||Określono wpływ obróbki termicznej na właściwości dwu rodzajów koksu, symulując ich zmiany zachodzące w wielkim piecu. Porównawczo przebadano koks pobrany z poziomu dysz wielkiego pieca. Przy temperaturze 1400°C wystąpiło minimum reakcyjności i maksimum CSR. Ubytek masy koksu po osiągnięciu poziomu dysz jest niewielki, dotyczy to również zmiany wytrzymałości i składu granulometrycznego. Na przewiewność wsadu wpływa głównie wielkość kawałków koksu i jego wytrzymałość mechaniczna; reakcyjność ma drugorzędne znaczenie.
||The paper discusses the effect of heat treatment on physical and chemical properties of blast furnace coke. Two kinds of coke were tested. The first one (coke no 1), produced in a coke plant utilising the gravity charging system and dry quenching of coke, was characterised by the following indices: CRI = 29,9 % and CSR = 60,2 %. The second one (coke no 2), produced in a plant utilising the stamping technology of coke oven charging and wet quenching of coke, was featured by the indices: CRI = 47,2 % and CSR = 40,8 %. Both kinds of coke were subjected to heat treatment under laboratory conditions. Additionally, for the sake of comparison, the coke taken from the tuyere zone of a blast furnace was also tested. Heat treatment of coke no 2 in the temperature of 1100°C caused significant changes of its quality when compared with the skip coke. Due to the heat treatment of coke no 1 and coke no 2 in the temperature of 1400°C, the CRI - index reached its minimal value while the CSR - index reached its maximal value. A further growth in the heat treatment temperature caused an increase in the value of CRI - index and a decrease in the value of CSR - index. Significant changes were also reported in the mass, true density and composition of both mineral and organic matter of coke. A comparison of the size of graphite crystallites in coke samples subjected to heat treatment under laboratory conditions and in the sample taken from a blast furnace made it possible to conclude that the temperature in the tuyere zone was equal to about 1650°C. At the next stage of examinations the samples of the skip coke, the coke after heat treatment and the coke taken out from a blast furnace were subjected to the drum strength tests. On the basis of those tests it was concluded that before reaching the tuyere zone of a blast furnace, the coke does not undergo significant changes as regards its mass, mechanical properties and the size of grains. As far as gas permeability of blast furnace is concerned, mechanical properties and the size of coke grains are important, whereas the role of coke reactivity is insignificant.