Wet type gravity sorter

Abstract

To provide a wet type gravity sorter which can sort waste plastics having different gravities, even in a case in which a mixing ratio of the waste plastics varies with time.SOLUTION: A wet type gravity sorter 100 includes a sorting chamber 51 to which a substance to be sorted is charged, a pulsation chamber 52 for giving a pulse to the substance to be sorted in the sorting chamber 51 through a liquid X, a net 53 which is arranged between the sorting chamber 51 and the pulsation chamber 52, and can pass the liquid X therethrough, a displacement sensor 55 for measuring displacement of a liquid surface of the liquid X, a pressure sensor 56 for measuring the pressure, a pipe 57 whose one end is connected to the pressure sensor 56, and the other end is adjustably arranged in the vicinity of the lowermost surface of the layer of the substance to be sorted formed of the pulse, and an estimation control part 10 for estimating variation of layer thickness of a target recovery object in the substance to be sorted, on the basis of the data of the change with time of a pressure loss, wherein the pipe 57 is filled with gas, and the pressure sensor 56 measures the pressure in the pipe 57.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wet specific gravity separator. [Background technology]

[0002] Plastics are used in a wide variety of fields, including automobiles and home appliances, and the increase in the amount of plastic waste has become a major issue in recent years. In order to promote the recycling of discarded plastics (waste plastics) and reduce the use of fossil fuel raw materials, active development of recycling technologies is underway.

[0003] To obtain raw materials for material recycling and chemical recycling, technology is required to separate waste plastics by type with high accuracy. One method for separating materials by type is wet specific gravity separation.

[0004] When using wet gravity separation to selectively recover low-gravity, high-quality coal from raw coal, a known method is to place a float with the maximum specific gravity of the high-quality coal to be recovered in the separation chamber, detect the layer thickness of the recovered material from the float position, and recover the high-quality product while controlling the discharge speed.

[0005] Generally, raw coal processed by jig separators is often only a few centimeters in size, and since large volumes are processed with a thick layer, even if the float size is large, there is no problem with sorting accuracy. However, in the processing of waste plastic, the particles are small, at only a few millimeters, and the specific gravity difference is small and low, so it has been observed that disturbances in particle behavior near the float disrupt the stratification of the particles, and improvements to the float have been proposed (Patent Document 1).

[0006] However, there is a limit to how small the float shape can be, and for precise sorting, an alternative method of estimating layer thickness is useful. Patent Document 2 describes a method of estimating layer thickness, which is a recovery control device that is installed in a screen-under-air-chamber-type wet specific gravity separator that includes a sorting chamber into which the material to be sorted is fed, a pulsation chamber located below the sorting chamber, and a mesh located between the sorting chamber and the pulsation chamber, The device disclosed is characterized in that it is equipped with one pressure sensor placed at a predetermined location within the sorting chamber, or multiple pressure sensors placed at predetermined locations spaced apart vertically within the sorting chamber, and is configured to control the recovery of the sorted material based on previously obtained data on the pressure generated when pulsation of the sorting medium is applied for multiple layer thicknesses of the sorted material. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2008-132484 A [Patent Document 2] JP 2008-132485 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology in Patent Document 2 requires that the first and second substances to be treated be placed separately in the sorting chamber in advance and that the pressure waveform during pulsation be measured with a pressure sensor. This is difficult to apply to mixtures of multiple types of plastics, such as mixed plastics generated from discarded home appliances, where the mixing ratio of each type of plastic changes over time.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a wet specific gravity sorter that can sort waste plastics with different specific gravities even when the mixing ratio of the waste plastics changes over time. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention proposes the following means. (1) The wet specific gravity separator according to aspect 1 of the present invention is a sorting chamber that holds a liquid and into which the material to be sorted is introduced; a pulsation chamber that holds the liquid and applies pulsation to the sorting chamber via the liquid; a screen disposed between the sorting chamber and the pulsation chamber, the screen having a mesh size smaller than that of the material to be sorted and allowing the liquid to pass through; a displacement sensor for measuring a displacement of a liquid level of the liquid; A pressure sensor for measuring pressure; a tube having one end connected to the pressure sensor and the other end adjustably positioned near the bottom surface of the layer of the material to be selected formed by the pulsation; an estimation control unit that estimates a layer thickness of a target material in the layer of the sorting material based on data of a change in pressure loss over time calculated from data of the displacement measured by the displacement sensor and data of a pressure measured by the pressure sensor; Equipped with The tube is filled with a gas; The pressure sensor measures the pressure within the pipe. (2) A second aspect of the present invention is the wet specific gravity separator of the first aspect, wherein the concentration criterion of the material to be separated is 1.5 or more. (3) A third aspect of the present invention is the wet specific gravity separator of the first or second aspect, wherein the pressure sensor is an air sensor. (4) A fourth aspect of the present invention is the wet specific gravity separator of any one of the first to third aspects, wherein the pressure sensor has a resolution of 0.001 to 0.05 kPa. (5) A fifth aspect of the present invention is a wet specific gravity separator according to any one of the first to fourth aspects, The liquid is water. (6) A sixth aspect of the present invention is a wet specific gravity separator according to any one of the first to fifth aspects, The gas is air. (7) A seventh aspect of the present invention is the wet density separator of any one of the first to sixth aspects, further comprising a discharge section that discharges the material to be sorted based on the layer thickness estimated above. Effect of the Invention

[0011] According to the present invention, it is possible to provide a wet specific gravity separator capable of separating waste plastics having different specific gravities even when the mixing ratio of the waste plastics varies over time. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a wet specific gravity separator according to an embodiment of the present invention. [Diagram 2] 1 is a flowchart of a sorting method using a wet specific gravity sorter according to an embodiment of the present invention. [Diagram 3] FIG. 13 is a graph showing the change in pressure loss over time and the analysis results thereof. [Figure 4] FIG. 1 is a schematic diagram of a wet density separation system according to an embodiment of the present invention. [Diagram 5] Figure 5(a) shows the results of liquid surface vibration when the lagging material layer is 5 cm, Figure 5(b) shows the results of liquid surface vibration when the lagging material layer is 10 cm, and Figure 5(c) shows the results of liquid surface vibration when the lagging material layer is 15 cm. [Figure 6] FIG. 6(a) shows the change in pressure drop over time measured with the tube filled with water, and FIG. 6(b) shows the change in pressure drop over time measured with the tube filled with air. [Figure 7] FIG. 1 is a graph showing the relationship between Pp(t) / Pp(0) and the content ratios of PC and POM. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First Embodiment Hereinafter, a wet specific gravity separator according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a wet specific gravity separator 100 according to the first embodiment. The wet specific gravity separator 100 comprises a sorting chamber 51 which holds liquid X and into which a material to be sorted is introduced, a pulsation chamber 52 which holds liquid X and applies pulsation to the material to be sorted in the sorting chamber 51 via the liquid X, a net 53 which is disposed between the sorting chamber 51 and the pulsation chamber 52 and has a mesh size smaller than the material to be sorted and through which the liquid X can pass, a displacement sensor 55 which measures the displacement of the liquid level of the liquid X, a pressure sensor 56 which measures the pressure, and a pressure sensor 57 which has one end connected to the pressure sensor 56 and the other end connected to the layer of the material to be sorted formed by the pulsation. the pressure sensor 56 measures the pressure inside the pipe 57. The sorting apparatus includes a pipe 57 adjustably arranged near the bottom surface of the sorting apparatus, an estimation control unit 10 that estimates a variation in layer thickness of a target material in the sorted material based on data on a time-dependent change in pressure loss calculated from data on the displacement measured by a displacement sensor 55 and data on the pressure measured by the pressure sensor, and a discharge unit 60 that discharges the target material based on the variation in layer thickness estimated by the estimation control unit 10, the pipe 57 being filled with gas, and a pressure sensor 56 measuring the pressure inside the pipe 57. Here, a case will be described in which the sorted material contains a light material A having a low specific gravity and a heavy material B having a high specific gravity. The target material is, for example, the heavy material B.

[0014] (Sorting Room 51) The sorting chamber 51 includes an inlet 54 for introducing the material to be sorted, a heavy material outlet 61 for discharging the heavy material B, and a light material outlet 63 for discharging the light material A. The material to be sorted is introduced into the sorting chamber 51 from the inlet 54 at a predetermined introduction speed from a feeder (not shown). A liquid X is held in the sorting chamber 51. The introduced material to be sorted sinks in the liquid X and accumulates on the net 53. The sorting chamber 51 further includes a light material outlet 63 for discharging the light material A. The light material outlet 63 is preferably located, for example, higher than the liquid level of the liquid X before pulsation is applied and lower than the liquid level of the liquid X when pulsation is applied. In this way, the light material A can be discharged when pulsation is applied.

[0015] (pulsating chamber 52) The pulsation chamber 52 holds the liquid X and applies a pulsation to the material to be sorted in the sorting chamber 51 through the liquid X. Here, pulsation refers to the up and down movement of the liquid X. Methods for applying a pulsation include, for example, a plunger type and a compressed air type. Here, air is introduced and discharged from an air inlet / outlet port 59 disposed in the air chamber 58 to raise and lower the liquid level of the liquid X in the air chamber 58, thereby raising and lowering the liquid level of the liquid X in the sorting chamber 51. This allows a pulsation to be applied to the liquid X in the sorting chamber 51. By applying a pulsation to the material to be sorted present in the liquid X, layers according to specific gravity (layers of the material to be sorted) are formed. In the example of FIG. 1, the layer of the material to be sorted is composed of a layer of a light material to be sorted A having a low specific gravity and a layer of a heavy material to be sorted B having a high specific gravity. By applying a pulsation, a layer of the target recovery material (layer of the heavy material to be sorted B) is formed, and the target recovery material can be sorted. In the following description, the heavy sorted material B is the target material, but the target material may be the light sorted material A. When the target material is the light sorted material A, the target material is discharged from the light sorted material discharge port 63.

[0016] (Net 53) The mesh 53 is disposed between the sorting chamber 51 and the pulsation chamber 52, and has a mesh size smaller than that of the material to be sorted, allowing the liquid to pass through. Since the mesh size is smaller than that of the material to be sorted, the material to be sorted introduced into the sorting chamber 51 does not pass through the mesh 53, but accumulates on the mesh 53. The size of the mesh of the mesh 53 is not particularly limited as long as it does not impede the transmission of pulsation and does not allow the material to be sorted to pass into the pulsation chamber 52.

[0017] (Displacement Sensor 55) The displacement sensor 55 measures the displacement of the liquid surface of the liquid X in the sorting chamber 51, and sends data of the measured displacement to the estimation control unit 10. The displacement sensor is, for example, a laser displacement meter.

[0018] (Pressure Sensor 56) The pressure sensor 56 measures the pressure in the tube 57 and sends the data of the pressure to the estimation control unit 10. The pressure sensor 56 is connected to one end of the tube 57 filled with the gas Y. The other end of the tube 57 is adjustably arranged near the bottom surface of the layer of the sorted material formed by the pulsation. For example, when a rectifying layer described later is not provided, the other end of the tube 57 is preferably arranged at a position 0 to 5 mm away from the net 53 in a direction perpendicular to a plane parallel to the net 53. When a rectifying layer described later is not provided, the lower end of the tube 57 is arranged at the boundary between the net 53 and the layer of the sorted material. When a rectifying layer described later is provided, the lower end of the tube 57 is preferably arranged at a position 0 to 5 mm away from the rectifying layer in a direction perpendicular to a plane parallel to the net 53. "Adjustably arranged near the bottom surface" means that the position of the other end (lower end) of the tube 57 can be adjusted to match the position of the bottom surface (layer of the target collection material) of the layer of the sorted material when sorting the material. The position adjustment of the lower end can be performed by a known means. The position may be adjusted manually, or may be adjusted using a motor (not shown). When pulsation is applied to liquid X, differences in settling speed appear due to differences in the specific gravity of the particles in the material to be sorted. This causes a change in pressure loss over time. This change in pressure over time is measured by pressure sensor 56 via gas Y. By measuring via gas, the difference in pressure density can be measured more precisely, making it possible to perform sorting even when there are many materials to be sorted that have low specific gravity.

[0019] The resolution of the pressure sensor 56 is preferably 0.001 to 0.05 kPa. More preferably, the pressure sensor 56 has a resolution of 0.001 to 0.05 kPa in the range of -10 kPa to +10 kPa. A higher resolution is preferable because it allows for more precise measurement.

[0020] (tube 57) One end of the tube 57 is connected to the pressure sensor 56. The other end of the tube 57 is disposed near the bottom surface of the layer of the material to be selected formed by pulsation. The inside of the tube is filled with gas Y. The other end of the tube 57 is in liquid X. The pressure sensor 56 is fixed to the tube 57 with a sealing material so as not to be affected by the atmospheric pressure outside the tube 57.

[0021] (Estimation control unit 10) The estimation control unit 10 estimates the layer thickness of the target material in the sorted material based on the data of the change in pressure loss over time calculated from the displacement data measured by the displacement sensor 55 and the pressure data measured by the pressure sensor 56. The pressure loss is calculated by multiplying the water surface position h measured by the displacement sensor 55 by the hydrostatic pressure P w =ρ×g×h (ρ: water density, g: gravitational acceleration) is calculated and subtracted from the pressure sensor value P of the pressure sensor 56 to obtain the pressure loss P due to the fluid / particle interaction. p (P p =PP w ). This pressure loss P p The layer thickness fluctuation of the target recovered material in the sorted material is estimated from the data of the time-dependent change in the thickness of the target recovered material in the sorted material by a method described later. Based on the estimated layer thickness fluctuation, the estimation control unit 10 controls the discharge speed of the discharge unit 60 and the input speed of the sorted material from a feeder (not shown) to discharge the target sorted material, which is the sorted material after sorting.

[0022] The discharge section 60 is connected to the heavy sorted material discharge port 61 of the sorting chamber 51, and discharges the target recovered material by rotating the screw 62. When a rise / fall in the layer boundary position of the light sorted material A / heavy sorted material B is indicated, the recovery speed of the screw 62 is controlled to discharge the target recovered material while maintaining the layer boundary position appropriately.

[0023] (rectifying layer) The wet specific gravity separator 100 preferably further includes a straightening layer (not shown) for forming a uniform upward flow to suppress disturbance of the material to be sorted. The straightening layer is disposed on the net 53. The presence of the straightening layer makes the upward flow uniform, further improving the accuracy of sorting. Examples of the straightening layer include a layer made of lagging material and a layer with a honeycomb structure. Here, lagging material refers to heavy particles that are not lifted by the upward flow during pulsation. When the straightening layer is present, the lower end of the pipe 57 is disposed at the boundary between the straightening layer and the layer of the material to be sorted.

[0024] The thickness of the straightening layer is, for example, 5 to 15 cm. More preferably, the thickness of the straightening layer is 10 to 20 cm. Examples of the lagging material constituting the straightening layer include iron balls and alumina balls. The particle size of the lagging material is, for example, 3 mm to 10 mm.

[0025] (Sorting method using a wet specific gravity separator) Next, a sorting method using the wet specific gravity separator 100 according to this embodiment will be described. FIG. 2 is a flow chart of the sorting method using the wet specific gravity separator according to the first embodiment of the present invention. In the sorting method according to this embodiment, first, the material to be sorted is put into the sorting chamber 51 (first step S1). Next, air is introduced and discharged from the air inlet / outlet 59 to raise and lower the liquid level in the air inlet / outlet 59, and pulsation is applied to the material to be sorted through the liquid X in the sorting chamber 51 (second step S2). After applying pulsation under a predetermined pulsation condition, the displacement of the liquid level of the liquid X and the pressure value of the pressure sensor 56 are acquired at a predetermined timing by the displacement sensor 55 and the pressure sensor 56 (third step S3). After the third step S3, the estimation control unit 10 calculates the pressure loss based on the displacement and pressure data, and acquires data on the change over time. Next, the fluctuation in the layer thickness of the target recovered material is estimated based on a layer thickness estimation method described later (fourth step S4). After the fourth step S4, the discharge speed of the target material is adjusted based on the estimated layer thickness fluctuation (here, the fluctuation of the boundary layer position of the light sorted material A / heavy sorted material B) (fifth step S5). If the discharge amount of the target material exceeds a specified value, the sorting is terminated (S6 YES), and if it is less than the specified value, the process returns to the second step S2 (S6 No). Each step will be described below.

[0026] (1st process S1) The material to be sorted is introduced through an inlet 54 of the sorting chamber 51. The introduction method is not particularly limited, and for example, the material may be introduced continuously or discontinuously from a feeder (not shown). The introduced material to be sorted sinks in the liquid X and accumulates on the net 53. "Substance to be sorted" The substances to be sorted that are input are not particularly limited. In the sorting method according to this embodiment, sorting is performed based on the difference in settling velocity between the substances to be sorted, which is caused by the difference in specific gravity between the substances to be sorted. The settling velocity Vt of the substances to be sorted is expressed by the following formula (1A). Here, μ in the following formula (1A) is the viscosity of the liquid X (Pa s), g is the gravitational acceleration (m / s 2 )ρ is the density of liquid X (kg / m 3 ) and ρ p is the density of the material to be sorted (kg / m 3 ) and D p is the particle size (m) of the material to be sorted. A particle (specific gravity ρ A , particle diameter D A ) and B particles (specific gravity ρ B , particle diameter D B ) settles at the same speed, the uniform falling ratio is the particle diameter D A and particle size D B It is expressed by. Using this uniform drop ratio, it is possible to select a material to be sorted that is easier to sort. In the case of free settling, the uniform drop ratio is expressed by the following formula (1B), and in the case of hindered settling, it is expressed by the following formula (1C). In particular, the uniform drop ratio during hindered settling is called the Concentration Criterion (CC) and can be expressed by the following formula (2). In the following formula (2), SG_heavy material is the specific gravity of the heavy material to be sorted B, SG_light material is the specific gravity of the light material to be sorted A, and SG_fluid is the specific gravity of the liquid X. In the sorting method using the wet specific gravity sorter 100, it is preferable that the CC of the material to be sorted is 1.5 or more. The larger the CC of the material to be sorted, the easier it is to sort. When multiple types of materials are included in the material to be sorted, the CC can be calculated from the specific gravity of the target material and the specific gravity of the material to be sorted that is closest to the specific gravity of the target material.

[0027] "Liquid X" Liquid X is not particularly limited as long as it is a liquid. Liquid X can be appropriately selected depending on the substance to be selected. Liquid X can be an organic solvent such as methanol or dimethyl sulfoxide, or water. Liquid X is preferably water.

[0028]

number

[0029]

number

[0030] (2nd process S2) In the second step S2, air is let in and out through the air inlet / outlet 59 to raise and lower the liquid level in the air inlet / outlet 59, thereby applying pulsation to the material to be sorted via the liquid X in the sorting chamber 51. The pulsation mainly consists of four steps. Specifically, there are four steps: an ascending step for raising the liquid level, a first holding step for holding the raised liquid level, a descending step for processing the liquid level, and a second holding step for holding the lowered liquid level.

[0031] (Upward step) In the ascending step, the liquid level is raised. By raising the liquid level of liquid X, all particles of the material to be sorted are lifted. In this case, the maximum height to which the liquid level can be raised is preferably the height at which all particles can be lifted. This height may be determined by investigation in advance. In the ascending step, it is appropriate to operate at an ascending flow velocity (fluidization start velocity) at which particles with a heavy specific gravity are lifted by the ascending flow and begin to move. This ascending flow velocity may also be determined in advance after investigation for the material to be sorted that is being fed. During the ascending step, light material A to be sorted is discharged from the light material to be sorted outlet 63.

[0032] (First holding step) In the first retention step, the liquid level is retained. During this retention, the materials to be sorted settle. The retention time of the liquid level in the retention step is preferably equal to or longer than the time required for all the materials to be sorted to settle and accumulate on the net 53.

[0033] (Downward step) In the descending step, the liquid level is lowered, and the descending step preferably begins after the particles have stopped moving.

[0034] (Second holding step) In the second holding step, the lowered liquid level is held. It is preferable to hold the level until the lowering of the liquid level of Liquid X has finished and the movement of the liquid level has settled down. After the second holding step, if necessary, the liquid level can be returned to the rising step and layers based on specific gravity can be formed by repeating the pulsation.

[0035] (3rd process S3) In the third step S3, the displacement sensor 55 and the pressure sensor 56 acquire the displacement of the liquid level of the liquid X and the pressure value of the pressure sensor 56 at a predetermined timing. The displacement sensor 55 and the pressure sensor 56 measure the displacement of the liquid level and the pressure of the liquid X at a predetermined interval (for example, every 10 ms) from the start of the rising step (t=0 ms) to the end of the first holding step, and send the results to the estimation control unit 10. Since the end (lower end) of the tube 57 is near the bottom surface of the layer of the sorted material formed by the pulsation, the gas Y is affected by the pressure loss caused by the pulsation. Since the inside of the tube 57 is filled with the gas Y, the effect is transmitted to the pressure sensor 56 through the gas Y. That is, the pressure sensor 56 measures the effect of the pressure loss caused by particles of the sorted material through the gas Y. By measuring the pressure through the gas Y, the effect of the pressure fluctuation can be measured with higher accuracy.

[0036] "Gas Y" The gas Y is not particularly limited as long as it can transmit the fluctuation in pressure loss to the pressure sensor 56. As the gas Y, air is preferable.

[0037] (4th step S4) In the fourth step S4, the estimation control unit 10 calculates the pressure loss based on the displacement and pressure data obtained in the third step S3, and obtains data on the change in pressure loss over time. The pressure loss is calculated by multiplying the water surface position h measured by the displacement sensor 55 by the hydrostatic pressure P w =ρ×g×h (ρ: water density, g: gravitational acceleration) is calculated, and the hydrostatic pressure P is calculated from the pressure sensor value P of the pressure sensor 56. w By subtracting the pressure loss P due to fluid / particle interaction, p (i.e., P p =PP w ).

[0038] Next, in the fourth step S4, the fluctuation of the layer thickness of the target recovered material is estimated based on the acquired data of the change in pressure loss over time. FIG. 3 shows the change in pressure loss over time and the analysis results when pulsation is applied to the water and light sorted material A / heavy sorted material B (light sorted material A with a low specific gravity is in the upper layer, and heavy sorted material B with a high specific gravity is in the lower layer) are stratified. The horizontal axis is time and the vertical axis is pressure loss (kPa). In the rising pulsation step, the light sorted material A and heavy sorted material B are lifted up as the water level rises, so the pressure loss reaches a peak value. In the first retention step, the light sorted material A and heavy sorted material B start to settle. In the early stage of the first retention step, the heavy sorted material B has a faster settling speed, so the settling of the heavy sorted material B finishes first (most of the heavy sorted material B lands on the net 53).

[0039] In the latter part of the first retention step, the remaining lightly sorted material A settles, so the rate of decrease in pressure drop changes between the early and later parts. Specifically, the rate of decrease in pressure drop in the later part of the first retention step is more gentle than the rate of decrease in pressure drop in the early part of the first retention step. That is, at the inflection point P p (t) appears. As shown in Figure 3, P p It can be seen that a bending point appears in (t). The change in this bending point allows us to estimate the change in the layer boundary position between the light material A and the heavy material B. p As (t) becomes smaller, the thickness of the layer of the target material becomes thinner, and the inflection point P pThe larger (t) is, the thicker the layer of the target material is. p(t) can be obtained by a known analytical method. p The layer thickness itself may be estimated by examining the relationship between (t) and layer thickness.

[0040] In Figure 3, the cause of the turbulence near the peak is the phenomenon of the liquid level swaying when the liquid level goes from rising to stopping. The main cause of this swaying is the air vibration in the air chamber (vibration of the liquid level in the air chamber) caused by the sudden cessation of air intake into the air chamber. There is not much difference between the analysis in which this mechanically caused turbulence in pressure loss (near time 0) is included in the analysis and the analysis in which it is excluded, so it is fine to leave the area near time 0 included in the analysis.

[0041] (5th step S5) In the fifth step S5, the discharge speed of the target material is adjusted based on the fluctuation in the layer thickness of the target material estimated in the fourth step S4 (here, the fluctuation in the boundary layer position of the light material A / heavy material B). Here, the estimation control unit 10 adjusts the discharge speed by adjusting the rotation speed of the screw 62 based on the fluctuation in the layer thickness of the target material. During continuous operation, if the mixture ratio of the light material A and the heavy material B changes, for example (1) when the ratio of the heavy material B decreases, if the discharge speed is not changed, the discharge speed of the heavy material B will be larger than the input speed, so the layer thickness of the heavy material B, which is the target material, will gradually become thinner, and light particles will be caught in the material during recovery, causing the quality of the target material to decrease. (2) On the other hand, if the ratio of the heavy material B increases, the discharge of the heavy material B will not keep up with the flow of the material if the discharge speed is maintained, and the heavy material B will reach the light material discharge port 63, causing the quality of the light material A to decrease. In the fifth step S5, the discharge speed is controlled based on the variation of the bending point, so that the product can be discharged while maintaining the layer boundary position appropriately. This allows the target product to be recovered with high quality. In the fifth step S5, the feeder (not shown) may also be controlled to control the input speed.

[0042] The wet specific gravity sorter 100 and sorting method according to the first embodiment have been described above. The wet specific gravity sorter 100 according to this embodiment can sort waste plastics even when the mixture ratio of waste plastics with different specific gravities varies over time.

[0043] <Second embodiment> Next, a wet specific gravity sorting system 200 according to a second embodiment will be described with reference to Fig. 4. As shown in Fig. 4, the wet specific gravity sorting system 200 includes a first wet specific gravity sorter 100A, a second wet specific gravity sorter 100B, a third wet specific gravity sorter 100C, and an estimation control unit 10C. The material to be sorted is first input into the first wet specific gravity sorter 100A. The material to be sorted used in the second embodiment includes, for example, a first light material to be sorted having the lightest specific gravity, a second light material to be sorted having the second lightest specific gravity, a third light material to be sorted having the third lightest specific gravity, and the heaviest heavy material to be sorted.

[0044] (First wet specific gravity separator 100A) The first wet specific gravity separator 100A comprises a sorting chamber 51A which holds liquid X and into which the material to be sorted is introduced, a pulsating chamber 52A which holds liquid X and imparts pulsation to the sorting chamber 51A via the liquid X, a net 53A which is arranged between the sorting chamber 51A and the pulsating chamber 52A and has a mesh size smaller than the material to be sorted and through which the liquid X can pass, a displacement sensor 55A which measures the displacement of the liquid level of the liquid X, a pressure sensor 56A which measures the pressure, a pipe 57A which has one end connected to the pressure sensor 56A and the other end which is adjustably arranged near the bottom surface of the layer of the material to be sorted formed by the pulsation, and a discharge unit 60 which discharges the first target recovered material based on the fluctuation in the layer thickness of the target material in the sorting chamber 51A estimated by the estimation control unit 10C. The estimation control unit 10C estimates the fluctuation in the layer thickness of the first target recovery material in the sorting material in the sorting chamber 51A based on data on the change in pressure loss over time calculated from displacement data measured by the displacement sensor 55A and pressure data measured by the pressure sensor 56A.

[0045] The first wet specific gravity sorter 100A estimates the variation in the layer thickness of the target material and controls the discharge speed of the first target material in the same manner as the wet specific gravity sorter 100 of the first embodiment. The first target material in the first wet specific gravity sorter 100A is a mixture of the input material to be sorted and the first light material to be sorted. The first light material to be sorted is discharged, for example, from a first light material to be sorted outlet 63A (not shown). The first light material to be sorted outlet 63A is preferably located, for example, higher than the liquid level of the liquid X before the pulsation is applied in the sorting chamber 51A and lower than the liquid level of the liquid X when the pulsation is applied. In this way, the first light material to be sorted can be discharged when the pulsation is applied. The first target material sorted by the first wet specific gravity sorter 100A is discharged from the heavy material to be sorted outlet 61A and sent to the second wet specific gravity sorter 100B.

[0046] (Second wet specific gravity separator 100B) The second wet specific gravity separator 100B includes a sorting chamber 51B that holds liquid X and into which the first target material is introduced, a pulsation chamber 52B that holds liquid X and imparts pulsation to the sorting chamber 51B via the liquid X, a net 53B that is arranged between the sorting chamber 51B and the pulsation chamber 52B and has a mesh size smaller than the material to be sorted and through which the liquid X can pass, a displacement sensor 55B that measures the displacement of the surface of the liquid X, a pressure sensor 56B that measures the pressure, a pipe 57B having one end connected to the pressure sensor 56B and the other end that is adjustably arranged near the bottom surface of the layer of the material to be sorted formed by the pulsation, and a discharge unit 60B that discharges the second target material based on the variation in the layer thickness of the second target material in the sorting chamber 51B estimated by the estimation control unit 10C. The estimation control unit 10C estimates the fluctuation in the layer thickness of the second target recovery material in the sorting material in the sorting chamber 51B based on data on the change in pressure loss over time calculated from displacement data measured by the displacement sensor 55B and pressure data measured by the pressure sensor 56B.

[0047] The second wet specific gravity sorter 100B estimates the variation in the layer thickness of the target material and controls the discharge speed of the second target material in the same manner as the wet specific gravity sorter 100 of the first embodiment. The second target material in the second wet specific gravity sorter 100B is, for example, a mixture of the first target material and the second light material. The second light material is discharged, for example, from a second light material discharge port 63B (not shown). The second light material discharge port 63B is preferably located, for example, higher than the liquid level of the liquid X before the pulsation is applied in the sorting chamber 51B and lower than the liquid level of the liquid X when the pulsation is applied. In this way, the second light material can be discharged when the pulsation is applied. The second target material sorted by the second wet specific gravity sorter 100B is discharged from the heavy material discharge port 61B and sent to the third wet specific gravity sorter 100C.

[0048] (Third wet specific gravity separator 100C) The third wet specific gravity separator 100C includes a sorting chamber 51C that holds liquid X and into which the second target material is introduced, a pulsation chamber 52C that holds liquid X and imparts pulsation to the sorting chamber 51C via the liquid X, a net 53C that is disposed between the sorting chamber 51C and the pulsation chamber 52C and has a mesh size smaller than the material to be sorted and through which the liquid X can pass, a displacement sensor 55C that measures the displacement of the surface of the liquid X, a pressure sensor 56C that measures the pressure, a pipe 57C having one end connected to the pressure sensor 56C and the other end that is adjustably disposed near the bottom surface of the layer of the material to be sorted formed by the pulsation, and a discharge unit 60C that discharges the third target material based on the fluctuation in the layer thickness of the target material in the sorting chamber 51C estimated by the estimation control unit 10C. The estimation control unit 10C estimates the fluctuation in layer thickness of the third target recovery material in the sorting material in the sorting chamber 51C based on data on the change in pressure loss over time calculated from displacement data measured by the displacement sensor 55C and pressure data measured by the pressure sensor 56C.

[0049] The third wet specific gravity separator 100C estimates the variation in the layer thickness of the target material and controls the discharge speed of the third target material in the same manner as the wet specific gravity separator 100 of the first embodiment. The third target material in the third wet specific gravity separator 100C is, for example, a mixture in which the third light sorted material is removed from the second target material. The third light sorted material is discharged, for example, from a third light sorted material discharge port 63C (not shown). The third light sorted material discharge port 63C is preferably located, for example, higher than the liquid level of the liquid X before the pulsation is applied in the sorting chamber 51C and lower than the liquid level of the liquid X when the pulsation is applied. In this way, the third light sorted material can be discharged when the pulsation is applied. The third target material sorted by the third wet specific gravity separator 100C is discharged from a heavy sorted material discharge port 61C.

[0050] The wet specific gravity separation system 200 according to the second embodiment has been described above. According to the wet specific gravity separation system 200 according to this embodiment, even when three or more types of waste plastics are mixed and the mixture ratio changes over time, the waste plastics can be separated.

[0051] The estimation control units 10 and 10C may be realized by recording a program for implementing the functions of the estimation control units 10 and 10C on a computer-readable recording medium, and reading and executing the program recorded on the recording medium into a computer system. Note that the term "computer system" here includes hardware such as an OS and peripheral devices.

[0052] Here, "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" also includes those that dynamically hold a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such cases. Furthermore, the above program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system.

[0053] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. In addition, the components in the above embodiment can be appropriately replaced with well-known components without departing from the spirit of the present invention, and the above-mentioned modified examples can be appropriately combined. EXAMPLES

[0054] Next, an embodiment of the present invention will be described, but the conditions in the embodiment are merely an example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to this example of conditions. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0055] (Verifying the effectiveness of lagging materials) Alumina lagging material (particle size 5mm) was placed on a net (mesh size 3mm) with a thickness of 5cm to 15cm, and the results of measuring the fluctuation in the displacement of the liquid surface when pulsation was applied under the condition of a wave height of 35mm are shown in Figure 5. Figure 5(a) shows the results when the lagging material layer was 5cm thick, Figure 5(b) shows the results when the lagging material layer was 10cm thick, and Figure 5(c) shows the results when the lagging material layer was 15cm thick. The horizontal axis of each figure is time (seconds) and the vertical axis is displacement (cm). When the lagging material layer was 5cm thick, there was some vibration of the liquid surface, but when the lagging material layer was 10cm or more thick, it was found that the vibration could be sufficiently suppressed. From this, it was found that a lagging material layer of 10cm or more is capable of uniform rectification.

[0056] (Check the effect of the medium inside the pipe) A sorting experiment was conducted with the configuration shown in Figure 1, in which the tube was filled with water (water-oil-air multipurpose sensor: Keyence AP-125 / AP-V80) and the configuration in which the tube was filled with air (air, noncorrosive gas sensor: Keyence AP-C35: pressure measurement range -10 to +10.00 kPa, resolution 0.02 kPa). As the substance to be sorted, a mixture of polycarbonate PC (specific gravity: 1.17, particle size 2-8 mm) and polyacetal POM (specific gravity 1.42, particle size 2-8 mm) in a weight ratio of 50:50 (CC: 2.5) was used, and pulsation was applied, and the change in pressure loss over time was obtained from the pressure and water level using the method described above. The results are shown in Figure 6. Figure 6(a) shows the change in pressure loss over time measured with the tube filled with water, and Figure 6(b) shows the change in pressure loss over time measured with the tube filled with air. As is clear from a comparison of Figure 6(a) and Figure 6(b), the noise can be significantly reduced by filling the tube with air. This makes it possible to more accurately determine the position of the bending point mentioned above.

[0057] Plastic samples PC (specific gravity: 1.17, particle size 2-8 mm) and POM (specific gravity 1.42, particle size 2-8 mm) were mixed at ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 to prepare samples, and pulsation was added using a wet specific gravity separator. A pressure sensor (Keyence, AP-c35) and a displacement sensor (Keyence, IL-300 / IL-1000) were installed as shown in the figure, and pressure loss was calculated using the above-mentioned method from the pressure / water level sensor data values ​​during pulsation. Figure 3 shows the change over time in pressure loss for the sorted material with a mixture ratio of 50:50 in the rising step and first retention step. Using Excel's Solver analysis of the obtained data on the change over time, it was found that the rate of decrease in pressure loss bends at 1075 mS. After all particles had settled, the pressure loss settled at around zero. Figure 7 shows the bending point P p (t) is the peak value P p The vertical axis of Fig. 7 shows the relationship between the value divided by (0) and the PC / POM content ratio. p (t) is the peak value P p The values ​​are divided by (0), and the horizontal axis shows the polycarbonate mass / total sample mass. From Figure 7, it was found that by detecting the position of the bending point, it is possible to grasp the fluctuation of the boundary layer position of light / heavy particles. Therefore, by controlling the discharge speed based on the fluctuation of this bending point, it was found that sorting is possible even if the mixture ratio changes over time. [Industrial Applicability]

[0058] INDUSTRIAL APPLICABILITY The wet specific gravity separator of the present invention is highly industrially applicable since it can separate waste plastics having different specific gravities even when the mixing ratio of the waste plastics varies over time. [Explanation of symbols]

[0059] 10 Estimation control unit, 51 Sorting room, 52 Pulsation room, 53 Net, 54 Feeding port, 55 Displacement sensor, 56 Pressure sensor, 100 Wet specific gravity sorter, 200 Wet specific gravity sorting system

Claims

1. a sorting chamber that holds a liquid and into which the material to be sorted is introduced; a pulsation chamber that holds the liquid and applies pulsation to the material to be sorted in the sorting chamber via the liquid; a screen disposed between the sorting chamber and the pulsation chamber, the screen having a mesh size smaller than that of the material to be sorted and allowing the liquid to pass through; a displacement sensor for measuring a displacement of a liquid level of the liquid; A pressure sensor for measuring pressure; a tube having one end connected to the pressure sensor and the other end adjustably positioned near the bottom surface of the layer of the material to be selected formed by the pulsation; an estimation control unit that estimates a variation in layer thickness of a target recovered material in the layer of the sorting material based on data of a time-dependent change in pressure loss calculated from data of the displacement measured by the displacement sensor and data of the pressure measured by the pressure sensor; Equipped with The tube is filled with a gas; The pressure sensor measures the pressure inside the pipe.

2. 2. The wet specific gravity separator according to claim 1, wherein the concentration criterion of the material to be separated is 1.5 or more.

3. 3. The wet specific gravity separator according to claim 1, wherein the pressure sensor is an air sensor.

4. The wet specific gravity separator according to claim 3, wherein the resolution of the pressure sensor is 0.001 to 0.05 kPa.

5. 3. The wet density separator according to claim 1 or 2, wherein the liquid is water.

6. 3. The wet specific gravity separator according to claim 1, wherein the gas is air.

7. 3. The wet specific gravity separator according to claim 1, further comprising a discharge section that discharges the material to be sorted based on the layer thickness estimated by the estimation control section.

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