JP7569759B2 - Granulation system, tank for granulation system, and method for producing pellets - Google Patents

Description

The present invention relates to a granulation system, a tank for a granulation system, a foreign matter removal technology, and a pellet manufacturing technology, and, for example, to a technology that is effective when applied to a granulation system, a tank for a granulation system, a foreign matter removal technology, and a pellet manufacturing technology that can save on the amount of liquid used.

Patent Publication No. 3751014 (Patent Document 1) describes technology related to underwater cutting devices.

Patent No. 3751014

For example, in a granulation system that produces pellets, pellets are produced in a sealed chamber filled with liquid, and then transported from the sealed chamber by circulating liquid.

Here, in the above-mentioned granulation system, demineralized water, from which chlorine has been removed, is often used as the liquid, particularly to prevent adverse effects on the pellets.

In this regard, desalinated water is more expensive than general industrial water. Furthermore, in the desert regions of the Middle East, where liquid-based granulation systems are often installed, water is a precious resource, and it is desirable to minimize the use of desalinated water. In other words, it is desirable to conserve the liquid (water) used in granulation systems.

The granulation system in one embodiment includes a tank for the granulation system. A first drainage line equipped with an on-off valve and a second drainage line provided at a higher position than the first drainage line are connected to the tank for the granulation system.

The foreign matter removal method in one embodiment includes a first step that is performed while the device is in operation, and a second step that is performed while the device is not in operation. In the first step, an on-off valve is opened to drain liquid containing foreign matter from the tank into a first drainage line equipped with an on-off valve. Meanwhile, in the second step, an on-off valve equipped in the first drainage line is closed to drain liquid containing foreign matter from the tank into a second drainage line that is located higher than the first drainage line.

In one embodiment of the pellet manufacturing method, the first step performed while the granulator is in operation includes opening an on-off valve to drain liquid from the tank into a first drainage line equipped with an on-off valve. On the other hand, the second step performed while the granulator is not in operation includes closing an on-off valve in the first drainage line to drain liquid from the tank into a second drainage line that is located higher than the first drainage line.

According to one embodiment, it is possible to conserve liquid.

FIG. 1 is a diagram showing a schematic configuration of a granulation system. FIG. 2 is a diagram showing a schematic configuration of a resin cutting device. FIG. 2 is a plan view showing a schematic configuration example of a die. FIG. 2 is a plan view showing a schematic configuration example of a cutter head. FIG. 1 is a diagram illustrating a flow of liquid in a tank in the related art. FIG. 1 is a diagram illustrating a flow of liquid in a tank in the related art. FIG. 2 is a diagram showing a schematic configuration of a tank according to an embodiment. FIG. 4 is a diagram showing a schematic diagram of a connection configuration between a tank and a drain line. FIG. 4 is a diagram illustrating the flow of liquid in a tank. FIG. 4 is a diagram illustrating the flow of liquid in a tank. 1 is a flowchart showing a procedure of a foreign matter removal method.

In all drawings used to explain the embodiments, the same components are generally given the same reference numerals, and repeated explanations will be omitted. In addition, hatching may be used even in plan views to make the drawings easier to understand.

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

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 dehydrator 8, and a vibrating screen 9.

The extruder 1 is configured to knead the resin raw material 20 with a rotating screw and extrude the kneaded resin from multiple nozzles provided on the die of the resin cutting device 2.

The resin cutting device 2 is configured to cut the molten resin extruded from multiple nozzles provided in the die with multiple cutter blades to produce pellets.

The piping section 4 functions as a flow path for liquid, such as desalinated water, which is water from which chlorine has been removed. This piping section 4 includes a supply piping section 4a for supplying liquid from the tank 7 to the granulator 10, a discharge piping section 4b for discharging a mixture of pellets and liquid from the granulator 10, a return piping section 4c for returning the liquid separated in the dehydrator 6 to the tank 7, a return piping section 4d for returning the liquid separated in the centrifugal dehydrator 8 to the tank 7, a bypass piping section 4e for returning the liquid to the tank 7 by the three-way valve 5a, and a liquid supply piping section 4f for supplying liquid to the tank 7.

The pump 5 has the function of circulating the liquid flowing through the piping section 4. The three-way valve 5a is provided in the supply piping section 4a, and is configured to be able to switch between a flow path that flows the liquid from the tank 7 to the granulator 10 and a flow path that returns the liquid from the tank 7 to the tank 7 via the bypass piping section 4e by using the switching control section 5b.

The tank 7 is a storage tank for storing liquid, the dehydrator 6 has the function of separating the pellets from the liquid, and the centrifugal dehydrator 8 has the function of drying the pellets. The vibrating sieve 9 is configured to separate the pellets by size.

The granulation system 100 configured in this manner operates as follows. That is, first, the resin raw material 20 is supplied to the extruder 1. The resin raw material 20 supplied to the extruder 1 is then kneaded by the screw, and the molten resin is extruded from multiple nozzles provided in the die. The extruded resin is cut by multiple cutter blades provided in the resin cutting device 2. This cutting of the resin is performed inside an enclosed chamber in which liquid flows. 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, solidified pellets 30 are manufactured by the granulator 10 including the extruder 1 and the resin cutting device 2.

At this time, liquid is circulated between the tank 7 and the sealed chamber by the piping section 4 and the pump 5. That is, liquid is supplied from the tank 7 to the sealed chamber through the supply piping section 4a, while the slurry 3, which is a mixture of the pellets 30 and the liquid generated in the sealed chamber, is transported 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 returned to the tank 7 through the return piping section 4c. Meanwhile, the slurry 3, which is a mixture of a small amount of liquid and the pellets 30, is transported to the centrifugal dehydrator 8. In the centrifugal dehydrator 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 dehydrator 8 are transported to the vibrating sieve 9, and the small amount of liquid separated in the centrifugal dehydrator 8 is returned to the tank 7 through the return piping section 4d. After that, in the vibrating sieve 9, the pellets 30 are separated by size.

In this manner, pellets 30 can be produced using the granulation system 100.

<Basic configuration of resin cutting device>
Next, the configuration of the resin cutting device 2, which is a component of the granulation system 100, will be described.

Figure 2 shows a schematic configuration of the resin cutting device 2.

In FIG. 2, the resin cutting device 2 has 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.

The die 50 is provided on the resin discharge side of the extruder that mixes and extrudes the resin, and this die 50 is provided with multiple nozzles. Each of these multiple nozzles is designed to discharge the resin extruded from the extruder.

The cutter head 51 is positioned so that it is pressed against the die 50, and is provided with multiple cutter blades. These multiple cutter blades have the function of cutting the resin discharged from the multiple nozzles provided in the die 50 into pellets.

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, the cutter head 51 is attached to the rotating shaft 52 that is rotated by the motor 53, and is therefore configured to be rotatable.

A sleeve 54 that can slide in the axial direction of the rotating shaft 52 is provided around the rotating shaft 52, and a housing 55 is provided on the outside of this sleeve 54. Here, the rotating shaft 52 is rotatable with respect to the sleeve 54, but is configured so that it cannot move relative to the sleeve 54 in the axial direction of the rotating shaft 52. In other words, 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 so that it can move relative to the housing 55 in the axial direction of the rotating shaft 52.

The sealed chamber 60 forms a sealed space in contact with the cutter head 51. The sealed chamber 60 is provided with an inlet 60a through which liquid, such as desalted water, flows in, and an outlet through which the liquid and pellets flow out of the sealed chamber 60.

<<Example of die configuration>>
FIG. 3 is a plan view showing a schematic configuration example of the die 50. As shown in FIG.

In FIG. 3, the die 50 has, for example, a substantially circular planar shape and has multiple nozzles 50a. Each of the multiple nozzles 50a ejects the resin that has been mixed and melted in the extruder.

<<Example of cutter head configuration>>
FIG. 4 is a plan view showing a schematic configuration example of the cutter head 51. As shown in FIG.

In FIG. 4, the cutter head 51 has, for example, a substantially circular planar shape, and is provided with a plurality of cutter blades 51a. Each of the plurality of cutter blades 51a has a substantially rectangular planar shape.

The cutter head 51 is configured to rotate while being pressed against the die 50, so that the multiple cutter blades 51a provided on the cutter head 51 cut the resin extruded from the multiple nozzles 50a provided on the die 50.

<Necessity to control the cutter blade pressing force>
Here, the cutter blade pressing force for pressing the multiple 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 blades are pressed against the die 50, the cutter blades wear out. If the cutter blade pressing force for pressing the cutter blades against the die is too large, the amount of wear on the cutter blades increases, while if the cutter blade pressing force is too small, the cutter blades come off the die, causing cutting troubles in which the resin cannot be properly cut into pellets. Therefore, the resin cutting device 2 has a configuration for controlling the cutter blade pressing force to a constant value. This configuration will be described below.

<Configuration for controlling cutter blade pressing force>
In FIG. 2 , the resin cutting device 2 has a control unit 70 , a rotation shaft forward force generating unit 80 , and a rotation shaft backward force generating unit 90 .

The rotating shaft forward force generating unit 80 is configured to generate a rotating shaft forward force Ff on the rotating shaft 52. For example, the rotating shaft forward force generating unit 80 is configured to generate a rotating shaft forward force by the pressure of the pressure medium injected into the first void chamber. Specifically, the product of the pressure-receiving area of the first void chamber and the pressure by the pressure medium becomes the rotating shaft forward force Ff. This rotating shaft forward force Ff is a force in a direction that brings the rotating shaft 52 (sleeve 54) closer to the die 50, and is a force generated by the rotating shaft forward force generating unit 80.

The rotating shaft retraction force generating unit 90 is configured to generate a rotating shaft retraction force Fb on the rotating shaft 52. For example, the rotating shaft retraction force generating unit 90 is configured to generate a rotating shaft retraction force by the pressure of the pressure medium injected into the second void chamber. Specifically, the product of the pressure-receiving area of the second void chamber and the pressure by the pressure medium is the rotating shaft retraction force Fb. The rotating shaft forward force Fb is a force in a direction that moves the rotating shaft 52 (sleeve 54) away from the die 50, and is a force generated by the rotating shaft retraction force generating unit 90.

The control unit 70 is configured to control the cutter blade pressing force that presses the multiple cutter blades against the die 50, and is configured to control the cutter blade pressing force expressed by the following relational expression so that it is constant. Specifically, if the cutter blade pressing force is F, the rotation shaft forward force is Ff, the cutter blade thrust force generated by the rotation of the multiple cutter blades and whose magnitude changes depending on the rotation speed of the rotation shaft is Fs, the rotation shaft backward force is Fb, the backward force caused by the fluid pressure of the fluid filled in the sealed chamber is Fw, and the sliding resistance force caused by the forward or backward movement of the rotation shaft is Fr, the cutter blade pressing force F is expressed as F=Ff+Fs-Fb-Fw±Fr. The control unit 70 is configured to control the cutter blade pressing force F expressed in this way so that it is constant.

<Basic operation of 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.

First, the resin kneaded in the extruder is discharged in a molten state from multiple nozzles provided on the die 50 into the sealed chamber 60. The discharged molten resin is cut by multiple cutter blades provided on the cutter head 51, which is attached to the rotating shaft 52 rotated by the motor 53 and rotates at high speed. The cut resin is cooled and solidified by the liquid flowing in from the inlet 60a of the sealed chamber 60, and pellets are generated. At this time, the liquid flowing into the sealed chamber 60 flows out from the outlet 60b of the sealed chamber 60, so the generated pellets are also discharged from the outlet 60b. The discharged slurry, which is a mixture of the liquid and pellets, is transported to the dehydrator 6 through the discharge piping section 4b, for example, as shown in FIG. 1. The subsequent operation is as described in the operation of the granulation system shown in FIG. 1. In this way, the resin cutting device 2 can produce solidified pellets by cutting the molten resin.

<The need for water conservation>
As described above, in the granulation system 100, a liquid is circulated, and in order to suppress adverse effects on the pellets and to prevent corrosion of the piping section 4 made of stainless steel, for example, demineralized water from which chlorine has been removed is often used as the liquid.

Here, desalted water is more expensive than general industrial water. Therefore, it is desirable to prevent waste of the desalted water used in the granulation system 100. In other words, there is a need for a way to conserve water in the granulation system 100. In this regard, the present inventor has focused on the configuration of the tank 7 in order to reduce the discharge of liquid that is wasted in the granulation system 100.

Description of Related Art
The following describes areas of improvement that exist for the tank 7a in the related art.

In this specification, "related technology" refers to technology that is not publicly known, but has problems that the inventor has discovered, and is the premise of the present invention.

Figure 5 shows a schematic configuration of tank 7a in related technology.

In FIG. 5, the tank 7a is connected to the supply pipe section 4a, which 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 section 4a provided with the three-way valve 5a. The three-way valve 5a is connected to the bypass pipe section 4e, which is connected to the tank 7a.

As shown in FIG. 5, the tank 7a is connected to a return pipe section 4c that is connected to a dehydrator (not shown), and is also connected to a return pipe section 4d that is connected to a centrifugal dehydrator (not shown). Furthermore, the tank 7a is also connected to a liquid supply pipe section 4f that supplies liquid to the tank 7a. The tank 7a is then connected to a drainage line 300 for discharging the liquid. In this manner, the tank 7a is configured.

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, when the granulator is operating, the tank 7a is connected to the granulator through 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 where it is mixed with the pellets produced by the granulator. Then, the liquid 200 discharged from the discharge pipe section is separated from the pellets by the dehydrator and then returns to the tank 7a through the return pipe section 4c. Furthermore, a small amount of the liquid 200 attached to the pellets separated by the dehydrator is separated by a centrifugal dehydrator and then returns to the tank 7a through the return pipe section 4d.

Here, the liquid 200 separated by the dehydrator and returned to the tank 7a and the liquid 200 separated by the centrifugal dehydrator and returned to the tank 7a contain resin debris. For this reason, in order to discharge the resin debris from the tank 7a, a small amount of new 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 portion of the liquid 200 stored in the tank 7a is discharged from the drain line 300 together with the resin debris floating on the surface of the liquid 200. This allows the resin debris to be removed from the tank 7a.

Next, the flow of 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 liquid 200 is returned from tank 7a to tank 7a via bypass piping section 4e. As a result, a large amount of liquid 200 temporarily flows into tank 7a due to liquid 200 returning to tank 7a through bypass piping section 4e and liquid 200 returning to tank 7a through both return piping section 4c and return piping section 4d. This large amount of liquid 200 that temporarily flows into tank 7a is discharged to the outside through drain line 300.

In other words, in the tank 7a in the related technology, a large amount of liquid 200 is returned by stopping the operation of the granulator and switching the three-way valve 5a, but most of this returned large amount of liquid 200 is discharged from the drain line 300 to the outside of the granulation system. This means that with the configuration of the tank 7a in the related technology, a large amount of liquid 200 is wasted. Thus, there is room for improvement in the related technology from the perspective of reducing the discharge of wasted liquid 200 from the tank 7a and saving water.

Therefore, in this embodiment, we have implemented measures to overcome the room for improvement that exists in the related art. The technical concept of this embodiment that incorporates these measures is explained below.

<Tank configuration>
FIG. 7 is a diagram showing a schematic configuration of the tank 7 in this embodiment.

In FIG. 7, tank 7 is a tank for a granulation system, and is configured to store liquid (e.g., demineralized water) used in the granulation system. This tank 7 has a first connection part 400a and a second connection part 400b. At this time, the first connection part 400a is configured to be connectable to a first drainage line equipped with an opening and closing valve. On the other hand, the second connection part 400b is configured to be connectable to a second drainage line, and the position (height) of the second connection part 400b is higher than the position (height) of the first connection part 400a.

Specifically, Figure 8 is a diagram showing a schematic diagram of the connection configuration between the tank 7 and the drain line.

As shown in FIG. 8, the first connection part 400a of the tank 7 is connected to the first drainage line 500a, and the first drainage line 500a is provided with an opening/closing valve 510. The opening and closing of this opening/closing valve 510 is controlled by an opening/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 drainage line 500b. Here, for example, the discharge capacity of the second drainage line 500b is larger than the discharge capacity of the first drainage line 500a. In this manner, the tank 7 is configured.

<Flow of liquid in a 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 through the supply pipe section 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 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 where it is mixed with the pellets produced by the granulator. Then, the liquid 200 discharged from the discharge pipe section is separated from the pellets by the dehydrator and then returns to the tank 7 through the return pipe section 4c. Furthermore, a small amount of the liquid 200 attached to the pellets separated by the dehydrator is separated by a centrifugal dehydrator and then returns to the tank 7 through the return pipe section 4d.

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 contain resin debris. For this reason, in order to discharge the resin debris from the tank 7, a small amount of new liquid 200 is always supplied to the tank 7 from the liquid supply pipe section 4f. Then, while the granulator is in operation, the opening and closing valve 510 provided in the first drainage line 500a is opened by the opening and closing 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 drainage line 500a with the opening and closing valve 510 open, together with the resin debris floating on the surface of the liquid 200. This allows the resin debris to be removed from the tank 7.

Next, focusing on tank 7, the flow of liquid 200 when the operation of the granulator is stopped will be explained. In FIG. 10, when the operation of the granulator is stopped, three-way valve 5a is switched so that liquid 200 is returned from tank 7 to tank 7 again via bypass piping section 4e. As a result, a large amount of liquid 200 temporarily flows into tank 7 due to liquid 200 returning to tank 7 through bypass piping section 4e and liquid 200 returning to tank 7 through both return piping section 4c and return piping section 4d.

When the operation of the granulator is stopped, the opening/closing control unit 520 closes the opening/closing valve 510 provided in the first drainage line 500a. As a result, as shown in FIG. 10, the large amount of liquid 200 that temporarily flows 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 in the tank 7 reaches the second drainage line 500b, which is located higher than the first drainage line 500a, the liquid 200 is discharged to the outside from the second drainage line 500b.

<Features of the embodiment>
Next, features of this embodiment will be described.

The feature of this embodiment is that, for example, as shown in FIG. 7, the tank 7 is provided with a first connection part 400a and a second connection part 400b located higher than the first connection part 400a, and as shown in FIG. 8, a first drainage line 500a provided with an opening/closing valve 510 is connected to the first connection part 400a, and a second drainage line 500b is connected to the second connection part 400b.

As a result, for example, as shown in FIG. 9, when the granulator is in operation, the opening/closing valve 510 provided in the first drainage line 500a is opened by the opening/closing control unit 520, and a portion of the liquid 200 stored in the tank 7, together with the resin debris floating on the surface of the liquid 200, is discharged from the first drainage line 500a with the opening/closing valve 510 open.

On the other hand, for example, as shown in FIG. 10, immediately after the granulator is switched to the operation stop state, a large amount of liquid 200 temporarily flows into the tank 7. At this time, the opening and closing control unit 520 closes the opening and closing valve 510 provided in the first drainage line 500a, and as a result, the large amount of liquid 200 that temporarily flows 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 in the tank 7 reaches the second drainage line 500b, which is higher than the first drainage line 500a, only the liquid 200 that exceeds the water level is discharged to the outside from the second drainage line 500b. In this way, most of the large amount of liquid 200 that temporarily flows into the tank 7 can be stored in the tank 7 without being discharged to the outside. Specifically, the amount of liquid 200 shown by the "shaded" in FIG. 10 is stored in the tank 7 without being discharged to the outside. In this way, according to this embodiment, the valuable liquid 200 (demineralized water) can be used for the next start-up of the granulator without being wasted. As a result, the amount of liquid 200 used in the granulation system 100 can be reduced.

For example, depending on the size of the plant constituting the granulation system 100 and the piping design, when the granulator is in operation, about 10 ^m3 of liquid (demineralized water) circulates inside the granulation system 100, and the tank 7 has a sufficiently large storage capacity (e.g., about 40 ^m3 ).

As an example, during operation of the granulator, the liquid 200 is filled up to the first drainage line 500a as shown in FIG. 9. Then, immediately after the operation of the granulator is stopped, a part of the liquid 200, about 10 ^m3, circulating inside the granulation system 100 is returned to the tank 7. At this time, in this embodiment, the opening and closing valve 510 provided in the first drainage line 500a is closed by the opening and closing control unit 520 at the timing when the operation of the granulator is stopped, so that the liquid 200 can be stored in the tank 7 up to the water level that flows out to the second drainage line 500b as shown in FIG. 10. For example, if it is assumed that 50% of the circulating 10 ^m3 of the liquid 200 is returned to the tank 7, the amount of water saved is about 5 ^m3 at most.

In addition, from the viewpoint of increasing the amount of liquid 200 that can be stored in the tank 7 out of the large amount of liquid 200 that temporarily flows into the tank 7 immediately after the granulator is switched to a stopped operation state, 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 amount of liquid 200 "shaded" in FIG. 10 will increase, which means that the amount of liquid 200 that can be stored in the tank 7 out of the large amount of liquid 200 that temporarily flows into the tank 7 will increase.

It is also desirable that the discharge capacity of the second drainage line 500b is greater than that of the first drainage line 500a. This is because, in the operating state of the granulator shown in FIG. 9, if the discharge capacity of the first drainage line 500a is small, the amount of liquid 200 used to remove the resin debris from the tank 7 can be saved. On the other hand, if the second drainage line 500b has a small discharge capacity, when too much liquid 200 temporarily flows into the tank 7, the excess liquid 200 cannot be discharged and the liquid 200 overflows from the tank 7. For this reason, from the viewpoint of preventing the liquid 200 from overflowing from the tank 7, it is desirable that the discharge capacity of the second drainage line 500b is as large as possible.

From the above, according to the features of this embodiment, it is possible to conserve the amount of liquid 200 used in the granulation system 100 without wasting precious liquid 200 (demineralized water). In other words, it can be said that the features of this embodiment have great technical significance in that it can achieve the remarkable effect of conserving liquid 200, which cannot be achieved with related technologies.

<Application Examples>
In the above-described embodiment, an example has been described in which the technical idea for saving the liquid 200 is applied to the granulation system 100, but the present invention is not limited to this, and the technical idea can be widely applied to foreign matter removal techniques that remove foreign matter using a liquid. That is, in the granulation system 100, resin scraps are taken as the foreign matter, but the technical idea in the embodiment can be applied to foreign matter removal techniques that remove a wide variety of foreign matter, not limited to resin scraps, from a liquid.

For example, FIG. 11 is a flowchart showing the flow of a foreign matter removal method that incorporates the technical idea of the embodiment. In FIG. 11, first, it is assumed that the device is in operation. As in the embodiment, a first drainage line and a second drainage line are connected to the tank.

Then, for example, a pump is used to supply liquid from the tank to the device (S101). Next, an opening/closing valve is provided in the first drainage line, and if this opening/closing valve is closed (S102), the opening/closing valve is opened by the opening/closing control unit (S103). At this time, it is desirable to open the opening/closing valve when the liquid level has dropped to near the position of the first drainage line. This is because if the opening/closing valve is opened before the liquid level has dropped to near the position of the first drainage line, liquid will be unnecessarily discharged from the first drainage line.

Here, it is assumed that foreign matter will become mixed into the liquid supplied to the device as a result of processing in the device, and the liquid containing the foreign matter is returned from the device to the tank (S104). The liquid containing the foreign matter that has returned to the tank is then discharged from the first drainage line, which is located lower than the second drainage line. In this way, the foreign matter that has become mixed into the tank can be discharged from the first drainage line (S105).

If operation of the device is to continue (S106), the process returns to step S101. Since the on-off valve is already open (S102), the process proceeds to step S104. On the other hand, if the device is to stop operation (S106), the on-off valve provided in the first drainage line is closed by the on-off control unit (S107). After that, the liquid is returned to the tank again without being supplied from the tank to the device (S108). At this time, the liquid containing foreign matter that has already been discharged from the device is also returned to the tank (S109).

As a result, a large amount of liquid temporarily flows into the tank. At this time, because the opening and closing valve on the first drainage line connected to the tank is closed, the flowing liquid is stored in the tank without being discharged from the first drainage line. Then, when the water level in the tank reaches the second drainage line, which is higher than the first drainage line, the liquid containing the foreign matter is discharged from the tank into the second drainage line (S110). In this way, the foreign matter removal method, which is an application example, can be implemented.

In this application example as well, most of the large amount of liquid that temporarily flows into the tank immediately after the device is stopped can be stored in the tank without being discharged to the outside. Therefore, in this application example as well, valuable liquid is not wasted and the amount of liquid used can be saved.

The invention made by the inventor has been specifically described above based on the embodiment thereof, but it goes without saying that the invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention.

LIST OF SYMBOLS 1 Extruder 2 Resin cutting device 3 Slurry 4 Piping section 4a Supply piping section 4b Discharge piping section 4c Circulation piping section 4d Circulation piping section 4e Bypass piping section 4f Liquid supply piping section 5 Pump 5a Three-way valve 5b Switching control section 6 Dehydrator 7 Tank 7a Tank 8 Centrifugal dehydrator 9 Vibrating sieve 10 Granulator 20 Resin raw material 30 Pellets 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 generating section 90 Rotating shaft backward force generating section 100 Granulation system 200 Liquid 300 Drain line 400a: First connection portion 400b: Second connection portion 500a: First drain line 500b: Second drain line 510: Opening/closing valve 520: Opening/closing control portion

Claims (7)

Granulation system, including:
A pelletizer to produce pellets;
Tanks for storing liquids;
a supply pipe section for supplying the liquid from the tank to the granulator;
a discharge line for discharging the mixture of pellets and liquid from the granulator;
a dehydrator for separating said pellets and said liquid from said mixture;
a return piping section for returning the liquid separated by the dehydrator to the tank;
a three-way valve provided in the supply piping section;
A bypass piping section for returning the liquid to the tank by the three-way valve; and a switching control section for controlling switching of the three-way valve.
Here, the tank includes:
A first drain line having an on-off valve;
A second drainage line provided at a higher position than the first drainage line;
is connected ,
In the operating state of the granulator, the on-off valve is open,
When the granulator is not in operation, the on-off valve is closed. The granulation system according to claim 1,
The switching control unit switches the three-way valve when the operation of the granulator is stopped from an operating state in which the liquid is supplied to the granulator from the tank so that the liquid is returned from the tank to the tank via the bypass piping unit. The granulation system according to claim 1,
The second drain line has a larger discharge capacity than the first drain line. The granulation system according to claim 1,
The liquid separated by the dehydrator contains resin waste. The granulation system according to claim 1,
The liquid is demineralized water. Tanks for granulation systems that can be connected to granulators , including:
a first connection part connectable to a first drain line having an on-off valve; and a second connection part connectable to a second drain line.
Here, the second connection portion is located higher than the first connection portion,
In the operating state of the granulator, the on-off valve is open,
When the granulator is not in operation, the on-off valve is closed. A method for producing pellets, comprising:
(a) a first step carried out while the granulator is in operation; and (b) a second step carried out while the granulator is not in operation.
Here, the first step includes the following steps:
(a1) supplying liquid from a tank to the granulator;
(a2) opening an on-off valve provided in a first drainage line connected to the tank;
(a3) producing pellets in the granulator;
(a4) discharging the mixture comprising the liquid and the pellets from the granulator;
(a5) separating the pellets and the liquid from the mixture;
(a6) obtaining the separated pellets; and (a7) returning the separated liquid to the tank.
(a8) draining the liquid from the tank into a first drain line;
Here, the second step includes the following steps:
(b1) closing the on-off valve provided in the first drainage line;
(b2) returning the liquid to the tank without supplying it to the granulator;
(b3) returning the liquid containing the foreign matter to the tank; and (b4) discharging the liquid containing the foreign matter from the tank to a second drain line located at a higher position than the first drain line.

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