Development of Rapid Curing Process of Reactive Coke Agglomerate

Abstract

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.

Reaction Behaviors of Various Agglomerates in Reducing the Temperature of the Thermal Reserve Zone of the Blast Furnace

“…Both the rate of carbon consumption (RCC) and carbon consumption ratio (CCR) were evaluated using Eqs. (5) and (6). In addition, reduction degree was similarly evaluated using Eq.…”

“…The RCC during the tests was evaluated using Eq. (5). The CCR of the agglomerates was evaluated using Eq.…”

“…2) FeO CO Fe CO Although the high reactivity of CA was known, 3) we previously observed an excellent potential of reinforced CAs with high carbon content toward reducing the RAR, 4) and accordingly, we commercialized the aforementioned CAs as reactive coke agglomerate (RCA). 5) The second type of agglomerate is Ferro-coke, which has a structure with homogeneously distributed fine metallic iron in a coke matrix. It also has high carbon reactivity 6,7) because of the redox cycle between the direct reduction of iron oxide (Eq.…”

Morphology Change and Carburization Characteristic of Iron Ore-Coal Composite During Reduction under a Simulated Condition of Blast Furnace

“…That procedure included 12 hours of primary curing, 5 hours of stream curing at 80°C and 1 hour of drying. 21) On the other hands, Kasai et al demonstrated that the hot briquette procedure without adding any binder also can enhance the strength of green composite. 4,5) However, comparing to the method of pan palletizer to produce the agglomerate, hot briquette procedure seems not only increasing the cost but also decreasing the production rate in the perspective of industrial production.…”

Design for Carbon Core Pellet toward Co-production with Sinter

“…For example, a metal that exhibits a catalytic effect is dispersed in the carbonaceous material to lower the starting temperature of the solution-loss reaction, [2][3][4][5][6][7][8][9][10][11][12][13][14][15] or the carbonaceous material is dispersed or included in the ore agglomerate to accelerate the reduction and gasification reactions. [16][17][18][19][20] These reduce the temperature of the heat reserve zone, which limits the reduction efficiency in the blast furnace, and increase the CO gas utilization rate, so further reduction of the reducing agent ratio is expected. 21,22) In recent years, there are also concerns about an increase in the slag ratio of sinter and the phosphorus concentration in hot metal due to the depletion of high-grade iron deposits.…”