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WO1991006371A1 - Commande multiple de l'organe de frappe pour un filtre electrostatique - Google Patents

Commande multiple de l'organe de frappe pour un filtre electrostatique Download PDF

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Publication number
WO1991006371A1
WO1991006371A1 PCT/US1989/004850 US8904850W WO9106371A1 WO 1991006371 A1 WO1991006371 A1 WO 1991006371A1 US 8904850 W US8904850 W US 8904850W WO 9106371 A1 WO9106371 A1 WO 9106371A1
Authority
WO
WIPO (PCT)
Prior art keywords
rapper
memory
computer
appropriate information
sending
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.)
Ceased
Application number
PCT/US1989/004850
Other languages
English (en)
Inventor
David F. Johnston
Michael M. Mahler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BHA Group Inc
Original Assignee
BHA Group Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by BHA Group Inc filed Critical BHA Group Inc
Priority to PCT/US1989/004850 priority Critical patent/WO1991006371A1/fr
Priority to PCT/US1990/003748 priority patent/WO1991006372A1/fr
Priority to CA002072129A priority patent/CA2072129C/fr
Publication of WO1991006371A1 publication Critical patent/WO1991006371A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • B03C3/74—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

  • This invention relates generally to electrostatic precipitators for air pollution control and, more specifically, concerns the control of the rapping process used to clean the internal collection plates and discharge electrodes of electrostatic precipitators.
  • An electrostatic precipitator is an air pollution control device designed to electrically charge and col ⁇ lect particulates generated from industrial processes such as those occurring in cement plants, pulp and paper mills and utilities. Particulate laden gas flows through the precipitator where the particulate is negatively charged. These negatively charged particles are attracted to, and collected by, positively charged metal plates. The cleaned process gas may then be further processed or safely discharged to the atmos ⁇ phere.
  • the cleaning mechanism typically consists of a mechanical rapper that acts as a hammer to dislodge by mechanical vibration any par ⁇ ticulate from the collector plate surfaces and discharge electrodes.
  • An electronic rap ⁇ per controller determines the sequence, intensity, and duration of rapping. Once the particulate is dislodged from the plates, it falls into collection hoppers at the bottom of the precipitator.
  • rapper control has been limited to manually controlling and adjusting the current level to an entire group of rappers, rather than individual rapper control.
  • rappers in different locations within the group may operate more efficiently with different current levels. Since the number of rapper groups, as well as the number of rappers within each group, may vary and prior art rapper control only allows for intensity adjustment of an entire group, a compromise in control standards therefore prevails. The result is often rapper inefficiencies that reduce precipitator and production capacity as well as increase emission levels.
  • the prior art uses fuse or relay technology to detect and isolate fault conditions. This technology is slow in that the devices re- quire up to several full cycles before electrical protection can be assured. Within several full cycles of a fault condition significant damage can occur to rapper circuitry.
  • Some commercial rapper control systems purport to incorporate solid state fault detection, but the trip level is set high because all rappers are required to have the same trip level. The trip level cannot be individually adjusted to a specific single rap ⁇ per within these systems and a compromise in control standards results.
  • Another drawback of the prior art is that rapper control technology is an open looped system. The current level is set at a particular point in time, considering the present rapper conditions in the electrostatic precipitator. But, rapper conditions are not static.
  • the prior art does not provide an easy or economical way to check the present operating conditions of rappers in large precipitators.
  • technicians must per ⁇ sonally walk near each precipitator while watching and listening to determine whether a specific rapper is operating.
  • large precipitators for instance, 250 rappers or more
  • the present invention provides an improved way to control power to a rapper within an electrostatic precipitator. Since manually adjusting current to rappers as a unit is inherently inefficient, an important object of this invention is to provide a means for individually pre-setting electrical operating conditions for each rapper within a multiple rapper precipitator. Another object of this invention is to provide a means for individually setting short and open trip conditions for each rapper within a multiple rapper precipitator. This will eliminate the compromise required in the prior art and increase rapper ef ⁇ ficiency.
  • Still another object of this invention is to provide fault protection which assures detecting and isolating a fault condition within 1/2 cycle from the moment a fault oc ⁇ curs. Reducing fault trip response times from several full cycles to 1/2 cycle will great ⁇ ly increase circuit protection and increase the useful life expectancy of the rappers and precipitator as a whole.
  • Another object of this invention is to provide a closed-loop control means for a rapper. Enabling the rapper current control to sense, measure and adjust the input current in the event the actual current is not substantially similar to the pre-set electri ⁇ cal input current will greatly aid rapper efficiency.
  • Another important object of this invention is to provide present operating con ⁇ ditions for each rapper within a precipitator and to store the rapper operating condi ⁇ tions. This will provide an economical way to check the actual operating conditions of each rapper as well as provide information for troubleshooting and trending.
  • Fig. 1 is a block diagram illustrating a multiple rapper control constructed in accordance with a preferred embodiment of the invention
  • Fig.2 is a block diagram showing the power source and power control means of the multiple rapper control in more detail
  • Fig.3 is a block diagram showing the current detecting means of the multiple rapper control in greater detail.
  • Fig.4 is a block diagram showing the power source and power control means, along with an optional voltage selection relay and the AC DC relay of the multiple rapper control.
  • This invention specifically contemplates the control of a plurality of rappers for an electrostatic precipitator.
  • This description uses two rappers for illustrative pur ⁇ poses and not as as a limitation on the number of rappers to be used in practicing the invention.
  • Control block 10 is connected to a central computer 12, a power source 18 and a plurality of rappers as schematically indicated by Rapper 1 and Rapper 2 blocks. More specifically, central computer 12 is bi-directionally connected to a microcomputer 14 which in turn is connected to both a power control means 16 and a TRIAC switch device 20. Power control means 16 is connected between a power source 18 and TRIAC switch device 20. A current detecting means 22 senses and measures the current between power control means 16 and TRIAC switch device 20. Current detecting means 22 is connected to the output of power control means 16 and is bi-directionally connected to microcomputer 14.
  • Rapper 1 and Rapper 2 are each individually connected to a TRIAC within the TRIAC switch device 20.
  • each rapper is connected to only one TRIAC and, conversely, each TRIAC is connected to only one rapper.
  • the TRIAC may be typically characterized as a silicon bi-directional triode thyristor, such as T6420M of Motorola designated for a 600 volt rating for 40 amps.
  • the power control means 16 and power source 18 are illustrated in Fig. 2.
  • Power control means 16 comprises an SCR firing circuit 28, a full-wave rectifier 30, an SCR 1 and an SCR 2.
  • Power source 18 comprises a transformer 26 and two input terminals 24 to which power is applied. The input terminals 24 are connected to the primary of transformer 26.
  • One side of the secondary of transformer 26 is connected to an inverse parallel SCR 1 and SCR 2 which connects, along with the other side of the secondary of transformer 26, to full-wave rectifier 30.
  • SCR firing circuit 28 is con ⁇ nected serially between microcomputer 14 and the inverse parallel SCR 1 and SCR 2.
  • the current detecting means 22 is best illustrated in Fig.3.
  • One sense resistor 32 is connected serially between power control means 16 and TRIAC switch device 20.
  • the sense resistor 32 is also connected across a conventional input protection cir ⁇ cuit 33 and then to an isolation amplifier 34 connected serially with a precision rec- tifier 36.
  • Precision rectifier 36 is connected with a peak detector 38 which bi-directionally connects to microcomputer 14.
  • Isolation amplifier 34 may typically comprise an AD202JN chip such as manufactured by Analog Devices of Norwood, Massachusetts.
  • Precision rectifier 36 comprises two operational amplifiers and two high speed switching diodes (such as 1N4148 diodes) appropriately biased to rectify the input characteristic to a DC level that is independent of the voltage drop across the diodes.
  • the two operational amplifiers may comprise TL032CP operational amplifiers characterized as an enhanced JFET (junction field effect transistor), low power, low offset, analog operational amplifier such as manufactured by Texas Instru ⁇ ments of Dallas, Texas.
  • the peak detector 38 may typically comprise a PKD01FP chip such as manufactured by Precision Monolithics Inc. of Santa Clara, California and characterized as a monolithic peak detector with reset and hold mode.
  • Microcomputer 14 is connected to both a voltage selection relay 40 and an AC/DC relay 42.
  • Voltage selection relay 40 is connected to a normally open contact 44 and a normally closed contact 46.
  • Normal- ly closed contact 46 is connected to the 240 volt lead of power source 18, and normal ⁇ ly open contact 44 is connected to the 120 volt lead of power source 18.
  • Both contacts 44 and 46 are connected to the inverse parallel SCRl and SCR2.
  • the AC/DC relay 42 is connected to two normally open contacts 48 and 50 and two normally closed con ⁇ tacts 52 and 54.
  • Normally open contact 48 is connected to the inverse parallel SCRl and SCR2 while normally open contact 50 is connected directly to the power source 18. Both normally open contacts 48 and 50 are connected to TRIAC switch device 20. Normally closed contacts 52 and 54 are connected to the positive and negative output of bridge rectifier 30, respectfully. Both normally closed contacts 52 and 54 connect with TRIAC switch device 20. In operation, a look-up table including characteristics for each individual rap ⁇ per is determined, entered and stored in central computer 12.
  • the look-up table parameters comprise the location of each rapper, the rapper type (i.e., AC or DC volt ⁇ age), the voltage level, the pre-set current characteristic of each rapper, open and short trip conditions for each rapper, the maximum duration of energization and the mini ⁇ mum time delay between energization cycles for each rapper.
  • Microcomputer 14 is a slave to central computer 12 in that the microcomputer 14 waits for instruction from the central computer 12 before beginning operation. Upon receiving instruction from central computer 12 to energize Rapper 1, the microcomputer receives the location of Rapper 1, the voltage type and level of Rapper 1, the pre-set current characteristic for Rapper 1, the time duration of energization and the open and short trip conditions for Rapper 1.
  • the pre-set current characteristic is stored in local memory at microcomputer 14 and then transmitted to power control means 16.
  • the duration of energization is converted into a time equivalent number of frequency 1/2 cycles. This number of half cycles is transmitted to power control means 16.
  • the open and short trip conditions are also stored in local memory at the microcomputer 14.
  • the loca ⁇ tion of Rapper 1 is translated at microcomputer 14 into a specific TRIAC switch and information to energize the appropriate TRIAC is transmitted to TRIAC switch device 20.
  • SCR firing circuit 28 of the power control means 16 receives the pre-set Rap ⁇ per 1 current characteristic, and duration of energization in terms of half cycles, from microcomputer 14.
  • the SCR firing circuit 28 translates the pre-set current charac ⁇ teristic for Rapper 1 into a firing angle, Theta, which is sent to SCR 1 and SCR 2.
  • Power is applied to the rapper in terms of SCR firing angle degrees.
  • the sinusoidal electrical cycle contains 360 degrees, and consists of a positive half cycle and a nega ⁇ tive half cycle with respect to polarity. Each SCR can be fired anywhere from 0 degrees to 180 degrees in the electrical cycle, 0 degrees being full power and 180 degrees being 0 power.
  • an SCR When an SCR is fired at 45 degrees, for example, it will conduct from 45 degrees to 180 degrees. Therefore, a difference in firing angles can be represented as a distance along the abscissa of the sine wave. Due to polarity reversal, the SCR stops conducting at 180 degrees.
  • SCR 1 and SCR 2 The normal operating state of SCR 1 and SCR 2 is 180 degrees which allows 0 power from transformer 26 to pass through to the rappers.
  • SCR firing circuit 28 After SCR firing circuit 28 translates the pre-set current characteristic into the appropriate firing angle, it sends this angle to SCR 1 and SCR 2 which begins allowing the appropriate current to pass through to full-wave rectifier 30.
  • SCR firing circuit 28 also counts the number of half cycles that pass through the SCR combination. SCR 1 and SCR 2 remain ener- gized until the number of half cycles counted equals the number of half cycles trans- mitted from microcomputer 14. At this point SCR firing circuit 28 sends SCR 1 and SCR 2 a firing angle of 180 degrees, in effect ceasing power flow.
  • Full-wave rectifier 30 converts the AC signal which passes through SCR 1 and SCR 2 into a pulsating DC signal. As the pulsating DC signal exits full-wave rectifier
  • TRIAC switch device 20 a multi-layered solid-state device, acts as an AC switch. There is one TRIAC per rapper. When a rapper is ener ⁇ gized, its associated TRIAC is energized. Microcomputer 14, having translated the location of Rapper 1 into Rapper l's corresponding switch and transmitted this infor-
  • TRIAC switch device 20 may consists of a number of circuit boards with up to 16 TRIACs per board.
  • Microcomputer 14 can typically accommodate a total of 16 cir ⁇ cuit boards with 16 TRIACs per board. Thus, one microcomputer could characteris-
  • control block 10 including a second microcomputer, current detecting means, power control means and TRIAC switch means
  • the central computer 12 and power source 18 would be connected to any additional control block 10 added
  • the pulsating DC signal exiting power control means 16 is sensed and measured by current detecting means 22.
  • This actual rapper input current is sensed and converted to a voltage by external sense resistors 32.
  • This voltage passes through isolation amplifier 34, the output of which is an AC voltage proportional to the cur ⁇ rent flowing to Rapper 1.
  • the output of isolation amplifier 34 is routed to precision
  • rectifier 36 which rectifies an analog input to a DC level that is proportional to the sensed rapper input current.
  • the DC level is independent of the voltage drop across the diodes within precision rectifier 36.
  • the output of precision rectifier 36 is routed to a peak detector 38.
  • the peak detector 38 upon a command from microcomputer 14 will detect the peak value of the
  • microcomputer 14 While Rapper 1 is being energized, microcomputer 14 instructs peak detector 38 to detect peak current. The microcomputer 14 takes the output of peak detector
  • current detecting means 22 must sense and measure the actual peak current entering Rapper 1; microcomputer 14 must take that information, convert it to a digital word, compare it to the stored short and open trip conditions, determine that a trip condition is met, and transmit information to SCR firing circuit 28 to designate a firing angle of 180 degrees before the SCRs are fired a second time. Preventing the SCRs from firing a second time in the event of a short or open condi ⁇ tion is a significant improvement over the prior art and can be best accomplished by utilizing the speed inherent in microcomputers.
  • the same digital word is compared within microcomputer 14 to the previously stored pre-set input current characteristic for Rapper 1. Based on that comparison, information is transmitted to power control means 16 to perform any adjustments required to have the actual current entering Rapper 1 be substantially similar to the stored input current characteristic for Rapper 1.
  • microcomputer 14 converts the output of peak detector 38 into a digital word, this same information is transmitted to central computer 12 and stored. This information is stored according to its corresponding rapper and is available for present operating conditions and trending purposes.
  • Fig.4 The embodiment of Fig.4 is used to allow the rappers within a precipitator to operate at different voltage levels and with different signal types (AC or DC).
  • the rapper type AC or DC
  • voltage level is included.
  • Microcomputer 14 transmits to voltage selection relay 40 the required voltage level. If 240 volts is needed, the normally closed contact 46 remains closed, and normally open contact 44 remains open, allowing all 240 volts available from power source 18 to pass. If 120 volts is needed, voltage selection relay 40 causes normally closed con ⁇ tact 46 to open and normally open contact 44 to close, which allows only 120 volts to pass from power source 18. Further, microcomputer 14 transmits to AC/DC relay 42 which voltage type the energized rapper requires.

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • Ac-Ac Conversion (AREA)
  • Rectifiers (AREA)
  • Electrostatic Separation (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

Commande multiple de l'organe de frappe pour un filtre électrostatique servant à contrôler et à commander individuellement chaque organe de frappe parmi une pluralité d'organes de frappe, à base des caractéristiques d'organe de frappe stockées sur ordinateur (12) telles que le type de tension, le niveau de tension, le courant électrique d'entrée présélectionné, l'augmentation minimale entre les cycles d'excitation, et la durée maximale de l'excitation. Chaque organe de frappe est connecté à un dispositif de commutation TRIAC (20) associé à un ordinateur (14) et à un moyen régulateur de la puissance (16) afin de régler la puissance d'entrée appliquée à chaque organe de frappe et provenant d'une source de courant (18). Le moyen détecteur de courant (22) est connecté de manière bidirectionnelle à l'ordinateur (14) et connecté au moyen régulateur de la puissance (16) afin de détecter et de mesurer le courant électrique de crête d'entrée appliqué à chaque organe de frappe. Une séquence logique présélectionnée et stockée dans l'ordinateur (12) règle l'alimentation en puissance de chaque organe de frappe.
PCT/US1989/004850 1989-10-30 1989-10-30 Commande multiple de l'organe de frappe pour un filtre electrostatique Ceased WO1991006371A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
PCT/US1989/004850 WO1991006371A1 (fr) 1989-10-30 1989-10-30 Commande multiple de l'organe de frappe pour un filtre electrostatique
PCT/US1990/003748 WO1991006372A1 (fr) 1989-10-30 1990-06-29 Commande multiple pour decrasseurs a marteaux
CA002072129A CA2072129C (fr) 1989-10-30 1990-06-29 Dispositif de commande de plusieurs heurtoirs utilise dans un depoussiereur electrique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1989/004850 WO1991006371A1 (fr) 1989-10-30 1989-10-30 Commande multiple de l'organe de frappe pour un filtre electrostatique

Publications (1)

Publication Number Publication Date
WO1991006371A1 true WO1991006371A1 (fr) 1991-05-16

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PCT/US1989/004850 Ceased WO1991006371A1 (fr) 1989-10-30 1989-10-30 Commande multiple de l'organe de frappe pour un filtre electrostatique
PCT/US1990/003748 Ceased WO1991006372A1 (fr) 1989-10-30 1990-06-29 Commande multiple pour decrasseurs a marteaux

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PCT/US1990/003748 Ceased WO1991006372A1 (fr) 1989-10-30 1990-06-29 Commande multiple pour decrasseurs a marteaux

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WO (2) WO1991006371A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8404020B2 (en) * 2008-09-03 2013-03-26 Babcock & Wilcox Power Generation Group, Inc. Systems and methods for monitoring a rapping process

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4008057A (en) * 1974-11-25 1977-02-15 Envirotech Corporation Electrostatic precipitator electrode cleaning system
US4035165A (en) * 1974-10-02 1977-07-12 Wahlco, Inc. Rapper monitor
US4086646A (en) * 1976-12-30 1978-04-25 Belco Pollution Control Corporation System for the control of rappers in an electrostatic precipitator
US4255775A (en) * 1979-05-29 1981-03-10 Research Cottrell, Inc. Electrostatic precipitator rapper control system with enhanced accuracy
US4290003A (en) * 1979-04-26 1981-09-15 Belco Pollution Control Corporation High voltage control of an electrostatic precipitator system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4111669A (en) * 1975-01-28 1978-09-05 Koppers Company, Inc. Magnetic impulse rapper control system
US4928456A (en) * 1988-06-16 1990-05-29 Nwl Transformers Process for rapping of electrostatic precipitator surfaces

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4035165A (en) * 1974-10-02 1977-07-12 Wahlco, Inc. Rapper monitor
US4008057A (en) * 1974-11-25 1977-02-15 Envirotech Corporation Electrostatic precipitator electrode cleaning system
US4086646A (en) * 1976-12-30 1978-04-25 Belco Pollution Control Corporation System for the control of rappers in an electrostatic precipitator
US4290003A (en) * 1979-04-26 1981-09-15 Belco Pollution Control Corporation High voltage control of an electrostatic precipitator system
US4255775A (en) * 1979-05-29 1981-03-10 Research Cottrell, Inc. Electrostatic precipitator rapper control system with enhanced accuracy

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8404020B2 (en) * 2008-09-03 2013-03-26 Babcock & Wilcox Power Generation Group, Inc. Systems and methods for monitoring a rapping process

Also Published As

Publication number Publication date
CA2072129C (fr) 1995-06-13
CA2072129A1 (fr) 1991-05-01
WO1991006372A1 (fr) 1991-05-16

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