US3342721A

US3342721A - Apparatus for treating liquids in an electrical discharge including means for directing the liquid in a continuous curtain

Info

Publication number: US3342721A
Application number: US411192A
Authority: US
Inventors: Norman R Dibelius; James C Fraser
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1964-11-16
Filing date: 1964-11-16
Publication date: 1967-09-19
Anticipated expiration: 1984-09-19

Description

p 1967 N. R. DIBELIUS ETAL 3,342,721

APPARATUS FOR TREATING LIQUIDS IN AN ELECTRICAL DISCHARGE INCLUDING MEANS FOR DIRECTING THE LIQUID IN A CONTINUOUS CURTAIN Filed Nov. 16, 1964 2 SheetsSheet l [n ventors- Norman R D/Lbeh'us,

James C. Fraser", by a/a M The/r- Atizorney.

Sept. 19, 17

N. R. DIBELIUS ETAL APPARATUS FOR TREATING LIQUIDS IN AN ELECTRICAL DISCHARGE INCLUDING MEANS FOR DIRECTING THE LIQUID IN A CONTINUOUS CURTAIN Filed Nov. 16, 1964 2 Sheets-Sheet 2 [nventor-s Narmarv R D/be/HJS,

James C. Fraser;

Patented Sept. 19, 1967 3,342,721 APPARATUS FGR TREATING LIQUIDS IN AN ELECTRICAL DISCHARGE INCLUD- ING MEANS FOR DIREQTING THE LIQ- UID IN A CONTINUOUS CURTAIN Norman R. Dibelius, Ballston Spa, and James C. Fraser,

Schenectady, N.Y., assignors to General Electric Company, a corporation of New York Filed Nov. 16, 1964, Ser. No. 411,192 Claims. (Cl. 204-312) The present invention relates to an improved apparatus for contacting a moving liquid film with a corona discharge.

The term corona discharge is applied to the soft, diffused visual display produced by capacitatively exciting a gas lying between two spaced electrodes, at least one of which is insulated from the gaseous media by a dielectric barrier. When a gas is placed in an electric field generated by spaced electrodes connected to a source of alternating current, the gas absorbs energy from the electric field. The energy absorption may result in activating electrons into higher energy orbitals, in dissociating diatomic gases into free radicals, or even in forming gaseous ions. The presence of an interposed dielectric barrier prevents the ionized gas from providing an ionic conductive bridge or arc between the electrodes thereby collapsing the field and destroying the corona effect.

The use of a corona discharge in causing a gas to react with itself has long been recognized. In perhaps the most common piece of corona discharge equipment, the ozonizer, oxygen is converted to ozone by a corona discharge generated in the annulus between two concentric dielectric tubes. Further investigation of corona effects has indicated that a corona discharge may be used to catalyze numerous types of chemical reactions of both organic and inorganic materials. Corona discharge has been used to catalyze reactions, for example between mixed gases, within liquids, and between liquids and gases.

While the applications of corona discharge have advanced to liquid phase reactions, the equipment employed has remained patterned on the conventional ozonizer. Certain difficulties have been experienced with such equipment in catalyzing liquid phase reactions, since a corona discharge is a gas phase phenomenon and cannot be propagated in a liquid. conventionally employed apparatus fails to make provision for maintenance of a liquidgas interface, whereby the gaseous corona can act on the liquid. Additionally, such apparatus is deficient in failing to insure uniform dimensions of the liquid stream passing through the apparatus so that a uniform and controlled corona can be maintained. Further, the fluid inlet of a conventional ozonizer will fragment an entering liquid stream into a plurality of streams or droplets. Passing a conductive liquid in such a fragmented form through a corona discharge will result in arcing. Accordingly, conventional corona reactor equipment is limited to dielectric liquids.

It is an object of the invention to provide a corona reactor capable of efliciently catalyzing chemical reactions in the presence of a liquid phase.

It is an additional object to provide a corona reactor capable of treating a curtain of conducting liquid.

It is another object to provide a corona reactor capable of treating one or more dielectric liquid curtains through an electric field.

It is a further object to provide an apparatus capable of delivering a corona activated gas uniformly to the surface of a body of liquid.

These and other objects of our invention are accomplished by providing a corona discharge apparatus including an inner electrode assembly mounted within an outer electrode assembly and spaced therefrom. Either a conductive or dielectric liquid to be subjected to a corona discharge is passed between the electrode assemblies as a descending curtain. The liquid curtain is generated by a fluid guide such as nozzle directed non-radially against either the inner or outer electrode assembly, an annular guide ring sloping downwardly towardeither the inner or outer electrode assembly, or an annular nozzle directing liquid axially downwardly. When a dielectric liquid is to be treated, a plurality of liquid curtains may be generated.

Our invention may be better understood by reference to the following description taken in connection with the drawings in which:

FIGURE 1 is an elevation, partly in section, of a corona reactor with attendant electrical and fluid connections schematically indicated;

FIGURE 2 is a cross section taken along line 22 in FIGURE 1;

FIGURE 3 is a cross section similar to FIGURE 2 of a modified form of the apparatus;

FIGURE 4 is a detail, partly in section, of a further modified form of the apparatus;

FIGURE 5 is a cross section taken along line 5-5 in FIG. 4;

FIGURE 6 is a detail, partly in section, of a form of the apparatus employing an annular liquid guide;

FIGURE 7 is a cross section taken along line 7-7 in FIGURE 6;

FIGURE 8 is a detail, partly in section, of a reactor employing an annular nozzle; and

FIGURE 9 is a cross section taken along line 99 in FIGURE 8.

The corona reactor shown in FIGURE 1 includes an inner electrode assembly 1 which employs a dielectric container 2 confining an electrically conductive liquid 3. The conductive liquid may be circulated through conduits 4 and 5 mounted in a closure 6 at the upper end of the container. In the particular electrode assembly shown, the conduit 4 is copper tubing so that it can conduct electricity to the electrode. When it is desired to control the temperature of the inner electrode assembly, an additional aperture in the closure may be used in which a thermometer is mounted extending into the electrically conductive liquid. The conductive liquid itself may be chosen from a wide range of materials including tap water, aqueous alkaline, acidic, and salt solutions, and mercury. While circulation of the electrically conductive liquid is desirable for temperature control purposes, circulation is not essential. Further, it is not essential that the electrically conductive material within the electrode be a liquid. Electrically conductive particulate materials such as metal turnings or filings may be employed alone or in combination with a liquid. Finally, in treating a dielectric liquid, it is not necessary that the inner electrode include a dielectric container. The container may be formed of electrically conductive material or the entire inner electrode assembly may be formed of an electrically conductive rod as shown, for example, in US. Patent 1,986,885.

The inner electrode assembly 1 is mounted within an outer electrode assembly 7. As shown in FIGURE 1, the outer electrode assembly includes a substantially cylindrical fluid conduit 9 formed of dielectric material and connected to the container 2 by an annular weld 8. Two side arms 1% and 11 are shown for circulating gas between the inner and outer electrode assemblies. As shown, one of the side arms is provided with a plug 12. Spaced, enlarged

diameter portions

13 and 14 are formed in the conduit 9. An electrode 15 is mounted on the conduit 9 between the enlarged diameter portions. In its most preferred form, the electrode 15 is a substantially transparent electrically conductive coating such as tin X- ide. Current collectors 16 are mounted on the electrode 15 at spaced intervals. The portion of the fluid conduit 9 below the enlarged diameter portion 14 terminates in fluid outlet 17. A nozzle receiving side arm 18 is shown attached to the enlarged diameter portion 13.

While the form of the outer electrode assembly 7 shown in FIGURE 1 is preferred, numerous modified forms of outer electrode assemblies are contemplated, In treating a dielectric liquid, the fluid conduit 9 may be formed of electrically conductive material. Alternately, only the portion of the fluid conduit 9 extending between the

enlarged portions

13 and 14 may be formed of conductive material. In either instance no separate electrode would be required. The electrode 15 may be formed of any type of electrically conductive material desired, including vacuum deposited or cathode sputtered metal coatings, conductive paints, metal foils, or metal shims as shown, for example, in U.S. Patent 2,944,951. Alternately, a water electrode may be employed as taught in US. Patent 1,986,885. The upper and lower enlarged diameter portions are not essential and may be omitted. In working with liquids in which oxidation is not a factor, the upper and/ or lower end of the outer electrode assembly may be open to the atmosphere.

As shown in FIGURE 1, the copper tubing 4 is connected to the current collectors 16 through external leads 19 attached to a source of alternating current 20. For purposes of illustrating the operation of the corona reactor certain optional elements of equipment are shown in combination with the corona reactor. These include an outer cooling jacket 21 having

spacing gaskets

22 and 23 as well as inlet and

outlet ports

24 and 25. A fluid outlet tube 26 is shown attached to outlet 17 and extending into receptacle 27 having an outlet tube 28 and control valve 29. A gas circulation tube 30 extends from receptacle 27 to gas inlet side arm 10. A pump 31 is provided to circulate gas and conduit 32 is provided to supply make-up gas. A liquid circulation tube 33 extends from within receptacle 27 to the fluid nozzle side arm 18 and is provided with a pump 34 and a liquid make-up conduit 35.

A liquid guide for the purpose of generating a liquid curtain between the electrode assemblies is provided in the form of nozzle 36 mounted in nozzle side arm 18 as most clearly shown in FIGURE 2. The nozzle is provided with a bent neck 37 directing the terminal orifice 38 toward the inner surface of the enlarged diameter portion 13 at an acute angle as indicated by flow arrow 39. As shown, the nozzle is formed of dielectric material and is joined to the side arm 18 at 40. The nozzle 36 may be removed from the side arm and replaced with a nozzle of differing size or angle of impingement whenever a liquid of differing properties is to be used in the reactor. The nozzle arrangement shown in FIGURES 1 and 2 is equally applicable to both dielectric and conductive liquids. If desired, the nozzle 36 may be coupled to the side arm by a mechanical connection rather than by a weld as shown. For easy removal and replacement, a frictional fit between the side arm and nozzle, such as a ground glass joint, may be desirable. The nozzle need not be formed of a dielectric such as glass but may be formed of any material having the requisite structural strength, including ceramics, metals, and plastics.

An alternate form of liquid guide applicable only to dielectric liquids is shown in FIGURE 3. A plurality of guides in the form of nozzles 41 are shown including diverging bent neck portions 42. and 43 terminating in

orifices

44 and 45, respectively. The liquid emitted from orifice 44 impinges the inner surface of enlarged diameter portion 13 at an acute angle as illustrated by flow arrow 46. The liquid emitted from orifice 45 impinges the outer surface of the inner electrode assembly at an acute angle as indicated by flow arrow 47. While impingement with the inner surface of the enlarged diameter portion 13 is preferred, it is appreciated that the orifices 44 may be plugged or omitted bringing the liquid into impingement with only the outer surface of the inner electrode assembly. In such instance, the apparatus could be used with either a conductive or dielectric liquid.

In FIGURES 4- and 5, a detail of a modified form of the invention is illustrated in which the straight walled enlarged diameter portion 13 is replaced with a curved wall enlarged diameter portion 48. Additionally, a modi fied liquid guide in the form of nozzle 49 combining the function of a nozzle and side arm is illustrated. As illus: trated in FIGURE 4, the nozzle 49 is canted from the horizontal by an angle 0:, while FIGURE 5 illustrates the guide canted from the radial by an angle {3. The angle on may be any angle less than degrees including Q degree and is preferably 45 degrees. [3 maybe any finite acute angle or a 90 degree angle, but is preferably greater than 45 degrees when impingement with the inner surface of the enlarged diameter portion 48 is desired. The em bodiment shown in FIGURES 4 and 5 is applicable to both dielectric and conductive liquid treatment.

It is appreciated that each of the liquid guides in FIG- URES 1-5, inclusive, may be directed such that the liquid is brought tangentially into contact with the correspond ing enlarged diameter portion of the apparatus. The terms acute angle and acute angle of impingement" as herein employed are inclusive of a tangential impingement as the minimum acute angle of impingement.

In FIGURES 6 and 7, alternate forms of liquid guides are shown. An inner electrode assembly 1 is mounted in an outer electrode assembly 51 Outer electrode assembly 50 differs from outer electrode assembly 7 only by the omission of enlarged diameter portion 13. An outer liquid guide 51 is shown tapering downwardly and out wardly whereby an annular curtain of liquid is formed on the inner surface of the outer electrode assembly. An inner liquid guide 52 is shown tapering downwardly and inwardly so that an annular curtain of liquid is formed on the outer surface of the inner electrode assembly. Liq' uid is supplied to the liquid guides by a nozzle 53 having

orifices

54 and 55 directed toward the outer and inner guides respectively. The inner and outer guides are supported spaced between the inner and outer electrode as semblies by a spider 56 frictionally engaging the outer surface of the inner electrode assembly.

When both the inner and outer guides are employed, the apparatus may be used with a dielectric liquid. When one of the

liquid orifices

54 and 55 is plugged or omitted from the apparatus, the reactor may be used to treat either a dielectric or conductive liquid. In such modification, the corresponding guide may be omitted from the apparatus. The use of spacers formed integrally with the guides is contemplated in place of the spider 56.

An additional form of liquid guide is shown in FIG- URES 8 and 9. Mounted between the inner electrode assembly 1 and the outer electrode assembly 50 is a liquid guide in the form of an annular nozzle 57 having an annular orifice 58 directed axially of the annulus between the electrode assemblies. The annular nozzle is supported and supplied with liquid through the conduit 59. It is appreciated that the annular orifice 58 may be directed inwardly toward the inner electrode assembly or outwardly toward the outer electrode assembly.

In operation of the apparatus shown in FIGURE 1, a liquid to be treated with a corona discharge is supplied through make-up conduit 35. The liquid is jetted from the nozzle 36 into impingement with the inner surface of the enlarged diameter portion 13 of the outer electrode assembly 7. The liquid jet follows the inner surface of the enlarged diameter portion 13 while continuing to travel in a substantially horizontal direction. Inasmuch as the direction of the liquid jet is constantly changing, a radial acceleration and corresponding centrifugal force is produced holding the liquid in contact with the inner surface. The tendency of the fluid to flow downwardly is partially offset by the reduced diameter of the fluid conduit 9 below the inner surface which requires an inward flow against the centrifugal force. In using a single nozzle, it is preferred that the velocity of the liquid jet be sufliciently high for the liquid to follow the inner surface of the enlarged diameter portion through a full 360 degrees, with at least a portion of the liquid returning to or just below the nozzle. When N number of nozzles are employed, the liquid or a portion thereof should traverse a portion of the inner surface defining a 360/N degree arc.

Simultaneously with the admission of liquid to the nozzle, as gas is supplied to the reactor through gas makeup conduit 32. The gas may be reactive toward or inert to the liquid. In some applications, it may be desired that a purge gas be supplied before operation and that no additional gas be supplied during operation. In supplying a reactive gas, the rate of admission may be determined with reference to chemical stoichiometry. In supplying an inert gas the rate of admission may be maintained at the minimum necessary to insure a positive pressure within the apparatus.

As the liquid circulating in the enlarged diameter portion 13 loses its velocity, the centrifugal force decreases and is overcome by the downward pull of gravity. A thin uniform film or curtain of liquid is generated on the inner surface of the fluid conduit 9 below the portion 13. Simultaneously, a body of gas contacts the inner surface of the liquid film in a uniform manner.

When a high voltage of alternating polarity is impressed across the inner and outer electrode assemblies, the gas lying between the inner and outer electrodes is excited to emit a corona discharge. In the case of inert gas, photons may be given off by the cyclic transfer of electrons from higher to lower energy orbitals. In the case of more active diatomic gases, the molecules may be disrupted to form free radicals and/or ions.

When the curtain of liquid descending through the corona discharge is a dielectric liquid, the curtain itself acts as a dielectric barrier retarding or preventing arcing between the electrodes. When a dielectric curtain is to be treated, the thickness of one or both of the dielectric barriers associated with the electrode assemblies may be reduced allowing the dielectric curtain to aid in maintaining the dielectric barrier between the electrodes. In a modified form of the apparatus, both the fluid conduit 9 and the inner electrode assembly may be formed of electrically conductive material. In such case, the dielectric curtain serves as the sole dielectric barrier between the electrodes and it is unnecessary to employ dielectric materials in the construction of the electrode assemblies.

In the case of a conductive liquid under treatment, the formation of a liquid curtain without fragmentation of the liquid stream within the corona prevents arcing as occurs when a conductive liquid is introduced into a conventional ozonizer type reactor.

The coron discharge is terminated sharply at the enlarged diameter portion 14 which is designed to reduce edge effects. A similar function is performed by enlarged diameter portion 13. A sharply defined electric field possesses advantages in reducing power losses and in allowing an easy determination of the exact limits of the corona treatment.

The liquid leaves the reactor through the outlet tube 26 which delivers the liquid to the receptacle 27. The liquid or a portion thereof may be removed through outlet tube 28 or may be recirculated through circulation tube 33. The gas is collected in the upper portion of the receptacle and is recirculated through gas recirculation tube 30. Gas may be withdrawn from the apparatus through side arm 12.

While the operation has been described in the instance where liquid impinges only the outer electrode assembly, the reactor may be operated with a thin uniform film or curtain of liquid descending in contact with the inner electrode assembly. Noting the arrangement shown in FIGURE 3, liquid is directed toward the outer surface of the inner electrode assembly at an acute angle. The liquid will travel in contact with outer surface through an arcuate path, being held in contact with the outer surface by the force of surface tension. With loss of velocity, the liquid descends along the outer surface forming a thin, uniform liquid film or curtain. As indicated by FIGURE 3, it is contemplated that two separate liquid curtains may be simultaneously transported through the reactor. Although limited to the treatment of dielectric liquids, plural liquid curtains provide the advantage of a greatly increased reaction surface. Whereas the outer film is generated by centrifugal force, the inner film is generated by surface tension. It may be desired therefore to separately design each of the nozzle orifices so that fluid may be impinged on the inner and outer electrode assemblies at differing velocities.

The form of the invention shown in FIGURES 4 and 5 operates substantially the same as the apparatus shown in FIGURES 1 and 2. The vertical cant of the guide 49 allows the achieving of a liquid curtain over a somewhat wider fluid velocity range. The form of the invention shown in FIGURES 6 and 7 operates substantially similarly as the apparatus shown in FIGURE 3. The annular guides shown in FIGURES 6 and 7 do not, however, depend on the generation of a centrifugal force.

The liquid guide in the form of an annular nozzle 57 shown in FIGURES 8 and 9 extrudes an annular column of liquid downwardly between the inner and outer electrode assemblies. This form of the liquid guide finds particular utility with liquids that are highly viscous or which tend to form solids within the corona environment. In dealing with liquids having low viscosity which tend to form fragmented streams or droplets after extrusion, the liquid curtain may be maintained intact by directing the liquid toward either the inner or outer wall of the annulus between the electrode assemblies.

While the invention has been described pointing out specific embodiments and discussing certain advantageous modifications, numerous additional modifications will be readily apparent to one skilled in the art. Accordingly, it is intended that the scope of the invention be determined by reference to the claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In an apparatus for treating fluids in a corona discharge including a vertically disposed hollow tube defining a vertical cylindrical space and comprising a first electrode, a cylindrical member concentrically disposed within said tube to define an annular space radially between the interior surface of said tube and the exterior surface of said member, said member comprising a second electrode, means for providing an insulating dielectric barrier betwen at least one of said electrodes and said annular space, means including said electrodes disposed axially along a substantial portion of said space for effecting a corona discharge across said annular space and thereby defining a reaction zone, at least one means for supplying fluid through said reaction zone and means for receiving fluid from said reaction zone, the improvement wherein said fluid supply means includes means for directing a liquid into said space above said reaction zone to form substantially all of said liquid into a descending continuous film curtain flowing over at least one of said surfaces and wherein said annular space is substantially free of liquid droplets.

2. An apparatus according to claim 1 wherein said liquid directing means comprises a liquid guide.

3. An apparatus according to claim 2 wherein said liquid guide comprises a nozzle.

Z 4'. An apparatus according to claim 3 wherein said nozzle is directed toward at least one of said surfaces at' I an acute angle. r r

5. An apparatus according to claim, 2 wherein said liquid guide is annular and tapers downwardly toward at i least one of said surfaces. w

2/1940 .Mathescn 204-412

Claims

1. IN AN APPARATUS FOR TREATING FLUIDS IN A CORONA DISCHARGE INCLUDING A VERTICALLY DISPOSED HOLLOW TUBE DEFINING A VERTICAL CYLINDRICAL SPACE AND COMPRISING A FIRST ELECTODE, A CYLINDRICAL MEMBER CONCENTRICALLY DISPOSED WITHIN SAID TUBE TO DEFINE AN ANNULAR SPACE RADIALLY BETWEEN THE INTERIOR SURFACE OF SAID TUBE AND THE EXTERIOR SURFACE OF SAID MEMBER, SAID MEMBER COMPRISING A SECOND ELECTRODE, MEANS FOR PROVIDING AN INSULATING DIELECTRIC BARRIER BETWEEN AT LEAST ONE OF SAID ELECTRODES AND SAID ANNULAR SPACE, MEANS INCLUDING SAID ELECTODES DISPOSED AXIALLY ALONG A SUBSTANTIAL PORTION OF SAID SPACE FOR EFFECTING A CORONA DISCHARGE ACROSS SAID ANNULAR SPACE AND THEREBY DEFINING A REACTION ZONE, AT LEAST ONE MEANS FOR SUPPLYING FLUID THROUGH SAID REACTION ZONE AND MEANS FOR RECEIVING FLUID FROM SAID REACTION ZONE, THE IMPROVEMENT WHEREIN SAID FLUID SUPPLY MEANS INCLUDES MEANS FOR DIRECTING A LIQUID INTO SAID SPACE ABOVE SAID REACTION ZONE TO FORM SUBSTANTIALLY ALL OF SAID LIQUID INTO A DESCENDING CONTINUOUS FILM CURTAIN FLOWING OVER AT LEAST ONE OF SAID SURFACES AND WHEREIN SAID ANNULAR SPACE IS SUBSTANTIALLY FREE OF LIQUID DROPLETS.