Thermodynamic Calculation of the Behaviour of Coke at High Temperatures

Abstract

The main purpose of this paper was to analyze the behavior of coke in the blast furnace. The analysis of changes in chemical composition of coke due to impact of inert gas and air at different temperatures was made. By applying the FactSage three groups of substances can be distinguished. The chemical composition of blast furnace coke and the results of calculations of changes of chemical composition of coke heat treated under certain conditions were compared. The structural studies of these materials were presented. The results of the analysis of ash produced from one of Polish cokes was taken for consideration. This is not the average composition of Polish coke ashes, nevertheless it is representative of most commonly occurring chemical compositions.Keywords: coke, ash in coke, thermochemical calculations 1 Introduction Coke contains approx. 1% of volatile substances and approx. 10% of mineral substances. So, it is legitimate to claim that the liberation of these volatile substances and a slight evaporation of the mineral compounds will occur under the blast-furnace conditions [1 -10]. As a fuel and an iron oxide reducer, coke performs also the function of a framework supporting the charge. However, in the lower part of the blast furnace shaft, the mechanical properties of the coke worsen. The change of these properties is affected by factors, such as [11][12][13][14][15][16]: 1) gasification reactions; 2) thermal factors; 3) blast-furnace blast. These factors contribute to the formation of coke dust that densifies the primary slag thus making its flowing down difficult and also reducing the charge permeability. The thermal interactions reduce the strength of the coke due to the change in internal stresses in the structure. This is also associated with the presence of mineralogical and organic inclusions in coals subjected to coking. The thermal conductivity of the coke increases as its volatile matter contents decreases. As the volatile substances are released from the coke, a loss and a shrinkage of the solid part result, which leads to a reduction in strength [17].