US3309300A - Method for the production of ozone using a plasma jet - Google Patents

Description

March 14, 1967 A. v. GROSSE ETAL METHOD FOR THE PRODUCTION OF OZONE USING A PLASMA JET Filed Aug. 21, 1963 5 Sheets-Sheet l 5 5 R Y mww M m a W WW A Mi K #3 March 14, 1967 A. v. GROSSE ETAL 3,309,300

METHOD FOR THE PRODUCTION OF OZONE USING A PLASMA JET Filed Aug. 21, 1963 5 Sheets-Sheet 2 BQ/ u/ /Wm rAi ATTORNEYS March M, 1%? A. v. GROSSE ETAL 3,3093% METHOD FOR THE PRODUCTION OF OZONE USING A PLASMA JET Filed Aug. 21, 1963 3 Sheets-Sheet 5 so no I30 I50 K CAL/MOLEHQ uouto OXYGEN 30o COLLECTION\ GRAMS/HR [00 WW M, a t

I eAsEous OXYGEN CIOLLEOTION LITERS/NHN O (BASED ON GAS) INVENTORS A firm M Q$$ am? 3 M's BY W, M Y

ATTORNEYS United States Patent f 3,309,300 METHOD FOR THE PRODUCTION OF OZONE USING A PLASMA JET Aristid V. Grosse, Haverford, and Charles S. Stokes, Willow Grove, Pa, assignors to The Welsbach Corporation, Phi adelphia, Pa., a corporation of Delaware Filed Aug. 21, 1963, Ser. No. 303,550 12 Claims. (Cl. 204176) This invention relates generally to the production of ozone and more particularly to a method and apparatus for the production of ozone using a plasma jet.

If an explosive gas or an explosive mixture of gases is subjected to conditions which will initiate a flame, an explosion can develop in the body of the gas if the flame can be maintained. 'If the flame can be quenched in a short distance, no combustion occurs and therefore no explosion can take place. The distance in which the flame must be quenched to prevent explosion is known as the quenching distance or quenching diameter. This varies with the particular gas or gas mixture and temperature and pressure conditions.

It has been known that ozone can be held in a vessel in high concentrations or in substantially pure form where material has been added to an explosive gas or explosive mixture of gases which are subjected to conditions which will initiate a flame if the flame is quenched in a short distance. We have found that ozone may be synthesized by a new method involving the use of an inert gas plasma jet quenched by liquid oxygen.

Accordingly, it is an object. of this invention to provide an improved method and apparatus for synthesizing ozone.

Another object of this invention is to provide an improved method and apparatus for synthesizing ozone using a plasma jet.

A further object of this invention is to provide an improved method and apparatus for synthesizing ozone which is simple in operation and economical in construction.

In carrying out this invention in one form thereof, an inert carrier gas is subject to an electrical discharge in a plasma generator, the inert gas being used as a plasma carrier. The high thermal energy produced by the inert gas are both evaporates and dissociates liquid oxygen which is fed into the arc. The dissociated atoms then either recombine with themselves or react with oxygen molecules to produce ozone. The arc is quenched by excess liquid oxygen which is not dissociated. The solution of ozone and liquid oxygen is passed to a collection chamber from which the ozone may be recovered by a conventional recovery process.

In another feature of this invention, an inert carrier gas is subject to an electrical discharge in a plasma generator. Oxygen is then subject to the influence of the plasma jet and the arc discharge. Liquid oxygen is fed into the arc and partly dissociated, the excess liquid oxygen causing the arc to be quenched. The dissociated atoms either recombine with themselves or react with oxygen molecules to form ozone. The solution of ozone and liquid oxygen is passed to a liquid collection chamber while the gaseous products of the arc discharge, including ozone, are passed to a gas collection chamber. The ozone may be recovered by a conventional recovery process.

Although it is not known with theoretical exactness whether the production of ozone arises from the action of high energy atoms, ions or radiation, experimental results teach that ozone may be successfully recovered by quenching the arc discharge of a plasma generator with liquid oxygen. It is theorized that the ozone is produced by the high velocity helium atoms, excited atoms or by Patented Mar. 14, 1967 protons. The ozone yields may be controlled by varying the power level or by varying the liquid oxygen flow.

While the specification concludes with claims which particularly point out and distinctly claim the subject matter regarding the invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings:

FIGURE 1 is a diagrammatic illustration of the apparatus employed in a production of ozone by the use of a plasma jet;

FIGURE 2 is a fragmentary View, partly in section, of the apparatus employed particularly illustrating the plasma generator;

FIGURE 3 is a fragmentary view, partly in section, of apparatus employed particularly showing the oxygen feed ring and liquid oxygen feed ring;

FIGURE 4 is a cross-sectional view of the oxygen feed ring taken along line 4-4 of FIGURE 3;

FIGURE 5 is a cross-sectional view of the liquid oxygen feed ring taken along line 5-5 of FIGURE 3;

FIGURE 6 is a cross-sectional view of the inert gas distributor ring taken along line 66 of'FIGUR-E 2;

'FIGURES 7 and 8 are graphical illustrations of the results of sample runs conducted for the production of ozone in accordance with the principles of this invention.

Referring now to FIGURE 1, there is shown a diagrammatic illustration of the apparatus 1t) employed in the production of ozone by the use of a plasma jet.

A coaxial jet-electrode plasma generator 11, having an inert carrier gas input 12,'is utilized for generation of the arc discharge and plasma. A suitable power source 13 which may have an output of, for example, 0 to volts at O to 750 amperes, is connected across the electrodes of the plasma generator. The arc may be initiated by means of a high frequency starter (not shown) in the power source 13, or by shorting out the electrode with a shorting rod.

The inert gas plasma carrier, which may be helium or argon, serves to carry the generated plasma past an oxygen feed ring 14 through which oxygen is introduced into the area of the arc and path of the plasma. Aflixed directly below the oxygen feed ring is a liquid oxygen feed ring 15 to which a suitable source of liquid oxygen is connected. The liquid oxygen both evaporates and partly dissociates due to the high thermal energy pro duced by the helium arc. The dissociated atoms then recombine either with themselves or react with oxygen molecules pro-duced. The arc is quenched by the ex cess liquid oxygen being fed to ring 15 and the ozone is translated or carried out of the reaction zone by the excess liquid oxygen to the ozone recovery system 16.

The ozone recovery system comprises a water-cooled reaction chamber 17, a Dewar adapter ring 18 and a Dewar 19 for collecting the ozone-liquid oxygen solution. Suitable connection is made to a gas storage chamber 29 for recovery of the ozone-containing gases. .The ozone in the liquid oxygen solution and in the gases may be recovered by any known process, such as, for example, absorption by silica gel.

Plasma generators, in general, are known in the art and have been found suitable for a variety of uses. Such plasma generators generally provide an electric are which is condensed or constricted into a smaller circular crosssection than would ordinarily exist in an open arc-type device. This construction generates a very high temperature (l0,000 K.) so that a superheated plasma working fluid may be ejected through a suitable nozzle structure and used in any desired manner. The mass flow through the nozzle structure and the composition of the plasma determines the use to which the plasma genera- 3 tor is put. Plasma generators have been used elfectively for cutting, welding, metal spraying and chemical processing. In the chemical processing area, plasma generators have opened the possibility for the production of new alloys and compositions nad processing of less commonly used materials.

Referring to FIGURE 2, there is illustrated a coaxial jet-electrode plasma generator for use in this invention. Plasma generator 11 comprises a high-pressure, cylindrical housing having a water-cooled cathode assembly and a water-cooled anode assembly 26 separated by an insulative nylon cathode enclosure member 27.

Cathode assembly 25 comprises a hollow cathode support 30 having a cover plate 32. The inner walls 33 and 34 of the cathode support 30 and cover plate 32, respectively, define a cathode cooling chamber 35 provided with suitable inlet and outlet openings (not shown) for connecting the cooling chamber 35 to a suitable source of coolant, such as water. The outer surface of cathode support 35 is provided, along its central axis, with a hollow cylindrical extension 36 for supporting the thoriated tungsten cathode electrode 37 in a manner such that the tip 38 of cathode 37 protrudes beyond the cylindrical extension 36 and coaxially with the anode assembly 26.

The anode assembly 26 comprises a hollow anode support 40 within which is mounted a hollow copper anode electrode 41. The inner wall 42 of anode 41 converges from the upper end of the anode 41 towards its vertical axis forming, thereby, a nozzle-like arc chamber 39 which meets at its apex with the cylindrical passage 43 formed by the inner wall 42 of the lower end of anode 41. The outer wall 44 of anode 41 and the inner wall 45 of anode support 40 define the anode cooling chamber 46 having an inlet 47 and outlet 48 con nected to a suitable source of coolant.

The cathode and anode assemblies 25 and 26, respectively, are rigidly secured by a threaded cover member or collar 49 in threaded engagement with anode support 40. To this end, nylon enclosure member 27 is provided with a threaded opening 50 and flange 51 which seats on the top wall surface of anode support 40. Suitable fastening means, such as screw 52, serves to fasten the nylon enclosure member 27 around cathode support and cover member 49 maintains the units tightly secured by the force applied on flange 51 of nylon enclosure member 27. For properly sealing the mating surfaces of the various component parts, 0 rings 53 are utilized in a manner well known in the art.

To effectively distribute the flow of the carrier gas in the arc chamber 39, a gas distributor plate 60, more clearly shown in FIGURE 6, is mounted around the cylindrical extension 36 of the cathode support 30. The outer wall of cathode support 30 is recessed in the area directly adjacent the extension 36 to provide a chamber 59 in which the carrier gas may circulate before passing through openings 61 of the distributor plate. Conduit 62, which is connected to a suitable source of inert gas, such as helium or argon, extends through openings 63 and 64 in cover plate 32 and cathode support 3%), respectively, and is terminated flush with the recessed walls of cathode support 30.

In the operation of the plasma generator 11, prior to striking the arc, the arc chamber 39 is pressurized by injecting through the conduit 62 an inert gas, such as helium or argon. The gas will in turn flow over distributing plate 60, through openings 61 and into the arc chamber 39. The distributor plate 60 causes the gas to flow evenly around the cathode 37 and parallel to its axis. Anode 41 forms a nozzle with a converging throat which concentrates the fiow of inert gas past the tip 38 of the cathode 37 in th area of the arc discharge between the coacting anode and cathode electrodes 41 and 37, respectively.

For generating the arc discharge, the cathode electrode 37 and anode electrode 41 of the plasma generator 11 4% are provided with suitable terminals (not shown) which are connected to a conventional low voltage, high current power source which may be either A.C. or DC. as desired. In any manner known in the art, the output of the power source 13 is made variable to provide a variable power level input to the plasma generator.

Starting the arc may be accomplished by means of a high frequency starter in the power source 13 or by shorting the electrodes with a graphite rod (not shown). If desirable, the arc may be initiated by placing a small piece of fuse wire between the anode 41 and cathode 37. This wire will melt when power is applied and the arc will continue.

After the arc is initiated, the arc discharge will be maintained between the cathode 37 and the anode 41. The tip 3d of the cathode 37 extends slightly into the cylindrical passage 43 formed by the inner wall 42 of anode 41 so that the arc will be formed in the constricted chamber. The concentrated high pressure inert gas flow past tip 38 of the cathode 37 will cause the arc to extend downwardly through the passage 43 and through the central openings 68, 69 of the oxygen feed ring 14 and the liquid oxygen feed ring 15, respectively. The anode nozzle structure causes the plasma produced to exit through the oxygen and liquid oxygen feed rings 14 and 15, respectively.

The coolant fluids in chambers 35 and 45 of cathode 37 and anode 41, respectively, serve to maintain the average temperature of the component parts of the plasma generator 11 below the melting point of the materials from which they are constructed. These parts may be constructed from any suitable good heat conductive material and electrically conductive material, where electrical continuity is desired. For example, the cathode 37 is of thoriated tungsten While the cathode assembly 25 is made of copper. Anode 41 may likewise be made of copper, while the anode support 49 and collar 49 may be made of stainless steel.

Referring now to FIGURES 3 and 5, there is shown in detail the oxygen feed ring 14 and the liquid oxygen feed ring 15, which are mounted between the plasma generator 11 and the water-cooled reaction chamber 17 of the ozone recovery system 16 by suitable fastening means extending through the openings 72. Affixed within the oxygen feed ring 14 is a stainless steel insert or channel member 73 having a central bore for defining the opening or passage 68 extending along the vertical axis of the feed ring 14. Suitable inlet and outlet openings 74 and 75 are provided along the horizontal axis of the oxygen feed ring 14. Inlet coolant conduit 76 is arranged within inlet 74, while an outlet conduit 77 is arranged within inlet 75. The inlet and outlet conduits 76 and 77 are connected to a suitable source of coolant medium such as, for example, water for providing coolant within the chamber 80. The mating surfaces of insert 73 and liquid oxygen feed ring 14 are sealed by means of 0 rings 81 in a manner well known in the art.

Oxygen is introduced into the chamber 63 by means of conduit 82 arranged to be received within aligned openin s 83 and $4 extending along the horizontal axis of the oxygen feed ring 14 and insert 73, respectively. One end of opening 83 is threaded and receives a fitting 85 through which the conduit 82 is connected. 0 ring 86 serves to seal the fitting 85 within the opening 84 insert 73.

For purposes of rapid quenching, the liquid oxygen feed ring 15 is arranged adjacent and below the oxygen feed ring 14 and includes means to be connected to a suitable source of liquid oxygen. To this end, there is provided along the horizontal axis of liquid oxygen feed ring 15, an opening 37 within which is mounted conduit 88. Mounted within the central chamber of the liquid oxygen feed ring 15 is a stainless steel liquid oxygen distributor insert 39 which divides the chamber into an outer passage and an inner passage. Liquid oxygen entering through conduit 88 enters the outer passage and circulates around the insert entering the central chamber through a plurality of openings 90 provided along the periphery of the insert 89. The number of openings 90 may be varied as desired dependent upon the volume of liquid oxygen flow.

The liquid oxygen entering the central chamber is partly dissociated by the arc. The dissociated atoms then recombine either with themselves or react with oxygen molecules to produce ozone. The are is quenched by the excess liquid oxygen and the resultant reaction products then are passed to the ozone recovery system 16 through the water-cooled reaction chamber 17. The water-cooled reaction chamber 17 includes a central conduit 91 having an outer jacket 92 which is provided with a suitable coolant inlet and outlet 93 and 94, respectively, to permit cooling of the reaction products as they are passed to the recovery system.

It should be readily appreciated that the various fluid conduits may be arranged with suitable control valves in a manner well known in the art to control the flow of the fluid into the system so as to provide various levels of oxygen flow, liquid oxygen flow, or coolant flow.

We have found that when subjecting oxygen to the arc the results of the exit gas stream analysis. It was found that in the second run where the liquid ozone-oxygen collection Dewar was not pre-cooled, the ozone volume by percent was considerably increased.

TABLE 2.OZO; TE FORMATION USING LIQUID OXYGEN (LOX) QUENCH EFFLUENT GAS STREAM ANALYSIS Helium Liquid Are Characteristics Ozone, Flow, Oxygen Vol. liters/min Flow, Percent liters/min. Volts Amps. Kw.

1 The liquid ozone-oxygen collection Dewar was not preeooled with liquid oxygen.

The production of ozone by the inert gas plasma jet may be varied by varying the power level, varying the liquid oxygen (LOX) flow or by varying both the power level and the liquid oxygen flow. Table 3 shows the effects on the production of ozone in the helium plasma jet with varying power level.

TABLE 3 Are Characteristics Mtge- 26 28 28.5 29 29 29.5 28 27.5 28.8 Amperage 340 360 350 320 310 280 320 315 300 Kilcwatts" 8.85 10.05 10.0 9.3 9 8.3 9.95 8.65 8.65 Helium flow, l./n1in 12.2 14.1 15.2 15.2 .152 15.2 18.0 18.9 21.7 Keal/Moie He 141 138 128 119 115 106 97 88 76 Liquid Oxygen flow, l./min- 3 3 3 3 3 3 3 3 Ozone Yield:

Weight percent 0.24 0.20 0.29 0.46 0.38 0.23 0.35 0.23 0.23 Lbs/hr. collected 0.78 0.49 0.77 1.13 1.17 0.57 1.07 0.62 0.61 Lbs/hr. liquid oxygen fiow 1.08 0.00 1.30 2.06 1.70 1.06 1.58 1.06 1.05

discharge of aninert gas plasma jet and rapidly quenching the arc discharge with liquid oxygen, ozone is produced. The liquid oxygen is allowed to flow fast enough through the liquid oxygen feed ring 15 so as to provide an excess of liquid oxygen which is not dissociated for quenching the arc and carrying the ozone produced to a Dewar fiask 19 or other suitable collection means at the bottom of the reaction chamber 17. The gaseous products may becollected in a separate gas storage chamber 20, and the ozone may be recovered from the solution and from the gas by conventional processes.

If desired, the gaseous oxygen feed ring 14 may be removed, and it has been found that there is no effect on the ozone produced in solution. The following table summarizes the results of several runs using the apparatus hereinbefore described. The determination of ozone content of the liquid oxygen-ozone mixture was made by the evaporation method. The vapor pressure and boiling point of a concentrated sample were identical with those of ozone.

The results of Table 3 are illustrated graphically in FIGURE 7 which is a plot of ozone yields in lbs/hr. vs. power level. Power level and helium flow have been combined as one variable as follows:

kw. to arc l434 KcaL/min. kw. Helium flow l./min. X 00907 mole/1.

(2) Power 1eve1=Keal./mo1e He (1) Power level TABLE 1.OZONE FORMATION USING LIQUID OXYGEN (LOX) QUENCH 1 Oxygen feed ring removed. 2 Very small.

A series of runs were made to analyze the exit gas stream, that is, to determine the amount of ozone in the gas from the plasma jet collected beyond the liquid ozoneon the total liquid oxygen (LOX) flow fed into the plasma jet from the plasma generator. I

As hereinbefore mentoned, the amount of ozone prooxygen recovery system. The following table summarizes duced can also be varied by maintaining the power level constant and varying the liquid oxygen (LOX) flow. Although the weight by percent of ozone produced varies appreciably with liquid oxygen (LOX) flow, the production of ozone in lbs./ hr. reaches a maximum with a liquid oxygen (LOX) how of three liters per minute (l./min.) and a. power level of between 110 to 120 KcaL/mole He. Table 4 illustrates the eitect on ozone yield of varying the li uid oxygen (LOX) tlow at a power level of 111 KcaL/mole He.

TABLE 4 Are Characteristics:

Voltage Amperage 340 340 345 345 Kilowatts.

Helium flow, 1 Kcal/Molc He.

Liquid Oxygen flow, liters/min 1. 25 2 4 5 Ozone Yield:

Weight Percent 0. 23 0. 23 0.21 O. 20 Lbs/hr. collected 0. 35 0. 63 1. O4 1. O1 Lbs/hr. liquid oxygen flow O. 44 0. 7 1. 24 1. 35

TABLE 5 Power Helium Oxygen Vol. Ozone Run (kw.) Flow F w Percent Yield (L/min.) (l./min.) O (g./l1r.)

10.7 15. 2 137 0. 001 O. '28 10. 5 l5. 2 191 0.011 2. 5 1 10. 6 15. 2 216 0. 020 5. 26 10.7 15. 2 218 0. 025 G. 42 10. 1 l5. 2 268 0. 045 15. 10. 0 l5. 2 340 0. 057 22. 0 10. 15. 2 520 0. 059 36. 3 10. 5 15. 2 585 0. 008 48. 6 10. 5 15. 2 558 0. 078 49. 7 10. 5 15. 2 185 0. 085 48. 3

Referring to FIGURE 8, it should be noted that the maximum gas flow obtainable before liquid oxygen started to flow from the water-cooled chamber was 600 liters/ min. This maximum fiow leaves a gap between the gas and liquid experiments of some 500 liters/min. (gas flow). Also, the slope of the gas-production curve deviates from the extension of the slope of the liquid oxygen flow curve (expressed in gas flow units, liters/ min.). This is theorized to be due to the loss of oxygen by evaporation in the liquid experiments. The ozone may be recovered from the collection chamber 19 by any suitable process, such as adsorption on silica gel or adsorption in a suitable solvent.

Although particular embodiments of the subject invention have been described, many modifications may be made, and it is intended by theappended claims to cover all such modifications which fall within the true spirit and scope of the invention.

What is claimed is:

1. A method of producing ozone in a solution of liquid oxygen comprising the steps of: subjecting a flow of inert gas to an arc discharge, introducing liquid oxygen into said arc discharge whereby said liquid oxygen is partly dissociated, quenching the are discharge with the excess liquid oxygen and passing the reaction products of said are discharge to a storage chamber.

2. A method of producing ozone as set forth in claim 1 wherein said inert gas is helium.

3. A method of producing ozone as set forth in claim 1 wherein said inert gas is argon.

A method of producing ozone in a solution of liquid oxygen comprising the steps of: subjecting a flow of inert gas under pressure to an arc discharge, subjecting a fiow of liquid oxygen to said are discharge for partly dissociating said liquid oxygen, rapidly quenching the arc discharge with the excess liquid oxygen, and rapidly passing the products of said are discharge to a storage chamber.

5. A method of producing ozone comprising the steps of: subjecting a flow of inert gas to an arc discharge, introducing gaseous oxygen in the vicinity of said are discharge, introducing liquid oxygen into said arc discharge for partly dissociating said liquid oxygen, quenching the arc discharge with the excess liquid oxygen and passing the products of said arc discharge to a storage chamber.

6. A method of producing ozone as set forth in claim 5 wherein said inert gas is helium.

7. A method of producing ozone as set forth in claim 5 wherein said inert gas is argon.

8. A method of producing ozone comprising the steps of: subjecting a flow of inert gas to an arc discharge for producing a high energy plasma, introducing gaseous oxygen in the vicinity of said plasma and said are discharge, introducing liquid oxygen into said plasma and said are discharge whereby said liquid oxygen is partly dissociated, quenching the arc discharge with the excess liquid oxygen, reacting the dissociated atoms of the liquid oxygen with themselves and oxygen molecules, and passing the excess liquid oxygen and reaction products in solution to a first storage chamber, and passing the gaseous reaction products to a second storage chamher.

9. A method of producing ozone in a solution of liquid oxygen comprising the steps of: subjecting a flow of inert gas in a range of 10 to 25 liters/min. to an arc discharge capable of producing a high energy plasma at a power level in a range of to 150 Kcal./mole gas, rapidly quenching the arc discharge with the liquid oxygen flowing at a rate within the range of 1 to 6 liters/min. and rapidly passing the reaction products to a storage chamber.

10. The method of producing ozone as set forth in claim 9 wherein said inert gas is helium.

11. The method of producing ozone as set forth in claim 9 wherein said inert gas is argon.

12. The method of producing ozone as set forth in claim 9 wherein said power level is within the range of to KcaL/mole and said liquid oxygen flow is approximately 3 liters/min.

References Cited by the Examiner UNITED STATES PATENTS Re. 25,218 8/1962 Schallus et al. 204178 906,468 12/1908 Steynis 204176 1,074,106 9/1913 Dumars 204l76 2,271,895 2/1942 Hartman 204l76 2,992,540 7/1961 Grosse et al. 62-48 3,062,730 11/1962 Ruehrwein 204176 3,090,745 5/1963 Berghavs 2043l2 JOHN H. MACK, Primary Examiner. R, K. MiHALEK, Assistant Examiner,

Claims (1)

1. A METHOD OF PRODUCING OZONE IN A SOLUTION OF LIQUID OXYGEN COMPRISING THE STEPS OF: SUBJECTING A FLOW OF INERT GAS TO AN ARC DISCHARGE, INTRODUCING LIQUID OXYGEN INTO SAID ARC DISCHARGE WHEREBY SAID LIQUID OXYGEN IS PARTLY DISSOCIATED, QUENCHING THE ARC DISCHARGE WITH THE EXCESS LIQUID OXYGEN AND PASSING THE REACTION PRODUCTS OF SAID ARC DISCHARGE TO A STORAGE CHAMBER.

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