Preparation method for converting waste catalyst tail water aluminum sulfate into aluminum ammonium sulfate

Abstract

The invention discloses a preparation method for converting waste catalyst tail water into aluminum ammonium sulfate through aluminum sulfate, and relates to the technical field of waste catalyst tail water treatment.The method comprises the following steps that waste catalyst tail water is filtered in advance, solid impurities are removed, and meanwhile residual trace heavy metal ions in the waste catalyst tail water are further removed through ion exchange resin; the filtered tail water is concentrated; the method comprises the following steps: screening ammonium sulfate with the purity of more than 98% as an ammonium sulfate raw material, grinding the ammonium sulfate until the granularity is refined to 100-200 meshes, recrystallizing and purifying the ammonium sulfate, and filtering to obtain high-purity ammonium sulfate crystals; and chemical reaction equations. According to the method, aluminum sulfate in the waste catalyst tail water is effectively utilized and converted into aluminum ammonium sulfate, so that the utilization rate of valuable elements is increased, waste of aluminum sulfate resources is avoided, and the production cost is greatly reduced by utilizing the waste catalyst tail water; the heavy metal pollution index of the finally discharged wastewater is reduced, and the harm to the water body environment is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of waste catalyst tail water treatment, and in particular to a method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water. Background Art

[0002] Waste catalysts from petrochemicals often contain some toxic components, mainly heavy metals and volatile organic compounds, which pose great environmental risks. It is particularly important to treat and dispose of them harmlessly. In addition, waste catalysts from petrochemicals contain high levels of precious metals or other valuable metals, some of which are even much higher than the content of corresponding components in some lean mines. They have high metal grades and can be recycled as secondary resources. Comprehensive utilization of waste catalysts from petrochemicals can not only improve resource utilization, but also avoid environmental problems caused by waste catalysts and achieve sustainable development.

[0003] At present, waste catalysts are hazardous wastes unloaded from the petroleum refining process, which contain about 40-55% alumina. During the acid leaching process, part of the aluminum will form aluminum sulfate and exist in the tail water. The recovery of aluminum is of particular importance. At the same time, there are two ways to treat nickel-aluminum slag. Form a matte nickel alloy through fire reduction smelting or extract nickel through acid leaching. Although the process of fire smelting is simple, its equipment and production costs are very high, and a large amount of auxiliary materials are required, and certain waste gas emissions are generated to the environment. In order to meet the emission requirements, the investment in environmental protection facilities is increased, which affects the overall operating pressure. Acid leaching has a short process, less investment in environmental protection facilities, and lower cost, and has certain economic advantages. Therefore, there is an urgent need for a tail water treatment process containing aluminum sulfate produced by extracting nickel after acid leaching of nickel and aluminum, which is of practical significance in the current social responsibility of energy conservation, emission reduction and water saving.

[0004] Currently, no effective solution has been proposed for the problems in the related technologies. Summary of the invention

[0005] In view of the problems in the related art, the present invention proposes a method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water to overcome the above-mentioned technical problems existing in the existing related technology.

[0006] The technical solution of the present invention is achieved in this way:

[0007] A method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water comprises the following steps:

[0008] The waste catalyst tail water is filtered in advance to remove solid impurities, and ion exchange resin is used to further remove the trace heavy metal ions remaining in the waste catalyst tail water, and the filtered tail water is concentrated;

[0009] The ammonium sulfate raw material with a purity greater than 98% is selected, and the ammonium sulfate is ground to a particle size of 100 to 200 meshes, and the ammonium sulfate is recrystallized and purified, and filtered to obtain high-purity ammonium sulfate crystals;

[0010] According to the chemical reaction equation, aluminum sulfate and ammonium sulfate are mixed at a molar ratio of 1:1, expressed as:

[0011] Al2(SO4)3+(NH4)2SO4+24H2O=2[NH4Al(SO4)2·12H2O];

[0012] Add the prepared aluminum sulfate solution and ammonium sulfate solution into the reactor, and precisely control the temperature of the reaction solution at 60-70°C, and monitor the pH value of the reaction solution in real time. When the pH value deviates from 9.5, automatically add dilute ammonia water with a concentration of 1-2 mol / L for adjustment;

[0013] The method comprises the following steps: after the reaction is completed, the reaction solution is slowly cooled to room temperature to allow the ammonium aluminum sulfate to crystallize out, and the separated ammonium aluminum sulfate crystals are washed with a small amount of cold water to remove impurities adsorbed on the surface of the crystals.

[0014] Furthermore, the use of ion exchange resin to further remove trace heavy metal ions remaining in the waste catalyst tail water includes: using a strong acid cation exchange resin to allow the tail water to pass through a resin column at a flow rate of 5 to 10 mL / min to adsorb heavy metal ions and improve the purity of the raw materials.

[0015] Further, the recrystallization and purification of ammonium sulfate comprises the following steps:

[0016] Dissolve ammonium sulfate in hot water at 70-80°C until saturated;

[0017] Slowly cool to 10-15°C to keep the impurities in the mother liquor;

[0018] Filtration yields high-purity ammonium sulfate crystals.

[0019] Furthermore, the step of adding the prepared aluminum sulfate solution and ammonium sulfate solution into the reactor further comprises the following steps:

[0020] The reaction system is stirred, and seed crystals are added into the reaction system, wherein the seed crystals account for 0.5% to 1% of the total mass of the system, and the reaction time is 2 to 3 hours.

[0021] Further, the stirring of the reaction system comprises the following steps:

[0022] Use an anchor-type agitator with variable frequency speed regulation, and run it at a high speed of 400-500r / min at the initial stage of the reaction to quickly mix the aluminum sulfate solution and ammonium sulfate evenly;

[0023] When a small amount of ammonium aluminum sulfate crystal nuclei are observed, the stirring speed is adjusted to 200-300 r / min.

[0024] Furthermore, the crystallization separation includes: controlling the cooling rate to be 1-2°C / min, and after the crystals are precipitated, separating the crystals from the mother liquor by vacuum filtration or centrifugal separation.

[0025] Furthermore, the purification includes: washing the separated ammonium aluminum sulfate crystals with cold water for 2 to 3 times, and placing the washed crystals in a drying oven for drying at a drying temperature of 60 to 80° C. for 4 to 6 hours.

[0026] Beneficial effects of the present invention:

[0027] The invention pre-filters the waste catalyst tail water to remove solid impurities, and uses ion exchange resin to further remove the trace heavy metal ions remaining in the waste catalyst tail water, and concentrates the filtered tail water, and selects the tail water with a purity greater than 98% as the ammonium sulfate raw material, and grinds the ammonium sulfate to refine the particle size to 100-200 meshes, and recrystallizes and purifies the ammonium sulfate, and filters to obtain high-purity ammonium sulfate crystals, and at the same time, adds the prepared aluminum sulfate solution and ammonium sulfate solution to the reactor, and accurately controls the temperature of the reaction solution at 60-70°C, and monitors the pH value of the reaction solution in real time, and when the pH value deviates from 9.5, automatically drips dilute ammonia water, and adjusts the concentration by 1-2 mol / L, and after the reaction is completed, slowly cools the reaction solution to room temperature. The temperature is increased to make the ammonium aluminum sulfate crystallize, and the separated ammonium aluminum sulfate crystals are washed with a small amount of cold water to remove impurities adsorbed on the surface of the crystals, so as to achieve effective utilization of aluminum sulfate in the waste catalyst tail water and convert it into ammonium aluminum sulfate, which not only improves the utilization rate of valuable elements, but also has good chemical stability of the ammonium aluminum sulfate product, can maintain its chemical properties during storage and use, and plays a reliable role in industrial applications, avoiding the waste of aluminum sulfate resources. At the same time, it turns waste into treasure and reduces costs. Compared with directly extracting aluminum from raw materials such as ores to prepare ammonium aluminum sulfate, the use of waste catalyst tail water as raw material greatly reduces the production cost; in addition, in the treatment process of waste catalyst tail water, the content of heavy metals in the tail water can be effectively reduced. When preparing ammonium aluminum sulfate, some heavy metals will be removed during precipitation and filtration, so that the heavy metal pollution index of the final discharged wastewater is reduced, reducing the harm to the water environment.

[0028] In addition, the present invention achieves the goal of obtaining a high-purity ammonium aluminum sulfate product by precisely controlling the temperature of the reaction solution, monitoring the pH value of the reaction solution in real time, and automatically adding dilute ammonia water for adjustment. The ammonium aluminum sulfate crystals grow more completely, reduce the inclusion of impurities, and improve the purity of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 The present invention is a schematic flow chart of a method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 belong to the scope of protection of the present invention.

[0032] According to an embodiment of the present invention, a method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water is provided.

[0033] like Figure 1 As shown, the method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to an embodiment of the present invention comprises the following steps:

[0034] Step S1, filtering the waste catalyst tail water in advance to remove solid impurities, and using ion exchange resin to further remove trace heavy metal ions remaining in the waste catalyst tail water, and concentrating the filtered tail water;

[0035] In this technical solution, the waste catalyst tail water is filtered to remove the solid impurities that may exist therein, such as catalyst particles, insoluble salts, etc. Filter paper or a sand core funnel can be used for filtering. For example, if the waste catalyst tail water contains a small amount of silica particles, they can be effectively removed by filtering to prevent them from interfering with subsequent reactions.

[0036] At the same time, after the initial filtration to remove large particle impurities, ion exchange resin is used to further remove trace heavy metal ions that may remain in the waste catalyst tail water, such as copper, nickel, etc. Even if these heavy metal ions are present in very small amounts, they may affect product purity or catalyze side reactions in subsequent reactions.

[0037] Specifically, a strong acid cation exchange resin is selected and the tail water is passed through the resin column at a flow rate of 5 to 10 mL / min to ensure effective adsorption of heavy metal ions and improve the purity of the raw materials.

[0038] In addition, the filtered tail water is concentrated. The water can be evaporated at a lower temperature by reduced pressure evaporation to increase the concentration of aluminum sulfate. This is because if the concentration of aluminum sulfate is too low, it will lead to low reaction efficiency in subsequent reactions and increase the difficulty of product separation and purification.

[0039] Step S2, screening the ammonium sulfate raw material with a purity of more than 98%, grinding the ammonium sulfate to refine the particle size to 100-200 mesh, and recrystallizing and purifying the ammonium sulfate, filtering to obtain high-purity ammonium sulfate crystals;

[0040] In this technical solution, for the above-mentioned ammonium sulfate raw material, a higher purity ammonium sulfate is selected, and the purity of ammonium sulfate should be above 98%. If the purity of ammonium sulfate is not enough, the impurities therein may participate in the reaction, generate by-products, and affect the quality of aluminum ammonium sulfate. Before use, the ammonium sulfate needs to be stored in a dry environment to prevent it from absorbing water and deliquescing. Because the deliquesced ammonium sulfate will change the content of its active ingredients, thereby affecting the stoichiometric ratio of the reaction.

[0041] Among them, the ammonium sulfate is ground to refine its particle size to 100-200 mesh. Fine-particle ammonium sulfate can dissolve faster in the subsequent reaction, mix more evenly with the aluminum sulfate solution, accelerate the reaction process, ensure the synchronization of the reaction, and reduce the generation of by-products caused by uneven concentration of local reactants.

[0042] In addition, ammonium sulfate is purified by recrystallization. Ammonium sulfate is dissolved in hot water at 70-80°C to saturation, and then slowly cooled to 10-15°C to leave impurities in the mother liquor. High-purity ammonium sulfate crystals are obtained by filtration to further ensure the quality of the raw materials.

[0043] Step S3, according to the chemical reaction equation, aluminum sulfate and ammonium sulfate are prepared at a molar ratio of 1:1, which is expressed as:

[0044] Al2(SO4)3+(NH4)2SO4+24H2O=2[NH4Al(SO4)2·12H2O];

[0045] This technical solution can be appropriately adjusted in actual operation according to the specific requirements of the product and the reaction conditions. Specifically, if the aluminum content in the obtained ammonium aluminum sulfate product is expected to be slightly higher, the amount of aluminum sulfate can be appropriately increased.

[0046] Step S4, adding the prepared aluminum sulfate solution and ammonium sulfate solution into the reactor, and accurately controlling the temperature of the reaction solution at 60-70° C., and monitoring the pH value of the reaction solution in real time. When the pH value deviates from 9.5, automatically adding dilute ammonia water, the concentration of which is 1-2 mol / L for adjustment;

[0047] This technical solution uses a high-precision temperature control system to accurately control the temperature of the reaction solution at 60-70°C. Using a PID control algorithm and equipped with a platinum resistance temperature sensor, the temperature error is controlled within ±0.5°C. The stable temperature environment ensures a stable reaction rate and is conducive to the orderly formation of ammonium aluminum sulfate crystal nuclei.

[0048] In addition, specifically, an online pH monitoring and automatic alkali addition adjustment device is used to monitor the pH value of the reaction solution in real time. When the pH value deviates from 9.5, dilute ammonia water is automatically added with a concentration of 1 to 2 mol / L for adjustment. The alkali addition speed is dynamically adjusted according to the pH change rate to prevent excessive pH fluctuations from causing side reactions, such as the formation of aluminum hydroxide precipitation, to ensure that the reaction proceeds as expected.

[0049] Additionally, the following steps are included:

[0050] Step S401, stirring the reaction system, using an anchor stirrer with variable frequency speed regulation, running at a high speed of 400-500r / min at the initial stage of the reaction, so that the aluminum sulfate solution and ammonium sulfate are quickly mixed and evenly, shortening the diffusion time of the reactants. As the reaction proceeds, when a small amount of ammonium aluminum sulfate crystal nuclei are observed to appear, the stirring speed is adjusted to 200-300r / min to avoid strong stirring to destroy the crystal nuclei and promote crystal growth.

[0051] Step S402, adding a small amount of seed crystals (about 0.5% to 1% of the total mass of the system) to the reaction system, wherein the seed crystals are selected from ammonium aluminum sulfate crystals with uniform particle size and high purity. The introduction of seed crystals provides a growth template for the crystallization of ammonium aluminum sulfate, reduces the energy barrier required for nucleation, accelerates the crystallization process, and improves the product yield.

[0052] Specifically, the reaction time is 2 to 3 hours. Within this time period, the reaction is basically completed, so that aluminum sulfate and ammonium sulfate fully react to generate ammonium aluminum sulfate.

[0053] Step S5, performing crystallization separation and purification, which includes: after the reaction is completed, slowly cooling the reaction solution to room temperature to allow ammonium aluminum sulfate to crystallize, and washing the separated ammonium aluminum sulfate crystals with a small amount of cold water to remove impurities adsorbed on the crystal surface.

[0054] Specifically, for the above-mentioned crystallization separation, after the reaction is completed, the reaction solution is slowly cooled to room temperature to allow ammonium aluminum sulfate to crystallize out.

[0055] The cooling rate should not be too fast, otherwise the crystal particles may be too small, which is not conducive to subsequent filtration and separation. The cooling rate is controlled at 1-2 °C / min. When a large number of crystals are precipitated, vacuum filtration or centrifugal separation can be used to separate the crystals from the mother liquor.

[0056] Specifically, a Buchner funnel is used for vacuum filtration to collect the ammonium aluminum sulfate crystals on filter paper, and the mother liquor can be recycled.

[0057] In addition, for the above purification, washing and drying are used: the separated ammonium aluminum sulfate crystals are washed with a small amount of cold water to remove impurities adsorbed on the surface of the crystals. The washing times are 2 to 3 times, and the amount of washing liquid used each time should not be too much to avoid product loss. The washed crystals are placed in a drying oven for drying. The drying temperature can be controlled at 60 to 80°C and the drying time is 4 to 6 hours until the water content of the crystals reaches the product standard requirements to obtain a pure ammonium aluminum sulfate product.

[0058] In summary, with the help of the above technical solution of the present invention, the following effects can be achieved:

[0059] The invention pre-filters the waste catalyst tail water to remove solid impurities, and uses ion exchange resin to further remove the trace heavy metal ions remaining in the waste catalyst tail water, and concentrates the filtered tail water, and selects the tail water with a purity greater than 98% as the ammonium sulfate raw material, and grinds the ammonium sulfate to refine the particle size to 100-200 meshes, and recrystallizes and purifies the ammonium sulfate, and filters to obtain high-purity ammonium sulfate crystals, and at the same time, adds the prepared aluminum sulfate solution and ammonium sulfate solution to the reactor, and accurately controls the temperature of the reaction solution at 60-70°C, and monitors the pH value of the reaction solution in real time, and when the pH value deviates from 9.5, automatically drips dilute ammonia water, and adjusts the concentration by 1-2 mol / L, and after the reaction is completed, slowly cools the reaction solution to room temperature. The temperature is increased to make the ammonium aluminum sulfate crystallize, and the separated ammonium aluminum sulfate crystals are washed with a small amount of cold water to remove impurities adsorbed on the surface of the crystals, so as to achieve effective utilization of aluminum sulfate in the waste catalyst tail water and convert it into ammonium aluminum sulfate, which not only improves the utilization rate of valuable elements, but also has good chemical stability of the ammonium aluminum sulfate product, can maintain its chemical properties during storage and use, and plays a reliable role in industrial applications, avoiding the waste of aluminum sulfate resources. At the same time, it turns waste into treasure and reduces costs. Compared with directly extracting aluminum from raw materials such as ores to prepare ammonium aluminum sulfate, the use of waste catalyst tail water as raw material greatly reduces the production cost; in addition, in the treatment process of waste catalyst tail water, the content of heavy metals in the tail water can be effectively reduced. When preparing ammonium aluminum sulfate, some heavy metals will be removed during precipitation and filtration, so that the heavy metal pollution index of the final discharged wastewater is reduced, reducing the harm to the water environment.

[0060] In addition, the present invention achieves the goal of obtaining a high-purity ammonium aluminum sulfate product by precisely controlling the temperature of the reaction solution, monitoring the pH value of the reaction solution in real time, and automatically adding dilute ammonia water for adjustment. The ammonium aluminum sulfate crystals grow more completely, reduce the inclusion of impurities, and improve the purity of the product.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. After considering the disclosure of the specification and the examples, those skilled in the art will easily think of other embodiments of the present disclosure. This application is intended to cover any modification, use or adaptive change of the present disclosure, which follows the principle of the present disclosure and includes common knowledge or customary technical means in the technical field that are not disclosed in the present disclosure. The specification and the examples are only regarded as exemplary, and the true scope and spirit of the present disclosure are indicated by the claims.

[0062] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water, characterized in that: The following steps are involved: The waste catalyst tail water is filtered in advance to remove solid impurities, and ion exchange resin is used to further remove the trace heavy metal ions remaining in the waste catalyst tail water, and the filtered tail water is concentrated; The ammonium sulfate raw material with a purity greater than 98% is selected, and the ammonium sulfate is ground to a particle size of 100 to 200 meshes, and the ammonium sulfate is recrystallized and purified, and filtered to obtain high-purity ammonium sulfate crystals; According to the chemical reaction equation, aluminum sulfate and ammonium sulfate are mixed at a molar ratio of 1:1, expressed as: Al2(SO4)3+(NH4)2SO4+24H2O=2[NH4Al(SO4)2·12H2O]; Add the prepared aluminum sulfate solution and ammonium sulfate solution into the reactor, and precisely control the temperature of the reaction solution at 60-70°C, and monitor the pH value of the reaction solution in real time. When the pH value deviates from 9.5, automatically add dilute ammonia water with a concentration of 1-2 mol / L for adjustment; Carry out crystal separation and purification, which includes: After the reaction is completed, the reaction solution is slowly cooled to room temperature to allow ammonium aluminum sulfate to crystallize, and the separated ammonium aluminum sulfate crystals are washed with a small amount of cold water to remove impurities adsorbed on the crystal surface.

2. The method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to claim 1, characterized in that: The method of using ion exchange resin to further remove trace heavy metal ions remaining in the waste catalyst tail water includes: using a strong acid cation exchange resin to allow the tail water to pass through a resin column at a flow rate of 5 to 10 mL / min to adsorb heavy metal ions and improve the purity of the raw materials.

3. The method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to claim 1, characterized in that: The method of recrystallizing and purifying ammonium sulfate comprises the following steps: Dissolve ammonium sulfate in hot water at 70-80°C until saturated; Slowly cool to 10-15°C to keep the impurities in the mother liquor; Filtration yields high-purity ammonium sulfate crystals.

4. The method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to claim 1, characterized in that: The step of adding the prepared aluminum sulfate solution and ammonium sulfate solution into the reactor also includes the following steps: The reaction system is stirred, and seed crystals are added into the reaction system, wherein the seed crystals account for 0.5% to 1% of the total mass of the system, and the reaction time is 2 to 3 hours.

5. The method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to claim 4, characterized in that: The stirring of the reaction system comprises the following steps: Use an anchor-type agitator with variable frequency speed regulation, and run it at a high speed of 400-500r / min at the initial stage of the reaction to quickly mix the aluminum sulfate solution and ammonium sulfate evenly; When a small amount of ammonium aluminum sulfate crystal nuclei are observed, the stirring speed is adjusted to 200-300 r / min.

6. The method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to claim 1, characterized in that: The crystallization separation comprises: controlling the cooling speed to be 1-2°C / min, and after the crystals are precipitated, separating the crystals from the mother liquor by vacuum filtration or centrifugal separation.

7. The method for preparing ammonium aluminum sulfate by converting aluminum sulfate from waste catalyst tail water according to claim 6, characterized in that: The purification comprises: washing the separated ammonium aluminum sulfate crystals with cold water for 2 to 3 times, and placing the washed crystals in a drying oven for drying at a temperature of 60 to 80° C. for 4 to 6 hours.

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