【作者】 王耀武；

【导师】 冯乃祥；

【作者基本信息】 东北大学 ， 有色金属冶金， 2009， 博士

【摘要】 2008年我国工业铝产量达到1300万吨以上,约占世界总产量的1/3,但我国用于生产氧化铝的铝土矿自给率已低于50%,铝土矿的缺乏已经成为制约我国铝行业发展的首要问题,低品位铝土矿的选矿拜耳法生产氧化铝将成为我国未来铝工业发展的主要方向之一,但在铝土矿浮选过程中产生约25%的尾矿,这部分尾矿如果不加以利用不仅造成资源的浪费,而且污染环境。目前,25%以上的原铝被用于生产铝硅合金,以低品位铝土矿为原料电热法生产一次铝硅合金,一次铝硅合金精炼加铝稀释后直接配制应用合金,不仅可以节约纯铝而且可以降低能耗,缩短流程。本论文首先对以铝土矿浮选尾矿为原料,烟煤为还原剂在电弧炉内直接熔炼生产一次铝硅合金和工业电热法生产铸造用共晶铝硅合金的生产工艺进行研究,得出以铝土矿浮选尾矿为原料生产的一次铝硅合金由于含铁量较高应用现阶段的生产工艺不适合用于铸造用铝硅合金的生产。对铝土矿浮选尾矿盐酸溶液除铁生产低铁尾矿,然后以低铁尾矿为原料电热法生产一次铝硅合金的工艺进行了研究。浮选尾矿的盐酸浸出除铁过程中,影响氧化铁浸出率的最主要因素为浸出温度,其次是浸出溶液的盐酸浓度,然后是浸出时间,影响最小的是浸出液固比。尾矿中氧化铁浸出率随浸出温度越高、浸出时间增长、浸出液盐酸浓度增大和浸出液固比的增大而越高,但同时氧化铝的浸出率也越高。较佳的浸出条件为：浸出温度80℃,浸出液固比5：1,浸出溶液盐酸浓度22%,浸出时间120分钟,在该条件下氧化铁的浸出率可以达到95%以上,氧化铝的浸出率在4.3%以下,浸出后尾矿中的氧化铁含量可以从10.52%降低到0.6%以下。浸出后的浆料加入絮凝剂进行固液分离,以聚丙烯酰胺为絮凝剂加入浸出料浆中可实现固液的快速分离,沉降后获得的上清液固含在0.2g/L以下。对尾矿盐酸浸出除铁的动力学分析得出,尾矿在盐酸溶液浸出的过程中可分为两个阶段：当氧化铁的浸出率小于55%时,浸出过程速率由界面化学反应控制,其表观活化能为86715J/mol;当氧化铁的浸出率大于60%时,浸出速率由流体反应物HCl在多孔固体中的非稳态扩散控制,其表观活化能为119647J/mol。由于尾矿浸出过程中氯化氢的利用率较低(只有14%),采用浸出液反复蒸馏浸出的方法可提高氯化氢的利用率。浸出液经蒸馏—浸出—蒸馏—浸出后可进行最多五次的反复浸出。每次蒸馏较佳的体积百分比为10%,经五次蒸馏浸出后,浸出液中的氯化铁浓度可达到18.50%,原浸出液中氯化氢的利用率超过50%,每1L浸出液可处理尾矿约0.8公斤。浸出后获得的浸出液可通过先蒸馏浓缩然后高温焙烧的方法处理,处理后获得氯化氢和含部分氧化铝的氧化铁的粉末,氯化氢可通过水吸收进行回收再利用,氧化铁可作为炼铁原料。每吨尾矿的除铁成本在300元以下。以除铁后的尾矿为原料,以神府烟煤为还原剂,亚硫酸纸浆废液为粘结剂,经配料计算和团块性能测试得出较佳的配料及制团条件为：每100公斤尾矿配入烟煤52.34公斤,干粉粘结剂9公斤,水9公斤,较佳的制团压力为20-25MPa,物料粒度为0.087-0.124mm。配好的团块在电弧炉内熔炼获得的一次铝硅合金含铝量达到了55%以上,含铁量低于1.7%,合金其它主要杂质为钙、钛、钾和钠,熔炼后尾矿中的铝元素的回收率达到了90%以上,硅元素的回收率达到85%以上。获得的一次铝硅合金可用于生产钛含量较高的铸造用铝硅合金或新型的铝硅钛多元合金。在真空碳管炉内对一次铝硅合金的还原机理进行了研究,通过对除铁尾矿在真空碳管炉内不同温度下获得产物进行物相分析,得到除铁尾矿在真空碳管炉内的还原过程为：首先是在较低温度下(1600℃以下),尾矿中的氧化硅与碳反应生成SiC,少量的氧化硅被还原成为硅并与由铁的氧化物还原成的单质铁结合成为硅铁化合物(主要是Fe2Si、Fe5Si3和Fe3Si),当温度继续上升到1700-1800℃时,尾矿中的氧化铝开始与碳反应生成铝氧碳化物(主要是Al4O4C,还有少量的A12OC),当温度继续升高到1800-1900℃时,在较低温度生成的铝氧碳化物被碳化硅分解,生成铝和硅,最终成为一次铝硅合金。实验结果证明铝土矿浮选尾矿经盐酸浸出除铁后生产的一次铝硅合金可作为生产铸造用铝硅合金的原料,该方法生产一次铝硅合金不仅节约了资源而且保护了环境,具有一定的实际意义。更多还原

【Abstract】 The production of aluminum in China is more than 13 million tons in 2008, which is about one-third of the world’s total output. But the bauxite self-sufficiency rate has been below 50% and the lack of bauxite in China has become the the primary issue to constrain the development of aluminum industry. The method producing Al2O3 by ore-dressing Bayer process with low-grade bauxite is one of the main directions of aluminum industrial development. It is about 25% of the low grade bauxite becomes tailings in the process. If the tailings is not be used, it will not only waste the resources, but also pollute the environment. At present more then 25% of the industrial aluminum was used in the production of Al-Si alloys. Producing the coarse Al-Si alloy by using bauxite tailings as raw material and then the cast Al-Si alloys can be obtained after the coarse Al-Si alloy diluted by pure aluminum and refined by purificant. This method can save industrial aluminum, reduce power consumption and shorten the process.In this paper, the process was studied that is producing coarse Al-Si alloys by using bauxite tailings as raw material, soft coal as reductant in arc furnace and the process of producing cast eutectic Al-Si alloys by carbothemal reduction in industry were studied. The results show that the content of iron in the coarse Al-Si alloys is too high to producing cast Al-Si alloys by using the production technique at the present stage.The removing iron process of bauxite tailings by leaching with hydrochloric acid to produce low iron bauxite tailings and the process of producing coarse Al-Si alloy used the bauxite tailings which removed iron as raw material were studied.In the removing iron process of bauxite tailings by leaching with hydrochloric acid, the most important influencing factor is leaching temperature, followed by the concentration of hydrochloric acid, and then the leaching time, the minimal is liquid-solid ratio. The leaching rate of iron oxide in tailings rise with the rising of leaching temperature, the accreting of the concentration of hydrochloric acid, the growing of leaching time and the increasing of liquid-solid ratio. The optimal leaching factors are leaching temperature 80℃, concentration of hydrochloric acid 22%, leaching time 120min and liquid-solid ratio 5:1. On this conditions, the leaching rate of iron oxide is more than 95%, the leaching rate of aluminum oxide is less than 4.3%, and the iron oxide content can be reduced from 10.52% to 0.6% after leaching process.The result of kinetics analysis of leaching of bauxite tailings with hydrochloric acid shows that there are two phases in the process:the rate of iron dissolution is controlled by the interface chemical reaction when the leaching rate of Fe2O3 is lower than 55%. Its apparent activation energy is 86715J/mol. The rate of iron dissolution is controlled by the non-steady-state diffusion in porous solids of the fluid reactant HCl when the leaching rate of Fe2O3 is higher than 60%. Its apparent activation energy is 119647J/mol.The flocculants were used for solid-liquid separation in the slurry of leaching tailings. The tailings and leaching solution can rapid separation used as polyacrylamide flocculant and the solid content in the supernatant is below 0.2g/L.Because of the low utilization of HCl (only 14%), the method of repeated distillation and leaching was investigated to increase the utilization of hydrogen chloride. The leaching solution can leach five times by distillation-leaching- distillation-leaching, the better distillation rate is 10% every time. After fifth leaching, the utilization of HCl is more than 50%, the Ferric chloride concentration is about 18.5%, and it can deal with 0.8 kg bauxite tailings every liter hydrochloric acid.The solution obtained by leaching of bauxite tailings was concentrated by distillation firstly and then baked on high temperature. Hydrogen chloride vapor and ferric oxide which concluded some aluminum oxide can be obtained after the leaching solution treated, the hydrogen chloride vapor can be absorbed by water to produce hydrochloric acid and recycle, the ferric oxide can be used as raw materials of iron. The cost is below three hundred yuan per ton bauxite tailings.Mixture and briquetting by using bauxite tailings which removed ferric oxide as raw materials, soft coal as reductant, sulfite pulp waste liquor as agglomerant. Based on the mixture calculating and the testing of conglomeration property, the optimum condition of mixture and briquetting are as following:adding 52.34 kilograms soft coal, nine kilograms agglomerant power and nine kilograms water every one hundred kilograms tailings. The pressure of briquetting is 20-25MPa and the grain of raw materials is 0.087-0.124mm.The coarse Al-Si alloy produced in arc furnace which used the tailings removed ferric oxide as raw material contained more than 55% aluminum,30.87% silicon and lower than 1.7% Fe. The main impurities were calcium, titanium, potassium and sodium. The aluminum recovery was 91.78%, the silicon recovery was 87.89%. the coarse can be used to produce cast Al-Si alloys or new type of Al-Si-Ti complex alloys.The reduction mechanism of bauxite tailings was studied in vacuum carbon tube furnace. The phases of products in different temperatures and carbon additions were analyzed by XRD. The reaction process of producing coarse Al-Si alloy was studied. It showed that the carborundum was gained in low temperature (below 1600℃) when the raw materials deoxidized in the vacuum carbon tube furnace. When temperature rised to 1700-1800℃, alumina began to react with carbon to form aluminum oxygen carbide. When the temperature was higher than 1900℃, the carborundum decomposed aluminum oxygen carbide into aluminum and silicon, and the aluminum and silicon reacted to form coarse Al-Si alloy.The results show that the coarse Al-Si alloy produced by carbothermal reduction used the bauxite tailings which removed iron by leaching with hydrochloric acid as raw material can be to produce cast Al-Si alloys or new type of Al-Si-Ti complex alloys. The process not only save save resources but also protect the environment, and It has significance for practice reference.更多还原