Method for treating titanium tetrachloride refining vanadium-removing slurry

Abstract

The present application relates to the technical field of metallurgical chemical industry, and particularly relates to a method for treating titanium tetrachloride refining vanadium-removing slurry, which comprises the following steps: hot air preparation: coke and dry oxygen are used to continuously produce high-temperature flue gas in a first stage fluidized combustion furnace; slurry drying and separation: the high-temperature flue gas is introduced into a second stage fluidized drying furnace, so that the continuously added refined vanadium-removing slurry in the second stage fluidized drying furnace is dried in a predetermined temperature range, dust-containing gaseous titanium tetrachloride and vanadium slag particles generated in the process are discharged from the second stage fluidized drying furnace, and the solid phase is dried into granular vanadium slag; product recovery: the dust-containing gaseous titanium tetrachloride and vanadium slag particles are subjected to gas-solid separation, the separated titanium tetrachloride gas enters a condensing device, and liquid titanium tetrachloride is recovered after condensation. The present application realizes continuous and efficient treatment of the slurry, the titanium tetrachloride recovery rate is greater than or equal to 98%, the enrichment ratio of vanadium in the solid phase is greater than or equal to 5 times, and the energy consumption of the system is reduced by more than 20% compared with the traditional process.

Description

Technical Field

[0001] This invention relates to the field of metallurgical and chemical technology, and in particular to a method for treating titanium tetrachloride vanadium removal slurry. Background Technology

[0002] In the refining process of crude titanium tetrachloride, to remove vanadium impurities (mainly in the form of VOCl3), industrial production often employs methods such as adding aluminum powder, organic matter, or hydrogen sulfide to reduce and precipitate them. This produces a large amount of titanium tetrachloride slurry containing low-valent vanadium compounds (such as VCl3 and VOCl2), unreacted reducing agents, and solid impurities. This type of slurry typically contains 30%–60% titanium tetrachloride and 1%–5% vanadium (calculated as V), and has extremely high recycling value. Direct disposal not only results in the loss of valuable resources but also readily hydrolyzes upon contact with water, producing irritating hydrogen chloride gas, classifying it as hazardous waste with high treatment costs.

[0003] Existing processing technologies mostly employ intermittent evaporators or paddle dryers. For example, some existing technologies disclose the recovery of titanium tetrachloride through sedimentation and heated evaporation. However, such methods have significant drawbacks: (1) low processing efficiency, with a single batch processing cycle lasting several hours, and continuous feeding and discharging are not possible; (2) unreasonable heat utilization, with low heat transfer coefficient and high energy consumption due to indirect heating; (3) prone to clogging and hydrolysis, with wet materials adhering to the inner wall of the equipment, making cleaning difficult, and moisture easily introduced when the seal is not tight, leading to the hydrolysis of titanium tetrachloride, reducing the recovery rate and corroding the equipment. Therefore, there is an urgent need for a method that can achieve continuous, efficient, and clogging-proof processing in a strictly anhydrous environment, increasing the recovery rate of titanium tetrachloride to over 95%, and effectively enriching vanadium slag.

[0004] Therefore, existing technologies still need improvement. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for treating titanium tetrachloride vanadium removal slurry, thereby resolving the technical issues existing in the prior art for treating titanium tetrachloride vanadium removal slurry.

[0006] To address the aforementioned technical problems, some embodiments of the present invention disclose a method for treating titanium tetrachloride refined vanadium removal slurry, comprising the following steps: Step 1, Hot air preparation: High-temperature flue gas is continuously produced in a first-stage fluidized bed combustion furnace using coke and dry oxygen; Step 2, Slurry Drying and Separation: The high-temperature flue gas is introduced into the second-stage fluidized bed dryer, so that the refined vanadium-removing slurry continuously added to the second-stage fluidized bed dryer is dried within a predetermined temperature range. The dust-containing gaseous titanium tetrachloride and vanadium slag particles are discharged from the second-stage fluidized bed dryer, and the solid phase is dried into granular vanadium slag. Step 3, Product Recovery: The dust-containing gaseous titanium tetrachloride and vanadium slag particles are separated by gas-solid separation. The separated titanium tetrachloride gas enters the condensation device, and the liquid titanium tetrachloride is recovered after condensation.

[0007] Furthermore, the method involves purging the entire system with dry nitrogen gas until the dew point is below -40°C before operation to ensure a waterless environment.

[0008] Furthermore, in step one, the particle size of the coke is 1-5 mm, and the mass ratio of the dry oxygen to the coke is controlled to be 2.0-2.5:1.

[0009] Furthermore, in step one, the bed temperature of the first-stage fluidized bed combustion furnace is 950–1150℃, and the apparent gas velocity is 1.5–3.0 m / s.

[0010] Furthermore, the high-temperature flue gas generated in step one undergoes gas-solid separation before entering the second-stage fluidized bed dryer, so that the dust content of the high-temperature flue gas entering the second-stage fluidized bed dryer is less than 50 mg / Nm³.

[0011] Furthermore, in step two, the apparent gas velocity of the second-stage fluidized bed dryer is 0.8–2.5 m / s, the bed pressure drop is maintained at 2000–5000 Pa, and the furnace temperature is 200–350 °C. Alternatively, the granular vanadium slag produced after drying has a particle size range of 50–500 μm, a median particle size of 120–280 μm, an apparent density of 1.2–1.8 g / cm³, and a bulk density of 0.6–1.0 g / cm³.

[0012] Furthermore, in step two, the refined vanadium-removing slurry is preheated to 50-80°C before being added to the second-stage fluidized bed dryer.

[0013] Furthermore, in step two, the residence time of the material in the second-stage fluidized bed dryer is 5 to 30 minutes.

[0014] Furthermore, in step two, the refined vanadium-removing slurry is added at a position 500-1000 mm above the second gas distribution plate inside the furnace.

[0015] Furthermore, in step three, the condensation device employs a two-stage condensation process, where the first stage condenses the titanium tetrachloride gas to 35-45°C, and the second stage condensation uses a condensing medium at -25°C to -15°C for condensation.

[0016] By adopting the above technical solution, the present invention has at least the following beneficial effects: This invention provides a method for treating vanadium-removing slurry refined from titanium tetrachloride, solving problems such as low efficiency, unreasonable heat utilization, easy clogging, and hydrolysis in existing technologies. It achieves continuous and efficient slurry treatment, resulting in a titanium tetrachloride recovery rate of ≥98%, a vanadium enrichment ratio in the solid phase of ≥5 times, and a system energy consumption reduction of over 20% compared to traditional processes. It offers significant advantages such as continuous high efficiency, high product recovery rate, good product quality, and environmental friendliness. Attached Figure Description

[0017] 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 based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the system for treating titanium tetrachloride vanadium-removing slurry as disclosed in Embodiment 1 of the present invention. Detailed Implementation

[0019] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of this disclosure by way of example, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0020] These embodiments are provided to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0021] It should be noted that, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Furthermore, the terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after the word, and do not exclude the possibility of encompassing other elements as well.

[0023] It should also be noted that, in the description of this disclosure, unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this disclosure depending on the specific circumstances. When a particular device is described as being located between a first device and a second device, an intermediary device may or may not be present between the particular device and the first or second device.

[0024] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0025] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0026] On one hand, some embodiments of the present invention disclose a method for treating titanium tetrachloride refining and vanadium removal slurry, aiming to achieve continuous and efficient treatment of titanium tetrachloride refining and vanadium removal slurry, so that the titanium tetrachloride recovery rate is ≥98%, the vanadium enrichment ratio in the solid phase is ≥5 times, and the system energy consumption is reduced by more than 20% compared with the traditional process. The method includes the following steps: Step 1, Hot Air Preparation: High-temperature flue gas is continuously produced in a first-stage fluidized bed combustion furnace using coke and dry oxygen. The particle size of the added coke is generally controlled to be 1-5 mm, and the mass ratio of the dry oxygen to the coke is controlled to be 2.0-2.5:1. The oxygen has a purity of ≥99.5%, so that the coke is combusted in a fluidized state to produce high-temperature flue gas. The bed temperature is preferably controlled at 950-1150℃, and the apparent gas velocity is preferably controlled at 1.5-3.0 m / s. The high-temperature flue gas produced by combustion, carrying unburned coke dust, enters the first gas-solid separation device for gas-solid separation. The separated dust is discharged periodically or continuously to obtain clean high-temperature dry hot air at 800-1000℃. It is ensured that the dust content of the high-temperature flue gas entering the second-stage fluidized bed dryer for drying slurry is less than 50 mg / Nm³. This value is based on a comprehensive balance of factors such as the quality of downstream products (titanium tetrachloride), the lifespan of core equipment (condenser / condensation device), the stability of the entire process system, and industrial feasibility.

[0027] Step 2, Slurry Drying and Separation: The high-temperature flue gas is introduced into the bottom of the second-stage fluidized bed dryer, so that the refined vanadium-removing slurry continuously added to the second-stage fluidized bed dryer is dried within a predetermined temperature range. The generated dust-containing gaseous titanium tetrachloride and vanadium slag particles are discharged from the second-stage fluidized bed dryer, and the solid phase is dried into granular vanadium slag.

[0028] In this step, high-temperature flue gas can be uniformly sprayed out through the air cap on the second gas distribution plate, controlling the apparent gas velocity of the second-stage drying furnace to be 0.8–2.5 m / s, and maintaining the bed pressure drop at 2000–5000 Pa. Preheated titanium tetrachloride vanadium-removing slurry to 50–80°C is continuously added into the furnace through the slurry inlet. The slurry is added 500–1000 mm above the second gas distribution plate inside the furnace. Simultaneously, the amount of slurry added can be controlled to match the hot air volume, maintaining the furnace temperature at 200–350°C, with an average residence time of 5–30 minutes for the material. The liquid titanium tetrachloride in the slurry rapidly evaporates into a gaseous state upon heating, and the solid vanadium slag is dried into granules.

[0029] Step 3, Product Recovery: The dust-containing gaseous titanium tetrachloride and vanadium slag particles are separated by gas-solid separation. The separated titanium tetrachloride gas enters the condensation device, and the liquid titanium tetrachloride is recovered after condensation.

[0030] Preferably, to remove moisture from the treatment system, the method purges the entire system with dry nitrogen until the dew point is below -40°C to ensure a water-free environment before operation. The condensation device can employ two-stage condensation. The first stage uses circulating water to condense the titanium tetrachloride gas to 35-45°C, while the second stage uses a condensing medium of -25°C to -15°C. During the treatment process, the bed pressure drop of the first-stage fluidized bed combustion furnace and the second-stage fluidized bed drying furnace is maintained at a slightly negative pressure by adjusting the induced draft. The entire treatment process is carried out continuously in a closed system, with the gas dew point consistently controlled below -40°C. In the first-stage condensation, the circulating water outlet temperature of the tubular cooler can be set to not exceed 45°C, effectively preventing scaling and microbial growth. The return water after heat exchange is typically below 42.5°C and is returned to the cooling tower for cooling and reuse. This allows the condensation of titanium tetrachloride gas to 35-45°C to be achieved directly using the sensible heat exchange capacity of the circulating cooling water, eliminating the need for an additional refrigeration unit and significantly reducing equipment investment and operating energy consumption. Furthermore, titanium tetrachloride has a boiling point of 136.4℃ and a freezing point of -25℃. Within the temperature range of 35–45℃, TiCl4 is a stable liquid, much higher than its freezing point, preventing freezing and pipe blockage. Its saturated vapor pressure is moderate; according to physical property data, the vapor pressure of TiCl4 is approximately 1.33 kPa at 20℃, approximately 3.5–4.0 kPa at 35℃, and approximately 6.5–7.5 kPa at 45℃. The TiCl4 in the condenser is essentially liquid, with very little uncondensed gas, resulting in a low condensation load on the second-stage chilled brine. At this temperature, TiCl4 has a low viscosity (approximately 0.7–0.8 mPa·s), exhibiting good fluidity and facilitating transport in storage tanks and pipelines.

[0031] This embodiment employs a two-stage condensation strategy: the first stage uses inexpensive circulating water for preliminary condensation, cooling gaseous TiCl4 at 240℃ to 35-45℃, recovering approximately 85%-95% of titanium tetrachloride; the second stage uses -25 to -15℃ chilled brine for deep condensation, capturing the remaining TiCl4 and achieving a total recovery rate of ≥98.5%. If the first-stage temperature is above 45℃, the condensation efficiency decreases, the chilled brine load in the second stage increases, and operating energy consumption rises; if it is below 35℃, ordinary circulating water cannot stably reach this temperature (especially in summer), requiring additional investment in cooling equipment. If the temperature is even lower (e.g., <30℃), the circulating water side may experience localized condensation due to excessive temperature differences, increasing the risk of hydrolysis.

[0032] The selection of key process parameters disclosed in the above embodiments of the present invention is based on fluidized bed engineering principles, material characteristics, and engineering experience. Specifically, the coke particle size should be controlled between 1 and 5 mm. Larger particles require higher fluidization velocities, increasing energy consumption; smaller particles are prone to entrainment and incomplete combustion. The oxygen-to-coke ratio is controlled between 2.0 and 2.5:1. This is because coke generally has ≥85% fixed carbon, and the theoretical oxygen requirement for complete combustion is approximately 2.27 kg O2 / kg C. Considering a combustion efficiency of 90%, this ratio ensures complete combustion and avoids excessive oxygen. If the ratio is higher than 2.5:1, excessive oxygen increases the proportion of complete combustion, causing the temperature to rise rapidly to above 1200°C, resulting in ash melting, coking, and bed stagnation. Energy consumption also increases. If the ratio is lower than 2.0:1, incomplete combustion and low thermal efficiency will occur: a large amount of carbon will generate CO, whose calorific value is only 1 / 3 of the heat of CO2 formation, resulting in insufficient hot air temperature (<800°C), failing to meet the requirements of the second-stage drying. Furthermore, CO may reduce some vanadium oxides, altering the vanadium slag phase and affecting subsequent vanadium extraction.

[0033] In the above embodiments, the apparent gas velocity of the first-stage fluidized bed combustion furnace is controlled at 1.5–3.0 m / s, corresponding to the rapid fluidization range of coke, ensuring good fluidization and controllable entrainment. If the apparent gas velocity of the first-stage combustion furnace is higher than 3.0 m / s, the gas velocity exceeds the terminal velocity of the particles, and a large amount of fine coke powder (<0.5 mm) is carried out of the furnace without complete combustion, resulting in a decrease in fuel utilization and a drop in hot air temperature; a sharp increase in dust concentration, a decrease in cyclone separator efficiency, and an outlet dust content far exceeding 50 mg / Nm³, contaminating the second-stage dried product. If the apparent gas velocity of the first-stage combustion furnace is lower than 1.5 m / s, coke particles accumulate on the distribution plate, forming a dead bed or channel, resulting in extremely unstable combustion; uneven oxygen distribution, with CO generated in local oxygen-deficient areas and a sudden temperature rise in local oxygen-over-oxygen areas, ash melting leading to coking, and blockage of the air cap. The apparent gas velocity in the second-stage fluidized bed dryer is controlled at 0.8–2.5 m / s. If the apparent gas velocity in the second-stage dryer exceeds 2.5 m / s, the gas velocity exceeds the terminal velocity of the vanadium slag particles, and a large number of incompletely dried fine particles are carried into the second separator, increasing the separation load and even entering the condensation system to contaminate TiCl4. At the same time, the residence time of the material in the furnace is shortened to <5 minutes, the titanium tetrachloride is not completely evaporated, the residual TiCl4 in the vanadium slag is >0.3%, and the recovery rate decreases. In order to adapt to the changes in particle size and density during the drying process, the particle size range of the vanadium slag produced after drying is stable at 50–500 μm, the median particle size is 120–280 μm, the apparent density is 1.2–1.8 g / cm³, and the bulk density is 0.6–1.0 g / cm³. The formation of this particle size and density range is the result of the synergistic effect of multiple mechanisms: the solid particles in the original slurry have a particle size of approximately 1–50 μm. After entering the fluidized bed dryer, the rapid vaporization of liquid titanium tetrachloride (expanding in volume by approximately 350 times) generates a liquid bridge agglomeration effect, causing fine particles to adhere and form agglomerates. At the same time, the internal stress generated by vaporization leads to the breakup of agglomerates. In addition, collision and wear between particles and selective entrainment (fine powder <50 μm is carried away by hot air) ultimately lead to a dynamic equilibrium between agglomeration and breakup within 5–30 minutes, forming uniform particles of 50–500 μm. Furthermore, the volatilization of titanium tetrachloride leaves behind a large number of micropores and microcracks, which significantly reduces the apparent density of the particles from the true density of the original solid phase (2.2–2.8 g / cm³) to 1.2–1.8 g / cm³, exhibiting a porous and loose structure.This particle size and density range brings significant benefits: In terms of fluidization, 50–500 μm particles belong to Geldart B-type particles, which is the optimal operating range for conventional fluidized beds. The bed expands uniformly, the pressure drop is stable (2000–5000 Pa), and excessive entrainment of fine powder or dead zones of coarse particle deposition are avoided. In terms of gas-solid separation, the median particle size is much larger than 10 μm, the cyclone separator efficiency can reach over 99%, the vanadium slag entrainment loss is minimal, and the dust content of the outlet gas is easily controlled below 50 mg / Nm³. In terms of subsequent vanadium extraction, the porous structure (apparent density of only 1.2–1.8 g / cm³) increases the specific surface area, improves the penetration efficiency of the leaching agent, and increases the vanadium leaching rate by 15%–25% compared to dense particles. At the same time, the reduced particle mechanical strength reduces the energy consumption of subsequent grinding by 20%–30%, and the residual titanium tetrachloride is less than 0.3%, avoiding HCl corrosion of equipment caused by hydrolysis. Furthermore, this particle size range (median particle size > 100 μm) results in low dust generation during stacking and conveying, improving the operating environment and fully demonstrating the scientific nature of the process parameter selection and the superior technical effect of this patent. It also avoids premature entrainment or poor fluidization.

[0034] In the above embodiments, the drying temperature can be controlled at 200-350℃, higher than the boiling point of titanium tetrachloride (136℃), and heat transfer enhancement is considered; the upper limit of the temperature is limited by the temperature resistance of the material and the physical properties of vanadium slag. The slurry preheating temperature can be set to 50-80℃. Preheating can reduce the heat load of the drying furnace, avoid thermal stability problems caused by "cold shock", and reduce viscosity to prevent fluidized bed collapse caused by "cold material". When the preheating temperature is below 50℃: the slurry viscosity increases significantly, the fluidity deteriorates, the pressure drop increases during pipeline transportation, and it is easy to cause the feed pump to be overloaded or even clog the filter; more importantly, when the low temperature slurry directly enters the fluidized bed drying furnace at 200-350℃, it will form a violent "cold shock" effect, causing a sudden drop in local temperature, slowing down the gasification rate of titanium tetrachloride, and the slurry cannot be dispersed in time near the distribution plate, which easily wets the air cap and bed particles, causing particle agglomeration and dead bed phenomenon. In severe cases, the entire fluidized bed collapses, and the system is forced to shut down for cleaning. When the preheating temperature exceeds 80℃: Titanium tetrachloride has a boiling point of only 136℃, but its saturated vapor pressure increases significantly above 80℃ (approximately 37 kPa at 80℃). This can lead to premature vaporization in the conveying pipeline, forming a gas-liquid two-phase flow, causing fluctuations in the feed rate and even gas resistance, preventing the slurry from continuously and stably entering the drying furnace. Furthermore, excessively high preheating temperatures can cause some titanium tetrachloride to volatilize before entering the furnace. The volatilized TiCl4 gas may condense and flow back into the pipeline upon cooling, causing blockages and reducing the actual amount of titanium tetrachloride entering the furnace, thus affecting drying efficiency. Only by controlling the preheating temperature within the range of 50–80℃ can we ensure good slurry fluidity, prevent cold shock and bed collapse, and prevent gas resistance in the conveying pipeline, achieving continuous and stable feeding and ensuring the efficient operation of the two-stage fluidization system.

[0035] In the above embodiments, the residence time in the second-stage fluidized bed dryer can be controlled between 5 and 30 minutes, adjusted according to the titanium tetrachloride content and heat transfer efficiency in the slurry to ensure complete evaporation. Specifically, in the second-stage fluidized bed dryer, the average residence time of the material (vanadium slag particles formed after slurry drying) is mainly determined by the bed level height and discharge rate, and the specific control method is as follows: Material level control: Pressure transmitters or level gauges installed at different heights on the side wall of the drying furnace are used to monitor the bed pressure drop (corresponding to the bed height) in real time. When the bed pressure drops below the set lower limit (e.g., 2000 Pa), the discharge rate is reduced or the feed rate is increased; when the pressure drop exceeds the upper limit (e.g., 5000 Pa), the discharge rate is increased. By adjusting the opening of the discharge valve or the frequency of the discharge screw, the bed height is kept stable, thereby ensuring that the material residence time in the furnace is within the design range.

[0036] Discharge rate matching: The second-stage dryer continuously feeds (slurry) and discharges (vanadium slag), with the residence time approximately equal to the total amount of solid material in the bed divided by the discharge mass flow rate. During stable operation, the bed holding capacity is calculated using a weighing sensor or level gauge, and the opening of the discharge valve is adjusted to match the discharge rate with the feed rate, thereby controlling the residence time between 5 and 30 minutes.

[0037] If the residence time is too short (<5 minutes), the titanium tetrachloride in the slurry is discharged from the furnace before it has fully evaporated, resulting in a significant increase in the residual titanium tetrachloride content in the vanadium slag (>1%). This not only reduces the recovery rate but also causes slow hydrolysis and corrosion of the equipment during subsequent cooling and storage. Simultaneously, due to insufficient drying, liquid TiCl4 remains attached to the surface of the vanadium slag particles, making them prone to agglomeration and blockage of the discharge port, disrupting the stable operation of the fluidized bed. If the residence time is too long (>30 minutes), the material is over-dried in the high-temperature fluidized bed, and prolonged collision and friction between vanadium slag particles generate a large amount of fine powder (<50 μm). This fine powder is easily carried by hot air into the cyclone separator, increasing the separation load, and may even penetrate the separator into the condensation system, contaminating the titanium tetrachloride product. Furthermore, over-drying further breaks down the vanadium slag particles, reducing the apparent density to below 1.0 g / cm³, leading to severe dust generation during subsequent transport, and the fine powder increases the difficulty of solid-liquid separation after entering the vanadium extraction process. Only by controlling the residence time within the optimized range of 5–30 minutes can we ensure complete evaporation of titanium tetrachloride (residual <0.3%), while avoiding excessive crushing and the generation of fine powder, thus ensuring product quality and long-term stable system operation. The system dew point should be <-40℃ to ensure an anhydrous environment and prevent hydrolysis of titanium tetrachloride. The condensation temperature should be controlled between -25℃ and -15℃, at which temperature the saturated vapor pressure of titanium tetrachloride is extremely low, ensuring a recovery rate of ≥98%.

[0038] On the other hand, such as Figure 1 As shown, some embodiments of the present invention also disclose a system for treating titanium tetrachloride refining and vanadium removal slurry, which can be used in the aforementioned method for treating titanium tetrachloride refining and vanadium removal slurry. The system aims to solve problems such as low efficiency of intermittent operation, unreasonable heat utilization, easy clogging, and hydrolysis in the prior art, achieving continuous and efficient slurry treatment, with a titanium tetrachloride recovery rate ≥98%, a vanadium enrichment ratio in the solid phase ≥5 times, and a system energy consumption reduction of more than 20% compared to traditional processes. The system includes a first-stage fluidized bed combustion furnace 1, a first gas-solid separation device 2, a second-stage fluidized bed drying furnace 3, and a product recovery device. The first-stage fluidized bed combustion furnace 1 is used to react coke with dry oxygen to generate high-temperature drying hot air; the second-stage fluidized bed drying furnace 3 is used to fluidize and dry the slurry using the high-temperature drying hot air, achieving the evaporation of titanium tetrachloride and the separation of solid vanadium slag.

[0039] The high-temperature flue gas outlet 11 at the upper end of the first-stage fluidized bed combustion furnace 1 is connected to the first gas-solid separation device 2. The gas phase outlet of the first gas-solid separation device 2 is connected to the hot air inlet 31 of the second-stage fluidized bed drying furnace 3 via a hot air duct 4. The hot air duct 4 may be covered with insulation material to reduce heat loss. The product outlet 32 ​​at the upper end of the second-stage fluidized bed drying furnace 3 is connected to the product recovery device. The bottom of the first gas-solid separation device 2 may also be connected to an ash discharge mechanism 8, which may include an ash hopper and an ash discharge valve. The ash hopper is connected to the first gas-solid separation device 2 via the ash discharge valve for periodically or continuously discharging the dust separated by the first gas-solid separation device 2.

[0040] Furthermore, the first-stage fluidized bed combustion furnace 1 has an oxygen inlet 12 at its bottom and a coke feeding port 13 on its side wall; the second-stage fluidized bed drying furnace 3 has a slurry inlet 33 on its side wall. The first-stage fluidized bed combustion furnace 1 has a first gas distribution plate 14 at its bottom to distribute oxygen entering the furnace, and the second-stage fluidized bed drying furnace 3 has a second gas distribution plate 34 at its bottom to distribute hot air entering the furnace. The diameter-to-height ratio of the first-stage fluidized bed combustion furnace 1 can be set to 1:(5-8), and the diameter-to-height ratio of the second-stage fluidized bed drying furnace 3 can be set to 1:(6-9) to ensure sufficient gas-solid contact time and prevent premature particle entrainment. The slurry inlet 33 is preferably located 500-1000 mm above the second gas distribution plate 34 to ensure that the slurry is rapidly fluidized by the hot air after entering.

[0041] In the above embodiments, the product recovery device may include a second gas-solid separation device 5, a condensation device 6, and a titanium tetrachloride storage tank 7. The product outlet 32 ​​at the upper end of the second-stage fluidized bed dryer 3 is connected to the second gas-solid separation device 5, and the gas phase outlet of the second gas-solid separation device 5 is connected to the condensation device 6 for condensing gaseous titanium tetrachloride into liquid for recovery. The outlet of the condensation device 6 is connected to the titanium tetrachloride storage tank 7. The condensation device 6 may use chilled brine at -25°C to -15°C as a refrigerant. The solid outlet of the second gas-solid separation device 5 is used to discharge vanadium slag.

[0042] In the above embodiments, to ensure uniform distribution, multiple air caps are arranged on the first gas distribution plate 14, and multiple air caps are also arranged on the second gas distribution plate 34. Furthermore, the air caps are side-hole type or bell-shaped type to prevent solid particles from backflowing and clogging the gas delivery pipes of the air caps. The exhaust holes of the air caps face downwards or to the side of the distribution plate. The width of the exhaust hole gap is designed to be 2-5 mm. A gap that is too narrow is prone to clogging, while a gap that is too wide results in insufficient airflow penetration. Empirical values ​​ensure uniform air distribution and prevent clogging. The opening ratio (the ratio of the total area of ​​the exhaust holes of all air caps to the effective area of ​​the air distribution plate) is controlled at 3%-8%, so that the bed resistance of the gas distribution plate and the second gas distribution plate 34 is 25%-30%. According to the relationship ΔP ∝ 1 / φ², this opening ratio can achieve the target resistance. The first gas-solid separation unit 2 can be a high-efficiency cyclone separator or a high-temperature resistant ceramic filter to separate dust generated by coke combustion, ensuring that the dust content of the hot air entering the second-stage fluidized bed dryer 3 is less than 50 mg / Nm³. The second gas-solid separation unit 5 can be a high-temperature, high-efficiency cyclone separator, with a separation efficiency of not less than 99% for vanadium slag particles larger than 10 μm, ensuring the purity of titanium tetrachloride gas.

[0043] In the above embodiments, the connection between the wind cap and the distribution plate can be achieved in the following three ways: (1) Socket welding connection: The core tube passes through the reserved hole of the air distribution plate and is socket welded below the air distribution plate. This method has high connection strength and good sealing performance, and is suitable for long-term high-temperature operation. Hot air enters from the air chamber on the lower side of the air distribution plate, is transported through the stainless steel short pipe and blown out through the air distribution hole of the air cap, so as to fluidize the material on the upper bed of the air distribution plate.

[0044] (2) Threaded connection: The upper end of the core tube is provided with an external thread, and the bottom of the vent cap is provided with a matching internal thread. It is fixed by tightening the threads. This method is convenient for disassembly and maintenance, but it requires high precision in thread fit.

[0045] (3) Flange connection: The bottom of the wind cap is equipped with a flange, which is connected to the flange seat on the wind distribution plate by bolts. This method is the most convenient for installation and disassembly, but it occupies a large space.

[0046] The thickness of the protective layer on the air distribution plate is generally 100-150 mm, depending on the height of the wind cap. The bottom of the wind cap is embedded in the protective layer, which is usually made of refractory castable. Its function is to protect the air distribution plate from direct erosion by high-temperature airflow and to prevent the wind cap from deforming due to high temperature.

[0047] To further clarify the function of the device, the functional design differences between the two-stage fluidization devices are shown in Table 1.

[0048] Table 1

[0049] The differences in the diameter-to-height ratio design of the two-stage fluidization device are explained in Table 2.

[0050] Table 2

[0051] The system for treating titanium tetrachloride vanadium removal slurry disclosed in the above embodiments of the present invention can achieve continuous and efficient treatment of the slurry. Employing a two-stage fluidization device, it achieves a fully continuous operation from material input to product output, increasing efficiency by 5-8 times compared to traditional batch reactor processes. It enables highly efficient heat coupling utilization; the high-temperature hot air generated by the first-stage combustion directly serves as the heat source and fluidization medium for the second-stage drying, achieving a heat utilization rate of over 85%, reducing energy consumption by 25-30% compared to traditional indirect heating methods. It completely avoids clogging and hydrolysis; both gas distribution plates (first and second gas distribution plates) are designed with air caps, effectively preventing solid particles from clogging the air distribution plates. The entire system uses dry oxygen / nitrogen sealing, with the dew point controlled below -40°C, preventing moisture ingress and ensuring that the titanium tetrachloride hydrolysis rate is below 0.5%. The product boasts high recovery rate and excellent quality. Through precise temperature-controlled fluidized bed drying, titanium tetrachloride in the slurry evaporates completely, achieving a recovery rate of over 98.5%. The resulting vanadium slag has a vanadium content 5-8 times higher than the original slurry and is in a loose granular form, facilitating subsequent hydrometallurgical leaching. Environmentally friendly, the system operates under a fully enclosed negative pressure system, preventing the escape of harmful gases (such as HCl and Cl2). This transforms hazardous waste slurry into high-value vanadium slag and valuable titanium tetrachloride, achieving true resource utilization.

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0053] Example 1 Adopting such Figure 1The apparatus shown is used to process vanadium-removing slurry from titanium tetrachloride refining at a certain factory. The composition of the slurry to be treated is as follows: titanium tetrachloride 55 wt%, vanadium (as V) 3.2 wt%, and other solid phases (including AlCl3, Al2O3, C, etc.) 41.8 wt%. The coke used is petroleum coke with a particle size of 2-4 mm and a fixed carbon content of 86%.

[0054] Step 1: System preheating and preparation Purge the system with dry nitrogen until the exhaust gas dew point is below -45°C. Start the ignition system of the first-stage combustion furnace (first-stage fluidized bed combustion furnace), add a small amount of coke through the coke inlet, and ignite with a small amount of oxygen. Once the bed temperature rises above 600°C, begin continuous feeding.

[0055] Step 2: Hot air preparation The coke feed rate was controlled at 85 kg / h, and the dry oxygen (99.6% purity) feed rate was 180 Nm³ / h (oxygen to coke mass ratio approximately 2.25:1). The induced draft was adjusted to maintain a slight negative pressure (-50 to -100 Pa) inside the furnace (first-stage fluidized bed combustion furnace). The fluidized bed temperature was stabilized at 1050 ± 20℃, and the apparent gas velocity was 2.2 m / s. The high-temperature flue gas (approximately 1050℃) generated by combustion entered the first cyclone separator (first gas-solid separation device), with a separation efficiency of 98%. The separated dust (approximately 6 kg / h) was periodically discharged through the ash removal system. Clean, high-temperature dry hot air was obtained, with a temperature of 1020℃ and a dust content of approximately 30 mg / Nm³.

[0056] Step 3: Mud Drying and Separation The slurry (vanadium removal slurry refined from titanium tetrachloride) is preheated to 65°C. High-temperature hot air at 1020°C enters the bottom of the second-stage fluidized bed dryer through a hot air duct, flows upwards after being evenly distributed by the air cap, and the apparent gas velocity in the second-stage dryer is controlled at 1.5 m / s, with a bed pressure drop of 3200 Pa. The preheated slurry to 65°C is continuously added through the slurry inlet at a rate of 300 kg / h.

[0057] Under the impact of high-temperature hot air, the slurry disperses and fluidizes instantly, and the temperature in the middle of the furnace rapidly drops to 280-320℃ and remains stable. Titanium tetrachloride in the slurry is rapidly vaporized, and the solid vanadium slag is dried into particles. The gas-solid mixture is discharged from the top of the furnace and enters the second cyclone separator (second gas-solid separation device), with a separation efficiency of 99.2%.

[0058] The separated high-temperature vanadium slag (approximately 250°C) is discharged from the vanadium slag outlet, cooled by a spiral cooler, and collected, with a yield of approximately 128 kg / h. Analysis shows that the residual titanium tetrachloride in the vanadium slag is <0.3%, and the vanadium grade is enriched to approximately 16.2 wt%, meeting the requirements for vanadium extraction raw materials.

[0059] The separated dust-laden titanium tetrachloride gas (approximately 240°C) enters the condensation system. It first enters a primary condenser (cooled by circulating water, condensing to 40°C), then a secondary condenser (cooled by -20°C chilled brine). After two stages of condensation, liquid titanium tetrachloride flows into a titanium tetrachloride storage tank, with a recovery rate of approximately 164 kg / h. The purity was tested to reach 99.2%, and the total titanium tetrachloride recovery rate reached 99.4%. Non-condensable gases (mainly nitrogen and a small amount of CO2) are purified by an alkaline scrubbing tower before being discharged.

[0060] Results: The method operated continuously and stably for 72 hours without any clogging, and the inner wall of the equipment remained dry and free of adhesion. Compared with a traditional 2000L batch evaporator, for processing the same 300kg / h of slurry, the unit product energy consumption was reduced by 28%, and the number of operators was reduced by 60%.

[0061] Example 2 This embodiment is basically the same as Embodiment 1, except that the operating parameters of the second-stage drying furnace were adjusted. The hot air temperature (clean, high-temperature drying hot air) was adjusted to 900℃, the slurry addition rate was adjusted to 250 kg / h, and the slurry preheating temperature was adjusted to 70℃. The operating results showed that the furnace temperature stabilized at 200–240℃, and the material residence time was extended to approximately 25 minutes. The final titanium tetrachloride recovery rate was 98.8%, and the vanadium grade in the vanadium slag was enriched to 18.1 wt%. This indicates that by adjusting the parameters, good treatment results can be obtained under different processing volumes.

[0062] Example 3 like Figure 1 As shown, a two-stage fluidization device for treating titanium tetrachloride vanadium removal slurry has the following main structural dimensions and parameter design: The first-stage fluidized bed combustion furnace is cylindrical with an inner diameter of Φ800mm and a height of H=6000mm, resulting in a diameter-to-height ratio of approximately 1:7.5. A 30mm thick first gas distribution plate, made of heat-resistant stainless steel (310S), is installed at the bottom. Forty-nine bell-shaped air caps are evenly installed on the distribution plate, arranged in an equilateral triangle. The air caps have a diameter of Φ60mm, with side openings of 3mm and an open area ratio of 5%. A coke inlet (coke feeding port) is located on the furnace side wall, and a dry oxygen inlet is located at the bottom.

[0063] The second-stage fluidized bed dryer is cylindrical with an inner diameter of Φ1200mm and a height of H=8000mm. A second gas distribution plate is installed at the bottom, also equipped with 61 side-hole air caps with the same parameters as the first stage. A slurry inlet is located 800mm above the second gas distribution plate on the side wall of the furnace body.

[0064] The first gas-solid separation unit is a high-efficiency cyclone separator with a cylinder diameter of Φ400mm and a separation efficiency of 98%. The second gas-solid separation unit is a high-temperature cyclone separator with a cylinder diameter of Φ650mm and a separation efficiency of 99.2%. The titanium tetrachloride condensation and recovery system (product recovery unit) includes a two-stage condenser (condensation unit) and a titanium tetrachloride storage tank. The condensers use circulating water and -20℃ chilled brine as refrigerants.

[0065] Example 4 This embodiment is basically the same as Embodiment 1, except that: the inner diameter of the first-stage fluidized combustion furnace 1 is Φ1000mm and the height is 7500mm; the inner diameter of the second-stage fluidized drying furnace 2 is Φ1500mm and the height is 10000mm; the opening ratio of the air cap is adjusted to 6% to meet the needs of larger processing capacity.

[0066] In summary, the apparatus and method for treating vanadium-removing titanium tetrachloride slurry disclosed in the above embodiments of the present invention solve the problems of low efficiency and unreasonable heat utilization in the prior art due to intermittent operation. It simplifies the complex slurry treatment into a standardized three-step process of "hot air preparation—slurry drying—product recovery," which can replace the existing intermittent evaporation process. This increases the recovery rate of titanium tetrachloride in the slurry from 85%–90% to over 98.5%, and the enrichment ratio of vanadium in the solid phase is ≥5 times. Furthermore, the system energy consumption is reduced by more than 20% compared to traditional processes. It has advantages such as continuous high efficiency, high product recovery rate, good quality, and environmental friendliness. It achieves standardized operation, reduces personnel skill requirements, and improves production stability. It can be widely applied in sponge titanium and chloride-process titanium dioxide enterprises.

[0067] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0068] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner.

Claims

1. A method for treating titanium tetrachloride refined vanadium removal slurry, characterized in that, Includes the following steps: Step 1, Hot air preparation: High-temperature flue gas is continuously produced in a first-stage fluidized bed combustion furnace using coke and dry oxygen; Step 2, Slurry Drying and Separation: The high-temperature flue gas is introduced into the second-stage fluidized bed dryer, so that the refined vanadium-removing slurry continuously added to the second-stage fluidized bed dryer is dried within a predetermined temperature range. The dust-containing gaseous titanium tetrachloride and vanadium slag particles are discharged from the second-stage fluidized bed dryer, and the solid phase is dried into granular vanadium slag. Step 3, Product Recovery: The dust-containing gaseous titanium tetrachloride and vanadium slag particles are separated by gas-solid separation. The separated titanium tetrachloride gas enters the condensation device, and the liquid titanium tetrachloride is recovered after condensation.

2. The method according to claim 1, characterized in that, Before operation, the method involves purging the entire system with dry nitrogen until the dew point is below -40°C to ensure a waterless environment.

3. The method according to claim 1, characterized in that, In step one, the coke has a particle size of 1-5 mm, and the mass ratio of the dry oxygen to the coke is controlled to be 2.0-2.5:

1.

4. The method according to claim 1 or 3, characterized in that, In step one, the bed temperature of the first-stage fluidized bed combustion furnace is 950–1150℃, and the apparent gas velocity is 1.5–3.0 m / s.

5. The method according to claim 1, characterized in that, The high-temperature flue gas generated in step one undergoes gas-solid separation before entering the second-stage fluidized bed dryer, so that the dust content of the high-temperature flue gas entering the second-stage fluidized bed dryer is less than 50 mg / Nm³.

6. The method according to claim 1, characterized in that, In step two, the apparent gas velocity of the second-stage fluidized bed dryer is 0.8 to 2.5 m / s, the bed pressure drop is maintained at 2000 to 5000 Pa, and the furnace temperature is 200 to 350 °C. Alternatively, the granular vanadium slag produced after drying has a particle size range of 50–500 μm, a median particle size of 120–280 μm, an apparent density of 1.2–1.8 g / cm³, and a bulk density of 0.6–1.0 g / cm³.

7. The method according to claim 1 or 6, characterized in that, In step two, the refined vanadium-removing slurry is preheated to 50-80°C before being added to the second-stage fluidized bed dryer.

8. The method according to claim 1 or 6, characterized in that, In step two, the residence time of the material in the second-stage fluidized bed dryer is 5 to 30 minutes.

9. The method according to claim 1 or 6, characterized in that, In step two, the refined vanadium-removing slurry is added at a position 500-1000 mm above the second gas distribution plate inside the furnace.

10. The method according to claim 1, characterized in that, In step three, the condensation device employs a two-stage condensation process. The first stage of condensation condenses the titanium tetrachloride gas to 35-45°C, while the second stage uses a condensing medium at -25°C to -15°C for condensation.

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