配加生石灰的两段式圆筒铁矿制粒行为研究

Study of iron ore granulation behaviors in two-stage drum granulation process with the addition of quicklime

针对铁矿烧结厂普遍采用的两段式圆筒制粒工艺,在配加生石灰强化制粒和原料适宜的制粒水分范围内研究其制粒过程中制粒颗粒的粒度组成、黏附粉黏附率、成分均匀性、显微结构变化以及原始颗粒的制粒行为。研究结果表明:生石灰在二混阶段前消化程度小于6.53%,其主要是在二混阶段起到强化制粒作用。当制粒水分(质量分数)从6.92%增加到7.53%,二混阶段后粒径>3 mm粒级占比和黏附粉的高强度黏附率(Arb)分别提高了22.80%和10.55%,制粒颗粒各粒级间的w(CaO)/w(SiO_(2))标准差下降了10.32%。在制粒过程中,粒径≤0.25 mm颗粒和>1 mm颗粒作为核颗粒的分配系数变化范围分别为0~0.20和0.93~1.00,基本是分别作为黏附粉和核颗粒存在,(0.25,0.50]mm颗粒和(0.5,1.0]mm颗粒的分配系数变化范围分别为0~0.83和0.68~0.98,是制粒的中间粒子。制粒颗粒的长大机理可分为2个阶段,二混阶段之前遵循成层长大机理,二混阶段则同时遵循成层和聚合长大机理。

For the two-stage drum granulation process commonly used in iron ore sintering plants,the size distribution of granules,adhesion rate of adhesive fines,composition uniformity,microstructural change,and granulation behavior of primitive particles in the granulation process strengthened by quicklime addition were studied within a suitable range of granulation moisture content.The results show that as the hydration ratio of quicklime before secondary mixing is less than 6.53%,quicklime mainly strengthens granulation in the secondary mixing stage.When the granulation moisture content increases from 6.92%to 7.53%,the content of>3 mm granules and the high strength adhesion rate(Arb)of adhesive fines increase by 22.80%and 10.55%,respectively.Additionally,the standard deviation of w(CaO)/w(SiO_(2))among granule size fractions decreases by 10.32%.In the granulation process,≤0.25 mm primitive particles and>1 mm primitive particles have partition coefficients in the ranges 0−0.20 and 0.93−1.00,respectively,and basically serve as adhesive fines and core particles,respectively.The(0.25,0.50]mm primitive particles and(0.5,1.0]mm primitive particles have partition coefficients in the ranges 0−0.83 and 0.68−0.98,respectively,and act as intermediate particles.The growth of granules can be divided into two stages and follows the layer-by-layer growth mechanism before secondary mixing and the layer by-layer and agglomeration growth mechanisms simultaneously in the secondary mixing stage.