US2623608A

US2623608A - System for energizing electrical precipitators

Info

Publication number: US2623608A
Application number: US169019A
Authority: US
Inventors: Herbert J Hall
Original assignee: Research Corp
Current assignee: Research Corp
Priority date: 1950-06-19
Filing date: 1950-06-19
Publication date: 1952-12-30
Anticipated expiration: 1969-12-30
Also published as: GB706929A

Description

Dec. 30, 1952 H. J. HALL 2,623,608

SYSTEM FOR ENERGIZING ELECTRICAL PRECIPITATORS Filed June 19, 1950 INVENTOR HERBERT J. HALL SEQUENC ATTORNEYS Patented Dec. 30, 1952- SYSTEM FOR ENERGIZIN G ELECTRICAL PRECIPITATORS Herbert J. Hall, Princeton, N. J'., assignor to Research Corporation, New York, N. Y., a corporation of New York Application June 19, 1950, Serial No. 169,019

- 6 Claims. 1

This invention relates to a system for energizing electrical precipitators and the like, and more particularly to a system in which the voltage applied to the electrodes of the precipitator is automatically regulated to provide a predetermined rate of sparking between the electrodes.

In the operation of electrical precipitators, contrary to previously accepted ideas, it has been found that optimum performance is attained when the voltage between the electrodes of the precipitator is maintained at a value substantially higher than that at which sparks start to jump between the electrodes. The sparks referred to are not the disruptive power arcs that sometimes occur between the electrodes, but are sparks of relatively low power that occur more orless frequently, depending upon operating conditions, and that do not put sudden serious overloads on the energization system. In an electrical precipitator, there is an optimum rate or sparking above and below which collection efliciency declines. Although the optimum sparking rate will vary for difierent precipitators, it typically is of the order of fifty to one hundred sparks per minute per precipitator section.

An object of the invention is to provide a system for energizing the electrodes of electrical precipitators that automatically sets and holds the voltage at a value corresponding to substantially optimum sparking rate.

Another object is to provide a relatively simple control system for automatically regulating voltage.

Another object is to provide in such a control system a device that counts each inter-electrode spark to form the basis for control.

The foregoing and other objects, as will more fully appear hereinafter, are typically achieved in a system for energizing the electrodes of an electrical precipitator including a voltage regulator, a device responsive to disturbances in the system caused by an inter-electrode spark, means for integrating the responses of the device, means responsive to the deviation of the integrand of the integrating means from a preselected value, and circuit elements operatively connected to the deviation responsive means for controlling the voltage regulator in accordance with the deviation determined by the deviation responsive means. The sense of control imposed by the deviation responsive means on the voltage regulator is determined by the sense of the deviation.

. The voltage control changes may be made in fixed steps at predetermined time intervals, or they may be in steps of variable degree applied 2 at variable time intervals depending upon the rate of deviation of the sparking rate from a preselected value.

In the drawing the figure is a diagrammatic view of a system in accordance with the invention for energizing an electrical precipitator including a control system.

Referring to the figure, the electrical precipitator indicated includes an extended surface collecting electrode l0, which may be in the form of a vertically disposed, grounded, metallic tube, and a line wire discharge electrode H depending axially into the tube. These components are conventional and illustrative only. When the discharge electrode II is supplied with high tension current of the order of 60,000 volts, corona discharge occurs. Gas bearing suspended particles or material is passed through the tube It) wherein the suspended particles are charged and deposited principally on the inner surface of the tube H) from which the collected material is removed from time to time. In this well known manner, the gas is relieved of its suspended material.

Current for energizing the electrodes of the precipitator may be supplied by a source of alternating current I! to the input terminals 13 of a switch II. The output terminals l5 oi the switch are connected to the end terminals II and H of an adjustable auto-transformer l 8 having a control arm l9, adjustment or which varies the output voltage appearing across the terminals i1 and 20 or the auto-transformer.

A power transformer 2| has its primary winding 22 connected to the output terminals or the auto-transformer, through a surge-damping resistor 23. The secondary winding 24 01' the power transformer supplies high voltage alternating current to a, rectifier 25 that may be or any usual type such as a mechanical rotary switch rectifier or an electron tube rectifier.

One rectifier output terminal 20, preferably the negative terminal, is connected through a cable 2'! to the discharge electrode II or the precipitator. The other output terminal 28 is grounded and thus is indirectly connected to the extended surface electrode I0 01 the precipitator.

The energizing system, as thus far described, is merely illustrative, and other similar energizing apparatus having means for adjusting the voltage applied to the precipitator electrodes may be employed instead. In a characteristic embodiment, the current source I! supplies C. P. S. current at 440 volts which is stepped up by the power transformer 2| to about 60,000 volts.

- 3 I through 31 is connected across of condenser 11 and resistor 18. The glow tube is gas filled and has a cold cathode 34, an auxiliary electrode 35 and an anode 35. A condenser ode and anode of the latter.

vA source of direct current 38, which may take In the sys-v 4 f The control system of .the invention also has a device responsive to the deviation from a preselected value of the integrand of the integrating means or motor referred to herelnbefore, This device includes a switch designated by the gen eral reference. numeral 48. The switch has a I conductive arm 49 pivoted at 50, the free end of tion in which the glow tube to the oaththe form of the battery shown, is used to charge the condenser 31. The battery is connected to the terminals of the condenser through the coil of a solenoid 39 and through a switch 40,- the positive terminal of the battery being connected to that side of the condenser that is connected to the glow tube anode. When the switch is closed,

a charge of fixed value isapplied to the condenser, I

This charge is also applied across the glow tube,

which is balanced to a point just below break-.

electrode 35 and cooperat-- ing resistor 4| and by the control grid and cooperating balance resistors 42 and43. A slight increase in positive charge of thegrid 30, such as down by the auxiliary ance picked up hereinbefore described, discharges the condenser glow tube thereafter quickly becomes nonconducting and the condenser 31 is recharged by the battery through the coil of the solenoid '39.

The armature of the solenoid carriesa pawl 44 that is drawn to the left, as seen in the figure,

through the capacitive coupling fires the golw tube 3| and I by the magnetic field generated by the solenoidcoil during the time of flow of the condenser recharging current therethrough. This advances the ratchet wheel 41 one notch in a counter-clockwise direction.

The pawl 44 has a collar 45 engaging a leaf 31 very rapidly. The

is occasioned by an inter-electrode spark disturb-1 the arm being arranged t0 sweep across the COmplementary switch segments 5|, 52 and 53 between the terminal stop members or abu-tmen-ts 54 and 55. A spring 55 biases the switch arm in a clockwise direction towards the starting posithe arm abuts the stop member 54.

The switch arm is drivingly connected, as indicated at 51, to the ratchet wheel 4];- this drivmay include conventional speed- I reducinggearing (not shown). The arm is also ing connection electrically connected to one side 58a of a source of current 58 through a wire 59, a sequence timer 60, a wire 5|, a switch 52 and a wire 63.

--Stop member 55 is carried bythe swinging end of a lever arm, pivoted at 19, which operates switch 80 through a linkage 89. Switch 80, that is held in a normally-closed position by spring 79a, ,is connected in series wi-ththe sequence timer 65 to solenoid device 12.

The opposite terminal 58b of the current source 58 is connected to the common terminal 54 of a reversing motor designated by the general reference numeral55. This motor drives the adjustable arm I!) of the auto-transformer I through conventional mechanism, indicated at 65, that I may include speed-reducing gearing. When one of the windings 51 of the motor is energized, the

motor drives theadiustable auto-transformer in a direction to raise the output voltage of the latter; when the other motor winding 68 is energized, the motor .is driven in a direction to lower connected respectively to the separate ends of the'output voltage of the auto-transformer.

The'segments 5| and 53 of the switch 48 are the.

motor windings

51 and 68 through wires 69 spring 45,-whereby the spring is flexed as the pawl moves to the left. After the condenser is charged and the magnetic field of the solenoid has de-.

- cayed, the spring 45 returns the pawl-44 to its norma1 position and exerts a downward pressure so that the pawl properly engages the next'tooth in ratchet wheel 41.

It will thus-be seen'tnat the ratchet wheel 41 'is advanced one notch for each spark that flashes between the electrodes 'of the precipitator. It

will also be apparent that the glow tube- 1 condenser-battery circuit, as coupled to the high tension electrode energizing system of the precipitator, may be considered as beinga device responsive to disturbances in the charging system caused by an inter-electrode spark and that the solenoid-pawl-ratchet wheel system may be considered as being means for integrating the re:- sponses of the spark responsive device. I Various equivalents of these elements of the control system may be employed without departing fromthe' invention. spark sensing device-may be used instead of the For example, a resistance dividerthe position of the and"; Segments 5i and 53 of the switch 48 are electrically conductive whereas segment 52 is electrically insulating. It will, therefore, be perceived that'when electric power is applied between motor terminal and the. switch arm 49, three conditions are possible depending upon switch arm: (a) if the switch arm isin contact with segment 5|, the motor is energized in the "raise voltage direction; (b) if the arm is in contact with segment 53, the motor is energized in the .lower voltage direction;-and

(c) if the arm is in contact with the segment 52, the motor isnot energized. I

sequence timer 40 is conventional in oonstruction and operation, It is supplied with current from the source through wires 6i and 1| which energizes the timer motor and also provides electrical energy for actlvating the solenoid devices 12 and I; at the proper time. The solenoid device 12 has a link I4 extending from'its armature to' the blade of switch 40.

Upon energization of the solenoid device-12,

capacitive type shown and described. A step- 1 motor may be employed as an integrator instead of the solenoid-pawl-raitchet wheel'- motor 11-. 'lu'strated. Various other equivalents will be readily apparent.

a the teeth ofthe ratchet wheel 41, thus allowing switch 40 is closed and upon deenergization, the switch returns to open I 13 has a. link 15 extending position; The solenoid device from its armature, which link terminates inla loop 15 encircling the pawl 44 of the ratchet motor. When the cello! the device 13 is ener-- gized, the pawl is'lifted from engagement with the spring 55 toreturn the switch arm 49 and the ratchet wheel to starting position. Upon de- 7 energization of the solenoid device 13, the pawl I 44 is returned to operative engagement with the ratchet wheel under the action of gravity and the assistance of the leaf spring 48.

.A manually operated switch 8| is provided for adjusting the setting of the auto-transformer control motor 88, whereby to vary the output voltage of the auto-transformer. This switch has a conducting arm 88, pivoted at 82, and cooperating

contacts

84 and 88. Contact 84 is connected by wire 85 to wire 18; contact 88 is connected by wire 81 to wire 89; and switch arm 88 is connected by wire 83 to wire 88 that is connected to the terminal 58a of current source 58. To raise the output voltage of the auto-transformer, the circuit is closed between arm 88 and contact-88; to lower the voltage, the circuit is closed between arm 88 and contact 84. The arm 88 rests normally in the center position and is manually thrown to the raise voltage and lower voltage" positions.

In operation, the switch I4 of the energizing system of the precipitator is closed and the auto-transformer output voltage is manually adjusted by operation of switch 8| to approximately the desired operating value. Switch 82 is then closed to energize the sequence timer 88 and the control system. It will be assumed that when the switch 82 is closed, the timing switches contained in the sequence timer 88 are in such position that switch 88 is closed, the solenoid device 12 is energized, whereby the switch 48 is closed, the-solenoid device 13 is not energized, whereby the pawl 44 is in position to operate on the ratchet wheel 41, the arm 49 of the switch 48 is in starting position adjacent the stop 54, and no driving current is applied to the auto transformer motor 85.

The spark responsive device including the glow tube 3| detects inter-electrode sparks as they occur in the precipitator. Each spark is registered by a one tooth advancement of the ratchet wheel 47, the motion of the ratchet wheel being transmitted to the arm 48 of the switch 48.

The sequence timer is so constructed and arranged that, after a predetermined period of time, solenoid I2 is deenergized to open the switch 48, thus de-energizing the spark counting system and stopping motion of the ratchet wheel 41. This time interval is selected with relation to other parameters of the control system such that if the number of sparks counted is the number corresponding to optimum precipitator operating conditions, the arm 49 is stopped at the mid-point of the insulated segment 52. Segment 52 extends over an arc of sufllcient width to permit the arm 49 to be stopped in contact with this segment although the number of sparks departs from the optimum number by a reasonable margin. If the number of sparks counted in the period falls outside of the optimum range, the arm will come to rest on one of the terminal segments 5| or 58 depending on whether the sparking rate is lower or higher than optimum.

Next, the sequence timer directs motor driving current to the switch arm 49 for a predetermined short interval of time sufficient to activate the motor 85 to change the output voltage of the auto-transformer l8 by a substantially constant amount. If the switch arm is in contact with some portion of the segment 5|, owing to a sparking rate less than optimum, the motor 85 will raise the voltage; if the arm is in contact with the segment 53, owing to a sparking rate higher than desired, the motor will lower the voltage. Of course, if the sparking rate has been in the optimum range, the arm 49 will be in contact with the insulated segment 82 and no change in the output voltage'of the auto-transformer will be effected.

Thereafter, the sequence timer energizes the solenoid I8 to disengage the pawl 44 from the ratchet wheel to allow the spring 58 to return the switch arm 49 and the ratchet wheel to starting osition.

Next, the sequence timer cuts oil the current flowing to the coil of solenoid device I3 and the pawl 44 reensages the ratchet wheel.

Finally, the sequence timer energizes the solenoid device 12 and switch 48 closes to begin the cycle anew.

Typically, the spark counting time interval may be about ten minutes and, although the control cycle may be repeated immediately, it has been found desirable to repeat the control cycle at mtervals of about one-half an hour or one hour. More frequent adjustment is ordinarily not necessary. Each step in the adjustment of the autotransformer may eflect a change of about onehalf to one kilovolt in the potential of the current applied to the precipitator electrodes.

Under certain operating conditions, the sparkingrate may be high enough for the arm 49 of switch 48 to complete its travel to stop member 55 before the end of the particular counting interval selected, in which event, the arm moves the stop member 55 in a direction to open the switch 88 and thereby to de-energize solenoid 12, thus opening switch 48 and shutting off the counter circuit, whereupon motion 01' ratchet wheel 41 stops. When this occurs, arm 48 remains in contact with segment 53 of switch 48 so that at the end of the selected counting interval, normal action of the sequence timer applies power to winding 88 to lower the precipitator voltage.

After the sequence timer has eflected regulation of the precipitator voltage and has operated to return the switch arm 49 of switch 48 to starting position, the spring 180. returns the stop member 55 to normal position and closes the switch 88 to connect the solenoid 12 to the sequence timer 88 in readiness for a new control cycle,

From the foregoing description, it will be seen that the present invention provides a system for energizing electrical precipitators and the like that is responsive to sparking rate and that eilectively maintains the sparking rate at or near the optimum value. Moreover, in the light of this description, alternative arrangements within the purview of the invention will occur to those skilled in the art.

It will be apparent that the control system of the invention may be employed in an electrical precipitation system wherein two or more electrical precipitator sections are energized from a common power supply controlled by a, common voltage control system. In thi case, each precipitator section has its own pick-up element coupled in common to the trigger circuit of the glow tube. Voltage control is thus responsive to the average sparking rate of the plurality of precipitator sections energized from the single power supply.

I claim:

1. A system for energizing the electrodes of an electrical precipitator comprising a. voltage regulator, a. device responsive to disturbances in the system caused by an inter-electrode spark, means for integrating the responses of said device, means responsive to the deviation of the integrand of said integrating means from a preselected value,

lator, a device responsive to disturbances in the system caused by an inter-electrode spark, means for integrating the responses of said device, means responsive to the deviation of the integrand of said integrating means from a preselected value, and circuit elements operatively connected to said deviation responsive means for controllin said voltage regulator in a sense determined by the sense of the deviation of said: deviation respon sive means.

1 electrical precipitator comprising a voltage regu- :tion of the switch, a device responsive to disturb--' 3. A system for energizing the electrodes of an electrical precipitator comprising a voltage regulator, a device responsive to disturbances in the system caused by an inter-electrode spark, means for integrating the responses of said device over a predetermined period of time, means responsive to the deviation of the integrand of said integrating means from a preselected value, and

' circuit elements operatively connected to said deviation responsive mean's'ror controlling said drive said switch progressively through said positions, and circuit elements including said switch for actuating said voltage regulator.

5. Asystem as defined in claim 4 including means for stopping said motor after a predetermined period of time and means for resetting said switchtostarting position. '6. A system for energizing the electrodes 0 an electrical precipitator including a voltage regulator a-motor for actuating-said voltage regui lator, a multiple position switch, circuit elements connecting said switch with said motor to energize the motor in a sense determined by the posiances in the systemcaused by an inter-electrode spark, asecond motor for advancing said switch progressively through positionscorresponding to raise voltage," "neutra -"and lower voltage actuation of the voltage regulator, said second motor being actuated by said device at a rate proportional to the responses of said device, and

a means for periodically energizing said circuit voltage regulator in accordance with the deviation determined by said deviation responsive elements and sai first motor through said switch and thereafter returning the switch to starting position.

, HERBERT J. HALL.

, 3 unanimous crren The following references are of record in th means. .l

4. A system for energizing the electrodes of an 9 1 i I electrical'precipitator comprising a. voltage regui 4 U D AT PATENTS I lator, a device, responsive to disturbances in the i a Number I i' m t system caused by an inter-electrode spark,"-a mo-r 2,050,367 Myhre g Aug. 11, 1936 tor actuated by said device for integrating-the 2,162,501. Draper June 13, 193'! responses of said device over a predetermined 2,22191768 Ar'tzt 1 Apr. 29, 1941 period of time, a switch having a raise vo1tage 2,297,740 1 ,Brown a-r Oct. 6, 1942 Position, 9- n utra position and a "lower volt? 2,297,841 MacKenzie -Oct, 6, 1942 age" position,-- means connecting said motorto I l Disclaimer- 2,623,08."-Herbert Hall; Princeton; N. J SYsrriM ro z Eminorznvc Erino TRICAL PRECIPITATQRS. Patent datetl- Dec. ,30, 1952'. Disclaimer filed Aug. 14:, 1953, by the assignee, Research car al-arm. h a v Herebyentersthis disclaimerto claims 1, '2, and 3 of said patent.

[Ofim'alGazettefieptember 2.9, 1.253;] v