25 - Carbon

Abstract

This chapter discusses preparation and various uses of carbon. Carbon bricks are made from coke or petroleum coke, crushed, size-graded, and bonded with tar or pitch. The mixture is molded or extruded and fired at about 1000°C to make the grade called carbon, or up to 2500°C in a resistance furnace to produce graphite. These materials are stronger than natural graphite and more readily produced in the shapes and sizes required by industry. These bricks have excellent hot strength and, with a high thermal conductivity, good resistance to thermal spalling. Both carbon and graphite are used as electrodes in arc furnaces particularly, but also in electrolysis plant such as that producing aluminum. Graphite is preferred where a high current density is involved for its lower electrical resistivity, but it is considerably more costly. The main application of carbon bricks or blocks is in iron blast furnaces. On smaller scale work, graphite has many applications in laboratories and in industry. It has a wide range of potential uses in rocket engines, heat transfer systems, and as a moderator in some atomic piles, where high purity is demanded.