An on-line Fourier near-infrared detection probe suitable for high temperature and high pressure environment

Abstract

The application discloses an online Fourier near-infrared detection probe suitable for a high-temperature and high-pressure environment, which comprises coaxially arranged long barrel assembly, mirror assembly and optical fiber assembly, the front end of the long barrel assembly is provided with a sapphire window sheet and a sealing structure; the mirror assembly comprises a sapphire corner pyramid and a compression spring, a measuring gap is formed between the plane of the corner pyramid and the surface of the window sheet, the compression spring automatically compensates thermal expansion and cold shrinkage, and high-temperature sealing is ensured; the optical fiber assembly realizes infrared light collimation through a focusing mirror, and double optical fibers are inserted into the long barrel assembly to form incident and emergent light paths.

Description

Technical Field

[0001] This invention belongs to the field of Fourier transform near-infrared spectroscopy online detection technology, specifically relating to an immersion-type online Fourier transform near-infrared detection probe adapted to industrial liquid phase processes. It is mainly used for in-situ continuous online monitoring of the composition, concentration, and quality of liquid materials in scenarios such as chemical synthesis, pharmaceutical fermentation, oil processing, and water treatment. Background Technology

[0002] Fourier transform near-infrared spectroscopy (FT-NIR) relies on the near-infrared characteristic absorption of molecules to achieve reagent-free, contactless, real-time, and non-destructive detection. It is a core analytical method for intelligent online quality control in process industries. Immersion transmission probes, as the optical interface between the spectrometer and the process fluid, directly determine the accuracy, stability, and adaptability of online detection.

[0003] The near-infrared online detection equipment market has maintained rapid growth in recent years. Industries such as chemical, pharmaceutical and fine processing have seen a continuous increase in demand for continuous in-situ monitoring. However, there is a significant shortage in the supply of high-end online near-infrared immersion probes in China.

[0004] Most domestically produced near-infrared probes are low-end, simple reflective structures. High-precision transmission immersion probes lag significantly behind Hellma's imported products in key technologies such as precision optical path integration, fully sealed helium leak detection, temperature and pressure resistant optical packaging, and low stray light optical path structure. Domestically developed products on the market generally suffer from large optical path tolerances, poor spectral repeatability during long-term immersion, difficulty in cleaning sanitary dead zones, and leakage under high-pressure conditions, failing to meet the high-standard online monitoring requirements of pharmaceutical GMP and continuous chemical synthesis.

[0005] For example, patent document CN116448663A discloses an insertion-type near-infrared detection probe, but this probe is a solid probe that can be inserted into a stacked substance. The internal probe rod is equipped with a reflective lens at an angle. The reflective lens allows the light passing through the window to enter the optical fiber for measurement. It does not have the ability to test liquids or withstand high temperatures and pressures.

[0006] Therefore, there is an urgent need for an independent online immersion near-infrared detection probe that is modular in structure, can be quickly maintained, is compatible with domestic Fourier transform near-infrared spectrometers, and combines corrosion resistance, high temperature and high pressure resistance with full-band optical performance. This will solve the industry pain points of imported products, such as high cost, poor compatibility, long maintenance cycle and limited supply chain, and promote the localization of online spectral detection equipment in the process industry. Summary of the Invention

[0007] The purpose of this invention is to address the current situation where domestic technologies are imperfect and lack online near-infrared high-temperature and high-pressure liquid detection probes, and to propose an online Fourier near-infrared detection probe suitable for high-temperature and high-pressure environments, so as to achieve in-situ continuous and stable monitoring under high-temperature and high-pressure liquid conditions.

[0008] The technical solution of the present invention is as follows: An online Fourier near-infrared detection probe suitable for high temperature and high pressure environments is characterized by comprising a reflector assembly, a long tube assembly, an optical fiber socket tube assembly, and an optical fiber assembly that are coaxially and sequentially mounted. The reflector assembly is disposed at the front end of the elongated cylinder assembly, the fiber optic socket cylinder assembly is disposed at the rear end of the elongated cylinder assembly, and the fiber optic assembly is connected to the fiber optic socket cylinder assembly. The reflector assembly includes a sapphire pyramid and an elastic clamping assembly for applying a continuous axial thrust to the sapphire pyramid; the fiber optic socket assembly is provided with a sapphire window; the end of the fiber optic assembly is provided with a focusing lens, the infrared light transmitted by the fiber optic assembly is collimated into a parallel beam by the focusing lens, the parallel beam passes through the sapphire window into the liquid to be tested, and after being reflected parallel by the sapphire pyramid, it passes through the liquid to be tested again, returns to the sapphire window, is focused by the focusing lens and returns to the fiber optic assembly, so as to form a two-way detection optical path that penetrates the liquid to be tested.

[0009] Furthermore, the fiber optic socket cylinder assembly includes a fiber optic socket cylinder, a window plate, a sapphire window sealing ring, and a window plate sealing ring. The fiber optic socket cylinder has two symmetrically arranged through holes for inserting the end of the fiber optic assembly. The sapphire window is embedded in the light-transmitting hole of the window plate, and the sapphire window sealing ring is fitted around the outer ring of the sapphire window. The window plate sealing ring is fitted around the outer ring of the window plate, and the window plate is press-fitted to the front end of the fiber optic socket cylinder via the window plate sealing ring to form a high-pressure axial seal.

[0010] Furthermore, the reflector assembly also includes a pyramidal reflector base, a cap, a pyramidal sealing ring, and a cap sealing ring; the elastic clamping assembly is a compression spring; the pyramidal sealing ring is installed in the sealing groove of the inner ring of the pyramidal reflector base; the front end of the sapphire pyramid has a circular boss, which expands the pyramidal sealing ring and forms an axial seal; the compression spring is disposed between the tail end of the sapphire pyramid and the cap; the cap is screwed onto the pyramidal reflector base, and the cap sealing ring is fitted onto the outer ring of the cap; when the cap is screwed on, it compresses the compression spring and keeps the compression spring always maintaining an elastic thrust on the sapphire pyramid; by controlling the step height of the pyramidal reflector base, the distance between the boss plane of the sapphire pyramid and the sapphire window can be adjusted to form different measurement optical paths.

[0011] Furthermore, the optical fiber assembly includes an optical fiber base, two symmetrically arranged metal-clad optical fibers, two optical fiber fixing rods, and an optical fiber focusing head; Two optical fiber fixing rods are symmetrically arranged on the optical fiber base, and two metal-clad optical fibers pass through and are fixed in the two optical fiber fixing rods respectively; The fiber focusing head is disposed at the end of the metal-clad fiber, the focusing lens is installed in the internal channel of the fiber focusing head, and the fiber focusing head is also provided with a focusing adjustment ring, which is used to adjust the distance between the end face of the metal-clad fiber and the focusing lens, so that the end face of the metal-clad fiber is located at the focal point of the focusing lens.

[0012] Furthermore, it also includes a clamping nut, an adapter nut, and a metal protective sleeve; the clamping nut is sleeved on the outside of the fiber optic socket of the fiber optic assembly, and is used to clamp and fix the fiber optic socket of the fiber optic assembly to the tail end of the fiber optic socket cylinder; the adapter nut is sleeved and tightened on the outside of the clamping nut, forming an interlocking anti-loosening structure; the metal protective sleeve is fixedly connected to the periphery of the fiber optic socket cylinder through the adapter nut, and covers the outside of the fiber optic connector of the fiber optic assembly to protect the fiber optic connector from bumps and contamination.

[0013] The working principle of this invention is as follows: Infrared light is transmitted through the incident optical fiber to the corresponding optical fiber focusing head, converted into parallel light by the focusing lens, and then penetrates the sapphire window and the liquid sample layer in sequence before being incident perpendicularly onto the plane of the sapphire pyramid. Since the three reflective surfaces of the sapphire pyramid are perpendicular to each other, according to the back reflection characteristics of the pyramidal prism, the parallel light undergoes three total internal reflections, maintaining a strict parallel relationship with the incident light (parallelism deviation < 5″), and then travels back along the original optical path, penetrating the liquid sample layer and the sapphire window again. The light is then converged by the optical fiber focusing head at the exit end to the end face of the exit optical fiber and transmitted back to the detector of the spectrometer. The infrared light penetrates the sample twice, and the total effective optical path is twice the measurement gap. This process relies entirely on the inherent mechanical and optical properties of the pyramidal prism, requiring no active alignment or adjustment, thus avoiding the problem of outgoing light direction deviation caused by mechanical vibration and temperature deformation in traditional reflector structures.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses a sapphire window sealing ring and a window pressing sealing ring to form a double radial seal, and with the sapphire pyramidal circular boss opening the inner lip of the pyramidal sealing ring to form an axial expansion sealing structure, a self-tightening sealing mechanism is achieved where the higher the fluid pressure, the better the sealing effect.

[0015] 2. The traditional inclined or right-angle reflector structure is abandoned in favor of a sapphire pyramid as the reflecting element. The three reflecting surfaces of the pyramidal prism are perpendicular to each other (dihedral angle accuracy 90°±3″), exhibiting a constant back reflection characteristic—regardless of slight deviations in the incident light direction, the outgoing light always maintains a strictly parallel relationship with the incident light (parallelism deviation <5″) and returns along the original path. This optical characteristic fundamentally eliminates the inherent defect of traditional probes being extremely sensitive to the reflector angle, significantly reducing the dependence on mechanical assembly precision. This eliminates the need for any optical path alignment operations after replacing the reflector assembly on-site, greatly improving engineering applicability and maintenance convenience.

[0016] 3. The four main modules—long tube assembly, reflector assembly, fiber optic assembly, and metal protective sleeve—are assembled independently. Any damaged or aged module can be replaced individually, eliminating the need for complete system disposal. It can perform online Fourier transform infrared measurements of liquids ranging from ambient temperature and pressure to high temperature and pressure, making it suitable for a wide range of applications. Employing an adjustable optical path, it meets the common optical path requirements for online Fourier transform infrared measurements of liquids within the same structural framework. Attached Figure Description

[0017] Figure 1 This is an overall assembly diagram of an online Fourier transform near-infrared detection probe suitable for high-temperature and high-pressure environments according to the present invention.

[0018] Figure 2 This is a schematic diagram of the fiber optic socket tube in this invention.

[0019] Figure 3 This is a schematic diagram of the reflector assembly in this invention.

[0020] Figure 4 This is a schematic diagram of the optical fiber assembly in this invention.

[0021] Figure 5 This is a cross-sectional view of the fiber optic focusing head in this invention.

[0022] Figure 6 This is a schematic diagram of the optical fiber assembly being fixed inside the cylindrical assembly in this invention.

[0023] In the diagram: 1-Long tube assembly, 2-Reflector assembly, 3-Fiber optic assembly, 4-Metal protective sleeve, 5-Fiber optic socket tube, 6-Window plate clamping plate, 7-Sapphire window plate, 8-Sapphire window plate sealing ring, 9-Window plate clamping plate sealing ring, 10-Pyramidal reflector mount, 11-Sapphire pyramid, 12-Cap, 13-Compression spring, 14-Pyramidal sealing ring, 15-Cap sealing ring, 16-Fiber optic mount, 17-Metal-clad fiber optic cable, 18-Fiber optic fixing rod, 19-Fiber optic focusing head, 20-Focusing lens, 21-Focusing adjustment ring, 22-Compression nut, 23-Adapter nut. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings, but this should not be construed as limiting the scope of protection of the invention. Conventional substitutions or parameter adjustments made by those skilled in the art based on the concept of the present invention should all fall within the scope of protection claimed in this application.

[0025] Please see Figure 1 An online Fourier near-infrared detection probe suitable for high-temperature and high-pressure environments, such as... Figure 1 As shown, this is a cylindrical insertion-type liquid probe with a coaxial modular structure design. An online Fourier transform near-infrared (FTIR) detection probe suitable for high-temperature and high-pressure environments includes a coaxially mounted elongated assembly 1, a reflector assembly 2, an optical fiber assembly 3, and a metal protective sleeve 4. This invention is based on the principles of infrared fiber optic guidance and the permanent parallel reflection of sapphire pyramids. The infrared beam emitted by the Fourier transform infrared spectrometer is guided into the optical fiber, and the beam is made to penetrate the sample twice in parallel at the probe tip to achieve the required optical path for measurement. Finally, the beam returns to the spectrometer, where the detector receives the infrared light absorbed by the sample, obtaining the spectral information of the measured object for qualitative and quantitative analysis.

[0026] During operation, the reflector assembly 2 is directly immersed in the high-temperature, high-pressure sample, serving as the actuator for spectral sampling and optical path reflection. For example... Figure 3 As shown, the cornerstone reflector base 10 serves as the main load-bearing component, with a sapphire cornerstone 11 and a compression spring 13 sequentially installed inside. Externally, a cover 12 is screwed tightly onto the cornerstone reflector base 10. The inner ring of the cornerstone reflector base 10 has a sealing ring groove for installing a cornerstone sealing ring 14.

[0027] The sapphire cone 11 has a circular boss. During installation, this boss expands the cone sealing ring 14, forming the first axial seal. When the cap 12 is tightened, it not only completes the second outer ring seal through the cap sealing ring 15, but also compresses the internal compression spring 13. Under high temperature and pressure, the preload force of the compression spring 13 can continuously hold the sapphire cone 11, offsetting the effects of thermal expansion and contraction, ensuring that the cone sealing ring 14 and the cap sealing ring 15 are always under pressure and expanded, preventing high-pressure liquid leakage.

[0028] The height of the step inside the pyramidal reflector mount 10 is controlled by machining, thereby adjusting the distance between the sapphire pyramidal boss plane 11 and the sapphire window 7 inside the elongated assembly 1. This distance is the effective optical path. Different reflector mounts with different step sizes can be replaced according to liquid samples with different transmittance (transparent to turbid) to achieve flexible matching of the optical path.

[0029] The long cylindrical assembly 1 is located in the middle section of the probe, serving to connect the front-end reflector assembly 2 and the rear-end fiber optic assembly, and also undertaking the task of pressure bearing and sealing. For example... Figure 2As shown, the long cylindrical assembly 1 includes a fiber optic socket cylinder 5, a window clamping plate 6, a sapphire window 7, a sapphire window sealing ring 8, and a window clamping plate sealing ring 9. The fiber optic socket cylinder 5 has two symmetrical through holes machined inside for inserting the focusing head of the tail fiber optic assembly, forming a symmetrical "one in, one out" incident / outgoing optical path. At the front end of the fiber optic socket cylinder 5, two stepped sapphire windows 7 are installed inside the window clamping plate 6, corresponding to the two through holes inside the fiber optic socket cylinder 5. The outer rings of the two sapphire windows 7 are fitted with sapphire window sealing rings 8. Simultaneously, the outer ring of the window clamping plate 6 is also fitted with a window clamping plate sealing ring 9. The clamping assembly, composed of the window clamping plate 6, sapphire windows 7, sapphire window sealing rings 8, and window clamping plate sealing ring 9, is tightly pressed into the front end of the fiber optic socket cylinder 5, ensuring unobstructed optical path from the pressure-resistant section to the atmospheric section and providing excellent high-pressure sealing.

[0030] Fiber optic assembly 3 is responsible for guiding the infrared light emitted by the spectrometer into the probe and transmitting the light absorbed by the sample back. For example... Figure 4 As shown, the fiber optic assembly 3 includes a fiber optic base 16, two metal-clad optical fibers 17, two fiber optic fixing rods 18, a fiber optic focusing head 19, a focusing lens 20, and a focusing adjustment ring 21.

[0031] One end of the metal-clad optical fiber 17 is a long metal tube, the middle is an armored section, and the tail end is a standard SMA threaded interface. The two long metal tubes of the metal-clad optical fibers 17 pass through symmetrical fiber fixing rods 18 and are fixed to the fiber mount 16. At the end of the long metal tube, an optical fiber focusing head 19 is assembled, inside which a focusing lens 20 is placed via a focusing adjustment ring 21, so that the fiber end face is exactly at the focal point of the focusing lens 20. After assembly, it is fixed with special adhesive or welding, such as... Figure 5 As shown.

[0032] After inserting the two fiber optic focusing heads into the fiber optic socket cylinder 5, use the clamping nut 22 to tighten the fiber optic socket, ensuring no internal movement. Then, use the adapter nut 23 to tighten the clamping nut 22, achieving long-term anti-loosening through the double-nut interlocking structure; simultaneously, the adapter nut 23 also serves to connect the metal protective sleeve 4. The external metal protective sleeve 4 primarily protects the fragile fiber optic connectors, preventing impact damage and external contamination, ensuring the cleanliness of the optical path end face, such as... Figure 6 As shown.

[0033] The working principle of this invention is as follows: This invention operates based on a bidirectional optical loop of "point light emission converted into parallel light and parallel light converted back into point light": Inlet light path: The infrared light emitted by the Fourier spectrometer is transmitted to the fiber optic focusing head 19 through the metal-clad fiber optic cable 17, and is converted into a parallel beam by the focusing lens 20, which then passes through the fiber optic socket tube 5 and the sapphire window 7.

[0034] Sample absorption and reflection: The parallel light beam passes through the liquid sample in the high-pressure chamber, hits the reflective surface of the sapphire pyramid 11, and is reflected back along the original path, penetrating the sample again to form a "two-way optical path" detection.

[0035] Signal feedback: The parallel beam carrying the sample absorption information is fed back to the focusing lens 20, where it is precisely focused again into a point light source and enters the optical fiber, and finally fed back to the detector of the spectrometer.

[0036] Spectroscopic analysis: By receiving the absorption spectrum through a detector, qualitative (component identification) and quantitative (concentration determination) analysis of media in high-temperature and high-pressure environments can be achieved.

[0037] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. Where there is no conflict, the above embodiments and features described therein can be combined with each other.

Claims

1. An online Fourier transform near-infrared detection probe suitable for high temperature and high pressure environments, characterized in that, It includes a reflector assembly (2), a long tube assembly (1), a fiber optic socket tube assembly, and a fiber optic assembly (3) that are installed coaxially in sequence. The reflector assembly (2) is disposed at the front end of the long tube assembly (1), the fiber optic socket tube assembly is disposed at the rear end of the long tube assembly (1), and the fiber optic assembly (3) is connected to the fiber optic socket tube assembly. The reflector assembly (2) includes a sapphire pyramid (11) and an elastic clamping assembly for applying a continuous axial thrust to the sapphire pyramid (11); the fiber optic socket assembly is provided with a sapphire window (7); the end of the fiber optic assembly (3) is provided with a focusing lens (20), the infrared light transmitted by the fiber optic assembly (3) is collimated into a parallel beam by the focusing lens (20), the parallel beam passes through the sapphire window (7) into the liquid to be tested, and after being reflected parallel by the sapphire pyramid (11), it passes through the liquid to be tested again and returns to the sapphire window (7), is focused by the focusing lens (20) and returns to the fiber optic assembly (3) to form a two-way detection optical path that penetrates the liquid to be tested.

2. The online Fourier near-infrared detection probe suitable for high-temperature and high-pressure environments according to claim 1, characterized in that, The fiber optic socket cylinder assembly includes a fiber optic socket cylinder (5), a window plate (6), a sapphire window sealing ring (8), and a window plate sealing ring (9). The fiber optic socket cylinder (5) has two symmetrically arranged through holes for the insertion of the end of the fiber optic assembly (3). The sapphire window (7) is embedded in the light-transmitting hole of the window plate (6), and the sapphire window sealing ring (8) is fitted around the outer ring of the sapphire window (7). The window plate sealing ring (9) is fitted around the outer ring of the window plate (6), and the window plate (6) is pressed onto the front end of the fiber optic socket cylinder (5) via the window plate sealing ring (9) to form a high-pressure axial seal.

3. The online Fourier near-infrared detection probe suitable for high-temperature and high-pressure environments according to claim 1, characterized in that, The reflector assembly (2) further includes a pyramidal reflector base (10), a cover (12), a pyramidal sealing ring (14), and a cover sealing ring (15); the elastic clamping assembly is a compression spring (13); the pyramidal sealing ring (14) is installed in the sealing groove of the inner ring of the pyramidal reflector base (10); the front end of the sapphire pyramid (11) is provided with a circular boss, the circular boss opens the pyramidal sealing ring (14) and forms an axial seal; the compression spring (13) is located at the tail end of the sapphire pyramid (11) and the cover (15). Between 12); the cover (12) is screwed onto the corner cone reflector base (10), and the cover sealing ring (15) is fitted onto the outer ring of the cover (12). When the cover (12) is screwed on, the compression spring (13) is compressed and the compression spring (13) always maintains an elastic thrust on the sapphire corner cone (11). By controlling the step height of the corner cone reflector base (10), the distance between the boss plane of the sapphire corner cone (11) and the sapphire window (7) can be adjusted to form different measurement optical paths.

4. The online Fourier near-infrared detection probe suitable for high-temperature and high-pressure environments according to claim 1, characterized in that, The optical fiber assembly (3) includes an optical fiber base (16), two symmetrically arranged metal-clad optical fibers (17), two optical fiber fixing rods (18), and an optical fiber focusing head (19). Two optical fiber fixing rods (18) are symmetrically arranged on the optical fiber base (16), and two metal-clad optical fibers (17) pass through and are fixed in the two optical fiber fixing rods (18). The fiber focusing head (19) is disposed at the end of the metal-clad fiber (17), the focusing lens (20) is installed in the internal channel of the fiber focusing head (19), and the fiber focusing head (19) is also provided with a focusing adjustment ring (21). The focusing adjustment ring (21) is used to adjust the distance between the end face of the metal-clad fiber (17) and the focusing lens (20) so that the end face of the metal-clad fiber (17) is located at the focal point of the focusing lens (20).

5. The online Fourier near-infrared detection probe suitable for high temperature and high pressure environments according to claim 1, characterized in that, It also includes a clamping nut (22), an adapter nut (23), and a metal protective sleeve (4); the clamping nut (22) is sleeved on the outside of the fiber optic socket of the fiber optic assembly (3) and is used to clamp and fix the fiber optic socket of the fiber optic assembly (3) to the tail end of the fiber optic socket cylinder (5); the adapter nut (23) is sleeved and tightened on the outside of the clamping nut (22) to form an interlocking anti-loosening structure; the metal protective sleeve (4) is fixedly connected to the periphery of the fiber optic socket cylinder (5) through the adapter nut (23) and covers the outside of the fiber optic connector of the fiber optic assembly (3) to protect the fiber optic connector from bumps and contamination.

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