Modified fly ash, its preparation method and desulfurization application

Abstract

The present invention relates to modified fly ash, its preparation method and application, which include the following steps: adding a modifier to dry fly ash, where the modifier is a water-soluble carbonic compound and a water-soluble hydroxide compound, then adding water and stirring and mixing for 1 - 4 h, drying at a temperature below 100 °C, and grinding evenly to obtain modified fly ash; the water-soluble carbonic compound is one or more of sodium carbonate and potassium carbonate; the water-soluble hydroxide compound is one or more of sodium hydroxide and potassium hydroxide. The adsorbent of the present invention can achieve a 100% removal rate of hydrogen sulfide within 5 minutes.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption materials, and particularly relates to modified fly ash, a preparation method thereof, and desulfurization applications. Background Art

[0002] Fly ash generally refers to the material discharged from the flue gas of a coal-fired power plant after combustion in a boiler and collected by a dust collector. Fly ash is grayish-brown, usually acidic, and belongs to aluminosilicate glassy pozzolanic active materials. Its particles are mostly spherical, with a smooth surface, gray or light gray in color. The average particle size is generally 8 - 20 μm, and the specific surface area can reach 300 - 600 m 2 / kg. The main chemical components of fly ash are SiO2 (mass fraction 45 - 60%), Al2O3 (mass fraction 20 - 30%), Fe2O3 (mass fraction 5 - 10%). In addition, it also contains CaO, MgO, and unburned carbon. The main components of fly ash are solid microspheres and hollow microspheres with diameters in the micron range, as well as a small amount of porous glass bodies, glass body fragments, crystals, and unburned carbon particles, etc. Fly ash is a typical heterogeneous substance, containing unburned carbon, unchanged minerals (such as quartz, etc.), and fragments, etc. The composition, structure, and properties of various particles vary widely, and it is a huge and disordered artificial mineral resource. At present, fly ash concrete has been widely used in civil engineering, water conservancy construction projects, and the production of precast concrete products, etc.

[0003] Fly ash belongs to solid waste and is one of the industrial waste residues with a large discharge volume. If not treated, it will generate dust, causing air pollution and haze. If discharged into water systems, it will cause river siltation, and the toxic chemical substances in it will also harm the human body and organisms, and will also cause great harm to the ecological environment, occupying a large amount of land resources. The pollution of fly ash to water resources, soil, and air will directly affect people's lives. Residents living in a high-dust environment for a long time have a high incidence of nasopharyngitis, upper respiratory tract infections, etc. The radioactive elements in fly ash will also accumulate in the soil and be absorbed by plants, and then enter the human body through the food chain. Therefore, there is an urgent need to convert the toxic waste fly ash into valuable assets.

[0004] In the prior art, for example, Chinese Patent CN111569821A discloses a composite adsorbent for biogas desulfurization and decarbonization, which uses metal oxides such as iron oxide as additives and loads them on solid wastes such as fly ash to form a composite adsorbent, and prepares it into an alkaline slurry for biogas desulfurization and decarbonization. The removal rate of hydrogen sulfide gas does not exceed 90%. However, the removal rate of hydrogen sulfide using the modified fly ash as an adsorbent is still not ideal. Summary of the Invention

[0005] To solve the pollution problems caused by solid waste fly ash and the technical problem that the removal rate of hydrogen sulfide using fly ash as an adsorbent is still not ideal, the present invention provides modified fly ash, its preparation method, and its application in desulfurization. The adsorbent of the present invention can achieve a 100% removal rate of hydrogen sulfide within 5 minutes.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0007] A preparation method of modified fly ash, comprising the following steps: adding a modifier to dry fly ash, where the modifier is a water-soluble carbonate compound and a water-soluble hydroxide compound, then adding water and stirring and mixing for 1 - 4 hours, and then drying at a temperature below 100°C and grinding evenly to obtain modified fly ash.

[0008] Further, the water-soluble carbonate compound is one or more of sodium carbonate and potassium carbonate; the water-soluble hydroxide compound is one or more of sodium hydroxide and potassium hydroxide. Preferably, it is potassium carbonate and sodium hydroxide.

[0009] Further, the mass ratio of the fly ash to the modifier is 1:(0.1 - 0.5), preferably 1:0.2; the mass ratio of the water-soluble carbonate compound to the water-soluble hydroxide compound is 2:(1 - 5), preferably 1:1.

[0010] On the other hand, the present invention provides the modified fly ash obtained by the above preparation method.

[0011] Finally, the present invention provides the application of the modified fly ash prepared by the above preparation method in desulfurization treatment. The desulfurization treatment is the desulfurization of hydrogen sulfide gas. Using the modified fly ash as the desulfurization adsorbent of hydrogen sulfide gas in a fixed-bed reactor, the filling height of the desulfurization adsorbent in the quartz tube is 0.9% of the total length of the quartz tube, and quartz wool is filled at both ends of the quartz tube; the simulated flue gas composition: hydrogen sulfide gas concentration 120 - 140 ppm, 5 - 15% water vapor, under anaerobic conditions, nitrogen with a purity of at least 4N is used as the balance gas, the total gas flow rate is 100 mL / min, and the space velocity is 5000 - 30000 h -1 , and the desulfurization treatment is carried out at 50 - 100°C.

[0012] Further, the simulated flue gas composition: hydrogen sulfide gas concentration 130 ppm, 15% water vapor, under anaerobic conditions, nitrogen with a purity of at least 4N is used as the balance gas; the temperature of the desulfurization treatment is 70 - 80°C.

[0013] Beneficial technical effects:

[0014] By modifying the difficult-to-treat waste fly ash, the present invention uses water-soluble carbon compounds and water-soluble hydroxide compounds to act on fly ash together, endowing the surface of fly ash with a large number of active functional groups. The water-soluble carbon compound increases the active sites, and the water-soluble hydroxide compound increases the basic sites. The two act together to improve the adsorption and removal effect of fly ash on hydrogen sulfide gas. It not only solves the problem of waste disposal of fly ash, but also provides a simple and feasible solution for preparing high-performance desulfurization adsorbents, achieving the purpose of "treating waste with waste" and protecting the environment, which has very important practical significance. The present invention has low price cost, is environmentally friendly and easy to prepare, and is simply easy to obtain for the resource utilization of waste, effectively realizing the treatment of waste with waste. It has great potential market application value in the field of gas pollution treatment and solves the cost problem of enterprises. Brief Description of the Drawings

[0015] Figure 1 It is a curve showing the change of the desulfurization effect of raw material fly ash and the modified fly ash of Example 1, Comparative Example 1, and Comparative Example 2 on hydrogen sulfide over time. Detailed Embodiments

[0016] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0017] Unless otherwise specifically stated, the numerical values set forth in these embodiments do not limit the scope of the present invention. Technologies and methods known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies and methods should be regarded as part of the specification. In all examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0018] The experimental methods without specific conditions in the following embodiments are usually determined according to national standards; if there is no corresponding national standard, they are carried out according to general international standards or the standard requirements proposed by relevant enterprises. Unless otherwise specified, all parts are by weight and all percentages are by weight percentage.

[0019] Example 1

[0020] A preparation method of modified fly ash includes the following steps:

[0021] Put 2 g of fly ash into an oven and dry it at 80 °C for 4 h for later use;

[0022] Mix 2 g of the dried fly ash with 0.2 g of KCO3, 0.2 g of NaOH and water on a magnetic stirrer for 4 h. After mixing evenly, directly put the solid-liquid mixture into an 80 °C oven until it is completely dried, take it out and grind it evenly to obtain modified fly ash.

[0023] Example 2

[0024] A method for preparing modified fly ash, comprising the following steps:

[0025] Put 2 g of fly ash into an oven and dry it at 80 °C for 4 h for later use;

[0026] Mix 2 g of the dried fly ash with 0.2 g of KCO3, 0.1 g of NaOH and water on a magnetic stirrer for 4 h. After mixing evenly, directly put the solid-liquid mixture into an 80 °C oven until it is completely dried, take it out and grind it evenly to obtain modified fly ash.

[0027] Example 3

[0028] A method for preparing modified fly ash, comprising the following steps:

[0029] Put 2 g of fly ash into an oven and dry it at 80 °C for 4 h for later use;

[0030] Mix 2 g of the dried fly ash with 0.2 g of KCO3, 0.3 g of NaOH and water on a magnetic stirrer for 4 h. After mixing evenly, directly put the solid-liquid mixture into an 80 °C oven until it is completely dried, take it out and grind it evenly to obtain modified fly ash.

[0031] Comparative Example 1

[0032] The preparation process of the modified fly ash in this comparative example is the same as that in Example 1, except that 0.4 g of ammonium molybdate is used.

[0033] Comparative Example 2

[0034] The preparation process of the modified fly ash in this comparative example is the same as that in Example 1, except that 0.4 g of potassium carbonate is used.

[0035] Comparative Example 3

[0036] The preparation process of the modified fly ash in this comparative example is the same as that in Example 1, except that 0.4 g of sodium hydroxide is used.

[0037] Comparative Example 4

[0038] The preparation process of the modified fly ash in this comparative example is the same as that in Example 1, except that 0.2 g of sodium hydroxide and 0.2 g of ammonium molybdate are used.

[0039] Example 4

[0040] The modified fly ashes of the above-mentioned examples and comparative examples were respectively applied to the desulfurization of hydrogen sulfide gas, and the specific steps were as follows:

[0041] Using the modified fly ashes of the above-mentioned examples and comparative examples as desulfurization adsorbents for hydrogen sulfide gas on a fixed-bed reactor; adding 50 mg of quartz wool into a quartz tube, adding 0.05 g of catalyst on it, the height of the catalyst in the quartz tube was 0.5 cm, and adding another 10 mg of quartz wool at the upper half to prevent leakage; the simulated flue gas composition: hydrogen sulfide gas concentration 130 ppm, 15% water vapor, using nitrogen with a purity of 99.999% as the balance gas under anaerobic conditions, the total gas flow rate was 100 mL / min, and desulfurization was carried out at 70 °C for 4 min at space velocities of 6000 h -1 、30000 h -1 respectively, and the hydrogen sulfide removal rate was calculated. The specific results are shown in Table 1.

[0042] Table 1 Desulfurization adsorption effects of examples and comparative examples on hydrogen sulfide

[0043]

[0044]

[0045] As can be seen from Table 1, the adsorption removal rate of the untreated raw material fly ash for hydrogen sulfide gas at 4 min was 45.76% at a space velocity of 6000 h -1 while the adsorption removal rate for hydrogen sulfide gas at 4 min was 7% at a space velocity of 30000 h -1 . Generally, when industrially treating hydrogen sulfide gas, the space velocity is set at 5 - 6000 h -1 . Under the more stringent condition of a space velocity of 30000, the raw material fly ash basically did not show a removal effect on hydrogen sulfide gas. While for the modified fly ashes obtained by treating fly ash with ammonium molybdate, potassium carbonate, and sodium hydroxide respectively, under the more stringent condition of a space velocity of 30000, only potassium carbonate showed a good hydrogen sulfide gas removal effect at 4 min. The modified effects of ammonium molybdate and sodium hydroxide on the removal of hydrogen sulfide gas were not much different, but the modified effect of sodium hydroxide was slightly better than that of ammonium molybdate. Therefore, in the present invention, co-modifying fly ash with sodium hydroxide and potassium carbonate has a synergistic effect on the adsorption removal effect of hydrogen sulfide.

[0046] The curves of the desulfurization effects of the above raw material fly ash and the modified fly ashes of Example 1, Comparative Example 1, and Comparative Example 2 on hydrogen sulfide varying with time are as Figure 1 shown. As can be seen from Figure 1 , it can be seen from the figure that when the initial concentration of H2S was 130 mg·L -1When it comes to this, the modified fly ash of the present invention has a good removal efficiency for H2S at 4 minutes. Since the concentration of H2S is continuously rising, the overall removal rate of hydrogen sulfide decreases as the reaction time gets longer; however, compared with the raw material fly ash, it still has an obvious removal effect even after a long reaction time. The removal effect of fly ash modified with ammonium molybdate is significantly inferior to that of fly ash modified with potassium carbonate. The present invention simultaneously uses potassium carbonate and sodium hydroxide to modify fly ash, which has the effect of increasing the basic sites of fly ash, and the modified fly ash of the present invention has a significantly better effect on removing hydrogen sulfide.

[0047] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. Application of modified fly ash in desulfurization treatment, characterized in that, The desulfurization treatment is the desulfurization of hydrogen sulfide gas. Modified fly ash is used as the desulfurization adsorbent for hydrogen sulfide gas in a fixed-bed reactor. The filling height of the desulfurization adsorbent in the quartz tube is 0.9% of the total length of the quartz tube, and quartz wool is filled at both ends of the quartz tube. The simulated flue gas composition is as follows: the concentration of hydrogen sulfide gas is 120 - 140 ppm, 5 - 15% water vapor, and nitrogen with a purity of at least 4N is used as the balance gas under anaerobic conditions. The total gas flow rate is 100 mL / min, and the space velocity is 6000 - 30000 h -1 , and the temperature of the desulfurization treatment is 70 - 80 °C; The preparation method of the modified fly ash comprises the following steps: adding a modifier, which is a water-soluble carbonate compound and a water-soluble hydroxide compound, to dry fly ash, then adding water and stirring and mixing for 1-4 h, drying at a temperature below 100 °C, and grinding evenly to obtain the modified fly ash; The water-soluble carbonate compound is potassium carbonate; the water-soluble hydroxide compound is sodium hydroxide; The mass ratio of the fly ash to the modifier is 1:0.2; the mass ratio of the water-soluble carbonate compound to the water-soluble hydroxide compound is 1:

1.

2. The application according to claim 1, wherein Simulated flue gas composition: hydrogen sulfide gas concentration of 130 ppm, 15% water vapor, and nitrogen with a purity of at least 4N as the balance gas under anaerobic conditions.

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