DIELECTRIC BARRIER DISCHARGE PLASMA SYSTEM AND METHOD FOR IN-SITU HYDROGEN PEROXIDE PRODUCTION

Abstract

The disclosure deals with system/apparatus and corresponding and/or associated method for an open plasma reactor assembly provided to study pulsed reactive species produced in a dielectric barrier discharge (DBD) in He—H.sub.2O and He—H.sub.2O—O.sub.2 mixture in atmospheric conditions using photo fragmentation laser-induced fluorescence (PFLIF). The objective is to detect and quantify hydroxyl radicals and hydrogen peroxide produced in the DBD. An OH laser-induced fluorescence (LIF) signal is acquired from LIF (using 282 nm laser) whereas LIF from OH generated from H.sub.2O.sub.2 is measured by from the PFLIF signal (using 213 nm+ 282 nm lasers). A known concentration of H.sub.2O.sub.2 in He serves to calibrate for H.sub.2O.sub.2 while the OH is calibrated with a chemical model. For both gas mixtures, there is both OH and H.sub.2O.sub.2 production in the discharge, while the H.sub.2O.sub.2 concentration was noticeably increased for the added O.sub.2 case.

Claims

1. A method for in-situ hydrogen peroxide production from water vapor and electricity, comprising: providing an open plasma reactor assembly having a feed end and a plasma reaction end; introducing a flow of a mixture of He and water (H.sub.2O) into the assembly feed end; and using high voltage pulses with the open plasma reactor assembly to produce hydrogen peroxide (H.sub.2O.sub.2) in a plasma discharge at the plasma reaction end.

2. The method according to claim 1, wherein both OH and H.sub.2O.sub.2 are produced in the discharge.

3. The method according to claim 1, wherein the open plasma reactor assembly includes an electrode configured for integration with a dielectric barrier plasma discharge driven by high voltage pulses.

4. The method according to claim 3, wherein the electrode comprises a mechano-chemical electrode comprising a powered copper cylinder housed concentrically in a compression sleeve, and receiving a mica cylinder in the copper cylinder, and the electrode further forms a concentric channel formed therethrough from the feed end to the plasma reaction end, to receive through the concentric channel the flow of the He—H.sub.2O mixture.

5. The method according to claim 1, further comprising: introducing a flow of O.sub.2 with the mixture of He and water (H.sub.2O) into the assembly feed end; and wherein both OH and H.sub.2O.sub.2 are produced in the discharge.

6. The method according to claim 5, further comprising: detecting and quantifying hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) produced in the discharge; and wherein average OH concentration in the discharge is at least about 0.5 ppm and the concentration of H.sub.2O.sub.2 in the discharge is at least about 20 ppm.

7. The method according to claim 2, further comprising detecting and quantifying hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) produced in the discharge.

8. The method according to claim 7, further comprising using photo fragmentation laser-induced fluorescence (PFLIF) associated with the assembly plasma reaction end for detecting and quantifying hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) produced in the discharge.

9. The method according to claim 8, wherein the photo fragmentation laser-induced fluorescence (PFLIF) includes use of a photo dissociation laser beam and an excitation laser beam.

10. The method according to claim 7, further comprising calibrating the discharge production for OH and H.sub.2O.sub.2.

11. The method according to claim 10, wherein calibrating for H.sub.2O.sub.2 includes using a known concentration of H.sub.2O.sub.2 in He to calibrate for H.sub.2O.sub.2.

12. The method according to claim 10, wherein calibrating for OH includes using a chemical model.

13. Methodology for the production of reactive oxidizing species in a plasma discharge, comprising generating nonthermal plasma (NTP) discharges in the presence of water and He for in-situ production of hydrogen peroxide (H.sub.2O.sub.2) in the NTP discharge.

14. The methodology according to claim 13, further comprising using photo fragmentation laser-induced fluorescence (PFLIF) for detecting H.sub.2O.sub.2 in the NTP discharge.

15. The methodology according to claim 13, further comprising providing an open plasma reactor assembly having an electrode with a feed end and a plasma reaction end, and configured for integration with a dielectric barrier plasma discharge driven by high voltage pulses; introducing a flow of a mixture of He and water (H.sub.2O) into the assembly feed end; and using high voltage pulses with the open plasma reactor assembly to produce hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) in a plasma discharge at the plasma reaction end.

16. The methodology according to claim 15, wherein the electrode comprises a powered copper cylinder housed concentrically in a compression sleeve, and with a quartz dielectric fused to the copper adjacent the plasma reaction end, and the electrode further forms a concentric channel formed therethrough from the feed end to the plasma reaction end, to receive through the concentric channel the flow of the He—H.sub.2O mixture.

17. The methodology according to claim 16, further comprising: detecting and quantifying hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) produced in the discharge; and wherein average OH concentration in the discharge is at least about 0.5 ppm and the concentration of H.sub.2O.sub.2 in the discharge is at least about 20 ppm.

18. The methodology according to claim 17, further comprising calibrating the discharge production for OH and H.sub.2O.sub.2.

19. A system for in-situ hydrogen peroxide production from water vapor and electricity, comprising: an open plasma reactor assembly having a powered electrode having a feed end and a plasma reaction end; a flow of a mixture of He and water (H.sub.2O) controllably fed into the assembly feed end; and a pulser for selectively providing high voltage pulses to the powered electrode for producing hydrogen peroxide (H.sub.2O.sub.2) in a plasma discharge at the electrode plasma reaction end.

20. The system according to claim 19, wherein high voltage pulses provided to the powered electrode further produces OH in the plasma discharge.

21. The system according to claim 19, wherein the electrode comprises a powered copper cylinder housed concentrically in a compression sleeve, and with a quartz dielectric fused to the copper adjacent the plasma reaction end, and the electrode further forms a concentric channel formed therethrough from the feed end to the plasma reaction end, to receive through the concentric channel the flow of the He—H2O mixture.

22. The system according to claim 19, further comprising: a flow of O.sub.2 combined with the mixture of He and water (H.sub.2O) into the assembly feed end; and wherein both OH and H.sub.2O.sub.2 are produced in the plasma discharge, average OH concentration in the discharge is at least about 0.5 ppm, and concentration of H.sub.2O.sub.2 in the discharge is at least about 20 ppm.

23. The system according to claim 20, further comprising: laser spectrometer diagnostics for detecting and quantifying hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) produced in the discharge.

24. The system according to claim 23, wherein said laser spectrometer diagnostics further comprises photo fragmentation laser-induced fluorescence (PFLIF) lasers for detecting and quantifying hydroxyl radicals (OH) and hydrogen peroxide (H.sub.2O.sub.2) produced in the discharge.

25. The system according to claim 24, wherein the photo fragmentation laser-induced fluorescence (PFLIF) lasers includes a photo dissociation laser beam and an excitation laser beam.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0027] A full and enabling disclosure of the present subject matter, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures in which:

[0028] FIG. 1(a) illustrates a schematic of a presently disclosed experimental setup for working with the presently disclosed production subject matter;

[0029] FIGS. 1(b), 1(c), and 1(d) illustrate side, cross-sectional, and bottom detailed configuration views, respectively, of an exemplary electrode for use in the presently disclosed subject matter;

[0030] FIG. 2 illustrates an exemplary laser diagnostics setup;

[0031] FIGS. 3(a) and 3(b) comprise exemplar discharge photographs of dielectric barrier discharge (DBD) (i.e., discharge photographs of He—H2O discharge) in humid helium;

[0032] FIGS. 4(a) and 4(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 20000 .Math.s;

[0033] FIGS. 4(c) and 4(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 20000 .Math.s;

[0034] FIGS. 5(a) and 5(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 20000 .Math.s;

[0035] FIGS. 5(c) and 5(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 20000 .Math.s;

[0036] FIGS. 6(a) and 6(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 10 ms;

[0037] FIGS. 6(c) and 6(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 10 ms;

[0038] FIGS. 7(a) and 7(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 10 ms;

[0039] FIGS. 7(c) and 7(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 10 ms;

[0040] FIG. 8(a) illustrates discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for pure He for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s;

[0041] FIG. 8(b) illustrates discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for pure He for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s;

[0042] FIG. 9(a) illustrates discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for He+5%O.sub.2 for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s;

[0043] FIG. 9(b) illustrates discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for He+5%O.sub.2 for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s;

[0044] FIG. 10(a) illustrates discharge photographic graph results for pure He at first through fifth pulses, respectively; and

[0045] FIG. 10(b) illustrates discharge photographic graph results for He+5%O.sub.2 at first through fifth pulses, respectively.

[0046] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features, elements, or steps of the presently disclosed subject matter.

DETAILED DESCRIPTION OF THE PRESENTLY DISCLOSED SUBJECT MATTER

[0047] Reference will now be made in detail to various embodiments of the disclosed subject matter, one or more examples of which are set forth below. Each embodiment is provided by way of explanation of the subject matter, not limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present disclosure without departing from the scope or spirit of the subject matter. For instance, features illustrated or described as part of one embodiment, may be used in another embodiment to yield a still further embodiment.

[0048] In general, the present disclosure is directed to system/apparatus and corresponding and/or associated method for an open plasma reactor assembly provided to study pulsed reactive species produced in a dielectric barrier discharge (DBD) in He—H.sub.2O and He—H.sub.2O—O.sub.2 mixture in atmospheric conditions using photo fragmentation laser-induced fluorescence (PFLIF). An objective is to detect and quantify hydroxyl radicals and hydrogen peroxide produced in the dielectric barrier discharge (DBD). An OH laser-induced fluorescence (LIF) signal is acquired from LIF (using 282 nm laser) whereas LIF from OH generated from H.sub.2O.sub.2 is measured by from the PFLIF signal (using 213 nm+ 282 nm lasers). A known concentration of H.sub.2O.sub.2 in He serves to calibrate for H.sub.2O.sub.2 while the OH is calibrated with a chemical model. For both gas mixtures, there is both OH and H.sub.2O.sub.2 production in the discharge, while the H.sub.2O.sub.2 concentration was noticeably increased for the added O.sub.2 case.

[0049] Per the presently disclosed subject matter, we studied the generation of OH and H.sub.2O.sub.2 from atmospheric pressure dielectric barrier discharge in two different carrier gas mixtures: He— H.sub.2O and He—H.sub.2O—O.sub.2 mixtures at the highest attainable water vapor concentration at 293 K. The densities of H.sub.2O.sub.2 and OH were measured using PF-LIF and LIF respectively. He is used as the carrier gas since it has lesser reaction pathways that involve OH kinetics that is expected to facilitate modeling the discharge [11] and being the only monatomic inert gas, possesses lower quenching ability than other polyatomic inert gases. The H.sub.2O.sub.2 concentration was calibrated by flowing a He—H.sub.2O.sub.2 mixture. The OH concentration was calibrated from a chemical model. The results from these experiments will serve as an effective measurement for the in-situ production of active species from high water vapor concentration by the designed electrode assembly. It will also provide data for model validation for similar discharge configurations, which are not readily available in the literature.

Experimental Setup

[0050] FIG. 1(a) illustrates a schematic of a presently disclosed experimental setup for working with the presently disclosed production subject matter. FIGS. 1(b), 1(c), and 1(d) illustrate side, cross-sectional, and bottom detailed configuration views, respectively, of an electrode for use in the presently disclosed subject matter.

[0051] With reference to the schematic of the experimental setup as shown in FIG. 1(a), He gas is continuously passed through an MKS (MKS Instruments) mass flow controller at 500 sccm (standard cubic centimeter per minute) following a bubbler containing filtered water in a water bath (not shown here) at 298 degrees K. The resultant He—H.sub.2O mixture flows into the top of the electrode (as shown) through the center and forms a stagnation plane in the 4 mm interelectrode spacing between the quartz dielectric (disc on the bottom of the electrode) and a grounded SS (stainless steel) plate (not shown here). The water vapor concentration is calculated by the assumption that the He—H.sub.2O mixture flowing out of the electrode nozzle in the bottom is saturated with water vapor at 298 degrees K. An Eagle Harbor Technologies Model No. NSP-20-30F nanosecond pulser, operating at 1 kHz, is used to provide high voltage pulses to the powered electrode. The frequency of the burst mode is controlled by a function generator synchronized with a delay generator, as illustrated per FIG. 1(a). The voltage and current profiles may be recorded such as with a North Star PVM-4 high voltage probe and Pearson 6015 current monitor.

[0052] The detailed configuration of the powered electrode is shown in FIG. 1(b). It consists of a powered copper cylinder housed concentrically in a Delrin cylindrical block (with Delrin sleeves comprising known compression sleeves, a form of plastic O-rings used when connecting PEX or other plastic pipe to a compression fitting). A tapered mica cylinder is drilled into the copper to induce structural rigidity as well as discharge leaking from the sides of the copper. A concentric channel is drilled into the mica as well to flow the He—H.sub.2O mixture. Finally, a quartz dielectric with a center hole is fused to the copper and Delrin using an adhesive with high dielectric strength.

Laser Diagnostics Setup

[0053] FIG. 2 illustrates an exemplary laser diagnostics setup, in particular illustrating an exemplary laser generation system for Laser-induced fluorescence (LIF) and photofragmentation laser induced fluorescence (PFLIF) diagnostics.

[0054] More specifically, per the exemplary arrangement illustrated, the 5.sup.th harmonic from Nd:YAG laser (Quanta Ray Pro) was used to generate the photo dissociation beam (213 nm) to fragment H.sub.2O.sub.2 to OH radicals. A tuned frequency-doubled dye laser (Sirah Precision Scan), with Rhodamine 6 G dye, pumped by an Nd:YAG laser (Quanta Ray Pro) was used to generate an excitation beam (282.594 nm), which, induced fluorescence from OH at 315 nm. The benefits of using this transition are mentioned in [13]. To measure OH generated solely from the DBD, the 213 nm beam was blocked with a beam dump. The laser pulses were produced at a frequency of 10 Hz. As generally understood regarding Nd:YAG lasers are Neodymium (Nd) where YAG represents Yttrium Aluminum Garnet crystals to generate the laser. YAG lasers work by focusing a very brief pulse of laser light at a precise point in 3D space, to create a small concentrated light energy or an explosion of plasma for a very brief time. Details as recited in FIG. 2 are intended as incorporated into this disclosure.

Results

[0055] Absolute calibration of H.sub.2O.sub.2 PF-LIF signals is performed using a He—H.sub.2O—H.sub.2O.sub.2 reference mixture, which consists of a 2 slm (standard liters per minute flow rate) He bubbling through a 50%(wt) hydrogen peroxide solution, maintained at 293 degrees K by a water bath. The reference concentration of H.sub.2O and H.sub.2O.sub.2 in the vapor phase is calculated using Raoult’s law by considering that the mixture is saturated with 50%(wt) hydrogen peroxide at 298 degrees K. This gives an H.sub.2O concentration of 2.05% and H.sub.2O.sub.2 concentration to be 0.09% in the vapor phase. For He bubbling through H.sub.2O only, the reference concentration of H.sub.2O in the vapor phase is calculated to be 3.13%. The H.sub.2O.sub.2 concentration generated in the plasma is calculated by comparing the photofragmentation LIF signal from the plasma discharge to the photofragmentation LIF signal from the reference mixture of H.sub.2O—H.sub.2O.sub.2. The OH concentration is calculated by measuring the OH LIF decay and a chemical model.

Exemplar Discharge Photographs of He—H2O Discharge

[0056] FIGS. 3(a) and 3(b) comprise exemplar discharge photographs of dielectric barrier discharge (DBD) (i.e., discharge photographs of He—H2O discharge) in humid helium. As seen, a distinct core is visible along with a weaker surrounding discharge. It is observed that the typical average OH concentration in the afterglow is ~ 1.5 ppm and the H.sub.2O.sub.2 concentration is around 20 ppm. With the addition of O.sub.2, the concentration of OH decreased to ~0.5 ppm; however, the H.sub.2O.sub.2 concentration increased to ~35 ppm.

Additional Results

[0057] FIGS. 4(a) through 10(b) illustrate additional exemplary discharge photographs of dielectric barrier discharge (DBD) under various conditions of examining results obtained relative to use of the in-situ hydrogen peroxide (H.sub.2O.sub.2) production otherwise disclosed herein. In particular, FIGS. 4(a) and 4(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 20000 .Math.s. Similarly, FIGS. 4(c) and 4(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 20000 .Math.s.

[0058] FIGS. 5(a) and 5(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 20000 .Math.s. Similarly, FIGS. 5(c) and 5(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 20000 .Math.s.

[0059] FIGS. 6(a) and 6(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 10 ms. Similarly, FIGS. 6(c) and 6(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for five pulses at a time t = 10 ms.

[0060] FIGS. 7(a) and 7(b) illustrate discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 10 ms. Similarly, FIGS. 7(c) and 7(d) illustrate discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for, respectively, pure He and He+5%O.sub.2, for ten pulses at a time t = 10 ms.

[0061] FIG. 8(a) illustrates discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for pure He for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s. Similarly, FIG. 8(b) illustrates discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for pure He for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s.

[0062] FIG. 9(a) illustrates discharge photographic graph results for OH mole fraction (ppm) along the x-axis thereof for He+5%O.sub.2 for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s. Similarly, FIG. 9(b) illustrates discharge photographic graph results for H.sub.2O.sub.2 mole fraction (ppm) along the x-axis thereof for He+5%O.sub.2 for 1 slm, 2 slm, 3 slm, 4 slm, and 5 slm flow rates, respectively, for time t = 5000 .Math.s.

[0063] Lastly, FIG. 10(a) illustrates discharge photographic graph results for pure He at first through fifth pulses, respectively. Similarly, FIG. 10(b) illustrates discharge photographic graph results for He+5%O.sub.2 at first through fifth pulses. respectively.

[0064] While certain embodiments of the disclosed subject matter have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the subject matter.

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