Filtering method for rolling oil of aluminum foil roughing mill

Abstract

The invention belongs to the technical field of metal processing, and relates to a method for filtering rolling oil of an aluminum foil roughing mill. Rolling oil and diatomaceous earth with the mass ratio of 20: (0.6-1.0) are added into the stirring barrel for pre-coating; after running for 15-20 minutes according to the proportioning speed of the normal full tank 16h light absorption filter aid, adding filter aid carclazyte and cellulose, and after the rolling oil is fully added, settling according to the mass ratio of the rolling oil in the stirring barrel to all the filter aids being 20: (1.0-1.75); and after the normal filtering stage is finished, entering a cleaning stage, and starting a next filtering period. By adopting the method for filtering the rolling oil, the light transmittance of a rough rolling oil product is improved from 40-60% to 85% or above, the filtering period is directly doubled from less than 24 h to 48-52 h, the filtering period is effectively prolonged, and the production time occupied by filter cleaning is shortened; the hazardous waste discharge amount and the rolling oil loss are reduced, and meanwhile the labor intensity of operators is relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing, relates to aluminum foil processing, and in particular to a method for filtering rolling oil of an aluminum foil rough rolling mill. Background Art

[0002] In the field of aluminum alloy rolling processing, rolling oil is mainly used for lubrication, cooling and cleaning. During the rolling and rolling process of aluminum alloy plates and strips, the generated metal aluminum chips, oxides and dust impurities will be mixed into the rolling oil and washed into the circulating oil tank by the rolling oil. If it is not filtered online, the used rolling oil will become dirty and black and form metal soap, which will not only seriously affect the lubrication effect, but also easily cause secondary pollution to the rolled plates and strips. Therefore, it is necessary to filter the rolling oil online to improve the light transmittance of the rolling oil and ensure the quality of the rolling oil.

[0003] In the existing conventional rolling oil filtering method, plate filters are usually used, and diatomaceous earth and kaolin are used as conventional filter aids for online filtration. Diatomaceous earth is a powdery substance extracted and calcined from algae minerals. It has diverse microscopic morphology, is porous, low-density, has a large specific surface area, is relatively incompressible, chemically stable, insoluble, and has a certain adsorption capacity. It can filter out particles larger than 1μm from rolling oil; kaolin is a white or off-white powder with a microporous network structure and a large specific surface area. It has a strong adsorption capacity and can filter metal particles smaller than 1μm in rolling oil.

[0004] The process of online filtration includes pre-coating stage, filtration stage and cleaning stage. In the pre-coating stage, rolling oil and filter aid are added to the mixing barrel in proportion. After mixing evenly, they are pumped into the dirty oil pipeline through the filter pump and mixed with the dirty oil into the filter box. The filter aid mixture forms a pre-coated filter cake layer on the filter cloth in the filter box; after the pre-coating is completed, the filter aid enters the timed small-proportion distribution stage and is pumped into the dirty oil pipeline and enters the filter box for filtration. This cycle forms a continuous circulation filtration cycle of rolling oil to filter out impurities such as aluminum powder in the rolling oil. In the filtration stage, rolling oil or filter aid is added to the mixing barrel every 8 to 12 hours. When this filtration method is used in the finishing mill for producing finished aluminum foil, due to the small amount of pass reduction and small amount of aluminum powder falling in the finished stage, the adsorption capacity of the filter aid can usually meet the requirements of the light transmittance of the rolling oil.

[0005] However, on the rough rolling mill for producing aluminum foil, due to the large absolute pressure reduction and fast speed, a large amount of aluminum powder falls off, and the conventional filtration process has the following shortcomings: 1. The light transmittance of the rolling oil after filtration cannot be stable, and is often less than 60%; 2. A filtration cycle is less than 16 to 24 hours, and a new cycle must be shut down for 30 to 60 minutes for cleaning, affecting production efficiency; 3. Costs increase, the discharge of hazardous waste filter aids is large, and the loss of filter paper increases; 4. The labor intensity of operators increases. Summary of the invention

[0006] Aiming at the problems in the prior art of low light transmittance and short filtration cycle of roughing mill rolling oil, increased production cost and hazardous waste, the present invention discloses a filtering method for aluminum foil roughing mill rolling oil.

[0007] Technical Solution

[0008] A method for filtering rolling oil of an aluminum foil rough rolling mill, using a plate filter for filtering, when entering a new filtering cycle, comprises the following steps:

[0009] (1) Cleaning the mixing barrel: Empty the rolling oil and filter aid in the mixing barrel, mainly to ensure that the cellulose content in the mixing barrel is less than 1‰;

[0010] (2) Pre-coating stage: Add rolling oil and diatomaceous earth in a mass ratio of 20:1 to 1.5 into the mixing barrel. Fill the mixing barrel with rolling oil, stir evenly, turn on the pre-coating mode, pump the mixture in the mixing barrel into the filter plate box for pre-coating, and the pre-coating amount is 25 to 40% of the liquid level in the mixing barrel;

[0011] (3) Sedimentation stage: After the pre-coating mode is completed, the mixing speed of the normal full tank 16h light-absorbing filter aid is run for 15 to 25 minutes. After the filter aid in the board box is settled and solidified to form a pre-coating layer, filter aids kaolin and cellulose are added to make the mass ratio of diatomaceous earth: kaolin: cellulose in the mixing barrel be 3.0 to 4: 2.0 to 1: 1 to 0.5. After the rolling oil is filled up again, the mass ratio of rolling oil and all filter aids in the mixing barrel is 20: 1.0 to 1.75;

[0012] (4) Normal filtration stage: Set the batching cycle of the filter aid to 16 hours when the mixing barrel is full, and fill the mixing barrel with rolling oil every 8 hours. From the 24th hour, diatomaceous earth, kaolin and cellulose need to be added to fill the mixing barrel again. The mass ratio of the added diatomaceous earth, kaolin and cellulose is 2.5-1.5:1.5-1:0.5-1. After stirring evenly, pump it into the filter box for filtration. According to the filter pressure, add filter aid 2-3 times according to this ratio;

[0013] (5) Cleaning stage: After the filter has been running for more than 8h×5, add rolling oil to the mixing barrel according to the filtration pressure displayed on the filter box, and no longer add filter aid; when the filter box pressure reaches 0.34~0.4MPa, the filtration is terminated and the next filtration cycle is entered after cleaning.

[0014] According to a preferred embodiment of the present invention, in step (2), rolling oil and diatomaceous earth are added into the stirring barrel in a mass ratio of 20:1.25, and the stirring barrel is filled with the rolling oil.

[0015] In a preferred disclosed embodiment of the present invention, in step (2), the pre-coating amount is 30% of the liquid level in the stirring barrel.

[0016] According to a preferred embodiment of the present invention, in step (3), the pre-coating layer sedimentation and curing time is 20 minutes.

[0017] According to a preferred embodiment of the present invention, in step (3), the activation degree of the cellulose is between 2400 and 3400 mol / 100 g, and the active cellulose content in the contents is ≥50%.

[0018] According to a preferred embodiment of the present invention, in step (3), the mass ratio of diatomaceous earth: clay: cellulose in the stirring barrel is 3.5:2.5:1.

[0019] According to a preferred embodiment of the present invention, in step (3), after the rolling oil is filled up again, the mass ratio of the rolling oil to all the filter aids in the stirring barrel is 20:1.5.

[0020] According to a preferred embodiment of the present invention, in step (4), the mass ratio of diatomaceous earth, white clay and cellulose is 2:1:0.5.

[0021] In step (4), the batching cycle is achieved by adjusting the time for adsorbing the filter aid within a unit time period, in units of s / min.

[0022] Beneficial Effects

[0023] By adopting the method of the present invention to filter rolling oil, the transmittance of crude rolling oil products is increased from 40-60% to more than 80%, and the filtration period is directly doubled from less than 24 hours to 48-52 hours, which effectively prolongs the filtration period and reduces the production time occupied by filter cleaning; reduces the emission of hazardous waste and the loss of rolling oil, and at the same time reduces the labor intensity of operators; the adsorption capacity of the organic filter aid cellulose exceeds that of activated clay, and can effectively adsorb tiny aluminum powder in the rolling oil, which is intercepted by the filter cake layer after flocculation; at the same time, because its fiber structure has excellent elasticity and toughness, it can shrink and recover with pressure fluctuations, so that the filter layer has a higher porosity, thereby achieving the effect of extending the filtration period. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 .Schematic diagram of the structure of the plate filter, in which the names of the components are: 1. Mixing barrel, 2. Filter aid dosing valve, 3. Filter pump, 4. Filter plate box, 5. Dirty oil tank, 6. Clean oil tank. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with the embodiments so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0026] The embodiment of the present invention uses a commonly used plate filter for illustration. The main components of the plate filter include a filter plate box 4, a filter pump 3, a mixing barrel 1, a clean oil tank 6, a dirty oil tank 5, and a filter aid dosing valve 2. The filtration process includes cleaning the mixing barrel, pre-coating, sedimentation, filtration, and replenishment. The filter aids used include diatomaceous earth, clay, and cellulose. For ease of understanding, please refer to Figure 1 .

[0027] Example 1

[0028] A method for filtering rolling oil of an aluminum foil rough rolling mill, using a plate filter for filtering, comprises the following steps:

[0029] (1) Cleaning the mixing barrel: Before cleaning, use the pre-coating mode to empty the rolling oil and filter aid in the mixing barrel, add 10% rolling oil again, rinse and suck it out, and ensure that the content of organic cellulose in the mixing barrel is less than 1‰ during the pre-coating stage;

[0030] (2) Pre-coating stage: add about 1000L rolling oil and 80kg diatomaceous earth into the mixing barrel, fill the mixing barrel with rolling oil, and the liquid level is about 2000L at 100%. After stirring evenly, start the pre-coating mode and pump the filter aid into the filter plate box for pre-coating; when the liquid level reaches 70%, turn off the pre-coating mode;

[0031] (3) Sedimentation stage: Enter the normal filtration mode and run for 20 minutes to allow the pre-coated filter aid in the filter box to settle and solidify to form a firm pre-coating layer of a certain thickness. Then, add 50 kg of white clay and 20 kg of cellulose to the mixing barrel, and fill the mixing barrel with rolling oil again;

[0032] (4) Normal filtration stage: Set the cycle of light absorption filter aid when the mixing barrel is full to 16 hours (achieved by adjusting the time of adsorption of filter aid in unit time period, unit s / min), fill the mixing barrel with rolling oil again after 8 hours, and from the 24th hour onwards, add 10kg diatomaceous earth, 5kg white clay and 3kg cellulose each time, and add filter aid twice according to this ratio;

[0033] (5) Cleaning stage: After the rough rolling mill has been running for more than 8h×5, no filter aid will be added; when the pressure in the filter box exceeds 0.3MPa, no rolling oil will be added; when the pressure in the filter box reaches 0.34~0.4MPa, the filtration is terminated and the mixing barrel is prepared for cleaning before entering the next filtration cycle.

[0034] The plate filter used is a 16-layer Schneider plate filter.

[0035] Transmittance test results: After 8 hours of the above filtration process, the transmittance was 85%, after 24 hours it was 88%, and after 48 hours it was 83%.

[0036] Comparative Example 1

[0037] Pre-coating amount less than 25%

[0038] (1) Cleaning the mixing barrel: Before cleaning, use the pre-coating mode to empty the rolling oil and filter aid in the mixing barrel, add 10% rolling oil again, rinse and suck it out, and ensure that the cellulose content in the mixing barrel is less than 1‰ during the pre-coating stage;

[0039] (2) Pre-coating stage: add about 1000L of rolling oil and 80kg of diatomaceous earth into the mixing barrel, and then fill the mixing barrel with rolling oil. The liquid level is about 2000L at 100%. After stirring evenly, turn on the pre-coating mode and pump the filter aid into the filter plate box for pre-coating. When the liquid level reaches 95%, turn off the pre-coating mode; this is equivalent to pre-coating 5%.

[0040] (3) Normal filtration stage: After the pre-coating is completed, the cycle of the mixing barrel full of light-absorbing filter aid is set to 16 hours. After 20 minutes of normal operation to allow the pre-coating filter aid to settle and solidify, 50kg of kaolin and 20kg of assimilated cellulose are added; the mixing barrel is required to be filled with rolling oil again every 8 hours. Starting from the 16th hour, each time the oil is added, 10kg of diatomaceous earth, 5kg of kaolin and 3kg of cellulose are required to be added. Subsequently, the filter aid is added twice according to this ratio based on the pressure in the filter plate;

[0041] (4) Cleaning stage: After the filter has been operating normally for more than 8h*4h, due to the poor transmittance of the oil, the filter aid will no longer be added. In order to prevent product quality problems, the filtration is terminated and cleaning is prepared to enter the next filtration cycle.

[0042] Transmittance test results: After 8 hours of the above filtration process, the transmittance was 55%, the oil began to turn black, 50% after 24 hours, and 48% after 32 hours.

[0043] The oil transmittance is unqualified. The filter runs for 32 hours. When the pressure is 2.3 Bar, no more rolling oil is added. The remaining amount is emptied and cleaned.

[0044] Comparative Example 2

[0045] Pre-coat not settled

[0046] (1) Cleaning the mixing barrel: Before cleaning, use the pre-coating mode to empty the rolling oil and filter aid in the mixing barrel, add 10% rolling oil again, rinse and suck it out, and ensure that the content of organic cellulose in the mixing barrel is less than 1‰ during the pre-coating stage;

[0047] (2) Pre-coating stage: add about 1000L rolling oil and 80kg diatomaceous earth into the mixing barrel, and then fill the mixing barrel with rolling oil, and the liquid level is about 2000L at 100%. After stirring evenly, turn on the pre-coating mode and pump the filter aid into the filter plate box for pre-coating; when the liquid level in the mixing barrel reaches 70%, turn off the pre-coating mode;

[0048] (3) Normal filtration stage: After the pre-coating is completed, immediately add 50kg of clay and 20kg of cellulose to the mixing barrel, and fill the mixing barrel with rolling oil again. Set the filter aid distribution cycle to 16 hours when the mixing barrel is full; fill the mixing barrel with rolling oil again after 8 hours; starting from the 16th hour, add 10kg of diatomaceous earth, 5kg of clay and 3kg of cellulose each time you add oil, and then add filter aid twice according to this ratio according to the filter plate pressure;

[0049] (4) Cleaning stage: After the rolling mill was started and operated for more than 8h×4h, it was found that the oil transmittance was less than 60% and gradually deteriorated. It was decided not to add filter aids. At this time, the pressure in the filter box was 0.2MPa. No more rolling oil was added. As the transmittance trended worse, it was prepared to clean and enter the next filtration cycle.

[0050] Since the pre-coating layer was not solidified, the cellulose was mixed with the filter aid in the pre-coating stage, resulting in the loosening of the subsequent pre-coating layer and the cross-filtration of aluminum powder. The transmittance test results were as follows: after 8 hours of filtration process, the transmittance was 70%, 65% after 24 hours, and 60% after 32 hours.

[0051] Comparative Example 3

[0052] Mixing bucket not cleaned

[0053] (1) Pre-coating stage: 50% of the liquid level remains in the mixing barrel during the last filtration cycle (estimated to contain about 10 kg of diatomaceous earth, 5 kg of clay, and 3 to 5 kg of cellulose). The mixing barrel is not emptied according to the process requirements, and 70 kg of diatomaceous earth is directly added to the mixing barrel. Then, the rolling oil is filled to the mixing barrel. The liquid level is 100%, about 2000 L. After stirring evenly, the pre-coating mode is turned on and the filter aid is pumped into the filter plate box for pre-coating; when the liquid level reaches 70%, the pre-coating mode is turned off;

[0054] (2) Sedimentation stage: Enter the normal filtration mode and run for 20 minutes to allow the pre-coating layer to settle and solidify, then add 50 kg of white clay and 20 kg of cellulose to the mixing barrel, and fill the mixing barrel with rolling oil again;

[0055] (3) Normal filtration stage: Set the mixing tank to be full of filter aids for a 16-hour batching cycle. After 8 hours, fill the mixing tank with rolling oil again. Starting from the 16th hour, add 10 kg of diatomaceous earth, 5 kg of clay and 3 kg of cellulose each time you add oil. Subsequently, add filter aids twice in this proportion according to the filter pressure.

[0056] (4) Cleaning stage: After the rough rolling mill has been running for more than 8h×4h, sampling shows that the oil transmittance is 70%. The filter aid is replenished once according to step (3). After 40 hours, the filter aid is no longer replenished. When the pressure in the filter box exceeds 0.3MPa, the rolling oil is no longer replenished in the mixing barrel. When the pressure in the filter box reaches 0.34-0.4MPa, the filtration is terminated and the next filtration cycle is entered after cleaning.

[0057] Transmittance test results: 75% after 16 hours of the above filtration process, 70% after 32 hours, and 65% after 48 hours.

[0058] Analysis shows that the presence of cellulose in the pre-coating results in a relatively small density of the pre-coating and an increased possibility of aluminum powder cross-filtration. However, due to the small amount of cellulose in the pre-coating, the light transmittance does not affect the production quality.

[0059] Comparative Example 4

[0060] No cellulose

[0061] (1) Pre-coating stage: directly add 100 kg of diatomaceous earth into the mixing barrel, then fill the mixing barrel with rolling oil, the liquid level is 100% about 2000 L, after stirring evenly, turn on the pre-coating mode, pump the filter aid into the filter plate box for pre-coating; when the liquid level reaches 70%, turn off the pre-coating mode;

[0062] (2) Normal filtration stage: fill the mixing barrel with rolling oil again, set the filter aid batching cycle when the mixing barrel is full to 16 hours, add 50 kg of white clay after the pre-coating is cured for 20 minutes, and fill the mixing barrel with rolling oil again after 8 hours. Whether to add filter aid is determined based on the pressure in the filter box;

[0063] (4) Cleaning stage: When the above process runs for 12 hours, the pressure in the filter box reaches 0.28 MPa. Considering that the pressure alarm margin is insufficient, the rolling oil is no longer added. As the rolling oil filtration pressure increases, the filter is prepared to be cleaned and the next filtration cycle is started.

[0064] Transmittance test results: After the above filtration process was run for 12 hours, the transmittance fluctuated to a certain extent, but still maintained at 80-85%, which affected the production efficiency.

[0065] Table 1. Comparison of rolling oil permeability and filtration cycle of the filtration process of Example 1 and Comparative Example

[0066]

[0067] It can be seen from the table that the rolling oil transmittance of the filtering method of Example 1 can reach more than 80%, which has the highest cost performance and can fully meet the quality requirements of crude rolling oil products. The filtering cycle can reach more than 48 hours.

[0068] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for filtering rolling oil of an aluminum foil rough rolling mill, using a plate filter for filtering, characterized in that: The following steps are involved: (1) Empty the rolling oil and filter aid in the mixing barrel to make the cellulose content in the mixing barrel less than 1‰; (2) Add rolling oil and diatomaceous earth in a mass ratio of 20:1 to 1.5 into the mixing barrel, fill the mixing barrel with rolling oil, stir evenly, turn on the pre-coating mode, pump the mixture in the mixing barrel into the filter plate box for pre-coating, and the pre-coating amount is 25 to 40% of the liquid level in the mixing barrel; (3) Turn off the pre-coating mode, run the machine for 15 to 25 minutes at the normal 16-hour light-absorbing filter aid dosing speed, wait for the filter aid in the filter box to settle and solidify to form a pre-coating layer, then add filter aids such as clay and cellulose, so that the mass ratio of diatomaceous earth: clay: cellulose in the mixing barrel is 3.0 to 4: 2.0 to 1: 1 to 0.5, and after filling up the rolling oil again, the mass ratio of rolling oil and all filter aids in the mixing barrel is 20: 1.0 to 1.75; (4) Set the batching cycle of the filter aid to 16 hours when the mixing tank is full, and fill the mixing tank with rolling oil every 8 hours. Starting from the 24th hour, diatomaceous earth, kaolin and cellulose need to be added when the mixing tank is filled with oil again. The mass ratio of diatomaceous earth, kaolin and cellulose added is 2.5-1.5:1.5-1:0.5-1. After stirring evenly, pump it into the filter box for filtration. According to the filter pressure, add filter aid 2-3 times according to this ratio; (5) After the filter has been running for more than 8h×5, add rolling oil to the mixing barrel according to the filtration pressure displayed on the filter box, and no longer add filter aid; when the filter box pressure reaches 0.34~0.4MPa, the filtration is terminated and the next filtration cycle is entered after cleaning.

2. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (2), the mass ratio of adding to the stirring barrel is 20: 1.25 of rolling oil and diatomaceous earth, fill the mixing barrel with rolling oil.

3. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (2), the pre-coating amount is 30% of the liquid level in the mixing barrel.

4. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (3), the activation degree of the cellulose is 2400-3400 mol / 100 g, and the active cellulose content in the content is ≥50%.

5. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (3), the curing time of the pre-coating layer is 20 minutes.

6. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (3), the mass ratio of diatomaceous earth: clay: cellulose in the stirring barrel is 3.5:2.5:

1.

7. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (3), after the rolling oil is filled up again, the mass ratio of the rolling oil to all the filter aids in the stirring barrel is 20:1.

5.

8. The method for filtering rolling oil of an aluminum foil rough rolling mill according to claim 1, characterized in that: In step (4), the mass ratio of diatomaceous earth, clay and cellulose is 2:1:0.5.

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