基于CFD-DEM耦合的还原竖炉多相传输过程模拟及优化调控

The digitization of metallurgical reactors is a key foundation and an important means to achieve intelligent manufacturing and green development in the steel industry. The main difficulty of digitalized analytical metallurgical reactor is that the multi-phase and multi-scale structure consisting of discrete phases are difficult modeled. Considering the issue of insufficient central gas supply in large-scale reduction shaft furnace, in this project, the gas-solid multiphase system in a shaft furnace with central-circumferential gas suppling is taken as research object. Firstly, the digital reconstruction method of non-sphere particles is explored. The constructed digital particles can effectively characterize the actual material structure and physical properties, and they are provided for the next simulation model. Secondly, a trans-scale CFD-DEM mathematical model coupled with heat and mass transfer is developed. The gas-solid transmission process and reaction mechanism in the shaft furnace under the condition of central-circumferential gas suppling are described in detail. Finally, based on the developed CFD-DEM model, the operation parameters and the reasonable design of furnace structure of the shaft furnace with central-circumferential gas suppling are optimized by considering the gas-solid motion matching index and metallization rate as evaluation indexes. Relevant research results can provide theoretical basis for accurate simulation of gas-solid reactor, and provide technical support for cost reduction, efficiency improving and consumption reduction in reduction shaft furnace, which has very important theoretical and practical significance.

冶金反应器数字化是实现钢铁行业智能制造和绿色发展的关键基础和重要手段，而数字化解析冶金反应器的主要困难是反应器内存在的离散相构成的多相多尺度结构难以建模。结合大型化还原竖炉中心供气不足的实际问题，本项目以中心-圆周协同供气还原竖炉内煤气流-颗粒流多相体系为研究对象，首先，探索非球形颗粒数字化重构方法，构建有效表征实际物料结构、物性特征的数字颗粒，为模型提供模拟样本；其次，开发跨尺度、耦合传热传质的CFD-DEM数学模型，详细描述还原竖炉中心-圆周供气条件下的气固传输过程和炉内反应机理；最后，基于开发的CFD-DEM模型，以气固运动匹配指数及金属化率为评价指标，优化调控中心-圆周供气还原竖炉操作参数及炉型结构合理设计。相关研究成果可为气固反应器精准模拟提供理论依据，为实现还原竖炉降本增效和减排降耗提供技术支持，具有十分重要的理论与现实意义。

随着我国“碳达峰、碳中和”战略和智能制造创新发展战略的实施，对化石能源消耗高、碳排放量大、流程工业特征显著的钢铁冶金工业提出了新的挑战。发展竖炉直接还原工艺具有流程短、碳排放少等优点，受到了越来越多的重视。还原竖炉作为典型气固逆流反应器，气固两相流动-传递-反应效率越高，其对应的能耗越低，而竖炉数字化精准建模有利于获得高效的操作制度及结构设计。因此本研究围绕基于多球组合模型的非球形颗粒数字化重构、基于CFD-DEM 耦合的还原竖炉多相传输模型、中心-圆周供气还原竖炉操作参数及炉型结构优化调控三个方面内容开展研究。首先，利用多球组合模型形成了还原竖炉常用原料，测定其基本物性参数，并赋值形成非球形数字化颗粒，明确了典型非球形颗粒的堆积休止角、空隙率特征，发现了多元非球形颗粒料仓流动过程中的偏析行为，为后续精准模拟物料流动、偏析等行为奠定基础。其次，建立了描述典型中心-圆周供气竖炉物料运动行为、气固流动特征、多相传输行为的数学模型。最后，基于建立的数学模型，研究设计了磨损少、能耗低的炉料均匀下降螺旋结构，明确了面向流速均匀性或者压差最小为目标的上部适宜料面形状，提出了竖炉最高金属化率为目标的适宜的供气比例、供气温度以及中心供气装置结构等建议。通过本项目研究构建了气固反应器精准数学模型，相关成果可应用于实际还原竖炉，为其降本增效和减排降耗提供技术支持。.受本项目资助，发表学术论文21篇，授权发明专利2项，参加国内外学术会议8人次，作口头汇报5人次；辅助培养毕业博士研究生1人，培养毕业研究生3人，本科生2人。