Laser rapid detection device and method for heavy metal in solid fuel

Abstract

The invention belongs to the field of flue gas detection, and particularly discloses a laser rapid detection device and method for heavy metal in solid fuel, and in the detection device, a sample unit is used for placing a sample to be detected; the laser generating unit is used for emitting incident laser to a sample to be measured, the microwave generating unit is used for coupling microwaves to the incident laser, when the content of heavy metal is measured, the laser intensity is 100-300 mJ / fuse, the microwave power is 160-200 W, when the form of the heavy metal is measured, the laser intensity is 40-140 mJ / fuse, and the microwave power is 100-150 W; and the signal receiving unit is connected with the data processing unit. The method does not need to perform pretreatment on the to-be-detected sample, can realize in-situ online detection of the heavy metal in the solid fuel, can realize detection of the content and form of the heavy metal by adjusting the laser intensity and the microwave power, and has the advantages of high speed, high sensitivity, strong accuracy and the like.

Description

Technical Field

[0001] The present application belongs to the field of smoke detection, and more specifically, to a device and method for rapid laser detection of heavy metals in solid fuels. Background Art

[0002] Solid fuels (coal, coal coke, organic solid waste, biomass, etc.) contain heavy metals such as mercury, arsenic, lead, selenium, cadmium, etc. During the combustion and utilization of solids, heavy metals can be released and transferred to the environment. Heavy metals are highly toxic, difficult to fix and easy to enrich, which can destroy the ecosystem and cause human poisoning. With the rapid development of industrialization and urbanization, the increase in heavy metal emissions caused by fuel combustion, metal smelting and other activities has posed a great threat to the ecological environment and human health. Therefore, it is very important to control heavy metal emissions in the process of solid fuel utilization. Among them, source control can reduce heavy metals before use by screening solid fuels with low heavy metal content and difficult to release. Based on this, accurate testing of the content and form of heavy metals in solid fuels is particularly important for heavy metal emission reduction.

[0003] The current main method for testing heavy metals in solid fuels is the digestion test method. Digestion of samples (placing samples with acids, oxidants or catalysts in a reflux or closed device for sample decomposition) is a necessary condition for testing their concentration. The heavy metal concentration of the digestion solution can be tested by ICP / MP / ICP-MS, and then the heavy metal content in the solid fuel can be inverted. There is also the use of hydrogenation atomic absorption spectrometry (HGAA), which reduces heavy metal elements to hydrides through selective chemical reduction reactions and then tests. In addition, based on RFID wireless passive sensors, the flexible heavy metal sensor reacts with the digestion solution to produce a target resistance, causing the antenna communication capability to attenuate to achieve the detection of heavy metal concentrations.

[0004] Although the above three methods have solved the problem of heavy metal content detection, there are many challenges. First, for ICP / MP / ICP-MS technology, its digester is expensive, has low applicability, incomplete digestion reaction, and long digestion time; secondly, for HGAA technology, it is still difficult to determine multiple elements simultaneously; for RFID wireless passive sensors, its driving circuit is too complicated, the sensor sensitivity is low, the detection range is small, and the stability is not high. In addition, the forms of heavy metals in solid fuels are complex and diverse, including organic binding, water-soluble, sulfide binding, carbonate binding, iron / manganese oxide binding, and residual state. The main method for analyzing the form of heavy metals in solid fuels is the step-by-step extraction method, including the Tessier five-step extraction method and the BCR sequential extraction, that is, the heavy metal forms in the sample are analyzed by a series of extractants at different temperatures and extraction times. However, the recovery rate of the form distribution test of heavy metals in the sample to be tested by this method is poor and the accuracy is low. Summary of the invention

[0005] In view of the defects of the prior art, the present application provides a device and method for rapid laser detection of heavy metals in solid fuels, aiming to solve the problems of poor recovery rate and low accuracy of existing heavy metal detection methods.

[0006] The present application provides a device for rapid detection of heavy metals in solid fuel by laser, which specifically includes a sample unit, a laser generating unit, a microwave generating unit, a signal receiving unit and a data processing unit, wherein: the sample unit is used to place a sample to be tested; the laser generating unit is used to emit an incident laser to the sample to be tested, and when measuring the heavy metal content, the laser intensity is 100mJ / pluse~300mJ / pluse, and when measuring the heavy metal form, the laser intensity is 40mJ / pluse~140mJ / pluse; the microwave generating unit is used to couple microwaves to the incident laser, and when measuring the heavy metal content, the microwave power is 160W~200W, and when measuring the heavy metal form, the microwave power is 100W~150W; the signal receiving unit is connected to the data processing unit, and is used to receive the plasma signal generated by the sample to be tested and transmit it to the data processing unit for data analysis, so as to use microwave-assisted laser induced breakdown spectroscopy to perform online detection of the heavy metal content and form in the sample to be tested.

[0007] Through the above technical scheme conceived by the present application, compared with the prior art, since the present application uses microwave-assisted laser induced breakdown spectroscopy to perform online detection of the heavy metal content in the sample to be tested, it is possible to realize in-situ online detection of heavy metals in solid fuels, and the detection of heavy metal content and morphology can be achieved by adjusting the laser intensity and microwave power.

[0008] As a further preference, the sample unit includes a sample stage and an electric translation stage, one end of the sample stage is arranged above the electric translation stage so that it can move up and down driven by the electric translation stage, and the other end of the sample stage extends outward to fix the sample to be tested, and the sample stage is also used to drive the sample to be tested to move left and right.

[0009] As further preferred, the laser generating unit includes a digital delay, a laser generator and at least one reflector, wherein the digital delay is connected to the laser generator and is used to control the laser generator to emit the incident laser at a timed interval; and the reflector is used to reflect the incident laser to the position of the sample to be tested.

[0010] As further preferred, the microwave generating unit comprises a microwave generator and a microwave radiator, the microwave generator is used to emit microwaves, and the microwave radiator is connected to the microwave generator and is used to couple the microwaves to the incident laser.

[0011] As a further preferred embodiment, the signal receiving unit includes a focusing lens, a spectrometer and an ICCD which are sequentially arranged along the light propagation direction. The focusing lens is used to focus the characteristic spectrum radiated by the plasma and send it to the spectrometer and the ICCD. At the same time, the ICCD is also connected to a digital delay device and a data processing unit respectively to convert the optical signal into an electrical signal and send it to the data processing unit.

[0012] As further preferred, the signal receiving unit further includes a polarizer, which is arranged at the entrance of the spectrometer and is used to enhance or suppress the spectral lines of specific elements.

[0013] As further preferred, the signal receiving unit further includes a light beam receiver, which is arranged behind the sample to be tested along the light propagation direction and is used to receive the light signal and convert it into an electrical signal to assist in signal processing.

[0014] As a further preference, when measuring the heavy metal content, the gain of the ICCD is 1000-2500, the gate width is 100ns-500ns, and the delay time is 5μs-10μs; when measuring the heavy metal form, the gain of the ICCD is 100-500, the gate width is 10ns-100ns, and the delay time is 1μs-5μs.

[0015] According to another aspect of the present application, a method for rapid laser detection of heavy metals in solid fuels is provided, specifically: an incident laser coupled with microwaves is emitted to a sample to be tested to excite a plasma signal, and then the plasma signal is collected and data analysis is performed to perform online detection of the heavy metal content and morphology in the sample to be tested using microwave-assisted laser induced breakdown spectroscopy, wherein when measuring the heavy metal content, the laser intensity is 100mJ / pluse~300mJ / pluse, and the microwave power is 160W~200W, and when measuring the heavy metal morphology, the laser intensity is 40mJ / pluse~140mJ / pluse, and the microwave power is 100W~150W.

[0016] As a further preference, when using ICCD to collect plasma signals and measure the heavy metal content, the gain of the ICCD is 1000-2500, the gate width is 100ns-500ns, and the delay time is 5μs-10μs; when measuring the heavy metal form, the gain of the ICCD is 100-500, the gate width is 10ns-100ns, and the delay time is 1μs-5μs.

[0017] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art:

[0018] 1. The present application uses microwave-assisted laser-induced breakdown spectroscopy to perform online detection of the heavy metal content in the sample to be tested, which does not require pre-treatment of the sample to be tested, and can realize in-situ online detection of heavy metals in solid fuels. Moreover, by adjusting the laser intensity and microwave power, the heavy metal content and morphology can be detected, which has the advantages of fast speed, high sensitivity, and high accuracy.

[0019] 2. In particular, the present application optimizes the structure of the sample unit, which can drive the sample to be tested to move up and down, so as to monitor heavy metals in solid fuels at multiple locations;

[0020] 3. In addition, the present application also optimizes the parameters of the ICCD, which can work together with the laser intensity and microwave power to improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a laser rapid detection device for heavy metals in solid fuels provided in an embodiment of the present application.

[0022] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0023] 1-digital delay device, 2-laser generator, 3-reflector, 4-microwave generator, 5-microwave radiator, 6-electric translation stage, 7-data processing unit, 8-ICCD, 9-spectrometer, 10-polarizer, 11-focusing lens, 12-microwave, 13-beam receiver, 14-sample stage, 15-sample to be tested. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] like Figure 1 As shown, the present application provides a laser rapid detection device for heavy metals in solid fuels, which specifically includes a sample unit, a laser generating unit, a microwave generating unit, a signal receiving unit and a data processing unit 7, wherein: the sample unit is used to place a sample to be tested 15;

[0026] The laser generating unit is used to emit incident laser to the sample 15 to be tested, and includes a digital delayer 1, a laser generator 2 and at least one reflector 3. The digital delayer 1 is connected to the laser generator 2 and is used to control the laser generator 2 to emit the incident laser at a fixed time. Each reflector 3 is used to reflect the incident laser to the position of the sample 15 to be tested. When measuring the heavy metal content, the laser intensity of the incident laser is 100mJ / pluse to 300mJ / pluse, and when measuring the heavy metal form, the laser intensity of the incident laser is 40mJ / pluse to 140mJ / pluse.

[0027] The microwave generating unit is used to couple microwaves 12 to the incident laser, and includes a microwave generator 4 and a microwave radiator 5. The microwave generator 4 is used to emit microwaves, and the microwave radiator 5 is connected to the microwave generator 4 and is used to couple microwaves to the incident laser. When measuring the heavy metal content, the power of the microwave is 160W to 200W, and when measuring the heavy metal form, the power of the microwave is 100W to 150W.

[0028] The signal receiving unit is connected to the data processing unit 7, and is used to receive the plasma signal generated by the sample to be tested and transmit it to the data processing unit 7 for data analysis, so as to use microwave-assisted laser induced breakdown spectroscopy to perform online detection of the heavy metal content and form in the sample to be tested.

[0029] The present application utilizes microwave-assisted laser-induced breakdown spectroscopy to perform online detection of the heavy metal content in the sample to be tested, and does not require pre-treatment of the sample to be tested, and can achieve in-situ online detection of heavy metals in solid fuels. At the same time, the present application adjusts the laser intensity and microwave power to achieve detection of heavy metal content and morphology, and at the same time, considering that the laser intensity will affect the self-absorption effect and determine whether the signal can be excited, and the microwave power will directly affect the outer surface temperature of the sample to be tested 15, and will also produce a self-absorption effect, and there is a relatively complex interaction relationship. The present application optimizes the laser intensity and microwave power in the process of heavy metal content and heavy metal morphology detection, which can effectively improve the measurement accuracy.

[0030] Furthermore, the sample unit includes a sample table 14 and an electric translation stage 6. One end of the sample table 14 is arranged above the electric translation stage 6 so that it can move up and down under the drive of the electric translation stage 6. At the same time, the other end of the sample table 14 extends outward to fix the sample to be tested 15, and is also used to drive the sample to be tested 15 to move left and right. When working, the electric translation stage 6 moves up and down to drive the sample to be tested 15 to move up and down. At the same time, the sample table 14 can also drive the sample to be tested to move left and right, so as to monitor heavy metals in solid fuels at multiple positions.

[0031] Furthermore, the signal receiving unit includes a focusing lens 11, a spectrometer 9 and an ICCD 8 which are sequentially arranged along the propagation direction of the light. The focusing lens 11 is used to focus the characteristic spectrum radiated by the plasma and send it to the spectrometer 9 and the ICCD 8. Meanwhile, the ICCD 8 is also connected to the digital delay device 1 and the data processing unit 7 respectively, and is used to convert the optical signal into an electrical signal, and send the delay data of the digital delay device 1 and the electrical signal together to the data processing unit 7 for processing.

[0032] Preferably, the signal receiving unit further includes a polarizer 10, which is disposed at the entrance of the spectrometer 9 and is used to enhance or suppress the spectral lines of specific elements, reduce interference from background light, and improve the selectivity and sensitivity of spectral analysis.

[0033] Preferably, the signal receiving unit further comprises a light beam receiver 13, which is arranged behind the sample to be tested 15 along the light propagation direction, and is used to receive the light signal and convert it into an electrical signal and transmit it to the data processing unit 7 to assist in signal processing.

[0034] Furthermore, the parameters of ICCD8 can also play a role in suppressing the self-absorption effect, and there is an interactive relationship between the laser intensity and the microwave power. For gain, too high a gain will lead to signal saturation and may introduce nonlinearity; while too low a gain will cause the signal to be buried in the noise and reduce the detection sensitivity. For the gate width, too wide will include unnecessary background signals and reduce the signal-to-noise ratio; too narrow will miss some useful signals and affect the intensity and quality of the spectrum. For the delay time, improper setting will lead to the loss of spectral data, and the characteristic peaks of important elements may not be collected. Therefore, in order to improve the measurement accuracy, this application optimizes the parameters of ICCD8. When measuring the heavy metal content, the gain of ICCD8 is 1000-2500, the gate width is 100ns-500ns, and the delay time is 5μs-10μs; when measuring the heavy metal form, the gain of ICCD8 is 100-500, the gate width is 10ns-100ns, and the delay time is 1μs-5μs.

[0035] According to another aspect of the present application, a method for rapid laser detection of heavy metals in solid fuels is provided, specifically: an incident laser coupled with microwaves is emitted to a sample to be tested 15 to excite a plasma signal, and then the plasma signal is collected and data analysis is performed to utilize microwave-assisted laser induced breakdown spectroscopy to perform online detection of the heavy metal content and morphology in the sample to be tested, wherein when measuring the heavy metal content, the laser intensity is 100mJ / pluse~300mJ / pluse, and the microwave power is 160W~200W, and when measuring the heavy metal morphology, the laser intensity is 40mJ / pluse~140mJ / pluse, and the microwave power is 100W~150W.

[0036] Furthermore, when ICCD8 is used to collect plasma signals and measure the heavy metal content, the gain of ICCD8 is 1000-2500, the gate width is 100ns-500ns, and the delay time is 5μs-10μs; when measuring the heavy metal form, the gain of ICCD8 is 100-500, the gate width is 10ns-100ns, and the delay time is 1μs-5μs.

[0037] The technical solution provided in this application is further described below based on specific embodiments.

[0038] Example 1

[0039] Taking the detection of heavy metals in coal as an example, first select a representative coal sample, perform appropriate crushing and homogenization treatment to ensure the representativeness of the sample to be tested and the accuracy of the test, and then place the processed coal sample on the sample table 14. Then adjust the equipment of the laser rapid detection device for heavy metals in solid fuel to the optimal working state. When measuring the heavy metal content, set the laser intensity to 200mJ / pulse, microwave power to 130W, ICCD8 gain to 1500, gate width to 230ns, and delay time to 7.5μ; when analyzing the heavy metal form, set the laser intensity to 90mJ / pulse, microwave power to 120W, ICCD gain to 300, gate width to 50ns, and delay time to 3μs. Finally, collect the obtained spectral data and convert it into heavy metal content data through the fitting model.

[0040] The final measured contents of heavy metal mercury, arsenic and lead in coal were 0.5 mg / kg, 3.7 mg / kg and 10.3 mg / kg respectively; the occurrence forms of mercury, arsenic and lead were organic bound, sulfide bound and carbonate bound, and the correlation coefficients were 0.872, 0.924 and 0.817 respectively.

[0041] Example 2

[0042] Taking the detection of heavy metals in domestic waste as an example, first collect domestic waste samples, screen and crush them to remove large impurities and non-target substances; then optimize and adjust the heavy metal laser rapid detection device according to the physicochemical characteristics of domestic waste. When measuring the heavy metal content, set the laser intensity to 230mJ / pulse, microwave power to 165W, ICCD8 gain to 1700, gate width to 270ns, and delay time to 6.5μs; when analyzing the heavy metal form, set the laser intensity to 110mJ / pulse, microwave power to 140W, ICCD gain to 350, gate width to 70ns, and delay time to 2μs. Finally, collect the obtained spectral data and convert them into heavy metal content data through fitting model.

[0043] The final measured contents of heavy metal arsenic, lead and chromium in domestic waste were 8.7, 21.5 and 35.3 mg / kg respectively; the occurrence forms of arsenic, lead and chromium were sulfide-bound, water-soluble and residual, and the correlation coefficients were 0.785, 0.839 and 0.764 respectively.

[0044] Example 3

[0045] Taking the detection of heavy metals in sludge as an example, the sludge sample is first appropriately diluted and homogenized to reduce the viscosity of the sample and improve the operability of the test; then, according to the particularity of the sludge sample, the equipment of the laser rapid detection device for heavy metals in solid fuel is adjusted to the optimal working state. When measuring the heavy metal content, the laser intensity is set to 280mJ / pulse, the microwave power is 195W, the ICCD8 gain is 1900, the gate width is 420ns, and the delay time is 8.5μs; when analyzing the heavy metal morphology, the laser intensity is set to 130mJ / pulse, the microwave power is 110W, the ICCD gain is 400, the gate width is 40ns, and the delay time is 2.5μs; then, multi-point tests are performed on the surface of the sludge sample, paying special attention to the unevenness of the sample to ensure the comprehensiveness of the test results; finally, the spectral data obtained from the test are analyzed in detail and converted into heavy metal content and morphology data using a fitting model.

[0046] The final measured contents of heavy metals copper, zinc and nickel in the sludge were 107.8, 85.6 and 56.7 mg / kg respectively; the occurrence forms of copper, zinc and nickel were sulfide-bound, carbonate-bound and water-soluble, and the correlation coefficients were 0.937, 0.783 and 0.831 respectively.

[0047] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0048] In addition, references throughout this specification to "one embodiment"; "one embodiment", "an example" or similar language indicate that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment"; "in one embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0049] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A laser rapid detection device for heavy metals in solid fuels, characterized in that: The detection device comprises a sample unit, a laser generating unit, a microwave generating unit, a signal receiving unit and a data processing unit (7), wherein: the sample unit is used to place a sample to be tested (15); the laser generating unit is used to emit incident laser to the sample to be tested (15), when measuring the heavy metal content, the laser intensity is 100mJ / pluse-300mJ / pluse, when measuring the heavy metal form, the laser intensity is 40mJ / pluse-140mJ / pluse; the microwave generating unit is used to couple microwaves (12) to the incident laser, when measuring the heavy metal content, the microwave power is 160W-200W, when measuring the heavy metal form, the microwave power is 100W-150W; the signal receiving unit is connected to the data processing unit (7), and is used to receive the plasma signal generated by the sample to be tested and transmit it to the data processing unit (7) for data analysis, so as to use microwave-assisted laser induced breakdown spectroscopy to perform online detection of the heavy metal content and form in the sample to be tested.

2. The detection device according to claim 1, characterized in that The sample unit comprises a sample stage (14) and an electric translation stage (6). One end of the sample stage (14) is arranged above the electric translation stage (6) so as to move up and down under the drive of the electric translation stage (6). Meanwhile, the other end of the sample stage (14) extends outwards and is used to fix the sample to be tested (15). The sample stage (14) is also used to drive the sample to be tested (15) to move left and right.

3. The detection device according to claim 1, characterized in that: The laser generating unit comprises a digital delay device (1), a laser generator (2) and at least one reflecting mirror (3); the digital delay device (1) is connected to the laser generator (2) and is used to control the laser generator (2) to emit incident laser light at a fixed time; the reflecting mirror (3) is used to reflect the incident laser light to the position of a sample to be tested (15).

4. The detection device according to claim 1, characterized in that: The microwave generating unit comprises a microwave generator (4) and a microwave radiator (5); the microwave generator (4) is used to emit microwaves; the microwave radiator (5) is connected to the microwave generator (4) and is used to couple microwaves to incident laser light.

5. The detection device according to claim 1, characterized in that: The signal receiving unit comprises a focusing lens (11), a spectrometer (9) and an ICCD (8) which are arranged in sequence along the light propagation direction. The focusing lens (11) is used to focus the characteristic spectrum radiated by the plasma and then send it to the spectrometer (9) and the ICCD (8). At the same time, the ICCD (8) is also connected to the digital delay device (1) and the data processing unit (7) respectively, and is used to convert the optical signal into an electrical signal and send it to the data processing unit (7).

6. The detection device according to claim 5, characterized in that: The signal receiving unit further comprises a polarizing plate (10), which is arranged at the entrance of the spectrometer (9) and is used to enhance or suppress the spectral lines of specific elements.

7. The detection device according to claim 5, characterized in that: The signal receiving unit further comprises a light beam receiver (13), which is arranged behind the sample to be tested (15) along the light propagation direction and is used to receive the light signal and convert it into an electrical signal to assist in signal processing.

8. The detection device according to claim 5, characterized in that: When measuring the heavy metal content, the gain of the ICCD (8) is 1000-2500, the gate width is 100ns-500ns, and the delay time is 5μs-10μs; when measuring the heavy metal form, the gain of the ICCD (8) is 100-500, the gate width is 10ns-100ns, and the delay time is 1μs-5μs.

9. A laser rapid detection method for heavy metals in solid fuels, characterized in that: The detection method comprises: emitting a microwave-coupled incident laser to a sample to be tested (15) to excite a plasma signal, then collecting the plasma signal and performing data analysis, so as to use microwave-assisted laser-induced breakdown spectroscopy to perform online detection of the heavy metal content and form in the sample to be tested, wherein when measuring the heavy metal content, the laser intensity is 100mJ / pluse to 300mJ / pluse, and the microwave power is 160W to 200W; when measuring the heavy metal form, the laser intensity is 40mJ / pluse to 140mJ / pluse, and the microwave power is 100W to 150W.

10. The detection method according to claim 9, characterized in that: The ICCD (8) is used to collect plasma signals. When measuring the heavy metal content, the gain of the ICCD (8) is 1000-2500, the gate width is 100ns-500ns, and the delay time is 5μs-10μs; when measuring the heavy metal form, the gain of the ICCD (8) is 100-500, the gate width is 10ns-100ns, and the delay time is 1μs-5μs.

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