Dolomite stabilized refractory

Stability. Both quicklime and calcined dolomite are refractory substances, as evidenced by their high melting points. They react with water in both the liquid and vapour state (see below). Many reactions apparently involving quicklime and calcined dolomite proceed via the hydrated products. Such reactions are described in section 19.2, but see also the reactions with carbon dioxide below. 

There is another product known as stabilized refractory dolomite. It is manufactured by a process similar to that of Portland clinker. Dolomite and serpentine, with small amounts of... 

Phase Diagram Calcium silicates are the most important constituents of hydraulic Portland cements (see Chapter 5), as well as of basic and acidic blast furnace slags and stabilized refractories based on dolomite they also occur as devitrification products of some technical CNS (calcium sodium silicate) glasses. The phase diagram is complicated, as shown in Figure 3.24. 

Dead-burned dolomite is a specially sintered or double-burned form of dolomitic quicklime which is further stabilized by the addition of iron oxides. Historically, it was used as a refractory for lining steel furnaces, particularly open hearths, but as of this writing is used primarily in making dolomite refractory brick (see Refractories). 

PefractoTy lime is synonymous with dead-burned dolomite, an unreactive dolomitic quicklime, stabilized with iron oxides, that is used primarily for lining refractories of steel furnaces, particularly open hearths. 

For the manufacture of stabilized dolomite clinker, the raw material is mixed with a silicate material, e.g. serpentine 3 MgO. 2 Si02.2 H2O. The mix composition may be chosen so as to bind — at the firing temperature — the CaO to tricalcium silicate exhibiting hydraulic binding properties. Nowadays, refractories of this type are rarely manufactured. 

They are normally cast in the form of brick and are sometimes bonded to assure stability. The outstanding property of these materials is their ability to act as insulators. The most important are fireclay (aluminum silicates), silica, high alumina (70-80% ALjOj), mullite (clay-sand), magnesite (chiefly MgO), dolomite (CaO-MgO), forsterite (MgO-sand), carbon, chrome ore-magnesite, zirconia, and silicon carbide. (2) Characterizing the ability to withstand extremely high temperature, e.g., tungsten and tantalum are refractory metals, clay is a refractory earth, ceramics are refractory mixtures. 

Dead-burned basic refractory material, e.g. stabilized dolomite clinker. 

Figure 4.9 Areas of stability, and eutectic and peritectic temperatures, respectively, of calcium silicate and calcium magnesium silicate associations, depending on the Ca0/Si02 ratio of the raw materials used as precursor for magnesia and dolomite refractories.

As for all basic bricks, refractoriness of dolomite is also very high—above 1750°C. The RUL is 1450°C to 1550°C for stabilized dolomite and 1350°C to 1450°C for semi-stable dolomite. The spalling resistance of stabilized dolomite is poor, but the resistance of semi-stable dolomite is moderately good. Semi-stable dolomite can withstand 20 cycles. Slag resistance is poor for both the types of dolomite. In order to increase this resistance, dolomite is doped with magnesia, which combines with silica to form forsterite. Forsterite has better resistance to slag. Semi-stable dolomite has better resistance than stabilized dolomite. 

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