Dry processing method for aluminum dross ash

Abstract

To develop a simple and efficient method of treating aluminum dross ash.SOLUTION: There is provided a dry treatment method of aluminum dross ash, including a step of contacting aluminum dross ash including aluminum nitride with steam to produce ammonia.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for dry processing of aluminum dross (aluminum dross) ash, and further to a method for producing high-concentration ammonia using the dry processing of aluminum dross ash. [Background technology]

[0002] In the process of manufacturing aluminum products, aluminum bullion and scrap are melted in a melting furnace. The slag produced during this process, including oxygen compounds on the surface of the molten metal and nitrogen compounds produced by reaction with air, is called aluminum dross. Usable aluminum components remain in the aluminum dross, and approximately 40% of the aluminum components are recovered using a squeezing machine or other equipment.

[0003] Aluminum dross ash is a by-product of extracting metallic aluminum from aluminum dross, and because it contains little aluminum, it is disposed of as industrial waste. However, aluminum nitride contained in this aluminum dross ash reacts with water to generate ammonia gas, so aluminum dross ash discarded outdoors reacts with rainwater, etc., producing a foul odor and becoming a source of pollution.

[0004] Known methods for treating aluminum dross ash include a dry method in which the ash is oxidized and dehalogenated at high temperatures to recover aluminum oxide raw material (e.g., Patent Document 1), and a wet method in which the ash is immersed in water for treatment (e.g., Patent Documents 2 to 5, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 09-206727 [Patent Document 2] JP 2002-322519 A [Patent Document 3] JP 2002-045824 [Patent Document 4] Patent Publication No. 2020-142190 [Patent Document 5] JP 2005-177556 [Non-patent literature]

[0006] [Non-Patent Document 1] 30th Conference of the Japan Society of Material Cycles and Waste Management, Lecture manuscript 2019, C3-4, "Practical resource utilization of aluminum dross residue" Summary of the Invention [Problem to be solved by the invention]

[0007] Conventional dry methods for treating aluminum dross ash require special equipment and high energy consumption to oxidize and dehalogenate the ash at high temperatures, creating cost issues. Furthermore, wet methods for treating aluminum dross ash require long processing times and produce a low concentration of ammonia water, making recycling difficult. Therefore, there was a need to develop a simple and efficient method for treating aluminum dross ash. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive research to solve the above problems, and as a result have found that by performing dry processing using steam in aluminum dross ash processing, it is possible to oxidize the remaining aluminum nitride, remove nitrogen components, and generate ammonia at a lower temperature than conventional dry methods. Furthermore, with this method, the processing time is shorter than conventional wet methods, and the collected ammonia can be recycled at a high concentration. Furthermore, it has been found that by processing while renewing the surface of the aluminum dross ash, the nitrogen removal rate can be improved in a shorter time. Based on this finding, Thus, the present invention has been completed. That is, the gist of the present invention relates to the following.

[0009] [1] A step of contacting aluminum dross ash containing aluminum nitride with water vapor to produce ammonia; A method for dry processing of aluminum dross ash, comprising: [2] A method for producing ammonia by contacting aluminum dross ash with water vapor, characterized in that the surface of the aluminum dross ash is renewed. [1] The dry processing method for aluminum dross ash described in [1]. [3] The surface renewal of aluminum dross ash is carried out by contacting the aluminum dross ash with a surface renewal material, [2] The dry processing method for aluminum dross ash described in [2]. [4] The surface renewal material is one or more selected from glass beads, alumina balls, zirconium balls, and ceramic balls, [3] The dry processing method for aluminum dross ash described in [3]. [5] The surface renewal of aluminum dross ash is carried out by injecting gas into a container containing aluminum dross ash and a surface renewal material, and mixing and contacting the aluminum dross ash with the surface renewal material. The dry processing method for aluminum dross ash according to [3] or [4]. [6] The surface renewal of aluminum dross ash is carried out by vibrating or rotating a container containing aluminum dross ash and a surface renewal material to mix and contact the aluminum dross ash with the surface renewal material. The dry processing method for aluminum dross ash according to [3] or [4]. [7] A method characterized in that the water vapor concentration in the reaction atmosphere between aluminum dross ash and water vapor is 10 to 100 vol%. The dry processing method for aluminum dross ash according to any one of [1] to [6]. [8] The temperature of the reaction atmosphere between aluminum dross ash and water vapor is 100 to 200 °C. characterized by: The dry processing method for aluminum dross ash according to any one of [1] to [7]. [9] A step of contacting aluminum dross ash containing aluminum nitride with water vapor to produce ammonia; A method for producing ammonia, comprising:

[10] further collecting ammonia; The method for producing ammonia according to [9], comprising:

[11] Collecting ammonia as ammonia gas or aqueous ammonia;

[10] The method for producing ammonia according to

[10] . [Effects of the Invention]

[0010] According to the aluminum dross ash treatment method of the present invention, treatment can be performed at low temperatures using a small amount of steam and aluminum dross ash, so treatment can be performed without the need for special equipment or high energy. Furthermore, the treatment time is short, and the extracted ammonia can be recycled at a high concentration. Furthermore, by treating the aluminum dross ash while renewing its surface, treatment can be performed in a shorter time, and the nitrogen removal rate can also be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of one form of aluminum dross ash treatment apparatus used in the method of the present invention. [Figure 2] FIG. 2 is a graph showing the nitrogen removal rate from aluminum dross ash by wet treatment in Examples and Comparative Examples. [Figure 3] FIG. 3 is a graph showing the nitrogen removal rate from aluminum dross ash by dry treatment in Examples with different reaction temperatures. [Figure 4] FIG. 4 is a graph showing the nitrogen removal rate from aluminum dross ash by treatment without surface renewal in Examples and Comparative Examples with different blending amounts of surface renewal material. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below. <Dry processing method for aluminum dross ash> One aspect of the present invention is a method for producing ammonia by contacting aluminum dross ash containing aluminum nitride with water vapor; The present invention relates to a dry processing method for aluminum dross ash (hereinafter, sometimes referred to as the "processing method of the present invention"), which includes the steps of:

[0013] Aluminum nitride in aluminum dross ash reacts with water according to the following reaction formula: AlN + 3H2O → Al(OH)3+ NH3↑ (1)

[0014] Aluminum nitride in aluminum dross ash treated as industrial waste reacts readily with moisture in the air to produce harmful ammonia. Therefore, it is necessary to remove nitrogen from the aluminum dross and stabilize it (to render it harmless). Conventional stabilization methods include wet treatment, which separates the ash into a solid and treated water (ammonia water), and dry treatment, which involves oxidation and dehalogenation at high temperatures. Dry treatment has drawbacks, such as the need for specialized equipment for high-temperature oxidation and dehalogenation and the large energy consumption. Wet treatment is effective for large-scale processing and low cost, and is therefore the mainstream stabilization method. However, it has drawbacks, such as long processing times and the need for large processing equipment. The most significant drawback is the generation of low-concentration ammonia wastewater, which has little utility value. This necessitates treatment of the ammonia wastewater itself.

[0015] The treatment method of the present invention is a dry treatment using low-temperature steam, and by using steam, the ammonia produced is recovered as a gas. Furthermore, by carrying out the treatment in a fluidized state of the aluminum dross ash, the reaction occurs more easily, enabling treatment to be completed in a short period of time. The use of low-temperature steam and the short treatment period are expected to reduce the costs required for aluminum dross treatment and improve treatment efficiency. Furthermore, after recovering the ammonia as a gas, it can be converted into high-concentration ammonia gas, which can then be converted into hydrogen using a catalyst, potentially enabling reuse as a new energy source. This may provide a new way to utilize the ammonia after treatment.

[0016] Another aspect of the present invention is a process for producing ammonia by contacting aluminum dross ash containing aluminum nitride with water vapor. The present invention relates to a method for removing nitrogen from aluminum dross ash, comprising:

[0017] In yet another embodiment, a step of contacting aluminum dross ash containing aluminum nitride with water vapor to generate ammonia; The present invention relates to a method for producing ammonia from aluminum dross ash, comprising:

[0018] In yet another embodiment, a step of contacting aluminum dross ash containing aluminum nitride with water vapor to generate ammonia; The present invention relates to a method for extracting ammonia from aluminum dross ash, comprising:

[0019] <Aluminum dross ash> Aluminum dross ash is a by-product of extracting metallic aluminum from aluminum dross, which is the slag produced by oxygen compounds generated when aluminum is melted and nitrogen compounds generated by reacting with air. Generally, the aluminum dross ash is mainly composed of an oxygen compound of aluminum, and also contains metallic aluminum, a nitrogen compound of aluminum, etc. The nitrogen compound of aluminum is a compound containing aluminum and nitrogen, which generates ammonia upon contact with water, and includes, for example, aluminum nitride. The aluminum dross ash used in the present invention is not particularly limited as long as it contains at least aluminum nitride.

[0020] The component composition ratio of the aluminum dross ash is not particularly limited. For example, the aluminum dross ash may be the above-mentioned by-product itself, or may be a processed by-product. For example, the processed product may be a composition in which the content of a desired component (aluminum nitride, metallic aluminum, aluminum oxide, etc.) in the aluminum dross ash has been adjusted.

[0021] The form of the aluminum dross ash is not particularly limited and may be, for example, particles. The particle size is not particularly limited, but small particles are preferable from the viewpoints of flowability, contactability, etc. The aluminum dross ash may be pulverized to an appropriate particle size using a pulverizer such as a ball mill before use in the reaction. For example, the particle size of the aluminum dross ash particles may be about 10 to 1,000 μm.

[0022] The aluminum dross ash may be contacted with steam in the form of a fixed bed or a fluidized bed. From the viewpoint of contactability, a fluidized bed is preferable. A fluidizing agent may be added to improve fluidity. The fluidizing agent is not particularly limited as long as it does not affect the reaction, and known fluidizing agents can be used. For example, silica sand can be used.

[0023] For example, in one embodiment, a gas containing water vapor is blown into a container containing aluminum dross ash from below, causing the aluminum dross ash filled in the container to rise. During this process, the aluminum dross ash is stirred and mixed, forming a fluidized bed and coming into contact with water vapor. The water vapor-containing gas is not particularly limited as long as it does not affect the reaction, and examples of the gas that can be used include nitrogen gas and air. The gas flow rate can be set appropriately depending on the materials used, the desired reaction rate, and the like, and is not limited.

[0024] In another embodiment, a container containing aluminum dross ash is vibrated or rotated. During this process, the aluminum dross ash is stirred and mixed, forming a fluidized bed, and contacted with water vapor. The device for providing the vibration or rotation is not particularly limited, and known devices can be used. The amount of vibration or rotation, etc., can be appropriately set depending on the material used, the desired reaction rate, etc., and is not limited.

[0025] <Water vapor> In the treatment method of the present invention, aluminum dross ash is brought into contact with water vapor. The water vapor is not particularly limited, and for example, water vapor generated by evaporating water using an evaporator or the like can be used. The water vapor concentration can be appropriately set depending on the materials used, the desired reaction rate, etc., and is not limited, but may be, for example, 10 to 100 vol%, 30 to 60 vol%, or 40 to 50 vol% in the reaction atmosphere. From the viewpoint of reaction efficiency, etc., the concentration is preferably 40 to 50 vol%, and more preferably around 40 vol%.

[0026] In this specification, the term "water" is not particularly limited as long as it does not have a negative effect on the reaction, and may be water in which an electrolyte is dissolved or pure water. The water may be, for example, ion-exchanged water, pure water, or the like, or may be prepared using them.

[0027] In the treatment method of the present invention, water vapor may be supplied to the vessel as a mixed gas with a gas other than water vapor (a gas containing water vapor). The gas other than water vapor is not particularly limited as long as it does not affect the reaction, and for example, nitrogen gas, air, etc. can be used. . In the treatment method of the present invention, the amount of water vapor or a gas containing water vapor passed through the vessel can be appropriately set depending on the material used, the target reaction rate, etc., and is not limited thereto. For example, the superficial velocity is 0.01 to 0.1 m / s, 0.012 to 0.050 m / s, or 0.015 to 0.030 m / s. From the viewpoint of reaction efficiency and the like, it is preferably 0.015 to 0.030 m / s.

[0028] Furthermore, a further aspect of the present invention is characterized in that in the treatment method of the present invention, the surface of the aluminum dross ash is renewed in the step of contacting the aluminum dross ash with steam to produce ammonia.

[0029] As will be described later in the Examples, when aluminum dross ash reacts with water vapor, protective films such as oxide films and hydroxide films are formed on the surface of the aluminum dross ash particles over time, inhibiting the reaction of aluminum nitride. It was confirmed that the reaction was improved and continued by renewing the surface of the aluminum dross ash particles. That is, in the treatment method of the present invention, the surface of the aluminum dross ash is renewed, thereby improving the reactivity and achieving continuous reactivity.

[0030] The surface renewal of aluminum dross ash is not particularly limited, and can be carried out, for example, by contacting the aluminum dross ash with a surface renewal material. The surface renewal material is not particularly limited as long as it does not have a negative effect on the reaction, and known materials can be used. For example, one or more materials selected from glass beads, alumina balls, zirconium balls, and ceramic balls can be used, and alumina balls are preferred from the viewpoints of improving reactivity and cost. Commercially available surface renewal materials can be used. The amount of surface renewal material used can be set appropriately depending on the material used, the desired reaction rate, etc., and is not limited thereto. For example, the mass ratio of surface renewal material to aluminum dross ash may be 0.1:1 to 5:1, or 0.3:1 to 2:1.

[0031] The contact between the aluminum dross ash and the surface renewal material can be promoted by injecting gas into a container containing the aluminum dross ash and the surface renewal material, or by vibrating or rotating the container.

[0032] The particle size of the surface renewal material can be appropriately set depending on the material used, the target reaction rate, etc., and is not limited thereto. For example, F70 (particle size 250 to 180 μm) and F80 ( Examples include those with a particle size of 212 to 150 μm.

[0033] The temperature of the reaction system in which the aluminum dross ash is brought into contact with water vapor can be appropriately set depending on the materials used, the desired reaction rate, etc., and is not limited thereto. For example, the reaction atmosphere may be at 100 to 300°C, 110 to 200°C, 130 to 170°C, or 140 to 160°C. From the viewpoint of reaction efficiency, the temperature is preferably 140 to 160°C, and more preferably around 150°C. The treatment method of the present invention allows treatment at a relatively low temperature compared to conventional dry methods, and is advantageous in terms of simplicity and cost.

[0034] The end point of the treatment method of the present invention can be appropriately determined by achieving a target nitrogen removal rate from the aluminum dross ash, and this can be confirmed by analyzing the composition of the aluminum dross ash. The nitrogen removal rate from aluminum dross ash can be calculated by the method described later in the Examples. The nitrogen removal rate from aluminum dross ash by the treatment method of the present invention varies depending on the materials used, reaction conditions, etc., and is not limited, but for example, after 5 hours of reaction, the nitrogen removal rate is 10% or more, 20% or more, 30% or more, 40% or more, or 45% or more.

[0035] By separating the aluminum dross ash after the dry treatment of the present invention, the treated aluminum dross Ash is obtained. The treatment method of the present invention may include such a separation operation as needed. In addition, the recovered ammonia may also include an operation such as purification as needed. Separation, purification, etc. can be performed based on conventional methods.

[0036] <Ammonia manufacturing method> Another aspect of the present invention relates to a method for producing ammonia (hereinafter, may be referred to as the "production method of the present invention"), which includes a step of bringing aluminum dross ash containing aluminum nitride into contact with water vapor to produce ammonia.

[0037] In the manufacturing method of the present invention, aluminum dross ash is dry-treated with water vapor to oxidize the remaining aluminum nitride and remove nitrogen components, thereby producing ammonia. That is, ammonia can be produced from aluminum dross ash. Compared to conventional wet methods, the processing method of the present invention allows for shorter processing times and allows for the extraction of highly concentrated ammonia, making it advantageous in terms of efficiency, cost, etc. The production method of the present invention may further include a step of collecting ammonia.

[0038] The produced ammonia can usually be collected as ammonia water by dissolving the gas generated by the dry treatment in water; for example, the gas can be taken out of the system and recovered through a tube connected from the reaction tube and having an opening in the water of a recovery container. Furthermore, depending on the conditions in the system, the produced ammonia can also be recovered as a gas; for example, it can be taken out of the system as ammonia gas and recovered through a tube connected from the reaction tube and having an opening in the recovery container, or through a tube connected from the space above the water surface of the recovery container and having an opening in a gas bag. The method for recovering ammonia water or ammonia gas is not particularly limited, and for example, an existing method can be used.

[0039] The matters explained above in relation to the processing method of the present invention are all applicable to the explanation of the manufacturing method of the present invention.

[0040] <Aluminum dross ash treatment equipment> One embodiment of the treatment device used in the treatment method of the present invention is an aluminum dross ash treatment device having at least a container capable of holding aluminum dross ash containing aluminum nitride and a gas supply device for supplying water vapor to the container.

[0041] Each component of the processing device will be described below. ≪Container≫ The container is not particularly limited as long as it can accommodate aluminum dross ash and has sufficient chemical stability and mechanical strength to carry out the dry treatment of the aluminum dross ash. The shape of the container is also not particularly limited.

[0042] <Gas supply device> The gas supply device is not particularly limited as long as it can supply water vapor to the container. The gas supply device may be composed of, for example, a water vapor generator and a gas supply member that supplies gas into the container.

[0043] The water vapor generator is a device for generating water vapor, and may be a known evaporator or the like. The gas supply member is not particularly limited as long as it has sufficient resistance to water vapor and can supply water vapor so as to bring the aluminum dross ash into sufficient contact with the water vapor. For example, the gas supply member may be a pump, a gas supply pipe, etc. In addition, when a gas other than water vapor is introduced into the container together with water vapor, the gas supply device , a pump, a gas cylinder, etc., and a gas supply member for supplying gas into the container.

[0044] <Other configurations> The processing device may further include components other than the container and gas supply device described above, as long as the effects of the present invention are achieved. Examples of such components include a collection container, a gas bag, a temperature control device, a sensor, and a vibration or rotation device.

[0045] The recovery vessel is a device for recovering the gas generated or the unreacted gas in the vessel. The recovery vessel may include, for example, a pipe connected to the vessel, a gas recovery vessel, and an aqueous medium such as water for gas recovery. The gas bag is a device for collecting gas generated or unreacted gas in a container, or gas delivered from a collection container. There are no particular limitations on the gas bag as long as it can accommodate these gases.

[0046] The temperature control device is, for example, a device for controlling the temperature of the reaction atmosphere inside the container. The temperature control device can be appropriately selected from known temperature control devices depending on the shape of the container. Examples include a ribbon heater and a heat insulator disposed on the outer circumferential surface of the container.

[0047] A sensor is a device for detecting the state of the reaction system in a vessel. There may be one or more types of sensors. Examples of sensors include a thermometer for detecting the temperature of the reaction atmosphere in the vessel, a hygrometer for detecting the water vapor concentration in the reaction atmosphere in the vessel, etc.

[0048] The vibrating or rotating device is a device for stirring the aluminum dross ash (or the aluminum dross ash and the surface renewal material, if such a material is included) in the container. Any known device can be used as the vibrating or rotating device.

[0049] The matters explained in the processing method of the present invention and the manufacturing method of the present invention are all applicable to the processing apparatus.

[0050] <<Specific Embodiments of Processing Device>> One form of processing apparatus used in the processing method of the present invention will be described with reference to FIG. 1, but the present invention is not limited to this form.

[0051] As shown in FIG. 1, the processing apparatus includes a reaction tube, a gas supply pipe, an evaporator, a pump, a gas cylinder, a collection container, and a gas bag.

[0052] Here, the reaction tube is a glass tube and is an example of the container.

[0053] The gas supply pipe is fixed to the reaction tube and connected below the aluminum dross ash in the reaction tube. The evaporator is connected to the gas supply pipe and generates water vapor. The pump is connected to the evaporator and quantitatively supplies water vapor to the reaction tube via the evaporator and the gas supply pipe. The gas cylinder is connected to the evaporator and quantitatively supplies gas containing water vapor to the reaction tube via the evaporator and the gas supply pipe. The gas supply pipe, the vaporizer, the pump, and the gas cylinder are examples of the gas supply device.

[0054] Here, the recovery vessel is a glass flask. The recovery vessel is connected to the gas phase in the reaction tube by a tube having an opening in the water of the recovery vessel. The gas bag is connected to the space above the water surface of the recovery vessel by a tube having an opening in the gas bag.

[0055] For example, the dry treatment of aluminum dross ash of the present invention is carried out by placing aluminum dross ash in a reaction tube and supplying a gas containing water vapor to the reaction tube, thereby removing nitrogen components from aluminum nitride in the aluminum dross ash. [Example]

[0056] The present invention will be specifically described below with reference to examples, but these are merely examples of the present invention and the scope of the present invention is not limited to these examples.

[0057] (Preparation of aluminum dross ash) Aluminum dross ash provided by an aluminum manufacturer was used in the experiment. The aluminum content of the aluminum dross ash used was 68.1%, and the nitrogen content was 4.18%. The aluminum content was measured using an energy dispersive X-ray fluorescence analyzer (XRF: EDX-7000; Shimadzu Corporation). The nitrogen content was measured by the following method.

[0058] (Preparation of silica sand and alumina) The fluidization material is silica sand (particle size 106-177 μm), and the surface renewal material is alumina (particle size 180 ~250 μm) was used.

[0059] (Determination of nitrogen in aluminum dross ash) ·method Preparation of reagents, preparation of aluminum dross ash decomposition samples, ammonia recovery, and ammonia quantification are performed.

[0060] Preparation of reagents Hydrochloric acid (1+1) Mix hydrochloric acid and ion-exchanged water in a 1:1 ratio to prepare 6 mol / L hydrochloric acid. Hydrogen peroxide (1+9) Prepare by mixing hydrogen peroxide and ion-exchanged water in a ratio of 1:9. 0.5 mol / L (F=1.000) sulfuric acid standard solution If you have purchased and prepared standardized reagents and are using them several months after purchase, standardize the sulfate ions in the sulfuric acid standard solution using anion chromatography. 12.5 mol / L sodium hydroxide solution Take 15 g of sodium hydroxide and dilute to 30 mL with ion-exchanged water. 0.2 mol / L sodium hydroxide standard solution (1) Take 16 mL of the supernatant of the 12.5 mol / L sodium hydroxide solution and add ion-exchanged water to make 1 L. (2) Prepare 20 mL of a 5-fold dilution of the 0.5 mol / L (F=1.000) sulfuric acid standard solution. (3) Add 3 drops of BTB solution to the solution in (2) and perform neutralization titration with 0.2 mol / L sodium hydroxide solution. To target. ·BTB solution Prepare what is prepared.

[0061] Preparation of aluminum dross ash decomposition samples (1) Weigh out 2 g of aluminum dross ash that has been crushed for 2 hours using a ball mill and place it in a beaker. put in. (2) Cover the beaker with a watch glass and add 30 mL of hydrochloric acid (1+1) little by little. (3) After the reaction has calmed down, add 10 mL of hydrogen peroxide (1+9) little by little. (4) Heat to completely decompose the soluble matter and then cool to room temperature. (5) Wash the underside of the watch glass with ion-exchanged water and pour the washings into a beaker.

[0062] Ammonia recovery (1) Assemble the semi-micro Kjeldahl nitrogen distillation apparatus glass set. (2) Place the aluminum dross ash decomposition sample in a Kjeldahl flask and set it in place. (3) Prepare two Erlenmeyer flasks as collection containers, each filled with 60 mL of ion-exchanged water, and place the first Erlenmeyer flask so that the distillation outlet of the condenser is immersed in the solution in the flask. (4) Distill for about an hour. (5) After the distillation is completed, separate the distillation outlet of the condenser from the distillate and release the pinchcock.

[0063] Ammonia determination Analysis using an ammonia quantitative analyzer AT-2000 (manufactured by Central Scientific Co., Ltd.) (1) Take a certain amount of the distillate and dilute it 10 times with ultrapure water. (2) Analyze the ammonia concentration in the distillate in a measurement range of 0 to 200.0 mg / L (sample volume 0.1 mL). (3) Calculate the amount of ammonia recovered from the analysis results and calculate the nitrogen content in the aluminum dross ash. do.

[0064] The nitrogen content Nc is expressed by the following formula, where M1 is the amount of ammonia (mass) in the distillate and M2 is the amount of aluminum dross ash (mass).

[0065] Nc(%)={M1×(14.01 / 17.03) / M2}×100

[0066] (GC-BID analysis of ammonia) Equipment: Gas chromatograph equipped with a dielectric barrier discharge ionization detector (GC-BID: Nexis GC-2030; Shimadzu Corporation) Column: Rtx-Wax; manufactured by RESTEK ·Analysis conditions Sample injection volume: 1.0 μL Split ratio: 10 Column oven temperature: 80 °C Temperature Program: 80°C → (3°C / min) 90°C (hold for 1 min) → (40°C / min) 200°C (hold for 1 min)

[0067] (Experimental equipment) Dry processing of aluminum dross ash was carried out using a processing device such as that shown in Figure 1. Ion-exchange water flowing from a syringe pump was controlled by software and turned into steam in an evaporator. Steam and nitrogen were flowed from below onto the aluminum dross ash in the reaction tube, fluidizing it and causing it to react. The steam flowed into the liquid (recovery liquid) used to recover ammonia in the recovery vessel, and ammonia was recovered. Figure 1 shows three recovery vessels, with a gas bag at the latter stage, but it was found that most of the ammonia was recovered in the first recovery vessel. For this reason, most experiments used only one recovery vessel and did not use a gas bag.

[0068] <Comparison with wet processing> Example 1 1.0 g of aluminum dross ash and 0.3 g of silica sand were placed in a reaction tube. Ion-exchanged water flowing from a syringe pump was converted into steam using an evaporator. Nitrogen gas (1.67 × 10) was introduced from a gas cylinder. -6 m 3 / s, and the reaction tube (cross-sectional area 1.13 × 10 -4 m 2 The aluminum dross ash was fed from below the gas supply (superficial velocity: 0.015 m / s). The loss ash becomes a fluidized bed. The amount of ion-exchanged water is adjusted so that the water vapor concentration reaches the set concentration (40 vol% The reaction tube was heated with a heater, and the temperature of the reaction atmosphere was raised to the set temperature (150 °C). Then, the dry treatment of the aluminum dross ash began. During the dry treatment The recovered liquid was then taken out and analyzed by GC-BID to measure the ammonia concentration. The amount of ammonia recovered was calculated, and the nitrogen removal rate from the aluminum dross ash by dry treatment was calculated.

[0069] The nitrogen removal rate RN up to the elapsed time was calculated as the value expressed by the following formula, where N1 is the amount of ammonia generated from the aluminum dross ash before dry treatment (theoretical value) and N2 is the amount of ammonia recovered in the dry treatment (integrated value up to the elapsed time).

[0070] RN(%)={N2 / N1}×100

[0071] (Comparative Example 1) As a comparative example, 1.0 g of aluminum dross ash was immersed in 50 mL of water (room temperature) to measure the wet During the wet treatment, the reaction solution was sampled and analyzed by GC-BID to measure the ammonia concentration. The amount of ammonia recovered was calculated, and the nitrogen removal rate from aluminum dross ash by wet treatment was calculated.

[0072] <Comparison of nitrogen removal rate at different water vapor concentrations> (Examples 2 and 3) Dry treatment of aluminum dross ash was carried out in the same manner as in Example 1, except that the water vapor concentration was set to 30 vol% (Example 2) and 60 vol% (Example 3).

[0073] <Comparison of nitrogen removal rate with and without fluidization> Example 4 Dry treatment of aluminum dross ash was carried out in the same manner as in Example 1, except that the aluminum dross ash layer in the reaction tube was prevented from fluidizing and reacted with steam in the form of a fixed bed.

[0074] <Result> The results are shown in Figure 2. The graph shows the changes over time for steam treatment and wet treatment. The vertical axis represents the nitrogen removal rate [%], and the horizontal axis represents the elapsed time [h]. The reaction conditions are as shown in the graph.

[0075] Comparison of Example 1 (steam treatment (steam concentration 40 vol%)) and Comparative Example 1 (wet treatment) It was found that there was a big difference in the way the reaction progressed when aluminum dross ash was immersed in water and reacted with water vapor. When aluminum dross ash was immersed in water, the nitrogen removal rate hardly increased for up to 10 hours, but after a delay of 25 hours, the nitrogen removal rate reached approximately 8%. This means that the reaction rate is very low immediately after immersion in water. In contrast, when aluminum dross ash is reacted with steam, the nitrogen removal rate reaches 20% in 5 hours, and then reaches 40% in 25 hours. A nitrogen removal rate of over 80% was achieved. In the steam reaction, the reaction rate was high immediately after the start of the reaction, and the nitrogen removal rate continued to increase for a while afterwards. The nitrogen removal rate gradually decreased.

[0076] Possible factors behind the reaction with water vapor include the aluminum nitride already exposed on the surface of the aluminum dross powder reacting with water vapor, causing a sudden reaction, and the formation of an oxide film on the surface of the aluminum nitride over time, making it more difficult for the reaction to proceed. From the above, in terms of the reaction with aluminum dross ash, steam treatment was overwhelmingly more effective, especially immediately after the reaction started, and it was found that there is great potential for treatment in a short period of time.

[0077] Looking at reactions with water vapor as a whole, the reaction rate is highest immediately after the reaction starts, and the reaction tends to slow down as time passes. Comparing Example 2 (water vapor concentration 30 vol%), Example 1 (water vapor concentration 40 vol%), and Example 3 (water vapor concentration 60 vol%), the nitrogen removal rate was higher at 40 vol% than the others. This shows that the higher the water vapor concentration, the higher the nitrogen removal rate, and there are suitable conditions. It was found that...

[0078] The reason why the nitrogen removal rate was higher at a steam concentration of 40 vol% than at 60 vol% is thought to be the effect of the rate at which an oxide film forms on the particle surface. When the steam concentration is high, an oxide film forms on the particle surface at an early stage of the reaction, which may inhibit the reaction.

[0079] Example 1 (water vapor concentration in the fluidized state is 40 vol%) and Example 4 (solid without fluidization) When comparing the water vapor concentration of 40 vol% in the fixed bed, the reaction rate of the fixed bed was higher in the early stage of the reaction. The reaction rate increased, but as time passed, the reaction rate in the fluidized state became higher. This is thought to be because by reacting with steam in the fixed bed, the aluminum nitride in the aluminum dross ash that was already exposed came into contact with more of the water compared to when the bed was fluidized, causing a reaction. As time passed, the lack of fluidization made it difficult for the new aluminum nitride on the particle surface to react with steam, which may have led to the nitrogen removal rate remaining constant.

[0080] <Comparison of nitrogen removal rates at different reaction temperatures> (Examples 5 to 8) In Example 1, nitrogen gas was 3.34 × 10 -6 m 3 / s, the reaction temperatures were 110°C in Example 5, 150°C in Example 6, 170°C in Example 7, and 200°C in Example 8, and the reaction time was 1 hour. Other than that, the dry treatment of aluminum dross ash was carried out in the same manner as in Example 1.

[0081] <Result> The results are shown in Figure 3. The figure shows a comparison of nitrogen removal rates at different reaction temperatures. The vertical axis is the nitrogen removal rate [%], and the horizontal axis is the reaction temperature of the reaction tube [°C]. The reaction conditions were as shown in the graph. It is.

[0082] As can be seen from the graph, the nitrogen removal rate was highest when the reaction temperature was 150°C. The reaction rate peaked at 150°C, and decreased at lower or higher temperatures. The reason why the nitrogen removal rate decreases at high temperatures above 150°C is thought to be the effect of the oxide film that forms on the aluminum nitride surface. When aluminum dross ash is reacted with water vapor, it is thought that both a reaction in which ammonia is produced from aluminum nitride and an oxidation reaction of aluminum occur. When the speed of both reactions becomes higher than the reaction temperature of 150°C, Aluminum oxidation reaction>Reaction in which ammonia is produced from aluminum nitride This means that aluminum nitride is oxidized before it can react with water vapor, possibly resulting in less aluminum nitride available to react with water vapor.

[0083] <Changes and effects of particle surface renewal during steam treatment on nitrogen removal rate> Examples 9 to 11 It was found that with steam treatment, a protective film of aluminum oxide forms on the particle surface over time, which may have inhibited the reaction of aluminum nitride, and so it was thought that renewing the particle surface would improve and sustain the reaction.Therefore, we changed the silica sand added to aluminum dross ash to a high-density alumina, aiming to improve particle surface renewal, and conducted an investigation.

[0084] The experiment was carried out as follows. (1) After packing quartz wool into the bottom of the reaction tube, weigh out 1.0 g of aluminum dross ash and 0.3 g of Alumina (Example 9), 1.0 g of aluminum dross ash, 1.0 g of alumina (Example 10), and 1.0 g of aluminum dross ash, 2.0 g of alumina (Example 11) were added and mixed by shaking. (2) Fill the top of the reaction tube with quartz wool, place it in the device together with the collection container, and use a ribbon heater. It was wrapped around the outside and then covered with insulation. (3) The reaction tube and evaporator were heated to the set temperatures. (4) 40 mL of ion-exchanged water was measured and placed in the collection container, and the collection containers were connected to each other and to the reaction tube. (When the analysis was performed using three collection containers, the second and third collection containers had a combined nitrogen removal rate of several percent.) Because this was an order, experiments analyzing elapsed time were performed using one collection container.) (5) After the temperature was raised, nitrogen and water were introduced to start the reaction (superficial velocity: 0.015 m / s). (6) After the reaction was completed, the collection vessel was removed and the volume was adjusted to 50 mL with ion-exchanged water. (7) The solution was transferred to a vial and analyzed by GC-BID. (8) After the second collection vessel is installed, in order to ensure that the surface is renewed, the superficial velocity of the sample for the surface renewal is increased between 0.045 and 0.15 m / s for 5 minutes as follows: Ta. When the alumina:aluminum dross ash (mass ratio) was 1:1 and 0.3:1, the velocity was 0.075 m / s when the second installation was performed. , and from the third time onwards it was set to 0.15 m / s. When the alumina:aluminum dross ash (mass ratio) was 2:1, the speed was set to 0.045 m / s from the second time onwards. The reason for the different superficial velocities is that in the mixed layer of aluminum dross ash and alumina during the experiment, the flow behavior of the layer appeared to differ depending on the state of the layer at the time, so surface renewal was carried out at a superficial velocity that was visually judged to show similar behavior.

[0085] <Result> The results are shown in Figure 4. The figure shows a comparison of the time course of reactions without surface renewal and reactions with surface renewal by steam treatment. The vertical axis is the nitrogen removal rate [%] and the horizontal axis is the elapsed time [h]. The circle (Example 11), diamond (Example 10), and triangle (Example 9) points are the results of experiments in which the additive was alumina and time for renewal of the particle surface was set. Surface renewal (m / m=100 / 100) means that the alumina This means that the ratio of lumina to aluminum dross ash (by mass) is 1:1. The square dots represent additives. This is the result for silica sand, which is the same as the water vapor concentration of 40 vol% (Example 1) shown in Figure 2. The reaction conditions are as shown in the graph.

[0086] As can be seen from this graph, when the water vapor concentration is the same, the nitrogen removal rate is higher when the additive is alumina. This is thought to be because the density of the particles increases when silica sand is changed to alumina, which increases the collision energy with the aluminum dross ash when fluidized, improving the ability to renew the particle surface. When the alumina ratio increases from 30% to 100%, the nitrogen removal rate is higher. The increase in the alumina content is thought to be due to the improved particle surface renewal ability.

[0087] <Consideration> As described above, by performing the dry treatment of aluminum dross ash using steam according to the present invention, nitrogen components were able to be removed from residual aluminum nitride. In particular, it was found that the reaction with the aluminum dross ash immediately after the reaction started was overwhelmingly better with steam treatment than with wet treatment in which the aluminum dross ash was immersed in water. The optimum conditions for steam treatment of aluminum dross ash were lower temperatures than those for conventional dry treatment. In addition, it was found that the reaction mechanism of aluminum dross ash is thought to be greatly influenced by protective films such as oxide films and hydroxide films that are thought to be formed on the particle surface, and that surface renewal contributes to improved reactivity. In terms of the reaction with aluminum dross ash, steam treatment is overwhelmingly more effective, especially immediately after the reaction begins. The short treatment time and the favorable conditions of a relatively low reaction temperature and steam concentration make it possible to operate at low cost. Therefore, the dry treatment process, which uses low-temperature steam for a short treatment time, is considered to be highly advantageous. Further improvement in nitrogen removal rate is expected through surface renewal. Furthermore, the ammonia produced can be reused as high-concentration ammonia water, and ammonia gas can be converted into hydrogen using a catalyst and reused as a new energy source. [Industrial Applicability]

[0088] The present invention is expected to popularize the treatment of aluminum dross ash and to increase industrial use because it enables the use of ammonia as a resource.

Claims

1. a step of contacting aluminum dross ash containing aluminum nitride with water vapor to generate ammonia; A method for dry processing of aluminum dross ash, comprising: The water vapor concentration in the reaction atmosphere between aluminum dross ash and water vapor is 40 to 50 vol%. and the temperature of the reaction atmosphere is 100 to 200°C.

2. The method is characterized in that the surface of the aluminum dross ash is renewed in the step of contacting the aluminum dross ash with water vapor to generate ammonia. The dry processing method for aluminum dross ash according to claim 1.

3. The surface renewal of aluminum dross ash is carried out by contacting the aluminum dross ash with a surface renewal material. The dry processing method for aluminum dross ash according to claim 2.

4. The surface renewal material is one or more selected from glass beads, alumina balls, zirconium balls, and ceramic balls. The dry processing method for aluminum dross ash according to claim 3.

5. The surface renewal of aluminum dross ash is carried out by injecting gas into a container containing aluminum dross ash and a surface renewal material, and mixing and contacting the aluminum dross ash with the surface renewal material. The method for dry processing of aluminum dross ash according to claim 3 or 4.

6. The surface renewal of the aluminum dross ash is carried out by vibrating or rotating a container containing the aluminum dross ash and the surface renewal material to mix and contact the aluminum dross ash with the surface renewal material. The method for dry processing of aluminum dross ash according to claim 3 or 4.

7. a step of contacting aluminum dross ash containing aluminum nitride with water vapor to generate ammonia; A method for producing ammonia, comprising: The water vapor concentration in the reaction atmosphere between aluminum dross ash and water vapor is 40 to 50 vol%. and the temperature of the reaction atmosphere is 100 to 200°C.

8. Further, collecting ammonia; The method for producing ammonia according to claim 7, comprising:

9. Collecting ammonia as ammonia gas or aqueous ammonia; The method for producing ammonia according to claim 8.

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