钢渣中二价氧化物活化及其胶凝活性研究

发布时间：2018-09-01 08:05

【摘要】：钢渣是将炼钢过程中高温熔渣冷却得到的一种固态废渣。因含铁量高且存在约20%的无活性二价氧化物固溶体(简称RO相),导致钢渣质硬难磨、胶凝活性低,无法实现大规模的高附加值利用。本文依托国家自然科学基金课题“转炉钢渣原位氧化及其熟料烧成化学基础研究”(编号:21566008),以广西柳钢的热闷转炉钢渣为研究对象,基于RO相置换型固溶体特性,提出将外掺CaO、Al_2O_3与RO相分离所得组分等进行高温化合,再形成具有胶凝性的硅酸盐矿物,从而从本质上提升钢渣活性的技术思路。开展了RO相分离及硅酸盐矿物再化合工艺研究,探讨了组分、温度、矿化剂等因素对改性钢渣胶凝活性的影响。围绕上述研究,主要具体研究工作及取得成果如下:首先,借鉴TG-DSC和XRD等表征方法探索热处理工艺对钢渣中RO相演变趋势及存在形态的影响:随着热处理温度的升高和保温时间的延长,熔渣中RO相和铁酸盐相含量逐渐减少直至消失,MgO和Fe_2O_3固溶加剧,此时Fe_2O_3和MgO活度较高。在风冷有条件下RO相演变成铁镁尖晶石MgFe_2O_4。进而在熔渣中Fe_2O_3活度较高的状态下,即在物相反应中Fe_2O_3参与反应的有效浓度较高时,探究调节组份CaO和Al_2O_3对钢渣中RO相活化、硅酸盐矿物再化合的影响。XRD和SEM-BEI分析表明:在Al_2O_3掺量为3%的条件下,CaO掺量在10%~25%时,随着CaO掺量增加RO相消失,演变为过渡相MgFe_2O_4;随后MgFe_2O_4逐渐减少,C_2S和C_2F逐渐增加;当CaO掺量达到15%时,MgFe_2O_4消失,逐渐出现游离氧化镁(f-MgO),掺入CaO先后分别与SiO2、MgFe_2O_4反应。当钙掺量达到25%时为极限掺量值,转炉钢渣中出现了游离氧化钙。在高温状态下,CaO按酸性氧化物的强弱依次与SiO2及RO相分离出的Fe_2O_3再化合形成硅酸盐矿物和铁酸盐矿物。最后,向重构钢渣中加入矿化剂稳定RO相分离出的MgO。实验结果表明:矿化剂可促进胶凝矿物相包裹f-MgO,但无法消化所有f-MgO,对MgO固溶量微弱。石膏促进效果优于五氧化二磷。CaSO4不仅有助于钢渣中的RO相活化及固溶MgO,还有效提高了钢渣的胶凝活性。在CaO和CaSO4掺量分别为15%、3%时,钢渣水化热提高了2.78倍,3d和28d强度分别提高的28%和4.6%。总体研究表明,调节剂和矿化剂可有效活化RO相,提高了钢渣的水化放热总量和力学性能,保证了钢渣掺合料的安定性。为实现钢渣高附加值的广泛应用奠定了基础。
[Abstract]:Steel slag is a kind of solid waste slag which is obtained by cooling the high temperature slag in the steelmaking process. Because of the high iron content and the existence of 20% inactive divalent oxide solid solution (RO phase), the steel slag is hard and hard to grind, and the cementitious activity is low, which can not realize the large-scale utilization of high added value. In this paper, based on the National Natural Science Foundation of China, "basic Research on the Chemistry of Converter Slag In-situ Oxidation and clinker Sintering" (No.: 21566008), the hot stuffing converter slag of Guangxi Liugang is taken as the research object, based on the characteristics of RO phase replacement solid solution. The technical idea of improving the activity of steel slag is put forward by combining the components separated by CaO,Al_2O_3 and RO phase at high temperature and then forming the silicate mineral with cementitious property. RO phase separation and silicate mineral recombination were studied. The effects of composition, temperature and mineralizer on the cementitious activity of modified steel slag were discussed. Around the above research, the main research work and achievements are as follows: first, The influence of heat treatment process on the evolution trend and morphology of RO phase in steel slag was explored by using TG-DSC and XRD characterization methods: with the increase of heat treatment temperature and the prolongation of heat preservation time, The content of RO phase and ferrate phase in slag decreased gradually until the disappearing MgO and Fe_2O_3 solution increased, and the activities of Fe_2O_3 and MgO were higher. Evolution of RO phase into ferrite spinel MgFe_2O_4. under air-cooled condition Furthermore, when the activity of Fe_2O_3 in slag is high, that is, when the effective concentration of Fe_2O_3 to participate in the reaction is higher, the activation of RO phase in steel slag by adjusting the components of CaO and Al_2O_3 is explored. The effect of silicate mineral recombination. XRD and SEM-BEI analysis show that when the content of Al_2O_3 is 3%, the RO phase disappears with the increase of CaO content, and then the MgFe_2O_4 decreases gradually, C2S and C2F increase gradually with the increase of CaO content. When the CaO content reached 15%, the MgFe _ 2O _ 4 disappeared and the free magnesium oxide (f-MgO) appeared gradually, and then the CaO reacted with SiO2,MgFe_2O_4 respectively. When the content of calcium is up to 25, the free calcium oxide appears in converter slag. At high temperature, the Fe_2O_3 recombined with SiO2 and RO to form silicate minerals and ferrate minerals according to the strength of acidic oxides. Finally, MgO. was separated by adding mineralizer to the reconstructed steel slag to stabilize the RO phase. The experimental results show that the mineralizer can promote the encapsulation of f-MgO in the cementitious mineral phase, but it can not digest all f-MgO, and the solution to MgO is weak. The effect of gypsum is better than that of phosphorus pentoxide. CaSO4 not only contributes to the activation of RO phase and solution of MgO, in steel slag, but also improves the cementitious activity of steel slag. When the content of CaO and CaSO4 is 15 and 3 respectively, the hydration heat of steel slag increases by 2.78 times and 28 days and the strength increases by 28% and 4.6%, respectively. The overall study shows that the modifier and mineralizer can effectively activate the RO phase, improve the total hydration heat release and mechanical properties of steel slag, and ensure the stability of steel slag admixture. It lays a foundation for the wide application of steel slag with high added value.
【学位授予单位】：桂林理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X757;TQ132.2

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