One method of improving the quality of magnesite and dolomite metallurgical powders is preservationby oiling.

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One of the most important causes of the low life of periclase chromite linings in the sintering zone of rotary kilns used to fire Portland cement clinker is the increase in their diameter.Thus, an increase in furnace diameter from3.2-4m to 5.6-6.4 m when all other conditions were the same led to a reduction in the service life by a factor of 2-3 and accordingly to a sharp reduction in the efficiency factor of the furnace, a rise in the specific consumption of refractories, and a fall in the output of Portland cement clinker.It became necessary to develop a technology for producing new types of magnesia refractories which will ensure at least a doubling of the furnace life for large-diameter furnaces.The linings of large-diameter furnaces abroad [i] are being effectively made from dolomite tarred refractories with a ceramic bond.It is noted that these refractories are clinker resistant and have outstanding physical and ceramic properties.High-purity dolomites are used to make dolomite refractories that are ceramically bonded. The large stocks of dolomites in our country with low contents of mineral impurities, meeting the requirements of raw materials for the production of dolomite refractories, make their output highly promising and desirable.The organization of the manufacture of such goods will also lead to a considerable reduction (by 100,000-200,000 tons) in the consumption of periclase powder and the exclusion of ineffective utilization of large amounts of chromite ores.The use of dolomite tarred refractories with a ceramic bond is also prospective for steel-melting production.For the development of the main technical parameters of dolomite tarred ceramic bonded refractories we selected five samples from dolomites taken from 83 deposits: Kvarkensk, Bosninsk, Lis'egorsk, Kuzinsk, and Tkvarchel'sk. These dolomites have a low (not more than 2%) concentration of impurity oxides (Table i); their deposits are situated in regions not far from the main centers of the cement and metallurgical industries and close to iron ores. As a result of petrographic analysis it was found that the samples investigated consist of dolomite with inclusions of calcite. The sizes of the crystals, the open porosity and the mass proportion of calcite are shown in Table 2.

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