Apparatus and method for semi-continuous alkaline pressure digestion leaching of tungsten from tungsten minerals

Abstract

This invention belongs to the field of hydrometallurgical technology, specifically disclosing an apparatus and method for semi-continuous alkaline pressure leaching of tungsten minerals. The apparatus includes a vertical pressure leaching vessel, a flash tank, and a compressed air supply system. The inlet of the flash tank is connected to the outlet of the pressure leaching vessel, and the compressed air pipeline is connected to the top of the pressure leaching vessel. After pressure leaching, the pressure inside the vessel naturally drops to 0.3~0.4 MPa. Compressed air is then introduced to force the slurry into the flash tank, rapidly reducing the pressure to atmospheric pressure before discharge. The diameter ratio of the flash tank to a single pressure leaching vessel is 0.7~0.8, and the volume ratio of the flash tank to the total volume of the pressure leaching vessel is 0.1~0.2. This invention combines flash leaching with compressed air-assisted discharge, solving the problems of slow low-pressure discharge and easy clogging caused by the high viscosity and high solids content of tungsten ore slurry. The low-pressure discharge time is reduced from several hours to several minutes, significantly improving equipment utilization, maintaining batch leaching flexibility, and allowing for waste heat recovery. It is suitable for alkaline pressure leaching of wolframite, scheelite, and mixed ores.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, and particularly relates to an apparatus and method for semi-continuous alkaline pressure leaching of tungsten from tungsten minerals. Background Technology

[0002] The main tungsten minerals used in industrial production are wolframite and scheelite. With the decreasing availability of high-quality wolframite resources, scheelite and low-grade complex wolframite-wolframite mixtures have become the main raw materials for tungsten smelting. Currently, alkaline pressure leaching remains the mainstream process for tungsten smelting, mainly including soda ash (Na2CO3) pressure leaching and caustic soda (NaOH) pressure leaching. Existing alkaline pressure leaching processes primarily employ two types of equipment: one is the vertical pressure leaching kettle intermittent leaching process, which uses a single vertical pressure leaching kettle to complete a full cycle of feeding, heating, leaching, depressurization, and discharge under high temperature (170~240℃) and high pressure (0.8~3.0MPa) before proceeding to the next batch; the other is the horizontal multi-compartment pressure leaching kettle continuous leaching process, which allows for continuous feeding and discharge, resulting in large processing capacity and high production efficiency.

[0003] Both of the above processes have insurmountable technical drawbacks. For the vertical pressure cooker intermittent leaching process, the main drawback lies in the excessively long depressurization and discharge phase. After leaching, the pressure inside the cooker must be reduced from high pressure to atmospheric pressure before the cooker door can be opened for discharge. The depressurization time for the high-pressure phase (from 0.8~3.0 MPa to 0.3~0.4 MPa) is relatively short (approximately a few minutes), but the depressurization time for the low-pressure phase (from 0.3~0.4 MPa to atmospheric pressure) can be as long as several hours. This is because the gas phase volume expands in the cooker during the low-pressure phase, but the mass transfer driving force at the gas-liquid interface weakens, making natural diffusion alone extremely inefficient for depressurization. This results in the equipment being in a waiting state for a long time, significantly reducing equipment utilization. For the horizontal multi-compartment pressure cooker continuous leaching process, a significant drawback is the severe lag in process parameter adjustments. When raw material quality fluctuates or process conditions need optimization, the material progresses step-by-step within the vessel during continuous leaching. Parameter adjustments require waiting for the entire system to reach a new equilibrium, resulting in response times of several hours. During this period, a large amount of substandard slurry may be generated, leading to resource waste and increased processing burdens. Furthermore, the tungsten smelting industry generally has small production capacity, and the equipment investment and operation and maintenance costs of continuous leaching processes are high, making it less cost-effective for most companies.

[0004] However, tungsten ore slurry possesses high viscosity and high solids content. During alkaline pressure leaching, the slurry has a low liquid-to-solid ratio and fine mineral particle size. Furthermore, the fine particles generated by mineral structure disruption during leaching, along with the synergistic effect of dissolved salts in the liquid phase, significantly increase the slurry's flow resistance. Especially at the low-pressure stage (0.3–0.4 MPa), gas gradually precipitates from the slurry, forming a complex gas-liquid-solid three-phase system. This significantly increases the slurry's yield stress, making it highly susceptible to deposition and blockage at the bottom of the vessel, the outlet, and in the pipelines. This characteristic makes it difficult to directly apply conventional chemical processing techniques such as flash evaporation or compressed air conveying to the pressure leaching process of tungsten ore slurry. Specifically, while flash evaporation technology is widely used in the chemical, food, and pharmaceutical industries for depressurizing and cooling liquid materials, it is primarily used for low-viscosity, low-solids solutions or slurries. If only a flash tank is installed without auxiliary power, high-viscosity tungsten ore slurry cannot flow smoothly into the flash tank under its own weight at low pressure. Furthermore, insufficient gas-liquid separation during flash evaporation leads to a large amount of slurry being carried away by steam, causing material loss and pipeline blockage. While compressed air discharge is commonly used in mining and metallurgy for conveying low-viscosity slurries or powders, in the pressure cooking and discharge of tungsten ore slurry, if compressed air is only introduced during the high-pressure stage, the excessive pressure difference can cause the slurry to splash instantly, resulting in severe equipment impact and wear. If compressed air is used alone during the low-pressure stage without a flash tank, the volume expansion and gas release caused by phase change during slurry cooling and depressurization cannot be resolved, making stable discharge difficult to achieve.

[0005] In summary, existing alkaline pressure leaching processes for tungsten minerals suffer from the following technical deficiencies: intermittent vertical pressure leaching kettles experience prolonged low-pressure natural depressurization, resulting in low equipment utilization; continuous horizontal pressure leaching kettles suffer from sluggish parameter adjustments, easily producing substandard slurry, and incurring high investment costs and low cost-effectiveness; furthermore, the high viscosity and high solids content of tungsten slurry make discharge difficult during the low-pressure stage, and existing technologies lack effective discharge solutions for this unique physical property system. To address these shortcomings, this invention provides an apparatus and method for semi-continuous alkaline pressure leaching of tungsten minerals. Summary of the Invention

[0006] In view of the above-mentioned problems, the present invention provides an apparatus and method for semi-continuous alkaline pressure leaching of tungsten minerals. This invention combines flash evaporation with compressed air-assisted discharge, solving the problems of slow low-pressure discharge and easy clogging caused by the high viscosity and high solids content of tungsten ore slurry. The low-pressure discharge time is reduced from several hours to several minutes, significantly improving equipment utilization, maintaining batch leaching flexibility, and allowing for waste heat recovery. It is suitable for alkaline pressure leaching of wolframite, scheelite, and mixed ores.

[0007] To address the above problems, the present invention provides an apparatus for semi-continuous alkaline pressure leaching of tungsten minerals, comprising: At least one vertical pressure vessel for leaching tungsten mineral slurry; A flash evaporator, wherein the inlet of the flash evaporator is connected to the outlet of the vertical pressure cooker via a discharge pipe; A compressed air supply system is connected to the top of the vertical pressure cooker via a compressed air pipeline. It is used to introduce compressed air into the cooker when the pressure inside the vertical pressure cooker drops to 0.3~0.4MPa, thereby forcibly and stably pressing the slurry into the flash evaporation tank. The top of the flash tank is equipped with an exhaust port for quickly discharging the steam generated during the depressurization of the slurry to atmospheric pressure, and the bottom of the flash tank is equipped with a discharge port for discharging the depressurized slurry. The diameter ratio of the flash evaporator to that of a single vertical pressure cooker is 0.7 to 0.8, and the volume ratio of the flash evaporator to the total volume of the vertical pressure cooker is 0.1 to 0.2.

[0008] Preferably, multiple vertical pressure cookers are used in conjunction with a single flash tank, with each vertical pressure cooker alternating to perform leaching operations and sharing the same flash tank for discharge.

[0009] Preferably, the compressed air supply system provides compressed air pressure of 0.3~0.4MPa.

[0010] Preferably, the top exhaust port of the flash tank is connected to a waste heat recovery system for recovering the steam generated during the flash evaporation process.

[0011] Based on the same inventive concept, the present invention also provides a method for semi-continuous alkaline pressure leaching of tungsten minerals using any of the above-described apparatus, comprising the following steps: S1. Tungsten minerals are ground with water to obtain a slurry; wherein, the slurry contains more than 96% tungsten minerals with a particle size of less than 44 μm and has a solid content of 65% to 70%; S2. Add alkali to the slurry and mix with water to obtain a slurry after conditioning; wherein, the liquid-to-solid volume-to-mass ratio of the slurry after conditioning is 3~5:1, the volume of liquid in the slurry after conditioning is in mL, and the mass of solid is in g; the excess coefficient of the alkali added is 2.5~3.0; S3. The prepared slurry is added to a vertical pressure cooking kettle, and steam is introduced for pressure cooking and leaching treatment to obtain the pressure-leached slurry. S4. Open the exhaust valve of the vertical pressure cooker to naturally reduce the pressure inside the cooker to 0.3~0.4MPa; then introduce compressed air into the vertical pressure cooker to force the pressure-cooked leaching slurry into the flash tank in a stable manner. The pressure-cooked leaching slurry is rapidly reduced to atmospheric pressure through the flash tank. The pressure-cooked leaching slurry is discharged through the bottom discharge port of the flash tank, and the steam generated by flash evaporation is discharged through the top exhaust port of the flash tank.

[0012] Preferably, in step S4, the pressure of the compressed air introduced is 0.3~0.4MPa.

[0013] Preferably, multiple vertical pressure cookers are used in conjunction with a flash evaporation tank, with each vertical pressure cooker performing leaching operations alternately and the flash evaporation tank being used sequentially for material discharge.

[0014] Preferably, in step S4, the steam discharged from the top of the flash tank is recovered by a waste heat recovery system.

[0015] Preferably, in step S1, the tungsten mineral is wolframite, scheelite, or a mixture of wolframite and scheelite.

[0016] Preferably, in step S3, the temperature of the pressure cooking leaching treatment is 170~230℃, the pressure is 0.8~2.8Mpa, and the time is 3~4h; in step S4, the pressure inside the vessel is 0.8~2.8Mpa.

[0017] Compared with existing intermittent leaching processes in vertical pressure cookers and continuous leaching processes in horizontal pressure cookers, the present invention has the following advantages: (1) Addressing the technical challenge of existing vertical pressure cookers where natural depressurization takes several hours due to the high viscosity and high solids content of tungsten ore slurry during the low-pressure stage (0.3~0.4MPa), this invention, for the first time, combines a flash tank with compressed air-assisted discharge. After the pressure inside the cooker drops to 0.3~0.4MPa, compressed air is immediately introduced from the top of the cooker, using positive pressure to stably pressurize the slurry into the flash tank, where gas-liquid separation is quickly completed and the pressure is reduced to atmospheric pressure. This effect is not a simple superposition of flash evaporation and compressed air, but rather the result of their synergistic effect: flash evaporation provides a phase change channel for rapid cooling and depressurization, while compressed air provides continuous power to overcome the yield stress of the slurry and prevents solid particles from depositing and clogging it.

[0018] (2) This invention retains the core advantages of batch leaching in vertical pressure cookers. The leaching temperature, pressure, time, and excess alkali coefficient can be flexibly adjusted according to the grade of tungsten ore (wolfonite, scheelite, or mixed ore) and impurity content, ensuring that each batch of slurry is leached to the required standard before discharge. This fundamentally avoids the defect of unqualified slurry caused by the parameter adjustment lag (response time as long as several hours) in horizontal continuous pressure cookers. At the same time, by using multiple vertical pressure cookers in alternating combinations with a flash tank, the flash tank serves as a shared discharge unit that rotates among multiple cookers, making the system throughput close to that of the horizontal continuous pressure cooker leaching process, while significantly reducing equipment investment. This fills the technological gap between the intermittent leaching process of vertical pressure cookers and the leaching process of horizontal continuous pressure cookers.

[0019] (3) This invention fully recognizes the physical characteristics of tungsten ore slurry, which has extremely high apparent viscosity and thixotropy under low pressure, and solid particles are prone to deposit to form a dense packing layer, making conventional discharge methods ineffective. By connecting the compressed air pipeline to the top of the vertical pressure cooker, compressed air is introduced at low pressure (0.3~0.4MPa). The gas pressure is used to break the static yield stress of the slurry, forming a pneumatic conveying effect, which forces the slurry to flow into the flash tank along the discharge port. This effectively avoids slurry blockage in the pipeline and slurry residue in the cooker during the discharge process, and greatly reduces equipment cleaning, downtime and maintenance costs.

[0020] (4) In this invention, compressed air is introduced only in the low-pressure stage, requiring a lower air pressure, which is far lower than the high-pressure air supply requirement, resulting in low energy consumption. At the same time, the high-temperature steam discharged from the top of the flash tank can be used by the waste heat recovery system to preheat the slurry or heat other processes. In addition, the forced discharge of the slurry by compressed air (with a pressure not lower than that inside the vertical pressure cooker) avoids the slurry from remaining in the cooker for a long time, reducing the heat loss of the slurry after leaching and further improving the overall energy efficiency.

[0021] (5) ф(flash evaporation) / ф(single vessel) = 0.7~0.8, and the volume ratio satisfies V(flash evaporation) / (n×V(single vessel)) = 0.1~0.2 (n is the number of vertical pressure cooking vessels). This ratio range has a criticality; below the lower limit, gas-liquid separation is insufficient, and the slurry is easily entrained by steam; above the upper limit, the residual pressure after discharge is still high, and the risk of slurry deposition increases. This invention achieves a synergistic effect of thorough discharge, efficient gas-liquid separation, and complete pressure release through precise matching.

[0022] (6) This invention shortens the discharge time and improves production efficiency without negatively impacting the leaching effect. For wolframite, scheelite, and mixed wolframite ores, regardless of whether soda ash or caustic soda is used as the leaching alkali, the tungsten leaching rate can reach over 97%, which is comparable to or slightly improved compared to traditional vertical reactors. This is because rapid discharge reduces side reactions (such as silicate reprecipitation) of the slurry under high temperature and pressure after leaching, which is beneficial to improving the tungsten recovery rate.

[0023] In summary, this invention, through systematic innovation of "flash evaporation tank + compressed air-assisted discharge + multi-reactor alternating operation + optimized equipment ratio + waste heat recovery", solves the dual contradictions of "slow low-pressure decompression" and "lag in continuous process adjustment" in the prior art, and overcomes the problem of discharge blockage caused by the high viscosity and high solid content of tungsten ore slurry. It has significant technological progress and industrial application value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the apparatus for semi-continuous alkaline pressure leaching of tungsten minerals according to the present invention. Figure 2 This is a process flow diagram of the semi-continuous alkaline pressure leaching method for extracting tungsten from tungsten minerals according to the present invention.

[0025] Explanation of reference numerals in the attached figures: 1. Vertical pressure cooker; 2. Flash evaporator; 3. Feed inlet; 4. Discharge outlet; 5. Exhaust outlet. Detailed Implementation

[0026] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to specific embodiments. Obviously, the described embodiments are only a portion, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] It should be noted that the alkali excess coefficient in this application refers to the ratio of the actual amount of alkali used (mol) to the theoretical amount of alkali used (mol) during the pressure boiling leaching reaction.

[0031] Currently, the intermittent vertical pressure leaching process in tungsten smelting suffers from long natural depressurization times in the low-pressure stage, resulting in low equipment utilization. Continuous horizontal pressure leaching processes suffer from sluggish parameter adjustments, easily producing substandard slurry, and incurring high investment costs and low cost-effectiveness. Furthermore, the high viscosity and high solids content of tungsten slurry make discharge difficult during the low-pressure stage. To address these issues, this invention provides a semi-continuous alkaline pressure leaching apparatus and method for extracting tungsten from tungsten minerals. This invention combines flash evaporation with compressed air-assisted discharge, solving the problems of slow low-pressure depressurization and easy clogging caused by the high viscosity and high solids content of tungsten slurry. The low-pressure discharge time is reduced from several hours to several minutes, significantly improving equipment utilization, maintaining batch leaching flexibility, and allowing for waste heat recovery. It is suitable for alkaline pressure leaching of wolframite, scheelite, and mixed ores.

[0032] The following examples and comparative models further illustrate this point.

[0033] Example 1 An apparatus for semi-continuous alkaline pressure leaching of tungsten from tungsten minerals, such as... Figure 1 As shown, it includes: 5 vertical pressure cookers 1 ( Figure 1 Only three vertical pressure cookers were shown (two vertical pressure cookers were omitted), used for leaching tungsten mineral slurry; One flash evaporation tank 2, wherein the feed inlet 3 of the flash evaporation tank 2 is connected to the discharge outlet 4 of the vertical pressure cooker 1 through a discharge pipeline; A compressed air supply system is connected to the top of the vertical pressure cooker 1 via a compressed air pipeline. It is used to introduce compressed air into the cooker when the pressure inside the vertical pressure cooker 1 drops to 0.3 MPa, thereby forcing the slurry into the flash tank 2. The top of the flash tank 2 is provided with an exhaust port 5 for quickly discharging the steam generated during the process of depressurizing the slurry to atmospheric pressure. The bottom of the flash tank 2 is provided with a discharge port for discharging the depressurized slurry. The diameter ratio of the flash evaporator 2 to the vertical pressure cooker 1 is ф(flash evaporation) / ф(single cooker)=0.71, and the volume ratio satisfies V(flash evaporation) / (n×V(single cooker))=0.13, n=5.

[0034] A semi-continuous alkaline pressure leaching method for extracting tungsten from tungsten minerals, such as Figure 2 As shown, it includes the following steps: (1) 6t of wolframite (WO3 55%, FeO 18%, MnO 17%) was water-milled to obtain a slurry with tungsten minerals of less than 44μm in size accounting for 96% of the total mineral content and a solid content of 66wt%. (2) Add soda to the slurry and add water to adjust the slurry; wherein the liquid-to-solid volume ratio of the adjusted slurry is 5:1 (mL / g); and the excess alkali coefficient is 2.9. (3) The prepared slurry is added to one vertical pressure cooker (the other vertical pressure cookers are also fed in the same way), and steam is alternately introduced into each vertical pressure cooker for pressure cooking and leaching treatment to obtain the pressure cooked and leached slurry (the leaching rate of tungsten is 98%). The pressure cooking and leaching treatment is carried out at a temperature of 190°C, a pressure of 1.2 MPa, and a time of 3 hours. (4) Alternately open the exhaust valve of each vertical pressure cooker to naturally reduce the pressure inside the cooker from 1.2 MPa to 0.3 MPa; then introduce compressed air (0.3 MPa) into the vertical pressure cooker to force the pressure-cooked leaching slurry into the flash tank. The pressure-cooked leaching slurry is rapidly reduced to atmospheric pressure through the flash tank. The pressure-cooked leaching slurry is discharged through the bottom discharge port of the flash tank and undergoes liquid-solid separation. The solution is sent to the subsequent tungsten smelting process to recover tungsten, and the pressure-cooked residue is sent to the slag yard for storage. The steam generated by flash evaporation is discharged through the exhaust port at the top of the flash tank.

[0035] Example 2 The difference between this embodiment and Embodiment 1 is as follows: Replace the baking soda in step (2) with caustic soda, and the excess coefficient of the alkali added is 2.6; The temperature of the pressure leaching treatment in step (3) is 180℃ and the pressure is 1.0 MPa, resulting in a pressure leaching slurry (the leaching rate of tungsten is 97.8%).

[0036] Step (4) The pressure inside the kettle is naturally reduced from 1.0 MPa to 0.3 MPa; then compressed air (0.3 MPa) is introduced into the vertical pressure cooking kettle to force the slurry after pressure cooking and leaching into the flash evaporation tank.

[0037] The other steps and parameters are the same as in Example 1.

[0038] Example 3 The difference between this embodiment and Embodiment 1 is as follows: Replace the 6t wolframite (WO3 55%, FeO 18%, MnO 17%) in step (1) with 7.5t scheelite (WO3 32%, CaO 35%). In step (2), the excess coefficient of alkali added is 2.9, and the liquid-to-solid volume ratio of the slurry after conditioning is 4:1 (mL / g). The pressure leaching treatment in step (3) was carried out at a temperature of 200℃, a pressure of 1.6 MPa, and a time of 3.5 h, resulting in a slurry after pressure leaching (the leaching rate of tungsten was 97.7%). Step (4) The pressure inside the reactor is naturally reduced from 1.6 MPa to 0.35 MPa. Then compressed air (0.35 MPa) is introduced into the vertical pressure cooking reactor to force the slurry after pressure cooking and leaching into the flash evaporation tank.

[0039] The other steps and parameters are the same as in Example 1.

[0040] Example 4 The difference between this embodiment and Embodiment 1 is as follows: Replace the 6t wolframite (WO3 55%, FeO 18%, MnO 17%) in step (1) with 7.5t scheelite (WO3 32%, CaO 35%). Replace the soda ash in step (2) with caustic soda, the excess coefficient of the alkali added is 2.7, and the liquid-solid volume ratio of the slurry after conditioning is 4:1 (mL / g). The pressure leaching treatment in step (3) was carried out at a temperature of 190℃, a pressure of 1.2 MPa, and a time of 3.5 h, resulting in a slurry with a tungsten leaching rate of 97.6%. Step (4) The pressure inside the reactor is naturally reduced from 1.2 MPa to 0.35 MPa. Then compressed air (0.35 MPa) is introduced into the vertical pressure cooking reactor to force the slurry after pressure cooking and leaching into the flash evaporation tank.

[0041] The other steps and parameters are the same as in Example 1.

[0042] Example 5 The difference between this embodiment and Embodiment 1 is as follows: Replace the 6t wolframite (WO3 55%, FeO 18%, MnO 17%) in step (1) with 10t wolframite (WO3 24%, FeO 13%, CaO 17%). In step (2), the excess coefficient of alkali added is 3.0, and the liquid-to-solid volume ratio of the slurry after conditioning is 3:1 (mL / g). The pressure leaching treatment in step (3) was carried out at a temperature of 220°C, a pressure of 2.4 MPa, and a time of 4.0 h, resulting in a slurry with a tungsten leaching rate of 97.2%. Step (4) The pressure inside the reactor is naturally reduced from 2.4 MPa to 0.4 MPa. Then, compressed air (0.4 MPa) is introduced into the vertical pressure cooking reactor to force the leached slurry into the flash evaporation tank.

[0043] The other steps and parameters are the same as in Example 1.

[0044] Example 6 The difference between this embodiment and Embodiment 1 is as follows: Replace the 6t wolframite (WO3 55%, FeO 18%, MnO 17%) in step (1) with 10t wolframite (WO3 24%, FeO 13%, CaO 17%). Replace the soda in step (2) with caustic soda, the excess coefficient of the alkali added is 2.8, and the liquid-solid volume ratio of the slurry after conditioning is 3:1 (mL / g). The pressure leaching treatment in step (3) was carried out at a temperature of 210℃, a pressure of 1.8 MPa, and a time of 4.0 h, resulting in a slurry with a tungsten leaching rate of 97.1%. Step (4) The pressure inside the reactor is naturally reduced from 1.8 MPa to 0.4 MPa. Then, compressed air (0.4 MPa) is introduced into the vertical pressure cooking reactor to force the slurry after pressure cooking and leaching into the flash evaporation tank.

[0045] The other steps and parameters are the same as in Example 1.

[0046] The differences between Examples 1 to 6 are summarized in Table 1 below.

[0047] Table 1:

[0048] Example 7 and Comparative Examples 1-3: The differences between Comparative Examples 1-3 and Example 7 are shown in Table 2 below. Other steps and parameters are the same as in Example 1.

[0049] Table 2:

[0050] Comparative Example 4 The difference between this comparative example and Example 7 is that no flash evaporation tank is used; only a single vertical pressure cooker is employed, and compressed air is not introduced. After pressure cooking is completed, the pressure is naturally released to atmospheric pressure before discharge. Other steps and parameters are the same as in Example 7.

[0051] Comparative Example 5 The difference between this comparative example and Example 7 is that a flash evaporator is set up, and only one vertical pressure cooker is used, but compressed air is not introduced; the slurry flows into the flash evaporator by gravity for discharge. Other steps and parameters are the same as in Example 7.

[0052] Comparative Example 6 The difference between this comparative example and Example 7 is that only one vertical pressure cooker is used, and compressed air is introduced when the pressure inside the cooker drops to 0.6 MPa (high-pressure section). Other steps and parameters are the same as in Example 7.

[0053] The differences between Comparative Examples 4 and 6 are shown in Table 3 below.

[0054] Table 3:

[0055] In Table 3, “—” indicates that it is not applicable or there is no data.

[0056] Results analysis: Table 2 shows that Example 7 (diameter ratio 0.71, volume ratio 0.13, compressed air introduced) had a low-pressure discharge time of 6 minutes and a tungsten leaching rate of 97.5%. Comparative Example 1 reduced the diameter ratio to 0.5 and the volume ratio to 0.05 (below the scope of this invention), extending the discharge time to 14 minutes and decreasing the leaching rate to 96.8%. This indicates that excessively small volume leads to insufficient gas-liquid separation, severe equipment erosion and wear, and slurry entrainment by steam. Comparative Example 2 (diameter ratio 0.9, volume ratio 0.25, above the upper limit) had a discharge time of 11 minutes, which is better than Comparative Example 1 but significantly worse than Example 7. This indicates that excessive volume increases the risk of slurry deposition in the flash tank, and the residual pressure is not completely released after discharge. Comparative Example 3 (volume ratio 0.25, diameter ratio 0.71) also showed a discharge time of 10 minutes, further confirming the hazards of exceeding the volume ratio limit. Therefore, a diameter ratio of 0.7 to 0.8 and a volume ratio of 0.1 to 0.2 are the critical ranges for ensuring rapid and stable material discharge.

[0057] As shown in Table 3, Comparative Example 4 (no flash tank, no compressed air, natural depressurization to atmospheric pressure) had a discharge time as long as 270 minutes (4.5 hours), resulting in extremely low equipment utilization. Comparative Example 5 (with flash tank but no compressed air) still required a discharge time of 28 minutes, which was a significant improvement over natural depressurization, but it could not completely solve the problem of high-viscosity slurry sedimentation. Comparative Example 6 introduced compressed air at an internal pressure of 0.6 MPa (high-pressure section), resulting in a discharge time of only 8 minutes, but the increased compressed air pressure and high pressure differential caused slurry splashing and impact, exacerbating equipment wear. In contrast, Example 7 introduced compressed air at a low pressure of 0.35 MPa, achieving smooth discharge, no blockage, and lower energy consumption. It is evident that 0.3~0.4 MPa is the optimal intervention window.

[0058] The above embodiments and comparative examples demonstrate that the present invention can treat wolframite, scheelite, and mixed wolframite ores, respectively, using soda ash or caustic soda as the alkaline pressure leaching agent, achieving leaching rates of 97.1% to 98.0%. In contrast, in the comparative examples, regardless of the modifications, any deviation from the core characteristics of the present invention significantly reduces performance. This proves that the method of the present invention has broad applicability to various tungsten minerals.

[0059] In summary, this invention, through its systematic innovation of "flash evaporation tank + compressed air-assisted discharge + critical equipment proportioning + multiple reactor alternation + waste heat recovery," significantly outperforms existing technologies and various comparative schemes in terms of discharge efficiency, equipment utilization, process flexibility, anti-clogging capability, energy consumption, and product quality, achieving excellent technical results.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An apparatus for semi-continuous alkaline pressure leaching of tungsten from tungsten minerals, characterized in that, include: At least one vertical pressure vessel for leaching tungsten mineral slurry; A flash evaporator, wherein the inlet of the flash evaporator is connected to the outlet of the vertical pressure cooker via a discharge pipe; A compressed air supply system is connected to the top of the vertical pressure cooker via a compressed air pipeline. It is used to introduce compressed air into the cooker when the pressure inside the vertical pressure cooker drops to 0.3~0.4MPa, thereby forcibly and stably pressing the slurry into the flash evaporation tank. The top of the flash tank is equipped with an exhaust port for quickly discharging the steam generated during the depressurization of the slurry to atmospheric pressure, and the bottom of the flash tank is equipped with a discharge port for discharging the depressurized slurry. The diameter ratio of the flash evaporator to that of a single vertical pressure cooker is 0.7 to 0.8, and the volume ratio of the flash evaporator to the total volume of the vertical pressure cooker is 0.1 to 0.

2.

2. The apparatus for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 1, characterized in that, Multiple vertical pressure cookers are used in conjunction with a single flash tank. Each vertical pressure cooker alternates to perform leaching operations and shares the same flash tank for discharge.

3. The apparatus for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 2, characterized in that, The compressed air supply system provides compressed air at a pressure of 0.3~0.4MPa.

4. The apparatus for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 1, characterized in that, The top exhaust port of the flash evaporator is connected to a waste heat recovery system for recovering the steam generated during the flash evaporation process.

5. A method for semi-continuous alkaline pressure leaching of tungsten minerals based on the apparatus according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Tungsten minerals are ground with water to obtain a slurry; wherein, the slurry contains more than 96% tungsten minerals with a particle size of less than 44 μm and has a solid content of 65% to 70%; S2. Add alkali to the slurry and mix with water to obtain a slurry after conditioning; wherein, the liquid-to-solid volume-to-mass ratio of the slurry after conditioning is 3~5:1, the volume of liquid in the slurry after conditioning is in mL, and the mass of solid is in g; the excess coefficient of the alkali added is 2.5~3.0; S3. The prepared slurry is added to a vertical pressure cooking kettle, and steam is introduced for pressure cooking and leaching treatment to obtain the pressure-leached slurry. S4. Open the exhaust valve of the vertical pressure cooker to naturally reduce the pressure inside the cooker to 0.3~0.4MPa; then introduce compressed air into the vertical pressure cooker to force the pressure-cooked leaching slurry into the flash tank in a stable manner. The pressure-cooked leaching slurry is rapidly reduced to atmospheric pressure through the flash tank. The pressure-cooked leaching slurry is discharged through the bottom discharge port of the flash tank, and the steam generated by flash evaporation is discharged through the top exhaust port of the flash tank.

6. The method for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 5, characterized in that, In step S4, the pressure of the compressed air introduced is 0.3~0.4MPa.

7. The method for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 5, characterized in that, Multiple vertical pressure cookers are used in conjunction with a flash tank. Each vertical pressure cooker performs leaching operations alternately, and the flash tank is used sequentially for material discharge.

8. The method for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 5, characterized in that, In step S4, the steam discharged from the top of the flash tank is recovered by the waste heat recovery system.

9. The method for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 5, characterized in that, In step S1, the tungsten mineral is wolframite, scheelite, or a mixture of wolframite and scheelite.

10. The method for semi-continuous alkaline pressure leaching of tungsten minerals according to claim 5, characterized in that, In step S3, the temperature of the pressure cooking leaching treatment is 170~230℃, the pressure is 0.8~2.8Mpa, and the time is 3~4h; in step S4, the pressure inside the vessel is 0.8~2.8Mpa.

Images