Preparation method of adsorbent, adsorbent and high-temperature flue gas deacidification method

Abstract

The invention discloses a preparation method of an adsorbent, the adsorbent and a high-temperature flue gas deacidification method.The preparation method of the adsorbent is based on waste incineration slag, the waste incineration slag is crushed, screened and dried, and pretreated slag is obtained; adding a calcium source into the pretreated slag, and uniformly mixing to obtain a calcium reinforced slag mixture; adding a hydrogen peroxide solution into the calcium-reinforced slag mixture, and enabling metal ions to react with hydrogen peroxide by utilizing an alkaline environment of the waste incineration slag, so as to obtain an in-situ generated metal peroxide solution; and preliminarily drying and calcining the in-situ generated metal peroxide solution to decompose the in-situ generated metal peroxide so as to realize internal pore forming, thereby obtaining the adsorbent. And the slag is converted into the adsorbent, so that solid waste treatment and flue gas purification are realized, the cost of raw materials is reduced, and the land occupation and pollution risk of slag landfill are reduced.

Description

Technical Field

[0001] This application belongs to the technical field of environmental engineering and adsorption materials, specifically relating to a method for preparing an adsorbent, the adsorbent, and a method for deacidifying high-temperature flue gas. Background Technology

[0002] With the acceleration of urbanization and the continuous increase in the amount of municipal solid waste generated, waste-to-energy incineration technology has become one of the main methods of municipal solid waste treatment due to its advantages in volume reduction, harmlessness, and resource recovery. However, the waste incineration process produces a large amount of acidic gases, such as sulfur dioxide (SO2) and hydrogen chloride (HCl), as well as incinerator ash. The efficient treatment and resource utilization of these byproducts is a key challenge currently facing the waste incineration industry.

[0003] Currently, flue gas desulfurization in waste incineration mainly uses calcium-based desulfurizing agents, such as slaked lime (Ca(OH)2) and sodium bicarbonate (NaHCO3), through dry or semi-dry processes for neutralization. Although calcium-based desulfurizing agents are widely available and inexpensive, their small specific surface area and low porosity result in limited desulfurization efficiency. Large quantities are needed to meet increasingly stringent emission standards (such as SO2 emission concentrations below 30 mg / m³), which not only increases operating costs but also generates more fly ash. Furthermore, traditional desulfurization processes are mostly carried out at low temperatures (<200°C), leading to high energy consumption, easy formation of dioxins, and waste of flue gas heat.

[0004] In recent years, researchers have attempted to improve the specific surface area and reactivity of deacidifying agents by adding modifiers (such as KOH and lanthanum oxide) or utilizing industrial waste (such as calcium carbide slag). Some patents have also explored incorporating rare earth slag into the composition of deacidifying agents. While this has improved dioxin removal rates to some extent, the poor high-temperature stability of these agents limits their application to the basic framework of low- and medium-temperature deacidification, and the addition of rare mineral components increases costs. However, these improvements still fail to fully utilize the resources inherent in the incineration process itself, nor do they effectively address the problems associated with high-temperature deacidification. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, this application provides a method for preparing an adsorbent, an adsorbent, and a method for high-temperature flue gas deacidification. Using incinerator slag as raw material, the transition metal oxides therein are combined with calcium oxide (CaO) through optimized processing to form a highly efficient adsorbent with dual catalytic and absorption functions. This adsorbent can be used for the adsorption treatment of acidic gaseous pollutants under high-temperature conditions.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] A method for preparing an adsorbent based on waste incinerator slag, comprising:

[0008] The waste incineration slag is crushed, screened, and dried to obtain pretreated slag;

[0009] A calcium source is added to the pretreated slag and mixed evenly to obtain a calcium-strengthened slag mixture.

[0010] Hydrogen peroxide solution is added to the calcium-fortified slag mixture to utilize the alkaline environment of the waste incineration slag to react metal ions with hydrogen peroxide, thereby obtaining an in-situ generated metal peroxide solution; and

[0011] The in-situ generated metal peroxide solution is initially dried and calcined to decompose the in-situ generated metal peroxide and achieve internal pore formation, thereby obtaining an acidic gas adsorbent.

[0012] As a preferred embodiment, the particle size of the screened waste incineration slag is 100–150 μm; the moisture content of the pretreated slag obtained after drying is less than 3%.

[0013] As a preferred embodiment, the pretreated slag contains not less than 5% transition metal oxides.

[0014] As a preferred embodiment, the calcium source is at least one of calcium oxide or calcium hydroxide.

[0015] As a preferred embodiment, the amount of calcium source added is 10%-30% of the pretreated slag.

[0016] As a preferred embodiment, the mass concentration of the hydrogen peroxide solution is 10%–15%;

[0017] During the process of adding hydrogen peroxide solution to the calcium-strengthened slag mixture, the pH value is controlled at 10-12 and the temperature at 15-30℃.

[0018] As a preferred embodiment, the initial drying temperature is 120°C, and after initial drying, the material is transferred to a muffle furnace for calcination.

[0019] As a preferred embodiment, the calcination is performed by raising the temperature from room temperature to 450–550°C at a heating rate of 3–8°C / min, holding the temperature for 1–3 hours, and then cooling the temperature to room temperature.

[0020] In addition, this application also provides an adsorbent prepared by the above-described method for preparing an adsorbent based on waste incinerator slag, wherein the acidic gas adsorbent has a specific surface area of ​​25–40 m² / g and a porosity of ≥40%.

[0021] In addition, this application also provides a method for high-temperature flue gas deacidification using the adsorbent described above, wherein the temperature of the high-temperature flue gas is 300-800°C and the high-temperature flue gas contains sulfur dioxide and hydrogen chloride.

[0022] Compared with the prior art, this application has the following advantages:

[0023] Achieving high-temperature, high-efficiency, and synergistic deacidification: The adsorbent of this application, within a high-temperature range of 300–800°C, can efficiently convert SO2 in flue gas into easily treatable SO3 through catalysis, and simultaneously neutralize it using composite calcium-based components (such as CaO). This process achieves synergy between catalytic oxidation and chemical absorption, and the reaction temperature range includes the boiler's second and third flue ducts, superheater, and economizer areas. The removal efficiencies for SO2 and HCl can reach over 90% and 85%, respectively, breaking through the limitation of high-temperature deactivation of traditional calcium-based deacidifying agents.

[0024] Significantly improving resource recycling and economic benefits; the core technology lies in "treating waste with waste," transforming the slag from waste incineration into a high-value-added acidic gas adsorbent, simultaneously solving the two major problems of solid waste disposal and flue gas purification. This significantly reduces raw material costs (estimated to be reduced by about 30%), and reduces the land occupation and environmental risks associated with slag landfill, thus achieving resource recycling.

[0025] The material structure is optimized and environmental risks are reduced. A unique in-situ peroxide generation and controlled calcination process creates abundant micropores within the material, increasing its specific surface area to 25–40 m² / g and porosity to ≥40%, significantly improving the contact efficiency between gas and active sites. High-temperature deacidification inhibits the low-temperature resynthesis of dioxins at the source. Simultaneously, the pH of the leachate from the fly ash remains stable in the weakly alkaline range of 9.0–10.5, effectively stabilizing heavy metals (such as Pb and Cd), reducing their leaching concentration and subsequent fly ash stabilization and disposal costs.

[0026] It exhibits good process compatibility and is easy to promote; the obtained adsorbent is in powder form, facilitating material transport, thus requiring no large-scale modification of existing flue gas purification systems for application. It demonstrates excellent process compatibility and economic feasibility, making it suitable for industrial-scale promotion. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of the application and, together with their description, serve to explain the application, but do not constitute an undue limitation of the application. In the drawings:

[0028] Figure 1 This is a flowchart of the method in this application;

[0029] Figure 2This is a comparison of the adsorption performance of Examples 1-3 with that of ordinary calcium-based adsorbents;

[0030] Figure 3 A microscopic image of waste incineration ash;

[0031] Figure 4 This is a microscopic image of the adsorbent of this application. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0033] In the description of this application, it should be understood that the relationship between the method steps can be sequential or non-sequential, as long as it does not affect the overall technical effect, and therefore should not be construed as a limitation of this application. The following description of this application is merely a description of individual embodiments of the technical solution of this application; other embodiments are not shown in the following description, but this does not mean that this application excludes these other embodiments, nor is the technical solution of this application limited to the specific implementations described below, and the scope of protection of this application is not limited to the specific implementations described below. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0034] It should be noted that if the terms "first," "second," etc., appear in the specification, claims, and accompanying drawings of this application, such descriptions are only used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0035] Waste incineration ash is a solid residue produced during the incineration process, accounting for approximately 20%-30% of the original waste mass. Its main components are vitreous matter, metal oxides, and inorganic substances, rich in transition metal oxides such as iron, copper, and nickel. Currently, the resource utilization of ash mainly focuses on metal recycling and building material preparation (such as road paving and brick making), but this approach has a low level of utilization, low added value, and carries the risk of heavy metal leaching. This application innovatively utilizes the catalytic potential of the transition metal oxides (such as Fe2O3 and CuO) abundant in the ash. These transition metals can catalyze the oxidation of SO2 to SO3 at high temperatures, which then reacts with alkaline substances to form stable sulfates.

[0036] In some embodiments, such as Figure 1 The present application provides a method for preparing an adsorbent based on waste incineration slag, comprising:

[0037] S1: The waste incineration slag is crushed, screened and dried to obtain pretreated slag;

[0038] Specifically, the particle size of the screened waste incineration slag is 100–150 μm; the moisture content of the pretreated slag obtained after drying is less than 3%. The pretreated slag contains not less than 5% transition metal oxides.

[0039] S2: Add a calcium source to the pretreated slag and mix evenly to obtain a calcium-strengthened slag mixture;

[0040] Specifically, the calcium source is at least one of calcium oxide or calcium hydroxide. Preferably, the amount of calcium source added is 10%-30% of the pretreated slag. Dry ball milling can be used to ensure uniform dispersion of the calcium source and pretreated slag particles, forming a composite matrix.

[0041] S3: Add hydrogen peroxide solution to the calcium-strengthened slag mixture, and use the alkaline environment of the waste incineration slag to react metal ions with hydrogen peroxide to obtain an in-situ generated metal peroxide solution.

[0042] Specifically, the mass concentration of the hydrogen peroxide solution is 10%–15%; the pH value is controlled at 10–12 and the temperature at 15–30°C during the process of adding the hydrogen peroxide solution to the calcium-strengthened slag mixture.

[0043] S4: The in-situ generated metal peroxide solution is preliminarily dried and calcined to decompose the in-situ generated metal peroxide to achieve internal pore formation, thereby obtaining an acidic gas adsorbent.

[0044] Specifically, the initial drying temperature is 120℃, and after initial drying, the material is transferred to a muffle furnace for calcination. The calcination involves raising the temperature from room temperature to 450–550℃ at a rate of 3-8℃ / min and holding it at that temperature for 1-3 hours, followed by cooling to room temperature. During this process, metal peroxides (such as calcium peroxide and iron peroxide) decompose upon heating, releasing oxygen and forming micron-nano-scale porous channels within the material. The calcined adsorbent is a porous composite material prepared by calcining waste incinerator slag with calcium supplementation and reaction with hydrogen peroxide. It contains alkali metal / alkaline earth metal oxides as acid-base adsorption sites, transition metal oxides as catalytic active sites, and silica as the material framework. Its specific surface area can be increased to 25–40 m² / g, and its porosity ≥40%, significantly enhancing gas diffusion efficiency. The final product is a grayish-brown powder, with effective components including CaO and Fe₂O₃, exhibiting high-temperature deacidification activity.

[0045] As examples, the following are Examples 1-3 and performance tests of common calcium-based adsorbents.

[0046] Example 1

[0047] Pretreatment of waste incinerator slag: Slag discharged from a waste incineration plant was selected, impurities were removed, and the slag was ground for 30 minutes using a planetary ball mill. The slag was then passed through a 100-mesh standard sieve to collect fine powder. 12g of fine powder was weighed and placed in a corundum ceramic boat, then placed in a muffle furnace and calcined at 500℃ for 2 hours in an air atmosphere. The slag was then allowed to cool naturally to room temperature. The calcined slag powder was transferred to a 500mL beaker and magnetically stirred for 30 minutes (200r / min). The solid was filtered through qualitative filter paper and collected. The solid was repeatedly washed with deionized water, and the pH of the filtrate was measured after each wash until pH=7. The solid was placed in a vacuum drying oven and dried at 80℃ for 12 hours to obtain pretreated slag, which was then sealed in a desiccator for later use.

[0048] Calcium oxide loading: Weigh 5g of calcium oxide, dissolve it in 100mL of deionized water, and stir until completely dissolved to obtain a 5% CaO solution; weigh 12g of pretreated slag, add it to the CaO slurry, and stir magnetically at 300r / min for 4h at room temperature, then let it stand for 12h; filter with a Buchner funnel, collect the solid, and quickly wash the filter with deionized water; transfer the solid to an electric thermostatic oven, dry at 80℃ for 6h, and then heat to 105℃ for 1h to obtain CaO-loaded slag, which is then sealed for later use.

[0049] In-situ generation of peroxides: CaO-supported slag was placed in a 150 mL beaker, 50 mL of deionized water was added, and the mixture was magnetically stirred for 5 min (200 r / min). The pH of the system was adjusted to 10 with 0.1 mol / L sodium hydroxide solution, and then 35 mL of 30% H2O2 solution was slowly added dropwise using a separatory funnel (dropping rate 1 mL / min). After the addition was complete, stirring was continued for 2 h. The solid was collected by vacuum filtration and washed three times with 10 mL of anhydrous ethanol (analytical grade). After each washing, the solid was filtered until no liquid dripped out. The solid was placed in a vacuum drying oven and dried at 60 °C for 6 h to obtain the peroxide intermediate product, which was then sealed in a desiccator.

[0050] Preliminary drying and calcination: The peroxide intermediate was transferred to a corundum ceramic boat, placed in a tube furnace, and N2 (flow rate 50 mL / min) was introduced. The temperature was increased to 500℃ at a rate of 5℃ / min. The tube furnace was then turned off, and the temperature was lowered to room temperature. The sample was then removed to obtain an in-situ peroxide adsorbent based on waste incinerator slag, which was named A-1.

[0051] Example 2

[0052] The difference from Example 1 is that in step 3, when the peroxide is generated in situ, the pH is adjusted to 11 with a saturated calcium hydroxide solution. All other steps and parameters are the same as in Example 1, and the material is named A-2.

[0053] Example 3

[0054] The difference from Example 1 is that in step 3, when the peroxide is generated in situ, the pH is adjusted to 12 with 0.1 mol / L sodium hydroxide solution. All other steps and parameters are the same as in Example 1, and the material is named A-3.

[0055] Performance testing

[0056] The high-temperature adsorption performance of the adsorbents prepared in Examples 1-3 was tested (with HCl and SO2 as target pollutants, and the test temperature was 500℃). The results are as follows:

[0057] 1) Example 1 Adsorbent: SO2 adsorption capacity is 68.2 mg / g, adsorption efficiency is 77.5%; hydrogen chloride adsorption capacity is 78.3 mg / g, hydrogen chloride adsorption efficiency is 85.2%.

[0058] 2) Adsorbent in Example 2: SO2 adsorption capacity is 76.5 mg / g, adsorption efficiency is 83.8%; hydrogen chloride adsorption capacity is 84.7 mg / g, hydrogen chloride adsorption efficiency is 89.6%.

[0059] 3) Adsorbent in Example 3: SO2 adsorption capacity is 72.7 mg / g, adsorption efficiency is 80.4%; hydrogen chloride adsorption capacity is 81.6 mg / g, hydrogen chloride adsorption efficiency is 87.3%.

[0060] Common calcium-based adsorbent (comparative sample): SO2 adsorption capacity 49.3 mg / g, adsorption efficiency 60.2%. Hydrogen chloride adsorption capacity 61.6 mg / g, hydrogen chloride adsorption efficiency 73.5%.

[0061] Test results show that, Figure 2 As shown, the adsorbent prepared in this application has significantly better adsorption performance than ordinary calcium-based adsorbents at high temperatures, and its adsorption performance is optimal when the pH is controlled at around 10-12 when peroxides are generated in situ.

[0062] In one embodiment, this application also provides an adsorbent prepared by the method described above for preparing an adsorbent based on waste incinerator slag, wherein the acidic gas adsorbent has a specific surface area of ​​25–40 m² / g and a porosity ≥40%. Figure 3-4 As shown, Figure 3 The SEM test results of the original slag are presented as needle-like shapes. Figure 4 The SEM test results after calcination are presented in a composite porous form.

[0063] In one embodiment, this application also provides a high-temperature flue gas deacidification method using the adsorbent described above, wherein the temperature of the high-temperature flue gas is 300-800°C, and the high-temperature flue gas contains sulfur dioxide and hydrogen chloride. The adsorbent utilizes the catalytic activity of transition metal oxides at high temperatures (300-500°C) to catalytically convert SO2 into easily treatable SO3, and achieves efficient neutralization through composite CaO, avoiding the energy consumption and dioxin generation risks of traditional low-temperature deacidification. The adsorbent of this application improves the removal efficiency of various acidic gases (such as SO2 and HCl) through the synergistic effect of catalytic oxidation and chemical absorption, and is particularly suitable for high-concentration flue gas conditions.

[0064] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims. The selected and described embodiments are intended to best elucidate the principles of this application and its practical application, thereby enabling other those skilled in the art to best utilize this application with various modifications suitable for the contemplated specific purpose, as well as the various described embodiments.

Claims

1. A method for preparing an adsorbent based on waste incinerator slag, characterized in that, include: The waste incineration slag is crushed, screened, and dried to obtain pretreated slag; A calcium source is added to the pretreated slag and mixed evenly to obtain a calcium-strengthened slag mixture. Hydrogen peroxide solution is added to the calcium-strengthened slag mixture to utilize the alkaline environment of the waste incineration slag to allow metal ions to react with hydrogen peroxide, thereby obtaining an in-situ generated metal peroxide solution. as well as The in-situ generated metal peroxide solution is initially dried and calcined to decompose the in-situ generated metal peroxide and achieve internal pore formation, thereby obtaining an acidic gas adsorbent.

2. The method for preparing an adsorbent based on waste incinerator slag according to claim 1, characterized in that: The particle size of the screened waste incineration slag is 100–150 μm; the moisture content of the pretreated slag obtained after drying is less than 3%.

3. The method for preparing an adsorbent based on waste incinerator slag according to claim 1 or 2, characterized in that: The pretreated slag contains no less than 5% transition metal oxides.

4. The method for preparing an adsorbent based on waste incinerator slag according to claim 1, characterized in that: The calcium source is at least one of calcium oxide or calcium hydroxide.

5. The method for preparing an adsorbent based on waste incinerator slag according to claim 1, characterized in that: The amount of calcium source added is 10%-30% of the pretreated slag.

6. The method for preparing an adsorbent based on waste incinerator slag according to claim 1, characterized in that: The mass concentration of the hydrogen peroxide solution is 10%–15%; During the process of adding hydrogen peroxide solution to the calcium-strengthened slag mixture, the pH value is controlled at 10-12 and the temperature at 15-30℃.

7. The method for preparing an adsorbent based on waste incinerator slag according to claim 1, characterized in that: The initial drying temperature is 120°C, and after initial drying, the material is transferred to a muffle furnace for calcination.

8. The method for preparing an adsorbent based on waste incinerator slag according to claim 7, characterized in that: The calcination process involves raising the temperature from room temperature to 450–550°C at a rate of 3–8°C / min, holding the temperature for 1–3 hours, and then cooling the temperature back to room temperature.

9. An adsorbent prepared by the method for preparing an adsorbent based on waste incinerator slag as described in any one of claims 1-8, characterized in that: The acidic gas adsorbent has a specific surface area of ​​25–40 m² / g and a porosity of ≥40%.

10. A method for high-temperature flue gas deacidification using the adsorbent as described in claim 9, characterized in that: The temperature of the high-temperature flue gas is 300-800℃, and the high-temperature flue gas contains sulfur dioxide and hydrogen chloride.

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