US3360902A - Electrode rapping control for an electrostatic precipitator - Google Patents

Electrode rapping control for an electrostatic precipitator Download PDF

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Publication number
US3360902A
US3360902A US449569A US44956965A US3360902A US 3360902 A US3360902 A US 3360902A US 449569 A US449569 A US 449569A US 44956965 A US44956965 A US 44956965A US 3360902 A US3360902 A US 3360902A
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United States
Prior art keywords
precipitator
current
rapping
electrodes
particles
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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 - Lifetime
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US449569A
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English (en)
Inventor
Melvin L Glaeser
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Beazer East Inc
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Koppers Co Inc
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Publication date
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Priority to US449569A priority Critical patent/US3360902A/en
Priority to DE19661457350 priority patent/DE1457350A1/de
Priority to CH561066A priority patent/CH448029A/de
Priority to GB17381/66A priority patent/GB1091398A/en
Application granted granted Critical
Publication of US3360902A publication Critical patent/US3360902A/en
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    • 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
    • B03C3/74—Cleaning the electrodes
    • B03C3/76—Cleaning the electrodes by using a mechanical vibrator, e.g. rapping gear ; by using impact
    • B03C3/763—Electricity supply or control systems therefor

Definitions

  • a high voltage direct current is applied to the discharge electrodes which current then flows to the collector electrodes in the form of a corona discharge.
  • the corona discharges charges the particles of matter entrained in the gas flowing past the electrodes and the charged particles are attracted to and collect on the collector electrodes.
  • the particles are dislodged and collected.
  • the particles are dislodged by vibrating or, as it is called, rapping the electrodes.
  • Rapping of the electrodes causes the particles collected on the collector electrode to fall from the collector electrode into a hopper or the like. A small amount of reentrainment of the particles tends to occur. So long as the voltage applied to the discharge electrodes remains at a high level, any of the particles tending to be re-entrained are recollected on the collector electrodes at a point below the location where they were originally dislodged. This occurs until the particles are finally collected in a hopper or the like.
  • an object of the present invention is to provide a system for stopping the rapping of the electrodes during periods of severe sparking and consequent reduced voltage in the discharge electrodes.
  • Another object of this invention is to provide rapping controls to increase the efiiciency of the precipitator during adverse operating conditions thus permitting the precipitator to be designedto meet the requirements of less operating severity.
  • This invention contemplates the provision of means actuated when the excitation to an electrode drops below a preselected value in response, for example, to increased sparkings to render inelfective the rappers, for example, to de-energize the power supply for the electrode rappers should the excitation remain at a low level beyond a desired length of the time. Should the excitation rise during the delay period, the rappers will not be rendered ineffective. Once rendered ineffective the rappers will not be rendered efiective until the efficiency of the precipitator is increased to its normal condition for the desired time.
  • FIGURE 1 schematically shows an elevation of the general arrangement of the electrode structure of an electrostatic precipitator facing in the direction of gas flow;
  • FIGURE 2 schematically illustrates the excitation and control for the precipitator of FIG. 1;
  • FIGURE 3 illustrates schematically by block diagram an electrical circuit in accordance with the invention for controlling the amount of rapping during periods of severe sparking of the precipitator of FIG. 1;
  • FIGURE 4 illustrates by detailed circuit an embodiment of the invention.
  • an electrostatic precipitator generally designated by the numeral 20.
  • An outer shell 28 directs the flow of gases past discharge electrodes 31 and collector electrodes 35.
  • the discharge electrodes are supported by structural members 37 which are themselves supported by hanger rods 39 extend ing through insulators 41 which electrically isolate the electrodes 31 from the shell 28 and the collector electrodes 35.
  • the electrical precipitator is represented schematically as having a source 40 for supplying alternating current, a transformer 42 for raising the voltage level of the alternating current, a rectifier 43 for changing the alternating current to direct current, a discharge electrode 31 for charging the particles, a collecting electrode 35 for collecting the particles, a current control circuit generally designated as 44 for maintaining a constant current flow to the discharge electrode, and a spark-rate control system generally designated as 45 for regulating the voltage in accordance with a predetermined spark rate.
  • the particles As the gas, bearing suspended particles of matter, passes through shell 28, the particles are charged by electrode 31 and deposited principally on the surface of electrode 35.
  • the material collected on electrode 35 is removed by rapping or vibration at selected intervals.
  • the characteristics of the corona may vary with changes in the gas concentration and composition. These changes may greatly affect the power input to the precipitator.
  • the power input is controlled to obtain maximum efliciency by the current control circuit 44 which is operative to maintain the current flow at a preset value in the absence of sparking, and spark-rate control circuit 45 which is operative to regulate the voltage at sparking.
  • the changes in normal current flow and at spark-over are sensed by the current sensing device 49.
  • the changes of current flow caused by normal variation in corona discharge are reflected in gradual variations in the current flow from the preset value. These gradual variations in current are in contrast to the transient surges of current occurring at sparkover which result in substantially instantaneous increase in current flow usually of greater 'magnitude than the current flow variation during corona discharge.
  • a rapping source 56 is connected to the hanger rod 39 so that vibratory motion is transmitted through the structural member 37 and into the electrode 31.
  • a suitable rapping means is disclosed in the patent to John W. Pennington No. 3,030,753.
  • the collector electrodes 35 are supported by structural members 38 which are an integral part of the shell 28.
  • the collector electrodes 35 are also rapped by a suitable vibrating source 59, similar to the rapping source 56, connected to the electrodes by a rod 60.
  • an automatic power control unit 61 embodies elements 44 and 45 of FIG. 2, and includes a primary voltage circuit 62, a primary current circuit 63, a secondary voltage circuit 64 and a secondary current circuit 65. These circuits have voltage and current levels which are lowered in response to increased sparking between the electrodes. Any one of these voltage or current levels may be used to develop a sensing signal in accordance with this invetnion. This signal then operates a time delay circuit 66 interposed between the signal source and a rapper timer control 67.
  • the rapper timer control 67 as is conventional energizes the rappers 56, 59 in a predetermined sequence for a predetermined time interval. Such controls are usually capable of being adjusted to vary the cycle and the time interval between rapping cycles as well as the time length of the cycles. Because control 67 is conventional, no further description is necessary for an understanding of this invention.
  • the rapping of electrodes has heretofore taken place in a timed sequence and at intermittent time intervals.
  • the disadvantage has been that the time intervals of rapping do not always coincide with the period of efficient operation of the precipitator. Consequently, there is a great tendency for the entrained particles to be carried out of the precipitator with the gas if the operating conditions during rapping are so adverse that sparking is occurring or that the voltage or current levels have been lowered so that the precipitator is not operating at its optimum efficiency.
  • the rapping of the precipitator is carired out during the normal steady state operation of the precipitator as it has heretofore, that is, by a cycle of operation which cycle of operation takes place over predetermined intervals of time; but inasmuch as adverse conditions are apt to occur at any time, provision is made for rendering the rapping system ineffective during the period that the precipitator is operating at a low level of efiiciency. Since the condition of low precipitator efliciency may be transient, this low efficiency of operation must persist of a period of time before the the rapping system is rendered ineffective.
  • the rapping system is maintained ineffective until after the precipitator has operated at its normal efficiency for a predetermined period of time. This reduces or eliminates any tendency toward a hunting effect where the rapping system is rapidly shifting from an ineffective to effective condition over a short interval of time.
  • the overall efliciency of the precipitator is maintained or increased because the particles which would have escaped with the gases during the rapping period at low efficiency in the arrangements heretofore known are retained in the unit.
  • FIG. 3 there is schematically illustrated a monitoring circuit 66 for rendering ineffective the operation of the rappers of the electrodes during the time that severe sparking is occurring within the precipitator.
  • Such adverse condition is reflected in parameters such as the voltage and current levels of the aforementioned circuits 63, 64 and 65 in the power control unit 61.
  • a level of a parameter will have changed from a normal level to a different level.
  • FIG. 4 There is illustrated in FIG. 4 the sensing of a parameter by providing a means responsive to the existence of a low level of current for a predetermined period :of time for rendering the rapping means ineffective to operate. For example, if the parameter is below a preset level for a period exceeding a preset time the power supply to the rapper timing control 67 will be dc-energized.
  • the novel monitoring system is illustrated in FIG. 4 as being responsive to the current level supplied to the electrode.
  • a current sensitive transformer 70 is provided for sensing the current flowing to the precipitator.
  • the signal current induced in circuit 70 is fed into the operating coil 71 of a conventional current sensitive time delay device 75.
  • the delay device 75 may be current sensing relay such as the type COD sold by Westinghouse and described, for example, in US. Patent Nos. 2,697,187 and 2,488,443 and in Westinghouse Bulletin 4l-l00B, published September 1961.
  • the relay has an induction disc unit, which embodies an E-type laminated magnetic structure.
  • a main current coil (either tapped or untapped) is placed on the center leg of the magnetic structure. Flux produced by this coil returns through the two outer legs of the electromagnet.
  • a shading coil on one of the outer legs creates an out of phase flux which reacts with the main coil flux to cause rotation of the disc in the air gap in the electromagnet, which rotation is opposed by a spiral spring on the disc shaft, which also carries the moving contact. Torque created by the electromagnet is balanced by the opposing torque of the spiral spring, and the disc shaft assembly with the moving contact assumes a position corresponding to the current applied to the electromagnet, unless the travel is limited by the setting of the stationary contacts.
  • Disc rotation is damped by a horseshoe shaped permanent magnet.
  • the signal from current transformer 70 is applied to the operating coil of the relay and the adjustable high and low current closing contacts are adjusted to the desired time and current change to maintain the rappers in their normal cyclic and timed operation until the precipitator has operated at a lowered efiiciency for a sutticient length of time to justify the rappers being taken out of operation or rendered ineifective to operation.
  • the contacts of the delay switch are provided with circuits which maintain the rapper system either effective to operate or ineffective to operate.
  • the fixed contacts 84 and 89 are con.- nected in parallel circuits between the excitation lead 80 and the ground lead 78 to energize respective relays 86 and 87.
  • a holding circuit is provided for each relay so that once energized the relay will remain energized even though the fixed contact that originally energized the relay opens.
  • contact 84 is bridged by lead 90, normally open contact 91, lead 92, normally closed contact 93 and lead 94.
  • Contact 89 is bridged by lead 95, normally closed contact 96, lead 97, normally open contact 98 and lead 99.
  • contacts 84 are engaged thus ener gizing relay 86.
  • the normally closed contact 96 is disengaged. This opens the holding circuit for relay 87 and de-energizes relay 87. Thereupon, contact 93 returns to its normally closed position, as illustrated.
  • the energization of relay 86 has closed the normally open contact 91 thereby rendering effective the holding circuit for relay 86 so relay 86 remains energized even though the contact 84 may be opened by subsequent less efficient operation of the precipitator. Due to this holding circuit, the relay 84 remains energized until such time as the induction disc reaches the low terminal at which time contacts 89 are closed and the holding circuit for relay 84 de-energized by the disengagement of contact 93.
  • the relays 86 and 87 control the rappers by way of contacts 110 and 111 relay solenoid 86 operating contact 110 and relay solenoid 87 operating contact 111. These contacts, as illustrated in FIG. 4, are connected in parallel between power lead 113 and connecting lead 115 to the rapper timer circuit 67 which operates rappers 56 and 59.
  • contact 111 is open and when relay solenoid 84 is energized contact 110 is closed.
  • the induction disc of device 75 When the magnitude of the signal current, as sensed by sensor 70, is less than desired, the induction disc of device 75 is caused to rotate until contacts 89 are closed to energize the low current circuit. When the magnitude of the signal current is at or exceeds the desired value, the induction disc will rotate until contact 84- closes to close the high current circuit. Signal current valves between the high and low valves will cause the moving contacts to float between the high and low contacts 84 and 89. Relays 86 and 87 are provided to lock in either the high or low current circuits once the contacts 84 or 89 have been closed so that, for instance, if the high current circuit 5 is locked in and the signal current valve is decreased, the high current circuit will not open until the moving contact has closed the low current circuit.
  • the stationary contacts 84, 89 may be positioned relative to each other, the time required for the moving contacts to move from 10 one to the other may be varied.
  • the high current circuit will remain locked in unless the signal current falls below the low contact setting for a preselected time interval.
  • the low current circuit will remain locked in until the signal current exceeds the high contact setting for a preselected time.
  • the high current circuit is interposed in the power line permitting current to flow to the circuit 67 to operate the rappers in their programmed sequence. Should the signal current as rendered by sensor 7 0 decrease for a preselected time interval in response to operating conditions within the precipitator, then the high current circuit will open contact 110 thus preventing current fiow' to the rapper timer control. This condition will be maintained until the signal current again reaches a satisfactory level.
  • the device 75 is adjusted to be responsive to a sensing signal corresponding to a level of voltage potential in the discharge electrodes below which it is desired that rapping of the electrodes should not occur.
  • relay is further adjusted for the time interval desired before which the rappers are deenergized after the sensing signal has dropped to the preset level.
  • control means for said rapping means for operating said rapping means
  • An electrostatic precipitator comprising:
  • control means interposed between and operably connected to said power supply and said rapping control means,v and responsive to the current supply to the discharge electrodes for interrupting the rapping of the electrodes during a low level of current supply.
  • control means permits a resumption of electrode rapping after a predetermined elapsed time following an increase in said current level.
  • control means is adjustable so as to vary the elapsed time after which rapping is prevented following a reduction in said current level.
  • control means is adjustable so as to vary the elapsed time after which rapping is permitted following an increase in said current level.
  • control means is adjustable so as to vary the current level to which the control means is responsive.
  • control means is a current-sensitive relay having a movable contact which assumes a position corresponding to the current applied and high current and low current closing contacts, independently adjustable in a manner to vary the elapsed time from a closed high contact position to a closed low contact position in response to a reduction in said current level.
  • relay means are operably connected to the control means in a manner to maintain either of the said closing contacts closed until such time that the said movable contact closes the said closing contact not being maintained closed.
  • An electrostatic precipitator comprising:
  • rapper control means for cyclically operating said rapper

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • Electrostatic Separation (AREA)
US449569A 1965-04-20 1965-04-20 Electrode rapping control for an electrostatic precipitator Expired - Lifetime US3360902A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US449569A US3360902A (en) 1965-04-20 1965-04-20 Electrode rapping control for an electrostatic precipitator
DE19661457350 DE1457350A1 (de) 1965-04-20 1966-04-16 Verfahren und Vorrichtung (Elektrofilter) zum Reinigen eines Schwebeteilchen mitfuehrenden Gases
CH561066A CH448029A (de) 1965-04-20 1966-04-18 Verfahren zum Reinigen eines Schwebeteilchen mitführenden Gases und Elektrofilter zur Ausführung des Verfahrens
GB17381/66A GB1091398A (en) 1965-04-20 1966-04-20 Improvements in or relating to method and apparatus for an electrostatic precipitator

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US449569A US3360902A (en) 1965-04-20 1965-04-20 Electrode rapping control for an electrostatic precipitator

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CH (1) CH448029A (de)
DE (1) DE1457350A1 (de)
GB (1) GB1091398A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3469371A (en) * 1967-05-02 1969-09-30 Buell Eng Co Apparatus for controlling the removal of particle accumulations from the electrodes of an electric precipitator
US4255775A (en) * 1979-05-29 1981-03-10 Research Cottrell, Inc. Electrostatic precipitator rapper control system with enhanced accuracy
US5114442A (en) * 1990-12-27 1992-05-19 Neundorfer, Inc. Rapper control system for electrostatic precipitator
US20080196579A1 (en) * 2005-02-10 2008-08-21 Alstom Technology Ltd Method and apparatus for the acceleration of an electromagnetic rapper
US8328902B2 (en) 2007-03-05 2012-12-11 Alstom Technology Ltd Method of estimating the dust load of an ESP, and a method and a device of controlling the rapping of an ESP
US20140251371A1 (en) * 2011-11-29 2014-09-11 Alstom Technology Ltd Method and a device for cleaning an electrostatic precipitator
US20200009580A1 (en) * 2016-12-21 2020-01-09 Koninklijke Philips N.V. Systems and methods for detecting the status of an electrostatic filter

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3326040A1 (de) * 1983-07-20 1985-01-31 Siemens AG, 1000 Berlin und 8000 München Verfahren zum betriebsmaessigen feststellen des vorhandenseins eines klopftaktoptimums fuer die elektrodenklopfung eines elektrofilters

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1339471A (en) * 1917-10-23 1920-05-11 Research Corp Means for removing deposits from electrodes
FR609426A (fr) * 1925-01-16 1926-08-14 Siemens Schuckertwerke Gmbh Procédé pour empêcher la propagation d'explosions dans des installations électriques de précipitation de poussières
US2756839A (en) * 1954-10-26 1956-07-31 Research Corp Electrostatic precipitator
US2854089A (en) * 1955-01-18 1958-09-30 Research Corp Electrostatic precipitator rapping system
US2858900A (en) * 1954-11-08 1958-11-04 Western Precipitation Corp Control circuit for electro-magnetic rappers for precipitators
US2943697A (en) * 1957-07-22 1960-07-05 Joy Mfg Co Automatic field strength control for precipitators
US2961577A (en) * 1959-08-04 1960-11-22 Koppers Co Inc Electrostatic precipitators
US2976951A (en) * 1958-10-17 1961-03-28 Koppers Co Inc Electrostatic precipitator
US2978065A (en) * 1957-07-03 1961-04-04 Svenska Flaektfabriken Ab Regulating electric precipitators
US3030753A (en) * 1958-04-10 1962-04-24 Koppers Co Inc Rapper
US3039252A (en) * 1956-01-12 1962-06-19 Research Corp Electrical precipitator power system

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1339471A (en) * 1917-10-23 1920-05-11 Research Corp Means for removing deposits from electrodes
FR609426A (fr) * 1925-01-16 1926-08-14 Siemens Schuckertwerke Gmbh Procédé pour empêcher la propagation d'explosions dans des installations électriques de précipitation de poussières
US2756839A (en) * 1954-10-26 1956-07-31 Research Corp Electrostatic precipitator
US2858900A (en) * 1954-11-08 1958-11-04 Western Precipitation Corp Control circuit for electro-magnetic rappers for precipitators
US2854089A (en) * 1955-01-18 1958-09-30 Research Corp Electrostatic precipitator rapping system
US3039252A (en) * 1956-01-12 1962-06-19 Research Corp Electrical precipitator power system
US2978065A (en) * 1957-07-03 1961-04-04 Svenska Flaektfabriken Ab Regulating electric precipitators
US2943697A (en) * 1957-07-22 1960-07-05 Joy Mfg Co Automatic field strength control for precipitators
US3030753A (en) * 1958-04-10 1962-04-24 Koppers Co Inc Rapper
US2976951A (en) * 1958-10-17 1961-03-28 Koppers Co Inc Electrostatic precipitator
US2961577A (en) * 1959-08-04 1960-11-22 Koppers Co Inc Electrostatic precipitators

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3469371A (en) * 1967-05-02 1969-09-30 Buell Eng Co Apparatus for controlling the removal of particle accumulations from the electrodes of an electric precipitator
US4255775A (en) * 1979-05-29 1981-03-10 Research Cottrell, Inc. Electrostatic precipitator rapper control system with enhanced accuracy
US5114442A (en) * 1990-12-27 1992-05-19 Neundorfer, Inc. Rapper control system for electrostatic precipitator
US20080196579A1 (en) * 2005-02-10 2008-08-21 Alstom Technology Ltd Method and apparatus for the acceleration of an electromagnetic rapper
US7459010B2 (en) * 2005-02-10 2008-12-02 Alstom Technology Ltd Method and apparatus for the acceleration of an electromagnetic rapper
US8328902B2 (en) 2007-03-05 2012-12-11 Alstom Technology Ltd Method of estimating the dust load of an ESP, and a method and a device of controlling the rapping of an ESP
US20140251371A1 (en) * 2011-11-29 2014-09-11 Alstom Technology Ltd Method and a device for cleaning an electrostatic precipitator
US9630186B2 (en) * 2011-11-29 2017-04-25 General Electric Technology Gmbh Method and a device for cleaning an electrostatic precipitator
US20200009580A1 (en) * 2016-12-21 2020-01-09 Koninklijke Philips N.V. Systems and methods for detecting the status of an electrostatic filter

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Publication number Publication date
CH448029A (de) 1967-12-15
GB1091398A (en) 1967-11-15
DE1457350A1 (de) 1969-04-17

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