Method and apparatus for cleaning seamless aluminum cans

Abstract

To provide an aluminum seamless can washing method and washing device that achieve reduction in environmental load and employ a wastewater treatment process capable of reusing treated wastewater.SOLUTION: A washing method for an aluminum seamless can be molded by drawing and ironing, includes at least a degreasing step for degreasing the aluminum seamless can with a degreasing agent; a water-washing step for using water to wash the degreased aluminum seamless can; and a wastewater treatment step for using a membrane separation activated sludge treatment to treat wastewater from the degreasing step and the water-washing step, where the amount of aluminum in the wastewater supplied for the wastewater treatment step is 5-200 mg / L.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for cleaning aluminum seamless cans, and more particularly to a method and apparatus for cleaning aluminum seamless cans that is equipped with a cleaning wastewater treatment method capable of reducing the burden on the environment. [Background technology]

[0002] Conventionally, aluminum seamless cans (hereinafter, simply referred to as "aluminum seamless cans" or "seamless cans") have been widely used as containers for food and beverages such as beer and carbonated drinks. Such seamless cans are obtained by subjecting aluminum sheets to severe processing such as drawing and ironing, and are generally formed using a lubricant and a coolant. As a result, lubricant and smut adhere to the seamless can after drawing and ironing. In addition, a coating of aluminum oxide is formed on the surface of the aluminum sheet. Cans on which such lubricants and the like have been attached and on which an aluminum oxide film has formed must have the attached lubricants and the like removed before being subjected to the painting and printing process. Also, in order to form a good chemical conversion coating on the aluminum surface, it is necessary to degrease the aluminum surface with a degreaser containing a surfactant and an etching agent, and to rinse the degreaser with water.

[0003] Conventional cleaning processes for aluminum seamless cans generally include a degreasing step using a degreaser or the like to remove lubricants and the like, a water rinsing step to remove the degreaser, and, if necessary, a surface treatment step using a surface treatment liquid, and a water rinsing step to remove the surface treatment liquid (Patent Documents 1 to 3, etc.). The washing wastewater discharged from such a washing process contains lubricants and degreasers used in forming the aluminum seamless cans, fluorides in the surface treatment solution, phosphate compounds, aluminum, and the like. Conventionally, the washing wastewater has been treated by adding a chemical such as a coagulant to cause coagulation and precipitation or pressure flotation, and then separated and treated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 2587916 [Patent Document 2] Patent No. 3451187 [Patent Document 3] JP 2002-346672 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned wastewater treatment methods require large amounts of chemicals and water, and the wastewater treatment equipment must be large to treat a large amount of wastewater, and a large amount of land is required to install the equipment, which causes problems in terms of economic efficiency. In addition, there is also a problem that the environmental load is large because the entire amount of treated wastewater is discharged into a sewer or the like. The membrane bioreactor activated sludge process, which uses microorganisms to treat wastewater from factories, is also known as a method for treating wastewater from factories. However, wastewater from washing seamless aluminum cans contains large amounts of the aforementioned lubricants and other substances, which results in large biochemical oxygen consumption (BOD) and chemical oxygen consumption (CODcr), making it difficult to apply the membrane bioreactor activated sludge process to the wastewater as is.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a cleaning method and apparatus for cleaning seamless aluminum cans, which is capable of efficiently treating wastewater by a membrane separation activated sludge process. Another object of the present invention is to provide a method and apparatus for cleaning seamless aluminum cans, which is provided with a wastewater treatment method that does not require a large site and allows the treated wastewater to be reused. [Means for solving the problem]

[0007] According to the present invention, a method for cleaning aluminum seamless cans formed by drawing and ironing includes at least a degreasing step of degreasing the aluminum seamless cans with a degreaser, a water washing step of washing the degreased aluminum seamless cans with water, and a wastewater treatment step of treating wastewater from the degreasing step and the water washing step by a membrane separation activated sludge process, and the amount of aluminum in the wastewater supplied to the wastewater treatment step is Without adding flocculants The present invention provides a method for cleaning seamless aluminum cans, characterized in that the concentration is 5 to 200 mg / L.

[0008] In the method for cleaning aluminum seamless cans of the present invention, 1. The BOD of the wastewater supplied to the wastewater treatment process is 300 mg / L or less and the CODcr is 700 mg / L or less; 2. The TOC of the wastewater supplied to the wastewater treatment process is 500 mg / L or less; 3. The degreasing agent contains a surfactant and at least one of sulfuric acid, sodium hydroxide, and potassium hydroxide; 4. The above-mentioned fatwork a surface treatment step using a surface treatment liquid containing a phosphoric acid compound and / or a fluoride, and a neutralization step for neutralizing the wastewater to be supplied to the wastewater treatment step; 5. The amount of fluoride ions in the wastewater supplied to the neutralization treatment step is 40 mg / L or less. 6. Further comprising a pre-cleaning step prior to the degreasing step; 7. The cleaning water in the preliminary cleaning step is not heated; 8. Further comprising a filtration process for filtering the treated water obtained in the wastewater treatment process by reverse osmosis membrane filtration, and reusing the filtrate obtained in the filtration process as washing water in the water washing process and / or the preliminary washing process. 9. Reusing the filtrate so that the proportion of the filtrate in the cleaning water used in the water washing step and / or the preliminary cleaning step is 30 to 95%; 10. The drawing and ironing process is a drawing and ironing process that does not use a lubricant; is preferred.

[0009] According to the present invention, there is further provided a cleaning device for cleaning aluminum seamless cans formed by drawing and ironing, comprising: a pre-cleaning means for the aluminum seamless cans supplied from a forming means; a degreasing means for degreasing the aluminum seamless cans supplied from the pre-cleaning means with a degreaser; a water-washing means for rinsing the aluminum seamless cans supplied from the degreasing means with water; a drying means for drying the aluminum seamless cans supplied from the water-washing means; Without adding flocculants The present invention provides an aluminum seamless can cleaning device comprising at least a wastewater treatment means for treating the aluminum seamless cans by a membrane separation activated sludge process, and a transport means for continuously transporting the aluminum seamless cans from at least the forming means to the drying means.

[0010] In the cleaning device for aluminum seamless cans of the present invention, 1. Having a surface treatment means using a surface treatment liquid containing a phosphoric acid compound and / or a fluoride downstream of the degreasing means, and further having a neutralization treatment means for neutralizing wastewater to be supplied to the wastewater treatment means; 2. Having a filtration means for filtering the treated liquid obtained by the wastewater treatment means through a reverse osmosis membrane, and a circulation means for supplying the filtrate obtained by the filtration means to the water washing means and / or the preliminary washing means; is preferred. Effect of the Invention

[0011] In the method for washing seamless aluminum cans of the present invention, efficient wastewater treatment is possible by the membrane separation activated sludge method, so that conventional wastewater treatment equipment that required a large amount of land can be made smaller, and the treated wastewater can be reused as washing water after being treated with a reverse osmosis membrane, which is economical. In addition, there is an advantage in that the burden on the environment can be reduced because the amount of sludge and the amount of wastewater discharged into sewage, etc. are small. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a flow chart showing a preferred flow of the washing process for aluminum seamless cans according to the present invention. [Diagram 2] FIG. 1 is a diagram for explaining an example of wastewater treatment using a membrane separation activated sludge method. [Diagram 3] FIG. 1 is a side view illustrating an example of a cleaning device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] One important feature of the method for washing aluminum seamless cans of the present invention is that a membrane bioreactor (MBR) process is used for wastewater treatment, and another important feature is that the amount of aluminum in the wastewater supplied to the wastewater treatment process is 5 to 200 mg / L. The MBR method employed as the wastewater treatment method in the present invention is a method in which organic matter, such as lubricants, contained in washing wastewater is decomposed by microorganisms and the microorganisms are filtered out using an MF membrane (microfiltration membrane) or a UF membrane (ultrafiltration membrane). The obtained treated water (filtrate) can be purified to a level that allows it to be reused as washing water by further filtering using an RO membrane. Therefore, by reusing such treated water as washing water, it is possible to reduce the amount of water supplied for new use in the washing process of aluminum seamless cans and also reduce the amount of wastewater discharged into sewers, etc., thereby reducing the burden on the environment. In the present invention, the amount of aluminum is a value measured by ICP atomic emission spectrometry in accordance with JIS K 102, a test method for industrial wastewater.

[0014] In the cleaning method of the present invention, the amount of aluminum in the cleaning wastewater is in the range of 5 to 200 mg / L, particularly 5 to 100 mg / L, so that the oil and other components in the cleaning wastewater after neutralization form aggregates with the aluminum and are separated, thereby efficiently purifying the wastewater. In addition, when surface treatment is performed, fluoride ions, phosphate ions, and the like can be efficiently removed by the presence of aluminum. In addition, the amount of fluoride ions that affect microorganisms can be reduced, and it is possible to efficiently perform wastewater treatment by the MBR method. If the amount of aluminum is less than the above range, the above-mentioned effects of aluminum may not be sufficiently achieved, while if the amount of aluminum is more than the above range, the amount of precipitated aluminum after neutralization may be excessive, which may actually reduce the filtration efficiency by the MBR method.

[0015] In the present invention, the wash wastewater supplied to the treatment step using the MBR method preferably has an aluminum content within the above range, a biochemical oxygen consumption (BOD) of 300 mg / L or less, a chemical oxygen consumption (CODcr) of 700 mg / g or less, and a total organic carbon (TOC) of 500 mg / L or less, which enables efficient treatment using the MBR method. BOD is the amount of oxygen (mg / L) consumed by aerobic microorganisms in the presence of dissolved oxygen at 20°C for 5 days, and CODcr is the amount of potassium dichromate consumed when potassium dichromate is added as an oxidant and reacted at 100°C for 30 minutes, converted into oxygen (mg / L). These are indicators of the degree of water pollution caused by organic matter. TOC is a water quality indicator that expresses the total amount of organic matter present in water as the amount of carbon contained in the organic matter (mg / L), and is a water quality indicator that expresses the amount of organic matter that can be oxidized as carbon. By controlling the BOD, CODcr, and TOC of the washing wastewater supplied to the MBR treatment process to be below the above values, combined with the aluminum content being within the above range, more efficient wastewater treatment by the MBR method is possible.

[0016] (Seamless aluminum cans) In the cleaning method of the present invention, the aluminum seamless cans to be cleaned are not particularly limited in terms of their forming method, etc., and any conventionally known aluminum seamless cans can be used. However, from the viewpoint of reducing the BOD, COD, and TOC of the cleaning wastewater to be supplied to the wastewater treatment step using the MBR process to below the aforementioned values, it is preferable that the cans be aluminum seamless cans in which the amount of lubricant used during forming is reduced. Aluminum seamless cans are generally made by forming aluminum sheets made of well-known aluminum or aluminum alloys such as 3004 material, 3104 material, etc., through severe processes such as drawing, drawing / deep drawing, drawing / ironing, and drawing / bending / stretching / ironing, using conventional lubricants such as mineral oil and synthetic oil, and water as necessary. Examples of aluminum seamless cans having a reduced amount of adhering lubricant as described above include aluminum seamless cans formed by drawing and ironing in dry forming without using any lubricant, and aluminum seamless cans formed by wet forming using a lubricant but using a water-soluble lubricant or reducing the amount of lubricant used. In addition to the lubricant, smut generated during molding is also present on the aluminum seamless can. Also, a film of aluminum oxide is formed on the surface of the aluminum plate.

[0017] (Cleaning process) FIG. 1 is a diagram showing an example of the method for washing seamless aluminum cans of the present invention, in which seamless cans formed in a can-making process are continuously conveyed to a drying process after passing through a preliminary washing process, a degreasing process, a first water-rinsing process, a surface treatment process, and a second water-rinsing process. Washing wastewater discharged from each process passes through a neutralization process and a treatment process using an MBR, and the filtrate is purified to a level that can be reused as washing water through an RO membrane. In the specific example shown in the figure, the washing process includes a preliminary washing process, a surface treatment process, and a second water-rinsing process, and the wastewater treatment process includes a rough filtration process, a neutralization process, and a filtration process using a reverse osmosis membrane, but these processes are not essential and may be added as necessary, as described later. In the present specification, the preliminary washing process to the second water-rinsing process are roughly referred to as a washing process, and the three processes of the rough filtration process, the neutralization process, and the wastewater treatment process using an MBR method are roughly referred to as a wastewater treatment process. The washing water used in the washing step may be industrial water, distilled water, pure water (deionized water), etc., but in the present invention, treated water (filtered water) that has been through a wastewater treatment step can be reused, and 30 to 95% of the total washing water used in the preliminary washing step and the water washing step can be replaced with the treated water, resulting in excellent water saving properties.

[0018] [Pre-cleaning process] The pre-cleaning process is a process for removing impurities that have adhered to the can during the can-making process before the subsequent degreasing process, and may be omitted depending on the condition of the aluminum seamless can after forming. In the pre-washing step, washing water whose temperature has been adjusted to 50 to 75°C using a heating device is generally used. However, in the present invention, since the amount of lubricant used in the can making process is reduced as described above, the washing water used in the pre-washing step can exhibit sufficient washing ability without a separate heating device.

[0019] [Degreasing process / first washing process] The aluminum seamless cans, which have been pre-cleaned as necessary in the above-mentioned pre-cleaning step, are continuously conveyed at high speed with their bottoms facing up to the degreasing step of the cleaning device. In the degreasing process, a degreaser is sprayed onto the seamless aluminum cans from above and below to remove the lubricant and smut adhering to the surfaces of the seamless aluminum cans, as well as the aluminum oxide coating formed on the surfaces of the aluminum cans. As the degreasing agent, a conventionally known degreasing agent can be used, for example, an acid cleaning solution or an alkaline cleaning solution containing a surfactant and an acid or an alkali can be used, but it is preferable to use a degreasing agent containing a surfactant and one of sulfuric acid, sodium hydroxide, and potassium hydroxide. As the surfactant, any of cationic surfactants, anionic surfactants, nonionic surfactants, and ionic surfactants can be used without limitation, but it is particularly preferable to use a nonionic surfactant. In the present invention, as described above, since it is preferable that the BOD, CODcr and TOC in the washing wastewater are reduced, measures such as dry forming without using a lubricant or reducing the amount of lubricant used are taken in the can making process. Therefore, a degreaser with a reduced content of surfactants, acid or alkali components, etc. can be used, and the degreaser components in the wastewater discharged from the degreasing treatment process can be reduced. In addition, the amount of aluminum desorbed from seamless cans by the degreasing treatment can be adjusted by adjusting the type and amount of degreaser used. The amount of aluminum in the wastewater supplied to the wastewater treatment process can be kept within a suitable range by adjusting the amount of aluminum desorbed by the degreasing treatment and the amount of water used in the subsequent washing process.

[0020] The aluminum seamless cans that have been subjected to the degreasing process are washed with water in the first washing step, and then transported to the surface treatment step. In the specific example shown in Fig. 2, the first washing step is performed in one step, but it may also be performed in two steps, with a pure water rinsing step being added after the first water washing step, and this can be modified as appropriate. The washing wastewater discharged from the degreasing step and the first water-washing step contains organic matter derived from the lubricant removed by the degreasing treatment. In the present invention, however, it is desirable that the BOD of the wastewater finally supplied to the wastewater treatment step is 300 mg / L or less, the CODcr is 700 mg / g or less, and the TOC is 500 mg / L or less.

[0021] [Surface treatment process / second cleaning process] The surface treatment step can be a chemical conversion treatment using a conventionally known surface treatment agent such as a zirconium-, titanium-, or chromium-based agent in order to improve the coating film stability and corrosion resistance of the degreased seamless aluminum can. Note that the surface treatment step itself is not an essential step, and is unnecessary, for example, in the case of a resin-coated seamless aluminum can formed using a resin-coated aluminum sheet, or when other methods such as conditioning using phosphate are used instead. The surface treatment agent may be a conventionally known one, and is not limited thereto. Surface treatment agents containing phosphate compounds such as zirconium phosphate, sodium phosphate, and phosphoric acid, and fluorides such as aluminum fluoride, zirconium fluoride, and hydrofluoric acid can be suitably used. In the present invention, as described above, the washing wastewater supplied to the wastewater treatment step contains 5 to 200 mg / L of aluminum, and the phosphate compounds and fluorides in the washing wastewater react with aluminum to precipitate, so that separation of the phosphate compounds and fluorides in the washing wastewater can be promoted. It is desirable that the amount of fluoride ions in the wastewater discharged from the surface treatment process is less than 40 mg / L when the wastewater is mixed with the wastewater from the first cleaning process and supplied to the wastewater treatment process. If the amount of fluoride ions is greater than the above value, it becomes difficult to sufficiently reduce the amount of fluoride ions in the neutralization treatment process described below, which may affect the microorganisms used in the wastewater treatment process using the MBR method. After the surface treatment process, the seamless aluminum cans go through a second cleaning process and then are transported to a drying process.

[0022] [Drying process] The surface-treated seamless aluminum cans are transported to the drying process, where they are heated and dried in a dryer such as an oven. The aluminum cans that have undergone the surface treatment process are dried at a temperature of 170 to 210°C for 60 to 100 seconds, and then transported to the painting and printing process.

[0023] (Wastewater treatment process) As shown in Figure 1, the washing wastewater discharged from the preliminary washing process, degreasing process, first water washing process, surface treatment process, and second water washing process is subjected to a rough filtration process, a neutralization process, a wastewater treatment process using the MBR method, and a filtration process, and the filtered water can be reused as washing water. The coarse filtration step is not essential depending on the state of the washing wastewater and can be omitted. The neutralization step can be omitted when the above-mentioned surface treatment step is omitted. Furthermore, the filtration step using a reverse osmosis membrane is also an optional step.

[0024] [Neutralization process] In the neutralization treatment process, phosphate ions, fluoride ions, etc. in the surface treatment agent discharged from the surface treatment process are neutralized to make them insoluble, allowing them to be easily filtered through an MF membrane or UF membrane in the subsequent wastewater treatment process using the MBR method. The neutralization process itself can be carried out by a conventionally known method, but as described above, the washing wastewater of the present invention contains aluminum in an amount of 5 to 200 mg / L, preferably 5 to 100 mg / L, and the aluminum plays the role of an inorganic flocculant by neutralization, becomes the nucleus for oil flocculation, and reacts with phosphate ions, fluoride ions, etc. That is, phosphate ions become aluminum phosphate and are insolubilized and flocculated, and fluoride ions become aluminum fluoride and are insolubilized and flocculated. In addition, sulfate ions in the degreasing agent also become aluminum sulfate and are insolubilized and flocculated. As described above, the amount of fluoride ions in the cleaning wastewater discharged from the surface treatment process is controlled to be less than 40 mg / L when it is supplied to the wastewater treatment process. This makes it possible to reduce the amount of fluoride ions in the treated water to less than 20 mg / L by the neutralization treatment process, thereby reducing the impact on microorganisms in the subsequent wastewater treatment process.

[0025] [Wastewater treatment process using the MBR method] The washing wastewater after the neutralization process is separated into sludge and treated water by a membrane bioreactor (MBR) process using an MF membrane or UF membrane. The MBR process used in the present invention can be carried out by a conventional method. FIG. 2 is a diagram for explaining an example of a membrane bioreactor activated sludge treatment. The membrane bioreactor activated sludge tank is installed in an aeration tank 1 with a membrane unit 2 equipped with a plurality of membrane modules 2a and a water collection pipe 2b submerged therein. Below the membrane unit 2, an air bubble diffuser 3 is installed, which diffuses air supplied from a blower 4 toward the MF membrane constituting the membrane unit 2. The air bubbles clean the MF membrane and generate a circulation in the tank, promoting the mixing and stirring of the activated sludge and the water to be treated. In addition, oxygen in the air bubbles comes into contact with the liquid to be treated and dissolves in the liquid to be treated as dissolved oxygen. The aeration tank 1 is equipped with a supplying means 5 for supplying a fixed amount of wastewater (water to be treated) from the neutralization treatment process, which is the preceding process, a drainage means 6 equipped with a suction pump for discharging the treated water out of the tank, and a discharge means 7 equipped with a suction pump for discharging the sludge out of the tank.

[0026] The membrane cartridge constituting the membrane unit installed in the membrane separation activated sludge tank can be, for example, an MF membrane or an UF membrane, but it is preferable to use an MF membrane of 0.2 to 0.5 μm. In addition, although it depends on the supply amount of the water to be treated, in a typical wastewater treatment device using an aluminum seamless can, the tank is 300 to 600 m. 3 It is preferable that the volume of the liquid crystal display device be 100 or more, and the size of the device can be reduced. It is also preferable that the amount of activated sludge suspended solids (MLSS) in the tank is in the range of 5,000 to 10,000 mg / L. The wastewater (water to be treated) supplied to the wastewater treatment process using the MBR method has the amount of fluoride ions reduced to less than 20 mg / L, especially less than 15 mg / L, through a neutralization process, so there is no impact on microorganisms. In addition, the wastewater (water to be treated) supplied to the wastewater treatment process can be efficiently treated using the MBR method because its BOD is reduced to 300 mg / L or less, its CODcr to 700 mg / L or less, and its TOC to 500 mg / L or less.

[0027] [Filtration process] The treated water discharged from the wastewater treatment process using the MBR method is sufficiently purified, but if it is to be reused as washing water, it is preferable to further subject it to a filtration process using a reverse osmosis membrane. The filtration step using a reverse osmosis membrane can itself be carried out by a conventionally known method, and the pressure difference (filtration pressure) and the like can be appropriately adjusted depending on the reverse osmosis membrane used. The filtered water obtained by filtration using a reverse osmosis membrane has impurities such as sodium ions removed, and can therefore be suitably reused as cleaning water. The amount of the filtered water that can be used is 30 to 90% of the amount of cleaning water used in the cleaning process.

[0028] (Cleaning Equipment) The cleaning apparatus for cleaning seamless aluminum cans of the present invention, as shown in FIG. 3 described later, roughly consists of a cleaning apparatus A in the narrow sense, which performs the process from cleaning to drying of seamless aluminum cans, and a wastewater treatment apparatus B, which treats wastewater from the cleaning apparatus. The cleaning device A in the narrow sense includes a pre-cleaning means for aluminum seamless cans supplied from a molding means for the aluminum seamless cans, a degreasing means for degreasing the aluminum seamless cans supplied from the pre-cleaning means with a degreaser, a water washing means for washing the aluminum seamless cans supplied from the degreasing means, a drying means for drying the aluminum seamless cans supplied from the water washing means, and a transport means for continuously transporting the aluminum seamless cans at least from the molding means to the drying means. As described above, in cleaning of seamless aluminum cans, surface treatment can be performed after degreasing, so that a surface treatment means using the above-mentioned surface treatment liquid can be provided downstream of the degreasing means, if necessary.

[0029] The wastewater treatment device B is equipped with at least a wastewater treatment means for treating the wastewater discharged from the preliminary washing means, the degreasing means, and the water washing means by the MBR method. The treatment device is also provided with a neutralization treatment means for neutralizing the pH of the wastewater to be supplied to the wastewater treatment means and for neutralizing fluoride ions and the like in the wastewater. Furthermore, when the treated water treated by the wastewater treatment device is reused as washing water for the washing device, the wastewater treatment device is optionally equipped with a filtration means for filtering the treated liquid obtained by the wastewater treatment means using a reverse osmosis membrane, and a circulation means for supplying the filtrate obtained by the filtration means to the water washing means and / or the preliminary washing means.

[0030] 3 is a side view that shows a schematic diagram of one example of the cleaning apparatus of the present invention, in which seamless aluminum cans 10 having lubricants and the like attached thereto are carried in from a molding apparatus and are continuously transported by a transport means 11 to a drying means 17. As the transport means, a conventionally known transport means such as a mesh conveyor or a net conveyor can be used, and a plurality of seamless aluminum cans are placed in a line in the width direction of the transport means (perpendicular to the traveling direction) with their openings facing downward, and are continuously transported. As is clear from FIG. 3, in a preferred embodiment of the cleaning apparatus of the present invention, a preliminary cleaning means 12, a degreasing means 13, a first water-washing means 14, a surface treatment means 15, a second water-washing means 16 and a drying means 17 are installed along the conveying means 11 from the upstream (left side of FIG. 3) to the downstream (right side of FIG. 3) of the cleaning apparatus. Each of the preliminary cleaning means 12, degreasing means 13, first water washing means 14, surface treatment means 15, and second water washing means 16 is provided with spray devices 20, 20, 20... having multiple outlets capable of spraying degreaser, cleaning water, pure water, surface treatment agent, and cleaning water from above and below the aluminum seamless can in each process, and is also provided with drainage pipes 21, 21, 21... for introducing cleaning wastewater into the wastewater treatment process.

[0031] Drain pipes 21, 21... which supply the washing wastewater from each of the means of preliminary washing means 12, degreasing means 13, first water washing means 14, surface treatment means 15, and second water washing means 16 to a wastewater treatment process are connected to a wastewater tank 22. From the wastewater tank 22, the wastewater is supplied quantitatively to a neutralization treatment means 31. Although not shown, if the washing wastewater contains impurities, it may be passed through a coarse filtration means such as a metal filter before being supplied to the neutralization treatment means. The neutralization treatment means 31 includes an agitation means 31b and a supply device 31c for supplying a neutralizing agent such as sodium hydroxide to the reaction tank 31a. The oil content in the wastewater supplied from the wastewater tank 22 to the reaction tank 31a is separated by the coagulation effect of aluminum, and the phosphoric acid compounds and fluorides contained in the second cleaning wastewater are removed by coagulation and precipitation of aluminum phosphate, aluminum fluoride, etc., so that the amount of fluoride ions becomes less than 20 mg / L. The wastewater from which the coagulated material produced by the neutralization treatment has been removed is supplied to wastewater treatment means 32 using an MBR method through pipe 31d, and the coagulated and settled sludge is discharged through discharge pipe 31e.

[0032] The wastewater treatment means 32 using the MBR method is as shown in Fig. 2 above, and includes a treatment tank 1 equipped with a membrane unit 2 and an air bubble diffusing means 3, and a blower 4. Treated water obtained through a water collection pipe 2b passes through a drainage means 6 and is supplied to a filtration means 33 equipped with a reverse osmosis membrane module, which is subsequently performed as necessary. The treated water that has passed through the filtration means using a reverse osmosis membrane is supplied to the above-mentioned preliminary washing means 11 and water washing means 14, 16 by a circulation means 35 consisting of a suction pump .

[0033] The cleaning device of the present invention is not limited to the specific example shown in FIG. 3, and it is sufficient to install the required number or length (line length) of cleaning means before and after the degreasing means and the surface treatment means. Similarly, the number of nozzles of the spray device and the number of blower devices can also be changed appropriately. [Explanation of symbols]

[0034] Reference Signs List 1 membrane separation activated sludge tank, 2 membrane unit, 3 air bubble diffusion means, 4 blower, 5 supply means, 6 drainage means, 10 aluminum seamless can, 11 transport means, 12 preliminary cleaning means, 13 degreasing means, 14 first cleaning means, 15 surface treatment means, 16 second cleaning means, 17 drying means, 20 spray device, 21 drain pipe, 22 drainage tank, 31 neutralization treatment means, 32 wastewater treatment means by MBR method, 33 filtration means, 34 treated water tank, 35 circulation means.

Claims

1. A method for cleaning aluminum seamless cans formed by drawing and ironing, comprising the steps of: The method includes at least a degreasing step of degreasing the aluminum seamless cans with a degreaser, a water washing step of washing the degreased aluminum seamless cans with water, and a wastewater treatment step of treating wastewater from the degreasing step and the water washing step by a membrane separation activated sludge process, The method for cleaning aluminum seamless cans, wherein the amount of aluminum in the wastewater supplied to the wastewater treatment step is 5 to 200 mg / L without adding a coagulant.

2. 2. The cleaning method according to claim 1, wherein the wastewater to be supplied to the wastewater treatment step has a BOD of 300 mg / L or less and a CODcr of 700 mg / L or less.

3. 3. The cleaning method according to claim 1, wherein the wastewater to be supplied to the wastewater treatment step has a TOC content of 500 mg / L or less.

4. 4. The cleaning method according to claim 1, wherein the degreasing agent contains a surfactant and at least one of sulfuric acid, sodium hydroxide, and potassium hydroxide.

5. The cleaning method according to any one of claims 1 to 4, further comprising a surface treatment step using a surface treatment liquid containing a phosphoric acid compound and / or a fluoride after the degreasing step, and a neutralization treatment step for neutralizing wastewater to be supplied to the wastewater treatment step.

6. 6. The cleaning method according to claim 5, wherein the amount of fluoride ions in the wastewater supplied to the neutralization treatment step is 40 mg / L or less.

7. 7. The cleaning method according to claim 1, further comprising a pre-cleaning step prior to the degreasing step.

8. 8. The cleaning method according to claim 7, wherein the cleaning water in the pre-cleaning step is not heated.

9. 8. The cleaning method according to claim 7, further comprising a filtration step of filtering the treated water obtained in the wastewater treatment step by reverse osmosis membrane filtration, and reusing the filtrate obtained in the filtration step as cleaning water in the water-washing step and / or the preliminary cleaning step.

10. The cleaning method according to claim 9, wherein the filtrate is reused in an amount of 30 to 95% of the cleaning water used in the water-washing step and / or the preliminary cleaning step.

11. The cleaning method according to any one of claims 1 to 10, wherein the drawing and ironing is drawing and ironing without using a lubricant.

12. A cleaning apparatus for cleaning aluminum seamless cans formed by drawing and ironing, comprising at least a pre-cleaning means for the aluminum seamless cans supplied from a forming means, a degreasing means for degreasing the aluminum seamless cans supplied from the pre-cleaning means with a degreaser, a water-washing means for rinsing the aluminum seamless cans supplied from the degreasing means with water, a drying means for drying the aluminum seamless cans supplied from the water-washing means, a wastewater treatment means for treating wastewater discharged from the pre-cleaning means, the degreasing means and the water-washing means by a membrane separation activated sludge process without adding a coagulant, and a transport means for continuously transporting the aluminum seamless cans at least from the forming means to the drying means.

13. The cleaning apparatus according to claim 12, further comprising a surface treatment means using a surface treatment liquid containing a phosphoric acid compound and / or a fluorine compound downstream of the degreasing means, and a neutralization treatment means for neutralizing wastewater to be supplied to the wastewater treatment means.

14. 14. The cleaning apparatus according to claim 12 or 13, further comprising: a filtration means for filtering the treated liquid obtained by the wastewater treatment means through a reverse osmosis membrane; and a circulation means for supplying the filtrate obtained by the filtration means to the water washing means and / or the preliminary cleaning means.

Images