Desulfurizing agents, their preparation methods, and their applications in flue gas desulfurization.

Abstract

This invention provides a desulfurizing agent, its preparation method, and its application in flue gas desulfurization. The structural formula of the desulfurizing agent is X. n1 Y n2 Z n3 M n4 O n5 In the formula, X represents La and / or V, Y represents Ce and / or Cs, Z represents Ca and / or Mg, and M represents Al and / or Ti; 0 < n1 ≤ 2, 0 < n2 ≤ 6, 0 < n3 ≤ 3, 0 < n4 ≤ 3, and n5 satisfies the balance of positive and negative valence states of the desulfurizing agent; and the desulfurizing agent has a porous structure. In the desulfurizing agent, the volume of pores with a diameter less than 2.2 nm accounts for 3-4% of the total pore volume, the volume of pores with a diameter of 2.2-5.5 nm accounts for 25-40% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm and less than 100 nm accounts for 56-72% of the total pore volume. This desulfurizing agent has a high sulfur dioxide removal rate and a high sulfur capacity.

Description

Technical Field

[0001] This invention belongs to the field of sulfur-containing gas purification, specifically relating to a desulfurizing agent, its preparation method, and its application in flue gas desulfurization. Background Technology

[0002] Sulfur dioxide is a byproduct of petroleum, natural gas, and coal processing, and is one of the most harmful air pollutants. Current materials for removing sulfur dioxide mainly include activated carbon, alumina, silicon dioxide, calcium oxide, and magnesium oxide. Alternatively, activated carbon and alumina can be modified with alkaline substances and loaded with certain metal oxides to catalyze the conversion of sulfur dioxide to sulfur trioxide, which is then used to produce sulfuric acid.

[0003] However, the above methods have the following problems: (1) Existing sulfur dioxide adsorption materials are effective for low concentrations of sulfur dioxide, but cannot achieve a high removal rate when the sulfur dioxide concentration is high; (2) Existing adsorbents are difficult to regenerate after adsorption due to the use of activated carbon, activated alumina, etc.; (3) Existing adsorbents are prone to sulfur dioxide penetration during the adsorption process. The initial effect is very good, but the sulfur dioxide concentration in the adsorption outlet gas increases in a short time.

[0004] Therefore, it is necessary to provide a new desulfurizing agent to improve the above-mentioned problems. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a desulfurizing agent, its preparation method and its application in flue gas desulfurization, wherein the desulfurizing agent has a high sulfur dioxide removal rate and a high sulfur capacity.

[0006] To achieve the above objectives, the present invention provides a desulfurizing agent with the structural formula X. n1 Y n2 Z n3 M n4 O n5 In the formula, X represents La and / or V, Y represents Ce and / or Cs, Z represents Ca and / or Mg, and M represents Al and / or Ti; 0 < n1 ≤ 2, 0 < n2 ≤ 6, 0 < n3 ≤ 3, 0 < n4 ≤ 3, and n5 satisfies the balance of positive and negative valence states of the desulfurizing agent; and the desulfurizing agent has a porous structure, with the volume of pores with a diameter less than 2.2 nm accounting for 3-4% of the total pore volume, the volume of pores with a diameter of 2.2-5.5 nm accounting for 25-40% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm and less than 100 nm accounting for 56-72% of the total pore volume.

[0007] The oxides of elements X and Y have vacancy structures and strong oxygen-carrying capacity. At the same time, the lattice oxygen has a stronger ability to release oxygen at a certain temperature, which can promote the oxidation and conversion of sulfur dioxide in sulfur-containing flue gas more quickly. The oxide of element Z reacts faster with acidic sulfur dioxide compounds. Moreover, its synergistic effect with the oxidation-promoting effect of the oxides of elements X and Y can further accelerate the oxidation of free radicals in the reaction process of acidic sulfur dioxide gas, thereby increasing the reaction rate. The oxide of element M can build the desulfurizer skeleton structure during the molding process and further synergize with the porous structure to achieve the beneficial effect of enabling sulfur dioxide gas to quickly and stably enter the active sites distributed with metal oxide components and react rapidly.

[0008] The volume of pores with a diameter less than 2.2 nm accounts for 3-4% of the total pore volume, the volume of pores with a diameter of 2.2-5.5 nm accounts for 25-40% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounts for 56-72% of the total pore volume. This allows sulfur dioxide gas to quickly enter the active sites where metal oxide components are distributed and react rapidly.

[0009] Based on this, the desulfurizing agent of this invention can more efficiently remove sulfur dioxide from sulfur-containing flue gas involved in current oil refining, natural gas, and coal processing through catalytic oxidation (sulfur dioxide is oxidized to sulfate and sulfite), and has a high sulfur capacity. Furthermore, after desulfurization, the sulfate and sulfite generated by the desulfurizing agent reaction can be reduced to hydrogen sulfide using reducing gases, and then returned to the sulfur recovery unit's combustion furnace. Sulfides are then recovered through the combustion furnace and Claus catalyst, reducing sulfide emissions. The total sulfur recovery rate is high, and the production process involves no chemical additives, no wastewater or waste residue, and the desulfurizing agent can be recycled with stable recycling performance.

[0010] In addition, the valence states of La are +3, Ce are +4, Ca are +2, Ti are +4, Al are +3, V are +5, Cs are +4, and Mg are +2.

[0011] In addition, the pore size distribution parameters were obtained using GB / T 5816-1995 Method for Determination of Surface Area of ​​Catalysts and Adsorbents and SH / T 0572-1993 Method for Calculation of Pore Size Distribution of Catalysts (Calculation Method of Nitrogen Desorption Isotherm).

[0012] Furthermore, 0.2≤n1≤2, 0.5≤n2≤6, 1≤n3≤3, 0.6≤n4≤3, and n5 satisfy the balance of positive and negative valence states of the desulfurizing agent. In some optional embodiments, the desulfurizing agent has the structural formula La. 0.5 Ce1Ca2Ti 1.5 O 7.75 La 1.5 Cs 0.5 Ca1Al 0.6 O5.15 V 0.2 Cs3Mg3Ti 2.3 O 14.1 V 0.2 Ce3Mg3Al 2.3 O 12.95 or V2Cs6Mg 1.5 Al3O 23 .

[0013] According to another aspect of the present invention, a method for preparing the aforementioned desulfurizing agent is provided, comprising the following steps:

[0014] The oxides of element X, element Y, element Z, and element M are dissolved in dilute nitric acid to form nitric acid solutions of element X, element Y, element Z, and element M, respectively.

[0015] After adjusting the pH values ​​of the nitric acid solutions of element X, element Y, element Z, and element M to 7-9, the solutions are sequentially filtered, dried once, crushed, and ground to obtain intermediate products of element X, element Y, element Z, and element M.

[0016] The intermediate products of element X, element Y, element Z and element M are mixed and then calcined once to obtain a calcined product.

[0017] The desulfurizing agent is obtained by mixing the primary roasting product with a pore-forming agent and water, followed by kneading, shaping, secondary drying, and secondary roasting.

[0018] Compared to conventional single-stage roasting, this invention first roasts the mixture of intermediate products, then adds a pore-forming agent for a second roasting. In this way, the intermediate products of each element decompose to form oxide particles, which aggregate through primary and secondary particles to form an initial pore structure with different pore sizes. The pore-forming agent and the particles formed in the first roasting are roasted again under high temperature to form tertiary particles and aggregates, thereby realizing a desulfurizing agent with different pore size distributions.

[0019] Furthermore, the primary roasting temperature is 300–400℃, the time is 3–6 hours, and the temperature rise rate from room temperature to the primary roasting temperature is 10–25℃ / min. The secondary roasting temperature is 500–600℃, the time is 4–12 hours, and the temperature rise rate from 15–25℃ to the secondary roasting temperature is 10–20℃ / min.

[0020] Excessive temperature can cause the gases produced by nitrate decomposition to expand and crack the desulfurizer's framework structure, leading to a higher wear rate. Furthermore, excessively high temperatures can cause the desulfurizer's framework structure to collapse, with metal components within the framework agglomerating into clumps or blocks, hindering contact between the reacting gases and the metal components. A rapid heating rate can cause metal components to evaporate too quickly within and around the desulfurizer's framework structure, resulting in greater migration to the surface. This leads to fewer metal components on the inner surface and more on the outer surface, resulting in a large difference in the number of active sites between the inner and outer surfaces.

[0021] Too low a temperature results in incomplete decomposition of the nitrate metal component, and the nitrate metal compound does not have a good effect on oxidizing sulfur dioxide. At the same time, too low a temperature prevents the organic matter in the pore-forming agent during the molding process from decomposing, thus failing to form desulfurizing agent channels and suitable pore sizes. Too slow a heating rate will lead to decreased production efficiency and higher energy consumption.

[0022] In some alternative embodiments, the solvent for the dilute nitric acid is water, and the mass concentration of nitric acid in the dilute nitric acid is 5-10%.

[0023] In a preferred embodiment, the pore-forming agent is selected from one or more combinations of guar gum, polyacrylamide, graphite, cellulose, citric acid, acetic acid, and oxalic acid. The amount of pore-forming agent used is 1-6% of the total weight of the product from a single calcination. More preferably, the pore-forming agent is selected from guar gum powder. Utilizing the disordered cross-linked network structure and the main structure of rod-shaped, columnar, and irregular particle shapes of guar gum powder, it helps to achieve adhesion between material particles and increase the mechanical strength of the desulfurizer during the molding process, as well as lubrication of the material and equipment during the molding process.

[0024] Furthermore, the primary drying process is carried out at a temperature of 50–150°C for 24–36 hours.

[0025] Furthermore, the moisture content of the material after secondary drying is controlled to be <6%. In a preferred embodiment, the shaped material is first placed in a dry and ventilated place for 8–72 hours. When the moisture content is found to be less than 30%, the air-dried material is then transferred to a drying oven and dried for another 4–8 hours under hot air conditions of 80–150°C. The secondary drying is completed when the moisture content is found to be less than 6%.

[0026] In a preferred embodiment, the product from the first calcination, the pore-forming agent, and water are mixed in a mixer, and the mixed material is then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material is then transferred to an extruder, where it is loaded with a perforated plate with a diameter of 1-4 mm and extruded into strips.

[0027] Furthermore, the particle size of the ground material is controlled to be 200-400 mesh.

[0028] According to another aspect of the present invention, the application of the aforementioned desulfurizing agent in flue gas desulfurization is provided.

[0029] Based on the reasons stated above, the desulfurizing agent of this invention can more efficiently remove sulfur dioxide from sulfur-containing flue gas involved in current oil refining, natural gas, and coal processing through catalytic oxidation (sulfur dioxide is oxidized to sulfate and sulfite), exhibiting high sulfur capacity. Furthermore, after desulfurization, the sulfate and sulfite generated by the desulfurizing agent reaction can be reduced to hydrogen sulfide using reducing gases, which are then returned to the combustion furnace of the sulfur recovery unit. Sulfides are then recovered through the combustion furnace and Claus catalyst, reducing sulfide emissions and achieving a high total sulfur recovery rate. The production process involves no chemical additives and generates no wastewater or waste residue. Simultaneously, the desulfurizing agent of this invention is recyclable with stable recycling performance. Such a desulfurizing agent is particularly suitable for sulfur recovery units where achieving sulfur dioxide standards in exhaust gas is difficult. Detailed Implementation

[0030] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0031] Example 1

[0032] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0033] 8.145 g of lanthanum oxide, 16.412 g of cerium oxide, 11.215 g of calcium oxide, and 10.780 g of titanium oxide were dissolved in 120 mL of 10% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 7.2, and then the mixtures were sequentially filtered, dried once (at 80°C for 28 h), crushed, and ground to obtain lanthanum nitrate with a particle size of 265 mesh, cerium nitrate with a particle size of 325 mesh, calcium nitrate with a particle size of 232 mesh, and titanium nitrate with a particle size of 356 mesh.

[0034] The above-mentioned lanthanum nitrate, cerium nitrate, calcium nitrate, and titanium nitrate were mixed and then subjected to a first roasting (temperature 320℃, time 5h, heating rate 15℃ / min). The product of the first roasting was then mixed with guar gum powder (3.4wt% of the product of the first roasting) and 80mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 2.3mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 24h. When the moisture content was found to be less than 30%, it was air-dried and then transferred to a drying oven for further drying at 120℃ hot air for 36h. When the moisture content was found to be less than 6%, the material was then subjected to a second roasting (temperature 520℃, time 4.5h, heating rate 20℃ / min) to obtain the desulfurizing agent. The structural formula of the desulfurizing agent is La. 0.5 Ce1Ca2Ti 1.5 O 7.75 The volume of pores with a diameter less than 2.2 nm accounted for 3.2% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounted for 28% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounted for 68.8% of the total pore volume.

[0035] Example 2

[0036] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0037] 8.145 g of lanthanum oxide, 16.412 g of cerium oxide, 11.215 g of calcium oxide, and 10.780 g of titanium oxide were dissolved in 180 mL of 6% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 8.7, and then the mixtures were sequentially filtered, dried once (at 105℃ for 36 h), crushed, and ground to obtain lanthanum nitrate with a particle size of 210 mesh, cesium nitrate with a particle size of 325 mesh, calcium nitrate with a particle size of 325 mesh, and aluminum nitrate with a particle size of 400 mesh.

[0038] The above-mentioned lanthanum nitrate, cerium nitrate, calcium nitrate, and titanium nitrate were mixed and then subjected to a first roasting (temperature 350℃, time 3h, heating rate 10℃ / min). The product of the first roasting was then mixed with guar gum powder (2.2wt% of the product of the first roasting) and 26mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 3.2mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 36h. When the moisture content was found to be less than 30%, it was air-dried and then transferred to a drying oven for further drying at 150℃ hot air for 24h. When the moisture content was found to be less than 6%, the material was then subjected to a second roasting (temperature 600℃, time 4h, heating rate 10℃ / min) to obtain a desulfurizing agent. The structural formula of this desulfurizing agent is La. 0.5 Ce1Ca2Ti 1.5 O 7.75 The volume of pores with a diameter less than 2.2 nm accounts for 4% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounts for 25% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounts for 71% of the total pore volume.

[0039] Example 3

[0040] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0041] 24.436 g of lanthanum oxide, 7.045 g of cesium oxide, 5.068 g of calcium oxide, and 3.059 g of aluminum oxide were dissolved in 180 mL of 6% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 8.7, and then the mixtures were sequentially filtered, dried once (at 105℃ for 36 h), crushed, and ground to obtain lanthanum nitrate with a particle size of 210 mesh, cesium nitrate with a particle size of 325 mesh, calcium nitrate with a particle size of 325 mesh, and aluminum nitrate with a particle size of 400 mesh.

[0042] The above-mentioned lanthanum nitrate, cerium nitrate, calcium nitrate, and titanium nitrate were mixed and then subjected to a first roasting (temperature 350℃, time 3h, heating rate 10℃ / min). The product of the first roasting was then mixed with guar gum powder (2.2wt% of the product of the first roasting) and 26mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 3.2mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 36h. When the moisture content was found to be less than 30%, it was air-dried and then transferred to a drying oven for further drying at 150℃ hot air for 24h. When the moisture content was found to be less than 6%, the material was then subjected to a second roasting (temperature 600℃, time 4h, heating rate 10℃ / min) to obtain a desulfurizing agent. The structural formula of this desulfurizing agent is La. 1.5 Cs 0.5 Ca1Al 0.6 O 5.15 The volume of pores with a diameter less than 2.2 nm accounted for 3.8% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounted for 26% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounted for 70.2% of the total pore volume.

[0043] Example 4

[0044] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0045] 1.819 g of vanadium oxide, 49.236 g of cerium oxide, 12.091 g of magnesium oxide, and 16.529 g of titanium oxide were dissolved in 200 mL of 10% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 8.5 and then subjected to filtration, drying (at 150℃ for 24 h), crushing, and grinding to obtain vanadium nitrate with a particle size of 200 mesh, cerium nitrate with a particle size of 325 mesh, magnesium nitrate with a particle size of 350 mesh, and titanium nitrate with a particle size of 325 mesh.

[0046] The above-mentioned vanadium nitrate, cerium nitrate, magnesium nitrate, and titanium nitrate were mixed and then subjected to a first roasting (temperature 400℃, time 6h, heating rate 15℃ / min). The product of the first roasting was then mixed with guar gum powder (3.2wt% of the product of the first roasting) and 70mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 2.5mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 36h. When the moisture content was found to be less than 30%, it was air-dried and then transferred to a drying oven for further drying at 120℃ hot air for 32h. When the moisture content was found to be less than 6%, the material was then subjected to a second roasting (temperature 560℃, time 8h, heating rate 15℃ / min) to obtain the desulfurizing agent. The structural formula of this desulfurizing agent is V. 0.2 Ce3Mg3Ti 2.3 O 14.1 The volume of pores with a diameter less than 2.2 nm accounted for 3.8% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounted for 32% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounted for 64.2% of the total pore volume.

[0047] Example 5

[0048] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0049] 18.188 g of vanadium oxide, 84.543 g of cesium oxide, 6.046 g of magnesium oxide, and 15.294 g of aluminum oxide were dissolved in 360 mL of 8% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 7.2, and then the mixtures were sequentially filtered, dried once (at 150℃ for 26 h), crushed, and ground to obtain vanadium nitrate with a particle size of 325 mesh, cesium nitrate with a particle size of 200 mesh, magnesium nitrate with a particle size of 400 mesh, and aluminum nitrate with a particle size of 325 mesh.

[0050] The above-mentioned vanadium nitrate, cesium nitrate, magnesium nitrate, and aluminum nitrate were mixed and then subjected to a first roasting (temperature 350℃, time 6h, heating rate 12℃ / min). The product of the first roasting was then mixed with guar gum powder (3.7wt% of the product of the first roasting) and 93mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 2.5mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 36h. When the moisture content was found to be less than 30%, it was air-dried and then transferred to a drying oven for further drying at 120℃ hot air for 28h. When the moisture content was found to be less than 6%, the material was then subjected to a second roasting (temperature 580℃, time 6h, heating rate 10℃ / min) to obtain a desulfurizing agent. The structural formula of this desulfurizing agent is V2Cs6Mg. 1.5 Al3O 23 The volume of pores with a diameter less than 2.2 nm accounts for 3.5% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounts for 38% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounts for 58.5% of the total pore volume.

[0051] Example 6

[0052] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0053] 8.145 g of lanthanum oxide, 16.412 g of cerium oxide, 11.215 g of calcium oxide, and 10.780 g of titanium oxide were dissolved in 120 mL of 10% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 9.0 and then subjected to filtration, drying (at 150℃ for 28 h), crushing, and grinding to obtain lanthanum nitrate with a particle size of 325 mesh, cerium nitrate with a particle size of 400 mesh, calcium nitrate with a particle size of 325 mesh, and titanium nitrate with a particle size of 325 mesh.

[0054] The above-mentioned lanthanum nitrate, cerium nitrate, calcium nitrate, and titanium nitrate were mixed and then subjected to a first calcination (temperature 380℃, time 3.5h, heating rate 20℃ / min). The product of the first calcination was then mixed with guar gum powder (3.2wt% of the product) and 77mL of water in a mixer. The mixture was then transferred to a kneader to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 2.3mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 32h. When the moisture content was less than 30%, it was air-dried and then transferred to a drying oven for further drying at 150℃ hot air for 26h. When the moisture content was less than 6%, the material was then subjected to a second calcination (temperature 580℃, time 5.5h, heating rate 18℃ / min) to obtain the desulfurizing agent. The structural formula of the desulfurizing agent is La. 0.5 Ce1Ca2Ti 1.5 O 7.75 The volume of pores with a diameter less than 2.2 nm accounts for 3% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounts for 35% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounts for 62% of the total pore volume.

[0055] Example 7

[0056] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0057] 1.819 g of vanadium oxide, 42.272 g of cesium oxide, 12.091 g of magnesium oxide, and 16.529 g of titanium oxide were dissolved in 200 mL of 10% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 8.5 and then subjected to filtration, drying (treatment temperature 150℃, treatment time 24 h), crushing, and grinding to obtain vanadium nitrate with a particle size of 200 mesh, cesium nitrate with a particle size of 325 mesh, magnesium nitrate with a particle size of 350 mesh, and titanium nitrate with a particle size of 325 mesh.

[0058] The above-mentioned vanadium nitrate, cesium nitrate, magnesium nitrate, and titanium nitrate were mixed and then subjected to a first roasting (temperature 400℃, time 6h, heating rate 15℃ / min). The product of the first roasting was then mixed with guar gum powder (3.2wt% of the product of the first roasting) and 70mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 2.5mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 36h. When the moisture content was less than 30%, it was air-dried and then transferred to a drying oven for further drying at 120℃ hot air for 32h. When the moisture content was less than 6%, the material was then subjected to a second roasting (temperature 560℃, time 8h, heating rate 15℃ / min) to obtain the desulfurizing agent. The structural formula of this desulfurizing agent is V. 0.2 Cs3Mg3Ti 2.3 O 14.1 The volume of pores with a diameter less than 2.2 nm accounts for 3.5% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounts for 31% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounts for 65.5% of the total pore volume.

[0059] Example 8

[0060] The example provides a method for preparing a desulfurizing agent, comprising the following steps:

[0061] 1.819 g of vanadium oxide, 42.272 g of cerium oxide, 12.091 g of magnesium oxide, and 11.725 g of aluminum oxide were dissolved in 200 mL of 10% dilute nitric acid to form corresponding mixtures. The pH of each mixture was adjusted to 8.5 and then subjected to filtration, drying (treatment temperature 150℃, treatment time 24 h), crushing, and grinding to obtain vanadium nitrate with a particle size of 200 mesh, cerium nitrate with a particle size of 325 mesh, magnesium nitrate with a particle size of 350 mesh, and aluminum nitrate with a particle size of 325 mesh.

[0062] The above-mentioned vanadium nitrate, cerium nitrate, magnesium nitrate, and aluminum nitrate were mixed and then subjected to a first roasting (temperature 400℃, time 6h, heating rate 15℃ / min). The product of the first roasting was then mixed with guar gum powder (3.2wt% of the product of the first roasting) and 70mL of water in a mixer. The mixed material was then transferred to a kneader for kneading to agglomerate the powder particles. The agglomerated material was then transferred to an extruder and extruded into strips using a 2.5mm diameter perforated plate. The formed material was then placed in a dry and ventilated place for 36h. When the moisture content was found to be less than 30%, it was air-dried and then transferred to a drying oven for further drying at 120℃ hot air for 32h. When the moisture content was found to be less than 6%, the material was then subjected to a second roasting (temperature 560℃, time 8h, heating rate 15℃ / min) to obtain the desulfurizing agent. The structural formula of this desulfurizing agent is V. 0.2 Ce3Mg3Al 2.3 O 12.95 The volume of pores with a diameter less than 2.2 nm accounted for 3.7% of the total pore volume, the volume of pores with a diameter between 2.2 and 5.5 nm accounted for 33% of the total pore volume, and the volume of pores with a diameter greater than 5.5 nm but less than 100 nm accounted for 63.3% of the total pore volume.

[0063] Comparative Example 1

[0064] A comparative example provides a method for preparing modified activated carbon, comprising the following steps:

[0065] 100 mL of activated carbon was soaked in a mixed solution of 200 mL of magnesium nitrate (12% by mass) and calcium nitrate (8% by mass) for 12 h, drained for 8 h, dried at 80 °C for 24 h, and calcined at 500 °C for 4.2 h under a nitrogen atmosphere to obtain the modified activated carbon sample.

[0066] Comparative Example 2

[0067] A comparative example provides a method for preparing a modified molecular sieve, comprising the following steps:

[0068] 100 mL of molecular sieve (4A) was immersed in a mixed solution of 200 mL of lanthanum nitrate (8% by mass), magnesium nitrate (15% by mass), and cerium nitrate (6% by mass) for 4 h, drained for 12 h, dried at 120 °C for 36 h, and calcined at 560 °C for 3.8 h in an oxygen atmosphere to obtain the modified molecular sieve sample.

[0069] Performance evaluation:

[0070] The effectiveness of oxidation and adsorption treatment was verified using flue gas emitted by a chemical plant as raw material. The sulfur dioxide concentration in the flue gas was 3000–6000 mg / m³. 3The oxygen content is 5-8%, the water content is 10-20%, and the flue gas flow rate is 5000 Nm³. 3 / h. Table 1 shows the comparison data of sulfur dioxide treatment before and after treatment. The sulfur dioxide removal rate is calculated as η = (C0 - C) / C0 × 100%, where C0 is the sulfur dioxide concentration at the adsorption inlet of the adsorbent (mg / m³). 3 C represents the sulfur dioxide concentration at the adsorbent outlet (mg / m³). 3 ); Where C0 is the sulfur dioxide concentration at the adsorbent inlet, C is the sulfur dioxide concentration at the adsorbent outlet, T is the treatment time (h), and V is the flue gas flow rate (Nm³). 3 / h); m cat. The mass (g) of the desulfurizing agent.

[0071] Table 1

[0072]

[0073] Compared with existing conventional modified activated carbon and modified molecular sieves, the desulfurizing agent of the present invention has a high sulfur dioxide removal rate and a high sulfur capacity.

[0074] Furthermore, increasing the pH value of the mixture to a certain extent, the primary drying temperature, secondary drying temperature, primary calcination temperature, and secondary calcination temperature will reduce the pore volume with a pore size of 5.5–100 nm, leading to increased resistance to gas diffusion during the catalytic reaction, decreased desulfurization performance, and slightly reduced sulfur capacity of the adsorbent. Therefore, Example 2 is slightly better than Example 1, and Example 4 is slightly better than Example 5.

[0075] Furthermore, compared with alkaline earth metal Cs, V, La and rare earth metal Ce have a strong synergistic catalytic effect, which can significantly accelerate the oxidation of free radicals in the reaction process of acidic gas sulfur dioxide, and improve the sulfur capacity of the adsorbent. Therefore, Example 2 is better than Example 3, and Example 4 is better than Example 7.

[0076] Furthermore, compared with rare earth metal La, transition metal V has a stronger synergistic catalytic effect with rare earth metal Ce, which can accelerate the reaction and promote the redox reaction. Therefore, Example 4 is superior to Example 2. Alumina and titanium oxide both play a role in supporting the framework structure of the desulfurization adsorbent. The influence of these two metal oxides on the pore structure of the desulfurization adsorbent is relatively weak. Under the condition that the contents of the other three metal oxides are kept constant, the sulfur capacity of the desulfurization adsorbents in Example 4 and Example 8 is not much different.

Claims

1. A desulfurizing agent, wherein, The structural formula is X n1 Y n2 Z n3 M n4 O n5 In the formula, X represents La and / or V, Y represents Ce and / or Cs, Z represents Ca and / or Mg, and M represents Al and / or Ti; 0 < n1 ≤ 2, 0 < n2 ≤ 6, 0 < n3 ≤ 3, 0 < n4 ≤ 3, and n5 satisfies the balance between the positive and negative valence states of the desulfurizing agent; The desulfurizing agent has a porous structure. In the desulfurizing agent, the volume of pores with a diameter of less than 2.2 nm accounts for 3-4% of the total pore volume, the volume of pores with a diameter of 2.2-5.5 nm accounts for 25-40% of the total pore volume, and the volume of pores with a diameter of greater than 5.5 nm and less than 100 nm accounts for 56-72% of the total pore volume.

2. The desulfurizing agent according to claim 1, wherein, 0.2≤n1≤2, 0.5≤n2≤6, 1≤n3≤3, 0.6≤n4≤3, and n5 satisfy the balance of positive and negative valence states of the desulfurizing agent.

3. The desulfurizing agent according to claim 1, wherein, The desulfurizing agent has the structural formula La. 0.5 Ce1Ca2Ti 1.5 O 7.75 La 1.5 Cs 0.5 Ca1Al 0.6 O 5.15 V 0.2 Cs3Mg3Ti 2.3 O 14.1 V 0.2 Ce3Mg3Al 2.3 O 12.95 or V2Cs6Mg 1.5 Al3O 23 .

4. A method for preparing a desulfurizing agent according to any one of claims 1 to 3, wherein, Includes the following steps: The oxides of element X, element Y, element Z, and element M are dissolved in dilute nitric acid to form nitric acid solutions of element X, element Y, element Z, and element M, respectively. The pH values ​​of the nitric acid solutions of element X, element Y, element Z, and element M were adjusted to 7-9 respectively, and then sequentially subjected to filtration, drying, crushing, and grinding to obtain intermediate products of element X, element Y, element Z, and element M. The intermediate products of element X, element Y, element Z and element M are mixed and then calcined once to obtain a calcined product. The desulfurizing agent is obtained by mixing the primary roasting product, pore-forming agent, and water, followed by kneading, molding, secondary drying, and secondary roasting.

5. The method for preparing the desulfurizing agent according to claim 4, wherein, The temperature of the first roasting is 300-400℃, and the time is 3-6 hours.

6. The method for preparing the desulfurizing agent according to claim 5, wherein, The heating rate from 15-25°C to the temperature of the first firing is 10-25°C / min.

7. The method for preparing the desulfurizing agent according to claim 4, wherein, The secondary roasting temperature is 500-600℃, and the time is 4-12 hours.

8. The method for preparing the desulfurizing agent according to claim 7, wherein, The heating rate from 15 to 25°C to the secondary calcination temperature is 10 to 20°C / min.

9. The method for preparing the desulfurizing agent according to claim 4, wherein, The pore-forming agent is selected from one or more of the following: guar gum, polyacrylamide, graphite, cellulose, citric acid, acetic acid, and oxalic acid.

10. The method for preparing the desulfurizing agent according to claim 4, wherein, The amount of the pore-forming agent is 1 to 6% of the total weight of the primary calcination product.

11. The method for preparing the desulfurizing agent according to claim 4, wherein, The primary drying process is carried out at a temperature of 50–150°C for 24–36 hours.

12. The method for preparing the desulfurizing agent according to claim 4, wherein, The moisture content of the material after the secondary drying is controlled to be less than 6%.

13. The application of any one of the desulfurizing agents according to claims 1 to 3 in flue gas desulfurization.

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