A device for detecting fluoride ions in nitric acid media.

Abstract

The present invention relates to a device for detecting fluoride ions in a nitrate medium, and the device is -A detection probe (1) including a zirconium measuring element (6) and a zirconium reference element (7); - Measuring conductors (11, 12, 13, 14) and; - Connected to the measuring conductors (11, 12, 13, 14), and an electrical resistance measuring circuit suitable for measuring the relative electrical resistance of a portion of the measuring element (6) to a portion of the reference element (7); - A suitable detection circuit to correlate the relative increase in resistance with the presence of fluoride ions in the nitrate medium. This includes devices.

Description

Technical Field

[0001] The present invention relates to the field of detection of chemical elements, and more specifically, to the detection of the chemical element fluorine (F) in its free form, i.e., in the form of fluoride ions.

Background Art

[0002] In particular, it is known to detect the presence of elemental fluorine in a solution via a reaction tube, by spectroscopic means, or by chromatographic means.

[0003] Current methods and devices are costly to implement and typically require destructive sampling of the solution. Their implementation is generally time-consuming and it is difficult to integrate them into continuous industrial processes.

[0004] In addition, these methods and devices are generally limited to the detection of total elemental fluorine, regardless of whether the elemental fluorine is present in complexed form or in free form, and cannot distinguish fluoride ions from elemental fluorine present in complexed form (for example, when it is bound to a metal cation or when it is bound to a proton to form hydrofluoric acid).

Summary of the Invention

Problems to be Solved by the Invention

[0005] The object of the present invention is to improve the detection devices of the prior art.

Means for Solving the Problems

[0006] For this purpose, the present invention is a device for detecting fluoride ions in a nitric medium, the device comprising A detection probe comprising: a measuring element made of zirconium having a wall that defines a closed internal space, the measuring element being intended to be immersed in a nitric acid medium to be tested; and a reference element made of zirconium, the reference element being disposed within the internal space of the measuring element and electrically connected by a first end of the measuring element; - A measuring conductor electrically connected to a measuring element and a reference element, wherein the measuring conductor is adapted for measuring the electrical resistance of a portion of the measuring element and a portion of the reference element; -A circuit for measuring electrical resistance, wherein the circuit is connected to the measuring conductor and is adapted to measure the relative electrical resistance of the portion of the measuring element to the portion of the reference element; -A detection circuit adapted to correlate the aforementioned increase in relative resistance with the presence of fluoride ions in the nitric acid medium, It is directed towards devices that include [this].

[0007] This invention enables the accurate detection of only fluoride ions in a nitric acid medium.

[0008] The device according to the present invention can be installed inline in a continuous process and enables near real-time continuous monitoring and detection of the presence of fluoride ions in the nitrate medium being tested without requiring sampling or intervention in the nitrate medium.

[0009] The device according to the present invention can provide information with high accuracy without necessarily relying on expensive resources.

[0010] The present invention can be implemented, for example, in the industry of nitric acid production, or in any method of using nitric acid, in the manufacture of structures intended to receive nitric acid (e.g., acid storage tanks, or for the processing of spent nuclear fuel), in the field of manufacture of chemical monitoring and control devices, or in the field of laboratory chemistry.

[0011] The devices according to the present invention may, either alone or in combination, include the following additional features: - The measuring conductor includes: a first measuring conductor electrically connected to a measuring element at a first measurement point; a second measuring conductor electrically connected to a measuring element at a second measurement point located at a predetermined distance from the first measurement point; a first reference measuring conductor electrically connected to a reference element at a first reference measurement point; and a second reference measuring conductor electrically connected to a reference element at a second reference measurement point located at a predetermined distance from the first reference measurement point. - The device further includes a first power supply conductor electrically connected to a measuring element and a second power supply conductor electrically connected to a second end of a reference element; - The conductor is made of the same material as the measuring element; - The detection probe includes a main body, the measuring element is sealed and mounted on top of the main body, and the conductor is connected to external wiring at the output of the main body; - The main body is made of the same material as the measuring element; - The measuring element has a tubular shape, and the reference element has a long shape extending longitudinally within the measuring element, and the reference element is electrically connected to the measuring element at one end of the measuring element and on one end of the measuring element; - The measuring element is formed by a tube closed by a plug, and the reference element is electrically connected to the plug; - The detection probe contains an electrical insulating material, which is in contact with the inner surface of the measuring element and also in contact with the reference element, and this electrical insulating material has a thermal conductivity greater than 1.15 W / mk; - The conductor is welded onto the measuring element by vacuum welding; - The circuit for measuring electrical resistance is adapted to a "4-wire" type resistance meter; - The reference element is obtained from the same metallurgical casting process as the measurement element.

[0012] Other features and advantages of the present invention will become apparent from the following non-limiting description with reference to the accompanying drawings. [Brief explanation of the drawing]

[0013] [Figure 1] This figure schematically illustrates a device for detecting fluoride ions in a nitric acid medium according to the present invention. [Figure 2] Figure 1 shows a perspective view of the detection probe of the device. [Figure 3] This is a cross-sectional view of the detection probe. [Figure 4] This diagram illustrates an example of relative resistance measurement using a detection probe. [Modes for carrying out the invention]

[0014] Similar elements shared by various embodiments are given the same reference numerals in the figures.

[0015] Figure 1 schematically illustrates a device for detecting fluoride ions in a nitric acid medium according to the present invention.

[0016] The detection device includes a detection probe 1 intended to come into contact with a nitric acid medium, and an electronic measurement module 2 containing the components necessary for the operation of the detection device. Module 2 is connected to detection probe 1 by one or more cables 3, includes an interface adapted to the device, and in particular, an interface for viewing or exporting the data and alerts produced, either directly or via additional computer means. Module 2 includes a circuit 25 for measuring electrical resistance and a detection circuit 26. Circuits 25, 26 can be formed by any known electronic and / or computer means with appropriate programming, and optionally, by an external computer with an appropriate communication interface.

[0017] The nitric acid medium 4 is here schematically represented inside a portion of a container (circulation duct, tank, etc.) defined by a wall portion 5.

[0018] The detection probe 1 includes a measurement element 6, which is a closed envelope adapted to come into contact with the nitric acid medium 4, has a wall portion defining a closed inner space, and is impermeable to this medium. In this exemplary embodiment, the detection probe 1 is adapted to be mounted on the wall portion 5 in a sealed manner such that the measurement element 6 is in contact with the nitric acid medium 4.

[0019] The nitric acid medium 4 can be any solution that contains nitric acid at least partially.

[0020] Figure 2 is a perspective view of the detection probe 1, with the measurement element 6 shown as transparent so that its internal components can be seen.

[0021] Also, Figure 3 shows the detection probe 1 here according to a cross-sectional view.

[0022] The measuring element 6 is formed by a metal wall made of zirconium.

[0023] Referring to Figures 2 and 3, the measuring element 6 surrounds the reference element 7. The reference element 7 is made of the same material as the measuring element 6. The reference element 7 has a long shape that extends longitudinally within the measuring element 6. The reference element can be made of any long shape: a wire, blade or slat, cylinder, etc. In this example, this long shape is a blade.

[0024] The reference element 7 is manufactured from the same material as the measuring element 6, preferably obtained from the same metallurgical casting as the measuring element 6, and therefore made of zirconium.

[0025] In this example, the measuring element 6 consists of a tube 8 that is sealed tightly at its end by a plug 9. The detection probe 1 includes a main body 10, and the measuring element 6 is tightly attached to this main body 10, for example by welding.

[0026] The reference element 7 is positioned inside the measuring element 6 and is electrically connected to the measuring element 6. In this example, the reference element 7 is electrically connected to the measuring element 6 at the plug 9 by one of its ends. In this example, the reference element 7 also extends along the entire length of the measuring element 6.

[0027] Therefore, the measuring element 6 has a tubular shape, and in this example, the blade constituting the reference element 7 extends longitudinally within the measuring element 6, and the reference element 7 is electrically connected to the measuring element 6 at one end of the blade, on the tubular end of the measuring element 6.

[0028] The electrical connection between the reference element 7 and the measuring element 6 can be made by any means that does not impair the sealing of the assembly (e.g., welding, gluing, etc.).

[0029] An electrically insulating and thermally conductive material 24 is cast inside the measuring element 6, holding the reference element 7 in place, while electrically insulating the reference element 7 from the measuring element 6, but thermally connecting them.

[0030] Also, the device is - Measurement of the electrical resistance of a portion of the measuring element 6; and, - Measurement of the electrical resistance of a portion of reference element 7 (taken as a reference). Includes measuring conductors 11, 12, 13, and 14 conforming to the standard.

[0031] Therefore, the device here includes a first measuring conductor 11 electrically connected to the measuring element 6 at a first measuring point 15, and a second measuring conductor 12 electrically connected to the measuring element 6 at a second measuring point 16. These measuring points 15 and 16 are located on the inner surface of the measuring element 6.

[0032] Similarly, the device here includes a first reference measuring conductor 13 electrically connected to the reference element 7 at a first reference measuring point 17, and a second reference measuring conductor 14 electrically connected to the reference element 7 at a second reference measuring point 18.

[0033] The electrical connections between the measuring conductors 11, 12, 13, and 14 at measurement points 15, 16, 17, and 18 are made by any known appropriate means, such as welding.

[0034] On the one hand, the first and second measurement points 15 and 16 of the measurement element 6, and on the other hand, the first and second reference measurement points 17 and 18 of the reference element 7, are spaced apart by a predetermined distance, respectively, defining the portion of the measurement element 6 and the portion of the reference element 7 for which the corresponding electrical resistance is measured.

[0035] The measurement of electrical resistance between each pair of measurement points 15, 16; 17, 18 can be carried out by any known means. In this example, this electrical resistance measurement is carried out by a "4-wire" measurement.

[0036] In this implementation, the device includes a first power supply conductor 20, which is electrically connected on its inner surface to the base of the measuring element 6 at a first power supply point 22. In this case, the first supply point 22 is located at the contact between the first power supply conductor 20 and the inner surface of the measuring element 6. Alternatively, the first power supply conductor 20 can be electrically connected on the main body 10, preferably near the junction between the main body 10 and the measuring element 6 (thus, the first power supply point 22 is located at the junction between the main body 10 and the measuring element 6). This alternative allows for a simplification of the method for manufacturing the device.

[0037] The device also includes a second power supply conductor 21, which is electrically connected to the reference element 7 at a second power supply point 23. The second power supply point 23 is located at the end of the reference element 7 opposite to the end where the reference element is electrically connected to the measuring element 6. Thus, the power supply conductor allows current to flow in series through the measuring element 6 and the reference element 7.

[0038] The measuring conductors 11, 12, 13, 14 and the power supply conductors 20, 21 are connected at the output of the main unit 10 to the external wiring (circularly shown by cable 3 in Figure 1) necessary for connection to the module 2. The conductors 11, 12, 13, 14, 20, 21 are coated, for example, with a suitable electrical insulating polymer.

[0039] Figure 4 schematically illustrates a 4-wire resistance measurement applied to both the measuring element 6 and the reference element 7. In Figure 4, the resistor 19 schematically represents the resistance to be measured of the portion of the measuring element 6 or the reference element 7 located between two measurement points 15, 16 or 17, 18.

[0040] 4. In a known form relating to wire resistance measurement, a current source (contained within module 2 (within resistance measurement circuit 25)) circulates a constant current between two power supply points 22 and 23. This current flows through the measuring element 6 and the reference element 7. Thus, the voltage between two measuring points 15 and 16, on the one hand, and the voltage between two measuring points 17 and 18, on the other hand, are accurately measured (via the voltage measuring means contained within module 2 (within resistance measurement circuit 25)), from which the value of the resistance 19 is estimated by Ohm's law. Thus, accurate measurement of the electrical resistance of the portion of the measuring element 6 and the portion of the reference element 7 in question is performed continuously, and minute changes in resistance are detected.

[0041] Furthermore, module 2 performs a relative measurement of the resistance of the portion of the measurement element 6 to the resistance of the portion of the reference element 7 via the measurement circuit 25. In other words, the measurement circuit 25 determines the change in the electrical resistance of the portion of the measurement element 6 that exceeds the change in the electrical resistance of the portion of the reference element 7. This relative measurement can be performed by individual measurements of the resistance of the portion of the measurement element 6 and the resistance of the portion of the reference element 7, and the ratio of these voltages is determined by module 2 and optionally by a computer means connected to module 2 via an appropriate interface. To obtain this relative resistance, the value of the electrical resistance of the reference element 7 can be continuously subtracted from the value of the electrical resistance of the measurement element 6.

[0042] This relative electrical resistance measurement allows for the quantification of the electrical resistance value (of the aforementioned portion of the measuring element) independently of temperature. Since the insulating material 24 is thermally conductive, the measuring element 6 and the reference element 7 are exposed to substantially the same temperature, and the change in electrical resistance with respect to temperature is experienced by both the measuring element 6 and the reference element 7. Therefore, these changes in electrical resistance due to temperature are not taken into account in the measurement of the relative electrical resistance, and thus the relative electrical resistance changes only under the influence of the interaction between the measuring element 6 and the nitric acid medium 4.

[0043] When the detection device is in operation, the measuring element 6 is immersed in the nitric acid medium 4, and fluoride ions present in the nitric acid medium react with the material forming the measuring element 6. Therefore, the presence of fluoride ions in the nitric acid medium 4 results in a reduction in the thickness of the measuring element 6 in contact with the nitric acid medium 4, without affecting the reference element 7 protected inside the measuring element 6.

[0044] The presence of fluoride ions in the nitric acid medium results in a decrease (even a small) in the thickness of the zirconium of the measuring element 6, and this presence is detected by an increase in the relative electrical resistance exceeding a predetermined threshold. The detection circuit 26 of module 2 is adapted (by configuration or programming) to correlate the increase in the value of the relative resistance with the presence of fluoride ions in the nitric acid medium 4. The detection circuit 26 is adapted to detect the presence of fluoride ions in the nitric acid medium in accordance with the increase in the relative electrical resistance. The detection circuit 26 can be calibrated, for example, experimentally or by calculation.

[0045] In a particularly advantageous embodiment, the measuring conductors 11, 12, 13, 14, the power supply conductors 20, 21, and the main body 10 are made of the same material as the measuring element 6 (which is made of zirconium). Thus, the entire detection probe 1 can be produced by a welding technique (for example, a high-energy-density welding method such as vacuum electron beam welding or resistance welding), which allows for both the assembly of the tubes 8 and plugs 9 and the welding of the conductors at the measuring points 15, 16, 17, 18 and the supply points 22, 23.

[0046] Module 2 is programmed according to any suitable method, for example, to continuously verify the change in the relative resistance and thus determine the progression of the presence of fluoride ions in the nitric acid medium 4.

[0047] Alternative embodiments of the device are also possible; for example, the shape and arrangement of the measuring element 6, or the means for measuring relative resistance, can be different. [Explanation of symbols]

[0048] 1. Detection probe 2. Electronic measurement module 3 Cables 4 Nitric acid medium 5 Wall 6 measuring elements 7 Reference elements 8 tubes 9 plugs 10 Main body 11 First measuring conductor 12. Second measuring conductor 13. First reference measuring conductor 14. Second reference conductor 15. First measurement point 16. Second measurement point 17. First reference measurement point 18. Second reference measurement point 19 resistor 20 First power supply conductor 21 Second power supply conductor 22 First power supply point 23. Second power supply point 24 Electrical insulating materials 25 Resistance Measurement Circuit 26 Detection Circuit

Claims

1. A device for detecting fluoride ions in a nitric acid medium, wherein the device is A detection probe (1) comprising: a measuring element (6) made of zirconium having a wall that defines a closed inner space, the measuring element (6) being intended to be immersed in the nitric acid medium (4) to be tested; and a reference element (7) made of zirconium, the reference element (7) being disposed within the inner space of the measuring element (6) and electrically connected to the measuring element (6) by a first end; - Measuring conductors (11, 12, 13, 14) electrically connected to the measuring element (6) and the reference element (7), wherein the measuring conductors (11, 12, 13, 14) are adapted for measuring the electrical resistance of a portion of the measuring element (6) and a portion of the reference element (7); - A circuit (25) for measuring electrical resistance, wherein the circuit (25) is connected to the measuring conductors (11, 12, 13, 14) and is adapted to measure the relative electrical resistance of the portion of the measuring element (6) with respect to the portion of the reference element (7); - A detection circuit (26) is configured to correlate the aforementioned increase in relative resistance with the presence of fluoride ions in the nitric acid medium (4), A device characterized by including

2. The aforementioned measuring conductors (11, 12, 13, 14) are - A first measuring conductor (11) electrically connected to the measuring element (6) at a first measuring point (15), and a second measuring conductor (12) electrically connected to the measuring element (6) at a second measuring point (16) located at a predetermined distance from the first measuring point (15); - A first reference measurement conductor (13) electrically connected to the reference element (7) at a first reference measurement point (17), and a second reference measurement conductor (14) electrically connected to the reference element (7) at a second reference measurement point (18) located at a predetermined distance from the first reference measurement point (17), The device according to claim 1, characterized by including

3. The device according to claim 1, further comprising a first power supply conductor (20) electrically connected to the measuring element (6) and a second power supply conductor (21) electrically connected to the second end of the reference element (7).

4. The device according to claim 1, characterized in that the conductor is made of the same material as the measuring element (6).

5. The device according to claim 1, characterized in that the detection probe (1) includes a main body (10), the measuring element (6) is sealed and mounted on the main body (10), and the conductor is connected to an external wiring (3) at the output of the main body (10).

6. The device according to claim 5, characterized in that the main body (10) is made of the same material as the measuring element (6).

7. The device according to claim 1, characterized in that the measuring element (6) has a tubular shape, the reference element (7) has a long shape extending longitudinally within the measuring element (6), and the reference element (7) is electrically connected to the measuring element (6) at one end of the reference element (7) on one end of the measuring element (6).

8. The device according to claim 1, characterized in that the measuring element (6) is formed by a tube (8) closed by a plug (9), and the reference element (7) is electrically connected to the plug (9).

9. The device according to claim 1, wherein the detection probe (1) includes an electrical insulating material (24), the electrical insulating material (24) is in contact with the inner surface of the measuring element (6) and the reference element (7), and the electrical insulating material (24) has a thermal conductivity greater than 1.15 W / m·k.

10. The device according to claim 1, characterized in that the conductor is welded onto the measuring element by vacuum welding.

11. The device according to claim 1, characterized in that the circuit (25) for measuring electrical resistance is adapted for a "4-wire" type resistance measurement.

12. The device according to any one of claims 1 to 11, characterized in that the reference element (7) is obtained from the same metallurgical casting as the measuring element (6).

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