US1522143A - Method of conditioning electrodes - Google Patents

Description

JIanJG. 1925': 1,522,143

R. B; RATHBUN METHOD OF CONDITIONING "ELECTRODES Filed June 5, 1921 2 Sheets-Sheet I.

avwemtoz Jan. 60 R. B. RATH'BuN 7 METHOD OF CONDITIONING ELECTRODES Filed Jun e :5, 1921 2 Sheets-Sheet 2 lllllll I l I I I I I U fiu El- INVENTOR Boss film/"Z010 [Edi/Maia ATTORNEY atented .tan. 6, 1925 ROSS BUXTON RATHBUN, OF SALT LAKE ING AND REFINING COMPANY, OF

JERSEY.

CITY, UTAH, ASSIGNOR TO AMERICAN SMELT- NEW YORK. N. Y., A CORPORATIONOF NEW METHOD OF CONDITIONING ELECTRODES.

Application filed June 3,

To all whom it may concern:

Be it known that 1, Ross BUXTON RATH- BUN,

a citizen of the United States, and resident of Salt Lake City,

in the county of 5 Salt Lake and State of Utah, have invented certain new and useful Improrements in Methods of Condi tioning Electrodes, of

tality for carrying out the method.

It is understood that in the practicing of this method of ele ctric precipitation, the

solid, precipitated matter especially when dry has a tendency trodes and as 1t has to collect on the elee high dielectric strength it acts to insulate the electrodes, automatically reducing the value below what current strength to :1 1s required. Numerous attempts have been made to remedy this defeet, among which might be mentioned that it has been suggested to moisten the gases carrying the particles or eipitate'd particles or acid as they come trodes. These meth to moisten the prethemselves with water in contact with the elecods however, use. up too much acid to be economical; the acid and water both act to deteriorate. the apparatus, and the cooling of the gases effects the natural draft through the discharging stacks.

Again it has been suggested to wet the electrodes themselves with a contlnuous stream of water but this gi ves rise to a slimy precipitate which cannot be readily handled.

Accordingly, one

of the objects of the invention is to provide a simple method for effecting a constant,

complete precipitation of the solids from the gases and in which method practically all of the solids are precipitated in a dry, readily handleable condition and, of most wde a method which inexpensively.

I attain this inve treating the actlve serious import, to prowill attain these results ntion by intermittently faces of the electrode,

while not in active operation, 'or while 1n ac- .tive operatlon, w th a thin film or rather mist of a readily diifuslble conducting liquid such as sulph So treating the e uric acid. lectrodes has the effect 1921. Serial No. 474,798.

of elin'iinating the disadvantages in the prior methods, except possibly corrosive actions, but the use of acid of high concentration usually about 136., minimizes any acid reaction especially as the parts are protected somewhat by the dry dust coating.

It is apparently necessary for the successful operation of this method that the acid be applied uniformly over the electrode sur faces in the form of finely divided particles. and therefore one of the objects of the apparatus features of this disclosure is toproride a'simple form of apparatus which will condition all of the electrodes with the same amount of acid applied in substantially the same cloud-like mist, for the wetting of any electrode with too much acid acts so as to require a lower voltage than is desirable. to prevent sparking over at the electrodes.

It is sometimes more convenient to. apply the cloud of acid mist to the electrodes by introducing it with the gas periodically, just before it passes through the'electrodes, the mist being precipitated with the dust, but the fact that the gas or smoke is there is incidental rather than necessary, but in so far as the method feature of the disclosure is concerned the electrodes are initially treated during the period when there is no gas flow-with an atomized cloud of concentrated sulphuric acid G06(l Be. applied to the electrodes for a period of about a half minute or until all parts thereof are presumably covered with closely-positioned, minute drops but not so copiously applied as to cause anything in the nature of streams or a running'coating of any nature. The mist is carried into contact with the electrodes by means of a current of air produeed by the draft or pull of the chimney. The gas from which the solid matteris to be precipitated is then passed through the electrostatic field formed by the energized electrodes in the manner which is well known in the practicing of the Cottrell method. The solids are precipitated from the gases; the gases pass from the electrostatic field practically clear, and this clearing of\the gases will continue until the effect of the acid becomes dissipated. The flow of gas is then interrupted; all of the precipitate possible shaken from the electrodes to enable the acid mist to contact with the electrode itself rather than the precipitated turned on coat of dust, the electrodes are again treated to an acid mist; the gas is again and the operation repeated. A usual practice is to treat the electrodes once every twenty-four hours but this period may vary from a much shorter period to a longer one, depending on the amount of solid matter suspended in the gas, its dryness and the amount of matter present, such as lime or compounds of zinc, which have a tendency to neutralize the acid.

While the present disclosure features the spraying of the electrodes with an atomized mistof the acids, it is to be understood that this method of handling the conditioning liquids is largely to feature economy in the amount of .material used and it is sug gested that the acids might be otherwise applied as by painting the electrodes provided, of course, that the acids were not thickly applied or applied in any other way which might interfere with the necessary electric conditions.

Sulphuric acid has been suggested due to its relative cheapness over other suitable treating liquids; due to the fact that it is extremely divisible; due to its high boiling point; due to its high rate of diffusion over matter and due to the fact that it breaks up into three extremely mobile hydrogen radicals. It is, however, suggested that other treating materials might be used and for an illustration of one such material reference is made to nitric acid.

Referring to the apparatus features of the disclosure reference is made to the ac c'ompanying drawings of two forms of electrode treating apparatus, suitable for use in practicing the method herein featured. Figure 1 is a diagrammatic view of a screen type of treater in which the upper part is shown in plan and the lower part in eleva-' tion. Figure 2 is a similar view of a treater of the pipe type and Figures 3 and 4 are each enlarged transverse views of the dis-- tributing pipe shown in Figure 2 and taken 7 respectively on the lines 3-3 and 4--4 of the figure.

Referringspecifically to the showing in Figure 1 there are shown gas conducting conduits or flues 10 and 11, through which the gases pass horizontally and in which are hung a plurality of electrodes 12 and 13 electrically connected so as to precipitate the dust from the gas fumes passing through the flue in the manner well-known in connection with the operation of electrolytic precipitation in the screen typeof treater.

The discharge electrodes which are in the form of wires, are hung from supporting pipes 14, which pipes have heretofore been in the form of conducting rods for leading the electric current to the electrodes but which, in this instance, are in the form of pipes provided with a series of closely positioned small vents, 15, opening downwardly for the purpose of distributing the atomized acid as hereinafter more fully described.

The assive or rounded electrodes which pressure is introduced to as large a number of points as is possible and in this way the pressure is kept fairly uniform over the entire system. For this purpose the acid inlet, 29, discharges into a main pipe, 16, of

relatively large conducting capacity, which pipe, 16, branches in two ways and discharges into a plurality of distributing header pipes, 17,18 and 19, the latter of which is positioned within the outline of a gas conduit and discharges directly into the set of spraying pipes, .14, located in the gas conduit. In so far as is possible each set of pipes collectively has a conducting capacity equal to the conducting capacity of the pipe which supplies the set so as to insure uniform velocity of the mist, thus keeping it in suspension in the several branches and preventing any of it from settling out in droplets as would be the case if the mist has too slow' a velocity due to too large a pipe.

It is necessary to connect the main pipe to the supply system simply during the time when it is required to condition the electrodes and while the electric precipitating features of the device arefunctioning it is necessary to insulate the structure from the conditioning system. This is most readily eifected by disconnecting the part of conditioning piping exteriorly of the system from the part within the gas conduit and one means for effecting this is to make a part of the piping, such as the part shown at 20, in the form of a short length of pipe connected by means of two unions which can-be readil broken.

In this system it s required that air in large volume, and preferably dry, be supplied to the atomizing device and for this purpose there is disclosed an-approved form of air charging conduit including, in order. a source of air under compression indicated by the supply pipe 21. This leads to a moisture trap, 22, and from the moisture trap through an air dryer, 23, from which the dried air is discharged into an air storing receptacle. 2%. From the air storing receptacle, 24. the air is discharged through a system of relatively large air supplying pipes, 25, leading to the several atomizing devices supplied from this air source.

The acid is supplied to'the atomizer from an acid supply tank, 26, through a conducting pipe, 27, which leads past the control valve, 28, to a spray nozzle, 29. having a perforated head, 30. and facing in the direction of air flow through the vaporizer as is well-known in devices of this character. It is not essential that the device, 29, act. as an atomizer but may serve only as a means of conveying the acid into the air stream, the atomization taking place at the small orifices. I

Air pressure is maintained on the acid level in the tank, 26, from a source of air supply indicated by the pipe, 31. It is understood that the pipes 21. and 31 may be supplied from some common source of compressed air usually found in metallurgical plants.

In operation and assuming that the electrodes in the conduit, 10. and 11 are to be conditioned, the set of distributing pipes in these conduits are connected up by the reinsertion of the replaceable pipe connection, 20. The receiver, 24, having been filled with air to about six atmospheres, pressure, is allowed to exhaust itself through the main valve. 32, into the header system. At the same time air pressure, acting on the acid in the supply tank, forces acid therefrom through the atomizer where it is separated into extremely fine particles. The fine particles are'conducte'd with a relatively large amount of air through the piping system, where it is divided approximately evenly and is discharged from the vents, 15. onto the electrodes as an extremely fine cloud-like mist. This cloud of mist passes through the electrodes, some of it adhering to them due to contact in passing. The remainder passes on out the main flue to the stack. Vhen the electrodes are barely covered, as hereinbefore suggested, the supply of acid is cut off from the electrodes; the supply pipes cut off from the gas conduit, and the precipitating action is rein-augurated and continued until the gases leaving the treater begin to cloud with solids, at which time the precipitating action is stopped and the electrode reconditioned.

It is understood that the method of ap-- plying the mist to the screen and wire electrodes is not necessarily confined to the procedure described. It may be found more convenient, for instance, to introduce the cloud of acid mist in the chamber or conduit before the gas reaches the electrodes, the mist being carried into contact with the electrodes with air or gas currents.

Referring to the disclosure in Figure 2 it will be understood that the atomizing device 29 and the parts leading thcrctororrespond to the similarly numbered parts in Figure 1. The atomizing device discharges into a distributing pipe 31 which extends centrally across either the top chamber or the bottonrchamber 32 of a gas compart ment in a well known form of pipe treater. The treater includes a plurality of pipes 33 through which the gases rise vertically. Discharge electrodes 34 are stretched axially through the pipes. The acid distributing pipe 31 is provided with a reduced extension 35 and both pipes 31 and 35 are provided with downwardly-directiug discharge parts 36.

The second method. used in connection with the showing in Figure 2 is essentially like that described. It is the intent in this case to pass the cloud of mist for a few moments at intervals through the pipes, conditioning their surfaces. This is accomplished by liberating the acid mist in either the top chamber or bottom chamber of gas compartment. \Vhen it is released in the upper chamber, it is necessary to do so with the gas excluded so that the mist may be carried down throughthe pipes by a current of air. TVhen it is released in the bottom chamber it may be introduced iuthe gas column and conveyed to the electrodes by this means. It has not been found necessary to insulate the spraying apparatus in this method. Considerable advantage is obtained in having it grounded so that. permanent connection may be made to the outside service.

Having thus described my invention, I

claim 1. In the. art of electrical precipitation of suspended solid matter from gases, the method of maintaining a metailic electrode conductive in cases where the precipitated material is non-conducting and tends to accumulate a charge by the action of the elec: tric field, which method consists in applying directly to the face of the electrode surface. an acid in the form of a fine/mist to form on the electrode surface a thin layer capable of defeating any tendency of the charge to impair the conductivity of the metallic electrode surface.

2. In the art of precipitating suspended particles from gases'by electric action, the method of maintaining conductivity between the particles and an impenetrable electrode surface which consists in confining a thin film of a conducting liquid containing sulphuric acid to the electrode surface.

3. In the art of precipitating suspended particles from gases by electric action, the method of maintaining conductivity between the particles and the active face of the electrode surface which consists in distributing loo a thin film of sulphuric acid in finely divided particles over said active face.

4. In the art of precipitating suspended particles from gases by electric action, the method of maintaining conductivity between the particles and the electrode surface which consists in distributing a film of sulphuric acid in the form of a fine mist over the elec- 'trode surface.

5. In the art of precipitating suspended particles from gases by electric action, the method of maintaining conductivity between the particles and the electrode surface which consists in directing onto the electrode-surface and in the absence of the gases to be precipitated a line mist of liquid constituting an electric conductor.

6. In the art of precipitating suspended particles from gases by electric action, the method or maintaining conductivity between the particles and the electrode surface which consists in distributing over the electrode surface and in the absence of the gases to be precipitated. a layer of an acid distributed in finely divided particles constituting an electric conductor and capable of reducing the dielectric constant of any surface film on the particles.

7. In the art of conditioning electrodes used in the precipitation or" suspended solid matter from gases, the method which con sists in subjecting the active surface of the electrode to a coating film of sulphuric acid deposited in the form of a fine mist.

8. In the art of conditioning electrodes used in the precipitation of suspended solid matter from gases, the method which con sistsin intermittently subjecting the active surface of the electrode to a coating film of sulphuric acid.

9. In the art of precipitating suspended solid matter from gases by electric action, the process which consists in spraying the electrodes with sulphuric acid until the ac tive surfaces thereof are coated with the acid, interrupting the acid spraying action. causing the preclpitation of the suspended matter from the gas onto the sprayed electrodes Without addition oft" any substance, interrupting the precipitating action as the electrodes become free of the acid coating and again spraying the electrodes with the acid.

10. In the art of conditioning electrodes which consists in causing a mist of finely divided particles of sulphuric acid to adhere to an active face of the electrode and thus form a thin film on the same.

11. An electrode for use in the electric precipitation of solids from gases including a metallic conductor having a thin llOlbfiOW- ring coating of sulphuric acid on an active face thereof.

Signed at Tacoma in the county of Pierce and State of Washington this 21st day of April, A. i 1921.,

ROSS BUXTON RATHBUN.

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