A steel slag gradient distribution anti-co2 poisoning blast furnace gas desulfurization catalyst and a preparation method thereof

Abstract

The application discloses a kind of steel slag gradient distribution's anti CO2 poisoning blast furnace gas desulfurization catalyst and its preparation method, belong to blast furnace gas hydrolysis catalysis field.For the problem that CO2 in blast furnace gas is easy to make CoO active site poisoning inactivation, the application will steel slag with the way that concentration gradually reduces from particle surface to center gradient distribution, utilize CaO in outer layer high concentration steel slag and CO2 reaction to generate CaCO3, and physically isolate CO2 and inner layer active site.Catalyst includes steel slag, γ-Al2O3 carrier and the active component of CoO and CeO2 distributed in the inside, steel slag total mass accounts for 2-8% of total mass of catalyst, steel slag ratio in outer layer 50 μm range is >60%.Its preparation method is: pretreated γ-Al2O3 is immersed in low, medium, high concentration steel slag suspension in turn to build concentration gradient, then immerse cobalt cerium mixed solution and calcine.The application has novel structure, effectively blocks CO2 poisoning, steel slag is low in amount and realizes waste treatment with waste, with excellent desulfurization performance.

Description

Technical Field

[0001] This invention relates to the field of hydrolysis catalysis of blast furnace gas, specifically to a blast furnace gas desulfurization catalyst with steel slag gradient distribution that resists CO2 poisoning and its preparation method. Background Technology

[0002] Blast furnace gas is the largest by-product gas produced by steel enterprises, widely used in hot blast stoves, rolling mill heating furnaces, and self-owned power plants. Blast furnace gas contains sulfides such as COS (carbonyl sulfide) and H2S, which produce SO2 upon combustion, making it a significant source of air pollution from steel enterprises. With the promulgation of the "Opinions on Promoting the Implementation of Ultra-Low Emissions in the Steel Industry" (Environmental Protection and Control

[2019] No. 35), the SO2 emission limit for blast furnace hot blast stoves was set at 50 mg / Nm³. 3 The SO2 emission limit for gas-fired boilers in self-owned power plants is 35 mg / Nm³. 3 Fine desulfurization of blast furnace gas has become an urgent need for the green transformation of the steel industry.

[0003] The sulfides in blast furnace gas are mainly organic sulfur (COS) (accounting for approximately 60%-70%), with inorganic sulfur (H2S) as a secondary component. Currently, COS hydrolysis catalysis technology is one of the most effective desulfurization routes. Commonly used hydrolysis catalysts use γ-Al2O3 as a support, loading active components such as CoO. However, blast furnace gas contains 16%-20% CO2, which reacts with CoO to form CoCO3, occupying active sites and causing rapid catalyst deactivation.

[0004] Steel slag is a major solid waste generated during steelmaking. Its main chemical components are CaO, SiO2, and Fe2O3, and it has a porous structure and an alkaline surface. The CaO in steel slag can react with CO2 through carbonation to form stable CaCO3, thus blocking the poisoning of active sites by CO2. Meanwhile, steel slag has been studied as a catalyst carrier or additive in fields such as flue gas denitrification and catalytic combustion. In existing technologies, steel slag is mainly distributed in catalysts in two ways: one is uniform mixing, such as in Chinese patent (CN117504931A), where steel slag powder is uniformly mixed and dispersed with active components, and steel slag and CoO are randomly distributed, allowing CO2 to contact CoO at any point inside the catalyst; the other is core-shell coating, such as the porous core-shell Fenton catalyst disclosed in Chinese patent (CN118204088A), where both the core and shell contain steel slag, with the shell components concentrated on the outer layer and a clear physical interface between them and the core. This is an abrupt rather than a continuous gradient distribution, resulting in weak interlayer bonding and a tendency for shell peeling during long-term operation. Furthermore, the lack of a concentration transition region leads to a decrease in outer layer porosity and an increase in mass transfer resistance. More importantly, there has never been a report in existing technologies of distributing steel slag in catalyst particles in a manner where the concentration gradually decreases from the outside to the inside.

[0005] To address the aforementioned technological gaps, this invention proposes a blast furnace gas desulfurization catalyst with a gradient distribution of steel slag to resist CO2 poisoning. For the first time, steel slag is distributed in the catalyst particles with a concentration that gradually decreases from the outside to the inside. The high concentration of steel slag in the outer layer preferentially captures CO2, protecting the active sites of CoO in the inner layer from poisoning, while simultaneously realizing the resource utilization of steel slag solid waste. Summary of the Invention

[0006] In existing desulfurization catalysts, CO2 and COS compete for adsorption on the catalyst surface. CO2 preferentially occupies the active sites of CoO to generate CoCO3, leading to rapid catalyst deactivation. This invention proposes a catalyst with a steel slag concentration gradient structure, in which the steel slag concentration gradually decreases from the surface to the center of the catalyst particles. The high concentration of steel slag in the outer layer preferentially captures CO2, while the inner CoO catalyzes the hydrolysis of COS, structurally blocking the poisoning of active sites by CO2.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a blast furnace gas desulfurization catalyst with steel slag gradient distribution to resist CO2 poisoning, wherein the catalyst is granular and contains steel slag and catalytically active components, and the concentration of steel slag in the catalyst particles gradually decreases from the particle surface to the center.

[0008] Preferably, the mass of steel slag within the outer 50 μm layer of the catalyst particles accounts for more than 60% of the total mass of steel slag.

[0009] Preferably, the total mass of the steel slag accounts for 2-8% of the total mass of the catalyst.

[0010] Preferably, the catalytically active components are CoO and CeO2, distributed in the internal region of the catalyst particles, with the CoO loading being 5-15% of the total catalyst mass and the CeO2 loading being 1-5% of the total catalyst mass.

[0011] Preferably, the catalyst support is γ-Al2O3.

[0012] Preferably, the average particle size of the steel slag is 50-300 nm, and the specific surface area of ​​the γ-Al₂O₃ support is 200-300 m². 2 / g.

[0013] The present invention also provides a method for preparing the above-mentioned catalyst, the specific steps of which are as follows:

[0014] S1 support pretreatment: Dry the γ-Al2O3 support at 100-120℃ for 10-14 h;

[0015] Construction of S2 steel slag gradient distribution: Pretreated γ-Al2O3 was sequentially impregnated in steel slag suspensions with mass fractions of 0.1-0.3%, 0.4-0.6%, and 0.8-1.2%, respectively. After each impregnation, the suspension was dried at 60-80℃ for 20-40 min, so that the total mass of steel slag accounted for 2-8% of the total mass of the catalyst.

[0016] S3 Active component loading: The material obtained in step S2 is impregnated in a mixed solution of cobalt nitrate hexahydrate and cerium nitrate, wherein the concentration of Co ions is 0.5-1.2 mol / L and the concentration of Ce ions is 0.05-0.15 mol / L. The pH is adjusted to 8.0-9.0 with alkaline solution, and the mixture is impregnated at 50-70℃ for 3-6 h. After filtration, the mixture is dried at 100-120℃ for 10-14 h.

[0017] S4 Calcination: The material obtained in step S3 is heated to 350-450℃ under N2 atmosphere at a heating rate of 0.5-2℃ / min and calcined at a constant temperature for 2-4 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. Structural innovation: For the first time, steel slag is distributed in the catalyst particles in a gradient manner with the concentration gradually decreasing from the outside to the inside, which is different from the uniform mixing or uniform coating in the existing technology.

[0020] 2. Innovative anti-poisoning mechanism: Utilizing the high concentration of steel slag in the outer layer to preferentially capture CO2, physically isolating CO2 from the active sites of CoO, blocking CO2 poisoning at the source, rather than relying on chemical tolerance or external assistance.

[0021] 3. Low steel slag usage: The steel slag usage is only 2-8%, which is much lower than the existing steel slag desulfurization technology (40-80%), avoiding pore blockage and maintaining a high specific surface area and space velocity tolerance.

[0022] 4. Solid waste resource utilization: Steel slag from steelmaking is used for desulfurization of blast furnace gas, realizing waste treatment. Attached Figure Description

[0023] Figure 1 This is a diagram of the internal structure of the catalyst. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The steel slag used in this invention is taken from the converter steelmaking process of an iron and steel enterprise, and its main chemical composition is shown in Table 1.

[0026] Table 1. Chemical composition of steel slag (mass fraction / %)

[0027] content 39.91 31.31 12.72 4.31 3.69 2.87 5.19

[0028] To compare the desulfurization performance of different types of catalysts, this patent uses the COS hydrolysis rate (φ) COS ), catalyst desulfurization rate (D) S The catalyst was evaluated using COS hydrolysis rate and breakthrough sulfur capacity S. COS hydrolysis rate represents the proportion of H2S converted during the reaction, calculated using equation (1); catalyst desulfurization rate represents the sulfur removal rate during the reaction, calculated using equation (2); breakthrough sulfur capacity S represents the total mass of sulfur removed per unit mass of catalyst within a certain time, calculated using equation (3). To facilitate the evaluation of the desulfurization activity of catalysts doped with different metal oxides, the time corresponding to maintaining COS hydrolysis rate and catalyst desulfurization rate above 90% was defined as the high hydrolysis activity time and the high activity desulfurization time, respectively.

[0029] (1)

[0030] (2)

[0031] (3)

[0032] In the formula, C0 represents the mass concentration of COS in the intake air, in mg / m³. 3 C COS-t This represents the mass concentration of COS in the exhaust gas at time t, in mg / m³. 3 ; The mass concentration of H2S in the exhaust gas at time t is expressed in mg / m³. 3 S represents the breakthrough sulfur capacity of the catalyst, mg·S / g; Q represents the gas flow rate at the inlet, mL / min; t0 represents the time when the catalyst desulfurization rate is maintained above 90%, min; M represents the catalyst mass, g.

[0033] Example 1 (Concentration gradient structure catalyst of the present invention)

[0034] (1) Pretreatment of the support: 100g of γ-Al2O3 was dried at 110℃ for 12 hours to obtain pretreated γ-Al2O3. The specific surface area of ​​the γ-Al2O3 support was 200-300 m². 2 / g 。

[0035] (2) Steel slag preparation: Steel slag was ball-milled to an average particle size of 120 nm, and steel slag aqueous suspensions of 1.0 wt%, 0.5 wt%, and 0.2 wt% were prepared respectively.

[0036] (3) Gradient impregnation: Take 50 g of pretreated γ-Al2O3, first impregnate it in 0.2 wt% steel slag suspension, stir for 30 minutes, filter, and dry at 80℃ for 30 minutes; then impregnate it in 0.5 wt% steel slag suspension, stir for 30 minutes, filter, and dry at 80℃ for 30 minutes; finally impregnate it in 1.0 wt% steel slag suspension, stir for 30 minutes, filter, and dry at 80℃ for 30 minutes. The total mass percentage of steel slag is 5.2%.

[0037] (4) Loading of active components: The above materials were immersed in 200 mL of a mixed solution containing cobalt nitrate hexahydrate (0.9 mol / L) and cerium nitrate (0.09 mol / L), the pH was adjusted to 8.5 with ammonia, the materials were immersed at 60℃ for 4 hours, filtered, and dried at 110℃ for 12 hours.

[0038] (5) Calcination: The temperature was increased to 380°C at 1°C / min under N2 atmosphere and calcined at a constant temperature for 3 hours to obtain the catalyst.

[0039] Example 2 (Effect of different total steel slag usage)

[0040] The catalyst was prepared according to the method in Example 1. The concentration of the staged suspension was adjusted to achieve a total steel slag mass percentage of 2%, 3.8%, 5.2%, and 8%, respectively. Test conditions were the same as the comparative example. 5 g of catalyst was loaded into a fixed-bed reactor, and simulated blast furnace gas (COS 200 mg / m³) was introduced. 3 (CO2 20%, H2O 5%, N2 equilibrium), at 70℃ and space velocity 12000 h⁻¹ -1 Tested under the specified conditions.

[0041] Comparative Example 1 (Traditional homogeneous mixed catalyst)

[0042] 76 parts of γ-Al2O3, 5 parts of steel slag, 9 parts of cobalt nitrate hexahydrate, and 3 parts of cerium nitrate were mixed evenly, and an appropriate amount of water was added to form a slurry. After impregnation and loading, the mixture was dried at 110℃ for 12 hours and calcined at 450℃ for 2 hours under N2 atmosphere to obtain a traditional uniformly mixed desulfurization catalyst.

[0043] Comparative Example 2 (Physically Partitioned Catalyst)

[0044] Core particles were prepared according to the method in Example 1: 76 parts γ-Al₂O₃, 9 parts cobalt nitrate hexahydrate, and 3 parts cerium nitrate. 5 parts steel slag were mixed with 10 parts γ-Al₂O₃, and a binder was added to coat the surface of the core particles, resulting in a shell-to-core mass ratio of 4:1. The mixture was dried at 110°C for 12 hours and calcined at 450°C for 2 hours under a N₂ atmosphere to obtain a physically partitioned desulfurization catalyst. In this catalyst, the steel slag is concentrated in the outer shell layer, and there is a clear physical boundary between the shell and the core, with no concentration gradient transition.

[0045] Comparative Example 3 (Comparison of excessive steel slag usage)

[0046] The catalyst was prepared according to the method of Example 1, with the total mass of steel slag accounting for 12%, and the other conditions were the same as in Example 1.

[0047] Test Results

[0048] Table 2 Comparison of catalyst performance under different steel slag dosages

[0049] 2% 72% 19.87 232 3.8% 70% 21.56 258 5.2% 68% 22.48 276 8% 65% 21.93 268 Comparative Example 1 — 15.82 186 Comparative Example 2 100% 17.23 210 Comparative Example 3 (12%) 60% 18.42 208

[0050] (1) As shown in Table 2, the breakthrough sulfur capacity (22.48 mg·S / g) of the concentration gradient structure catalyst of the present invention is 42.1% higher than that of Comparative Example 1 (uniform mixing, 15.82 mg·S / g) and 30.5% higher than that of Comparative Example 2 (physical partitioning, 17.23 mg·S / g);

[0051] (2) The amount of steel slag can achieve the effect of resisting CO2 poisoning in the range of 2-8%, with 5.2% being the optimal amount. Excessive amount will lead to pore blockage and performance degradation.

[0052] (3) When the proportion of steel slag in the 50 μm range of the surface is 65-75%, the catalyst’s sulfur penetration capacity and high-activity desulfurization time reach the optimal.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A blast furnace gas desulfurization catalyst with steel slag gradient distribution for resistance to CO2 poisoning, characterized in that, The catalyst is granular and contains steel slag and catalytically active components. The concentration of steel slag in the catalyst particles gradually decreases from the particle surface to the center.

2. The catalyst according to claim 1, characterized in that, The mass of steel slag within the outer 50 μm layer of the catalyst particles accounts for more than 60% of the total steel slag mass.

3. The catalyst according to claim 1, characterized in that, The total mass of the steel slag accounts for 2-8% of the total mass of the catalyst.

4. The catalyst according to claim 1, characterized in that, The catalytically active components are CoO and CeO2, which are distributed in the internal region of the catalyst particles. The CoO loading is 5-15% of the total catalyst mass, and the CeO2 loading is 1-5% of the total catalyst mass.

5. The catalyst according to claim 1, characterized in that, The catalyst support is γ-Al2O3.

6. The catalyst according to claim 5, characterized in that, The steel slag has an average particle size of 50-300 nm, and the γ-Al₂O₃ support has a specific surface area of ​​200-300 m². 2 / g.

7. A method for preparing a catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: S1 support pretreatment: Dry the γ-Al2O3 support at 100-120℃ for 10-14 h; Construction of S2 steel slag gradient distribution: Pretreated γ-Al2O3 was sequentially impregnated in steel slag suspensions with mass fractions of 0.1-0.3%, 0.4-0.6%, and 0.8-1.2%, respectively. After each impregnation, the suspension was dried at 60-80℃ for 20-40 min, so that the total mass of steel slag accounted for 2-8% of the total mass of the catalyst. S3 Active component loading: The material obtained in step S2 is impregnated in a mixed solution of cobalt nitrate hexahydrate and cerium nitrate, wherein the concentration of Co ions is 0.5-1.2 mol / L and the concentration of Ce ions is 0.05-0.15 mol / L. The pH is adjusted to 8.0-9.0 with alkaline solution, and the mixture is impregnated at 50-70℃ for 3-6 h. After filtration, the mixture is dried at 100-120℃ for 10-14 h. S4 Calcination: The material obtained in step S3 is heated to 350-450℃ under N2 atmosphere at a heating rate of 0.5-2℃ / min and calcined at a constant temperature for 2-4 hours.

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