Efficient calcium-based low-temperature desulfurizing agent based on pore channel blending technology as well as preparation method and application thereof

Abstract

The invention discloses an efficient calcium-based low-temperature desulfurizing agent based on a pore channel blending technology and a preparation method and application thereof, and belongs to the technical field of desulfurizing agent preparation. A binder, a pore-forming agent and an active agent are added into a system to serve as active auxiliaries, the pore-forming agent is a mixture of zeolite and one of diethyl azodicarboxylate, diisopropyl azodicarboxylate, urea and ammonium carbonate, other materials are combined, and due to the fact that diethyl azodicarboxylate and the like have high mesopore forming performance, the pore-forming agent and the active agent are added into the system to serve as the active auxiliaries, and the pore-forming agent is a mixture of zeolite and one of diethyl azodicarboxylate, diisopropyl azodicarboxylate, urea and ammonium carbonate. The zeolite is doped to increase the number of micropores of the desulfurizing agent, and diethyl azodicarboxylate or others are added to enable the desulfurizing agent to generate mesopores, so that the internal mass transfer performance of the desulfurizing agent is improved. A three-dimensional pore channel structure can be constructed, the micropore area is increased, meanwhile, a mass transfer channel is improved, and the desulfurization performance is further enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of desulfurizing agent preparation, and in particular relates to a high-efficiency calcium-based low-temperature desulfurizing agent based on pore channel deployment technology, and a preparation method and application thereof. Background Art

[0002] Flue Gas Desulfurization (FGD) is one of the current desulfurization methods. Its principle is mainly to use various alkaline absorbents or adsorbents to react with SO in flue gas. 2 Physical or chemical reactions occur to convert it into relatively stable sulfates or sulfites that are easy to separate mechanically. Since the 1960s, countries around the world have begun to vigorously develop and apply flue gas desulfurization technology. Flue gas desulfurization is divided into dry desulfurization, semi-dry desulfurization and wet desulfurization technology.

[0003] Dry flue gas desulfurization technology refers to the use of desulfurization adsorbents in a dry state without the participation of liquid phase to remove SO from flue gas. 2 , desulfurizers are mostly powdery or granular, containing adsorption, desulfurization and other properties. The types of desulfurizers are generally carbon materials (activated carbon / coke, activated carbon fiber, carbon nanotubes), metal oxides (activated alumina, activated manganese oxide, magnesium oxide, aluminum-based copper oxide), molecular sieves, silica gel, zeolites, solid amine organic-inorganic composite materials, and new desulfurizers include metal organic framework materials (MOFs). Calcium-based desulfurizer is one of the commonly used desulfurizers in dry desulfurization. This is because calcium-based desulfurizers are simple to prepare, low in cost, and have no secondary pollution. Compared with the wet method, the advantages of the traditional dry method are low cost and environmental friendliness, and the process is better than the wet process. The wet process generally has the disadvantage of generating wastewater, and the subsequent flue gas treatment requires reheating. The dry desulfurization process is relatively simple, and generates less secondary pollution. The adsorbent is renewable, the facilities are not easy to scale and corrode, and the investment and operating costs are low. However, the desulfurization efficiency of the traditional dry calcium-based desulfurizer is low. This is because the CaSO generated during the desulfurization process 4 Molar volume relative to Ca(OH) 2 The larger the particles are, the more pores on the particle surface are blocked, which hinders the contact between the gas and the fresh desulfurizer, resulting in the inability of the non-surface part of the desulfurizer to be sulfurized, forming an unreacted core. Summary of the invention

[0004] The purpose of the present invention is to provide a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology and a preparation method and application thereof, so as to solve the technical problem of low desulfurization efficiency of traditional dry calcium-based desulfurizers.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology, comprising the following steps:

[0007] Ca(OH) 2 After mixing with fly ash, a binder, an active agent, a pore-forming agent, a dissolving agent and water are added to obtain a paste mixture after mixing; after stirring the paste mixture, a clay mixture is obtained, and the clay mixture is repeatedly kneaded and then extruded, and then dried to obtain a desulfurizer.

[0008] Furthermore, the Ca(OH) 2 The dosage ratio of fly ash, binder, pore-forming agent, dissolving agent and activating agent is (1900~2100)g: (220~230)g: (50~60)g: (130-140)g: (100~110)g: (100~110)g.

[0009] Furthermore, the weight of the water accounts for 25%-30% of the total weight of the desulfurizer; and the stirring time is 1 to 2 hours.

[0010] Furthermore, the binder is a mixture of bentonite and polyacrylamide or a mixture of bentonite and sodium silicate;

[0011] The weight ratio of the polyacrylamide to bentonite is 1:10; the weight ratio of the sodium silicate to bentonite is 1:10.

[0012] Furthermore, the active agent is Fe 2 O 3 or MnO 2 .

[0013] The dissolving agent is NaOH;

[0014] The pore-forming agent is a mixture of one of diethyl azodicarboxylate, diisopropyl azodicarboxylate, urea and ammonium carbonate and zeolite; the dosage ratio of diethyl azodicarboxylate or diisopropyl azodicarboxylate to zeolite is (1.6-1.8) mL: (120-130) g;

[0015] The usage ratio of the urea or ammonium carbonate to the zeolite is (5-10) g:(120-130) g.

[0016] Furthermore, the drying process includes sequential air-drying and baking processes.

[0017] Furthermore, the drying is performed by natural drying at room temperature for 12 to 24 hours.

[0018] Furthermore, the drying process is carried out at a temperature of 120 to 180° C. and for a time of 150 to 200 minutes.

[0019] The invention also discloses a high-efficiency calcium-based low-temperature desulfurizing agent based on pore mixing technology and prepared by the preparation method.

[0020] The invention also discloses the application of the high-efficiency calcium-based low-temperature desulfurizer based on the pore channel blending technology in the desulfurization of low-temperature boilers.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The invention discloses a method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology, wherein a binder, an active agent, a pore-forming agent and a dissolving agent are added as raw materials in the system, diethyl azodicarboxylate and urea have strong mesopore-forming performance, zeolite is added to increase the number of micropores of the desulfurizer, diethyl azodicarboxylate or urea is added to generate mesopores in the desulfurizer, and the internal mass transfer performance of the desulfurizer is improved. A three-dimensional pore structure can be constructed, and the three-dimensional pore structure solves the technical problem of low desulfurization efficiency of traditional dry calcium-based desulfurizers.

[0023] Furthermore, when 0.4%-1% of diethyl azodicarboxylate, diisopropyl azodicarboxylate, urea, one of ammonium carbonate and 5%-8% of zeolite are added, the desulfurizer has good desulfurization performance. The desulfurization performance of the desulfurizer does not only depend on the specific surface area, but is more affected by the micropore area and mass transfer performance in the desulfurizer. In summary, the addition of zeolite increases the number of micropores in the desulfurizer, and the addition of several other pore-forming agents makes the desulfurizer generate mesopores, which improves the internal mass transfer performance of the desulfurizer. A three-dimensional pore structure can be constructed.

[0024] The present invention also discloses a high-efficiency calcium-based low-temperature desulfurizer based on pore blending technology prepared by the above method. The desulfurizer improves the distribution of active sites and mass transfer performance inside the desulfurizer, and reconstructs the internal structure of the desulfurizer by adding a pore-forming agent, thereby increasing its micropore area and improving the mass transfer channel, thereby further enhancing the advantages of desulfurization performance.

[0025] Furthermore, a three-dimensional pore structure was constructed based on the reaction mechanism of the catalyst itself, which greatly reduced the daily operating costs of the boiler on the basis of improving the utilization efficiency of the desulfurization catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The pore size distribution diagrams of different desulfurizers obtained in Comparative Examples 3 and 4;

[0027] Where: a-N of four desulfurizer samples 2 Adsorption-desorption isotherms; b-pore size distribution of four desulfurizer samples;

[0028] Figure 2is the desulfurization efficiency of different desulfurizers;

[0029] Among them: a-Ca(OH) 2 N before and after reaction of -DF with commercial calcium-based desulfurizer 2 Adsorption-desorption isotherm; b-Ca(OH) 2 -Pore size distribution of DF before and after reaction with commercial calcium-based desulfurizer;

[0030] Figure 3 This is an analysis diagram of the appearance of the desulfurizer prepared by the present invention;

[0031] Among them: a-SEM image of desulfurizer without iron doping (12μm); b-SEM image of desulfurizer without iron doping (80μm); c-SEM image of desulfurizer without iron doping (200μm); d-SEM image of desulfurizer after iron doping (12μm); e-SEM image of desulfurizer after iron doping (80μm); f-SEM image of desulfurizer after iron doping (200μm);

[0032] Figure 4 This is a physical sample picture of the desulfurizer prepared by the present invention;

[0033] Figure 5 Ca(OH) 2 -DF and commercial calcium-based desulfurizer samples SO 2 Plot of adsorption amount versus time;

[0034] Figure 6 These are the test data of desulfurizer activity under different metal oxide doping conditions. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0036] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0037] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0038] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0039] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0040] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0041] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0042] Example 1

[0043] A method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology comprises the following steps:

[0044] 2000gCa(OH) 2 Mix well with 225g fly ash, add 5g sodium silicate and 50g bentonite, weigh 125g zeolite and 5g urea, and then add 105g MnO 2 As an active agent, 105 g of NaOH was added, and 950 mL of deionized water was added to obtain a paste mixture, and the paste mixture was stirred in a blender for 60 min to ensure that the ingredients were evenly mixed to obtain a clay-like mixture;

[0045] The obtained clay-like mixture was kneaded in a vacuum mud extruder and finally extruded into a columnar desulfurizer with a diameter of 7 mm; the columnar desulfurizer was naturally dried at room temperature for 12 hours and then dried in an oven at 150°C for 180 minutes to obtain a high-efficiency calcium-based low-temperature desulfurizer based on pore formulation.

[0046] Example 2

[0047] A method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology comprises the following steps:

[0048] 500gCa(OH) 2 Mix well with 56.25g fly ash, add 1.25g sodium silicate and 12.5g bentonite, weigh 31.25g zeolite and 0.425mL diethyl azodicarboxylate, and then add 26.25g Fe 2 O 3 As an active agent, 26 g of NaOH was added, and 237.5 mL of deionized water was added to obtain a paste mixture, and the paste mixture was hydrated in a mixing mixer for 65 min to ensure that the ingredients were evenly mixed to obtain a clay-like mixture;

[0049] The obtained clay-like mixture was repeatedly kneaded in a screw extruder and finally extruded into a columnar desulfurizer with a diameter of 7 mm; the columnar desulfurizer was naturally dried at room temperature for 16 hours and then dried in an oven at 160°C for 190 minutes to obtain a high-efficiency calcium-based low-temperature desulfurizer based on pore formulation.

[0050] Example 3

[0051] A method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology comprises the following steps:

[0052] 4100Ca(OH) 2 Mix well with 440g fly ash, add 8g polyacrylamide and 100g bentonite, weigh 240g zeolite and 50g ammonium carbonate, and then add 200g MnO 2 As an active agent, 210 g of NaOH was added, and 2000 mL of deionized water was added to obtain a paste mixture, and the paste mixture was hydrated in a mixing mixer for 80 min to ensure that the ingredients were evenly mixed to obtain a clay-like mixture;

[0053] The obtained clay-like mixture was repeatedly mixed in a screw extruder and finally extruded into a columnar desulfurizer with a diameter of 7 mm; the columnar desulfurizer was naturally dried at room temperature for 18 hours and then dried in an oven at 120°C for 200 minutes to obtain a high-efficiency calcium-based low-temperature desulfurizer based on pore formulation.

[0054] Example 4

[0055] A method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology comprises the following steps:

[0056] 5900gCa(OH) 2Mix well with 680g fly ash, add 15g polyacrylamide and 150g bentonite, weigh 380g zeolite and 5mL diisopropyl azodicarboxylate, and then add 320g Fe 2 O 3 As an active agent, 320 g of NaOH was added, and 2900 mL of deionized water was added to obtain a paste mixture, and the paste mixture was hydrated in a mixing mixer for 90 min to ensure that the ingredients were evenly mixed to obtain a clay-like mixture;

[0057] The obtained clay-like mixture was repeatedly kneaded in a screw extruder and finally extruded into a columnar desulfurizer with a diameter of 7 mm; the columnar desulfurizer was naturally dried at room temperature for 24 h, and then dried in an oven at 180 ° C for 150 min to obtain a high-efficiency calcium-based low-temperature desulfurizer (Ca(OH) 2 -DF).

[0058] Comparative Example 1

[0059] This comparative example uses a commercial desulfurizer.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the active agents are Zn 2 O 3 、CeO 2 、Al 2 O 3 , CuO and Cr 2 O 3 The remaining steps and parameters are the same as those in the embodiment to obtain several desulfurization agent samples.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that only azo, urea and zeolite are added as pore-forming agents, and the remaining steps and descriptions are the same as those of Example 1, thereby obtaining a desulfurization agent sample.

[0064] Comparative Example 4

[0065] Different from Example 1, no pore-forming agent was added to obtain a desulfurization agent sample.

[0066] Figure 1 Four samples N obtained from Comparative Examples 3 and 4 2From the adsorption and desorption isotherms and the DFT model pore size distribution diagram, it can be seen that as shown in Figure (a), all samples have a typical H3 type hysteresis loop at a relatively high relative pressure (0.8-1.0) in the second half, which is usually related to the capillary condensation phenomenon in the desulfurizer structure, and the curves all belong to the type IV isotherm classified by IUPAC, indicating that most of the desulfurizer samples exist in the form of mesopores. From Figure (b), it can be seen that all samples have a wide pore size distribution, which further indicates that the catalyst exists in the form of mesopores and is composed of many irregular particles stacked. In summary: DEAD and urea can increase the mesopore and macropore area of ​​the sample because they have similar pore-forming principles: when drying, the gas is decomposed by heat to produce pores, and these pores are mostly mesopores. Zeolite, due to its own high specific surface area structure, its incorporation can increase the micropore area of ​​the sample.

[0067] Figure 2 N of this desulfurizer and commercial desulfurizer 2 Adsorption, desorption isotherms and DFT model pore size distribution diagram show that although Ca(OH) 2 -DF Ca(OH) 2 The utilization rate is higher than that of commercial calcium-based desulfurizers, but the specific surface area, mesopore and macropore area of ​​the former are not higher than those of the latter, and only the micropore area is higher. This further shows that the desulfurization performance is not positively correlated with the specific surface area of ​​the adsorbent, but is more dependent on high micropore area and good mass transfer performance. Ca(OH) before and after the reaction 2 -DF and commercial calcium-based desulfurizers have reduced specific surface areas. This is because the calcium sulfate and calcium sulfite molecules generated during the reaction adhere to the surface of the desulfurizer pores, causing the pores to be blocked and the number of pores to decrease. Among them, the specific surface area of ​​the commercial desulfurizer decreased by 7.63%, Ca(OH) 2 The reduction in specific surface area of ​​-DF is 33.8%, which is much higher than that of commercial desulfurizers, indicating that during the reaction, Ca(OH) 2 -DF reacts with Ca 2+ More, the pore utilization rate is higher.

[0068] Figure 3 The desulfurizer prepared by the present invention is shown in the figure (af). It can be seen that the desulfurizers have similar morphologies, which are porous structures composed of nanoparticles of uneven sizes. Such nanoparticle-sized desulfurizers can often show good desulfurization performance. 2 O 3 Before, Ca(OH) 2 The grains are densely packed, irregular in shape and angular, with no obvious surface pores and only a few large pores. 2 O 3After that, the 2μm size Fe 2 O 3 The particles aggregate under the action of van der Waals forces on Ca(OH) 2 The surface layer has a slightly ellipsoidal shape, forming a rugged and rough surface, and the mesopores on the surface of the desulfurizer are significantly increased, which is beneficial to SO 2 As can be seen from Figure (c) and Figure (d), many Ca(OH) 2 The grains are accumulated into 50-150μm particle clusters, Fe 2 O 3 The particles agglomerated into 30-80 μm particles and attached to the large Ca(OH) 2 Some are on the surface of the grains, while others are near the pores. Figures (e) and (f) show that in Fe 2 O 3 After the addition of Fe 2 O 3 Evenly distributed on the surface of the desulfurizer, and can break up Ca(OH) 2 The accumulation of crystals will lead to the formation of more pores inside the desulfurizer, improving the internal mass transfer performance.

[0069] Figure 4 This is a sample of the desulfurizer prepared by the present invention. It can be seen that the surface of the desulfurizer is smooth and cylindrical particles are easy to transport and store.

[0070] Figure 5 The Ca(OH) prepared by the present invention 2 -SO of DF samples and commercial desulfurizer samples 2 The curve of adsorption amount versus adsorption time shows that in the initial stage of adsorption, the slope of the curve is large, indicating that SO 2 The adsorption amount increases rapidly, and all SO in the mixed gas 2 are all adsorbed on the desulfurizer. At this time, the adsorption mainly takes place in the macropores of the desulfurizer. In the middle and late stages of adsorption, the slope of the curve decreases and the desulfurization efficiency begins to decline. This is because the adsorption sites on the surface of the desulfurizer are gradually occupied by SO 2 The molecules occupy the pores, the adsorption reaction turns to the micropores, and the mass transfer resistance increases. In the adsorption equilibrium stage, the adsorption amount no longer increases, and the curve tends to be parallel. 2 The equilibrium adsorption capacity qe of -DF is 99.68 mg / g, and that of commercial desulfurizer is 65.63 mg / g.

[0071] Figure 6 The activity test of the desulfurizer under different metal oxide doping shows that other metal oxides have different degrees of enhancement effect on the low temperature performance of the desulfurizer, and the enhancement effect is ranked as follows: Fe 2 O3 >MnO 2 >Zn 2 O 3 >CeO 2 >Al 2 O 3 >CuO>Cr 2 O 3 .

[0072] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology, characterized in that: The following steps are involved: After mixing Ca(OH)2 with fly ash, a binder, an activator, a pore-forming agent, a dissolving agent and water are added to obtain a paste mixture after mixing; after stirring the paste mixture, a clay mixture is obtained, and the clay mixture is repeatedly kneaded and extruded, and then dried to obtain a desulfurizer.

2. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology according to claim 1 is characterized in that: The dosage ratio of Ca(OH)2, fly ash, binder, pore-forming agent, dissolving agent and activating agent is (1900-2100) g: (220-230) g: (50-60) g: (130-140) g: (100-110) g: (100-110) g.

3. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology according to claim 1 is characterized in that: The weight of the water accounts for 25%-30% of the total weight of the desulfurizer; the stirring time is 1 to 2 hours.

4. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology according to claim 1 is characterized in that: The binder is a mixture of bentonite and polyacrylamide or a mixture of bentonite and sodium silicate; The weight ratio of the polyacrylamide to bentonite is 1:10; the weight ratio of the sodium silicate to bentonite is 1:

10.

5. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology according to claim 1 is characterized in that: The active agent is Fe2O3 or MnO2; The dissolving agent is NaOH; The pore-forming agent is a mixture of one of diethyl azodicarboxylate, diisopropyl azodicarboxylate, urea and ammonium carbonate and zeolite; the dosage ratio of diethyl azodicarboxylate or diisopropyl azodicarboxylate to zeolite is (1.6-1.8) mL: (120-130) g; The usage ratio of the urea or ammonium carbonate to the zeolite is (5-10) g:(120-130) g.

6. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology according to claim 1, characterized in that: The drying process includes air-drying and oven-drying processes performed sequentially.

7. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore channel deployment technology according to claim 6, characterized in that: The drying is performed naturally at room temperature for 12 to 24 hours.

8. The method for preparing a high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology according to claim 6, characterized in that: The drying process is carried out at a temperature of 120 to 180° C. and for a time of 150 to 200 minutes.

9. A high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. Use of the high-efficiency calcium-based low-temperature desulfurizer based on pore mixing technology as claimed in claim 9 in desulfurization of low-temperature boilers.

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