Large-scale molten salt chlorination furnace structure optimization design method

Abstract

The present application relates to the technical field of titanium metallurgical equipment design, and specifically discloses a large-scale molten salt chlorination furnace structure optimization design method, which comprises the following steps: S10, establishing an initial three-dimensional geometric model of a furnace body based on design capacity to preliminarily determine the optimization direction of the furnace structure; S20, building a cold-state physical simulation test bench according to the optimized furnace structure of step S10 to simulate a hot-state working condition; S30, iteratively adjusting key structure parameters according to the simulation model calibrated in step S20; S40, integrating the optimized structure parameters determined in step S30 into the three-dimensional model of the furnace body to complete the finalization of the furnace body structure, and performing full-working-condition numerical simulation verification on the complete furnace body structure after finalization to complete the finalization of the structure design. The method of the present application accurately optimizes the furnace structure through CFD three-dimensional modeling, further calibrates key parameters in combination with cold-state physical simulation, realizes sufficient reaction of chlorine gas and titanium slag, uniform and stable flow field in the furnace, and achieves a capacity load of 240 t / d or more.

Description

Technical Field

[0001] This invention belongs to the field of titanium metallurgical equipment design technology, specifically relating to a structural optimization design method for a large molten salt chlorination furnace. Background Technology

[0002] Molten salt chlorination is a core process in sponge titanium production, and the structural design of its core equipment, the molten salt chlorination furnace, directly determines the reaction efficiency between chlorine and titanium slag, titanium yield, and equipment operational stability. With the large-scale development of the titanium industry, the trend towards larger molten salt chlorination furnaces has emerged. However, compared to fluidized bed chlorination technology, existing large molten salt chlorination furnace designs still have the following problems: ① Poor reaction uniformity within the furnace: Traditional molten salt chlorination furnaces often employ a cylindrical structure with equal diameter. After chlorine gas is introduced from the bottom spray gun, localized areas of concentrated airflow are easily formed, leading to insufficient contact between the gas, liquid, and solid phases, resulting in a low titanium yield (usually below 90%) and severe localized overheating, exacerbating furnace lining erosion. ② Lack of scientific basis in structural design: Existing large furnace structure optimization relies heavily on empirical iterations or physical model experiments, resulting in long design cycles and difficulty in accurately matching the flow field and temperature field distribution requirements within the furnace. This leads to multiple modifications after equipment commissioning, resulting in high design and modification costs. ③ Insufficient gas-solid separation efficiency: With the increase in scale, the content of solid particles (such as unreacted titanium slag and carbon particles) entrained in the furnace gas increases. A large number of solid particles enter the dust collection and subsequent washing system, causing equipment blockage and wear, and shortening the service life of subsequent equipment.

[0003] Existing technologies have proposed the use of large-scale molten salt chlorination furnace structures. For example, patent CN202211568842.8 proposes a large-scale molten salt chlorination furnace, the furnace body of which includes an inverted conical platform section at the bottom and a cylindrical section at the top. The angle between the inverted conical platform section and the ground is greater than 70°. The lower end of the inverted conical platform section is equipped with a spray gun for introducing chlorine gas and a bottom salt discharge port. An AC heating electrode is set in the middle of the inverted conical platform section, and a feeding port is set in the middle of the cylindrical section. A flue gas passage is set in the upper part of the cylindrical section. Patent CN20181121705.0 also adopts a variable diameter furnace body composed of a lower conical section and an upper straight cylindrical section. Its core improvement is that a furnace top hopper with a screw feeder is set at the furnace top. By uniformly dispersing a mixture of high-calcium magnesium titanium slag, petroleum coke and sodium chloride salt into the furnace, the uniformity of solid material distribution is improved, and the single furnace capacity reaches 157~200t / d. However, the aforementioned patents all lack quantitative analysis methods for the flow field and temperature field inside the furnace, and the determination of furnace size parameters lacks scientific basis, making it difficult to systematically evaluate and effectively control the uniformity of the reaction inside the furnace. In addition, existing large-scale molten salt chlorination furnaces generally suffer from problems such as difficulty in stabilizing the production capacity load to above 200t / d, low titanium yield, and short furnace life.

[0004] Therefore, developing a structural optimization design method for large-scale molten salt chlorination furnaces, accurately matching key structural parameters, and solving the aforementioned technical defects has significant industrial application value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a structural optimization design method for large-scale molten salt chlorination furnaces. By using CFD three-dimensional modeling to accurately optimize the furnace structure and combining it with cold water simulation to further calibrate key parameters, the method achieves full reaction between chlorine and titanium slag, uniform and stable flow field inside the furnace, and ultimately achieves the goals of a production capacity of over 240 t / d, a titanium yield increase of 3-5%, and a furnace lifespan of over 12 months. At the same time, it shortens the design cycle and reduces design costs.

[0006] To solve at least one of the above-mentioned technical problems, the present invention adopts the following technical solution: According to the present invention, a structural optimization design method for a large molten salt chlorination furnace is provided, applicable to the optimization design of large molten salt chlorination furnaces with a capacity load of 240 t / d or more. The method includes the following steps: S10, establishing an initial three-dimensional geometric model of the furnace body based on the designed capacity, meshing the initial three-dimensional geometric model, and then importing it into simulation software for multi-field coupled numerical simulation to obtain the flow field distribution characteristics inside the furnace, identify dead zones, local overheated areas, and incomplete reaction areas, and preliminarily determine the direction of furnace structure optimization; S20, based on the furnace structure optimized in step S10, building a cold-state physical simulation test bench to simulate hot-state conditions, capturing the flow field distribution through flow field visualization technology, and comparing the flow field distribution data measured by the cold-state physical simulation with the numerical simulation results. If key areas... If the relative error of the flow field parameters exceeds the preset threshold, the boundary conditions and / or physical parameters of the numerical simulation model are corrected until the error is within an acceptable range; S30, the key structural parameters are iteratively adjusted according to the simulation model calibrated in step S20 until the proportion of the dead zone area in the flow field does not exceed 5%, and the optimized structural parameters are determined; S40, the optimized structural parameters determined in step S30 are integrated into the three-dimensional model of the furnace body to complete the furnace body structure finalization, and the finalized complete furnace body structure is verified by full-condition numerical simulation. After confirming that the stability of titanium tetrachloride generation concentration, furnace temperature gradient, and production capacity load all reach the preset target values, the structural design finalization is completed.

[0007] According to an embodiment of the present invention, in step S10, the meshing of the initial three-dimensional geometric model includes: refining the mesh of the furnace reaction area, the nozzle outlet, and the electrode periphery, with a total number of mesh cells of not less than 1.2 million.

[0008] According to an embodiment of the present invention, in step S10, the multi-field coupled numerical simulation adopts the k-ε turbulence model, and the boundary conditions are: furnace wall adiabatic, chlorine inlet flow rate 1~5 kg / s, titanium slag-petroleum coke-sodium chloride mixture feeding rate 1~4 kg / s, initial pressure in the furnace 0.1~0.3 MPa, and initial temperature 700~900℃.

[0009] According to an embodiment of the present invention, in step S10, the multi-field coupling simulation includes the coupling simulation of the flow field, temperature field and concentration field inside the furnace; the flow field distribution characteristics include the gas flow velocity distribution, temperature gradient and titanium tetrachloride generation concentration distribution cloud map inside the furnace.

[0010] According to one embodiment of the present invention, in step S20, the step of constructing a cold-state physical simulation test bench to simulate hot-state conditions includes: constructing a cold-state water simulation test bench at a scale of 1:10 to 50, using water to simulate molten salt, air to simulate chlorine gas, and solid particles to simulate titanium slag-carbon mixtures. The difference in Reynolds number between the cold-state physical simulation and the hot-state conditions is within a predetermined range.

[0011] According to one embodiment of the present invention, in step S30, the key structural parameters include at least one of the following: the height-to-diameter ratio of the straight section of the furnace body, the height-to-diameter ratio of the frustum section, the number and installation angle of the chlorine nozzles, the position of the heating electrode, the position of the feeding port, and the position and angle of the flue gas outlet.

[0012] According to one embodiment of the present invention, in step S30, the optimized structural parameters include: the height-to-diameter ratio of the straight section is 2~4:1; the height-to-diameter ratio of the frustum section is 1.5~2.5:1; and there are 6~8 chlorine nozzles with an angle of 30~75° to the frustum section.

[0013] According to one embodiment of the present invention, in step S40, the furnace body structure is a variable diameter furnace body structure composed of a lower truncated cone and an upper cylinder.

[0014] According to one embodiment of the present invention, a gas-solid separation device optimization step is further included between step S30 and step S40: a cyclone gas-solid separation device is installed at the furnace top outlet, and the inner diameter, guide plate angle and exhaust pipe insertion depth of the separation device are optimized by numerical simulation.

[0015] According to one embodiment of the present invention, the cyclone gas-solid separation device has 3 to 6 spiral guide plates with an inclination angle of 30 to 45°, and a dust discharge port at the bottom that is connected to the furnace body salt discharge system.

[0016] By adopting the above technical solution, the present invention has at least one of the following advantages compared with the prior art: (1) Through dual optimization and calibration of CFD numerical simulation and cold physical simulation, the key structural parameters of the furnace body are accurately matched, so that chlorine gas and titanium slag can form sufficient contact and the reaction uniformity is greatly improved. The large-scale molten salt chlorination furnace optimized by the method of this invention can stably reach a capacity load of more than 240 t / d, and the annual capacity of a single furnace can reach more than 80,000 tons. The titanium yield can be increased to more than 95%, which meets the needs of large-scale production.

[0017] (2) The optimized variable diameter furnace body structure effectively improves the uniformity of the flow field inside the furnace, eliminates local overheating areas, reduces molten salt deterioration and furnace lining erosion caused by uneven temperature distribution, and effectively extends the service life of the furnace body. Combined with the precisely arranged heating electrodes and chlorine nozzles, component wear is effectively reduced, and the service life of the chlorination furnace can be extended to more than 12 months.

[0018] (3) The optimized cyclone gas-solid separation device has an excellent capture effect on solid particles entrained in the furnace gas, which greatly reduces the wear and blockage of the subsequent dust collection and washing system caused by solid particles. The gas-solid separation efficiency is high, the subsequent equipment operates stably, and the overall equipment maintenance cost is reduced.

[0019] (4) The present invention adopts “CFD numerical simulation + cold physical simulation” to replace the traditional experience iteration and full-scale physical model test. The design cycle can be shortened from the traditional 6-8 months to 2-3 months, the design and test costs are reduced by 40-50%, the design cycle is greatly shortened, the economic benefits are significant, and the repeated rectification after the application is avoided, which significantly improves the design economy.

[0020] (5) This invention achieves precise control of the flow field and temperature field in the furnace through dual simulation optimization, reduces parameter fluctuations in the production process, significantly improves the quality stability of titanium tetrachloride products, and has environmental benefits. At the same time, the efficient recycling of solid particles realizes resource recycling, reduces solid waste emissions, and has both environmental and economic benefits.

[0021] (6) The method of the present invention is applicable to the design and modification of various large-scale molten salt chlorination furnaces. The optimized structural parameters can directly guide industrial production, effectively solving the core technical pain points in the large-scale production of titanium tetrachloride manufacturing enterprises. It has strong universality and good prospects for promotion and application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a flowchart of a structural optimization design method for a large molten salt chlorination furnace according to an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0025] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0026] To address the shortcomings of existing large-scale molten salt chlorination furnace structural designs, such as poor reaction uniformity, insufficient gas-solid separation efficiency, limited capacity and service life, as well as the technical deficiencies of traditional design methods that rely on experience iteration, have long design cycles, and are costly, this invention provides a structural optimization design method for large-scale molten salt chlorination furnaces. Through dual optimization and calibration using CFD (Computational Fluid Dynamics) numerical simulation and cold-state physical simulation, precise matching of the flow field, temperature field, and concentration field within the furnace is achieved, thereby increasing capacity, improving titanium yield, extending furnace life, and shortening the design cycle.

[0027] The structural optimization design method for a large molten salt chlorination furnace according to an embodiment of the present invention is applicable to the optimization design of large molten salt chlorination furnaces with a capacity load of 240 t / d or more. Figure 1 As shown, it includes the following steps: S10. Based on the designed capacity, establish an initial three-dimensional geometric model of the furnace body, perform meshing on the initial three-dimensional geometric model, and then import it into simulation software for multi-field coupled numerical simulation to obtain the flow field distribution characteristics inside the furnace, identify dead zones, local overheated areas and incomplete reaction areas, and preliminarily determine the direction of furnace structure optimization. S20. Based on the furnace structure optimized in step S10, a cold physical simulation test bench is built in proportion to simulate hot working conditions. The flow field distribution is captured by flow field visualization technology. The flow field distribution data measured by the cold physical simulation is compared with the numerical simulation results. If the relative error of the flow field parameters in the key area exceeds the preset threshold, the boundary conditions and / or physical parameters of the numerical simulation model are corrected until the error is within an acceptable range. S30. Iteratively adjust the key structural parameters based on the simulation model calibrated in step S20 until the proportion of the dead zone area in the flow field does not exceed 5%, and determine the optimized structural parameters. S40. Integrate the optimized structural parameters determined in step S30 into the three-dimensional model of the furnace body to complete the furnace body structure design. Then, perform full-condition numerical simulation verification on the complete furnace body structure after the design is finalized. After confirming that the stability of titanium tetrachloride production concentration, furnace temperature gradient, and production capacity load have all reached the preset target values, the structural design is finalized.

[0028] Step S10 involves CFD 3D modeling and multi-field coupled simulation. Specifically, 3D modeling software such as SolidWorks is used to create an initial 3D geometric model of the furnace body, including key structures such as the furnace bottom, furnace body (containing straight and conical sections), furnace top, chlorine nozzle mounting holes, heating electrode mounting holes, feeding port, salt discharge port, flue gas discharge port, and gas-solid separation device mounting interface. Preferably, ICEM software is used to mesh the initial model, with mesh refinement applied to key areas such as the furnace body reaction zone, nozzle outlet, and electrode periphery. The total number of mesh cells is no less than 1.2 million to ensure simulation accuracy. In one embodiment of the present invention, the pre-defined mesh model is imported into simulation software such as Fluent, and the physical parameters of the molten salt, chlorine, and titanium slag-carbon mixture are defined, such as density, specific heat capacity, thermal conductivity, and viscosity. The turbulence model is set as the k-ε model, and the boundary conditions can be set as follows: furnace wall adiabatic, chlorine inlet flow rate 1~5 kg / s, titanium slag-petroleum coke-sodium chloride mixture feeding rate 1~4 kg / s, initial furnace pressure 0.1~0.3 MPa, and initial temperature 700~900℃. More specifically, the multi-field coupled simulation includes coupled simulation of the flow field, temperature field, and concentration field inside the furnace, obtaining the gas velocity distribution, temperature gradient, and titanium tetrachloride formation concentration distribution cloud map inside the furnace, identifying dead zones, local overheated areas, and incomplete reaction areas in the flow field, and initially determining the direction of furnace structure optimization.

[0029] In the CFD 3D modeling and multi-field coupled simulation steps, the molten salt chlorination furnace involves gas-liquid-solid three-phase flow, heat transfer, and chemical reactions, with various physical fields coupling and influencing each other. Through CFD numerical simulation, the flow state and reaction process in each region of the furnace can be quantitatively described based on first principles such as mass conservation, momentum conservation, and energy conservation, without relying on empirical assumptions. Mesh refinement ensures the calculation accuracy of key areas such as the high-speed jet region of the nozzle and the strong hot flow region near the electrodes. The k-ε turbulence model can effectively capture the strong swirling and anisotropic turbulence characteristics within the furnace, thus providing a scientific and quantitative basis for subsequent structural optimization and overcoming the blindness of the "black box" operation in traditional empirical design. Through 3D modeling and multi-field coupled simulation, the locations of dead zones, localized overheated regions, and incompletely reacted regions in the furnace flow field can be accurately identified, providing clear guidance for the directional optimization of the furnace structure and avoiding the inefficiency and uncertainty of repeated adjustments required by traditional empirical design.

[0030] Step S20 is the cold-state physical simulation verification and CFD model calibration step. Preferably, a cold-state water simulation test bench is built at a scale of 1:10~50, using water to simulate molten salt, air to simulate chlorine gas, and solid particles to simulate titanium slag-carbon mixtures. More preferably, Particle Image Velocimetry (PIV) technology is used to capture the flow field distribution. The Reynolds number of the cold-state physical simulation and the hot-state operating condition should be approximately similar, i.e., the difference between the two should be within a predetermined range, to ensure that the cold-state simulation results can effectively reflect the flow field characteristics of the hot-state operating condition.

[0031] In one embodiment of the present invention, the flow field distribution data measured by cold physical simulation can be compared with the numerical simulation results. If the relative error of the flow field parameters in the key area exceeds a preset threshold, the boundary conditions and / or physical parameters of the numerical simulation model are corrected until the error is within an acceptable range.

[0032] In the cold-state physical simulation verification and CFD model calibration steps, the Reynolds number is the core dimensionless criterion number characterizing the fluid flow state. Maintaining the Reynolds number between the cold-state simulation and the hot-state operating conditions within a certain range ensures that both have similar flow structures and turbulent characteristics, thus enabling the flow field observation results at the laboratory scale to be effectively mapped to the actual furnace at the industrial scale. PIV technology, by tracking the motion trajectory of tracer particles, can non-contactly acquire the transient velocity distribution of the entire flow field, making it one of the most accurate quantitative testing methods for flow field visualization. Comparing and calibrating PIV measured data with CFD simulation results can correct calculation deviations in the CFD model caused by simplification of physical parameters, boundary condition assumptions, or inherent errors in the turbulence model. Independently verifying and calibrating CFD simulation results through cold-state physical simulation overcomes the model error problems that may exist in relying solely on numerical simulation, significantly improves the reliability of simulation predictions, and ensures the accuracy of subsequent structural optimization directions.

[0033] Step S30 is the iterative optimization step for key structural parameters. Specifically, based on the simulation model calibrated in step S20, the key structural parameters are iteratively adjusted until the dead zone area of ​​the flow field does not exceed 5%, thus determining the optimized structural parameters. The key structural parameters include at least one of the following: the height-to-diameter ratio of the straight section of the furnace body, the height-to-diameter ratio of the frustum section, the number and installation angle of the chlorine nozzles, the position of the heating electrode, the position of the feed port, and the position and angle of the flue gas outlet. Preferably, the optimized structural parameters include: a height-to-diameter ratio of 2~4:1 for the straight section, a height-to-diameter ratio of 1.5~2.5:1 for the frustum section, and 6~8 chlorine nozzles at an angle of 30~75° to the frustum section.

[0034] In the iterative optimization of key structural parameters, the uniformity of the flow field within the furnace directly determines the contact efficiency and reaction saturation between chlorine and titanium slag. The aspect ratio of the straight section affects the residence time and rising velocity distribution of the gas phase within the furnace, while the aspect ratio of the frustum section affects the initial diffusion morphology and molten salt circulation pattern in the bottom jet zone. The number and angle of the nozzles determine the momentum distribution and coverage of the chlorine jet, and the position of the heating electrodes affects the spatial distribution of the temperature field. These structural parameters are interconnected and jointly determine the flow field, temperature field, and concentration field distribution within the furnace. Systematic iterative optimization using a calibrated high-fidelity simulation model allows for a quantitative assessment of the impact weight of each parameter change on the flow field uniformity, gradually approaching the optimal parameter combination. Controlling the dead zone area ratio within 5% means that the effective reaction area within the furnace reaches over 95%, ensuring sufficient contact and reaction of the gas-solid-liquid three phases from a fluid dynamics perspective. This step, driven by iterative optimization based on quantitative indicators (dead zone area ≤ 5%), ensures a uniform distribution of the flow field within the furnace, eliminating potential process hazards such as localized overheating and incomplete reaction from the source, and creating ideal fluid dynamic conditions for the full reaction of chlorine and titanium slag.

[0035] Step S40 involves finalizing the furnace structure and conducting full-condition simulation verification. Specifically, the optimized structural parameters determined in step S30 are integrated into the three-dimensional model of the furnace body to complete the finalization of the furnace structure. The furnace structure is a variable-diameter furnace structure consisting of a lower frustum and an upper cylinder. Full-condition numerical simulation verification is performed on the finalized furnace structure to confirm that the stability of titanium tetrachloride production concentration, furnace temperature gradient, and production capacity load all meet the preset target values, thus completing the structural design finalization.

[0036] In the furnace structure finalization and full-condition simulation verification steps, the design of the variable-diameter furnace structure is based on the fundamental principles of fluid mechanics—the lower conical structure guides and diffuses the chlorine jet entering from the bottom, preventing the high-speed jet from concentrating in the central area of ​​the furnace. This promotes the uniform distribution of the gas flow along the conical surface before entering the upper straight section reaction zone, thereby expanding the gas-solid contact area and extending the gas phase residence time. The upper straight section provides ample reaction space for the countercurrent / cross-flow contact between chlorine and titanium slag. Full-condition simulation verification is a comprehensive evaluation of the design scheme before the final structure is finalized. By simulating the furnace state under different operating conditions, it confirms the stability of the titanium tetrachloride production concentration, the controllability of the furnace temperature gradient, and the achievability of the production capacity load, thus confirming the feasibility of the final scheme in a virtual environment. This step, through full-condition simulation verification, ensures that the finalized furnace structure meets the design specifications under various operating conditions, significantly reducing engineering risks and modification costs.

[0037] In a preferred embodiment of the present invention, a gas-solid separation device optimization step is further included between step S30 and step S40: A cyclone-type gas-solid separator is installed at the furnace top outlet. The inner diameter, guide plate angle, and exhaust pipe insertion depth of the separator are optimized through numerical simulation. The cyclone-type gas-solid separator has 3 to 6 spiral guide plates with an inclination angle of 30 to 45°, and a dust discharge port at the bottom that connects to the furnace body's salt discharge system.

[0038] Large molten salt chlorination furnaces often carry a large amount of solid particles in their flue gas, such as unreacted titanium slag and carbon particles. If these particles enter the subsequent dust collection and scrubbing systems, they can cause equipment blockage and wear. Cyclone separation utilizes the high-speed rotation of the dust-laden airflow guided by spiral guide plates. Solid particles are thrown towards the wall under centrifugal force and fall along the wall into the bottom dust discharge port, thus achieving gas-solid separation. The optimization of the number and angle of the spiral guide plates affects the matching relationship between the tangential and axial velocities of the rotating airflow, determining the dust removal efficiency and pressure drop loss of the separation device. This invention, through CFD simulation optimization, presents a cyclone-type gas-solid separation device that can efficiently capture solid particles in the furnace gas, significantly reducing wear and blockage of subsequent equipment and extending their service life. Simultaneously, the separated and recovered solid particles are connected to the furnace's salt discharge system through the bottom dust discharge port, achieving resource recycling and combining environmental and economic benefits.

[0039] The following is a specific embodiment of a structural optimization design method for a large molten salt chlorination furnace according to the present invention.

[0040] Example This embodiment focuses on a large-scale molten salt chlorination furnace with an annual capacity of 80,000 tons (corresponding to a daily capacity of 240 tons / day). The structural optimization design is carried out using the method of this invention. The specific steps are as follows: S10, CFD 3D Modeling and Multi-Field Coupled Simulation: The initial furnace body model was established using SolidWorks, with an initial design height of 14m, an inner diameter of 4m for the straight section, and a bottom diameter of 5m for the conical section. The mesh was generated using ICEM, with the mesh size in the reaction region refined to 20mm and a total of 1.35 million mesh elements. The model was imported into Fluent software, with the chlorine inlet flow rate set to 3kg / s, the titanium slag-carbon mixture feeding rate set to 2kg / s, and the initial pressure and temperature inside the furnace set to 0.2MPa and 750℃. The simulation revealed two dead zones in the initial flow field and a local temperature deviation of 45℃. The optimization directions for the straight section height-to-diameter ratio and the conical section angle were preliminarily determined.

[0041] S20, Cold Water Simulation Optimization and Key Parameter Calibration: A cold water simulation test bench was built at a 1:20 scale. A water-air-solid particle system was used to simulate hot working conditions, and the flow field was captured using PIV technology. After iterative adjustments, the key structural parameters were finally determined: the height-to-diameter ratio of the straight section was 3:1 (straight section height 12m, inner diameter 4m), the height-to-diameter ratio of the cone was 2.0:1 (cone height 5m, bottom diameter 2.5m), there were 7 chlorine nozzles at a 45° angle to the cone, three sets of heating electrodes were evenly arranged 0.5m from the furnace bottom, the flue gas outlet was 0.5m from the bottom of the straight section at a 60° angle to the straight section, and the feed port was located on the straight section, 5m from the bottom of the straight section. The cold simulation showed that the dead zone area of ​​the flow field accounted for 3%, and the airflow distribution was uniform.

[0042] S30, Furnace body structure finalization and gas-solid separation device optimization: The above parameters were incorporated into the furnace body model to complete the finalization. The inner diameter of the furnace top cyclone separator is 1.2m, with 4 built-in spiral guide plates, an inclination angle of 35°, and an exhaust pipe insertion depth of 0.8m. CFD simulation verification shows that the dust removal efficiency for solid particles with a particle size ≥20μm reaches 98.5%.

[0043] S40, full-condition simulation verification: Full-condition simulation confirmed that the titanium slag conversion rate was 95.8%, the TiCl4 formation concentration was stable at over 99.2%, the furnace temperature gradient was controlled within ±12℃, and the production capacity load could reach 245t / d, meeting the design requirements and completing the structural design finalization.

[0044] After the optimized molten salt chlorination furnace was put into operation, actual operation data showed that the capacity load was stable at over 240t / d, the titanium yield was over 95%, the chlorination furnace operated continuously for over 3 years, the design cycle was shortened to 2.5 months, and the production cost per ton of titanium tetrachloride was reduced by 3%.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications or equivalent substitutions made to the present invention without departing from the spirit and scope thereof should be covered within the protection scope of the claims of the present invention.

[0046] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of the present invention is limited to these examples; within the framework of the embodiments of the present invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of the present invention should be included within the protection scope of the embodiments of the present invention.

Claims

1. A method for optimizing the structure of a large molten salt chlorination furnace, characterized in that, An optimized design method applicable to large molten salt chlorination furnaces with a capacity load of 240 t / d or more includes the following steps: S10. Based on the designed capacity, establish an initial three-dimensional geometric model of the furnace body, perform meshing on the initial three-dimensional geometric model, and then import it into simulation software for multi-field coupled numerical simulation to obtain the flow field distribution characteristics inside the furnace, identify dead zones, local overheated areas and incomplete reaction areas, and preliminarily determine the direction of furnace structure optimization. S20. Based on the furnace structure optimized in step S10, a cold physical simulation test bench is built in proportion to simulate hot working conditions. The flow field distribution is captured by flow field visualization technology. The flow field distribution data measured by the cold physical simulation is compared with the numerical simulation results. If the relative error of the flow field parameters in the key area exceeds the preset threshold, the boundary conditions and / or physical parameters of the numerical simulation model are corrected until the error is within an acceptable range. S30. Iteratively adjust the key structural parameters based on the simulation model calibrated in step S20 until the proportion of the dead zone area in the flow field does not exceed 5%, and determine the optimized structural parameters. S40. Integrate the optimized structural parameters determined in step S30 into the three-dimensional model of the furnace body to complete the furnace body structure design. Then, perform full-condition numerical simulation verification on the complete furnace body structure after the design is finalized. After confirming that the stability of titanium tetrachloride production concentration, furnace temperature gradient, and production capacity load have all reached the preset target values, the structural design is finalized.

2. The method according to claim 1, characterized in that, In step S10, the meshing of the initial three-dimensional geometric model includes: The reaction area of ​​the furnace body, the nozzle outlet, and the area around the electrodes are densified with a grid, with a total number of grid units of no less than 1.2 million.

3. The method according to claim 2, characterized in that, In step S10, The multi-field coupled numerical simulation adopts the k-ε turbulence model, with the following boundary conditions: furnace wall adiabatic, chlorine inlet flow rate of 1~5 kg / s, titanium slag-petroleum coke-sodium chloride mixture feeding rate of 1~4 kg / s, initial furnace pressure of 0.1~0.3 MPa, and initial temperature of 700~900℃.

4. The method according to claim 3, characterized in that, In step S10, The multi-field coupled simulation includes coupled simulation of the flow field, temperature field, and concentration field inside the furnace; The flow field distribution characteristics include the furnace airflow velocity distribution, temperature gradient, and titanium tetrachloride formation concentration distribution cloud map.

5. The method according to claim 1, characterized in that, In step S20, the step of constructing a scaled-down cold-state physical simulation test bench to simulate hot-state conditions includes: A cold water simulation test bench was built at a scale of 1:10 to 50, using water to simulate molten salt, air to simulate chlorine gas, and solid particles to simulate titanium slag-carbon mixture. The difference between the Reynolds number in the cold physical simulation and the hot operating condition is within a predetermined range.

6. The method according to claim 1, characterized in that, In step S30, the key structural parameters include at least one of the following: the height-to-diameter ratio of the straight section of the furnace body, the height-to-diameter ratio of the frustum section, the number and installation angle of the chlorine nozzles, the position of the heating electrode, the position of the feeding port, and the position and angle of the flue gas outlet.

7. The method according to claim 6, characterized in that, In step S30, the optimized structural parameters include: The height-to-diameter ratio of the straight section is 2~4:1; The height-to-diameter ratio of the frustum section is 1.5~2.5:1; There are 6 to 8 chlorine nozzles, which are at an angle of 30 to 75° to the cone section.

8. The method according to claim 1, characterized in that, In step S40, the furnace body structure is a variable diameter furnace body structure composed of a lower truncated cone and an upper cylindrical part.

9. The method according to claim 1, characterized in that, Between step S30 and step S40, there is also a gas-solid separation device optimization step: A cyclone-type gas-solid separation device is installed at the furnace top outlet, and the inner diameter, guide plate angle, and exhaust pipe insertion depth of the separation device are optimized through numerical simulation.

10. The method according to claim 9, characterized in that, The cyclone gas-solid separation device has 3 to 6 spiral guide plates with an inclination angle of 30 to 45°, and a dust discharge port at the bottom that connects to the furnace body's salt discharge system.

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