JP2015097997A - Centrifugal machine, management system, and method of manufacturing glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal machine which exhibits high quality of recovery objects and high recovery efficiency, and can be automatically controlled with high precision, a management system of a polishing liquid used in the centrifugal machine, and a method of manufacturing a glass substrate using the management system.SOLUTION: A centrifugal machine 1 includes: a bowl 2 for holding input slurry; a screw conveyer 3 for scraping a concentrated liquid, which contains a recovery object substance 10 separated from the slurry, from the bowl; drive means which rotates the bowl and the screw conveyer respectively; a first sensor 11a for monitoring one or more first parameters related to a state of the slurry; a second sensor 11b for monitoring one or more second parameters related to an operation state of the centrifugal machine; and a third sensor 11c for monitoring one or more third parameters related to a state of the concentrated liquid recovered from the centrifugal machine. Control means 12 controls other parameters so that at least one or more of the parameters become a desired value.

Description

  The present invention relates to a centrifuge, a management system, and a method for manufacturing a glass substrate.

  In recent years, a technique for collecting rare substances such as rare earths has attracted attention. As an example of a rare substance recovery method, a method of recovering a recovery target substance with a reusable quality (for example, high concentration) from a waste slurry containing the recovery target substance (hereinafter, slurry) using a centrifuge Is mentioned.

  In the collection method using a centrifuge, the quality variation and the collection efficiency of the substance to be collected largely depend on the state of the slurry to be introduced into the centrifuge, the operating conditions of the centrifuge, and the like. Therefore, various methods are employed for the purpose of stabilizing the quality of the substance to be collected and improving the collection efficiency.

  Specifically, Japanese Patent Application Laid-Open No. H10-228667 suppresses a reduction in control accuracy depending on the slurry charging condition by controlling the differential speed between the main drive and the back drive based on the drive current of the centrifuge. Technology is disclosed.

JP2013-91130A

  However, in the method of Patent Document 1, the quality variation and recovery efficiency of the recovery target substance are still not sufficient. For this reason, there have been problems such as the need for a process for uniformizing the quality after the recovery process and the need to change the operating conditions at all times.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a centrifuge that is high in the quality and efficiency of a recovery object and can be automatically controlled with high accuracy.

According to the present invention,
A centrifuge for separating the concentrated liquid containing the recovery target substance from the slurry containing the recovery target substance,
The centrifuge is
A bowl holding the slurry;
A screw conveyor for scooping out the concentrate from the bowl;
Drive means for rotationally driving each of the bowl and the screw conveyor;
A first sensor for monitoring one or more first parameters relating to the state of the slurry being charged to the bowl;
A second sensor for monitoring one or more second parameters relating to the operating state of the centrifuge;
A third sensor for monitoring one or more third parameters relating to the state of the concentrate recovered from the centrifuge;
Control means including a recording medium and an arithmetic processing unit, and controlling the operation of the centrifuge;
Have
The recording medium records a correlation equation including the one or more first parameters, the one or more second parameters, and the one or more third parameters, and the control means includes: Controlling the other parameters to values based on the correlation equation so that at least one of the one or more third parameters has a desired value.
A centrifuge is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the quality and collection | recovery efficiency of a collection target object are high, and the centrifuge which can be automatically controlled with high precision can be provided.

It is a schematic block diagram of an example of the centrifuge which concerns on this embodiment. It is the schematic which shows an example of the management system of the polishing liquid which concerns on this embodiment. It is the schematic for demonstrating an example of the effect of the collection | recovery method which concerns on this embodiment. It is the schematic for demonstrating the other example of the effect of the collection | recovery method which concerns on this embodiment. It is the schematic for demonstrating the collection | recovery method which concerns on embodiment of a comparison.

[centrifuge]
First, the configuration of the centrifuge according to the present embodiment will be described. The centrifuge according to the present embodiment can be used for the purpose of separating and recovering a recovery object by applying a centrifugal force to a sample including an arbitrary recovery object. In this specification, as an example of a sample, a slurry containing cerium oxide after a glass substrate polishing process (for example, used polishing liquid, dressing water, washing water, drainage) is used to collect a concentrated liquid of cerium oxide. An example will be described.

  The centrifuge may be called, for example, a centrifugal settling machine or a centrifugal dehydrator depending on the type of slurry to be input, the application, the process, and the like. The centrifugal sedimentator is generally classified into a separation plate type, a cylindrical type, and a decanter type, and the centrifugal dehydrator may be classified as a batch type or a continuous type. In the present embodiment, an example in which a decanter type centrifugal settling machine having stable and long-time separation / concentration performance is used will be described. However, the present invention is not limited in this respect, and all types of centrifuges described above are used. Applicable to separators. Further, the centrifuge according to the present embodiment may be a reverse cleaning type centrifuge provided with a back cleaning unit (not shown).

  In FIG. 1, the schematic block diagram of an example of the centrifuge which concerns on this embodiment is shown. The centrifuge 1 according to the present embodiment mainly includes a bowl 2 that rotates at a high speed and a screw conveyor 3 that is accommodated in the bowl 2 and that can continuously discharge the concentrated liquid. In addition, the centrifuge 1 is provided on a dam plate (weir plate) 4 provided on one end wall portion of the bowl 2 and on the other end wall portion side of the bowl 2, and a substance to be collected 10 (in this embodiment) Has a feeding pipe 5 for feeding a slurry containing cerium oxide) to the centrifuge 1.

  The bowl 2 includes a straight barrel-shaped straight portion 6, a cone portion 7 that is formed continuously with the straight portion 6, and has a tapered shape that decreases in diameter toward the side where the input pipe 5 is provided. Consists of

  The dam plate 4 is provided on the end wall portion of the bowl 2 on the straight portion 6 side, and is provided so as to cover the outer edge portion of the first tip opening 8 of the bowl 2. Therefore, the dam plate 4 is provided in a direction orthogonal to the rotation axis X of the bowl 2. The dam plate 4 functions as a weir in the first tip opening 8 for discharging the concentrate.

  The input pipe 5 is inserted and arranged in the second tip opening 9 on the cone portion 7 side of the bowl 2, and slurry is supplied into the centrifuge 1 through the input pipe 5.

  The bowl 2 and the screw conveyor 3 are each connected to driving means (not shown) such as a motor, and are independently rotated about the rotation axis X. Generally, the driving means for driving the bowl 2 is called a main drive, and the driving means for driving the screw conveyor 3 is called a back drive.

  In addition, the centrifuge 1 according to the present embodiment includes a first sensor 11 a that monitors parameters relating to the state of the slurry that is input to the centrifuge 1 via the input pipe 5, and parameters that are related to the operating state of the centrifuge 1. Monitoring means is provided, including a second sensor 11b for monitoring and a third sensor 11c for monitoring parameters relating to the state of the concentrate recovered from the centrifuge.

  The first sensor 11a is a sensor that monitors a parameter (corresponding to one or more first parameters) related to the state of the slurry in the input pipe 5. The first sensor 11 a is provided in the tank storing the slurry to be input to the centrifuge 1 or the input pipe 5. Specific examples of the parameters of the state of the slurry to be charged into the centrifuge 1 include the concentration of the substance to be collected in the slurry and / or the flow rate of the slurry into the bowl 2 from the input pipe 5.

  The second sensor 11b is a sensor that monitors a parameter related to the operating state of the centrifuge 1 (corresponding to one or more second parameters). The second sensor 11b is arranged at an appropriate position in the component of the centrifuge 1 according to the type of parameter or the like. Specific examples of the parameters relating to the operating state of the centrifuge 1 include an intermittent time, a waiting time from the back washing to the next back washing, a waiting time from the low speed washing to the next slow washing, the bowl 2 Drive current value, screw conveyor 3 drive current value, and / or screw conveyor rotation frequency. Details of each parameter will be described later.

  The third sensor 11 c is a sensor that monitors a parameter (corresponding to one or more third parameters) related to the concentrated liquid recovered from the centrifuge 1. The third sensor 11c is provided, for example, in a tank (not shown) in which the concentrate is stored. Specific examples of the parameters related to the concentrated liquid collected from the centrifuge 1 include the concentration of the substance to be collected in the concentrated liquid and / or the discharge flow rate of the concentrated liquid.

  As the first sensor 11a, the second sensor 11b, and the third sensor 11c, known sensors can be used according to the parameters to be monitored. A plurality of sensors 11a to 11c may be provided according to the type and number of parameters. Moreover, the structure which provides each sensor 11a-11c in multiple numbers with respect to one parameter may be sufficient. Information obtained by the sensors 11a to 11c is transmitted to the control means 12 to be described later via known communication means by wire or wireless.

  Further, the centrifuge 1 according to the present embodiment has a control means 12. The control means 12 includes an arithmetic processing unit (not shown) made of, for example, a CPU and a recording medium (not shown) made of, for example, a hard disk.

  The recording medium of the control means 12 stores a program in which a collection method described later is recorded and a correlation equation described later. Further, the measurement data measured by the sensors 11a to 11c is recorded on this recording medium via a well-known communication means by wire or wireless.

  The arithmetic processing unit of the control means 12 controls the operation of the centrifuge 1 according to a program or the like recorded on the recording medium.

  Note that the concentration rate of the collection target is greatly affected by the flow rate ratio between the first tip opening 8 side of the straight portion 6 and the second tip opening 9 side of the cone portion 7. Therefore, by changing the height of the dam plate 4, the liquid level in the centrifuge 1 can be adjusted and the concentration rate can be changed. In the present embodiment, the height of the dam plate 4 is not changed and is set to a constant height.

[Recovery method]
Next, the collection method of the collection object using the centrifuge according to the present embodiment will be described.

  In general, in order to recover a concentrated liquid containing a substance to be recovered from a slurry containing the substance to be collected, first, the slurry is put into the centrifuge 1 while the bowl 2 and the screw conveyor 3 are rotated. .

  At this time, a part of the slurry (used polishing liquid containing cerium oxide, dressing water, washing water, drainage, etc. in this embodiment) (cerium oxide or the like) is removed from the bowl 2 of the centrifuge 1. Deposits on the inner wall of.

  In general, the rotation direction of the bowl 2 and the rotation direction of the screw conveyor 3 are the same. However, the present invention is not limited to the rotation direction, and the rotation direction of the bowl 2 and the rotation direction of the screw conveyor 3 are the same. May be in the opposite direction.

  By concentrating the collection target material 10 deposited on the inner wall of the bowl 2 by the screw conveyor 3 having a different rotation speed with respect to the rotation speed of the bowl 2, the concentrated liquid in which the collection target material 10 is concentrated can be collected.

  The quality and recovery efficiency of the recovery target substance (that is, the concentration of the recovery target substance in the concentrate and the discharge flow rate of the concentrate) in the recovery of the recovery target using the centrifuge is input to the above-described centrifuge. It is affected by the state of the slurry and the operating state of the centrifuge described above. Further, the concentration of the substance to be collected in the concentrate and the discharge flow rate of the concentrate influence each other.

  Therefore, in the recovery method of the present embodiment, a parameter (one or more first parameters) relating to the state of the slurry charged into the bowl 2 of the centrifuge 1 and a parameter (one or more parameters) relating to the operating state of the centrifuge 1. The correlation equation including the second parameter) and the parameter (one or more third parameters) relating to the concentrate recovered from the centrifuge 1 is obtained using multivariate analysis. Based on this correlation formula, the remaining parameters included in the correlation formula are based on the correlation formula so that one or more of the third parameters included in the correlation formula have a desired value. The optimum value is determined and the centrifuge is controlled with this parameter.

  In general, the drive data of the centrifuge accumulated in advance is used as the data for obtaining the correlation equation. However, the concentration and flow rate of the resulting concentrate may vary even under the same process conditions depending on the usage state of the centrifuge. For this reason, the control unit 12 of the present embodiment may have a configuration in which a learning function is mounted by adding a known filter or the like to software for performing various calculations, and the correlation equation is updated. More specifically, a configuration in which data currently collected by the above-described sensor is fed back and the correlation equation is updated may be employed.

  In the collection method according to the present embodiment, although not limited, multiple regression analysis is used as multivariate analysis from the viewpoint of easy calculation and obtaining a prediction formula with few errors. However, other multivariate analysis is used. May be used.

  That is, the recovery method according to the present embodiment has a first parameter (a state of slurry to be introduced into the centrifuge), a second parameter (a parameter related to the operating state of the centrifuge), and a third parameter (recovered). The optimum centrifuge operating state is predicted and controlled using a correlation equation including parameters related to the concentrate. Therefore, the quality and / or recovery efficiency of the obtained recovery target substance can be controlled with high accuracy by automatic control by the control means. In addition, the quality and / or recovery efficiency of the obtained substance to be collected can be made uniform by automatic control by the control means without suffering from human hands.

  Furthermore, the recovery method according to the present embodiment can be applied to various substances other than the cerium oxide as the recovery target substance used in the embodiment. According to the selected substance to be collected, a correlation equation including the first parameter, the second parameter, and the third parameter is obtained using multivariate analysis, and centrifugation is performed using the parameters obtained based on the correlation equation. Control the machine.

  As described above, each of the first parameter, the second parameter, and the third parameter includes a plurality of parameter candidates, but it is preferable to obtain a correlation equation using as many parameters as possible. By obtaining a correlation equation using many parameters, a concentrated liquid having desired characteristics can be obtained with higher accuracy.

  In the case where the concentration of the substance to be collected in the concentrate and / or the discharge flow rate of the concentrate detected by the third sensor 11c is different from a desired value, that is, a predicted value based on the correlation equation, by a predetermined value or more. The control means sets parameters relating to the state of the slurry to be introduced into the centrifuge and the operation state of the centrifuge so that the concentration of the substance to be collected in the concentrate and / or the discharge flow rate of the concentrate approaches a desired value. The configuration may be changed automatically.

  Next, the effect of the parameters relating to the state of the slurry charged into the centrifuge and the operating state of the centrifuge on the characteristics of the resulting concentrate will be briefly described.

As described above, as a parameter regarding the state of the slurry to be introduced into the centrifuge,
P1: Concentration of the substance to be collected in the slurry P2: Slurry input flow rate to the centrifuge, etc.

  Generally, when the concentration of the recovery target substance in the slurry increases, the concentration of the recovery target substance in the resulting concentrated liquid increases.

  In addition, when the flow rate of slurry into the centrifuge increases, the concentration of the substance to be recovered in the resulting concentrated liquid decreases, but the recovered amount of the concentrated liquid (discharged liquid amount, discharged flow rate) increases.

In addition, as described above, as a parameter regarding the operating state of the centrifuge,
P3: Intermittent time P4: Standby time from reverse cleaning to next reverse cleaning P5: Standby time from low speed cleaning to next low speed cleaning P6: Drive current value of bowl 2 P7: Screw conveyor 3 Drive current value P8: Rotational frequency of screw conveyor 3 P9: Size of dam plate 4 and the like.

  The intermittent time means an operation time during which the slurry is temporarily stopped during the recovery operation. By temporarily stopping the operation of the centrifuge during the collection operation, the concentration of the substance to be collected in the resulting concentrated liquid increases. Further, by increasing the intermittent time, the concentration of the substance to be collected in the concentrated liquid increases.

  Backwashing means that the slurry and concentrated liquid are caused to flow in the direction opposite to the normal direction of movement, thereby discharging the adhering matter such as turbid substances accumulated inside the device. As a result, the concentration of the substance to be collected in the resulting concentrated liquid increases.

  Low-speed washing means an operation of washing deposits such as turbid substances accumulated in the apparatus by a washing nozzle while rotating the centrifuge at a low speed, and the concentrated liquid obtained by carrying out this operation The concentration of the substance to be collected becomes smaller.

  The driving current value of the bowl 2 means a value of current applied to the driving means when the bowl 2 is rotationally driven. The driving current value of the bowl 2 depends on the supply flow rate of the slurry to be charged, the concentration of the substance to be collected in the slurry, the difference in rotational speed between the bowl 2 and the screw conveyor 3, and the like.

  The drive current value of the screw conveyor 3 means the value of current applied to the drive means when the screw conveyor 3 is rotationally driven. The drive current value of the screw conveyor 3 is dependent on the supply flow rate of the slurry to be charged, the concentration of the substance to be collected in the slurry, the difference in the rotation speed between the bowl 2 and the screw conveyor 3, etc. To do.

  The rotational frequency of the screw conveyor 3 is a parameter that represents the rotational speed of the screw conveyor 3. By increasing the rotational frequency, the concentration of the substance to be recovered in the resulting concentrated liquid is reduced. growing. In general, the rotation frequency of the bowl 2 is a fixed value, but the rotation frequency of the bowl 2 may be variable as a parameter of the operation state of the centrifuge. Further, the rotation frequency of the screw conveyor 3 may be a fixed value, and only the rotation frequency of the bowl 2 may be variable.

  As described above, the dam plate 4 is provided on the end wall portion of the bowl 2 on the straight portion 6 side, and is provided so as to cover the outer edge portion of the first tip opening 8 of the bowl 2. The dam plate 4 functions as a weir in the first tip opening 8 for discharging the concentrate. The size of the dam plate 4 means the width size of the dam plate 4, and the opening area of the first tip opening 8 is reduced by increasing the width size. As a result, the concentration of the substance to be collected in the discharged concentrated liquid is reduced, and the recovered amount of the concentrated liquid is increased.

Moreover, as a parameter regarding the concentrate to be recovered,
P10: Concentration of the substance to be collected in the concentrate P11: Discharge flow rate of the concentrate, etc.

  In addition, as a parameter regarding the concentrate which is collect | recovered, it is preferable from the viewpoint of quality that the density | concentration of the collection | recovery object substance in a concentrate is high. From the viewpoint of recovery efficiency, it is preferable that the concentration of the substance to be recovered in the concentrate is high and the discharge flow rate of the concentrate is large. However, in addition, it is preferable that the quality of the collected concentrate is uniform (constant). The collection method of the present embodiment also has a feature that the quality of the collected concentrate is uniform by automatic control by the control means.

  As described above, the concentration of the substance to be collected in the concentrate and / or the discharge flow rate of the concentrate detected by the third sensor 11c is greatly different from a desired value, that is, a predicted value based on the correlation equation. The control means relates to the state of the slurry to be introduced into the centrifuge and the operating state of the centrifuge so that the concentration of the substance to be collected in the concentrate and / or the discharge flow rate of the concentrate approaches a desired value. The configuration may be such that the parameters are automatically changed. In this case, the control means first changes P2: the slurry flow rate to the centrifuge, P8: the rotational frequency of the screw conveyor and / or P3: the intermittent time, and controls to approach the desired value. It is preferable. This is because the parameters P2, P3, and P8 described above greatly affect the characteristics of the concentrate obtained as compared with other parameters.

[Polishing liquid management system]
Next, as an example of the substance to be collected, a polishing liquid management system having the centrifuge 1 according to the present embodiment when the abrasive grains contained in the polishing liquid of the glass substrate are selected will be described with reference to the drawings. I will explain.

  FIG. 2 is a schematic diagram showing an example of a polishing liquid management system according to this embodiment.

  The polishing liquid management system 100 includes the centrifuge 1, the coarse particle separator 150, the component adjustment tank 160, and other tanks as necessary. Examples of other tanks include a slurry tank 120, a discharge water tank 130, a water tank 140, and a dispersion tank.

  By using the management system 100 according to the present embodiment, for example, slurry (for example, used polishing liquid, dressing water, washing water, drainage, etc.) from the polishing apparatus 110 when manufacturing a glass substrate for display is used. The polishing liquid recovered, treated, and regenerated and the water from which the abrasive grains have been removed can be circulated through a slurry tank and a water tank provided in the polishing apparatus, respectively.

  The polishing apparatus 110 is an apparatus that polishes glass using polishing abrasive grains. For example, a glass that polishes glass such as a glass substrate for display, a glass substrate for magnetic recording medium, glass for optical components, glass for photomask, and the like. A polishing device can be used.

  The abrasive grains contained in the polishing liquid include, for example, cerium oxide particles, silica particles, alumina particles, zirconia particles, zircon particles, silicon carbide particles, boron carbide particles, diamond particles, manganese oxide particles, titania particles, and oxidation. One or more kinds of particles selected from iron particles can be used.

  Polishing abrasive grains used in the polishing apparatus are stored in the slurry tank 120 and circulate repeatedly between the polishing apparatus and the slurry tank.

  For example, the water used for cleaning the glass substrate or the like is stored in the water tank 140 and supplied through the water nozzle.

  The discharge water tank 130 is a tank for storing slurry (for example, used polishing liquid, dressing water, cleaning water, drainage, etc.), and is usually stirred to prevent precipitation and aggregation of abrasive grains in the slurry. Has been. The slurry in the discharge water tank 130 is conveyed to the centrifuge 1 according to the present embodiment periodically or continuously and separated into a concentrated liquid containing concentrated abrasive grains and a separated liquid. Thereafter, the concentrated liquid is conveyed to the coarse particle separator 150. The separation liquid is usually discarded, but may be returned to the water tank 140 and reused.

  FIG. 2 shows an example in which the concentrated liquid from the centrifuge 1 according to this embodiment is conveyed to the coarse particle separator 150. However, the concentrate from the centrifuge 1 according to this embodiment may be transported to the coarse particle separator 150 after being transported to a dispersion tank (not shown). In this case, in the dispersing tank, a dispersing agent and water are added regularly or continuously, and redispersion processing is performed. The dispersion tank is usually stirred in order to prevent precipitation and aggregation. The dispersant is not particularly limited, and for example, oxycarboxylic acid, polyacrylic acid, or a salt thereof can be used.

  The concentrated liquid or the re-dispersed concentrated liquid is transported to a centrifugal separator such as the coarse particle separator 150, where coarse particles (for example, those having an average particle size larger than 5 μm) are removed. Be transported. Usually, the coarse particles separated here are discarded.

  In the present specification, the average particle size is measured using a dynamic light scattering type particle size distribution analyzer (for example, product name: FPAR-1000AS manufactured by Otsuka Electronics Co., Ltd.) or laser diffraction / scattering. It is measured using a particle size distribution analyzer of the type (for example, product name: Microtrac HRA manufactured by Nikkiso Co., Ltd.).

  In the component adjustment tank 160, component adjustment such as concentration adjustment and pH adjustment is performed, and a dispersant is added as necessary. At this time, the component adjustment tank 160 is usually stirred to prevent precipitation and aggregation. The polishing liquid regenerated by adjusting the concentration of the concentrated liquid is returned to the slurry tank 120 and used again for polishing.

  If necessary, a filter may be installed at an arbitrary location in the polishing liquid management system.

  Moreover, generally, the pressure gauge P is provided in the pipe | tube which connects each tank and a slurry and a solution move inside as shown in FIG. 2, and monitors the pressure of a slurry or a solution.

[Glass substrate manufacturing method]
The surface of a glass substrate such as a glass substrate for display, a glass substrate for magnetic recording medium, glass for optical components, glass for photomask, etc. is desired to be highly flat. Therefore, in the manufacturing process of a glass substrate, the grinding | polishing process which grind | polishes the surface of a glass plate is provided. In the polishing step, usually, a polishing liquid containing polishing grains is supplied between the polishing surface of the polishing pad and the glass plate while relatively rotating a polishing pad (not shown) of the polishing apparatus 110 and the glass plate. The surface of the glass plate is mirror-polished. In recent years, with an increase in the cost of raw materials for abrasive grains, it has been demanded to recover and reuse the abrasive grains from the slurry used in this polishing process. However, the slurry after the polishing step includes polishing debris such as an object to be polished, a polishing pad, and abrasive grains. These polishing debris causes scratches on the surface of the object to be polished, and the polishing rate decreases due to a decrease in polishing abrasive concentration, etc., and therefore cannot be reused as it is. The polishing management system according to the present embodiment collects and processes the slurry from the polishing apparatus 110, separates it into regenerated polishing liquid and service water from which polishing debris has been removed, and these can be recycled. System.

  Here, the case where the polishing liquid management system of the present invention is applied to a method for producing a glass substrate for a flat panel display will be described.

The manufacturing method of the glass substrate for flat panel displays according to the present embodiment, for example,
(1) A shape imparting step of chamfering the outer peripheral side surface after cutting the glass substrate into a desired shape,
(2) An outer peripheral end surface polishing step for polishing the outer peripheral end surface of the glass substrate,
(3) a main plane polishing step for polishing at least one main plane of the upper and lower main planes of the glass substrate;
(4) A cleaning step of precisely cleaning and drying the glass substrate to obtain a glass substrate for flat panel display,
It is manufactured by such processes. Although this invention is not limited to the said method, the slurry (for example, used polishing liquid and dressing water) used by the outer peripheral end surface grinding | polishing process of (2) and / or the main plane grinding | polishing process of (3). By applying the cleaning water, drainage, etc.) to the polishing liquid management system of the present invention, the abrasive grains can be efficiently recovered.

  The polishing step may be only primary polishing, primary polishing and secondary polishing may be performed, or tertiary polishing may be performed after secondary polishing.

In the present embodiment, the glass of the glass substrate for flat panel display is not particularly limited, and silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), boron oxide (B ₂ O ₃ ), and alkaline earth metal. Examples thereof include aluminosilicate glass having a composition containing the above oxide and so-called alkali-free aluminoborosilicate glass which does not substantially contain an alkali metal component in the glass composition. In addition, that an alkali metal component is not included substantially means that content of the alkali metal oxide in a glass composition is 1 mass% or less. Moreover, the manufacturing method of the glass substrate of this embodiment is not specifically limited, It manufactures by methods, such as a float glass process, a fusion method, a redraw method, and a press molding method.

[First Embodiment]
Next, an example of an embodiment in which the effects of the centrifuge and the recovery method according to this embodiment are confirmed will be described.

In the first embodiment, as a parameter for creating a correlation equation,
P2: Select the flow rate of the slurry into the centrifuge as a parameter regarding the state of the slurry to be charged into the centrifuge.
As parameters relating to the operating state of the centrifuge, P3: intermittent time, P4: standby time from reverse cleaning to the next reverse cleaning, P5: standby time from low speed cleaning to the next low speed cleaning, P6: Select the drive current value for bowl 2, P7: drive current value for screw conveyor 3,
As a parameter for the concentrate to be recovered,
P11: The discharge flow rate of the concentrate was selected.

  Using the third sensor 11c, P11: the value of the discharge flow rate of the concentrate (actual value) when parameters other than the discharge flow rate of the concentrate were assigned to various predetermined values.

  Moreover, the correlation equation was calculated | required by performing multivariate analysis (multiple regression analysis) using all the above-mentioned parameters using the measurement data (accumulation data) corresponding to each parameter obtained in the embodiment. . And P11: The calculated value (predicted value) regarding the discharge flow rate of a concentrate was calculated | required by substituting each parameter other than the discharge flow rate of a concentrate into a correlation equation.

  In FIG. 3, the schematic for demonstrating an example of the effect of the collection | recovery method which concerns on this embodiment is shown. More specifically, FIG. 3 is a correlation diagram in which measured values and calculated values are plotted for each combination of parameters, with the horizontal axis representing measured values and the vertical axis representing calculated values.

  Since the purpose is to examine the degree of correlation between the actually measured value and the calculated value, FIG. 3 does not describe specific numerical values and shows the difference with respect to a predetermined value. Specifically, the horizontal axis in FIG. 3 shows a difference from a predetermined value a (l / min) related to the actual measurement value, and the vertical axis in FIG. 3 shows a predetermined value related to the calculated value. The difference from b (l / min) is shown.

The straight line in the drawing is an approximate straight line obtained by linear regression calculation for each plot. Then, in order to examine the correlation degree between an observed value and a calculated value to obtain the coefficient of determination R ^2.

As shown in FIG. 3, in the present embodiment, the coefficient of determination ^{R 2} was 0.72. The coefficient of determination as R ² is close to 1, found that there and can determine the correlation between the calculated values, the values according to the present embodiment, for 0.5 or more, the measured values and the calculated values It was enough to judge that there was a sufficient correlation between the two.

  According to the present embodiment, it has been found that there is a correlation between the actually measured value and the calculated value related to the recovery characteristic of the concentrate. This means that a correlation equation is created in advance based on measurement data accumulated in the past, and when the recovery method is performed, a desired recovery characteristic relating to the concentrate is input, so that the control means is based on the correlation equation. This means that the centrifuge can be controlled by automatically selecting the operating conditions for obtaining the desired recovery characteristics.

  From the above results, it was found from the results of the first embodiment that the recovery target substance can be recovered with desired recovery characteristics by the recovery method using the correlation equation of the present embodiment. Moreover, it turned out that the collection | recovery method concerning this embodiment can be automatically controlled with high precision, and can set the quality and collection | recovery efficiency of a collection target object to a desired collection | recovery characteristic.

[Second Embodiment]
Next, another example of the embodiment in which the effect of the centrifuge and the recovery method according to this embodiment is confirmed will be described.

In the second embodiment, as a parameter for creating a correlation equation,
P2: Select the flow rate of the slurry into the centrifuge as a parameter regarding the state of the slurry to be charged into the centrifuge.
As parameters relating to the operating state of the centrifuge, P3: intermittent time, P4: standby time from reverse cleaning to the next reverse cleaning, P5: standby time from low speed cleaning to the next low speed cleaning, P6: Drive current value of bowl 2, P8: Select the rotation frequency of the screw conveyor,
As a parameter for the concentrate to be recovered,
P10: The concentration of the substance to be collected in the concentrate was selected.

  P10: When the values of the parameters other than the concentration of the collection target substance in the concentrate are distributed to various values, P10: The third concentration value (actual measurement value) of the collection target substance in the concentrate It measured using the sensor 11c.

  Moreover, the correlation equation was calculated | required by performing multivariate analysis (multiple regression analysis) using all the above-mentioned parameters using the accumulation | storage data obtained by embodiment. Then, P10: A calculated value (predicted value) related to the concentration of the recovery target substance in the concentrate was obtained by substituting each parameter other than the concentration of the recovery target substance in the concentrate into the correlation equation.

  FIG. 4A is a schematic diagram for explaining another example of the effect of the recovery method according to the present embodiment. More specifically, FIG. 4A is a correlation diagram in which the abscissa represents an actual measurement value and the ordinate represents a calculated value, and the actual measurement value and the calculated value are plotted for each combination of parameters.

  Since the purpose is to examine the degree of correlation between the actually measured value and the calculated value, in FIG. 4A, specific numerical values are not described, and the difference with respect to a predetermined value is shown. Specifically, the horizontal axis in FIG. 4A shows the difference from a predetermined value c (Baume) regarding the actual measurement value, and the vertical axis in FIG. 4A shows the calculation value. The difference from a certain predetermined value d (Baume) is shown.

The straight line in the drawing is an approximate straight line obtained by linear regression calculation for each plot. Then, in order to examine the correlation degree between an observed value and a calculated value to obtain the coefficient of determination R ^2.

As shown in FIG. 4 (a), in the present embodiment, the coefficient of determination ^{R 2} was 0.61. As described above, the closer to the coefficient of determination R ² is 1, the measured and calculated values and can be determined that there is a correlation between the value according to the present embodiment, for 0.5 or more, measured The value was sufficient to determine that there was a sufficient correlation between the value and the calculated value using the correlation equation.

Further, as a modification of the second embodiment, a control parameter that uses the discharge flow rate of the concentrate as the correlation formula is further selected as a parameter for creating the correlation formula, and the same method as in the second embodiment is used. P10: Measured values and calculated values related to the concentration of the substance to be collected in the concentrate were obtained. FIG. 4B is a schematic diagram for explaining another example of the effect of the collecting method according to this embodiment. More specifically, FIG. 4B is a correlation diagram in which the measured value and the calculated value are plotted for each combination of parameters, with the horizontal axis representing the actual measurement value and the vertical axis representing the calculated value.

  Since the purpose is to examine the correlation between the actually measured value and the calculated value, in FIG. 4B, specific numerical values are not described, and a difference with respect to a predetermined value is shown. Specifically, the horizontal axis in FIG. 4B shows the difference from a certain predetermined value e (Baume) regarding the actual measurement value, and the vertical axis in FIG. 4B shows the calculation value. The difference from a certain predetermined value f (Baume) is shown.

The straight line in the drawing is an approximate straight line obtained by linear regression calculation for each plot. Then, in order to examine the correlation degree between an observed value and a calculated value to obtain the coefficient of determination R ^2.

As shown in FIG. 4, in the present embodiment, the coefficient of determination ^{R 2} was 0.53. As described above, the closer to the coefficient of determination R ² is 1, the measured and calculated values and can be determined that there is a correlation between the value according to the present embodiment, for 0.5 or more, measured It was a value sufficient to judge that there was a sufficient correlation between the value and the calculated value.

[Comparison embodiment]
Further, as a comparative embodiment of the second embodiment, P10: the concentration of the substance to be collected in the concentrate and P11: the discharge flow rate of the concentrate, which are parameters relating to the collected concentrate, were manually measured. . P10: Check whether the measured value (actual value) of the concentration of the substance to be collected in the concentrate is the desired concentrate concentration (target value), and if it is outside the desired concentration of the concentrate P2: Slurry flow rate into the centrifuge, parameters related to the operating state of the centrifuge, P3: intermittent time, and P8: screw conveyor The rotation frequency was adjusted manually.

  In the comparative example, it is confirmed that P10: the concentration of the substance to be collected in the concentrate, which is a parameter relating to the collected concentrate recovered again by the above-described series of procedures, is a desired concentrate concentration. Until now, it is necessary to adjust the parameter (P2) relating to the state of the slurry to be introduced into the centrifuge and the parameters (P3 and P8) relating to the operating state of the centrifuge.

  Since the comparative example is performed manually, parameter monitoring and control in real time as in the embodiment cannot be performed, so that it is difficult to always obtain a desired concentration of the concentrate.

  FIG. 5 is a schematic diagram for explaining a recovery method according to a comparative embodiment. More specifically, FIG. 5 is a correlation diagram in which the actual value and the target value are plotted for each combination of parameters, with the horizontal axis representing the actual measurement value and the vertical axis representing the target value.

  Since the purpose is to examine the degree of correlation between the actually measured value and the target value, FIG. 5 does not describe specific numerical values, but shows the difference with respect to a predetermined value. Specifically, the horizontal axis in FIG. 5 shows the difference from a predetermined value g (Baume) related to the actual measurement value, and the vertical axis in FIG. 5 shows a predetermined value h ( It is shown so that the difference from Baume) can be seen.

The straight line in the drawing is an approximate straight line obtained by linear regression calculation for each plot. Then, in order to examine the correlation degree between an observed value and a calculated value to obtain the coefficient of determination R ^2.

As shown in FIG. 5, in the embodiment of the comparison corresponding to the second embodiment, the coefficient of determination R ² was 0.19.

The value of the coefficient of determination R ² in the embodiment of the comparison for less than 0.5, and a value is determined that there is no correlation between the measured and calculated values.

  According to the second embodiment and the comparative embodiment, in the example, it is possible to obtain a desired concentration of the concentrate by real-time parameter monitoring and control. Since control was impossible, it turned out that it was difficult to always obtain the density | concentration of a desired concentrate.

DESCRIPTION OF SYMBOLS 1 Centrifugal separator 2 Bowl 3 Screw conveyor 4 Dam plate 5 Input pipe 6 Straight part 7 Cone part 8 1st tip opening 9 2nd tip opening 10 Collection object substance 11a, 11b, 11c Sensor 12 Control means

Claims (7)

A centrifuge for separating the concentrated liquid containing the recovery target substance from the slurry containing the recovery target substance,
The centrifuge is
A bowl holding the slurry;
A screw conveyor for scooping out the concentrate from the bowl;
Drive means for rotationally driving each of the bowl and the screw conveyor;
A first sensor for monitoring one or more first parameters relating to the state of the slurry being charged to the bowl;
A second sensor for monitoring one or more second parameters relating to the operating state of the centrifuge;
A third sensor for monitoring one or more third parameters relating to the state of the concentrate recovered from the centrifuge;
Control means including a recording medium and an arithmetic processing unit, and controlling the operation of the centrifuge;
Have
The recording medium records a correlation equation including the one or more first parameters, the one or more second parameters, and the one or more third parameters, and the control means includes: Controlling the other parameters to values based on the correlation equation so that at least one of the one or more third parameters has a desired value.
centrifuge. The correlation equation is calculated in advance by multivariate analysis using an actual measurement value related to at least one of the third parameters when each of the other parameters is a predetermined value. is there,
The centrifuge according to claim 1. The multivariate analysis is a multiple regression analysis.
The centrifuge according to claim 2. The control means causes the value monitored by the third sensor to approach the desired value when the desired value differs from the value monitored by the third sensor by a predetermined value or more. To control the other parameters to be changed,
The centrifuge according to any one of claims 1 to 3. The one or more first parameters include at least one parameter of a concentration of the substance to be collected in the slurry and an input flow rate of the slurry to the centrifuge.
The one or more second parameters are intermittent time, standby time from reverse cleaning to next reverse cleaning, standby time from low speed cleaning to next low speed cleaning, driving current value of the bowl One or more parameters selected from the group of the drive current value of the screw conveyor and the rotational frequency of the screw conveyor,
The one or more third parameters include at least one parameter of a concentration of the substance to be collected in the concentrate and a discharge flow rate of the concentrate.
The centrifuge according to any one of claims 1 to 4. The material to be collected is abrasive grains, and the slurry is a polishing liquid,
The centrifuge according to any one of claims 1 to 5,
A coarse particle separator,
An ingredient adjustment tank;
A polishing liquid management system containing abrasive grains. A method for producing a glass substrate having a polishing step,
The polishing process uses the polishing liquid management system according to claim 6.
A method for producing a glass substrate.

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