Method for resource utilization of nitrogen and aluminum in secondary aluminum ash

Abstract

The invention discloses a method for resource utilization of nitrogen and aluminum in secondary aluminum ash, and belongs to the technical field of solid waste treatment, the method comprises the following steps: S1, bio-enzyme pretreatment: drying and crushing the secondary aluminum ash, mixing with a buffer solution containing a specific bio-enzyme, carrying out a stirring reaction under proper temperature and pH conditions, and carrying out solid-liquid separation; aluminum nitride and other aluminum-containing compounds are decomposed; s2, bio-enzyme catalytic hydrolysis: transferring the pretreated mixture into a hydrolysis reactor, adding bio-enzyme and adjusting conditions, performing catalytic hydrolysis on aluminum nitride and an aluminum-containing compound, and releasing nitrogen and aluminum ions; according to the method, the secondary aluminum ash is pretreated through the biological enzyme to decompose aluminum nitride and other aluminum-containing compounds, and the specificity of the biological enzyme is utilized, so that the resource recovery efficiency is improved, and the environmental pollution is reduced. The pH value and the temperature of the hydrolysate are monitored through the online pH meter and the temperature sensor, so that accurate control on the reaction process is realized.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste treatment, and specifically to a method for resource utilization of nitrogen and aluminum in secondary aluminum ash. Background Art

[0002] Secondary aluminum ash refers to the waste generated during the aluminum processing process. It is a by-product of aluminum smelting and casting. Secondary aluminum ash is mainly composed of aluminum oxide, aluminum nitride (AlN), metallic aluminum and other impurities.

[0003] Aluminum resource recovery refers to the process of converting aluminum-containing waste or by-products into useful products or raw materials, aiming to reduce resource waste and environmental pollution while increasing the recycling rate of resources. As an important metal resource, aluminum is widely used in many fields such as construction, transportation, packaging, electricity and electronics.

[0004] In the chemical leaching method, the use of strong acid or strong base for leaching will produce harmful waste gas and wastewater. In order to improve the leaching efficiency, high temperature and high pressure conditions are often required, which will increase energy consumption. At the same time, the pH and reaction conditions need to be precisely controlled, which makes the operation difficult. In the high-temperature melting method, high temperature is required to melt the secondary aluminum ash, and the energy consumption is very high. Harmful gases such as nitrogen oxides and sulfides are produced during the melting process. To this end, a method for resource utilization of nitrogen and aluminum in secondary aluminum ash is proposed.

[0005] The above information disclosed in this background technology is only used to increase the understanding of the background technology of the present invention and therefore, it may include information that does not constitute the prior art known to ordinary technicians in this field. Summary of the invention

[0006] The present invention aims to at least solve the problem in the prior art that in the chemical leaching method, the use of strong acid or strong base for leaching will produce harmful waste gas and waste water. In order to improve the leaching efficiency, high temperature and high pressure conditions are often required, which will increase energy consumption. At the same time, it is necessary to accurately control the pH and reaction conditions, which makes the operation difficult. In the high-temperature melting method, high temperature is required to melt the secondary aluminum ash, and the energy consumption is very high. One of the technical problems is that harmful gases are generated during the melting process. To this end, one purpose of the present invention is to propose a method for resource utilization of nitrogen and aluminum in secondary aluminum ash.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for resource utilization of nitrogen and aluminum in secondary aluminum ash comprises the following steps:

[0009] S1. Bio-enzyme pretreatment: The secondary aluminum ash is dried, crushed, mixed with a buffer solution containing a specific bio-enzyme, and stirred under appropriate temperature and pH conditions to decompose aluminum nitride and other aluminum-containing compounds;

[0010] S2. Enzyme-catalyzed hydrolysis: transferring the pretreated mixture to a hydrolysis reactor, adding enzymes and adjusting conditions to catalyze the hydrolysis of aluminum nitride and aluminum-containing compounds to release nitrogen and aluminum ions;

[0011] S3. Immobilized microbial conversion: Select and immobilize microorganisms that can convert nitrogen and aluminum ions, and convert the hydrolyzate into recyclable compounds through an immobilized microbial reactor;

[0012] S4. Separation and purification: Collecting ammonia-containing gas from the reactor and separating aluminum hydroxide precipitate by centrifugation, then washing, drying and heat-treating the precipitate to obtain a high-purity aluminum oxide product, while concentrating and purifying the ammonia water;

[0013] S5. Resource utilization: Use purified alumina for aluminum production or industrial applications, and use the prepared nitrogen fertilizer for agricultural production.

[0014] As a further optimization scheme of the present invention, in step S1, the specific steps are:

[0015] Collect the secondary aluminum ash generated during the aluminum processing process and ensure that it does not contain harmful substances and impurities. Use an oven to dry the secondary aluminum ash at a temperature not exceeding 80°C to remove moisture;

[0016] The dried secondary aluminum ash is crushed by a ball mill to obtain powder with uniform particle size, so that the biological enzyme can contact and react evenly.

[0017] In a reaction container, secondary aluminum ash powder is mixed with a buffer solution of a biological enzyme, wherein the pH value of the buffer solution is 5.0-7.0 and the temperature is 30-60°C.

[0018] Use a stirrer to stir the mixture so that the bio-enzyme is fully in contact with the secondary aluminum ash powder. The pretreatment process lasts for 1-4 hours. During this period, the pH value and temperature of the reaction mixture are regularly monitored and adjusted when necessary to ensure the activity of the bio-enzyme.

[0019] As a further optimization scheme of the present invention, in step S2, the specific steps are: after the mixture is transferred to the hydrolysis reactor, phosphatase is added to the reactor, and the temperature is adjusted to 40-60°C and the pH value is adjusted to 6.0-7.5, the pH value and temperature of the hydrolyzate are monitored by an online pH meter and a temperature sensor, and a constant pH value is maintained by adding acid or alkali. The hydrolysis process lasts for 2-6 hours, during which samples are taken regularly to analyze the release of nitrogen and aluminum.

[0020] As a further optimization scheme of the present invention, in step S3, Pseudomonas aeruginosa is selected as the microorganism, and polyacrylamide is selected as the carrier.

[0021] As a further optimization scheme of the present invention, in step S4, the specific steps are: pumping the hydrolyzate in the reactor into a centrifuge, the rotation speed of the centrifuge is 1000-4000r / min, the centrifugation time is 10-25min, and when drying, the drying temperature does not exceed 90°C.

[0022] As a further optimization scheme of the present invention, the biological enzymes are protease and lipase.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In the present invention, the secondary aluminum ash is pretreated by biological enzymes to decompose aluminum nitride and other aluminum-containing compounds, and the specificity of biological enzymes is utilized to improve resource recovery efficiency and reduce environmental pollution. Phosphatase is added to the hydrolysis reaction to further promote the release of nitrogen and aluminum. The pH value and temperature of the hydrolyzate are monitored by an online pH meter and a temperature sensor to achieve precise control of the reaction process.

[0025] In the present invention, Pseudomonas aeruginosa is used as a microorganism, and polyacrylamide is used as a carrier to immobilize the microorganism, and the conversion efficiency and the purity of the product are improved by using an immobilized microorganism reactor. Finally, the precipitation is separated by centrifugation to achieve efficient separation and purification.

[0026] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the method for resource utilization of nitrogen and aluminum in secondary aluminum ash. DETAILED DESCRIPTION

[0028] The following will be combined with the 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 without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1 , the present invention provides a technical solution:

[0030] Prepare the buffer solution of protease and lipase, and use the buffer solution ratio formula as follows:

[0031] C1V1+C2V2=C f V f , where C1V1 is the concentration and volume of sodium dihydrogen phosphate (NaH2PO4), C2V2 is the concentration and volume of disodium hydrogen phosphate (Na2HPO4), and C f V f is the final buffer concentration and volume.

[0032] When the pH value needs to be 5, the molar ratio is 1:2, that is, 1 mole of NaH2PO4 is mixed with 2 moles of Na2HPO4.

[0033] When the pH value needs to be 6, the molar ratio is 1:1.5, that is, 1 mole of NaH2PO4 is mixed with 1.5 moles of Na2HPO4.

[0034] When the pH value needs to be 7, the molar ratio is 1:1. The commonly used molar ratio is 1:1, that is, 1 mole of NaH2PO4 is mixed with 1 mole of Na2HPO4.

[0035] Prepare the buffer solution: First, dissolve the calculated amounts of sodium dihydrogen phosphate and disodium hydrogen phosphate in deionized water, ensuring that the pH of the solution is between 5.0 and 7.0. If the pH is high, add an appropriate amount of sodium dihydrogen phosphate; if the pH is low, add an appropriate amount of disodium hydrogen phosphate.

[0036] Monitor the pH of the buffer solution using a pH meter and make minor adjustments using dilute hydrochloric acid or sodium hydroxide solution until the desired pH is reached. Adjustments to the pH should be made slowly to avoid adverse effects on enzyme activity. After adjusting the pH, store the buffer solution in a sealed container to prevent pH changes. Finally, store the buffer solution in a refrigerator to maintain stability and activity.

[0037] Embodiment 1

[0038] A method for resource utilization of nitrogen and aluminum in secondary aluminum ash comprises the following steps:

[0039] S1. Collect the secondary aluminum ash generated during the aluminum processing process and ensure that it does not contain harmful substances and impurities. Use an oven to dry the secondary aluminum ash at a temperature not exceeding 80°C to remove moisture;

[0040] In a reaction container, the secondary aluminum ash powder is mixed with a buffer solution of protease and lipase, wherein the pH value of the buffer solution is 5.0 and the temperature is 30°C.

[0041] A stirrer was used to stir the mixture so that the bio-enzyme was fully in contact with the secondary aluminum ash powder. The pretreatment process lasted for 1 hour. During this period, the pH value and temperature of the reaction mixture were regularly monitored and adjusted when necessary to ensure the activity of the bio-enzyme.

[0042] S2. After the mixture is transferred to the hydrolysis reactor, phosphatase is added to the reactor, and the temperature is adjusted to 40°C and the pH value is adjusted to 6.0. The pH value and temperature of the hydrolyzate are monitored by an online pH meter and a temperature sensor, and a constant pH value is maintained by adding acid or alkali. The hydrolysis process lasts for 2 hours, during which samples are taken regularly to analyze the release of nitrogen and aluminum.

[0043] S3. Immobilized microbial conversion: Select and immobilize microorganisms that can convert nitrogen and aluminum ions, and convert the hydrolyzate into recyclable compounds through an immobilized microbial reactor;

[0044] Among them, Pseudomonas aeruginosa or is selected as the microorganism, and polyacrylamide is selected as the carrier.

[0045] Specifically, Pseudomonas aeruginosa is cultured under laboratory conditions, LB (Luria-Bertani) medium is selected, the medium is dissolved in deionized water, and the pH value is adjusted to a suitable range. The prepared medium is sterilized by high-pressure steam (121° C., 15-20 min) to kill bacteria and spores therein.

[0046] Take out an appropriate amount of bacterial liquid from the preserved Pseudomonas aeruginosa strain, and use a sterile pipette to inoculate the bacterial liquid into a sterilized culture medium plate or test tube, ensuring that the surface of the culture medium or the inside of the test tube is evenly coated or filled after inoculation.

[0047] Place the inoculated culture medium plate in an incubator and adjust the temperature and humidity according to the growth characteristics of Pseudomonas aeruginosa. The growth temperature of Pseudomonas aeruginosa is 37°C.

[0048] Regularly observe the size, shape, and color of the colonies on the culture medium, record the growth of the colonies, and when the colonies grow to an appropriate stage, scrape them off the culture medium, dilute them with sterile water, and store them. Store them by continuous passage. Cross-link and surface modify the polyacrylamide to improve its surface activity and increase the attachment area of ​​microorganisms. Inoculate the cultured Pseudomonas aeruginosa onto the pretreated polyacrylamide carrier by coating to ensure that the microorganisms are evenly distributed on the carrier.

[0049] The immobilized microorganisms are filled into the fluidized bed reactor to ensure that the microorganisms are evenly distributed. The hydrolyzate is pumped into the reactor to contact with the immobilized microorganisms. Under the action of the microorganisms, nitrogen and aluminum ions are converted into ammonia and aluminum hydroxide. The pH value and temperature of the reactor are monitored by an online pH meter and temperature sensor, and acid or base is added when necessary to maintain a constant pH value. The reaction time is 2-6 hours.

[0050] Ammonia-containing gas is collected from the top of the reactor and converted into liquid ammonia by condensation, and aluminum hydroxide precipitate is separated from the reactor by centrifugation.

[0051] S4. Separation and purification: Collecting ammonia-containing gas from the reactor and separating aluminum hydroxide precipitate by centrifugation, then washing, drying and heat-treating the precipitate to obtain a high-purity aluminum oxide product, while concentrating and purifying the ammonia water;

[0052] Specifically, the hydrolyzate in the reactor is pumped into the centrifuge to ensure that the mixed liquid is evenly distributed. The centrifuge is started and the speed is adjusted to an appropriate value. During the centrifugation process, the aluminum hydroxide precipitate will settle to the bottom of the centrifuge tube due to its high density, while other suspensions are located in the upper layer. The centrifuge is turned off, the centrifuge tube is opened, and the precipitate is taken out to avoid bringing in the upper liquid. The upper liquid is sucked out with a pipette, and the bottom precipitate is retained. The aluminum hydroxide precipitate is washed several times to remove possible residual unreacted aluminum ions and other metal ions. Deionized water or a solution with a low ion concentration is used as the washing liquid. The washed aluminum hydroxide precipitate is dried to remove residual moisture, and the dried aluminum hydroxide precipitate is heat-treated to remove the remaining moisture and convert it into aluminum oxide.

[0053] The hydrolyzate in the reactor is pumped into a centrifuge, the rotation speed of the centrifuge is 1000 r / min, the centrifugation time is 10 min, and during drying, the drying temperature does not exceed 90°C.

[0054] S5. Resource utilization: Use purified alumina for aluminum production or industrial applications, and use the prepared nitrogen fertilizer for agricultural production.

[0055] Experimental results: The release amounts of nitrogen and aluminum were 100 mg / L and 200 mg / L respectively. The bio-enzyme pretreatment and hydrolysis steps effectively promoted the release of nitrogen and aluminum.

[0056] Embodiment 2

[0057] A method for resource utilization of nitrogen and aluminum in secondary aluminum ash comprises the following steps:

[0058] S1. Collect the secondary aluminum ash generated during the aluminum processing process and ensure that it does not contain harmful substances and impurities. Use an oven to dry the secondary aluminum ash at a temperature not exceeding 80°C to remove moisture;

[0059] In a reaction container, the secondary aluminum ash powder is mixed with a buffer solution of a biological enzyme, wherein the pH value of the buffer solution is 6.0 and the temperature is 45°C.

[0060] A stirrer was used to stir the mixture so that the bio-enzyme was fully in contact with the secondary aluminum ash powder. The pretreatment process lasted for 2.5 h. During this period, the pH value and temperature of the reaction mixture were regularly monitored and adjusted when necessary to ensure the activity of the bio-enzyme.

[0061] S2. After the mixture is transferred to the hydrolysis reactor, phosphatase is added to the reactor, and the temperature is adjusted to 55°C and the pH value is adjusted to 7. The pH value and temperature of the hydrolyzate are monitored by an online pH meter and a temperature sensor, and a constant pH value is maintained by adding acid or alkali. The hydrolysis process lasts for 4 hours, during which samples are taken regularly to analyze the release of nitrogen and aluminum.

[0062] S3. Immobilized microbial conversion: Select and immobilize microorganisms that can convert nitrogen and aluminum ions, and convert the hydrolyzate into recyclable compounds through an immobilized microbial reactor;

[0063] Among them, Pseudomonas aeruginosa or is selected as the microorganism, and polyacrylamide is selected as the carrier.

[0064] S4. Separation and purification: Collecting ammonia-containing gas from the reactor and separating aluminum hydroxide precipitate by centrifugation, then washing, drying and heat-treating the precipitate to obtain a high-purity aluminum oxide product, while concentrating and purifying the ammonia water;

[0065] The hydrolyzate in the reactor is pumped into a centrifuge, the rotation speed of the centrifuge is 2500 r / min, the centrifugation time is 15 min, and during drying, the drying temperature does not exceed 90°C.

[0066] S5. Resource utilization: Use purified alumina for aluminum production or industrial applications, and use the prepared nitrogen fertilizer for agricultural production.

[0067] Experimental results: The release of nitrogen and aluminum is 150mg / L and 250mg / L respectively. The release of nitrogen and aluminum can be further increased by adjusting the pretreatment time and hydrolysis conditions.

[0068] Embodiment 3

[0069] A method for resource utilization of nitrogen and aluminum in secondary aluminum ash comprises the following steps:

[0070] S1. Collect the secondary aluminum ash generated during the aluminum processing process and ensure that it does not contain harmful substances and impurities. Use an oven to dry the secondary aluminum ash at a temperature not exceeding 80°C to remove moisture;

[0071] In a reaction container, the secondary aluminum ash powder is mixed with a buffer solution of a biological enzyme, wherein the pH value of the buffer solution is 7.0 and the temperature is 60°C.

[0072] A stirrer was used to stir the mixture so that the bio-enzyme was fully in contact with the secondary aluminum ash powder. The pretreatment process lasted for 4 hours. During this period, the pH value and temperature of the reaction mixture were regularly monitored and adjusted when necessary to ensure the activity of the bio-enzyme.

[0073] S2. After the mixture is transferred to the hydrolysis reactor, phosphatase is added to the reactor, and the temperature is adjusted to 60°C and the pH value is adjusted to 7.5. The pH value and temperature of the hydrolyzate are monitored by an online pH meter and a temperature sensor, and a constant pH value is maintained by adding acid or alkali. The hydrolysis process lasts for 6 hours, during which samples are taken regularly to analyze the release of nitrogen and aluminum.

[0074] S3. Immobilized microbial conversion: Select and immobilize microorganisms that can convert nitrogen and aluminum ions, and convert the hydrolyzate into recyclable compounds through an immobilized microbial reactor;

[0075] Among them, Pseudomonas aeruginosa or is selected as the microorganism, and polyacrylamide is selected as the carrier.

[0076] S4. Separation and purification: Collecting ammonia-containing gas from the reactor and separating aluminum hydroxide precipitate by centrifugation, then washing, drying and heat-treating the precipitate to obtain a high-purity aluminum oxide product, while concentrating and purifying the ammonia water;

[0077] The hydrolyzate in the reactor is pumped into a centrifuge, the rotation speed of the centrifuge is 4000 r / min, the centrifugation time is 25 min, and during drying, the drying temperature does not exceed 90°C.

[0078] S5. Resource utilization: Use purified alumina for aluminum production or industrial applications, and use the prepared nitrogen fertilizer for agricultural production.

[0079] Experimental results: The release of nitrogen and aluminum was 200 mg / L and 300 mg / L respectively. The release of nitrogen and aluminum can be further increased by increasing the pretreatment time and hydrolysis time.

[0080] Comparative Example 1

[0081] Experimental conditions: Existing chemical methods were used for pretreatment and hydrolysis, using strong acids and strong bases.

[0082] Experimental results: The release of nitrogen and aluminum is low, 50mg / L and 100mg / L respectively. Traditional chemical methods are more polluting to the environment and have low efficiency.

[0083] Comparative Example 2

[0084] Experimental conditions: high temperature calcination method was used for pretreatment, followed by hydrolysis.

[0085] Experimental results: The release amounts of nitrogen and aluminum were 80 mg / L and 150 mg / L respectively. The physical method has less pollution to the environment, but has low efficiency and high energy consumption.

[0086] Parts not involved in the present invention are the same as the prior art or can be implemented by the prior art. Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for resource utilization of nitrogen and aluminum in secondary aluminum ash, characterized in that: The steps include: S1. Bio-enzyme pretreatment: The secondary aluminum ash is dried, crushed, mixed with a buffer solution containing a specific bio-enzyme, and stirred under appropriate temperature and pH conditions to decompose aluminum nitride and other aluminum-containing compounds; S2. Enzyme-catalyzed hydrolysis: transferring the pretreated mixture to a hydrolysis reactor, adding enzymes and adjusting conditions to catalyze the hydrolysis of aluminum nitride and aluminum-containing compounds to release nitrogen and aluminum ions; S3. Immobilized microbial conversion: Select and immobilize microorganisms that can convert nitrogen and aluminum ions, and convert the hydrolyzate into recyclable compounds through an immobilized microbial reactor; S4. Separation and purification: Collecting ammonia-containing gas from the reactor and separating aluminum hydroxide precipitate by centrifugation, then washing, drying and heat-treating the precipitate to obtain a high-purity aluminum oxide product, while concentrating and purifying the ammonia water; S5. Resource utilization: Use purified alumina for aluminum production or industrial applications, and use the prepared nitrogen fertilizer for agricultural production.

2. The method for resource utilization of nitrogen and aluminum in secondary aluminum ash according to claim 1, characterized in that: In step S1, the specific steps are: Collect the secondary aluminum ash generated during the aluminum processing process and ensure that it does not contain harmful substances and impurities. Use an oven to dry the secondary aluminum ash at a temperature not exceeding 80°C to remove moisture; The dried secondary aluminum ash is crushed by a ball mill to obtain a powder with uniform particle size, so that the biological enzyme can contact and react evenly; In a reaction vessel, the secondary aluminum ash powder is mixed with a buffer solution of a biological enzyme, wherein the pH value of the buffer solution is 5.0-7.0 and the temperature is 30-60°C; Use a stirrer to stir the mixture so that the bio-enzyme is fully in contact with the secondary aluminum ash powder. The pretreatment process lasts for 1-4 hours. During this period, the pH value and temperature of the reaction mixture are regularly monitored and adjusted when necessary to ensure the activity of the bio-enzyme.

3. The method for resource utilization of nitrogen and aluminum in secondary aluminum ash according to claim 1, characterized in that: In step S2, the specific steps are as follows: after the mixture is transferred to the hydrolysis reactor, phosphatase is added to the reactor, and the temperature is adjusted to 40-60°C and the pH value is adjusted to 6.0-7.

5. The pH value and temperature of the hydrolyzate are monitored by an online pH meter and a temperature sensor, and a constant pH value is maintained by adding acid or alkali. The hydrolysis process lasts for 2-6 hours, during which samples are taken regularly to analyze the release of nitrogen and aluminum.

4. The method for resource utilization of nitrogen and aluminum in secondary aluminum ash according to claim 1, characterized in that: In step S3, Pseudomonas aeruginosa or is selected as the microorganism, and polyacrylamide is selected as the carrier.

5. The method for resource utilization of nitrogen and aluminum in secondary aluminum ash according to claim 1, characterized in that: In step S4, the specific steps are: pumping the hydrolyzate in the reactor into a centrifuge, the rotation speed of the centrifuge is 1000-4000 r / min, the centrifugation time is 10-25 min, and during drying, the drying temperature does not exceed 90°C.

6. The method for resource utilization of nitrogen and aluminum in secondary aluminum ash according to claim 2, characterized in that: The biological enzymes are protease and lipase.

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