【作者】 杨栋；

【导师】 冯乃祥；

【作者基本信息】 东北大学 ， 有色金属冶金， 2010， 博士

【摘要】 选矿拜耳法生产氧化铝工艺的开发,对提高我国氧化铝工业的市场竞争力,合理利用中低品位铝土矿资源做出了重大贡献。但是,选矿过程中要产出占原矿25%左右的尾矿,这部分尾矿如不加以利用不仅会浪费资源,而且还会占用土地,污染环境。目前,大约60%的铝是以铝合金的形式进入消费领域的,其中,尤以铝硅合金的消费量为大。以铝土矿浮选尾矿为原料,碳热还原法生产铝硅合金较之传统的兑掺法,可以缓解铝土矿资源的压力,充分利用二次资源,减少设备投资,降低能耗,提高能量利用率,是未来铝工业发展的趋势。本文首先对以铝土矿浮选尾矿、烟煤、亚硫酸盐纸浆废液为制团原料的物料配比进行了准确地计算,得出理论物料配比为铝土矿浮选尾矿:氧化铝:烟煤:干粉粘结剂:水=100:25.1:74.0:19.7:7.91。然后,在此基础上,以抗压强度和气孔率作为衡量生团块性能的指标,通过单因素实验和正交实验考察了制团压力、干粉粘结剂配入量、配水量及尾矿粒度对生团块性能的影响。结果表明,对生团块抗压强度和气孔率影响最大的分别是干粉粘结剂含量和尾矿粒度,配水量对二者的影响最小。最佳的工艺条件为:制团压力22.5 MPa,干粉粘结剂含量9%,配水量13%,尾矿粒度0.420～0.178 mm,此时生团块的抗压强度为27.8 MPa,气孔率为18.4%,均优于实际工业指标。实验同时研究了焙烧条件对团块性能的影响规律。结果发现,团块的气孔率随着焙烧温度的升高及焙烧时间的延长而逐渐增大,且增大的幅度较大,而抗压强度则不断下降,下降的幅度逐渐变小。在焙烧温度升至500℃之前,团块几乎不导电,此后在700℃焙烧时,其电阻率下降明显,1000℃后电阻率降幅趋缓,并有逐渐增大的趋势。在真空碳管炉中以氩气为保护气体进行了碳热还原铝土矿浮选尾矿制取一次铝硅合金的研究。结果表明,当气体压力接近常压,反应温度1900℃,反应时间1h,烟煤配入量为理论量的95 wt.%时,可获得质量较优的一次铝硅合金。所获得的一次铝硅合金由6个相组成,包括Al-Si-Fe相,碳化物相及氧化物相。电弧炉冶炼过程中,当输出电流稳定在1100 A时,合适的输出电压为25～30 V。配煤量为理论量的93 wt.%时,所得炉底残渣中Al₂O₃及SiC的含量较小。所获得的一次铝硅合金包括有6个相,主要是一次合金相,其中铝含量为52.5%,硅含量为23.2%,另含有很少量的的金属杂质钛、钙等以及氧化物和碳化物。烟气的主要成分为Al₂O₃、SiO₂。对碳热共同还原Al₂O₃、SiO₂制取铝硅合金的热力学行为进行了分析,得出该还原反应需很高的温度,合适的反应温度为2000～2100℃。利用XRD、SEM-EDS等技术分别对真空碳管炉中各不同反应温度及电弧炉内不同反应区带的产物进行了分析,利用TG/DTA技术研究了在动态气氛下的整个碳热还原反应过程。结果表明,碳热共还原Al₂O₃、SiO₂的反应过程与碳热还原铝土矿尾矿的反应过程极为相近,可分为4个阶段:烟煤热解阶段;Al₂O₃、SiO₂的晶型转变阶段;碳化物的生成与分解阶段;生成物的损失阶段。关于碳热共还原Al₂O₃、SiO₂的4种还原机理中,碳化物生成与分解机理能较好地解释反应过程中出现的反应现象,并根据实验现象对这一理论进行了修正,提出了具体的反应方程为:SiO₂+3C=SiC+2CO, 2Al₂O₃ + 9C = Al₄C₃ + 6CO,3SiO₂+2Al₄C₃=8Al+3Si+6CO,3SiC+Al₂O₃=2Al+3Si+3CO。利用DTA技术在动态高纯氩气气氛下以不同的升温速率10,15,20和25 K/min对碳热法制取铝硅合金的动力学行为进行了研究。结果表明,不同的升温速率下均存在6个吸热峰,这6个峰所处的温度范围大致在1220～1240 K、1340～1360 K、1680～1730 K、1850～1950 K、1970～2050 K、2100～2160 K。利用Flynn-Wall-Ozawa（FWO）法和Kissinger法计算了碳热还原过程中各个吸热峰的表观活化能,每个吸热峰的平均表观活化能依次为:848.9,945.4,569.7,325.7,431.9和723.1kJ/mol,并进一步应用Kissinger法获得了反应级数（n）、频率因子（A）等重要的动力学参数,结合所得的活化能E值,确定了反应动力学方程为:而后,通过理论分析和实验对其进行了解释和验证。更多还原

【Abstract】 The development of ore dressing Bayer process contributes to improving the alumina market competitiveness and to using soundly the middle-low grade resources in China. In the process of ore dressing, however, has to produce plenty of floated tailings occupied about 25% of raw ore.It would not only consume resources,but also occupy land and pollute environments if these tailings cannot be used. At present time, the consumption quantity of Al-base alloys accounts for 60% in Al consumption field, and of all the Al-base alloys, the largest consumption quantity is Al-Si alloy. Compared with fusion method, preparation of primary Al-Si alloy by carbothermal reduction owning lots of merits such as lower requirement of materials, better usage of the secondary resources, lower price equipments and higher energy ratio, is the future development trends of aluminum industry.The ratio of raw materials, consists of bauxite floated tailings, alumina, bituminite and sulphite pulp liquor, was calculated exactly in this paper. The results shown that the theoretical ratio were tailings: alumina: bituminite: sulphite pulp liquor: water=100: 25.1:74.0:19.7:7.91.Based on these, the influences of pressing pressure, dry agglomerant content, moisture content and particle size on the properties of green pellets were investigated by single factor and orthogonal experiments using the compressing strength and pore ratio as indexes. The optimum conditions for the properties of green pellets are as follows: the pressing pressure 22.5 MPa, dry agglomerant content 9%, moisture content 13% and particle size 0.420～0.178 mm. Under the optimum conditions, the compressing strength and pore ratio of green pellets are 27.8 MPa and 18.4%, respectively. Both of them are better than industry applied indexes.The properities of roasted pellets were also be tested in the study.The results indicated that with the roasting temperature rising and the roasting time prolonging,the pore ratio of pellets increased,and the increasing amplitude was great.Meanwhile,the compressing strength decreased continuously,the decreasing amplitude,however,became small.When the roasting temperature bellowed 500℃,the pellets hardly conducted.Nevertheless, when the roasting temperature rised to 700℃,the resistivity decreased apparently.After 1000℃, the decreasing amplitude of resistivity was small,and the increasing tendency emerged inversely.Preparation of primary Al-Si alloy from bauxite floated tailings by carbothermal reduction process was studied in vacuum graphite furnace with argon as the protective atmosphere. It was found that when the atmospheric pressure approach to 0.1 MPa, heating temperature 1900℃wintering time 1 h and bituminite content 95 wt.% of theoretic bituminite content, the composition of the products was preferable.The primary alloy obtained consisted of 6 phases, besides primary Al-Si alloy phases, there were oxides and carbides phases existed.In the process of smelting operated in arc furnace, when the output current was 1100 A, the suitable voltage was 25～30 V. Meanwhile, when the bituminite content was 93 wt.% of the theoretic amount, the content of Al₂O₃ and SiC in the slag was relatively small. The alloy obtained composed of 6 phases including mainly primary Al-Si alloy phases, and minute impurities such as Ti,Ca,oxidants and carbides.The Al content was 52.5%, Si content was 23.2% in the obtained alloy.The producted fume was mainly composed of Al₂O₃ and SiO₂.The thermodynamic analysis on the carbothermal reduction of Al₂O₃ and SiO₂ was carried out, the results shown that the reduction temperature was high to 2000～2100℃.The composition of products obtained under different temperature in vacuum graphite furnace and different reaction zone in arc furnace was studied by XRD, SEM coupled with EDS methods and the process of carbothermal reduction was tested by TG/DTA technology. It was found that the process of carbothermal reduction of bauxite floated tailings is similar to that of Al₂O₃ and SiO₂, which can be divided into 4 stages: bituminite pyrolysis stage, the crystal phase transformation of Al₂O₃ and SiO₂ stage, the formation and decomposition of carbides stage and products loss stage.Of the 4 mechanisms of carbothermal reduction of Al₂O₃ and SiO₂, the formation and decomposition of carbides theory might be the best one to interpret the reaction phenomena, and this theory was amended according to test phenomena as well,the concrete reaction equations were as follows: SiO₂+3C=SiC+2CO, 2Al₂O₃ + 9C = Al₄C₃ + 6CO,3SiO₂+2Al₄C₃=8Al+3Si+6CO,3SiC+Al₂O₃=2Al+3Si+3CO.The kinetics of preparation of Al-Si alloy by carbothermal reduction of Al₂O₃ and SiO₂ was studied by means of differential temperature analysis （DTA） at different temperature rising rates of 10,15,20,25 K/min. It was shown that there were 6 endothermic peaks in each different heating-up velocity,and the temperature ranges of these 6 endothermic peaks were in 1220～1240 K, 1340～1360 K, 1680～1730 K, 1850～1950 K,1970～2050 K, 2100～2160 K,respectively.The apparent activation energy of each endothermic peak was obtained by Flynn-Wall-Ozawa and Kissinger methods as follows: 848.9, 945.4, 569.7, 325.7,431.9 and 723.1 kJ/mol. Reaction orders, frequency factors and kinetic equations were also determined: Furthermore, the feasibility was verified by theory and test.更多还原