 Approximate Pyrometric Cone Equivalent (PCE) Values of Generic Classes of Fireclay and High Alumina Refractory Brick...

The annual world production of refractories is about 25 million tons. About 60% of this is consumed in metallurgy, the rest in the glass and cement industries, etc. The following shares of the individual types were reported for the late sixties 70% fireclay and high-alumina refractories, 17% basic refractories, 8% silica refractories and 5% other products. 

The 90% alumina refractory showed a sharp drop in the amount of alpha-alumina present as the temperature was increased. The depletion of alpha-alumina does not occur unless excess soda is available and the temperature is above 2000°F, or unless the amount of SiOz present is not sufficient to tie up the soda as a sodium aluminum silicate. Finally, the free alumina existent in the lower silica-containing samples is depleted by the formation of beta-alumina and alkali aluminate. 

Fig. 18. Photograph of 90% alumina refractory before and after reaction with soda vapor at 1350°C/12 h.

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