Foreign object removal method

Abstract

To conserve liquid used in a granulation system.SOLUTION: A granulation system includes a tank 7. The tank 7 is connected to a first drainage line 500a equipped with an on-off valve 510 and a second drainage line 500b provided at a higher position than the first drainage line 500a.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a granulation system, a tank for a granulation system, a foreign matter removal technique, and a pellet manufacturing technique, and is related to a technique effective when applied to, for example, a granulation system capable of saving the liquid used, a tank for a granulation system, a foreign matter removal technique, and a pellet manufacturing technique.

Background Art

[0002] Japanese Patent No. 3751014 (Patent Document 1) describes a technique related to an underwater cutting device.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in a granulation system for manufacturing pellets, pellets manufactured in a sealed chamber filled with a liquid are conveyed from the sealed chamber by the liquid circulating therein.

[0005] Here, in the granulation system described above, in particular, in order to prevent adverse effects on the pellets, demineralized water from which chlorine has been removed is often used as the liquid.

[0006] In this regard, demineralized water is more expensive than general industrial water. Also, in the desert areas of the Middle East where granulation systems using liquids are often installed, water is a precious resource, and it is desired to minimize the use of demineralized water. That is, in a granulation system, it is desired to save the liquid (water) used.

Means for Solving the Problems

[0007] The granulation system in one embodiment includes a tank for the granulation system. The tank is connected with a first drain line equipped with an on-off valve and a second drain line provided at a position higher than the first drain line.

[0008] The foreign matter removal method in one embodiment includes a first step carried out during the operation state of the device and a second step carried out during the operation stop state of the device. In the first step, the on-off valve is opened to discharge the liquid containing foreign matter from the tank to the first drain line equipped with the on-off valve. On the other hand, in the second step, the on-off valve provided in the first drain line is closed, and the liquid containing foreign matter is discharged from the tank to the second drain line located at a position higher than the first drain line.

[0009] In the pellet manufacturing method in one embodiment, the first step carried out during the operation state of the granulator includes the step of opening the on-off valve to discharge the liquid from the tank to the first drain line equipped with the on-off valve. On the other hand, the second step carried out during the operation stop state of the granulator includes the step of closing the on-off valve provided in the first drain line and discharging the liquid from the tank to the second drain line located at a position higher than the first drain line.

Advantages of the Invention

[0010] According to one embodiment, the liquid used can be saved.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0012] In all the diagrams for explaining the embodiments, the same members are basically given the same reference numerals, and repeated explanations thereof are omitted. Note that, in order to make the drawings easy to understand, hatching may be added even to a plan view.

[0013] <Granulation System> FIG. 1 is a diagram showing a schematic configuration of a granulation system 100.

[0014] The granulation system 100 includes a granulator 10 including an extruder 1 and a resin cutting device 2, a piping section 4, a pump 5, a three-way valve 5a, a dehydrator 6, a tank 7, a centrifugal dehydration dryer 8, and a vibration sieve 9.

[0015] The extruder 1 is configured to knead a resin raw material 20 by a rotating screw and extrude the kneaded resin from a plurality of nozzles provided in a die of the resin cutting device 2.

[0016] The resin cutting device 2 is configured to cut the molten resin extruded from a plurality of nozzles provided in a die with a plurality of cutter blades to produce pellets.

[0017] The piping section 4 functions as a flow path through which a liquid, typified by, for example, demineralized water from which chlorine has been removed, flows. This piping section 4 includes a supply piping section 4a for supplying the liquid from the tank 7 to the granulator 10, a discharge piping section 4b for discharging the mixture of pellets and the liquid from the granulator 10, a reflux piping section 4c for refluxing the liquid separated by the dehydrator 6 to the tank 7, a reflux piping section 4d for refluxing the liquid separated by the centrifugal dehydration dryer 8 to the tank 7, a bypass piping section 4e for returning the liquid to the tank 7 by means of the three-way valve 5a, and a liquid supply piping section 4f for supplying the liquid to the tank 7.

[0018] The pump 5 has a function of circulating the liquid flowing through the piping section 4. Further, the three-way valve 5a is provided in the supply piping section 4a and is configured to be capable of switching, by the switching control section 5b, between a flow path for flowing the liquid from the tank 7 to the granulator 10 and a flow path for refluxing the liquid from the tank 7 to the tank 7 again via the bypass piping section 4e.

[0019] The tank 7 is a storage tank for storing the liquid. The dehydrator 6 has a function of separating the pellets from the liquid, and the centrifugal dehydration dryer 8 further has a function of drying the pellets. The vibrating screen 9 is configured to classify the pellets by size.

[0020] The granulation system 100 configured as described above operates as follows. That is, first, the resin raw material 20 is supplied to the extruder 1. Then, the resin raw material 20 supplied to the extruder 1 is kneaded by the screw, and then the molten resin is extruded from a plurality of nozzles provided in the die. The extruded resin is cut by a plurality of cutter blades provided in the resin cutting device 2. This cutting of the resin is performed inside a sealed chamber through which the liquid is flowing. As a result, the molten resin is cut into pellets 30 of a predetermined size and then cooled and solidified by the liquid. In this way, the solidified pellets 30 are manufactured by the granulator 10 including the extruder 1 and the resin cutting device 2.

[0021] At this time, the liquid circulates between the tank 7 and the sealed chamber by the piping section 4 and the pump 5. That is, the liquid is supplied from the tank 7 to the sealed chamber through the supply piping section 4a. On the other hand, the slurry 3, which is a mixture of the pellets 30 and the liquid generated in the sealed chamber, is conveyed to the dehydrator 6 through the discharge piping section 4b. In the dehydrator 6, the pellets 30 and the liquid are separated, and the liquid is refluxed to the tank 7 through the reflux piping section 4c. On the other hand, the slurry 3, which is a mixture of a small amount of liquid and the pellets 30, is conveyed to the centrifugal dehydrating dryer 8. In the centrifugal dehydrating dryer 8, a small amount of liquid adhering to the pellets 30 is separated. Then, the pellets 30 separated from the small amount of liquid and dried in the centrifugal dehydrating dryer 8 are conveyed to the vibrating screen 9, and the small amount of liquid separated in the centrifugal dehydrating dryer 8 is refluxed to the tank 7 through the reflux piping section 4d. Thereafter, in the vibrating screen 9, the pellets 30 are sorted by size.

[0022] As described above, the pellets 30 can be manufactured by the granulation system 100.

[0023] <Basic Configuration of Resin Cutting Device> Subsequently, the configuration of the resin cutting device 2, which is a component of the granulation system 100, will be described.

[0024] FIG. 2 is a diagram showing a schematic configuration of the resin cutting device 2.

[0025] In FIG. 2, the resin cutting device 2 includes a die 50, a cutter head 51, a rotating shaft 52, a motor 53, a sleeve 54, a housing 55, a sealed chamber 60, an inlet 60a, and an outlet 60b.

[0026] The die 50 is provided on the resin discharge side of an extruder that kneads and extrudes the resin, and a plurality of nozzles are provided on the die 50. Resin extruded from the extruder is discharged from each of these plurality of nozzles.

[0027] The cutter head 51 is arranged to be pressed against the die 50, and a plurality of cutter blades are provided on the cutter head 51. These plurality of cutter blades have a function of cutting the resin discharged from a plurality of nozzles provided on the die 50 into pellets.

[0028] Further, a rotating shaft 52 is attached to the cutter head 51, and a motor 53 is attached to the rotating shaft 52. As a result, since the cutter head 51 is attached to the rotating shaft 52 that rotates by the motor 53, it is configured to be rotatable.

[0029] A sleeve 54 that is slidable in the axial direction of the rotating shaft 52 is provided around the rotating shaft 52, and a housing 55 is provided outside the sleeve 54. Here, the rotating shaft 52 is rotatable with respect to the sleeve 54, while the relative movement of the rotating shaft 52 in the axial direction with respect to the sleeve 54 is configured not to be possible. That is, the rotating shaft 52 and the sleeve 54 are configured to move integrally in the axial direction of the rotating shaft 52. This sleeve 54 is configured to be relatively movable in the axial direction of the rotating shaft 52 with respect to the housing 55.

[0030] The sealed chamber 60 constitutes a sealed space in contact with the cutter head 51. The sealed chamber 60 is provided with an inlet 60a for flowing in a liquid such as deionized water, and an outlet for flowing out the liquid and pellets from the sealed chamber 60.

[0031] <<Configuration example of die>> FIG. 3 is a plan view showing a schematic configuration example of the die 50.

[0032] In FIG. 3, the die 50 has, for example, a substantially circular planar shape and a plurality of nozzles 50a. From each of these plurality of nozzles 50a, the resin kneaded and melted by an extruder is discharged.

[0033] <<Configuration example of cutter head>> FIG. 4 is a plan view showing a schematic configuration example of the cutter head 51.

[0034] In FIG. 4, the cutter head 51 has, for example, a substantially circular planar shape, and a plurality of cutter blades 51a are provided on the cutter head 51. Each of these plurality of cutter blades 51a has a substantially rectangular planar shape.

[0035] The cutter head 51 is configured to rotate while being pressed against the die 50, and thereby, the resin discharged from the plurality of nozzles 50a provided on the die 50 is cut by the plurality of cutter blades 51a provided on the cutter head 51.

[0036] <Necessity of Controlling the Cutter Blade Pressing Force> Here, the cutter blade pressing force for pressing the plurality of cutter blades provided on the cutter head 51 against the die 50 needs to be controlled to an appropriate constant value. This is because when the cutter blade is pressed against the die 50, the cutter blade wears. Thus, if the cutter blade pressing force for pressing the cutter blade against the die is too large, the wear amount of the cutter blade increases. On the other hand, if the cutter blade pressing force is small, the cutter blade will separate from the die, which will cause a cutting trouble where the resin cannot be normally cut into pellets. Therefore, the resin cutting device 2 has a configuration for controlling the cutter blade pressing force to be constant. This configuration will be described below.

[0037] <Configuration for Controlling the Cutter Blade Pressing Force> In FIG. 2, the resin cutting device 2 includes a control unit 70, a rotating shaft forward force generating unit 80, and a rotating shaft backward force generating unit 90.

[0038] The rotational shaft forward force generating unit 80 is configured to generate a rotational shaft forward force Ff on the rotational shaft 52. For example, the rotational shaft forward force generating unit 80 is configured to generate the rotational shaft forward force by the pressure of the pressure medium injected into the first gap chamber. Specifically, the product of the pressure receiving area of the first gap chamber and the pressure of the pressure medium becomes the rotational shaft forward force Ff. This rotational shaft forward force Ff is a force in the direction of approaching the die 50 for the rotational shaft 52 (sleeve 54), and is a force generated by the rotational shaft forward force generating unit 80.

[0039] The rotational shaft backward force generating unit 90 is configured to generate a rotational shaft backward force Fb on the rotational shaft 52. For example, the rotational shaft backward force generating unit 90 is configured to generate the rotational shaft backward force by the pressure of the pressure medium injected into the second gap chamber. Specifically, the product of the pressure receiving area of the second gap chamber and the pressure of the pressure medium becomes the rotational shaft backward force Fb. The rotational shaft forward force Ff is a force in the direction of moving the rotational shaft 52 (sleeve 54) away from the die 50, and is a force generated by the rotational shaft backward force generating unit 90.

[0040] The control unit 70 is configured to control the cutter blade pressing force for pressing a plurality of cutter blades against the die 50. For example, it is configured to control so that the cutter blade pressing force represented by the following relational expression becomes constant. Specifically, letting the cutter blade pressing force be F, the rotational shaft forward force be Ff, the cutter blade propulsion force generated by the rotation of the plurality of cutter blades, and the cutter blade propulsion force whose magnitude changes according to the rotational speed of the rotational shaft be Fs, the rotational shaft backward force be Fb, the backward force caused by the fluid pressure of the fluid filled in the sealed chamber be Fw, and the sliding resistance force caused by the forward or backward movement of the rotational shaft be Fr, the cutter blade pressing force F is represented by F = Ff + Fs - Fb - Fw ± Fr. The control unit 70 is configured to control so that the cutter blade pressing force F represented in this way becomes constant.

[0041] <Basic operation of the resin cutting device> The resin cutting device 2 is configured as described above, and its operation will be described below with reference to FIG. 2. The operation of the resin cutting device 2 is performed while the cutter blade pressing force F is controlled by the control unit 70.

[0042] First, the resin kneaded by the extruder is discharged in a molten state from a plurality of nozzles provided in the die 50 into the sealed chamber 60. The discharged molten resin is cut by a plurality of cutter blades provided on the cutter head 51 that is attached to the rotating shaft 52 rotated by the motor 53 and rotates at high speed. Then, the cut resin is cooled and solidified by the liquid flowing in from the inlet 60a of the sealed chamber 60, thereby producing pellets. At this time, since the liquid flowing into the sealed chamber 60 flows out from the outlet 60b of the sealed chamber 60, the produced pellets are also discharged from the outlet 60b. The slurry, which is a mixture of the discharged liquid and pellets, is conveyed to the dehydrator 6 through the discharge pipe portion 4b, for example, as shown in FIG. 1. The subsequent operations are as described in the operation of the granulation system shown in FIG. 1. As described above, in the resin cutting device 2, solidified pellets can be produced by cutting the molten resin.

[0043] <Necessity of water conservation> As described above, in the granulation system 100, the liquid is circulated to suppress adverse effects on the pellets and, for example, demineralized water from which chlorine has been removed is often used as the liquid from the viewpoint of preventing corrosion of the pipe portion 4 made of stainless steel.

[0044] Here, demineralized water is more expensive than general industrial water. Therefore, it is desirable to save the waste of demineralized water used in the granulation system 100. That is, in the granulation system 100, a device for water conservation is desired. In this regard, the inventor has focused on the configuration of the tank 7 in order to reduce the discharge of waste liquid in the granulation system 100.

[0045] <Description of related art> Hereinafter, the room for improvement in the tank 7a in the related art will be described.

[0046] As used in this specification, the "related art" refers to a technology that is not a known technology but has the problems found by the inventor and is a technology that is a premise of the invention of this application.

[0047] FIG. 5 is a diagram showing a schematic configuration of a tank 7a in the related art.

[0048] In FIG. 5, the tank 7a is connected to a supply pipe portion 4a, and this supply pipe portion 4a is connected to a granulator (not shown in FIG. 5) via a three-way valve 5a. That is, the tank 7a is connected to the granulator via the supply pipe portion 4a provided with the three-way valve 5a. And a bypass pipe portion 4e is connected to the three-way valve 5a, and this bypass pipe portion 4e is connected to the tank 7a.

[0049] Also, as shown in FIG. 5, the tank 7a is connected to a reflux pipe portion 4c connected to a dehydrator (not shown) and is also connected to a reflux pipe portion 4d connected to a centrifugal dehydration dryer (not shown). Further, the tank 7a is also connected to a liquid supply pipe portion 4f for supplying liquid to the tank 7a. And the tank 7a is connected to a drain line 300 for discharging liquid. In this way, the tank 7a is configured.

[0050] Next, focusing on the tank 7a, the flow of the liquid 200 in the operating state of the granulator will be described. In FIG. 5, in the operating state of the granulator, the tank 7a is connected to the granulator via the supply pipe section 4a by the three-way valve 5a. Therefore, the liquid 200 stored in the tank 7a is supplied to the granulator through the supply pipe section 4a by, for example, a pump (not shown). Then, the liquid 200 supplied to the granulator is discharged from the granulator to the discharge pipe section in a state of being mixed with the pellets produced by the granulator. And the liquid 200 discharged from the discharge pipe section returns to the tank 7a through the reflux pipe section 4c after being separated from the pellets by the dehydrator. Further, a small amount of the liquid 200 adhering to the pellets separated by the dehydrator returns to the tank 7a through the reflux pipe section 4d after being separated by the centrifugal dehydration dryer.

[0051] Here, resin scraps are mixed in the liquid 200 separated by the dehydrator and returned to the tank 7a and the liquid 200 separated by the centrifugal dehydration dryer and returned to the tank 7a. Therefore, in order to discharge the resin scraps from the tank 7a, a new small amount of the liquid 200 is constantly supplied to the tank 7a from the liquid supply pipe section 4f. As a result, as shown in FIG. 5, a part of the liquid 200 stored in the tank 7a is discharged from the drain line 300 together with the resin scraps floating on the surface of the liquid 200. Thereby, the resin scraps can be removed from the tank 7a.

[0052] Next, the flow of the liquid 200 when the operation of the granulator is stopped will be described. In FIG. 6, when the operation of the granulator is stopped, the three-way valve 5a is switched so that the liquid 200 is refluxed from the tank 7a to the tank 7a via the bypass pipe section 4e. As a result, a large amount of the liquid 200 temporarily flows into the tank 7a due to the liquid 200 returning to the tank 7a through the bypass pipe section 4e and the liquid 200 returning to the tank 7a through each of the reflux pipe section 4c and the reflux pipe section 4d. This large amount of the liquid 200 that temporarily flows into the tank 7a is discharged to the outside from the drain line 300.

[0053] That is, in the tank 7a in the related art, by stopping the operation of the granulator and switching the three-way valve 5a, a large amount of liquid 200 will flow back. However, most of this large amount of refluxed liquid 200 is discharged from the drain line 300 to the outside of the granulation system. This means that in the configuration of the tank 7a in the related art, a large amount of liquid 200 is wasted. Thus, there is room for improvement in the related art from the perspective of reducing the discharge of the wasted liquid 200 from the tank 7a to save water.

[0054] Therefore, in the present embodiment, a device is provided to overcome the room for improvement existing in the related art. Hereinafter, the technical idea in the present embodiment with this device will be described.

[0055] <Configuration of the tank> FIG. 7 is a diagram showing a schematic configuration of the tank 7 in the present embodiment.

[0056] In FIG. 7, the tank 7 is a tank for a granulation system and is configured to store a liquid (for example, demineralized water) used in the granulation system. This tank 7 has a first connection site 400a and a second connection site 400b. At this time, the first connection site 400a is configured to be connectable to a first drain line provided with an on-off valve. On the other hand, the second connection site 400b is configured to be connectable to a second drain line, and the position (height) of the second connection site 400b is higher than the position (height) of the first connection site 400a.

[0057] Specifically, FIG. 8 is a diagram schematically showing the connection configuration between the tank 7 and the drain line.

[0058] As shown in FIG. 8, the first connection part 400a of the tank 7 is connected to the first drain line 500a, and an on-off valve 510 is provided in the first drain line 500a. The opening and closing of this on-off valve 510 is controlled by an opening and closing control unit 520. On the other hand, as shown in FIG. 8, the second connection part 400b of the tank 7 is connected to the second drain line 500b. Here, for example, the discharge capacity of the second drain line 500b is larger than the discharge capacity of the first drain line 500a. In this way, the tank 7 is configured.

[0059] <Flow of liquid in the tank> Next, focusing on the tank 7, the flow of the liquid 200 in the operating state of the granulator will be described. In FIG. 9, in the operating state of the granulator, the tank 7 is connected to the granulator via the supply pipe part 4a by the three-way valve 5a. Therefore, the liquid 200 stored in the tank 7 is supplied to the granulator through the supply pipe part 4a by, for example, a pump (not shown). Then, the liquid 200 supplied to the granulator is discharged from the granulator to the discharge pipe part in a state of being mixed with the pellets produced by the granulator. Then, the liquid 200 discharged from the discharge pipe part is separated from the pellets by the dehydrator and then returns to the tank 7 through the reflux pipe part 4c. Further, a small amount of the liquid 200 adhering to the pellets separated by the dehydrator is separated by the centrifugal dehydration dryer and then returns to the tank 7 through the reflux pipe part 4d.

[0060] Here, the liquid 200 separated by the dehydrator and returned to the tank 7 and the liquid 200 separated by the centrifugal dehydrator and returned to the tank 7 are mixed with resin scraps. Therefore, in order to discharge the resin scraps from the tank 7, a small amount of new liquid 200 is constantly supplied to the tank 7 from the liquid supply pipe section 4f. And in the operating state of the granulator, the on-off valve 510 provided in the first drain line 500a is opened by the on-off control section 520. As a result, as shown in FIG. 9, a part of the liquid 200 stored in the tank 7 is discharged from the first drain line 500a where the on-off valve 510 is open, together with the resin scraps floating on the surface of the liquid 200. Thereby, the resin scraps can be removed from the tank 7.

[0061] Subsequently, focusing on the tank 7, the flow of the liquid 200 when the operation of the granulator is stopped will be described. In FIG. 10, when the operation of the granulator is stopped, the three-way valve 5a is switched so that the liquid 200 is refluxed from the tank 7 to the tank 7 via the bypass pipe section 4e. As a result, a large amount of the liquid 200 temporarily flows into the tank 7 due to the liquid 200 returning to the tank 7 through the bypass pipe section 4e and the liquid 200 returning to the tank 7 through each of the reflux pipe sections 4c and 4d.

[0062] Here, when the operation of the granulator is stopped, the on-off control section 520 closes the on-off valve 510 provided in the first drain line 500a. As a result, as shown in FIG. 10, the large amount of the liquid 200 that has temporarily flowed into the tank 7 is stored in the tank 7 without being discharged to the outside from the first drain line 500a. And when the water level of the tank 7 reaches the second drain line 500b which is at a position higher than the first drain line 500a, the liquid 200 is discharged to the outside from the second drain line 500b.

[0063] <Features in the Embodiment> Subsequently, the characteristic points in this embodiment will be described.

[0064] The characteristic point in this embodiment is, for example, as shown in FIG. 7, on the premise that a first connection part 400a and a second connection part 400b located at a position higher than the first connection part 400a are provided in the tank 7, as shown in FIG. 8, a first drainage line 500a provided with an on-off valve 510 is connected to the first connection part 400a, and a second drainage line 500b is connected to the second connection part 400b.

[0065] Thereby, for example, as shown in FIG. 9, in the operating state of the granulator, the on-off valve 510 provided in the first drainage line 500a is opened by the on-off control unit 520, and a part of the liquid 200 stored in the tank 7 is discharged from the first drainage line 500a where the on-off valve 510 is open, together with the resin chips floating on the surface of the liquid 200.

[0066] On the other hand, for example, as shown in FIG. 10, immediately after shifting to the operation stop state of the granulator, a large amount of the liquid 200 temporarily flows into the tank 7. At this time, as a result of the on-off control unit 520 closing the on-off valve 510 provided in the first drainage line 500a, the large amount of the liquid 200 that has temporarily flowed into the tank 7 is stored in the tank 7 without being discharged to the outside from the first drainage line 500a. Then, when the water level of the tank 7 reaches the second drainage line 500b located at a position higher than the first drainage line 500a, only the liquid 200 exceeding the water level is discharged to the outside from the second drainage line 500b. In this way, most of the large amount of the liquid 200 that has temporarily flowed into the tank 7 can be stored in the tank 7 without being discharged to the outside. Specifically, the amount of the liquid 200 indicated by the "hatched line" in FIG. 10 is stored in the tank 7 without being discharged to the outside. In this way, according to this embodiment, the precious liquid 200 (demineralized water) can be used for starting up the next granulator without being wasted. As a result, the usage amount of the liquid 200 in the granulation system 100 can be saved.

[0067] For example, depending on the size of the plant constituting the granulation system 100 and the piping design, in the operating state of the granulator, 10m 3A certain amount of liquid (demineralized water) circulates inside the granulation system 100, and the tank 7 has a sufficient storage capacity (for example, 40 m 3 or so).

[0068] As an example, during the operation of the granulator, for example, as shown in FIG. 9, assume that the liquid 200 is filled up to the first drainage line 500a. Immediately after the operation of the granulator is stopped, a part of the 10 m 3 or so of the liquid 200 that was circulating inside the granulation system 100 returns to the tank 7. At this time, in this embodiment, since the on-off valve 510 provided in the first drainage line 500a is closed by the opening / closing control unit 520 at the timing when the operation of the granulator is stopped, as shown in FIG. 10, the liquid 200 can be stored in the tank 7 up to the water level flowing out to the second drainage line 500b. For example, assuming that 50% of the 10 m 3 of the circulating liquid 200 returns to the tank 7, the maximum amount of water saved is 5 m 3 or so.

[0069] Note that, immediately after shifting to the operation stop state of the granulator, from the viewpoint of increasing the amount of the liquid 200 that can be stored in the tank 7 among the large amount of the liquid 200 that temporarily flows into the tank 7, it is desirable that the position (height) of the first drainage line 500a and the position (height) of the second drainage line 500b are separated. In this case, for example, the "hatched" liquid 200 shown in FIG. 10 increases, which means that the amount of the liquid 200 that can be stored in the tank 7 among the large amount of the liquid 200 that temporarily flows into the tank 7 increases.

[0070] Also, it is desirable that the discharge capacity of the second drain line 500b is larger than that of the first drain line 500a. This is because, in the operating state of the granulator shown in FIG. 9, if the discharge capacity of the first drain line 500a is small, the amount of the liquid 200 used to remove resin scraps from the tank 7 can be saved. On the other hand, if the amount of the liquid 200 temporarily flowing into the tank 7 is too large and the discharge capacity of the second drain line 500b is small, the surplus liquid 200 cannot be completely discharged and the liquid 200 will overflow from the tank 7. For this reason, from the viewpoint of suppressing the overflow of the liquid 200 from the tank 7, it is desirable that the discharge capacity of the second drain line 500b is as large as possible.

[0071] From the above, according to the characteristic points in the present embodiment, the amount of the liquid 200 (demineralized water) used in the granulation system 100 can be saved without wastefully discharging the precious liquid 200. That is, the characteristic points in the present embodiment have a very great technical significance in that they can achieve a remarkable effect of saving the liquid 200 that cannot be obtained in the related art.

[0072] <Application Example> In the above-described embodiment, an example of applying the technical idea for realizing the saving of the liquid 200 to the granulation system 100 has been described. However, the present invention is not limited to this, and this technical idea can be widely applied to foreign matter removal techniques for removing foreign matters using liquids. That is, in the granulation system 100, resin scraps are cited as foreign matters, but the technical idea in the embodiment is also applicable to foreign matter removal techniques for removing a wide variety of foreign matters from liquids, not limited to resin scraps.

[0073] For example, FIG. 11 is a flowchart showing the flow of a foreign matter removal method incorporating the technical idea in the embodiment. In FIG. 11, first, it is assumed that the device is in an operating state. Similar to the embodiment, a first drain line and a second drain line are connected to the tank.

[0074] Then, for example, a pump is used to supply liquid from the tank to the apparatus (S101). Next, an on-off valve is provided in the first drain line. When this on-off valve is closed (S102), the on-off control unit opens this on-off valve (S103). At this time, it is desirable that the on-off valve opens when the liquid level has dropped to near the position of the first drain line. This is because if the on-off valve is opened before the liquid level drops to near the position of the first drain line, the liquid will be discharged from the first drain line wastefully.

[0075] Here, on the premise that foreign matter is mixed into the liquid supplied to the apparatus by the treatment in the apparatus, the liquid containing foreign matter from the apparatus flows back to the tank (S104). After that, the liquid containing foreign matter that has flowed back to the tank is discharged from the first drain line, which is located at a position lower than the second drain line. In this way, the foreign matter mixed into the tank can be discharged from the first drain line (S105).

[0076] Subsequently, when continuing the operation of the apparatus (S106), it returns to step S101. And since the on-off valve is already open (S102), it proceeds to step S104. On the other hand, when the apparatus shifts to the operation stop (S106), the on-off control unit closes the on-off valve provided in the first drain line (S107). After that, without supplying liquid from the tank to the apparatus, it flows back to the tank again (S108). At this time, the liquid containing foreign matter that has already been discharged from the apparatus also flows back to the tank (S109).

[0077] As a result, a large amount of liquid temporarily flows into the tank. Here, since the on-off valve provided in the first drain line connected to the tank is closed, the inflowing liquid is stored in the tank without being discharged from the first drain line. And when the water level of the tank reaches the second drain line, which is at a position higher than the first drain line, the liquid containing foreign matter is discharged from the tank to the second drain line (S110). In this way, the foreign matter removal method, which is an application example, can be implemented.

[0078] Even in this application example, immediately after the operation of the device stops, most of the large amount of liquid that has temporarily flowed into the tank can be stored in the tank without being discharged to the outside. Therefore, also in the application example, the amount of liquid used can be saved without wasting precious liquid.

[0079] As described above, the invention made by the present inventor has been specifically described based on its embodiments. However, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

Explanation of Reference Numerals

[0080] 1 Extruder 2 Resin Cutting Device 3 Slurry 4 Pipe Section 4a Supply Pipe Section 4b Discharge Pipe Section 4c Reflux Pipe Section 4d Reflux Pipe Section 4e Bypass Pipe Section 4f Liquid Supply Pipe Section 5 Pump 5a Three-way Valve 5b Switching Control Section 6 Dehydrator 7 Tank 7a Tank 8 Centrifugal Dehydration Dryer 9 Vibration Sieve 10 Granulator 20 Resin Raw Material 30 Pellet 50 Die 50a Nozzle 51 Cutter Head 51a Cutter Blade 52 Rotating Shaft 53 Motor 54 Sleeve 55 Housing 60 Sealed Chamber 60a Inlet 60b Outlet 70 Control Section 80 Rotating Shaft Forward Force Generation Section 90 Rotating Shaft Retreating Force Generating Section 100 Granulation System 200 Liquid 300 Drainage Line 400a First Connection Site 400b Second Connection Site 500a First Drainage Line 500b Second Drainage Line 510 On-Off Valve 520 On-Off Control Section

Claims

1. A foreign matter removal method including the following steps: (a) A first step carried out in the operating state of the apparatus; and (b) A second step carried out in the stopped state of the operation of the said apparatus, wherein the said first step includes the following steps: (a1) A step of supplying a liquid from a tank to the said apparatus; (a2) A step of opening an on-off valve provided in a first drain line connected to the said tank; (a3) A step of refluxing the liquid containing foreign matter from the said apparatus to the said tank; and (a4) A step of discharging the liquid containing foreign matter to the said first drain line. wherein the said second step includes the following steps: (b1) A step of closing the on-off valve provided in the said first drain line; (b2) A step of refluxing the liquid to the said tank without supplying the liquid from the said tank to the said apparatus; (b3) A step of also refluxing the liquid containing foreign matter from the said apparatus to the said tank; and (b4) A step of discharging the liquid containing foreign matter to a second drain line located at a position higher than the said first drain line from the said tank.

2. In the foreign matter removal method according to Claim 1, the said foreign matter is resin chips.

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