拜耳法赤泥综合回收铝和铁的研究

【作者】 常军；

【导师】 邵延海； 朱从杰；

【作者基本信息】 昆明理工大学 ， 矿业工程（专业学位）， 2018， 硕士

【摘要】 赤泥是氧化铝工业生产氧化铝过程中所产生的工业废渣,具有粒度细、组成复杂、放射性和强碱性的特点,极易引起土壤碱化、地下水污染、大气污染、放射性污染等一系列环境问题,而且还有赤泥坝溃坝风险。但同时,赤泥中含有铁、铝、钛、钠及多种稀土元素,是一种宝贵的二次资源。本论文以广西平果铝业拜耳法赤泥为试验对象,在对其进行一定工艺矿物学分析的基础上,采用“还原（碱性）焙烧-碱浸-磁选”工艺,对赤泥中的铝和铁进行综合回收。主要结论如下:1.论文查明了试验用拜耳法赤泥的工艺矿物学特性。研究发现:试验用拜耳法赤泥全铁含量24.32%,主要以Fe₂O₃（赤铁矿）和α-FeO（OH）（针铁矿）的形式存在,且前者分布量远高于后者;赤泥中Al₂O₃含量16.90%,Al主要以AlO（OH）和Al（OH）₃（氢氧化铝）的形式存在,亦有部分Fe和Al以类质同象的形式存在于Ca₃(Al_0.13Fe_0.87)₂（SiO₄）_1.15（OH）_5.4（水化石榴石）中;赤泥中有益元素主要为铁、铝、钛,脉石及造渣元素主要为二氧化硅和氧化钙;试验用拜耳法赤泥粒径细小,-45μm粒级占72.82%,铁在该粒级的分布率为66.44%。2.论文明确了在还原（碱性）焙烧、碱浸、磁选过程中各因素对赤泥中铝、铁提取的影响规律,并确定了赤泥综合回收铝和铁的最佳工艺条件。研究发现:采用“还原（碱性）焙烧-碱浸-磁选”工艺,在焙烧温度1150℃,焙烧时间60min,氧化钙添加量5 g·（100 g red mud）^-1,碳酸钠添加量15 g·（100 g red mud）^-1,活性炭添加量15 g·（100 g red mud）^-1,冷却方式为水淬急冷,磨矿细度96.84%-0.038mm（磨矿时间30min）,磁滚筒激磁电流5A（1370Oe）)的条件下,拜耳法赤泥中铝的浸出率为88.37%,磁选铁精矿品位为83.38%,回收率为72.46%。3.论文对焙烧过程中主要元素的物相变化进行了研究。研究发现:在添加适宜比例氧化钙、碳酸钠、活性炭的情况下,经还原（碱性）焙烧,赤泥中的铝主要转化为了可溶性铝酸钠、铁主要被还原为强磁性的铁单质及部分磁性铁,硅主要转化为了硅酸钙,为后续硅、铝、铁的分离奠定了基础。更多还原

【Abstract】 Red mud is an industrial waste residue produced in alumina production process.It has the characteristics of fine granularity,complex composition,high radioactivity and strong alkalinity,thus causing environmental problems,such as soil alkalization,groundwater pollution,atmospheric pollution,radioactive pollution.Besides,it has the risk of dam-break.However,red mud,at the same time,contains iron,aluminum,titanium,sodium and a variety of rare earth elements,which is a valuable secondary resource.In this paper,the red mud of Pingguo aluminum-Bayer process in Guangxi was taken as the experimental object.On the basis of certain mineralogical analysis,the process of“reduction（alkaline）roasting-alkali leaching-magnetic separation”was adopted to recover the aluminum and iron from red mud comprehensively.The main conclusions are as follows:1.The technological mineralogical characteristics of red mud from bayer process were investigated in this paper.The results shows that the total iron content of red mud used in the test is 24.32%.It mainly exits in the form of Fe₂O₃（hematite）andα-FeO（OH）（goethite）,and the distribution of the former is much higher.The content of Al₂O₃ in red mud is 16.90%and Al is mainly in the form of AlOOH（diaspore）and Al（OH）₃（aluminum hydroxide）,and some Fe and Al exist in the form of isomorphism in Ca₃(Al_0.13Fe_0.87)₂（SiO₄）_1.15（OH）_5.4（hydrated garnet）.The beneficial elements in red mud are mainly iron,aluminum,titanium.The gangue and slagging elements are mainly silicon dioxide and calcium oxide.The particle size of red mud by Bayer method is fine,particle size of-45μm counts for 72.87%in which the distribution of iron is 66.44%.2.The effects of various factors on the extraction of aluminum and iron in red mud during“reduction（alkaline）roasting-alkali leaching-magnetic separation”process were clarified in this paper,and the optimum technological conditions for comprehensive recovery of aluminum and iron from red mud were determined.Research shows that the leaching rate of aluminium can reach 88.37%,and the iron concentrate of 83.38%grade and 72.46%recovery can be be obtained by“reduction（alkaline）roasting-alkali leaching-magnetic separation”process under the optimum conditions as follows:addition amount of 5 g·（100 g red mud）^-1 CaO,15 g·（100 g red mud）^-1 Na₂CO₃,and 15 g·（100 g red mud）^-1 actived carbon powder,roasting temperature of 1150℃,roasting time of 60 min,cooling mode of water quenching,grinding fineness of 95.84%-0.038mm（grinding time 30 min）and exciting current of5A（1370Oe）.3.The phase transformation of the main elements during the roasting process were studied in this paper.It was found that under appropriate proportion of calcium oxide,sodium carbonate and activated carbon,after reduction（alkaline）roasting,the aluminum in red mud mainly converts to soluble sodium aluminate,and iron was reduced to strong magnetic metallic iron and part magnetic iron.While silicon mainly transforms calcium silicate,which laid the foundation for the subsequent separation of silicon,aluminum and iron.更多还原