气流床气化炉熔渣层碳的赋存规律及与熔体的理化作用机理

The clean and efficient conversion of coal and the long-term stable operation of the plant are essential for the development of large-scale entrained flow coal gasification technology. Residual carbon occurrence in the molten slag layer, which is caused by the carbon particle deposition, is the key factor for clean and efficient conversion of the gasifier, and for heat transfer, phase change and flow of the slag layer. Based on the visualized hot state experiments of high-temperature stage microscope and entrained flow gasifier, this project uses combined technologies of high resolution-high speed imaging, high-temperature structure detection, confocal micro-Raman spectrometer, scanning electron microscope, transmission electron microscope and time-of-flight secondary ion mass spectrometer, etc., to study the rule of residual carbon occurrence in the slag layer of the entrained flow gasifier and its physicochemical mechanism with the melt. The main researches include: the structure, evolution, and distribution of residual carbon in the high-temperature molten slag layer caused by the adhered carbonaceous particles; the diffusivity, chemical reactivity, and thermal diffusion-reaction mechanism model of residual carbon occurrence in high-temperature slag; the physical and chemical mechanism between residual carbon occurrence and aluminosilicate melt structure. These studies can reveal the formation mechanism of residual carbon, carbonaceous minerals and micro-carbon structure in the gasifier slag chunk, and enrich the basic theoretical study of the phase transition of carbon-containing molten slag. Besides, theoretical guidance is provided for the prediction, regulation and optimal operation of the viscosity-temperature characteristics in the entrained flow gasifier.

面向大型气流床煤气化技术发展的需求，入炉煤炭的清洁高效转化及装置的长周期稳定运行至关重要，因含碳颗粒沉积诱发炉壁渣层的残碳赋存是影响气化炉对煤炭清洁高效转化、炉壁渣层的传热、相变及流动等性能的关键因素。本项目基于高温热台显微镜和气流床气化炉的可视化热态实验，借助高分辨率-高速摄像仪、共聚焦显微拉曼光谱仪、扫描电子显微镜、透射电镜和飞行时间二次离子质谱仪等，开展气流床气化炉熔渣层中残碳的赋存规律及其与熔体的理化作用机理研究。将重点研究：粘附含碳颗粒在高温熔渣层中残碳的结构、演化程度及分布等赋存特征；赋存残碳在高温熔渣中的扩散性、化学反应性及其热扩散-反应机理模型的构建；残碳的赋存与硅铝酸盐熔体结构的理化作用机理等科学问题。这些研究可揭示气化炉渣块内残碳、含碳矿物及碳微结构的形成机理，丰富含碳熔渣体系相变的基础理论研究，为气流床气化炉中含碳熔渣的粘温特性预测、调控及装置的优化运行提供理论指导。

随着双碳政策和行动的逐步推进，大型气流床煤气化技术对煤炭清洁高效利用的要求及装置的长周期稳定运行至关重要，含碳颗粒沉积诱发炉壁渣层的碳赋存及对灰渣理化特性的影响是影响上述问题的关键因素。本项目借助搭建的高温热态显微镜实验平台和气流床气化炉，研究了粘附含碳颗粒在高温熔渣层中碳的赋存、扩散-反应及与熔渣硅铝酸盐结构的相互作用机理。结果表明，熔渣对石油焦类低活性含碳颗粒的影响显著，抑制其界面反应，但在煤灰中K+和Na+的增加后，熔渣对石油焦气化有明显的催化作用。熔渣中K+并未失活，随着K含量的增加，对煤焦等高活性颗粒在熔渣表面的完全反应时间可缩短至67%。K元素向颗粒与熔渣界面迁移并积累，积累量随碳转化率和K含量的增加而增加。气化过程煤焦颗粒下方的低温区是导致K与Si、Al等元素迁移的关键。气化炉渣层残碳在迁移过程中易与含铁矿物质发生碳热反应，在碳/渣界面形成金属铁，生成量随熔渣温度和停留时间增加，形貌由层状转变为球形。熔渣层中残碳的石墨化结构随熔渣温度和停留时间的增加而降低，无序结构程度的增加会促进碳热反应，碳迁移和碳热反应促进了渣层矿物转化和结晶行为。气流床煤气化热模实验发现，碳是导致渣中多个矿物阶段化发展。残碳主要以非晶态存在于煤渣中，促使煤渣矿物种类转化，由钙长石转变为透辉石。利用FactSage热力学计算获得了残碳及灰渣矿物与温度的三维分布关系图，构建赋存碳及熔体结构在理化作用过程中的三维分布，结合高温熔渣中碳的赋存、热扩散及反应，揭示碳的赋存与多元相硅铝酸盐熔体结构的理化作用机理。这些研究为气流床气化炉中含碳熔渣的粘温特性预测、调控及装置的优化运行提供理论指导。