A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide

Abstract

This application relates to the technical field of chemical catalytic reaction engineering, and specifically discloses a fixed-bed conversion system for the catalytic oxidation of sulfur dioxide, including a reactor shell with multiple catalytic beds inside. An isothermal module is provided in the high-exothermic bed section, which is composed of multiple isothermal liners and a main catalyst layer stacked alternately. The isothermal liners and the main catalyst layer are arranged at intervals along the axial direction of the catalytic bed. In the main catalyst layer, main catalyst particles and inert thermally conductive particles are uniformly co-filled, enhancing the thermal conductivity inside the bed. The system also includes a coupling module, including a catalyst booster layer and a micro-liquid phase absorption unit. A modular cylindrical filling unit includes multiple detachable filling boxes with vents. The control unit includes temperature sensors and a control system arranged within the bed, enabling real-time monitoring and intelligent adjustment of the temperature distribution. This application achieves the effect of uniform temperature distribution within the fixed bed.

Description

Technical Field

[0001] This application relates to the technical field of chemical catalytic reaction engineering, and in particular to a fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide. Background Technology

[0002] The catalytic oxidation of sulfur dioxide (SO2) to sulfur trioxide (SO3) is a core process in sulfuric acid production, smelting flue gas acid production, and deep treatment of sulfur-containing waste gas. With increasingly stringent environmental standards (such as ultra-low emission requirements for SO2 concentration below 10-50 mg / Nm³), industrial converters not only need to achieve a total conversion rate of over 99.7%, but also need to cope with complex operating conditions such as fluctuating inlet gas concentration, gas humidity, and interference from impurities (such as As, Cl, F, and dust). At the same time, they must also consider the isothermal properties of the reactor (to suppress local sintering and deactivation of the catalyst), low pressure to reduce energy consumption, low acid mist emissions, and long-term stable operation.

[0003] Traditional multi-stage fixed-bed conversion processes typically rely on heat exchangers or intermediate absorption towers between the bed layers to remove the heat of reaction and drive equilibrium. However, this method suffers from uneven temperature distribution within the bed. Summary of the Invention

[0004] To address the problem of uneven temperature distribution within existing fixed-bed conversion systems, this application provides a fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide.

[0005] This application provides a fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide, which adopts the following technical solution: A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide, comprising: The reactor shell and one or more catalytic beds sequentially disposed within the reactor shell; An isothermal module, located in a high exothermic bed section within the reactor shell, includes an isothermal liner and a main catalyst layer. Multiple isothermal liners are provided and spaced apart along the axial direction of the catalyst bed. The main catalyst layer includes main catalyst particles and inert thermally conductive particles uniformly co-filled with the main catalyst particles. The isothermal liner and the main catalyst layer are stacked alternately. The coupling module includes a catalyst booster layer disposed upstream of the end section of the catalyst bed, and a micro-liquid phase absorption unit disposed downstream of the end section or integrated with the end section of the catalyst bed. The micro-liquid phase absorption unit is used to remove part of the reaction product SO3. The modular cylindrical filling unit includes multiple independent filling boxes, which are used to house the main catalyst layer, the catalyst booster layer and / or the isothermal liner. The filling boxes are provided with vent holes. The control unit includes multiple temperature sensors installed in the catalyst bed and a control system connected to the temperature sensors. The control system is configured to dynamically adjust the air intake distribution, the inlet temperature of the catalyst bed, and the operating parameters of the micro-liquid phase absorption unit based on the axial and radial temperature distribution information fed back by the temperature sensors, and associate abnormal temperature distribution information with the filling parameters of the corresponding modular cylindrical filling unit.

[0006] By adopting the above technical solutions, the heat transfer efficiency inside the bed is significantly improved and local overheating is avoided through the co-filling structure of isothermal modules and thermally conductive particles; the coupling module further improves the conversion efficiency; modular filling simplifies the maintenance process; and the intelligent control system realizes precise control of the reaction process, thereby improving the overall stability and adaptability of the system. In some embodiments, the isothermal liner has a porous structure, and the isothermal liner is one or more of silicon carbide honeycomb, foam metal, and sintered alumina plate; the porosity of the isothermal liner is 50%-95%, the thickness is 3-20 mm, and the thickness of two adjacent isothermal liners is 50-150 mm. In some embodiments, the inert thermally conductive particles are made of one or more of silicon carbide, α-alumina, cordierite, or mullite; the particle size d_inert of the inert thermally conductive particles and the particle size d_cat of the main catalyst particles satisfy: 0.8≤d_inert / d_cat≤1.2; the volume fraction of the inert thermally conductive particles in the catalyst layer is 5%-30%.

[0007] In some embodiments, the absorbent used in the micro-liquid phase absorption unit is sulfuric acid with a mass fraction of 95%-99%, the liquid-to-gas ratio is 0.2-1.0 L / (1000 Nm³), and the gas-liquid contact time is 0.05-0.5 s.

[0008] In some embodiments, the catalyst booster layer comprises the active component V2O5 and the support SiO2, and is promoted by Cs2O, wherein the Cs2O content is 0.2-0.8 wt%, the equivalent diameter of V2O5 / SiO2 is 2.5-4.0 mm, and the layer thickness is 50-300 mm.

[0009] In some embodiments, the filling box is installed inside the reactor shell and is detachably connected to the reactor shell. The filling box includes a box body, a first support mesh and a second support mesh. The first support mesh and the second support mesh are respectively disposed at both ends of the box body. A receiving cavity is provided between the first support mesh and the second support mesh. The receiving cavity is used to accommodate the main catalyst layer, the catalyst booster layer and / or the isothermal liner.

[0010] In some embodiments, a dust collection drawer is provided at the bottom of the filling box, and a track is provided inside the reactor shell, with the dust collection drawer slidingly engaged with the track.

[0011] In some embodiments, the filling box is made of any one of 316L stainless steel, 904L stainless steel, duplex steel, or enamel-lined steel.

[0012] In some embodiments, 3 to 6 temperature sensors are arranged at intervals along the axial direction of the catalyst bed, and 2 to 4 temperature sensors are arranged at intervals along the radial direction of the catalyst bed; and / or, the temperature sensors include a distributed optical fiber temperature measurement system arranged along the height direction of the catalyst bed.

[0013] In some implementations, the control system is configured to execute a three-level closed-loop control strategy: L1 level radial isothermal closed loop: with the objective function of minimizing the radial temperature difference of a specified temperature measurement section, the opening offset of each radial air inlet regulating valve of the reactor is adjusted. L2 level thermal peak suppression closed loop: When the local temperature in the catalyst bed exceeds the first temperature threshold and the temperature rise rate exceeds the set rate threshold, a small amount of temperature-regulating gas is introduced into the corresponding position, and the control weight of the L1 level closed loop is increased. L3-level outlet temperature stabilization closed loop: After the system experiences a disturbance, the total heat input is adjusted to allow the bed outlet temperature to smoothly recover to the set value.

[0014] Compared with the prior art, this application includes at least one of the following beneficial technical effects: 1. The isothermal liner adopts a porous structure with high porosity, which can ensure gas flow and enhance axial heat transfer. The main catalyst layer is uniformly doped with inert thermally conductive particles, which significantly improves the overall thermal conductivity of the bed, reduces catalyst deactivation caused by local high temperature, and extends catalyst life. 2. The catalyst booster layer uses Cs2O-promoted V2O5 and SiO2, which still have high activity at low temperatures, helping the reaction to move towards equilibrium. The micro-liquid phase absorption unit uses high-concentration sulfuric acid, which selectively absorbs part of SO3 in a very short time, further improving the overall conversion rate of the system. It is especially suitable for low-concentration SO2 and enhances the system's adaptability to intake gas fluctuations. 3. By setting up modular filling boxes, it is easy to fill, replace and clean the catalyst. The bottom of the filling box is equipped with a dust collection drawer, which can be pulled out along the track to clean the accumulated dust, reduce the impact of dust accumulation on the reaction, significantly shorten maintenance time, improve the operating rate of the unit and reduce operation and maintenance costs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the axial fixed-bed reactor in an embodiment of this application.

[0016] Figure 2 This is a schematic diagram of the radial fixed-bed reactor in the embodiments of this application.

[0017] Figure 3 This is a schematic diagram of the filling box structure in an embodiment of this application.

[0018] Figure 4 This is a schematic diagram of the overall process flow of an embodiment of this application.

[0019] Figure 5 This is a schematic diagram of the process of the isothermal liner in the embodiments of this application.

[0020] Figure 6 This is a schematic diagram of the catalyst booster layer in the embodiments of this application.

[0021] Figure 7 This is a temperature control logic diagram in an embodiment of this application.

[0022] In the picture: 1. Reactor shell; 2. Filling box; 21. Box body; 22. First support net; 23. Second support net; 24. Receiving cavity; 25. Baffle; 26. Connecting rod; 27. Inner box; 28. Outer box; 3. Dust collection drawer; 31. Screen. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Furthermore, the character " / " in this document, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0025] Reference Figures 1 to 7This application provides a fixed-bed conversion system for the catalytic oxidation of sulfur dioxide, including a reactor shell 1 with multiple catalytic beds inside. An isothermal module is provided in the high-exothermic bed section, which consists of multiple isothermal liners and a main catalyst layer stacked alternately. The isothermal liners and the main catalyst layer are arranged at intervals along the axial direction of the catalytic beds. In the main catalyst layer, main catalyst particles and inert thermally conductive particles are uniformly co-filled, enhancing the thermal conductivity inside the bed. The system also includes a coupling module, including a catalyst booster layer and a micro-liquid phase absorption unit, used to improve the conversion rate and remove some SO3 at the end of the reaction. A modular cylindrical filling unit includes multiple detachable filling boxes 2, each with vents. The control unit includes temperature sensors and a control system arranged within the bed, enabling real-time monitoring and intelligent adjustment of the temperature distribution. The control system is configured to dynamically adjust the air intake distribution, catalytic bed inlet temperature, and operating parameters of the trace liquid phase absorption unit based on the axial and radial temperature distribution information fed back by the temperature sensor, and to correlate abnormal temperature distribution information with the corresponding filling parameters of the modular cylindrical filling unit. The co-filling structure of the isothermal module and thermally conductive particles significantly improves the heat transfer efficiency inside the bed, avoiding localized overheating; the coupling module further improves the conversion efficiency; modular filling simplifies the maintenance process; and the intelligent control system achieves precise control of the reaction process, improving the overall stability and adaptability of the system.

[0026] Reference Figure 5 Furthermore, the isothermal liner has a porous structure, and is one or more of silicon carbide honeycomb, foamed metal, and sintered alumina plate. The porosity of the isothermal liner is 50%-95%, and the thickness is 3-20 mm. In this embodiment, the porosity is preferably 70%, the thickness is preferably 10 mm, and the spacing between two adjacent isothermal liners is 50-150 mm, preferably 100 mm in this embodiment. The porous structure ensures smooth airflow and enhances the uniform distribution of axial heat. By optimizing the material and structural parameters of the isothermal liner, the axial dispersion capability of the reaction heat is further improved, effectively suppressing the formation of hot spots and extending the catalyst lifespan.

[0027] In some embodiments, the inert thermally conductive particles are made of one or more of silicon carbide, α-alumina, cordierite, or mullite; the particle size d of the inert thermally conductive particles is... inert The particle size d of the main catalyst particles cat Satisfy: 0.8≤d inert / d cat ≤1.2; the volume fraction of inert thermally conductive particles in the main catalyst particles is 5%-30%. This ratio ensures uniform contact and efficient heat conduction between particles. The uniform co-filling of inert thermally conductive particles significantly improves the overall thermal conductivity of the bed, promotes radial temperature homogenization, and reduces catalyst performance degradation caused by local temperature differences.

[0028] The micro-liquid phase absorption unit uses sulfuric acid with a mass fraction of 95%-99% as the absorbent, a liquid-to-gas ratio of 0.2-1.0 L / (1000 Nm³), and a gas-liquid contact time of 0.05-0.5 s. This design efficiently removes the reaction product SO3 without excessively increasing the system pressure drop. By optimizing the absorbent concentration and operating parameters, highly efficient and selective absorption of SO3 is achieved, shifting the reaction equilibrium to the right and further improving the final conversion rate.

[0029] Reference Figure 6 The catalyst booster layer comprises the active component V₂O₅ and the support SiO₂, promoted by Cs₂O, with a Cs₂O content of 0.2-0.8 wt%. The equivalent diameters of V₂O₅ and SiO₂ are 2.5-4.0 mm, and the layer thickness is 50-300 mm. This combination maintains high activity at low temperatures, facilitating complete reaction. The catalyst booster layer provides additional catalytic activity upstream of the final stage, maintaining high conversion rates even under low SO₂ concentrations, and enhancing the system's adaptability to intake gas fluctuations.

[0030] Reference Figure 1 and Figure 3 Furthermore, in some embodiments, in the axial fixed-bed reactor, each loading box 2 includes a box body 21, a first support net 22, and a second support net 23. The first support net 22 and the second support net 23 are respectively disposed at both ends of the box body 21. A receiving cavity 24 is provided between the first support net 22 and the second support net 23. The receiving cavity 24 is used to accommodate the main catalyst layer, the catalyst booster layer, and / or the isothermal liner. A baffle 25 is provided inside the receiving cavity 24. The baffle 25 is horizontally arranged, that is, the baffle 25 is arranged perpendicular to the axis of the box body 21. The baffle 25 can prolong the reaction time in the loading box 2. The first support net 22 and the second support net 23 are detachably connected to the box body 21, specifically by sliding through a sliding groove and a slider. A connecting rod 26 is provided between multiple loading boxes 2, and multiple loading boxes 2 are fixedly connected by the connecting rod 26 to facilitate the assembly and disassembly of the loading box 2 from the reactor shell 1.

[0031] Furthermore, a dust collection drawer 3 is provided at the bottom of the filling box 2, and a track is provided inside the reactor shell 1. The dust collection drawer 3 slides in conjunction with the track, and a screen 31 is provided at the bottom of the dust collection drawer 3. The screen 31 can intercept dust particles while allowing gas to pass through. The dust collection drawer 3 can be slid out along the track for easy cleaning of accumulated dust and replacement of catalyst.

[0032] Reference Figure 2In some embodiments, in a radial fixed-bed reactor, the packing box 2 includes an inner box 27 and an outer box 28. The inner box 27 has multiple internal holes on its sidewall, and the outer box 28 has multiple external holes on its sidewall, with the flow direction from the outside to the inside. A reaction chamber is provided between the outer box 28 and the inner box 27, and the catalyst is placed in the reaction chamber. The packing box 2 is made of any one of 316L stainless steel, 904L stainless steel, duplex steel, or enamel-lined steel; in this embodiment, 316L stainless steel is preferred. The modular packing design significantly simplifies the catalyst replacement and system maintenance process, reduces downtime, and improves the economic efficiency of the unit's operation.

[0033] Temperature sensors are arranged at 3-6 points along the axial direction of the catalytic bed and 2-4 points radially, enabling continuous monitoring of the temperature field across the entire cross-section using a distributed fiber optic temperature measurement system. A fiber optic temperature measurement system is a technology that uses optical fiber itself as a sensor to measure temperature. Instead of connecting numerous independent sensors with a single cable, it transforms the entire optical fiber into a continuous, distributed "thermometer." Fiber optic temperature measurement systems are existing technology and will not be elaborated upon further. The high-density temperature monitoring network provides the control system with accurate temperature distribution data, offering a reliable basis for real-time adjustment and early warning.

[0034] Reference Figure 7 In this embodiment, the control system is configured to execute a three-level closed-loop control strategy: L1 level radial isothermalization closed loop: with minimizing the radial temperature difference of the specified temperature measurement section as the objective function, the opening bias of each radial air inlet regulating valve of the reactor is adjusted; L2 level heat peak suppression closed loop: when the local temperature in the catalyst bed is detected to exceed the first temperature threshold and the temperature rise rate exceeds the set rate threshold, a small amount of temperature regulating gas is introduced into the corresponding position, and the control weight of the L1 level closed loop is increased; L3 level outlet temperature stabilization closed loop: after the system experiences a disturbance, the total heat input is adjusted so that the bed outlet temperature is smoothly restored to the set value.

[0035] The implementation principle of this application embodiment is as follows: Process gas containing SO2 enters the reactor shell 1. The gas is uniformly distributed across the cross-section of the catalyst bed by a radial inlet regulating valve regulated by the control system. The gas first passes through a loading box 2, in which a main catalyst layer and an isothermal liner are alternately stacked. In the main catalyst layer, the gas comes into contact with catalyst particles doped with inert thermally conductive particles, resulting in a strongly exothermic SO2 oxidation reaction. The inert thermally conductive particles rapidly carry away the reaction heat, promoting radial heat diffusion. The isothermal liner, as a highly efficient heat conductor, further smooths out the temperature peak in the axial direction, preventing local overheating. Upstream of the final stage of the reaction, the gas passes through a booster layer containing V2O5 and SiO2 catalysts. This catalyst layer remains highly active at lower temperatures, providing additional driving force for the reaction and further improving the conversion rate. The gas then enters a micro-liquid phase absorption unit, in which a small amount of high-concentration sulfuric acid (95%-99%) is injected as an absorbent, which briefly (0.05-0.5 seconds) comes into countercurrent or cocurrent contact with the gas. Some of the reaction product SO3 is selectively absorbed to form sulfuric acid or fuming sulfuric acid, thereby removing SO3 from the reaction equilibrium.

[0036] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide, characterized in that, include: The reactor shell (1) and one or more catalyst beds sequentially disposed within the reactor shell (1); An isothermal module is provided in the high exothermic bed section inside the reactor shell (1), including an isothermal liner and a main catalyst layer. Multiple isothermal liners are provided and are arranged at intervals along the axial direction of the catalyst bed. The main catalyst layer includes main catalyst particles and inert thermally conductive particles uniformly filled with the main catalyst particles. The isothermal liner and the main catalyst layer are stacked alternately. The coupling module includes a catalyst booster layer disposed upstream of the end section of the catalyst bed, and a micro-liquid phase absorption unit disposed downstream of the end section or integrated with the end section of the catalyst bed, wherein the micro-liquid phase absorption unit is used to remove part of the reaction product SO3. The modular cylindrical filling unit includes multiple independent filling boxes (2), the filling boxes (2) are used to accommodate the main catalyst layer, the catalyst booster layer and / or the isothermal liner, and the filling boxes (2) are provided with vent holes; The control unit includes multiple temperature sensors disposed within the catalytic bed and a control system connected to the temperature sensors. The control system is configured to dynamically adjust the air intake distribution, the catalytic bed inlet temperature, and the operating parameters of the micro-liquid phase absorption unit based on the axial and radial temperature distribution information fed back by the temperature sensors, and to associate abnormal temperature distribution information with the corresponding filling parameters of the modular cylindrical filling unit.

2. The fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The isothermal liner has a porous structure and is one or more of silicon carbide honeycomb, foam metal, and sintered alumina plate; the porosity of the isothermal liner is 50%-95%, the thickness is 3-20 mm, and the thickness of two adjacent isothermal liners is 50-150 mm.

3. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The inert thermally conductive particles are made of one or more of silicon carbide, α-alumina, cordierite, or mullite; the particle size d of the inert thermally conductive particles is... inert The particle size d of the main catalyst particles cat Satisfy: 0.8≤d inert / d cat ≤1.2; the volume fraction of the inert thermally conductive particles in the catalyst layer is 5%-30%.

4. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The absorbent used in the micro-liquid phase absorption unit is sulfuric acid with a mass fraction of 95%-99%, a liquid-to-gas ratio of 0.2-1.0 L / (1000 Nm³), and a gas-liquid contact time of 0.05-0.5 s.

5. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The catalyst booster layer comprises active component V2O5 and support SiO2, and is promoted by Cs2O, wherein the Cs2O content is 0.2-0.8 wt%, the equivalent diameter of V2O5 and SiO2 is 2.5-4.0 mm, and the layer thickness is 50-300 mm.

6. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The filling box (2) is installed inside the reactor shell (1). The filling box (2) is detachably connected to the reactor shell (1). Each filling box (2) includes a box body (21), a first support net (22) and a second support net (23). The first support net (22) and the second support net (23) are respectively disposed at both ends of the box body (21). A receiving cavity (24) is provided between the first support net (22) and the second support net (23). The receiving cavity (24) is used to accommodate the main catalyst layer, the catalyst booster layer and / or the isothermal liner.

7. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 6, characterized in that: The bottom of the filling box (2) is provided with a dust collection drawer (3), and a track is provided inside the reactor shell (1). The dust collection drawer (3) is slidably engaged with the track.

8. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 6, characterized in that: The filling box (2) is made of any one of 316L stainless steel, 904L stainless steel, duplex steel or enamel-lined steel.

9. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The temperature sensors are arranged at intervals of 3 to 6 along the axial direction of the catalyst bed, and at intervals of 2 to 4 along the radial direction of the catalyst bed; and / or, the temperature sensors include a distributed optical fiber temperature measurement system arranged along the height direction of the catalyst bed.

10. A fixed-bed conversion system for the oxygen catalytic oxidation of sulfur dioxide according to claim 1, characterized in that: The control system is configured to execute a three-level closed-loop control strategy: L1 level radial isothermal closed loop: with the objective function of minimizing the radial temperature difference of a specified temperature measurement section, the opening offset of each radial air inlet regulating valve of the reactor is adjusted. L2 level thermal peak suppression closed loop: When the local temperature in the catalyst bed exceeds the first temperature threshold and the temperature rise rate exceeds the set rate threshold, a small amount of temperature-regulating gas is introduced into the corresponding position, and the control weight of the L1 level closed loop is increased. L3-level outlet temperature stabilization closed loop: After the system experiences a disturbance, the total heat input is adjusted to allow the bed outlet temperature to smoothly recover to the set value.

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