Interaction between molten coal ash and coke in raceway of blast furnace

In the raceway of a blast furnace, part of the mineral matter in coal melts and/or vaporizes since high-temperature air exceeding 1273 K is supplied with coal. Under this condition, molten coal ash deposits on the coke surface in the region of relatively low temperature. When the molten coal ash deposits on coke lumps, they may agglomerate through the binding agency of the molten ash, while if the molten coal ash reacts with the coke lumps, its strength may be degraded, thus leading to fine coke production. As these phenomena could affect blast furnace operation, it is necessary to study the interaction between molten coal ash and coke, as well as the effect of molten coal ash on coke reaction and/or degradation. In this study, a horizontal pulverized coal reactor with a precombustor was used to simulate the pulverized coal injection technology. A cubic coke lump was inserted in the reactor. In order to discuss the interaction precisely, liquefied petroleum gas was also introduced as a fuel, instead of coal. Reaction behavior, surface temperature, and changes in coke mass were measured quantitatively and visually. Furthermore, thereacted coke was inserted into an I-type tumbler for a degradation test. The results obtained show that coal ash with a high melting temperature tends to deposit on the coke surface easily. Therefore, the coke reaction rate is decelerated since the reaction surface of the coke is covered with molten ash. In contrast, coal ash with a low melting temperature tends to fall down on the coke surface with the coke molten ash due to its low viscosity. In this case, the coke reaction rate increases a little bit. The presence of molten coal ash with high iron content may affect the internal structure of coke.