Gaseous mercury and granular mercury synchronous high-sensitivity online detection method and system

Abstract

The invention relates to a synchronous high-sensitivity online detection method and system for gaseous mercury and granular mercury, which adopts the coupling and quality control technology of an X-ray fluorescence spectrometry detection system and an atomic absorption spectrometry detection system, and performs system integration of equipment. The device mainly comprises a gas sampling, transmission and pretreatment part, a filter membrane acquisition module and a high-selectivity enrichment module, a dual-detection system mercury analysis unit, a data acquisition, processing and transmission part and a man-machine interaction part, and a novel dual-detection method capable of realizing synchronous on-line high-precision measurement of Hg0, Hg < 2 + > and Hg polymorphic mercury is established. Compared with the prior art, high-precision and high-accuracy measurement of gaseous mercury is realized.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection and gas detection, and is mainly aimed at the analysis and online detection of various forms of mercury in the atmosphere and flue gas, involving coupled cold atomic absorption method and X-ray fluorescence detection method, respectively, for gaseous zero-valent mercury (Hg 0 ), oxidized mercury (Hg 2+ ) and particulate mercury (Hg p ) for synchronous online detection. Background Art

[0002] Mercury is a global pollutant that has attracted much attention due to its biotoxicity and neurotoxicity. As the main route for global migration of mercury, atmospheric mercury deposition can lead to varying degrees of pollution of surface water and ecosystems, and cause serious harm to human and ecological health. The different chemical forms of mercury in the atmosphere determine the speed of its removal through wet or dry deposition. Mercury exists in the atmosphere in three main forms: gaseous elemental mercury (Hg 0 ), gaseous oxidized mercury (Hg 2+ ) and particulate mercury (Hg p In order to deeply understand the geochemical behavior of atmospheric mercury and clarify the contribution of industrial mercury emission reduction to the reduction of total atmospheric mercury, and to meet the needs of the international Minamata Convention on Mercury, it is crucial to accurately quantify the concentrations of the three main forms of mercury in the atmosphere.

[0003] At present, the monitoring methods of gaseous mercury content mainly include two categories: manual offline mercury sampling test method and mercury online measurement system (Hg-CEMS), and the mercury content in the sample is analyzed by combining spectral instruments. Manual offline sampling methods mainly include wet chemical sampling method (US EPA Method 29, US EPA Method 101A, Ontario method and China HJ 543-2009, etc.) and solid adsorbent sampling method (US EPA Method 30B and China HJ917-2017, etc.). Mercury analysis and monitoring methods based on spectral instruments include cold atomic absorption spectroscopy (CVAAS), cold atomic fluorescence spectroscopy (CVAFS), Zeeman modulation atomic absorption spectroscopy (ZAAS), etc.

[0004] Patent application CN202310830164.6 discloses a real-time online analysis system and analysis method for measuring the content of mercury in various valence states in flue gas. Through a highly integrated sampling unit, pretreatment unit, enrichment and analysis unit, detection unit and calibration unit, the enrichment area uses gold-plated quartz sand and high-temperature resistant quartz wool to improve the enrichment efficiency and measurement accuracy; the detection unit uses atmospheric pressure glow discharge atomic emission spectrometry to achieve efficient, accurate and synchronous online quantitative analysis of flue gas mercury, but this technology can only measure gaseous Hg 0 and Hg 2+.

[0005] Existing detection technologies are usually limited to Hg 0 , Hg 2+ Detection and analysis, Hg p Currently, offline manual sampling is still the main method used for measurement, which results in problems such as low precision and low time resolution of synchronous online monitoring. Summary of the invention

[0006] The purpose of the present invention is to provide a method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury in order to overcome the defects of the above-mentioned prior art, use the coupling and quality control technology of the dual detection system of X-ray fluorescence spectroscopy and atomic absorption spectroscopy, establish a mutual verification model of the dual detection system, thereby achieving high-precision and high-accuracy measurement of gaseous mercury, and performing system integration of equipment.

[0007] The object of the present invention can be achieved by the following technical solution: A method for synchronously detecting gaseous mercury and particulate mercury with high sensitivity online comprises the following steps:

[0008] (1) The gas sample to be detected is collected through the gas sampling and transmission module and the flow rate is distributed;

[0009] (2) The gas sample treated in step (1) is respectively introduced into the X-ray fluorescence spectrometry detection system and the cold atomic absorption spectrometry detection system through a valve switching system to detect particulate mercury (Hg p ), elemental mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for separate testing;

[0010] (3) The X-ray fluorescence spectrometry detection system and the cold atomic absorption spectrometry detection system are operated online simultaneously. The two systems detect particulate mercury (Hg p ), gaseous elemental mercury (Hg 0 ) and gaseous oxidized mercury (Hg 2+ ) for synchronous and highly sensitive online detection.

[0011] Furthermore, the gas sampling and transmission module described in step (1) includes a sampling probe, a constant speed sampling device, a heating pipeline and a flow distribution device, wherein the sampling probe is arranged at the front end of the constant speed sampling device, the constant speed sampling device is connected to the flow distribution device through the heating pipeline, and a pump is provided on the heating pipeline; the environmental gas sample is collected through the sampling probe and the constant speed sampling device, and the stability of the gas sample is maintained through the heating pipeline to prevent mercury vapor condensation.

[0012] Furthermore, the cold atomic absorption spectrometry detection system described in step (2) is provided with a filter membrane and a highly selective enrichment module at the front end, and the gas introduced into the cold atomic absorption spectrometry detection system first passes through the filter membrane to remove particulate mercury, and then enters the highly selective enrichment module to remove gaseous mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for enrichment and separation, and finally enters the cold atomic absorption spectrometry detection unit.

[0013] Furthermore, the filter membrane is a quartz filter membrane or a polytetrafluoroethylene filter membrane to remove particulate matter and interfering substances to ensure the accuracy of the detection.

[0014] Furthermore, the highly selective enrichment module is a gold-based material, including a gold film, gold particles, gold nuggets, gold wires or gold-plated quartz sand, which can absorb and desorb gaseous elemental mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for enrichment and separation to improve the sensitivity of the detection system.

[0015] Furthermore, the gas introduced into the X-ray fluorescence spectrometry detection system is first pre-enriched by a filter paper tape, and then detected online by an X-ray fluorescence spectrometry detection method.

[0016] Furthermore, the filter paper tape is a polytetrafluoroethylene / quartz filter paper tape, which is used to separate and capture particulate mercury (Hg p )

[0017] Furthermore, the cold atomic absorption spectrometry detection unit is based on the selective absorption of 253.7nm ultraviolet light by mercury atomic vapor, and the detection unit mainly detects gaseous element mercury (Hg 0 ) and oxidized mercury (Hg 2+ ).

[0018] Furthermore, the X-ray fluorescence spectrum detection unit excites mercury atoms in the sample by high-energy X-rays, causing them to emit characteristic fluorescent X-rays, and determines the mercury content according to the intensity of the fluorescent X-rays; the detection unit mainly detects particulate mercury (Hg p ).

[0019] The present invention also provides a synchronous and highly sensitive online detection system for gaseous mercury and particulate mercury for implementing the method, comprising a gas sampling module, a filter membrane collection module, a highly selective enrichment module, a dual detection system mercury analysis unit, a data collection, processing and transmission module and a human-computer interaction module; the dual detection system mercury analysis unit comprises an X-ray fluorescence spectrum detection unit and a cold atomic absorption spectrum detection unit, and the data obtained from the dual detection system mercury analysis unit is collected, processed and transmitted by the data collection, processing and transmission module, the detection results are analyzed in real time, and the data is transmitted to a remote monitoring system through an interface, and the system is controlled by the human-computer interaction module.

[0020] Furthermore, the data acquisition, processing and transmission module includes a program logic controller (PLC) and a data processing system.

[0021] Furthermore, the human-computer interaction module includes a display screen and a control panel.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) In view of the limitations of a single detection system for mercury form detection, the present invention adopts the coupling and quality control technology of the dual detection system of X-ray fluorescence spectroscopy and atomic absorption spectroscopy, and performs system integration of the equipment. Atomic absorption spectroscopy (AAS) is an analytical method for determining the concentration of elemental mercury. It mainly uses the selective absorption of 253.7nm ultraviolet light by mercury atomic vapor, and the absorbance is proportional to the mercury concentration within a certain range, which can quantitatively analyze the concentration of particulate mercury. X-ray fluorescence spectroscopy (XRF) is an analytical method based on the emission of secondary X-rays by substances after being excited. Its working principle is to use X-rays to excite mercury atoms, which will emit characteristic X-rays when they return to the ground state. By detecting the intensity of these characteristic X-rays, the concentration of particulate mercury can be quantitatively analyzed.

[0024] (2) The present invention establishes a method for achieving Hg 0 , Hg 2+ and Hg p The new "dual detection" method for simultaneous online high-precision measurement of multi-form mercury effectively overcomes the difficulty of simultaneous detection of particulate mercury. The detection limit of different forms of mercury can be as low as gaseous mercury (Hg 0 )ng / m 3 Level, oxidized mercury (Hg 2+ )pg / m 3 Level and particle mercury (Hgp) pg / m 3It solves the current problems of low precision and low time resolution of synchronous online monitoring, accurately quantifies the concentrations of three main forms of mercury in the atmosphere, meets the needs of the international Minamata Convention on Mercury, and the detection method is more efficient and accurate.

[0025] It can be used for long-term monitoring of atmospheric mercury at national control stations and super stations. It can also be used for online mercury monitoring and analysis of flue gas mercury, such as in coal-fired industries and industrial boilers, to evaluate mercury emission concentrations, improve environmental protection quality, and avoid harm to human and ecological health. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the key equipment units and integration of the "dual detection" system of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical solution of the present invention more clear and specific to those skilled in the art, the present invention is described in detail below in conjunction with specific embodiments, but the present invention is not limited to these embodiments.

[0028] Since atmospheric mercury exists in various forms and is at trace levels (ng / m 3 Level), it is a severe challenge to conduct long-term high-precision online monitoring and early warning, especially for particulate mercury in the atmosphere with low concentration. Existing methods often use offline sampling methods, which further aggravates the online accuracy of atmospheric mercury. This invention, aimed at the limitations of a single detection system for mercury form detection, proposes a coupling and quality control technology of a dual detection system of X-ray fluorescence spectroscopy and atomic absorption spectroscopy, and carries out system integration of equipment, mainly including gas sampling, transmission, flow distribution part → filter membrane acquisition module, high-selectivity enrichment module → dual detection system mercury analysis unit → data acquisition processing transmission part → human-computer interaction part, and establishes a system that can realize Hg 0 , Hg 2+ and Hg p A new "dual detection" method for simultaneous online high-precision measurement of multi-form mercury, as shown in the following example: Figure 1 As shown, the present invention adopts a "dual detection" system to perform simultaneous and highly sensitive online detection of gaseous mercury and particulate mercury. The specific detection method is as follows:

[0029] (1) The gas sample to be detected is collected and pre-processed through a gas sampling and transmission module. Specifically, the gas sampling and transmission module includes a sampling probe 1, an isokinetic sampling device, a heating pipeline 2 and a flow distribution device. The sampling probe is arranged at the front end of the isokinetic sampling device. The isokinetic sampling device (a commercially available DEKATI FPS-4000 sampler is used in a preferred embodiment of the present invention) is connected to the flow distribution device through a heating pipeline (a preferred embodiment of the present invention uses a commercially available RMZK-BX heating pipe, which has the characteristics of acid and alkali corrosion resistance) and a pump is provided on the heating pipeline; the environmental gas sample is collected through the sampling probe and the isokinetic sampling device, and the stability of the gas sample is maintained through the heating pipeline to prevent mercury vapor condensation, and the gas sample is transmitted to the flow distribution device through the pump.

[0030] (2) The treated gas in step (1) is distributed through the flow distribution valve switching system 3. 5L of sample gas is first distributed through the flow distribution valve switching system 3 to 500ml of gas, first passes through the front filter membrane (quartz filter membrane) to remove particulate matter and interfering substances, and then enters the high-selectivity enrichment module 4 for gaseous mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) is enriched and separated, and finally enters the cold atomic absorption spectrometer detection unit 5; the highly selective enrichment module 4 uses gold-plated quartz sand to adsorb and desorb gaseous mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for enrichment and separation to improve the sensitivity of the detection system.

[0031] The cold atomic absorption spectrometer detection unit (in a preferred embodiment of the present invention, a commercially available Shedilon MODEL1080Hg cold atomic absorption spectrometer) is based on the fact that mercury atomic vapor selectively absorbs 253.7nm ultraviolet light. Within a certain concentration range, the absorbance is proportional to the mercury concentration. This detection unit mainly detects gaseous elemental mercury (Hg 0 ) and oxidized mercury (Hg 2+ ).

[0032] (3) The treated gas in step (1) is distributed through the flow distribution valve switching system 3 to distribute 500 ml of gas through the filter paper tape to filter the particulate mercury (Hg p ), and then enters the X-ray fluorescence spectrum detection unit 6. In a preferred embodiment, the filter membrane paper tape adopts a quartz filter membrane paper tape (47mm).

[0033] The X-ray fluorescence spectrometer detection unit (in a preferred embodiment of the present invention, a commercially available Newtonscientific XSPA-200 X-ray fluorescence spectrometer) uses high-energy X-rays to excite the mercury atoms in the sample, causing them to emit characteristic fluorescent X-rays, and determines the mercury content based on the intensity of the fluorescent X-rays. This detection unit mainly detects particulate mercury (Hg p ).

[0034] (4) The X-ray fluorescence spectrometry detection system and the cold atomic absorption spectrometry detection system are synchronously tested online, and the acquired data are transmitted to the data acquisition, processing and transmission module, which includes a program logic controller (PLC) and a data processing system. Among them, the input information: data collected from the mercury analysis unit of the dual detection system, including the original detection signal of the mercury content (such as spectral data, concentration signal, etc.). Processing process: real-time data acquisition and preliminary processing, such as signal filtering, normalization and amplification, are realized through PLC; then, the data is further processed and analyzed.

[0035] Output information: The test result data obtained after processing, including mercury concentration value, analysis curve and working status information of the detection unit. The final processed data is transmitted to the remote monitoring system through the communication interface (such as Modbus protocol interface or Ethernet interface) of the data acquisition processing and transmission module to achieve real-time monitoring and data storage.

[0036] (5) The processing of the data obtained in step (5) is controlled by a human-computer interaction module. The human-computer interaction module includes a display screen and a control panel for displaying detection data, system status and operation prompts. The specific implementation is as follows: Input information: The user inputs the operating parameters of the detection equipment (such as detection sensitivity, sampling frequency, alarm threshold, etc.) and control instructions (such as start, pause, calibration, etc.) through the control panel. Processing process: The human-computer interaction module parses the data input by the user based on touch screen operation technology and embedded software (in a preferred embodiment of the present invention, an ARM platform and a Linux system are used), and sends the control instructions to the data acquisition processing transmission module and the dual detection system; the embedded software integrates the existing control logic algorithm and performs real-time verification of abnormal parameters input by the user to ensure the safe operation of the system. Output information: The display screen displays the processed detection data (such as mercury concentration), equipment operation status (such as temperature, pressure and other parameters) and operation prompts (such as fault warnings, calibration success prompts, etc.) in real time.

[0037] Example 1

[0038] In this embodiment, a bypass pipe is opened in the coal-fired flue gas pipeline of A power plant in Baoshan District, Shanghai, and the multi-form mercury concentration in the coal-fired flue gas of A power plant in Baoshan District, Shanghai is tested online by the method and equipment of the present invention. The sampling flow rate is 2-30L / h, the heating temperature of the insulation pipe is 120℃, and the total sampling time is 0.2-2h. After the sample passes through the high-sensitivity online detection instrument for gaseous mercury and particulate mercury, the concentration of mercury in ng / m 3 The concentration of gaseous mercury (Hg 0 ), oxidized mercury (Hg 2+ The concentrations of mercury (Hgp) and particulate mercury (Hgp) were 3.88±0.51μg / m 3 9.569±0.76ng / m 3 、31.194±2.57ng / m 3 .

[0039] Example 2

[0040] In this example, atmospheric mercury sampling was carried out in the super monitoring station in Qingpu District, Shanghai. The method and equipment of the present invention were used to test the concentration of multi-form mercury in the coal-fired flue gas of Power Plant A in Baoshan District, Shanghai online. The sampling flow rate was 2-30L / h, the heating temperature of the insulation pipe was 120°C, and the total sampling time was 0.2-2h. After the sample was tested by the high-sensitivity online detection instrument for gaseous mercury and particulate mercury, the concentration of pg / m 3 The concentration of gaseous mercury (Hg 0 ), oxidized mercury (Hg 2+ ) and particulate mercury (Hg p ) concentrations were 4.456±0.38ng / m 3 16.086pg±2.22 / m 3 , 10.715±1.65pg / m 3 .

[0041] The above shows and describes the basic process, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury, characterized in that: The following steps are involved: (1) The gas sample to be detected is collected through the gas sampling and transmission module and the flow rate is distributed; (2) The gas sample treated in step (1) is respectively introduced into the X-ray fluorescence spectrometry detection system and the cold atomic absorption spectrometry detection system through a valve switching system to detect particulate mercury (Hg p ), elemental mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for separate testing; (3) The X-ray fluorescence spectrometry detection system and the cold atomic absorption spectrometry detection system are operated online simultaneously. The two systems detect particulate mercury (Hg p ), gaseous elemental mercury (Hg 0 ) and gaseous oxidized mercury (Hg 2+ ) for synchronous and highly sensitive online detection.

2. A method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury according to claim 1, characterized in that: The gas sampling and transmission module described in step (1) includes a sampling probe, a constant speed sampling device, a heating pipeline and a flow distribution device, wherein the sampling probe is arranged at the front end of the constant speed sampling device, the constant speed sampling device is connected to the flow distribution device through the heating pipeline, and a pump is provided on the heating pipeline; the environmental gas sample is collected by the sampling probe and the constant speed sampling device, and the stability of the gas sample is maintained by the heating pipeline to prevent the condensation of mercury vapor.

3. A method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury according to claim 1, characterized in that: The cold atomic absorption spectrometry detection system described in step (2) is provided with a filter membrane and a highly selective enrichment module at the front end. The gas introduced into the cold atomic absorption spectrometry detection system first passes through the filter membrane to remove particulate mercury, and then enters the highly selective enrichment module to collect gaseous mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for enrichment and separation, and finally enters the cold atomic absorption spectrometry detection unit.

4. A method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury according to claim 3, characterized in that: The filter membrane is a quartz filter membrane or a polytetrafluoroethylene filter membrane to remove particulate matter and interfering substances to ensure the accuracy of the detection.

5. A method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury according to claim 3, characterized in that: The highly selective enrichment module is a gold-based material, including a gold film, gold particles, gold nuggets, gold wires or gold-plated quartz sand, which can absorb and desorb the gaseous elemental mercury (Hg 0 ) and oxidized mercury (Hg 2+ ) for enrichment and separation to improve the sensitivity of the detection system.

6. The method for synchronously and highly sensitively detecting gaseous mercury and particulate mercury online according to claim 1, characterized in that: The gas introduced into the X-ray fluorescence spectrometry detection system is first pre-enriched by a filter paper tape and then detected online by the X-ray fluorescence spectrometry detection method.

7. A method for simultaneous high-sensitivity online detection of gaseous mercury and particulate mercury according to claim 6, characterized in that: The filter paper tape is a polytetrafluoroethylene / quartz filter paper tape, which is used to separate and capture particulate mercury (Hg p ).

8. The method for synchronously and highly sensitively detecting gaseous mercury and particulate mercury online according to claim 1, characterized in that: The cold atomic absorption spectrometry detection unit is based on the selective absorption of 253.7nm ultraviolet light by mercury atomic vapor. The detection unit mainly detects gaseous element mercury (Hg 0 ) and oxidized mercury (Hg 2+ ).

9. The method for synchronously and highly sensitively detecting gaseous mercury and particulate mercury online according to claim 1, characterized in that: The X-ray fluorescence spectrum detection unit is an analytical method for determining the mercury content based on the intensity of the characteristic fluorescent X-rays that are excited by the high-energy X-rays in the mercury atoms in the sample. The detection unit mainly detects particulate mercury (Hg p ).

10. A system for synchronously detecting gaseous mercury and particulate mercury with high sensitivity online for implementing the method according to any one of claims 1 to 9, characterized in that: It includes a gas sampling and transmission module, a filter membrane, a high-selectivity enrichment module, a dual-detection system mercury analysis unit, a data acquisition, processing and transmission module and a human-computer interaction module; the dual-detection system mercury analysis unit includes an X-ray fluorescence spectrum detection unit and a cold atomic absorption spectrum detection unit, and the data obtained from the dual-detection system mercury analysis unit is collected, processed and transmitted by the data acquisition, processing and transmission module, the detection results are analyzed in real time, and the data is transmitted to the remote monitoring system through an interface, and is controlled by the human-computer interaction module.

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