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.
The process is based on smelting reduction of basic (steelmaking slags), acidic industrial residues (fly ash, bottom ash, etc.) and additives like bauxite, lime, etc. based on requirement. The process uses electrically heated ladle furnace or smelting reduction . This process can be used to produce fluxes of the required composition by treating ...
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.
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 ...
The Bayer process: How alumina is produced from bauxite. The Bayer process is carried out in four steps. First, after the bauxite is crushed, washed and dried, it is dissolved with caustic soda at high temperatures. Next, the mixture is filtered to remove the impurities, called "red mud," which is properly discarded. The remaining alumina ...
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 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 ...
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 ...
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)
Based on lime sintering method, a novel process of alumina production from lowgrade bauxite containing sulfur or fly ash is carried out in this paper. The phase of alumina transforms from 12CaO·7Al 2 O 3 (C 12 A 7) to 4CaO·3Al 2 O 3 ·SO 3 (C 4 A 3 S), whose alumina leaching property is better, through decreasing sinter temperature and time ...
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 ...
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 ...
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).
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.
The present study deals with the recovery of metallic Fe and an Alionrich liquid from bauxite residue (BR), with an Naionrich liquid phase that could potentially be recycled or recovered as NaOH. First, BR was mixed with sodium hydroxide in mass ratios of 80/20 and 74/26, respectively. Then, each mixture was roasted under pure H2 for 2 h at 500 °C, 550 °C and 600 °C. The thermal ...
The bauxite soda/lime sinter process, used for lowgibbsite highsilica bauxites, is discussed below in Section One of the byproducts of the sinter process is calcium silicate 2CaO·SiO 2, also known as Portland cement. Portland cement is one of the world's largest industrial production products at around 5 billion tonnes a year (an order ...
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 ...
Lime is used extensively within the Bayer process, where it performs many useful functions. In particular, it can enhance the extraction of alumina (improving the dissolution of boehmite and diaspore or the conversion of aluminogoethite), control liquor impurities (desilication, causticisation or phosphorous control), assist with the removal of impurities from the pregnant liquor (liquor ...
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 ...
During the digestion process of the Bayer method, lithium and gallium in bauxite will enter into the sodium aluminate solution (Tang et al. 2020; Xu et al. 2018 ), which will return to the digestion process for recycling after the precipitation of aluminum hydroxide from the decomposition of crystal species.
The mechanochemical processing of bauxite with lime has been investigated. The milling of bauxite and lime mixtures in an attritor mill resulted in the formation of an iron rich hydrogarnet phase in bauxite/lime slurries containing greater than 9% CaO. ... The role of lime in the Bayer process with less lime is to eliminate the harmful effect ...
The basis of the Bayer process is an understanding of the characteristics of the sodiumhydroxide—sodiumaluminate solution relationship, namely its ability to keep sodiumaluminate in a dissolved state over a wide range of conditions, especially on the temperature and caustic soda concentrations.
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 ...
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.
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).
1. Milling The bauxite is washed and crushed, reducing the particle size and increasing the available surface area for the digestion stage. Lime and "spent liquor" (caustic soda returned from the precipitation stage) are added at the mills to make a pumpable slurry. 2. Desilication
Of all Bayer process impurities, few attract more attention than the simplest dicarboxylate. While some oxalate enters the Bayer process with bauxite as oxalic acid adsorbed on various minerals, the majority is created by the oxidation and pyrolysis of bauxite organics under Bayer digestion conditions. The rate of its formation in digestion is ...
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 ...
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 ...
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).
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
The flotationBayer process has been widely applied in the alumina refineries, but it introduces large amounts of hazardous organic reagents and produces tailings totaling of about 25% of the initial bauxite ores in weight. 25,26 The lime Bayer process has been also employed to process a portion of highsilica bauxite, but it cannot ...
The lime used was industrialgrade lime, and the digestion liquid was prepared by industrial sodium aluminate solution and analyticalgrade sodium ... The review can advance the current technology on the comprehensive utilization of gibbsitic bauxite, especially process discharge reduction approaches and largescale abatement ways for red mud. ...
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 ...
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 ...
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