RU2362157C1 - Method of obtaining local electric discharge in liquid and device to this end (versions) - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention is meant for use in determining elemental composition of a substance. The proposed method of obtaining local electric discharge in a liquid involves passing electric current through the given liquid using electrodes, separated by a partition wall made from dielectric material with a diaphragm, through which passes the liquid current conductor. An element made from current conducting material is placed in the zone of local electric discharge. Potential of this element is chosen based on maximum intensity of the local electric discharge while maintaining its stability. According to one version, the device which realises the proposed method contains a dielectric case with electroconductive liquid and electrodes, connected a high voltage source, immersed in the said liquid and separated by a partition wall made from dielectric material with a diaphragm. In another version the device for obtaining local electric discharge in a liquid has a case with electroconductive liquid and electrodes connected to a high voltage source. One of the electrodes is immersed in the liquid and the other is hermetically attached to the dielectric wall of the said case on the outside and is linked to the said liquid through a diaphragm, made in the said dielectric wall of the case. According to both versions of the device, an element made from current conducting material is put in the zone of local electric discharge.

EFFECT: invention increases intensity of spectral lines of a wide range of elements.

12 cl, 2 dwg

Description

The invention relates to the field of technical physics, in particular to methods and devices for producing a high voltage electric discharge in a liquid, and is intended for use in determining the elemental composition of a substance.

It is known to use electric discharges on the free surface of a liquid as sources of atomization and excitation in optical sensors for multi-element analysis in a stream. For example, a droplet-spark discharge (CIR) is known that occurs when menisci approach each other, the voltage between them exceeds 600 volts [Yagov V.V., Korotkov A.S., Zuev B.K. RAS reports. 1998, t. 359, No. 2, p.208]. Despite the high voltage required to ignite the KIR, due to the pulse mode of operation, the power consumption of the device does not exceed 0.1 watts. KIR simultaneously provides atomization of the liquid and serves as a source of atomic spectra.

The device operates as follows. In the containers with electrolyte and the analyzed liquid, respectively, the positive and negative electrodes are located, to which a high voltage (about 600 volts) is supplied from a direct current source charging a discharge capacitor (with a capacity of about 2 μF). When the menisci of the electrolyte and the analyzed liquid come closer, KIR is ignited, which provides atomization of the analyzed liquid and serves as a source of the atomic spectrum of the analyte, which is detected using a photoelectron multiplier with a light filter and displayed by an optical spectrometer.

A device based on KIR is applicable, in particular, for determining the flow of the main cationic components (Na, K, Ca, Mg) of natural and technological waters [Yagov V.V., Getsina M.L., Zuev B.K., Korotkov A .FROM. Abstracts of the 4th All-Russian Conference “Eco-Analytics 2000”, Krasnodar, 2000, p. 79-80.]. In this case, the analytical signal is the integrated radiation intensity of atomic lines of metals that have passed by sputtering from catholyte to the positive column of a glow discharge.

Advantages of the described method: lack of memory effect, low power consumption (due to the use of pulsed discharge), lack of complex structural elements.

The disadvantages of the described method include:

- the complexity of the fluid supply to the KIR zone;

- discharge instability;

- care products analysis in the atmosphere.

The closest analogue of the present invention is a method of producing a local electric discharge in a liquid, which consists in passing an electric current through said liquid by means of electrodes separated by a baffle made of a dielectric material with a diaphragm through which the liquid conductors pass [RF patent for invention No. 2243546, G01N 27/62 12/27/2004].

In this method, the concentration of electric power dissipated in a unit volume of the liquid, sufficient to obtain and maintain a stable discharge, is provided by reducing the volume of the liquid participating in the discharge and increasing the discharge voltage due to the creation of a small cross-sectional area and length in the area of the local discharge liquid conductor.

This method can be implemented in two versions [RF patent for the invention No. 2243546, G01N 27/62, 12/27/2004]:

- liquid volumes connecting electrically isolated from each other volumes of liquid in which the electrodes are immersed;

- either a volume of the indicated liquid, into which an electrode is immersed, and an electrode of the opposite sign are connected electrically isolated from each other by a liquid current lead.

The ionization or atomization of the analyzed fluid by the specified method is carried out by maintaining a local high-voltage discharge in this fluid. At the same time, high specific power is dissipated in a unit volume of the liquid due to the use of electrodes, which are supplied with a high voltage, sufficient to maintain a high-voltage local electric discharge, and a partition separating them from a dielectric material with a diaphragm, the opening area of which in combination with the thickness of the partition (axial length specified hole) provides the necessary degree of localization of the discharge.

The limits for increasing the voltage and decreasing the volume of the liquid in which the discharge occurs (localization of the electric discharge) are determined by obtaining in the local volume of the liquid such a concentration of electric power that is sufficient to ensure the stability of this local discharge. In this case, the specific values of these three quantities (thickness and length of the liquid conductor and the magnitude of the voltage) can be different (depending on the nature of the analytical problem).

Two variants of this method are implemented in two variants of designs [RF patent for the invention No. 2243546, G01N 27/62, 12/27/2004].

In a first embodiment, the device comprises a housing with an electrically conductive liquid and electrodes connected to a high voltage source. These electrodes are immersed in a liquid and separated by a baffle of dielectric material with a diaphragm. The diaphragm opening area is determined based on the thickness of the partition, the magnitude of the voltage at the electrodes, thermal conductivity and electrical conductivity of the liquid.

In a second embodiment, the device also includes a housing with an electrically conductive liquid and electrodes connected to a high voltage source. In this case, one of the electrodes is immersed in the liquid, and the other is hermetically adjacent to the dielectric wall of the specified housing from the outside and communicates with the specified liquid by a diaphragm made in the specified dielectric wall of the housing. The diaphragm opening area in this case is determined based on the thickness of the specified dielectric wall of the housing, the magnitude of the voltage at the electrodes, thermal conductivity and electrical conductivity of the liquid.

With all the advantages described above, the considered method of obtaining a local electric discharge in a liquid, being used for atomization and ionization in the spectral analysis of the elemental composition of a substance, has a very significant drawback:

- when using a local electric discharge in a liquid as a source of emission spectra, their intensity for most elements, including alkaline earth metals, is much lower than for alkali metals.

This drawback sharply reduces the possibility of using such a method for producing a local electric discharge in a liquid in the emission analysis.

The technical result of the proposed method for obtaining a local electric discharge in a liquid is to increase the intensity of the spectral lines of a wide range of elements.

The proposed method for producing a local electric discharge in a liquid consists in passing an electric current through the specified liquid by means of electrodes separated by a baffle made of a dielectric material with a diaphragm through which the liquid conductors pass, while an element of a conductive material is introduced into the local electric discharge zone, and the potential of the indicated element from conductive material is selected based on the maximum intensity of a local electric discharge while maintaining lnenii its stability.

In particular, the potential of said conductive element can be chosen equal to the potential of an electrode located in that volume of liquid in which an element of conductive material is placed.

Implementing in aggregate the essential features of the proposed method, it is possible to provide a stable high-voltage discharge in a liquid, the luminous intensity of which is sufficient for reliable reproduction of emission spectral lines of a wide range of analyzed elements.

A stable discharge in a liquid is achieved by its localization and an increase in electric voltage to a value that ensures the stability of the discharge. Localization of the discharge is achieved by minimizing the volume of liquid in which the discharge occurs. A significant (more than an order of magnitude) increase in the intensity of the emission lines of the discharge provides the introduction of an element of conductive material into the zone of local electric discharge.

To implement the proposed method, there is a device for producing a local electric discharge in a liquid, comprising a dielectric casing with an electrically conductive liquid and electrodes connected to a high voltage source immersed in said liquid and separated by a partition from a dielectric material with a diaphragm, while an element is located in the zone of local electric discharge from conductive material.

Another embodiment of the proposed method is a device for producing a local electric discharge in a liquid, comprising a dielectric body with an electrically conductive liquid and electrodes connected to a high voltage source, one of which is immersed in the liquid, and the other is hermetically adjacent to the dielectric wall of the said case from the outside and communicates with the specified liquid diaphragm made in the specified dielectric wall of the housing, while in the zone of local electric discharge is located conductive material tape.

Both in one and in other embodiments of the proposed device, the conductive element can be made of corrosion-resistant and temperature-resistant material.

In both versions of the device, the element of conductive material can be electrically isolated from these electrodes.

Alternatively, an element of a conductive material can be connected to a high voltage source, in which case it can serve as an electrode immersed in a liquid, i.e. the potential of the specified conductive element is chosen equal to the potential of one of the electrodes.

The possibility of practical implementation and the effectiveness of the proposed method for producing a local electric discharge in a liquid is confirmed by the work of two design options of the proposed device. These designs were completed and tested, which confirms not only the feasibility, but also the industrial applicability of this technical solution.

Figure 1 schematically shows a first embodiment of a device for implementing the proposed method, where

1 - housing;

2a, 2b - electrodes;

3 - electrically conductive liquid;

4 - aperture;

5 - dielectric partition;

6 - source of high voltage;

7 - zone of local discharge;

8 - an element of conductive material;

9 - spectrometer.

The device operates as follows. The high voltage applied to the electrodes 2a, 2b located in the housing 1 creates an electric discharge in the electrically conductive liquid 3, which the housing 1 is filled with. This discharge, being localized in a small volume of liquid 3, located in the hole of the diaphragm 4, made in the dielectric separating housing 1 the partition 5, creates a high concentration of power dissipation, sufficient for ionization or atomization of the liquid 3. The high voltage supply is provided by a high voltage voltage source 6, the current stabilization of which is one of the conditions for the stability of a local electric discharge.

In zone 7 of the local discharge, which is located near the opening of the diaphragm 4, an element 8 of conductive material is installed. This element 8, when connected to a high voltage voltage source 6, can act as an electrode 2a or 2b for the volume of liquid 3 in which it is located. The radiation from the zone 7 of the local discharge near the element 8 of the conductive material is recorded by a spectrometer 9.

Figure 2 schematically shows a second embodiment of a device for implementing the proposed method for producing a local electric discharge in a liquid, where

1 - housing;

2a - internal electrode;

2b - external electrode;

3 - electrically conductive liquid;

4 - aperture;

6 - source of high voltage;

7 - zone of local discharge;

8 - an element of conductive material;

9 - spectrometer.

The device operates as follows. A high voltage applied between the inner electrode 2a located inside the housing 1 and the outer electrode 2b located outside the housing 1 creates an electric discharge in the electrically conductive liquid 3. This discharge, being localized in a small volume of liquid 3, located in the hole of the diaphragm 4 made in the dielectric wall case 1, creates a high concentration of power dissipation for ionization or atomization of the liquid 3. The high voltage supply is provided by a high voltage voltage source 6, stabilization I current which is one of the conditions for the stability of a local electric discharge.

In the zone 7 of the local discharge, which is located near the opening of the diaphragm 4, there is an element 8 of conductive material, which when connected to a high voltage voltage source 6 can act as an electrode 2a. The radiation from the zone 7 of the local discharge near the element 8 of the conductive material is recorded by a spectrometer 9.

Despite the high temperature in the discharge zone 7, due to the intense heat removal by the liquid 3 in which the discharge occurs, long-term and stable operation of the diaphragm 4 and the element 8 of conductive material is ensured.

The hole area of the diaphragm 4 is determined based on the voltage at the electrodes 2a and 2b, the thermal conductivity and electrical conductivity of the liquid 3 and the thickness of the dielectric partition 5 or the dielectric wall of the housing 1 with the diaphragm 4.

In particular, the potential of the conductive element 8 is chosen equal to the potential of the electrode 2a immersed in the volume of liquid 3 in which the element 8 is located.

To obtain a stable local discharge in liquid 3, a voltage in the range of values from 5 to 15 kV with a thickness of the partition 5 (or the wall of the housing 1) with a diaphragm 4 from 0.2 to 1.5 mm and a hole diameter of the diaphragm 4 from 0.05 to 0.5 mm

In the practical implementation of the proposed method and device, the partition 5 and the wall of the housing 1 were made of quartz glass with a thickness of 0.2 to 1.5 mm with a diaphragm 4 provided with an opening with a diameter of 0.1 to 0.5 mm, i.e. the volume of the liquid conductor ranged from 0.1 to 0.5 cubic meters. mm As source 6, an adjustable source 6 of 0-10 kV was used, which was connected to stabilize the current through a ballast of 20 kOhm and more. When using a KCl solution with a concentration of 0.0001 M to 1 M, the voltage of occurrence (ignition) of the discharge, depending on the conductivity of the solution, varied from 3 to 10 kV, the voltage drop across the discharge gap (liquid conductor) ranged from 0.5 to 2 kV , and the current value varied from 0.02 to 0.1 A. Thus, the value of the specific power released in the volume of the liquid current lead was in the range of tens to hundreds of watts per cubic meter. mm (i.e. up to hundreds of kilowatts per cubic cm). At high currents (tens or more milliamps), the discharge, while remaining stable, spatially exceeded the limits of diaphragm 4.

Thus, the magnitude of the specific power released in the volume of the liquid conductor was in the range of tens to hundreds of watts per cubic meter. mm (i.e. up to hundreds of kilowatts per cubic cm). At high currents (tens or more milliamps), the discharge, while remaining stable, spatially exceeded the limits of diaphragm 4.

Tests have shown that both quartz glass and corundum are suitable materials for the manufacture of the diaphragm 4, allowing to implement this method, since the temperature difference between the inner part of the diaphragm 4 along the channel axis and the rest of the liquid volume 3 is more than a thousand degrees.

In practice, a conductive element 8 was used, made of a corrosion-resistant and temperature-resistant material, for example, carbon.

Since the value of the electrical resistance of the channel (liquid conductor), including due to a change in the state of the substance inside the specified conductor, varies nonlinearly, it is not possible to give a rigorous analytical expression connecting the electrical quantities and geometric parameters of the device. It can be noted, however, that (unlike a gas-discharge system, where the initialization of the discharge is determined by the gas ionization potential and is accompanied by a significant decrease in the electrical resistance of the discharge gap and, accordingly, an increase in current), in this case, the initialization of the discharge is determined by the transition of the liquid in the volume of the liquid current conduit to the gaseous state, why it is necessary to concentrate a certain specific power in the liquid conductor, and the resistance value of the specified conductor can while both increase and decrease.

Initialization of the discharge is facilitated by air bubbles (gas, steam) arising in the liquid conductor or falling into it. This occurs due to an increase in the resistance of the liquid conductor, which at a given current leads to an increase in the voltage drop across it and, consequently, to an increase in the specific power dissipated in the liquid conductor, which to some extent eliminates the dependence of the power required to initiate the discharge on the conductivity of the liquid .

In experimental studies of the effectiveness of using the proposed method for obtaining a local discharge as a source of emission spectra, a quartz cell with a diaphragm with a diameter of 0.1 mm filled with a solution containing potassium, magnesium and calcium ions of 10 mg / l was used for spectral analysis of the elemental composition of the substance. The radiation from the local electric discharge region in such a solution was recorded using an AvaSpec 2048 scanning spectrometer from Avantes. Comparison of the spectra obtained using the source, made in accordance with the claimed method, with the spectra obtained using the source described in the prototype, showed that the spectrum obtained from the source in accordance with the claimed method contained lines of all elements introduced into the solution, whereas in the spectrum obtained from the source in accordance with the prototype, only the potassium line was detected, which confirms the achievement of the claimed technical result.

Claims (12)

1. A method of obtaining a local electric discharge in a liquid, which consists in passing an electric current through said liquid by means of electrodes separated by a baffle made of a dielectric material with a diaphragm through which a liquid conductor passes, characterized in that an element of a conductive material is introduced into the local electric discharge zone, the potential of the indicated element from the conductive material is selected based on the maximum intensity of the local electric discharge while maintaining its stability. 2. The method according to claim 1, characterized in that the potential of said conductive element is chosen equal to the potential of an electrode located in that volume of liquid in which an element of conductive material is placed. 3. A device for producing a local electric discharge in a liquid, comprising a dielectric body with an electrically conductive liquid and electrodes connected to a high voltage source, immersed in said liquid and separated by a baffle of dielectric material with a diaphragm, characterized in that an element of conductive material. 4. The device according to claim 3, characterized in that said conductive element is made of corrosion-resistant and temperature-resistant material. 5. The device according to claim 3, characterized in that said element of conductive material is electrically isolated from said electrodes. 6. The device according to claim 3, characterized in that said element of conductive material is connected to said high voltage source. 7. The device according to claim 6, characterized in that said element of conductive material is an electrode. 8. A device for producing a local electric discharge in a liquid, comprising a dielectric body with an electrically conductive liquid and electrodes connected to a high voltage source, one of which is immersed in the liquid, and the other is hermetically adjacent to the dielectric wall of the said case from the outside and communicates with the specified liquid by a diaphragm made in the specified dielectric wall of the housing, characterized in that in the zone of local electric discharge is an element of conductive material. 9. The device according to claim 8, characterized in that said conductive element is made of corrosion and temperature-resistant material. 10. The device according to claim 8, characterized in that said element of conductive material is electrically isolated from said electrodes. 11. The device according to claim 8, characterized in that said element of conductive material is connected to said high voltage source. 12. The device according to claim 11, characterized in that said element of conductive material is an electrode immersed in a liquid.

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