A method for harmless treatment of secondary aluminum ash combustion

Abstract

This invention relates to the field of hazardous waste treatment technology, specifically to a method for the harmless treatment of secondary aluminum ash through combustion. The specific technical solution is as follows: after grinding and sieving the secondary aluminum ash, fuel is added, the ash is compressed into tablets, and then burned in an oxygen atmosphere, thus achieving the harmless treatment of the secondary aluminum ash. This invention utilizes the combustible components (i.e., elemental aluminum, aluminum nitride, and other active components) in the secondary aluminum ash, adds a certain amount of fuel, and allows the secondary aluminum ash to burn in a high-purity oxygen environment, oxidizing the active components in the secondary aluminum ash and achieving harmlessness.

Description

Technical Field

[0001] The invention relates to the technical field of hazardous waste treatment, and in particular to a method for harmless treatment of secondary aluminum ash combustion. Background Art

[0002] Secondary aluminum ash is a hazardous waste generated after aluminum extraction from primary aluminum ash produced by electrolytic aluminum, cast aluminum or other aluminum processing industries. The general components are elemental aluminum, aluminum carbide, aluminum oxide, aluminum nitride, silicon dioxide, magnesium oxide, potassium chloride, sodium chloride and a small amount of fluoride, among which the active substances are mainly elemental aluminum, aluminum nitride and aluminum carbide. When secondary aluminum ash comes into contact with water, aluminum nitride will hydrolyze to produce ammonia, elemental aluminum will react with water to produce hydrogen, aluminum carbide will hydrolyze to produce methane, and fluoride will dissolve in water to pollute water sources, which is very harmful. Since 2021, secondary aluminum ash has been listed as a hazardous waste, which shows that the harmless treatment of secondary aluminum ash is of great significance.

[0003] The main methods for converting secondary aluminum ash into general solid waste or even into products are currently wet and pyrometallurgy, and the traditional method is wet harmless treatment. The wet harmless treatment process is long, the leaching time is long, and hydrogen, ammonia and methane will be produced during the leaching process. These gases are prone to explosion. In addition, the leaching liquid after leaching needs to be evaporated and crystallized to recover the soluble salts. It can be seen that although the wet process has low energy consumption, the equipment investment is large and the risk of explosion is relatively high, which is difficult for most small and medium-sized aluminum processing companies to bear.

[0004] The pyrometallurgical process, also known as the dry process, is to mix the secondary aluminum ash with some additives, and then place it at high temperature to oxidize the active substances. This process has high energy consumption, but the equipment investment is low. It is generally combined with resource recovery. The benefits of pyrometallurgical harmlessness alone are too low, and almost no company is willing to do it. At present, the products produced by the resource recovery of secondary aluminum ash will change with the changes in market demand, and the demand is also fluctuating, but secondary aluminum ash cannot be stored for a long time. Therefore, in general, the secondary aluminum ash is first harmlessly treated and then stored, and then related products are made according to market demand in the later stage.

[0005] Based on the above-mentioned deficiencies and needs, the present invention provides a secondary aluminum ash harmless treatment method with low energy consumption and less investment. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for harmless combustion treatment of secondary aluminum ash, which utilizes the combustible components in the secondary aluminum ash (i.e., active components such as elemental aluminum and aluminum nitride) and adds a certain amount of fuel to allow the secondary aluminum ash to burn in a high-purity oxygen environment to oxidize the active components in the secondary aluminum ash and achieve harmlessness.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] The invention discloses a method for harmless combustion treatment of secondary aluminum ash. The secondary aluminum ash is ground and screened, fuel is added, tabletted, and burned in an oxygen atmosphere to achieve harmless treatment of the secondary aluminum ash.

[0009] Preferably, the fuel is any one or more of starch, pine wood powder, glutinous rice flour, cassava flour, and charcoal powder.

[0010] Preferably, the added amount of the fuel is 5-20% of the secondary aluminum ash.

[0011] Preferably, the tabletting pressure is 1 MPa to 15 MPa.

[0012] Preferably, the purity of the oxygen is 80% to 100%.

[0013] Preferably, the secondary aluminum ash passes through a sieve of ≥100 mesh.

[0014] Preferably, in terms of mass percentage, the main components of the secondary aluminum ash are 3% to 15% elemental aluminum, 5% to 20% aluminum nitride, and 0% to 5% aluminum carbide.

[0015] The present invention has the following beneficial effects:

[0016] 1. The present invention does not require continuous heating or related equipment. Compared with conventional pyrolysis, the energy consumption is much lower, the investment is much smaller, the land occupation is much smaller, and the processing time is much shorter. The harmless treatment can be started and stopped quickly. As long as a certain part of the secondary aluminum ash mixture is burned red, oxygen can be blown to start combustion. If the combustion needs to be stopped, the oxygen blowing can be stopped.

[0017] 2. The comprehensive operating cost of the treatment method disclosed in the present invention is less than that of the conventional pyrolysis method. The comprehensive operating cost of the conventional pyrolysis method is about 1,000 yuan / ton, and the comprehensive operating cost of the combustion method is generally no more than 600 yuan / ton, of which the fuel cost is about 300 yuan / ton and the oxygen supply cost is about 200 yuan / ton. The treatment method disclosed in the present invention has high feasibility, small investment, low risk, low operating cost, and is worthy of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0019] 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.

[0020] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0021] refer to Figure 1 As shown, the present invention discloses a method for harmless treatment of secondary aluminum ash combustion, comprising the following steps:

[0022] (1) Grind the secondary aluminum ash and sieve it through a 100-mesh sieve to remove the larger particles of elemental aluminum and other impurities. These larger particles of elemental aluminum can be recycled into the smelting furnace. In terms of mass percentage, the main components of the secondary aluminum ash are 3% to 15% elemental aluminum, 5% to 20% aluminum nitride, and 0% to 5% aluminum carbide. Grinding is generally performed using a ball mill; sieving is generally performed through a 100-mesh sieve, or a sieve with a larger mesh number. The larger the mesh number of the sieve, the smaller the particle size obtained, and the easier it is for the active components in the secondary aluminum ash to burn and oxidize.

[0023] (2) Add fuel to the sieved secondary aluminum ash and mix evenly; the fuel is a powder that can be burned and has a little stickiness, such as any one or more of starch, pine wood powder, glutinous rice powder, cassava powder, and charcoal powder. The amount of fuel added is 5-20% of the secondary aluminum ash. The more active ingredients in the secondary aluminum ash, the less fuel is added. If it is flue ash from an aluminum processing enterprise, it can be directly burned after forming without adding fuel because it contains a large amount of activated carbon.

[0024] (3) After the secondary aluminum ash is evenly mixed with the fuel, it is pressed into a tablet press. The tablet press pressure is 1MPa to 15MPa, and it is generally pressed into a rectangular sheet.

[0025] (4) Place the formed (tabletted) mixture in a refractory container, and then use a flamethrower to spray flames on the edge of the tablet mixture until it burns red. Refractory container: Generally, it is a can-shaped metal container with insulation cotton wrapped around the outside of the container, which has the function of heat preservation and oxygen storage.

[0026] (5) Extinguish the flamethrower, and use high-purity oxygen to blow the red-burned part of the mixture through the high-temperature resistant small flat tube to make the mixture burn. During the combustion process, the high-temperature resistant small flat tube moves with the movement of the burning point, and keeps blowing oxygen to the burning point. The purity range of high-purity oxygen is 80% to 100%. When blowing oxygen through the high-temperature resistant small flat tube, try to get as close to the burning point as possible. The gas flow rate can make the mixture burn. The wind speed is 2 to 6 m / s. It should not be too large or too small. If it is too large, the combustion speed will be too fast, and the active substances in the secondary aluminum ash will not be fully oxidized. If it is too small, it may not burn. The high-temperature resistant small flat tube is generally made of metal small flat tube, and the gap size is: 1 to 3 cm long and 1 to 2 mm wide.

[0027] (6) After the flaky mixture is completely burned, stop blowing oxygen, and the secondary aluminum ash harmless treatment is completed.

[0028] The present invention will be further described below in conjunction with specific embodiments.

[0029] Example 1

[0030] A secondary aluminum ash combustion harmless treatment method comprises the following steps:

[0031] 1. Take the secondary aluminum ash from an aluminum recycling enterprise, the elemental aluminum content is about 12%, and the aluminum nitride content is about 6%. Then ball mill, and then pass through a 100-mesh sieve to obtain the secondary aluminum ash powder, the elemental aluminum content is about 6%, and the aluminum nitride content is about 8%.

[0032] 2. Add starch at a mass ratio of 15%, mix evenly, and then use a tablet press to press the tablets. The mold size is 3cm×6cm, the amount of mixed powder added is 8g, the pressure is 10MPa, and the mixed powder is pressed into a biscuit shape.

[0033] 3. Place the flaky mixture into a short cylindrical metal can, and then use a flamethrower to spray flames at the short sides of the flaky mixture until it burns red.

[0034] 4. After the mixture is red hot, turn off the flamethrower, and then blow 80% pure oxygen through the metal flat tube towards the red hot part, and you can see the mixture slowly burning. During the combustion process, keep moving the metal flat tube to blow oxygen towards the ignition point.

[0035] 5. When the entire mixture is burned out and no red fire spots are visible, stop blowing oxygen and the harmless treatment is completed.

[0036] 6. After the harmless treatment is completed, cool it down, and then test the aluminum content at about 2%, with a removal rate of about 65%; the aluminum nitride content is about 1.5%, with a removal rate of about 80%.

[0037] Example 2

[0038] A secondary aluminum ash combustion harmless treatment method comprises the following steps:

[0039] 1. Take the secondary aluminum ash from an aluminum power plant, the elemental aluminum content is about 6%, and the aluminum nitride content is about 10%. Then ball mill, and then pass through a 100-mesh sieve to obtain the secondary aluminum ash powder, the elemental aluminum content is about 4%, and the aluminum nitride content is about 14%.

[0040] 2. Add glutinous rice flour at a mass ratio of 15%, mix evenly, and then use a tablet press to press the tablets. The mold size is 3cm×6cm, the amount of mixed powder added is 8g, the pressure is 12MPa, and the mixed powder is pressed into biscuit shape.

[0041] 3. Place the flaky mixture into a short cylindrical metal can, and then use a flamethrower to spray flames at the short sides of the flaky mixture until it burns red.

[0042] 4. After the mixture is red hot, turn off the flamethrower, and then blow 100% pure oxygen to the red hot part through the metal flat tube, and you can see the mixture slowly burning. During the combustion process, keep moving the metal flat tube to blow oxygen to the ignition point.

[0043] 5. When the entire mixture is burned out and no red fire spots are visible, stop blowing oxygen and the harmless treatment is completed.

[0044] 6. After the harmless treatment is completed, cool it down, and then test the aluminum content at about 0.8%, with a removal rate of about 80%; the aluminum nitride content is about 1.5%, with a removal rate of about 90%.

[0045] Example 3

[0046] A secondary aluminum ash combustion harmless treatment method comprises the following steps:

[0047] 1. Take mixed secondary aluminum ash, the elemental aluminum content is about 10%, and the aluminum nitride content is about 15%. Then ball mill, and then pass through a 100-mesh sieve to obtain secondary aluminum ash powder, the elemental aluminum content is about 8%, and the aluminum nitride content is about 18%.

[0048] 2. Add pine wood powder at a mass ratio of 10%, mix evenly, and then use a tablet press to tablet. The mold size is 3cm×6cm, the amount of mixed powder added is 8g, the pressure is 8MPa, and the mixed powder is pressed into biscuit shape.

[0049] 3. Place the flaky mixture into a short cylindrical metal can, and then use a flamethrower to spray flames at the short sides of the flaky mixture until it burns red.

[0050] 4. After the mixture is red hot, turn off the flamethrower, and then blow 80% pure oxygen to the red hot part through the metal flat tube, and you can see the mixture slowly burning. During the combustion process, keep moving the metal flat tube to blow oxygen to the ignition point.

[0051] 5. When the entire mixture is burned out and no red fire spots are visible, stop blowing oxygen and the harmless treatment is completed.

[0052] 6. After the harmless treatment is completed, cool it down, and then test the aluminum content at about 2.5%, with a removal rate of about 70%; the aluminum nitride content is about 3%, with a removal rate of about 85%.

[0053] The results show that the treatment method disclosed in the present invention can remove about 90% of the active components in secondary aluminum ash. For secondary aluminum ash produced by small and medium-sized aluminum recycling enterprises with high active components, this method can be used to significantly reduce the content of active components and reduce the harmfulness, and then slowly recycle the secondary aluminum ash according to demand.

[0054] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for harmless treatment of secondary aluminum ash combustion, characterized in that: After the secondary aluminum ash is ground and sieved, fuel is added, and after tableting, a flame-spraying device is used to spray fire at the edge of the flaky mixture until it burns red, and then high-purity oxygen is blown to the red-burned part of the flaky mixture through an oxygen-blowing device to make the flaky mixture burn. During the combustion process, the oxygen-blowing device moves with the movement of the combustion point and keeps blowing oxygen at the combustion point. The purity range of oxygen is 80% to 100%, and the flow rate of oxygen is 2 to 6 m / s. After the flaky mixture is burned, the oxygen blowing is stopped, and the harmless treatment of the secondary aluminum ash is achieved; The fuel is any one or more of starch, pine wood powder, glutinous rice flour, cassava flour and charcoal powder.

2. The method for harmless treatment of secondary aluminum ash combustion according to claim 1, characterized in that: The added amount of the fuel is 5% to 20% of the secondary aluminum ash.

3. The method for harmless treatment of secondary aluminum ash combustion according to claim 1, characterized in that: The tabletting pressure is 1 MPa to 15 MPa.

4. The method for harmless treatment of secondary aluminum ash combustion according to claim 1, characterized in that: The secondary aluminum ash is sieved through a 100-mesh sieve.

5. The method for harmless treatment of secondary aluminum ash combustion according to claim 1, characterized in that: Calculated by mass percentage, the main components of the secondary aluminum ash are 3% to 15% of elemental aluminum, 5% to 20% of aluminum nitride, and 0% to 5% of aluminum carbide.

Images