Magnetic adsorbent as well as preparation method and application thereof
By preparing a magnetic adsorbent and utilizing Fe3O4 and CuCl2 to enhance its magnetic and chlorine activity, the problems of low mercury removal efficiency and high cost in existing technologies have been solved, achieving a highly efficient and economical mercury removal effect from flue gas.
Patent Information
- Application Number
- CN202511940309.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-02-17
AI Technical Summary
Among existing mercury removal technologies, activated carbon injection technology suffers from problems such as low adsorption capacity, high operating costs, impact on ash and slag resource utilization, and competitive adsorption by acidic gases such as SO2 and HCl, leading to decreased efficiency. It is difficult to remove elemental mercury from coal-fired flue gas in an economical and efficient manner.
A magnetic adsorbent preparation method is adopted, in which magnetic beads are impregnated in situ in a metal salt solution and subjected to a redox reaction to generate Fe3O4 and CuCl2, thereby enhancing the magnetism and controlling the proportion of active species, forming chlorine active adsorption sites, and achieving efficient mercury removal.
It achieves efficient and economical removal of elemental mercury from coal-fired flue gas, reducing production costs and pipeline corrosion risks, and is suitable for industrial production.
Smart Images
Figure CN121534657A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of air pollution control technology, and in particular to a magnetic adsorbent, its preparation method, and its application. Background Technology
[0002] Mercury (Hg) is listed by the United Nations Environment Programme as one of the "Top Ten Chemicals Hazardous to Public Health" due to its persistence, bioaccumulation, and neurotoxicity. Global mercury emissions inventories show that coal-fired power plants are the largest single source of emissions. During combustion, mercury in coal is primarily emitted as elemental mercury (Hg). 0 It volatilizes into the flue gas in the form of Hg, which has a high saturated vapor pressure and low water solubility, making it difficult to capture in conventional desulfurization and denitrification devices. 0 It can be transported over long distances in the atmosphere and transformed into methylmercury, which accumulates through the food chain, leading to health problems such as fetal neurodevelopmental disorders.
[0003] Currently, among existing mercury removal technologies, activated carbon injection (ACI) mercury removal technology has the highest maturity, but it suffers from the following bottlenecks: 1) low adsorption capacity, leading to high consumption; 2) high operating costs (USD 60,000-100,000 / kg mercury); 3) reduced ash quality after mixing with fly ash, affecting ash resource utilization; 4) competitive adsorption by acidic gases such as SO2 and HCl, resulting in a 20-40% decrease in efficiency. However, if it is to be practically applied to mercury capture in power plants, comprehensive factors such as cost and efficiency must be considered. Therefore, how to develop a method for enhanced and efficient mercury removal from flue gas, capable of economically and efficiently removing elemental mercury from coal-fired flue gas, is an urgent problem to be solved in this field. Summary of the Invention
[0004] In view of this, the present invention provides a magnetic adsorbent, its preparation method and application. The magnetic adsorbent prepared by the method provided by the present invention can efficiently remove mercury at a low cost.
[0005] This invention provides a method for preparing a magnetic adsorbent, comprising the following steps: The magnetic adsorbent is obtained by immersing magnetic beads in a metal salt solution in situ and then subjecting them to oxidation and reduction reactions in a moist state. The metal salt solution is obtained by mixing copper chloride solution and ferric chloride solution.
[0006] Preferably, the mass concentrations of the copper chloride solution and the ferric chloride solution are independently 3% to 6%; the volume ratio of the copper chloride solution to the ferric chloride solution is 1:1.
[0007] Preferably, the mass ratio of the metal salt solution to the magnetic beads is 10~20:100.
[0008] Preferably, the oxidation reaction is carried out at a temperature of 300~500℃ and the holding time is 0.5 h~2 h.
[0009] Preferably, the oxidation reaction is carried out in an oxidizing atmosphere; the volume concentration of oxygen in the oxidizing atmosphere is 3% to 9%.
[0010] Preferably, the temperature of the reduction reaction is 300~500℃, and the holding time is 10~30 min.
[0011] Preferably, the reduction reaction is carried out in a reducing atmosphere; the volume concentration of CO in the reducing atmosphere is 200~500 ppm.
[0012] The present invention also provides a magnetic adsorbent obtained by the preparation method described above, comprising magnetic beads, a modifier loaded on the magnetic beads, and chlorine active species adsorbed on the surfaces of the magnetic beads and the modifier; the modifier comprises Fe3O4 and CuCl2.
[0013] Preferably, the magnetic adsorbent has a particle size of 50~150 μm.
[0014] The present invention also provides the application of the magnetic adsorbent obtained by the preparation method described above, or the magnetic adsorbent described above, in the adsorption of mercury.
[0015] This invention provides a method for preparing a magnetic adsorbent, which has the following advantages: (1) FeCl3 decomposes and releases Cl2 simultaneously in an atmosphere of 300~500℃. Cl2 is immediately re-adsorbed / re-coordinated on the surface of the magnetic beads, maintaining sufficient active adsorption sites for chlorine.
[0016] (2) This invention utilizes the in-situ strengthening of FeCl3 by magnetic beads to enhance the Fe content in FeCl3. 3+ The active component generates Fe3O4, a strongly magnetic material, under an oxidizing and reducing atmosphere at a specific temperature. This enhances the magnetism of the original magnetic beads, making them easier to magnetically separate from fly ash after subsequent mercury removal.
[0017] (3) By controlling the ratio of the active species copper chloride and ferric chloride, this invention reduces Cu content while satisfying the mercury removal performance. 2+ The intake of these substances significantly reduces the production cost of adsorbents and the risk of pipeline corrosion during operation.
[0018] (4) The preparation method provided by the present invention has simple steps, is easy to operate, has high feasibility, good safety, and is suitable for industrial production.
[0019] This invention also provides the application of the magnetic adsorbent described in the above-described scheme or the magnetic adsorbent prepared by the above-described scheme in the field of mercury adsorption. This invention proposes a "chlorine self-replenishment" strategy, in which Cl... -While being consumed, the chlorine-active species loaded on the surface of the magnetic beads replenish the active components, maintaining the chemisorption between Cl and Hg. Through the above method, the magnetic adsorbent provided by this invention can efficiently remove mercury from flue gas with in-situ magnetic enhancement, at a low cost, solving the problems of high operating costs, corrosion risks, and complex magnetic separation modes of current copper-chlorine modified adsorbents.
[0020] In summary, the magnetic adsorbent provided by this invention can efficiently remove mercury from flue gas in situ with enhanced magnetic properties. It is economical and safe, and suitable for use in the field of mercury adsorption, especially for the removal of mercury from flue gas in coal-fired power plants. It has good social and economic benefits. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a schematic diagram of the mercury removal process of the magnetic adsorbent of the present invention; Figure 2 This is a schematic diagram of the apparatus for testing the mercury removal performance of the magnetic adsorbent of the present invention; Figure 3 A comparison of the magnetic properties of the magnetic adsorbent prepared in Example 1 (after modification) and the original magnetic beads (before modification); Figure 4 The mercury removal effects of the magnetic adsorbents prepared in Examples 1-3 and the original magnetic beads are compared. Detailed Implementation
[0023] This invention provides a method for preparing a magnetic adsorbent, comprising the following steps: The magnetic adsorbent is obtained by immersing magnetic beads in a metal salt solution in situ and then subjecting them to oxidation and reduction reactions in a moist state. The metal salt solution is obtained by mixing copper chloride solution and ferric chloride solution.
[0024] In one embodiment of the present invention, the magnetic beads are preferably obtained from fly ash.
[0025] In one embodiment of the present invention, the mass concentrations of the copper chloride solution and the ferric chloride solution are independently 3% to 6%, more preferably 4% to 5%; the volume ratio of the copper chloride solution to the ferric chloride solution is preferably 1:1. In another embodiment of the present invention, the mass ratio of the metal salt solution to the magnetic beads is preferably 10 to 20:100, more preferably 15:100.
[0026] In one embodiment of the present invention, the in-situ impregnation temperature is preferably room temperature; the in-situ impregnation time is preferably 2-24 h, more preferably 8-12 h. The present invention uses an equal-volume in-situ impregnation method to modify magnetic beads, so that copper, iron, and chlorine triatoms are uniformly distributed on the surface of the magnetic beads.
[0027] In one embodiment of the present invention, the temperature of the oxidation reaction is preferably 300~500℃, more preferably 350~450℃, and the holding time is preferably 0.5~2 h, more preferably 1~1.5 h; the oxidation reaction is preferably carried out in an oxidizing atmosphere; the volume concentration of oxygen in the oxidizing atmosphere is preferably 3%~9%, more preferably 6%.
[0028] In one embodiment of the present invention, the temperature of the reduction reaction is preferably 300~500℃, more preferably 350~450℃, and the holding time is preferably 10~30 min, more preferably 20 min; the reduction reaction is preferably carried out in a reducing atmosphere; the volume concentration of CO in the reducing atmosphere is preferably 200~500ppm, more preferably 300ppm.
[0029] This invention enables the active component Fe on the surface of magnetic beads to undergo oxidation and reduction reactions under a specific atmosphere. 3+ The magnetic beads are transformed in situ on the surface into a strongly magnetic material, iron(III) oxide (Fe3O4), thereby enhancing the magnetism of the beads. After the enhanced magnetism is removed, the magnetic beads are more easily separated from fly ash by magnetic separation. The specific reaction mechanism is shown in equations (1) and (2). As for the other active species, copper chloride, from the perspective of redox and thermodynamics, it does not react with O2 and CO and remains in the form of a stable compound throughout the process.
[0030] 4FeCl3+ 3O2→ 2Fe2O3+ 6Cl2↑ (1); 3Fe2O3+ CO → 2Fe3O4+ CO2↑ (2).
[0031] The present invention also provides a magnetic adsorbent prepared by the preparation method described above, comprising magnetic beads, a modifier loaded on the magnetic beads, and chlorine active species adsorbed on the surface of the magnetic beads; the modifier comprises Fe3O4 and CuCl2.
[0032] In one embodiment of the present invention, the particle size of the magnetic adsorbent is preferably 50~150 μm, more preferably 75~125 μm.
[0033] The present invention also provides the application of the magnetic adsorbent obtained by the preparation method described above or the magnetic adsorbent described above in the adsorption of mercury.
[0034] As one embodiment of the present invention, the method of application preferably includes the following steps: injecting the magnetic adsorbent into the flue gas for mercury removal, followed by sequential recovery and regeneration.
[0035] In one embodiment of the present invention, the preferred spraying amount of the magnetic adsorbent is 0.05 ~ 0.25 g / m³. 3 More preferably, it is 0.10~0.15 g / m 3 .
[0036] In one embodiment of the present invention, the mercury removal temperature is preferably 120 °C, and the holding time is preferably 0.5~2 h, more preferably 1~1.5 h.
[0037] As one embodiment of the present invention, the regeneration method preferably includes the following steps: heating the adsorbent that adsorbs mercury to desorb it, the mercury compound (mainly HgCl2) in the magnetic adsorbent is desorbed and decomposed into gaseous Hg, and then elemental Hg is recovered by condensation.
[0038] In this invention, when the magnetic adsorbent is injected into the flue gas for mercury removal, the chlorine-containing chemisorption sites on the surface of CuCl2 are lost, forming CuCl. The Cl active species on the surface of the magnetic adsorbent combine with CuCl to replenish the Cl vacancies consumed during the mercury removal reaction, thereby forming a new active species CuCl2. The specific reaction mechanism is shown in equations (3) and (4). Figure 1 As shown.
[0039] 2CuCl2+Hg→HgCl2+2CuCl (3); CuCl+1 / 2Cl2→CuCl2 (4).
[0040] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.
[0041] Example 1 This embodiment prepares a magnetic adsorbent, and the specific steps are as follows: First, magnetic beads are sorted from fly ash, and the obtained magnetic beads are used as carriers. A 3% (w / w) ferric chloride solution was prepared using ferric chloride as the active component. A 3% (w / w) copper chloride solution was prepared using copper chloride as the active component. Ferric chloride solution and copper chloride solution were mixed at a volume ratio of 1:1 to obtain a metal salt solution. Magnetic beads were then impregnated in situ with the metal salt solution for 8 hours, with a mass ratio of metal salt solution to magnetic beads of 20:100. Subsequently, the wetted magnetic beads were placed in an oxidizing atmosphere (O2, volume concentration 9%) at 500℃ for 30 minutes, followed by a reaction at 350℃ in a reducing atmosphere (CO, volume concentration 500 ppm) for 10 minutes to obtain a magnetic adsorbent.
[0042] The magnetic adsorbent prepared in this embodiment is used for the removal of mercury from flue gas, and the apparatus used is as follows: Figure 2 As shown, the specific steps are as follows: First, place the mercury tube into one end of the U-shaped tube and silica gel into the other end to absorb moisture from the gas. Use N2 as the mercury carrier gas. Turn on the water bath, temperature controller, heating belt, and other experimental equipment. Control the temperature of the water bath at 70 ℃ and maintain the mercury concentration in the tube at 100 μg / m³. 3 0.05 g of magnetic adsorbent was placed in the reactor bed inside the tubular furnace to adsorb and fix gaseous mercury, completing mercury removal (mercury removal temperature was 120 ℃, and mercury removal time was 1 h). Simulated flue gas flowed through the tubular furnace reactor and then into the inlet pipe of an online mercury analyzer to monitor changes in gaseous mercury concentration in real time. Its outlet pipe was connected to an activated carbon absorber to absorb residual toxic gaseous mercury.
[0043] Example 2 This embodiment prepares a magnetic adsorbent, and the specific steps are as follows: First, magnetic beads are sorted from fly ash, and the obtained magnetic beads are used as carriers. A 6% (w / w) ferric chloride solution was prepared using ferric chloride as the active component. A 6% (w / w) copper chloride solution was prepared using copper chloride as the active component. Ferric chloride solution and copper chloride solution were mixed in a volume ratio of 1:1 to obtain a metal salt solution. Magnetic beads were then impregnated in situ with the metal salt solution for 8 hours, with a mass ratio of metal salt solution to magnetic beads of 10:100. Subsequently, the wetted magnetic beads were placed in an oxidizing atmosphere (O2, volume concentration 3%) at 300 °C for 30 min, followed by a reaction in a reducing atmosphere (CO, volume concentration 200 ppm) at 350 °C for 30 min to obtain a magnetic adsorbent.
[0044] The magnetic adsorbent prepared in this embodiment is used for the removal of mercury from flue gas, and the apparatus used is as follows: Figure 2As shown, the specific steps are as follows: First, place the mercury tube into one end of the U-shaped tube and silica gel into the other end to absorb moisture from the gas. Use N2 as the mercury carrier gas. Turn on the water bath, temperature controller, heating belt, and other experimental equipment. Control the temperature of the water bath at 70 ℃ and maintain the mercury concentration in the tube at 100 μg / m³. 3 0.05 g of magnetic adsorbent was placed in the reactor bed inside the tubular furnace to adsorb and fix gaseous mercury, completing mercury removal (mercury removal temperature was 120 ℃, and mercury removal time was 1 h). Simulated flue gas flowed through the tubular furnace reactor and then into the inlet pipe of an online mercury analyzer to monitor changes in gaseous mercury concentration in real time. Its outlet pipe was connected to an activated carbon absorber to absorb residual toxic gaseous mercury.
[0045] Example 3 This embodiment prepares a magnetic adsorbent, and the specific steps are as follows: First, magnetic beads are sorted from fly ash, and the obtained magnetic beads are used as carriers. A 4% (w / w) ferric chloride solution was prepared using ferric chloride as the active component. A 4% (w / w) copper chloride solution was prepared using copper chloride as the active component. Ferric chloride solution and copper chloride solution were mixed in a volume ratio of 1:1 to obtain a metal salt solution. Magnetic beads were then impregnated in situ with this metal salt solution for 12 h, with a mass ratio of metal salt solution to magnetic beads of 15:100. Subsequently, the wetted magnetic beads were placed in an oxidizing atmosphere (O2, volume concentration 6%) at 400 °C for 30 min, followed by a reaction in a reducing atmosphere (CO, volume concentration 400 ppm) at 350 °C for 20 min to obtain a magnetic adsorbent.
[0046] The magnetic adsorbent prepared in this embodiment is used for the removal of mercury from flue gas, and the apparatus used is as follows: Figure 2 As shown, the specific steps are as follows: First, place the mercury tube into one end of the U-shaped tube and silica gel into the other end to absorb moisture from the gas. Use N2 as the mercury carrier gas. Turn on the water bath, temperature controller, heating belt, and other experimental equipment. Control the temperature of the water bath at 70 ℃ and maintain the mercury concentration in the tube at 100 μg / m³. 3 0.05 g of magnetic adsorbent was placed in the reactor bed inside the tubular furnace to adsorb and fix gaseous mercury, completing mercury removal (mercury removal temperature was 120 ℃, and mercury removal time was 1 h). Simulated flue gas flowed through the tubular furnace reactor and then into the inlet pipe of an online mercury analyzer to monitor changes in gaseous mercury concentration in real time. Its outlet pipe was connected to an activated carbon absorber to absorb residual toxic gaseous mercury.
[0047] Test Example 1 Figure 3For the magnetic comparison of the magnetic adsorbent prepared in Example 1 and the original magnetic beads, by... Figure 3 It can be seen that the magnetic adsorbent prepared in Example 1 ( Figure 3 The magnetic properties of the modified magnetic beads are further improved, which is beneficial for the efficient separation of magnetic beads in fly ash. Figure 4 The mercury removal effect of the magnetic adsorbents prepared in Examples 1-3 and the original magnetic beads is compared. Figure 4 As shown, the mercury removal efficiency of the magnetic adsorbents in Examples 1-3 all reached over 95%, with the magnetic adsorbent in Example 2 exhibiting an exceptionally high mercury removal efficiency of 99%. From the above examples, it is evident that the magnetic adsorbent provided by this invention can efficiently remove mercury from flue gas through in-situ magnetic enhancement, is economical and safe, and is suitable for use in the field of mercury adsorption, especially for the removal of mercury from flue gas in coal-fired power plants, demonstrating significant social and economic benefits.
[0048] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for producing a magnetic adsorbent, characterized by, The method comprises the following steps: The magnetic beads are immersed in a metal salt solution in situ, and then subjected to oxidation and reduction reactions in a wet state to obtain the magnetic adsorbent; The metal salt solution is obtained by mixing a copper chloride solution and a ferric chloride solution.
2. The production method according to claim 1, characterized by, The mass concentration of the copper chloride solution and the ferric chloride solution is independently 3% to 6%; the volume ratio of the copper chloride solution to the ferric chloride solution is 1:
1.
3. The production method according to claim 1 or 2, characterized by, The mass ratio of the metal salt solution to the magnetic beads is 10 to 20:
100.
4. The production method according to claim 1, characterized by, The temperature of the oxidation reaction is 300 to 500℃, and the holding time is 0.5 to 2 h.
5. The production method according to claim 1 or 4, characterized by, The oxidation reaction is carried out in an oxidation atmosphere; the volume concentration of oxygen in the oxidation atmosphere is 3% to 9%.
6. The method of claim 1, wherein, The temperature of the reduction reaction is 300 to 500℃, and the holding time is 10 to 30 min.
7. The production method according to claim 1 or 6, characterized by, The reduction reaction is carried out in a reduction atmosphere; the volume concentration of CO in the reduction atmosphere is 200 to 500 ppm.
8. The magnetic adsorbent produced by the production method according to any one of claims 1 to 7, characterized by, The magnetic adsorbent comprises magnetic beads, a modifier loaded on the magnetic beads, and chlorine active species adsorbed on the surface of the magnetic beads; the modifier comprises Fe3O4 and CuCl2.
9. The magnetic adsorbent of claim 8, wherein, The particle size of the magnetic adsorbent is 50 to 150 μm.
10. The magnetic adsorbent prepared by the preparation method of any one of claims 1 to 7 or the magnetic adsorbent of any one of claims 8 to 9 is applied to adsorbing mercury.