Research progress on desulfurization technology of high-sulfur bauxite

Bauxite is the main raw material of the alumina industry. However, high-sulfur bauxite constitutes a relatively large proportion of bauxite resource in China. Excessive sulfur impurities in bauxite have significant impact on the Bayer process, such as corrosion of equipment and pipelines, increased consumption of alkali, and difficulties in sedimentation of red mud particles after digestion. As the mainstreams of bauxite desulfurization technologies, the bauxite pre-desulfurization (roasting, electrochemistry, biology, flotation, etc) and Bayer process desulfurization (oxidation and precipitation) need to be fully understood for the further improvement of desulfurization performance. Here, an in-depth review on their mechanisms and advantages/disadvantages is presented.     

Residues recycling: Reducing costs and helping the environment

The aluminum production chain from bauxite to primary aluminum includes refining using the Bayer process, and smelting through electrolysis. This production chain produces two main solid residues, red mud at the refinery and spent pot lining at the smelter. The use of these residues as raw material for other industrial processes can save large amounts of energy, reduce the overall environmental impact, and even improve the emissions of other processes. This paper shows the results of ten years of co-processing of spent pot lining in the cement industry in Brazil and the efforts to develop technologies to reduce the reactivity and use the red mud as raw material for several different processes. This approach, although engineering intensive, can reduce C0₂ emissions and save huge amounts of wasted energy in transport and processing when compared with dedicated recycling or neutralizing processes.     

Enhanced conversion mechanism of Al-goethite in gibbsitic bauxite under reductive Bayer digestion process

The conversion mechanism of Al-goethite under the action of different additives (lime or reductant for typical or reductive Bayer digestion) was investigated by thermodynamic calculation, XRD, and SEM?EDS. The results show that the formation of Fe-substituted hydrocalumite is crucial to converting Al-goethite to hematite during Bayer digestion by adding lime. However, the conversion proceeds more easily under the action of reductant due to the rapid formation of magnetite. Additionally, Bayer liquor composition significantly affects the product composition and also the conversion rate of Al-goethite. Compared to typical Bayer digestion with Al-goethite containing gibbsitic bauxite as raw material, the red mud yield of reductive Bayer digestion decreases from 39.02% to 31.19%, and the grade of TFe in red mud increases from 41.66% to 53.80%.     

平果铝土矿伴生镓的综合利用前景

镓是一种性能优良的电子材料,在现代高新技术和光学领域应用广泛。镓主要以类质同象置换的形式进入其他矿物晶格、微量分散于铝土矿中。我国铝土矿中镓的资源储量丰富,平果铝土矿的镓含量高。系统查明平果铝土矿矿石、赤泥及母液中伴生有益组分的含量及赋存状态,提高矿石中伴生有益组分镓的综合回收率,对提高企业的济效益,具有十分重要的现实意义。     

THE REMOVAL OF SULPHUR COMPOUNDS IN SODA-LIME SINTERING PROCESS FOR PRODUCTION OF ALUMINA

用碱石灰烧结法生产Al_2O_3过程中,由铝土矿、石灰石和燃料等带入的黄铁矿及其他硫的化合物,在烧结时转变为Na_2SO_4,造成碱消耗量的增加和一些生产操作的困难。例如,熟料窑中的“结圈”等。在入窑生料中加入一定数量的还原剂,可以将Na_2SO_4还原为硫化物,并主要以FeS的形式与赤泥一起排走。这个方法从1961年起应用于我国的磁石灰烧结法及Bayer-烧结联合法生产,效果良好。本文提出了部分有关的工厂实践结果和试验数据以及讨论意见。     

Surface charge properties of red mud particles generated from Chinese diaspore bauxite

Acid/basic potentiometric titration can be used to quantify the red mud surface charge properties. The amount of surface active --OH groups and surface charge density on the red mud particles generated from Chinese diaspore bauxite were evaluated from the acid/basic potentiometric titration data in 0.1 mol/L or 0.5 mol/L NaCl solution. The results show that the adsorption of sodium polyacrylate（SPA） on the red mud surface causes the increase of the surface active --OH groups, which makes the point of zero charge（PZC） shift to a lower pH value. However, the adsorption of polyacrylamide（PAM） causes little change. As the concentration of NaCl solution increases, the surface charge becomes more positive in acidic solution and more negative in alkaline solution, which can be attributed to the presence of a porous surface gel coating on the red mud particles.     

高Al2O3浓度拜耳体系生产氧化铝工艺研究

研究了铝土矿的高氧化铝浓度溶出浆的赤泥沉降性,并与生产稀释浆进行了对比分析;考察了体系氧化铝浓度、体系粘度及辅助试剂对高浓度铝酸钠溶液分解产出率及所得氢氧化铝质量的影响.     

碳分母液深度蒸发工艺技术理论研究与工业应用

开发碳分母液深度蒸发工艺新技术，对降低混联法氧化铝生产中赤泥浆总量，降低矿耗和碱耗，缓解熟料窑压力意义巨大。     

Reduction of Red Mud Discharge by Reductive Bayer Digestion: A Comparative Study and Industrial Validation

JOM - A novel design incorporating both reductive Bayer digestion and iron recovery into diasporic bauxite processing is proposed to remarkably reduce red mud discharge. This paper presents a...     

Transformation of hematite in diasporic bauxite during reductive Bayer digestion and recovery of iron

The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate (desilication product, DSP) based on the differences of their surface properties. The results show that the differences of surface properties between magnetite and DSP in zeta potential, wettability and solvation trend facilitate magnetite to agglomerate, grow up and thus to dissociate from DSP. The increments of reductant amount and alkali concentration favor the transformation of hematite in digestion with the relative alumina recovery of 98.91%. Processing the resultant red mud can obtain qualified iron concentrate with iron grade of approximate 60% and recovery of about 86% through magnetic separation, resulting in reduction of red mud emission higher than 70%. The results are potential to develop a novel technology for processing high iron diasporic bauxite efficiently and provide references for comprehensive utilization of high iron red mud.     

贵州某地区含钛铝土矿的溶出行为

对贵州某地区的含钛铝土矿进行了溶出研究,主要考查不同条件对矿石中Al2O3和TiO2溶出率的影响以及钛、铝溶出关系.结果表明,只需添加少量石灰,矿石中的钛在溶出过程便会生成扁平楔状的榻石,不会对矿物形成包裹,消除了钛对铝溶出的阻碍作用;较佳溶出条件为苛碱浓度245g/L,石灰添加量4％,温度240℃,溶出时间70min,该条件下,铝相对溶出率达到95％以上,钛溶出率仅为5.5％.     

Modifying alumina red mud to support a revegetation cover

Alumina red mud, a fine-textured, iron-rich, alkaline residue, is the major waste product of bauxite digestion with caustic soda to remove alumina. The high alkalinity and salinity as well as the poor nutrient status are considered to be the major constraints of red mud revegetation. This research was conducted to evaluate the ameliorating effect of gypsum, sewage sludge, ferrous sulfate, ammonium sulfate, ammonium nitrate, and calcium phosphate on alumina red mud. The effectiveness of the mixtures was evaluated by applying extraction tests and performing experiments using six plant species. Gypsum amendment significantly reduced the pH, electrical conductivity, and sodium and aluminum content of red mud. Sewage sludge application had an extended effect in improving both the soil structure and the nutrient status of the gypsum-amended red mud. Together with the gypsum and sewage sludge, calcium phosphate application into red mud enhanced plant growth and gave the most promising results. For more information, contact A. Xenidis, National Technical University of Athens, Laboratory of Metallurgy, School of Mining Engineering and Metallurgy, GR 157 80 Zografos, Athens, Greece; axen@central.ntua.gr.     

平果铝土矿降低洗矿含泥率的生产实践

针对平果岩溶堆积型铝土矿含泥率较高的特点,为了控制并降低洗矿产品的含泥率,同时保持较高的洗矿生产效率,平果铝土矿通过不断改进并优化洗矿流程生产工艺,有效降低了洗矿含泥率,保证了供矿质量,为氧化铝厂提产降本创造有利条件。     

浅析赤泥堆场防渗工艺设计

结合文山800 kt/a氧化铝赤泥堆场的设计,阐述了赤泥堆场的防渗标准、防渗结构、防渗材料选择、防渗层铺设和污染监测,探讨了确定安全、环保、经济合理的防渗结构的前提和方法.     

铝土矿悬浮溶出技术研究

本文通过溶出试验研究，发现一水硬铝石型铝土矿中粒度对溶出速度影响较大，粗颗粒较难溶出，这表明粗粒赶的矿石是影响一水硬铝石溶出效果的一个重要原因。为了解决粗颗粒的溶出问题，分析了拜耳法氧化铝生产过程中铝土矿溶出器的现状。应用反应工程学理论和工程流体力学理论，提出了铝土矿悬浮溶出技术，并研究开发了有针对性的悬浮溶出装置。经过工业试验，仅改变第一赶溶出反应釜进料方式，在相同的溶出条件下，即可明显改善溶出效果，赤泥A／S平均低0．32，相对溶出率提高1．93％，取得了好的技术经济指标。     

堆积型铝土矿生产氧化铝选址应注意的问题

根据目前部分拟建氧化铝厂前期工作碰到的一些问题,提出了利用堆积型铝土矿生产氧化铝的工厂选址时,应当重视供水、厂外货物运输、赤泥堆放和环境影响4个主要问题,这些问题可供同类工厂选址时参考。     

中等品位铝土矿强化石灰烧结机理及溶出试验研究

针对我国资源特点,本文提出不同干传统的石灰烧结法的强化石灰烧结法机理,采用铝硅比为3.84的矿石,按照钙铝比为1.2～1.6进行配矿,配料以生成铝酸-钙和钙铝黄长石为目的,在烧结温度1290℃和烧结时间90min条件下进行熟料烧成.实验结果表明,强化石灰烧结法烧姑熟料的溶出性能较好,烧结熟料氧化铝溶出率达到了82.8%.物相分析表明,熟料主要物相为铝酸一钙和钙铝黄长石,赤泥中的主要物相为钙铝黄长石.     

锂在氧化铝生产过程中的存在行为

本文对氧化铝生产过程各种物料中锂的含量进行了检测，分别对拜耳法、烧结法和联合法生产氧化铝流程中锂的存在行为、平衡状态进行了分析。氧化铝生产中锂由铝矿石带入，部分锂由氧化铝产品带出，对产品质量有一定影响，生产过程中锂基本处于动态平衡状态，锂对物料中全碱的测定影响可忽略不计。     

低铝硅比时代的中国氧化铝工艺选择

随着中国现阶段氧化铝产能和产量的飞速增长,中国国内铝土矿的矿石品位持续下降,单位产品生产成本持续升高。在此条件下本文按目前的生产现状及价格条件,定量地研究了中低品位铝土矿不同矿石A/S对典型拜耳法、选矿拜耳法及典型串联法的原燃材料和动力消耗费用的影响。找出了在氧化铝生产过程中不同矿石A/S区间内适应的生产工艺。     

初探混联法生产氧化铝的工艺优化

在目前的生产条件下。通过大量的混联法物料衡算，定量地研究了供矿铝硅比、熟料铝硅比和拜年法赤泥铝硅比对混联法的制造成本、能耗和拜年法与烧结法的生产比例的影响规律，提出我国混联法生产进一步优化的方向和途径。并开发了研究和评价的计算软件。为混联法的生产和设计的进一步优化奠定基础。