MgO在熟料中的形态演化、作用机制及熟料的性能优化研究

Cement industry in China is now facing a serious shortage of high-quality limestone mining resources. A large number of low-grade high-magnesium limestone is becoming raw materials for cement production. Thus, it is urgent to control the behavior of MgO in clinker to improve the stability of the manufacturing process and the performance of clinker with high MgO content. However, the rules of MgO behavior and the mechanism are still not clear due to the complexity of the structure of clinker and the diversity of the existing forms and roles of MgO in clinker. Based on our previous work, this project will begin with studying the form evolution of MgO in clinker for different kinds of magnesium compound from the raw material. Secondly, the relationship between liquid, ferrite phase and MgO will be studied, and the formation process of periclase will be investigated and thoroughly discussed. Thirdly, the combined influence of MgO with various minor elements (such as F, S, P and so on) on clinker will be studied. Finally, by taking into account of changes in the clinker mineral composition, alite crystal forms, periclase and clinker grindability as a whole, the effects of MgO on the hydration property of clinker will be evaluated. The role and mechanism of MgO in clinker will be stated. Attempts will be made to regulate the existing form and behavior of MgO in clinker to optimize the performance of high magnesium Portland cement clinker. The results will provide technical support for the use of low grade high-magnesium limestone and the production of low calcium Portland cement clinker with high magnesium. In addition, it will greatly enrich and develop the basic theory of cement clinker chemistry, which has important theoretical and practical values.

随着优质石灰石矿山资源的日益短缺，大量高镁的低品位石灰石正在成为水泥企业不得不使用的原材料，亟需解决MgO引发的熟料生产不稳定和性能裂化的难题。控制和优化熟料中MgO的作用行为是解决问题的根本和关键所在。但熟料的组成结构极其复杂，且熟料中MgO的存在形态及作用方式多样，MgO的作用规律和机制至今尚不明确。因此，申请人基于前期工作，从研究不同镁质矿物中MgO在熟料中的形态演化过程入手，深入研究液相、铁相与MgO的相互影响关系，以及高温形成和冷却析晶形成方镁石的时空作用关系，探讨MgO与微量元素的复合作用规律和机制，从熟料烧成、阿利特晶型、方镁石以及熟料易磨性等多个层次和方面，阐明熟料中MgO的作用规律和机制，探索控制和优化熟料性能的方法，为安全使用低品位高镁石灰石和高镁低钙熟料的生产等提供技术支撑。此外，项目成果还将极大地丰富和发展水泥熟料化学的基础理论，具有重要的理论价值和实际意义。

随着水泥工业的发展，低品位高镁石灰石及各类含镁富钙固废被越来越多的用作水泥生产原料。开展氧化镁（MgO）在熟料中的作用行为及可控性的研究，既是形势所迫，也是发展趋势。项目采用化学试剂和工业原料相结合，由三元液相体系到复杂四元熟料体系，探究了不同形式及不同含量镁质矿物在熟料中的形态演化规律及对熟料烧成的影响，揭示了液相（高钙、低钙）、铁相/铝率IM与MgO在熟料中形态演化的相互影响关系及机制，阐明了IM和冷却方式耦合对MgO形态演化及冷却析晶的作用机理，探明了MgO影响熟料性能的关键和本质，提出了运用高镁石灰石、钢渣等高镁含量、非传统原料优化高镁水泥熟料烧成和性能的方法。结果表明，不同形式的镁源矿物中MgO化合、固溶与结晶等形态演化过程基本相同。MgO掺入使硅酸三钙（C3S）和铁铝酸四钙（C4AF）含量增多，硅酸二钙（C2S）和铝酸三钙（C3A）含量相对降低。但Mg(OH)2更利于铁酸盐形成，MgSiO3显著提高C3S含量。IM为1.1时，熟料中MgO固溶量最高，方镁石含量最低。IM减少有利于改善熟料易烧性并促进C3S形成；IM增大，可使方镁石由四边形和六边形转变为细小圆粒状。提高冷却速率也有利于增大MgO固溶量，降低方镁石含量，同时促进方镁石向细小的圆粒状发展。反之，MgO通过影响熟料矿物组成和C3S晶型直接影响熟料强度。MgO掺入促使C3S晶型由M1转变为低活性的M3晶型。在低IM慢冷和高IM淬冷的熟料中，C3S含量均相对较高。当MgO在熟料中达到固溶置换极限（约2%）时，C3S含量及晶型不再变化，各熟料矿物总含量相对减少，熟料强度随MgO掺量而呈显著降低趋势。工业生产应用含镁原料时，应考虑MgO修正石灰饱和系数。项目成果丰富水泥熟料化学理论的同时，为低品位高镁石灰石、高镁工业固废等原料在水泥工业的高效利用提供了理论与技术支撑。