【作者】 刁江；

【导师】 谢兵；

【作者基本信息】 重庆大学 ， 冶金工程， 2010， 博士

【摘要】 铁矿石资源是十分重要的非可再生自然资源，是人类社会赖以生存和发展的不可或缺的物质基础。随着钢铁行业的飞速发展，世界范围内高品位优质铁矿石资源逐渐枯竭。以储量丰富的高磷铁矿为代表的低品位复杂铁矿资源的开发利用逐渐受到关注。作者通过文献和调研，分析了选矿方法、化学方法、冶炼方法以及微生物方法等主要脱磷方法各自的优缺点，认为冶炼方法尤其是转炉双联冶炼工艺为解决我国高磷铁矿石资源利用的有效方法。本论文以中高磷铁水转炉双联脱磷过程为对象，通过开展热力学、动力学、石灰溶解行为、双联炉渣资源化利用等方面的研究，丰富中高磷铁水脱磷基础理论；探索转炉双联工艺处理中高磷铁水的可行性；为其工业应用提供理论依据和实践指导。采用无氟CaO-FetO-SiO₂渣系，以少量Na₂O和Al₂O₃作助熔剂对磷含量0.42%的铁水进行了热力学实验。脱磷率为74⁹1%；磷分配比P log L为1.75¹.92；P₂O₅活度系数logγP₂O₅为-15^-17；磷酸盐容量43-PO logC为19²1。研究发现有关脱磷热力学分析的经典公式并不适用于本实验条件。本文在分析脱磷渣组分和光学碱度对P log L、logγP₂O₅和43-PO logC的影响的基础上，用SPSS软件回归出了组分、光学碱度与上述热力学参数的关系式。计算结果与实测结果较为吻合。采用CaO-FetO-SiO₂-（Al₂O₃, Na₂O）炉渣进行了中高磷铁水脱磷动力学研究。发现2⁶%的Al₂O₃与Na₂O均能起到提高初期脱磷速度的作用。Na₂O还可抑制回磷现象。低硅铁水具有较好的脱磷效果。基于双膜理论建立了脱磷动力学方程，从表观脱磷速率常数kP、总传质系数kO和传质参量A·kO三个方面对脱磷动力学方程进行了多角度解析。实验各炉次的kP在0.868⁸.602×10-3g/（cm2·s）之间；kO在0.005⁰.024cm/s之间。Al₂O₃和Na₂O可明显增加kO。铁水硅含量越低，kO越大。各炉次前两分钟平均A·kO值在0.16⁰.36cm3/s之间，随着反应的进行，A·kO值逐渐降低。对于无回磷现象的炉次，A·kO逐渐降低直至趋近于零；对于发生回磷现象的炉次，A·kO逐渐降低为负值。基于Robertson模型建立了多组分耦合反应动力学模型。模型计算结果与实测结果趋势一致。分析了界面氧活度aO*与炉渣组分和铁水成分的关系，炉渣FeO含量越高，铁水碳、硅、锰含量越低，则aO*值越大。分析了渣量和CO析出的表观速率常数GCO对计算结果的影响。渣量越大、GCO越小的条件下aO*越大，越有利于脱磷。采用二次回归正交组合设计的方法研究了CaO-FetO-SiO₂-Al₂O₃-Na₂O-P₂O₅炉渣对石灰溶解行为的影响。分析了各因素的单独影响及其交互作用效应。进行了石灰在CaO-SiO₂-FetO-P₂O₅-X系炉渣中的旋转溶解动力学实验。发现CaO在液相中的传质是石灰溶解的限制性环节。CaF2对促进石灰溶解的作用最强,Na₂O次之,Al2O3的影响最弱。回归出高P2O5含量炉渣中石灰溶解速度与线速度的关系式和对流传质方程。传质系数计算值为7.63×10-4¹.70×10-3。根据Arrhenius公式计算出的石灰溶解活化能为43kcal/mol。对于中高磷铁水冶炼,如欲在低氟或无氟的情况下造好具有一定碱度的脱磷初渣,应保证一定的铁水温度、炉渣ΣFeO/SiO₂比和动力学搅拌等一系列的工艺条件。在双联炉渣资源化利用方面,分析了脱磷渣和脱碳渣的矿相组成;探讨了脱磷渣的黏性特征和脱碳渣的熔化特征;分析了利用高磷炉渣制钢渣磷肥的可行性。由于CaF2极易同磷结合生成氟磷灰石,使脱磷渣枸溶率急剧降低,制备钢渣磷肥需走无氟路线。用改性-磁选的方法探索了脱磷渣中磷的富集与分离行为,发现可以取得良好的效果,实现了大部分磷的回收。采用正规离子溶液模型计算炉渣组元有效浓度,并将其应用于前人建立的返回渣利用配方模型。结合计算结果进行了脱碳渣返回利用热态实验,发现本实验条件下20%的返回渣比例较合适。返回渣冷却效果计算结果表明其冷却能力低于原脱磷剂。此外,用分子动力学方法对CaO-SiO₂-P₂O₅-（CaF₂）熔渣结构进行了模拟计算,丰富了熔渣结构理论。对于深入了解转炉渣结构,尤其是高P₂O₅含量炉渣结构和性质有着重要的意义。进行了80t转炉双联脱磷工业试验。铁水磷含量0.25⁰.3%的条件下,脱磷炉平均脱磷率73%,脱磷渣平均P₂O₅含量5.01%;铁水磷含量0.37⁰.44%的条件下,脱磷炉脱磷率67.6%,脱磷渣平均P₂O₅含量7.25%。脱磷渣中P₂O₅含量高,是制造钢渣磷肥的良好原料。半钢经脱碳炉少渣冶炼后,终点磷含量均小于0.015%,满足低磷钢冶炼要求。针对中高磷铁水冶炼的特点,对各种脱磷工艺进行了综合评价,认为利用转炉双联工艺冶炼低磷钢的技术路线可行。转炉双联工艺对于处理国内的高磷铁矿具有良好的应用前景。更多还原

【Abstract】 Iron ore resources are precious non-renewable natural resources, which are the indispensable material foundation of the existence and development of human society. With the rapid development of iron and steel industry, the supply of high quality, low phosphorus iron ores becomes depleted gradually. In recent years, some evidence has suggested that the development and utilization of low grade complex iron ores represented by high phosphorus iron ores have attracted more and more attention of metallurgists. In the paper, according to synthetic analysis for the vast majority of literatures, the advantages and disadvantages of different dephosphorization treatment like mineral separation, chemical method, refining method and microorganism method were analyzed. In the author’s view, the refining method, especially the duplex process, is an effective way to utilize the high phosphorus iron ores in our country. Taking duplex process refining as subject, the paper concentrates on the enrichment of fundamental research for medium and high phosphorus hot metal refining by studying the thermodynamics and kinetics of dephosphorization, the dissolution behavior of lime and the resource utilization of duplex refining slags. The feasibility of refining medium and high phosphorus hot metal by duplex process was also discussed. The comprehensive evaluation result could provide a theoretic basis and direction for industrial application of duplex process.Dephosphorization thermodynamics of high phosphorus hot metal (0.42%) was investigated by using CaO-FetO-SiO2 slags, which contained small amounts of Na2O and Al2O3. The results show that the dephosphorization ratio, log LP , logγP2O5 and log C POwere 74~91%, 1.75~1.92, -15~-17 and 19~21, respectively. It was found that the classical and experiential formulae about dephosphorization analysis are not applicable to the case of medium and high phosphorus hot metal refining. Based on the analysis for the effect of optical basicity and slag components on log LP , logγP2O5 and log C PO, the correlations between optical basicity, slag components and these thermodynamic parameters were developed by regression analysis method. The kinetics of dephosphorization was studied by using CaO-FetO-SiO2-(Al2O3, Na2O) slags. The results indicate that both 2~6% Al2O3 and Na2O could increase the initial dephosphorization velocity. Na2O could also inhibit the rephosphorization phenomena. Low Si hot metal had better dephosphorization effect. Based on the double film theory, a dephosphorization dynamic model was set up. The present paper made a systematic and multi-angle analysis of the model from the following three aspects: the apparent dephosphorization rate constant kP, the overall mass transfer coefficient kO and the mass transfer parameter A·kO. The experimental results show that kP were in the range of 0.868~8.602×10-3g/(cm2·s). kO were in the range of 0.005~0.024cm/s. Al2O3 and Na2O could obviously increase kO. Si content in hot metal was lower, kO was higher. In all the 11 heats of experiments, the average A·kO in the first two minutes were in the range of 0.16~0.36cm3/s. As the reaction process continues, the value of A·kO decreased gradually. To the heats without rephosphorization phenomena, the value of A·kO decreased gradually and finally approach zero. To the heats with rephosphorization phenomena, the value of A·kO decreased gradually and finally become negative. Based on the Robertson model, a coupled reaction model to the medium and high phosphorus hot metal dephosphorization process was set up. The calculated results agreed well with the measured data. The relationship between the oxygen activity at slag-metal interface aO* and hot metal and slag components were discussed. The higher the FeO content in slag was, the lower the C, Si and Mn in hot metal were and the higher the aO* at slag-metal interface was. The effect of GCO and slag amount on calculation were also discussed. The higher the slag amount was, the lower the GCO was and the higher the aO* was. Higher aO* facilitates dephosphorization.The dissolution behavior of lime into CaO-FetO-SiO2-Al2O3-Na2O-P2O5 slag was investigated with the help of quadratic regression orthogonal composite design method. The influence of different factors and interactions between major factors were discussed. The dissolution rate of CaO in CaO-SiO2-FetO-P2O5-X was studied by rotating cylinder method. From the analysis of experiment results, it was concluded that the dissolution rate was controlled by the mass transport of CaO in liquid phase. The effect of additives to CaO-SiO2-FetO-P2O5 slag on raising the dissolution rate of CaO was CaF2 > Na2O > Al2O3. The convective mass transfer equation and relational expression between linear velocity and CaO dissolution rate in the high P2O5 slag were obtained by regression analysis. The calculated mass transfer coefficient were in the range of 7.63×10-4~1.70×10-3. Based on the Arrhenius equation, the apparent activation energy for the dissolution rate was calculated to be 43 kcal/mol. For the medium and high phosphorus hot metal refining, in order to accelerate the slagging process under low fluorine or fluorine-free condition, a series of technology parameters such as adequate hot metal temperature,ΣFeO/SiO2 in the slag, stirring and so on should be guaranteed. In the aspect of resource utilization of duplex refining slags, mineralogy of De-P and De-C slags were investigated by SEM, EDS and XRD. Viscosity characters of De-P slags and melting characters of De-C slags were also discussed. In view of the high P2O5 content in De-P slags, the way of developing steel slag phosphate fertilizer was put forward. Due to the formation of fluorine containing apatite Ca5(PO4)3F, solubility of slag samples in citric acid decreased rapidly with CaF2 addition. To get a higher solubility, production of steel slag phosphate fertilizer should follow the fluorine-free route. The recovery of phosphorus from De-P slag was studied in present work through slag modification and magnetic separation. It was found that most of the phosphorus could be separated by magnetic separation after slag modification. Consequently, the recovery of phosphorus from De-P slag is made possible by this method. The activities of typical slag components were calculated by regular ion solution model and applied to a previous mathematical model to calculate the substitution of dephosphorizing agent by return slags. According to the calculated data, the effect of De-C slag substitution on dephosphorization was checked with experiments in laboratory. The results show that 20% De-C slag in dephosphorizing agent is suitable in the present experiments. Furthermore, the structure of CaO-SiO2-P2O5-(CaF2) molten slags were investigated by molecular dynamics simulation. The results achieved here are very important for the enrichment of molten slag structure theory, especially for further realize the structure and properties of high P2O5 content slags.In order to evaluate the feasibility of refining medium and high phosphorus hot metal by duplex process, 80t scale plant trails have been conducted. For the [P] 0.25~0.30% hot metal, the average dephosphorization ratio in De-P furnace was 73%, the average P2O5 content in dephosphorized slag was 5.01%. For the [P] 0.37~0.44% hot metal, the average dephosphorization ratio in De-P furnace was 67.6%, the average P2O5 content in dephosphorized slag was 7.25%. The P2O5 content in dephosphorized slag was 7.25%. Both the P2O5 content in two slags were much higher than that in conventional BOF slags. The phosphorus enriched De-P slag could be used as raw material in fertilizer production. After less slag semi-steel refining in De-C furnace, the end point phosphorus content in steel were less than 0.015%, which satisfy the requirement of low phosphorus steel refining. In accordance with such a particular process for medium and high phosphorus hot metal refining, the primary dephosphorization technology were assessed comprehensively. The authors concluded that it is feasible to refining the medium and high phosphorus hot metal by duplex process. The duplex process for steel making has a bright future in the development and utilization of high phosphorus iron ores in China.更多还原