Desulfurization and denitrification agent as well as preparation method and application thereof

Abstract

The invention discloses a desulfurization and denitrification agent as well as a preparation method and application thereof. The desulfurization and denitrification agent has a core-shell structure, an inner core is calcium carbonate, an outer shell is calcium oxide, and the content of calcium oxide is gradually increased from the inner core to the outer shell. The preparation method comprises the following steps: crushing, grinding and sieving limestone to obtain limestone powder; and calcining the limestone powder at the temperature of 800 to 950 DEG C for 10 to 240 minutes to obtain the desulfurization and denitrification agent. The desulfurization and denitrification agent provided by the invention has a gradient-distributed pore structure, firstly, the gradient structure increases the surface area and porosity of the material, so that more active sites are provided for adsorption and reaction of pollutants, and efficient capture and conversion of high-concentration pollutants are realized. According to the method, only the raw material limestone needs to be ground, screened and calcined, the technological process is simple, meanwhile, the calcination temperature is low, the energy consumption is reduced, meanwhile, the utilization rate of the limestone is increased, and the method is a sustainable production process which is high in additional value and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a desulfurization and denitrification agent and a preparation method and application thereof. Background Art

[0003] So far, there are hundreds of flue gas desulfurization and denitrification technologies. Among them, wet desulfurization and denitrification has the advantages of small equipment size, simple operation, and high efficiency, and has been widely used in many fields and industries. However, wet desulfurization and denitrification have problems such as large water and electricity consumption, serious equipment corrosion, frequent maintenance, high investment and operating costs, and are gradually being replaced by emerging dry treatment technologies. Calcium-based dry desulfurization and denitrification technology has simple process and operation and maintenance, low investment and operating costs, but slow desulfurization rate and low efficiency, and cannot stably meet existing emission standards. It is only suitable for tail gas treatment with low concentrations of sulfide and nitrogen oxide emissions.

[0004] In addition, existing desulfurization and denitrification technologies usually use lengthy and cumbersome treatment systems to improve treatment efficiency, resulting in large amounts of water and electricity consumption and extremely high operating costs. Currently, commonly used desulfurization and denitrification agents generally use catalysts, molecular sieves, organic-inorganic hybrids and other technical means, which have significant defects such as small synthesis volume, high production cost, and short service life. Therefore, developing low-energy, low-cost, and efficient desulfurization and denitrification agents, reducing desulfurization and denitrification costs, and simplifying processes are the core of achieving efficient treatment of industrial tail gas, and are also the key difficulties in industrial tail gas treatment. Summary of the invention

[0005] In view of the above deficiencies in the prior art, the object of the present invention is to provide a desulfurization and denitrification agent and a preparation method and application thereof, so as to solve the problems of high production cost, slow desulfurization and denitrification rate, low efficiency and the like of the existing desulfurization and denitrification agents.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions: On the one hand, the present invention provides a desulfurization and denitrification agent having a core-shell structure, wherein the core is calcium carbonate and the shell is calcium oxide, and the content of calcium oxide gradually increases from the core to the shell.

[0007] Preferably, the mass percentage of calcium oxide in the desulfurization and denitrification agent is 8% to 40%.

[0008] Preferably, the mass percentage of calcium oxide in the desulfurization and denitrification agent is 10.5%.

[0009] Preferably, the shell has microporous, mesoporous and macroporous structures.

[0010] In another aspect, the present invention provides a method for preparing a desulfurization and denitrification agent, comprising the following steps: S1. crushing, grinding and sieving limestone to obtain limestone powder; S2. calcining limestone powder at 800-950° C. for 10-240 min to obtain the desulfurization and denitrification agent.

[0011] Preferably, the particle size of the limestone powder is 300-2500 μm.

[0012] Preferably, the particle size of the limestone powder is 600-2360 μm.

[0013] Preferably, the calcination temperature is 900° C. and the calcination time is 30 min.

[0014] Preferably, the limestone is high-grade limestone or waste limestone.

[0015] The present invention also provides a desulfurization and denitrification agent as described above or a desulfurization and denitrification agent prepared by the above method for removing sulfide and / or NO in flue gas. X Application in.

[0016] The beneficial effects of the present invention are: (1) Design of gradient pore structure: The desulfurization and denitrification agent provided by the present invention has a gradient pore structure. The unique gradient pore structure enables it to exhibit excellent performance in treating high-concentration sulfides and nitrogen oxides. First, this gradient structure increases the surface area and porosity of the material, thereby providing more active sites for the adsorption and reaction of pollutants. At the same time, the material optimizes the adsorption capacity and reaction rate in different pore sizes, thereby achieving efficient capture and conversion of high-concentration pollutants.

[0017] (2) The preparation method of the desulfurization and denitrification agent of the present invention only requires grinding, screening and calcining the raw material limestone. The process flow is simple and can be extended to low-grade limestone or waste limestone powder for reaction. At the same time, the calcination temperature is low, which reduces energy consumption and improves the utilization rate of limestone. It is a sustainable production process with high added value and environmental friendliness.

[0018] (3) The present invention prepares an adsorbent material with a gradient pore size distribution by precisely controlling the synthesis conditions, which effectively improves the treatment capacity for high-concentration sulfides and nitrogen oxides.

[0019] (4) High-efficiency adsorption and rapid conversion: Through advanced pore structure design and material composition optimization, the present invention combines strong adsorption capacity and efficient chemical conversion function to achieve rapid removal of high-concentration pollutants.

[0020] (5) Low-temperature and low-energy preparation: The present invention not only has a low calcination temperature, but also an extremely short calcination time, which can effectively improve production efficiency, greatly reduce energy consumption and CO2 emissions, and the production cost of the material is low, making it more economical and sustainable in industrial-scale applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0022] Figure 1 This is a SEM image of the desulfurization and denitrification agent prepared in Example 1 of the present application; Figure 2 XRD diagram of the desulfurization and denitrification agent prepared in Examples 1 and 2; Figure 3 This is a comparison chart of the desulfurization effects of Example 1 and Comparative Example 1; Figure 4 It is a comparison chart of the desulfurization effects of Example 2 and Comparative Example 2; Figure 5 This is a comparison chart of the desulfurization effects of Comparative Example 3 and Comparative Example 4. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The present invention proposes a new type of high-efficiency desulfurization and denitrification agent with a gradient pore structure and a preparation method thereof. The material has extremely strong adsorption capacity and can quickly capture sulfides and nitrogen oxides in flue gas. The captured pollutants undergo chemical reactions in the pores inside the material, greatly improving the removal efficiency of flue gas pollutants.

[0025] Specifically, an embodiment of the present invention provides a desulfurization and denitrification agent having a gradient-distributed pore structure. In some preferred embodiments, the desulfurization and denitrification agent is partially calcined limestone.

[0026] The present invention also provides a method for preparing a desulfurization and denitrification agent, comprising the following steps: S1. crushing, grinding and sieving limestone to obtain limestone powder; S2. Calcine limestone powder at 800-950°C for 10-240 min to obtain a desulfurization and denitrification agent.

[0027] The partially calcined limestone prepared by the preparation method of the present invention has a core-shell structure, wherein the core is calcium carbonate, and the content of calcium oxide gradually increases from the core to the shell. The formation process is as follows: as the limestone is calcined, a gradient distribution of nano calcium oxide is gradually formed from the inside to the outside, and as the calcium oxide content increases, the pores on the surface of the material gradually become denser, forming a pore structure with a gradient distribution of macropores, mesopores and micropores from the core to the outer layer. In addition, by strictly controlling the calcination temperature and time, the present invention allows the shell to have micropores, mesopores and macropores at the same time, thereby facilitating the efficient removal of high-concentration sulfur- and nitrogen-containing flue gas.

[0028] The desulfurization and denitrification principles of the present invention are: First, the sulfide and nitrogen oxide in the flue gas are quickly captured through its efficient adsorption capacity. This process mainly occurs in the micropores and mesopore structures on the surface of the material, which provide a large number of adsorption sites for pollutants. Subsequently, the captured pollutants undergo chemical reactions inside the material. This process is optimized in the gradient pore structure of the material, where the larger pore size helps provide the space and channels required for the reaction, promoting the chemical conversion efficiency. In addition, the material adjusts its surface and internal structure and chemical composition to improve the selective adsorption and conversion efficiency of specific pollutants.

[0029] The present invention is further described in detail below through specific examples.

[0030] Example 1 A method for preparing a desulfurization and denitrification agent, comprising the following steps: Limestone with an effective content of 92.1% of CaCO3 was selected, and after crushing, grinding and sieving, limestone powder with a particle size of 300-600µm was obtained. 30g of limestone powder with a particle size of 300-600µm was taken and calcined at 900℃ for 240min and then rapidly cooled in air to obtain 23.0g of product, recorded as PCL1.

[0031] Figure 1 This is the SEM image of the desulfurization and denitrification agent of Example 1. It can be seen that the surface of the material has micropores, mesopores and macropores, thereby increasing the surface area and facilitating the efficient adsorption of pollutants.

[0032] Example 2 A method for preparing a desulfurization and denitrification agent, comprising the following steps: Limestone with an effective content of 92.1% of CaCO3 was selected, and after crushing, grinding and sieving, limestone powder with a particle size of 600~2360µm was obtained. 30g of limestone powder was calcined at 900℃ for 30min and then rapidly cooled in air to obtain 27.7g of product, recorded as PCL2.

[0033] Figure 2The XRD diagrams of the products obtained in Example 1 and Example 2 and standard calcium oxide and calcium carbonate show that the structure of the new phase generated by the reaction is between CaO and CaCO3.

[0034] Comparative Example 1 Select a chemical analysis pure CaO reagent with the same CaO mass as PCL1, and take limestone powder with the same CaCO3 mass as PCL1, mix the analytical pure CaO reagent and the analytical pure limestone powder to obtain a desulfurization and denitrification agent, recorded as PCL1'.

[0035] It should be noted that in Comparative Example 1, in order to compare the excitation effects of the partially calcined limestone of Example 1 of the present invention with pure calcium oxide, the purity of the limestone used reached 92.1%, and the mass of the generated CaO can be calculated by the CO2 generated by the reaction of Example 1. After calculation, the product of Example 1 contains 8.9g of CaO and 14.1g of CaCO3. Therefore, the mass of the analytically pure CaO reagent in Comparative Example 1 is 8.9g, and the limestone powder is 14.1g.

[0036] Comparative Example 2 Select a chemical analysis pure CaO reagent with the same CaO mass as PCL2, and another limestone powder with the same CaCO3 mass as PCL2 (CaCO3 effective content 92.1%), and finally mix the analytical pure CaO reagent and limestone powder, and record it as PCL2'.

[0037] It should be noted that the mass of CaO generated can be calculated based on the CO2 generated by the reaction in Example 2, and the remaining is CaCO3; after calculation, the product of Example 2 contains 2.9g of CaO and 24.8g of CaCO3. Therefore, the mass of the analytically pure CaO reagent in Comparative Example 2 is 2.9g, and the mass of the limestone powder is 24.8g.

[0038] Comparative Example 3 Limestone with an effective CaCO3 content of 92.1% was selected, and after crushing, grinding and sieving, limestone powder with a particle size of 300~600µm was obtained. 30g of limestone powder with a particle size of 300~600µm was taken and calcined at 1000℃ for 240min and then quickly cooled in air to obtain 17.6g of product, recorded as PCL3.

[0039] Comparative Example 4 Select a chemical analysis pure CaO reagent with the same CaO mass as PCL3, and another limestone powder with the same CaCO3 mass as PCL3 (CaCO3 effective content 92.1%), and finally mix the analytical pure CaO reagent and limestone powder, which is recorded as PCL3'.

[0040] It should be noted that the mass of CaO generated can be calculated based on the CO2 generated by the reaction in Comparative Example 3, and the remaining is CaCO3; after calculation, the product of Comparative Example 3 contains 15.5g of CaO and 2.1g of CaCO3. Therefore, the mass of the analytically pure CaO reagent in Comparative Example 4 is 15.5g, and the limestone powder is 2.1g.

[0041] Desulfurization and denitrification test Test method: The desulfurization and denitrification agents obtained in Examples 1-2 and Comparative Examples 1-4 were placed in desulfurization and denitrification reactors respectively, and the flue gas after pre-dust removal passed through the desulfurization and denitrification reactor device, and then the flue gas was discharged from the chimney. After being treated with the desulfurization and denitrification agent, the flue gas data at the outlet was detected, and the test results are shown in Table 1 below.

[0042] Table 1

[0043] It can be seen from the above table that the desulfurization and denitrification agent with gradient pore structure distribution provided by the present invention can effectively remove sulfide and nitrogen oxides in flue gas. Compared with Example 1 and Example 2, it can be seen that the calcination time affects the surface composition and pore structure of the material, and further affects the desulfurization and denitrification effect.

[0044] Figure 3~4 The diagram is a diagram of the absorption effect of the embodiments and comparative examples on SO2. It can be seen that the desulfurization and denitrification agents prepared in embodiments 1 to 2 have a faster desulfurization rate and a higher efficiency than those prepared in comparative examples 1 to 3.

[0045] From Table 1 and Figure 5 It can be seen that the desulfurization effect of the partially calcined limestone in comparative example 3 is not as good as that of the composite system of calcium oxide and calcium carbonate. This is because the excessively high calcination temperature leads to an increase in the surface calcium oxide content, thereby increasing the density and failing to form a pore structure with a surface gradient distribution.

[0046] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0047] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A desulfurization and denitrification agent, characterized in that: The desulfurization and denitrification agent has a core-shell structure, wherein the core is calcium carbonate and the shell is calcium oxide, and the content of the calcium oxide gradually increases from the core to the shell.

2. The desulfurization and denitrification agent according to claim 1, characterized in that: The mass percentage of the calcium oxide in the desulfurization and denitrification agent is 8% to 40%.

3. The desulfurization and denitrification agent according to claim 2, characterized in that: The mass percentage of the calcium oxide in the desulfurization and denitrification agent is 10.5%.

4. The desulfurization and denitrification agent according to claim 1, characterized in that: The shell has microporous, mesoporous and macroporous structures.

5. A method for preparing a desulfurization and denitrification agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. crushing, grinding and sieving limestone to obtain limestone powder; S2. calcining the limestone powder at 800-950° C. for 10-240 min to obtain the desulfurization and denitrification agent.

6. The method for preparing a desulfurization and denitrification agent according to claim 5, characterized in that: The particle size of the limestone powder is 300-2500 μm.

7. The method for preparing a desulfurization and denitrification agent according to claim 6, characterized in that: The particle size of the limestone powder is 600-2360 μm.

8. The method for preparing a desulfurization and denitrification agent according to claim 5, characterized in that: The calcination temperature is 900° C. and the calcination time is 30 min.

9. The method for preparing a desulfurization and denitrification agent according to claim 5, characterized in that: The limestone is high-grade limestone or waste limestone.

10. The desulfurization and denitrification agent according to any one of claims 1 to 4 is used to remove sulfide and / or NO in flue gas. X Application in.

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