超高比例烟气循环-富氧铁矿烧结的基础研究

Iron ore sintering is the main air pollution source of iron & steel industry. For realizing zero emissions of NOx, SOx and COx, a novel sintering process of ultra-high proportion flue gas recirculation & oxygen enrichment is proposed. The process is characterized by applying industrial pure oxygen and 70%-80% of the circulated flue gas from the head and tail of sintering machine instead of air, by which CO2 and SO2 enriched in the mid flue gas are liquefied and recycled, while NO is degraded via recirculation. On the condition of COx-O2-H2O gaseous medium, the influences of gas compostions on fuels combustion, and on heat transfer behaviors between gaseous and solid phases are researched, then the moving rules of flame front and heat transfer front are analyzed. The changes of atmosphere during sintering process and thermal state in sinter bed and their influences on mineralization of sintering materials are revealed, and the relationships between compositions of gaseous medium and combustion, heat transfer, and mineralization are established, thus forming the fundamental theory for ultra-high proportion flue gas recirculation & oxygen-enriched sintering. Furthermore, coordination mechanism of reasonable flue gas recirculation and moderate oxygen enrichment is established, and key technologies upon regulating combustion performance of fuel, thermal conductivity of bed and mineralization behavior of raw materials are developed, making flame front and heat transfer front during ultra-high proportion flue gas recirculation & oxygen-enriched sintering moved synchronously, and mineralization of sintering materials optimized. Therefore, the sintering indexes are not affected at ultra-high proportion recirculation of flue gas and zero releases of pollutants are to be achieved, which contribute to the sustainable development of iron & steel industry.

铁矿烧结是钢铁工业的主要大气污染源。为实现烧结过程NOx、SOx、COx零排放，提出超高比例烟气循环-富氧烧结的减排新工艺：将占烟气总量70%-80%的烧结机头部和尾部烟气进行循环，与工业纯氧混合替代空气进行烧结，使CO2和SO2富集在中部烟气经压缩液化回收、NO循环降解。项目通过研究超高比例烟气循环-富氧烧结的气体介质COx-O2-H2O组成对燃料燃烧和气-固传热行为的影响，解析烧结燃烧前沿和传热前沿的迁移规律，揭示烧结过程气氛和热状态的变化及其对烧结成矿的影响，建立气体介质组成与燃烧、传热、成矿的关系，形成超高比例烟气循环-富氧烧结的基础理论。进而构建烟气合理循环与适度富氧的协调机制，开发调控燃料燃烧性能、料层导热性能、原料成矿性能的关键技术，使燃烧前沿和传热前沿同步迁移、烧结物料优化成矿，从而保证烧结指标不受影响，实现烟气超高比例循环和污染物零排放，为钢铁工业的可持续发展做出贡献。

烧结烟气排放量大、污染物种类多，导致其治理难度大。从烧结工艺过程减少烟气和污染物排放量，对烧结清洁生产意义重大。本项目开展了超高比例烟气循环-富氧烧结的基础理论与技术研究，通过系统分析烧结烟气特性和排放规律，提出了超高比例烟气循环的构建模式；通过查明超高比例烟气循环-富氧烧结的气体介质COx-O2-H2O组成对燃料燃烧影响，揭示了烧结燃烧前沿的迁移规律，发现循环烟气中CO2和O2含量之间的关系应满足η(O2)=11.77*η(CO2)^0.24，确保燃料燃烧达到和空气气氛条件下相当的燃烧速度和燃烧效率；应用多相理论和多孔介质模型，基于质量、动量和能量守恒方程，构建了烧结料层气-固传热模型、温度模拟模型和排放气体组成预测模型，达到了预测精度要求；查明了超高比例烟气循环烧结过程气氛和热状态的变化规律，及其对烧结成矿的影响，解析了COx-O2-H2O介质条件下烧结物料的成矿机理；构建了烟气合理循环与适度富氧的协调机制，开发了调控燃料燃烧性能、改善原料成矿性能等强化技术，使燃烧前沿和传热前沿同步迁移、烧结物料优化成矿，从而保证烧结指标不受影响，实现了50%-70%的高比例烟气循环, 减少CO、NOx的排放达到40%-60%、20%-50%，且外排烟气CO2、SO2浓度明显富集，有利于提升后续烟气处理的脱硫效率，以及CO2的捕集回收。本项目开发的超高比例烟气循环-富氧烧结的方法，具有投资省、适用范围广等特征，为烧结烟气余热利用、气体污染物减量排放提供了一条新的可行途径。