The manufacture of artefacts from coal

• Published in: Fuel (Guildford) 1981-01, Vol.60 (9), p.889-896
• Main Authors: Beech, Roy Nicholson, Price, Michael Stuart Thomas
• Format: Article
• Language: English
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/0016-2361(81)90154-X

A process is described in which a raw coking coal (NCB Type 301) is converted directly into structural carbon of high value. The origins of the process are traced to research at BCURA and in Powell Duffryn companies in the 1940s. For a raw-coal-based artefact there is a critical heating rate when the coal is plastic. Above this critical value the pyrolysis gases are unable to escape sufficiently rapidly and internal rupture takes place. A higher critical rate can be achieved by modification of the pyrolysis reactions with an oxidizing agent or by physical dilution with inert materials such as coke or graphite. Investigations have been concerned principally with coal/coke and coal/graphite mixtures. The nature of a coal from a particular seam may vary as the coal face moves. It is shown how, for a coal-based artefact made with a physical diluent, changes in quality can be accommodated, to a practical extent, by adjustment of the coal/diluent ratio. In addition, it is suggested that to achieve homogeneity fine grinding is essential. Direct manufacture of artefacts using an untreated coal tends to promote interference with the development of anisotropy in the coal-carbon and leads to reduced crystal growth during graphitization. The product is, therefore, not suitable for the major high tonnage applications of graphite. Nevertheless, the direct process is relatively simple and the special properties of carbons and graphites made in this way are their strength and hardness, which are a direct result of the restriction in the growth of anisotropy during pyrolysis as well as the general reduction in notch effects as a result of the fine texture.