拜耳法赤泥碳热还原熔炼直接制备低镍铬合金铸铁的研究

发布时间：2018-03-08 08:05

本文选题：拜耳法赤泥　切入点：碳热还原熔炼　出处：《广西大学》2017年博士论文　论文类型：学位论文

【摘要】：拜耳法生产氧化铝过程中产生的强碱性赤泥,因其颗粒细、化学组成复杂、难以回收和综合利用率低、对生态环境造成极大的威胁,严重阻碍了铝工业的可持续发展。针对以上问题,本工作以广西平果铝拜耳法赤泥为主要原料,引入与赤泥化学组成相近的含镍铬元素的红土镍矿,采用电弧炉碳热还原熔炼技术探索了从拜耳法赤泥直接制备低镍铬合金铸铁的可能性。首先,对熔融选择性还原有价金属元素的可能性进行了热力学分析,并进行了碳热还原熔炼的实验模拟;其次,在实验模拟基础上,设计了一台适用于工程化研究的单电极直流埋弧式电弧炉,实施了赤泥添加红土镍矿的碳热还原熔炼实验,直接制备了低镍铬合金铸铁;最后就低镍铬合金铸铁应用的一些关键问题进行了研究。主要结论如下:1.首次提出了采用单电极直流埋弧式电弧炉,通过加入红土镍矿和其他氧化物矿料,使赤泥中金属氧化物依次还原并使得金属与熔渣分离的赤泥材料利用方法。结合下游产业,探索了低镍铬合金铸铁的使用性能,并在实际生产情况下,证实了材料的使用性能优于现有材料,为实现拜耳法高碱赤泥材料化利用的工程化技术提供了试验依据。2.碳热还原热力学分析得出,在反应温度为700℃～1800℃之间,全赤泥中主要金属氧化物的还原容易程度为:FeVCrMnTiSiZr,还原得到的是金属/石墨或者金属/碳化物体系;Si、Zr、Al、Mg和Ca的氧化物会相互作用生成各种复杂化合物,形成炉渣。赤泥添加红土镍矿后,混合料中的Ni、Cr、Mn、V、Ti元素会随Fe元素一起被还原。3.往赤泥中适量添加红土镍矿,有助于获得还原熔炼所需的适宜碱度,促进多种氧化物的还原和进一步丰富铁合金的元素组成。真空碳热还原实验模拟表明,全赤泥碳热还原熔炼时,只有Cr、Ti、Si三种元素随铁元素一起得到了还原,且总直收率和Fe、Cr、Ti元素的直收率都比较低,分别只有76.45%、78.03%、45.64%和6.08%。而当赤泥添加红土镍矿后,碳热还原熔炼效果得到显著改善,合金的总直收率和Fe、Ni、Cr、Ti的直收率分别为84.86%、79.44%、83.72%、58.96%和39.74%。合金组织主要由铁基体和石墨相组成。4.采用单电极直流埋弧式电弧炉,以赤泥和红土镍矿为原料,利用高温碳热还原熔炼和中频感应电炉精炼工艺可以直接制备高质量低镍铬合金铸铁。所制备的合金铸铁中镍和铬含量分别为1.59-2.06%和0.76-0.83%。Ni、Cr元素均匀分布在铸铁的莱氏体基体中。随着铸铁中Ni、Cr元素含量的增加,硬度和腐蚀性能逐渐提高。5.通过碳热还原熔炼制备了与HT250、RuT380和QT450成分相近的低镍铬合金铸铁。随着镍铬元素添加,铸铁组织中相的种类没有变化,均是由石墨+珠光体+少量铁素体组成,但这些相的形态分布发生了相应变化,尤其是珠光体得到一定程度上的细化。从力学性能方面看,含有镍和铬元素的铸铁性能优于仅含有镍的铸铁,前者珠光体组织更细小更均匀。与标准的HT250、RuT380和QT450相比,开发的低镍铬合金铸铁的抗拉强度分别提高14.8%、31.3%和44.5%,铸铁的腐蚀性能也得到提高。
[Abstract]:From the Bayer process of alumina production of red alkaline mud, because of its fine grain, chemical composition is complex, difficult recovery and comprehensive utilization rate is low, causing a great threat to the ecological environment, seriously hindered the sustainable development of aluminum industry. To solve the above problems, this work in Guangxi Pingguo aluminum Bayer red mud as the main raw materials, the introduction of the chemical composition of red mud and similar elements containing nickel chromium nickel laterite, using carbon arc furnace smelting technology directly explores the possibility of preparation of nickel chromium alloy cast iron from Bayer red mud. First of all, the possibility of selective reduction of molten metal elements were analyzed and simulated, carbothermal reduction smelting experiment secondly, on the basis of; experimental simulation, design a suitable for Engineering Research of single electrode DC submerged arc furnace, the carbon heat of laterite nickel ore also add red mud The original melting experiments of nickel chromium alloy cast iron have been prepared directly; it makes a study of some key problems of low nickel chromium alloy cast iron application. The main conclusions are as follows: 1. first proposed the use of single electrode DC submerged arc furnace, by adding laterite and other oxide ore material, the metal oxide are reduced and red mud the separation of metal slag and red mud material utilization method. Combined with the downstream industry, explores the performance of nickel chromium alloy cast iron, and in the actual production situation, confirmed the performance is superior to the existing materials, in order to realize the engineering technology of high alkaline red mud material Bayer utilization provides the experimental basis for the carbothermal reduction of.2. thermodynamic analysis shows that the reaction temperature is between 700 to 1800 DEG C, the reduction degree of the main metal oxide easily all in red mud is FeVCrMnTiSiZr, is obtained by reduction of metal Graphite or metal carbide / system; Si, Zr, Al, Mg and Ca oxides will interact to generate various complex compounds, the formation of red mud slag. Addition of laterite, the mixture of Ni, Cr, Mn, V, Ti elements with Fe elements is reduced.3. to add the amount of red mud in laterite nickel, contributes to the reduction of suitable basicity to promote a variety of melting, the oxide reduction and further enrich the iron alloy elements. The experimental results show that vacuum carbothermal reduction, reduction smelting of red mud carbon hot, only Cr, Ti, Si three elements with the iron element together were reduced, and the total yield and Fe, Cr, yield of Ti elements are relatively low, only 76.45%, 78.03%, 45.64% and 6.08%. when adding red mud laterite, improved the carbon thermal reduction smelting effect, the total yield of alloy and Fe, Ni, Cr, the yield of Ti were 84.86%, 79.44%. 83.7 2%, 58.96% and 39.74%., the microstructure is mainly composed of iron matrix and graphite phase composition of.4. single electrode DC submerged arc furnace, with red mud and laterite, and reducing process of medium frequency induction furnace can direct the preparation of high quality nickel chromium alloy cast iron by carbon thermal refining process. The content of chromium and nickel alloy the preparation of iron were 1.59-2.06% and 0.76-0.83%.Ni, Cr elements are evenly distributed in the ledeburite cast iron matrix. With cast iron Ni, the increase of Cr content, hardness and corrosion resistance of.5. gradually improved by carbon thermal reduction smelting was prepared with HT250, nickel chromium alloy cast iron composition is similar to RuT380 and QT450 with. Ni Cr cast iron added, no change in phases are composed of graphite, pearlite and a small amount of ferrite, but the distribution of phase changes, especially to pearlite On the degree of refinement. The mechanical properties, cast iron containing nickel and chromium is better than only containing nickel, the finer pearlite is more uniform. Compared with standard HT250, RuT380 and QT450, the tensile strength of nickel chromium alloy cast iron development were increased by 14.8%, 31.3% and 44.5%, the corrosion resistance of cast iron has also been improved.

【学位授予单位】：广西大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG257

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