Basic refractory

In the class of basic refractories are included bricks manufactured from chrome ore [(MgFe)(AlCr)204], periclase (MgO), calcined dolomite (CaO, MgO), olivine [(MgFe)2SiOJ, and mixtures of these materials. 

When more than a small amount of magnesite is added, we enter a range of chrome ore-periclase compositions in which there are usually large grains of chromite in a matrix of fine MgO, MgFe204, and Mg2Si04. 

Precipitation of MgFe204 from MgO in basic refractory brick as (a) platelets parallel to (100) planes in MgO (500x) (b) dendritic precipitate (lOOOx) (c) spheroidal morphology (250x). 

A minor class of basic brick is manufactured from olivine (MgFe)2Si04. The major phase present is forsterite. 

Dolomite (MgCOg CaCOg) is a raw material of high refractoriness, low cost, and wide availability. Calcined dolomite consists of a mixture of CaO and MgO solid solutions plus a minor amoimt of silicate phase. 

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Basic refractory materials include lime, magnesia, various materials composed chiefly of alumina (bauxite, diaspore, laterite, gibb-site, etc.), dolomite and most of the rarer refractory oxides, particularly zirconia. 

J. R. Rait, Basic Refractories, Their Chemisty and TheirPeformance, Ilife Sons, Ltd., London, 1950. 

Acid refractories Basic refractories Neutral refractories Rarer... 

Alundum. A pure crystalline AlaOj in granular form, d 3.9-4.0, mp 2030-2050°, hardness on the Mohs scale 9- It has been used as an abrasive, a basic refractory material, as a component of low-expansion glasses, as a filtering material and for chemical apparatus. It is probably suitable as a component of primer compns in lieu of glass, etc... 

Moore, B., Frith, M. and Evans, D., Developments in basic refractories for cement kilns , World Cement, 1991 5-12. 

Sato, A., Tsuchiya, I., Takahashi, H., Ishii, T., Takebayashi, K. and Kawakami, T., Effect of thermal shock on the structural changes of the basic refractories for cement rotary kiln , Taikabutsu Overseas, 1986 8(1) 37-9. 

In contrast to the basic refractory services provided by their predecessors, today s gunited or cast liners are much more dependent upon the ability of the applied material to resist possible chemical attack. Additionally, the fact that the cementitious materials utilized in these applications are somewhat absorptive and brittle causes another type of concern which should also be considered when they are specified for "wet" chimneys. (Figure 48-8 illustrates a gunned lining placed over a membrane as a lining of a concrete shell. This same design may be followed in application to a steel liner.)... 

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 term basic refractories is used for materials with a high MgO and CaO content they include magnesite, chrome-magnesite, magnesite-chrome and dolomite refractories as the main types. 

Kainarskh j. S. and Dektyareva E. V., Basic Refractories (in Russian), MeialKirghia, Moscow, 1974... 

Staron 3., Body Composition and Processing of Magnesite and Other Basic Refractories, Paper presented at the In-Plant Training Workshop, UNIDO, Pilsen, 1974. 

This schematic representation is of course simplified, rather like the suggested classification of magnesite and other basic refractories published by Biggar and Weymouth (1976) on the basis of phase composition in the system MgO — CaO —.4I2O3—Si02- The latter authors distinguish the following materials ... 

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