铝业高铁赤泥用作炼钢冷却剂/造渣剂/脱磷剂的应用基础研究

A large amount of red mud has been being produced due to the rapid development of alumina industry in China. Since some red mud is rich in Fe resources, it reasonably should become the ideal raw materials of ironmaking and steelmaking industries. However, presently only a little red mud was used in sinter/ agglomeration procedure and the consuming amount is extremely limited, which is mainly caused by the serious vaporization of Na2O. Actually, the strong basic and oxidizing properties of highly Fe-bearing red mud are very useful in steelmaking process. In this research, a technical way was proposed during which the highly Fe-bearing red mud was used in BOF steelmaking process as cooling/fluxing/dephosphorization agents. For BOF operation, the biggest difference led by the application of red mud tends to be the formation of CaO-SiO2-?FeO-Al2O3-Na2O(-MgO) slag system instead of CaO-SiO2-?FeO. The main contents of this project include: to study the fluidity and dephosphozing ability of the slag above, and to get the interaction influencing mechanism of Al2O3 & Na2O, and find the optimized indexes for minimizing FeO content in slag; to investigate the dissolution behaviors of lime into the slag and the related kinetic information; to reveal the multiphase interacting mechanism between the slag above and Fe-C-Ti/Al/S melts in order to clarify the potential influence of red mud on the cleanness of steel; through thermal state experiments together with the help of mass and materials balance analysis, to study the burden pattern, slagging system, oxygen supplying and their combining principle in BOF process, and to form a technically practicable demonstration for the case of applying red mud in BOF process.

我国氧化铝工业的飞速发展带来大量赤泥产生。高铁赤泥含有丰富的铁资源，理应是钢铁企业的理想原材料，极少数企业应用于烧结/球团工序，消耗量非常有限。鉴于其强氧化性和高碱性特点，提出在炼钢过程使用高铁赤泥作为冷却剂/造渣剂/脱磷剂的工艺思路。转炉中加入高铁赤泥后与传统操作的最大不同是形成了CaO-SiO2-ΣFeO-Al2O3-Na2O(-MgO)渣系。主要内容：研究以上渣系的熔化流动性能及脱/固磷能力，掌握Al2O3、Na2O的交互影响机理，寻求最低FeO含量的优化参数；研究石灰在以上渣系中的溶解行为；研究以上渣系与Fe-C-Ti/Al/S熔体之间的多元多相反应机理，明晰高铁赤泥的使用对钢水洁净度的潜在影响以及对不同钢种的适用范围；通过热态模拟实验研究，并结合流程物料及能量平衡分析，探讨使用高铁赤泥后转炉的配料模式与成渣路线、造渣制度等之间的联动配合机制，形成可行的工艺技术原理示范。

传统炼钢工艺形成的是CaO-FetO-SiO2基渣系，该渣系熔点高、流动性差，是限制高效冶炼的关键因素，具体表现为前期脱磷效率低、冶炼后期脱磷负荷大导致过氧化出钢、钢水纯净度低。赤泥为氧化铝生产过程中伴生的固体废弃物，含有丰富的Fe2O3/Al2O3/Na2O资源，鉴于其强氧化性和高碱性特点，本项目提出在炼钢过程使用高铁赤泥作为冷却剂/造渣剂/脱磷剂的工艺思路，本质上为炼钢工艺发展了CaO-FetO-SiO2-Al2O3-Na2O基新渣系。围绕新渣系条件下炼钢工艺技术的优化提升，本项目重点开展了以下研究工作：CaO-FetO-SiO2-Al2O3-Na2O基新型炼钢渣系的基础物化性能测试研究，包括熔点、粘度、磷分配比、硫分配比、磷容量等。实验室研究工作中探讨了以上渣系与钢水间的交互反应机理及其对钢水纯净度的影响，分析了该渣系对炉衬的侵蚀影响。在以上实验室基础研究的基础上，已完成中试扩大试验（200Kg级）、工业试验（120t），工业试验中重点探讨了新渣系条件下的造渣制度，及其与枪位控制之间的联动配合机制。结果显示新渣系熔点低、液相区明显扩大，深度脱磷/脱硫明显提前，在半钢条件（[C]=2.5%-3.0%）下可实现：[P]<0.02%，[S]<0.02%，大大提高钢水纯净度。Al2O3、Na2O不但具有显著的助熔效果，还可以提高P2O5在渣中的溶解度。工业试验结果显示：在炼钢工艺中加入赤泥基熔剂，在炼钢初期能快速助熔化渣，能很好的解决后期炼钢的“返干”现象，完全避免了萤石类助熔剂的使用。具有更优秀的脱磷效果，其平均终点磷比原工艺降低0.012%、脱磷率提高12%。可实现半钢条件下深脱磷和高碳出钢，终渣(FeO)含量可降低至12-15%，非常有利于提高钢的品质。在以上研究的基础上，已发表各类学术论文25篇，发明专利1项，培养博硕士研究生8人。此项目不仅可实现在转炉炼钢前期高效脱磷，高碳出钢，促进钢的洁净化，推动了炼钢工艺技术进步，且为赤泥在炼钢工业中的大规模资源二次应用提供了重要的基础借鉴。