Pulse electric field treatment device

Abstract

The pulsed electric field treatment device (100) includes a pulse generator (102A) that outputs high-voltage pulses of positive and negative polarities, a treatment chamber (400) through which a treatment object (300) passes, an electrode (101) that is installed in the treatment chamber (400) and connected to the pulse generator (102A), and a control unit (102B) that controls the pulse generator (102A), wherein the control unit (102B) causes the pulse generator (102A) to output group pulses, each consisting of at least one high-voltage pulse, alternately with positive and negative polarities, and adjusts the number of high-voltage pulses included in the group pulse based on the amount of charge that flows in a single direction due to the group pulse.

Description

Technical Field

[0001] The present disclosure relates to a pulsed electric field treatment apparatus that applies a pulsed voltage to an object to be treated.

Background Art

[0002] Conventionally, a pulsed electric field treatment apparatus has been used to sterilize food or improve its quality. The pulsed electric field treatment apparatus includes a treatment chamber in which an object to be treated is disposed, electrodes installed in the treatment chamber, and a pulsed power supply device. The pulsed power supply device applies a high-voltage pulse from the electrodes to the object to be treated to perform pulsed electric field treatment on the object to be treated. The object to be treated is a liquid or a solid immersed in a liquid.

[0003] For example, when the liquid is a beverage, the beverage is transported by a pipe and an external pump, and pulsed electric field treatment is performed in the treatment chamber to sterilize the beverage. When the solid immersed in the liquid is root vegetables in tap water, the root vegetables are transported using a belt conveyor or the like that can be transported in water, and pulsed electric field treatment is performed in the treatment chamber to change the physical properties of the food ingredients. The change in the physical properties of the food ingredients refers to effects such as softening, improvement in cutability, promotion of drying, and improvement in extraction.

[0004] When performing pulsed electric field treatment by applying a unipolar pulsed voltage, there is a risk that the object to be treated may be electrolyzed, causing the device to malfunction due to a short circuit between the electrodes, or the electrodes may be electro-etched and metal particles may be mixed into the object to be treated.

[0005] Patent Document 1 discloses a saline water treatment method in which saline water is energized for sterilization treatment. The saline water treatment method disclosed in Patent Document 1 passes a saline water through a current application unit to which a pulse wave is applied, which rises a plurality of times at a preset voltage value in the positive direction and then rises the same number of times in the negative direction at the same voltage value as the voltage value in the positive direction, to sterilize the saline water.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the saline water treatment method disclosed in Patent Document 1 above, since a bipolar group pulse voltage is applied, the effects of electrolysis and electrocorrosion may be reduced to some extent compared to the case where a unipolar pulse voltage is applied. However, Patent Document 1 does not disclose a method for obtaining a high pulse electric field treatment ability while suppressing the effects of electrolysis and electrocorrosion, and there is a possibility that pulse electric field treatment with a high treatment ability may not be performed.

[0008] The present disclosure has been made in view of the above, and an object thereof is to obtain a pulse electric field treatment apparatus capable of performing pulse electric field treatment with a high treatment ability while suppressing the effects of electrolysis and electrocorrosion.

MEANS FOR SOLVING THE PROBLEMS

[0009] In order to solve the above-described problems and achieve the object, a pulse electric field treatment apparatus according to the present disclosure includes a pulse generator that outputs high voltage pulses of positive and negative polarities, a treatment chamber through which an object to be treated passes, an electrode installed in the treatment chamber and connected to the pulse generator, and a control unit that controls the pulse generator. The control unit alternately outputs a group pulse composed of at least one high voltage pulse to the pulse generator with positive and negative polarities, and adjusts the number of high voltage pulses included in the group pulse based on the amount of charge flowing in a single direction by the group pulse.

EFFECTS OF THE INVENTION

[0010] The pulse electric field treatment apparatus according to the present disclosure has an effect of being able to perform pulse electric field treatment with a high treatment ability while suppressing the effects of electrolysis and electrocorrosion.

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

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Mode for Carrying Out the Invention

[0012] Hereinafter, the pulse electric field processing apparatus according to the embodiment will be described in detail with reference to the drawings.

[0013] Embodiment 1. FIG. 1 is a diagram showing the configuration of the pulse electric field processing apparatus according to Embodiment 1. The pulse electric field processing apparatus 100 according to Embodiment 1 includes a processing chamber 400 through which a processing object 300 conveyed by a conveying device 200 passes, an electrode 101 installed in the processing chamber 400, a pulse power supply device 102 that applies a high voltage pulse to the electrode 101, and a current detector 103 that detects the value of the current flowing through the electrode 101 by the high voltage pulse.

[0014] When the processing object 300 is a liquid, the processing chamber 400 is connected to a pipe through which the liquid as the processing object 300 passes and constitutes a part of the flow path. The conveying device 200 when the processing object 300 is a liquid is a pump that forms the flow of the processing object 300 in the pipe. When the processing object 300 is a solid, the processing chamber 400 is a liquid tank filled with a processing liquid. The conveying device 200 when the processing object 300 is a solid is a belt conveyor that conveys the processing object 300 through the inside of the processing liquid filled in the processing chamber 400.

[0015] The pulse power supply device 102 includes a pulse generator 102A that outputs a positive-polarity high voltage pulse and a negative-polarity high voltage pulse to the electrode 101, and a control unit 102B that controls the output conditions of the positive-polarity and negative-polarity high voltage pulses output by the pulse generator 102A. The output conditions of the high voltage pulse include at least the voltage, pulse width, frequency, and polarity of the high voltage pulse.

[0016] The electrode 101 includes at least one high-voltage electrode 101A and at least one low-voltage electrode 101B. The high-voltage electrode 101A is connected to a pulse generator 102A by a high-voltage wire 104, and the low-voltage electrode 101B is connected to the pulse generator 102A by a low-voltage wire 105. The high-voltage electrode 101A and the low-voltage electrode 101B generate a pulsed electric field 500 between them by a high-voltage pulse supplied from the pulse generator 102A. A voltage corresponding to the peak of the high-voltage pulse is applied to the high-voltage electrode 101A by a high-voltage pulse of positive polarity or negative polarity. A ground-level voltage is applied to the low-voltage electrode 101B.

[0017] The current detector 103 is installed on the high-voltage wire 104 and outputs a measured value to the control unit 102B. The current detector 103 is insulated from the high-voltage electrode 101A. Here, a configuration in which the current detector 103 is installed on the high-voltage wire 104 is taken as an example, but the current detector 103 may be installed on the low-voltage wire 105. When the current detector 103 is installed on the low-voltage wire 105, it is necessary to insulate the low-voltage electrode 101B from the housing ground so that all the current flowing through the processing chamber 400 flows through the low-voltage electrode 101B. Note that the control unit 102B may estimate the current flowing through the electrode 101 based on the power consumption of the pulse generator 102A. In this case, the pulsed electric field processing apparatus 100 can have a configuration in which the current detector 103 is omitted.

[0018] The high-voltage electrode 101A and the low-voltage electrode 101B may be installed in the processing chamber 400 in pairs and in the same number, or one of the high-voltage electrode 101A and the low-voltage electrode 101B may be installed in the processing chamber 400 in a larger number than the other. In the processing chamber 400, the portion between the high-voltage electrode 101A and the low-voltage electrode 101B is an insulating member 401 formed of an insulating material, and the high-voltage electrode 101A and the low-voltage electrode 101B are insulated from each other except for the object to be processed 300.

[0019] FIG. 2 is a schematic diagram showing an example of a processing chamber in which the same number of high-voltage electrodes and low-voltage electrodes of the pulse electric field processing apparatus according to Embodiment 1 are installed. The processing chamber 400 is in the shape of a tank filled with a processing liquid three-dimensionally, but FIG. 2 schematically shows a cross section along the conveyance direction of the object to be processed 300. Note that the processing chamber 400 may be cylindrical three-dimensionally. The conveyance path of the object to be processed 300 is divided into two, and a processing chamber 400 is installed in each conveyance path. In each processing chamber 400, one high-voltage electrode 101A and one low-voltage electrode 101B are installed. The high-voltage electrode 101A and the low-voltage electrode 101B are connected to a pulse generator 102A by one high-voltage electric wire 104 and one low-voltage electric wire 105, respectively. Therefore, the electrode 101 and the pulse generator 102A are connected by four electric wires. An insulating member 401 is installed between the high-voltage electrode 101A and the low-voltage electrode 101B, and the high-voltage electrode 101A and the low-voltage electrode 101B are insulated from each other except for the object to be processed 300. In the configuration shown in FIG. 2, a pulse electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and one low-voltage electrode 101B.

[0020] As shown in FIG. 2, by dividing the conveyance path for conveying the object to be processed 300 into two for the two processing chambers 400 in which the same number of high-voltage electrodes 101A and low-voltage electrodes 101B are installed, the conveyance of the object to be processed 300 in the two conveyance paths can be stopped separately. For this reason, maintenance work such as replacement of the electrode 101 can be performed for each conveyance path. Here, a configuration in which the conveyance path of the object to be processed 300 is divided into two is taken as an example, but the same effect can be obtained when the conveyance path of the object to be processed 300 is divided into three or more.

[0021] FIG. 3 is a schematic diagram showing an example of a processing chamber in which a larger number of low-voltage electrodes are installed than the high-voltage electrode of the pulse electric field processing apparatus according to Embodiment 1. The processing chamber 400 is in a tank shape filled with a processing liquid three-dimensionally, but FIG. 3 schematically shows a cross section along the conveyance direction of the object to be processed 300. An electrode 101 is installed in the processing chamber 400 disposed on the conveyance path of the object to be processed 300. The electrode 101 includes one high-voltage electrode 101A and two low-voltage electrodes 101B. The high-voltage electrode 101A and the low-voltage electrodes 101B are arranged alternately side by side in a direction intersecting the conveyance direction of the object to be processed 300 in the processing chamber 400. For this reason, the high-voltage electrode 101A is disposed between the two low-voltage electrodes 101B. The high-voltage electrode 101A is connected to a pulse generator 102A by one high-voltage electric wire 104, and each of the low-voltage electrodes 101B is connected to the pulse generator 102A by one low-voltage electric wire 105. Therefore, the electrode 101 and the pulse generator 102A are connected by three electric wires. An insulating member 401 is installed between the high-voltage electrode 101A and the low-voltage electrodes 101B, and the high-voltage electrode 101A and the low-voltage electrodes 101B are insulated from each other. In the configuration shown in FIG. 3, a pulse electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and two low-voltage electrodes 101B.

[0022] Here, when the amount of the object to be processed 300 conveyed per unit time on the two conveying paths shown in FIG. 2 is the same as the amount of the object to be processed 300 conveyed per unit time on the conveying path shown in FIG. 3, the amount of the object to be processed 300 subjected to pulsed electric field treatment per unit time is the same. In the configuration where a pulsed electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and two low-voltage electrodes 101B shown in FIG. 3, the number of high-voltage electrodes 101A and the number of high-voltage electric wires 104 are smaller than those in the configuration shown in FIG. 2. For this reason, the pulsed electric field treatment apparatus 100 having a configuration in which a pulsed electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and two low-voltage electrodes 101B can reduce the number of parts and achieve cost reduction. Here, the pulsed electric field treatment apparatus 100 having a configuration in which a pulsed electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and two low-voltage electrodes 101B is taken as an example, but the same applies to the pulsed electric field treatment apparatus 100 having a configuration in which a pulsed electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and three or more low-voltage electrodes 101B. Also, here, the pulsed electric field treatment apparatus 100 having a configuration in which a pulsed electric field 500 by a high-voltage pulse is formed between one high-voltage electrode 101A and two low-voltage electrodes 101B is taken as an example, but the same applies to the pulsed electric field treatment apparatus 100 having a configuration in which a pulsed electric field 500 by a high-voltage pulse is formed between two or more high-voltage electrodes 101A and one low-voltage electrode 101B. Further, in the pulsed electric field treatment apparatus 100 having a configuration in which a pulsed electric field 500 by a high-voltage pulse is formed between a plurality of high-voltage electrodes 101A and a plurality of low-voltage electrodes 101B having a number different from the number of high-voltage electrodes 101A, the effect of cost reduction by reducing the number of parts can also be obtained.

[0023] In the configurations shown in FIGS. 2 and 3, two pulsed electric fields 500 are formed in parallel, but a configuration in which a plurality of pulsed electric fields 500 are formed in series may also be used.

[0024] FIG. 4 is a schematic diagram showing an example of a processing chamber in which a larger number of low-voltage electrodes are installed than the high-voltage electrode of the pulse electric field processing apparatus according to Embodiment 1. The processing chamber 400 is three-dimensionally cylindrical, but FIG. 4 schematically shows a cross section along the conveyance direction of the object to be processed 300. An electrode 101 is installed in the processing chamber 400 provided in the conveyance path of the object to be processed 300. The electrode 101 includes one high-voltage electrode 101A and two low-voltage electrodes 101B. An insulating member 401 is installed between the high-voltage electrode 101A and the low-voltage electrode 101B, and the high-voltage electrode 101A and the low-voltage electrode 101B are insulated from each other. Thus, the high-voltage electrode 101A and the low-voltage electrode 101B are alternately arranged side by side in the conveyance direction of the object to be processed 300 in the processing chamber 400. Therefore, the high-voltage electrode 101A is arranged between the two low-voltage electrodes 101B. The high-voltage electrode 101A is connected to the pulse generator 102A by one high-voltage electric wire 104, and each of the low-voltage electrodes 101B is connected to the pulse generator 102A by one low-voltage electric wire 105. Therefore, the electrode 101 and the pulse generator 102A are connected by three electric wires. In the configuration shown in FIG. 4, two pulse electric fields 500 by high-voltage pulses are formed in series between one high-voltage electrode 101A and two low-voltage electrodes 101B.

[0025] In the pulse electric field processing apparatus 100 shown in FIG. 4, since the object to be processed 300 passes through the pulse electric field 500 by high-voltage pulses twice, the processing ability of the pulse electric field processing can be enhanced as compared with the pulse electric field processing apparatus 100 shown in FIG. 2.

[0026] Alternatively, the pulsed electric field processing apparatus 100 may be configured to form one or more pulsed electric fields 500 using one low-voltage electrode 101B and multiple high-voltage electrodes 101A. FIG. 5 is a schematic diagram showing an example of a processing chamber in which more high-voltage electrodes than low-voltage electrodes are installed in the pulsed electric field processing apparatus according to embodiment 1. The processing chamber 400 is three-dimensionally cylindrical, but FIG. 5 shows a schematic cross section along the transport direction of the processing object 300. Three high-voltage electrodes 101A are installed around the transport path of the processing object 300, and one low-voltage electrode 101B is installed within the transport path. In the pulsed electric field processing apparatus 100 shown in FIG. 5, three pulsed electric fields 500 are formed in series by high-voltage pulses between the three high-voltage electrodes 101A and one low-voltage electrode 101B. In the pulsed electric field processing apparatus 100 shown in FIG. 5, a pulsed electric field 500 is continuously formed on the transport path by high voltage pulses, so that the object 300 to be processed does not pass through the processing chamber 400 during the interval between high voltage pulses, and the object 300 to be processed can be reliably subjected to pulsed electric field processing.

[0027] FIG. 6 is a diagram showing an example of the operation of the pulsed electric field processing apparatus according to the first embodiment. In the example shown in FIG. 6, the group pulse includes three high-voltage pulses. In FIG. 6, the horizontal axis represents time, and the vertical axis represents voltage. The pulsed electric field processing apparatus 100 performs pulsed electric field processing on the processing target 300 passing through the processing chamber 400 by repeating the output operation of a group pulse including three negative high-voltage pulses with a voltage of −Vn and a group pulse including three positive high-voltage pulses with a voltage of +Vp as one set. Note that since |Vp|=|Vn| and the number of high-voltage pulses included in the positive group pulse is the same as the number of high-voltage pulses included in the negative group pulse, the energy of the positive group pulse is the same as the energy of the negative group pulse.

[0028] The effects to be obtained by pulsed electric field treatment include sterilization and physical property changes, and the ability to cause these effects is defined as the treatment ability. Also, in pulsed electric field treatment, effects that are not practically preferable also occur. For example, due to the electrolysis of the moisture in the beverage, which is the object to be treated 300, a small amount of hydrogen may be generated in the beverage, which is the object to be treated 300, during the pulsed electric field treatment. As a result, bubbles will be generated in the object to be treated 300, but the bubbles may interfere with the pulsed electric field treatment or cause a discharge short circuit between the high-voltage electrode 101A and the low-voltage electrode 101B. Also, since the electrode 101 is electrically eroded by the pulsed electric field treatment, the shape of the electrode 101 changes due to long-term use, so that regular replacement work of the electrode 101 is required. These electrolysis and electrical erosion are collectively defined as adverse effects. In the pulsed electric field treatment apparatus 100, the treatment ability is improved while suppressing the adverse effects.

[0029] FIG. 7 is a diagram showing the relationship between the treatment ability, adverse effects, and the amount of charge flowing in a single direction of the pulsed electric field treatment apparatus according to Embodiment 1 and the number of high-voltage pulses included in the group pulses. In FIG. 7, the vertical axis indicates the treatment ability, adverse effects, and the amount of charge flowing in a single direction, and the horizontal axis indicates the number of high-voltage pulses included in the group pulses. The group pulses are a series of high-voltage pulses repeatedly applied a plurality of times with the same polarity. As the number of high-voltage pulses included in the group pulses increases, the treatment ability, adverse effects, and the amount of charge flowing in a single direction increase. The amount of charge flowing in a single direction increases or decreases linearly with respect to the change in the number of high-voltage pulses included in the group pulses.

[0030] If the amount of charge flowing through the pulsed electric field treatment is the same, when the number of high-voltage pulses included in the group pulse increases, the number of reversals of the polarity of the high-voltage pulse decreases. For example, in the pulsed electric field treatment where a group pulse including two high-voltage pulses is applied to the electrode 101 twice for each of the positive and negative polarities, and the pulsed electric field treatment where a group pulse including four high-voltage pulses is applied to the electrode 101 once for each of the positive and negative polarities, the amount of charge flowing through the pulsed electric field treatment is the same. However, in the pulsed electric field treatment where a group pulse including two high-voltage pulses is applied to the electrode 101 twice for each of the positive and negative polarities, three reversals of the polarity occur during the pulsed electric field treatment, while in the pulsed electric field treatment where a group pulse including four high-voltage pulses is applied to the electrode 101 once for each of the positive and negative polarities, one reversal of the polarity occurs during the pulsed electric field treatment.

[0031] The pulsed electric field treatment exerts its effect by destroying the cell membrane of the object to be treated 300 or the cell membrane of bacteria in the object to be treated 300 with a pulsed electric field 500 generated by a high-voltage pulse. Therefore, the effect does not appear simultaneously with the generation of the pulsed electric field 500, but appears with a delay after the generation of the pulsed electric field 500. Since the pulsed electric fields 500 generated by the high-voltage pulses are in opposite directions before and after the reversal of the polarity of the high-voltage pulse, when the polarity of the high-voltage pulse is reversed, the pulsed electric fields 500 cancel each other out before and after the polarity reversal, which causes a decrease in the processing ability. For this reason, when the number of high-voltage pulses included in the group pulse is small, the decrease in the processing ability due to one reversal of the polarity has a great influence, and the change in the processing ability accompanying the increase or decrease in the number of high-voltage pulses included in the group pulse becomes large. On the other hand, when the number of high-voltage pulses included in the group pulse is large, the influence of the decrease in the processing ability due to one reversal of the polarity is small, and the change in the processing ability accompanying the increase or decrease in the number of high-voltage pulses included in the group pulse becomes small.

[0032] For example, assume that the processing ability by high-voltage pulses before and after the polarity inversion is halved. When there is one high-voltage pulse included in the group pulse, that is, when the polarity is inverted every time a high-voltage pulse is applied, the processing ability of all high-voltage pulses is halved, so the effective value of the processing ability is 50%. On the other hand, when there are three high-voltage pulses included in the group pulse, since the number of high-voltage pulses not affected by the polarity inversion in the group pulse is one, the effective value of the processing ability is (1.0×1 + 0.5×2) / 3 = 66%. Also, when the number of high-voltage pulses included in the group pulse is five, since the number of high-voltage pulses not affected by the polarity inversion in the group pulse is three, the effective value of the processing ability is (1.0×3 + 0.5×2) / 5 = 80%.

[0033] On the other hand, the electrolysis of the object to be processed 300 or the processing liquid through which the object to be processed 300 passes and the electrical erosion of the electrode 101 do not occur simultaneously with the generation of the pulse electric field 500, but occur with a delay from the generation of the pulse electric field 500. For this reason, when the pulse electric fields 500 cancel each other out by inverting the polarity of the high-voltage pulses, the adverse effects are reduced. When comparing the influence of the number of high-voltage pulses included in the group pulse under the condition that the output periods of the high-voltage pulses included in the group pulse are the same, when the number of high-voltage pulses included in the group pulse is small, the number of times of polarity inversion of the high-voltage pulses increases, so the reduction effect of the adverse effects due to the polarity inversion is large. On the other hand, when the number of high-voltage pulses included in the group pulse is large, the number of times of polarity inversion of the high-voltage pulses decreases, so the reduction effect of the adverse effects due to the polarity inversion is small.

[0034] In the pulsed electric field processing apparatus 100 according to the first embodiment, the control unit 102B adjusts the number of high-voltage pulses included in the group pulse to an appropriate number when the set of group pulses is updated. The appropriate number of high-voltage pulses included in the group pulse is determined using the current value and pulse width of the high-voltage pulses. The amount of charge flowing with a single polarity can be calculated by calculating the product of the current value, the pulse width, and the number of high-voltage pulses included in the group pulse. Because the pulse width and the number of high-voltage pulses included in the group pulse are conditions set by the control unit 102B, the control unit 102B can calculate the amount of charge based on the measurement results obtained by the current detector 103.

[0035] If the calculated charge amount is greater than a predetermined first threshold, control unit 102B performs at least one of control to reduce the number of high-voltage pulses included in the group pulse and control to reduce the pulse width.On the other hand, if the calculated charge amount is smaller than a predetermined second threshold that is equal to or less than the first threshold, control unit 102B performs at least one of control to increase the number of high-voltage pulses included in the group pulse and control to increase the pulse width.

[0036] The first and second thresholds are values input from an external source or values preset in the pulsed electric field processing apparatus 100. When values input from an external source are used for the first and second thresholds, the pulsed electric field processing apparatus 100 can perform pulsed electric field processing under conditions suited to the type of object 300 to be processed by measuring in advance the processing capacity, adverse effects, and relationship between the amount of unidirectional electric charge flowing in one direction and the number of high-voltage pulses included in the group pulse for each type of object 300 to be processed. When values preset in the pulsed electric field processing apparatus 100 are used for the first and second thresholds, values preset based on the processing capacity, adverse effects, and relationship between the amount of unidirectional electric charge flowing in one direction and the number of high-voltage pulses included in the group pulse for water, a common processing liquid, are used for the first and second thresholds. This allows the pulsed electric field processing apparatus 100 to perform pulsed electric field processing without having to change the first and second thresholds each time depending on the type of object 300 to be processed.

[0037] The first threshold value and the second threshold value may be set based on the amount of charge flowing in a single direction when a preset processing capacity is obtained, or may be set based on the amount of charge flowing in a single direction when an adverse effect is less than a preset magnitude. By setting the first threshold value and the second threshold value based on the processing capacity as a reference, it is possible to perform pulsed electric field treatment on the object to be processed 300 with a processing capacity higher than the processing capacity used as the reference. On the other hand, by setting the first threshold value and the second threshold value based on the adverse effect as a reference, it is possible to perform pulsed electric field treatment on the object to be processed 300 so that the adverse effect is smaller than the magnitude used as the reference. Further, the first threshold value and the second threshold value may be set based on both the processing capacity and the adverse effect. FIG. 7 shows an example in which the first threshold value and the second threshold value are set to the same value, and the value is larger than the reference value A, which is the amount of charge flowing in a single direction when a preset processing capacity is obtained, and smaller than the reference value B, which is the amount of charge flowing in a single direction when an adverse effect of a preset magnitude occurs. By setting the first threshold value and the second threshold value based on both the processing capacity and the adverse effect, it is possible to perform pulsed electric field treatment on the object to be processed 300 with a processing capacity higher than the processing capacity used as the reference and an adverse effect smaller than the magnitude used as the reference.

[0038] For the current of the high-voltage pulse, a value directly measured for the current flowing through the electrode 101 may be used, or a value inferred from any voltage or current inside the pulse generator 102A may be used. In the former case, it is possible to measure the current with high precision, and in the latter case, since a detector can be provided regardless of the shapes of the processing chamber 400 and the electrode 101, it is advantageous for miniaturization.

[0039] The pulsed electric field treatment apparatus 100 according to Embodiment 1 can perform pulsed electric field treatment with high processing capacity while suppressing adverse effects by increasing the number of high-voltage pulses included in the group pulses within a range where the adverse effects do not become too large.

[0040] Embodiment 2. The configuration of the pulsed electric field treatment device 100 according to Embodiment 2 is the same as that of the pulsed electric field treatment device 100 according to Embodiment 1. The pulsed electric field treatment device 100 according to Embodiment 2 differs from the pulsed electric field treatment device 100 according to Embodiment 1 in that only the output cycle of the high-voltage pulse immediately after the polarity is reversed is changed.

[0041] FIG. 8 is a diagram showing an example of the operation of the pulsed electric field treatment device according to Embodiment 2. In the example shown in FIG. 8, the pulsed electric field treatment device 100 makes the output cycle Ts of the high-voltage pulse immediately after the polarity of the high-voltage pulse is reversed longer than the normal output cycle Tp. By making the output cycle Ts of the high-voltage pulse immediately after the polarity of the high-voltage pulse is reversed longer than the normal output cycle Tp, the pulsed electric field treatment device 100 according to Embodiment 2 can prevent the pulsed electric field 500 generated by the high-voltage pulse immediately before the polarity reversal and the pulsed electric field 500 generated by the high-voltage pulse immediately after the polarity reversal from canceling each other out. By doing so, it becomes possible to use the energy of the high-voltage pulse without waste for pulsed electric field treatment, and the energy saving property is improved.

[0042] On the other hand, when the conveyance speed of the object to be treated 300 is high, by making the output cycle of the high-voltage pulse immediately after the polarity of the high-voltage pulse is reversed shorter than the normal output cycle, the number of high-frequency pulses output while the object to be treated 300 passes through the treatment chamber 400 can be increased. In this case, although the energy efficiency decreases because the pulsed electric field 500 generated by the high-voltage pulse immediately before the polarity reversal and the pulsed electric field 500 generated by the high-voltage pulse immediately after the polarity reversal cancel each other out, it is possible to prevent the object to be treated 300 from passing through the treatment chamber 400 without pulsed electric field treatment being performed.

[0043] Embodiment 3. The pulse electric field treatment device 100 according to Embodiment 3 differs from the pulse electric field treatment device 100 according to Embodiment 1 in that the voltage of one of the high voltage pulses immediately before and immediately after the polarity inversion is changed to a voltage different from the voltage of the high voltage pulses other than immediately before and immediately after the polarity inversion. FIG. 9 is a diagram showing an example of the operation of the pulse electric field treatment device according to Embodiment 3. In the example shown in FIG. 9, the voltage of the high voltage pulse immediately after the polarity inversion is made higher than the voltage of the high voltage pulses other than immediately before and immediately after the polarity inversion. Note that the output period Ts of the high voltage pulse immediately after the polarity of the voltage pulse is inverted is the same as the normal output period Tp. In the example shown in FIG. 9, the pulse electric field treatment device 100 increases the voltage of either one of the high voltage pulses immediately before the polarity inversion and the high voltage pulse immediately after the polarity inversion to be higher than the voltage of the high voltage pulses other than immediately before and immediately after the polarity inversion, thereby suppressing a decrease in processing ability due to the pulse electric field 500 being canceled out.

[0044] The control unit 102B increases the voltage of either one of the high voltage pulses immediately before the polarity inversion and the high voltage pulse immediately after the polarity inversion as the conveyance speed of the object to be processed 300 is higher. Further, the control unit 102B increases the voltage of either one of the high voltage pulses immediately before the polarity inversion and the high voltage pulse immediately after the polarity inversion as the number of high voltage pulses included in the group pulses is smaller. Further, the control unit 102B increases the voltage of either one of the high voltage pulses immediately before the polarity inversion and the high voltage pulse immediately after the polarity inversion as the output period of the high voltage pulses included in the group pulses is shorter. By increasing the voltage of either one of the high voltage pulses immediately before the polarity inversion and the high voltage pulse immediately after the polarity inversion based on such conditions, it is possible to prevent the object to be processed 300 from passing through the processing chamber 400 without the pulse electric field treatment being performed.

[0045] Here, the relationship between the inversion period of the polarity of the high-voltage pulse and the conveyance speed of the object to be processed 300 will be described. FIG. 10 is a diagram showing the relationship between the voltage of the group pulse and the pulse electric field treatment effect in the pulse electric field treatment apparatus according to Embodiment 3. FIG. 10 shows the voltage of the group pulse with the voltage of the high-voltage pulse immediately after polarity inversion increased, and the pulse electric field treatment effect by the group pulse with the voltage of the high-voltage pulse immediately after polarity inversion increased. In FIG. 10, the broken-line graph represents the voltage of the high-voltage pulse, the solid-line graph represents the pulse electric field treatment effect, and the black double-headed arrow indicates the period during which the object to be processed 300 stays in the processing chamber 400. FIG. 11 is a diagram showing the relationship between the voltage of the group pulse and the pulse electric field treatment effect in the pulse electric field treatment apparatus according to the comparative example of Embodiment 3. The pulse electric field treatment apparatus according to the comparative example of Embodiment 3 is different from the pulse electric field treatment apparatus 100 according to Embodiment 3 in that the voltage of the high-voltage pulse immediately after polarity inversion is not changed. FIG. 11 shows the voltage waveform of the group pulse in which the voltage of the high-voltage pulse immediately after polarity inversion is not changed, and the pulse electric field treatment effect by the group pulse in which the voltage of the high-voltage pulse immediately after polarity inversion is not changed. In FIG. 11, the broken-line graph represents the voltage of the high-voltage pulse, the solid-line graph represents the pulse electric field treatment effect, and the black double-headed arrow indicates the period during which the object to be processed stays in the processing chamber.

[0046] In the pulse electric field treatment apparatus 100 according to Embodiment 3, as the conveyance speed of the object to be processed 300 increases, the period during which the object to be processed 300 stays in the processing chamber 400 becomes shorter. For this reason, in the pulse electric field treatment apparatus 100 according to Embodiment 3, when the conveyance speed of the object to be processed 300 is slow with respect to the inversion period of the polarity of the high-voltage pulse, the number of high-voltage pulses contributing to the pulse electric field treatment increases while the object to be processed 300 stays in the processing chamber 400. Further, in the pulse electric field treatment apparatus 100 according to Embodiment 3, when the conveyance speed of the object to be processed 300 is fast with respect to the inversion period of the polarity of the high-voltage pulse, the number of high-voltage pulses contributing to the pulse electric field treatment decreases while the object to be processed 300 stays in the processing chamber 400.

[0047] Similarly, in the pulsed electric field treatment apparatus according to the comparative example of Embodiment 3, the longer the conveyance speed of the object to be treated becomes, the shorter the period during which the object to be treated stays in the treatment chamber. For this reason, in the pulsed electric field treatment apparatus according to the comparative example of Embodiment 3, when the conveyance speed of the object to be treated is slow with respect to the inversion period of the polarity of the high voltage pulse, the number of high voltage pulses contributing to the pulsed electric field treatment increases while the object to be treated stays in the treatment chamber. Further, in the pulsed electric field treatment apparatus according to the comparative example of Embodiment 3, when the conveyance speed of the object to be treated is fast with respect to the inversion period of the polarity of the high voltage pulse, the number of high voltage pulses contributing to the pulsed electric field treatment decreases while the object to be treated stays in the treatment chamber.

[0048] In the pulsed electric field processing apparatus according to the comparative example of the third embodiment, when the transport speed of the objects to be processed is slow relative to the polarity reversal cycle of the high-voltage pulse, the period during which the objects to be processed reside in the processing chamber includes periods during which the pulsed electric field processing effect is large and periods during which the pulsed electric field processing effect is small. Therefore, in the pulsed electric field processing apparatus according to the comparative example of the third embodiment, if the length of the period during which the objects to be processed reside in the processing chamber is the same, the pulsed electric field processing effect generated while the objects to be processed pass through the processing chamber is roughly constant, regardless of the timing at which the objects to be processed pass through the processing chamber. Since periods A and B in FIG. 11 have the same length, the pulsed electric field processing effect generated during period A and the pulsed electric field processing effect generated during period B are both moderate. On the other hand, when the transport speed of the objects to be processed is fast relative to the polarity reversal cycle of the high-voltage pulse, the period during which the objects to be processed reside in the processing chamber may be only a period during which the pulsed electric field processing effect is large, only a period during which the pulsed electric field processing effect is small, or a period spanning both periods during which the pulsed electric field processing effect is large and a period during which the pulsed electric field processing effect is small. Therefore, the pulsed electric field treatment effect is high in period C, where the period during which the object to be treated stays in the treatment chamber is only the period during which the pulsed electric field treatment effect is large. The pulsed electric field treatment effect is small in period D, where the period during which the object to be treated stays in the treatment chamber is only the period during which the pulsed electric field treatment effect is small. Furthermore, the pulsed electric field treatment effect is medium in period E, where the period during which the object to be treated stays in the treatment chamber is a period spanning both periods during which the pulsed electric field treatment effect is large and periods during which the pulsed electric field treatment effect is small. Thus, when the transport speed of the object to be treated is fast relative to the polarity reversal cycle of the high-voltage pulse, the pulsed electric field effect differs depending on the timing at which the object to be treated passes through the treatment chamber.

[0049] In contrast, in the pulsed electric field treatment apparatus 100 according to Embodiment 3, since the voltage of the high-voltage pulse is increased immediately after the polarity is reversed, the decrease amount of the pulsed electric field treatment effect before and after the polarity switching is suppressed to be small. For this reason, the period during which the object to be treated stays in the treatment chamber is divided into a period C in which the pulsed electric field treatment effect is large only, a period D in which the pulsed electric field treatment effect is small only, and a period E that straddles the periods of large and small pulsed electric field treatment effects. The difference in the pulsed electric field treatment effect becomes small, and the pulsed electric field treatment effect becomes moderate regardless of the timing at which the object to be treated 300 passes through the treatment chamber 400. Therefore, by increasing the voltage of the high-voltage pulse immediately after the polarity is reversed, even when the conveyance speed of the object to be treated is high with respect to the reversal period of the polarity of the high-voltage pulse, it is possible to prevent the object to be treated 300 from passing through the treatment chamber 400 without the pulsed electric field treatment being performed.

[0050] On the other hand, if the voltage of the high-voltage pulse immediately before or after the polarity reversal is made higher than the voltage of the high-voltage pulse other than immediately before and after the polarity reversal, insulation becomes difficult. Specifically, there is a risk of an unintentional discharge short circuit occurring in the vicinity of the pulse generator 102A or the high-voltage electrode 101A. For this reason, when the conveyance speed of the object to be treated 300 is slow, since there is no risk of the object to be treated 300 passing through the treatment chamber 400 without the pulsed electric field treatment being performed, the voltage of the high-voltage pulse immediately before or after the polarity reversal may be decreased.

[0051] FIG. 12 is a diagram showing the relationship between the voltage of a group of pulses and the pulse electric field treatment effect in the pulse electric field treatment apparatus according to Embodiment 3. FIG. 12 shows the voltage waveform of a group of pulses with the voltage of the high-voltage pulse immediately after polarity inversion lowered, and the pulse electric field treatment effect by the group of pulses with the voltage of the high-voltage pulse immediately after polarity inversion lowered. In FIG. 12, the dashed-line graph represents the voltage of the high-voltage pulse, the solid-line graph represents the pulse electric field treatment effect, and the black double-headed arrows indicate the period during which the object to be treated 300 stays in the treatment chamber 400. When the conveyance speed of the object to be treated 300 is slow with respect to the polarity inversion period, even if the voltage of the high-voltage pulse immediately after polarity inversion is lowered, variations in the pulse electric field treatment effect are unlikely to occur. For this reason, both the pulse electric field treatment effect occurring during period A and the pulse electric field treatment effect occurring during period B in FIG. 12 are moderate. On the other hand, when the polarity is inverted, the risk of overvoltage occurring inside the pulse power supply increases. Therefore, the higher the voltage of the high-voltage pulse immediately after polarity inversion, the higher the possibility that the pulse power supply will be damaged due to a discharge short circuit, and the higher the risk of failure of the pulse electric field treatment apparatus 100. As shown in FIG. 12, by lowering the voltage of the high-voltage pulse immediately after polarity inversion, damage to the pulse power supply associated with polarity inversion can be suppressed, and the risk of failure of the pulse electric field treatment apparatus 100 can be reduced.

[0052] Embodiment 4. FIG. 13 is a diagram showing the configuration of the pulse electric field treatment apparatus according to Embodiment 4. The pulse electric field treatment apparatus 100 according to Embodiment 4 differs from the pulse electric field treatment apparatus 100 according to Embodiment 1 in that it includes a voltage detector 106 that measures the voltage of the high-voltage pulse applied to the high-voltage electrode 101A and an abnormality determination unit 102C that determines whether the high-voltage pulse output is normal or abnormal. The treatment chamber 400 is in the shape of a tank filled with a treatment liquid three-dimensionally, but FIG. 13 schematically shows a cross section along the conveyance direction of the object to be treated 300.

[0053] Here, a configuration in which the voltage detector 106 is installed on the high-voltage electric wire 104 is taken as an example. However, a configuration may be adopted in which the voltage of the high-voltage pulse applied to the high-voltage electrode 101A is estimated based on the voltage inside the pulse generator 102A.

[0054] When the number of high-voltage pulses included in the group pulses is too large, the object to be processed 300 in the processing chamber 400 or the processing liquid through which the object to be processed 300 passes is electrolyzed, and bubbles are generated. When bubbles are generated in the object to be processed 300 in the processing chamber 400 or the processing liquid through which the object to be processed 300 passes, a discharge short circuit occurs between the high-voltage electrode 101A and the low-voltage electrode 101B.

[0055] When the discharge short circuit between the high-voltage electrode 101A and the low-voltage electrode 101B is repeated, the pulse electric field processing apparatus 100 may malfunction. Therefore, in the pulse electric field processing apparatus 100 according to the fourth embodiment, when the abnormality determination unit 102C determines that a discharge short circuit has occurred, the control unit 102B reduces the number of group pulses or the pulse width, and performs control to suppress the electrolysis of the object to be processed 300 in the processing chamber 400 or the processing liquid through which the object to be processed 300 passes.

[0056] FIG. 14 is a diagram showing an example of a voltage waveform when a discharge short circuit occurs in the pulsed electric field treatment apparatus according to Embodiment 4. FIG. 15 is a diagram showing an example of a current waveform when a discharge short circuit occurs in the pulsed electric field treatment apparatus according to Embodiment 4. When a discharge short circuit occurs during the output of a high voltage pulse, the absolute value of the voltage decreases at the timing when the discharge short circuit occurs, and the current value increases instantaneously once and then decreases at the timing when the discharge short circuit occurs. The abnormality determination unit 102C determines a discharge short circuit based on at least one of the voltage value and the current value of the high voltage pulse. For example, the abnormality determination unit 102C determines that a discharge short circuit has occurred when at least one of a phenomenon in which the voltage value of the high voltage pulse falls below a preset third threshold value during the output of the high voltage pulse as shown in FIG. 14 and a phenomenon in which the current value of the high voltage pulse exceeds a preset fourth threshold value during the output of the high voltage pulse as shown in FIG. 15 occurs. The control unit 102B performs control to reduce at least one of the number and the pulse width of the high voltage pulses included in the group pulses based on the determination result of the abnormality determination unit 102C, so as not to continue the pulsed electric field treatment under conditions where a discharge short circuit occurs.

[0057] Furthermore, the abnormality determination unit 102C also determines the abnormal state immediately before the occurrence of the discharge short circuit. When electrolysis occurs, even if a discharge short circuit does not occur, the variation in the current value increases or the average value of the current value decreases due to the presence of bubbles. The abnormality determination unit 102C determines that the high voltage pulse is an abnormality due to a sign of a discharge short circuit when at least one of a phenomenon in which the variation in the current value of the high voltage pulse becomes larger than a preset range and a phenomenon in which the average value of the current value of the high voltage pulse becomes equal to or less than a preset fifth threshold value occurs. The control unit 102B performs control to reduce at least one of the number and the pulse width of the high voltage pulses included in the group pulses based on the determination result of the abnormality determination unit 102C, so as to make it difficult for a discharge short circuit to occur.

[0058] When an abnormality due to the occurrence of a discharge short circuit or an abnormality due to a sign of a discharge short circuit occurs in a high-voltage pulse, the pulse electric field treatment apparatus 100 according to Embodiment 4 reduces at least one of the number and pulse width of the high-voltage pulses included in the group pulses. For this reason, the pulse electric field treatment apparatus 100 according to Embodiment 4 can prevent the occurrence of a discharge short circuit, and even when a discharge short circuit has occurred, the pulse electric field treatment is not continued under the conditions where the discharge short circuit occurs.

[0059] Next, the hardware configuration of the control unit 102B included in the pulse electric field treatment apparatus 100 will be described. FIG. 16 is a diagram showing an example of a hardware configuration for realizing the control unit included in the pulse electric field treatment apparatus according to Embodiments 1 to 4. The control unit 102B is realized as a computer system by a processing circuit including a processor 91 that executes various processes, a memory 92 that is a main memory, and a storage device 93 that stores information.

[0060] The processor 91 may be an arithmetic means such as an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Further, as the memory 92, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory) can be used. A program for executing pulse electric field treatment is stored in the storage device 93. The processor 91 reads out the program stored in the storage device 93 to the memory 92 and executes it. By the processor 91 reading out the program stored in the storage device 93 to the memory 92 and executing it, the functions of the control unit 102B are realized.

[0061] The configurations shown in the above embodiments are examples of the content, and it is possible to combine them with other known technologies, and it is also possible to omit or change a part of the configuration without departing from the gist.

Description of Reference Numerals

[0062] 91 Processor, 92 Memory, 93 Storage Device, 100 Pulse Electric Field Processing Device, 101 Electrode, 101A High-Voltage Electrode, 101B Low-Voltage Electrode, 102 Pulse Power Supply Device, 102A Pulse Generator, 102B Control Unit, 102C Abnormality Determination Unit, 103 Current Detector, 104 High-Voltage Electric Wire, 105 Low-Voltage Electric Wire, 106 Voltage Detector, 200 Conveyor, 300 Object to be Processed, 400 Processing Chamber, 401 Insulating Member, 500 Pulse Electric Field.

Claims

1. A pulse generator that outputs high-voltage pulses of positive and negative polarities, A processing chamber through which an object to be processed passes, An electrode installed in the processing chamber and connected to the pulse generator, A control unit that controls the pulse generator, and The control unit Outputs a group pulse composed of at least one of the high-voltage pulses to the pulse generator alternately in positive and negative polarities, If the amount of charge flowing in a single polarity is greater than a preset first threshold, at least one of control to reduce the number of the high-voltage pulses included in the group pulse and control to reduce the pulse width of the high-voltage pulse is performed. If the amount of charge flowing in a single polarity is less than a preset second threshold that is less than or equal to the first threshold, at least one of control to increase the number of the high-voltage pulses included in the group pulse and control to increase the pulse width of the high-voltage pulse is performed, A pulse electric field processing apparatus, characterized in that the number of the high-voltage pulses included in the group pulse is adjusted so that the amount of charge flowing in a single direction by the group pulse falls within a preset range.

2. The control unit makes the pulse period of the high-voltage pulse immediately after inverting the polarity of the high-voltage pulse longer than the pulse period of the high-voltage pulse that is not immediately after inverting the polarity of the high-voltage pulse, according to the pulse electric field processing apparatus according to claim 1.

3. The control unit makes the voltage of either one of the high-voltage pulse immediately before inverting the polarity of the group pulse and the high-voltage pulse immediately after inverting the polarity of the group pulse different from the voltage of the high-voltage pulse other than immediately before and after inverting the polarity of the group pulse, according to the pulse electric field processing apparatus according to claim 1.

4. The pulse electric field processing apparatus according to claim 1, further comprising an abnormality determination unit that determines whether the high-voltage pulse is abnormal based on at least one of the voltage value and the current value of the high-voltage pulse.

5. When at least one of a phenomenon that the voltage value of the high-voltage pulse falls below a preset third threshold and a phenomenon that the current value of the high-voltage pulse exceeds a preset fourth threshold occurs, the abnormality determination unit determines that the high-voltage pulse is abnormal due to a discharge short circuit, according to the pulse electric field processing apparatus according to claim 4.

6. The abnormal determination unit determines that the high-voltage pulse is abnormal due to a sign of discharge short circuit when at least one of a phenomenon in which the variation in the current value of the high-voltage pulse becomes larger than a preset range and a phenomenon in which the average value of the current value of the high-voltage pulse falls below a preset fifth threshold value occurs. The pulse electric field processing apparatus according to claim 4.

7. The abnormal determination unit reduces at least one of the number of the high-voltage pulses included in the group of pulses and the pulse width of the high-voltage pulse when determining that the high-voltage pulse is abnormal. The pulse electric field processing apparatus according to claim 4.

8. The conveyance path of the object to be processed branches into two or more. The processing chamber is disposed at each of the branched conveyance paths of the object to be processed. The electrodes include a pair of a high-voltage electrode to which a voltage corresponding to the peak of the high-voltage pulse is applied and a low-voltage electrode to which a ground-level voltage is applied. The pulse electric field processing apparatus according to any one of claims 1 to 7, wherein the electrodes are disposed in each of the processing chambers.

9. The electrodes include at least one high-voltage electrode to which a voltage corresponding to the peak of the high-voltage pulse is applied and a low-voltage electrode to which a ground-level voltage different from that of the high-voltage electrode is applied. The high-voltage electrode and the low-voltage electrode are alternately arranged side by side in a direction intersecting the conveyance direction of the object to be processed in the processing chamber. The pulse electric field processing apparatus according to any one of claims 1 to 7.

10. The processing chamber is cylindrical. The electrodes include at least one high-voltage electrode to which a voltage corresponding to the peak of the high-voltage pulse is applied and a low-voltage electrode to which a ground-level voltage different from that of the high-voltage electrode is applied. The high-voltage electrode and the low-voltage electrode are alternately arranged side by side in the conveyance direction of the object to be processed in the processing chamber. The pulse electric field processing apparatus according to any one of claims 1 to 7.

11. The processing chamber is cylindrical. The electrodes include a plurality of high-voltage electrodes to which a voltage corresponding to the peak of the high-voltage pulse is applied and one low-voltage electrode to which a ground-level voltage is applied. The plurality of the high-voltage electrodes are installed around the conveyance path of the object to be processed, and the low-voltage electrode is installed in the conveyance path through which the object to be processed passes. The pulsed electric field processing apparatus according to any one of claims 1 to 7, characterized in that.

Images