(1) The course of formation of coke balls in a rotary retort (200mm∅×180mm) by low temperature carbonization with and without passing air stream, was observed. Samples examined were as follows: Miike coal-Tagawa senseki, Yubari coal-Sunagawa low temperatue coke, Yubari coal-Ashibetsu coal and Yubari coal-Sunagawa coal.
(2) When coal was carbonized without passing air stream, it was found that the charged coal which was heated to it's melting point, was changed wholly into mushy state and when it was held to a certain height, it failed down by it's weight along the retort wall. And when carbonization advanced and coal approached it's solidifing point, fluidity of coal decreased and coal paste was devided into several small pieces or was bended itself or such small piece was held by bended coal paste and then they started tambling in the rotary retort, some pieces of them adhered each other and formed a larger ball, which was solidified gradually.
When caking power of the charged coal was too high, the coke ball obtained had tendency to break into several pieces on cooling.
With the decrease of caking power (for example, as the caking coal was mixed with natural coke or coalite) the coke ball formed became smaller and the time of formation of coke balls was shortened.
(3) By passing air stream into a rotary retort, the time of formation of coke balls was shortened and as the flow rate of air increased, the coke balls formed became smaller.
Decrease of the size of the coke ball was observed by passing air stream in every period including not only the powder period, but also the plastic period and the coke ball forming period.
(4) Observation of the section of the coke ball revealed that the coke ball was made of several small soft coke pieces adhered each other or of a coke ball held with other soft coke.
(5) Analytical data of several portions of single coke ball gave the information that carbonization of coal substance proceeded rather evenly throughout the every portion of the coke ball formed.
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