CA1172686A - Method of controlling operation of an electrostatic precipitator - Google Patents
Method of controlling operation of an electrostatic precipitatorInfo
- Publication number
- CA1172686A CA1172686A CA000392279A CA392279A CA1172686A CA 1172686 A CA1172686 A CA 1172686A CA 000392279 A CA000392279 A CA 000392279A CA 392279 A CA392279 A CA 392279A CA 1172686 A CA1172686 A CA 1172686A
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- Prior art keywords
- voltage
- pulses
- increase
- turned
- level
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000012717 electrostatic precipitator Substances 0.000 title claims abstract description 9
- 230000003247 decreasing effect Effects 0.000 claims abstract description 7
- 230000007423 decrease Effects 0.000 claims description 22
- 230000001276 controlling effect Effects 0.000 claims description 19
- 230000001105 regulatory effect Effects 0.000 claims description 15
- 208000028659 discharge Diseases 0.000 description 26
- 239000012716 precipitator Substances 0.000 description 15
- 238000005259 measurement Methods 0.000 description 11
- 239000000428 dust Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 230000006872 improvement Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000008033 biological extinction Effects 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000002301 combined effect Effects 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000003455 independent Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000036647 reaction Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/66—Applications of electricity supply techniques
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/66—Applications of electricity supply techniques
- B03C3/68—Control systems therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S323/00—Electricity: power supply or regulation systems
- Y10S323/903—Precipitators
Abstract
Abstract A method is disclosed for controlling the DC voltage of an electrostatic precipitator of the type having electrodes en-ergized by a preset DC voltage in which the preset DC voltage has pulses superimposed thereon. According to the method, the the pulses are periodically turned off, Thereafter, the corona discharge current caused by the DC voltage is measured and com-pared against a preset value. Thereafter, the DC voltage is adjusted in dependence upon the measured corona discharge cur-rent, namely, it is increased or decreased depending upon whether the discharge current measured is lower or higher than the pre-set value.
Description
'~ '172~85 S6533.0~ METHOD OF CONTROLLING OPERATION
OF AN ELECTROSTATIC PRECIPITATOR
Technical Field The invention relates to a method of controlling the operating parameters of an electros-tatic precipitator which is energized by voltage pulses superimposed on a DC-voltageO
Back~round Art It is a documented fact that the performance of conventional two-electrode precipitators ~an be improved by pulse energization where high voltage pulses of suitable duration and repetition rate are superimposed on an operating DC-voltage.
The improvements obtained by pulse energization as compared with conventional DC energization are caused by the combined effect of the following advantages:
-Higher peak voltage without excessive sparkîng, and tharefore improved particle charging.
~ More effective extinguishing of sparks and better suppression of incipient back corona.
-The corona discharge current can be controlled by pulse repetition frequency and pulse amplitude. This allows the precipitator current to be reduced below the back corona onset level in case of high resistivity dust without reduclng precipitator voltage.
~ 1~268~
-For short duration pulses, the corona discharge takes place well above the corona onset level for constant DC voltage and is suppressed during the remaining part of the pulse by space charges. This results in a more 5 uniformly distributed corona discharge along the discharge electrode.
-Furthermore, corona discharges from short duration pulses are less influenced by variations in gas and dust conditions. This improves the internal current distribution of a separately energized field.
-Stable corona discharge is obtainable from surfaces with larger diameter curvatures. This permits the use of large diameter discharge wires or rigid type discharge electrodes with comparatively short and blunt tips, reducing the risk of discharge electrode failures.
The improvements found in precipitator performance, resulting in increased particle migration velocity, particularly for high resistivity dusts, permit reduction of the collection area for new installations or improvement of the efficiency of existing installations without increase of collection area.
OF AN ELECTROSTATIC PRECIPITATOR
Technical Field The invention relates to a method of controlling the operating parameters of an electros-tatic precipitator which is energized by voltage pulses superimposed on a DC-voltageO
Back~round Art It is a documented fact that the performance of conventional two-electrode precipitators ~an be improved by pulse energization where high voltage pulses of suitable duration and repetition rate are superimposed on an operating DC-voltage.
The improvements obtained by pulse energization as compared with conventional DC energization are caused by the combined effect of the following advantages:
-Higher peak voltage without excessive sparkîng, and tharefore improved particle charging.
~ More effective extinguishing of sparks and better suppression of incipient back corona.
-The corona discharge current can be controlled by pulse repetition frequency and pulse amplitude. This allows the precipitator current to be reduced below the back corona onset level in case of high resistivity dust without reduclng precipitator voltage.
~ 1~268~
-For short duration pulses, the corona discharge takes place well above the corona onset level for constant DC voltage and is suppressed during the remaining part of the pulse by space charges. This results in a more 5 uniformly distributed corona discharge along the discharge electrode.
-Furthermore, corona discharges from short duration pulses are less influenced by variations in gas and dust conditions. This improves the internal current distribution of a separately energized field.
-Stable corona discharge is obtainable from surfaces with larger diameter curvatures. This permits the use of large diameter discharge wires or rigid type discharge electrodes with comparatively short and blunt tips, reducing the risk of discharge electrode failures.
The improvements found in precipitator performance, resulting in increased particle migration velocity, particularly for high resistivity dusts, permit reduction of the collection area for new installations or improvement of the efficiency of existing installations without increase of collection area.
2~
~ For practical application, automatic control of any precipitator energization system is of major importance in order to secure optimum performance under changeable operating conditions and to eliminate the need for supervision of the setting of the electrical parameters.
With conventional DC energization, commonly used control systems regulate precipitator voltage and current, and in general terms, the strategy is aimed at giving _ 3 j_L~2~6 maximum voltage and current within the limits set by spark-over or back corona conditions. The possibilities of different stra-tegies are extremely limited, since the precipitator voltage is the only parameter which can be regulated independently.
In contradistinction, pulse energization allows indepen-dent control of the following parameters:
1. DC Voltage level 2. Pulse voltage level
~ For practical application, automatic control of any precipitator energization system is of major importance in order to secure optimum performance under changeable operating conditions and to eliminate the need for supervision of the setting of the electrical parameters.
With conventional DC energization, commonly used control systems regulate precipitator voltage and current, and in general terms, the strategy is aimed at giving _ 3 j_L~2~6 maximum voltage and current within the limits set by spark-over or back corona conditions. The possibilities of different stra-tegies are extremely limited, since the precipitator voltage is the only parameter which can be regulated independently.
In contradistinction, pulse energization allows indepen-dent control of the following parameters:
1. DC Voltage level 2. Pulse voltage level
3. Pulse repetition fre~uency
4. Pulse width The possibility of combining the setting of several para-meters enables development of highly efficient control strategies, if the phenomena taking place in the precipitator are measured and interpreted correctly.
As it is important for the efficiency of a precipitator that the DC-voltage is maintained as high as possible, a primary objective is to control this voltage to its highest permissible level, which level is determined by the permissible corona dis-charge current at the DC-level between pulses.
The need for a control is due to the fact that the corona discharge current is not only a function of the DC-voltage, but is also influenced by the actual application and variations in the conditions of the gas and of the dust to be precipitated.
I have invented a method of controlling these parameters to obtain an optimum functioning of a pulse energized precipita-tor. It will be apparent, however, that the method might also be used for conventional DC energized precipitators, only omit-ting the steps in the procedure relating to application of pulse voltages.
L ~ ~ 6 C~ ~
Disclosure of the Inventlon The present invention relates to a method of controlling the DC-voltage in an electrostatic precipitator having electrodes energized by pulses superimposed upon a preset DC-voltage, which comprises, periodically eliminating the pulses and thereafter measuring the corona discharge current in the precipitator, com-paring the measured corona discharge current against a predeter-mined value, and adjusting the DC-voltage in dependence upon the measured corona discharge current.
Thus, according to the invention the DC-voltage is con-trolled by turning off the pulses periodically; measuring the corona discharge current caused by the DC-voltage; comparing this measured value with a set value; and increasing or decreas-ing the DC-voltage depending on whether the measured value of the discharge current is lower or higher than the set value respectively.
During the periods with the pulses turned off the DC-voltage may be temporarily increased with a predetermined amount and maintained elevated during the measuring of the corona cur-rent. This temporary increase may star-t a little before the pulses are turned off so that :~ ~7268fi the pulses are not turned oEf until the temporary increase of the DC-voltage is established. In this manner the period in which the precipitator efficiency is reduced due to the turning off of the pulses, may be minimized as this turning off can be postponed until immediately before the measuring of the corona discharge current.
After a measurement at a temporary increased DC-level the corona discharge current caused by the pulses being turned on again towards the end of the measuring period will actually lower the DC-level to its desired level.
The increase or decrease of the original DC-voltage due ~o the controlling can be determined by a closed loop control regulating the DC-voltage to create a predetermined corona current or the original DC-voltage may be increased or decreased by a preselected discrete value.
-Brief Descri~tion of_the Drawin~s Preferred embodiments of the invention will now bedescribed with reference to the accompanying drawings wherein:
Fig. l illustrates schematically pulses superimposed on a DC-voltage for energizing an electrostatic precipitator, Fig. 2 is a voltage/time diagram illustrating schematically the progress of a DC-corona measuring period on a shortened time scale;
$
Fig. 3 is an alternate embodiment illustrating schemati-cally in the form of a voltage/time diagram the progress of a DC-corona measuring period on a shortened time scale;
Fig. 4 is another alternate embodiment illustrating sche-matically in the form of a voltage/time diagram the progress of a DC-corona measuring period on a shortened time scale; and Fig. 5 is still another alternate embodiment illustrating schematically in the form of a voltage/time diagram the progress of a DC-corona measuring period on a shortened time scale.
Best Mode For Carrying Out The Invention Referring to Fig. 1 there is shown schematically voltage pulses of height (i.e., amplitude) Up-superimposed on a DC-vol-; tage UDc for energizing on electrostatic precipitator. The Fig.
shows the voltage on the discharge electrode as a function of time. This voltage will usually be negative, so what is depic-ted here is the numeric (i.e., absolute) value of the voltage.
In the following explanation voltage levels and increases or de-creases accordingly refer to the numerical voltage.
In order to fully benefit from the pulse technique, it is important that the DC-level is maintained as high as possible, ; that is, slightly below the corona extinction voltage, or at a voltage creating a certain corona current depending on actual application.
l L7268~i For applications with high resistivity dust, optimum performance is obtained with the DC-voltage maintained slightly below the corona extinction voltage.
The o~ject is to extinguish completely the corona discharge after each pulse. Combined with suitably long intervals between pulses, this allows the DC field to remove the ion space charge from the interelectrode spacing, beEore the next pulse is applied, and thus permits high pulse peak voltages without sparking. Furthermore, it allows full control of the corona discharge current by means of pulse height and repetition frequency.
In applications with lower resistivity dust, a certain amount of corona discharge at the DC-voltage level 16 is advantageous to secur~ a continuous current flow through the precipitated dust.
In one embodiment, the DC-voltage level is determined by the so-called "finger-methodn~ illustrated in Fig. 2. With a ceFtain time interval (selectable for example between l and lO min), the DC voltage is continually increased to a plateau by a certain amount ~ U (selectable, for example, between 0 and lOkV). The voltage pulses (shown here as spikes) are reduced to maintain the DC plus pulse voltage at a constant level. When the desired DC level is reached, the voltage pulses are switched off and a circuit for measuring corona discharge current is activated. The measurement is performed during an even number of half periods of the power frequency to eliminate the effect of displacement current. The control compares the measured value with a set value (selectable for example between 0 and the rated precipitator current). If the limit value is exceeded, the DC-voltage is reset to a level a certain amount ~ U
6~
(selectable, for example, between 0.2 and lkV) below the DC
value prior to the measurement (i.e., as shown). If the set value is not exceeded, the DC level is reset to a value the same amount above the original setting. After the measurement is completed, the pulse voltage is turned on and maintained at a level corresponding to a fixed maximum value of DC plus pulse voltage. In the intervals between the finger or plateau voltages, the DC-voltage is maintained unchanged, provided that spark-over between pulses does not occur. The values set forth hereinabove in the parentheses are based on experiences from practical embodiments 4 In another embodiment, illustrated in Figq 3, the same procedure is used with the following modifications:
-The pulse voltage is turned off before the DC
voltage is raised.
-After completion of current measurement, the pulse voltage is turned on at a level a certain amount (selectable, for example, between 0.3kV and 6kV) below the value prior to its temporary increase and a special circuit raises the pulse voltage level exponentially to the value prior to the corona discharge current measurement within 5 seconds.
In another embodiment, illustrated in Fig. 4, the increase in DC voltage during measurement is set equal to 0. The pulses are stopped with certain time intervals (selectable for example, between 1 and 10 min), and remain stopped for the time necessary for per~orming a corona discharge current measurement. This measurement is performed during an even number of half-periods of power :~ 1 7 ~
g frequency. In this version, the DC-voltage is determined pre-ferably by a closed loop control of the measured current. (The current set value is selectable between 0 and maximum precipi-tator current).
In still another embodiment as illustrated in Fig. 5, the DC-voltage is continuously increasing very slowly linearly with time (with a slope selectable, for example, from 0 to maximum DC
voltage within a period of 0 to 20 min.). In a first (a) and a second (b) measuring period the corona current measured does not exceed the set value. During a third measuring period (c) the set value for the corona current is exceeded. Hereafter, the DC voltage is reduced a certain amount (selectable, for example, between 0.2 and lkV) and the linear rise is started ayain from the lower value. Alternatively when the set value is exceeded the continuous increase of the DC-voltage may be turned into a continuous decrease with the same very slight slope as the slope of the previous increase as shown at the measuring period (d).
During the next measurement (e) the corona current is still higher than the set value and the decrease of the DC-voltage is continued until a measurement (f) showing a corona current below the set value turns the decrease into an increase.
At start-up, the DC voltage is increased to a certain star-t value (selectable between lO and 50kV~. Hereafter, the DC voltage is increased linearly with time (with highest possi-ble speed) until the set value of permitted current has been exceeded for the first time. Then the DC voltage is decreased linearly with the same slope until the corona current again is below the permitted set value. Then the voltage pulses are activated and one of the control procedures above is used.
If a spark-over occurs at the DC-voltage between pulses, this may be taken as an indication of the DC-level being too high. Therefore, when such a spark-over is detected the DC-voltage is reduced bv a certain amount (selectable for example, between 0 and 6kV) and thereafter increased from this value . 5 controlled by one of the methods described above.
A spark-over between pulses may also be taken as an indi-cation of the DC-level being too close to the limit set by the permissible corona discharge current. Therefore, another reac-tion ls to increase the finger or plateau voltage by a certainamount (selectable between O-lOkV).
Combinations of the described embodiments may be used.
Accordingly, the "finger-method" may be used in any of the des-cribed embodiments, and closed loop control may be used in con-nection with the "finger-method".
As it is important for the efficiency of a precipitator that the DC-voltage is maintained as high as possible, a primary objective is to control this voltage to its highest permissible level, which level is determined by the permissible corona dis-charge current at the DC-level between pulses.
The need for a control is due to the fact that the corona discharge current is not only a function of the DC-voltage, but is also influenced by the actual application and variations in the conditions of the gas and of the dust to be precipitated.
I have invented a method of controlling these parameters to obtain an optimum functioning of a pulse energized precipita-tor. It will be apparent, however, that the method might also be used for conventional DC energized precipitators, only omit-ting the steps in the procedure relating to application of pulse voltages.
L ~ ~ 6 C~ ~
Disclosure of the Inventlon The present invention relates to a method of controlling the DC-voltage in an electrostatic precipitator having electrodes energized by pulses superimposed upon a preset DC-voltage, which comprises, periodically eliminating the pulses and thereafter measuring the corona discharge current in the precipitator, com-paring the measured corona discharge current against a predeter-mined value, and adjusting the DC-voltage in dependence upon the measured corona discharge current.
Thus, according to the invention the DC-voltage is con-trolled by turning off the pulses periodically; measuring the corona discharge current caused by the DC-voltage; comparing this measured value with a set value; and increasing or decreas-ing the DC-voltage depending on whether the measured value of the discharge current is lower or higher than the set value respectively.
During the periods with the pulses turned off the DC-voltage may be temporarily increased with a predetermined amount and maintained elevated during the measuring of the corona cur-rent. This temporary increase may star-t a little before the pulses are turned off so that :~ ~7268fi the pulses are not turned oEf until the temporary increase of the DC-voltage is established. In this manner the period in which the precipitator efficiency is reduced due to the turning off of the pulses, may be minimized as this turning off can be postponed until immediately before the measuring of the corona discharge current.
After a measurement at a temporary increased DC-level the corona discharge current caused by the pulses being turned on again towards the end of the measuring period will actually lower the DC-level to its desired level.
The increase or decrease of the original DC-voltage due ~o the controlling can be determined by a closed loop control regulating the DC-voltage to create a predetermined corona current or the original DC-voltage may be increased or decreased by a preselected discrete value.
-Brief Descri~tion of_the Drawin~s Preferred embodiments of the invention will now bedescribed with reference to the accompanying drawings wherein:
Fig. l illustrates schematically pulses superimposed on a DC-voltage for energizing an electrostatic precipitator, Fig. 2 is a voltage/time diagram illustrating schematically the progress of a DC-corona measuring period on a shortened time scale;
$
Fig. 3 is an alternate embodiment illustrating schemati-cally in the form of a voltage/time diagram the progress of a DC-corona measuring period on a shortened time scale;
Fig. 4 is another alternate embodiment illustrating sche-matically in the form of a voltage/time diagram the progress of a DC-corona measuring period on a shortened time scale; and Fig. 5 is still another alternate embodiment illustrating schematically in the form of a voltage/time diagram the progress of a DC-corona measuring period on a shortened time scale.
Best Mode For Carrying Out The Invention Referring to Fig. 1 there is shown schematically voltage pulses of height (i.e., amplitude) Up-superimposed on a DC-vol-; tage UDc for energizing on electrostatic precipitator. The Fig.
shows the voltage on the discharge electrode as a function of time. This voltage will usually be negative, so what is depic-ted here is the numeric (i.e., absolute) value of the voltage.
In the following explanation voltage levels and increases or de-creases accordingly refer to the numerical voltage.
In order to fully benefit from the pulse technique, it is important that the DC-level is maintained as high as possible, ; that is, slightly below the corona extinction voltage, or at a voltage creating a certain corona current depending on actual application.
l L7268~i For applications with high resistivity dust, optimum performance is obtained with the DC-voltage maintained slightly below the corona extinction voltage.
The o~ject is to extinguish completely the corona discharge after each pulse. Combined with suitably long intervals between pulses, this allows the DC field to remove the ion space charge from the interelectrode spacing, beEore the next pulse is applied, and thus permits high pulse peak voltages without sparking. Furthermore, it allows full control of the corona discharge current by means of pulse height and repetition frequency.
In applications with lower resistivity dust, a certain amount of corona discharge at the DC-voltage level 16 is advantageous to secur~ a continuous current flow through the precipitated dust.
In one embodiment, the DC-voltage level is determined by the so-called "finger-methodn~ illustrated in Fig. 2. With a ceFtain time interval (selectable for example between l and lO min), the DC voltage is continually increased to a plateau by a certain amount ~ U (selectable, for example, between 0 and lOkV). The voltage pulses (shown here as spikes) are reduced to maintain the DC plus pulse voltage at a constant level. When the desired DC level is reached, the voltage pulses are switched off and a circuit for measuring corona discharge current is activated. The measurement is performed during an even number of half periods of the power frequency to eliminate the effect of displacement current. The control compares the measured value with a set value (selectable for example between 0 and the rated precipitator current). If the limit value is exceeded, the DC-voltage is reset to a level a certain amount ~ U
6~
(selectable, for example, between 0.2 and lkV) below the DC
value prior to the measurement (i.e., as shown). If the set value is not exceeded, the DC level is reset to a value the same amount above the original setting. After the measurement is completed, the pulse voltage is turned on and maintained at a level corresponding to a fixed maximum value of DC plus pulse voltage. In the intervals between the finger or plateau voltages, the DC-voltage is maintained unchanged, provided that spark-over between pulses does not occur. The values set forth hereinabove in the parentheses are based on experiences from practical embodiments 4 In another embodiment, illustrated in Figq 3, the same procedure is used with the following modifications:
-The pulse voltage is turned off before the DC
voltage is raised.
-After completion of current measurement, the pulse voltage is turned on at a level a certain amount (selectable, for example, between 0.3kV and 6kV) below the value prior to its temporary increase and a special circuit raises the pulse voltage level exponentially to the value prior to the corona discharge current measurement within 5 seconds.
In another embodiment, illustrated in Fig. 4, the increase in DC voltage during measurement is set equal to 0. The pulses are stopped with certain time intervals (selectable for example, between 1 and 10 min), and remain stopped for the time necessary for per~orming a corona discharge current measurement. This measurement is performed during an even number of half-periods of power :~ 1 7 ~
g frequency. In this version, the DC-voltage is determined pre-ferably by a closed loop control of the measured current. (The current set value is selectable between 0 and maximum precipi-tator current).
In still another embodiment as illustrated in Fig. 5, the DC-voltage is continuously increasing very slowly linearly with time (with a slope selectable, for example, from 0 to maximum DC
voltage within a period of 0 to 20 min.). In a first (a) and a second (b) measuring period the corona current measured does not exceed the set value. During a third measuring period (c) the set value for the corona current is exceeded. Hereafter, the DC voltage is reduced a certain amount (selectable, for example, between 0.2 and lkV) and the linear rise is started ayain from the lower value. Alternatively when the set value is exceeded the continuous increase of the DC-voltage may be turned into a continuous decrease with the same very slight slope as the slope of the previous increase as shown at the measuring period (d).
During the next measurement (e) the corona current is still higher than the set value and the decrease of the DC-voltage is continued until a measurement (f) showing a corona current below the set value turns the decrease into an increase.
At start-up, the DC voltage is increased to a certain star-t value (selectable between lO and 50kV~. Hereafter, the DC voltage is increased linearly with time (with highest possi-ble speed) until the set value of permitted current has been exceeded for the first time. Then the DC voltage is decreased linearly with the same slope until the corona current again is below the permitted set value. Then the voltage pulses are activated and one of the control procedures above is used.
If a spark-over occurs at the DC-voltage between pulses, this may be taken as an indication of the DC-level being too high. Therefore, when such a spark-over is detected the DC-voltage is reduced bv a certain amount (selectable for example, between 0 and 6kV) and thereafter increased from this value . 5 controlled by one of the methods described above.
A spark-over between pulses may also be taken as an indi-cation of the DC-level being too close to the limit set by the permissible corona discharge current. Therefore, another reac-tion ls to increase the finger or plateau voltage by a certainamount (selectable between O-lOkV).
Combinations of the described embodiments may be used.
Accordingly, the "finger-method" may be used in any of the des-cribed embodiments, and closed loop control may be used in con-nection with the "finger-method".
Claims (29)
1. A method of controlling the DC-voltage in an electro-static precipitator having electrodes energized by pulses sup-erimposed upon a preset DC-voltage, which comprises:
periodically eliminating said pulses and thereafter measuring the corona discharge current between said electrodes;
comparing said measured corona discharge current against a predetermined value; and adjusting the DC-voltage in dependence upon said mea-sured corona discharge current.
periodically eliminating said pulses and thereafter measuring the corona discharge current between said electrodes;
comparing said measured corona discharge current against a predetermined value; and adjusting the DC-voltage in dependence upon said mea-sured corona discharge current.
2. A method of controlling the DC-voltage in an electro-static precipitator energized by pulses superimposed on a DC-voltage characterized in that the pulses are turned off periodically and the corona discharge current caused by the DC-voltage is measured and compared with a set value and the DC-voltage is increased or decreased depending on whether the discharge current measured is lower or higher than the set value.
3. The method according to claim 1 wherein the DC-voltage is permanently increased by a slight slope, and the increase is maintained when the discharge current is lower than the set value, and the DC-voltage is decreased by a discrete value if the discharge current measured is higher than the set value.
4. The method according to claim 1 wherein the DC-voltage is permanently increased or decreased with a slight slope, and an increase is maintained or a decrease changed into an increase when the discharge current measured is lower than the set value, and a decrease is maintained or an increase changed into a de-crease when the discharge current measured is higher than the set value.
5. The method according to claim 1, wherein the DC-voltage is temporarily increased by a predetermined amount and main-tained at said elevated level during the measuring of the corona current.
6. The method according to claim 3 wherein the DC-voltage is temporarily increased by a predetermined amount and main-tained at said elevated level during the measuring of the corona current.
7. The method according to claim 4 wherein the DC-voltage is temporarily increased by a predetermined amount and main-tained at said elevated level during the measuring of the corona current.
8. The method according to claim 5, 6 or 7, wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established.
9. The method according to claim 5, 6 or 7 wherein the pulses are turned on again towards the end of the period of temporary increased DC-level.
10. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established and the pulses are turned on again towards the end of the period of temporary increased DC-level.
11. The method according to claim 2 wherein the increase or decrease of the original DC-voltage due to the controlling is determined by a closed loop control regulating the DC-voltage to create a predetermined corona current.
12. The method according to claim 4 wherein the increase or decrease of the original DC-voltage due to the controlling is determined by a closed loop control regulating the DC-voltage to create a predetermined corona current.
13. The method according to claim 5, 6 or 7 wherein the increase or decrease of the original DC-voltage due to the controlling is determined by a closed loop control regulating the DC-voltage to create a predetermined corona current.
14. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established and the increase or decrease of the original DC-voltage due to the controlling is deter-mined by a closed loop control regulating the DC-voltage to create a predetermined corona current.
15. The method according to claim 5, 6 or 7 wherein the pulses are turned on again towards the end of the period of temporary increased DC-level and wherein the increase or de-crease of the original DC-voltage due to the controlling is determined by a closed loop control regulating the DC-voltage to create a predetermined corona current.
16. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established, the pulses are turned on again towards the end of the period of temporary increased DC-level, and the increase or decrease of the original DC-voltage due to the controlling is determined by a closed loop control regulating the DC-voltage to create a predetermined corona current.
17. The method according to claim 2 wherein the increase or decrease of the original DC-value due to the controlling is made by a preselected discrete value.
18. The method according to claim 3 wherein the decrease of the original DC-value due to the controlling is made by a preselected discrete value.
19. The method according to claim 5, 6 or 7 wherein the increase or decrease of the original DC-value due to the con-trolling is made by a preselected discrete value.
20. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established and the increase or de-crease of the original DC-value due to the controlling is made by a preselected discrete value.
21. The method according to claim 5, 6 or 7 wherein the pulses are turned on again towards the end of the period of temporary increased DC-level and the increase or decrease of the original DC-value due to the controlling is made by a preselected discrete value.
22. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established, the pulses are turned on again towards the end of the period of temporary increased DC-level and the increase or decrease of the original DC-value due to the controlling is made by a preselected discrete value.
23. The method according to claim 2 wherein the pulses, when the DC-level increases or decreases, are regulated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
24. The method according to claim 3 wherein the pulses, when the DC-level increases or decreases, are regulated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
25. The method according to claim 4 wherein the pulses, when the DC-level increases or decreases, are regulated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
26. The method according to claim 5, 6 or 7 wherein the pulses, when the DC-level increases or decreases, are regu-lated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
27. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established and the pulses, when the DC-level increases or decreases, are regulated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
28. The method according to claim 5, 6 or 7 wherein the pulses are turned on again towards the end of the period of temporary increased DC-level and the pulses, when the DC-level increases or decreases, are regulated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
29. The method according to claim 5, 6 or 7 wherein the pulses are not turned off until the temporary increase of the DC-voltage has been established, the pulses are turned on again towards the end of the period of temporary increased DC-level and the pulses, when the DC-level increases or de-creases, are regulated to keep the sum of the DC-voltage and the pulse-voltage constant before and after the measuring period.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB80.40463 | 1980-12-17 | ||
| GB8040463 | 1980-12-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1172686A true CA1172686A (en) | 1984-08-14 |
Family
ID=10518049
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000392290A Expired CA1172687A (en) | 1980-12-17 | 1981-12-15 | Method of controlling operation of an electrostatic precipitator |
| CA000392279A Expired CA1172686A (en) | 1980-12-17 | 1981-12-15 | Method of controlling operation of an electrostatic precipitator |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000392290A Expired CA1172687A (en) | 1980-12-17 | 1981-12-15 | Method of controlling operation of an electrostatic precipitator |
Country Status (13)
| Country | Link |
|---|---|
| US (2) | US4445911A (en) |
| EP (2) | EP0054378B2 (en) |
| JP (2) | JPS57127462A (en) |
| AU (2) | AU547654B2 (en) |
| BR (2) | BR8108193A (en) |
| CA (2) | CA1172687A (en) |
| DE (2) | DE3169116D1 (en) |
| DK (2) | DK158377C (en) |
| ES (2) | ES508027A0 (en) |
| IE (2) | IE52163B1 (en) |
| IN (2) | IN155609B (en) |
| NO (2) | NO814276L (en) |
| ZA (2) | ZA818629B (en) |
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-
1981
- 1981-12-02 EP EP81305677A patent/EP0054378B2/en not_active Expired - Lifetime
- 1981-12-02 DE DE8181305677T patent/DE3169116D1/en not_active Expired
- 1981-12-02 EP EP81305678A patent/EP0055525B1/en not_active Expired
- 1981-12-02 DE DE8181305678T patent/DE3165590D1/en not_active Expired
- 1981-12-07 AU AU78334/81A patent/AU547654B2/en not_active Ceased
- 1981-12-07 DK DK539081A patent/DK158377C/en active
- 1981-12-07 DK DK538981A patent/DK165050C/en not_active IP Right Cessation
- 1981-12-08 IE IE2883/81A patent/IE52163B1/en unknown
- 1981-12-08 IE IE2882/81A patent/IE52162B1/en unknown
- 1981-12-11 ZA ZA818629A patent/ZA818629B/en unknown
- 1981-12-11 ZA ZA818630A patent/ZA818630B/en unknown
- 1981-12-15 NO NO814276A patent/NO814276L/en unknown
- 1981-12-15 US US06/331,012 patent/US4445911A/en not_active Expired - Lifetime
- 1981-12-15 CA CA000392290A patent/CA1172687A/en not_active Expired
- 1981-12-15 CA CA000392279A patent/CA1172686A/en not_active Expired
- 1981-12-15 NO NO814274A patent/NO814274L/en unknown
- 1981-12-16 BR BR8108193A patent/BR8108193A/en unknown
- 1981-12-16 BR BR8108195A patent/BR8108195A/en unknown
- 1981-12-16 ES ES508027A patent/ES508027A0/en active Granted
- 1981-12-16 AU AU78567/81A patent/AU550175B2/en not_active Expired - Fee Related
- 1981-12-16 ES ES508028A patent/ES508028A0/en active Granted
- 1981-12-17 JP JP56204487A patent/JPS57127462A/en active Pending
- 1981-12-17 JP JP56204486A patent/JPS57127461A/en active Pending
- 1981-12-17 IN IN1428/CAL/81A patent/IN155609B/en unknown
- 1981-12-17 IN IN1427/CAL/81A patent/IN155698B/en unknown
-
1984
- 1984-04-30 US US06/605,180 patent/US4659342A/en not_active Expired - Lifetime
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| MKEC | Expiry (correction) | ||
| MKEX | Expiry | ||
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Effective date: 20011215 |