Bauxite residue is a highly salinesodic tailings material formed as a byproduct of the Bayer process for alumina production. In situ remediation of bauxite residue has the potential to provide an effective means for accelerated rehabilitation of residue storage areas. However, previous work has predominantly only used chemical and physical amendments to date, limiting rates of pH ...
Lime is an essential reagent required in various process steps of the Bayer process, in which bauxite ore is converted into alumina (Whittington et al. 1997), as illustrated in Fig. is used for improving conversion of goethite to hematite and dissolution of boehmite and diaspore during digestion; control of liquor impurities such as silica, oxalate, titanium and phosphorous; minimising ...
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.
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.
Bauxite residue is a hazardous solid waste generated during the Bayer process of extracting alumina from bauxite ore, the high alkalinity of which limits its largescale industrial applications. In order to reduce the alkalinity of bauxite residue, rich lime additions from 0 to 30 wt.% and high digestion temperatures from 250 °C to 300 °C were performed on a highferrite diasporic bauxite ...
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 ...
Ferric bauxite, a type of bauxite with high hematite content, has yet to be commercialized. Direct reduction [1−2] can realize ferric bauxite comprehensive utilization; however, the sodium carbonate consumption in direct reduction is considerably higher than that in the ordinary bauxite processing technology [3]. Previous research
The Bayer process is the principal method for the production of alumina from bauxite worldwide. The modern version of the process (developed in the 1880's) still maintains the key steps of dissolution of aluminarich minerals into hot caustic solution, separation of the insoluble phases, followed by gibbsite precipitation and calcination of the gibbsite to alumina (Al 2 O 3).
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.
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 ...
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.
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.
The production of alumina (Al2O3) from bauxite via the Bayer process is underpinned by the use of lime in a variety of process reactions. One of the most important is the causticisation of...
Most authors' studies have focused on the pyrometallurgical process, especially in the smeltingreduction process for treating lowgrade bauxite. Sellaeg et al. [74] processed the gibbsitic bauxite mixed with lime and coke via the Pedersen process at 1600 ℃ for 60 min. The separation of pig iron and calciumaluminate slag could be achieved ...
Clays are types of the lowgrade aluminum ores, they're also well abundant which make them a potential substitutes for Bauxite. In this work, lime soda sinter process was adopted for extracting ...
Bauxite residues (also known as 'red mud', 'Bayer process tailings' or 'bauxite process tailings') are generated from alumina production where bauxite is digested in hot NaOH solution via the Bayer process. 22 The production of 1 tonne of alumina generates between 1 and tonnes of bauxite residue. 23 Currently, the yearly global ...
A process flow diagram of the Bayer process is shown in Exhibit 3. The primary purpose of a Bayer plant is to process bauxite to provide pure alumina for the production of aluminum. All bauxite refineries share five common process steps: (1) ore preparation; (2) bauxite digestion; (3) clarification; (4) aluminum hydroxide precipi tation; and (5)
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 ...
To simulate the hydration process of bauxite tailings as supplementary cementitious material, the hydration kinetics of a calcination activated bauxite tailingslimegypsum ternary system was investigated. Hydration heat of the ternary system was measured at 50 °C by an isothermal calorimeter. Kinetics equations were used to simulate the hydration process of the ternary system.
1. Introduction The Bayer process accounts for over 90% of the world's commercial production of alumina. The process involves digestion of bauxite in a caustic soda solution at temperatures ranging from 100 to 250 °C, depending on the form of alumina in the bauxite, gibbsitic, boehmitic or diasporic.
The dominance of Ca in the sintering process is assigned to the excessive addition of lime. Depending upon the refining process adopted by the refinery, Al 2 O 3 ... Wu, Y.: Characterization of red mud derived from a combined Bayer process and bauxite calcination method. J. Hazard. Mater. 146(12), 255261 (2007) Google Scholar ...
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 ...
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...
Bayer process, bauxite is mixed with caustic soda, or sodium hydroxide, and heated under pressure. ... The lime slaker is used to prepare lime slurry which is pumped to the digestion unit Area 04 to improve boehmite extraction. Burnt (calcined) lime, which is produced externally, is stored on site in a large ...
Bauxite residue (BR) is generated as a byproduct of the Bayer process. Approximately tons of BR is generated per ton of alumina production but the quantity of bauxite residue depends upon on the quality of the processed bauxite ore and the processing parameter (Primary Aluminium Production).The annual generation of BR in 2019 alone was estimated as 175 million tons (Archambo and Kawatra ...
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.
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).
Milling: Several meters of rock and clay are removed by blasting, drilling, and bulldozers. The bauxite is then transported to the crushing and washing area, reducing the particle size and increasing the available surface area for the digestion stage. The material that is discharged from the mill is called slurry
The impact of bauxite slurry pumping on the refining process such as bauxite dewatering, additional evaporation requirements etc. must be taken into account in the design of the alumina plant. ... (= bauxite residue [incl. sand] + lime products) maximum t/tA (dry basis): the bauxite residue ("red mud") leaving the refinery after ...
Lime addition in the Bayer process enhances the phase transformation rate of goethite and the digestion performance of alumina in highiron bauxite (Chen and Peng, 1998; Peter, 2017). However, there is no report on the promotion scale, especially for the highcalcium medium system.
Therefore, lime (CaO) and limestone (CaCO 3) are used, as a source of calcium, to harvest cementing calcining RM alone, reactive aluminium phases begin to form at °C. However, at °C, they turn into crystalline corundum (Al 2 O 3 ), a more stable and less reactive phase.
The investigational trial explored the unconfined compression strength and stressstrain characteristics of the lime treated soil composites, treated using combinations of 7% lime and %, %, 1% and 2 % bauxite residue. The lime treated soil composites were moulded in to cylindrical specimens of 38 mm diameter and height of 76 mm, cured ...
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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