CN111606339A - Method for preparing aluminum-silicon oxide by using fly ash - Google Patents
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Abstract
The invention provides a method for preparing aluminum-silicon oxide by utilizing fly ash. The preparation method for extracting the aluminum-silicon oxide by utilizing the fly ash takes the fly ash as a raw material, reduces the reaction pressure and the equipment investment by two-stage normal pressure leaching, and has simple preparation process, easy operation and low preparation cost.
Description
Technical Field
The invention relates to a preparation method of high-purity aluminum-silicon oxide, belonging to the field of fly ash resource utilization.
Background
Bauxite resources in China are gradually exhausted, the external dependence of bauxite is promoted year by year, and the continuous development of the aluminum industry is seriously influenced. The inner Mongolia Ordos basin is rich in high-alumina coal, the alumina content in the calcined coal ash can reach more than 50 percent, and the full utilization of the aluminum, silicon and other resources in the calcined coal ash is an effective way for utilizing the coal ash with high added value.
In recent years, research and exploration on the resource utilization process of the high-alumina fly ash are actively carried out by universities and scientific research units in China, the resource of the high-alumina and high-silicon is mainly used, and the extraction of alumina is an important direction for the application of the high-alumina fly ash. The Tang group adopts a process of extracting alumina by a fly ash pre-desilication-soda lime sintering method, has been operated industrially for many years, but is difficult to operate due to large slag production and high unit cost; the Monte group adopts a limestone sintering method to comprehensively utilize and explore the fly ash, but the process is also stopped due to the problems of large slag production amount and the like; pilot test of producing alumina from fluidized bed fly ash by Shenhua group by acid process has the problems of high requirement for corrosion resistance of equipment, incapability of comprehensive utilization of silicon products such as white mud and the like.
Therefore, how to utilize the aluminum and the silicon in the fly ash synergistically becomes a problem to be solved urgently in the resource utilization of the fly ash at present. The invention takes pulverized coal furnace fly ash as a main raw material, removes impurities from the fly ash by chemical methods such as iron removal, calcium removal, phosphorus removal and the like to obtain high-purity aluminum-silicon oxide with less impurity amount, mixes the aluminum-silicon oxide with purchased alumina, and then carries out molten salt electrolysis by adopting the conventional common 400kA or 500kA electrolytic cell to directly produce aluminum-silicon alloy.
Disclosure of Invention
The invention aims to provide a method for preparing aluminum-silicon oxide by using fly ash aiming at the technical defects of the prior method for synergistically utilizing two main elements of silicon and aluminum in the fly ash2O3The contents of CaO, P and MgO are low, and the preparation process of the high-purity aluminum-silicon oxide is simple and easy to operate, the production cost is low, the solid waste discharge is obviously reduced, and the high-purity aluminum-silicon oxide has good economic and social benefits.
In order to achieve the purpose of the invention, the invention provides a method for preparing aluminum-silicon oxide by utilizing fly ash, which comprises the steps of sequentially carrying out alkali dissolution treatment, acid leaching treatment and roasting treatment on the fly ash.
Wherein, the aluminum-silicon content in the prepared aluminum-silicon oxide is respectively as follows: al (Al)2O3Greater than or equal to 50%, preferably greater than 55%; SiO 2245% or less, preferably less than 40%.
In particular, the prepared aluminum-silicon oxide contains Fe2O3≤0.5％、CaO≤0.2％、P≤ 0.005％、MgO≤0.1％。
The fly ash obtained by the method is fly ash obtained by burning coal in a fly ash furnace and collecting the coal by a dust remover. The fly ash is different due to different sources of fuel coal used by coal-fired boilers in different regions and different combustion modes of the boilers, but the common point of the fly ash is that the total content of alumina and silica is higher and generally accounts for more than 70 percent of the total content of the fly ash.
The total content of alumina and silicon dioxide in the fly ash is more than 50 percent, and is preferably more than or equal to 70 percent.
The raw material fly ash used in the invention is high-alumina fly ash, and the content of alumina in the high-alumina fly ash is more than 40%.
Wherein the mass ratio of alumina to silica in the high-alumina fly ash is more than 1.0.
Particularly, the content of alumina in the fly ash is 40-60%, preferably 50-60%; the content of silica is 30 to 50%, preferably 30 to 40%.
In particular, the total content of alumina and silica in the fly ash is 70-95%, preferably 85-95%.
The inventor of the invention researches and discovers that the fly ash mainly comprises crystalline phases of mullite and corundum and a part of glass phase, wherein the glass phase contains a large amount of amorphous silica and a small amount of amorphous alumina, and a large amount of ferric oxide and ferric oxide particles are adhered to the amorphous silica. In the normal pressure reaction process, crystalline mullite phase and corundum phase in the high-alumina fly ash do not react with alkali liquor, and amorphous silica and amorphous alumina in the glass phase in the high-alumina fly ash can be leached (dissolved) by the alkali liquor at the same time and react immediately to form sodalite type aluminosilicate; and (3) leaching the fly ash with alkali liquor to remove amorphous silicon dioxide to obtain the desiliconized fly ash.
The inventor of the present invention also finds that under normal pressure conditions, amorphous alumina in the glass phase of the fly ash can be leached (dissolved) by using a dilute acid solution, and amorphous silica does not react with the dilute acid solution, so that the amorphous alumina in the glass phase can be separated from mullite and corundum after acid treatment, so that sodalite phase formed in the desiliconized fly ash reacts with hydrochloric acid to destroy sodalite structure, and the mullite crystal phase and the corundum phase are not changed under the acid solution condition, and finally impurities (such as iron oxide, calcium oxide, magnesium oxide, sodium oxide and phosphorus pentoxide) in the glass phase can enter the liquid phase.
Wherein the alkali dissolution treatment is to mix the fly ash and an alkali solution, stir, react and filter to prepare the primary alkali-dissolved fly ash and the primary alkali-dissolved liquid.
In the alkali dissolution treatment process, the amorphous alumina and the amorphous silica of the glass phase in the fly ash are leached out and react to form sodalite-type aluminosilicate, so that the glass phase and the crystalline phase in the fly ash are better stripped, and the aim of removing impurities is fulfilled.
The alkali solution reacts with amorphous alumina and amorphous silicon dioxide in the fly ash and is dissolved in the alkali solution to form primary alkali solution; filtering the substances insoluble in the alkali liquor in the fly ash to obtain the fly ash dissolved out by the alkali.
In particular, the alkali solution is a mixed solution of sodium hydroxide and sodium carbonate.
Particularly, the concentration of the sodium hydroxide in the alkali solution is 50-230g/L, preferably 80-150 g/L; the concentration of sodium carbonate is 2-20g/L, preferably 5-18 g/L.
In particular, the ratio of the volume of the alkali solution to the mass of the fly ash is (2.5-6): 1, preferably (3.5-5): 1, namely mixing every 1g of fly ash with 2.5-6ml of alkali solution or every 100g of fly ash with 250-600ml of alkali solution or every 1kg of fly ash with 2.5-6L of alkali solution to carry out alkali dissolution treatment.
The acid leaching treatment is to mix the fly ash subjected to alkali leaching treatment with an acid solution, stir, react and filter to obtain secondary acid leached fly ash and secondary acid leachate.
The purpose of acid leaching is to separate the acid-soluble substances of iron, calcium and phosphorus in the fly ash from the fly ash, and the rest substances are mainly aluminum-silicon oxides which are insoluble in acid. The function is to remove substances dissolved in acid in the fly ash.
In the acid leaching process, sodalite-type aluminosilicate generated in the fly ash and the alkali leaching process is leached out by primary alkali, and impurities such as alumina, ferric oxide, calcium oxide, magnesium oxide and the like are leached out, so that the purity of the alumina-silica alumina in the residual solid phase is high.
The secondary acid leaching solution mainly contains aluminum chloride, calcium chloride, ferric chloride and sodium chloride; the secondary acid leached fly ash mainly contains mullite and corundum.
The acid solution is one or more of a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution, and preferably, the hydrochloric acid solution and the sulfuric acid solution.
In particular, the acid solution has a mass concentration of 10 to 30%, preferably 14 to 25%.
Particularly, the acid solution is a hydrochloric acid solution with the mass concentration of 14-25%, and preferably 14-18%; the acid solution is a sulfuric acid solution with the mass concentration of 14-25%, and is preferably 25%.
In the invention, common acid liquor, such as sulfuric acid, hydrochloric acid or nitric acid, is selected in the acid leaching treatment process, the invention does not limit the number of the types of the acid treatment agent, and the acid treatment agent can be an aqueous solution of any one of the acid liquor, or an aqueous solution of two mixed acid liquors in the acid liquor, 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 a mixture of two acid liquors, the invention does not limit the proportion of each acid liquor.
Particularly, the mass ratio of the volume of the acid solution to the primary alkali-leaching fly ash is (4.0-10.0): 1, preferably (5-8): 1, mixing the alkali-leached fly ash with 4-10ml of acid solution every 1g or mixing the alkali-leached fly ash with 400-1000ml of acid solution every 100g or mixing the fly ash with 4-10 of acid solution every 1kg, and carrying out the acid leaching treatment.
The invention also provides a method for preparing aluminum-silicon oxide by using fly ash, which comprises the following steps:
1) adding the fly ash into an alkali solution, uniformly mixing the fly ash with the alkali solution, and carrying out alkali dissolution treatment; then filtering and washing are carried out, and the obtained filter residue is the primary alkali-dissolved fly ash; mixing the filtrate with the washing solution to obtain primary alkali solution;
2) adding the fly ash dissolved out by the primary alkali into an acid solution, uniformly mixing the fly ash with the acid solution, and carrying out acid leaching treatment; then filtering and washing are carried out; the obtained filter residue is secondary acid leached fly ash; mixing the filtrate and the washing liquid to obtain secondary acid leaching liquid;
3) and roasting the secondary acid leaching fly ash to prepare the aluminum-silicon oxide.
Wherein, in the step 1), the fly ash is high-alumina fly ash, wherein the content of alumina in the high-alumina fly ash is more than 40%.
Particularly, the mass ratio of alumina to silica in the high-alumina fly ash is more than 1.0.
Particularly, the content of alumina in the fly ash is 40-60%, preferably 50-60%; the content of silica is 30 to 50%, preferably 30 to 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.
Particularly, the concentration of sodium hydroxide in the alkali solution is 50-230g/L, preferably 80-150 g/L; the concentration of sodium carbonate is 2-20g/L, preferably 5-18 g/L.
Wherein the ratio of the volume of the alkali solution to the mass of the fly ash is (2.5-6): 1, preferably (3.5-5): 1, namely mixing every 1g of fly ash with 2.5-6ml of alkali solution or every 100g of fly ash with 250-600ml of alkali solution or every 1kg of fly ash with 2.5-6L of alkali solution to carry out alkali dissolution treatment.
Particularly, the temperature is controlled to be 70-100 ℃ in the alkali dissolution treatment process, and preferably 80-90 ℃; the alkali dissolution treatment time is 2-8h, preferably 3-7 h.
Wherein, the filtration and washing in the step 1) are vacuum filtration and washing under vacuum condition.
In particular, the relative pressure under vacuum is less than 0MPa, 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, the residue after the alkali-leaching treatment and filtration is washed with tap water or distilled water.
Washing until the concentration of sodium hydroxide in the effluent (i.e. washing liquid) is less than 3 g/L. The number of washing is 3 to 5, preferably 4.
Particularly, the mass ratio of the washing water to the filtered filter 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 in the step 2) is one or more of a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution, and preferably the hydrochloric acid solution and the sulfuric acid solution.
In particular, the acid solution has a mass concentration of 10 to 30%, preferably 14 to 25%.
Particularly, the acid solution is a hydrochloric acid solution with the mass concentration of 14-25%, and preferably 14-18%; the acid solution is a sulfuric acid solution with the mass concentration of 14-25%, and is preferably 25%.
In the invention, common acid liquor, such as sulfuric acid, hydrochloric acid or nitric acid, is selected in the acid leaching treatment process, the invention does not limit the number of the types of the acid treatment agent, and the acid treatment agent can be an aqueous solution of any one of the acid liquor, or an aqueous solution of two mixed acid liquors in the acid liquor, 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 a mixture of two acid liquors, the invention does not limit the proportion of each acid liquor.
Wherein the temperature of the acid leaching treatment is 70-95 ℃, and preferably 75-90 ℃; the treatment time is 3-8h, preferably 3-6 h.
Particularly, the mass ratio of the volume of the acid solution to the primary alkali-leaching fly ash is (4.0-10.0): 1, preferably (5-8): 1, mixing the alkali-leached fly ash with 4-10ml of acid solution every 1g or mixing the alkali-leached fly ash with 400-1000ml of acid solution every 100g or mixing the fly ash with 4-10 of acid solution every 1kg, and carrying out the acid leaching treatment.
Wherein, the filtration and washing in the step 2) are vacuum filtration and washing under vacuum condition.
In particular, the relative pressure under vacuum is from-0.02 to-0.1 MPa, preferably from-0.02 to-0.08 MPa, and more preferably from-0.05 to-0.08 MPa.
Particularly, the residue after the acid leaching treatment and filtration is washed with tap water or distilled water.
Washing until the pH of the effluent (i.e., the wash) is greater than 3. The mass ratio of the washing water to the filtered filter 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.).
Particularly, the method also comprises the step 2A) of drying the washed filter residue to prepare the secondary acid leached fly ash.
Wherein the drying temperature is 100-110 ℃, preferably 105 ℃; the water content of the dried secondary acid leached fly ash is lower than 70%, preferably 55-65%, and more preferably 58-62%.
Wherein, the roasting treatment temperature in the step 3) is 600-1000 ℃, and preferably 800-1000 ℃; the roasting time is 0.5-2.0 h, preferably 1-2 h.
In particular, Al in the aluminum-silicon oxide prepared in step 3)2O3Greater than or equal to 50%, preferably greater than 52%; SiO 2245% or less, preferably less than 30%.
In particular, Fe in the prepared aluminum-silicon oxide2O3≤0.5％、CaO≤0.2％、P≤0.005％、 MgO≤0.1％。
The roasting treatment is to dehydrate the aluminum-silicon oxide after impurity removal and remove the unburned carbon. After roasting treatment, attached water and structural water in the secondary acid leached fly ash are discharged, and unburned carbon of the secondary acid leached fly ash is removed, so that a sample is white powder.
Particularly, the method also comprises a step 4) of measuring the concentration of silicon dioxide in the primary alkali solution prepared by the alkali dissolution treatment in the step 1) and calculating the mole number of the silicon dioxide in the primary alkali solution; then mixing the primary alkali solution with a calcium supply agent and a dispersing agent, stirring and reacting to generate calcium silicate precipitate; then the reaction system is filtered and washed, the filter residue is a byproduct calcium silicate, and the filtrate and the washing liquid are combined and concentrated.
Wherein, in the step 4), the calcium supplying agent is selected from lime milk or carbide slag; the dispersing agent is one or more of sodium dodecyl benzene sulfonate, azodicarbonamide, diethyl phthalate, dioctyl phthalate and sodium lignosulfonate, and is preferably sodium dodecyl benzene sulfonate, sodium lignosulfonate or diethyl phthalate.
In particular, the mole ratio of silicon dioxide in the primary alkali solution to calcium oxide in the calcium supplying agent is 1: (1.05-1.2), preferably 1: (1.05-1.14); the dosage of the dispersant is (0.02-0.6)%, preferably (0.06-0.3)%, of the mass of calcium silicate generated by all silicon in the primary alkali solution.
Wherein the stirring and reaction temperature in the step 4) is 70-100 ℃, and preferably 85-95 ℃; the reaction time is 0.5-2h, preferably 1-2 h.
Particularly, in the step 4), water (tap water or distilled water) with the temperature of 90-100 ℃ is adopted to wash the filtered by-product calcium silicate filter residue until the free alkali is less than 3g/L, the mass ratio of the washing water to the filter residue is controlled to be (2.5-8.0): 1, and the filter residue is the nano-pore calcium silicate.
Particularly, the washed filter residue is dried at the temperature of 100 ℃ and 100 ℃, and the water content is dried to be lower than 5 percent (usually 1.5 to 3.0 percent), so as to obtain the byproduct nano calcium silicate.
And 4) combining the filtered liquid and the washed washing liquid in the step 4), concentrating, and recycling or recycling the concentrated liquid, namely the alkali recycling treatment.
The calcium silicate as a byproduct is nanoporous calcium silicate, the present invention does not limit the kind and amount of the dispersant, and may be any one or more of the above dispersants, for example, the dispersant may be any one of sodium dodecylbenzene sulfonate and diethyl phthalate, or a mixture of sodium dodecylbenzene sulfonate 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, further comprising step 5): supplementing acid into the secondary acid leaching solution prepared in the step 2) until the mass concentration of the acid solution is 10-30%, and returning to the step 2) for recycling.
And (3) adding concentrated hydrochloric acid, concentrated sulfuric acid or concentrated nitric acid into the secondary acid leaching solution, so that the mass concentration of the hydrochloric acid, the sulfuric acid and the nitric acid in the solution reaches 10-30%.
In particular, further comprising step 6): carrying out resin adsorption treatment on the secondary acid leaching solution prepared by the acid leaching treatment in the step 2) to remove impurities such as calcium chloride, ferric chloride or calcium sulfate, ferric sulfate or calcium nitrate, ferric nitrate and the like in the secondary acid leaching solution; then evaporating and crystallizing to obtain the by-product aluminum chloride or aluminum sulfate or aluminum nitrate.
Wherein the resin adopted for the resin adsorption treatment is gel type strongly basic anion exchange resin, gel type weakly basic anion exchange resin, macroporous type strongly basic anion exchange resin or macroporous type weakly basic anion exchange resin.
In a further aspect the present invention provides an aluminium silicon oxide prepared according to the above method.
The aluminum-silicon oxide prepared by the method is used for producing aluminum-silicon alloy products in a molten salt electrolysis method.
The aluminum-silicon oxide prepared by the invention is applied to the electrolysis of aluminum-silicon alloy in a cryolite-fluoride salt molten salt electrolysis system.
The aluminum-silicon oxide of the present invention can be used as a raw material for producing an electrolytic aluminum-silicon alloy by a molten salt electrolysis method, or as a raw material for producing an aluminum-silicon alloy by a submerged arc method.
The preparation method of the aluminum-silicon oxide takes pulverized coal furnace fly ash as a raw material, the fly ash is subjected to normal-pressure alkali treatment, and finally, the conventional acid leaching is adopted, so that Fe is obtained2O3Aluminum silicon oxide with the content of less than or equal to 0.5 percent, CaO less than or equal to 0.2 percent, P less than or equal to 0.005 percent and MgO less than or equal to 0.1 percent greatly reduces the impurity content in the fly ash, thereby laying a foundation for the high added value utilization of the fly ash.
Compared with the prior art, the implementation of the invention has the following advantages:
1) the process method for extracting the aluminum-silicon oxide by utilizing the fly ash does not need special treatment, does not need preliminary treatment such as physical iron removal, calcium removal and the like, and can be implemented by two-step treatment, so that the process is simple;
2) the reaction temperature adopted by the method is below 100 ℃, and the purposes of iron removal, calcium removal and purification can be achieved by a wet process under the normal pressure condition, the aluminum-silicon oxide prepared by the method has high alumina and silicon oxide contents, and the alumina content reaches more than 50%; the content of silicon dioxide is less than 45 percent; and Fe2O3、CaO、P、MgOIs low, Fe in the product2O3≤0.5％、CaO≤0.2％、 P2O5Less than or equal to 0.005 percent and less than or equal to 0.1 percent of MgO, the reaction process is carried out under the normal pressure condition, and the requirement on equipment is lower;
3) the reduction treatment of the fly ash is realized, the amount of solid waste is obviously reduced, and the total amount of byproducts is greatly reduced compared with other processes (1 ton of raw ash generates about 0.3-0.35 ton of byproducts, and the byproducts have market sales prospects);
4) the equipment used by the process method is conventional equipment, and extra non-standard equipment does not need to be researched and manufactured, so that the equipment investment cost is reduced;
5) the adopted dilute acid solution treatment has small corrosion degree on equipment under the normal pressure condition, simple and convenient operation, small water consumption for washing and small acid loss in the separation process.
Drawings
FIG. 1 is a process flow diagram of the method for extracting silicon-aluminum oxide by using fly ash according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.
The method for extracting the silicon-aluminum oxide by utilizing the fly ash is used for extracting and preparing according to the process flow shown in figure 1.
Example 1
1) Alkali dissolution treatment
Adding the fly ash into an alkali solution, stirring and uniformly mixing, dissolving amorphous silicon dioxide, aluminum oxide and the like in a glass phase in the fly ash into the alkali solution, and performing alkali dissolution treatment; wherein the temperature during the alkali dissolution treatment is controlled to be 80 ℃ (usually 70-100 ℃); the ratio of the mass of the fly ash to the volume of the alkali solution is 1:5 (usually 1: 2.5-6), namely 5ml of alkali solution is used for every 1g of fly ash, or 500ml of alkali solution is used for every 100g of fly ash, or 5L of alkali solution is used for every 1kg of fly ash for alkali dissolution treatment; the alkali solution is a mixed solution of sodium hydroxide and sodium carbonate and water, the concentration of the sodium hydroxide in the alkali solution is 100g/L (usually 50-230g/L), and the concentration of the sodium carbonate in the alkali solution is 5g/L (usually 2-20 g/L);
in this example, the mass of fly ash used in the alkali elution treatment process was 100g, and the alkali solution was 500 ml. In the embodiment of the invention, the ratio of the mass of the fly ash to the volume of the alkali solution is 1:5, and the other ratio is 1: 2.5-6 are also suitable for use in the present invention.
The fly ash comprises the following chemical components: the mass content of the alumina is 45.25%; the mass content of the silicon oxide is 44.25%, and the mass ratio of the aluminum oxide to the silicon oxide is 1.02; the mass content of the iron oxide is 3.16 percent, and the mass content of the calcium oxide is 2.57 percent; the mass content of the magnesium oxide is 0.86 percent, and the mass content of the phosphorus pentoxide is 0.2 percent;
except the fly ash with the composition, the mass content of alumina in other fly ash is 40-60%; the mass content of the silicon oxide is 30-50%, and the fly ash with the mass ratio of the aluminum oxide to the silicon dioxide being more than 1.0 is suitable for the invention.
In the alkali dissolving treatment process, amorphous alumina and amorphous silica in the glass phase of the fly ash react with alkali liquor, and the amorphous alumina and the amorphous silica are dissolved in the alkali liquor and undergo chemical reaction to form sodalite type aluminosilicate, so that the glass phase can be better stripped from a crystal phase to achieve the purpose of impurity removal.
The purpose of alkali dissolution is to destroy the amorphous glass phase structure in the fly ash and dissolve amorphous silicon dioxide and aluminum oxide.
In the high-temperature combustion process of the coal dust, the non-crystalline silicon dioxide is fused and adhered with other components at high temperature to form fly ash particles of hollow microspheres, and in the alkali dissolution process, the amorphous silicon dioxide and aluminum oxide are decomposed and dissolved in alkali liquor, so that the particle structure of the fly ash is damaged; moreover, because a large amount of iron oxide and ferric oxide particles are adhered in the amorphous silicon dioxide, after the amorphous silicon dioxide is dissolved by alkali, the iron oxide and the ferric oxide particles are exposed, so that the efficiency of acid leaching and iron removal can be improved during the subsequent acid leaching and iron removal; and the amorphous alumina and the amorphous silicon dioxide are dissolved in alkali liquor and then undergo chemical reaction to form sodalite type aluminosilicate, and the specific reaction is as follows:
2NaOH+SiO2(amorphous state) ═ Na2SiO3+H2O
2NaOH+Al2O3(amorphous state) ═ 2NaAlO2+H2O
The main side reaction of extracting amorphous silicon dioxide from fly ash is as follows:
2NaAlO2+2Na2SiO3+4H2O＝Na2O·Al2O3·2SiO2·2H2O↓+4NaOH
after stirring for 3h (usually 2-8h), filtering under vacuum, and washing the filter cake with tap water at 90 deg.C (usually 90 + -5 deg.C), wherein the vacuum is controlled to be-0.06 MPa (usually-0.02 to-0.08 MPa) relative pressure, and washing for 4 times (usually 3-5 times) until the concentration of sodium hydroxide in the effluent (washing liquid) is lower than 3 g/L; washing is carried out under the vacuum condition, a washed filter cake is the obtained primary alkali-dissolving fly ash (86.67g), and the filtrate obtained by vacuum filtration and the washing liquid are combined into primary alkali-dissolving liquid (438 ml);
the content of silicon dioxide in the primary alkali solution is determined by a visible spectrophotometer molybdenum blue photometry (YS/T575 & lt- & gt 2007, bauxite chemical analysis method), and the determination result is as follows: the concentration of silicon dioxide is 29.904 g/L;
the content of alumina in the primary alkali solution is measured by adopting a lead salt back drop-ammonium fluoride replacement method (YS/T575) -2007, a bauxite chemical analysis method), and the alumina concentration is 1.02 g/L.
2) Acid leaching treatment
Adding the primary alkali-leached fly ash into an acid solution, stirring, uniformly mixing, dissolving substances (such as sodalite-type aluminosilicate generated in the alkali leaching treatment step and impurity phase iron oxide, calcium oxide, magnesium oxide and the like contained in the fly ash) dissolved in the acid solution in the fly ash, and performing acid leaching treatment; wherein the acid solution is a hydrochloric acid solution with a mass concentration of 14.0% (usually 10-30%); the ratio of the mass of the fly ash dissolved out by the alkali to the volume of the acid solution is 1:6 (usually 1: 4-10); namely, 6ml of acid solution is used for alkali-dissolved coal ash every 1g or 600ml of acid solution is used for alkali-dissolved coal ash every 100 g; the temperature of the acid leaching treatment is 90 ℃ (typically 70-95 ℃); the acid leaching treatment time is 4.5h (usually 3-8 h);
after 4.5h (usually 3-8h) of acid leaching treatment, filtering treatment is carried out under vacuum condition, and the filter cake is washed by tap water with the temperature of 90 ℃ (usually 90 +/-5 ℃), wherein the vacuum condition is controlled to be that the relative pressure is-0.06 MPa (usually-0.02 to-0.08 MPa); washing until the pH of an effluent liquid (washing liquid) is more than 3, wherein the ratio of the volume of tap water for washing to the mass of the fly ash is 2:1 (usually 1-4: 1); drying the washed filter cake at 105 ℃ (usually at 100 ℃ and 110 ℃) to obtain secondary acid leaching fly ash (65.6g) with water content of 60.15% (usually lower than 65%, preferably 58-62%); and combining the filtrate subjected to vacuum filtration and the washing liquid to prepare secondary acid leaching-filtrate, and performing secondary acid leaching-filtrate concentration and acid supplementation on the secondary acid leaching-filtrate to obtain an acid treatment agent solution for recycling or recycling the acid treatment agent solution until the concentration of aluminum chloride in the liquid phase reaches 50g/L, namely preparing the polyaluminum chloride by performing evaporation crystallization after removing residues by using resin.
In the acid leaching process, an acid solution is mixed with the primary alkali-leached fly ash to react, and impurities such as alumina, ferric oxide, calcium oxide, magnesium oxide and the like in the sodalite-type aluminosilicate contained in the primary alkali-leached fly ash are leached, so that the purity of the alumina-silica alumina in the residual solid phase is high.
Al2O3+6HCl＝2AlCl3+3H2O
Fe2O3+6HCl＝2FeCl3+3H2O
CaO+2HCl＝CaCl2+H2O
The acid leaching is to separate acid-soluble substances such as iron, magnesium, phosphorus, calcium, amorphous aluminum and the like in the fly ash from the fly ash, and the rest substances are mainly aluminum-silicon oxides which are insoluble in acid. The function is to remove substances dissolved in acid in the fly ash.
3) Roasting
Placing the secondary acid leaching fly ash in a roasting furnace, heating and raising the temperature, keeping the temperature at 800 ℃ (usually 600-1000 ℃) for roasting treatment, cooling and reducing the temperature after roasting treatment for 1h (usually 0.5-2h) to obtain the aluminum-silicon oxide.
The prepared aluminum-silicon oxide is measured by using YS/T630-2007 aluminum oxide impurity content measurement inductively coupled plasma atomic emission spectrometry, and the detection results are shown in Table 1.
Table 1 results of chemical composition test of aluminum silicon oxide prepared by the present invention
| Content (%) | Example 1 | Example 2 | Example 3 |
| Alumina oxide | 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) By-product preparation
Mixing the primary alkali solution with lime milk and dispersant, stirring, reacting for 1h (usually 0.5-2h) to generate calcium silicate precipitate and sodium hydroxide, wherein the stirring reaction temperature is 92 deg.C (usually 70-100 deg.C); controlling the mole ratio of silicon to calcium in the lime milk in the primary alkali solution to be 1:1.07 (usually 1: 1.05-1.2); the dispersant is sodium dodecyl benzene sulfonate, and the dosage of the dispersant is 0.08 percent (usually 0.02 to 0.6 percent) of the mass of calcium silicate generated by all silicon in the primary alkali solution;
the dispersing agent has the main effects that lime milk particles are uniformly dispersed into a sodium silicate solution, the contact area between the lime milk particles and calcium silicate is increased, the surface charge is increased by forming an adsorption layer on the surfaces of the lime milk particles, the degree of infiltration of the lime milk particles is increased, and finally, the lime milk is more uniformly distributed and more uniformly reacted with the sodium silicate, and the nano-pore calcium silicate is easily prepared.
Filtering the reaction system, washing the filter cake by using tap water with the temperature of 95 ℃ (usually 90-100 ℃), washing until the free alkali in the effluent is less than 3g/L, and drying the washed filter cake at 105 ℃ (usually 100-; the washing liquid is evaporated and concentrated and then recycled, namely alkali is recycled, for example, the washing liquid is concentrated to a specified concentration and then returns to the alkali dissolution treatment step for recycling.
In the embodiment, the concentration of the silicon dioxide in the primary alkali solution is 29.904g/L, and the mole number of the silicon dioxide in the primary alkali solution is 0.2183 mol. Completely precipitating silicon in the primary alkali solution, wherein the mass of the generated calcium silicate is 26.178 g; completely precipitating silicon in the primary alkali dissolution liquid, controlling the molar ratio of the silicon in the primary alkali dissolution liquid to calcium in the lime milk to be 1:1.07, and selecting the lime milk with the effective calcium concentration of 120g/L, wherein the dosage of the lime milk is 109 ml. The dosage of the dispersant sodium dodecyl benzene sulfonate is 26.178 multiplied by 0.08 percent to 0.02094 g.
Example 2
1) Alkali dissolution treatment
Except that the chemical components of the fly ash raw material are as follows: the mass content of the alumina is 45.25%; the mass content of silicon oxide is 44.25%, the mass content of ferric oxide is 3.16%, and the mass content of calcium oxide is 2.57%; the mass content of the magnesium oxide is 0.86 percent, and the mass content of the phosphorus pentoxide is 0.01 percent;
the mass ratio of the fly ash to the alkali solution is 1: 4.5; the concentration of sodium hydroxide in the alkali solution is 150g/L (usually 50-230g/L), and the concentration of sodium carbonate is 10g/L (usually 2-20 g/L); the alkali dissolution treatment temperature is 90 ℃; the alkali dissolution treatment time is 6.0 h; fly ash (85.4g) was first alkali-dissolved; primary alkali eluate (389 ml); the same alkali elution treatment as in step 1) of example 1 was carried out except that the concentration of silica in the primary alkali elution solution was 32.73 g/L;
2) acid leaching treatment
Except that the acid solution is 18.0% (usually 10-30%) by mass hydrochloric acid; the ratio of the mass of the fly ash dissolved out by the alkali to the volume of the acid solution is 1:5 (usually 1: 4-10); the temperature of the acid leaching treatment is 80 ℃ (typically 70-95 ℃); the acid leaching treatment time is 3h (usually 3-8 h); secondary acid leaching of 65.1g of fly ash; the acid leaching treatment in the step 2) of the example 1 is the same except that the water content is 63.12%;
and (3) performing secondary acid leaching, concentrating the filtrate to supplement acid, and then recycling the filtrate as an acid treatment agent solution or recycling the filtrate until the concentration of aluminum chloride in a liquid phase reaches 55g/L, and then removing residues by using resin and performing evaporative crystallization to prepare polyaluminum chloride.
3) Roasting
Except that the firing temperature is 1000 deg.C (typically 600 ℃ - & 1000 ℃); the calcination time is the same as that in the step 3) of the example 1 except that the calcination time is 2 hours (usually 0.5 to 2 hours);
4) by-product preparation
Mixing the primary alkali solution with lime milk and dispersant, stirring, reacting for 2h (usually 0.5-2h) to generate calcium silicate precipitate and sodium hydroxide, wherein the stirring reaction temperature is 85 deg.C (usually 70-100 deg.C); controlling the mole ratio of silicon to calcium in the lime milk in the primary alkali solution to be 1:1.05 (usually 1: 1.05-1.2); the dispersant is diethyl phthalate, and the dosage of the dispersant is 0.156 percent (usually 0.02 to 0.6 percent) of the mass of calcium silicate generated by all the silicon in the primary alkali solution;
filtering the reaction system, washing the filter cake by using tap water at the temperature of 95 ℃ (usually 90-100 ℃), washing until the concentration of free alkali in effluent is less than 3g/L, and drying the washed filter cake at the temperature of 105 ℃ (usually 100-; the washing liquid is evaporated and concentrated and then recycled, namely alkali is recycled, for example, the washing liquid is concentrated to a specified concentration and then returns to the alkali dissolution treatment step for recycling.
In this example, 389ml of primary alkali dissolution liquid, the concentration of silicon dioxide was 32.73g/L, and the mole number of silicon in the primary alkali dissolution liquid was 0.2122 mol. Completely precipitating silicon in the primary alkali solution, wherein the mass of the generated calcium silicate is 25.209 g; completely precipitating silicon in the primary alkali dissolution liquid, controlling the molar ratio of the silicon in the primary alkali dissolution liquid to calcium in the lime milk to be 1:1.05, and selecting the lime milk with the effective calcium concentration of 120g/L, wherein the dosage of the lime milk is 104 ml. The amount of diethyl phthalate used as a dispersant was 25.209 × 0.156% ═ 0.0393 g.
Example 3
1) Alkali dissolution treatment
Except that the chemical components of the fly ash raw material are as follows: the mass content of the alumina is 43.87%; the mass content of silicon oxide is 48.78%, the mass content of ferric oxide is 3.49%, and the mass content of calcium oxide is 3.22%; the mass content of the magnesium oxide is 1.07 percent, and the mass content of the phosphorus pentoxide is 0.24 percent;
the mass ratio of the fly ash to the alkali solution is 1: 3.5; the concentration of sodium hydroxide in the alkali solution is 80g/L (usually 50-230g/L), and the concentration of sodium carbonate is 18g/L (usually 2-20 g/L); the alkali dissolution treatment temperature is 95 ℃; the alkali dissolution treatment time is 7.0 h; fly ash (88.7g) was first alkali-leached; one alkali solution (282 ml); the same alkali dissolution treatment as in step 1) of example 1 was carried out except that the concentration of silica in the primary alkali dissolution solution was 44.36 g/L;
2) acid leaching treatment
Except that the acid solution is a sulfuric acid solution having a mass concentration of 25.0% (usually 10 to 30%); the ratio of the mass of the fly ash dissolved out by the alkali to the volume of the acid solution is 1:8 (usually 1: 4-10); the temperature of the acid leaching treatment is 75 ℃ (typically 70-95 ℃); the acid leaching treatment time is 6h (usually 3-8 h); 67.1g of fly ash is leached by secondary acid; the water content is 64.5%, and the rest is the same as the acid leaching treatment in the step 2) of the embodiment 1;
after secondary acid leaching and filtrate concentration and acid supplementation, the secondary acid leaching-filtrate can be used as an acid treating agent solution for recycling, or can be recycled until the concentration of aluminum sulfate in a liquid phase reaches 50g/L, and then aluminum sulfate can be prepared by resin deslagging and evaporation crystallization.
3) Roasting
Except that the roasting temperature is 900 ℃; the roasting time is 1.5h, and the rest is the same as the roasting time in the step 3) of the embodiment 1;
4) by-product preparation
Mixing the primary alkali solution with carbide slag and dispersant, stirring, reacting for 2h (usually 0.5-2h) to generate calcium silicate precipitate and sodium hydroxide, wherein the stirring reaction temperature is 95 deg.C (usually 70-100 deg.C); controlling the mole ratio of silicon in the primary alkali solution to calcium in the carbide slag to be 1:1.14 (usually 1: 1.05-1.2); the dispersant is sodium dodecyl benzene sulfonate and sodium lignosulfonate, and the dosage of the dispersant is 0.3 percent (usually 0.02 to 0.6 percent) of the mass of calcium silicate generated by all silicon in the primary alkali dissolution liquid;
filtering the reaction system, washing the filter cake by using tap water at the temperature of 95 ℃ (usually 90-100 ℃), washing until the concentration of free alkali in effluent is less than 3g/L, and drying the washed filter cake at the temperature of 105 ℃ (usually 100-; the washing liquid is evaporated and concentrated and then recycled, namely alkali is recycled, for example, the washing liquid is concentrated to a specified concentration and then returns to the alkali dissolution treatment step for recycling.
In this example, 282ml of the first alkali dissolution liquid had a silica concentration of 44.36g/L, and the mole number of silicon in the first alkali dissolution liquid was 0.20849 mol. Completely precipitating silicon in the primary alkali solution, wherein the mass of the generated calcium silicate is 28.2799 g; completely precipitating silicon in the primary alkali dissolution liquid, controlling the molar ratio of the silicon in the primary alkali dissolution liquid to the calcium in the carbide slag to be 1:1.14, and selecting 22.0g of the carbide slag with the effective calcium concentration of 60.5%. The dosage of dispersing agent sodium dodecyl benzene sulfonate and sodium lignosulfonate is 28.2799 × 0.3% ═ 0.0848 g. Among them, 0.0231g (0.082%) of sodium dodecyl benzene sulfonate and 0.0617g (0.218%) of sodium lignosulfonate.
The dispersant in embodiment 3 of the invention can also be 0.0848g of sodium dodecyl benzene sulfonate; or 0.0848g of sodium lignosulfonate; or the sodium dodecyl benzene sulfonate and the sodium lignin sulfonate in any proportion can be mixed, as long as the total mass of the sodium dodecyl benzene sulfonate and the sodium lignin sulfonate is 0.0848 g.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The method for preparing the aluminum-silicon oxide by using the fly ash is characterized by comprising the steps of sequentially carrying out alkali dissolution treatment, acid leaching treatment and roasting treatment on the fly ash.
2. The method according to claim 1, wherein the alkali-leaching treatment is to mix fly ash with an alkali solution, stir the mixture for reaction, and then filter the mixture to obtain primary alkali-leached fly ash and primary alkali-leached liquid.
3. The method according to claim 1, wherein the acid leaching is performed by mixing the fly ash subjected to the alkali leaching with an acid solution, stirring, reacting, and then filtering to obtain a secondary acid leached fly ash and a secondary acid leachate.
4. A method for preparing aluminum-silicon oxide by using fly ash is characterized by comprising the following steps:
1) adding the fly ash into an alkali solution, uniformly mixing the fly ash with the alkali solution, and carrying out alkali dissolution treatment; then filtering and washing are carried out, and the obtained filter residue is the primary alkali-dissolved fly ash; mixing the filtrate with the washing solution to obtain primary alkali solution;
2) adding the fly ash dissolved out by the primary alkali into an acid solution, uniformly mixing the fly ash with the acid solution, and carrying out acid leaching treatment; then filtering and washing are carried out; the obtained filter residue is secondary acid leached fly ash; mixing the filtrate and the washing liquid to obtain secondary acid leaching liquid;
3) and roasting the secondary acid leaching fly ash to prepare the aluminum-silicon oxide.
5. The method according to claim 4, wherein the alkali solution in step 1) is a mixed solution of sodium hydroxide and sodium carbonate; the acid solution in the step 2) is one or more of a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution.
6. The method of claim 5, wherein the concentration of sodium hydroxide in the alkaline solution in step 1) is 50 to 230 g/L; the concentration of sodium carbonate is 2-20 g/L; the mass concentration of the acid solution in the step 2) is 10-30%, preferably 14-25%.
7. The method of claim 4 or 5, wherein the ratio of the volume of alkali solution to the mass of fly ash in step 1) is (2.5-6): 1; the mass ratio of the volume of the acid solution to the primary alkali-dissolved fly ash in the step 2) is (4.0-10.0): 1.
8. The method according to claim 4 or 5, wherein the temperature during the alkali-leaching treatment in step 1) is controlled to be 70 to 100 ℃; the alkali dissolution treatment time is 2-8 h; the temperature of the acid leaching treatment in the step 2) is 70-95 ℃; the treatment time is 3-8 h.
9. The method according to claim 4 or 5, further comprising a step 4) of measuring the silica concentration in the primary alkali-eluted liquid prepared by the alkali-elution treatment of step 1) and calculating the mole number of silica in the primary alkali-eluted liquid; then mixing the primary alkali solution with a calcium supply agent and a dispersing agent, stirring and reacting to generate calcium silicate precipitate; then the reaction system is filtered and washed, the filter residue is a byproduct calcium silicate, and the filtrate and the washing liquid are combined and concentrated.
10. An aluminium silicon oxide, characterised in that it is prepared according to the method of any one of claims 1 to 9.
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| CN114853043A (en) * | 2022-04-29 | 2022-08-05 | 重庆工商大学 | Method for increasing Al content in polyaluminium chloride b Method of content |
| CN114853043B (en) * | 2022-04-29 | 2023-08-29 | 重庆工商大学 | Improve Al in polyaluminum chloride b Content method |
| CN116216731A (en) * | 2023-05-04 | 2023-06-06 | 内蒙古蒙泰集团有限公司 | Method for preparing aluminum silicon oxide by using fly ash and obtained aluminum silicon oxide |
| CN116216731B (en) * | 2023-05-04 | 2023-08-08 | 内蒙古蒙泰集团有限公司 | Method for preparing aluminum silicon oxide by using fly ash and obtained aluminum silicon oxide |
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