JP3039758B2 - Pulse charged electric precipitator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse charged electrostatic precipitator, and more particularly to a pulse charged electric precipitator provided with a pulse power supply for applying a pulse voltage and a DC base voltage in a superimposed manner.

[0002]

2. Description of the Related Art Conventionally, a pulse charging type electric dust collector (pulse type) having an excellent dust collecting performance for applying a pulse voltage to an electric dust collector comprising a discharge electrode and a dust collecting electrode to collect high-resistance dust. A charged electric dust collector is known. However, in a pulse-charging type electrostatic precipitator, dust collection performance is controlled not only by a pulse voltage and a pulse current, but also by a pulse waveform such as a pulse width and a pulse rising speed, a pulse frequency, and a pulse operation timing. Depends on many factors such as control of base voltage, base current on which pulse is superimposed,
Furthermore, since it changes depending on the properties of the dust to be collected and the processing gas, there is a problem that it is difficult to optimally control the pulse voltage applied to the electrostatic precipitator.

For this reason, conventionally, a method of controlling the pulse voltage and the pulse frequency by detecting the occurrence of a spark in the electrostatic precipitator and the spark frequency (Japanese Patent Publication No. 5-77465), A method of detecting the amount of dust and controlling the pulse frequency so that the amount of dust at the outlet is minimized
No. 4-15161) and the like.

[0004]

However, even if these conventional methods are used, for example, in the method of controlling at a spark frequency, the pulse voltage is increased to a voltage at which a spark is generated for control, so that the dust collection rate at the spark is reduced. In the region where the dust resistance is high, there are problems such as that the pulse voltage at which the spark is generated becomes too large than the voltage at which the maximum dust collection rate is obtained.

Further, in the method of detecting the amount of dust and dust at the outlet, an expensive dust concentration meter must be installed, and when the dust property changes due to fuel and combustion conditions, the weight concentration of dust is the same even if the indicated value of the dust concentration meter is the same. However, there is a problem that proper control cannot be performed. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pulse-charged electric precipitator that applies an optimum pulse to an electric precipitator according to dust properties.

[0006]

According to the present invention, in order to achieve the above object, a pulse charging voltage obtained by superposing a DC base voltage from a DC base power supply and a pulse voltage from a pulse power supply is stored in an electrostatic precipitator. A base current control for controlling a DC output from the DC base power supply to a predetermined constant current in a pulse-charged electric precipitator applied between the discharge electrode and the dust collection electrode provided for collecting dust. Means, a base voltage detecting means for detecting a voltage value of a DC output output from the DC base power supply, and a predetermined target value wherein the voltage value detected by the base voltage detecting means maximizes a dust collection rate. Control means for controlling a pulse output from the pulse power supply.

[0007] A pulse charging voltage obtained by superimposing a DC base voltage from a DC base power supply and a pulse voltage from a pulse power supply is applied between a discharge electrode and a dust collection electrode provided in an electrostatic precipitator. In a pulse-charged electrostatic precipitator for collecting dust, base voltage control means for controlling a DC output from the DC base power supply to a predetermined constant voltage,
Base current detection means for detecting a current value of a DC output output from the DC base power supply, and the DC value detected by the base current detection means is a predetermined target value to maximize the dust collection rate. And control means for controlling a pulse output output from the pulse power supply.

[0008]

According to the present invention, the DC base current of the DC base power supply for DC charging the discharge electrode and the dust collection electrode provided in the electric dust collector is controlled to a predetermined constant value by the base current control means. The base voltage detecting means detects the DC base voltage output from the DC base power supply, and discharges the electrode so that the DC base voltage becomes a predetermined constant value (target value) set to maximize the dust collection rate. And the pulse output of the pulse power supply that pulse-charges the dust collection electrode is controlled.

According to another aspect, a DC base voltage of a DC base power supply for DC charging a discharge electrode and a collection electrode provided in an electric dust collector is controlled to a predetermined constant value by base current control means. At the same time, the DC base current output from the DC base power supply is detected by the base current detection means, and the DC base current is set to a predetermined constant value (target value) set to maximize the dust collection rate. The pulse output of the pulse power supply that pulse-charges the discharge electrode and the dust collection electrode is controlled.

As described above, the DC base current and the DC base voltage output from the DC base power supply are maintained at the predetermined values set to maximize the dust collection rate, and the dust in the dust-containing gas is discharged at the maximum dust collection rate. Will be collected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a pulse-charged electric precipitator according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing one embodiment of a pulse-charged electric precipitator according to the present invention.

As shown in FIG. 1, the pulse-charged electric precipitator mainly comprises an electric precipitator 10, a pulse power source 20 comprising a base voltage generator 12, a pulse generator 14, and a controller 16.
It is composed of First, the dust removal flow of the pulse charged electric precipitator will be described. The dust-containing gas generated from a boiler (not shown) is supplied to the inlet 10E of the electric precipitator 10.
Is supplied to the dust collecting chamber 10A from the air. In the dust collection chamber 10A,
A pulse power supply 20 is connected between a discharge electrode 10B and a dust collection electrode 10C provided inside to apply a pulse voltage,
The dust in the dust-containing gas sent to the dust collection chamber 10A is charged by the discharge from the discharge electrode 10B, and is collected by the dust collection electrode 10C.

The dust collected by the dust collecting electrode 10C is separated from the dust collecting electrode 10C by a hammering operation, and
It is dropped and deposited on 0D. The deposited dust deposited on the hopper 10D is discharged out of the electrostatic precipitator 10 by a discharge device (not shown) according to the amount of deposition or at regular intervals. on the other hand,
The clean gas from which the dust has been removed is discharged from the exhaust port 10F of the electric dust collector 10 and discharged into the atmosphere.

As described above, the dust-containing gas generated from the boiler is removed by the discharge from the discharge electrode 10B to which the pulse voltage is applied, and is discharged from the exhaust port 10F as a clean gas. Next, a method of controlling the pulse power supply 20 that outputs the pulse voltage applied to the discharge electrode 10B as described above will be described.

FIG. 2 shows an example of the waveform of the pulse voltage output from the pulse power supply 20. FIG pulse voltage V _pe represents the voltage waveform outputted from the pulse power supply 20, from the pulse voltage V _pe DC voltage (base voltage) V _B and the pulse generator 14 to be outputted from the base voltage generator 12 The output pulse voltage _VP is obtained by being superimposed. In the figure, T represents a pulse period, and the number of pulses per unit time (pulse frequency) is represented by 1 / T. In the drawing, W represents a pulse width.

The base voltage V _B (or base current I _B ), pulse voltage V _P , pulse frequency 1 / T, and pulse width W shown in FIG. Atsumarichiriritsu) is controlled so as to maximize (base voltage V _B at this time, will be the base current I _B, the pulse voltage V _P, the pulse frequency 1 / T, the value of the pulse width W of the optimum value ). Also, the dust collection rate is affected by the value of the electrical resistance of the dust (dust electrical resistance),
The above optimum value is determined according to the dust electric resistance.

First, a method of determining the optimum values of the base voltage V _B , base current I _B , pulse voltage V _P , pulse frequency 1 / T, and pulse width W will be described with reference to FIGS. FIG. 3 is a graph showing the results of measuring the values of the outlet dust concentration and the base voltage under pulsed charging conditions in which the outlet dust concentration is minimized by performing a dust removal experiment by generating dust-containing gases under various dust conditions from the boiler. is there. The horizontal axis of the figure shows the dust electric resistance (logarithmic representation) as an index of the dust property, the left vertical axis shows the exit dust concentration, and the right vertical axis shows the base voltage. FIG. 4 is a graph showing the results of measurement of the exit dust concentration and the value of the base current under the pulse charging condition in the case where the exit dust concentration is minimized, similarly to FIG. The base current is shown on the right vertical axis.

In FIG. 3 and FIG. 4, the outlet dust concentration with respect to the dust electric resistance is indicated by points plotted within the range indicated by two solid lines in the figures, and the base voltage or base current with respect to the dust electric resistance is shown in the figures. It is indicated by points plotted within the range indicated by the two dotted lines. In addition, the dust concentration at the outlet is a dust containing gas having a constant dust concentration.
It shows the dust concentration detected at the exhaust port 10F when air is supplied from the inlet port 10E of 0, and shows the dust collection rate equivalently.

According to the experimental results shown in FIGS. 3 and 4, the exit dust concentration when the exit dust concentration becomes minimum increases slightly as the value of the dust electric resistance increases as shown in FIG. 3 or FIG. It can be seen that the base voltage and the base current at the time when the outlet dust concentration is minimum show almost constant values irrespective of the value of the dust electric resistance (the base current is the value of the dust electric resistance). Although it tends to decrease slightly as the value increases, it can be regarded as substantially constant in the range of dust electric resistance in which the pulse-charging type electrostatic precipitator is applied).

Therefore, from the experimental results shown in FIGS. 3 and 4, to maximize the dust collection rate, the base voltage V output from the base voltage generator 12 is independent of the value of the electrical resistance of the dust to be collected. _B and the base current I _B to it can be seen that may hold a constant value V _B0, I _B0 (i.e., the optimum value) shown in FIGS. That is, the pulse voltage V is forcibly set to the optimum value I _B0 base voltage I _B for outputting the base voltage generator 12 for any dust resistance, and outputs the base voltage V _B from the pulse generator 14 _P , pulse frequency 1
By controlling / T and the pulse width W to set the optimum value V _B0 , the maximum dust collection rate can be obtained.

[0021] Incidentally, setting the base voltage V _B to the optimum value V _B0 in Kawari to forcibly set to the optimum value I _B0 the base current I _B for outputting the base voltage generator 12 as described above, the base current pulse voltage V _P to output the I _B from the pulse generator 14, the pulse frequency 1 / T, may be set to the optimum value I _B0 by the pulse width W. Next, the pulse voltage V _P of the pulse output from the pulse generator 14,
Base frequency V _B depending on pulse frequency 1 / T and pulse width W
The following shows a method for setting the optimal value.

If any one of the pulse voltage V _P , the pulse frequency 1 / T, and the pulse width W is changed, the base voltage V _B changes accordingly. Therefore, the pulse voltage V _P, the pulse frequency 1 / T, the two values of the elements of the pulse width W is fixed to a predetermined value, by changing one element remains, so that the base voltage V _B is the optimum value To control. Therefore, first, the pulse frequency 1 / T and the pulse width W is fixed to a predetermined value will be described with reference to FIGS. 5 and 6 a method for controlling a base voltage V _B by changing the pulse voltage V _P.

[0023] Figure 5, the outlet dust concentration when the case of fixing the base current I _B to be output from the base voltage generator 12 to an optimum value by changing the pulse voltage V _P at two dust having different electrical resistance and is a graph showing the results of measuring the base voltage V _B. Curve shown by the broken line in the figure shows the outlet dust concentration with respect to the pulse voltage V _P, the straight line indicated by the solid line in the figure shows the base voltage V _B to the pulse voltage V _P. Also, a straight line A and a curve a in the same figure show the measurement results of the smaller dust electric resistance of the two types of dust, and straight lines B and a curve b in the same figure show the measurement results of the larger dust electric resistance.

The minimum points a ₀ , b of the curves a, b
₀ indicates the pulse voltage V _P to the outlet dust concentration is minimized, FIG base voltage V _B0 in this case indicates the optimum value of the base voltage V _B. As shown in the figure, there is a pulse voltage at which the exit dust concentration is minimized, and the base voltage decreases as the pulse voltage increases. This is because weak reverse ionization occurs in the dust layer collected at the dust collection electrode of the electrostatic precipitator, and as the pulse voltage increases, the reverse ionization increases and the base voltage decreases. It is considered that the dust collection rate of the electric precipitator decreased and the dust concentration at the outlet increased.

According to the figure, when the base voltage V _B is larger than the optimum value V _{B0 of the} base voltage, the pulse voltage V
_P increases, the base voltage V _B is the base voltage optimum value V
If _B0 is smaller than, if decreasing the pulse voltage V _P, it can be seen that reaching the optimum value V _B0 of the base voltage. The procedure for controlling the base voltage V _B and based on varying the pulse voltage V _P The results are shown in the flowchart of FIG.

First, the controller 16 controls the base voltage generator 12
(Step S10), and set the base current to the optimum value.
(Step S12). And the pulse generator 14
(Step S14), and discharge electrodes of the electrostatic precipitator 10
Pulse voltage V to 10B_PIs applied. The controller 16
Base voltage output from base voltage generator 12 at the time
V_BIs detected (step S16), and this voltage and the target value
(Optimum value of base voltage V _B0) (Step S)
18).

In step S18, if the detected base voltage V _B is smaller than the target value, the pulse voltage V
_P is decreased (step S20). Conversely, if the detected base voltage V _B is higher than the target value, the pulse voltage V _P
Is raised (step S22). And the base voltage V
_B is at a becomes equal to the target value, to stop the drop or rise of the pulse voltage V _P, to hold the pulse voltage V _P at that time (step S24).

By the above feedback control, the base voltage V _B is maintained at the optimum value V _B0 , and the maximum dust collection rate can be always obtained. Then the pulse voltage V _P and the pulse frequency 1 / T is fixed to a predetermined value will be described with reference to FIGS. 7 and 8 a method for controlling a base voltage V _B by changing the pulse width W. 7, the outlet dust concentration at the time of changing the pulse width W at three dust having different electrical resistivity in case of fixing the base current I _B to be output from the base voltage generator 12 to the optimum value and the base voltage V _B 5 is a graph showing the results of measuring the. The curve shown by the broken line in FIG. 4 shows the exit dust concentration with respect to the pulse width W, and the curve shown by the solid line in FIG. 4 shows the base voltage V _B with respect to the pulse width W. The curves A to C and a to c show the measurement results when the dust electric resistance increases in order.

According to the figure, when the base voltage V _B is larger than the optimum value V _{B0 of the} base voltage, the pulse width W is increased, and when the base voltage V _B is smaller than the optimum value V _{B0 of the} base voltage, It can be seen that when the pulse width W is reduced, the base voltage reaches the optimum value V _B0 . The procedure for controlling the base voltage V _B and based on varying the pulse width W of the results shown in the flowchart of FIG.

First, the controller 16 controls the base voltage generator 12
(Step S30), and set the base current to the optimum value.
(Step S32). And the pulse generator 14
(Step S34), and discharge electrodes of the electrostatic precipitator 10
Pulse voltage V to 10B_PIs applied. The controller 16
Base voltage output from base voltage generator 12 at the time
V_BIs detected (step S36), and this voltage and the target value
(Optimum value of base voltage V _B0) (Step S)
38).

In step S38, the detected vector
Source voltage V_BIs smaller than the target value, the pulse width W
It is decreased (step S40).
Pressure V _BIs larger than the target value, increase the pulse width W.
(Step S42). And the base voltage V_BIs the goal
When it becomes equal to the value, the pulse width W decreases or increases.
Is stopped, and the pulse width W at that time is held (step
S44).

By the above feedback control, the base voltage V _B is maintained at the optimum value V _B0 , and the maximum dust collection efficiency can always be obtained. The pulse charging control based on the pulse width shown in FIG. 8 and the pulse charging control based on the pulse voltage shown in FIG. 6 may be controlled in combination. For example, when it reaches the upper limit value the pulse voltage V _P is restricted by the device before the base voltage V _B in the flow of FIG. 6 reaches the target value enlarges the pulse width W. The pulse width W when the base voltage V _B is equal to or less than the lower limit set value
, The pulse voltage _VP is reduced.

Next, the pulse voltage _VP and the pulse width W are fixed to predetermined values, and the pulse frequency 1 / T is changed to change the base voltage VP.
A method for controlling _B will be described with reference to FIGS.
9, the outlet dust concentration and the base voltage V _B when in electric resistance different dust varying the pulse frequency 1 / T in the case of fixing the base current I _B to be output from the base voltage generator 12 to an optimum value It is the graph which showed the measurement result. Curve shown by the broken line in the figure shows the outlet dust concentration to the pulse frequency 1 / T, the curve indicated by the solid line in the figure shows the base voltage V _B to the pulse frequency 1 / T. The curves A to C and a to c show the measurement results when the dust electric resistance increases in order.

According to the figure, when the base voltage V _B is larger than the optimum value V _{B0 of the} base voltage, the pulse frequency 1 / T is increased, and when the base voltage V _B is smaller than the optimum value V _{B0 of the} base voltage. Reduces the pulse frequency 1 / T,
It can be seen that the optimum value of the base voltage V _B0 is reached. Based on the result, the pulse frequency 1 / T is changed to change the base voltage V
_The procedure for controlling _B is shown in the flowchart of FIG.

First, the controller 16 controls the base voltage generator 12
(Step S50), and set the base current to the optimum value.
(Step S52). And the pulse generator 14
(Step S54), and discharge electrodes of the electrostatic precipitator 10
Pulse voltage V to 10B_PIs applied. The controller 16
Base voltage output from base voltage generator 12 at the time
V_BIs detected (step S56), and this voltage and the target value
(Optimum value of base voltage V _B0) (Step S)
58).

[0036] In this step S58, the when the detected base voltage V _B is lower than the target value pulse frequency 1
/ T reduces (step S60), conversely, the pulse frequency 1 if the detected base voltage V _B is larger than the target value
/ T is increased (step S62). When the base voltage V _B becomes equal to the target value, the pulse frequency 1
/ T stops decreasing or increasing, and the pulse frequency at that time is 1
/ T is held (step S64).

By the above feedback control, the base voltage V _B is maintained at the optimum value V _B0 , and the maximum dust collection efficiency can always be obtained. The pulse frequency control based on the pulse width shown in FIG. 10 and the pulse charging control based on the pulse voltage shown in FIG. 6 may be controlled in combination.
For example, when it reaches the upper limit set value pulse voltage V _P is restricted by the device before the base voltage V _B in the flow of FIG. 6 reaches the target value, increase the pulse frequency 1 / T.
Further, when the base voltage V _B is equal to or less than the lower limit set value decreases the pulse voltage V _P after reducing the pulse frequency 1 / T.

The pulse voltage, pulse width and pulse frequency may be simultaneously controlled according to the base voltage by combining all the controls shown in FIGS.

[0039]

As described above, according to the pulse-charged electric precipitator according to the present invention, the base voltage is detected to control the pulse voltage, pulse width or pulse frequency of the pulse power supply, and a combination thereof. This makes it possible to control the dust collection rate to be the maximum even if the properties of the dust handled by the apparatus fluctuate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a pulse-charged electric precipitator according to the present invention.

FIG. 2 is an explanatory diagram showing a voltage waveform output from a pulse power supply in FIG. 1;

FIG. 3 is a graph showing a relationship among a dust electrical resistance, an outlet dust concentration, and a base voltage.

FIG. 4 is a graph showing the relationship among the electrical resistance of dust, the dust concentration at the outlet, and the base current.

FIG. 5 is a graph showing a relationship between a pulse voltage, an outlet dust concentration, and a base voltage.

FIG. 6 is a flowchart showing a procedure of pulse power supply control when a pulse voltage is variable.

FIG. 7 is a graph showing a relationship between a pulse width, an outlet dust concentration, and a base voltage.

FIG. 8 is a flowchart showing a procedure of pulse power supply control when the pulse width is variable.

FIG. 9 is a graph showing a relationship among a pulse frequency, an outlet dust concentration, and a base voltage.

FIG. 10 is a flowchart illustrating a procedure of pulse power supply control when the pulse frequency is variable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Electric dust collector 10A ... Dust collection chamber 10B ... Discharge electrode 10C ... Dust collection electrode 10D ... Hopper part 12 ... Base voltage generator 14 ... Pulse generator 16 ... Controller 20 ... Pulse power supply

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-127461 (JP, A) JP-A-5-3177751 (JP, A) JP-A-6-328004 (JP, A) JP-A 64-64 15161 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B03C 3/00-3/88

Claims (3)

(57) [Claims] 1. A pulse charging voltage obtained by superimposing a DC base voltage from a DC base power supply and a pulse voltage from a pulse power supply is applied between a discharge electrode and a dust collection electrode provided in an electrostatic precipitator. A pulse-charged electrostatic precipitator for collecting dust, base current control means for controlling a DC output output from the DC base power supply to a predetermined constant current, and a voltage of a DC output output from the DC base power supply. A base voltage detecting means for detecting a value, and controlling a pulse output output from the pulse power supply so that the voltage value detected by the base voltage detecting means becomes a predetermined target value for maximizing a dust collection rate. A pulse-charged electrostatic precipitator, comprising: control means; 2. A pulse charging voltage obtained by superimposing a DC base voltage from a DC base power supply and a pulse voltage from a pulse power supply is applied between a discharge electrode and a dust collection electrode provided in an electrostatic precipitator. A pulse-charged electrostatic precipitator for collecting dust, base voltage control means for controlling a DC output from the DC base power supply to a predetermined constant voltage, and a DC output current output from the DC base power supply. Base current detecting means for detecting a value, and controlling a pulse output from the pulse power supply so that the DC value detected by the base current detecting means becomes a predetermined target value for maximizing a dust collection rate. A pulse-charged electrostatic precipitator, comprising: control means; 3. The pulse-charged electric device according to claim 1, wherein said control means controls at least one of a pulse amplitude, a pulse width, and a pulse frequency of a pulse output output from said pulse power supply. Dust collector.