Method for producing 4A zeolite by using coal gangue with low aluminum-silicon ratio

Abstract

The invention relates to the technical field of 4A zeolite production, and discloses a method for producing 4A zeolite by using coal gangue with a low aluminum-silicon ratio, which comprises the following steps: carrying out pretreatment, sodium carbonate alkali fusion, water quenching, wet grinding, solid-liquid separation, caustic soda alkali fusion, dry powder dissolution, mold adjustment, slurrying, crystallization and drying on the coal gangue to obtain the 4A zeolite; the coal gangue is coal gangue with an aluminum-silicon ratio of less than 0.26. The coal gangue is used as a raw material, aluminum oxide and silicon dioxide in the coal gangue can be fully extracted through the method, the yield of the 4A zeolite is increased, and the obtained 4A zeolite has the advantages of being high in crystallinity and whiteness, low in impurity content, large in cation exchange capacity and the like.

Description

Technical Field

[0001] The invention relates to the technical field of 4A zeolite production, and in particular to a method for producing 4A zeolite by utilizing coal gangue with a low aluminum-silicon ratio. Background Art

[0002] Gangue is a solid waste discharged during the mining and washing process of coal. For every ton of coal mined, 150 kg to 250 kg of gangue will be produced. The accumulation of a large amount of gangue not only occupies land and causes surface water and groundwater pollution, but also because gangue contains some combustible carbon, sulfur and other components, the long-term accumulation of gangue mountains will naturally release a large amount of toxic and harmful gases and smoke such as sulfur dioxide, carbon monoxide, carbon dioxide, nitrogen oxides, etc., causing serious air pollution. In addition, due to the loose structure and poor stability of gangue mountains, geological disasters such as landslides, collapses, and mud-rock flows are very likely to occur.

[0003] The chemical formula of 4A zeolite is: 6Na2O·6Al2O3·12SiO2·27H2O. It is a non-toxic, odorless, tasteless white powder with good fluidity. It has strong calcium ion exchange capacity and is an aluminum silicate with high economic value. It is environmentally friendly and is an ideal phosphorus-free detergent additive to replace sodium tripolyphosphate in the production of phosphorus-free detergents.

[0004] In the prior art, some researchers have prepared 4A zeolite from coal gangue. However, during the extraction of alumina and silica, alumina and silica generate insoluble sodium aluminosilicate solids, and it is impossible to fully extract alumina and silica, resulting in low utilization of the coal gangue, low yield of the obtained 4A zeolite, and poor quality. In addition, since the aluminum-silicon ratio in the coal gangue is not fixed, if the same extraction method is used, it is impossible to achieve that the same method is applicable to coal gangue with any aluminum-silicon ratio, which will not only cause insufficient extraction of the aluminum-silicon ratio, but may even cause waste of aluminum and silicon in the coal gangue. Therefore, different treatment methods are required for coal gangue with different aluminum-silicon ratios, so as to fully utilize the coal gangue. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for producing 4A zeolite using coal gangue with a low aluminum-silicon ratio. With coal gangue as raw material, the method of the present invention can fully extract alumina and silicon dioxide in the coal gangue, thereby increasing the yield of 4A zeolite, and the obtained 4A zeolite has the advantages of high crystallinity, high whiteness, low impurity content and large cation exchange capacity.

[0006] The present invention provides a method for producing 4A zeolite by using coal gangue with a low aluminum-silicon ratio, comprising the following steps: 4A zeolite is obtained by using coal gangue through pretreatment, soda ash melting, water quenching, wet grinding, solid-liquid separation, caustic soda melting, dry powder dissolution, mold adjustment, slurrying, crystallization and drying.

[0007] Furthermore, the coal gangue is coal gangue with an aluminum-silicon ratio of less than 0.26.

[0008] Furthermore, the specific method of the pretreatment includes: grinding the coal gangue and then roasting it.

[0009] Furthermore, the particle size of the ground coal gangue is not less than 40 meshes.

[0010] Furthermore, the calcination temperature is 800° C.-1200° C., and the calcination time is 10 min-30 min.

[0011] Furthermore, the specific steps of melting the soda ash include: uniformly mixing the pretreated coal gangue and the soda ash and heating them.

[0012] Furthermore, based on mass, the ratio of the pretreated coal gangue to soda ash is (1:0.5-2.6).

[0013] Furthermore, the heating temperature is 1400° C.-1450° C., and the heating time is 50 min-60 min.

[0014] Furthermore, after the heating is completed, it is also necessary to ensure that the discharge temperature after heating is not lower than 1050°C.

[0015] Furthermore, the soda ash is sodium carbonate.

[0016] Furthermore, during the water quenching, the product after the soda ash is melted and the dilute caustic soda solution during the water quenching are, by mass, a ratio of the product after the soda ash is melted to the dilute caustic soda solution of (1:4-5).

[0017] The water quenching in the present invention refers to rapidly immersing the molten clinker obtained by the soda ash alkali melting treatment into a dilute caustic soda solution at high temperature for water quenching treatment to obtain solid fine particles.

[0018] Furthermore, the mass percentage concentration of the dilute caustic soda solution is 3%-5%.

[0019] Furthermore, the specific method of wet grinding includes: wet grinding the product after water quenching with a dilute caustic soda solution, when the particle size of the wet-milled product is between 200 mesh and 400 mesh.

[0020] In the present invention, those skilled in the art may use ball milling or other grinding methods to refine the particle size of the product after water quenching.

[0021] Furthermore, during wet grinding, the ratio of the dilute caustic soda solution to the product after water quenching is (3:1-5:1) by mass.

[0022] Furthermore, the mass percentage concentration of the dilute caustic soda solution is 3%-5%.

[0023] Furthermore, the method for preparing the dilute caustic soda solution comprises dissolving sodium hydroxide in water.

[0024] Furthermore, the specific method of solid-liquid separation includes: diluting the wet-milled product to a liquid-solid ratio of (8:1-10:1); and solid-liquid separation.

[0025] Furthermore, the caustic Na2O in the diluted solution K The concentration is not less than 200g / L.

[0026] Furthermore, the diluted solution includes a water-quenched solution and a dilute caustic soda solution.

[0027] In the present invention, it should be understood by those skilled in the art that, although the solution used for dilution is the water-quenched solution and the dilute caustic soda solution, the dilute solution is mainly the dilute caustic soda solution. Generally speaking, there is no strict dosage ratio between the water-quenched solution and the dilute caustic soda solution. As long as the caustic Na2O in the diluted solution can be controlled, K The concentration should be no less than 200g / L.

[0028] Furthermore, the mass percentage concentration of the dilute caustic soda solution is 3%-5%.

[0029] Furthermore, during the dilution process, by controlling the caustic Na2O K The concentration of sodium aluminate and sodium silicate can be completely separated, which is beneficial to the mold adjustment and slurry process. During the dilution process, stirring can be used to promote sufficient dilution and separation of sodium aluminate and sodium silicate. As an example, the stirring speed can be 20 rpm-30 rpm.

[0030] Furthermore, the specific method of caustic soda fusion comprises: adding caustic soda solution to the filter residue after solid-liquid separation, heating until the water evaporates completely, and obtaining dry powder.

[0031] Furthermore, the mass percentage concentration of the caustic soda solution is 45%-50%.

[0032] Furthermore, the heating temperature is 320°C-550°C.

[0033] Furthermore, the molar ratio of the filter residue to the caustic soda solution is (1:2-2.4), calculated as silicon dioxide in the filter residue and calculated as sodium hydroxide in the caustic soda solution.

[0034] Furthermore, the preparation method of the caustic soda solution includes: dissolving sodium hydroxide in water.

[0035] Furthermore, the specific method of dissolving the dry powder includes: dissolving the dry powder obtained by alkali melting of caustic soda in a dilute caustic soda solution with a mass percentage concentration of 3%-5%, and controlling the caustic Na2O in the dissolved solution. K The concentration is not less than 250g / L, filter and the filtrate is set aside.

[0036] Furthermore, the specific method for adjusting the mold includes: combining the filtrate after solid-liquid separation with the filtrate after dry powder dissolution, adding aluminum hydroxide to adjust the mold, and after adding aluminum hydroxide, the molar ratio of aluminum oxide to silicon dioxide in the filtrate is (1:1.57-1.62).

[0037] Furthermore, stirring is required during the mold adjustment process, and the stirring rate is 20 rpm to 30 rpm.

[0038] Furthermore, the specific process of the slurrying includes: adding a directing agent to the adjusted solution for mixing; during mixing, controlling the stirring speed to 60 rpm-120 rpm and the temperature to 60°C-80°C; after the mixing is completed, controlling the stirring speed to 60 rpm-120 rpm and the stirring time to 20min-30min.

[0039] Furthermore, the guiding agent is prepared with four substances: aluminum hydroxide, sodium hydroxide, sodium hydroxide and water. When preparing the guiding agent, the aluminum hydroxide is calculated as alumina, the sodium hydroxide is calculated as silicon dioxide, and the ratio of aluminum hydroxide, sodium hydroxide, sodium hydroxide and water is (1:15:19-20:300-350) by mass.

[0040] In the present invention, the guiding agent is prepared from four substances, aluminum hydroxide, sodium hydroxide, and water, to form a 4A zeolite seed solution. The amount of seeds in the 4A zeolite seed solution is calculated and determined based on 1%-3% of the designed 4A zeolite output. After determining the amount of seeds in the 4A zeolite seed solution, the ratio of aluminum hydroxide, sodium hydroxide, sodium hydroxide, and water is (1:15:19-20:300-350) according to the weight of aluminum hydroxide, sodium hydroxide, sodium hydroxide, and water, and the specific amount of raw materials aluminum hydroxide, sodium hydroxide, sodium hydroxide, and water when preparing the guiding agent can be determined.

[0041] Furthermore, the preparation process of the directing agent includes: controlling the temperature of the solution after mixing aluminum hydroxide, sodium hydroxide, sodium hydroxide and water to 45°C-65°C, continuously stirring for 20min-30min at a stirring speed of 60 rpm-90 rpm, and then letting the solution stand for 24h-48h. The directing agent after standing is used for slurrying within 30min-60min.

[0042] Furthermore, the specific process of the crystallization includes: heating the slurried solution.

[0043] Furthermore, the heating temperature is 90° C.-98° C., the heating time is 1 h-3 h, stirring is performed during the heating process, and the stirring speed is 20 rpm-30 rpm.

[0044] Furthermore, the specific process of the drying includes: washing and drying the crystallized solid to obtain 4A zeolite.

[0045] Furthermore, the drying temperature is 95°C-105°C.

[0046] It should be understood by those skilled in the art that the washing process is to remove the impurity ions adsorbed on the surface and in the crystal lattice of 4A zeolite, and to improve the ion adsorption and exchange capacity of the 4A zeolite product. Therefore, it is necessary to use deionized water for washing, and then dry to remove the adsorbed water. The selection of the drying temperature in the present invention is based on the stability of the product structure to achieve the effect of removing the adsorbed water.

[0047] The embodiments of the present invention have the following technical effects: 1. In the method of the present invention, the coal gangue is first activated by pretreatment, which not only allows the alumina and silica present in the coal-based kaolin in the coal gangue to be decomposed into free alumina and silica, but also facilitates the full conversion of alumina and silica in the coal gangue during the soda alkali melting; and the organic matter such as combustible carbon and humic acid in the coal gangue can also be removed by pretreatment roasting, which helps to improve the whiteness and quality of the obtained 4A zeolite; The product of the soda ash alkali melting is water quenched. Through water quenching, the high-temperature molten material after the soda ash alkali melting transformation is rapidly cooled by water and broken into fine particles under the action of surface tension, thereby increasing the specific surface area of ​​the particles, which not only paves the way for sufficient wet grinding, but also facilitates the alkali melting of caustic soda; Adding a dilute caustic soda solution to the product after water quenching and wet grinding can promote the decomposition of sodium aluminosilicate generated by alumina and silica in the soda ash fusion. On the one hand, it is beneficial to improve the extraction rate of alumina and silica in the raw material coal gangue, increase the output of 4A zeolite, and improve the economic efficiency of the utilization of coal gangue raw materials. On the other hand, it can reduce the residual amount of sodium aluminosilicate in the filter residue after solid-liquid separation, and reduce the subsequent caustic soda fusion treatment cost; In order to fully extract alumina and silica from coal gangue, the filter residue after solid-liquid separation needs to be treated with caustic soda fusion. K The concentration of 4A zeolite is increased to decompose all the residual sodium aluminosilicate in the filter residue, thereby increasing the yield of 4A zeolite. During the dry powder dissolution process, the caustic Na2O K The concentration can improve the reaction kinetics of sodium hydroxide, prevent the regeneration of sodium aluminosilicate, and is conducive to the maximum extraction of alumina and silicon dioxide, thereby increasing the yield of 4A zeolite; During the mold adjustment process, aluminum hydroxide is added as a mold adjustment agent. On the one hand, it is to adjust the concentration of aluminum oxide so that the chemical composition ratio of aluminum oxide and silicon dioxide meets the composition of 4A zeolite. On the other hand, aluminum hydroxide, a mold adjustment agent, will also consume part of the sodium hydroxide, reducing the concentration of sodium hydroxide, which is conducive to the atomic arrangement of the formed crystals in the direction of the 4A zeolite crystal structure, thus ensuring the quality of 4A zeolite. During the slurrying process, the directing agent of the present invention is prepared and used immediately, which is beneficial to further promote the atomic arrangement of the generated crystals to grow towards the 4A zeolite crystal structure; Finally, through crystallization, the 4A zeolite crystals are grown, and finally the 4A zeolite is obtained.

[0048] 2. Through the method of the present invention, for coal gangue with an Al2O3 mass percentage of 16.46%, an SiO2 mass percentage of 66.39%, and an aluminum-silicon ratio of 0.25<0.26, the extraction and utilization rate of Al2O3 in the coal gangue raw material of the present invention reaches 92.16%, and the extraction and utilization rate of SiO2 reaches 94.68%; the extracted alumina and silica account for a total of 94.18% of the total amount of alumina and silica in the coal gangue raw material, and more than 78% of the total amount of the coal gangue raw material.

[0049] 3. The calcium exchange capacity, whiteness, crystallinity, particle size and pH value of the 4A zeolite produced from coal gangue by the method of the present invention all meet the product quality standards of 4A zeolite for detergent additives. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0051] In a first aspect, some embodiments of the present invention provide a method for producing 4A zeolite using coal gangue with a low aluminum-silicon ratio, comprising the following steps: 4A zeolite is obtained by using coal gangue through pretreatment, soda ash melting, water quenching, wet grinding, solid-liquid separation, caustic soda melting, dry powder dissolution, mold adjustment, slurrying, crystallization and drying.

[0052] In some embodiments, the coal gangue has an aluminum-silicon ratio of less than 0.26.

[0053] In some embodiments, the specific method of pretreatment includes: grinding the coal gangue and then roasting it.

[0054] In some embodiments, the particle size of the ground coal gangue is not less than 40 mesh.

[0055] In some embodiments, the calcination temperature is 800° C.-1200° C., and the calcination time is 10 min-30 min.

[0056] In some embodiments, the specific step of melting soda ash includes: uniformly mixing the pretreated coal gangue and soda ash and heating them.

[0057] In some embodiments, the ratio of the pretreated coal gangue to soda ash is (1:0.5-2.6) by mass.

[0058] In some embodiments, the heating temperature is 1400° C.-1450° C., and the heating time is 50 min-60 min.

[0059] In some embodiments, after the heating is completed, it is also necessary to ensure that the discharge temperature after heating is not less than 1050°C.

[0060] In the present invention, by controlling the temperature of the soda ash fusion, it is ensured that the aluminum oxide and silicon dioxide in the coal gangue are fully converted into sodium aluminate and sodium silicate, and the sodium aluminosilicate formed between the aluminum oxide and silicon dioxide is reduced, which is conducive to extracting aluminum oxide and silicon dioxide from the coal gangue to the maximum extent.

[0061] In some embodiments, the soda ash is sodium carbonate.

[0062] In some embodiments, during the water quenching, the product after the soda ash is melted and the dilute caustic soda solution during the water quenching, by mass, the ratio of the product after the soda ash is melted to the dilute caustic soda solution is (1:4-5).

[0063] In some embodiments, the mass percentage concentration of the dilute caustic soda solution is 3%-5%.

[0064] In some embodiments, the specific method of wet grinding includes: wet grinding the product after water quenching with a dilute caustic soda solution, and when the particle size of the wet-milled product is between 200 mesh and 400 mesh, the wet grinding is completed.

[0065] In some embodiments, during wet grinding, the ratio of the dilute caustic soda solution to the product after water quenching is (3:1-5:1) by mass.

[0066] In some embodiments, the mass percentage concentration of the dilute caustic soda solution is 3%-5%.

[0067] In some embodiments, the method for preparing the dilute caustic soda solution includes dissolving sodium hydroxide in water.

[0068] In some embodiments, the specific method of solid-liquid separation includes: diluting the wet-milled product with a dilute caustic soda solution to a liquid-solid ratio of (8:1-10:1); separating the solid and the liquid, and setting the filtrate aside.

[0069] In some embodiments, the mass percent concentration of the dilute caustic soda solution is 3%-5%.

[0070] In some embodiments, the diluted solution contains caustic Na2O K The concentration is not less than 200g / L.

[0071] In some embodiments, during the dilution process, by controlling the caustic Na2O K The concentration of sodium aluminate and sodium silicate can be completely separated, which is beneficial to the mold adjustment and slurrying process. Therefore, during the dilution process, stirring can be used to promote sufficient dilution and separation of sodium aluminate and sodium silicate. As an example, the stirring speed can be 20 rpm-30 rpm.

[0072] In some embodiments, the specific method of caustic soda fusion comprises: adding caustic soda solution to the filter residue after solid-liquid separation, heating until the water is completely evaporated to obtain dry powder.

[0073] In some embodiments, the concentration of the caustic soda solution is 45%-50%.

[0074] In some embodiments, the heating temperature is 320°C-550°C.

[0075] In some embodiments, the molar ratio of the filter residue to the caustic soda solution is (1:2-2.4) based on silicon dioxide and the molar ratio of the caustic soda solution to sodium hydroxide.

[0076] In some embodiments, the specific method of dissolving the dry powder includes: dissolving the dry powder obtained by melting the caustic soda in a dilute caustic soda solution with a mass percentage concentration of 3%-5%, and controlling the caustic Na2O in the dissolved solution. K The concentration is not less than 250g / L, filter and the filtrate is set aside.

[0077] In some embodiments, the specific method of adjusting the mold includes: combining the filtrate after solid-liquid separation with the filtrate after dry powder dissolution, adding aluminum hydroxide to adjust the mold, and after adding aluminum hydroxide, the molar ratio of aluminum oxide to silicon dioxide in the filtrate is (1:1.57-1.62).

[0078] In some embodiments, stirring is required during the mold adjustment process, and the stirring rate is 20 rpm to 30 rpm.

[0079] In some embodiments, the specific process of the slurrying includes: adding a directing agent to the adjusted solution for mixing; during mixing, controlling the stirring speed to 60 rpm-120 rpm and the temperature to 60°C-80°C; after mixing, controlling the stirring speed to 60 rpm-120 rpm and the stirring time to 20min-30min.

[0080] In some embodiments, the guiding agent is prepared with four substances: aluminum hydroxide, sodium hydroxide, sodium hydroxide, and water; when preparing the guiding agent, the aluminum hydroxide is calculated as alumina, the sodium hydroxide is calculated as silicon dioxide, and the ratio of aluminum hydroxide, sodium hydroxide, sodium hydroxide, and water is (1:15:19-20:300-350) by mass.

[0081] In some embodiments, the preparation process of the directing agent includes: controlling the temperature of the solution after mixing aluminum hydroxide, sodium hydroxide, sodium hydroxide and water to 45°C-65°C, continuously stirring for 20min-30min at a stirring speed of 60 rpm-90 rpm, and then letting the solution stand for 24h-48h. The directing agent after standing is used for slurrying within 30min-60min.

[0082] In some embodiments, the specific process of the crystallization includes: heating the slurried solution.

[0083] In some embodiments, the heating temperature is 90° C.-98° C., the heating time is 1 h-3 h, stirring is performed during the heating process, and the stirring speed is 20 rpm-30 rpm.

[0084] In some embodiments, the specific process of drying includes: washing and drying the crystallized solid to obtain 4A zeolite.

[0085] In some embodiments, the drying temperature is 95°C-105°C.

[0086] The following is described in conjunction with some specific embodiments: Example 1

[0087] A coal gangue with an Al2O3 mass percentage of 16.46%, a SiO2 mass percentage of 66.39%, and an aluminum-silicon ratio of 0.25 is ground to a particle size of 50 meshes. The coal gangue is calcined at 1000° C. for 20 minutes to complete the pretreatment.

[0088] Soda ash melting: Mix the pretreated coal gangue and soda ash (sodium carbonate), heat and perform soda ash melting treatment to obtain molten clinker. The pretreated coal gangue and soda ash are mixed in a mass ratio of coal gangue: soda ash = 1:2, react at 1450°C for 55 minutes, maintain the discharge temperature above 1050°C, and obtain molten clinker.

[0089] Water quenching: The molten clinker obtained by the soda ash alkali melting treatment is rapidly quenched with a dilute caustic soda solution with a mass percentage concentration of 4% while at high temperature. During the water quenching, the ratio of the product after the soda ash alkali melting to the dilute caustic soda solution is 1:5 by mass to obtain solid fine particles; the solid fine particles are fed into the next wet grinding process; Wet grinding: The fine particles obtained by the water quenching process are wet-milled with a dilute caustic soda solution having a mass percentage concentration of 4%, and the fineness is ground to 300 mesh. The wet grinding is completed; the ratio of the dilute caustic soda solution to the product after water quenching is 4:1 by mass.

[0090] Solid-liquid separation: The slurry obtained by wet grinding is diluted with a water-quenched solution and a 4% by mass concentration of dilute caustic soda solution; diluted to a liquid-solid ratio of 8:1-10:1. In this range, the caustic Na2O in the diluted solution is controlled. K ≥200g / L, stir continuously at 25 rpm during dilution; filter immediately after dilution; Caustic soda fusion: add caustic soda solution with a mass percentage concentration of 47% to the filter cake after solid-liquid separation, the filter residue is calculated as silicon dioxide, and the caustic soda solution is calculated as sodium hydroxide. The molar ratio of the filter residue to the caustic soda solution is 1:2.2, and heat the reaction at 350°C until the material becomes dry powder; Dry powder dissolution: The dry powder obtained by the caustic soda fusion process is dissolved in a dilute caustic soda solution with a mass percentage concentration of 4%; during the dissolution, the caustic Na2O in the solution after dissolution is controlled. K ≥250g / L; after dissolution, filter immediately and set the filtrate aside; wash the filter cake obtained by filtration with water until pH ≤11.

[0091] Mold adjustment: combine the filtrate after solid-liquid separation with the filtrate after dry powder dissolution, add aluminum hydroxide for mold adjustment, adjust the molar ratio of Al2O3 and SiO2 in the solution, add solid aluminum hydroxide under continuous stirring at a stirring speed of 25 rpm to dissolve all the added aluminum hydroxide. After adding aluminum hydroxide, the molar ratio of alumina to silicon dioxide in the filtrate is 1:1.6.

[0092] Preparation of guiding agent: The dosage of guiding agent is determined by calculation based on 2% of the designed 4A zeolite output; the guiding agent is prepared with aluminum hydroxide, sodium hydroxide, sodium hydroxide and water, with aluminum hydroxide being calculated as alumina and sodium hydroxide being calculated as silicon dioxide; the ratio of aluminum hydroxide, sodium hydroxide, sodium hydroxide and water is 1:15:19:300 by mass, and the temperature of the mixed solution is controlled to be 55°C. After continuous stirring at a stirring speed of 75 rpm for 25 minutes, the solution is allowed to stand for 40 hours. The guiding agent after standing is used in the slurrying stage within 30 minutes.

[0093] Slurrying: The prepared 4A zeolite directing agent is slowly added to the solution adjusted with aluminum hydroxide under continuous stirring to obtain a dilute gel solution; during slurrying, the stirring speed of the two solutions is controlled at 100 rpm and the temperature after mixing is 70°C; after the two solutions are mixed, the stirring speed is maintained at 100 rpm for continuous stirring for 25 minutes.

[0094] Crystallization: Heat the slurried solution, quickly raise the temperature to 95°C, reduce the stirring speed to 25 rpm, and continue stirring for 2 hours to complete crystallization.

[0095] Drying: The 4A zeolite filter cake obtained by filtering and washing after crystallization is dried at a temperature of 100° C. to obtain a 4A zeolite product.

[0096] In this embodiment, the mass percentage concentration of the dilute caustic soda solution is 4%; the mass percentage concentration of the caustic soda solution is 47%.

[0097] Comparative Example 1: The preparation method of Comparative Example 1 is the same as that of Example 1, but Comparative Example 1 does not have a pretreatment step.

[0098] Comparative Example 2: The preparation method of Comparative Example 2 is the same as that of Example 1, but the heating temperature of Comparative Example 2 is 1200° C. and the heating time is 30 minutes in a soda ash melt.

[0099] Comparative Example 3: The preparation method of Comparative Example 3 is the same as that of Example 1, but in Comparative Example 3, no dilute caustic soda solution is added during wet grinding.

[0100] Comparative Example 4: The preparation method of Comparative Example 4 is the same as that of Example 1, but Comparative Example 4 has no pretreatment, and is heated to 1200° C. and for 30 minutes in a pure alkali melt.

[0101] Comparative Example 5: The preparation method of Comparative Example 5 is the same as that of Example 1, but the aluminum-silicon ratio of the coal gangue in Comparative Example 5 is 0.27.

[0102] The products obtained from the embodiments and comparative examples of the present invention were tested.

[0103] Calcium exchange capacity detection method: loss on ignition method.

[0104] Whiteness detection method: color difference method.

[0105] Method for detecting crystallinity: X-ray diffraction method.

[0106] Particle size detection method: sedimentation method.

[0107] pH value detection method: potentiometric method.

[0108] Results and analysis: Table 1 Test results of products obtained from the examples and comparative examples

[0109] It can be found in Table 1 that the 4A zeolite product obtained by the present invention meets the quality standards of 4A zeolite products for detergent builders in terms of calcium exchange capacity, whiteness, particle size, and pH value, and the product of the present invention is significantly better than Comparative Examples 1 to 5 in terms of calcium exchange capacity, whiteness, and crystallinity. It can be seen that through the interaction between the steps of the method of the present invention, not only the extraction rate of alumina and silica is improved, but also a 4A zeolite with better quality is obtained.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing 4A zeolite using coal gangue with a low aluminum-silicon ratio, characterized in that: The steps include: Using coal gangue, 4A zeolite is obtained through pretreatment, soda ash melting, water quenching, wet grinding, solid-liquid separation, caustic soda melting, dry powder dissolution, mold adjustment, slurrying, crystallization and drying; The coal gangue has an aluminum-silicon ratio of less than 0.

26.

2. The method according to claim 1, characterized in that The specific method of the pretreatment includes: grinding the coal gangue and then roasting it; The particle size of the ground coal gangue is not less than 40 mesh; The calcination temperature is 800° C.-1200° C., and the calcination time is 10 min-30 min.

3. The method according to claim 1, characterized in that The specific steps of the soda ash melting include: uniformly mixing the pretreated coal gangue and soda ash and heating them; The ratio of the pretreated gangue to soda ash is (1:0.5-2.6) by mass; The heating temperature is 1400°C-1450°C, and the heating time is 50min-60min; After heating is completed, it is also necessary to ensure that the discharge temperature after heating is not lower than 1050℃.

4. The method according to claim 1, characterized in that The specific method of wet grinding includes: wet grinding the product after water quenching with a dilute caustic soda solution, and when the particle size of the ground product is between 200 mesh and 400 mesh, the wet grinding is completed; During the water quenching, the product after the soda ash is melted and the dilute caustic soda solution during the water quenching, by mass, the ratio of the product after the soda ash is melted to the dilute caustic soda solution is (1:4-5); The mass percentage concentration of the dilute caustic soda solution is 3%-5%.

5. The method according to claim 1, characterized in that: The specific method of solid-liquid separation comprises: diluting the wet-milled product with a dilute caustic soda solution to a liquid-solid ratio of (8:1-10:1), separating the solid and the liquid, and setting the filtrate aside; The mass percentage concentration of dilute caustic soda solution is 3%-5%; The caustic Na2O in the diluted solution K The concentration is not less than 200g / L.

6. The method according to claim 1, characterized in that The specific method of caustic soda fusion comprises: adding caustic soda solution to the filter residue after solid-liquid separation, heating until the water evaporates completely, and obtaining dry powder; The mass percentage concentration of the caustic soda solution is 45%-50%; The heating temperature is 320°C-550°C; The filter residue is calculated as silicon dioxide, and the caustic soda solution is calculated as sodium hydroxide. The molar ratio of the filter residue to the caustic soda solution is (1:2-2.4).

7. The method according to claim 1, characterized in that The specific method of dissolving the dry powder comprises: dissolving the dry powder obtained by alkali melting of caustic soda in a dilute caustic soda solution with a mass percentage concentration of 3%-5%, and controlling the caustic Na2O in the dissolved solution. K The concentration is not less than 250g / L, filter and the filtrate is set aside.

8. The method according to claim 1, characterized in that: The specific method of adjusting the mold includes: combining the filtrate after solid-liquid separation with the filtrate after dry powder dissolution, adding aluminum hydroxide to adjust the mold, and after adding aluminum hydroxide, the molar ratio of aluminum oxide to silicon dioxide in the filtrate is (1:1.57-1.62); Stirring is also required during the mold adjustment process, and the stirring rate is 20 rpm-30 rpm.

9. The method according to claim 1, characterized in that: The specific process of the slurrying includes: adding a directing agent to the solution after mold adjustment for mixing; during mixing, controlling the stirring speed to 60 rpm-120 rpm and the temperature to 60° C.-80° C.; after the mixing is completed, controlling the stirring speed to 60 rpm-120 rpm and the stirring time to 20 min-30 min; The guiding agent is prepared with four substances: aluminum hydroxide, sodium hydroxide, sodium hydroxide and water. When preparing the guiding agent, the aluminum hydroxide is calculated as alumina, the sodium hydroxide is calculated as silicon dioxide, and the ratio of aluminum hydroxide, sodium hydroxide, sodium hydroxide and water is (1:15:19-20:300-350) by mass.

10. The method according to claim 1, characterized in that The specific process of the crystallization includes: heating the slurried solution; The heating temperature is 90°C-98°C, the heating time is 1h-3h, stirring is performed during the heating process, and the stirring speed is 20 rpm-30 rpm; the drying temperature is 95°C-105°C.

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