They found that the optimized process conditions were bauxite/anthracite/slaked lime weight ratio of 100::, reduction temperature at 1450°C and reduction time of 20 min. Under these conditions, highquality iron nuggets and calcium aluminate slag were obtained and shown in Figure 7. The largest size and the highest recovery rate of ...
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Introduction Due to its economics, the Bayer process is still the preferred and most used process globally for producing alumina. Bauxite is the main feedstock of Bayer process. Progressive bauxite quality deterioration is one of the main challenges to the alumina industry.
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Caption: In a demonstration of the basic chemical reactions used in the new process, electrolysis takes place in neutral water. Dyes show how acid (pink) and base (purple) are produced at the positive and negative electrodes. A variation of this process can be used to convert calcium carbonate (CaCO3) into calcium hydroxide (Ca(OH)2), which can then be used to make Portland cement without ...
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Overall typical composition of a bauxite residue is given in Table 2 and based on the process conditions and region, the bauxite residue composition is tabulated as Table 3 and 4, respectively. Next to the major elements like Fe, Al, Si, Ca, and Na, there are also valuable minor elements such as Ga, V, Zr, and rare earth elements (Evans, 2016).
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The excessive production of bauxite residue (red mud) in the Bayer process is one of the major challenges amongst alumina producers. The Pedersen process is known as a combination of smelting reduction of bauxite and leaching treatment of the produced slag for alumina production, and the process also produces an inert bauxite residue (grey mud), which is more suitable for further processing ...
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Therefore, the optimum lime addition in the digestion process of gibbsiteboehmite bauxite should be determined by tests. Mineral Composition Changes During Digestion The mineral compositions in the bauxite residues at 240 ℃ for different digestion times are shown in Fig. 5 .
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Following soda and carbon additions, the addition of lime into the sintering process of 20 g CaO to 100 g bauxite residue (80% excess to stoichiometric requirements to form Ca 2 SiO 4) is necessary to investigate the consumption of free and bound silica in desilication products, relying on higher thermodynamic affinity with calcium.
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In this process, bauxite is smelted and reduced, which yields pig iron and a calcium aluminate slag. Alumina is further produced from the slag through a hydrometallurgical process. In the present study, different bauxites with different chemical compositions are smelted with lime and reduced by coke.
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An improved lime sinter process based on the drysintering is proposed by adding Na 2 Ocontaining compounds to decrease CaO addition and increase alumina leaching property. The molar ratios of CaO to Al 2 O 3 and Na 2 O to Al 2 O 3 are and, respectively.
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In the lime sinter process the additive is a calcium salt (usually calcite — ... Based on the stability field of silica gel formation, a stepwise acid leaching process for bauxite residue is proposed to facilitate downstream processing of the critical metals. Extraction of scandium from bauxite residue by highpressure leaching in sulfuric ...
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An Improved Lime Sinter Process to Produce Al2O3 from LowGrade AlContaining Resources. Yongpan Tian, Xiaolin Pan, Haiyan Yu, Yuejiao Han, Ganfeng Tu, Shiwen Bi; ... and Bauxite Alloys, Processing, and Characterization Reduction Technology Shop Technology Technology Casting
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An improved lime sinter process based on the drysintering is proposed by adding Na2Ocontaining compounds to decrease CaO addition and increase alumina leaching property. The molar ratios of CaO ...
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The effect of lime on gibbsite bauxite digestion is different from its effect on diaspore bauxite due to its different composition and digestion properties [15, 16]. In one report, gibbsite bauxite was digested by adding 1% lime at 145 °C, achieving a better digestion efficiency of %. However, excessive lime addition will lead to excess ...
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Bauxite is generally extracted by open cast mining, being almost always found near the surface, with processes that vary slightly depending on the location. Before mining can commence the land needs to be cleared of timber and vegetation. Alongside this process may be the collection of seeds and/or saplings, for inclusion in a seedbank, which ...
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Soda sintering or limesoda sintering process, began from L ouis Le Chatelier's work in 1855 in obtaining aluminum hydroxide (Al(OH) 3 ) from sintering bauxite with soda at around 1000 °C which
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The common raw material for aluminium production, bauxite is composed primarily of one or more aluminium hydroxide compounds, plus silica, iron and titanium oxides as the main impurities. It is used to produce aluminium oxide through the Bayer chemical process and subsequently aluminium through the HallHeroult electrolytic Process. On a world ...
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Although lime is extensively used when processing diasporic bauxites, the studies on boehmitic bauxites and the overall effects on the process are limited. In this paper, lime impact was investigated at all stages of the Bayer process including the effect on alumina quality, energy and raw material consumptions.
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The Bayer process is the principal method for production of alumina from bauxite worldwide. The modern version of the process (developed in the 1880's) still maintains
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Introduction. Bauxite residue, or red mud, is a solid waste produced from the alumina refining of bauxite ore. Red mud is mostly collected from the Bayer process which uses sodium hydroxide to dissolve the aluminium silicate. Typically, about 1 to tonnes of red mud remains from the production of 1 t of alumina (Zhang et al., 2011).
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A process that involves treatment of ore with lime and soda is used in China and Russia. The Bayer process involves four steps: digestion, clarification, precipitation, and calcination. In the first step, bauxite is ground, slurried with a solution of caustic soda ( sodium hydroxide ), and pumped into large pressure tanks called digesters ...
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Lime can be used to overcome problems when using bauxites with specific and variable chemical and mineralogical characteristics. Although lime is extensively used when processing diasporic...
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Perovskite 1. Introduction Lime is often considered as a panacea in the Bayer process. Its uses are so widespread that there is virtually no unit operation where it does not find an application. Table 1 gives an overview of the main uses of lime in the Bayer process, including low temperature applications (not all applications are given).
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Diasporic bauxite is the major kind in China, characterized by highaluminum, highsilicon, low ratio of Al2O3 to SiO2 [1], complicated mineral compositions [2] and finely disseminated associations of aluminous minerals and silicate minerals [34]. Presently, to produce aluminum oxide in China is usually not Bayer process but sintering process ...
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Abstract The recovery of major components of bauxite residue by carbothermic reduction at °C and subsequent slag leaching in a Na3CO3(aq) solution is studied. Iron recovers primarily to pigiron and lime is added to tune the calcium aluminate slags towards the highly leachable mayenite phase. The concentration of aluminum in the leachate correlates well with the occurrence of ...
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As a hybrid process, bauxite residue undergoes a reductive smelting process with lime addition in an electric arc furnace in order to generate aluminaenriched slag. This slag is subsequently ...
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The Bayer process simulation is based on the modelling of selected and defined unit processes and inputoutput parameters from the published literatures, described in the following section. In the Bayer process simulation, the bauxite ore, extraction liquor and lime addition are mixed and heated in digesters in the pressure leaching step.
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Bauxite residue is the industrial solid waste discharged from the production of alumina by bauxite, which contains a certain amount of ferric oxide in a reddishbrown color, so it is also called "red mud", and is a typical nonferrous metallurgical solid waste (Wang et al. 2018; Xue et al. 2022).The varieties of bauxite residue depend on the grade of the bauxite and alumina production process.
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Sometimes [when?] lime is added at this stage to precipitate the silica as calcium silicate. The solution is clarified by filtering off the solid impurities, commonly with a rotary sand trap and with the aid of a flocculant such as starch, to remove the fine particles.
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A material supplier from Belgium would like to produce limestone powder for his custome...
India is rich in various mineral resources and it is an important mineral processing market
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