JP2008073666A - Sand filtration device and method, and method of hot-rolling steel sheet by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the clarification effect of filter sand by preventing flow-out of sand in back-washing in a sand filtration device. <P>SOLUTION: A net 30 is installed in a water flow-in port 14 of the sand filtration device 1. Scale generated in hot-rolling is filtered using the sand filtration device 1 to be separated from water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sand filtration device, a method, and a hot rolling method of a steel plate using the sand filtration device, and particularly suitable for use in filtering a scale by hot rolling to separate it from water. The present invention relates to an apparatus, a method, and a hot rolling method for a steel plate using the same.

  Industrial water is circulated and used in various factories mainly for cooling and washing.

  For example, in the steel industry, water is circulated and used in various manufacturing processes, and more specific examples will be described. As shown in FIG. 12, in the hot rolling process 100, the water is generated on the surface of the steel plate 21. In order to remove the iron oxide (hereinafter referred to as scale), water with pressure applied is sprayed directly onto the steel plate 21 through the spray nozzle 18 or the like, or the work roll 20 of the rolling mill is cooled. Similarly, water is supplied through the spray nozzle 19 or the like.

  Here, as for the former method of removing the scale, the removed scale is collected together with water into the pit 23 through the sluice 22 and passes through the sedimentation basin 24. In the sedimentation basin 24, the scale is precipitated and separated from the water, but the scale that has not been separated can be completely separated from the water by passing through the sand filtration device 1 together with the water, and the water can be reused. In other words, it is used for circulation. By the way, in the figure, all indicated by 4, 25 and 26 are pumps.

  As described above, the water to be circulated is also referred to as “circular water”. However, while the cyclic water (hereinafter simply referred to as “water”) is reused as many times as possible, the sand filter 1 is separated. The scales that have been accumulated accumulate. For this reason, flowing sand when separating a scale from water in one sand filter 1 (for example, one sand filter 1 in 6 units) out of a plurality of sand filters 1 exists. By allowing water to flow in the opposite direction, the operation of periodically removing the scale (hereinafter referred to as backwashing) is sequentially performed on each sand filtration device 1.

  As a technique related to the sand filtration device, for example, as in Patent Document 1, there is a technique in which fine bubble-generating water that generates fine bubbles is injected and backwashing is performed while preventing outflow of filter sand.

  The method of filtration and backwashing will be described with reference to FIGS. The sand filtration means that water is passed between the fine particles of the filter sand 16 so that impurities contained in the water are filtered and removed by the filter sand 16 so that the water can be reused. It can also be called processing. Filtration is performed by repeating a series of treatments of passing water → primary backwash → secondary backwash → full water → passing water. Hereinafter, each process will be described.

  FIG. 13 shows the original operation of the sand filtration apparatus 1, that is, the treatment of water flow (filtration), in which industrial water discharged from a factory is treated to separate and reuse the scale from the water. During water flow, the raw water valve 5 and the treated water valve 7 are open, and the other valves are closed. Impurities are removed from the water flowing into the sand filtration device 1 from the inlet 14 located above the surface of the filter sand 16 by the filtration water pump 4 while passing through the filter sand 16. After that, the water is reused by passing through the gravel 17, passing through the drainage port 15, and being supplied to the factory again.

  FIG. 14 shows the state of the primary backwash process. In the sand filter 1, backwashing treatment for washing impurities adhering to the filter sand 16 can be performed. At the time of the primary backwash, the intake / exhaust valve 2, the drain valve 6, the backwash valve 8, and the air valve 12 are open, and the other valves are closed. Backwash water is fed into the sand filtration device 1 from the drain port 15 by the backwash water pump 11. The backwash water cleans the gravel 17 and filter sand 16 and drains it through the inlet 14. In addition, as described in Patent Document 1, the cleaning effect is improved by sending air from the blower 13. In addition, by opening the intake / exhaust valve 2, even if a large amount of backwash water is sent, the pressure inside the sand filtration device 1 is not excessively increased.

  FIG. 15 shows the state of the secondary backwash process. At the time of the secondary backwash, the drain valve 6 and the backwash valve 8 are open, and the other valves are closed. Backwash water is fed from the drain port 15 into the sand filter 1 by the backwash water pump 11. The backwash water cleans the gravel 17 and filter sand 16 and drains through the inlet 14. Sending air from the blower 13 stops.

  FIG. 16 shows a state of full water treatment. The sand filtration apparatus 1 after the end of backwashing needs to be in a full state before water is passed again. When the water is full, the full water valve 3 and the backwash valve 8 are open, and the other valves are closed.

JP 2001-149712 A

  However, according to the examination by the inventors, it has been found that there are the following problems.

  In hot rolling, as shown in FIG. 12, a lubricant containing oil is supplied between the steel plate 21 and the work roll 20 and rolled. However, the oil adheres to the filter sand 16, and the filter sand 16 Is coarsened, the volume is increased and the specific gravity is apparently reduced. Therefore, as shown in FIG. 17, the filter sand 16 is put out of the sand filtration device 1 from the inlet 14 during the backwash process. It flows out and mixes in the waste water. As a result, (1) the filter sand 16 in the sand filter device 1 is reduced, so that the desired water quality cannot be obtained. (2) The spilled filter sand 16 must be collected and discarded. (3) Sand There is a problem that the filter sand 16 and gravel 17 in the filter device 1 must be newly replenished.

  In order to solve this problem, for example, (1) when a large amount of oil is attached to the filter sand 16, the chemical is injected from the chemical tank 9 into the backwash water by the chemical injection pump 10 and adheres to the filter sand 16. In addition, (2) when using chemicals during the primary backwashing, to avoid mixing chemicals into the water to be reused, during the secondary backwashing, the sand filtration device 1 In order to clean the chemicals inside, the cleaning time is longer than usual. However, there is no effect on the outflow of the filter sand 16, and the chemicals are not effective in the water to be reused. There was a problem that the desired quality and surface properties of the steel sheet could not be obtained.

  The present invention has been made to solve such problems of the prior art, and prevents sand from flowing out at the time of backwashing in the sand filtration device, and a sand filtration device and method for improving the effect of washing sand. And it aims at providing the hot rolling method of the steel plate using this.

The present invention for achieving this object is as follows. That is,
(1) A sand filtration device characterized in that a net is installed at the water inlet in the sand filtration device.
(2) The sand filtration device according to claim 1, wherein the net of (1) is detachable.
(3) In the filtration method using a sand filtration device, a sand filtration method characterized by installing a net at the water inlet.
(4) A method of hot rolling a steel sheet, wherein the scale is filtered and separated from water using the method of (3).

  By this invention, the outflow of the filter sand at the time of backwashing in a sand filter apparatus can be prevented, and the washing | cleaning effect of filter sand can be improved now. And it became possible to obtain a stable water quality, and to reduce the maintenance cost of the sand filtration device while ensuring the desired quality and surface properties of the steel sheet.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings as appropriate.

(First embodiment)
FIG. 1 shows one embodiment of a sand filtration device 1 of the present invention. The reference numerals are the same as those in FIGS. 13 to 16 described above. A net 30 is installed at the inlet 14 above the surface of the filter sand 16.

  FIG. 2 shows the operation of the present invention. As can be seen from a comparison with FIG. 17, the filter sand 16 is dammed up by the net 30 during backwashing, and the filter sand 16 is prevented from flowing out together with the water drained from the inlet 14. Can do.

  The size of the filter sand 16 is determined in accordance with the object to be supplemented, but in order to supplement the scale, generally one having an average particle diameter of 2 mm is used. The mesh opening of the net 30 is preferably smaller than the smallest particle size of the myriad filter sands 16, but if it is too small, the drainage will not go smoothly due to resistance during drainage. The size of the filter sand 16 having an average particle diameter of 2 mm and an opening size of 3.35 mm can be set to 3.35 mm so that the filter sand 16 whose apparent specific gravity is lightened by the adhesion cannot pass through.

  According to the investigations by the inventors, 85% of the filter sand 16 may not flow out as long as the mesh opening of the mesh 30 is 1.5 mm larger than the average particle size of the filter sand 16. know.

  In addition, if an average particle diameter is 2 mm, it will pass through the thing of the nominal opening W = 4mm prescribed | regulated to JISZ8801: 2000, and the thing which did not pass the thing of W = 1mm about the sand 16 The image of the microphotograph was taken, and for the filter sand that was entirely reflected in the field of view, the area on the image was obtained one by one, and the diameter of the circle of the same area was divided by the number of filter sand and averaged. It is evaluated with the value specified by the thing.

  Further, since the scale grains are generally smaller than the filter sand 16, even if there is a net 30, the scale grains are sufficiently discharged together with the water drained from the inlet 14.

  There are large grain scales in the sand filtration device 1 and it is not discharged from the sand filtration device 1. However, since the proportion of such large particle scales is extremely small, even if it remains in the sand filtration device 1, There is practically no problem.

  Next, the operation of backwashing using the sand filtration device of the present invention will be described below step by step.

  FIG. 3 shows a state of water passing (filtration) treatment. During water flow, the raw water valve 5 and the treated water valve 7 are open, and the other valves are closed. Impurities are removed from the water flowing into the sand filtration device 1 from the inlet 14 by the filtration water pump 4 while passing through the filter sand 16. After that, the water is reused by passing through the gravel 17, passing through the drainage port 15, and being supplied to the factory again.

  FIG. 4 shows the state of the primary backwash process. In the sand filter 1, backwashing treatment for washing impurities adhering to the filter sand 16 can be performed. At the time of the primary backwash, the intake / exhaust valve 2, the drain valve 6, the backwash valve 8, and the air valve 12 are open, and the other valves are closed. Backwash water is fed into the sand filtering device 1 from the drain port 15 by the backwash water pump 11. The backwash water cleans the gravel 17 and filter sand 16 and drains it through the inlet 14. In addition, the cleaning effect is improved by sending air from the blower 13.

  In addition, when a large amount of oil is attached to the filter sand 16, a chemical is injected from the chemical tank 9 into the backwash water by the chemical injection pump 10 to separate the oil attached to the filter sand 16. Good.

  As described above, it is desirable that the mesh opening of the mesh 30 is smaller than the average particle diameter of the filter sand 16, but this can prevent the filter sand 16 from flowing out from the inlet 14. By keeping the sand 16 in the sand filtration device 1, the number of times of contact between the water and the filter sand 16 is increased, whereby the separation of impurities attached to the filter sand 16 can be promoted.

  FIG. 5 shows the state of the secondary backwash process. At the time of the secondary backwash, the drain valve 6 and the backwash valve 8 are open, and the other valves are closed. Backwash water is fed from the drain port 15 into the sand filtration device 1 by the backwash pump 11. The backwash water cleans the gravel 17 and filter sand 16 and drains it through the inlet 14. Sending air from the blower 13 stops. In addition, when chemicals are used during the primary backwashing, the chemicals in the sand filter 1 are completely washed during the secondary backwashing in order to avoid mixing chemicals into the water to be reused. It is preferable to make the time longer than usual.

  FIG. 6 shows a state in the sand filtration device 1 at the time of secondary backwashing when the present invention is applied with the net 30 installed for the purpose of preventing the sand filter 16 from flowing out. As in the case of the primary backwashing, the filter sand 16 can be prevented from flowing out from the inlet 14 by the net 30, and the filter sand 16 is kept in the sand filter device 1, so that This contact can promote the separation of impurities.

  FIG. 7 shows a state of full water treatment. The sand filtration apparatus 1 after the end of backwashing needs to be in a full state before water is passed again. When the water is full, the full water valve 3 and the backwash valve 8 are open, and the other valves are closed.

  FIG. 8 shows a state of water passing (filtration) treatment. When the water passes through the inflow port 14, the mesh of the mesh 30 is washed, and the reduction of the filtration and backwashing effects due to the clogging of the mesh 30 can be prevented.

(Second Embodiment)
9 and 10 show the sand filtration device 1 in which the net 30 can be attached and detached. In this way, cleaning can be performed with the net 30 removed. Therefore, the net 30 can be cleaned without affecting the use of the sand filter 1. Moreover, the reduction of the filtration and backwashing effects due to clogging of the mesh 30 can be prevented.

  Thereby, lifetime improvement of the sand filter 16 and reduction of the maintenance cost of the sand filter apparatus 1 can be aimed at. The attachment / detachment may be performed manually, or may be performed automatically such that a cylinder using fluid pressure such as hydraulic pressure or air pressure, or an actuator other than an electric motor may be operated remotely.

  As described above, according to the present invention, in any of the above-described embodiments or another embodiment, the scale supplemented with the filter sand is prevented from flowing out of the filter sand in the sand filter device. The water can be discharged from the water inlet by backflow water.

  In this example, both the examples of the present invention and the comparative examples described below use filter sand having an average particle diameter of 2 mm, and use a nominal opening W = 3.35 mm defined in JIS Z 8801: 2000 as a net. If it was.

  FIG. 11 compares the outflow amount of the filter sand 16 when the present invention is applied (invention example) and when it is not (comparative example). It turns out that the outflow amount of the filter sand 16 is reduced significantly by application of this invention.

Pipeline diagram for explaining the first embodiment of the present invention Pipeline diagram for explaining the operation Pipeline diagram showing the state of water flow (filtration) treatment Pipeline diagram showing the state of the primary backwash process Pipeline diagram showing the state of the secondary backwash process Sectional drawing which shows the state in the sand filtration apparatus at the time of a secondary backwash process similarly Pipeline diagram showing the state of full water treatment Sectional view showing the state of water flow (filtration) treatment Sectional drawing of the principal part for demonstrating the 2nd Embodiment of this invention Sectional drawing which shows the state of a primary backwash process similarly Diagram for explaining the effect of the present invention Pipeline diagram for explaining the background art Pipeline diagram showing the state of water flow (filtration) treatment Pipeline diagram showing the state of the primary backwash process Pipeline diagram showing the state of the secondary backwash process Pipeline diagram showing the state of full water treatment Sectional drawing for demonstrating the problem of a prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sand filtration apparatus 2 ... Intake / exhaust valve 3 ... Full water valve 4 ... Filtration water pump 5 ... Raw water valve 6 ... Drain valve 7 ... Treated water valve 8 ... Backwash valve 9 ... Chemical tank 10 ... Chemical injection pump 11 ... Backwash Water pump 12 ... Air valve 13 ... Blower 14 ... Inlet 15 ... Drainage port 16 ... Filter sand 17 ... Gravel 18, 19 ... Spray nozzle 20 ... Work roll of rolling mill 21 ... Steel plate 22 ... Sluice 23 ... Pit 24 ... Sedimentation basin 30 ... Net 100 ... Hot rolling process

Claims (4)

In sand filter,
A sand filter characterized by a net installed at the water inlet.   The sand filter according to claim 1, wherein the net is detachable. In the filtration method using a sand filtration device,
A sand filtration method characterized by installing a net at the water inlet.   A method for hot rolling a steel sheet, wherein the scale is filtered and separated from water using the method according to claim 3.

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