CN116858625A - Real-time online analysis system and method for measuring content of mercury in each valence state in flue gas - Google Patents

Real-time online analysis system and method for measuring content of mercury in each valence state in flue gas Download PDF

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CN116858625A
CN116858625A CN202310830164.6A CN202310830164A CN116858625A CN 116858625 A CN116858625 A CN 116858625A CN 202310830164 A CN202310830164 A CN 202310830164A CN 116858625 A CN116858625 A CN 116858625A
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mercury
gas
flue gas
unit
content
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汪正
李熠豪
李青
梁凤飞
王陈燕
荣蓉
高猛
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Shanghai Baif Technology Co ltd
Shanghai Institute of Ceramics of CAS
Jiangsu Sujing Group Co Ltd
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Shanghai Baif Technology Co ltd
Shanghai Institute of Ceramics of CAS
Jiangsu Sujing Group Co Ltd
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Publication of CN116858625A publication Critical patent/CN116858625A/en
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2247—Sampling from a flowing stream of gas
    • G01N1/2258—Sampling from a flowing stream of gas in a stack or chimney
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/34—Purifying; Cleaning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/40—Concentrating samples
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
    • G01N1/40—Concentrating samples
    • G01N1/4044—Concentrating samples by chemical techniques; Digestion; Chemical decomposition
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/33—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using ultraviolet light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/71—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light thermally excited
    • G01N21/718—Laser microanalysis, i.e. with formation of sample plasma
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0022—General constructional details of gas analysers, e.g. portable test equipment using a number of analysing channels
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0045—Hg
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2247—Sampling from a flowing stream of gas
    • G01N1/2258—Sampling from a flowing stream of gas in a stack or chimney
    • G01N2001/2261—Sampling from a flowing stream of gas in a stack or chimney preventing condensation (heating lines)

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Abstract

The application relates to a real-time online analysis system and an analysis method for measuring the content of mercury in each valence state in flue gas, wherein the real-time online analysis system comprises a sampling unit for collecting a flue gas sample to be tested; the pretreatment unit is used for filtering macromolecular particles in the flue gas collected by the sampling unit; the enrichment analysis unit comprises a quartz tube which is communicated with the pretreatment unit, and gold-plated quartz sand is placed in the quartz tube and used for simultaneously enriching oxidized mercury and elemental mercury in the flue gas after the pretreatment unit; the heating pipes are closely arranged around the quartz tube and are used for heating and resolving and converting the enriched oxidized mercury into elemental mercury; the detection unit is directly communicated with the pretreatment unit through a first-level gas circuit and is used for measuring the content of elemental mercury in the flue gas; and the secondary gas circuit is communicated with an analysis gas outlet of the quartz tube and is used for measuring the total mercury content in the flue gas, and the content of oxidized mercury can be calculated from the difference value of the total mercury content and the elemental mercury content. The method has the advantages of good conversion effect and high instrument detection sensitivity.

Description

Real-time online analysis system and method for measuring content of mercury in each valence state in flue gas
Technical Field
The application belongs to the technical field of real-time online quantitative analysis of flue gas mercury, and particularly relates to a real-time online quantitative analysis system and an analysis method for the content of mercury in each valence state in flue gas.
Background
Mercury and its compounds are global pollution due to their high toxicity, high biotoxicity, bioaccumulation, and long distance transport, which are constantly threatening human and environmental safety. The sources of mercury pollution are mainly divided into two main categories: natural emissions sources and artificial emissions sources. Natural emission sources mainly include volcanic eruptions, rock efflorescence, forest fires and soil erosion; the mercury emission amount of the coal-fired power plant in the artificial emission source accounts for about 1/3 of the total artificial mercury emission amount, and is the largest artificial mercury emission source. Mercury in coal-fired flue gas mainly exists in three forms of oxidized mercury, elemental mercury and granular mercury. In the flue gas of different coal types, the proportion of oxidized mercury in combustion products is highest, and then the proportion of elemental mercury and granular mercury is very low. In order to control mercury emissions during coal combustion, the U.S. Environmental Protection Agency (EPA) issued the standard for Mercury and Air Toxic Substances (MATS) in month 12 of 2011. Therefore, the method has important significance for quantitative analysis of mercury in the flue gas.
Simple substance mercury is insoluble in water and is easy to detect. In addition, oxidized mercury can be reduced to elemental mercury by high temperature. Particulate mercury is typically removed by electrostatic precipitation or filters. Thus, the total mercury content in the flue gas can be determined by quantitatively analyzing the total amount of elemental mercury and oxidized mercury in the flue gas. The most common methods currently used for detecting elemental mercury are Atomic Absorption Spectroscopy (AAS) and Atomic Fluorescence Spectroscopy (AFS). However, the existing equipment is not suitable for online monitoring of the network due to large volume and high cost. Therefore, development of a small-sized, portable, low-cost flue gas mercury detection method is an important point of current research. In addition, the detection limit of the spectrum detection method cannot completely meet the detection standard of mercury in the flue gas. In order to determine the mercury pollution level of the flue gas and monitor the mercury content in the environment, it is necessary to enrich trace mercury elements in the flue gas. At the same time, SO exists in the flue gas 2 、CO 2 、NO x And other complex gas components can generate certain interference on the sensitivity of subsequent detection equipment, so that enrichment and purification of the sample before the sample is introduced into a detection device are very important.
Disclosure of Invention
According to one aspect of the application, a real-time online analysis system for measuring the content of mercury in each valence state in flue gas is provided, the pretreated flue gas mercury is divided into two paths, one path is directly connected to a detection unit under the action of hydrogen and helium, the other path enters an enrichment analysis unit for enrichment, and the mercury is released by electric heating and enters the detection unit for detection and data output; the method has the advantages of good conversion effect, improved instrument detection sensitivity and real-time on-line monitoring of mercury in each valence state in the flue gas.
In order to achieve the above purpose, the technical scheme adopted by the application is as follows:
a real-time online analysis system for measuring the content of mercury in each valence state in flue gas, comprising:
the sampling unit is used for collecting a smoke sample to be tested;
the pretreatment unit is used for filtering macromolecular particles in the flue gas collected by the sampling unit;
an enrichment resolution unit comprising:
the quartz tube is communicated with the filtered flue gas outlet of the pretreatment unit, and gold-plated quartz sand is placed in the quartz tube and used for simultaneously enriching oxidized mercury and elemental mercury in the flue gas after the pretreatment unit;
the heating pipes are closely arranged around the quartz tube and are used for heating and resolving and converting the enriched oxidized mercury into elemental mercury;
the detection unit is directly communicated with the filtered smoke outlet of the pretreatment unit through the first-stage gas circuit and is used for measuring the content of elemental mercury in the smoke; and the gas flow of the filtered flue gas passing through the first gas path and the second gas path is equal, and the content of oxidized mercury can be calculated from the difference value of the total mercury content and the elemental mercury content.
In some technical schemes, the detection unit comprises a microplasma excitation area, a hydrogen helium gas bomb for providing a discharge atmosphere and a third gas flow controller for controlling the flow rate of the hydrogen helium gas, and the analysis gas is transmitted into the microplasma excitation area along with the hydrogen helium gas to emit a characteristic spectrum signal of 253.6 nm.
In some technical schemes, the detection unit further comprises a data acquisition and analysis module for recording the characteristic spectrum signal intensity of 253.6nm and establishing a linear model based on the spectral line intensity and the mercury concentration, so that the content of mercury in each valence state in the smoke sample to be detected is obtained, and recording and transmission are performed.
In some technical schemes, the sampling unit comprises a sampling probe, a first gas flow controller, a sample gas pipeline and a temperature control display alarm device, wherein the temperature control display alarm device is used for controlling the temperature of the inside of the sampling probe and the temperature of the whole sample gas pipeline to be above 800 ℃ and preventing mercury vapor from condensing.
In some embodiments, the pretreatment unit includes a second gas flow controller and a filtration device connected by a sequential pipeline.
In some technical schemes, the device also comprises a calibration unit,
the calibration unit is provided with a mercury vapor generation device which is used for converting mercury standard substances with known concentration into elemental mercury, and then the elemental mercury is transmitted to the detection unit for detection through a first-stage gas circuit and a second-stage gas circuit respectively.
In some technical schemes, the content of the gold-plated quartz sand is 0.5-1.0g, and the number of the heating pipes is 3-5; and/or the number of the groups of groups,
the detection unit receives a 253.6nm characteristic spectrum signal through an optical fiber, and amplifies and records the signal by utilizing a spectrometer.
According to another aspect of the application, the application further provides a real-time online analysis method for measuring the content of mercury in each valence state in flue gas, which utilizes loosely arranged gold-plated quartz sand in a quartz tube to improve the enrichment efficiency of mercury in the pretreated flue gas, utilizes electric heating to release the mercury, and enters a mode without vacuum condition through a pipeline, namely, the mercury is excited and detected in microplasma generated in the atmospheric environment, and has the advantages of good conversion effect, improvement of the detection sensitivity of the existing instrument and the like.
In order to achieve the above purpose, the technical scheme adopted by the application is as follows:
a real-time on-line analysis method for measuring the content of mercury in each valence state in flue gas,
the real-time online analysis system comprises the following steps:
the sampling probe collects a smoke sample to be tested, controls the gas flow rate through the first gas flow controller, and transmits smoke at a constant flow rate and temperature in a sample gas pipeline;
the collected flue gas sequentially passes through a second gas flow controller and a filtering device to filter macromolecular particles;
the pretreated flue gas is divided into two paths at a fixed flow rate, one path is directly connected to the detection unit under the action of hydrogen and helium, and the other path enters the enrichment analysis unit for heating analysis, and then the hydrogen and helium are utilized for transporting elemental mercury, and detection and data output are carried out in the detection unit.
In some technical schemes, the calibration mode of the calibration unit is a standard gas calibration method, and the specific steps are as follows:
transferring mercury standard substances with known concentrations to a mercury vapor generating device for reduction and conversion into elemental mercury;
and the mercury vapor separated by pyrolysis enters a detection unit through a primary gas circuit and a secondary gas circuit to be detected.
In some technical schemes, the temperature of the flue gas in the sampling unit is controlled to be 800-1000 ℃; and/or the number of the groups of groups,
the enrichment time of the mercury-containing flue gas and/or mercury vapor in the enrichment analysis unit is 60-600 s, and the temperature of the enrichment area is controlled to be 700-1000 ℃ by the heating pipe; and/or the number of the groups of groups,
in the detection unit, the flow rate of hydrogen and helium is 400-1000 mL/min, and the ratio of hydrogen and helium is 1:99.
The technical scheme adopted by the application has at least the following beneficial effects:
1. the application integrates the sampling unit, the preprocessing unit, the enrichment analysis unit, the detection unit and the calibration unit to complete the real-time online quantitative analysis of the mercury in the flue gas on the basis of low cost, low power consumption, miniaturization and easy operation;
2. the enrichment area of the application is composed of gold-plated quartz sand, high temperature resistant quartz cotton for fixing the gold-plated quartz sand and a quartz tube, the gram weight of the gold-plated quartz sand is 0.5-1.0g, the purity is higher than 99%, the loose arrangement of the gold-plated quartz sand is utilized to improve the surface area and the density of the gold-plated sand, mercury in the flue gas and the gold-plated sand are fully and efficiently contacted to form gold amalgam alloy, and the enrichment efficiency can reach more than 98%; the method solves the problem of poor measurement accuracy caused by the defects of low sensitivity and large enrichment difference of the traditional enrichment module;
3. according to the application, a plurality of heating pipes are used for tightly surrounding the enrichment area to transfer heat from outside to inside, so that the quartz pipes of the enrichment analysis unit are uniformly heated, heat loss is reduced, no excessive requirements are imposed on the external environment, real-time detection of mercury-containing flue gas is easy to realize, the enrichment efficiency is improved, and the accuracy and the synchronism of measurement results are ensured to the greatest extent;
4. the detection unit adopts an atmospheric pressure glow discharge atomic emission spectrometry, and utilizes hydrogen helium microplasma to excite gaseous mercury emission characteristic spectral line, and the spectrometer is utilized to record and transmit data; the whole detection process is carried out in an atmosphere environment, so that the requirements on analysis environment and personnel are relatively relaxed;
5. the detection unit is directly communicated with a filtered smoke outlet of the pretreatment unit through a first-stage gas circuit and is used for measuring the content of elemental mercury in smoke; the device is communicated with an analysis gas outlet of the quartz tube through a second-level gas circuit and is used for measuring the total mercury content in the flue gas, wherein the flow of the flue gas which is filtered and passes through the first-level gas circuit is equal to that of the flue gas which is filtered through the second-level gas circuit, and the content of oxidized mercury can be calculated by the difference value of the total mercury content and the elemental mercury content;
6. the application is also provided with a calibration unit, and the detection precision of the system is corrected by adopting a standard gas calibration method.
Drawings
For a clearer description of the technical solutions of the embodiments of the present application, reference will be made to the drawings and the signs used in the embodiments, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a real-time online analysis system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of an enrichment analysis unit according to an embodiment of the present application;
FIG. 3 is a graph of time signals for unconverted mercury content of the same concentration in an embodiment of the present application;
FIG. 4 is a graph showing time signals of the same concentration of mercury content analyzed by heating in the example of the present application.
The meaning of the reference symbols in the figures is as follows:
the device comprises a 1-sampling probe, a 2-first gas flow controller, a 3-sample gas pipeline, a 4-temperature control display alarm device, a 5-second gas flow controller, a 6-filter device, a 7-quartz tube, 8-gold-plated quartz sand, 9-high temperature resistant quartz cotton, a 10-enrichment zone, a 11-heating tube, a 12-heating line, a 13-electric heating module, a 14-microplasma excitation zone, a 15-hydrogen helium gas bomb, a 16-third gas flow controller and a 17-data acquisition analysis module;
20-sampling unit, 30-preprocessing unit, 40-enrichment analysis unit and 50-detection unit.
Detailed Description
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following description will explain the specific embodiments of the present application with reference to the accompanying drawings. It is evident that the drawings in the following description are only examples of the application, from which other drawings and other embodiments can be obtained by a person skilled in the art without inventive effort.
For simplicity of the drawing, only the parts relevant to the application are schematically shown in each drawing, and they do not represent the actual structure thereof as a product. Additionally, in order to simplify the drawing for ease of understanding, components having the same structure or function in some of the drawings are shown schematically with only one of them, or only one of them is labeled. Herein, "a" means not only "only this one" but also "more than one" case.
It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
In this context, it should be noted that the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, unless explicitly stated or limited otherwise; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Referring to fig. 1 to 2 in combination, the present application provides a real-time online analysis system for measuring the content of mercury in each valence state in flue gas, which comprises a sampling unit 20, a preprocessing unit 30, an enrichment analysis unit 40, a detection unit 50 and a calibration unit. The sampling unit 20, the pretreatment unit 30, the enrichment analysis unit 40 and the detection unit 50 are sequentially connected through pipelines to form a detection path of mercury content of a flue gas sample; the calibration unit, the enrichment analysis unit 40 and the detection unit 50 are sequentially connected through pipelines to form a detection path of the mercury content of the standard substance.
The sampling unit 20 comprises a sampling probe 1, a first gas flow controller 2, a sample gas pipeline 3 and a temperature control display alarm device 4, wherein the sampling probe 1 is used for collecting a smoke sample to be tested, the first gas flow controller 2 is used for controlling the flow rate of the smoke, and the temperature control display alarm device 4 is used for controlling the temperature of the inside of the sampling probe 1 and the temperature of the whole sample gas pipeline 3 to be above 800 ℃ so as to prevent mercury vapor from condensing.
The pretreatment unit 30 includes a second gas flow controller 5 and a filtering device 6 connected in a pipeline in sequence, and is used for filtering macromolecular particles in the flue gas collected by the sampling unit 20.
The enrichment analysis unit 40 comprises an enrichment area 10 and an electric heating module 13, wherein the enrichment area 10 comprises a quartz tube 7, gold-plated quartz sand 8 arranged in the quartz tube 7 and high-temperature-resistant quartz cotton 9 used for fixing the gold-plated quartz sand 8; the electric heating module 13 comprises a plurality of heating pipes 11 and heating lines 12 closely surrounding the quartz tube 7.
In the embodiment, by utilizing the characteristics of excellent stability, difficult oxidation and easy processing of gold in the atmosphere, the mercury element is enriched to form gold amalgam, the gold amalgam is heated to enable the mercury element to be resolved, and meanwhile, oxidized mercury is converted into elemental mercury. Preferably, the weight of the gold-plated quartz sand is 0.5-1.0g, the purity is higher than 99%, the loose arrangement of the gold-plated quartz sand 8 is utilized to improve the surface area and the density of the gold-plated sand, so that mercury in the flue gas is fully and efficiently contacted with the gold-plated sand to form gold amalgam, and the enrichment efficiency can reach more than 98%; preferably, the number of heating pipes 11 is 3-5, the enrichment area 10 is integrally arranged at the central position of a plurality of heating pipes 11 of the electric heating module 13, the whole enrichment area 10 is completely wrapped by the heating pipes 11, electric energy is utilized to continuously heat the heating pipes 11, heat transfer is carried out from outside to inside, the quartz pipes 7 are uniformly heated, heat loss is reduced, excessive requirements on external environment are avoided, real-time detection of mercury-containing flue gas is easy to realize, enrichment efficiency is improved, and accuracy and synchronism of measurement results are guaranteed to the greatest extent.
The detection unit 50 is directly communicated with the filtered flue gas outlet of the pretreatment unit through a primary gas circuit and is used for measuring the content of elemental mercury in the flue gas; and the gas flow of the filtered flue gas passing through the first-stage gas circuit is equal to that of the second-stage gas circuit, and the content of bivalent oxidized mercury can be calculated from the difference value of the total mercury content and the elemental mercury content.
The detection unit 50 measures the concentration of mercury in the flue gas by an atmospheric pressure glow discharge atomic emission spectrometry, and comprises a microplasma excitation region 14, a hydrogen helium gas storage bottle 15 for providing a discharge atmosphere and a third gas flow controller 16 for controlling the flow rate of the hydrogen helium gas, wherein the analysis gas is transmitted into the microplasma excitation region 14 along with the hydrogen helium gas to emit a characteristic spectrum signal of 253.6 nm.
The detection unit 50 further comprises a data acquisition and analysis module 17 for recording the characteristic spectrum signal intensity of 253.6nm, and establishing a linear model based on the spectral line intensity and the mercury concentration, so as to obtain the concentration of each valence mercury in the flue gas sample to be detected, and recording and transmitting the concentration.
In a specific embodiment, the spectral signal of the characteristic wavelength generated by the detection unit 50 is received through an optical fiber, and the signal is amplified and recorded by using a spectrometer. Preferably, a fused ultraviolet quartz window is arranged at the front section of the optical fiber, so that the pollution of the optical fiber probe is avoided.
The collected flue gas is collected by a heat-preserving gas circuit and a pretreatment unit 30 and then is transmitted to an enrichment analysis unit 40 containing an enrichment zone 10, so that mercury in simulated flue gas contacts with the enrichment zone 10, is enriched and forms gold amalgam; then the enrichment zone 10 is heated rapidly by an electrothermal heating method, so that mercury in the enrichment zone 10 is resolved thermally, resolved mercury vapor is purged into the detection unit 50 by hydrogen helium, and the total mercury content in the flue gas is rapidly measured; and simultaneously, directly transmitting the same amount of pretreated flue gas into a detection unit from hydrogen and helium, measuring the content of elemental mercury in the flue gas, and calculating the content of oxidized mercury from the difference value of the total mercury content and the elemental mercury content.
The calibration unit is provided with a mercury vapor generating device, and is used for converting mercury standard substances with known concentration into elemental mercury, and then transmitting the elemental mercury to the detection unit 50 for detection through a primary gas path and a secondary gas path respectively. In this way, the detection accuracy of the analysis system is calibrated.
The application integrates the sampling unit 20, the preprocessing unit 30, the enrichment analysis unit 40, the detection unit 50 and the calibration unit to complete the real-time online quantitative analysis of the mercury in the flue gas on the basis of low cost, low power consumption, miniaturization and easy operation.
The application further provides a real-time online analysis method for measuring the content of mercury in each valence state in flue gas, which comprises the following steps:
the sampling probe 1 collects a smoke sample to be tested, the gas flow rate is controlled by the first gas flow controller 2, and the smoke is transmitted in the sample gas pipeline 3 at a constant flow rate and temperature;
preferably, the gas flow rate of the sampling unit 20 is controlled to be 1L/min; the working temperature of the sampling probe 1 and the sample gas pipeline 3 is 800-1000 ℃.
The collected flue gas sequentially passes through a second gas flow controller 5 and a filtering device 6 to filter macromolecular particles;
preferably, the gas flow rate of the pretreatment unit 30 is 1L/min; the material of the filtering device 6 is polytetrafluoroethylene filter membrane.
The pretreated flue gas is divided into two paths at a fixed flow rate, one path is directly connected to a detection unit under the action of hydrogen and helium, the other path enters an enrichment zone 10 for enrichment and heating analysis, the hydrogen and helium are utilized for transporting elemental mercury, and detection and data output are carried out in a detection unit 50;
preferably, the flow rate of hydrogen and helium is 400mL/min, and the ratio of hydrogen to helium is 1:99.
The calibration process comprises the following steps:
using stannous chloride as a reducing agent, and transmitting mercury standard substances with known concentration into a reaction bottle with stannous chloride with concentration of 2wt% to react to obtain elemental mercury through a peristaltic pump with the rotation speed of 0.312 mL/min;
the mercury vapor separated by pyrolysis enters the detection unit 50 through the primary gas path and the secondary gas path respectively, so that the content of mercury in the flue gas is detected, and calibration is performed.
The mercury-containing flue gas is filtered by the dust removing equipment, the granular mercury and macromolecular particulate matters in the flue gas are filtered, and elemental mercury, oxidized mercury and other flue gas components enter a next-stage conversion unit; dividing the primarily treated flue gas into two paths at a fixed flow rate through a gas path valve, wherein one path is directly connected to a detection unit under the action of hydrogen and helium, the other path enters an enrichment analysis unit and is introduced into a quartz tube 7 containing gold-plated quartz sand 8, elemental mercury and oxidized mercury are captured, other flue gas components and the gold-plated quartz sand 8 do not undergo any physical and chemical reaction, and the flue gas components enter a waste gas treatment unit through a gas transmission pipeline; heating a heating rod tightly surrounding the periphery of the quartz tube 7 to 700-1000 ℃ by electric heating, and preserving heat for 10min, wherein oxidized mercury is converted into elemental mercury at a high temperature, and the elemental mercury still keeps an original form; in the heating and heat preservation process, a hydrogen gas valve is opened, the fixed flow rate is 400mL/min, and the gaseous mercury released by heating is transmitted to a next-stage detection unit 50; the bimetallic rod of the detection unit 50 breaks down hydrogen and helium under the current of 30mA, and moves the metal rod, keeping the distance to be 9mm, so as to realize the excitation of gaseous mercury element, wherein the metal rod is made of a tungsten tube (anode) and a stainless steel tube (cathode); the spectral signal of the characteristic wavelength generated by the detection unit 50 is received through an optical fiber, and the signal is amplified and recorded by a spectrometer.
Example 1
In combination with the integral device shown in fig. 1, a peristaltic pump is used for transmitting a mercury (II) standard solution with the concentration of 50 mug/L into a reaction bottle filled with stannous chloride solution, and the gas generated by the reaction is respectively transmitted into a detection unit and an enrichment analysis unit along with carrier gas (hydrogen helium). The flow rate of hydrogen helium ranges from 400mL/min to 1L/min. After the enrichment is stopped, the electric heating unit is started, three heating pipes which are tightly surrounded are utilized to heat the enrichment area, the heating time is 60s, the temperature is controlled to be 700-900 ℃, after the electric heating is stopped, the flow rate is continuously introduced to 400mL/min, the proportion is 1:99, the hydrogen helium is used for loading the thermally resolved mercury into the detection unit, the experimental results shown in figures 3 and 4 are obtained, 11 times of data are collected, the obtained spectrum signal values are consistent, and the relative error of the net signal value is less than 2%.
Example 2
And in combination with the integral device shown in fig. 1, the collected flue gas is transmitted to an enrichment analysis unit. The flow rate of the mixed gas ranges from 400mL/min to 1L/min. The time of the flue gas is 600s, and the operation is performed in triplicate. After enrichment is stopped, any quartz tube is taken for electrothermal heating, three heating tubes which are tightly surrounded are utilized for heating an enrichment area, the heating time is 60s, the temperature is controlled to be 700-900 ℃, after electrothermal heating is stopped, hydrogen helium with the flow rate of 400mL/min and the proportion of 1:99 is continuously introduced, and thermally resolved mercury is loaded into a detection unit by using the hydrogen helium for quantitative analysis of mercury elements. The gold-plated quartz sand in the other two quartz tubes is detected by a direct mercury porosimeter, and the results are shown in table 1, which shows that the analysis method has higher accuracy.
TABLE 1
The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit of the application. The protection scope of the present application shall be subject to the appended claims.

Claims (10)

1. A real-time online analysis system for measuring the content of mercury in each valence state in flue gas, comprising:
the sampling unit is used for collecting a smoke sample to be tested;
the pretreatment unit is used for filtering macromolecular particles in the flue gas collected by the sampling unit;
an enrichment resolution unit comprising:
the quartz tube is communicated with the filtered flue gas outlet of the pretreatment unit, and gold-plated quartz sand is placed in the quartz tube and used for simultaneously enriching oxidized mercury and elemental mercury in the flue gas after the pretreatment unit;
the heating pipes are closely arranged around the quartz tube and are used for heating and resolving and converting the enriched oxidized mercury into elemental mercury;
the detection unit is directly communicated with the filtered smoke outlet of the pretreatment unit through the first-stage gas circuit and is used for measuring the content of elemental mercury in the smoke; and the gas flow of the filtered flue gas passing through the first gas path and the second gas path is equal, and the content of oxidized mercury can be calculated from the difference value of the total mercury content and the elemental mercury content.
2. The real-time online analysis system of claim 1, wherein,
the detection unit comprises a microplasma excitation area, a hydrogen helium gas bomb for providing a discharge atmosphere and a third gas flow controller for controlling the flow rate of the hydrogen helium gas, and the analysis gas is transmitted into the microplasma excitation area along with the hydrogen helium gas to emit a characteristic spectrum signal of 253.6 nm.
3. The real-time online analysis system of claim 2, wherein,
the detection unit further comprises a data acquisition and analysis module, wherein the data acquisition and analysis module is used for recording the characteristic spectrum signal intensity of 253.6nm, establishing a linear model based on the spectral line intensity and the mercury concentration, and accordingly obtaining the content of each valence mercury in the smoke sample to be detected, and recording and transmitting the content.
4. The real-time online analysis system of claim 1, wherein,
the sampling unit comprises a sampling probe, a first gas flow controller, a sample gas pipeline and a temperature control display alarm device, wherein the temperature control display alarm device is used for controlling the temperature of the inside of the sampling probe and the temperature of the whole sample gas pipeline to be above 800 ℃ and preventing mercury vapor from condensing.
5. The real-time online analysis system of claim 1, wherein,
the pretreatment unit comprises a second gas flow controller and a filtering device which are connected in sequence through pipelines.
6. The real-time online analysis system of claim 1, wherein,
the device also comprises a calibration unit, wherein the calibration unit comprises a calibration unit,
the calibration unit is provided with a mercury vapor generation device which is used for converting mercury standard substances with known concentration into elemental mercury, and then the elemental mercury is transmitted to the detection unit for detection through a first-stage gas circuit and a second-stage gas circuit respectively.
7. The real-time online analysis system of claim 1, wherein,
the content of the gold-plated quartz sand is 0.5-1.0g, and the number of the heating pipes is 3-5; and/or the number of the groups of groups,
the detection unit receives a 253.6nm characteristic spectrum signal through an optical fiber, and amplifies and records the signal by utilizing a spectrometer.
8. A real-time on-line analysis method for measuring the content of mercury in each valence state in flue gas is characterized in that,
use of the real-time online analysis system of any one of claims 1-7, comprising the steps of:
the sampling probe collects a smoke sample to be tested, controls the gas flow rate through the first gas flow controller, and transmits smoke at a constant flow rate and temperature in a sample gas pipeline;
the collected flue gas sequentially passes through a second gas flow controller and a filtering device to filter macromolecular particles;
the pretreated flue gas is divided into two paths at a fixed flow rate, one path is directly connected to the detection unit under the action of hydrogen and helium, and the other path enters the enrichment analysis unit for heating analysis, and then the hydrogen and helium are utilized for transporting elemental mercury, and detection and data output are carried out in the detection unit.
9. The method of real-time online analysis according to claim 8, wherein,
the calibration mode of the calibration unit is a standard gas calibration method, and the specific steps are as follows:
transferring mercury standard substances with known concentrations to a mercury vapor generating device for reduction and conversion into elemental mercury;
and the mercury vapor separated by pyrolysis enters a detection unit through a primary gas circuit and a secondary gas circuit to be detected.
10. The method of real-time online analysis according to claim 8, wherein,
the temperature of the flue gas in the sampling unit is controlled to be 800-1000 ℃; and/or the number of the groups of groups,
the enrichment time of the mercury-containing flue gas and/or mercury vapor in the enrichment analysis unit is 60-600 s, and the temperature of the enrichment area is controlled to be 700-1000 ℃ by the heating pipe; and/or the number of the groups of groups,
in the detection unit, the flow rate of hydrogen and helium is 400-1000 mL/min, and the ratio of hydrogen and helium is 1:99.
CN202310830164.6A 2023-07-07 2023-07-07 Real-time online analysis system and method for measuring content of mercury in each valence state in flue gas Pending CN116858625A (en)

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