US2756839A

US2756839A - Electrostatic precipitator

Info

Publication number: US2756839A
Application number: US464790A
Authority: US
Inventors: Lawrence M Roberts
Original assignee: Research Corp
Current assignee: Research Corp
Priority date: 1954-10-26
Filing date: 1954-10-26
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31

Description

July 31, 1956 1.. M. ROBERTS ELECTROSTATIC PRECIPITATOR Filed Oct. 26, 1954 INVENTOR LAWRENCE M. ROBERTS ATTORNEY United States Patent 2,756,839 ELECTRGSTATIC PRECIPITATOR Lawrence M. Roberts, Bound Brook, N. 1., assignor to Research Corporation, New York, N. Y., a corporation of New York Application October 26, 1954, Serial No. 464,790

4'Claims. c1. 183-7) This invention relates to apparatus for separating suspended particulate material from gas streams, and in parti'cular to improved liquid flush type electrostatic precipitators particularly adapted for separating inflammable material or material or a corrosive nature from a stream of gas.

In the precipitation of certain acid gases, fluorine compounds and the like which are particularly corrosive it is desirable to construct preeipitator shells and interior structura'l members of wood to reduce the cost of the initial installation and to reduce corrosion by the acid gases and the fluorine compounds. On such installations it is the general practice to employ water sprays or films of water tcremove the precipitated material, to condition the gases and to keep the wooden portions of the precipitator soaked; This form of equipment has also been used in electrostatic precipitators for collecting inflammable material, such as carbon. These Systems have generally proved to be satisfactory as long as there is a continuous fiow of water to the liquid flush or spray systems of the precipitator. However, upon the failure or accidental cutting off ofthe water supply to the electrostatic preci'pfl tator while the electrodes continue to be energized, the wood portions of the precipitator or the inflammable material precipitated from the gas stream is very likely to burn as soon as the water has evaporated therefrom.

In the caseof fire in a wood type electrostatic precipr ta'tor complete loss of the installation often results. In the case of non-inflammable type precipitator's' collecting inflammable material, the burning material often causes back corona discharges thus interfering'with the efficient precipitator action and such fires often result in the for mation of clinkers in the precipitator hopper 'cloggingthe' dust removal system. I

It is therefore a primary object of the present invention to provide control means interconnecting liquid flush or spray systems of electrostatic precipitators of wood type construction or those collecting inflammable material, and the high voltage energizing system'for the complementary electrodes whereby the precipitator is deenergizedupon the failure or accidental or intentional cutting oif of the source of spray or flushing liquid.

It is af'urthcr object of the invention to provide such a device that is dependable in' operation, relatively ineX- pensive to construct, and efficient in operation.

A further object of the invention is to provide such a system wherein the control means may be positioned in the liquid spray conduits or externally thereof in the field of the spray coverage. 7

These and other objects and advantages are provided by the control means for a liquid'flu'sh'type electrostatic pr'c'ipitator which generally comprises a shell having a dirty gas inlet and a clean gas outlet, complementary collecting and discharge electrodes supported within such shell between the gas inlet and gas outlet, a source of high voltage electricity for energizing said electrodes, a liquid spray system for said electrodes connected to a source of spray liquid, and control means interconnecting said liquid "ice spray means and said source of high voltage electricity for dee'n'ergizing the complementary electrodes upon failure of the liquid spray system.

7 The invention will be more particularly described with reference to theaccompanying drawings wherein:

Fig. 1 is a diagrammatic View of an electrostatic precipitator having liquid spray means and an energizing system for the electrodes including the control means of the present invention;

Fig. 2 is an enlarged fragmentary view of one form of the control means of the present invention; V

Fig. 3 is an enlarged fragmentary view of another form or the control means of the present invention; and

I Fig. 4 is an enlarged fragmentary view of still another form of the control means of the present invention.

Referring to' the drawings and in particular to Fig. l, 10" is the shell or casing of an electrostatic precipitatoi' having a gas inlet 12 and a gas outlet 14. The shell of the precipitator may be constructed of wood for use in the collection of certain acid gases, and fluorine compounds where it is desirable to use wood in the construction of the shell as it has high resistance to corrosion and is relatively inexpensive. V d

Supported, within the flow pass of the gas through the precipitator shell, are a plurality of collecting electrodes generally designated 16. In the drawings the electrodes are shown as a plurality of tubular extended surface col lecting pipes supported in a header sheet 18 connected to the sides of the precipitator casing. Vertically suspended within each of the tubular collecting electrodes 16 is a line wire discharge electrode 20. The lower ends of the discharge electrodes are provided with tensioning weights 22 and a steadying frame work generally indicated 24 which is insulatedly supported from the side walls of the precipitator casing.

The upper ends of the discharge electrodes 20 are connected to a bus bar 26 to which high voltage electrical cur} rent is connected through conduit 38 as is well known in the art.

The foregoing structural elements of the electrostatic precipitator have been shown by way of example only, and it is apparent that other well known forms of collect ing and discharge electrodes may be employed with the control system of the present invention.

The energization system for the complementary discharge and collecting electrodes generally comprises a source of alternating current 28 connected to a high ten sion transformer 30 through a magnetic switch 32 tobe more fully described hereinafter. Thesecondary 34 of the transformer 30 is connected to a rectifier 3 6 and hence to: the discharge and collecting electrodes through

electrical conduits

38 and 40. I v

The magnetic switch 32 generally comprises main contact members 42 holding contact member 44, starting but} tor-146, and solenoid 48 for actuating main and holding contact members 42'and 44. The solenoid 48' is energized from a source of alternating current 50 through

electrical conduits

52, 54, 54 and switch 56.

The electrostatic precipitator is also provided with one or more water or other liquid supply mains 58 and a plurality of liquid spray heads 60 to supply flushing liquid to the discharge and collecting electrodes, for conditioning the gas stream to be treated in the pre'cipitator', and for protecting the side walls of the precipitator shell on installations where such shell is constructed of inflammable material. v I I Means" generally designated 62, sensitive to the flew of flushing liquid are provided for actuating the switch 56 which controls the magnetic switch 32. The control means 62 which is sensitive to the how of flushing liquid to the electrostatic precipitator may take various forms as shown in detail in Figures 2 through 4.

. through the main 53.

I? In Figure 2 of the drawings the control means 62 includes a differential pressure control diaphragm 64 connected to the switch 56. The diaphragm 64- is contained in a housing 66 having a pair of ducts 63 and 70 connected to the water main 58 at one end and at the other end to the housing 66 on opposite sides of the diaphragm 64. The diaphragm 64 and the control switch 56 are so arranged that when fluid is flowing through the main 58 to spray devices 60 the switch is in the closed position as shown in the drawings. However, as soon as the flow of liquid through main 58 is interrupted the pressure on either side of the diaphragm 64 is effected and the contacts of switch 56 open deenergizing the solenoid 48, opening the main contacts 42 of the precipitator energizing control switch 32, which cuts ofi the flow of high voltage electricity to the complementary discharge and collecting electrodes of the precipitator.

In Figure 3 of the drawings another form of control device 62 is shown which is operated by the flow of fluid In this form of the invention a pivotally mounted control member 72 has a portion 74 projecting into the main 58 and an external portion 76 which makes contact with the switch 56. As long as flushing liquid is flowing in the main 5% in the direction of the arrows contact is made between element 76 and the contacts of the

lines

52 and 54. When the flow of liquid in main 58 stops or is reduced a predetermined amount, the portion 76 of lever 72 moves away from the switch 56 whereby the solenoid 48 is deenergized.

In Figure 4 of the drawings another form of the control means 62 is shown. In this form of the invention switch 56 is not directly actuated by the How of flushing liquid in the main 58 but by means of a mercury wet bulb thermometer 80 connected to a relay 82. When the bulb 80 of the thermometer is wetted by the liquid issuing from the sprays 60 in the switch 56 remains in the on position. However, as soon as the bulb 80 becomes dry the mercury column within the thermometer moves out and relay 82 opens the switch 56 controlling the flow of current to the solenoid 48. In the form of the invention shown in Figure 4 a plurality of wet bulb type thermometers 80 may be employed in the precipitator wherein one or more relays 32 may be connected in parallel and the groups of parallel connected relays may be further connected in series whereby the precipitator is deenergized only upon failure of more than one of the spray devices 60.

It is also evident that the fluid flow control means shown in Figures 2 and 3 may be connected to subrnains each controlling a battery of spray devices whereby the precipitator is deenergized only upon failure of, for example, more than one of the batteries of spray devices.

From the foregoing description it will be seen that the control means for liquid flush type electrostatic precipitators fully accomplishes the aims, objects and advantages of the invention. It will also be apparent that the embodiments shown are only exemplary particular forms of apparatus for carrying out the present invention and that various modifications can be made in the construction and arrangement of the elements within the scope of the invention as defined in the appended claims.

I claim:

1. Control means for a liquid flush type electrostatic precipitator comprising a shell having a dirty gas inlet and a clean gas outlet, complementary collecting and discharge electrodes supported within said shell between the gas inlet and gas outlet, a source of high voltage electricity for energizing said electrodes, a liquid spray system for said electrodes connected to a source of spray liquid and control means interconnecting said liquid spray system and said source of high voltage electricity for deenergizing the complementary electrodes upon failure of said liquid spray system.

2. Control means for a liquid flush type electrostatic precipitator comprising a shell having a dirty gas inlet and a clean gas outlet, complementary collecting and discharge electrodes supported within said shell between the gas inlet and gas outlet, a source of high voltage electricity for energizing said electrodes, a liquid spray system for said electrodes connected to a source of spray liquid including a conduit connecting such source to spray outlets, control means interconnecting said liquid spray system with said source of high voltage electricity for deenergizing the complementary electrodes on failure of said liquid spray system, said control means including a solenoid actuated switch between the source of high voltage electricity and the complementary discharge and collecting electrodes, a diaphragm type differential pressure indicator in the conduit supplying flushing liquid to the liquid spray system, and switch means actuated by said pressure indicator for energizing and deenergizing said solenoid switch.

3. Control means for a liquid flush type electrostatic precipitator comprising a shell having a dirty gas inlet and a clean gas outlet, complementary collecting and discharge electrodes supported within said shell between the gas inlet and gas outlet, a source of high voltage electricity for energizing said electrodes, a liquid spray system for said electrodes connected to a source of spray liquid including at least one spray head positioned to direct flushing liquid to the complementary discharge and collecting electrodes, a solenoid actuated switch between such source of high voltage electricity and the complementary discharge and collecting electrodes, control means interconnecting said liquid spray system and said source of high voltage electricity for deenergizing the complementary electrodes upon failure of said liquid spray system, said control means including a wet bulb thermometer positioned within the precipitator shell within the field of said spray head, a relay connected to said wet bulb thermometer and means actuated by said relay for energizing and deenergizing said solenoid switch means.

4. Control means for a liquid flush type electrostatic precipitator comprising a shell having a dirty gas inlet and a clean gas outlet, complementary collecting and discharge electrodes supported within said shell between the gas inlet and gas outlet, a source of high voltage electricity for energizing said electrodes, a liquid spray system for said electrodes connected to a source of spray liquid including a conduit connecting such source to spray outlets, control means interconnecting said liquid spray system with said source of high voltage electricity for deenergizing the complementary electrodes on failure of said liquid spray system, said control means including a solenoid actuated switch between the source of high voltage electricity and the complementary discharge and collecting electrodes, a pivotally mounted control member, one end of said control member projecting into the liquid flow path within said conduit, and switch means actuated by the other end of said control means for energizing and deenergizing said solenoid switch.

References Cited in the file of this patent UNITED STATES PATENTS 1,947,447 Brassert Feb. 20, 1934 FOREIGN PATENTS 568 Great Britain June 11, 1889