高钙硅酸盐矿物中含硫/氯/碱金属物相的迁移态变与多相反应机理

Cycle and enrichment of hazardous volatile components (sulfur/chlorine/alkali metal) in rotary kiln and precalcination system is a unique phenomenon during NSP cement production process, however, as a result, the problem of coating and blocking is difficult to solve, especially under the condition of using the low-quality fuel and raw materials. It is embarrassed that the mechanism close behind the phenomena and problem has not been uncovered due to the incomplete results obtained from different angles. From the view point of whole process, this project will conduct systematic and comprehensive research, and the state transformation of sulfur, chlorine, alkali metal minerals in specific conditions as well as all aspects of coating formation will be analyzed. During the study, the evaporation of species related to sulfur, chlorine and alkali metals is to be investigated and chemical speciation of sulfur, chlorine and alkali metals in different products will be characterized quantitatively, in order to describe the interaction among the alkali metals, sulfur, chlorine and high-calcium silicate minerals, furthermore, the solid phase reaction pathways and the melting and bonding behavior of these complex components should be well explored. Based on the experiments mentioned above, the kinetic models of evaporation, solid-solid reaction and melting process are desirable to be built, at last, both the migration behavior of sulfur, chlorine, alkali metals and the evolution of coating process can be revealed, which are valuable and useful for seeking the effective measures to fight against the coating and blocking. Most of all, the research results can facilitate the reasonable utilization of low-quality fuel and raw materials in cement industry.

易挥发有害组分（硫/氯/碱金属）在窑炉内的循环富集是新型干法水泥生产过程中特有的现象，由此产生的窑尾及预分解系统结皮堵塞问题却难以解决，特别是燃料和原料低质化的现实必然使之加剧。已有的"盲人摸象"般的孤立研究行为对藏于现象与难题背后的机理认知显得力不从心。本项目从整体思维角度出发对此展开系统深入的研究，剖析含硫、氯、碱金属物相在特定工况下的态变行为以及结皮形成的各个环节，考察高钙硅酸盐矿物中含硫、氯及碱金属组分的挥发特性，定量表征硫、氯及碱金属元素在多态产物中的赋存形态，刻画碱金属、硫、氯及高钙硅酸盐矿物之间的相互作用，探讨和调查这些复杂组分之间的固相反应途径与熔融粘结行为，构建较为精确的描述挥发、固固反应和熔融过程的动力学模型，阐明硫、氯、碱金属的迁移演化规律，揭示结皮的发生、发展和形成的过程机理，为寻求抗结皮堵塞的有效途径、低质燃料和原料在水泥工业上的合理应用提供科学依据。

新型干法水泥烧成系统中易挥发有害元素的富集行为是导致结皮堵塞的关键。本项目综合运用多学科知识分析了高温条件下碱金属钾钠典型盐类的挥发与冷凝行为，考察了碱土金属钙硫酸盐的高温分解与转化过程，构建了碱金属盐的挥发动力学以及硫酸钙的高温分解SUC模型，探索了不同试验条件下碱（土）金属盐与高钙、低钙硅酸盐矿物之间的多相反应行为以及二元复合盐的熔融机制，初步揭示了硫/氯/碱金属的循环富集规律以及窑尾特殊区域的结皮堵塞机制：与碱金属碳酸盐及氧化物相比，碱金属硫酸盐尤其是氯化物参与熟料烧成固相反应的活性并不强烈，易在高温过渡区和烧成区大量挥发进而在窑后形成硫酸盐沉积区以及尾部/预热器氯化物沉积区，烟气中高SO2浓度促进了碱金属的硫酸盐沉积和氯的释放，且与生料矿物形成固硫产物硫酸钙和固氯产物氯化钙，硫/氯的沉积以及二元盐的低温共熔进一步加剧了液相的低温形成，中温区硫酸钙向硫硅酸钙以及硫酸钾钙的转化增强了物料的粘结能力，最终导致结皮。