【作者】 陈永亮；

【导师】 张一敏；

【作者基本信息】 武汉科技大学 ， 化学工艺， 2012， 博士

【摘要】 铁尾矿是将铁矿石经过分选工艺选取铁精矿后剩余的废渣，是工业固体废弃物的主要组成部分。钢铁工业的快速发展，带来了尾矿的排放量与日俱增。长期以来对铁尾矿一般采取堆填处置，不仅占用土地，而且引起环境污染与安全问题。随着环境保护和可持续发展意识的增强，铁尾矿作为二次资源已受到普遍重视，其综合利用已引起广泛关注，特别是在利用铁尾矿制作建筑材料方面是当前国内外研究的热点。本论文在全面系统研究鄂西低硅铁尾矿基本性质的基础上，以该尾矿为主要原料，进行烧结普通砖和瓷质砖的制备技术研究，并对尾矿砖的性能和结构进行测试分析，探讨尾矿烧结普通砖和瓷质砖的烧结过程及机理。具体研究内容及结果如下：1．系统研究了鄂西低硅铁尾矿的基本性质。分析认为，该尾矿性能与粘土等矿物原料相近，具有粒度细、可塑性和干燥性能好的优点，但也存在尾矿中铁含量高、硅和铝含量低、尾矿烧结体的密度高、烧成收缩大等缺陷，经过适当调配，利用该尾矿烧结制砖是完全可行的。2．以鄂西低硅铁尾矿为主要原料添加少量的粘土、粉煤灰进行复配制备烧结砖，确定最佳的配方及制备工艺条件，并考察了标砖试验尾矿烧结砖样品综合性能。试验表明，添加少量粘土和粉煤灰对于提高尾矿烧结砖的性能起到积极作用，最佳原料配比为尾矿:粘土:粉煤灰=84:10:6，适宜工艺条件为成型水分12.5¹5%、成型压力20²5MPa、干燥制度：105℃下干燥6⁸h、温度制度：升温速率6℃/min左右、烧成温度范围980¹030℃、烧成保温时间2³h，在此条件下烧制的尾矿烧结砖的抗压强度为20.03²3.60MPa，吸水率为16.54¹7.93%，体积密度为1.85¹.90g/cm3。标砖试验结果与小样试验结果相符，尾矿烧结砖的抗压强度及其他耐久性能指标均达到《烧结普通砖》（GB/T5101-2003）中MU20合格品的要求。3．对尾矿烧结普通砖样品进行表征，分析了铁尾矿烧结砖的微观结构及性能的形成机理，并探讨了尾矿烧结普通砖的烧结过程。结果表明，烧结砖样品中主晶相为赤铁矿、石英、长石和磷灰石，构成烧结砖的主要骨架，赋予样品强度。长石与石英及硅铝酸盐形成低共熔物，充填于坯体的颗粒之间，促进砖坯的烧结致密，液相胶结各种形态的晶体颗粒相互穿插连接，保证了烧结砖样品的优良性能。此外，鄂西低硅铁尾矿烧结砖的烧结过程可分为：干燥预热、加热、烧成及冷却4个阶段，烧结过程主要以扩散传质机制为主，而在烧结后期坯体中会形成少量的高温液相，其对促进砖坯的烧结致密及固相反应起到不可忽视的促进作用。4．以鄂西低硅铁尾矿部分代替传统陶瓷原料制备无釉瓷质砖，确定了合理的铁尾矿瓷质砖基础成瓷配方范围及制备工艺条件，并对尾矿瓷质砖的各项性能进行综合检测。结果表明，铁尾矿全部取代长石的优化配方为铁尾矿55⁶5%，高岭土20²5%，石英砂10²0%，相应的坯体化学组成范围为SiO₂37⁴4%，Al₂O₃14¹6%，Fe₂O₃25²9%，CaO+MgO4⁵%，K2O+NaO0.7⁰.8%，烧失量为8.0⁹.5%，在1200℃附近可烧结成瓷，烧成温度范围大于40℃；适宜制备工艺条件为：成型压力30MPa，烧成温度1200℃，保温时间15min，尾矿瓷质砖样品的主要性能符合国家标准陶瓷砖（GB/T4100-2006）中干压瓷质砖要求及陶瓷砖环境标志产品技术要求（HJ/T297-2006）的规定，具有很好的环境协调性。5．研究了铁尾矿瓷质砖的微观结构，分析了铁尾矿降低液相生成温度，促进烧结的作用机理，以及铁尾矿加入引起产品烧结温度范围变窄的原因及可行的解决方法，并探讨了尾矿瓷质砖的煅烧过程。分析认为，尾矿瓷质砖具有良好的烧结程度，瓷坯结构中包含大量晶体颗粒，主要有残余石英、赤铁矿和方石英，以及少量的钙长石和莫来石，玻璃相充填其中，构成致密的玻璃相和晶体颗粒相互交织的网状结构，对尾矿瓷质砖强度的提高和成瓷都起到了重要作用。铁尾矿中含量较高的Fe₂O₃、CaO与原料中的石英及硅铝酸盐形成低共熔物降低液相生成温度，促进坯体的烧结致密，此外，氧化铁在烧结高温时形成液相，冷却时又从液相中析出生成赤铁矿的微晶，均匀的分布在玻璃相中，有利于提高瓷坯的强度和硬度。铁尾矿瓷质砖的烧结成瓷过程可分为低温阶段、氧化分解阶段、高温烧结阶段及冷却阶段，最终形成多相结构的致密瓷体。通过上述工作，验证了低硅铁尾矿在烧结制砖技术上的可行性，不仅解决了该类铁尾矿综合利用的难题，而且为烧结普通砖和瓷质砖开辟了新资源，具有环境保护和资源节约的双重效益。本论文全面系统的研究了尾矿基本性质，为尾矿的综合利用提供了必要的科学依据，烧结制砖机理研究丰富和发展了低硅尾矿资源化研究领域的理论体系，为铁尾矿利用技术及其发展应用提供了理论基础。更多还原

【Abstract】 Iron tailings as waste residues generated from the process of iron ore dressing is a kind ofmajor industrial solid wastes. The rapid development of iron and steel industry has led to theincreasing amount of iron tailings. The majority of iron tailings have been abandoned andstockpiled for a long time, not only taken large areas of land, but also resulted in environmentalpollution and safety problems. With the increasing awareness of environmental protection andsustainable development, iron tailings as secondary resources have been attached importance byall countries in the world, the utilization of iron tailings have widely received attention,especially, reuse in producing building materials is nowadays worldwide being investigated.This dissertation deals with the techniques of preparing fired bricks and porcelain tiles withthe low-silicon iron tailings from western Hubei province of China as the main raw materials,based on comprehensive analysis of the basic characteristics of tailings. Then, the properties andmicrostructure of the final fired samples were systematically investigated, the firing process andmechanism were probed. The research contents and results of the tests are summarized as thefollowing:1. The basic characteristics of the tailings were systematically studied. The results indicatedthat the tailings had similar properties with clay, with these advantages such as fine particles,good plasticity and easy drying. But it contained too high iron content and too low silica andalumina content for producing fired bricks and porcelain tiles，on the other hand the fired tailingsamples showed high bulk density and fired shrinkage. Through suitable formulation, it ispossible to prepare fired bricks and porcelain tiles using the iron tailings.2. Fired bricks were made with the low-silicon iron tailings from western Hubei as the mainmaterials together with clay and fly ash, the suitable process conditions and formulation wereinvestigated, the comprehensive properties of tailing bricks from large-scale test were measured.The results showed that the addition of clay and fly ash improved the brick quality. Therecommended mass ratio was the tailings: clay: fly ash=84:10:6, the optimum conditions werefound to be forming water content and forming pressure were respectively in the range of12.5¹5%and20²5MPa, the drying system were100¹05℃for6⁸h, the optimumtemperature system were found to be that the heating rate was about6℃/min, the firingtemperature and holding time were in the range of980¹030℃and2³h. Under theseconditions, the mechanical strength, water absorption and bulk density of the fired specimenswere20.03²3.60MPa,16.54¹7.93%and1.85¹.90g/cm3, respectively. The results oflarge-scale test were consistent with the bench-scale test, and the other physical properties anddurability were well conformed to Chinese Fired Common Bricks standards （GB/T5101-2003）. 3. The samples of tailing fired brick were characterized, the mechanism of formingproperties and microstructures of the bricks were analyzed, and the firing process was discussed.The results showed that the main mineral phases of the products were hematite, quartz, feldsparand apatite, which formed the main framework of fired specimens, were principally responsiblefor the mechanical strength of bricks. Part of feldspar phases reacting with quarts andaluminosilicate formed eutectic solution, which filled with among the crystals and promoted thecompactness of bricks. The brick samples showed the typical grain and bond microstructure, andcrystalline phases were embedded in glassy matrix forming strong entirety, which promoted thegood properties of bricks. Moreover, the firing process was concluded to four stages as drying,heating, firing and cooling. The diffusion predominated in firing process, while some meltingliquid generated in the latter stage of firing, which played an important role to the vitrificationand solid-phase reaction of bricks.4. The unglazed porcelain tiles were prepared using the iron tailings instead of parts oftraditional materials, the suitable formulation range of forming ceramics and the optimumprocess conditions were determined, and the properties of tiles were presented. Results indicatedthat the suitable formulation of the iron tailings substituting completely feldspar should beaddition tailings55⁶5wt.%, kaolin20²5wt.%, quartz sand10²0wt.%, the chemicalcompositions range of green body were SiO₂37⁴4%，Al₂O₃14¹6%，Fe₂O₃25²9%，CaO+MgO4⁵%，K2O+NaO0.7⁰.8%and loss on ignition8.0⁹.5%. The tailing porcelain tilescould achieve full vitrification at about1200℃, revealed a sintering interval of more than40℃.The optimum process conditions were found to be that forming pressure30MPa, firingtemperature1200℃and holding for15min. The obtained porcelain tiles as eco-friendlyproducts were well conformed to the requirements about drying press poecrlain tiles in Chinesestandard specifications Ceramic Tiles （GB/T4100-2006） and Specifications for EnvironmentalLabeling Products-Ceramic Tiles （HJ/T297-2006）.5. The microstructures of the tailing porcelain tiles were discussed, the mechanism of theiron tailings addition could lower the firing temperature and promote the firing densification, andthe main reasons of narrowing densification interval were analyzed, in addition the feasiblesolutions are proposed, the fired process and densification mechanism of porcelain tiles wereprobed.Results revealed that the tiles featured good degree of sintering, high crystallinity with mainmineral phases as residual quartz, hematite, cristobalite, together with small amount anorthite andmullite, and presented in dense glassy and crystalline phase solid solutions with low porosity,which contributed to the densification and full vitrification of porcelain tiles.The high content of Fe₂O₃and CaO in tailings reacted with quartz and aluminosilicate andformed eutectic solution at lower temperature, which promoted the densification of porcelain tiles. Furthermore, Fe₂O₃crystallized form the liquid phases in cooling and were uniformity embeddedin glassy phases, which favored the mechanical strength and hardness of the tiles. The firedprocess of the tailing tiles could be divided into four stages as low temperature heating, oxidizingand decomposing, high sintering and cooling, at last the densification porcelain tiles withmultiphase structure were formed.Through the above research, the feasibility of making fired bricks and porcelain tiles usingthe low-silicon iron tailings was proved, not only resolved the problem of utilizing this kinds oftailings, but also would offer a new resources for building materials, with the double effects ofenvironmental protection and resources saving. Meanwhile，the comprehensive investigation oftailings characterics provided the scientific proof for tailings utilization, the mechanism researchenriched the theoretical systems and offered the theoretical basis for the application anddevelopment of the utilizing low-silicon tailings technologies.更多还原