Development of Rapid Curing Process of Reactive Coke Agglomerate

We commercialized Reactive Coke Agglomerate (RCA), a cement-bonded pellet to decrease the thermal reserve zone temperature for the reduction of the reducing agent rate of blast furnaces. To achieve a high productivity of supplying RCA to large blast furnaces, a rapid curing process of RCA using steam was investigated. We obtained rapid curing of RCA within 18 h by combining primary curing for 12 h and stream curing at 80°C for 5 h subsequently with drying for 1 h. This combination provided sufficient strength to an RCA product when compared with the strength obtained after conventional yard curing, which requires a long curing time of 14 days. Plant trials revealed that a longer primary curing time was required because of the non-homogeneity of thermal conditions. Nevertheless, the curing period could be shortened by 12.5 days with drying and 9 days without drying. Mineralogy and morphology of hardened cement in RCA after rapid curing were investigated. XRD and thermal analysis revealed that the basic mineral composition of cement after rapid curing was comparable with that after conventional yard curing. In plant tests, during rapid curing, hydration and microstructural evolution of cement in RCA were accelerated by steam curing. RCA involving the steam curing process has been implemented in Oita works and it has been helping in a stable operation of two large blast furnaces under a low RAR.