Protection of refractories (review)

Abstract

UDC 666,76~ ~Under conditions where metallurgical and other heat processes are intensified, the high quality of the refractories is one of the main factors which provided a satisfactory life of the lining. However, it is not possible to achieve highly resistant heat assemblies only by a single improvement in the quality of the refractories. Measures must be devised and taken to protect the refractories, and this can be done in several ways: cooling the refractory lining, including the total replacement of the lining by water screening; restoring the eroded layer of refractories by guniting, plastering, coating, etc.; reducing the agressive nature of the corroding agents; normalizing the temperature and gas regimes for operating the refractory lining; and improving the design of the lining units and the lining as a whole in order to lower the thermomechanical stresses and to weaken the effect of other destructive factors.Cooling the Lining. The greatest success has been achieved in cooling blast furnaces. For further intensification of the cooling it is necessary [i] to increase the thermal conductivity of the special compensation mass tamped between the plates of the coolers and the refractory lining and to improve the fiber thermal insulation and compensation interlayer between the coolers and the furnace housing.Cooling the refractory linings of steel-smelting furnaces has a layered or gradient character, depending on the intensity [2]~ In a number of papers and patent applications [3,4] it is shown that water cooling of a shell type is highly effective also in the lining of steel-smelting arc furnaces, including very powerful furnaces. The increase in the consumption of electricity associated with intense cooling is compensated by the reduction in the costs of electrical power in associated branches of industry (the refractory industry and transportation). Water-cooled screens of an original design have been proposed which can be used in various heat assemblies for the prevention of local wear of the linings. In the power industry, the refractory lining of the firebox of steam boilers has been replaced by water screens which make it possible to eliminate, virtually completely, any damage to the firebox of boiler installations.Systems involving aerodynamic protection of refractories (blowing round), e.g., in ferrous-metal furnaces, have been developed and tested with excellent results [5]. It would be reasonable to test this method in relation to converters, steel-casting ladles, and other ferrous-metallurgy assemblies.Guniting a Refractory Lining. In spite of the obvious effectiveness, this is still not obligatory during the operation of all heat assemblies. The theory and process of guniting are now fairly well advanced, thanks to the work at the All-Union Institute of Refractories, the Ukrainian Scientific-Research Institute of Refractories, the Eastern Institute of Refractories, and other institutes~ The use of refractory protective coatings makes it possible in many cases to sharply increase the resistance...