阅读说明：本技术 一种煤矸石制备高纯氧化铝的方法 (Method for preparing high-purity alumina from coal gangue ) 是由 公彦兵 张永锋 张宇娟 于 2021-03-19 设计创作，主要内容包括：本发明属于工业固体废弃物高值化利用技术领域,公开了一种煤矸石制备高纯氧化铝的方法,本发明对煤矸石进行研磨、焙烧、酸浸、过滤、铵明矾结晶、氯化铝结晶、氯化铝纯化、煅烧等步骤,得到高纯氧化铝。本发明的制备方法能够将煤矸石制成具有高附加值的高纯氧化铝,高纯氧化铝纯度为99.95-99.999％,满足高纯氧化铝的要求。本发明工艺过程中所产生的结晶母液可以实现循环利用,降低了生产成本。本发明的制备方法具有条件温和、操作简单、能耗低、安全性好以及产品附加值高等优点。(The invention belongs to the technical field of high-value utilization of industrial solid wastes, and discloses a method for preparing high-purity alumina from coal gangue. The preparation method can prepare the coal gangue into high-purity alumina with high added value, the purity of the high-purity alumina is 99.95-99.999%, and the requirement of the high-purity alumina is met. The crystallization mother liquor generated in the process can be recycled, and the production cost is reduced. The preparation method has the advantages of mild conditions, simple operation, low energy consumption, good safety, high added value of products and the like.)

1. The method for preparing high-purity alumina from coal gangue is characterized by comprising the following steps of:

(1) grinding: grinding the coal gangue to obtain granular coal gangue;

(2) roasting: roasting the granular coal gangue obtained in the step (1) to obtain coal gangue clinker;

(3) acid leaching: mixing the coal gangue clinker obtained in the step (2) with sulfuric acid for leaching reaction to obtain a dissolved-out slurry;

(4) and (3) filtering: diluting the dissolved slurry in the step (3), and filtering and separating to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding ammonium sulfate into the aluminum sulfate solution in the step (4), cooling, crystallizing, filtering and separating to obtain ammonium alum crystals and ammonium alum crystallization mother liquor;

(6) crystallization of aluminum chloride: dissolving the ammonium alum crystals obtained in the step (5) by using hydrochloric acid, then introducing hydrogen chloride gas to perform crystal precipitation, and filtering and separating to obtain aluminum chloride crystals and aluminum chloride crystal mother liquor;

(7) and (3) purifying aluminum chloride: dissolving the aluminum chloride crystals obtained in the step (6) by using hydrochloric acid, then introducing hydrogen chloride gas to separate out the crystals, and filtering and separating to obtain purified aluminum chloride crystals and a purified aluminum chloride crystallization mother liquor;

(8) and (3) calcining: and (4) calcining the purified aluminum chloride crystal in the step (7) to obtain high-purity aluminum oxide.

2. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein the particle size of the granular coal gangue in step (1) is not more than 0.25 mm.

3. The method for preparing high-purity alumina from coal gangue as claimed in claim 1, wherein the calcination temperature in the step (2) is 500-.

4. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein the mass-to-volume ratio of the coal gangue clinker in the step (3) to the sulfuric acid is 1 g: 1-5mL, the mass fraction of the sulfuric acid is 30-55%, the leaching reaction temperature is 100-200 ℃, and the leaching reaction time is 60-240 min.

5. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein in the step (4), the digestion slurry is diluted by using distilled water, and the mass of the distilled water is 2-6 times of that of the coal gangue clinker; the filtration temperature is 90-100 ℃.

6. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein the ammonium sulfate in the step (5) is prepared according to a mass ratio of coal gangue clinker to ammonium sulfate of 2: 1-5 adding; the cooling crystallization temperature is 20-50 ℃; and (3) mixing the ammonium alum crystallization mother liquor with ammonium carbonate for evaporation to obtain evaporation mother liquor and ammonium sulfate, removing impurities from the evaporation mother liquor, returning to the step (3) for acid leaching of the coal gangue clinker, and returning to the step (5) for ammonium sulfate.

7. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein the dissolving temperature in the step (6) is 60-80 ℃; the volume ratio of the ammonium alum crystal to the hydrochloric acid is 1 g: 0.5-1.5mL, wherein the mass fraction of the hydrochloric acid is 30% -35%; the initial precipitation temperature of the crystal is 60-100 ℃, the final precipitation temperature is 30-50 ℃, and the precipitation time is 30-240 min; the hydrogen chloride gas is obtained by evaporating hydrochloric acid.

8. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein the dissolving of the aluminum chloride crystal in the step (7) is performed by dissolving hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) in water to generate hydrochloric acid solution, and the hydrogen chloride gas is obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6).

9. The method for preparing high-purity alumina from coal gangue according to claim 1, wherein the step (7) of purifying aluminum chloride is performed for 2-6 times; in the circulation process, the purified aluminum chloride crystal is dissolved by dissolving hydrogen chloride gas obtained by evaporating the previous purified aluminum chloride crystal mother liquor in water to generate hydrochloric acid, and the hydrogen chloride gas is obtained by evaporating the previous purified aluminum chloride crystal mother liquor.

10. The method for preparing high-purity alumina from coal gangue as claimed in claim 1, wherein the calcination temperature in the step (8) is 300-.

Technical Field

The invention relates to the technical field of high-value utilization of industrial solid wastes, in particular to a method for preparing high-purity alumina from coal gangue.

Background

The coal gangue is solid waste generated in the coal mining and coal washing processes, about 1400 million tons of coal gangue are discharged per 1 million tons of coal produced in China, and 1500-2000 million tons of coal gangue are discharged per 1 million tons of coal washed and selected in China. The accumulation of a large amount of coal gangue not only occupies land and pollutes atmosphere, but also has the risk of spontaneous combustion of residual coal in the coal gangue pile when the temperature reaches the combustion point of combustible substances. The method for high-value utilization of the coal gangue is searched, so that the pollution problem is solved, and the waste of aluminum resources is avoided.

High-alumina coal gangue Al₂O₃The content is usually more than 40 percent, is a good bauxite substitution resource and is mainly distributed in Shanxi, inner Mongolia, Henan and other areas. The comprehensive utilization of the existing coal gangue mainly adopts low-value utilization modes such as power generation, coal gangue building materials, reclamation backfilling and the like, the added value is not high, the economic benefit is low, and the actual application enthusiasm of enterprises is not high.

The high-purity alumina has the characteristics of high purity, uniform particle size distribution, stable chemical property and the like, and is a basic raw material for producing heat-resistant, wear-resistant and corrosion-resistant products. Can be used for manufacturing luminescent materials, transparent ceramics, single crystals, grinding materials, adsorbents and the like. High added value and good application prospect.

At present, the prior art discloses a plurality of comprehensive utilization ways of high-alumina coal gangue, for example, in the prior art, CN103979978A takes the high-alumina coal gangue and industrial alumina as raw materials to prepare mullite light refractory material, and on the basis of utilizing the high-alumina coal gangue, the expensive industrial alumina is also used, so that the production cost is improved, the added value of the refractory material is lower, and the whole technology and economy are not high. Also, for example, CN108975367A in the prior art provides a method for efficiently utilizing high-alumina coal gangue, which is to prepare the coal gangue into aluminum hydroxide or aluminum oxide, polymeric aluminum ferric sulfate products through a series of processes, which are conventional common products, and have low added value and poor economy.

On the basis, the coal gangue is also used for preparing high-purity alumina in a technical disclosure, for example, in the prior art, CN101759209A uses the coal gangue and sodium carbonate as raw materials, the high-purity alumina is prepared by adopting an improved Bayer process, and the process is complex after multiple procedures of desiliconization, iron removal, washing and the like, and whether the purity of the high-purity alumina meets the standard is not disclosed.

In summary, the utilization economy of the high-alumina coal gangue is poor, and the added value is not high, so that the method for preparing the high-purity alumina by utilizing the high-alumina coal gangue, which has high added value and good economy, is a problem to be solved urgently.

Disclosure of Invention

The invention aims to provide a method for preparing high-purity alumina by using coal gangue, which solves the problems that the utilization economy of the high-purity coal gangue is poor, the added value is not high and the purity of the high-purity alumina prepared by using the coal gangue is low in the prior art.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a method for preparing high-purity alumina from coal gangue, which comprises the following steps:

(1) grinding: grinding the coal gangue to obtain granular coal gangue;

(2) roasting: roasting the granular coal gangue obtained in the step (1) to obtain coal gangue clinker;

(3) acid leaching: mixing the coal gangue clinker obtained in the step (2) with sulfuric acid for leaching reaction to obtain a dissolved-out slurry;

(4) and (3) filtering: diluting the dissolved slurry in the step (3), and filtering and separating to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding ammonium sulfate into the aluminum sulfate solution in the step (4), cooling, crystallizing, filtering and separating to obtain ammonium alum crystals and ammonium alum crystallization mother liquor;

(6) crystallization of aluminum chloride: dissolving the ammonium alum crystals obtained in the step (5) by using hydrochloric acid, then introducing hydrogen chloride gas to perform crystal precipitation, and filtering and separating to obtain aluminum chloride crystals and aluminum chloride crystal mother liquor;

(7) and (3) purifying aluminum chloride: dissolving the aluminum chloride crystals obtained in the step (6) by using hydrochloric acid, then introducing hydrogen chloride gas to separate out the crystals, and filtering and separating to obtain purified aluminum chloride crystals and a purified aluminum chloride crystallization mother liquor;

(8) and (3) calcining: and (4) calcining the purified aluminum chloride crystal in the step (7) to obtain high-purity aluminum oxide.

Preferably, in the method for preparing high-purity alumina by using coal gangue, the particle size of the granular coal gangue in the step (1) is not more than 0.25mm, and more preferably 0.10-0.25 mm.

Preferably, in the method for preparing high-purity alumina from coal gangue, the roasting temperature in the step (2) is 500-800 ℃, more preferably 650-800 ℃, and the roasting time is 40-240min, more preferably 60-120 min.

Preferably, in the method for preparing high-purity alumina from coal gangue, the mass-to-volume ratio of the coal gangue clinker in the step (3) to the sulfuric acid is 1 g: 1-5mL, more preferably 1 g: 1-4mL, the mass fraction of the sulfuric acid is 30% -55%, and the preferable range is 40% -50%, the leaching reaction temperature is 100-.

Preferably, in the above method for preparing high-purity alumina from coal gangue, the step (4) uses distilled water to dilute the digestion slurry, wherein the mass of the distilled water is 2-6 times, and more preferably 3-5 times that of the coal gangue clinker; the filtration temperature is 90 to 100 ℃ and more preferably 90 to 95 ℃.

Preferably, in the method for preparing high-purity alumina from coal gangue, the ammonium sulfate in the step (5) is mixed according to a mass ratio of coal gangue clinker to ammonium sulfate of 2: 1-5, more preferably 2: 1-4; the cooling crystallization temperature is 20-50 ℃, and the cooling crystallization temperature is more preferably 20-40 ℃; and (3) adding ammonium carbonate into the ammonium alum crystallization mother liquor, mixing and evaporating to obtain evaporation mother liquor and ammonium sulfate, removing impurities from the evaporation mother liquor, returning to the step (3) for acid leaching of the coal gangue clinker, and returning to the step (5) for ammonium sulfate.

Preferably, in the method for preparing high-purity alumina from coal gangue, the dissolving temperature in the step (6) is 60-80 ℃; the volume ratio of the ammonium alum crystal to the hydrochloric acid is 1 g: 0.5-1.5mL, wherein the mass fraction of the hydrochloric acid is 30% -35%; the initial precipitation temperature of the crystal is 60-100 ℃, the further optimization is 70-80 ℃, the final precipitation temperature is 30-50 ℃, the further optimization is 30-40 ℃, the precipitation time is 30-240min, the further optimization is 60-180 min; the hydrogen chloride gas is obtained by evaporating hydrochloric acid.

Preferably, in the method for preparing high-purity alumina from coal gangue, the aluminum chloride crystal dissolution in the step (7) adopts the hydrogen chloride gas obtained by evaporating the aluminum chloride crystal mother liquor in the step (6) to be dissolved in hydrochloric acid generated by water, the hydrogen chloride gas is obtained by evaporating the aluminum chloride crystal mother liquor in the step (6), the aluminum chloride crystal mother liquor in the step (6) is continuously evaporated to obtain aluminum chloride containing impurities and an evaporation mother liquor, wherein the aluminum chloride is used as a byproduct, and the evaporation mother liquor is returned to the step (3) for acid leaching and batching.

Preferably, in the method for preparing high-purity alumina from coal gangue, the aluminum chloride purification in the step (7) is circulated for 2 to 6 times, and more preferably for 3 to 4 times; in the circulation process, dissolving the purified aluminum chloride crystals by dissolving hydrogen chloride gas obtained by evaporating the previous purified aluminum chloride crystallization mother liquor in water to generate hydrochloric acid solution, wherein the hydrogen chloride gas is obtained by evaporating the previous purified aluminum chloride crystallization mother liquor; and (4) after the circulation process is finished, returning the obtained final purified aluminum chloride crystallization mother liquor to the step (6) for dissolving the ammonium alum.

Preferably, in the method for preparing high-purity alumina from coal gangue, the calcination temperature in the step (8) is 300-600 ℃, more preferably 400-600 ℃, and the time is 30-180min, more preferably 60-120 min; and (4) recovering hydrogen chloride gas obtained by calcination, and separating out crystals in the step (6).

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

the preparation method can prepare the coal gangue into high-purity alumina with high added value, the purity of the high-purity alumina is 99.95-99.999%, and the requirement of the high-purity alumina is met. The crystallization mother liquor generated in the process can be recycled, and the production cost is reduced. The preparation method has the advantages of mild conditions, simple operation, low energy consumption, good safety, high added value of products and the like.

Drawings

FIG. 1 is a process flow diagram of the method for preparing high-purity alumina by using coal gangue according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The invention discloses a method for preparing high-purity alumina by utilizing coal gangue, which comprises the following steps:

(1) grinding: grinding the coal gangue to obtain granular coal gangue with the granularity of 0.15-0.25 mm;

(2) roasting: roasting the granular coal gangue at 750 ℃ for 120min to obtain coal gangue clinker;

(3) acid leaching: mixing 140g of coal gangue clinker with 220mL of distilled water and 150mL of concentrated sulfuric acid, and leaching for 180min at 110 ℃ to obtain dissolved slurry;

(4) and (3) filtering: adding 560mL of distilled water to dilute the dissolved slurry, adding 5mL of 2 per mill polyacrylamide flocculant, and filtering and separating at 90 ℃ to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding 122.3g of ammonium sulfate into an aluminum sulfate solution at the temperature of 90 ℃, cooling and crystallizing at the temperature of 30 ℃, and filtering and separating to obtain 664.2g of ammonium alum crystals and ammonium alum crystallization mother liquor; adding ammonium carbonate into the ammonium alum crystallization mother liquor, mixing and evaporating to obtain evaporation mother liquor and ammonium sulfate, adding ammonium bicarbonate into the evaporation mother liquor to remove impurities, and returning to the step (3) as an acid leaching solution to carry out acid leaching on the coal gangue clinker;

(6) crystallization of aluminum chloride: dissolving ammonium alum with 470mL of hydrochloric acid with the mass fraction of 35% at 70 ℃, introducing hydrogen chloride gas obtained by evaporating hydrochloric acid into the ammonium alum solution at 90 ℃ to perform crystal precipitation, wherein the crystal precipitation time is 120min, the final precipitation temperature is 30 ℃, and filtering and separating to obtain 238.8g of aluminum chloride crystals and aluminum chloride crystallization mother liquor;

(7) and (3) purifying aluminum chloride: the purification cycle is carried out for 3 times by adopting a mode of acid-soluble aluminum chloride-hydrogen chloride gas crystallization:

dissolving hydrochloric acid generated by dissolving hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) in water to dissolve aluminum chloride crystals at the temperature of 45 ℃, introducing the hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) into the aluminum chloride solution at the temperature of 70 ℃ to separate out crystals, and filtering and separating to obtain 212.1g of primary purified aluminum chloride crystals and primary purified aluminum chloride crystallization mother liquor; continuously evaporating the aluminum chloride crystallization mother liquor in the step (6) to obtain aluminum chloride containing impurities and evaporation mother liquor, wherein the aluminum chloride is used as a byproduct, and the evaporation mother liquor is returned to the step (3) for acid leaching and batching;

dissolving the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into water to generate hydrochloric acid, dissolving the primary purified aluminum chloride crystal by using the hydrochloric acid, introducing the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into the primary purified aluminum chloride solution at the temperature of 70 ℃ to separate out crystals, and filtering and separating to obtain 196.4g of secondary purified aluminum chloride crystals and secondary purified aluminum chloride crystal mother liquor;

dissolving the hydrogen chloride gas obtained by evaporating the secondary purified aluminum chloride crystal mother liquor in water to generate hydrochloric acid, dissolving the secondary purified aluminum chloride crystals in the hydrochloric acid at 42 ℃, introducing the hydrogen chloride gas obtained by evaporating the secondary purified aluminum chloride crystal mother liquor into the secondary purified aluminum chloride solution at 70 ℃ to separate out crystals, and filtering and separating to obtain 172.7g of tertiary purified aluminum chloride crystals and tertiary purified aluminum chloride crystal mother liquor; the mother liquor of the third purified aluminum chloride crystallization is returned to the step (6) to dissolve the ammonium alum;

(8) and (3) calcining: calcining the third purified aluminum chloride crystal at 400 ℃ for 60min, and recovering hydrogen chloride gas obtained by calcining for separating out hydrogen chloride gas for the crystal in the step (6); after calcination, 53g of high-purity alumina with a purity of 99.98% was obtained.

Example 2

The invention discloses a method for preparing high-purity alumina by utilizing coal gangue, which comprises the following steps:

(1) grinding: grinding the coal gangue to obtain granular coal gangue with the granularity of 0.10-0.20 mm;

(2) roasting: roasting the granular coal gangue at 800 ℃ for 180min to obtain coal gangue clinker;

(3) acid leaching: mixing 150g of coal gangue clinker with 240mL of distilled water and 200mL of concentrated sulfuric acid, and leaching at 140 ℃ for 120min to obtain a dissolving-out slurry;

(4) and (3) filtering: adding 600mL of distilled water to dilute the dissolved slurry, adding 5mL of 2 per mill polyacrylamide flocculant, and filtering and separating at 92 ℃ to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding 164.8g of ammonium sulfate into the aluminum sulfate solution, cooling and crystallizing at 25 ℃, filtering and separating to obtain 898.2g of ammonium alum crystals and ammonium alum crystallization mother liquor; adding ammonium carbonate into the ammonium alum crystallization mother liquor, mixing and evaporating to obtain evaporation mother liquor and ammonium sulfate, adding ammonium bicarbonate into the evaporation mother liquor to remove impurities, and returning to the step (3) as an acid leaching solution to carry out acid leaching on the coal gangue clinker;

(6) crystallization of aluminum chloride: dissolving ammonium alum with 590mL hydrochloric acid with the mass fraction of 32% at the temperature of 74 ℃, introducing hydrogen chloride gas into the ammonium alum solution at the temperature of 95 ℃ to separate out crystals, wherein the crystal separation time is 100min, the final separation temperature is 32 ℃, and filtering and separating to obtain 280.4g of aluminum chloride crystals and aluminum chloride crystal mother liquor;

(7) and (3) purifying aluminum chloride: the purification cycle is carried out for 4 times by adopting a mode of acid-soluble aluminum chloride-hydrogen chloride gas crystallization:

dissolving hydrochloric acid generated by dissolving hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) in water to dissolve aluminum chloride crystals at the temperature of 40 ℃, introducing the hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) into the aluminum chloride solution at the temperature of 70 ℃ to separate out crystals, and filtering and separating to obtain 259.1g of primary purified aluminum chloride crystals and the primary purified aluminum chloride crystallization mother liquor; continuously evaporating the aluminum chloride crystallization mother liquor in the step (6) to obtain aluminum chloride containing impurities and evaporation mother liquor, wherein the aluminum chloride is used as a byproduct, and the evaporation mother liquor is returned to the step (3) for acid leaching and batching;

dissolving the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor in water to generate hydrochloric acid, dissolving the primary purified aluminum chloride crystals in the hydrochloric acid at 42 ℃, introducing the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into the primary purified aluminum chloride solution at 70 ℃ to separate out crystals, and filtering and separating to obtain 232.6g of secondary purified aluminum chloride crystals and the secondary purified aluminum chloride crystal mother liquor;

dissolving secondary purified aluminum chloride crystals in hydrochloric acid generated by dissolving hydrogen chloride gas obtained by evaporating secondary purified aluminum chloride crystal mother liquor in water at 44 ℃, introducing the hydrogen chloride gas obtained by evaporating secondary purified aluminum chloride crystal mother liquor into the secondary purified aluminum chloride solution at 70 ℃ for crystal precipitation, and filtering and separating to obtain 214.2g of tertiary purified aluminum chloride crystals and tertiary purified aluminum chloride crystal mother liquor;

dissolving hydrogen chloride gas obtained by evaporating three times of purified aluminum chloride crystal mother liquor into water to generate hydrochloric acid, dissolving three times of purified aluminum chloride crystals at the temperature of 43 ℃, introducing the hydrogen chloride gas obtained by evaporating three times of purified aluminum chloride crystal mother liquor into the three times of purified aluminum chloride crystal dissolved liquor at the temperature of 70 ℃ to separate out crystals, and filtering and separating to obtain 198.9g of four times of purified aluminum chloride crystals and the four times of purified aluminum chloride crystal mother liquor; the mother liquor of the fourth purified aluminum chloride crystallization is returned to the step (6) to dissolve the ammonium alum;

(8) and (3) calcining: calcining the four-time purified aluminum chloride crystals at 500 ℃ for 120min, and recovering hydrogen chloride gas obtained by calcining for separating out hydrogen chloride gas for the crystals in the step (6); after calcination, 61g of high-purity alumina was obtained with a purity of 99.99%.

Example 3

The invention discloses a method for preparing high-purity alumina by utilizing coal gangue, which comprises the following steps:

(1) grinding: grinding the coal gangue to obtain granular coal gangue with the granularity of 0.20-0.25 mm;

(2) roasting: roasting the granular coal gangue at 650 ℃ for 150min to obtain coal gangue clinker;

(3) acid leaching: mixing 130g of coal gangue clinker with 200mL of distilled water and 260mL of concentrated sulfuric acid, and leaching for 180min at the temperature of 150 ℃ to obtain a dissolved slurry;

(4) and (3) filtering: adding 700mL of distilled water to dilute the dissolved slurry, adding 5mL of 2 per mill polyacrylamide flocculant by mass fraction, and filtering and separating at 95 ℃ to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding 150g of ammonium sulfate into the aluminum sulfate solution, cooling and crystallizing at 35 ℃, filtering and separating to obtain 828.3g of ammonium alum crystals and ammonium alum crystallization mother liquor; adding ammonium carbonate into the ammonium alum crystallization mother liquor, mixing and evaporating to obtain evaporation mother liquor and ammonium sulfate, adding ammonium bicarbonate into the evaporation mother liquor to remove impurities, and returning to the step (3) as an acid leaching solution to carry out acid leaching on the coal gangue clinker;

(6) crystallization of aluminum chloride: dissolving ammonium alum with 800mL of hydrochloric acid with the mass fraction of 30% at the temperature of 78 ℃, introducing hydrogen chloride gas into the ammonium alum solution at the temperature of 90 ℃ to separate out crystals, wherein the crystal separation time is 150min, the final separation temperature is 35 ℃, and filtering and separating to obtain 235.6g of aluminum chloride crystals and aluminum chloride crystal mother liquor;

(7) and (3) purifying aluminum chloride: the purification cycle is carried out for 5 times by adopting a mode of acid-soluble aluminum chloride-hydrogen chloride gas crystallization:

dissolving hydrochloric acid generated by dissolving hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) in water to dissolve aluminum chloride crystals at the temperature of 43 ℃, introducing the hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) into the aluminum chloride solution at the temperature of 73 ℃ to separate out crystals, and filtering and separating to obtain 204.4g of primary purified aluminum chloride crystals and primary purified aluminum chloride crystallization mother liquor; continuously evaporating the aluminum chloride crystallization mother liquor in the step (6) to obtain aluminum chloride containing impurities and evaporation mother liquor, wherein the aluminum chloride is used as a byproduct, and the evaporation mother liquor is returned to the step (3) for acid leaching and batching;

dissolving the primary purified aluminum chloride crystal with hydrochloric acid generated by dissolving hydrogen chloride gas obtained by evaporating primary purified aluminum chloride crystal mother liquor in water at 47 ℃, introducing the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into the primary purified aluminum chloride crystal solution at 73 ℃ for crystal precipitation, and filtering and separating to obtain 189.1g of secondary purified aluminum chloride crystal and secondary purified aluminum chloride crystal mother liquor;

dissolving the hydrogen chloride gas obtained by evaporating the secondary purified aluminum chloride crystal mother liquor in water to generate hydrochloric acid, dissolving the secondary purified aluminum chloride crystals in the hydrochloric acid at the temperature of 46 ℃, introducing the hydrogen chloride gas obtained by evaporating the secondary purified aluminum chloride crystal mother liquor into the secondary purified aluminum chloride solution at the temperature of 73 ℃ to separate out crystals, and filtering and separating to obtain 168.7g of tertiary purified aluminum chloride crystals and tertiary purified aluminum chloride crystal mother liquor;

dissolving hydrogen chloride gas obtained by evaporating three times of purified aluminum chloride crystal mother liquor into water to generate hydrochloric acid, dissolving three times of purified aluminum chloride crystals at the temperature of 43 ℃, introducing the hydrogen chloride gas obtained by evaporating three times of purified aluminum chloride crystal mother liquor into the three times of purified aluminum chloride crystal dissolved liquor at the temperature of 73 ℃ to separate out crystals, and filtering and separating to obtain 153.4g of four times of purified aluminum chloride crystals and four times of purified aluminum chloride crystal mother liquor;

dissolving hydrogen chloride gas obtained by evaporating the mother liquor of the four-time purified aluminum chloride crystals in water to generate hydrochloric acid, dissolving the hydrochloric acid at the temperature of 43 ℃ to obtain four-time purified aluminum chloride crystals, introducing the hydrogen chloride gas obtained by evaporating the mother liquor of the four-time purified aluminum chloride crystals into the four-time purified aluminum chloride dissolved liquor at the temperature of 73 ℃ to separate the crystals, and filtering and separating to obtain 144.2g of the five-time purified aluminum chloride crystals and the mother liquor of the five-time purified aluminum chloride crystals; the mother liquor of the five times of purified aluminum chloride crystallization is returned to the step (6) to dissolve the ammonium alum;

(8) and (3) calcining: calcining the five-time purified aluminum chloride crystals at 550 ℃ for 150min, and recovering hydrogen chloride gas obtained by calcining for separating out hydrogen chloride gas for the crystals in the step (6); calcination was complete to give 57g of high purity alumina, 99.995% purity.

Example 4

The invention discloses a method for preparing high-purity alumina by utilizing coal gangue, which comprises the following steps:

(1) grinding: grinding the coal gangue to obtain granular coal gangue with the granularity of 0.10-0.20 mm;

(2) roasting: roasting the granular coal gangue at 700 ℃ for 200min to obtain coal gangue clinker;

(3) acid leaching: mixing 160g of coal gangue clinker with 180mL of distilled water and 210mL of concentrated sulfuric acid, and leaching at 180 ℃ for 200min to obtain a dissolving-out slurry;

(4) and (3) filtering: adding 500mL of distilled water to dilute the dissolved slurry, adding 5mL of 2 per mill polyacrylamide flocculant, and filtering and separating at 98 ℃ to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding 210g ammonium sulfate into aluminum sulfate solution, cooling at 40 deg.C for crystallization, filtering, and separating to obtain 868.4g ammonium alum crystal and ammonium alum crystallization mother liquor; adding ammonium carbonate into the ammonium alum crystallization mother liquor, mixing and evaporating to obtain evaporation mother liquor and ammonium sulfate, adding ammonium bicarbonate into the evaporation mother liquor to remove impurities, and returning to the step (3) as an acid leaching solution to carry out acid leaching on the coal gangue clinker;

(6) crystallization of aluminum chloride: dissolving ammonium alum with 780mL of hydrochloric acid with the mass fraction of 35% at the temperature of 75 ℃, introducing hydrogen chloride gas into the ammonium alum solution at the temperature of 85 ℃ to separate out crystals, wherein the crystal separation time is 90min, the final separation temperature is 38 ℃, and filtering and separating to obtain 248.8g of aluminum chloride crystals and aluminum chloride crystal mother liquor;

(7) and (3) purifying aluminum chloride: the purification cycle is 6 times by adopting a mode of acid-soluble aluminum chloride-hydrogen chloride gas crystallization:

dissolving a hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor obtained in the step (6) in water to generate hydrochloric acid, dissolving aluminum chloride crystals at the temperature of 44 ℃, introducing the hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor obtained in the step (6) into the aluminum chloride solution at the temperature of 75 ℃ to separate out crystals, and filtering and separating to obtain 217.5g of primary purified aluminum chloride crystals and primary purified aluminum chloride crystallization mother liquor; continuously evaporating the aluminum chloride crystallization mother liquor in the step (6) to obtain aluminum chloride containing impurities and evaporation mother liquor, wherein the aluminum chloride is used as a byproduct, and the evaporation mother liquor is returned to the step (3) for acid leaching and batching;

dissolving the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into water to generate hydrochloric acid, dissolving the primary purified aluminum chloride crystal by using the hydrochloric acid at 42 ℃, introducing the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into the primary purified aluminum chloride solution at 75 ℃ to separate out crystals, and filtering and separating to obtain 186.3g of secondary purified aluminum chloride crystals and secondary purified aluminum chloride crystal mother liquor;

dissolving the hydrogen chloride gas obtained by evaporating the secondary purified aluminum chloride crystal mother liquor in water to generate hydrochloric acid, dissolving the secondary purified aluminum chloride crystals in the hydrochloric acid at 44 ℃, introducing the hydrogen chloride gas obtained by evaporating the secondary purified aluminum chloride crystal mother liquor into the secondary purified aluminum chloride solution at 75 ℃ to separate out crystals, and filtering and separating to obtain 169.7g of tertiary purified aluminum chloride crystals and tertiary purified aluminum chloride crystal mother liquor;

dissolving hydrogen chloride gas obtained by evaporating three times of purified aluminum chloride crystallization mother liquor into water to generate hydrochloric acid, dissolving three times of purified aluminum chloride crystals at the temperature of 43 ℃, introducing the hydrogen chloride gas obtained by evaporating three times of purified aluminum chloride crystallization mother liquor into the three times of purified aluminum chloride solution at the temperature of 75 ℃ to separate out crystals, and filtering and separating to obtain 147.2g of four times of purified aluminum chloride crystals and four times of purified aluminum chloride crystallization mother liquor;

dissolving hydrogen chloride gas obtained by evaporating the mother liquor of the four-time purified aluminum chloride crystals in water to generate hydrochloric acid, dissolving the hydrochloric acid at the temperature of 41 ℃ to obtain four-time purified aluminum chloride crystals, introducing the hydrogen chloride gas obtained by evaporating the mother liquor of the four-time purified aluminum chloride crystals into the dissolved liquor of the four-time purified aluminum chloride crystals at the temperature of 75 ℃ to separate the crystals, and filtering and separating to obtain 138.8g of the five-time purified aluminum chloride crystals and the mother liquor of the five-time purified aluminum chloride crystals;

dissolving hydrogen chloride gas obtained by evaporating the five times of purified aluminum chloride crystallization mother liquor into water to generate hydrochloric acid, dissolving the hydrochloric acid into the five times of purified aluminum chloride crystals at the temperature of 45 ℃, introducing the hydrogen chloride gas obtained by evaporating the five times of purified aluminum chloride crystallization mother liquor into the five times of purified aluminum chloride solution at the temperature of 75 ℃ to separate out the crystals, and filtering and separating to obtain 136.1g of six times of purified aluminum chloride crystals and six times of purified aluminum chloride crystallization mother liquor; the mother liquor of the six times of purified aluminum chloride crystallization is returned to the step (6) to dissolve ammonium alum;

(8) and (3) calcining: calcining the six purified aluminum chloride crystals at 600 ℃ for 180min, and recovering hydrogen chloride gas obtained by calcining for separating out hydrogen chloride gas for the crystals in the step (6); after calcination, 49g of high-purity alumina with a purity of 99.999% was obtained.

Example 5

The invention discloses a method for preparing high-purity alumina by utilizing coal gangue, which comprises the following steps:

(1) grinding: grinding the coal gangue to obtain granular coal gangue with the granularity of 0.10-0.15 mm;

(2) roasting: roasting the granular coal gangue at 650 ℃ for 150min to obtain coal gangue clinker;

(3) acid leaching: mixing 150g of coal gangue clinker with 200mL of distilled water and 160mL of concentrated sulfuric acid, and leaching at 130 ℃ for 240min to obtain a dissolved slurry;

(4) and (3) filtering: adding 450mL of distilled water to dilute the dissolved slurry, adding 5mL of 2 per mill polyacrylamide flocculant by mass fraction, and filtering and separating at 95 ℃ to obtain an aluminum sulfate solution and acid leaching residues;

(5) crystallizing ammonium alum: adding 119.4g of ammonium sulfate into an aluminum sulfate solution, cooling and crystallizing at 27 ℃, and filtering and separating to obtain 748.5g of ammonium alum crystals and ammonium alum crystallization mother liquor; adding ammonium carbonate into the ammonium alum crystallization mother liquor, mixing and evaporating to obtain evaporation mother liquor and ammonium sulfate, adding ammonium bicarbonate into the evaporation mother liquor to remove impurities, and returning to the step (3) as an acid leaching solution to carry out acid leaching on the coal gangue clinker;

(6) crystallization of aluminum chloride: dissolving ammonium alum with 420mL of hydrochloric acid with the mass fraction of 38% at the temperature of 76 ℃, introducing hydrogen chloride gas into the ammonium alum solution at the temperature of 100 ℃ to perform crystal precipitation, wherein the crystal precipitation time is 180min, the final precipitation temperature is 45 ℃, and performing filtration separation to obtain 204.7g of aluminum chloride crystals and aluminum chloride crystal mother liquor;

(7) and (3) purifying aluminum chloride: the purification cycle is carried out for 2 times by adopting a mode of acid-soluble aluminum chloride-hydrogen chloride gas crystallization:

dissolving hydrochloric acid generated by dissolving hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) in water to dissolve aluminum chloride crystals at the temperature of 42 ℃, introducing the hydrogen chloride gas obtained by evaporating the aluminum chloride crystallization mother liquor in the step (6) into the aluminum chloride solution at the temperature of 70 ℃ to separate out crystals, and filtering and separating to obtain 175.3g of primary purified aluminum chloride crystals and primary purified aluminum chloride crystallization mother liquor; continuously evaporating the aluminum chloride crystallization mother liquor in the step (6) to obtain aluminum chloride containing impurities and evaporation mother liquor, wherein the aluminum chloride is used as a byproduct, and the evaporation mother liquor is returned to the step (3) for acid leaching and batching;

dissolving the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into water to generate hydrochloric acid, dissolving the primary purified aluminum chloride crystal by using the hydrochloric acid at 42 ℃, introducing the hydrogen chloride gas obtained by evaporating the primary purified aluminum chloride crystal mother liquor into the primary purified aluminum chloride solution at 70 ℃ to separate out crystals, and filtering and separating to obtain 139.6g of secondary purified aluminum chloride crystals and secondary purified aluminum chloride crystal mother liquor; the secondary purified aluminum chloride crystallization mother liquor returns to the step (6) to dissolve ammonium alum;

(8) and (3) calcining: calcining the secondary purified aluminum chloride crystals at 600 ℃ for 90min, and recovering hydrogen chloride gas obtained by calcining for separating out hydrogen chloride gas for the crystals in the step (6); 58g of high-purity alumina with a purity of 99.95% is obtained after calcination.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.