Method and device for pneumatically separating multiple substances from solid red mud through low-temperature crushing

Abstract

The invention relates to a method and a device for pneumatically separating multiple substances from solid red mud through low-temperature crushing. The method comprises the following steps: adding a refrigerant and a dispersant into the solid red mud, and freezing and crushing the solid red mud at the low temperature of-12 DEG C or below by using a crushing device until the particle size is less than 20 microns and the span is Slt; the invention relates to a method and a device for separating various substances mixed in red mud by performing particle size grading on uniform powder of which the particle size is 1.5, and belongs to the technical field of red mud treatment. The device consists of three parts, namely a low-temperature crushing system, a dehydration system and a pneumatic grading system, and the treatment method comprises the following steps: grinding and crushing the red mud into fine powder at low temperature, carrying out pneumatic grading in a low-temperature state to separate out a material containing more ice crystals, heating, melting, and carrying out solid-liquid separation and dehydration to respectively obtain a part of powder and a solution dissolved with sodium aluminate and sodium hydroxide; and powder which is separated by pneumatic classification and contains less water is sublimated and dehydrated and then enters a multi-stage pneumatic centrifugal classifier group to subdivide iron oxide minerals and other powder. According to the method, the problem that particles formed by the red mud are difficult to crush and separate due to gelling and agglomeration formed by water is solved, the materials separated from the red mud are various in types, relatively high in purity, strong in activity, large in application additional value, low in energy consumption, low in cost and high in comprehensive utilization rate of the red mud.

Description

Technical Field

[0001] The invention relates to a method and device for separating various substances mixed in the red mud by grinding solid red mud at low temperature into powder with uniform particles by using a mill, dispersing and then grinding and grading the particles by using a high-speed airflow, and 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 discharged from the alumina production process. The solids are various mineral solids such as iron oxide, aluminum oxide, sodium aluminosilicate, calcium titanate, calcium aluminate, calcium silicate, silicon oxide, calcium oxide and rare metal oxides. The solution contains water and low concentrations of sodium aluminate and sodium hydroxide. The particle size distribution of solid particles in red mud is D 50 Between 7-8 μm, D 90 <23μm, D 10 =2.4μm, and particles smaller than 24μm account for 93% of the total volume. After red mud is dehydrated at room temperature, substances such as calcium aluminate, calcium aluminosilicate, and sodium aluminate with hydrated gelling properties gel or crystallize, wrapping with other microparticles, and causing the microparticles to agglomerate, condense, and compact to form solid red mud.

[0003] After the red mud becomes solid, the gelled calcium aluminate, calcium aluminosilicate, sodium aluminate, iron oxide, sodium aluminosilicate, etc. are mixed and solidified together. They need to be crushed into particles of a certain size before they can be further used. The commonly used method is room temperature ball milling. This method is difficult to crush into uniform particles because the crushing of solid red mud is affected by water content, gel, viscosity and the agglomeration of fine particles due to temperature rise. In addition, various substances are wrapped around each other and cannot be effectively separated. Crushing to less than 15μm and eliminating agglomeration in the treatment of solid red mud are the main difficulties in separating the substances.

[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 the red mud for high-temperature roasting above 800°C, improve the magnetic properties of iron oxide by carbon thermal reduction, 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] 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's Showa Denko has an application number JP2003061008A "Red mud treatment method and cement clinker production method" which discloses a technology that uses acidic substances to neutralize the alkali in red mud and dissolve and separate iron compounds. The remaining solid-liquid mixture is then dehydrated and roasted 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.

[0006] The method of treating iron oxide by heating and roasting to reduce ferrous oxide in red mud to form iron oxide to improve magnetic properties, and then magnetic separation is only a single separation of iron oxide for steel smelting. However, after high-temperature roasting, silicon-calcium-aluminum substances other than iron oxide crystallize to form solid phase transformation, making subsequent utilization more difficult. The method of adding acid to react with substances in red mud to generate various metal salts, and then separating them by crystallization precipitation, is a cumbersome process and has great pollution. Finally, the remaining silicon-calcium residue cannot be used and becomes a highly polluting waste.

[0007] There is an application number CN202410930814.9 "Alumina underflow red mud atomization, dispersion, freeze-drying, powdering and separation treatment method", which atomizes the underflow red mud in the alumina process and freeze-dries it to make powder, and then separates the freeze-dried powder according to the difference in specific gravity to achieve the effect of separating the substances. This method does not require high-temperature roasting or acid neutralization reaction, and can maintain the state of the original substances in the red mud. All separations are beneficial for subsequent utilization. Since this method treats the underflow red mud of the solid-liquid mixture that has not been dehydrated and solidified, it is impossible to effectively separate the solid red mud that has already solidified.

[0008] The solid waste red mud produced by alumina production mainly contains solid particles of iron oxide, sodium aluminosilicate, calcium aluminosilicate, calcium silicate, silicon oxide, calcium titanate and a small amount of sodium hydroxide, sodium aluminate, heavy metal minerals, etc. Among them, iron oxide and sodium aluminosilicate have the highest content, accounting for more than half. After the red mud becomes solid, the water content is about 8-10%. Iron oxide, sodium aluminosilicate and gelling calcium aluminate, calcium aluminosilicate and sodium aluminate are mixed and solidified together, and need to be crushed into particles for further processing. The commonly used method at present is room temperature ball milling. This method is difficult to break into uniform particles because the crushing of solid red mud is affected by water content, gel, viscosity and temperature rise agglomeration of fine particles. In addition, various substances are wrapped around each other, and the ground fine state is still bonded to each other and cannot be effectively separated. The application of separated materials is very limited, the comprehensive utilization rate is low, and it is impossible to use them with high added value. Summary of the invention

[0009] The technical solution to the crushing and separation of solid red mud in the present invention is to utilize the characteristics of solid red mud that it becomes drier and more brittle and has lower adhesion after being frozen at low temperature. After the red mud is crushed into fine powder at low temperature, the material containing more ice crystals is separated by pneumatic classification at low temperature, heated and melted, and then solid-liquid separation and dehydration are performed to obtain partial powder and solution containing sodium aluminate and sodium hydroxide respectively; the powder with less water is separated by pneumatic classification, sublimated and dehydrated, and then enters the multi-stage pneumatic centrifugal classifier group to separate iron oxide minerals and other powders. Under low temperature conditions, water and aqueous solution freeze into solids, which reduces the degree of gelation of red mud, reduces heating, agglomeration, and gelation during the grinding process, and allows different bonded substances to crack through shrinkage, vibration, collision, and thermal expansion. Dehydration is performed to prepare microparticles with relatively uniform particle size, and then different substances are sorted out according to specific gravity based on density differences. Density of the main components of red mud:

[0010] The density of frozen water is 0.9 g / cm 3 , freezing temperature 0℃;

[0011] The density of hydrated sodium aluminate is 1.5 g / cm 3 , the freezing temperature of sodium aluminate solution is -10℃;

[0012] The density of sodium hydroxide crystals is 2.13 g / cm 3 ;

[0013] The silicon oxide in red mud is mostly in the form of micropores with a density of 2.2 g / cm 3 ;

[0014] The alumina in red mud is mainly β and γ forms of alumina, with a density of 3.6-3.9 g / cm 3 ;

[0015] The density of sodium aluminosilicate containing frozen water in red mud is 2.56 g / cm 3 ;

[0016] The density of solid calcium aluminosilicate in red mud is 2.76 g / cm 3 , the density of calcium silicate is 2.9g / cm 3 , the density of calcium aluminate is 2.98g / cm 3 , calcium titanate density 4.1g / cm 3 , calcium oxide density 3.34g / cm 3 ;

[0017] The iron-containing minerals in red mud are mainly hematite and goethite, with a density of 5.1-5.7 g / cm 3 The density of heavy metal compounds and rare earth oxides is > 6 g / cm 3 ;

[0018] The water in red mud is mostly contained in sodium aluminate, sodium hydroxide and microporous silica materials. The hydrated solids of calcium aluminosilicate, calcium aluminate, calcium silicate, sodium aluminate and sodium aluminosilicate have a gelling effect. They are mutually wrapped and wrapped with other substances during the solidification process, and have a certain adhesion toughness. Through low-temperature freezing below -12°C, the main solution substances water, sodium aluminate and sodium hydroxide in the red mud are converted into solids and the humidity is greatly reduced. At the same time, the hydrate eliminates the viscosity of the gel and increases the brittleness to facilitate finer crushing. The crushing under low-temperature drying conditions with the addition of dispersants also eliminates the agglomeration phenomenon. Multiple frequency oscillations loosen and crack the mosaics, and separate them after airflow collision. Under low-temperature conditions, the frozen liquid and the powder containing more frozen water are separated for heating and melting solid-liquid separation and dehydration to separate the water-soluble substances and some solid powders; the separated powder containing a very small amount of frozen water can be separated by density at room temperature after sublimation and dehydration. In the process of low-temperature crushing, temperature dehydration and sublimation dehydration, the particles that originally constitute the red mud are ground, frozen, oscillated, collided and thermally expanded, causing the red mud to be deeply crushed and the gel to crack, gradually separating the particles that are mutually wrapped, gelled, and hydrated and crystallized into finer particles, and improving the purity of each particle. The dehydrated red mud powder is pneumatically graded according to the density difference to separate the powder in a certain density area, and the particulate matter in this density area can remove other impurities to achieve applicable indicators.

[0019] The solid red mud low-temperature crushing and pneumatic separation device of the technical solution of the present invention consists of three parts: a low-temperature crushing system, a dehydration system, and a pneumatic classification system.

[0020] The low temperature pulverization system is a system in which red mud is continuously crushed through a primary grinding device (1), an oscillator (16) and an air flow mill (5). The primary grinding device is a vibration mill, a stirring mill or a ball mill, and the primary grinding device is connected to a refrigerant storage tank (2) and a dispersant storage tank (3) through a pipeline; a low temperature gas tank (4) is provided in front of the air flow mill (5); and the oscillator is an ultrasonic oscillator with adjustable frequency or an air flow shock wave oscillator.

[0021] The inlet of the pneumatic centrifugal classifier (6) of the dehydration system is connected to the outlet pipeline of the airflow mill; the lower outlet of the pneumatic centrifugal classifier (6) for heavy density materials is connected to a sublimation dehydrator (9); the upper outlet of the light density materials is connected to a heating and melting storage tank (7); the heating and melting storage tank is connected to a solid-liquid separator (8); the solid-liquid separator is connected to a liquid storage tank (15) for collecting liquid, a powder bin (13) for collecting solids, and a packaging machine (14) for powder packaging.

[0022] The pneumatic classification system is composed of an intermediate storage tank (10) at room temperature, a fan (11) and a multi-stage pneumatic centrifugal classifier group (12). The inlet of the intermediate storage tank is connected to the outlet of the sublimation dehydrator through a pipeline, and the outlet is connected to the inlet of the pneumatic centrifugal classifier group (12) through a pipeline; the pipeline between the intermediate storage tank and the multi-stage pneumatic centrifugal classifier group is equipped with a fan (11), and the fan blows the red mud powder in the intermediate storage tank into the multi-stage pneumatic centrifugal classifier group for classification; the outlets of each pneumatic centrifugal classifier of the multi-stage pneumatic centrifugal classifier group are equipped with a powder storage bin (13) for separated powder and a packaging machine (14) for powder packaging.

[0023] The technical solution of the present invention includes the following method and device operation steps:

[0024] 1. Low-temperature freezing and grinding of red mud. Put the solid red mud into the primary grinding equipment, add refrigerant to reduce its temperature to below -12°C, and add dispersant to start grinding. After freezing, the water, sodium aluminate solution, and sodium hydroxide solution in the red mud freeze and become highly brittle solids with other hydrated gelling substances. After being crushed to a particle size of <35μm, it enters the oscillator through a pipeline to change the frequency of oscillation. The gelled and embedded different materials are cracked by the oscillation, and then sent to the air flow mill for crushing and separation with low-temperature gas. After the air flow mill crushes the red mud to a particle size of <20μm and a span S<1.5, it is transported to the pneumatic centrifugal classifier of the dehydration system. The material temperature is kept below -12°C during the grinding, oscillation and powder conveying processes.

[0025] 2. Powder dehydration. Set the density index of particle size classification for the pneumatic centrifugal classifier. The density index of classification is set to separate most of the solid powders with more frozen water and low density from the upper outlet of the pneumatic centrifugal classifier, and the powders with less frozen water and high density from the lower outlet of the pneumatic centrifugal classifier. The set density index range is ≥2.2g / cm 3 and ≤2.7g / cm 3 . After setting the particle size classification density index, the ground powder enters the pneumatic centrifugal classifier for classification. The classification process keeps the material temperature in the pneumatic centrifugal classifier below -12°C. The powder material containing more frozen water separated from the upper outlet of the pneumatic centrifugal classifier enters the heating and melting storage tank. The working temperature of the heating and melting storage tank is controlled to be greater than 5°C and less than 50°C to melt and thaw the material into a solid-liquid mixture, and then enters the solid-liquid separator for solid-liquid separation. The separated liquid is a mixed solution of water, sodium aluminate, and sodium hydroxide and is loaded into a liquid storage tank for filling or pipeline transportation; the separated solid enters the powder silo for storage or packaging by a packaging machine. The powder with less water separated from the lower outlet of the pneumatic centrifugal classifier enters the sublimation dehydrator for accelerated heating and sublimation dehydration. The working temperature of the sublimation dehydrator is controlled to be greater than 25°C and less than 50°C. The dry powder after sublimation and dehydration is loaded into the intermediate storage tank.

[0026] 3. Pneumatically classify and separate dry powders according to density differences. The classifying density of the multi-stage pneumatic centrifugal classifier group is set according to the required material or material combination, and the classifying density of the first pneumatic centrifugal classifier is set to 5g / cm 3 , used to separate the iron oxide and heavy metal minerals with higher density in red mud. Other pneumatic centrifugal classifiers can set the classification density as needed, and the setting density range is <5g / cm 3 And it is greater than the classification density set for dehydration. After setting the classification density, start the fan and use room temperature air to input the powder in the intermediate storage tank into the multi-stage pneumatic centrifugal classifier group for pneumatic classification. The density of the first stage separation is ≥5g / cm 3 The iron oxide and heavy metal mineral powders are separated into multiple set intervals <5g / cm 3 Density powders and powder components. The powders separated by each level of classifiers are stored in the powder bin connected to them or packaged by the packaging machine. The density range of the separated powders can be adjusted by adjusting the air volume and wind speed of the fan and adjusting the speed of the centrifugal impellers of each level of the multi-stage pneumatic centrifugal classifier group.

[0027] The refrigerant used in the present invention is liquid nitrogen, or dry ice, or a mixture of liquid nitrogen and dry ice; the dispersant used is one of anhydrous calcium carbonate, calcium silicate, and β-alumina with a particle size of less than 8 μm, or a mixture of two or more thereof; the amount of the dispersant added is proportional to the weight of the substance after water and iron oxide are removed from the red mud. When liquid nitrogen is used as the refrigerant during grinding, the dispersant addition ratio is 0.3% of the weight of the substance after water and iron oxide are removed from the red mud, and when dry ice is used as the refrigerant, the dispersant addition ratio is 0.1% of the weight of the substance after water and iron oxide are removed from the red mud.

[0028] The present invention deeply crushes the red mud and cracks the bonded mosaic by grinding, freezing, oscillating, colliding, and thermal expansion under a low temperature environment, and then dehydrates to prepare microparticles with relatively uniform particle size, and separates different substances by density difference. The separated multiple powder materials can continue to be finely separated and used in combination. At the same time, soluble sodium salt substances, substances containing iron oxide and heavy metals are concentrated in a specific interval, reducing the sodium content and alkalinity of substances separated in other intervals, so that each component substance is not affected by high iron content and high sodium content, and can be used to its full potential. Compared with the existing red mud acid reaction salt extraction and metal separation method and red mud high-temperature magnetic separation iron separation method, the present invention separates red mud with a variety of materials, strong activity, high fineness, low cost, low energy consumption, low pollution, less waste, high application added value, and high comprehensive utilization rate of red mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Attached Figure 1 Process flow chart

[0030] Attached Figure 2 Device composition diagram

[0031] Attached Figure 3 Flow chart of separation of red mud produced by smelting alumina from boehmite

[0032] Attached Figure 4 Flow chart of separation of red mud produced by smelting alumina from diaspore

[0033] Specific application examples

[0034] Application Example 1

[0035] The process of separating diaspore from aluminum oxide to produce red mud containing more than 35% iron oxide, combined with the attached Figure 3 The operation flow chart of the invention is used to illustrate the method and device of the present invention with a specific example. The separation goal is to separate the solid red mud into aluminum oxide and calcium titanate used as abrasives; iron oxide used for steelmaking; sodium aluminate and sodium hydroxide solution used in the aluminum oxide production process; calcium carbonate, calcium oxide, calcium aluminosilicate and calcium silicate used for cement; sodium aluminosilicate and microporous silica used as catalyst carriers and molecular sieve raw materials.

[0036] 1. Add red mud to the vibration mill and inject liquid nitrogen refrigerant, add calcium carbonate with a particle size of less than 5μm as a dispersant according to 0.3% of the weight of the red mud after dehydration and iron oxide, and grind it. After grinding to a particle size of less than 35μm, it enters the pneumatic shock wave oscillator through a pipeline to change the frequency of oscillation, and then is transported to the air flow mill with a low-temperature airflow to continue grinding until the particle size is less than 20μm and the span S is less than 1.5. During the grinding process, keep the temperature inside the vibration mill, the air flow mill and the powder conveying pipeline less than -12℃.

[0037] 2. Set the classification density of the pneumatic centrifugal classifier according to the classification density of 2.6g / cm 3 Set the classifier. After the setting is completed, the ground powder is sent to the pneumatic centrifugal classifier by low-temperature gas for classification. The classification process keeps the temperature inside the pneumatic centrifugal classifier <-12℃. The density of the separated powder is ≤2.6g / cm 3 The powder enters the heating and melting tank, and the powder with density > 2.6g / cm 3 The powder enters the sublimation dehydrator.

[0038] 3. The separated density is ≤2.6g / cm 3The powder material is a mixture of ice crystals, sodium hydroxide, sodium aluminate, silicon oxide, and sodium aluminosilicate, which is sent to a heating and melting tank to maintain a temperature of 10-35°C for heating and melting. After the material is heated and melted, the heating and melting tank contains a solid-liquid mixture, which is then sent to a solid-liquid separator for solid-liquid separation. The separated solids are silicon oxide and sodium aluminosilicate, which are stored in a powder bin or packaged in a packaging machine as raw materials for catalyst carriers and molecular sieves; the separated liquid is a mixed solution of sodium aluminate and sodium hydroxide, which is filled in a liquid storage tank or transported by pipeline and reused in alumina production.

[0039] 4. Separation density>2.6g / cm 3 The powdered material enters the sublimation dehydrator, the temperature of which is controlled at 40-45℃, and the sublimation dehydration is carried out quickly. The powder after sublimation dehydration is transported to the intermediate storage tank.

[0040] 5. The density of the intermediate storage tank is >2.6g / cm 3 The powder is separated by a three-stage pneumatic centrifugal classifier. The classification density of the two series-connected pneumatic centrifugal classifiers in the three-stage separation is set to 5g / cm 3 and 3.5g / cm 3 .

[0041] 6. After the density of the three-stage pneumatic centrifugal classifier is set, the fan is started. The powder in the intermediate storage tank is blown into the three-stage pneumatic centrifugal classifier for classification. The first-stage outlet separates ≥5g / cm 3 Iron oxide and heavy metal mineral powders are separated and stored in powder bins or packaged in packaging machines; the second-stage outlet separates <5g / cm 3 and >3.5g / cm 3 The mixed powder of calcium titanate and alumina enters the powder bin for storage or packaging by the packaging machine; the last outlet separates the powder >2.6g / cm 3 And ≤3.5g / cm 3 Calcium carbonate, calcium oxide, calcium aluminosilicate and calcium silicate mixed powder used for cement are stored in powder silos or packaged by packaging machines.

[0042] Application Example 2

[0043] The process of separating diaspore from alumina to produce red mud containing 10% iron oxide, combined with the attached Figure 4 The operation flow chart of the present invention is used to illustrate the method and device of the present invention with a specific example. This type of red mud contains a large amount of sodium aluminosilicate and a low amount of iron oxide. The separation goal is to separate the solid red mud into aluminum oxide and calcium titanate for abrasives; iron oxide and heavy metal minerals for steelmaking; sodium aluminate and sodium hydroxide solution for recycling in the aluminum oxide production process; calcium carbonate, calcium oxide, calcium aluminosilicate and calcium silicate for cement; sodium aluminosilicate for detergent additives; and microporous silica for kaolin fillers.

[0044] 1. Add red mud to the ball mill and inject dry ice refrigerant. Add calcium carbonate and β-alumina mixture with a particle size of less than 5μm as dispersant according to 0.1% of the weight of the red mud after dehydration and iron oxide. After grinding to a particle size of less than 30μm, it enters the ultrasonic oscillator through a pipeline to change the frequency of oscillation, and is transported to the air flow mill with a low-temperature airflow to continue grinding to a particle size of less than 15μm and a span S of less than 1.5. During the grinding process, keep the temperature in the ball mill, air flow mill and powder delivery pipeline less than -12℃.

[0045] 2. For the pneumatic centrifugal classifier, the classification density is 2.3g / cm 3 Set the separation standard. After setting, use low-temperature gas to send the ground powder into the pneumatic centrifugal classifier for classification. During the classification process, keep the temperature inside the pneumatic centrifugal classifier <-12℃. The density of the separated powder is ≤2.3g / cm 3 The powder enters the heating and melting tank, and the powder with density > 2.3g / cm 3 The powder enters the sublimation dehydrator.

[0046] 3. The powdered material entering the heating and melting storage tank is a mixture of ice crystals, sodium hydroxide, sodium aluminate, and silicon oxide. The temperature in the heating and melting storage tank is maintained at 40-45°C to melt the material. After the ice crystals melt, the tank contains a mixture of a solution containing sodium hydroxide, sodium aluminate, and silicon oxide powder, which is then sent to a solid-liquid separator for solid-liquid separation. The separated solid is silicon oxide, which is sent to a powder bin for storage or packaging machine for packaging; the separated liquid is a mixed solution of sodium aluminate, sodium hydroxide, and water, which is sent to a liquid storage tank and then transported back to alumina production by pipeline.

[0047] 4. Density entering sublimation dehydration machine>2.3g / cm 3 The powder material is quickly heated up and dehydrated by sublimation. The temperature of the sublimation dehydrator is controlled at 30-35℃. The dry powder after sublimation dehydration is transported to the intermediate storage tank.

[0048] 5. The powder in the intermediate storage tank is separated by a four-stage pneumatic centrifugal classifier. The density of the three series-connected pneumatic centrifugal classifiers for the four-stage separation is set at 5g / cm 3 , 3.5g / cm 3 and 2.7 g / cm 3 .

[0049] 6. After the density of the four-stage pneumatic centrifugal classifier is set, the fan is started. The powder in the intermediate storage tank is blown into the three-stage pneumatic centrifugal classifier for classification. The first-stage outlet separates ≥5g / cm 3 Iron oxide and heavy metal mineral powders used in steel smelting enter the powder bin for storage or packaging by packaging machine; the second-stage outlet separates <5g / cm 3and >3.5g / cm 3 The mixed powder of calcium titanate and alumina used as abrasive enters the powder bin for storage or packaging by the packaging machine; the third outlet separates >2.7g / cm 3 And ≤3.5g / cm 3 Calcium carbonate, calcium oxide, calcium aluminosilicate and calcium silicate mixed powder for cement are stored in powder bin or packaged by packaging machine; the fourth outlet separates ≤2.7g / cm 3 and >2.3g / cm 3 The sodium aluminosilicate powder is stored in the powder silo or packaged by the packaging machine.

Claims

1. A method and device for low temperature crushing of solid red mud to pneumatically separate various substances, characterized in that The device consists of three parts: low-temperature crushing system, dehydration system, and pneumatic classification system. Among them: the low-temperature crushing system is that the red mud is continuously crushed by the primary grinding equipment, oscillator and airflow mill. The primary grinding equipment is connected to the refrigerant storage tank and the dispersant storage tank through pipelines, and there is a low-temperature gas tank in front of the airflow mill; the pneumatic centrifugal classifier inlet of the dehydration system is connected to the airflow mill outlet pipeline, the heavy density material outlet at the bottom of the pneumatic centrifugal classifier is connected to the sublimation dehydrator, and the light density material outlet at the top is connected to the heating and melting tank, and the heating and melting tank is connected to the solid-liquid separator, and the solid-liquid separator is connected to the liquid collection The invention relates to a liquid storage tank, a powder silo for collecting powder, and a packaging machine; the inlet of the intermediate storage tank of the pneumatic classification system is connected to the outlet pipe of the sublimation dehydrator, and the outlet is connected to the inlet pipe of the pneumatic centrifugal classifier group; a fan is installed in the pipeline between the intermediate storage tank and the multi-stage pneumatic centrifugal classifier group, and the fan blows the red mud powder in the intermediate storage tank into the multi-stage pneumatic centrifugal classifier group for classification; the outlets of each pneumatic centrifugal classifier of the multi-stage pneumatic centrifugal classifier group are equipped with powder silos and packaging machines; the method and device for low-temperature crushing of solid red mud to pneumatically separate multi-stage substances also include the following method steps: (1) Solid red mud is put into the primary grinding equipment, and a refrigerant is added to reduce its temperature to below -12°C. A dispersant is added to grind it to a particle size of less than 35 μm, and then it enters an oscillator to change the frequency of oscillation, and then it is sent to the air flow mill for crushing with low-temperature gas. After the air flow mill crushes the red mud to a particle size of less than 20 μm and a span S of less than 1.5, it is transported to the pneumatic centrifugal classifier of the dehydration system; the material temperature is kept below -12°C during the grinding, oscillation and powder conveying process; (2) Set the classification density index range of the pneumatic centrifugal classifier to ≥2.2g / cm 3 And ≤2.7g / cm 3 ; The ground powder enters the pneumatic centrifugal classifier for classification, and the material temperature is kept below -12°C during the classification process; the powder separated from the lower outlet of the pneumatic centrifugal classifier enters the sublimation dehydrator for dehydration; the powder separated from the upper outlet enters the temperature-raising melting storage tank to melt into a solid-liquid mixture, and then enters the solid-liquid separator for solid-liquid separation, and the separated mixed solution of water, sodium aluminate and sodium hydroxide is loaded into the liquid storage tank, and the separated powder enters the powder bin or packaging machine for packaging; the dried powder after sublimation dehydration is loaded into the intermediate storage tank; (3) The multi-stage pneumatic centrifugal classifier group is set to a classification density according to the required material or material combination, wherein the classification density of the first pneumatic centrifugal classifier is set to 5 g / cm 3 , other levels of pneumatic centrifugal classifiers can set the classification density as needed, and the setting density range is <5g / cm 3 And it is greater than the classification density set before dehydration; after setting the classification density, start the fan to input the powder in the intermediate storage tank into the multi-stage pneumatic centrifugal classifier group for pneumatic classification, and the density of the separated powder at the first stage outlet is ≥5g / cm 3 The iron oxide and heavy metal mineral powders are separated into multiple set intervals <5g / cm 3 And the powders and powder combinations whose density is greater than the set classification density before dehydration; the powders separated by each level of classifier are stored in the connected powder silo or packaged by the packaging machine.

2. According to claim 1, a method and device for low temperature crushing of solid red mud to pneumatically separate various substances, characterized in that The primary grinding equipment is a vibration mill, a stirring mill, or a ball mill; the oscillator is an ultrasonic oscillator with adjustable frequency, or an air flow shock wave oscillator.

3. According to claim 1, the method and device for low temperature crushing of solid red mud to pneumatically separate various substances is characterized by: Control the working temperature of the heating and melting tank to be >5℃ and <50℃; control the working temperature of the sublimation dehydrator to be >25℃ and <50℃.

4. According to claim 1, the method and device for low temperature crushing of solid red mud to pneumatically separate various substances is characterized by: The refrigerant used is liquid nitrogen, dry ice, or a mixture of liquid nitrogen and dry ice.

5. According to claim 1, the method and device for low temperature crushing of solid red mud to pneumatically separate various substances is characterized by: The dispersant used is one of anhydrous calcium carbonate, calcium silicate, β-alumina with a particle size of less than 8 μm, or a mixture of two or more thereof; when liquid nitrogen is used as a refrigerant during grinding, the dispersant addition ratio is 0.3% of the weight of the substance after water and iron oxide are removed from the red mud; when dry ice is used as a refrigerant, the dispersant addition ratio is 0.1% of the weight of the substance after water and iron oxide are removed from the red mud.

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