低品位煤矸石制备Si基耐火材料过程中矿物质的演变行为及机理

Synthesis of silicate-based refractory at high temperatures is a value-added utilization of low-grade coal gangue with low calorific value and high ash content. Controlling the reactions among minerals through changing the feed ratios and process parameters to obtain the target phase is the fundamental and key issue in the synthetic reactions. However, the purity and performance of synthesized refractory is inadequate under the current technical conditions. The improvement of the synthesized materials is difficult due to the lack of understanding about the reaction mechanism and variations in structure and micro-topography at high temperatures to date. This study aims to investigate the mechanisms of reactions among minerals those between minerals and carbonaceous matters through analyzing the compositions and contents of minerals in coal gangue at high temperatures and different atmospheres. Moreover, the application of phase diagrams and thermodynamic calculation with FactSage software also facilitate the research of reaction mechanisms. The relationship between mineral reactions and structure and property of refractory is established by studying its chemical structure and micro-topography at high temperatures. Effects of various components of coal gangue on the reactions among its minerals are explored by modifying the ratios of different inorganic components, carbon content and reactivity of carbon. And the mechanism and interaction among various minerals at high temperature is elucidated based on the above analyses. This work provides significant guidance for optimizing the feed ratios and controlling side reactions in synthesizing reactions, and also benefits the improvement of performance of refractory made from coal gangue.

利用发热量低（<2800kJ/kg）、灰分高的低品位煤矸石在高温下合成Si基耐火材料是其高值利用的途径之一。通过调配原料比例和工艺参数来控制矿物质的反应得到目标物相，是利用煤矸石合成耐火材料的理论基础，也是关键问题。由于缺乏煤矸石中矿物质在不同条件下的反应机理、结构和微观形貌变化等方面的认识，使合成材料的纯度和性能难以提高。本项目拟通过分析煤矸石在高温不同气氛下的物相组成及含量，结合相图和FactSage热力学计算，研究煤矸石中矿物质之间、矿物质与含碳有机质的反应机理；通过研究高温样品的化学结构和微观形貌，建立矿物质反应与样品结构和形貌性质的关联。分别通过调节煤矸石中无机组分的比例、含碳量和碳的反应活性，研究煤矸石组分特点对高温下矿物质演变行为的影响规律，明确高温下矿物质竞争反应的相互作用机制。研究工作有望为利用煤矸石合成Si基耐火材料时原料比例调配、副反应控制和提高合成材料性能提供指导。

煤矸石是我国的大宗工业固体废弃物之一，其产生量大且利用率低，大量堆积严重危害着矿区生态环境。利用发热量低、灰分高的低品位煤矸石通过高温煅烧制备氮化硅和塞隆等耐火材料，是煤矸石资源化利用的途径之一。煤矸石中矿物质之间、矿物质与添加剂、矿物质与碳等发生相互反应形成新物相，是利用煤矸石制备硅基耐火材料的理论依据。研究高温不同条件下煤矸石中矿物质的演变行为，对利用煤矸石制备功能耐火材料具有重要的意义。.本项目围绕煤矸石中矿物质高温反应及其主要影响因素开展研究，研究了高温下不同组成特性煤矸石中矿物质演变行为，探讨了温度、气氛、无机组分和含碳还原剂等因素对煤矸石中矿物质碳热氮化还原反应的影响。研究发现，碳含量低于10%的煤矸石中矿物质难以直接发生碳热还原氮化反应，所添加含碳还原剂的层片间距越大，其反应活性越高，越有利于煤矸石中矿物质碳热还原氮化反应的进行。煤基固废煤泥和焦粉可作为廉价的碳还原剂用于材料的合成。气氛和气氛通入次序对高温下煤矸石中矿物质的碳热还原反应和样品形貌有较大的影响。先通入Ar并在设定温度停留1h后通入N2时，中间体碳硅石的生成促进了莫来石向β-Sialon相的转化。煤矸石中CaO、Fe2O3和MgO等组分的含量对高温下矿物质的碳热还原氮化反应有重要的影响。在1400℃、N2气氛下，随着CaO加入量增多，莫来石更趋于向钙长石转化；随着MgO加入量增多，样品熔点降低，在高温下发生烧结现象，从而阻碍碳热还原氮化反应的进行；当氧化铁含量低于5%时，产物中β-Sialon相的含量无明显变化，而当Fe2O3含量增加至7%时，β-Sialon相随氧化铁含量增加呈减少趋势，无定形相含量呈增加趋势，这是由于铝硅酸盐与氧化铁在高温下容易发生低温共熔。随着氮化产物含量的增加，高温样品的微观形貌由不规则状颗粒向絮棒状转变，棒状和絮状颗粒逐渐增多。.本项目所获得的基础数据可为煤矸石高温材料合成过程中煤矸石原料的选择、合成路线的设计与优化和副反应控制提供理论支撑。