GB847840A - Process of manufacturing coke - Google Patents

Abstract

Coke, which is suitable for the production of graphite electrodes, and which, when crushed to a fine size, shows a needle-like structure, is produced by removing from a high boiling liquefiable coal-derived bitumen the components which readily form an insoluble phase upon heating, coking the remaining residuum at a temperature between 400 DEG C. and 500 DEG C. under conditions substantially free from temperature gradients until the material solidifies and heating the resulting solid material at a temperature between 500 DEG C. and 600 DEG C. to complete the coking. Suitable coal-derived bitumens are coal gasification tars, coke oven tars, water gas tars and pitches derived therefrom. The insoluble phase may be removed by several methods. In one method, a charging stock of coal tar which contains up to 25% of matter substantially insoluble therein is heated to a temperature below 400 DEG C. and filtered at between 150 DEG and 250 DEG C. In another method a coal tar is flash distilled at atmospheric or sub-atmospheric pressure. In another embodiment bitumen is preheated in a pipe coil to a temperature of 400 DEG -600 DEG C., and then continuously passed to a flash distillation zone from which vapours are taken overhead and coked to form the needle-like coke. In another form the pitch or similar material has added thereto a solvent such as a paint thinner, to reduce its viscosity and the material is subsequently filtered. According to another method the bitumen with or without a solvent is treated to a centrifugation operation followed by recovery and coking of the comparatively solid-free fraction. The needle-like coke when calcined may be mixed with a binder such as electrode pitch and with coke flour produced from needle-like coke or from commercially produced petroleum coke and extruded or moulded into the desired configuration, the electrodes so produced being baked at a temperature up to 1200 DEG C. The baked pieces may be subsequently graphitised at temperatures between 2500 DEG C. and 3000 DEG C.