Device for detecting fluoride ions in nitrogen environment

Abstract

FIELD: chemical elements detection.SUBSTANCE: invention is intended for detecting the chemical element fluorine (F) in a free state, i.e. in the form of fluoride ions. A device for detecting fluoride ions in a nitrogen environment comprises: a detector probe comprising a zirconium measuring element and a zirconium control element; measuring conductors; a circuit for measuring electrical resistance, connected to the measuring conductors and suitable for measuring the relative electrical resistance of a section of the measuring element, relative to the electrical resistance of a section of the control element; and a detection circuit configured to correlate an increase in relative resistance with the presence of fluoride ions in a nitrogen environment.EFFECT: ability to detect fluoride ions in a nitrogen environment.12 cl, 4 dwg

Description

[0001] Field of technology to which the invention relates

[0002] The invention relates to the field of detecting chemical elements and, in particular, to detecting the chemical element fluorine (F) in a free state, that is, in the form of fluoride ions.

[0003] Technology Level

[0004] It is known that the presence of the fluorine element in a solution can be detected, in particular, using indicator tubes, spectroscopic or chromatographic means.

[0005] Current methods and devices are expensive to use and typically require destructive sampling of the solution. Their implementation is typically time-consuming and difficult to integrate into a continuous industrial process.

[0006] Furthermore, these methods and devices are generally limited to detecting the fluorine element as a whole, regardless of whether it is present in a bound state or in a free state, and are not capable of distinguishing fluoride ions from the fluorine element that is in a bound state (for example, when it is bound to a metal cation, or when it is bound to a proton to form hydrofluoric acid).

[0007] Disclosure of the essence of the invention

[0008] The purpose of the invention is to improve the detection devices of the prior art.

[0009] For this purpose, the invention is aimed at creating a device for detecting fluoride ions in a nitrogen environment, containing:

[0010] - a detector probe comprising: a zirconium measuring element having a wall defining a closed internal space, wherein this measuring element is designed with the possibility of immersion in a nitrogen environment to be monitored; a zirconium control element located in the internal space of the measuring element and electrically connected at its first end to the measuring element;

[0011] - measuring conductors electrically connected to the measuring element and to the control element and configured to measure the electrical resistance of a section of the measuring element and a section of the control element;

[0012] - a circuit for measuring electrical resistance, connected to said measuring conductors and configured to measure the relative electrical resistance of said section of the measuring element, relative to the electrical resistance of said section of the control element;

[0013] - a detection circuit configured to correlate an increase in said relative resistance with the presence of fluoride ions in a nitrogen environment.

[0014] The invention allows for the accurate determination of only fluoride ions in a nitrogen environment.

[0015] The device according to the invention can be installed directly in a continuous process, which allows for continuous monitoring and detection of the presence of fluoride ions in a controlled nitrogen environment in almost real time, without requiring sampling or intervention in the nitrogen environment.

[0016] The device according to the invention can provide information with high accuracy without necessarily resorting to expensive resources.

[0017] The invention can be implemented, for example, in the fields of nitric acid production or in any method using nitric acid, in production facilities intended for producing nitric acid (such as acid storage tanks or for processing spent nuclear fuel), in the field of producing chemical monitoring and control devices, or in the field of laboratory chemistry.

[0018] The device according to the invention may also comprise the following features, taken individually or in combination:

[0019] - said measuring conductors comprise: a first measuring conductor electrically connected to the measuring element at the first measuring point, and a second measuring conductor electrically connected to the measuring element at the second measuring point located at a predetermined distance from the first measuring point; a first control measuring conductor electrically connected to the control element at the first control measuring point, and a second control measuring conductor electrically connected to the control element at the second control measuring point located at a predetermined distance from the first control measuring point;

[0020] - the device also comprises a first supply conductor electrically connected to the measuring element, and a second supply conductor electrically connected to the second end of the control element;

[0021] - the mentioned conductors are made of the same material as the measuring element;

[0022] - the detector probe comprises a housing to which a measuring element is hermetically attached, and the said conductors are connected to external wiring at the output of this housing;

[0023] - the mentioned housing is made of the same material as the measuring element;

[0024] - the measuring element has a tubular shape, and the control element has an oblong shape and extends in the longitudinal direction in the measuring element, and the control element is electrically connected to the measuring element, at one end of the measuring element with one end of the measuring element;

[0025] - the measuring element is made in the form of a tube, closed with a plug, to which the control element is electrically connected;

[0026] - the detector probe contains an electrical insulating material in contact with the internal surfaces of the measuring element and with the control element, and this electrical insulating material has a thermal conductivity of more than 1.15 W / (m⋅K);

[0027] - the mentioned conductors are welded to the measuring element by vacuum welding;

[0028] - the circuit for measuring electrical resistance is designed with the ability to measure resistance using a four-pin circuit;

[0029] - The control element is made of the same metallurgical casting as the measuring element.

[0030] Description of drawings

[0031] Other features and advantages of the invention follow from the following non-limiting description with reference to the accompanying drawings, in which:

[0032] - Fig. 1 schematically shows a device for detecting fluoride ions in a nitrogen environment in accordance with the invention;

[0033] - Fig. 2 shows a perspective view of the detector probe of the device shown in Fig. 1;

[0034] - Fig. 3 shows a cross-sectional view of the detector probe;

[0035] - Fig. 4 shows an example of measuring relative resistance using a detector probe.

[0036] Similar elements used in different embodiments are designated by the same reference numerals in the drawings.

[0037] Detailed description of the invention

[0038] Fig. 1 schematically shows a device for detecting fluoride ions in a nitrogen environment in accordance with the invention.

[0039] The detection device comprises a detector probe 1, designed for contact with a nitrogen environment, and an electronic measuring module 2, containing the components necessary for the operation of the detection device. Module 2 is connected to the detector probe 1 by one or more cables 3 and contains interfaces adapted to the device, in particular for viewing or exporting data and generated warnings directly or using additional computer means. Module 2 contains 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, alternatively, an external computer with a suitable communication interface.

[0040] Nitrogen environment 4 is schematically represented here inside a section of a container (circulation channel, tank, etc.) that is limited by wall 5.

[0041] Detector probe 1 comprises a measuring element 6, which is a closed shell designed to contact with a nitrogen environment 4 and has a wall that defines a closed internal space and is impermeable to this environment. In this exemplary embodiment, detector probe 1 is configured to be hermetically mounted on wall 5 such that measuring element 6 is in contact with nitrogen environment 4.

[0042] The nitrogen medium 4 may be any solution at least partially containing nitric acid.

[0043] Fig. 2 shows a perspective view of the detector probe 1, with the measuring element 6 shown transparent so that its internal components can be seen.

[0044] Fig. 3 also shows the detector probe 1, in this case in cross section.

[0045] The measuring element 6 is formed by a metal wall made of zirconium.

[0046] With reference to Fig. 2 and 3, the measuring element 6 includes a control element 7. The control element 7 is made of the same material as the measuring element 6. The control element 7 has an elongated shape extending in the longitudinal direction in the measuring element 6. The control element can have any elongated shape: in the form of a wire, a plate or bar, a cylinder, etc. In this example, this elongated shape is the shape of a plate.

[0047] The control element 7 is made of the same material and, preferably, of the same metallurgical casting as the measuring element 6, and is therefore made of zirconium.

[0048] In this example, the measuring element 6 consists of a tube 8, hermetically sealed at the end by a plug 9. The detector probe 1 comprises a housing 10, and the measuring element 6 is hermetically connected to this housing 10, for example, by welding.

[0049] The control element 7 is located inside the measuring element 6 and is electrically connected to the measuring element 6. In this example, the control element 7 is electrically connected to the measuring element 6 through the plug 9 at one end of the control element 7. In this example, the control element 7 also extends along the entire length of the measuring element 6.

[0050] The measuring element 6 thus has a tubular shape, and the plate, which in this example is the control element 7, extends in the measuring element 6 in the longitudinal direction, wherein the control element 7 is electrically connected to the measuring element 6, at one end of which the said plate is connected to the end of the tubular shape of the measuring element 6.

[0051] The electrical connection between the control element 7 and the measuring element 6 can be made by any method that does not violate the tightness of the unit, such as welding, gluing, etc.

[0052] Electrically insulating and thermally conductive material 24 is molded inside the measuring element 6 and holds the control element 7 in place, while electrically insulating it from the measuring element 6, but thermally connecting it.

[0053] The device also contains measuring conductors 11, 12, 13, 14, designed to measure:

[0054] - electrical resistance of the section of the measuring element 6; and

[0055] - electrical resistance of the control element section 7, this electrical resistance is used as a control.

[0056] Thus, the device here comprises a first measuring conductor 11, electrically connected to the measuring element 6 at the first measuring point 15, as well as a second measuring conductor 12, electrically connected to the measuring element 6 at the second measuring point 16. These measuring points 15, 16 are located on the inner surface of the measuring element 6.

[0057] Similarly, the device here comprises a first control measuring conductor 13, electrically connected to the control element 7 at the first control measuring point 17, as well as a second control measuring conductor 14, electrically connected to the control element 7 at the second control measuring point 18.

[0058] The electrical connection between the measuring conductors 11, 12, 13, 14 at the measuring points 15, 16, 17, 18 is carried out by any known and suitable method, such as welding.

[0059] The first and second measuring points 15, 16 of the measuring element 6, as well as the first and second control measuring points 17, 18 of the control element 7 are spaced respectively by a predetermined distance, limiting the area of ​​the measuring element 6 and the area of ​​the control element 7, on which the corresponding electrical resistance is measured.

[0060] The electrical resistance measurement between each pair of measuring points 15, 16; 17, 18 can be performed by any known method. In this example, this electrical resistance measurement is performed using a four-terminal circuit.

[0061] To perform this measurement, the device comprises a first supply conductor 20, which is electrically connected to the base of the measuring element 6 on its inner surface at a first supply point 22. The first supply point 22 is located in this case at the contact point between the first supply conductor 20 and the inner surface of the measuring element 6. Alternatively, the first supply conductor 20 can be electrically connected to the housing 10, preferably near the junction between the housing 10 and the measuring element 6 (thus, the first supply point 22 is located at the junction between the housing 10 and the measuring element 6). This alternative allows for a simplified manufacturing method for the device.

[0062] The device also includes a second supply conductor 21, which is electrically connected to the control element 7 at a second supply point 23. The second supply point 23 is located at the end of the control element 7, which is opposite the end through which the control element is electrically connected to the measuring element 6. Thus, the supply conductors allow current to flow sequentially through the measuring element 6 and the control element 7.

[0063] The measuring conductors 11, 12, 13, 14 and the supply conductors 20, 21 at the output of the housing 10 are connected to the external wiring (schematically shown by cable 3 in Fig. 1) required for connection to the module 2. The conductors 11, 12, 13, 14, 20, 21 are, for example, covered with a suitable electrically insulating polymer.

[0064] Fig. 4 schematically shows the measurement of resistance using a four-terminal circuit, applied to both the measuring element 6 and the control element 7. In Fig. 4, the resistor 19 schematically represents the measured resistance of the section of the measuring element 6 or the control element 7, located between two measuring points 15, 16 or 17, 18.

[0065] In the known method for measuring resistance using a four-terminal circuit, the current source (contained in module 2, in the resistance measuring circuit 25) ensures the flow of direct current between two power supply points 22, 23. This current passes through the measuring element 6 and the control element 7. In this way, the voltage between the two measuring points 15, 16, on the one hand, and the measuring points 17, 18, on the other hand, is accurately measured (using the voltage measuring means contained in the resistance measuring circuit 25 in module 2), in order to derive a resistance value 19 from it based on Ohm's law. In this way, the accurate measurement of the electrical resistance of the section of the measuring element 6 under consideration and the section of the control element 7 is performed continuously, which makes it possible to detect minor changes in resistance.

[0066] Module 2 also performs a relative measurement of the resistance of said section of the measuring element 6 in relation to the resistance of said section of the control element 7 via the measuring circuit 25. In other words, the measuring circuit 25 determines a change in the electrical resistance of the section of the measuring element 6 that goes beyond the change in the electrical resistance of the section of the control element 7. This relative measurement can be performed by individually measuring the resistance of said section of the measuring element 6 and said section of the control element 7, and module 2 determines the ratio of these voltages, optionally using a computer means connected to module 2 via a suitable interface.To obtain this relative resistance, the value of the electrical resistance relative to the control element 7 can be continuously subtracted from the value of the electrical resistance relative to the measuring element 6.

[0067] Measuring this relative electrical resistance allows for the quantitative determination of the electrical resistance (of the said portion of the measuring element) regardless of temperature. Since the insulating material 24 is thermally conductive, the measuring element 6 and the control element 7 are essentially exposed to the same temperature, and a change in electrical resistance depending on temperature occurs in both the measuring element 6 and the control element 7. Therefore, these changes in electrical resistance caused by temperature are not taken into account in the case of measuring the said relative electrical resistance; therefore, the latter (the relative electrical resistance) changes only due to the influence of the interaction of the measuring element 6 with the nitrogen environment 4.

[0068] When the detection device is under operating conditions, the measuring element 6 is immersed in a nitrogen environment 4, and fluoride ions present in the nitrogen environment react with the material forming the measuring element 6. Thus, the presence of fluoride ions in the nitrogen environment 4 leads to a decrease in the thickness of the measuring element 6, which is in contact with the nitrogen environment 4, and does not affect the control element 7, which is protected inside the measuring element 6.

[0069] The presence of fluoride ions in a nitrogen environment leads to a decrease (even a slight one) in the thickness of the zirconium of the measuring element 6, and this presence is detected by an increase in the said relative electrical resistance above a predetermined threshold value. The detection circuit 26 of module 2 is designed (by design or programming) to correlate the increase in the value of said relative resistance with the presence of fluoride ions in the nitrogen environment 4. The detection circuit 26 is designed to determine the presence of fluoride ions in the nitrogen environment depending on the increase in the said relative electrical resistance. The detection circuit 26 can be calibrated, for example, experimentally or by calculation.

[0070] In a particularly preferred embodiment, the measuring conductors 11, 12, 13, 14, the supply conductors 20, 21 and the housing 10 are made of the same material as the measuring element 6 (zirconium). Thus, the entire detector probe 1 can be manufactured using a welding method, such as high-energy density welding, for example, vacuum electron beam or resistance welding, which makes it possible to connect the tube 8 and the plug 9, as well as weld the conductors at the measuring points 15, 16, 17, 18 and at the power supply points 22, 23.

[0071] Module 2 can be programmed in any suitable manner, for example, to continuously check the change in said relative resistance and thus to estimate the change in the content of fluoride ions in the nitrogen environment 4.

[0072] Alternative embodiments of the device are possible, for example, the shape and location of the measuring element 6 or the means for measuring the relative resistance may be different.

Claims

1. A device for detecting fluoride ions in a nitrogen environment, characterized in that it contains: - a detector probe (1) comprising: a measuring element (6) made of zirconium, having a wall defining a closed internal space, wherein this measuring element (6) is designed with the possibility of immersion in a nitrogen environment (4) to be monitored; a control element (7) made of zirconium, located in the internal space of the measuring element (6) and electrically connected at its first end to the measuring element (6); - measuring conductors (11, 12, 13, 14) electrically connected to the measuring element (6) and to the control element (7) and configured to measure the electrical resistance of a section of the measuring element (6) and a section of the control element (7); - a circuit (25) for measuring electrical resistance, connected to said measuring conductors (11, 12, 13, 14) and configured to measure the relative electrical resistance of said section of the measuring element (6), relative to the electrical resistance of said section of the control element (7); - a detection circuit (26) designed to correlate the increase in said relative resistance with the presence of fluoride ions in a nitrogen environment (4).

2. The device according to paragraph 1, characterized in that the said measuring conductors (11, 12, 13, 14) contain: - a first measuring conductor (11), electrically connected to the measuring element (6) at the first measuring point (15), and a second measuring conductor (12), electrically connected to the measuring element (6) at the second measuring point (16), located at a given distance from the first measuring point (15); - a first control measuring conductor (13), electrically connected to the control element (7) at the first control measuring point (17), and a second control measuring conductor (14), electrically connected to the control element (7) at the second control measuring point (18), located at a given distance from the first control measuring point (17).

3. A device according to one of the preceding paragraphs, characterized in that it also comprises a first supply conductor (20) electrically connected to the measuring element (6), and a second supply conductor (21) electrically connected to the second end of the control element (7).

4. A device according to one of the previous paragraphs, characterized in that the said conductors are made of the same material as the measuring element (6).

5. A device according to one of the preceding paragraphs, characterized in that the detector probe (1) comprises a housing (10) to which a measuring element (6) is hermetically attached, and the said conductors are connected to external wiring (3) at the output of the housing (10).

6. The device according to paragraph 5, characterized in that the said housing (10) is made of the same material as the measuring element (6).

7. A device according to one of the preceding paragraphs, characterized in that the measuring element (6) has a tubular shape, and the control element (7) has an elongated shape and extends in the longitudinal direction in the measuring element (6), and the control element (7), at one end of the control element (7), is electrically connected to the measuring element (6), with one end of the measuring element (6), 8. A device according to one of the previous paragraphs, characterized in that the measuring element (6) is made in the form of a tube (8), closed by a plug (9), with which the control element (7) is electrically connected.

9. A device according to one of the preceding paragraphs, characterized in that the detector probe (1) contains an electrically insulating material (24) in contact with the internal surfaces of the measuring element (6) and with the control element (7), and this electrically insulating material (24) has a thermal conductivity of more than 1.15 W / (m⋅K).

10. A device according to one of the preceding paragraphs, characterized in that the said conductors are welded to the measuring element by vacuum welding.

11. A device according to one of the previous paragraphs, characterized in that the circuit (25) for measuring electrical resistance is designed with the possibility of measuring resistance using a four-pin circuit.

12. A device according to one of the previous paragraphs, characterized in that the control element (7) is made from the same metallurgical casting as the measuring element (6).

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