In-situ construction-based mercury removal method for selenium site porous material flue

Abstract

The invention discloses an in-situ construction-based mercury removal method for a selenium site porous material flue. The method comprises the following steps: cleaning a porous carrier material, impregnating and absorbing a selenium-containing solution, drying to obtain a precursor material, putting the obtained precursor material into a flue, introducing mercury-containing waste gas, and adsorbing mercury in the waste gas while carrying out selenium in-situ reaction, thereby obtaining the mercury-containing porous carrier material. The valence state of the selenium element in the selenium-containing solution is + 4; the temperature of the mercury-containing waste gas is 60-100 DEG C, and the mercury-containing waste gas contains the following components in concentration: 80-120 ppm of mercury and 100-500 ppm of sulfur dioxide. According to the method, in-situ construction of selenium sites on a porous carrier material is achieved by means of reducibility of sulfur-containing components in mercury-containing waste gas, then selenium and mercury rapidly react with mercury to form mercury selenide in combination with high affinity of selenium and mercury, only waste heat of waste gas is utilized in the reaction process, heating and additional reagent are not needed, and related requirements of tail end treatment of industrial waste gas can be met.

Description

Technical Field

[0001] The invention relates to a flue mercury removal method, in particular to a flue mercury removal method based on in-situ constructed selenium site porous materials, belonging to the technical field of industrial waste gas treatment. Background Art

[0002] Mercury is a global pollutant that is widely distributed in the air, water and soil. Its sources mainly include natural processes and human activities. Human industrial activities, especially coal combustion, have significantly changed the natural cycle of global mercury, causing its concentration to continue to rise, posing a serious challenge to the environment and biological health. Coal is a component of the main energy source in many countries around the world, and the emission of mercury during coal combustion has become one of the largest sources of anthropogenic mercury emissions. According to statistics, mercury emitted by coal combustion accounts for about 20% of the total global mercury emissions. This mercury emission not only enters the atmosphere quickly, but also due to the volatility and persistence of mercury, it can stay in the atmosphere for a long time, and with the flow of the atmosphere, it crosses regions, countries, and even affects the global scope. Mercury in the flue gas produced during coal combustion is extremely volatile and persistent. It can be suspended in the atmosphere for a long time and eventually settle into the soil and water bodies through precipitation or airflow. In this process, the form of mercury will be transformed to form toxic compounds that are extremely harmful to the ecosystem and human health. Accumulated mercury pollution in water bodies and soil has become an environmental problem that cannot be ignored worldwide.

[0003] In response to the severe global air pollution situation, especially the emission of mercury and sulfur dioxide in industrial waste gas, there is an urgent need to develop more efficient and environmentally friendly waste gas purification technologies. At present, although some mature technical means, such as mercury capture and sulfur dioxide removal technology, can reduce the emission of these harmful substances to a certain extent, they are often handled independently, ignoring the synergistic purification potential between them. In addition, these existing technologies often face problems such as high cost and secondary pollution. For example, when using traditional desulfurization technology, waste or secondary waste gas containing heavy metals may be generated, further increasing the environmental burden. Therefore, it is urgent to develop a comprehensive purification technology that integrates the removal of mercury and sulfur, which can not only effectively reduce the emission of these pollutants, but also minimize the cost and environmental burden, thereby providing a practical solution to global environmental pollution problems.

[0004] Chinese patent (CN116639664A) discloses a method and product for preparing red selenium for absorbing gaseous mercury at room temperature. The initial material crude selenium is first oxidized and then reduced to finally obtain amorphous selenium with a high adsorption effect on mercury. Chinese patent (CN113521979A) discloses a method for capturing mercury from sulfur-containing and mercury-containing flue gas by chloro-selenium-mercury deposition. The mercury in the flue gas is converted into chloro-selenium-mercury and then deposited on the surface of the substrate using HCl in the flue gas. However, the above technical solution still inevitably involves the use of an oxidant, and the selenium element undergoes multiple chemical valence state conversions, resulting in a decrease in adsorption efficiency, and the resulting product also has the risk of secondary pollution. Therefore, the development of a fast and efficient flue mercury removal method is increasingly needed by the market. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a flue mercury removal method based on in-situ construction of selenium sites on porous materials. The method utilizes the reducibility of sulfur-containing components in mercury-containing waste gas to achieve in-situ construction of selenium sites on porous carrier materials, and then combines the high affinity of selenium and mercury to quickly react with mercury to form mercury selenide. The reaction process only utilizes waste heat from the waste gas, without the need for heating and adding external reagents, and can meet the relevant requirements for tail-end treatment of industrial waste gas.

[0006] To achieve the above technical objectives, the present invention provides a flue mercury removal method based on in-situ constructed selenium site porous materials, comprising:

[0007] Step S1, cleaning the porous carrier material, impregnating it with a selenium-containing solution, and then drying it to obtain a precursor material;

[0008] Step S2, placing the obtained precursor material in a flue, introducing mercury-containing waste gas, performing an in-situ reaction of selenium while adsorbing mercury in the waste gas, to obtain;

[0009] The valence state of selenium in the selenium-containing solution is +4; the temperature of the mercury-containing waste gas is 60-100° C., and it contains the following concentration components: 80-120 ppm mercury and 100-500 ppm sulfur dioxide.

[0010] The mercury removal method provided by the present invention loads +4-valent selenium on a porous carrier, uses sulfur dioxide in the exhaust gas as a reducing agent, reduces the +4-valent selenium to 0-valent selenium in situ, and then directly adsorbs mercury to the selenium site through the strong chemical affinity between selenium and mercury to form mercuric selenide. The kinetic rate of the reaction is fast and irreversible, and the reaction does not require high-temperature treatment or external reagents throughout the reaction, and can be achieved by only preheating the exhaust gas.

[0011] As a preferred solution, the porous carrier material is at least one of polyether foam, polyester staple fiber filter bag, aramid fiber filter bag, alumina, clay and activated carbon.

[0012] The selection criteria of the carrier of the present invention are mainly the following points: 1. Possessing a relatively high porosity, which can provide a high-density high-affinity selenium site, thereby improving the efficiency of the mercury adsorption reaction; 2. Having a certain chemical stability and thermal stability, the carrier material should be able to remain stable in complex sulfur-containing and mercury-containing flue gases and at high temperatures; 3. Having good binding force to selenium substances, supporting the effective load of selenium, and helping to form stable selenium sites that can react rapidly with mercury; 4. Having good flow compatibility, which will not affect the flow state of the flue gas through the system, while ensuring that the reaction can effectively occur when the flue gas passes through.

[0013] As a preferred solution, the selenium loading in the precursor material is 25-100 mg / cm 3 The selenium loading must be strictly implemented in accordance with the above requirements. If the selenium loading is too low, the number of selenium sites will be insufficient and unable to fully react with the mercury in the flue gas. If the selenium loading is too high, the carrier surface may be blocked or micropores may be blocked, hindering the exhaust gas penetration and mass transfer, reducing the reaction rate, and high concentration of selenium is also prone to agglomeration during the reduction process, resulting in insufficient contact between selenium and mercury.

[0014] As a preferred solution, the cleaning process of the porous carrier material is: the porous carrier material is completely immersed in an organic solution for ultrasonic cleaning, and then vacuum dried to obtain the porous carrier material.

[0015] As a preferred solution, the organic solvent is ethanol and / or acetone.

[0016] As a preferred solution, the ultrasonic cleaning treatment time is 30 to 45 minutes.

[0017] As a preferred solution, the vacuum drying conditions are: temperature of 60-85°C and time of 12-24h.

[0018] As a preferred solution, the process of immersing and absorbing the selenium-containing solution in step S1 is: using deionized water to completely soak the cleaned porous carrier material, and then dripping the selenium-containing solution to the porous carrier material under oscillation conditions. The entire process of loading the selenium-containing solution is performed under oscillation conditions, the purpose of which is to ensure that the selenium-containing solution can fully penetrate the internal pores of the porous carrier to avoid local accumulation, and on the other hand, it can promote the adsorption of selenium and the carrier, improve the stability of the selenium site, and avoid the shedding of selenium during subsequent use.

[0019] As a preferred solution, the dropwise addition time of the selenium-containing solution is 10 to 20 minutes.

[0020] As a preferred solution, the selenium-containing solution is continuously shaken for 6 to 12 hours after the dropwise addition is completed. The continuous shaking process is mainly because the selenium-containing solution is mainly enriched on the surface of the carrier during the dropwise addition stage and is not evenly distributed. In order to ensure the homogenization and nano-sizing of selenium, the shaking needs to be continued for a period of time after the dropwise addition of the selenium-containing solution is completed.

[0021] As a preferred solution, the selenium-containing solution is a selenious acid solution or a selenite solution, and its concentration is 0.5-1 mol / L.

[0022] As a preferred solution, the drying method in step S1 is one of vacuum drying, oven drying and freeze drying.

[0023] As a preferred solution, when the drying method in step S1 is freeze-drying, the conditions are: temperature is -20~-40°C, and time is 20~30h.

[0024] As a preferred solution, the precursor material is fixed in the flue gas duct by using a sandwich frame, which is orthogonal to the flow direction of the mercury-containing waste gas.

[0025] As a preferred solution, the number of layers of the precursor material is 1 to 3 layers, and the number of layers is positively correlated with the concentration of mercury in the mercury-containing waste gas.

[0026] As a preferred solution, when the content of mercury selenide in the selenium site porous material is ≥85%, the material is taken out and sequentially subjected to heating regeneration and condensation recovery to recover selenium and mercury.

[0027] SO in mercury-containing waste gas 2 The reducing activity (E0 = -0.17 V) is sufficient to convert Se 4+ Reduction to Se 0 (E0 = +0.74 V), the reaction process is: H 2 SeO 3 +3SO 2 +2H 2 O→Se+3H 2 SO 4 Through this process, sulfur dioxide in the waste gas can be effectively consumed, and the coordinated purification of sulfur and mercury can be achieved; compared with the prior art, the present invention can reduce the number of chemical valence changes of selenium, avoid the use of oxidants, and will not produce secondary pollution caused by sediments. At the same time, with the effective use of sulfur-containing components in flue gas, the construction and preparation of high-affinity nano-selenium on porous carrier materials is realized, thereby achieving mercury removal, so it is suitable for environmental management of heavy industrial industries that produce mercury-containing and sulfur-containing waste gas.

[0028] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are:

[0029] 1) The flue mercury removal method provided by the present invention utilizes the reducibility of sulfur-containing components in mercury-containing waste gas to achieve in-situ construction of selenium sites on porous carrier materials, and then combines the high affinity of selenium and mercury to quickly react with mercury to form mercury selenide. The reaction process only utilizes waste heat from the waste gas, without the need for heating and adding external reagents, and can meet the relevant requirements for tail-end treatment of industrial waste gas.

[0030] 2) In the technical solution provided by the present invention, there is no need to rely on external conditions to interfere in the mercury adsorption process. On the one hand, it effectively reduces the input of chemicals and labor resources and reduces the cost of mercury removal. On the other hand, it also effectively avoids the leakage of mercury-containing and sulfur-containing waste gas. In addition, the raw materials used in this method are widely available and the pretreatment process is simple, which can meet the requirements of large-scale industrial production.

[0031] 3) In the technical solution provided by the present invention, the mercury selenide formed by the in-situ adsorption of selenium and mercury is extremely stable within the temperature range of flue gas waste heat and will not cause secondary pollution to the surrounding environment. In addition, the mercury selenide enriched on the porous carrier material can be regenerated into mercury vapor and selenium by heating to ≥400°C, and then recovered by condensation to achieve the recovery of selenium and mercury and the recycling of the carrier material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The actual image and electron microscope image of the precursor material provided in Example 1 of the present invention;

[0033] in, Figure 1 (a) is a physical picture of the precursor material provided in Example 1 of the present invention, Figure 1 (b) is an electron microscope image of the precursor material provided in Example 1 of the present invention;

[0034] Figure 2 This is a curve diagram of the mercury removal effect of the selenium-site porous material provided in Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner in conjunction with the accompanying drawings and preferred embodiments of the specification. It should be noted that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] (1) For industrial waste gas containing mercury and sulfur with a sulfur dioxide concentration of 400 ppm, polyether foam was selected as the porous carrier material and processed into 50×50×1cm 3The shaped polyether foam was placed in an ethanol solution for ultrasonic treatment for 45 min, and then vacuum dried at 60 °C for 24 h to obtain the polyether foam to be modified.

[0038] (2) Place the polyether foam to be modified in a container, add a certain amount of water, and place it on a vibrating shaker for 30 minutes to allow the polyether foam to be completely soaked. Then use a titration pump to add 50 mL of 0.5 mol / L selenious acid solution into the container within 10 minutes. After the selenious acid solution is completely dropped, continue to vibrate for 6 hours until the surface of the polyether foam presents a uniform brick red color, such as Figure 1 As shown, the fully impregnated high-affinity selenium site polyether foam was freeze-dried at -20 °C for 24 h.

[0039] (3) The high-affinity selenium site polyether foam obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3 Under these conditions, a fixed layer of polyether foam with high affinity selenium sites can adsorb and treat more than 90% of the mercury in the flue gas.

[0040] Example 2

[0041] (1) For industrial waste gas containing mercury and sulfur with a sulfur dioxide concentration of 200 ppm, polyether foam was selected as the porous carrier material and processed into 50×50×1cm 3 The shaped polyether foam was placed in an ethanol solution for ultrasonic treatment for 45 min, and then vacuum dried at 60 °C for 24 h to obtain the polyether foam to be modified.

[0042] (2) Place the polyether foam to be modified in a container, add a certain amount of water, and then place it on a vibrating shaker for 30 minutes to allow the polyether foam to be completely soaked. Then, use a titration pump to add 50mL of a sodium selenite solution with a molar concentration of 0.5 mol / L into the container within 10 minutes. After the selenite solution is completely dripped in, continue to vibrate for 6 hours, and finally freeze-dry the fully soaked high-affinity selenium site polyether foam at -25 °C for 24 hours.

[0043] (3) The high-affinity selenium site polyether foam obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3Under these conditions, two layers of polyether foam with high affinity selenium sites can adsorb and treat more than 89% of mercury in flue gas.

[0044] Example 3

[0045] (1) For the mercury-containing and sulfur-containing industrial waste gas with a sulfur dioxide concentration of 100 ppm, polyester staple fiber filter bags were selected as porous carrier materials and processed into a circular cross-section shape with a diameter of 50 cm and a thickness of 0.5 cm. The shaped polyester staple fibers were ultrasonically treated in an acetone solution for 35 min, and then vacuum dried at 85 °C for 24 h to obtain the porous carrier material of the polyester staple fiber filter bag to be modified.

[0046] (2) Place the polyester staple fiber filter bag to be modified in a container, add a certain amount of water, and place it on a vibrating shaker for 60 minutes to completely soak the polyester staple fiber filter bag. Then, use a titration pump to add 100 mL of 1 mol / L selenious acid solution to the container within 20 minutes. After the selenious acid solution is completely dripped in, continue to vibrate for 10 hours, and finally freeze-dry the completely soaked high-affinity selenium site polyester staple fiber filter bag at -30 °C for 24 hours.

[0047] (3) The high-affinity selenium-site polyester staple fiber filter bag obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3 Under certain conditions, a polyester staple fiber filter bag with a fixed layer of selenium sites with high affinity can adsorb and treat more than 85% of the mercury in the flue gas.

[0048] Example 4

[0049] (1) For the mercury-containing and sulfur-containing industrial waste gas with a sulfur dioxide concentration of 100 ppm, alumina was selected as the basic unit of the porous carrier material and placed in an ethanol solution for ultrasonic treatment for 30 min. It was then vacuum dried at 85 °C for 12 h to obtain the basic unit of the alumina porous carrier material to be modified.

[0050] (2) Place the basic unit of the alumina porous material to be modified in a container, add a certain amount of water, and place it on a vibrating shaker for 60 minutes to allow the alumina to be completely infiltrated. Then, use a titration pump to add 80 mL of a selenious acid solution with a molar concentration of 0.78 mol / L to the container within 18 minutes. After the selenious acid solution is completely dripped, continue to vibrate for 12 hours. Spread the fully impregnated high-affinity selenium site alumina flat on a polytetrafluoroethylene template and freeze-dry it at -20 °C for 24 hours.

[0051] (3) The high-affinity selenium-site alumina obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3 Under these conditions, a layer of alumina porous material with high affinity selenium sites can adsorb and treat more than 87% of the mercury in flue gas.

[0052] Example 5

[0053] (1) For the mercury-containing and sulfur-containing industrial waste gas with a sulfur dioxide concentration of 200 ppm, activated carbon was selected as the basic unit of the porous carrier material and placed in an ethanol solution for ultrasonic treatment for 30 min. It was then vacuum dried at 85 °C for 12 h to obtain the basic unit of the activated carbon porous carrier material to be modified.

[0054] (2) Place the basic unit of the activated carbon porous material to be modified in a container, add a certain amount of water, and then place it on a vibrating shaker for 30 minutes to allow the activated carbon to be completely infiltrated. Then, use a titration pump to add 50 mL of a 1 mol / L selenious acid solution to the container within 18 minutes. After the selenious acid solution is completely dripped, continue to vibrate for 12 hours. Spread the fully impregnated high-affinity selenium site activated carbon onto a polytetrafluoroethylene template and freeze-dry it at -20 °C for 24 hours.

[0055] (3) The high-affinity selenium site activated carbon obtained after freeze drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3 Under these conditions, a layer of activated carbon porous material with high affinity selenium sites can adsorb and treat more than 80% of the mercury in flue gas.

[0056] Comparative Example 1

[0057] (1) For industrial waste gas containing mercury and sulfur with a sulfur dioxide concentration of 400 ppm, polyvinyl alcohol sponge was selected as the porous carrier material and processed into 50×50×1 cm 3 The shaped polyvinyl alcohol sponge was placed in an ethanol solution for ultrasonic treatment for 45 min, and then vacuum dried at 60 °C for 24 h to obtain the polyvinyl alcohol sponge to be modified.

[0058] (2) Place the polyvinyl alcohol sponge to be modified in a container, add a certain amount of water, and place it on a vibrating shaker for 30 minutes to allow the polyvinyl alcohol sponge to be completely soaked. Then, use a titration pump to add 50 mL of 0.5 mol / L selenious acid solution to the container within 10 minutes. After the selenious acid solution is completely dripped, continue to vibrate for 6 hours, and finally freeze-dry the fully soaked high-affinity selenium site polyvinyl alcohol sponge at -20 °C for 24 hours.

[0059] (3) The high-affinity selenium-site polyvinyl alcohol sponge obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3 Under these conditions, a polyvinyl alcohol sponge with a fixed layer of high-affinity selenium sites had an adsorption efficiency of only 65% ​​for mercury in flue gas.

[0060] From the above description, it can be seen that the mercury adsorption performance of the porous material obtained in Comparative Example 1 is poor. This is mainly because the polyvinyl alcohol sponge used therein has extremely poor thermal stability and it is difficult to maintain its structural integrity in the flue gas at this temperature, which in turn causes insufficient contact between the sulfur-containing and mercury-containing flue gas and the high-affinity nano-selenium sites on the carrier material; in addition, since the foaming technology used in the production of the polyvinyl alcohol sponge is very likely to leave residual surfactants, these residual impurities will make it difficult for selenium sites to be effectively formed and stably present on the polyvinyl alcohol sponge. Compared with other carriers that can form high-density selenium sites, it is difficult for the polyvinyl alcohol sponge to achieve the formation of selenium sites, and it is impossible to achieve the same level of mercury adsorption performance.

[0061] Comparative Example 2

[0062] (1) For industrial waste gas containing mercury and sulfur with a sulfur dioxide concentration of 400 ppm, polyether foam was selected as the porous carrier material and processed into 50×50×1 cm 3 The shaped polyether foam was placed in an ethanol solution for ultrasonic treatment for 45 min, and then vacuum dried at 60 °C for 24 h to obtain the polyether foam to be modified.

[0063] (2) Place the polyether foam to be modified in a container, add a certain amount of water, and place it on a vibrating shaker for 30 minutes to allow the polyether foam to be completely soaked. Then, use a titration pump to add 50 mL of a sodium selenate solution (containing +6-valent selenium) with a molar concentration of 0.5 mol / L into the container within 10 minutes. After the selenious acid solution is completely dripped in, continue to vibrate for 6 hours, and finally freeze-dry the fully soaked high-affinity selenium site polyether foam at -20 °C for 24 hours.

[0064] (3) The high-affinity selenium site polyether foam obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 60 °C and the mercury concentration was 100±10 μg / m 3 Under these conditions, a fixed layer of polyether foam with high affinity selenium sites has an adsorption effect of less than 10% on mercury in flue gas.

[0065] Comparative Example 3

[0066] (1) For industrial waste gas containing mercury and sulfur with a sulfur dioxide concentration of 400 ppm, polyether foam was selected as the porous carrier material and processed into 50×50×1 cm 3 The shaped polyether foam was placed in an ethanol solution for ultrasonic treatment for 45 min, and then vacuum dried at 60 °C for 24 h to obtain the polyether foam to be modified.

[0067] (2) Place the polyether foam to be modified in a container, add a certain amount of water, and place it on a vibrating shaker for 30 minutes to allow the polyether foam to be completely soaked. Then, use a titration pump to add 50 mL of 0.5 mol / L selenious acid solution to the container within 10 minutes. After the selenious acid solution is completely dripped, continue to vibrate for 6 hours, and finally freeze-dry the fully soaked high-affinity selenium site polyether foam at -20 °C for 24 hours.

[0068] (3) The high-affinity selenium site polyether foam obtained after freeze-drying was placed in the local pipeline of the industrial waste gas treatment component and fixed at the flange bayonet using an aluminum alloy sandwich frame. When the waste heat temperature of the industrial waste gas was about 25 °C and the mercury concentration was 100±10 μg / m 3 Under these conditions, a fixed layer of polyether foam with high affinity selenium sites can adsorb less than 15% of mercury in flue gas.

Claims

1. A flue mercury removal method based on in-situ constructed selenium site porous material, characterized in that: include: Step S1, cleaning the porous carrier material, impregnating it with a selenium-containing solution, and then drying it to obtain a precursor material; Step S2, placing the obtained precursor material in a flue, introducing mercury-containing waste gas, performing an in-situ reaction of selenium while adsorbing mercury in the waste gas, to obtain; The valence state of selenium in the selenium-containing solution is +4; the temperature of the mercury-containing waste gas is 60-100° C., and it contains the following concentration components: 80-120 ppm mercury and 100-500 ppm sulfur dioxide.

2. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 1, characterized in that: The porous carrier material is at least one of polyether foam, polyester staple fiber filter bag, aramid fiber filter bag, alumina, clay and activated carbon; the selenium loading in the precursor material is 25-100 mg / cm 3 .

3. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 1, characterized in that: The cleaning process of the porous carrier material is as follows: the porous carrier material is completely immersed in an organic solution for ultrasonic cleaning, and then vacuum dried to obtain the porous carrier material; the organic solvent is ethanol and / or acetone.

4. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 3, characterized in that: The ultrasonic cleaning treatment lasts for 30 to 45 minutes; the vacuum drying conditions are: temperature of 60 to 85° C., and time of 12 to 24 hours.

5. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 1, characterized in that: The process of immersing and absorbing the selenium-containing solution in step S1 is: using deionized water to completely soak the cleaned porous carrier material, and then dripping the selenium-containing solution into the porous carrier material under oscillation conditions.

6. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 5, characterized in that: The dropwise addition time of the selenium-containing solution is 10 to 20 minutes; after the dropwise addition of the selenium-containing solution is completed, the oscillation is continued for 6 to 12 hours.

7. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 1, characterized in that: The selenium-containing solution is a selenious acid solution or a selenite solution, and its concentration is 0.5-1 mol / L; the drying method in step S1 is one of vacuum drying, oven drying and freeze drying.

8. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 7, characterized in that: When the drying method in step S1 is freeze drying, the conditions are: temperature is -20 to -40°C and time is 20 to 30 hours.

9. The method for removing mercury from flue gas based on in-situ constructed selenium-site porous materials according to claim 1, characterized in that: The precursor material is fixed in the flue gas duct by a sandwich frame, which is orthogonal to the flow direction of the mercury-containing waste gas; the number of layers of the precursor material is 1 to 3, and the number of layers is positively correlated with the concentration of mercury in the mercury-containing waste gas.

10. A flue mercury removal method based on in-situ constructed selenium site porous material according to any one of claims 1 to 9, characterized in that: When the content of mercury selenide in the selenium site porous material is ≥85%, the material is taken out and the selenium and mercury are recovered by heating regeneration and condensation in sequence.

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