Pore structure development during coal carbonization. 1. Behaviour of single coals

Abstract

The object of this work was to obtain a preliminary indication of the principal factors influencing the development of the porous structure of coke during the carbonization of coal. Eleven coals representing a wide range of rank were carbonized at 3 K/min in a small oven heated from one side wall until the temperatures at the extreme ends of the charge were 300 °C and 1100 °C. A central horizontal section covering the temperature range 300–650 °C was then prepared for microscopic examination, quantitative data being obtained along isothermal traverses parallel to the hot wall. The carbonization of those coals producing a fused structure was characterized, within the temperature range of plasticity, by a highly porous zone the structure of which was related broadly to the dilatation of the coal as measured in the Ruhr dilatometer. Before the matrix resolidified, a compaction of the structure, explicable in terms of the interconnection of previously closed pores with the open pore structure of the semi-coke, took place. Thereafter little significant change occurred up to the highest temperature considered. Since the pore structure of the semi-coke was influenced by the degree of compaction which could not be inferred from available tests of the coking properties of coals, such tests provide little guidance as to the structure of the resultant coke.