Method for separating and enriching low-grade bauxite ore phase and co-producing ceramsite proppant

Abstract

The invention relates to a method for low-grade bauxite ore phase separation and enrichment and ceramsite proppant co-production, and the method comprises the following steps: carrying out crushing, first ore grinding and grading on bauxite in sequence to respectively obtain tailings, middlings and first concentrate; the first concentrate is subjected to second ore grinding and then graded, tailings, middlings and second concentrate are obtained, the tailings obtained after first ore grinding and the middlings obtained after second ore grinding are combined, and combined tailings and combined middlings are obtained; mixing a calcium source, alkali liquor and the combined middling to obtain mixed slurry; the mixed slurry is subjected to a hydrothermal reaction, and second concentrate and calcium-containing tailings are obtained after separation; and sequentially granulating, drying and calcining the mixed water, the combined tailings and the calcium-containing tailings to obtain the ceramsite proppant. The obtained middlings can be converted into concentrates after reaction, the obtained concentrates are high in grade and high in recovery rate, meanwhile, tailings can be used for preparing ceramsite proppants, and all-component utilization of middle-low-grade bauxite is achieved.

Description

Technical Field

[0001] The invention belongs to the technical fields of bauxite beneficiation, industrial solid waste resource utilization and new ceramsite materials, and relates to a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Background Art

[0002] Bauxite resources are primarily diaspore-type bauxite, characterized by high aluminum and silicon content. Most of the bauxite is low- to medium-grade, with an aluminum-to-silicon ratio (A / S) of less than 4. Numerous studies and practices have sought to improve the grade of bauxite through flotation desiliconization, followed by the economical Bayer process for alumina production. This method has indeed effectively improved bauxite resource utilization.

[0003] CN102755925A discloses a separation method suitable for medium and low-grade bauxite, which can process raw ores with an aluminum-silicon ratio of more than 4; CN101439317A and CN102806146A both disclose a bauxite beneficiation pre-desiliconization method. This method has a relatively simple process, but it also has the problem of difficult utilization of tailings, and the raw ores that can be processed have an aluminum-silicon ratio of more than 3.5.

[0004] CN102294304A discloses a method for flotation of bauxite, wherein the pulp with qualified fineness after grinding the raw ore or the flotation pulp with low concentration is concentrated and then subjected to flotation. However, the minimum aluminum-silicon ratio of the raw ore that can be processed by the above patent is 4. CN108554594A discloses a method for beneficiation of low-grade bauxite, which controls the grinding and crushes or ball-mills the monohydrate-type bauxite with an A / S of less than 3 to obtain bauxite powder, and then separates some of the fine particles through classification. The separated fine particles are the low aluminum-silicon ratio product, and the A / S of the low aluminum-silicon ratio product is less than 1.7. The remaining bauxite powder is a product with an A / S of greater than 3. Although this method can process bauxite with a lower aluminum-silicon ratio, it requires the raw ore to be finely ground to less than 10μm. This process consumes extremely high energy and the aluminum-silicon ratio of the selected concentrate does not exceed 4, and the aluminum-silicon ratio of the tailings is as high as 1.7.

[0005] With the rapid development of the alumina industry, the grade of selected bauxite is becoming lower and lower, from the early A / S ratio of >5 to below 3.5. In the next few years, the grade of selected bauxite will continue to decline. As a result, the flotation desiliconization of low-aluminum-silicon bauxite is becoming increasingly difficult, the performance index is deteriorating, and the production cost is increasing.

[0006] In addition, existing bauxite beneficiation and desiliconization methods rarely pay attention to the treatment of tailings. Kaolin is one of the main components of bauxite beneficiation tailings and is also one of the important raw materials for ceramsite preparation.

[0007] Therefore, it is of great significance to develop a new method for the separation and enrichment of low-grade bauxite and the co-production of ceramsite. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. The obtained middlings can be converted into concentrate after reaction. The obtained concentrate has high grade and high recovery rate. At the same time, the tailings can be used to prepare ceramsite proppant, realizing the full component utilization of low- and medium-grade bauxite.

[0009] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, the method comprising the following steps:

[0011] (1) crushing, first grinding and classification of bauxite in sequence to obtain tailings, middlings and first concentrate respectively;

[0012] (2) subjecting the first concentrate in step (1) to a second grinding and then classifying to obtain tailings, middlings, and a second concentrate, and combining the tailings and middlings obtained after the first grinding and the second grinding, respectively, to obtain combined tailings and combined middlings;

[0013] (3) mixing the calcium source, alkali solution and the combined middlings of step (2) to obtain a mixed slurry;

[0014] (4) subjecting the mixed slurry of step (3) to a hydrothermal reaction, and obtaining a second concentrate and calcium-containing tailings after separation;

[0015] (5) mixing water, the combined tailings of step (2) and the calcium-containing tailings of step (4), and sequentially granulating, drying and calcining to obtain a ceramsite proppant.

[0016] The method of the present invention comprises the following steps: subjecting medium- and low-grade bauxite particles to a first grinding and classification to obtain a first concentrate, a middling and a tailings; then subjecting the first concentrate to a second grinding for several times until the aluminum-silicon ratio (A / S) of the concentrate is ≥5.5; and combining the first grinding and the second grinding to obtain a second concentrate with an aluminum-silicon ratio ≥5.5; and then combining the middling and the tailings obtained from each grinding to obtain a combined middling and a combined tailings.

[0017] The method of the present invention comprises the following steps: combining the middling ore and a calcium raw material with calcium oxide as the main component in a specific proportion, mixing the mixture and adding the mixture to an alkaline solution; and then realizing a selective directional reaction through a hydrothermal reaction, so that the silicon-containing phase in the bauxite is converted into a calcium-containing tailing with a lower density. The density of the calcium-containing tailing, the directional conversion product, is significantly lower than the density of the mineral phase diaspore in the middling ore. At the same time, by controlling the specific hydrothermal reaction conditions, there is no obvious mutual wrapping phenomenon between the calcium-containing tailing and the diaspore. Therefore, the difference in density can be used to separate the silicon-containing product from the diaspore ore, thereby obtaining a diaspore concentrate (second concentrate) with a high aluminum-silicon ratio.

[0018] The aluminum-silicon ratio of the combined tailings obtained by the method of the present invention is ≤1.7, and the main component is kaolin, which is one of the main raw materials for firing ceramsite. In addition, the calcium-containing tailings obtained by the hydrothermal reaction can be converted into a liquid phase during the firing process of the ceramsite, thereby reducing the sintering temperature and providing a liquid phase environment for crystal growth. Therefore, after the combined tailings and the calcium-containing tailings are mixed and granulated, the ceramsite proppant can be fired at a lower temperature, thereby realizing the full utilization of the components of medium and low-grade bauxite.

[0019] It is worth noting that the method has a simple process and low cost, reduces the use of natural raw materials, saves resources, and "turns harm into benefit and waste into treasure", which plays a huge role in vigorously developing the green economy and circular economy, achieving the unity of the environment, society and economy, and promoting the sustainable development of society, economy and environment.

[0020] As a preferred technical solution of the present invention, bauxite particles are obtained after the crushing in step (1).

[0021] Preferably, the mass percentage of the bauxite particles with a particle size of 0.5 to 2 cm is 20% to 100%, for example, it can be 30%, 40%, 50%, 60%, 70%, 80% or 90%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0022] It is worth noting that pre-crushing the bauxite into a particle size range of 0.5 to 2 cm is conducive to the subsequent selective grinding. If it is directly ground, the silicon-rich phase and the aluminum-rich phase will be entangled with each other and difficult to separate, and the energy consumption of the ball mill will increase and the efficiency will decrease.

[0023] It is worth noting that the present invention is based on the differences in particle size, distribution form and hardness between silicon-containing minerals and aluminum-containing minerals in low-grade bauxite, and obtains first concentrate, middlings and tailings particles by grinding and classifying medium and low-grade bauxite particles. The selective grinding and classification method is simple but efficient, which can greatly reduce the feed amount of subsequent hydrothermal reaction, effectively reducing energy consumption and raw materials. The tailings screened by the first grinding, second grinding and classification have a low aluminum-silicon ratio. Although they cannot be used as aluminum extraction resources, they are high-quality raw materials for ceramsite. Therefore, the first grinding and second grinding are one of the key points of the present invention to achieve full resource utilization.

[0024] Preferably, the first grinding in step (1) includes dry grinding or wet grinding.

[0025] Preferably, the filling rate of the grinding media in the first grinding in step (1) is 5% to 60%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or 55%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0026] Preferably, the time for the first grinding in step (1) is 1 to 30 min, for example, 2 min, 5 min, 7 min, 10 min, 12 min, 15 min, 17 min, 20 min, 22 min, 25 min, 27 min or 29 min, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0027] It is worth noting that if the first grinding time is too short, the mineral separation is insufficient; if the first grinding time is too long, the mineral particles are too small and difficult to separate, and the energy consumption is high.

[0028] Preferably, the mill speed of the first grinding in step (1) is 5 to 300 r / min, for example, it can be 10 r / min, 30 r / min, 50 r / min, 70 r / min, 100 r / min, 120 r / min, 150 r / min, 170 r / min, 200 r / min, 220 r / min, 250 r / min, 270 r / min or 290 r / min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0029] Preferably, the mill filling rate of the first grinding in step (1) is 20% to 50%, for example, it can be 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47% or 49%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0030] In the present invention, the selection of the grinding medium filling rate, the mill speed and the mill filling rate is the result of comprehensive consideration of the overall cost and separation efficiency. Too high or too low will affect the effect of the first grinding.

[0031] Preferably, the classification in step (1) includes dry classification or wet classification.

[0032] In the present invention, the classification method includes any one of wind classification, hydrocyclone, chute or vibration screen classification, or a combination of at least two of them.

[0033] Preferably, the particle size of the tailings in step (1) is less than 150 μm, for example, it can be 140 μm, 130 μm, 120 μm, 110 μm, 100 μm or 90 μm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0034] Preferably, the particle size of the middling ore in step (1) is 150 to 250 μm, for example, it can be 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm or 240 μm, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0035] Preferably, the particle size of the first concentrate in step (1) is greater than 250 μm, for example, it can be 260 μm, 270 μm, 280 μm, 290 μm, 300 μm or 310 μm, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0036] As a preferred technical solution of the present invention, the second grinding in step (2) includes dry grinding or wet grinding.

[0037] Preferably, the number of times the second grinding is performed in step (2) is 1 to 10 times, for example, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times or 9 times, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 2 to 5 times.

[0038] In the present invention, the number of repetitions of the second grinding helps to improve the separation efficiency of minerals. If the number of the second grinding is too low, the grade difference between tailings, middlings and concentrates is too small. If the number of the second grinding is too high, the energy consumption is too high and the process is lengthy.

[0039] Preferably, the filling rate of the grinding medium in the second grinding in step (2) is 10% to 50%, for example, it can be 15%, 20%, 25%, 30%, 35%, 40%, 45% or 49%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0040] Preferably, the time for the second grinding in step (2) is 5 to 20 minutes, for example, 7 minutes, 10 minutes, 12 minutes, 14 minutes, 15 minutes, 16 minutes, 18 minutes or 19 minutes, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0041] Preferably, the mill speed of the second grinding in step (2) is 5 to 300 r / min, for example, it can be 10 r / min, 30 r / min, 50 r / min, 70 r / min, 100 r / min, 120 r / min, 150 r / min, 170 r / min, 200 r / min, 220 r / min, 250 r / min, 270 r / min or 290 r / min, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0042] Preferably, the mill filling rate of the second grinding in step (2) is 20% to 50%, for example, it can be 22%, 25%, 27%, 30%, 32%, 35%, 37%, 40%, 42%, 45%, 47% or 49%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0043] Preferably, the aluminum-silicon ratio of the second concentrate in step (2) is ≥5.5, for example, it can be 5.6, 5.7, 5.8, 5.9, 6.0, 6.2 or 6.5, but is not limited to the listed values. Other unlisted values within the numerical range are also applicable, preferably ≥6.0.

[0044] As a preferred technical solution of the present invention, the calcium source in step (3) includes industrial raw materials and / or waste residues containing calcium oxide, preferably any one or a combination of at least two of calcium hydroxide, lime or phosphogypsum.

[0045] In the present invention, the calcium source can be a single industrial raw material or waste residue with calcium oxide as the main component, or a mixture of at least two industrial raw materials or waste residues with calcium oxide as the main component. Exemplarily, it can be any one of calcium hydroxide, lime or phosphogypsum. Typical but non-limiting combinations are a combination of calcium hydroxide and lime, a combination of calcium hydroxide and phosphogypsum, a combination of lime and phosphogypsum, a combination of calcium hydroxide, lime and phosphogypsum, and the like.

[0046] Preferably, the alkali solution in step (3) includes NaOH solution and / or KOH solution.

[0047] Preferably, the concentration of the alkali solution in step (3) is 0.05-2.5 mol / L, for example, it can be 0.07 mol / L, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L or 2.4 mol / L, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 0.1-1 mol / L.

[0048] It is worth noting that controlling the concentration of the alkali solution within the range of 0.05-2.5 mol / L can better promote the dissolution reaction. When the alkali solution concentration is too low, the subsequent reaction is difficult to proceed completely; when the alkali solution concentration is too high, other products will be generated during the reaction, reducing the aluminum recovery rate.

[0049] As a preferred technical solution of the present invention, the molar ratio of CaO in the calcium source in step (3) to SiO2 in the combined ore is (0.4-1.5):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 13:1 or 1.4:1, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably (0.8-1.2):1;

[0050] It is worth noting that by controlling the molar ratio range of CaO in the calcium source and SiO2 in the combined medium ore, the silicon component can be utilized more effectively. When the molar ratio of CaO to SiO2 is too low or too high, the reaction effect of the silicon-rich ore phase will be affected.

[0051] Preferably, the ratio of the total mass of the calcium source and the combined middlings in step (3) to the volume of the alkali solution is 1:(2.5-40) g / mL, for example, 1:3 g / mL, 1:5 g / mL, 1:10 g / mL, 1:15 g / mL, 1:20 g / mL, 1:25 g / mL, 1:30 g / mL, 1:35 g / mL or 1:38 g / mL, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 1:(5-20) g / mL.

[0052] It is worth noting that the total mass ratio of the calcium source and the combined middlings to the volume of the alkali solution is a key factor in selective dissolution. When the mass-to-volume ratio is too high, the mixture of the mixed material and the alkali solution is difficult to mix evenly, and the volume of the reaction product will expand rapidly, making the reaction difficult to proceed; when the mass-to-volume ratio is too low, it will cause unnecessary energy consumption.

[0053] As a preferred technical solution of the present invention, the temperature of the hydrothermal reaction in step (4) is 100-250°C, for example, it can be 110°C, 120°C, 140°C, 150°C, 160°C, 180°C, 200°C, 220°C, 230°C or 240°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 140-220°C.

[0054] Preferably, the time of the hydrothermal reaction in step (4) is 1-30 h, for example, it can be 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 23 h, 25 h, 27 h or 29 h, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 2-10 h.

[0055] It is worth noting that when the temperature of the hydrothermal reaction is too low, the reaction power is insufficient, which reduces the conversion rate of silicon dioxide; when the temperature of the hydrothermal reaction is too high, additional energy consumption is increased, which increases costs. When the hydrothermal reaction time is too short, the reaction is incomplete and many raw materials cannot be converted, resulting in a waste of raw materials; when the hydrothermal reaction time is too long, it will lead to increased energy consumption and increase the cost of mineral processing. Therefore, the present invention controls the temperature and time of the hydrothermal reaction within the above range, which can improve the utilization rate of raw materials, efficiently achieve the directional conversion of silicon in bauxite, and at the same time reduce resource waste and reduce energy consumption.

[0056] As a preferred technical solution of the present invention, the separation in step (4) includes: performing solid-solid separation on the hydrothermal reaction product to obtain a second concentrate and a slurry, and then performing solid-liquid separation on the slurry to obtain calcium-containing tailings.

[0057] It is worth noting that the tailings produced by the method are rich in kaolin, one of the important raw materials for ceramsite production. At the same time, the calcium-containing tailings produced by the hydrothermal method can be added to the ceramsite body to regulate the liquid phase amount during the ceramsite sintering process, greatly improving the strength of the ceramsite product. Therefore, the present invention proposes to prepare ceramsite by mixing the combined tailings and the calcium-containing tailings to achieve the comprehensive utilization of the two.

[0058] Preferably, the solid-solid separation method includes sedimentation separation or centrifugal separation.

[0059] In the present invention, the solid-solid separation equipment includes any one of a sedimentation tank, a hydrocyclone, a chute or a centrifuge, or a combination of at least two of them. In addition to the above equipment, other equipment that uses density difference for separation can be used for separating bauxite concentrate and slurry.

[0060] It is worth noting that the solid-solid separation is performed based on the difference in density between the second concentrate and the calcium-containing tailings. The separated material with a high density is the second concentrate, and the separated material with a low density is the calcium-containing tailings.

[0061] It should be noted that the solid-liquid separation is carried out by conventional means in this field, and there is no special limitation as long as the calcium-containing tailings can be separated from the solution.

[0062] As a preferred technical solution of the present invention, the mass ratio of the total mass of the combined tailings and calcium-containing tailings to water in step (5) is 1:(0.06-0.4), for example, it can be 1:0.08, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3 or 1:0.35, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0063] It is worth noting that the present invention requires strict control of the amount of water added during the granulation process to ensure the sphericity and particle size of the final ceramsite proppant. By controlling the water content of the reaction mixture after adding water during the granulation process, the optimal technical effect can be achieved.

[0064] Preferably, the mixing time in step (5) is 1 to 30 min, for example, it can be 5 min, 7 min, 10 min, 12 min, 15 min, 17 min, 20 min, 22 min, 25 min, 27 min or 29 min, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0065] Preferably, the mixing in step (5) includes one-step mixing or step-by-step mixing, preferably step-by-step mixing.

[0066] Preferably, the step-by-step mixing includes: first adding 5wt% to 15wt% of water, which accounts for 5wt% to 15wt% of the mass fraction of the combined tailings and calcium-containing tailings, and mixing them with the combined tailings and calcium-containing tailings for 0.5 to 20 minutes, and then adding the remaining water and mixing for 0.5 to 20 minutes.

[0067] Preferably, the granulation time in step (5) is 1 to 40 min, for example, it can be 5 min, 7 min, 10 min, 12 min, 15 min, 17 min, 20 min, 22 min, 25 min, 27 min, 30 min, 32 min, 35 min, 37 min or 39 min, etc., preferably 5 to 30 min.

[0068] In the present invention, the mixing of the water and the mixed powder can be carried out in a granulation device, that is, the water and the mixed powder are first mixed in the granulation device, and then granulation is carried out.

[0069] Preferably, the granulation equipment in step (5) comprises any one of an inclined intensive mixer, a sugar coating pan granulator or a disc granulator, preferably an inclined intensive mixer.

[0070] Preferably, the barrel speed of the inclined intensive mixer is 10 to 1500 r / min, for example, it can be 20 r / min, 50 r / min, 60 r / min, 100 r / min, 50 r / min, 60 r / min, 100 r / min, 200 r / min, 300 r / min, 500 r / min, 700 r / min, 1000 r / min, 1200 r / min or 1400 r / min, etc., preferably 20 to 80 r / min.

[0071] Preferably, the rotor speed of the inclined intensive mixer is 300-6000 r / min, for example, it can be 400 r / min, 500 r / min, 700 r / min, 1000 r / min, 1500 r / min, 2000 r / min, 2500 r / min, 3000 r / min, 3500 r / min, 4000 r / min, 4500 r / min, 5000 r / min or 5500 r / min, etc., preferably 500-4000 r / min.

[0072] As a preferred technical solution of the present invention, the heating rate of the calcination in step (5) is 1 to 15°C / min, for example, 3°C / min, 5°C / min, 7°C / min, 9°C / min, 10°C / min, 12°C / min, 13°C / min or 14°C / min, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 5 to 10°C / min.

[0073] Preferably, the temperature rise endpoint of the calcination in step (5) is 1000-1700°C, for example, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C, 1650°C or 1690°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 1200-1500°C.

[0074] Preferably, the holding time of the calcination in step (5) is 0.1 to 12 h, for example, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h or 11 h, but is not limited to the listed values. Other values not listed within the numerical range are also applicable, preferably 0.5 to 8 h.

[0075] Preferably, the calcination in step (5) further includes furnace cooling.

[0076] In the present invention, the calcining equipment includes any one of an electric heating furnace, a gas furnace or a pulverized coal heating furnace.

[0077] As a preferred technical solution of the present invention, the method comprises the following steps:

[0078] (1) crushing, first grinding and classification of bauxite in sequence to obtain tailings, middlings and first concentrate respectively;

[0079] After the crushing, bauxite particles are obtained; the mass percentage of the bauxite particles with a particle size of 0.5 to 2 cm is 20% to 100%;

[0080] The first grinding process has a grinding medium filling rate of 5% to 60%, a grinding time of 1 to 30 minutes, a mill speed of 5 to 300 rpm, and a mill filling rate of 20% to 50%;

[0081] The particle size of the tailings is less than 150 μm; the particle size of the middlings is 150 to 250 μm; the particle size of the first concentrate is greater than 250 μm;

[0082] (2) subjecting the first concentrate in step (1) to a second grinding and then classifying to obtain tailings, middlings, and a second concentrate, and combining the tailings and middlings obtained after the first grinding and the second grinding, respectively, to obtain combined tailings and combined middlings;

[0083] The second grinding is performed 1 to 10 times, the grinding medium filling rate is 10% to 50%, the time is 5 to 20 minutes, the mill speed is 5 to 300 rpm, and the mill filling rate is 20% to 50%;

[0084] The aluminum-silicon ratio of the second concentrate is ≥5.5;

[0085] (3) mixing the calcium source, alkali solution and the combined middlings of step (2) to obtain a mixed slurry;

[0086] The calcium source includes industrial raw materials and / or waste residues containing calcium oxide; the alkali solution includes NaOH solution and / or KOH solution; the concentration of the alkali solution is 0.05-2.5 mol / L;

[0087] The molar ratio of CaO in the calcium source to SiO2 in the combined middlings is (0.4-1.5):1; the ratio of the total mass of the calcium source and the combined middlings to the volume of the alkali solution is 1:(2.5-40) g / mL;

[0088] (4) subjecting the mixed slurry of step (3) to a hydrothermal reaction at a temperature of 100-250° C. for 1-30 hours, subjecting the hydrothermal reaction product to solid-solid separation to obtain a second concentrate and a slurry, and then subjecting the slurry to solid-liquid separation to obtain a calcium-containing tailing;

[0089] (5) mixing water, the combined tailings described in step (2) and the calcium-containing tailings described in step (4), and sequentially granulating, drying and calcining to obtain a ceramsite proppant;

[0090] The mass ratio of the total mass of the combined tailings and calcium-containing tailings to water is 1:(0.06-0.4); the mixing time is 1 to 30 minutes;

[0091] The granulation time is 1 to 40 minutes;

[0092] The heating rate of the calcination is 1-15°C / min, the heating end point is 1000-1700°C, and the heat preservation time is 0.1-12h.

[0093] Compared with the prior art, the present invention has the following beneficial effects:

[0094] (1) The method of the present invention has a very low requirement for the aluminum-silicon ratio of the raw ore. The aluminum-silicon ratio of the second concentrate obtained after aluminum-silicon separation from the raw ore with an aluminum-silicon ratio of less than 3.0 can reach above 5.5, which fully meets the technical index requirements of the Bayer process alumina industrial production in my country;

[0095] (2) The method of the present invention can not only obtain bauxite concentrate through selective grinding, but also reduce the amount of subsequent hydrothermal treatment and reduce process costs. After the aluminum-rich phase and the silicon-rich phase are separated during the reaction process of the recycled ore, the ore in which diaspore and kaolinite are interwoven with each other is opened, and the aluminum-rich phase is activated in situ. The increased surface energy can reduce the energy consumption during the subsequent Bayer process dissolution. After that, the tailings produced by the ore dressing and the calcium-containing tailings are combined and fired into ceramsite proppant, thereby achieving 100% utilization of the raw materials.

[0096] (3) The method of the present invention is simple in process, low in cost, and reduces the use of natural raw materials, thus saving resources and "turning harm into benefit and waste into treasure". It plays a huge role in promoting the vigorous development of green economy and circular economy, achieving the unity of environment, society and economy, and promoting the sustainable development of society, economy and environment. DETAILED DESCRIPTION

[0097] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0098] In the following examples and comparative examples, if specific techniques or conditions are not specified, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments used without manufacturer indication are conventional products commercially available through regular channels.

[0099] Example 1

[0100] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, the method comprising the following steps:

[0101] (1) Bauxite with an aluminum-silicon ratio of 2.5 is crushed, first ground, and classified in sequence to obtain tailings, middlings, and first concentrate, respectively;

[0102] After the crushing, bauxite particles are obtained; the mass percentage of the bauxite particles with a particle size of 0.5 to 2 cm is 80%;

[0103] The first grinding process has a grinding medium filling rate of 30%, a grinding time of 30 min, a mill speed of 150 r / min, and a mill filling rate of 35%;

[0104] The particle size of the tailings is less than 150 μm; the particle size of the middlings is 150 to 250 μm; the particle size of the first concentrate is greater than 250 μm;

[0105] (2) subjecting the first concentrate in step (1) to two second grindings and then classifying to obtain tailings, middlings, and a second concentrate, and combining the tailings and middlings obtained after the first grinding and the second grinding to obtain combined tailings and combined middlings;

[0106] The second grinding process has a grinding medium filling rate of 30%, a grinding time of 5 min, a mill speed of 150 r / min, and a mill filling rate of 35%;

[0107] (3) mixing calcium hydroxide, a 0.5 mol / L NaOH solution, and the combined middlings from step (2) to obtain a mixed slurry;

[0108] The molar ratio of CaO in the calcium hydroxide to SiO2 in the combined middlings is 1.0:1; the ratio of the total mass of the calcium hydroxide and the combined middlings to the volume of the NaOH solution is 1:5 g / mL;

[0109] (4) subjecting the mixed slurry of step (3) to a hydrothermal reaction at a temperature of 180° C. for 2 h, subjecting the hydrothermal reaction product to solid-solid separation by sedimentation, washing to obtain a second concentrate and slurry, and then filtering the slurry to solid-liquid separation to obtain calcium-containing tailings;

[0110] (5) ball-milling the combined tailings of step (2) and the calcium-containing tailings of step (4) for 10 minutes, adding water thereto and mixing for 4 minutes, followed by granulation, drying, and calcining in sequence, and cooling in the furnace to obtain a ceramsite proppant;

[0111] The mass ratio of the total mass of the combined tailings and calcium-containing tailings to water is 1:0.25; the mixing time is 1 to 30 minutes; the mixing is performed in steps, first adding 15wt% of water to the combined tailings and calcium-containing tailings and mixing them for 1 minute, and then adding the remaining water and mixing;

[0112] The granulation time is 30 minutes; the granulation equipment is an inclined strong mixer, the barrel speed of the inclined strong mixer is 50r / min, and the rotor speed is 4000r / min;

[0113] The heating rate of the calcination is 5°C / min, the heating end point is 1300°C, and the holding time is 2h.

[0114] Example 2

[0115] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the mass percentage of the bauxite particles with a particle size of 0.5 to 2 cm in the bauxite particles in step (1) is 40%, other conditions are the same as those in Example 1.

[0116] Example 3

[0117] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the time for the first grinding in step (1) and the second grinding in step (2) are both 10 minutes, other conditions are the same as those in Example 1.

[0118] Example 4

[0119] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the second grinding is performed six times in step (2), other conditions are the same as those in Example 1.

[0120] Example 5

[0121] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, except that the molar ratio of CaO in the calcium hydroxide and SiO2 in the combined middling ore in step (3) is 0.6:1, other conditions are the same as those in Example 1.

[0122] Example 6

[0123] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the concentration of the NaOH solution in step (3) is 0.15 mol / L, other conditions are the same as those in Example 1.

[0124] Example 7

[0125] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, except that the ratio of the total mass of calcium hydroxide and the combined middlings to the volume of the NaOH solution in step (3) is 1:10 g / mL, the other conditions are the same as those in Example 1.

[0126] Example 8

[0127] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the temperature of the hydrothermal reaction in step (4) is 150°C, other conditions are the same as those in Example 1.

[0128] Example 9

[0129] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the time of the hydrothermal reaction in step (4) is 4 hours, other conditions are the same as those in Example 1.

[0130] Example 10

[0131] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the aluminum-silicon ratio of the bauxite in step (1) is 3.4, other conditions are the same as those in Example 1.

[0132] Example 11

[0133] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the mill speeds of step (1) the first grinding and step (2) the second grinding are both 50 r / min, other conditions are the same as those in Example 1.

[0134] Example 12

[0135] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, except that the grinding medium filling rate of step (1) the first grinding and step (2) the second grinding is 20%, other conditions are the same as those in Example 1.

[0136] Example 13

[0137] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, except that the mill filling rate of step (1) the first grinding and step (2) the second grinding is both 30%, other conditions are the same as those in Example 1.

[0138] Example 14

[0139] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the mass ratio of the total mass of the combined tailings and calcium-containing tailings to water in step (5) is 1:0.1, other conditions are the same as those in Example 1.

[0140] Example 15

[0141] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the granulation time in step (5) is 40 minutes, other conditions are the same as those in Example 1.

[0142] Example 16

[0143] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the barrel speed of the inclined intensive mixer in step (5) is 30 r / min, other conditions are the same as those in Example 1.

[0144] Example 17

[0145] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the heating end point of the calcination in step (5) is 1500°C, other conditions are the same as those in Example 1.

[0146] Example 18

[0147] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the heating rate of calcination in step (5) is 10°C / min, other conditions are the same as those in Example 1.

[0148] Example 19

[0149] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the holding time of the calcination in step (5) is 6 hours, other conditions are the same as those in Example 1.

[0150] Example 20

[0151] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the mass percentage of the bauxite particles with a particle size of 150 to 250 μm in the bauxite particles in step (1) is 80%, other conditions are the same as those in Example 1.

[0152] Example 21

[0153] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the second grinding time in step (2) is 3 minutes, other conditions are the same as those in Example 1.

[0154] Example 22

[0155] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the mass ratio of the total mass of the combined tailings and calcium-containing tailings to water in step (5) is 1:0.05, other conditions are the same as those in Example 1.

[0156] Example 23

[0157] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the mass ratio of the total mass of the combined tailings and calcium-containing tailings to water in step (5) is 1:0.5, other conditions are the same as those in Example 1.

[0158] Example 24

[0159] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the heating end point of the calcination in step (5) is 800°C, other conditions are the same as those in Example 1.

[0160] Example 25

[0161] This embodiment provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that the heating end point of the calcination in step (5) is 2000°C, other conditions are the same as those in Example 1.

[0162] Comparative Example 1

[0163] This comparative example provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that steps (1) and (2) are adjusted to direct ball milling to obtain ore particles with a particle size of 150 to 250 μm and then classification, other conditions are the same as those in Example 1.

[0164] Comparative Example 2

[0165] This comparative example provides a method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant. Except that step (2) is not performed, other conditions are the same as those in Example 1.

[0166] The contents of bauxite, concentrate, and tailings in the above examples and comparative examples were measured using an inductively coupled plasma mass spectrometer (ICP-OES), and the aluminum-silicon ratio was calculated. The results are shown in Table 1. The ceramsite proppant products prepared in the above examples and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0167] Table 1

[0168]

[0169]

[0170]

[0171] From Table 1 we can see that:

[0172] (1) The method provided in Examples 1-19 of the present invention is a method for phase separation and enrichment of low-grade bauxite, which not only ensures the grade of the second concentrate but also has a high recovery rate. The method is simple to operate, has strong applicability, and is easy to promote. The aluminum-silicon ratio of the obtained second concentrate is greater than 5.5, preferably greater than 6, the aluminum-silicon ratio of the tailings is less than 1.7, and the recovery rate of the second concentrate is greater than 50%. The 35MPa crushing rate of the obtained ceramsite proppant is less than 10%, the acid solubility is less than 1.5%, and the bulk density is between 1.1 and 1.5 g·cm -3 Within the specified range, it has excellent crushing resistance and acid corrosion resistance;

[0173] (2) From the comparison between Example 1 and Example 20, it can be seen that when the particle size of the crushed bauxite is too small, the particle size difference between the silicon-rich phase and the aluminum-rich phase is too small to be distinguished by screening, resulting in a decrease in the concentrate recovery rate;

[0174] (3) From the comparison between Example 1 and Example 21, it can be seen that when the time of the first grinding and the second grinding is too short, the mineral separation is insufficient, resulting in the second concentrate grade not reaching above 5.5;

[0175] (4) From the comparison between Example 1 and Examples 22-23, it can be seen that when the amount of water added during the preparation of the ceramsite proppant is too little, the green body is difficult to form, resulting in a decrease in the crushing resistance of the ceramsite proppant; when the amount of water added is too much, the green body is difficult to form, resulting in a decrease in the crushing resistance of the ceramsite proppant, and in addition, the energy consumption during calcination increases sharply, resulting in an increase in cost; from the comparison between Example 1 and Examples 24-25, it can be seen that when the calcination temperature of the ceramsite proppant is too low, the sintering strength is insufficient, the strength decreases, and the performance of the ceramsite proppant is reduced; when the calcination temperature of the ceramsite proppant is too high, the required energy consumption increases, and the economic efficiency deteriorates;

[0176] (5) From the comparison between Example 1 and Comparative Example 1, it can be seen that if selective grinding is not used for pretreatment and ball milling is performed directly, the grade of the obtained concentrate is low, the recovery rate is also reduced, and the performance of the ceramsite proppant is affected;

[0177] (6) From the comparison between Example 1 and Comparative Example 2, it can be seen that if the second grinding is not performed, high-grade concentrate cannot be obtained, the utilization rate of the concentrate decreases, and the performance of the ceramsite proppant is affected.

[0178] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for phase separation and enrichment of low-grade bauxite and co-production of ceramsite proppant, characterized in that: The method comprises the following steps: (1) crushing, first grinding and classification of bauxite in sequence to obtain tailings, middlings and first concentrate respectively; (2) subjecting the first concentrate in step (1) to a second grinding and then classifying to obtain tailings, middlings, and a second concentrate, and combining the tailings and middlings obtained after the first grinding and the second grinding, respectively, to obtain combined tailings and combined middlings; (3) mixing the calcium source, alkali solution and the combined middlings of step (2) to obtain a mixed slurry; (4) subjecting the mixed slurry of step (3) to a hydrothermal reaction, and obtaining a second concentrate and calcium-containing tailings after separation; (5) mixing water, the combined tailings of step (2) and the calcium-containing tailings of step (4), and sequentially granulating, drying and calcining to obtain a ceramsite proppant.

2. The method according to claim 1, characterized in that After the crushing in step (1), bauxite particles are obtained; Preferably, the mass percentage of the bauxite particles with a particle size of 0.5 to 2 cm is 20% to 100%; Preferably, the first grinding in step (1) comprises dry grinding or wet grinding; Preferably, the filling rate of the grinding media in the first grinding in step (1) is 5% to 60%; Preferably, the first grinding time in step (1) is 1 to 30 minutes; Preferably, the mill speed of the first grinding in step (1) is 5 to 300 r / min; Preferably, the mill filling rate of the first grinding in step (1) is 20% to 50%; Preferably, the classification in step (1) comprises dry classification or wet classification; Preferably, the particle size of the tailings in step (1) is less than 150 μm; Preferably, the particle size of the middling ore in step (1) is 150 to 250 μm; Preferably, the particle size of the first concentrate in step (1) is greater than 250 μm.

3. The method according to claim 1 or 2, characterized in that Step (2) the second grinding includes dry grinding or wet grinding; Preferably, the second grinding in step (2) is performed 1 to 10 times, preferably 2 to 5 times; Preferably, the filling rate of the grinding media in the second grinding in step (2) is 10% to 50%; Preferably, the second grinding time in step (2) is 5 to 20 minutes; Preferably, the speed of the mill for the second grinding in step (2) is 5 to 300 r / min; Preferably, the mill filling rate of the second grinding in step (2) is 20% to 50%; Preferably, the aluminum-silicon ratio of the second concentrate in step (2) is ≥5.5, preferably ≥6.

0.

4. The method according to any one of claims 1 to 3, characterized in that The calcium source in step (3) comprises industrial raw materials and / or waste residues containing calcium oxide, preferably any one or a combination of at least two of calcium hydroxide, lime or phosphogypsum; Preferably, the alkali solution in step (3) includes NaOH solution and / or KOH solution; Preferably, the concentration of the alkali solution in step (3) is 0.05-2.5 mol / L, preferably 0.1-1 mol / L.

5. The method according to any one of claims 1 to 4, characterized in that The molar ratio of CaO in the calcium source in step (3) to SiO2 in the combined ore is (0.4-1.5):1, preferably (0.8-1.2):1; Preferably, the ratio of the total mass of the calcium source and the combined middlings in step (3) to the volume of the alkali solution is 1:(2.5-40) g / mL, preferably 1:(5-20) g / mL.

6. The method according to any one of claims 1 to 5, characterized in that The temperature of the hydrothermal reaction in step (4) is 100-250° C., preferably 140-220° C.; Preferably, the hydrothermal reaction time in step (4) is 1-30 h, preferably 2-10 h.

7. The method according to any one of claims 1 to 6, characterized in that The separation in step (4) comprises: performing solid-solid separation on the hydrothermal reaction product to obtain a second concentrate and a slurry, and then performing solid-liquid separation on the slurry to obtain a calcium-containing tailing; Preferably, the solid-solid separation method includes sedimentation separation or centrifugal separation.

8. The method according to any one of claims 1 to 7, characterized in that The mass ratio of the total mass of the combined tailings and calcium-containing tailings to water in step (5) is 1:(0.06-0.4); Preferably, the mixing time in step (5) is 1 to 30 minutes; Preferably, the mixing in step (5) comprises one-step mixing or step-by-step mixing, preferably step-by-step mixing; Preferably, the stepwise mixing comprises: first adding 5wt% to 15wt% of water, which accounts for 5wt% to 15wt% of the mass fraction of the combined tailings and calcium-containing tailings, and mixing them with the combined tailings and calcium-containing tailings for 0.5 to 20 minutes, and then adding the remaining water and mixing for 0.5 to 20 minutes; Preferably, the granulation time in step (5) is 1 to 40 minutes, preferably 5 to 30 minutes; Preferably, the granulation equipment in step (5) comprises any one of an inclined intensive mixer, a sugar coating pan granulator or a disc granulator, preferably an inclined intensive mixer; Preferably, the barrel speed of the inclined intensive mixer is 10 to 1500 r / min, preferably 20 to 80 r / min; Preferably, the rotor speed of the inclined intensive mixer is 300 to 6000 r / min, preferably 500 to 4000 r / min.

9. The method according to any one of claims 1 to 8, characterized in that The heating rate of the calcination in step (5) is 1 to 15°C / min, preferably 5 to 10°C / min; Preferably, the temperature rise end point of the calcination in step (5) is 1000-1700° C., preferably 1200-1500° C.; Preferably, the calcination holding time in step (5) is 0.1 to 12 hours, preferably 0.5 to 8 hours; Preferably, the calcination in step (5) further includes furnace cooling.

10. The method according to any one of claims 1 to 9, characterized in that The method comprises the following steps: (1) crushing, first grinding and classification of bauxite in sequence to obtain tailings, middlings and first concentrate respectively; After the crushing, bauxite particles are obtained; the mass percentage of the bauxite particles with a particle size of 0.5 to 2 cm is 20% to 100%; The first grinding process has a grinding medium filling rate of 5% to 60%, a grinding time of 1 to 30 minutes, a mill speed of 5 to 300 rpm, and a mill filling rate of 20% to 50%; The particle size of the tailings is less than 150 μm; the particle size of the middlings is 150 to 250 μm; the particle size of the first concentrate is greater than 250 μm; (2) subjecting the first concentrate in step (1) to a second grinding and then classifying to obtain tailings, middlings, and a second concentrate, and combining the tailings and middlings obtained after the first grinding and the second grinding, respectively, to obtain combined tailings and combined middlings; The second grinding is performed 1 to 10 times, the grinding medium filling rate is 10% to 50%, the time is 5 to 20 minutes, the mill speed is 5 to 300 rpm, and the mill filling rate is 20% to 50%; The aluminum-silicon ratio of the second concentrate is ≥5.5; (3) mixing the calcium source, alkali solution and the combined middlings of step (2) to obtain a mixed slurry; The calcium source includes industrial raw materials and / or waste residues containing calcium oxide; the alkali solution includes NaOH solution and / or KOH solution; the concentration of the alkali solution is 0.05-2.5 mol / L; The molar ratio of CaO in the calcium source to SiO2 in the combined middlings is (0.4-1.5):1; the ratio of the total mass of the calcium source and the combined middlings to the volume of the alkali solution is 1:(2.5-40) g / mL; (4) subjecting the mixed slurry of step (3) to a hydrothermal reaction at a temperature of 100-250° C. for 1-30 hours, subjecting the hydrothermal reaction product to solid-solid separation to obtain a second concentrate and a slurry, and then subjecting the slurry to solid-liquid separation to obtain a calcium-containing tailing; (5) mixing water, the combined tailings described in step (2) and the calcium-containing tailings described in step (4), and sequentially granulating, drying and calcining to obtain a ceramsite proppant; The mass ratio of the total mass of the combined tailings and calcium-containing tailings to water is 1:(0.06-0.4); the mixing time is 1 to 30 minutes; The granulation time is 1 to 40 minutes; The heating rate of the calcination is 1-15°C / min, the heating end point is 1000-1700°C, and the heat preservation time is 0.1-12h.

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