LIBS Analysis System and LIBS Analysis Method

Abstract

To provide a novel and improved LIBS analysis system which is capable of spectroscopically analyzing measurement objects on a conveyance device more accurately.SOLUTION: Provided is an LIBS analysis system comprising: LIBS optical units which irradiate a measurement object conveyed on a conveyance device with laser for LIBS and receive plasma light emission from the measurement object; a spectroscopic analysis unit which acquires spectral information of the plasma light emission by spectroscopically analyzing the plasma light emission received by the LIBS optical units; and a chemical element concentration acquisition unit which acquires a kind and a concentration of a chemical element contained in the measurement object on the basis of the spectral information. In the LIBS analysis system, a plurality of LIBS optical units are arranged in a direction orthogonal to a conveyance direction of the measurement object on the conveyance device.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a LIBS analysis system and a LIBS analysis method.

Background Art

[0002] Measurement of the elemental concentration of a measurement object that is being conveyed and has a complex shape is essential in various fields such as, for example, sintered ore, iron ore, coal, limestone, or auxiliary raw materials on a belt conveyor in the steel industry, as well as in the manufacturing process of chemical products or pharmaceuticals, environmental measurement, wastewater treatment processes such as wastewater or oil, and food processing processes.

[0003] As a method for analyzing elemental concentration, for example, a method of sampling a measurement object as a sampling inspection and chemically analyzing it as an analysis sample is known and industrially utilized. However, with this method, it is not possible to inspect the entire quantity of the measurement object, and it is also not possible to perform on-line inspection or to detect whether the components of the measurement object on the conveyor are fluctuating in real time. Therefore, when sampling is performed, a statistical method is used in combination to prevent the above problems from occurring. However, when foreign matter is mixed in a normal measurement object, it is possible to overlook or miss it even by a statistical method. Therefore, there are limitations to statistical methods.

[0004] As an analysis technique that can overcome the above disadvantages, for example, as disclosed in Patent Document 1, a technique using laser-induced breakdown spectroscopy (hereinafter referred to as LIBS analysis method) is known. In the LIBS analysis method, a laser is focused and irradiated onto a measurement object to be analyzed. As a result, breakdown plasma is generated on the surface of the measurement object. Such breakdown plasma causes thermal excitation of the elements in the measurement object, and the measurement object emits light due to such thermal excitation (hereinafter, such light emission is also referred to as plasma light emission). In the LIBS analysis method, the plasma light emission from the measurement object is spectroscopically analyzed. Specifically, the element is identified from the wavelength of the plasma light emission, and the concentration is quantified from the emission intensity of the plasma light emission.

[0005] The analyzer used in LIBS analysis is composed of a high-power laser, a spectroscopic detector, and, if necessary, an optical fiber for transmitting light emission, a digital pulse generator, etc. In recent years, it has been increasingly applied to various fields, not only to moving objects such as the object to be measured on a conveyor, but also to high-temperature liquids, objects under high-pressure environments, such as rocks on the deep seabed, the nuclear field, molten metals, etc.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, when spectroscopically analyzing the object to be measured conveyed on a conveying device (for example, a belt conveyor) by LIBS analysis, conventionally, only one LIBS analyzer was installed at one location on the conveying path. For this reason, there were cases where the data obtained by continuously spectroscopically analyzing the object to be measured (for example, sintered ore) conveyed on the conveying device by LIBS analysis did not match the data obtained by sampling the object to be measured on the conveying device.

[0008] Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a novel and improved LIBS analysis system and LIBS analysis method capable of more accurately spectroscopically analyzing the object to be measured on the conveying device.

Means for Solving the Problems

[0009] In order to solve the above problems, according to an aspect of the present invention, there is provided a LIBS optical unit that irradiates a measurement object being conveyed on a conveyance device with a laser for LIBS and receives plasma light emission from the measurement object, a spectroscopic analysis unit that acquires spectral information of the plasma light emission by spectroscopically analyzing the plasma light emission received by the LIBS optical unit, and an element concentration acquisition unit that acquires the types and concentrations of elements contained in the measurement object based on the spectral information. The LIBS optical unit is arranged in a plurality in a direction intersecting the conveyance direction of the measurement object in the conveyance device. , the LIBS optical unit includes a laser transmission optical fiber for transmitting the LIBS laser, a plasma emission transmission optical fiber for transmitting the plasma emission, and a condensing optical system for condensing the LIBS laser and the plasma emission. The laser transmission optical fiber and the plasma emission transmission optical fiber are configured as a bundle fiber in which a plurality of optical fibers are bundled. The bundle fiber includes both the laser transmission optical fiber and the plasma emission transmission optical fiber. A LIBS analysis system is provided, which is characterized by the above.

[0010] Here, The condensing optical system may have a collimating lens and a focus variable condensing lens, and the focus variable condensing lens is of a hydraulic drive type. it may be.

[0011] Further, the spectroscopic analysis unit may acquire a plurality of spectral information by spectroscopically analyzing the plasma light emission received by each of the plurality of LIBS optical units, and the element concentration acquisition unit may obtain the concentration of the element contained in the measurement object based on each of the plurality of spectral information.

[0012] Further, the element concentration acquisition unit may acquire the concentration of the element by averaging the concentrations of the elements acquired based on the spectral information over a predetermined time for each LIBS optical unit.

[0013] Further, the element concentration acquisition unit may acquire the concentration distribution of the elements contained in the measurement object within a strip-shaped region having the width of the conveyance device and a predetermined conveyance distance as the length.

[0014] Further, an abnormal region determination unit that determines a region deviating from a preset element concentration range on the element concentration distribution as an abnormal region may be further provided.

[0015] Further, the spectroscopic analysis unit may acquire a plurality of spectral information by spectroscopically analyzing the plasma light emission received by each of the plurality of LIBS optical units, and the element concentration acquisition unit may obtain the element concentration based on each of the plurality of spectral information, and use the element concentration to obtain the average element concentration contained in the measurement object.

[0016] Further, the element concentration acquisition unit may obtain the average element concentration included in the object to be measured by obtaining the arithmetic mean of the element concentrations included in the object to be measured obtained based on each of the plurality of spectral information.

[0017] Further, the element concentration acquisition unit may obtain the average element concentration included in the object to be measured by obtaining the weighted average of the element concentrations included in the object to be measured obtained based on each of the plurality of spectral information.

[0018] Further, the element concentration may be the average of the element concentrations included in the object to be measured obtained based on each of the plurality of spectral information over a predetermined time for each LIBS optical unit.

[0019] Further, an object shape measurement unit that is arranged upstream of the plurality of LIBS optical units in the conveyance direction of the object to be measured and measures the surface shape of the object to be measured, and an automatic focusing tracking unit that adjusts the focus of the lens system of the LIBS optical unit based on the surface shape of the object to be measured measured by the object shape measurement unit may be further provided.

[0020] According to another aspect of the present invention, there is provided a LIBS analysis method characterized by acquiring the concentration distribution of elements included in an object to be measured in a strip-shaped region having the width of the conveyance device and a predetermined conveyance distance as the length, or determining a region deviating from a preset element concentration range on the concentration distribution of the elements as an abnormal region, or obtaining the average element concentration included in the object to be measured, using the above-described LIBS analysis system.

Effects of the Invention

[0021] According to the above aspect of the present invention, it becomes possible to perform spectroscopic analysis on the object to be measured on the conveyance device with higher accuracy.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0023] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the numerical limitation range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. A numerical value indicated by "more than" or "less than" is not included in the numerical range.

[0024] <1. Consideration by the Inventor of the Present Invention> First, the inventor of the present invention earnestly studied the means for solving the above-described problems and came up with the LIBS analysis system according to the present embodiment. Therefore, first, the consideration by the inventor of the present invention will be described.

[0025] The inventor of the present invention considered that the above-described problems might occur because the object to be measured is unevenly distributed in the width direction during conveyance. As an example of the occurrence of non-uniformity of the object to be measured, sintered ore conveyed on a belt conveyor can be mentioned. FIG. 1 schematically shows the distribution in the width direction of the sintered ore 110 and 111 conveyed on the belt conveyor 101. Note that FIG. 1 shows a cross section perpendicular to the length direction of the belt conveyor 101. The belt conveyor 101 is driven in the forward direction (or the back direction) in the figure by the driving device 100. Thereby, the sintered ore 110 and 111 are conveyed.

[0026] The crushed sintered ores 110 and 111 are classified while being conveyed on the belt conveyor 101. Fine-grained sintered ores 111 are distributed at both ends and the lower part in the width direction of the column of sintered ores (a column consisting of a large number of conveyed sintered ores), and the coarser-grained sintered ores 110 increase as it gets closer to the central part of the column of sintered ores. Thus, the sintered ores on the belt conveyor 101 are classified along with vibrations during conveyance and the like. Although details will be described in the examples, the fine-grained sintered ores 111 contain more CaO than the coarser-grained sintered ores 110. For this reason, when the column of sintered ores is spectroscopically analyzed in this embodiment, a large amount of CaO is detected from both ends in the width direction.

[0027] In the above, an example of conveying sintered ores by a belt conveyor was used to explain that the object to be measured is unevenly distributed in the width direction. However, it is considered that such non-uniformity can also occur in other types of conveying devices and objects to be measured.

[0028] Therefore, the inventor of the present invention constructed a LIBS analysis system by arranging a plurality of LIBS optical units (devices that irradiate a laser for LIBS to the object to be measured conveyed on the conveying device and receive plasma light emission from the object to be measured) in a direction intersecting the conveying direction of the object to be measured in the conveying device. Thereby, in addition to the conveying direction of the conveying device over time, the width direction of the conveying device also becomes a measurement target area by the LIBS analysis system.

[0029] According to the LIBS analysis system according to the present embodiment, for example, the average component composition of the object to be measured over the entire predetermined area on the conveying device can be obtained. Furthermore, by taking into account differences such as the distribution amount in the width direction, the weighted average of each analysis value in the width direction can be obtained. Thereby, a more accurate average component concentration can be obtained. Furthermore, according to the LIBS analysis system according to the present embodiment, a two-dimensional distribution of the component composition of the object to be measured on the conveying device can be obtained.

[0030] Here, the LIBS optical unit may be composed of a laser transmission optical fiber for transmitting the LIBS laser, a plasma emission transmission optical fiber for transmitting the plasma emission, and a condensing optical system for condensing the LIBS laser and the plasma emission. In this case, space can be saved and the cost of the entire system can be reduced.

[0031] <2. Detailed Configuration of LIBS Analysis System> Next, based on FIGS. 2 to 4, the detailed configuration of the LIBS analysis system A according to the present embodiment will be described. In the examples of FIGS. 2 to 4, it is assumed that the conveying device 10 is a belt conveyor. The conveying device 10 conveys the object to be measured 9 in the right direction in FIG. 2.

[0032] The LIBS analysis system A according to the present embodiment includes an object to be measured shape measuring device (object to be measured shape measuring unit) B and a spectroscopic analyzer C. The LIBS analysis system A generally performs the following processes. That is, the distance between the object to be measured 9 (for example, sintered ore) and the LIBS optical unit 8 is measured by the object to be measured shape measuring device B. Then, based on the measured distance between the LIBS optical unit 8 and the object to be measured 9, the focus of the LIBS optical unit 8 is adjusted. Specifically, the focus of the LIBS optical unit 8 is adjusted so that the LIBS laser irradiated from the LIBS optical unit 8 forms a focus on the surface of the object to be measured 9. In addition, in the present embodiment, the object to be measured shape measuring device B is not essential.

[0033] Next, a LIBS laser is irradiated from the LIBS optical unit 8 of the spectroscopic analyzer C to the object to be measured 9. Then, the LIBS optical unit 8 receives the plasma emission emitted from the object to be measured 9 and outputs it to the spectroscopic analysis unit 7. The spectroscopic analysis unit 7 spectroscopically analyzes the plasma emission. Specifically, the plasma emission is divided into wavelength and intensity. The spectroscopic analysis unit 7 generates spectral information regarding the wavelength and intensity of the plasma emission and outputs it to the element concentration acquisition unit 12. The element concentration acquisition unit 12 acquires the types and concentrations of the elements constituting the object to be measured 9 based on the spectral information. A plurality of LIBS optical units 8 are arranged in a direction (perpendicular in this example) intersecting the conveyance direction of the object to be measured 9 in the conveyance device 10. Therefore, in addition to the conveyance direction of the conveyance device 10 over time, the width direction of the conveyance device 10 also becomes a measurement target area by the LIBS analysis system A. Here, the intervals and numbers between the LIBS optical units for the abnormality detection unit 13 to be described later to detect abnormalities vary from case to case. However, for example, as a guideline, the interval between the LIBS optical units 8 may be about 1.5 times the maximum particle size of the object to be measured, and may be arranged so as to be able to analyze the entire width on which the object to be measured is loaded. For example, when an object to be measured having a maximum particle size of 70 mm is loaded on a belt conveyor with a width of 50 cm, six LIBS optical units 8 may be installed at intervals of about 100 mm.

[0034] Next, the detailed configuration of the LIBS analysis system A will be described. The LIBS analysis system A includes an object to be measured shape measurement device (object to be measured shape measurement unit) B and a spectroscopic analyzer C. The object to be measured shape measurement device B includes a laser distance meter 1, a bundle-type optical fiber 2, an optical fiber guide 3, and an autofocus tracking unit 11.

[0035] The optical fiber guide 3 is a guide through which the optical fiber 2 passes, and a plurality of them are arranged in a direction (perpendicular in this example) intersecting the conveyance direction of the object to be measured 9 in the conveyance device 10. The optical fiber 2 and the laser distance meter 1 are prepared in the same number as the number of the optical fiber guides 3. Alternatively, when the output of the laser distance meter 1 is sufficiently large, a ranging laser may be output from one (or a number less than the number of the optical fiber guides 3) laser distance meter 1.

[0036] As the laser distance meter 1, a type that can measure the distance to the object 9 to be measured on the transport device 10 and can keep up with the speed of the transport device (the speed of the belt conveyor) and the focusing by the autofocus tracking unit 11 may be selected. As a specific example of the laser distance meter 1, those using the triangulation method in which the detection method of the return light (light emission from the object 9 to be measured) is the CMOS method or the CCD method, and those using the time-of-flight measurement method in which the measurement method is the phase difference distance method or the pulse propagation method can be utilized.

[0037] The laser distance meter 1 generally irradiates the object 9 to be measured with a laser for distance measurement through the bundle-type optical fiber 2. The bundle-type optical fiber 2 is composed of an optical fiber for transmitting the laser light for distance measurement and an optical fiber for transmitting the light emission from the object 9 to be measured. That is, the bundle-type optical fiber 2 receives the light emission from the object 9 to be measured and outputs it to the laser distance meter 1. The laser distance meter 1 measures the distance to the object 9 to be measured (specifically, the distance from the focus variable condenser lens 15 of the LIBS optical unit 8 to the object 9 to be measured) based on the phase difference between the light emission from the object 9 to be measured and the laser for distance measurement. As the distance information, that which can measure with a distance measurement accuracy necessary for adjusting the focus of the LIBS laser, for example, within ±3 mm, is selected.

[0038] The laser distance meter 1 measures the surface shape of the object 9 to be measured from the distance to the object 9 to be measured, and outputs distance information regarding the measurement result to the autofocus tracking unit 11. The autofocus tracking unit 11 adjusts the focus of the LIBS optical unit 8 based on the distance information given from the laser distance meter 1. Specifically, the focus of the LIBS optical unit 8 is adjusted so that the LIBS laser irradiated from the LIBS optical unit 8 forms a focus on the surface of the object 9 to be measured. Here, in addition to the distance information from the laser distance meter 1, the autofocus tracking unit 11 is based on the moving speed information of the transfer device 10 and the focus distance change speed information of the focus variable condenser lens 15 (both are known), and at the timing when the object 9 to be measured is transferred right below the LIBS optical unit 8, it is preferable to control the LIBS optical unit 8 so that the focus of the LIBS laser forms a focus on the surface of the object 9 to be measured. The autofocus tracking unit 11 is composed of, for example, a pulse generator that can generate a pulse having an appropriate voltage on the order of microseconds.

[0039] In addition, in the above example, a laser distance meter is used as the distance meter, but the type of the distance meter is not limited to the laser distance meter. That is, any distance meter that can measure the surface shape of the object 9 to be measured may be used. Also, the LIBS analysis system according to the present embodiment does not require the object shape measuring device (object shape measuring unit) B as an essential component.

[0040] The spectroscopic analyzer C includes a bundle-type optical fiber 4, a branching unit 5, a LIBS laser oscillator 6, a spectroscopic analysis unit 7, a LIBS optical unit 8, an element concentration acquisition unit 12, and an abnormality detection unit 13.

[0041] As shown in FIG. 4, the bundle-type optical fiber 4 has a configuration in which a plurality of optical fibers 4a for transmitting the LIBS laser and a plurality of optical fibers 4b for transmitting plasma light are bundled. It is preferable to bundle the optical fibers 4a and 4b as evenly as possible so that the incident light of the LIBS laser and the light collection of the plasma light are coaxial as much as possible. As shown in FIG. 3, the branching unit 5 connects a plurality of optical fibers 4b for transmitting plasma light to the spectroscopic analysis unit 7.

[0042] The laser oscillator 6 for LIBS emits the LIBS laser to the optical fiber 4a. As shown in FIG. 3, the optical fiber 4a outputs the LIBS laser to the LIBS optical unit 8. Here, the LIBS laser may have specifications sufficient to excite and analyze the object to be measured. For example, the wavelength may be 355 nm to 1064 nm, the pulse width may be 1 ns to 10 ns, the repetition frequency may be 10 to 100 Hz, and the pulse energy may be 30 to 100 mJ / pulse.

[0043] A plurality of LIBS optical units 8 are arranged in a direction intersecting the conveyance direction of the object to be measured 9 in the conveyance device 10. The optical fibers 4 and the laser oscillator 6 for LIBS are prepared in the number corresponding to the number of LIBS optical units 8. Alternatively, when the output of the laser oscillator 6 for LIBS is sufficiently large, the LIBS laser may be output from one (or a number less than the number of LIBS optical units 8) laser oscillator 6 for LIBS.

[0044] As shown in FIG. 3, the LIBS optical unit 8 includes a fiber guide, a collimating lens 14, and a focus-variable condenser lens 15. From the viewpoint of space saving, it is preferable that the LIBS optical unit 8 is as small as possible. The collimating lens 14 collimates the LIBS laser from the optical fiber 4a and outputs the plasma light emission from the object to be measured 9 to the optical fiber 4b. The focus-variable condenser lens 15 is driven by the control of the autofocus tracking unit 11 to form the focus of the LIBS laser collimated by the collimating lens 14 on the surface of the object to be measured 9. Instead of the focus-variable condenser lens 15, a lens may be moved, but the size increases due to an increase in mechanical parts such as an actuator and a gear mechanism. Therefore, it is preferable to use the focus-variable condenser lens 15. As the focus-variable condenser lens 15, for example, a hydraulic drive type is preferably used. The plasma light emission generated on the surface of the object to be measured 9 is input to the optical fiber 4b through the focus-variable condenser lens 15 and the collimating lens 14. The optical fiber 4b outputs the plasma light emission to the spectroscopic analysis unit 7.

[0045] The spectroscopic analysis unit 7 generates spectral information regarding the wavelength and intensity of the plasma emission by spectroscopically analyzing the plasma emission provided from the optical fiber 4b. Here, since a plurality of LIBS optical units 8 are arranged in a direction intersecting the conveyance direction of the object to be measured 9 in the conveyance device 10, a plurality of spectral information is generated not only in the conveyance direction of the conveyance device 10 over time but also in the width direction of the conveyance device 10.

[0046] The element concentration acquisition unit 12 acquires the types and concentrations of the elements constituting the object to be measured 9 based on the spectral information. For example, the element concentration acquisition unit 12 may quantify the types and concentrations of the elements using a calibration curve based on a predetermined standard sample.

[0047] As described above, since a plurality of spectral information is generated not only in the conveyance direction of the conveyance device 10 over time but also in the width direction of the conveyance device 10, the types and concentrations of the elements are also generated in a plurality in not only the conveyance direction of the conveyance device 10 but also the width direction of the conveyance device 10. Therefore, for example, the types and concentrations of the elements can be mapped on a two-dimensional map with the time axis as the x-axis and the width direction of the conveyance device 10 as the y-axis. That is, a two-dimensional concentration distribution can be obtained. This mapping may be performed by the element concentration acquisition unit 12 or may be performed by a separately prepared electronic computer (PC).

[0048] Here, the element concentration acquisition unit 12 may average the concentrations of the elements acquired based on the spectral information over a predetermined time for each LIBS optical unit 8. In this case, each value of the two-dimensional map of the element concentration is a value averaged over a predetermined time. The predetermined time may be, for example, 0.5 seconds or the like.

[0049] The abnormality detection unit 13 searches the two-dimensional map obtained by the element concentration acquisition unit 12 and detects a region where the element concentration deviates from a predetermined element concentration range. Then, the detected region is set as an abnormal region. The abnormality detection unit 13 preferably performs marking or the like at the position where the abnormality is detected. Thereafter, the element concentration acquisition unit 12 displays the obtained two-dimensional map. As a result, the operator can easily find the abnormality of the object to be measured 9 without stopping the transfer device 10.

[0050] (2-1. Method for obtaining average concentration) The element concentration acquisition unit 12 may obtain an average concentration for each element based on the spectrum information given from the spectroscopic analysis unit 7. Here, a typical method for obtaining the average concentration will be described.

[0051] The element concentration acquisition unit 12 may obtain the average concentration by arithmetically averaging the concentrations of the elements obtained from all or part of the plurality of spectrum information given from the spectroscopic analysis unit 7. For example, the average concentration may be obtained using only the spectrum information near the central part of the column of the object to be measured 9. In this case, the element concentration acquisition unit 12 obtains the type and concentration of the element from the spectrum information near the central part of the column of the object to be measured 9, for example, and arithmetically averages these for each element. As described above, when the object to be measured 9 is a sintered ore, the coarse-grained sintered ore concentrates near the central part. Coarse-grained sintered ore often occupies most of the entire sintered ore. Therefore, an average concentration close to the overall average value can be obtained. In the above, only a part of the element concentrations at the ends may be incorporated. In this case, by incorporating only a part of the element concentrations at the ends, an average concentration closer to the overall average value can be obtained with respect to the element concentration obtained by measuring only the central part.

[0052] As another method, for example, the element concentration acquisition unit 12 may weight-average the concentrations obtained based on the spectrum information given from the spectroscopic analysis unit 7 for each element. For example, the concentrations are weight-averaged for each element based on the following formula (1). Cave = α1C1 + α2C2 + ··· + αnCn (1) In formula (1), Ci (where i is an integer from 1 to n) represents the concentration calculated based on the spectral information given by the i-th LIBS optical unit 8. αi is the weighting coefficient of the concentration Ci. The coefficient αi can be obtained by multiple regression analysis or the like from the measurement results in a sufficient number (quantity) of charges of the object to be measured 9. Alternatively, the weight ratio of particles with a particle size equal to or greater than a predetermined particle size and particles with a particle size less than the predetermined particle size may be measured, and the coefficient αi may be determined based on this weight ratio.

[0053] Note that when the object to be measured 9 is sintered ore, as long as the process conditions of crushing and classification do not change significantly, the coefficient αi obtained by any of the above methods can be continuously used without change. However, when the analysis location is changed, when there is a manufacturing trouble, when the manufacturing conditions are changed, etc., the coefficient αi may be determined again.

[0054] (2-2. Monitoring of operation, process control) The operator visually checks the two-dimensional map obtained by the method described above. For example, when the concentration of a certain element at both ends of the column of the object to be measured 9 is less than (or greater than) the threshold value, operations such as cutting both ends may be performed. Thereby, the homogenization of the object to be measured 9 can be achieved. Further, when the object to be measured 9 is sintered ore, there may be a large difference in the CaO concentration between both ends and the central part of the column of the sintered ore. In this case, since troubles such as poor sintering in the sintering process and poor sieving after crushing the sintered cake are suspected, the operator can investigate the cause and take various measures such as maintaining the sieve as necessary or optimizing the temperature and air supply conditions in the sintering process. Alternatively, an optical camera may be installed in the above-described LIBS analysis system A, and the image obtained from the optical camera may be combined with the above-described spectroscopic analysis. In this case, the object to be measured 9 can be spectroscopically analyzed more accurately.

[0055] As described above, according to the LIBS analysis system A according to the present embodiment, it is possible to spectroscopically analyze the object to be measured on the transport device with higher accuracy.

Example

[0056] <1. Configuration of the System> A belt conveyor was used as the conveying device 10, and sintered ore was used as the object to be measured 9. The moving speed of the belt conveyor was set to 2 m / sec. The sintered ore was loaded on the belt conveyor without gaps and was being transported. The LIBS analysis system A was installed on the conveying device.

[0057] As the distance meter, the laser distance meter 1 shown in Fig. 2, that is, the coaxial confocal type laser distance meter 1 was adopted. Other configurations of the object shape measuring device B were the same as those shown in Fig. 2. That is, the laser distance meter 1 measures the surface shape of the object to be measured 9 from the distance to the object to be measured 9 and outputs the distance information regarding the measurement result to the autofocus tracking unit 11. The autofocus tracking unit 11 adjusts the focus of the LIBS optical unit 8 based on the distance information given from the laser distance meter 1. Specifically, the focus of the LIBS optical unit 8 is adjusted so that the LIBS laser irradiated from the LIBS optical unit 8 forms a focus on the surface of the object to be measured 9. Here, in addition to the distance information from the laser distance meter 1, the autofocus tracking unit 11 is based on the moving speed information of the conveying device 10 and the focal length change speed information of the focus variable condenser lens 15 (both are known), and at the timing when the object to be measured 9 is transferred directly below the LIBS optical unit 8, it is preferable to control the LIBS optical unit 8 so that the focus of the LIBS laser is formed on the surface of the object to be measured 9. In this embodiment, the autofocus tracking unit 11 is composed of a pulse generator. In each of the following embodiments, the function of the object shape measuring device B was not applied.

[0058] As the laser oscillator 6 for LIBS, a diode-pumped type was selected, with an output of 30 mJ / pulse and operating at 80 Hz. The bundled optical fiber 4 was made up of 32 bundles, with a total length of 25 m and bifurcated from 5 m in the middle. In order to be able to irradiate the laser over the entire width direction of the belt conveyor (conveyor width: 120 cm) as much as possible, the LIBS optical unit 8 including nine optical fibers was installed at approximately 10 cm intervals. The laser oscillator 6 for LIBS and the bundled optical fiber 4 were prepared in the same number as the number of LIBS optical units 8. The LIBS optical unit 8 includes, in addition to the above optical fiber, a collimating lens 14 with a dielectric multilayer coating, and a focus-variable condenser lens 15 whose focal length can be changed by about 10 cm by an applied voltage. The focus-variable condenser lens 15 is an Optotune EL-10-30-Ci-NIR-LD, and the response speed is 2.5 msec at about 10 cm. Since the speed of the belt conveyor is 2 m / sec, when the focus is variably adjusted at maximum, the object on the conveyor will move about 5 mm.

[0059] The focus-variable condenser lens 15 was focused near the surface of the object to be measured 9 under the control of the autofocus tracking unit 11. Incidentally, the weight of the spectroscopic analyzer C including the fiber guide was several kg, and attachment / detachment and maintenance could be easily performed by one person's manpower.

[0060] For the spectroscopic analysis unit 7, a small Czerny-Turner type spectroscope with a back-illuminated CCD as a detector was used. The spectroscopic analysis unit 7 corrected the spectral information with a zero-point correction function provided in the software. Thereafter, the spectroscopic analysis unit 7 used a filter function to determine and remove spectra with intensities above or below a certain level as emission failures. The spectroscopic analysis unit 7 integrated signals for 40 Hz (about 0.5 seconds, corresponding to the load on 1 m of the belt conveyor) in order to obtain a certain amount of average information. The spectroscopic analysis unit 7 generated spectral information through the above processing.

[0061] The element concentration acquisition unit 12 (composed of a CPU, ROM, RAM, etc.) converted the emission intensity into an element concentration by performing multivariate analysis on the spectral information with respect to a calibration curve prepared in advance. Through the above processing, the element concentration acquisition unit 12 generated the element concentration information and position information of the sintered ore on the belt conveyor. Subsequently, the element concentration acquisition unit 12 output these information to an electronic computer. The electronic computer created and visualized a contour map (2D map) with software. By creating the contour map, operators can visually confirm the component variations. Using the above LIBS analysis system A, the following Examples 1 and 2 were conducted.

[0062] (Example 1) The Ca concentration distributions (converted to CaO concentration) of the sintered ore for 175 m of the same belt conveyor were generated in two types (operation cases 1 and 2). These CaO concentration distributions are data collected at different operation timings. In any of the concentration distributions, the Ca concentration of the sintered ore at both ends of the belt conveyor was about 1 - 2 mass% higher than that of the sintered ore at the center of the belt conveyor.

[0063] In this Example 1, when obtaining the average composition of the sintered ore conveyed over a predetermined length (175 m) on the conveyor, the time-averaged concentration obtained by averaging the CaO concentration based on the spectral information obtained by each LIBS optical unit 8 over a time period of 0.5 seconds was arithmetically averaged over the entire measurement length (175 m), and the resulting CaO concentration was used. Among the nine LIBS optical units 8 arranged in the width direction of the conveyor, the arithmetic mean value of the measurement values (CaO concentration) obtained by a total of five LIBS optical units, including the central unit and two units on both sides thereof, was defined as the central mean value, and the arithmetic mean value of the measurement values (CaO concentration) obtained by a total of four LIBS optical units at both ends was defined as the end mean value. Also, the measurement value of only the central LIBS optical unit was defined as the central measurement value. This corresponds to a comparative example.

[0064] In operation case 1, the central average value was 13.11 mass% and the end average value was 14.69 mass%. In operation case 2, the central average value was 12.98 mass% and the end average value was 14.53 mass%. Therefore, it was confirmed that in both cases, a difference of 1 mass% or more occurred between the central part and both ends.

[0065] (Example 2) Sintered ore with a particle size of less than 5 mm was defined as fine particles, and sintered ore with a particle size of 5 mm or more was defined as coarse particles. It was confirmed that in the raw materials on the conveyor examined in this example, the fine particles accounted for 7% of the total by weight and the coarse particles accounted for 93% of the total by weight. Based on this result, when the analysis results of the above-mentioned operation cases 1 and 2 were weighted, the analysis value of the entire sintered ore on the conveyor in operation case 1 was 13.11 mass% × 0.93 + 14.69 mass% × 0.07 = 13.22 mass%, and the analysis value of the entire sintered ore in operation case 2 was 12.98 mass% × 0.93 + 14.53 mass% × 0.07 = 13.09 mass%.

[0066] On the other hand, for comparison, sampling was carried out all at once in the width direction at a location with a row of sintered ore, and the CaO concentration was analyzed manually. This operation was repeated 3 times, and the obtained values were arithmetically averaged (offline analysis values. Table 2). As a result, it was 13.21 mass% in operation case 1 and 13.10 mass% in operation case 2. These values were in good agreement with the weighted average values described above.

[0067] Table 1 shows a comparison of each average value and the offline analysis value. The central average value and the weighted average value were in good agreement with the offline analysis value. In particular, the weighted average value was in good agreement with the offline analysis value. On the other hand, the central measurement value deviated significantly from the offline analysis value.

[0068]

Table 1

[0069]

Table 2

[0070] (Example 3) As described above, since there is a correlation between the particle size and the concentration, when performing image analysis using an optical camera and there are many small particle sizes, by combining this example with the image analysis, changes in the operation can be captured more accurately. For example, when there are few fine particles, operations such as adopting the central part average value and when the fine particles increase, adopting the weighted average value become possible.

[0071] Also, when image analysis was performed, it was confirmed that in operation case 1, the sintered ore at the center of the conveyor had a homogeneous composition, but in operation case 2, there was a certain variation in the particle size at the center of the conveyor. It is assumed that there were variations such as a partially small amount of lime added in the previous process for this part. Therefore, after removing it in the subsequent process, it was possible to verify why the amount of lime added varied in the previous process. The cause of the variation in the components in operation case 2 was the clogging of the lime feeder, and it could be immediately maintained and appropriately treated.

Explanation of Signs

[0072] A LIBS analysis system B Measured object shape measuring device C Spectroscopic analyzer 1 Laser rangefinder 2 Optical fiber 3 Optical fiber guide 4 Optical fiber 5 Branch unit 6 LIBS laser oscillator 7 Spectroscopic analysis unit 8 LIBS optical unit 9 Measured object 10 Conveyor device 11 Auto-focus tracking unit 12 Element concentration acquisition unit 13 Abnormality detection unit 14 Collimating lens 15 Focus-variable condenser lens

Claims

1. An LIBS optical unit that irradiates a measurement object being conveyed on a conveying device with a laser for LIBS and receives plasma light emission from the measurement object; A spectroscopic analysis unit that obtains spectral information of the plasma light emission by spectroscopically analyzing the plasma light emission received by the LIBS optical unit; An element concentration acquisition unit that obtains the types and concentrations of elements contained in the measurement object based on the spectral information, comprising: The LIBS optical unit is arranged in a plurality in a direction intersecting the conveying direction of the measurement object in the conveying device, The LIBS optical unit, An optical fiber for transmitting the laser for LIBS; An optical fiber for transmitting the plasma light emission; And a condensing optical system that condenses the laser for LIBS and the plasma light emission. The optical fiber for transmitting the laser and the optical fiber for transmitting the plasma light emission are configured as a bundle fiber in which a plurality of each optical fiber is bundled, and the bundle fiber includes both the optical fiber for transmitting the laser and the optical fiber for transmitting the plasma light emission. An LIBS analysis system characterized by this.

2. The LIBS analysis system according to claim 1, wherein the condensing optical system has a collimating lens and a focus-variable condensing lens.

3. The LIBS analysis system according to claim 2, wherein the focus-variable condensing lens is a hydraulic drive type.

4. The spectroscopic analysis unit obtains a plurality of spectral information by spectroscopically analyzing the plasma light emission received by each of the plurality of LIBS optical units, The element concentration acquisition unit obtains the concentration of an element contained in the measurement object based on each of the plurality of spectral information. The LIBS analysis system according to any one of claims 1 to 3.

5. The element concentration acquisition unit acquires the concentration of the element by averaging the concentrations of the elements acquired based on the spectral information over a predetermined time for each of the LIBS optical units, and is characterized in that it acquires the concentration of the element. The LIBS analysis system according to any one of claims 1 to 4.

6. The element concentration acquisition unit acquires the concentration distribution of the elements contained in the object to be measured within a strip-shaped region having the width of the transport device and a predetermined transport distance as the length, and is characterized in that it acquires the concentration distribution of the elements. The LIBS analysis system according to any one of claims 1 to 5.

7. The LIBS analysis system according to claim 6, further comprising an abnormal region determination unit that determines a region deviating from a preset element concentration range on the concentration distribution of the elements as an abnormal region.

8. The spectroscopic analysis unit acquires a plurality of spectral information by spectroscopically analyzing the plasma emission received by each of the plurality of LIBS optical units. The element concentration acquisition unit obtains the element concentration based on each of the plurality of spectral information, and obtains the average element concentration contained in the object to be measured by using the element concentration. It is characterized by The LIBS analysis system according to any one of claims 1 to 3.

9. The element concentration acquisition unit obtains the average element concentration contained in the object to be measured by obtaining the arithmetic mean of the element concentrations contained in the object to be measured obtained based on each of the plurality of spectral information, and is characterized in that it obtains the average element concentration. The LIBS analysis system according to claim 8.

10. The element concentration acquisition unit obtains the average element concentration contained in the object to be measured by obtaining the weighted average of the element concentrations contained in the object to be measured obtained based on each of the plurality of spectral information, and is characterized in that it obtains the average element concentration. The LIBS analysis system according to claim 8.

11. The LIBS analysis system according to any one of claims 8 to 10, characterized in that the element concentration is an average of the element concentrations contained in the object to be measured obtained based on each of the plurality of spectral information over a predetermined time for each LIBS optical unit.

12. An object shape measurement unit that is disposed upstream of the plurality of LIBS optical units in the conveyance direction of the object to be measured and measures the surface shape of the object to be measured; The LIBS analysis system according to any one of claims 1 to 10, further comprising an autofocus tracking unit that adjusts the focus of the lens system of the LIBS optical unit based on the surface shape of the object to be measured measured by the object shape measurement unit.

13. Using the LIBS analysis system according to any one of claims 1 to 12, Obtaining the concentration distribution of elements contained in the object to be measured within a strip-shaped region having the width of the conveyance device and a predetermined conveyance distance as the length, Alternatively, determining a region that deviates from a preset element concentration range on the concentration distribution of the elements as an abnormal region, Alternatively, an LIBS analysis method characterized by obtaining the average element concentration contained in the object to be measured.

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