Carbon blocks used for blast furnace hearth lining...

Carbon blocks used for blast furnace hearth lining  One of the largest users of refractory materials in a blast furnace (BF) is the BF hearth. This region of the BF exhibits more varied designs, conflicting practices and vastly different performance histories of the hearth lining.  The traditional materials used in hearth construction have been carbonaceous in nature. Various grades of amorphous and hot pressed carbon conventionally baked and hot pressed semi-graphite, semi-graphitized carbon and fully graphitized materials, are the basic refractories used in any modern BF hearth refractory lining design. However, the nomenclature of these materials must first be clarified, because they represent an entire family of materials with varying compositions, processing and resulting properties. The words, carbon and graphite, are often used interchangeably, but the two are not synonymous. The following briefly describes the major differences and characteristics of the carbonaceous materials used as refractories in the blast furnace. Carbon refractories – Carbon, formed carbon, manufactured carbon, amorphous carbon and baked carbon are the terms which refer to those refractories that result from the process of mixing carbonaceous filler materials such as calcined anthracite coal, petroleum coke or carbon black with binder materials such as coal tar or petroleum pitch. These mixtures are formed by moulding or extrusion, and the formed pieces conventionally baked in furnaces at temperatures between 800 deg C to 1400 deg C to carbonize the binder. The resulting product contains carbon particles with a carbon binder. Typically, conventionally baked carbon is manufactured in relatively large blocks. As the binders carbonize and the liquids volatilize, they escape through the block, resulting in porosity. This porosity results in a permeable material that can absorb elements from the BF environment such as alkalis. These contaminants use the same passages for entering the...