Decarburization and impurity removal method for high-carbon bauxite

Abstract

The invention relates to the technical field of impurity removal and quality improvement of non-ferrous metal ores, in particular to a decarburization and impurity removal method of high-carbon bauxite, which comprises the following steps: blending qualified mother liquor by using liquid caustic soda, grinding the bauxite to obtain ore pulp with qualified granularity, and feeding the ore pulp into a decarburization device for decarburization reaction; the decarbonized ore pulp is subjected to liquid-solid separation, and concentrate and filtrate are obtained; the concentrate enters a Bayer process desilicication system by preparing a proper amount of circulating mother liquor; after being recycled, the filtrate enters an ore grinding system after being blended; part of the filtrate enters a light calcium carbonate production system after the sodium carbonate content is detected; the decarburization and impurity removal of the high-carbon bauxite are carried out by adopting a mother liquor preparation-ore grinding-normal pressure decarburization-concentrate-light calcium carbonate-causticization decarburization technology, and the method has the characteristics of low energy consumption, low production cost, high recovery rate, strong process adaptability, stable production and high comprehensive utilization rate.

Description

Technical Field

[0001] The present invention relates to the technical field of impurity removal and quality improvement of nonferrous metal ores, and in particular to a method for decarbonizing and removing impurities from high-carbon bauxite. Background Art

[0002] Bauxite, as one of the main raw materials for alumina production, is widely used in industrial sectors such as high-temperature refractory materials, refractory cement, ceramic materials, and precision casting. In recent years, with the rapid development of the alumina industry and the increasing depletion of high-quality aluminum resources, domestic bauxite, which accounts for only 3% of the reserves and is increasingly "poor, fine, and mixed", is far from meeting production needs. Therefore, the industry has gradually begun to use imported bauxite to produce alumina, which has led to a year-on-year increase in bauxite imports. Since 2019, the annual import volume of bauxite has exceeded 10 million tons. In 2023, a total of 141.5659 million tons of bauxite was imported, a record high, and the self-sufficiency rate was less than 20%.

[0003] High-sulfur and high-carbon bauxite has become an important potential resource for the aluminum industry. Due to its complex properties and fine ore distribution, high-sulfur bauxite has a high content of impurities such as sulfur, carbon, and iron. Breakthroughs have been made in the desulfurization technology of high-sulfur ores. Methods such as flotation desulfurization, wet oxidation desulfurization, and the addition of oxidants are used to convert elemental sulfur into sulfate and other forms for discharge, thereby controlling corrosion to equipment and pipes. However, high-carbon ores cause the precipitation of sodium carbonate during the dissolution process, and during flash evaporation, the carbon alkali will precipitate and block the discharge port, which can easily cause secondary steam entrainment.

[0004] At present, the main technology for decarbonizing alumina is: to increase the concentration through forced efficiencies in the evaporation workshop and then remove salt, and to enrich the carbon and alkali and then add lime milk for causticization. This method has shortcomings: low decarbonization output, loss of alumina caused by causticization, and decreased decomposition rate caused by impurities during the decomposition process; excessive carbon and alkali cause the preheater to be blocked, affecting output and comprehensive energy consumption, so it has not been able to be used in large quantities. As long as the problems of desulfurization, decarbonization and impurity removal of high-carbon bauxite can be solved, the current resource shortage situation faced by the industry can be alleviated. Therefore, it is necessary to study the decarbonization and impurity removal of high-carbon ores. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for decarbonizing and removing impurities from high-carbon bauxite, which solves the technical problems in the prior art of high-carbon bauxite decarbonization, impurity removal and quality improvement, such as low decarbonization yield, loss of alumina caused by causticization, and decreased decomposition rate caused by impurities during the decomposition process.

[0006] To achieve the above object, the present invention provides a method for decarbonizing and removing impurities from high-carbon bauxite, comprising the following steps:

[0007] Use liquid caustic soda to prepare a qualified mother liquor until the preset mother liquor concentration is reached, obtaining a mother liquor with a qualified concentration, and then configure the mother liquor to obtain a qualified mother liquor;

[0008] Use an ore grinding system to grind bauxite, and after grinding, add the qualified mother liquor to the bauxite to obtain a slurry with a qualified particle size after grinding the bauxite;

[0009] Send the slurry to a decarbonization system, and let the siderite and calcite in the slurry react with sodium hydroxide in the decarbonization system and exist in the form of organic matter and carbonate;

[0010] Perform liquid-solid separation on the reacted slurry to obtain concentrate and filtrate;

[0011] The concentrate enters the Bayer digestion system by configuring an appropriate amount of circulating mother liquor. After detecting the concentration of sodium carbonate in a part of the filtrate, it is used to produce light sodium carbonate by adding calcium hydroxide. Another part of the filtrate is mixed with the liquid caustic soda and then recycled into the next ore grinding system for recycling.

[0012] Among them, the concentration of the qualified mother liquor obtained by configuration is 160 - 210 g / L.

[0013] Among them, after the bauxite is ground, the solid content in the obtained slurry is 300 - 500 g / L.

[0014] Among them, the liquid-solid separation method of the slurry is: use a plate and frame filter press for liquid-solid separation.

[0015] Among them, the bauxite is high-carbon bauxite. In terms of mass fraction, its chemical composition includes: aluminum oxide ≥ 47.7%, iron oxide ≤ 7.69%, sulfur 0.26% - 0.3%, carbon 1.4% - 1.8%, and the rest are inevitable impurities.

[0016] Among them, the filtrate exists in the form of sodium carbonate, and by adding lime milk, the by-product light calcium carbonate is produced.

[0017] Among them, the specific steps of grinding the bauxite are:

[0018] Crush the bauxite and screen it with a preset particle size to obtain coarse-grained bauxite and fine-grained bauxite respectively;

[0019] Crush the coarse-grained bauxite again to the preset particle size and mix it with the previously obtained fine-grained bauxite to obtain qualified bauxite.

[0020] A decarbonization and impurity removal method for high-carbon bauxite of the present invention, the method comprising: using liquid caustic soda to prepare a qualified mother liquor, grinding the bauxite to obtain a slurry with a qualified particle size, and feeding it into a decarbonization device for decarbonization reaction; performing liquid-solid separation on the decarbonized slurry to obtain concentrate and filtrate; the concentrate enters the Bayer desilication system by configuring an appropriate amount of recycled mother liquor; after the filtrate is recycled, it is adjusted and fed into the ore grinding system; after detecting the sodium carbonate content of a part of the filtrate, it enters the system for producing light calcium carbonate; by adopting the "preparation of mother liquor - grinding - atmospheric decarbonization - concentrate - light calcium carbonate - caustic decarbonization technology" to carry out decarbonization and impurity removal of high-carbon bauxite, it has the characteristics of low energy consumption, low production cost, high recovery rate, strong process adaptability, stable production, and high comprehensive utilization rate. Brief Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art.

[0022] Figure 1 It is a flow step diagram of the decarbonization and impurity removal method for high-carbon bauxite in the first embodiment of the present invention.

[0023] Figure 2 It is a specific step diagram of grinding bauxite in the decarbonization and impurity removal method for high-carbon bauxite in the first embodiment of the present invention.

[0024] Figure 3 It is an operation step diagram of the decarbonization and impurity removal method for high-carbon bauxite in the first embodiment of the present invention. Detailed Description of the Embodiments

[0025] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0026] First Embodiment:

[0027] Please refer to Figures 1 to 3 , the present invention provides a decarbonization and impurity removal method for high-carbon bauxite, comprising the following steps:

[0028] S101. Use liquid caustic soda to prepare a qualified mother liquor until it reaches a preset mother liquor concentration to obtain a mother liquor with a qualified concentration, and then configure the mother liquor to obtain a qualified mother liquor.

[0029] Specifically, use liquid caustic soda to prepare a qualified mother liquor until it reaches a preset mother liquor concentration to obtain a mother liquor with a qualified concentration, and then configure the mother liquor to obtain a qualified mother liquor. Among them, the concentration of the obtained qualified mother liquor is 160 - 210 g / L, and its optimal concentration is 180 g / L.

[0030] S102. Use an ore grinding system to grind bauxite, and after grinding, add the qualified mother liquor to the bauxite to obtain a slurry with qualified particle size after grinding the bauxite.

[0031] Specifically, use an ore grinding system to grind the bauxite, and after grinding, add the qualified mother liquor to the bauxite to obtain a slurry with qualified particle size after grinding the bauxite. Among them, the bauxite is high-carbon bauxite. In terms of mass fraction, its chemical composition includes: aluminum trioxide ≥ 47.7%, iron trioxide ≤ 7.69%, sulfur 0.26% - 0.3%, carbon 1.4% - 1.8%, and the rest are inevitable impurities. After grinding the bauxite, the solid content in the obtained slurry is 300 - 500 g / L, and the optimal content is 400 g / L.

[0032] Among them, the specific steps for grinding the bauxite are as follows:

[0033] S1021. Crush the bauxite and screen it with a preset particle size to obtain coarse-grained bauxite and fine-grained bauxite respectively.

[0034] S1022. Crush the coarse-grained bauxite again to the preset particle size and mix it with the previously obtained fine-grained bauxite to obtain the qualified bauxite.

[0035] S103. Send the slurry to a decarbonization system, and let the siderite and calcite in the slurry react with sodium hydroxide in the decarbonization system and exist in the form of organic matter and carbonate.

[0036] Specifically, send the slurry to a decarbonization system, and let the siderite and calcite in the slurry react with sodium hydroxide in the decarbonization system and exist in the form of organic matter and carbonate. Among them, before the siderite and calcite in the slurry react with sodium hydroxide in the decarbonization system, they need to be heated with a sleeve and condensed water to control the temperature in the decarbonization system at 40 - 80°C. The reaction temperature when the slurry is put into the decarbonization system for decarbonization reaction is 40 - 80°C, and the reaction time for the slurry to be put into the decarbonization system for decarbonization reaction is 6 - 10 h.

[0037] S104. Perform liquid-solid separation on the reacted slurry to obtain concentrate and filtrate.

[0038] Specifically, perform liquid-solid separation on the reacted slurry to obtain concentrate and filtrate. Among them, the liquid-solid separation method of the slurry is: use a plate and frame filter press for liquid-solid separation.

[0039] S105. The concentrate enters the Bayer digestion system by configuring an appropriate amount of circulating mother liquor. After detecting the concentration of sodium carbonate in a part of the filtrate, it is used to produce light sodium carbonate from calcium hydroxide. After another part of the filtrate is blended with the liquid caustic soda, it is recycled into the next ore grinding system for recycling.

[0040] Specifically, the concentrate enters the Bayer digestion system by configuring an appropriate amount of circulating mother liquor. After detecting the concentration of sodium carbonate in a part of the filtrate, it is used to produce light sodium carbonate from calcium hydroxide. After another part of the filtrate is blended with the liquid caustic soda, it is recycled into the next ore grinding system for recycling. Among them, the filtrate obtained by liquid-solid separation exists in the form of sodium carbonate, and by adding lime milk, the by-product light calcium carbonate is produced.

[0041] When using the decarbonization and impurity removal method for high-carbon bauxite of this embodiment, the method includes: using liquid caustic soda to blend qualified mother liquor, grinding bauxite to obtain a slurry with qualified particle size, and feeding it into a decarbonization device for decarbonization reaction; performing liquid-solid separation on the decarbonized slurry to obtain concentrate and filtrate; the concentrate enters the Bayer desilication system by configuring an appropriate amount of circulating mother liquor; after the filtrate is recycled, it is blended and enters the ore grinding system; a part of the filtrate enters the light calcium carbonate production system after detecting the sodium carbonate content; by adopting the "preparation of mother liquor - grinding - atmospheric decarbonization - concentrate - light calcium carbonate - caustic decarbonization technology" to carry out the decarbonization and impurity removal of high-carbon bauxite, it has the characteristics of low energy consumption, low production cost, high recovery rate, strong process adaptability, stable production, and high comprehensive utilization rate.

[0042] Among them:

[0043] 1. The bauxite is high-carbon bauxite, taken from a certain place in Guizhou. In terms of mass fraction, the chemical composition of the bauxite includes:

[0044]

[0045] 2. The useful minerals are diaspore and gibbsite, and the gangue minerals are mainly chlorite, hematite, siderite, calcite, pyrite, rutile, etc.; among them, the harmful impurities are pyrite, hematite, limonite, calcite, organic carbon, and siderite containing inorganic carbon.

[0046] 2.1. The main component of siderite is FeCO3 (ferrous carbonate). When siderite reacts with sodium hydroxide (NaOH) solution, it is actually a chemical reaction between ferrous carbonate and sodium hydroxide. Since siderite also contains other impurities such as SiO2 (silicon dioxide), CaCO3 (calcium carbonate), and Al2O3 (aluminum oxide), these impurities will also produce different products when reacting with sodium hydroxide. For example, silicon dioxide will react with sodium hydroxide to form sodium silicate (Na2SiO3), while aluminum oxide will form sodium aluminate (NaAlO2). These side reactions help to further purify the iron component in siderite.

[0047] 2.2. Calcite does not undergo an obvious chemical reaction with sodium hydroxide (NaOH). This is because calcium carbonate is a weakly acidic salt and sodium hydroxide is a strong base, and the two will not undergo a significant neutralization reaction at room temperature. Under high temperature and high pressure conditions, calcium carbonate can undergo a double decomposition reaction with sodium hydroxide to form sodium carbonate (Na2CO3) and calcium hydroxide (Ca(OH)2), i.e., CaCO3 + 2NaOH → Na2CO3 + Ca(OH)2.

[0048] 2.3. Using liquid caustic soda for caustic washing to adjust the NK concentration to 160 - 210 g / L:

[0049]

[0050]

[0051] 2.4. Pulp grinding index:

[0052] Test number Addition amounts of ore and liquid caustic Blended solid content First round 500 ML (NK 180 g / L) liquid caustic + 200 g / L ore 400 g / L Second round 400 ML filtrate + 160 g / L ore 320 g / L

[0053] In the present invention, the mother liquor NK160 - 210 g / l after preparation enters the raw material ball mill for grinding the pulp, and the solid content is controlled to 300 - 500 g / L.

[0054] 2.5. Decarbonization reaction temperature 40 - 80 °C, reaction time 6 - 10 hours:

[0055] 2.5.1 Liquid phase analysis index:

[0056]

[0057] 2.5.2 Solid phase analysis index:

[0058]

[0059] In the present invention, the condensed water in the decarbonization system is heated to 40 - 80 °C through a casing and stays in the container for 6 - 10 hours, so that siderite, calcite, etc. react chemically with caustic soda, and the carbonate reacts with caustic soda.

[0060] 2.6. The pulp after chemical reaction is subjected to liquid-solid separation by a plate-and-frame filter press. The filtrate after separation is added with lime milk for causticization to produce by-product light calcium carbonate.

[0061] 2.7. Part of the filtrate is re-prepared into qualified mother liquor and enters the next cycle.

[0062] 3. Removal rate

[0063] 3.1. Calculated by solid phase:

[0064]

[0065] According to the experimental results, when treating domestic high-sulfur bauxite, the carbon removal rate of the ore can reach 85.25%, and a small amount of AO is precipitated at the same time; the carbon conversion situation can also be verified according to the solid-phase results after treatment; the result of the secondary alkali leaching of the filtrate of Experiment 1# shows that the carbon precipitation still has a good effect, and the mother liquor can be recycled until it reaches a high concentration and then causticized. The subsequent plan is to verify the precipitation situation of aluminum oxide under the condition of further reducing the temperature, and the influence of different alkali concentrations on its precipitation.

[0066] The above-disclosed are only one or more preferred embodiments of the present application, and the scope of rights of the present application cannot be limited thereby. Those of ordinary skill in the art can understand the entire or partial processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present application still fall within the scope covered by the present application.

Claims

1. A decarbonization and impurity removal method for high-carbon bauxite, characterized in that, It includes the following steps: Use liquid caustic soda to prepare a qualified mother liquor until the preset mother liquor concentration is reached to obtain a mother liquor with a qualified concentration, and then configure the mother liquor to obtain a qualified mother liquor; Use an ore grinding system to grind bauxite, and after grinding, add the qualified mother liquor to the bauxite to obtain a pulp with a qualified particle size after grinding the bauxite; Send the pulp to a decarbonization system, and let the siderite and calcite in the pulp react with sodium hydroxide in the decarbonization system and exist in the form of organic matter and carbonate; Perform liquid-solid separation on the reacted pulp to obtain concentrate and filtrate; The concentrate enters the Bayer digestion system by configuring an appropriate amount of recycled mother liquor. After detecting the concentration of sodium carbonate in a part of the filtrate, it is used to produce light sodium carbonate by adding calcium hydroxide. Another part of the filtrate is mixed with the liquid caustic soda and then recycled to the next ore grinding system for recycling; 2. The decarbonization and impurity removal method for high-carbon bauxite according to claim 1, characterized in that: The concentration of the qualified mother liquor obtained by configuration is 160 - 210 g / L.

3. The decarbonization and impurity removal method for high-carbon bauxite according to claim 2, characterized in that: After the bauxite is ground, the solid content in the obtained pulp is 300 - 500 g / L.

4. The decarbonization and impurity removal method for high-carbon bauxite according to claim 3, characterized in that: The liquid-solid separation method of the pulp is: perform liquid-solid separation using a plate and frame filter press.

5. The decarbonization and impurity removal method for high-carbon bauxite according to claim 1, characterized in that: The bauxite is high-carbon bauxite. In terms of mass fraction, its chemical composition includes: aluminum trioxide ≥ 47.7%, iron trioxide ≤ 7.69%, sulfur 0.26% - 0.3%, carbon 1.4% - 1.8%, and the rest are inevitable impurities.

6. The decarbonization and impurity removal method for high-carbon bauxite according to claim 1, characterized in that: The filtrate exists in the form of sodium carbonate, and by adding lime milk, a by-product light calcium carbonate is produced.

7. The decarbonization and impurity removal method for high-carbon bauxite according to claim 1, characterized in that: The specific steps of grinding the bauxite are: Crush the bauxite and screen it with a preset particle size to obtain coarse-grained bauxite and fine-grained bauxite respectively; Crush the coarse-grained bauxite again to the preset particle size and mix it with the previously obtained fine-grained bauxite to obtain qualified bauxite.

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