Study on the Physicochemical Properties of Burnt Dolomite for the Steelmaking

对日本6个地区生产的白云石的几种性质进行了研究。另外还进行了白云石烧成后的水化活性与熔渣助熔性之间的关系研究。烧成白云石的反应过程：烧成白云石的反应过程可分为水化和熔融两个阶段。一种是破碎阶段，烧成的白云石由于宏观裂隙而破碎成小颗粒悬浮在搅拌水或矿渣中。另一种是溶解阶段，由于化学反应，CaO和MgO从每个颗粒表面溶解。焙烧白云石的活性由宏观比表面积和微观比表面积决定。这是制动阶段产生的每个颗粒的表面积，这是由于在焙烧过程中形成的微小颗粒之间的间隙造成的。水化反应活性：在较低的焙烧温度下，焙烧白云石的水化反应活性受生态颗粒大小的影响。即使在较低的温度下，粗大的颗粒也会促进大量宏观裂纹的形成，从而保持较高的水化反应活性。另一方面，随着焙烧温度的升高，细粒白云石的水化活性增加，宏观裂缝增多。然而，在较高的焙烧温度下，由于再结晶导致的微观比表面积减小，导致水化反应活性降低，而与颗粒大小无关。助熔性：随着焙烧温度的升高，助熔性变小。但是，这种助熔剂性能的降低不如水化反应活性显著。这是因为所用的酸性渣，包括大量的FeO，对焙烧白云石的侵蚀能力很大，所以在较高的焙烧温度下，助熔剂的性能不会下降太多。

Several properties of dolomites, produced from six areas in Japan, were investigated. Additional experiments were carried out to study the relationship between hydration reactivity of burnt dolomites and fluxing property to molten slag.1. Reaction process of burnt dolomite: The reaction process of burnt dolomites can be divided into two stages in both hydration and fluxing. One is breaking stage in which the burnt dolomite breaks into small particles to be suspended in agitated water or slag due to macro crack. Another is dissolution stage in which CaO and MgO are dissolved from the surface of each particle due to chemical reactions. The reactivity of burnt dolomites is determined by macroscopic surface area and microscopic surface area. That is the area of surface of each particle produced in braking stage and this is due to clearance among micro grains formed in calcination.2. Hydration reactivity: In lower calcination temperature, hydration reactivity of burnt dolomite is affected by the grain size at raw state. Large grain promotes the formation of so many macro cracks even at lower temperature as to kept the hydration reactivity high. On the other hand, hydration reactivity of burnt dolomite with small grain size becomes higher according to formation of more macro cracks at higher calcination temperature. At much higher calcination temperature, however, decrease of microscopic surface area due to recrystallization leads the reduction of hydration reactivity regardless of the grain size.3. Fluxing property: Fluxing property becomes smaller with increase of calcination temperature. But, this reduction in fluxing property is not so remarkable as that in hydration reactivity. The reason is that the erosion ability of employed acid slag, including a plenty of FeO, to burnt dolomite is large, so fluxing property does not fall down so much at high calcination temperature.