The selection of refractories for any particular application is made with a view to achieve the best performance of the equipment furnace, kiln or boiler and depends on their properties. Further, the choice of a refractory material for a given application will be determined by the type of furnace or heating unit and the prevailing conditions e.g. the gaseous atmosphere, the presence of slags, the type of metal charge etc. It is, therefore, clear that temperature is by no means the only criterion for selection of refractories.
Any furnace designer or industry should have a clear idea about the service conditions which the refractory is required to face. The furnace manufacturers or users have to consider the following points, before selecting a refractory.
i) Area of application.
ii) Working temperatures.
iii) Extent of abrasion and impact.
iv) Structural load of the furnace.
v) Stress due to temperature gradient in the structures and temperature fluctuations.
vi) Chemical compatibility to the furnace environment.
vii) Heat transfer and fuel conservation
viii) Cost considerations.
It is therefore, essential to have an objective evaluation of the above conditions. A proper assessment of the desired properties would provide guidelines for selection of the proper refractory materials.
It would be important to mention here that the furnace manufacturer or a user is also concerned with the conservation of energy. Fuel can be saved in two ways: either by insulation or by faster working. Both these methods give low energy cost per tonne of product.
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