A mercury removal material and preparation and application thereof

Abstract

The application belongs to the field of gaseous mercury removal, and particularly relates to a mercury removal material, which comprises M2S with a chemical formula of lattice intercalation and O-S double defects x -N2O y The application further provides an ultrasonic aging-mechanical activation preparation process of the material. The material has excellent adsorption effect on gaseous mercury.

Description

Technical Field

[0001] This invention belongs to the field of mercury removal from coal-fired flue gas, and specifically relates to a mercury removal material for flue gas. Background Technology

[0002] Coal is a major primary energy source, and mercury emissions from coal-fired power plants have attracted widespread global attention due to their extreme toxicity, long-distance transport, environmental persistence, and bioaccumulation. With the promulgation of the "Emission Standard of Air Pollutants for Thermal Power Plants" (GB13223-2011) and the signing of the "Minamata Convention on Mercury," achieving near-zero mercury emissions from coal-fired power plants in my country remains a challenging task. The main form of mercury emitted from coal-fired power plants is elemental mercury (Hg). 0 ), oxidized mercury (Hg) 2+ ) and particulate mercury (Hg p Hg 2+ Because of its water solubility, Hg can be removed by wet desulfurization equipment in coal-fired power plants. p Mercury present in fly ash particles can be captured by dust removal devices in coal-fired power plants (electrostatic precipitators, bag filters, etc.). 0 Due to its high volatility, poor water solubility, and chemical stability, Hg is difficult to remove by conventional pollutant control devices in coal-fired power plants. 0 The removal of mercury is the key and challenging aspect of mercury removal technology for coal-fired flue gas.

[0003] Adsorbent jet mercury removal is a relatively mature mercury removal technology, and the development of high-performance adsorbents is key to its success. Based on the mercury removal mechanism, the currently used mercury removal materials are mainly catalysts and adsorbents. The catalyst is only responsible for removing Hg... 0 The oxidation process involves the transfer of mercury pollution from the flue gas to a wet mercury removal unit, which is essentially a transfer of mercury pollution and does not fundamentally reduce mercury emissions. Adsorbents include carbon-based adsorbents, mineral adsorbents, and fly ash. Among these, carbon-based adsorbents currently have the potential for highly efficient mercury removal. Their mercury removal capacity is generally enhanced through halogen modification. However, these adsorbents suffer from drawbacks such as low impregnation solution utilization, secondary pollution from waste liquid, secondary release of mercury after removal, and the inability to regenerate and recycle the adsorbent. Summary of the Invention

[0004] To address the problem of unsatisfactory mercury removal efficiency (mercury-containing components present in the gaseous state) in flue gas, the primary objective of this invention is to provide a novel mercury removal material, aiming to improve the removal efficiency and effectiveness of mercury in flue gas, and to regulate the phase and purity of the removal products, thereby reducing secondary pollution.

[0005] The second objective of this invention is to provide a method for preparing the aforementioned mercury removal material, aiming to obtain a new material with a special storage structure and excellent mercury removal capability from flue gas based on the aforementioned composition and ultrasonic-mechanical dual reinforcement.

[0006] A third objective of this invention is to provide the application of the aforementioned mercury removal material in flue gas mercury.

[0007] Unlike conventional liquid and solid mercury removal, the removal of mercury from flue gas requires addressing issues such as unsatisfactory gaseous adsorption capacity and stability, unsatisfactory phase stability of the removal products, and susceptibility to secondary pollution. To address these problems, this invention provides the following solutions:

[0008] A mercury removal material comprising M2S with the chemical formula of intercalation and OS double defects. x -N2O y Nanomaterials;

[0009] Wherein, M is at least one of Zn, Cu, and Mo; N is at least one of Fe, Mn, and Ce; and the molar ratio of M to N is 1:1.5 to 5.

[0010] This invention provides a novel mercury removal material. Based on the combined control of the aforementioned components and the unique lattice intercalation structure between them, it achieves synergistic effects, synergistically improving the removal capacity and efficiency of mercury from flue gas. Furthermore, it can unexpectedly transform the mercury removal product into a β-HgS phase, improving the product phase purity and thus enhancing the stability of the mercury removal product, reducing secondary pollution problems encountered in the gas-phase adsorption process. Moreover, the mercury removal material of this invention exhibits excellent lattice stability and superior regeneration and repair capabilities.

[0011] In this invention, x and y are compounds of M and N, respectively. When the valence is even, M2S x N2O y They can be recorded as MS respectively x / 2 NO y / 2 .

[0012] In this invention, preferably, M is Cu and N is Mn. The preferred elements in this invention can further synergistically improve the mercury removal effect of the material.

[0013] Preferably, the molar ratio of M to N is 1:2 to 4, more preferably 1:2.5 to 3.5. Studies have found that this preferred ratio further enhances the synergistic effect of the ratio, thereby further improving performance.

[0014] The present invention also provides a method for preparing the aforementioned mercury removal material, wherein M2S x and N2Oy The mercury-removing material is prepared by ultrasonic and aging treatment followed by mechanochemical treatment.

[0015] In this invention, M2S is innovatively used. x and N2O y Combined with ultrasonic aging and mechanical activation, this process can construct a lattice intercalation interface structure, create abundant surface active sites, improve the structural stability of the components, and enhance the adsorption capacity, adsorption stability, and regeneration capacity of flue gas mercury. In addition, it can facilitate the conversion of flue gas mercury into β-HgS with high phase purity, which can effectively reduce the secondary pollution problem that is common in the field of flue gas mercury adsorption.

[0016] In this invention, M2S x It can be prepared using existing methods, such as the M2S described above. x It is prepared by precipitation reaction of water-soluble salt of M and alkali metal sulfide.

[0017] In this invention, the M2S x and N2O y The combination of composition and ultrasound-mechanical interaction is key to the synergistic construction of the aforementioned special structure and the improvement of mercury removal capacity from flue gas. This invention has discovered that through the combined action of composition and ultrasound-mechanical interaction, a unique intercalation structure and suitable active sites for gaseous mercury adsorption can be unexpectedly created. This facilitates the adsorption of mercury from flue gas and promotes the formation of β-HgS removal products, thereby improving the adsorption stability of mercury from flue gas.

[0018] As a preferred option, M2S x and N2O y After being dispersed in the solution, it is subjected to ultrasonic treatment;

[0019] The ultrasonic power can be adjusted as needed. For example, the ultrasonic power is 50-600W, and considering the preparation efficiency, it can be further preferred to be 100-250W.

[0020] The ultrasound processing time can be adjusted as needed. For example, when the power is high, the processing time can be shortened appropriately as needed, and when the power is low, the processing time can be extended according to conventional understanding. For example, the ultrasound processing time is 15 to 120 minutes, further can be 20 to 60 minutes, and more preferably 20 to 40 minutes.

[0021] In this invention, the aging treatment temperature is, for example, 10-50°C. Considering the processing cost, room temperature is preferred, for example, 20-35°C.

[0022] In this invention, the aging treatment time is, for example, 1 to 6 hours, and more specifically, 2 to 4 hours.

[0023] As a preferred method, the mechanochemical treatment is ball milling.

[0024] Preferably, the ball-to-material ratio during the ball milling stage is 5:1 to 10:1, the rotation speed is 100-600 rpm / min, and the revolution speed is 50-300 rpm / min.

[0025] In this invention, the ball milling stage takes 10-60 minutes, and can be further reduced to 20-40 minutes to improve efficiency and effectiveness.

[0026] The present invention provides a preferred method for preparing a mercury removal material, comprising the following steps:

[0027] (1) A certain amount of metallic nitrate [M(NO3)] x MS was prepared by magnetic stirring with Na2S. x .

[0028] (2) Add a certain amount of NO to (1) y .

[0029] (3) The mixture in (2) is subjected to ultrasonic treatment and aging.

[0030] (4) The particulate matter obtained in (3) is rinsed with deionized water and then separated by centrifugation.

[0031] (5) The centrifuged particles are dried to obtain intermediate product particles.

[0032] (6) The intermediate product particles are treated by a mechanochemical method to finally obtain the mercury-free material.

[0033] The present invention also provides an application of the aforementioned mercury removal material, for use as a mercury removal material for flue gas;

[0034] Preferably, the mercury removal material is used to convert the mercury in the flue gas into β-HgS phase products.

[0035] The present invention also provides a method for the cyclic removal of mercury from flue gas, wherein the mercury removal material described in the present invention is used to adsorb mercury from flue gas, and then the adsorbed mercury removal material is subjected to thermal regeneration treatment, and the regenerated mercury removal material is recycled for the removal of mercury from flue gas.

[0036] Preferably, the temperature during the thermal regeneration stage is 250-400℃.

[0037] Preferably, there are no special requirements for the thermal regeneration time; for example, it can be 10-30 minutes.

[0038] Preferably, the thermal regeneration stage is carried out under a protective atmosphere, such as at least one of nitrogen, air, and an inert gas.

[0039] For example, when the mercury removal efficiency of the mercury removal material drops to 70-80%, subsequent regeneration treatment is carried out.

[0040] Beneficial effects:

[0041] 1. This invention provides a novel mercury removal material with a novel phase structure, which has excellent mercury removal efficiency from flue gas and excellent regeneration and repair capabilities. Moreover, it facilitates the conversion of flue gas mercury into β-HgS, which helps improve the phase purity and stability of the removal products and can effectively reduce secondary pollution from flue gas mercury.

[0042] 2. This invention innovatively integrates M2S x and N2O y The ultrasonic-mechanical dual enhancement, thanks to the combination of components and the ultrasonic-mechanical dual effect, can unexpectedly construct a special interlocking structure, which is conducive to improving the mercury removal behavior and mechanism in flue gas and thus improving the mercury removal effect. Attached Figure Description

[0043] Figure 1 The following are SEM images of the materials in Example 1, where (a) SEM CuS, (b) SEM MnO2, and (c) SEM CuS / MnO2.

[0044] Figure 2 The image shows the SEM-EDS image of the mercury removal agent prepared in Example 1. According to SEM and SEM-EDS, the composite particles are nanoscale and the elements have a certain degree of interlocking.

[0045] Figure 3 This is an Hg-TPD diagram. The main mercury removal product is β-HgS. The mercury removal products are stable and singular.

[0046] Figure 4 The graph shows the mercury removal efficiency of the adsorbent in 2 hours for different cases (Examples 1-3).

[0047] Figure 5 The graphs show the mercury removal performance of the materials in Example 4. Note: S2Fe2: molar ratio CuS:Fe2O3 = 2:2, S2Fe3: molar ratio CuS:Fe2O3 = 2:3, S2Fe4: molar ratio CuS:Fe2O3 = 2:4. Removal efficiency: mercury removal rate, Oxidation rate: oxidation rate, Adsorption rate: adsorption rate.

[0048] Figure 6 The image shows the Hg-TPD diagrams of the mercury removal products from the adsorbent in Comparative Group 1 and Experimental Group A of Example 4. Detailed Implementation

[0049] The mercury removal reaction conditions used in this embodiment of the invention are as follows: adsorption temperature: 150℃; total flow rate of reaction gas: 1L / min, wherein the volume content of CO2 is 12%, the volume content of O2 is 6%, and N2 is used as the balance gas; the various gases are mixed in the flue gas preheating and mixing system after being passed through a mass flow meter, and then fed into the fixed-bed adsorption reactor. The initial mercury concentration is stabilized at 50 μg / m³. 3 The amount of adsorbent used each time is 0.1g. After the temperature and mercury concentration of the fixed bed stabilize, the bypass is switched to the main circuit of the adsorption reaction device containing the adsorbent to start the evaluation experiment of mercury removal by the adsorbent.

[0050] The mercury removal performance of the mechanochemically enhanced adsorption mercury removal material was evaluated using the following method, which was determined by the mercury removal performance of Hg. 0 Removal efficiency (Hg) re ) and Hg 0 Adsorption rate (Hg) ad It is defined by ), and its definition expression is as follows:

[0051]

[0052]

[0053] In the formula: The Hg levels in the flue gas before and after the adsorbent are respectively 0 Concentration, μg / m 3 m is the total mass of mercury in the adsorbent (μg); V is the simulated flue gas volumetric flow rate (1×10⁻⁶). -3 m 3 / min, where t is the mercury removal time of the adsorbent, in min. Detailed Implementation

[0055] Example 1:

[0056] (1) Add Na2S (Cu / S molar ratio of 1:1) to 100 mL of 0.5 M [Cu(NO3)2] aqueous solution and stir magnetically to obtain CuS (M source).

[0057] (2) Add MnO2 (N source, Cu / Mn molar ratio is 1:3) to (1).

[0058] (3) The mixed solution in (2) is subjected to ultrasonic treatment and aging, wherein the ultrasonic power is 100W, the time is 30min, the aging temperature after ultrasonic treatment is 20℃, and the time is 3h.

[0059] (4) The particles from (3) are separated by filtration, and then washed and dried to obtain intermediate product particles.

[0060] (5) The intermediate product particles were subjected to solid-phase ball milling. The ball milling conditions were: ball-to-material ratio = 6-8:1, rotation: 300-350 rpm / min, revolution: 200-250 rpm / min, and time: 30 min. The mercury-free material was then separated.

[0061] SEM and SEM-EDS of the materials are shown in the following figures. Figure 1 , 2 It displays a special interlocking structure.

[0062] The obtained mercury-removing material was subjected to mercury adsorption studies in flue gas under the above conditions. The Hg-TPD diagram of the adsorbed material is shown below. Figure 3 This indicates the formation of a specific β-HgS phase; test results are shown in [reference needed]. Figure 4 Its adsorption efficiency was close to 100% both at the beginning and after 120 minutes.

[0063] Example 2:

[0064] Compared with Example 1, the only difference is that the amount of adsorbent used in the adsorption test is doubled. All other operations and parameters are the same as in Example 1. The adsorption rate graph is shown below. Figure 4 It exhibits excellent adsorption rate (up to 100%) and stability.

[0065] Example 3:

[0066] Compared with Example 1, the only difference is that the Cu / Mn molar ratio in (2) is changed, and the experimental groups are as follows:

[0067] A: The Cu / Mn molar ratio is 1:1;

[0068] B: The Cu / Mn molar ratio is 1:2;

[0069] Other operations and parameters are the same as in Example 1.

[0070] The mercury removal efficiency of the adsorbent within 2 hours is shown in the graph. Figure 4 Group A initially had an adsorption rate of 80%, which decreased to about 45% after 120 minutes of adsorption. Group B initially had an adsorption capacity of 99.7%, and after 120 minutes of cycling, it still achieved an adsorption retention rate of 96%, demonstrating good stability.

[0071] Example 4

[0072] Compared to Example 1, the only difference is the change of M and N; specifically, the M source is CuS, and the N source is an iron source, specifically Fe2O3. The experimental groups are as follows:

[0073] Comparison Group 1: Only N source was added, without M source;

[0074] Comparative Group 2: The Cu / Fe molar ratio in the M and N sources is 2:1;

[0075] Comparative group 3: The Cu / Fe molar ratio in the M source and N source is 2:2;

[0076] Experimental Group A: The Cu / Fe molar ratio in the M source and N source is 2:3;

[0077] The experimental results are shown in Figure 5 It can be seen that the initial adsorption rate of experimental group A was 99%; the adsorption rate after 120 min was 93%, achieving excellent treatment results. The Hg-TPD diagram of the product obtained from experimental group A is shown below. Figure 6 The obtained β-HgS is shown.

[0078] Example 5

[0079] Compared to Example 1, the only difference is the change of M and N, where the source of M is CuS and the source of N is CeO2; all other operations and parameters are the same as in Example 1.

[0080] The initial adsorption rate was 98%; the adsorption rate after 120 min was 90%.

[0081] A comparison of Examples 1, 4, and 5 shows that using the metals specified in this invention, combined with the control of the process, can achieve synergy and obtain good adsorption performance and adsorption stability. However, when M is Cu and N is Mn, a better synergistic effect can be obtained.

[0082] Example 6

[0083] Compared to Example 1, the only differences are that the ultrasonic power is 200W and the time is 20min; the aging temperature is 30℃ and the time is 2h; and the ball milling stage takes 40min.

[0084] The adsorption was measured in the manner described in Example 1, and the results were similar to those in Example 1, with adsorption rates exceeding 99.5% at both the initial stage and 120 min.

[0085] Comparative Example 1

[0086] Compared to Example 1, the only difference is that M and N are changed, and the experimental groups are:

[0087] In A: (2), MnO2 is missing, and CuS is used for subsequent ultrasonic-ball milling. Other operations and parameters are the same as in Example 1.

[0088] B: Step 1 is missing, that is, CuS is not added, and MnO2 is used for subsequent ultrasonic-ball milling treatment. Other operations and parameters are the same as in Example 1.

[0089] C: In step (1), only sodium sulfide is added instead of copper nitrate. In step 4, the sodium chloride-manganese oxide composite solid is obtained by evaporation. Other operations and parameters are the same as in Example 1.

[0090] D: Use CuS and MnS2 (sulfides of MN, with the same Cu / Mn molar ratio as in Example 1);

[0091] The method described in Example 1 was used for determination, and the results are as follows:

[0092] A: The initial mercury removal efficiency can reach 100%, but the adsorption rate is only 52.6% after 120 minutes;

[0093] B: The initial mercury removal rate can reach 81.5%, and the adsorption rate after 120 min is 60.2%;

[0094] C: The initial mercury removal efficiency can reach 73.6%, but the adsorption rate is only 49.2% after 120 min;

[0095] D: The initial mercury removal efficiency can reach 100%, but the adsorption rate is only 79.1% after 120 min;

[0096] Comparative Example 2

[0097] Compared to Example 3, the only difference is that ultrasonic treatment was not performed; instead, a single ball milling process was used. Additionally, the ultrasonic time was compensated for by ball milling. All other procedures and parameters are the same as in Example 1.

[0098] The results showed that the mercury removal efficiency was 94% and the adsorption rate was 92.6%.

[0099] Comparative Example 3

[0100] Compared to Example 3, the only difference is that ball milling was not performed; instead, a single ultrasonic treatment was performed. Furthermore, the ball milling time was compensated for by ultrasonic treatment. All other procedures and parameters are the same as in Example 1.

[0101] The results showed that the mercury removal efficiency was 92.1% and the adsorption rate was 89.2%.

Claims

1. A mercury removal material, characterized in that, M2S containing chemical formulas of lattice interlocking and OS double defects x -N2O y Nanomaterials; Wherein, M is Cu; N is Mn; the molar ratio of M to N is 1:2.5~3.5; The method for preparing the mercury removal material is as follows: M2S x and N2O y The mercury-removing material is prepared by ultrasonic and aging treatment followed by mechanochemical treatment. The mechanochemical treatment method is ball milling.

2. A method for preparing the mercury removal material according to claim 1, characterized in that, M2S x and N2O y The mercury-removing material is prepared by ultrasonic and aging treatment followed by mechanochemical treatment. The mechanochemical treatment method is ball milling.

3. The method for preparing the mercury removal material as described in claim 2, characterized in that, The M2S x It is prepared by precipitation reaction of water-soluble salt of M and alkali metal sulfide.

4. The method for preparing the mercury removal material as described in claim 2 or 3, characterized in that, M2S x and N2O y After being dispersed in a solution, it is subjected to ultrasonic treatment.

5. The method for preparing the mercury removal material as described in claim 4, characterized in that, The power of ultrasound is 50~600W.

6. The method for preparing the mercury removal material as described in claim 5, characterized in that, The power of ultrasound is 100~250W.

7. The method for preparing the mercury removal material as described in claim 4, characterized in that, The ultrasound treatment time is 15~120 minutes.

8. The method for preparing the mercury removal material as described in claim 4, characterized in that, The ultrasound treatment time is 20-60 minutes.

9. The method for preparing the mercury removal material as described in claim 4, characterized in that, The ultrasound treatment time is 20-40 minutes.

10. The method for preparing the mercury removal material as described in claim 2, characterized in that, The aging process is carried out at temperatures ranging from 10 to 50°C. The aging process takes 1 to 6 hours.

11. The method for preparing the mercury removal material as described in claim 2, characterized in that, The ball-to-material ratio during the ball milling stage is 5:1 to 10:1, with a rotation speed of 100 to 600 rpm and a revolution speed of 50 to 300 rpm.

12. The application of a mercury removal material according to claim 1 or a mercury removal material prepared by the preparation method according to any one of claims 2 to 11, characterized in that, Mercury removal materials for flue gas.

13. The application as described in claim 12, characterized in that, The aforementioned mercury removal material is used to convert mercury in flue gas into β-HgS phase products.

14. A method for the cyclic removal of mercury from flue gas, characterized in that, The application method described in claim 12 or 13 is used to adsorb mercury from flue gas, and then the adsorbed mercury removal material is subjected to thermal regeneration treatment. The regenerated mercury removal material is then recycled for the removal of mercury from flue gas.

15. The method for cyclic removal of mercury from flue gas as described in claim 14, characterized in that, The temperature during the thermal regeneration stage is 250~400℃.

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