阅读说明：本技术 一种利用铝灰和水氯镁石制取镁铝尖晶石的方法 (Method for preparing magnesia-alumina spinel by using aluminum ash and bischofite ) 是由 冯乃祥 杨超 于 2020-07-15 设计创作，主要内容包括：一种利用铝灰和水氯镁石制取镁铝尖晶石的方法,按以下步骤进行：(1)将铝灰水洗后,加入到氢氧化钠溶液中搅拌反应,使铝灰中的Al和AlN与NaOH反应生成NaAlO<Sub>2</Sub>；反应完成的物料过滤,获得的滤液为含NaAlO<Sub>2</Sub>和NaOH的混合溶液；(2)在搅拌条件下,向混合溶液中加入水氯镁石,使MgCl<Sub>2</Sub>与NaAlO<Sub>2</Sub>和NaOH反应生成MgO·Al<Sub>2</Sub>O<Sub>3</Sub>沉淀和Mg(OH)<Sub>2</Sub>沉淀；反应后的物料过滤,获得滤渣；(3)将滤渣在≥350℃条件下煅烧热处理,制成富镁的镁铝尖晶石。本发明的方法使铝灰和水氯镁石得到资源化利用,具有很好的经济效益和社会效益。(A method for preparing magnesia-alumina spinel by using aluminum ash and bischofite comprises the following steps: (1) washing the aluminum ash water, adding the washed aluminum ash water into a sodium hydroxide solution, stirring and reacting to ensure that Al and AlN in the aluminum ash react with NaOH to generate NaAlO 2 (ii) a Filtering the material after the reaction is completed to obtain a filtrate containing NaAlO 2 And NaOH; (2) adding bischofite into the mixed solution under stirring to obtain MgCl 2 With NaAlO 2 Reacting with NaOH to produce MgO-Al 2 O 3 Precipitation and Mg (OH) 2 Precipitating; filtering the reacted materials to obtain filter residues; (3) calcining the filter residue at the temperature of more than or equal to 350 ℃ for heat treatment to prepare the magnesium-rich magnesia-alumina spinel. According to the inventionThe method makes the aluminum ash and the bischofite be recycled, and has good economic benefit and social benefit.)

1. A method for preparing magnesia-alumina spinel by using aluminum ash and bischofite is characterized by comprising the following steps:

(1) washing aluminum ash with water to remove water-soluble components, adding the aluminum ash into a sodium hydroxide solution, stirring and reacting to enable Al and AlN in the aluminum ash to react with NaOH to generate NaAlO₂(ii) a The concentration of the sodium hydroxide solution is 25-35%; use of sodium hydroxide solutionThe amount of NaOH is added according to the proportion that the NaOH is completely reacted with Al and AlN and the excess amount is 5-10%; filtering the material after the reaction is completed to obtain a filtrate containing NaAlO₂And NaOH;

(2) adding bischofite into the mixed solution under stirring to obtain MgCl₂With NaAlO₂Reacting with NaOH to produce MgO-Al₂O₃Precipitation and Mg (OH)₂Precipitating; the bischofite is added in an amount according to MgCl₂With NaAlO₂Completely reacting with NaOH; filtering the reacted material to obtain MgO-Al as main solid component in the filter residue₂O₃And Mg (OH)₂A mixture of (a);

(3) calcining the filter residue at the temperature of more than or equal to 350 ℃ for heat treatment to prepare the magnesium-rich magnesia-alumina spinel.

2. The method for preparing magnesia-alumina spinel by using aluminum ash and bischofite as claimed in claim 1, wherein in step (1), the complete reaction is based on the following reaction formula:

Al+NaOH+H₂O＝NaAlO₂+3/2H₂↓ (1) and

AlN+NaOH+H₂O＝NaAlO₂+NH₃↑ (2)。

3. the method for preparing magnesia-alumina spinel by using aluminum ash and bischofite as claimed in claim 1, wherein in step (1), NaAlO is generated by reaction₂In the process of (1), H is produced₂And NH₃And respectively recovering.

4. The method for preparing magnesia-alumina spinel by using aluminum ash and bischofite as claimed in claim 1, wherein in step (2), the complete reaction is based on the following reaction formula:

2NaAlO₂+MgCl₂＝MgO·Al₂O₃↓ +2NaCl (3) and

2NaOH+MgCl₂＝2NaCl+Mg(OH)₂↓ (4)。

5. the method for preparing magnesia-alumina spinel by using aluminum ash and bischofite as claimed in claim 1, wherein in step (2), the filtrate obtained after filtration is NaCl solution.

6. The method for preparing magnesia-alumina spinel by using aluminum ash and bischofite as claimed in claim 1, wherein in step (3), the purity of the magnesia-alumina spinel is greater than or equal to 98%.

7. The method for preparing magnesia alumina spinel using aluminum ash and bischofite as claimed in claim 1, wherein in step (1), Al and AlN form NaAlO₂The conversion rate is more than or equal to 99 percent.

8. The method for preparing magnesia alumina spinel by using aluminum ash and bischofite as claimed in claim 1, wherein in step (2), NaAlO is added₂The precipitation rate of the medium Al is more than or equal to 99 percent.

Technical Field

The invention relates to the technical field of resource utilization of industrial hazardous waste solid materials, in particular to a method for preparing magnesia-alumina spinel by using aluminum ash and bischofite.

Background

Aluminum is the second largest metal which has the most resources on the earth and has the second best yield than steel; the aluminum has the characteristics of light weight and good oxidation and corrosion resistance, can be used for forming aluminum alloys with various purposes with a plurality of metal elements, and has recyclability. The aluminum is produced by a method of electrolyzing aluminum oxide by cryolite flux molten salt, and is basically applied in the form of various aluminum alloy materials in the aspect of application; adding intermediate alloy of various alloy elements into a part of aluminum material from an original aluminum melt in an electrolytic aluminum plant, degassing, deslagging and casting to obtain an aluminum alloy material; the other part is cast into a common aluminum ingot after deslagging by an electrolytic aluminum plant, then transported to an aluminum product manufacturer to be melted, added with intermediate alloy of alloy elements, and then degassed and decontaminated to prepare the aluminum alloy material.

Aluminum ash is generated in the casting process of various aluminum and aluminum alloys, and the amount of aluminum ash slag generated by casting aluminum alloy (aluminum silicon) is different according to different aluminum alloy casting products, such as about 30kg/t of aluminum ash generated by casting aluminum alloy (aluminum silicon), about 35kg/t of aviation aluminum material, about 5kg/t of original aluminum casting (common aluminum ingot) and about 20kg/t of other aluminum alloys; the overall average amount is about 20 kg/t.

The aluminum ash contains soluble chloride and fluoride of alkali metal potassium and sodium, and the nitride in the aluminum ash is hydrolyzed in water to generate NH₃And water-soluble NaAlO produced by the reaction₂: it has an impact on the environment and is therefore considered a toxic and harmful solid waste.

At present, many researches on the treatment of aluminum ash and resource utilization methods thereof are carried out, and the methods can be basically divided into the following types:

one method is to use aluminum ash to prepare aluminum hydroxide or aluminum oxide, such as patents CN108239704A, CN105271327A, CN104261445A, CN106830023A, CN108439444A, CN108529658A, CN1224723C, CN106830030A, CN109928413A, CN1903725A, etc.; the technologies are basically similar in principle and method, namely, washing aluminum ash with water, removing soluble substances (mainly chloride) in the aluminum ash, mixing the aluminum ash with sodium carbonate, sodium hydroxide or lime (CaO), sintering at the temperature of more than 700-900 ℃, converting alumina in the aluminum ash into water-soluble aluminate, leaching the generated sodium aluminate with water, and preparing the aluminum hydroxide and the alumina by using the carbon content and seed precipitation process of the sodium aluminate.

Bischofite is a byproduct generated in potassium extraction of Qinghai salt lake in China, and the yield of bischofite (MgCl) is about 10 tons per ton of KCl extracted₂·6H₂O); KCl is increased by 500 ten thousand tons in a Qinghai salt lake every year, bischofite by-product is generated by 5000 ten thousand tons/year every year, only a small amount of bischofite by-product is used for preparing dehydrated raw materials for preparing metal magnesium by electrolysis, and the rest is accumulated in a salt field.

The magnesium aluminate spinel is made of MgO and Al₂O₃The compound is a high-grade refractory material, and the magnesia-alumina spinel has the characteristics of high temperature resistance, small expansion coefficient, high thermal stability and strong erosion resistance, and is widely applied to kilns in the metallurgical industry, the cement industry and the glass industry; the high-grade magnesia-alumina spinel is made of industrial alumina and high-purity magnesia MgO, and has high manufacturing cost and high price; therefore, the method for preparing the magnesium aluminate spinel with low cost is developed and has important significance.

Disclosure of Invention

The invention aims to provide a method for preparing magnesia-alumina spinel by using aluminum ash and bischofite, wherein aluminum and aluminum nitride in the aluminum ash are converted into sodium aluminate by using sodium hydroxide, and bischofite (MgCl)₂·6H₂O) neutralizing the magnesium aluminate spinel under the stirring condition, filtering the magnesium aluminate spinel and magnesium hydroxide, and finally performing heat treatment at the temperature of more than or equal to 350 ℃ to prepare magnesium-rich magnesium aluminate spinel so as to recycle industrial solid wastes.

The method of the invention is carried out according to the following steps:

1. washing aluminum ash with water to remove water-soluble components, adding the aluminum ash into a sodium hydroxide solution, stirring and reacting to enable Al and AlN in the aluminum ash to react with NaOH to generate NaAlO₂(ii) a The concentration of the sodium hydroxide solution is 25-35%; the amount of the sodium hydroxide solution is added according to the condition that NaOH completely reacts with Al and AlN and the excess amount is 5-10%; filtering the material after the reaction is completed to obtain a filtrate containing NaAlO₂And NaOH;

2. adding bischofite into the mixed solution under stirring to obtain MgCl₂With NaAlO₂Reacting with NaOH to produce MgO-Al₂O₃Precipitation and Mg (OH)₂Precipitating; the bischofite is added in an amount according to MgCl₂With NaAlO₂Completely reacting with NaOH; reaction ofFiltering the obtained material to obtain MgO-Al as main solid component in the filter residue₂O₃And Mg (OH)₂A mixture of (a);

3. calcining the filter residue at the temperature of more than or equal to 350 ℃ for heat treatment to prepare the magnesium-rich magnesia-alumina spinel.

In the step 1, the complete reaction is based on the following reaction formula:

Al+NaOH+H₂O＝NaAlO₂+3/2H₂↓ (1) and

AlN+NaOH+H₂O＝NaAlO₂+NH₃↑ (2)。

in the step 1, NaAlO is generated by reaction₂In the process of (1), H is produced₂And NH₃And respectively recovering.

In the step 2, the complete reaction is based on the following reaction formula:

2NaAlO₂+MgCl₂＝MgO·Al₂O₃↓ +2NaCl (3) and

2NaOH+MgCl₂＝2NaCl+Mg(OH)₂↓ (4)。

in the step 2, the filtrate obtained after filtration is a NaCl solution.

In the step 1, NaAlO is generated from Al and AlN₂The conversion rate is more than or equal to 99 percent.

In the above step 2, NaAlO₂Conversion of medium Al into MgO-Al₂O₃The conversion rate is more than or equal to 99 percent.

In the step 3, the purity of the magnesium-rich magnesia-alumina spinel is more than or equal to 98 percent.

In step 2, bischofite (MgCl)₂·6H₂O) is bischofite which is a byproduct in the process of extracting potassium from the Qinghai salt lake.

In the step 2, the filtrate is evaporated, concentrated, crystallized and dehydrated to obtain the industrial product NaCl.

The aluminum ash water washed solid contains 10-13% of Al and 18-20% of AlN by weight.

In the above method, when the filtrate of step 1 contains Al₂O₃With SiO₂In a weight ratio of<And (5) at 100, carrying out desiliconization treatment on the filtrate to remove sodium silicate, and carrying out step 2 on the liquid phase obtained after the filtrate is subjected to desiliconization as a mixed solution.

In the above-mentioned method, the desiliconization of the filtrate is carried out according to the method described on page 80 of "Bayer Process for producing alumina" (2007 Metallurgical industry Press).

The invention takes hazardous waste solid material aluminum ash produced in the aluminum industry and byproduct bischofite which becomes 'magnesium harm' after potassium is extracted from salt lake as raw materials to prepare magnesia-alumina spinel with high added value, so that the aluminum ash and the bischofite are recycled, and the invention provides a new preparation method of magnesia-alumina spinel which is a high-grade refractory material with low cost and has good economic benefit and social benefit.

Detailed Description

The aluminum ash adopted in the embodiment of the invention is the aluminum ash generated after aluminum is extracted from aluminum ash slag generated in electrolytic aluminum plants and aluminum alloy production processes.

In the embodiment of the invention, the solid component of the aluminum ash after being washed by water contains Al according to weight percentage₂O₃57.2％，SiO₂0.5％，Al11.0％，AlN 19％，Fe₂O₃0.3％，Ca(Mg)O+Ca(Mg)F₂12％。

The bischofite (MgCl) used by the invention is bischofite (MgCl) which is produced after extracting potassium and lithium from salt lake and filtering silt₂·6H₂O)。

In the embodiment of the invention, the filtrate is subjected to desiliconization treatment to remove sodium silicate, and the liquid phase obtained after the filtrate is subjected to desiliconization is used as a mixed solution.

In the examples of the present invention, the filtrate was desiliconized according to the method described on page 80 of "Bayer Process for producing alumina" (2007 Metallurgical industry Press)