Treatment method for atomizing, dispersing, freeze-drying, pulverizing and separating aluminum oxide underflow red mud

Abstract

Separating the specific gravity gt of the solid-liquid mixture type underflow red mud discharged in aluminum oxide production from liquid; continuously grading and separating out ferric oxide, trace heavy metal minerals and rare earth from the 5 g / cm < 3 > material, and carrying out solid-liquid separation treatment; the separated materials with the specific gravity smaller than or equal to 5 g / cm < 3 > are atomized and dispersed into particles and liquid drops, the particles and the liquid drops are quickly freeze-dried to prepare fine particles, and the fine particles are divided into sodium aluminosilicate and silicon oxide mixed particles, calcium compound mixed particles and crystallized sodium hydroxide, sodium aluminate and ice crystal particles through multi-stage specific gravity classification in the environment with the temperature smaller than-5 DEG C; and sublimating and dehydrating the separated sodium aluminosilicate and silicon oxide mixed particles and calcium compound mixed particles to form powder materials, and melting sodium hydroxide, sodium aluminate and ice crystal particles at normal temperature to form a solution containing sodium aluminate and sodium hydroxide.

Description

Technical Field

[0001] The invention relates to a method for atomizing and dispersing the bottom flow red mud discharged from alumina production, freeze-drying it to make powder, and performing multiple classifications according to specific gravity to separate particles of materials with different specific gravities, belonging to the technical field of red mud treatment. Background Art

[0002] Red mud is the waste residue after alumina extraction. It is a solid-liquid mixture when discharged as underflow from the alumina production process. The solid content of washed red mud is about 40%. The particle size distribution of solid particles in red mud is D 50 Between 7-8 μm, D 90 <23μm, D 10 =2.4μm. Solid particles less than 24μm in red mud account for 93% of the total volume, and particles less than 10um account for about 63% of the total volume. Red mud solution is an aqueous solution containing low concentrations of sodium aluminate, sodium hydroxide, and potassium hydroxide. The solids are various solid substances such as iron oxide, sodium aluminosilicate, calcium titanate, calcium aluminate, calcium silicate, silicon oxide, calcium oxide, and rare metal oxides. Calcium aluminate, calcium aluminosilicate, sodium aluminate and other substances in red mud have gelling properties. After dehydration at room temperature, red mud forms gelation and crystallization, causing the particles to agglomerate and condense and harden.

[0003] There is a technology that converts iron oxide into water-soluble iron salts by subjecting red mud to acid reaction, and then separates the salts of iron, aluminum, lithium and sodium through precipitation, so as to achieve chemical separation and recovery of some elemental substances in red mud. Canada Alumina Co., Ltd. has application number CN201380010871 "Method for treating red mud", and Xi'an University of Architecture and Technology has application number CN201210164515 "Method for co-producing ultrafine ferroferric oxide and alumina from Bayer red mud", etc., which discloses the technology of soaking red mud with HCL to obtain a chloride solution containing iron ions and aluminum ions, and separating iron and aluminum by generating iron oxide and aluminum hydroxide precipitation respectively. Japan Showa Denko has application number JP2003061008A "RED MUDTREATMENT METHOD AND CEMENT CLINKER PRODUCTION METHOD" which discloses a technology that uses acidic substances to neutralize the alkali in red mud, dissolve and separate iron compounds, and then dehydrates and roasts the remaining solid-liquid mixture to dissolve and separate the sodium aluminate therein, and the remaining calcium silicate, calcium aluminosilicate, and calcium titanate substances are used as cement raw materials.

[0004] The iron oxide in bauxite is ferrous oxide with weak magnetic properties. It is now mostly separated and recovered by magnetic separation in solid red mud after the extraction of alumina. Application No. CN201610956537 "A method for magnetic roasting and magnetic separation of red mud", Publication No. CN118127314A, Publication No. CN104818381A, Publication No. CN103290207A, U.S. Patent No. US2015203362 (A1), etc. all disclose the technology of reducing iron oxide in red mud, increasing iron magnetization and magnetic separation, which is to add carbon material to red mud for high-temperature roasting, improve the magnetic properties by carbon thermal reduction of iron oxide, and then enrich it by magnetic separation to separate iron oxide from red mud. Application No. CN202310972695 "Method for recovering fine-grained iron oxide minerals" discloses a technology of adding a magnetic adsorbent for agglomeration and then magnetic separation. The red mud containing fine-grained iron oxide minerals to be processed is mixed with iron powder and nitrite for wet grinding. A coupled redox system is constructed with iron-nitrite-iron oxide and mechanical activation is coordinated during the wet grinding process. This allows the surface of the weakly magnetic fine-grained iron oxide minerals (such as Fe2O3) in the raw material to be processed to form stable and uniform strong magnetic Fe3O4 oxides, thereby allowing the fine-grained iron oxide minerals to be relatively selectively agglomerated due to the enhanced surface magnetism, and then enriched and separated by strong magnetic separation.

[0005] The existing technology for separating various substances in red mud uses dried solid as raw material. After red mud is dehydrated at room temperature, the hydrated gelling calcium aluminate, calcium aluminosilicate, sodium aluminate and other substances are gelled or crystallized, and are wrapped with other microparticles, and the microparticles are agglomerated and hardened. When the dehydrated solid red mud is processed, the broken and dispersed particles are relatively large, and various substances are wrapped with each other, making separation difficult. Summary of the invention

[0006] The red mud discharged as the underflow in the alumina production process, its solid particles are mainly sodium aluminosilicate, calcium titanate and a small amount of calcium aluminosilicate separated in the desiliconization process, and iron oxide, calcium oxide, silicon oxide, calcium silicate, heavy metal minerals and rare earth separated in the original ore slurry sedimentation process. The solid particles in the red mud with a size of less than 24μm account for 93% of the total volume. The underflow red mud is a solid-liquid mixture after washing, with a solid content of less than 40%. The various gelling substances and adsorbed particles in the solution have not undergone agglomeration and hydration crystallization. All kinds of substances exist in the form of particles of the substance, rarely mixed and condensed with other substances, and are all in a dispersed state, so it is relatively easy to separate the various component substances. Conventional red mud separation treatment is to dehydrate and solidify the red mud. The particles are mutually wrapped and aggravated by gelation and crystallization, which makes it very difficult to handle and separate, and the purity of the separated material is low.

[0007] The present invention is to separate the red mud in the form of solid-liquid mixture discharged from the alumina production process into liquid with a specific gravity of more than 5g / cm 3 The material is continuously graded to separate iron oxide and trace heavy metal minerals and rare earths, and solid-liquid separation is performed; the separated specific gravity is ≤5g / cm 3 The material is dispersed into microparticles and droplets by atomization and quickly freeze-dried to form fine particles, and is subjected to multi-level specific gravity classification in an environment of less than -5°C to be divided into sodium aluminosilicate and silicon oxide mixed microparticles, calcium compound mixed microparticles, and crystallized sodium hydroxide, sodium aluminate and ice crystal microparticles; the separated sodium aluminosilicate and silicon oxide mixed microparticles and calcium compound mixed microparticles are sublimated and dehydrated to form powder materials, and the sodium hydroxide, sodium aluminate and ice crystal microparticles are melted at room temperature to form solutions containing sodium aluminate and sodium hydroxide.

[0008] The specific gravity of each material in red mud is as follows:

[0009] The sodium aluminate crystals and ice crystal particles after the solution is frozen have a specific gravity of 1.5-0.9g / cm 3 ;

[0010] The specific gravity of sodium hydroxide crystals after the solution is frozen is 2.04-2.13g / cm 3 ;

[0011] Specific gravity of silicon oxide: 2.23 g / cm 3 ;

[0012] The sodium aluminosilicate particles formed during the desiliconization process have a specific gravity of 2.2-2.6 g / cm 3 ;

[0013] Calcium aluminosilicate, calcium titanate and calcium silicate particles formed by desiliconization and detitaniumization have a specific gravity of 3.2-4.9g / cm 3 ;

[0014] Iron oxide specific gravity 5.2g / cm 3 ;

[0015] The specific gravity of heavy metal compounds and rare earths is > 6g / cm 3 ;

[0016] The process flow of the alumina underflow red mud atomization dispersion freeze-drying powder separation treatment method of the present invention is as follows:

[0017] 1. Adjust the solid content of the bottom flow red mud discharged after washing in the alumina process to between 45-55%.

[0018] 2. Use a dispersion device to disperse the bottom flow red mud. The dispersion device is a mechanical dispersion device or an ultrasonic dispersion device, or a combination of the two types of dispersion devices.

[0019] 3. The dispersed bottom flow red mud enters the liquid cyclone density classifier and is classified according to the specific gravity of 5g / cm 3 Set the separation standard to specific gravity > 5g / cm 3 Iron oxide, heavy metal minerals, rare earth and other materials with a specific gravity of ≤5g / cm 3 Separate the materials.

[0020] 4. The specific gravity of the separated particles is > 5g / cm 3 The solid-liquid mixture enters the Zippy centrifuge gravity classifier and runs according to the specific gravity of 6g / cm 3 Adjust the centrifuge speed according to the separation standard. The centrifuge is running with a specific gravity of > 6g / cm 3 Heavy metal minerals, rare earth materials and specific gravity <6g / cm 3 and >5g / cm 3 The solid-liquid mixture containing heavy metal minerals and rare earths is separated into particles of heavy metal minerals and rare earths and a solution containing sodium aluminate and sodium hydroxide. The solid-liquid mixture containing iron oxide is separated into particles of iron oxide and a solution containing sodium aluminate and sodium hydroxide.

[0021] 5. The specific gravity of the separated particles is ≤5g / cm 3 A solid-liquid mixture mainly containing particles of sodium aluminosilicate, calcium titanate, calcium silicate, calcium aluminosilicate and a small amount of silicon oxide, as well as a dissolved salt solution containing sodium aluminate and sodium hydroxide. 3 The solid-liquid mixture is sprayed and atomized to disperse into particles and droplets, and the particles and droplets are quickly frozen into solid particles with airflow below -8℃, and the temperature of the solid particles in the container is kept below -5℃. Since the bottom flow red mud does not form gelation and crystallization in the liquid, most of the sodium aluminosilicate, calcium titanate, calcium silicate, and calcium aluminosilicate become solid particles in the form of this substance. Sodium aluminate and sodium hydroxide in the liquid also form hydrated crystal particles, and water also forms ice crystal particles. The specific gravity of the particles formed by freezing is all <5g / cm 3 .

[0022] 6. Use an airflow of less than -5℃ to transport the frozen particles into the pneumatic density classifier, according to the specific gravity of 3g / cm 3 Set the separation standard to a specific gravity of <3g / cm 3 and >5g / cm 3 Calcium titanate, calcium silicate, calcium aluminosilicate particles with a specific gravity of ≤3g / cm 3 Sodium aluminosilicate, sodium aluminate, sodium hydroxide, ice crystals and other particles are separated. The material temperature and the temperature inside the classifier are kept below -5°C during the classification process. The specific gravity of the separated particles is less than 3g / cm 3 and >5g / cm 3 The particles are sublimated and dehydrated to become a mixture of calcium titanate, calcium silicate and calcium aluminosilicate particles.

[0023] 7. Use <-5℃ airflow to separate the ≤3g / cm 3 The particles are transported into the pneumatic gravity classifier and the specific gravity is 2.2g / cm 3 Set the separation standard and set the specific gravity to 2.2-3g / cm 3 Sodium aluminosilicate, silicon oxide particles and specific gravity <2.2g / cm 3 The sodium aluminate, sodium hydroxide, ice crystals and other particles are separated. The material temperature and the temperature inside the classifier are kept below -5℃ during the classification process. 3 The particles are dehydrated by sublimation to form a mixture of sodium aluminosilicate and silicon oxide particles. The particles of sodium aluminate, sodium hydroxide, ice crystals, etc. melt at room temperature to form a solution containing sodium aluminate and sodium hydroxide.

[0024] 8. After the spray atomization and freezing process to produce fine particles, the temperature is kept below -5°C. The temperature of the material transported to the pneumatic specific gravity classifier is kept below -5°C. The temperature of the pneumatic classification process is kept below -5°C.

[0025] The present invention separates red mud to keep all kinds of materials in the form of particles of the material, without gelation and crystallization, and the particles formed at low temperature are mainly amorphous and microcrystalline, with high activity. The separation method has lower cost than conventional separation and dehydration of solid red mud, higher purity of separated materials, and no pollution in the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attached Figure 1 Process flow chart

[0027] Specific application examples

[0028] Treatment of the bottom flow red mud from the Bayer process of alumina production.

[0029] 1. Adjust the solid content of the bottom flow red mud discharged after washing in the Bayer process alumina production process to 50%.

[0030] 2. Use ultrasonic dispersion device to disperse the bottom flow red mud.

[0031] 3. According to the specific gravity 5g / cm 3 Set the separation standard and set the liquid cyclone density classifier. Use a pump to input the dispersed bottom flow red mud into the set liquid cyclone density classifier, and set the specific gravity > 5g / cm 3 Iron oxide, heavy metal minerals, rare earth and other materials with a specific gravity of ≤5g / cm 3 Separate the materials.

[0032] 4. According to the specific gravity 6g / cm 3 Adjust the speed of the centrifuge according to the separation standard. 3The solid-liquid mixture is fed into the Zippy centrifuge gravity classifier for operation. The centrifuge operation sets the specific gravity to > 6g / cm 3 The heavy metal minerals and rare earth materials are enriched and the specific gravity is less than 6g / cm 3 and >5g / cm 3 The solid-liquid mixture containing heavy metal minerals and rare earths is separated into particles of heavy metal minerals and rare earths and a solution containing sodium aluminate and sodium hydroxide. The solid-liquid mixture containing iron oxide is separated into particles of iron oxide and a solution containing sodium aluminate and sodium hydroxide.

[0033] 5. The specific gravity of the separated particles should be ≤5g / cm 3 The solid-liquid mixture is sprayed and atomized in a container, dispersed into particles and droplets, and quickly passed into the container with a ≤-8℃ airflow to freeze the particles and droplets into solid particles. The solid particles are a mixture of sodium aluminosilicate, calcium titanate, calcium silicate, calcium aluminosilicate, crystalline sodium aluminate, crystalline sodium hydroxide, and ice crystal particles. The specific gravity of the frozen particles is <5g / cm 3 . Keep the particles in the container < -5℃.

[0034] 6. According to the specific gravity 3g / cm 3 Separation standard setting pneumatic classifier. Use <-5℃ airflow to transport the frozen particles into the pneumatic specific gravity classifier, and the specific gravity is <3g / cm 3 and >5g / cm 3 The particle size of calcium titanate, calcium silicate and calcium aluminosilicate should be less than 3g / cm 3 Sodium aluminosilicate, silicon oxide, sodium aluminate, sodium hydroxide, ice crystals and other particles are separated, and the material temperature is kept below -5℃ during the classification process. The specific gravity of the separated particles is below 3g / cm 3 and >5g / cm 3 The material particles are sublimated and dehydrated to become a mixture of calcium titanate, calcium silicate and calcium aluminosilicate particles.

[0035] 7. According to the specific gravity 2.2g / cm 3 Separation standard setting pneumatic classifier. Use airflow below -5℃ to separate ≤3g / cm 3 The particles are transported into the pneumatic gravity classifier and the specific gravity is 2.2-3g / cm 3 Sodium aluminosilicate, silicon oxide particles and specific gravity <2.2g / cm 3 The sodium aluminate, sodium hydroxide, ice crystals and other particles are separated, and the material temperature is kept below -5℃ during the classification process. The specific gravity of the separated particles is 2.2-3g / cm 3 The particles are dehydrated by sublimation to form a mixture of sodium aluminosilicate and silicon oxide particles. The particles of sodium aluminate, sodium hydroxide, ice crystals, etc. melt at room temperature to form a solution containing sodium aluminate and sodium hydroxide.

Claims

1. A method for treating alumina underflow red mud by atomization, dispersion, freeze-drying, powdering and separation, characterized in that The solid-liquid mixed bottom flow red mud is separated by a multi-stage specific gravity classifier, and the materials with different specific gravities in the bottom flow red mud are classified into the initial separation specific gravity>5g / cm 3 The material is further graded to separate iron oxide and trace heavy metal minerals and rare earth, and solid-liquid separation is performed; the initially separated ≤5g / cm 3 The solid-liquid mixture of the bottom flow red mud is atomized and dispersed into microparticles, and the droplets are quickly frozen into particles. Multi-stage pneumatic specific gravity classification is continued in a low-temperature environment. The solid part of the separated frozen material is sublimated and dehydrated into solid microparticles, and the separated ice crystals and particles dissolved with sodium aluminate and sodium hydroxide are heated and melted into liquids. The treatment method includes the following processes: (1) The solid content of the bottom flow red mud is adjusted to between 45% and 55%; (2) using a dispersion device to disperse the bottom flow red mud solid-liquid mixture into particles; (3) The dispersed bottom flow red mud enters the liquid cyclone specific gravity classifier and is classified according to the specific gravity of 5g / cm 3 Set the separation standard to specific gravity > 5g / cm 3 Iron oxide and heavy metal minerals rare earth and other materials with specific gravity ≤ 5g / cm 3 to separate the materials; (4) The specific gravity of the separated particles is greater than 5 g / cm 3 The solid-liquid mixture enters the Zippy centrifuge gravity classifier and runs according to the specific gravity of 6g / cm 3 Separation standard specific gravity> 6g / cm 3 Heavy metal minerals, rare earth materials and specific gravity <6g / cm 3 and >5g / cm 3 The iron oxide material is separated, and the solid-liquid mixture of iron oxide and heavy metal minerals and rare earths is separated to separate the liquid containing sodium aluminate and sodium hydroxide and the solid particles of iron oxide and heavy metal minerals and rare earths; (5) The specific gravity should be ≤5g / cm 3 The solid-liquid mixture is sprayed and atomized to disperse into particles and droplets, and quickly frozen into solid particles by airflow at a temperature of less than -8°C, and the temperature of the solid particles is kept less than -5°C without melting; (6) Use an airflow of less than -5℃ to transport the frozen particles into a pneumatic specific gravity classifier, according to the specific gravity of 3g / cm 3 Set the separation standard and set the specific gravity to <3g / cm2 in an environment <-5℃ 3 and >5g / cm 3 Particles with specific gravity ≤3g / cm 3 The particles are separated, and the specific gravity is less than 3g / cm 3 and >5g / cm 3 The particles are sublimated and dehydrated to form a mixture of calcium titanate, calcium silicate and calcium aluminosilicate particles; (7) Use <-5℃ airflow to separate the ≤3g / cm 3 The particles are transported into the pneumatic gravity classifier and the specific gravity is 2.2g / cm 3 Set the separation standard and set the specific gravity to 2.2-3g / cm2 in an environment of <-5℃ 3 Particles with a specific gravity of <2.2g / cm 3 The particles are separated; the separated 2.2-3g / cm 3 The particles are dehydrated by sublimation to become a mixture of sodium aluminosilicate and silicon oxide particles; specific gravity <2.2g / cm 3 The particles of sodium aluminate, sodium hydroxide, ice crystals, etc. are melted by heating to form a solution containing sodium aluminate and sodium hydroxide.

2. The method for treating alumina underflow red mud by atomization, dispersion, freeze-drying, powdering and separation according to claim 1, characterized in that After being sprayed and frozen into fine particles, the solid particles are transported to the pneumatic specific gravity classifier and the pneumatic classification process is carried out to keep the temperature of the solid particles less than -5°C.

3. The method for treating alumina underflow red mud by atomization, dispersion, freeze-drying, powdering and separation according to claim 1, characterized in that The dispersion device is mechanical dispersion or ultrasonic dispersion, or a combination of the two dispersion devices.

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