Electrostatic precipitator and method for operating the electrostatic precipitator

Abstract

To provide an electric dust collector which is a wet type, and can further enhancing a power saving effect while maintaining dust collection efficiency during an operation by intermittent charge.SOLUTION: An electric dust collector 10 comprises: an electric dust collector main body 1; a power source 2 which has, as a switching element, an insulation gate bipolar transistor (IGBT); an intermittent charge control unit 3; and a dust density meter 4 for measuring dust density of an exhaust gas discharged from the electric dust controller main body 1. The intermittent charge control unit 3 outputs a signal for instructing change of a combination of charge time and non-charge time, to a power source 2 so that the dust density of the exhaust gas measured by the dust density meter 4, is in a prescribed range of density.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrostatic precipitator and a method for operating the electrostatic precipitator. More specifically, the present invention relates to a wet electrostatic precipitator that performs charging by intermittent charging as a means for power saving, and a method for operating the same.

Background Art

[0002] Conventionally, wet electrostatic precipitators have been widely used for the purpose of collecting harmful dust from exhaust gases generated in waste incineration processes such as aluminum refining exhaust gas treatment (see Patent Documents 1 to 3).

[0003] In such a wet electrostatic precipitator, as a general method for increasing the dust collection efficiency of dust containing heavy metals, a method is known in which the voltage between the dust collecting electrode and the discharge electrode, that is, the applied voltage to the discharge electrode, is set to a high voltage of a certain voltage or more (for example, 70 kV or more). And, as a means for saving power in the operation at such a high voltage, when the dust concentration of the exhaust gas to be treated temporarily decreases, an operation method of switching the application to the discharge electrode from continuous charging to intermittent charging is implemented (see Patent Document 4).

[0004] According to the above-described operation method by intermittent charging, in a wet electrostatic precipitator, it is possible to enjoy the power saving effect due to power saving while generally maintaining the dust collection efficiency. However, in the operation method by intermittent charging, when the dust concentration of the exhaust gas to be treated suddenly increases for some reason, there is also a risk that the dust collection efficiency will decrease beyond the allowable range.

[0005] For this reason, conventionally, in the operation of a wet electrostatic precipitator, in order to avoid the above risk, a combination in which the charging time is sufficiently long in consideration of a safety margin has been set for the combination of the charging time and the non-charging time during the operation by intermittent charging. And, on the other hand, it has been demanded to further optimize the combination of the charging time and the non-charging time during the operation by intermittent charging for the operation method of the wet electrostatic precipitator to further improve the power saving effect.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to further improve the power saving effect while maintaining the dust collection efficiency during intermittent charging operation in a wet electrostatic precipitator.

Means for Solving the Problems

[0008] The inventor of the present invention uses a power supply equipped with an insulated gate bipolar transistor (IGBT) as a switching element for the power supply of an electrostatic precipitator that performs intermittent charging (hereinafter also referred to as a "power supply of the IGBT method"). In addition, by feeding back the dust concentration of the exhaust gas to the operation of the power supply and controlling the change of the combination of the charging time and the non-charging time, it has been found that the above problems can be solved, and the present invention has been completed. Specifically, the present invention provides the following. Note that an insulated gate bipolar transistor (IGBT) refers to a power switching element using a MOSFET for the input part and a bipolar transistor for the output part.

[0009] (1) An electrostatic precipitator apparatus comprising: an electrostatic precipitator main body; a power supply having an insulated gate bipolar transistor (IGBT) as a switching element; an intermittent charging control device; and a dust concentration meter for measuring the dust concentration of the exhaust gas discharged from the electrostatic precipitator main body, wherein the intermittent charging control device outputs a signal instructing the power supply to change the combination of the charging time and the non-charging time so that the dust concentration of the exhaust gas measured by the dust concentration meter stays within a predetermined concentration range.

[0010] According to the invention of (1), in an electrostatic precipitator that performs intermittent charging, it is possible to further enhance the power saving effect while maintaining the dust collection efficiency.

[0011] (2) An operation method of the electrostatic precipitator apparatus according to (1), wherein the minimum unit of the change range of the combination of the charging time and the non-charging time is 10 milliseconds or less.

[0012] According to the invention of (2), by controlling the combination of the charging time and the non-charging time in an extremely short time unit, which was impossible with the thyristor power supply widely used in the past, the effect achieved by the invention of (1) can be enjoyed as an even more excellent effect.

[0013] (3) An operation method of an electrostatic precipitator apparatus, wherein the electrostatic precipitator apparatus comprises: an electrostatic precipitator main body; a power supply having an insulated gate bipolar transistor (IGBT) as a switching element; an intermittent charging control device; and a dust concentration meter for measuring the dust concentration of the exhaust gas, and the intermittent charging control device instructs the power supply to change the combination of the charging time and the non-charging time according to the appropriate combination of the charging time and the non-charging time corresponding to the fluctuation of the dust concentration of the exhaust gas measured by the dust concentration meter during the operation of the electrostatic precipitator apparatus.

[0014] According to the invention of (3), in an electrostatic precipitator that performs intermittent charging by appropriately switching the combination of the charging time and the non-charging time without stopping the operation of the device and while continuing the operation, the power saving effect can be further enhanced while maintaining the dust collection efficiency.

[0015] (4) The method for operating an electrostatic precipitator according to (3), wherein the minimum unit of the change range of the combination of the charging time and the non-charging time is 10 milliseconds or less.

[0016] According to the invention of (4), by controlling the combination of the charging time and the non-charging time in an extremely short time unit, which was impossible to achieve with the thyristor power supply that has been widely used in the past, the effect achieved by the invention of (3) can be enjoyed as an even more excellent effect.

Effect of the Invention

[0017] According to the present invention, in a wet electrostatic precipitator, during operation by intermittent charging, the power saving effect can be further improved while maintaining the dust collection efficiency.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0019] <Electrostatic Precipitator> One embodiment of the electric dust collector 10 of the present invention is a wet electric dust collector that collects harmful dust contained as fine particles in various exhaust gases. And, as shown in FIG. 1, this electric dust collector 10 is configured by a "power control system" including an electric dust collector main body 1, an IGBT type power supply 2, an intermittent charging control device 3, and a dust concentration meter 4.

[0020] The above-mentioned "power control system" constituting the electric dust collector 10 controls the operation of the IGBT type power supply 2 that performs intermittent charging during the operation of the electric dust collector 10 by reflecting the information on the dust concentration of the treated exhaust gas measured by the dust concentration meter 4 in the operation of the intermittent charging control device 3.

[0021] [Electric dust collector main body] As shown in FIG. 2, the electric dust collector main body 1 constituting the electric dust collector 10 includes an upper casing 11, a dust collecting electrode 12 that also functions as a side casing, a lower casing 13, and a framework 14. The upper casing 11, the dust collecting electrode 12, and the lower casing 13 are combined in that order from above to form the housing of the electric dust collector main body 1. Also, the housing of the electric dust collector main body 1 is usually installed at a predetermined distance above the ground by the framework 14.

[0022] As shown in FIG. 2, an upper grid 121, a dust collecting electrode 12, a lower grid 122, an electrode rod 123, a discharge line 124, and a weight 125 are provided inside the housing of the electric dust collector main body 1. The upper grid 121, the dust collecting electrode 12, and the lower grid 122 are arranged horizontally and substantially parallel to each other at a predetermined distance from each other in that order from above. Also, inside the housing of the electric dust collector main body 1, a spray nozzle and a cleaning pipe for washing away the dust attached to the dust collecting electrode 12 are provided.

[0023] As a preferable example of the material of the casing of the electric dust collector main body 1, conductive FRP (Fiber Reinforced Plastic) can be mentioned. The exhaust gas treated by the electric dust collector 10 may contain, in addition to harmful dust, so-called corrosive substances such as hydrofluoric acid and sulfurous acid gas. For this reason, in recent years, as a material constituting the gas-contact parts such as the casing and the dust collecting electrode of the electric dust collector, conductive fiber reinforced plastic has been adopted in place of the conventional metal material. By adopting FRP, mainly the corrosion resistance is enhanced, and it is possible to manufacture at a lower cost than high corrosion-resistant metal materials.

[0024] [Power control system] The "power control system" composed of a power supply 2 equipped with an insulated gate bipolar transistor (IGBT) as a switching element, an intermittent charging control device 3, and a dust concentration meter 4 feeds back the dust concentration of the exhaust gas discharged from the electric dust collector main body 1 measured by the dust concentration meter 4 to the intermittent charging control device 3, and controls the combination of the charging time and the non-charging time in the power supply 2 that performs intermittent charging with a preset dust concentration threshold value as the target value.

[0025] In order to execute the above control, the "power control system" measures the above dust concentration in real time by the dust concentration meter 4 during the operation of the electric dust collector 10. Then, the intermittent charging control device 3 appropriately outputs a signal instructing the power supply 2 to change the combination of the charging time and the non-charging time so that the dust concentration of the above exhaust gas stays within a preset predetermined concentration range.

[0026] (Power supply) The power supply 2 constituting the "power control system" is a DC high-voltage power supply equipped with an insulated gate bipolar transistor (IGBT) as a switching element. This power supply 2 includes, as an example, a DC high-voltage generation unit 2A and a DC high-voltage input unit 2B as shown in FIG. 2. A negative DC high voltage is applied from this power supply 2 to the electrode rod 123 constituting the discharge electrode of the electric dust collector main body 1.

[0027] In the DC high-voltage generation unit 2A, a high-voltage DC obtained by performing a series of processes such as boosting and rectifying on the AC voltage supplied from an AC power source (not shown in FIG. 2; the AC power source 25 in FIG. 3) is output.

[0028] FIG. 3 shows an equivalent circuit of the power conversion circuit that constitutes the power supply 2. As shown in the figure, in the power conversion circuit C1, an AC power source 25, an input-side rectifier 24, a switching element 23, a transformer 22, and an output-side rectifier 21 are sequentially connected from the input side to the output side. And in the power conversion circuit C1, the switching element 23 is an insulated gate bipolar transistor (IGBT).

[0029] Also, in the power conversion circuit C1, for example, when the particulate concentration in the gas introduced into the electrostatic precipitator main body 1 becomes below a certain concentration, etc., a charging method switching means (not shown) for switching the charging method for the electrostatic precipitator main body 1 from continuous charging to intermittent charging is also installed.

[0030] And as shown in FIG. 3, in the power conversion circuit C1, further, during operation by intermittent charging, an intermittent charging control device 3 for controlling the operation of the power supply 2 according to the dust concentration of the treated exhaust gas discharged from the electrostatic precipitator main body 1 is installed.

[0031] (Intermittent Charging Control Device) As described above, the intermittent charging control device 3 can be configured by an information processing device having a function of controlling the combination of the charging time and the non-charging time in the power supply 2 which is a "power supply of the IGBT type" according to the dust concentration of the exhaust gas.

[0032] Specifically, the control of the operation of the above power supply according to the combination of the charging time and the non-charging time is performed by using, as an input value, the dust concentration of the exhaust gas measured by the dust concentration meter 4, and when the difference between this input value and a preset reference value exceeds a threshold value, outputting a signal to the power supply 2 to instruct a change in the combination of the charging time and the non-charging time. The intermittent charging control device 3 can also be configured by, for example, making necessary improvements to a general-purpose "control panel for the electric dust collector main body" installed in an existing electric dust collector and adding the above function.

[0033] [Operation of the Electrostatic Precipitator] The basic operation and operation method of the electrostatic precipitator 10 having the above-described configuration will be described. In the electrostatic precipitator 10, the negative DC high voltage generated by the DC high voltage generation unit 2A (FIG. 2) is applied as a DC high voltage to the discharge electrodes (electrode rods 123 and discharge wires 124) via the DC high voltage input unit 2B (FIG. 2). Then, when the value of the DC high voltage increases, a negative corona discharge occurs between the discharge electrode and each side surface of the "chamber" of the dust collecting electrode 12 surrounding the discharge electrode. As a result, negative ions migrate from the discharge electrode in the direction toward each of the side surfaces of the "chamber" of the dust collecting electrode 12, and at the same time, an ionic wind is generated in the same direction.

[0034] In this way, in the electrostatic precipitator 10, the peripheral space of the dust collecting electrode 12 becomes an ion space. Therefore, as shown in FIG. 2, when the exhaust gas G1 to be treated containing fine particles such as mist and dust is supplied to the lower part of the housing of the electrostatic precipitator and flows through the peripheral space of the dust collecting electrode 12, the fine particles are charged by the collision of negative ions. The charged fine particles adhere to the side surface of the dust collecting electrode 12. In this way, the fine particles are removed from the exhaust gas G1 to be treated. The treated exhaust gas G2 from which the fine particles have been removed is discharged from the upper part of the housing of the electrostatic precipitator 10.

[0035] Then, when the dust concentration in the exhaust gas to be treated of the electrostatic precipitator 10 becomes equal to or lower than a certain concentration, the electrostatic precipitator 10 is operated by an operation method of switching the charging method for the electrostatic precipitator main body 1 from continuous charging to intermittent charging.

[0036] (Control of Intermittent Charging) In the electrostatic precipitator 10, when the operation by intermittent charging is performed, a "power supply control system" including a power supply 2 equipped with an insulated gate bipolar transistor (IGBT) as a switching element, an intermittent charging control device 3, and a dust density meter 4 controls the combination of the charging time and the non-charging time in the power supply 2 for intermittent charging so as to be an appropriate combination as appropriate.

[0037] Here, in the thyristor-type power supply that has been widely adopted in the past, due to the characteristics of the thyristor type, the setting of the combination of the charging time and the non-charging time is limited to the setting in multiples of 20 milliseconds, such as 20 milliseconds, 40 milliseconds, and 60 milliseconds for each time. Also, those setting values need to be set in advance before the start of the operation of the electrostatic precipitator, and it was impossible to change the time of the above combination during the operation.

[0038] On the other hand, in the electrostatic precipitator 10 equipped with a "power supply of IGBT type" as the power supply 2, since the switching element of the IGBT type operates at a high frequency, it is easily possible to make the minimum unit of the change range of the combination of the charging time and the non-charging time 10 milliseconds or less, and it is also possible to set the combination of the charging time and the non-charging time in units of 1 millisecond. Also, the change of the set time during the operation can be freely set in an arbitrary time unit of 1 millisecond as well.

[0039] Therefore, according to the combination of the power supply 2 which is a "power supply of IGBT type" and the intermittent charging control device 3 that controls the operation of the power supply 2 according to the dust density of the treated exhaust gas discharged from the electrostatic precipitator main body 1, during the operation of the electrostatic precipitator 10 by intermittent charging, the combination of the charging time and the non-charging time can be changed to a more appropriate combination with extremely high freedom and speed that cannot be achieved by other configurations. In this way, in the electrostatic precipitator 10, by the operation of such a "power supply control system", the maximum energy-saving effect is realized within a predetermined dust density allowable range.

Example

[0040] The following are examples based on test operations to describe the present invention more specifically. However, the present invention is not limited to the following examples in any way.

[0041] (Comparative Example: Thyristor-Type Power Supply) In an electrostatic precipitator apparatus including an electrostatic precipitator main body having the structure shown in FIG. 2 and a thyristor-type power supply, a test operation was performed for 8 hours to confirm the variation in power consumption due to the switching between continuous charging and intermittent charging. In this electrostatic precipitator apparatus, the average dust concentration of the exhaust gas during continuous charging was 10 mg / Nm 3 and the power consumption was 591 kWh.

[0042] Subsequently, an 8-hour test operation with intermittent charging was performed in the above-described electrostatic precipitator apparatus equipped with a thyristor-type power supply. At this time, the combination of the charging time and the non-charging time was set to a fixed combination of a charging time of 100 milliseconds and a non-charging time of 80 milliseconds. In this test operation, the average dust concentration was maintained at 10 mg / Nm 3 (average over 8 hours), and the power consumption could be reduced to 403 kWh (see Table 1).

[0043] (Example: IGBT-Type Power Supply) In an electrostatic precipitator apparatus including an electrostatic precipitator main body having the same configuration as the above comparative example and an IGBT-type power supply, by controlling the combination of the charging time and the non-charging time by feeding back the dust concentration of the exhaust gas in real time, the average dust concentration during operation was maintained at 10 mg / Nm 3 or less. The power consumption at that time could be reduced to 296 kWh (see Table 1).

[0044]

Table 1

[0045] From the test results in Table 1 above, it can be seen that the present invention can further improve the power-saving effect while maintaining the dust collection efficiency during operation by intermittent charging in a wet electrostatic precipitator.

Explanation of Symbols

[0046] 1 Electrostatic Precipitator Main Body 11 Upper Casing 12 Dust Collection Electrode (Side Casing) 13 Lower Casing 14 Framework 121 Upper Grid 122 Lower Grid 123 Electrode Rod 124 Discharge Wire 125 Weight 2 Power Supply 2A DC High Voltage Generation Unit 2B DC High Voltage Input Unit 3 Intermittent Charging Control Device 4 Dust Concentration Meter 10 Electrostatic Precipitation Device 21 Output Side Rectifier 22 Transformer 23 Switching Element (IGBT) 24 Input Side Rectifier 25 AC Power Supply C1 Power Conversion Circuit G1 Exhaust Gas to be Treated G2 Treated Exhaust Gas

Claims

1. An electrostatic precipitator main body, a power supply including an insulated gate bipolar transistor (IGBT) as a switching element, an intermittent charging control device, a dust concentration meter for measuring the dust concentration of the exhaust gas discharged from the electrostatic precipitator main body, charging method switching means for switching the charging method for the electrostatic precipitator main body from continuous charging to intermittent charging when the dust concentration of the exhaust gas measured by the dust concentration meter becomes equal to or lower than a certain concentration, comprising: When the operation by intermittent charging is performed, the intermittent charging control device outputs a signal instructing the power supply to change the combination of the charging time and the non-charging time so that the dust concentration of the exhaust gas measured by the dust concentration meter stays within a predetermined concentration range, wherein the minimum unit of the change width of the combination of the charging time and the non-charging time is 10 milliseconds or less, an electrostatic precipitator.

2. An operation method of an electrostatic precipitator, wherein the electrostatic precipitator comprises an electrostatic precipitator main body, a power supply including an insulated gate bipolar transistor (IGBT) as a switching element, an intermittent charging control device, a dust concentration meter for measuring the dust concentration of the exhaust gas, charging method switching means for switching the charging method for the electrostatic precipitator main body from continuous charging to intermittent charging when the dust concentration of the exhaust gas measured by the dust concentration meter becomes equal to or lower than a certain concentration, comprising: When the operation by intermittent charging is performed, by instructing the power supply by the intermittent charging control device with an appropriate combination of the charging time and the non-charging time according to the variation of the dust concentration of the exhaust gas measured by the dust concentration meter, during the operation of the electrostatic precipitator, the combination of the charging time and the non-charging time is changed, wherein the minimum unit of the change width of the combination of the charging time and the non-charging time is 10 milliseconds or less, an operation method of an electrostatic precipitator.

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