JP2005230608A - Alkali washing liquid recycling apparatus and method for using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkali washing liquid recycling apparatus capable of effectively separating an oil component and an iron component in an alkali washing liquid to extend the life of the alkali washing liquid, and a method for using it. <P>SOLUTION: The alkali washing liquid recycling apparatus is constituted so as to separate impurities in the waste alkali washing liquid by the flotation and sedimentation of impurities and has a separation tank 1 into which the waste alkali washing liquid is introduced, a plurality of weirs 2 provided in the separation tank so as to have an inclination of 20-40° with respect to the side wall of the separation tank and a waste liquid introducing device equipped with the inflow distribution pipe 3 arranged under the weirs and introducing the waste liquid from an inflow port 4 to lead out the same into the separation tank from an outflow port 5. Each of the weirs desirably has a corrugated shape having grooves in a vertical direction and, if the waste liquid is allowed to flow between the flow channels between the plurality of weirs so that a Reynolds number becomes 3,000 or less, impurities can be separated effectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention continuously removes impurities, such as oil and iron powder, which deteriorate cleaning properties from an alkaline degreasing solution used for cleaning steel materials, and recycles the alkaline cleaning solution that extends the life of the alkaline degreasing solution and the apparatus. About how to use.

  When manufacturing a steel product, for example, in a cold drawing process or a cold rolling process of a steel pipe, a processing oil mainly composed of mineral oil is used for the purpose of lubrication and cooling. Therefore, the processing oil adheres to the entire surface of the workpiece.

  When, for example, heat treatment or the like is performed on the workpiece with the processing oil attached thereto in the next step, the appearance is not good, the appearance is deteriorated, and the carburization or the like may be deteriorated. Therefore, usually, the workpiece is degreased with an alkaline aqueous solution containing an organic solvent or a surfactant. Conventionally, degreasing using, for example, an organic solvent such as trichloroethane has been widely performed. However, there is a problem of disposal of sludge (soil contamination, etc.) discharged by the treatment of waste solvent after use, or deterioration of the working environment. Due to problems such as (adverse effects on the human body), degreasing using an alkaline aqueous solution is now becoming common.

  In the degreasing using this alkaline aqueous solution, mixing of the oil content brought about by the work material and iron powder caused by abrasion is unavoidable, and the degreasing performance of the alkaline aqueous solution deteriorates as the concentration (content ratio) increases. Therefore, it is common to set in advance an upper limit of a concentration (especially oil concentration) that can ensure detergency, to dispose of the alkaline cleaning liquid exceeding that concentration, and to construct a new cleaning liquid. However, when the expense required for the disposal of the cleaning liquid is combined with the expense of newly bathing the cleaning liquid, the cost becomes high, and the profitability of the product is significantly hindered.

  As a method of removing impurities such as oil and iron powder mixed in the alkaline cleaning liquid, a method of leaving the cleaning liquid and removing floating oil with an oil adsorption mat is simple, but each time the operation is stopped. To reduce production efficiency.

  Moreover, although the filtration process by an electromagnetic filter is effective in removing iron, it is insufficient for removing oil. In order to eliminate this defect, Patent Document 1 discloses that iron powder in which clean iron powder is added to and mixed with an alkaline cleaning liquid mixed with oil and iron powder to adsorb the oil to the particles, and then the oil is adsorbed by an electromagnetic filter. A method of filtering is proposed. However, clean and fine iron powder is required, and a large-scale device such as a mixing and stirring device or a filtering device using an electromagnetic filter is required, resulting in an increase in manufacturing cost.

  In Patent Document 2, an alkali component is added to an alkali cleaning liquid mixed with solid dirt components such as oil, sand, and metal powder in excess of the limit at which the surfactant contained in the cleaning liquid is salted out and separated. , A method of recovering and recycling an alkaline cleaning liquid that is an aqueous phase by separating into an oil phase, an aqueous phase, and a solid phase. However, this method requires a separate tank and a centrifugal separator for salting out the alkaline cleaning liquid mixed with oil and solid soil components, and it is difficult to continuously remove the oil. is there.

  Patent Document 3 discloses that a large amount of bubbles generated by a chemical reaction between a rolling oil or the like and a cleaning liquid are efficiently removed when a metal material with rolling oil or the like attached to the surface is cleaned using an alkaline aqueous solution or the like as a cleaning liquid. A cleaning facility is described that is configured to be thoroughly defoamed and to be reused as a cleaning liquid after impurities (soap, iron, etc.) in the resulting antifoaming liquid are separated and removed. However, this equipment is mainly intended for defoaming. Also, in order to allow the impurities to settle and separate, a plurality of partition plates suspended from the upper part of the separation tank and the lower part immersed in the cleaning liquid and weirs standing on the tank bottom are provided alternately in the liquid flow direction. However, there is only one flow path, which is inefficient, and the separation effect is particularly small in the vicinity of the inlet having a high flow rate. Furthermore, in order to ensure the length at which the flow velocity is sufficiently reduced, the equipment must be enlarged.

  As described above, there is no technique for removing impurities such as oil and iron powder mixed in the alkali cleaning liquid at low cost and extending the life of the alkali cleaning liquid, and the development thereof is desired.

Japanese Patent Laid-Open No. 5-117886

JP-A-7-286290 JP 2001-234377 A

  The present invention has been made in view of such a situation, and its purpose is to remove oil, iron powder and the like (hereinafter also referred to as “impurities”) that adversely affect the degreasing performance from the alkaline cleaning liquid, and to improve the life of the cleaning liquid. It is an object of the present invention to provide an alkaline cleaning liquid recycling apparatus and a method for using the same. Specifically, when removing oil and iron powder, it is possible to remove impurities continuously without stopping the operation, and it is as simple as possible and the space required for installation can be minimized. It is to provide an inexpensive device that can be used and a method of using the device.

  As a result of repeated studies to solve the above-described problems, the present inventors have obtained the following knowledge.

  (A) In order to obtain an inexpensive apparatus, it is appropriate to use a separate tank for removing impurities and to separate impurities using a specific gravity difference.

  (B) In order to separate the impurities in the fluid by utilizing the difference in specific gravity, it is necessary to slow down the fluid, but efficient processing is possible with only one fluid path (flow path) in the tank. It is difficult. In order to increase the processing efficiency, it is preferable to install a partition plate (weir) in the tank and provide a plurality of flow paths.

  (C) When the partition plate (weir) of the flow path has an appropriate angle, the sedimentation and separation of impurities becomes easy.

  (D) This apparatus should be equipped with a mechanism capable of removing the floating impurities, mainly oil, continuously or semi-continuously.

  (E) Reynolds number (inter-weir Reynolds number) Re of the fluid (dirty cleaning liquid, hereinafter also referred to as “waste liquid”) Re flowing continuously into the flow path divided by the partition plate (weir) in the tank is 3000 If it is set as follows, the sedimentation separation of impurities in the fluid can be effectively performed.

  The present invention has been made on the basis of such findings, and the gist of the present invention is the following (1) recycling apparatus and (2) the method of using the apparatus.

  (1) An alkali cleaning liquid recycling apparatus for separating impurities in waste liquid of alkaline cleaning liquid by floating and settling of impurities, having a separation tank for storing the waste liquid and an inclination of 20 to 40 ° with respect to the side wall of the separation tank. A recycling apparatus for alkaline cleaning liquid, comprising a plurality of weirs and a waste liquid introducing device that is disposed below the weirs and includes an inflow pipe that introduces waste liquid from an inflow port and leads out from the outflow port into a separation tank.

  In this recycling apparatus, if the weir has a corrugated shape with grooves in the vertical direction, impurities can be effectively separated.

  In addition, if the vertical cross-sectional area of the portion of the inflow distribution pipe where the waste liquid flows is made smaller as it moves away from the inlet, the flow rate of the waste liquid flowing through the plurality of channels divided by the weir can be made similar. Impurities can be separated efficiently.

  (2) The method of using the recycling apparatus for alkaline cleaning liquid according to (1), wherein the waste liquid flows between a plurality of weirs (flow paths) so that the number of lay nozzles is 3000 or less.

  As used herein, “waste liquid of alkaline cleaning liquid” or simply “waste liquid” refers to an alkaline cleaning liquid in which impurities such as oil and iron powder are mixed in excess of a predetermined management standard as a result of being used for cleaning steel materials.

  The “vertical cross-sectional area of the portion where the waste liquid flows in the inflow distribution pipe” refers to the cross-sectional area of the hollow portion of the pipe in a plane perpendicular to the central axis (or the direction in which the waste liquid flows) of the inflow distribution pipe.

  According to the alkaline cleaning liquid recycling apparatus and the method of using the same according to the present invention, it is possible to effectively and continuously separate oil and iron in the alkaline cleaning liquid, thereby extending the life of the cleaning liquid. Also, this recycling device is very compact and inexpensive.

  As described above, the alkaline cleaning liquid recycling apparatus of the present invention is an alkaline cleaning liquid recycling apparatus that separates impurities in the waste liquid of the alkaline cleaning liquid by the floating and settling of impurities, and includes a separation tank for storing the waste liquid, and a separation tank. Waste liquid having a plurality of weirs having an inclination of 20 to 40 ° with respect to the side wall of the tank and an inflow distribution pipe arranged below the weir and introducing the waste liquid from the inlet and leading out from the outlet into the separation tank. An alkaline cleaning liquid recycling device having an introduction device ”.

  The premise that this recycling device is a device that “separates impurities in the waste liquid of alkaline cleaning liquid by the floating and settling of impurities” is to use the difference in specific gravity without using an electromagnetic filter or centrifuge. This is to provide an inexpensive facility for separating impurities.

  The reason for having the “separation tank for storing the waste liquid” is to introduce the waste liquid into the separation tank and settle and separate impurities in the waste liquid without stopping the operation. In addition, the “several weirs having an inclination of 20 to 40 ° with respect to the side wall of the separation tank” are installed in the separation tank by providing a plurality of flow paths inclined by dividing the inside of the tank by the weirs. This is because the impurities are effectively separated by settling or floating the impurities in the flow path. In a simple tank having no weir, convection occurs and effective separation of impurities is not performed, and in a vertical weir type tank attached to the separation tank of the cleaning device described in Patent Document 3 described above, Since there is only one waste liquid flow path, a large facility is required to effectively separate the impurities.

  The reason why the inclination angle of the weir is set to 20 to 40 ° with respect to the side wall of the separation tank is to effectively raise or sink impurities, as will be described later.

  Furthermore, the apparatus of the present invention has a “waste liquid introduction device provided with an inflow distribution pipe that is disposed below the weir, introduces the waste liquid from the inlet, and leads out from the outlet into the separation tank” This is because the waste liquid is led out (inflowed) into the tank from the lower side of the weir through the inflow distribution pipe, and passed through the plurality of flow paths divided by the weir. It is desirable that the outlet for discharging the waste liquid is provided below the corresponding flow path.

  FIG. 3 is a schematic longitudinal sectional view showing a configuration example of a separation tank of a type divided by a plurality of weirs. The separation tank 1 is finely divided by a plurality of weirs 2 ′, a plurality of flow paths are secured, and the waste liquid of the alkaline cleaning liquid is caused to flow between the respective weirs of the plurality of weirs 2 ′ below the tank 1. An inflow distribution pipe 3 is attached. The inflow distribution pipe 3 is provided with an outlet 5 for ejecting fluid at a portion corresponding to the lower part of each flow path so that the waste liquid of the cleaning liquid spreads through the respective flow paths, and the diameter of the pipe 3 increases toward the tip. It is getting thinner.

  If the separation tank having the configuration shown in FIG. 3 is used, impurities, particularly oil, can be efficiently levitated and separated with a compact facility that does not require a large installation area. However, since the waste liquid flows upward in the separation tank, sedimentation separation cannot be performed effectively.

  Therefore, in the present invention, “a plurality of weirs having an inclination of 20 to 40 ° with respect to the side wall of the separation tank” is attached in the separation tank.

  FIG. 1 is a longitudinal sectional view showing a configuration example of a main part of an alkaline cleaning liquid recycling apparatus according to the present invention. As shown in the drawing, the plurality of weirs 2 that finely divide the inside of the separation tank 1 into a plurality of flow paths have an inclination of θ (20 to 40 °) with respect to the side wall of the separation tank 1. Below, an inflow distribution pipe 3 of the waste liquid introduction device is disposed. The inflow distribution pipe 3 is for introducing the waste liquid of the alkaline cleaning liquid into the separation tank 1 and for introducing the introduced waste liquid between the weirs of the plurality of weirs 2 in the separation tank 1. As in the case of the separation tank shown in FIG. 3, the inflow distribution pipe 3 becomes smaller in diameter as it goes to the tip. This is because the flow rate of the waste liquid flowing through each flow path is the same.

  In addition, the inflow distribution pipe 3 may normally use one or a plurality of pipes having a circular cross section, but the inflow distribution pipe 3 is not limited thereto, and may have any cross sectional shape such as a rectangle or a semicircle. .

  FIG. 2 is a diagram for explaining the effect of separating impurities by the weir having the slope. While the waste liquid passes through the flow path 6 formed by the two weirs 2a and 2b in the direction of the arrow 7, light particles (mainly oil, indicated by a circle) move upward (floating). Then, it is trapped in the weir 2a, aggregates there, and rises along the surface of the weir 2a. On the other hand, heavy particles (mainly iron powder) move downward (sediment) and are trapped by the weir 2b where they aggregate and settle along the surface of the weir 2b. Agglomeration increases the volume of the particles, which facilitates floating or settling.

  Thus, when the weirs 2a and 2b have an inclination, particles that float or settle are easily trapped and aggregated by the weir 2a or 2b. However, if the inclination is too large, the trapped particles and the weirs 2a and 2b The effect of the frictional resistance is large, and it becomes difficult for the particles to float or settle. On the other hand, if the inclination of the weirs 2a and 2b is too small, a desired agglomeration effect cannot be obtained.

  FIG. 4 is a diagram showing the relationship between the inclination angle of the weir and the oil concentration and the iron concentration in the alkaline cleaning liquid after the impurities are separated, and passes through the flow path formed between the weirs using the following alkaline cleaning liquid. It is the result obtained by the experiment which performed the flow velocity (this is called "flow velocity between weirs") of the washing liquid at 0.2 m / s. As the surfactant, a nonionic surfactant was used, and the oil concentration and the iron concentration were adjusted using rolling oil and iron powder (particle size: 0.1 to 20 μm).

[Alkaline cleaning solution]
NaOH concentration: 5.0% by volume
Surfactant concentration: 0.4% by volume
Oil content: 2.0% by volume
Iron concentration: 0.08% by mass
Liquid temperature: 80 ° C
In FIG. 4, the oil content is “good” if the oil concentration in the alkaline cleaning liquid after treatment (indicated by a mark ●) is 0.5% by volume or less as indicated by an arrow in the figure. In regard to, the iron concentration (indicated by □) in the cleaning solution after treatment was determined to be “good” if it was 0.03% by mass or less.

  As shown in FIG. 4, the effect of separating and removing the oil and iron components deteriorates if the weir inclination angle (the angle with respect to the side wall of the separation tank) is too large or too small. The inclination angle of the weir that is “good” for the oil component is 10 to 40 °, and the inclination angle that is “good” for the iron powder is 20 to 52 °, and both the oil component and the iron powder can be effectively separated and removed. The inclination angle of the weir is 20 to 40 °.

  In the recycling apparatus of the present invention, if the weir has a corrugated shape with a groove in the vertical direction, impurities can be more effectively separated. The “vertical direction” means a vertical direction when the weir is upright.

  In order to effectively separate the oil and iron powder, it is effective to float or sink vertically while suppressing their movement in the horizontal direction as much as possible. Therefore, it is preferable that the weir is inclined at the predetermined angle and has a corrugated shape having a groove (curved depression) in the vertical direction.

  For example, the entire weir should be a channel-shaped corrugated plate so that the resistance to the flow of waste liquid in the horizontal direction is increased. By adopting the channel corrugated plate as the weir, impurities can be easily trapped in the channel corner portion, and a secondary effect that separation is performed more effectively can be obtained.

  Further, in the recycling apparatus of the present invention, if the vertical cross-sectional area of the portion where the waste liquid in the inflow distribution pipe flows is reduced as it goes away from the inlet, the flow rate of the waste liquid flowing through the plurality of channels divided by the weirs is the same. The impurity can be separated efficiently. That is, in the inflow distribution pipe 3 illustrated in FIG. 1, the inner diameter of the inflow distribution pipe 3 is adjusted so that the total pressure (all heads) of the waste liquid flowing through the inflow distribution pipe 3 is constant over the entire length of the inflow distribution pipe 3. If it is made thinner as it goes, the waste liquid having the same flow rate can be passed through each flow path divided by the weir, so that impurities can be separated efficiently.

  The method of using the alkaline cleaning liquid recycling apparatus of the present invention is “use method of flowing waste liquid between the plurality of weirs (flow paths) so that the number of lay nozzles is 3000 or less in the recycling apparatus of the present invention”. is there.

  As parameters that greatly affect the effective separation of impurities in the waste liquid, in addition to the “inclination angle of the weir”, the “flow rate between the weirs” and the “weir interval” of the cleaning liquid can be cited. The “inter-weir flow velocity” is an average flow velocity (m / s) of a fluid flowing between two adjacent weirs (referred to as “inter-weir fluid”).

  If the flow rate between the weirs is too high, separation is difficult because the impurity particles are transported along with the fluid (waste liquid) before they float or settle. On the other hand, when the flow rate between the weirs is low, the separation is effectively performed. However, when the flow rate is too slow, the amount of processing per unit time is small, and it is necessary to provide a very large separation tank to compensate for this. Further, the narrower the weir interval, the greater the pressure loss of the fluid, and the lower the inter-weir flow velocity, which is advantageous for separation.

  Therefore, the effects of inter-weir flow velocity and weir spacing on the separation of impurities in the waste liquid were investigated by experiment, and were organized by the Reynolds number of the inter-weir fluid (this is referred to as “inter-Reynolds number Re”). The inter-weir Reynolds number Re is a dimensionless quantity represented by the following equation (1). FIG. 5 is an explanatory diagram of symbols used in the equation (1).

  FIG. 6 is a diagram showing the relationship between the Reynolds number Re between the weirs and the oil concentration and the iron concentration in the alkaline cleaning liquid after the impurity separation, and the inclination angle θ of the weir shown in FIG. And the results obtained by experiments conducted by changing the inter-weir Reynolds number Re in the range of 300 to 3700 by changing the weir interval W or the inter-weir flow velocity U (see FIG. 5). As the surfactant, a nonionic surfactant was used, and the oil concentration and the iron concentration were adjusted using rolling oil and iron powder (particle size: 0.1 to 20 μm). As in the case of FIG. 4, the oil concentration in the alkaline cleaning liquid after treatment is 0.5% by volume or less for oil, and the iron concentration in the cleaning liquid after treatment is 0. If it was 03 mass% or less, it was set as "good".

[Alkaline cleaning solution]
NaOH concentration: 5.0% by volume
Surfactant concentration: 0.4% by volume
Oil content: 2.0% by volume
Iron concentration: 0.08% by mass
Liquid temperature: 80 ° C
As shown in FIG. 6, both the oil concentration and the iron powder concentration show an increasing tendency as the inter-weir Reynolds number Re increases, and rapidly increase from around 3000. The Reynolds number Re between the weirs that is “good” for the oil content is 3000 or less, and the Reynolds number Re between the weirs that is “good” for the iron powder is about 3300 or less. The inter-weir Reynolds number Re is 3000 or less.

  Generally, the critical Reynolds number Re at which turbulent flow transitions to laminar flow is Re≈2300. If Re is larger than this value, the flow becomes turbulent, and if Re is smaller, the flow becomes laminar. From this, the condition obtained by the above-described experiment indicates that the fluid between the weirs must be in a laminar flow or a turbulent flow state with extremely low energy. This is presumed to be due to the fact that in high-energy turbulent flow with vortices, impurity particles are trapped in the vortex, making it difficult to float or sink.

  Note that the height of the weir (vertical height relative to the horizontal plane) is sufficient for the fluid flowing into the flow path formed by two adjacent weirs in a turbulent state with low energy to sufficiently dissipate the turbulent energy. Is preferably at least 10 times the weir interval (interval in the horizontal direction, W in FIG. 5). More desirably, it is about 20 times. Thereby, the turbulent energy can be sufficiently eliminated from the fluid, and the state can be made close to a laminar flow to facilitate the separation of impurities.

  As described above, according to the method of using the alkaline cleaning liquid recycling apparatus of the present invention that causes the waste liquid to flow between the plurality of weirs (flow paths) so that the number of lay nozzles is 3000 or less, the impurities in the waste liquid are effectively removed. Can be separated.

  In the recycling apparatus of the present invention, ensuring the continuity of the operation for separating and removing impurities in the waste liquid of the alkaline cleaning liquid is an important factor. That is, it is desirable that the dirty cleaning liquid in the degreasing tank flows continuously or semi-continuously into the separation tank and the impurities are separated to a predetermined concentration or less, and then continuously or semi-continuously return to the degreasing tank. .

  FIG. 7 is a diagram showing a configuration of a main part of an example of an apparatus that can enable such continuous or semi-continuous operation. In FIG. 7, a cleaning liquid return port 8 from which impurities are separated is provided on the side wall of the separation tank 1, and is connected to a regenerated cleaning liquid storage unit 10 also attached to the side wall by a pipe 9. The cleaning liquid extracted (recovered) from the return port 8 is once stored in the regenerated cleaning liquid storage unit 10 and recycled to the degreasing tank.

  When extracting the cleaning liquid from the return port 8, it is ideal to extract the cleaning liquid from which dirt is most removed in the vicinity immediately below the layer of floating impurities (oil) (11 layers of floating oil). However, since the flow of the cleaning liquid is disturbed during extraction, if the attachment portion of the return port 8 is too close to the floating oil 11 layer, the floating oil 11 may be caught in the extracted (collected) cleaning liquid. Therefore, for example, as shown in FIG. 7, the attachment position of the return port 8 is lifted up to a portion slightly below the liquid surface 12 of the cleaning liquid below the floating oil 11 layer in the separation tank 1 (the flow of the cleaning liquid by extraction). It is desirable to set it to a part where the oil 11 is not involved, and it may be determined empirically.

  Further, in consideration of the change in the height of the liquid surface 12 of the cleaning liquid, the position of the spout 13 through which the cleaning liquid extracted (recovered) from the return port 8 flows into the regenerated cleaning liquid container 10 is a screw or the like. It is preferable that the height can be adjusted by this mechanism. That is, since the cleaning liquid cannot be extracted when the position of the jet nozzle 13 is higher than the level of the liquid level, it can be moved up and down by a mechanism such as a screw on the outlet side of the extracted cleaning liquid in the pipe 9 (for example, upward when the screw is loosened). A mechanism that can be adjusted so that the spout 13 is always located directly below the liquid level 12 may be employed.

  In addition, it is desirable to provide the return ports between weirs (not shown here) installed in the separation tank. This is because, if it is installed only at an arbitrary location in the separation tank, a flow in that direction occurs in the tank, and impurities are not effectively separated. In order to reduce the flow velocity of the liquid flowing into the return port as much as possible, it is desirable to provide a plurality of return ports and increase the inflow cross-sectional area of the return port (total cross-sectional area of the plurality of return ports).

  FIG. 8 is a diagram illustrating a configuration of a main part of an example of an apparatus for removing impurities (oil) that have floated. In FIG. 8, the inner diameter in the vicinity of the upper end of the separation tank 1 is widened, and a floating oil extraction nozzle 14 for extracting the floating oil 11 at that portion to the outside of the tank 1 is attached. When the floating oil is extracted, as shown in the drawing, the upper tip of the nozzle 14 may be aligned slightly above the liquid level 12 of the cleaning liquid below the floating oil 11 layer. It is desirable that the nozzle 14 has a mechanism capable of adjusting the height in accordance with the height fluctuation of the liquid surface in the same manner as the above-described nozzle.

  If the apparatus comprised in this way is used, a floating oil can be extracted through the floating oil extraction nozzle 14 as needed, and can be discarded. For example, if the nozzle 14 is mounted on the side opposite to the portion where the return port 8 (see FIG. 7) is provided, even if the liquid surface 12 is disturbed due to the extraction of the cleaning liquid, It is desirable because the influence does not reach the opposite side and the floating oil can be extracted without hindrance.

  FIG. 9 is a diagram illustrating a configuration of a main part of an example of an apparatus for removing settled impurities. In FIG. 9, the bottom of the separation tank 1 has an inverted conical shape, and a disposal valve 15 is attached to the lower end thereof. Since the settled impurities (iron powder or the like) 16 settle and accumulate at the bottom of the inverted cone, the valve 15 may be opened periodically to be removed and discarded. The use of the apparatus configured in this way is desirable because it is easy to collect settled impurities, and it is possible to prevent the settled impurities from getting involved in the rising flow of waste liquid.

  If the separation tank having the configuration shown in FIGS. 7 to 9 is used, it is possible to continuously or semi-continuously perform the operation of returning the cleaning liquid from which impurities have been separated and removed to the degreasing tank. Alternatively, settled impurities (oil, iron powder, etc.) can be easily removed, and the alkali cleaning liquid can be smoothly recycled.

  The recycling equipment of the following specifications was produced and applied to the treatment of the waste liquid of the actual alkaline cleaning liquid, and the effect was investigated.

・ Inclination θ of weir: 30 ° with respect to the side wall of the separation tank
・ Weir Reynolds number Re: 2500
The distance between weirs W was 60 mm, and the liquid level rising speed u was 0.7 mm / s (see FIG. 5).

          The liquid level rising speed = flow rate to the separation tank / tank cross-sectional area. By controlling the flow rate to the tank by the inflow valve, the liquid level rising speed u can be set to 0.7 mm / s.

・ If it is assumed that 15m ³ of cleaning solution is treated in 6 hours, the flow rate to be introduced into the separation tank is 6.94 × 10 ^-4 [m ³ / s].

15 [m ³ ] ÷ 6 [h] ÷ 3600 [s / h] = 6.94 × 10 ⁻⁴ [m ³ / s]
・ To make the inter-weir flow velocity the above value, the cross-sectional area of the separation tank should be 0.99 [m ² ].

6.94 × 10 ⁻⁴ [m ³ /s]÷(0.7×10 ⁻³ [m / s])
= 0.99 [m ² ]
In other words, under the above assumption (15 m ³ of cleaning solution is processed in 6 hours), a compact separation tank having a cross-sectional area of about 1 meter square may be installed. Note that the cross-sectional area of the separation tank is determined by how long the cleaning liquid to be processed is processed, and therefore, the optimal cross-sectional area may be set according to the degree of contamination of the cleaning liquid.

  With the recycling apparatus of the present invention configured by attaching a waste liquid introduction device equipped with an inflow distribution pipe to the separation tank of the above specifications, separation and removal of impurities and recycling are performed on the actual alkaline cleaning liquid in the degreasing tank, and degreasing The change over time of the oil concentration in the alkaline cleaning liquid in the tank was investigated.

  The survey results are shown in FIG. For comparison, the results of a survey using a conventional method that does not have a separation tank (a method for setting and managing a disposal standard for oil concentration) are also shown.

  As is clear from the results shown in FIG. 10, in the conventional method, the oil concentration increased in a short period of time, and it was necessary to renew the alkaline cleaning liquid about every one month. By attaching, the oil concentration in the alkaline cleaning liquid was greatly reduced. Although not shown, the life of the cleaning liquid has been extended to about half a year.

  According to the alkaline cleaning liquid recycling apparatus and the method of using the same of the present invention, the life of the cleaning liquid can be greatly extended, and this apparatus is very compact and inexpensive. Therefore, this recycling apparatus can be easily used for cleaning and degreasing of the processing oil adhering to the surface of the steel material that has been subjected to cold drawing or cold rolling, and has a great effect.

It is a longitudinal cross-sectional view which shows the structural example of the principal part of the recycling apparatus of the alkaline cleaning liquid of this invention. It is a figure for demonstrating the separation effect of the impurity by the weir which has an inclination. It is a schematic longitudinal cross-sectional view which shows the example of a structure of the separation tank of the type divided by several sheets of weirs. It is a figure which shows the relationship between the inclination angle of a weir, and the oil content concentration and iron content concentration in an alkali washing liquid after isolate | separating an impurity. It is explanatory drawing of the symbol used for (1) Formula showing Reynolds number Re between weirs. It is a figure which shows the relationship between the Reynolds number Re between weirs, and the oil-component density | concentration and iron-component density | concentration in the alkaline cleaning liquid after impurity separation. It is a figure which shows the structure of the principal part of the example of an apparatus which can implement the isolation | separation removal operation of the impurity in an alkaline cleaning liquid continuously or semi-continuously. It is a figure which shows the structure of the principal part of the example of an apparatus for removing the impurity (oil content) which surfaced. It is a figure which shows the structure of the principal part of the example of an apparatus for removing the settled impurities (iron powder etc.). It is a figure which shows the time-dependent change of the oil-component density | concentration in the alkaline cleaning liquid after a process as a result of an Example.

Explanation of symbols

1: Separation tank 2, 2a, 2b, 2 ': Weir 3: Inflow distribution pipe 4: Inlet 5: Outlet 6: Flow path 7: Arrow 8: Return port 9: Pipe 10: Recycled cleaning liquid container 11: Floating Oil 12: Liquid level 13: Jet 14: Floating oil extraction nozzle 15: Disposal valve 16: Sedimented impurities

Claims (4)

  An alkaline cleaning liquid recycling apparatus for separating impurities in waste liquid of alkaline cleaning liquid by floating and settling of impurities, a separation tank for storing the waste liquid, and a plurality of sheets having an inclination of 20 to 40 ° with respect to a side wall of the separation tank An apparatus for recycling an alkaline cleaning liquid, comprising: a weir; and a waste liquid introducing device that is disposed below the weir and includes an inflow pipe that introduces the waste liquid from the inflow port and guides the waste liquid into the separation tank from the outflow port.   2. The alkaline cleaning liquid recycling apparatus according to claim 1, wherein the weir has a corrugated shape having grooves in the vertical direction.   The apparatus for recycling an alkaline cleaning liquid according to claim 1 or 2, wherein a vertical cross-sectional area of a portion through which the waste liquid flows in the inflow distribution pipe decreases as the distance from the inflow port increases. It is a usage method of the recycling apparatus of the alkaline cleaning liquid according to any one of claims 1 to 3, wherein the waste liquid is made to flow between the plurality of weirs so that the number of lay nozzles is 3000 or less. How to use cleaning fluid recycling equipment.

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