Gas Measuring Devices

Abstract

To provide a gas measuring device capable of increasing the spatial resolution of distribution measurement of a physical state of gas even when there are restrictions on the opening of a structure.SOLUTION: A gas measuring device 1 comprises: at least one irradiation unit 3a, 3b that irradiates the inside of a structure 2 with laser light through irradiation openings 8a, 8b of the structure 2; at least one light receiving unit 5a, 5b that receives laser light having transmitted through the gas inside the structure 2 through light receiving openings 9a, 9b of the structure 2; and a computer 7 that acquires absorbance data along a plurality of optical paths of laser light having transmitted through the gas inside the structure 2, to obtain the distribution of a physical state of the gas. Mirrors 11a to 11d for reflecting laser light are provided inside the structure 2 and on at least one optical path of the plurality of optical paths.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas measurement device that measures the distribution of the physical state (concentration, temperature, etc.) of gas inside a structure. Place Regarding. [Background technology]

[0002] There is a demand for analyzing the combustion state and transient behavior of gases inside structures such as furnaces and engines. The analysis is performed by measuring the physical state (concentration, temperature, etc.) of gases such as CO, CO2, NH3, and NO in the combustion exhaust gas inside the structure.

[0003] In recent years, absorption spectroscopy using laser light has been utilized as a highly sensitive and responsive method for measuring the physical state of gas inside a structure. Absorption spectroscopy is a technique that acquires absorption data when laser light passes through the gas inside a structure, and determines the physical state of the target gas component based on the absorption data.

[0004] A method has also been developed that combines this absorption spectroscopy with CT (Computed Tomography), which is used in the medical field, to measure the distribution of the physical state of gas (see Patent Document 1). In this measurement method, multiple laser beams are irradiated onto the gas inside a structure, and CT is applied to the absorbance data obtained from the transmitted light, thereby measuring the distribution, i.e., the variation, of the physical state of the gas inside the structure. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 119283 Summary of the Invention [Problem to be solved by the invention]

[0006] In a measurement method that combines absorption spectroscopy with CT, in order to accurately measure the distribution of the physical state of gas, it is necessary to install as many laser light paths as possible inside the structure from various directions.

[0007] However, in the case of high-temperature structures such as furnaces, if many laser light emitting and receiving units are installed inside the structure, the heat resistance of these devices and cables becomes an issue. If openings are made in the structure and the laser light is emitted and received through the openings, the heat resistance issue can be alleviated, but then problems arise with the airtightness and thermal insulation of the structure.

[0008] Therefore, it is desirable to reduce the number of openings in the structure, but if the number of openings is limited, the position and orientation of the optical paths that can be installed will be restricted, and the accuracy of distribution measurement will decrease. In particular, if there is a wall on which openings cannot be installed due to structural or construction issues, the position and orientation of the optical paths will be significantly restricted, which will also hinder distribution measurement. This is because the physical state of the gas cannot be measured in areas where there are no optical paths.

[0009] The present invention has been made in view of the above-mentioned problems, and provides a gas measurement device that can improve the spatial resolution of the distribution measurement of the physical state of gas even if there are restrictions on the opening of a structure. Place The purpose is to provide. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a gas measurement device for measuring the distribution of the physical state of gas inside a structure, the device comprising: Multiple a plurality of irradiation units that irradiate the interior of the structure with laser light through an irradiation opening; and a plurality of irradiation units that irradiate the laser light that has passed through the gas inside the structure at a position different from the irradiation opening of the structure. Multiple a plurality of light receiving sections that receive light through light receiving openings; and a computer that acquires absorbance data along a plurality of optical paths of laser light that has passed through a gas inside the structure and determines a distribution of the physical state of the gas, wherein a mirror that reflects the laser light is provided inside the structure and on at least one of the plurality of optical paths; Multiple Irradiation unit Either From the above Multiple Light receiving part Either A light path that can be connected by a straight line to Multiple Irradiation unit Either The laser light from the Multiple Light receiving part Either and a light path leading to the light source passes through the light irradiation opening and the light receiving opening. [Effects of the Invention]

[0012] According to the present invention, the position and direction of the optical path can be set in various ways by using mirrors installed inside the structure. Since the number of optical paths can be increased and the optical paths can be arranged in more directions, the spatial resolution of the distribution measurement of the physical state of the gas inside the structure can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing the configuration of a gas measurement device according to an embodiment of the present invention; [Figure 2] FIG. 10 is a diagram showing a comparative example in which a mirror is not installed inside the structure. [Figure 3] FIG. 2 is a diagram showing the configuration of a mirror of the gas measuring device of the present embodiment. [Figure 4] FIG. 2 is a diagram showing the configuration of a computer of the gas meter device of the present embodiment. [Figure 5] FIG. 2 is a diagram illustrating an optical path and a grid. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a gas measuring device according to an embodiment of the present invention will be described with reference to the accompanying drawings. Place However, the present invention can be embodied in various forms and is not limited to the embodiments described herein. The present embodiments are provided with the intention that the disclosure of the specification will be sufficient to enable those skilled in the art to fully understand the invention.

[0015] FIG. 1 is a diagram showing the configuration of a gas metering device 1 according to one embodiment of the present invention. The gas metering device 1 according to this embodiment measures the concentration distribution and temperature distribution of gases such as CO and NO in the combustion exhaust gas from a furnace such as an incinerator. FIG. 1 shows a horizontal cross-sectional view of a furnace or a boiler (structure 2) downstream of the furnace. Gas flows within the structure 2 in a direction perpendicular to the plane of the paper (from the back to the front of the paper).

[0016] The gas measuring device 1 includes irradiating units 3a and 3b, a laser control device 4, light receiving units 5a and 5b, an amplifier 6, and a computer .

[0017] The irradiation units 3a and 3b irradiate the interior of the structure 2 with laser light. The irradiation units 3a and 3b are composed of laser diodes capable of outputting laser light. Irradiation openings 8a and 8b corresponding to the irradiation units 3a and 3b are formed in the structure 2. The irradiation units 3a and 3b are arranged outside the structure 2 and irradiate the interior of the structure 2 with laser light through the irradiation openings 8a and 8b of the structure 2.

[0018] The laser control device 4 controls the irradiating units 3a and 3b to change the wavelength of the laser light output from the irradiating units 3a and 3b over time.

[0019] 1 shows one irradiation unit 3a or 3b for one irradiation opening 8a or 8b, but in reality, a number of irradiation units 3a or 3b equal to the number of optical paths are provided for one irradiation opening 8a or 8b. Furthermore, the irradiation units 3a and 3b may be formed by using a fiber splitter that branches the laser light output from a laser diode, which is the light source, and optical fibers that irradiate the branched laser light onto the inside of the structure 2. Furthermore, the irradiation units 3a and 3b may be formed by using a mirror that reflects the laser light output from the laser diode, which is the light source.

[0020] The light receiving units 5a and 5b receive the laser light that has passed through the gas inside the structure 2. The light receiving units 5a and 5b are equipped with light receiving elements such as photodiodes and phototransistors. The light receiving units 5a and 5b output an electrical signal according to the intensity of the received laser light. The structure 2 is formed with light receiving openings 9a and 9b corresponding to the light receiving units 5a and 5b. The light receiving units 5a and 5b are arranged outside the structure 2 and receive the laser light through the light receiving openings 9a and 9b of the structure 2.

[0021] 1 shows one light receiving unit 5a or 5b for one light receiving opening 9a or 9b, but in reality, a number of light receiving units 5a or 5b equal to the number of optical paths are provided for one light receiving opening 9a or 9b. Alternatively, mirrors that reflect laser light may be used as the light receiving units 5a and 5b, and light receiving elements such as photodiodes and phototransistors may be provided on the irradiation units 3a and 3b sides.

[0022] The amplifier 6 amplifies the electrical signals from the light receiving elements of the light receiving sections 5a and 5b and converts them into digital signals.

[0023] Mirrors 11a to 11d that reflect laser light are provided inside structure 2. Mirror 11a is provided on the optical path (the optical path is indicated by a broken line) from irradiating unit 3a to light-receiving unit 5b, and reflects the laser light from irradiating unit 3a to light-receiving unit 5b. Similarly, mirror 11b is provided on the optical path from irradiating unit 3b to light-receiving unit 5a, and reflects the laser light from irradiating unit 3a to light-receiving unit 5a. The same applies to mirrors 11c and 11d.

[0024] Mirrors 11a to 11d are installed on wall surfaces of structure 2 where openings cannot be provided. This allows optical paths to be arranged in places where straight lines cannot be connected due to opening restrictions, increasing the number of optical paths and allowing optical paths to be arranged in more directions. Figure 2 shows a comparative example in which no mirrors are installed inside structure 2. In this comparative example, the number and directions of optical paths are restricted.

[0025] The spatial resolution of gas concentration and temperature distributions measured using CT depends on the number and direction of optical paths. By increasing the number and direction of optical paths using mirrors 11a to 11d, the spatial resolution of gas concentration and temperature distribution measurements can be improved. This can be used for local measurements as well as overall measurements. By concentrating the optical paths by placing mirrors 11a to 11d in the area where the concentration and temperature distributions need to be measured with high precision, the spatial resolution can be improved without increasing the aperture.

[0026] The configuration of mirrors 11a and 11b will be described in detail below. Figure 3 shows a vertical cross-sectional view of structure 2. Reference numerals 3a and 3b denote irradiation units, and 5a and 5b denote light-receiving units. In Figure 3, gas flows from bottom to top. For ease of understanding, mirrors 11a and 11b are shown above irradiation units 3a and 3b and light-receiving units 5a and 5b in Figure 3, but in reality, mirrors 11a and 11b, irradiation units 3a and 3b, and light-receiving units 5a and 5b are arranged at the same height.

[0027] If mirrors 11a and 11b are placed inside structure 2, there is a risk that foreign matter such as ash or dust will adhere to mirrors 11a and 11b, causing them to stop reflecting laser light. To prevent this, it is desirable to provide purge gas ejection sections 12a and 12b (nozzles) upstream of the airflow relative to mirrors 11a and 11b. To prevent condensation on mirrors 11a and 11b, the purge gas must be at a temperature equal to or higher than the dew point temperature of the measurement site, and is preferably dry air, and is preferably nitrogen gas that does not absorb infrared rays. Although not shown, mirrors 11c and 11d have a similar configuration.

[0028] A purge gas pipe 15 is connected to the ejection parts 12a and 12b. The purge gas pipe 15 passes through the wall surface that is opened at the opening of the structure 2. Note that foreign matter adhering to the mirrors 11a and 11b may be removed by vibrating the mirrors 11a and 11b. However, since the vibrations cause the optical axis to shift, the vibrations must be small enough to fall within the receivable range.

[0029] It is desirable that the angles of the mirrors 11a and 11b are adjustable, in order to make it easier to align the optical axis and also to enable the optical axis to be realigned if it becomes misaligned due to temperature changes inside the structure 2 or the like.

[0030] It is desirable to control the angles of mirrors 11a and 11b by mirror control device 16. Mirror control device 16 controls a drive source such as a motor to control the angles of mirrors 11a and 11b, and switches the light receiving unit that receives the laser light, for example, from 5b to 5a. Furthermore, if the laser light no longer reaches light receiving units 5a and 5b due to a temperature change or the like inside structure 2, mirror control device 16 fine-tunes the angles of mirrors 11a and 11b so that the laser light reaches light receiving units 5a and 5b.

[0031] 1, a computer 7 acquires a signal (absorbance data) from the amplifier 6, calculates the distribution of gas concentration and temperature from the acquired absorbance data using CT, and generates a two-dimensional image showing the concentration distribution and temperature distribution. The method for calculating the distribution of gas concentration and temperature using CT will be described later.

[0032] 4 is a diagram illustrating the configuration of the computer 7. The computer 7 is configured, for example, as a personal computer. The computer 7 includes a control unit 21 that controls the overall operation thereof, a display unit 22 that displays various information, an operation unit 23 through which the user performs input operations, a RAM 24 that temporarily stores data, a storage unit 25 that stores data and programs, and a communication interface 26 for communicating with external devices.

[0033] The display unit 22 is a liquid crystal display, an organic EL display, or the like. The display unit 22 displays two-dimensional images showing the gas concentration distribution and temperature distribution. The operation unit 23 is a keyboard, mouse, touch panel, or the like, and accepts user operation input. The communication interface 26 communicates with the amplifier 6 in accordance with a predetermined communication standard. The RAM 24 is composed of semiconductor devices such as DRAM and SRAM, and temporarily stores data and functions as a work area for the control unit 21. The storage unit 25 is composed of a hard disk, SSD, or the like, and stores predetermined programs, data, etc. The control unit 21 is composed of a CPU, etc., and executes predetermined programs.

[0034] The following describes how to calculate the distribution of gas concentration and temperature using CT. First, the absorption method will be explained.

[0035] The absorption method is a measurement method that utilizes the property that when a laser beam of a certain wavelength is irradiated onto the gas to be measured, certain gas molecules contained in the gas absorb the laser beam of a specific wavelength, and the property that the amount of absorption depends on the concentration and temperature. λ0 ) and transmitted light intensity (I λ ) ratio (I λ / I λ0 ) can be used to measure the concentration and temperature of the target gas. λ / I λ0 is expressed by the following relational expression (1) using Lambert's formula:

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[0036] When laser light is irradiated onto a gas, the absorbance A at each optical path p is λ is expressed by the following relational expression (2).

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[0037] The optical paths p and grids q are set, for example, as shown in Fig. 5. In this example, grids 1 to 25 are set, and eight optical paths (optical paths (1) to (8)) exist.

[0038] According to equation (2), the absorbance A for a certain wavelength λ,p is the concentration n of the gas to be measured and the absorption coefficient α λ,q and the optical path length L. Since the optical path length L is known, the gas concentration n and absorption coefficient α for each of the multiple grids q included in each optical path p can be calculated. λ,q If we know the absorbance A for each light path p, λ,p where the absorption coefficient α λ,q is a function of temperature. Therefore, if the gas concentration n and temperature T of each of the multiple grids q included in each optical path p are known, the absorbance A λ,p is required.

[0039] Assuming the initial concentration and temperature, the actual measured value ((A λ,q ) data , absorbance data) and theoretical value ((A λ,q ) theory The concentration and temperature at each grid are converged so that the error in the above equation (Error) is minimized (see, for example, Patent Document 1). This makes it possible to calculate the gas concentration n and temperature T at each grid q.

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[0040] In the above embodiment, the gas concentration and temperature are measured in a two-dimensional region, but the present invention can be extended to a case where the gas concentration and temperature are measured in a three-dimensional region. [Explanation of symbols]

[0041] 1...Gas measuring device 2...Structure 3a, 3b…irradiation section 5a,5b...light receiving section 7. Computer 8a, 8b…Irradiation aperture 9a, 9b…light receiving aperture 11a~11d…Mirror 12a, 12b…Gushing part 16...Mirror control device

Claims

1. A gas measurement device that measures the distribution of a physical state of gas inside a structure, a plurality of irradiation units that irradiate the interior of the structure with laser light through a plurality of irradiation openings in the structure; a plurality of light receiving units that receive the laser light that has passed through the gas inside the structure through a plurality of light receiving openings that are located at positions different from the irradiation openings of the structure; a computer that acquires absorbance data along a plurality of optical paths of the laser light that has passed through the gas inside the structure and determines a distribution of the physical state of the gas; a mirror that reflects the laser light is provided inside the structure and on at least one of the plurality of optical paths; a light path that can be connected by a straight line from any one of the plurality of irradiation units to any one of the plurality of light receiving units, and a light path that reflects laser light from any one of the plurality of irradiation units by the mirror and reaches any one of the plurality of light receiving units, both of which pass through the irradiation opening and the light receiving opening.

2. 2. The gas measuring device according to claim 1, further comprising a purge gas ejection section for preventing foreign matter from adhering to said mirror.

3. 3. The gas measuring device according to claim 1, wherein the angle of the mirror is adjustable so that the direction in which the laser light is reflected can be changed.

4. 4. The gas measuring device according to claim 3, further comprising a mirror control device for controlling the angle of the mirror so that the light receiving portion for receiving the laser beam can be switched.

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