CN111606339A - A method for preparing aluminum-silicon oxide using fly ash - Google Patents

Abstract

The invention provides a method for preparing aluminum-silicon oxide by using fly ash. The method of the invention comprises the steps of performing alkali leaching treatment, acid leaching treatment and roasting treatment on the fly ash in sequence. The preparation method for extracting aluminum-silicon oxide from fly ash of the present invention uses fly ash as raw material, and through two-stage atmospheric leaching, the reaction pressure is reduced, equipment investment is reduced, the preparation process is simple and easy to operate, and the preparation cost is low.

Description

A method for preparing aluminum-silicon oxide using fly ash

technical field

The invention relates to a preparation method of high-purity aluminum-silicon oxide, and belongs to the field of fly ash resource utilization.

Background technique

my country's bauxite resources are increasingly depleted, and the external dependence of bauxite is increasing year by year, which seriously affects the sustainable development of the aluminum industry. The Ordos Basin of Inner Mongolia is rich in high-alumina coal, and the alumina content in the fly ash after calcination of the coal can reach more than 50%. Making full use of the resources such as aluminum and silicon is an effective way to utilize fly ash with high added value.

In recent years, major universities and scientific research units in my country have actively carried out research and exploration of high-alumina fly ash resource utilization technology, mainly using its high-aluminum and high-silicon resource endowment, and the extraction of alumina is an important direction of its application. , due to the low initial aluminum-silicon ratio of high-alumina fly ash, it cannot be directly used in alumina production. Datang Group has adopted the process of pre-desilication of fly ash and soda lime sintering to extract alumina, which has been in industrial operation for many years, but the operation is difficult due to the large amount of slag and the high unit cost; Mengxi Group uses limestone sintering However, the process was also stagnant due to problems such as huge slag production; Shenhua Group used the acid method to conduct a pilot test on the production of alumina from fluidized bed fly ash, which showed that the equipment was resistant to corrosion. There are many problems such as high requirements for performance and the inability of comprehensive utilization of silicon products such as white mud.

Therefore, how to synergistically utilize the two main elements of aluminum and silicon in fly ash has become an urgent problem to be solved in the current utilization of fly ash as a resource. In the invention, the fly ash of the pulverized coal furnace is used as the main raw material, and the fly ash is removed by chemical methods such as iron removal, calcium removal, phosphorus removal, etc. After mixing with purchased alumina, the existing ordinary 400kA or 500kA electrolytic cell is used for molten salt electrolysis to directly produce aluminum-silicon alloy. This process plan provides important technical support for the high value-added utilization of fly ash.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing aluminum-silicon oxide by utilizing fly ash for the technical defects existing in the current synergistic utilization method of two main elements of silicon and aluminum in fly ash, and the aluminum-silicon oxide prepared by the method of the present invention The content of aluminum and silicon is high, and the content of Fe ₂ O ₃ , CaO, P, and MgO is low, and the preparation process of the high-purity aluminum-silicon oxide of the present invention is simple and easy to operate, the production cost is low, the solid waste discharge is significantly reduced, and the high-purity aluminum-silicon oxide has good performance. economic and social benefits.

In order to achieve the purpose of the present invention, one aspect of the present invention provides a method for preparing aluminum-silicon oxide from fly ash, which comprises sequentially performing alkali leaching treatment, acid leaching treatment and roasting treatment on the fly ash.

Wherein, the aluminum-silicon content in the prepared aluminum-silicon oxide is respectively: Al ₂ O ₃ ≥50%, preferably greater than 55%; SiO ₂ ≤45%, preferably less than 40%.

In particular, Fe ₂ O ₃ ≤0.5%, CaO≤0.2%, P≤0.005%, and MgO≤0.1% in the prepared aluminum-silicon oxide.

The fly ash in the method of the invention refers to the fly ash obtained after coal is burned in a pulverized coal furnace and collected by a dust collector. Fly ash is different due to different sources of fuel coal used in coal-fired boilers in different regions and different combustion methods of boilers, but the common point is that the total content of alumina and silica is relatively high, generally accounting for 70% of the total fly ash. %above.

The total content of alumina and silica in the fly ash of the present invention should be greater than 50%, preferably ≥70%.

The raw material fly ash used in the present invention is high-alumina fly ash, and the alumina content in the high-alumina fly ash is greater than 40%.

Wherein, the mass ratio of alumina to silica in the high-alumina fly ash is greater than 1.0.

In particular, the content of alumina in the fly ash is 40-60%, preferably 50-60%; the content of silica is 30-50%, preferably 30-40%.

In particular, the total content of alumina and silica in the fly ash is 70-95%, preferably 85-95%.

The inventors of the present invention found that fly ash is mainly composed of crystalline phases mullite and corundum phases and part of glass phases, wherein the glass phase contains a large amount of amorphous silica and a small amount of amorphous alumina, and the amorphous A large number of iron oxide and ferric oxide particles are adhered to the silica. During the reaction at atmospheric pressure, the crystalline mullite and corundum phases in the high-alumina fly ash do not react with the lye, while the amorphous silica and non-crystalline vitreous phases in the high-alumina fly ash Crystalline alumina can be leached (dissolved) by lye at the same time, and react immediately to form sodalite-type aluminosilicate; fly ash is leached by lye to remove amorphous silica to obtain desiliconized pulverized coal Ash.

The inventors of the present invention also found that, under normal pressure conditions, the amorphous alumina in the glass phase of fly ash can be leached (dissolved) by the dilute acid solution, while the amorphous silica does not mix with the dilute acid solution. Therefore, after the acid treatment, the amorphous alumina in the glass phase can be separated from the mullite and corundum phases, so that the sodalite phase formed in the desiliconized fly ash can react with hydrochloric acid and destroy the sodalite structure. However, the crystalline phase mullite and corundum phases do not change under the acid condition, and finally the impurities (such as iron oxide, calcium oxide, magnesium oxide, sodium oxide, phosphorus pentoxide) in the glass phase can enter the liquid phase.

Wherein, in the alkali dissolution treatment, the fly ash and the alkali solution are mixed, stirred, and filtered after the reaction to obtain a primary alkali leaching fly ash and a primary alkali leaching solution.

In the process of alkali dissolution treatment, the amorphous alumina and amorphous silica of the glass phase in the fly ash are leached out and react to form a sodalite aluminosilicate, which makes the glass phase in the fly ash and the crystalline The phase is better peeled off to achieve the purpose of impurity removal.

The alkaline solution reacts with the amorphous alumina and amorphous silicon dioxide in the fly ash, and dissolves in the alkaline solution to form an alkaline solution; the insoluble substances in the fly ash are filtered to obtain an alkaline solution. fly ash.

In particular, the alkaline solution is a mixed solution of sodium hydroxide and sodium carbonate.

In particular, the concentration of sodium hydroxide in the alkaline solution is 50-230g/L, preferably 80-150g/L; the concentration of sodium carbonate is 2-20g/L, preferably 5-18g/L.

In particular, the ratio of the volume of the alkaline solution to the mass of the fly ash is (2.5-6): 1, preferably (3.5-5): 1, that is, per 1 g of fly ash to 2.5-6 ml of alkaline solution or per 100g of fly ash is mixed with 250-600ml of alkaline solution or 2.5-6L of alkaline solution per 1kg of fly ash, and the alkaline dissolution treatment is carried out.

Wherein, in the acid leaching treatment, the fly ash after alkali leaching treatment is mixed with an acid solution, stirred, and filtered after the reaction to obtain secondary acid leaching fly ash and secondary acid leaching solution.

The purpose of acid leaching is to separate the iron, calcium and phosphorus soluble substances in the fly ash from the fly ash, and the remaining substances are mainly acid-insoluble aluminum-silicon oxides. Its function is to remove acid-soluble substances in fly ash.

During the acid leaching process, the sodalite-type aluminosilicate, alumina, iron oxide, calcium oxide, magnesium oxide and other impurities in the fly ash are leached out of the fly ash, and the remaining solid phase aluminum-silicon The purity of alumina.

Secondary acid leaching solution mainly contains aluminum chloride, calcium chloride, ferric chloride and sodium chloride; secondary acid leaching fly ash mainly contains mullite and corundum.

Wherein, the acid solution is one or more of hydrochloric acid solution, sulfuric acid solution or nitric acid solution, preferably hydrochloric acid solution and sulfuric acid solution.

In particular, the mass concentration of the acid solution is 10-30%, preferably 14-25%.

In particular, the acid solution is a hydrochloric acid solution with a mass concentration of 14-25%, preferably 14-18%; the acid solution is a sulfuric acid solution with a mass concentration of 14-25%, preferably 25%.

In the present invention, a common acid solution, such as sulfuric acid, hydrochloric acid or nitric acid, is selected in the acid leaching treatment process, and the present invention does not limit the quantity of acid treatment agent types, which can be any aqueous solution of the above-mentioned acid solutions, or can be The aqueous solution of two mixed acid solutions in the above-mentioned acid solution, for example, the acid treatment agent can be any one of hydrochloric acid, sulfuric acid or nitric acid, or a mixture of hydrochloric acid, sulfuric acid or nitric acid, and when the acid treatment agent is two In the case of a mixture of acid solutions, the present invention does not limit the ratio between each acid solution.

In particular, the mass ratio of the volume of the acid solution to the primary alkali-dissolved fly ash is (4.0-10.0): 1, preferably (5-8): 1, that is, every 1 g of primary alkali-dissolved fly ash and 4-10ml of acid solution or alkali-leaching fly ash per 100g is mixed with 400-1000ml of acid solution or 4-10 acid solution per 1kg of fly ash to carry out the acid leaching treatment.

Another aspect of the present invention provides a method for preparing aluminum-silicon oxide using fly ash, comprising the following steps:

1) adding the fly ash to the alkaline solution, and mixing it with the alkaline solution evenly to carry out the alkaline dissolution treatment; then filter and wash, and the obtained filter residue is the primary alkaline dissolution fly ash; the filtrate and the washing solution are combined to obtain a primary alkaline leaching solution;

2) adding the primary alkali-leaching fly ash to the acid solution, and mixing with the acid solution evenly to carry out acid leaching treatment; then filter and wash; the obtained filter residue is the secondary acid leaching fly ash; the filtrate and the washing solution are combined , to obtain secondary acid leaching solution;

3) The secondary acid leaching fly ash is subjected to roasting treatment to obtain aluminum-silicon oxide.

Wherein, the fly ash in step 1) selects high-alumina fly ash, wherein the alumina content in the high-alumina fly ash is greater than 40%.

In particular, the mass ratio of alumina to silica in the high-alumina fly ash is greater than 1.0.

In particular, the content of alumina in the fly ash is 40-60%, preferably 50-60%; the content of silica is 30-50%, preferably 30-40%.

In particular, the total content of alumina and silica in the fly ash is 70-95%, preferably 85-95%.

Wherein, the alkali solution is a mixed solution of sodium hydroxide and sodium carbonate.

In particular, the concentration of sodium hydroxide in the alkaline solution is 50-230g/L, preferably 80-150g/L; the concentration of sodium carbonate is 2-20g/L, preferably 5-18g/L.

Wherein, the ratio of the volume of the alkaline solution to the mass of the fly ash is (2.5-6): 1, preferably (3.5-5): 1, that is, every 1 g of fly ash and 2.5-6 ml of alkaline solution or every 100 g The fly ash is mixed with 250-600 ml of alkaline solution or 2.5-6 L of alkaline solution per 1 kg of fly ash, and the alkaline dissolution treatment is carried out.

In particular, the control temperature in the alkali dissolution treatment process is 70-100°C, preferably 80-90°C; the alkali dissolution treatment time is 2-8h, preferably 3-7h.

Wherein, the filtration and washing described in step 1) are vacuum filtration and washing carried out under vacuum conditions.

In particular, the relative pressure of the vacuum condition is less than 0 MPa, preferably -0.02 to -0.1 MPa, preferably -0.02 to -0.08 MPa, and more preferably -0.05 to -0.08 MPa.

In particular, tap water or distilled water is used to wash the filter residue after the alkali elution treatment and filtration.

Wash until the concentration of sodium hydroxide in the effluent (ie, washing liquid) is less than 3 g/L. The number of washings is 3-5 times, preferably 4 times.

In particular, the mass ratio of the washing water to the filtered residue in each washing process is (0.8-0.9):1.

In particular, the temperature of tap water or distilled water used in the washing process is (95±5)°C.

Wherein, the acid solution described in step 2) is one or more of hydrochloric acid solution, sulfuric acid solution or nitric acid solution, preferably hydrochloric acid solution and sulfuric acid solution.

In particular, the mass concentration of the acid solution is 10-30%, preferably 14-25%.

In particular, the acid solution is a hydrochloric acid solution with a mass concentration of 14-25%, preferably 14-18%; the acid solution is a sulfuric acid solution with a mass concentration of 14-25%, preferably 25%.

In the present invention, a common acid solution, such as sulfuric acid, hydrochloric acid or nitric acid, is selected in the acid leaching treatment process, and the present invention does not limit the quantity of acid treatment agent types, which can be any aqueous solution of the above-mentioned acid solutions, or can be The aqueous solution of two mixed acid solutions in the above-mentioned acid solution, for example, the acid treatment agent can be any one of hydrochloric acid, sulfuric acid or nitric acid, or a mixture of hydrochloric acid, sulfuric acid or nitric acid, and when the acid treatment agent is two In the case of a mixture of acid solutions, the present invention does not limit the ratio between each acid solution.

Wherein, the temperature of the acid leaching treatment is 70-95°C, preferably 75-90°C; the treatment time is 3-8h, preferably 3-6h.

In particular, the mass ratio of the volume of the acid solution to the primary alkali-dissolved fly ash is (4.0-10.0): 1, preferably (5-8): 1, that is, every 1 g of primary alkali-dissolved fly ash and 4-10ml of acid solution or alkali-leaching fly ash per 100g is mixed with 400-1000ml of acid solution or 4-10 acid solution per 1kg of fly ash to carry out the acid leaching treatment.

Wherein, the filtration and washing described in step 2) are vacuum filtration and washing carried out under vacuum conditions.

In particular, the relative pressure under vacuum conditions is -0.02 to -0.1 MPa, preferably -0.02 to -0.08 MPa, and more preferably -0.05 to -0.08 MPa.

In particular, tap water or distilled water is used to wash the filter residue after acid leaching treatment and filtration.

Wash until the pH of the effluent (ie, wash) is greater than 3. The mass ratio of the washing water to the filtered cake is (1.5-3.0):1.

In particular, the temperature of tap water or distilled water used in the washing process is (95±5)°C.

In particular, it also includes step 2A) drying the washed filter residue to obtain the secondary acid leaching fly ash.

Wherein, the drying temperature is 100-110°C, preferably 105°C; the moisture content of the secondary acid leaching fly ash after drying is lower than 70%, preferably 55-65%, more preferably 58-62% %.

Wherein, the roasting treatment temperature in step 3) is 600-1000°C, preferably 800-1000°C; the roasting time is 0.5-2.0h, preferably 1-2h.

In particular, in the aluminum-silicon oxide prepared in step 3), Al ₂ O ₃ ≥ 50%, preferably more than 52%; SiO ₂ ≤ 45%, preferably less than 30%.

In particular, Fe ₂ O ₃ ≤0.5%, CaO≤0.2%, P≤0.005%, and MgO≤0.1% in the prepared aluminum-silicon oxide.

The roasting treatment is to dehydrate the aluminum-silicon oxide after removal of impurities and remove unburned carbon. After the roasting treatment, the adhering water and structural water in the secondary acid leaching fly ash are discharged, and the unburned charcoal is also removed, so that the sample is in the form of white powder.

In particular, it also includes step 4), measuring the concentration of silicon dioxide in the primary alkali eluate prepared by the alkali elution treatment in step 1), and calculating the number of moles of silica in the primary alkali eluate; The alkali eluate is mixed with calcium supply agent and dispersant, stirred and reacted to form calcium silicate precipitation; then the reaction system is filtered and washed, the filter residue is calcium silicate by-product, and the filtrate and washing liquid are combined and concentrated.

Wherein, the calcium supply agent described in step 4) selects milk of lime or calcium carbide slag; the dispersant selects sodium dodecylbenzenesulfonate, azodicarbonamide, diethyl phthalate, phthalic acid One or more of dioctyl ester and sodium lignosulfonate, preferably sodium dodecylbenzenesulfonate, sodium lignosulfonate or diethyl phthalate.

In particular, the molar ratio of silicon dioxide in the primary alkali eluate to calcium oxide in the calcium supply agent is 1:(1.05-1.2), preferably 1:(1.05-1.14); The dosage is (0.02-0.6) %, preferably (0.06-0.3) %, of the mass of the calcium silicate produced by the total reaction of silicon in the primary alkali eluate.

Wherein, the stirring and reaction temperature in step 4) is 70-100°C, preferably 85-95°C; the reaction time is 0.5-2h, preferably 1-2h.

Particularly, in step 4), adopt the water (tap water or distilled water) that temperature is 90-100 ℃ to wash the by-product calcium silicate filter residue after filtration, wash to free alkali less than 3g/L, control the mass ratio of washing water and filter residue It is (2.5～8.0):1, and the filter residue is nanoporous calcium silicate.

In particular, the washed filter residue is dried at 100-100° C. until the moisture content is lower than 5% (usually 1.5-3.0%) to obtain the by-product nano-calcium silicate.

In step 4), the filtrate after filtration and the washing solution after washing are combined and concentrated, and the concentrated solution is recovered or recycled, which is alkali recovery treatment.

The by-product calcium silicate is nanoporous calcium silicate. The present invention does not limit the type and quantity of the dispersing agent, and can be any one or more of the above-mentioned dispersing agents. For example, the dispersing agent can be dodecylbenzenesulfonic acid. Any of sodium, diethyl phthalate, or a mixture of sodium dodecylbenzenesulfonate and diethyl phthalate, and when the dispersant is a mixture of two or more dispersants , the present invention does not limit the proportion of each dispersant.

In particular, it also includes step 5): adding acid to the secondary acid leaching solution prepared in step 2) until the mass concentration of the acid solution is 10-30%, then returning to step 2) for recycling.

Add concentrated hydrochloric acid, concentrated sulfuric acid or concentrated nitric acid to the secondary acid leaching solution, so that the mass concentration of hydrochloric acid, sulfuric acid and nitric acid in the solution reaches 10-30%.

In particular, it also includes step 6): subjecting the secondary acid leaching solution prepared by the acid leaching treatment in step 2) to resin adsorption treatment to remove calcium chloride, ferric chloride or calcium sulfate, ferric sulfate or calcium nitrate in the secondary acid leaching solution , ferric nitrate and other impurities; then evaporate and crystallize to obtain by-product aluminum chloride or aluminum sulfate or aluminum nitrate.

Wherein, the resin used in the resin adsorption treatment is an anion exchange resin, which is a gel type strong base anion exchange resin, a gel type weak base anion exchange resin, a macroporous type strong base anion exchange resin or a macroporous type weak base. anion exchange resin.

Another aspect of the present invention provides an aluminum-silicon oxide prepared according to the above method.

The aluminum-silicon oxide prepared according to the above method is used for producing aluminum-silicon alloy products in the molten salt electrolysis method.

The application of the aluminum-silicon oxide prepared by the invention in the electrolysis of aluminum-silicon alloy in cryolite-fluoride salt molten salt electrolysis system.

The application of the above-mentioned aluminum-silicon oxide in molten salt electrolysis, wherein, the aluminum-silicon oxide of the present invention can be used as a raw material for producing electrolytic aluminum-silicon alloy by molten salt electrolysis method, and the aluminum-silicon oxide of the present invention can also be used. As a raw material for the production of aluminum-silicon alloys by ore-thermal method.

The preparation method of the aluminum-silicon oxide of the present invention takes the pulverized coal furnace fly ash as the raw material, performs normal pressure alkali treatment on the fly ash, and finally adopts conventional acid leaching to obtain Fe ₂ O ₃ ≤0.5%, CaO ≤0.2%, P≤0.005%, MgO≤0.1% Al-Si oxide greatly reduces the impurity content in fly ash, thus laying the foundation for the high value-added utilization of fly ash.

Compared with the existing, the implementation of the present invention has the following advantages:

1) The process method of utilizing fly ash to extract aluminum-silicon oxide of the present invention does not need to undergo special treatment, and there is no preliminary treatment such as physical iron removal and calcium removal, and two-step treatment can be used, and the flow process is relatively simple;

2) The reaction temperature used in the present invention is all below 100°C, and the wet process under normal pressure conditions can be used for iron removal, calcium removal and purification. In the aluminum silicon oxide prepared by the method of the present invention, aluminum oxide, silicon oxide High content, alumina content reaches more than 50%; silica content is less than 45%; and Fe ₂ O ₃ , CaO, P, MgO content is low, Fe ₂ O ₃ ≤ 0.5%, CaO ≤ 0.2%, P ₂ O ₅ ≤ 0.005%, MgO ≤ 0.1%, the reaction process is carried out under normal pressure conditions, and the equipment requirements are low;

3) The reduction treatment of fly ash is realized, the amount of solid waste is significantly reduced, and the total amount of by-products is greatly reduced compared with other processes (1 ton of raw ash produces about 0.3-0.35 tons of by-products, and the by-products have market sales prospects);

4) The equipment used in this process method is all conventional equipment, and there is no need to additionally develop non-standard equipment, reducing equipment investment costs;

5) The dilute acid solution used in the treatment under normal pressure has less corrosion to the equipment, easy operation, less washing water consumption, and less acid loss in the separation process.

Description of drawings

FIG. 1 is a process flow diagram of a method for extracting silicon-alumina oxide from fly ash according to the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, and Not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The method for extracting silicon-alumina oxide by using fly ash of the present invention is extracted and prepared according to the technological process shown in FIG. 1 .

Example 1

1) Alkali dissolution treatment

The fly ash is added to the alkali solution, stirred and mixed, and the amorphous silica and alumina in the glass phase in the fly ash are dissolved in the alkali solution, and the alkali dissolution treatment is carried out; wherein the alkali dissolution treatment process is controlled. The temperature in the medium is 80 °C (usually 70-100 °C); the ratio of the mass of fly ash to the volume of alkali solution is 1:5 (usually 1:2.5-6), that is, 5ml of alkali solution is used per 1g of fly ash Or use 500ml of alkaline solution per 100g of fly ash or use 5L of alkaline solution per 1kg of fly ash for alkaline dissolution treatment; the alkaline solution is a mixed solution of sodium hydroxide, sodium carbonate and water, and the concentration of sodium hydroxide in the alkaline solution is 100g/L (usually 50-230g/L), sodium carbonate concentration is 5g/L (usually 2-20g/L);

In this embodiment, the mass of fly ash used in the alkali dissolution treatment process is 100 g, and the alkali solution is 500 ml. In the embodiment of the present invention, the ratio of the mass of the fly ash to the volume of the alkali solution is 1:5 as an example, and other ratios of 1:2.5-6 are also applicable to the present invention.

The chemical composition of the fly ash raw material is as follows: the mass content of alumina is 45.25%; the mass content of silica is 44.25%, the mass ratio of alumina to silica is 1.02; the mass content of iron oxide is 3.16%, calcium oxide The mass content of magnesium oxide is 2.57%; the mass content of magnesium oxide is 0.86%, and the mass content of phosphorus pentoxide is 0.2%;

Except for the fly ash of the above composition, the mass content of alumina in other fly ash is 40%-60%; the mass content of silica is 30-50%, and the mass ratio of alumina to silica is greater than 1.0 The fly ash is suitable for the present invention.

Amorphous alumina and amorphous silica in the glass phase in the fly ash react with the lye during the alkali dissolution treatment, and the amorphous alumina and amorphous silica are dissolved in the lye and chemically After the reaction, a sodalite-type aluminosilicate is formed, so that the glass phase can be better peeled off from the crystalline phase to achieve the purpose of removing impurities.

The purpose of alkali dissolution is to destroy the amorphous glass phase structure in fly ash and dissolve amorphous silica and alumina.

In the process of high temperature combustion of pulverized coal, amorphous silica is melted and adhered to other components at high temperature to form fly ash particles with hollow microbeads. Dissolved into the alkali solution, thereby destroying the particle structure of fly ash; and because a large number of iron oxide and ferric oxide particles adhered to the amorphous silica, the alkali dissolved the amorphous silica and the iron oxide and the iron oxide were dissolved. After the ferric oxide particles are exposed, the efficiency of acid leaching to remove iron can be improved for subsequent acid leaching. Moreover, amorphous alumina and amorphous silica are dissolved in lye and undergo chemical reaction to form square sodium. Stone-type aluminosilicate, the specific reaction is as follows:

2NaOH+SiO ₂ (amorphous)=Na ₂ SiO ₃ +H ₂ O

2NaOH+Al ₂ O ₃ (amorphous)=2NaAlO ₂ +H2O

The main side reactions of fly ash extraction of amorphous silica are:

2NaAlO ₂ +2Na ₂ SiO ₃ +4H ₂ O=Na ₂ O·Al ₂ O ₃ ·2SiO ₂ ·2H ₂ O↓+4NaOH

After stirring for 3h (usually 2-8h), carry out filtration treatment under vacuum conditions, and wash the filter cake with tap water at a temperature of 90°C (usually 90±5°C), wherein the control vacuum condition is that the relative pressure is -0.06MPa (usually -0.02～-0.08MPa), wash 4 times (usually 3-5 times), wash until the concentration of sodium hydroxide in the effluent (washing solution) is lower than 3g/L; washing is carried out under vacuum conditions, The filter cake after washing is the obtained primary alkali leaching fly ash (86.67g), and the filtrate and washing solution of vacuum filtration are combined into primary alkali leaching solution (438ml);

Adopt visible light spectrophotometer molybdenum blue photometric method (YS/T 575-2007, chemical analysis method of bauxite ore) to measure the content of silicon dioxide in the primary alkali leaching solution, the measurement result: silicon dioxide concentration is 29.904g/L;

The content of alumina in the primary alkali leaching solution was determined by the lead salt back-dropping-ammonium fluoride replacement method (YS/T 575-2007, chemical analysis method of bauxite ore), and the alumina concentration was 1.02 g/L.

2) Acid leaching treatment

Add the primary alkali-dissolved fly ash to the acid solution, stir and mix evenly, and the acid-soluble substances in the fly ash (such as the sodalite-type aluminosilicate generated in the alkali-dissolving treatment step, and the fly ash) The impurities contained in the iron oxide, calcium oxide, magnesium oxide, etc.) are dissolved in the acid solution and subjected to acid leaching treatment; wherein, the acid solution is a hydrochloric acid solution with a mass concentration of 14.0% (usually 10-30%); primary alkali The ratio of the mass of the dissolved fly ash to the volume of the acid solution is 1:6 (usually 1:4-10); that is, 6ml of acid solution is used for every 1g of alkali-dissolved fly ash or 6ml of acid solution is used for every 100g of alkali-dissolved fly ash. 600ml acid solution is subjected to acid leaching treatment; the temperature of acid leaching treatment is 90°C (usually 70-95°C); the acid leaching treatment time is 4.5h (usually 3-8h);

After 4.5h (usually 3-8h) of acid leaching treatment, filter treatment is carried out under vacuum conditions, and the filter cake is washed with tap water at a temperature of 90°C (usually 90±5°C). -0.06MPa (usually -0.02～-0.08MPa); wash until the pH of the effluent (washing solution) is greater than 3, and the ratio of the volume of tap water for washing to the mass of fly ash is 2:1 (usually 1-4: 1); the filter cake after washing is dried at 105°C (usually 100-110°C) to obtain a secondary acid leaching with a moisture content of 60.15% (usually lower than 65%, preferably 58-62%). Fly ash (65.6g); the filtrate and washing liquid of vacuum filtration are combined to obtain secondary acid leaching-filtrate, and the secondary acid leaching-filtrate can be recycled as an acid treatment agent solution or recycled to the liquid phase after being concentrated and supplemented with acid After the concentration of aluminum chloride reaches 50g/L, polyaluminum chloride can be prepared by evaporating and crystallizing after removing slag from resin.

During the acid leaching process, the acid solution is mixed with the primary alkali leaching fly ash and reacts, and the alumina, iron oxide, calcium oxide, magnesium oxide, etc. in the sodalite-type aluminosilicate contained in the primary alkali leaching fly ash The impurities are leached out, thereby leaving the purity of the aluminosilicate alumina in the solid phase.

Al ₂ O ₃ +6HCl=2AlCl ₃ +3H ₂ O

Fe ₂ O ₃ +6HCl=2FeCl ₃ +3H ₂ O

CaO+2HCl=CaCl ₂ +H ₂ O

The purpose of acid leaching is to separate the iron, magnesium, phosphorus, calcium, amorphous aluminum and other acid-soluble substances in fly ash from fly ash, and the remaining substances are mainly acid-insoluble aluminum-silicon oxide. thing. Its function is to remove acid-soluble substances in fly ash.

3) Roasting

The secondary acid leaching fly ash is placed in a roasting furnace, heated and kept at 800°C (usually 600-1000°C) for roasting treatment. After roasting for 1h (usually 0.5-2h), the temperature is cooled down. , to obtain the aluminum silicon oxide of the present invention.

The prepared aluminum-silicon oxide was measured by YS/T 630-2007 Determination of Alumina Impurity Content Inductively Coupled Plasma Atomic Emission Spectrometry. The test results are shown in Table 1.

The chemical composition detection result of table 1 aluminum-silicon oxide prepared by the present invention

content(%) Example 1 Example 2 Example 3 Alumina 60.92% 58.74% 55.98% Silicon oxide 34.67% 35.87% 38.36% Iron oxide 0.38% 0.28% 0.43% Calcium Oxide 0.11% 0.09% 0.13% Magnesium oxide 0.02% 0.03% 0.04% phosphorus pentoxide 0.002% 0.004% 0.005%

4) Preparation of by-products

Mix the primary alkali leaching solution with lime milk and dispersant, stir, react for 1h (usually 0.5-2h) to generate calcium silicate precipitation and sodium hydroxide, wherein the stirring reaction temperature is 92°C (usually 70-100°C); The molar ratio of silicon and calcium in the milk of lime is controlled to be 1:1.07 (usually 1:1.05-1.2) in the primary alkali leaching solution; All the silicon in the liquid reacts to form 0.08% of the mass of calcium silicate (usually 0.02-0.6%);

The main function of the dispersant is to evenly disperse the lime milk particles into the sodium silicate solution, increase the contact area with calcium silicate, and increase the surface charge by forming an adsorption layer on the surface of the lime milk particles, which increases the infiltration of the lime milk particles. Finally, the distribution of lime milk is more uniform, the reaction with sodium silicate is more uniform, and it is easy to prepare nanoporous calcium silicate.

The reaction system is filtered, and the filter cake is washed with tap water at a temperature of 95°C (usually 90-100°C) until the free alkali in the effluent is less than 3 g/L, and the filter cake after washing is at 105°C (usually 90-100°C). 100-100°C) drying to obtain nano calcium silicate by-product, wherein the water content of calcium silicate is lower than 2.5% (usually lower than 5%, preferably 1.5-3.0%); the washing solution is recycled after evaporation and concentration , that is, alkali recovery treatment, for example, after concentrating to a specified concentration, it is returned to the alkali dissolution treatment step for recycling.

In this example, the primary alkali eluate is 438ml, the silica concentration is 29.904g/L, and the mole number of silica in the primary alkali eluate is 0.2183mol. Completely precipitate the silicon in the primary alkali leaching solution, and the quality of the calcium silicate generated is 26.178g; Precipitating the silicon in the primary alkali leaching solution completely, controlling the molar ratio of silicon and calcium in the milk of lime in the primary alkali leaching solution is 1: 1.07, select lime milk with an effective calcium concentration of 120g/L, and the amount of lime milk is 109ml. The dosage of dispersant sodium dodecylbenzenesulfonate is 26.178×0.08%=0.02094g.

Example 2

1) Alkali dissolution treatment

The chemical composition of the raw material except fly ash is as follows: the mass content of alumina is 45.25%; the mass content of silicon oxide is 44.25%, the mass content of iron oxide is 3.16%, and the mass content of calcium oxide is 2.57%; the mass content of magnesium oxide The content is 0.86%, and the mass content of phosphorus pentoxide is 0.01%;

The ratio of the mass of fly ash to the volume of the alkaline solution is 1:4.5; the concentration of sodium hydroxide in the alkaline solution is 150g/L (usually 50-230g/L), and the concentration of sodium carbonate is 10g/L (usually 2- 20g/L); the alkali dissolution treatment temperature is 90°C; the alkali dissolution treatment time is 6.0h; the first alkali dissolution of fly ash (85.4g); the first alkali dissolution solution (389ml); the silica concentration in the first alkali dissolution solution is Except 32.73g/L, the rest are the same as step 1 in Example 1) alkali dissolution treatment;

2) Acid leaching treatment

Except that the acid solution is a hydrochloric acid solution with a mass concentration of 18.0% (usually 10-30%); the ratio of the mass of the primary alkali-dissolved fly ash to the volume of the acid solution is 1:5 (usually 1:4-10); The temperature of acid leaching treatment is 80°C (usually 70-95°C); the acid leaching treatment time is 3h (usually 3-8h); the secondary acid leaching fly ash is 65.1g; the moisture content is 63.12%, the rest Same as step 2 in Example 1) acid leaching treatment;

Secondary acid leaching-the filtrate can be recycled as an acid treatment agent solution after being concentrated and supplemented with acid, or after the aluminum chloride concentration in the liquid phase reaches 55g/L, polyaluminum chloride can be prepared by evaporating and crystallizing resin after slag removal.

3) Roasting

Except that the roasting temperature is 1000°C (usually 600-1000°C); the roasting time is 2h (usually 0.5-2h), the rest are the same as in step 3) roasting in Example 1;

4) Preparation of by-products

The primary alkali leaching solution is mixed with lime milk and dispersant, stirred, and reacted for 2h (usually 0.5-2h) to generate calcium silicate precipitation and sodium hydroxide, wherein the stirring reaction temperature is 85°C (usually 70-100°C); The molar ratio of silicon and calcium in the milk of lime is controlled to be 1:1.05 (usually 1:1.05-1.2) in the primary alkali leaching solution; the dispersant is diethyl phthalate, and the consumption of the dispersing agent is the primary alkali leaching solution All the silicon in the reaction generates 0.156% of the mass of calcium silicate (usually 0.02-0.6%);

The reaction system is filtered, and the filter cake is washed with tap water at a temperature of 95°C (usually 90-100°C) until the free alkali concentration in the effluent is less than 3g/L, and the filter cake after washing is at 105°C (usually 90-100°C). drying at 100-100° C.) to obtain nano-calcium silicate by-products, wherein the water content of calcium silicate is lower than 2.1% (usually 1.5-3.0%); the washing liquid is recycled after evaporation and concentration, that is, alkali recovery treatment , for example, after concentrating to a specified concentration, it is returned to the alkali dissolution treatment step for recycling.

In this example, the primary alkali eluate is 389ml, the silica concentration is 32.73g/L, and the mole number of silicon in the primary alkali eluate is 0.2122mol. Completely precipitate the silicon in the primary alkali leaching solution, and the quality of the calcium silicate generated is 25.209g; Precipitating the silicon in the primary alkali leaching solution completely, controlling the molar ratio of silicon and calcium in the milk of lime in the primary alkali leaching solution is 1: 1.05, choose lime milk with an effective calcium concentration of 120g/L, and the amount of lime milk is 104ml. The dosage of dispersant diethyl phthalate is 25.209×0.156%=0.0393g.

Example 3

1) Alkali dissolution treatment

The chemical composition of the raw material except fly ash is as follows: the mass content of alumina is 43.87%; the mass content of silicon oxide is 48.78%, the mass content of iron oxide is 3.49%, and the mass content of calcium oxide is 3.22%; the mass content of magnesium oxide The content is 1.07%, and the mass content of phosphorus pentoxide is 0.24%;

The ratio of the mass of fly ash to the volume of the alkaline solution is 1:3.5; the concentration of sodium hydroxide in the alkaline solution is 80g/L (usually 50-230g/L), and the concentration of sodium carbonate is 18g/L (usually 2- 20g/L); the alkali dissolution treatment temperature was 95°C; the alkali dissolution treatment time was 7.0h; the first alkali dissolution of fly ash (88.7g); the first alkali dissolution solution (282ml); the silica concentration in the first alkali dissolution solution was Except 44.36g/L, the rest are the same as the step 1 of Example 1) alkali dissolution treatment;

2) Acid leaching treatment

Except that the acid solution is a sulfuric acid solution with a mass concentration of 25.0% (usually 10-30%); the ratio of the mass of the primary alkali-dissolved fly ash to the volume of the acid solution is 1:8 (usually 1:4-10); The temperature of acid leaching treatment is 75℃ (usually 70-95℃); the acid leaching treatment time is 6h (usually 3-8h); the secondary acid leaching fly ash is 67.1g; the moisture content is 64.5%, the rest Same as step 2 in Example 1) acid leaching treatment;

Secondary acid leaching-the filtrate can be recycled as an acid treatment agent solution after being concentrated and supplemented with acid, or after the aluminum sulfate concentration in the liquid phase reaches 50g/L, the resin can be used to remove slag and then evaporate and crystallize to prepare aluminum sulfate.

3) Roasting

Except that the roasting temperature is 900 ° C; the roasting time is 1.5h, the rest are the same as the step 3) roasting in Example 1;

4) Preparation of by-products

Mix the primary alkali leaching solution with calcium carbide slag and dispersant, stir, and react for 2h (usually 0.5-2h) to generate calcium silicate precipitation and sodium hydroxide, wherein the stirring reaction temperature is 95°C (usually 70-100°C); Control the molar ratio of silicon in primary alkali leaching solution to calcium in carbide slag to be 1:1.14 (usually 1:1.05-1.2); dispersant is sodium dodecylbenzenesulfonate, sodium lignosulfonate, dispersant The dosage is 0.3% (usually 0.02-0.6%) of the mass of calcium silicate produced by the total reaction of silicon in the primary alkali leaching solution;

The reaction system is filtered, and the filter cake is washed with tap water at a temperature of 95°C (usually 90-100°C) until the free alkali concentration in the effluent is less than 3g/L, and the filter cake after washing is at 105°C (usually 90-100°C). drying at 100-100° C.) to obtain nano-calcium silicate by-product, wherein the water content of calcium silicate is lower than 1.76% (usually 1.5-3.0%); the washing liquid is recycled after evaporation and concentration, that is, alkali recovery treatment , for example, after concentrating to a specified concentration, it is returned to the alkali dissolution treatment step for recycling.

In this example, the primary alkali eluate is 282ml, the silica concentration is 44.36g/L, and the mole number of silicon in the primary alkali eluate is 0.20849mol. Completely precipitate the silicon in the primary alkali leaching solution, and the quality of the calcium silicate generated is 28.2799g; Precipitating the silicon in the primary alkali leaching solution completely, controlling the molar ratio of silicon and calcium in the calcium carbide slag in the primary alkali leaching solution is 1: 1.14, select 22.0g of carbide slag with an effective calcium concentration of 60.5%. The dosage of dispersant sodium dodecylbenzenesulfonate and sodium lignosulfonate is 28.2799×0.3%=0.0848g. Among them, sodium dodecylbenzenesulfonate 0.0231g (accounting for 0.082%), sodium lignosulfonate 0.0617g (accounting for 0.218%).

The dispersant in Example 3 of the present invention can also be 0.0848g of sodium dodecylbenzenesulfonate; or 0.0848g of sodium lignosulfonate; it can also be any proportion of sodium dodecylbenzenesulfonate, lignosulfonate Sodium mixed, as long as the total mass of sodium dodecylbenzenesulfonate and sodium lignosulfonate is 0.0848g.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (10)

1. a method for utilizing fly ash to prepare aluminum-silicon oxide, is characterized in that, comprises carrying out alkali leaching treatment, acid leaching treatment and roasting treatment successively to fly ash. 2 . The method according to claim 1 , wherein the alkali dissolution treatment is to mix the fly ash with an alkaline solution, and after stirring and reacting, filter to obtain a primary alkali leaching fly ash and a primary alkali leaching solution. 3 . 3. method as claimed in claim 1, is characterized in that, described acid leaching treatment is to mix the fly ash after alkali leaching treatment and acid solution, stir, carry out filtration treatment after reaction, make secondary acid leaching powder Coal ash and secondary acid leachate. 4. a method utilizing fly ash to prepare aluminum-silicon oxide, is characterized in that, comprises the steps: 1) adding the fly ash to the alkaline solution, and mixing it with the alkaline solution evenly to carry out the alkaline dissolution treatment; then filter and wash, and the obtained filter residue is the primary alkaline dissolution fly ash; the filtrate and the washing solution are combined to obtain a primary alkaline leaching solution; 2) adding the primary alkali-leaching fly ash to the acid solution, and mixing with the acid solution evenly to carry out acid leaching treatment; then filter and wash; the obtained filter residue is the secondary acid leaching fly ash; the filtrate and the washing solution are combined , to obtain secondary acid leaching solution; 3) The secondary acid leaching fly ash is subjected to roasting treatment to obtain aluminum-silicon oxide. 5. method as claimed in claim 4 is characterized in that, the alkaline solution described in step 1) is the mixed solution of sodium hydroxide and sodium carbonate; The acid solution described in step 2) is hydrochloric acid solution, sulfuric acid solution or one or more of nitric acid solutions. 6. method as claimed in claim 5 is characterized in that, the concentration of sodium hydroxide in the alkaline solution described in step 1) is 50-230g/L; The concentration of sodium carbonate is 2-20g/L; Step 2) The mass concentration of the acid solution is 10-30%, preferably 14-25%. 7. The method according to claim 4 or 5, wherein the ratio of the volume of the alkaline solution described in step 1) to the mass of the fly ash is (2.5-6): 1; described in step 2) The volume ratio of the acid solution to the mass ratio of the primary alkali-dissolved fly ash is (4.0-10.0):1. 8. The method according to claim 4 or 5, wherein the control temperature in the alkali dissolution treatment process described in step 1) is 70-100°C; the alkali dissolution treatment time is 2-8h; The temperature of the acid leaching treatment is 70-95°C; the treatment time is 3-8h. 9. The method according to claim 4 or 5, further comprising step 4), measuring the silicon dioxide concentration in the primary alkali eluate prepared by step 1) alkali dissolution treatment, and calculating the primary alkali dissolution The number of moles of silicon dioxide in the liquid; then the primary alkali leaching solution is mixed with a calcium supply agent and a dispersant, stirred and reacted to generate calcium silicate precipitation; then the reaction system is filtered and washed, and the filter residue is a by-product calcium silicate , the filtrate and washings were combined and concentrated. 10. An aluminum-silicon oxide, characterized in that, it is prepared according to any one of claims 1-9.

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