Method for decomposing scheelite by using salt and alkali

Abstract

The invention discloses a method for decomposing scheelite by using salt and alkali, which comprises the following steps: mixing scheelite powder subjected to ball milling, sodium carbonate, aluminum oxide, sodium hydroxide and water into ore pulp, feeding the ore pulp into a horizontal continuous reaction kettle, and simultaneously introducing a heating medium into the reaction kettle for heating, and controlling the heating medium in the first partition stirring chamber to account for 80-90% of the total heating medium, so that loose and porous calcium carbonate is quickly generated, and reacting, discharging and filtering to obtain a sodium tungstate solution and tungsten slag with low tungsten content. According to the method, the scheelite sodium carbonate leaching reaction dynamic control stage time can be shortened, chemical reaction stage control can be rapidly started, the scheelite decomposition technological process is optimized, the scheelite leaching rate and the recovery rate of valuable metal tungsten are improved, the impurity content of leaching liquid and the tungsten content of tungsten slag are reduced, and good application prospects are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of scheelite leaching, and relates to a method for decomposing scheelite with salts and alkalis, and is particularly applicable to the high-temperature leaching of scheelite with sodium carbonate. Background Art

[0002] Tungsten belongs to rare refractory metals and has excellent physical, chemical and machining properties. Tungsten products are widely used in fields such as chemical industry, electronics, medical treatment, hard alloys, etc. Primary chemical products such as ammonium paratungstate (referred to as APT) and tungsten oxide play a connecting role in the entire tungsten industrial chain. With the booming development of downstream products such as wear-resistant materials, hard alloys, and catalysts, the demand for high-quality APT and tungsten oxide products has become increasingly prominent.

[0003] At home and abroad, the proportion of scheelite, black and white tungsten mixed ore, and complex low-grade mixed ore in tungsten smelting will be increasing. The leaching efficiency of tungsten ore decreases, and it is necessary to increase the production capacity through comprehensive methods such as increasing the number of leaching equipment and improving the leaching grade. However, effective technical breakthroughs are still needed to solve the problems.

[0004] In recent years, domestic APT enterprises have actively adopted new equipment and new processes, and have carried out a large amount of research and improvement in aspects such as leaching, purification, tungsten transformation, and crystallization. However, the research and application of continuous leaching technology or equipment for tungsten ore are blank. In the tungsten smelting industry, intermittent autoclaves (sodium hydroxide), sodium carbonate, sodium fluoride or hydrochloric acid processes are used to decompose scheelite, and an autoclave with a volume of less than 20 m 3 is indirectly heated by electricity or heat transfer oil, and the intermittent operation of "feeding, heating, heat preservation, cooling, discharging, and waiting for materials" is repeated. Many different (side) reactions occur along with changes in the temperature history and fluid form in the autoclave, and ultimately are reflected in the tungsten content index of tungsten slag. With the depletion of resources, the high requirements for valuable metal tungsten in minerals have become increasingly prominent. There are the following defects in affecting the effect of decomposing tungsten ore with salts and alkalis (that is, achieving a reduction in the tungsten content of tungsten slag):

[0005] 1. When decomposing scheelite with salts and alkalis in an intermittent autoclave, an anchor-type or frame-type stirrer is used to stir the pulp. The pulp moves in a circular motion along the inner wall of the reaction kettle around the stirring shaft as the center, and there is no relative movement between the upper and lower layers of the pulp in the axial direction, being in a relatively static state, forming a laminar flow phenomenon, and there are few effective collisions between substances, affecting the exchange between substances.

[0006] 2. During the operation of the batch reactor, six processes of "feeding, heating, heat preservation, cooling, discharging, and waiting for materials" are continuously carried out. The processes of "feeding" and "heating (heating to 150 °C)" take 40 minutes. At 150 - 230 °C, the decomposition process of scheelite is controlled by chemical reaction. The generated calcium carbonate is loose and porous, and internal diffusion does not become the controlling step of the process; when the temperature is lower than 150 °C, the dense calcium carbonate film generated by the reaction, which is not loose and porous, covers the surface of scheelite, hindering the migration of auxiliary materials such as sodium carbonate, the leaching agent, to the reaction center and the diffusion of the leaching product sodium tungstate molecules from the inside of the pores to the outer surface of the scheelite particles. The reaction is controlled by kinetics, directly affecting the leaching rate of scheelite and reducing the recovery rate of valuable metal tungsten.

[0007] 3. During the discharging and waiting-for-materials processes of the batch reactor operation, the batch reactor, which is a high-temperature pressure vessel, is insulated with asbestos. Although the processes of pressure relief and discharging have been carried out, the remaining temperature of the asbestos on the outer wall of the batch reactor after discharging is sufficient to dry the pulp adhering to the inner wall of the reactor and the bottom pulp at the bottom of the reactor, forming a hard "rice crust" that wraps tungsten. Its defects are as follows: First, it is easy to block the discharge pipe and wear the pipeline; second, it causes the tungsten content in the slag to be distorted.

[0008] In summary, it is urgent to solve problems such as the fluid form of the pulp in the reactor, the densification of calcium carbonate film, and the formation of "rice crust" of the remaining pulp in the reactor after discharging, so as to improve the level of decomposing scheelite with saline-alkali. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art. Particularly aiming at technical problems such as the fluid form of the pulp in the existing batch reactor, the densification of the generated calcium carbonate, and the formation of "rice crust" of the remaining pulp in the reactor after discharging, a method for decomposing scheelite with saline-alkali is provided, which can improve the leaching rate of scheelite, increase the recovery rate of valuable metal tungsten, and reduce the tungsten content in tungsten slag. This method can shorten the time of the kinetic control stage of the sodium carbonate leaching reaction of scheelite, quickly enter the chemical reaction stage control, and achieve the turbulence of the pulp in the reactor, the porosity of calcium carbonate, and the non-formation of "rice crust" of the remaining pulp in the reactor after discharging, etc.

[0010] To solve the above technical problems, the present invention adopts the following technical solutions.

[0011] A method for decomposing scheelite with saline-alkali, comprising the following steps:

[0012] S1. Grind scheelite to obtain scheelite powder, and mix the scheelite powder, sodium carbonate, alumina, sodium hydroxide, and water to obtain pulp;

[0013] S2. Feed the above-mentioned pulp into a horizontal continuous reactor. There are more than 3 partition stirring chambers arranged from left to right in the horizontal continuous reactor. Adjacent partition stirring chambers are separated by partition plates, and overflow grooves are provided on the partition plates. Feed the pulp obtained in step S1 into the first partition stirring chamber. The pulp flows through each partition stirring chamber by overflow. Feed a heating medium into the partition stirring chambers, and control the heating medium distributed in the first partition stirring chamber to account for 80% - 90% of the total heating medium in all partition stirring chambers, so as to generate porous calcium carbonate in the pulp in the first partition stirring chamber. Wait until the temperature in each partition stirring chamber rises to 180°C - 200°C, and the temperature of the whole system reaches the process decomposition temperature. After the reaction, obtain clinker, continuously discharge the clinker from the last partition stirring chamber, and then filter to obtain filtrate and tungsten slag. The filtrate is sodium tungstate solution.

[0014] For the above method of decomposing scheelite with saline-alkali, preferably, in step S2, the heating medium is heat-conducting oil, electricity or steam. When the heating medium is steam, the steam pressure corresponding to the reaction temperature is below 1.5 MPa; during the continuous feeding process, the pulp in the first partition stirring chamber is heated to above 150°C within a short time to generate porous calcium carbonate, and the short time is 0.3 min - 1 min; control the heating medium distributed in the second partition stirring chamber to account for 5% - 15% of the total heating medium in all partition stirring chambers.

[0015] For the above method of decomposing scheelite with saline-alkali, preferably, in step S2, control the reaction temperature in each partition stirring chamber to be 180°C - 190°C. When the heating medium is steam, the steam pressure corresponding to the reaction temperature is 1.05 MPa - 1.22 MPa.

[0016] For the above method of decomposing scheelite with saline-alkali, preferably, in step S2, the speed of the pulp is controlled at 7m 3 / h - 12m 3 / h, the temperature of the heating medium is 220°C - 350°C. During the reaction process, control the temperature difference between the first partition stirring chamber and the other partition stirring chambers to be ≤10°C, stir the pulp in each partition stirring chamber. The stirring speed of the first partition stirring chamber and the second partition stirring chamber is controlled at 140 r / min - 160 r / min, and the stirring speed of the other partition stirring chambers is controlled at 110 r / min - 140 r / min, and the stirring speed of each partition stirring chamber gradually decreases starting from the third partition stirring chamber.

[0017] For the above method of decomposing scheelite with saline-alkali, preferably, in step S2, the speed of the pulp is controlled at 8m 3 / h - 9m3 / h, the temperature of the heating medium is 250°C to 280°C. During the reaction process, the temperature difference between the first partition stirring chamber and the remaining partition stirring chambers is controlled to be ≤5°C.

[0018] In the above method for decomposing scheelite with salt and alkali, preferably, in step S2, the volume of the horizontal continuous reaction kettle is 40m 3 ~90m 3 , and the slurry inventory in the kettle is maintained at 50% to 70% of the volume of the horizontal continuous reaction kettle.

[0019] In the above method for decomposing scheelite with salt and alkali, preferably, in step S1, for every 1t of scheelite, 3m 3 ~5m 3 of slurry is prepared. The addition amount of the scheelite powder is configured by controlling the tungsten content in the slurry to be 0.08 tons / m 3 ~0.09 tons / m 3 . In the slurry, the addition amount of sodium carbonate is 180 kg / m 3 ~240 kg / m 3 , the addition amount of alumina is 8 kg / m 3 ~12.5 kg / m 3 , and the addition amount of sodium hydroxide is 4 kg / m 3 ~8 kg / m 3 .

[0020] In the above method for decomposing scheelite with salt and alkali, preferably, in step S1, the mass fraction of tungsten in the scheelite is 25% to 38%, and more than 95% of the scheelite powder can pass through a 325-mesh vibrating screen.

[0021] In the above method for decomposing scheelite with salt and alkali, preferably, in step S2, there are 3 to 10 partition stirring chambers. The volumes of the partition stirring chambers are the same, and each partition stirring chamber is provided with a stirrer. The overflow tank is arranged at the top of the partition plate.

[0022] In the above method for decomposing scheelite with salt and alkali, preferably, in step S2, the horizontal continuous reaction kettle adopts the continuous leaching reaction kettle for scheelite processing disclosed in CN116004980A.

[0023] In the present invention, the heat transfer oil heating can adopt coil-type indirect heating of the slurry, and the electric heating can be conducted to the slurry through heating the kettle body, but it is not limited thereto.

[0024] In the present invention, internal diffusion refers to the diffusion of the leaching agent sodium carbonate from the outer surface of the ore particles into the pore channels inside the particles, or the diffusion of the product sodium tungstate molecules from the inside of the pore channels to the outer surface of the scheelite particles.

[0025] In the present invention, the main reaction formula is as follows:

[0026] Na2CO3 + CaWO4 = Na2WO4 + CaCO3 (continuous reaction kettle: porous calcium carbonate)

[0027] The main innovation points of the present invention are as follows:

[0028] 1. The decomposition temperature of sodium carbonate decomposing scheelite is usually greater than 200 °C, and the corresponding pressure is usually greater than 1.6 MPa. For a small-volume batch kettle (conventional volume 8 m 3 ), the safety risk is small. However, for a large-volume continuous kettle (such as a volume of 70 m 3 ), the safety risk is large, and high pressure is not advisable. The higher the decomposition temperature in the kettle, the leaching rate of tungsten only increases slightly. However, the applicant's research found that this brings a series of problems, which are specifically manifested as follows:

[0029] (1) The leaching rates of impurity elements such as phosphorus, arsenic, and silicon increase as a whole, resulting in high impurity content in the leaching solution, reduced quality, and high pressure in subsequent impurity removal processes. Especially for arsenic, it increases the environmental protection risk;

[0030] (2) The higher the decomposition temperature, the higher the energy consumption, and the energy consumption needs to be increased by 10 - 20%;

[0031] (3) As the temperature or pressure in the kettle increases, during discharging, the slurry severely wears the facilities of the discharging system;

[0032] (4) Raising the temperature takes more time, and the production efficiency is reduced by about 10%.

[0033] Based on the above problems, on the premise of ensuring safety, on the one hand, the applicant puts forward higher requirements for the kettle design, and on the other hand, through continuous research on the production technology of the continuous kettle, it is realized that the continuous kettle can achieve a high leaching rate of tungsten at a lower temperature (≤200 °C) and a lower pressure (≤1.5 MPa).

[0034] 2. Due to the pumping of cold slurry in the first partition mixing chamber and the output of hot slurry in the tail chamber, the temperature and pressure inside the continuous kettle will continuously fluctuate, thus affecting the realization of safe, efficient, and high-quality continuous leaching technology. Therefore, through experimental research on the continuous leaching process, the applicant adopts two-step control, that is, overall control of low-temperature leaching and steam distribution system control of porous calcium carbonate, which can make the continuous leaching meet the requirements of safety, environmental protection, economy, efficiency, and high quality. The specific explanations are as follows:

[0035] By controlling the proportion of the heating medium allocated to each chamber, the present invention can affect the crystal form and morphology of the reaction product calcium carbonate. The present invention defines that 80-90% of the heating medium is allocated to the first partition stirring chamber, so that the pulp is rapidly heated to above 150°C within a short time in the first partition stirring chamber, generating loose and porous calcium carbonate, significantly improving the mass transfer efficiency, thus enabling low-temperature leaching and having a high leaching rate.

[0036] In the present invention, preferably, 5-10% of the heating medium is allocated to the second partition stirring chamber. When the heating medium is electricity, the distribution of the heating medium can be achieved by controlling the current.

[0037] In summary, the present invention can break through the fixed thinking understanding that the traditional process of decomposing tungsten minerals with sodium carbonate (or soda) requires a temperature higher than 200°C. The final working temperature drops to 180°C - 200°C (preferably 180°C - 190°C), and the corresponding pressure can be reduced to below 1.5 MPa (preferably 1.05 MPa - 1.22 MPa), realizing efficient decomposition at low temperature and low pressure, effectively reducing the leaching rate of impurity elements in the ore raw materials, improving the product quality, reducing the production cost, and simultaneously achieving the advantages of safety, environmental protection, economy and high efficiency.

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] (1) The method for decomposing scheelite with saline-alkali of the present invention adopts a continuous leaching reaction. There are two streams of materials in the partition stirring chamber. One is the pulp (raw pulp, 30 - 60°C), and the other is the heating medium. By distributing different heating media to different partition stirring chambers of the continuous reaction kettle, the maximum utilization of energy can be achieved. The present invention controls the heating medium allocated in the first partition stirring chamber to account for 80% - 90% of the total heating medium in all partition stirring chambers, so that the pulp is rapidly heated to above 150°C within a short time in the first partition stirring chamber, greatly shortening the time of the kinetic control stage of the sodium carbonate leaching reaction of scheelite and quickly entering the chemical reaction stage control. Thus, loose and porous calcium carbonate is generated in the first partition stirring chamber, significantly improving the mass transfer efficiency, promoting a high leaching rate at low temperature and low pressure, and finally achieving the optimal comprehensive economic indicators. The tungsten recovery rate of the present invention is ≥98.7%, and the tungsten content in the tungsten slag is ≤0.5%.

[0040] In the method of the present invention, as the kettle temperature continuously rises to 180 - 200°C, the degree of hydrolysis dissociation of the pulp becomes more severe, which will cause the pH of the entire leaching system to continuously decrease. It is difficult to maintain the alkalinity required for the entire leaching system only by the alkalinity of sodium carbonate hydrolysis. Therefore, sodium hydroxide is added to the pulp in the present invention to maintain the alkalinity of the leaching system.

[0041] In the method of the present invention, fresh ore pulp and heating medium are continuously fed into the first partition stirring chamber, and cooked ore pulp is continuously discharged from the terminal chamber, enabling continuous production. There is no operation of "feeding, heating up, keeping warm, cooling down, discharging, and waiting for materials", fundamentally avoiding problems such as the generation of hard "scale" containing tungsten during discharging and waiting for materials, blockage of the discharge pipe, high tungsten content in the leaching residue, and distortion, thus realizing the safe leaching of scheelite with salt and alkali.

[0042] (2) The method of the present invention has the advantages of high efficiency, high quality, safety, environmental protection, and economy, specifically as follows:

[0043] High efficiency and high quality: The present invention adopts low-temperature leaching. Firstly, the heating-up time is reduced, and the production efficiency can be increased by more than 10%. Secondly, the leaching rates of phosphorus, arsenic, silicon, and tin in the ore are reduced, alleviating the impurity removal pressure of the process liquor.

[0044] Safety: Compared with the conventional process with a decomposition temperature above 200°C and a corresponding pressure above 1.6 MPa, the working temperature of the present invention is in the range of 180°C - 200°C, and the corresponding pressure is below 1.5 MPa, achieving low-temperature and low-pressure operation;

[0045] Environmental protection: In the present invention, the leaching rates of impurities such as phosphorus and arsenic are low under low pressure, and are maximally solidified in the waste residue, alleviating the subsequent hazardous waste treatment pressure and reducing the environmental protection risk;

[0046] Economy: The present invention reduces the decomposition temperature, and the energy consumption can be reduced by 10 - 20%, which is beneficial to cost savings.

[0047] (3) In each partition stirring chamber of the present invention, strong stirring is carried out. Under the strong stirring of the ore pulp fluid in each partition stirring chamber, a turbulent flow is formed, which is different from the laminar flow of the prior art. It is conducive to achieving full stirring and collision between ore particles and the leaching agent sodium carbonate, and between particles. Firstly, it can greatly increase the effective collision probability of the ore decomposition reaction. Secondly, it accelerates the diffusion of the leaching agent sodium carbonate from the solution bulk to the reaction center of ore decomposition, and the leaching agent is timely replenished. Thirdly, the collision between particles helps the reaction product calcium carbonate to fall off due to collision, shortening the reaction distance between the reaction center and the solution bulk.

[0048] (4) The method of the present invention keeps the ore pulp inventory in the kettle at 60% - 70% of the designed volume of the horizontal continuous reaction kettle, which can further balance the production efficiency, leaching rate, safety, and equipment utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a three-dimensional structural schematic diagram of the continuous leaching reactor for scheelite processing used in Examples 1 - 3 of the present invention.

[0050] Legend:

[0051] 1. Partition mixing chamber; 2. Baffle; 3. Overflow tank; 4. Agitator. Detailed implementation mode

[0052] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available. Among them, the horizontal continuous reaction kettle adopts the continuous leaching reaction kettle for scheelite processing with the publication number CN116004980A, but is not limited thereto.

[0053] Example 1

[0054] A method for decomposing scheelite with saline-alkali of the present invention includes the following steps:

[0055] (1) Grind scheelite containing 35 wt% tungsten through a ball mill until more than 95% of the obtained scheelite powder can pass through a 325-mesh vibrating screen. First add clear water to the batching tank, then add scheelite powder, and then add sodium carbonate, alumina and sodium hydroxide for mixing. Among them, the addition amount of scheelite powder is controlled so that the tungsten content in the pulp is 0.086 tons / m 3 for configuration. The addition amount of sodium carbonate in the pulp is 200 kg / m 3 The addition amount of alumina is 8 kg / m 3 The addition amount of sodium hydroxide is 4 kg / m 3 . According to the ratio of configuring 1 t of scheelite into 3.5 m 3 of the total volume of pulp, dilute it to the corresponding volume with clear water to obtain pulp.

[0056] (2) Feed the above-mentioned pulp into a horizontal continuous reaction kettle with a volume of 70 m 3 . The horizontal continuous reaction kettle adopts the continuous leaching reaction kettle for scheelite processing disclosed in CN116004980A. As Figure 1 shown, the reaction kettle is provided with four partition mixing chambers 1, which are the first partition mixing chamber, the second partition mixing chamber, the third partition mixing chamber and the fourth partition mixing chamber in sequence from left to right. The volumes of the four partition mixing chambers 1 are the same, and all are provided with agitators 4. The adjacent partition mixing chambers 1 are separated by baffles 2. An overflow tank 3 is provided at the top of the baffle 2 for the overflow of materials. First pump the pulp into the first partition mixing chamber of the reaction kettle, and control the pulp speed at 8.5 m 3 / h, superheated steam at a temperature of 270°C and a pressure of 1.4 MPa is introduced into the first partition mixing chamber as the heating medium. The heating medium distributed in the first partition mixing chamber, the second partition mixing chamber, the third partition mixing chamber, and the fourth partition mixing chamber is controlled to account for 88%, 10%, 1.5%, and 0.5% of the total heating medium in all partition mixing chambers 1 respectively. During the continuous feeding process, the temperature in the first partition mixing chamber is rapidly increased to above 150°C in a short time to generate porous calcium carbonate in the pulp, and the heating-up time is 0.5 min. The heating medium continues to heat, raising the temperature of the first partition mixing chamber in the reaction kettle to 186°C and the temperatures of other chambers to 185°C, so that the temperature of the entire system reaches the process decomposition temperature, and the corresponding pressure is 1.1 MPa, and the saline-alkali decomposition reaction is carried out. During the reaction process, the stirring speeds of the first, second, third, and fourth partition mixing chambers are 146 r / min, 146 r / min, 130 r / min, and 115 r / min respectively. After the reaction, clinker is obtained. Taking the fourth partition mixing chamber as the discharging chamber, the clinker is continuously discharged from the fourth partition mixing chamber, and at the same time, the pulp inventory in the four chambers in the kettle is maintained at 40 m 3 , the clinker is filtered to obtain filtrate and tungsten slag. The filtrate is sodium tungstate solution, and the recovery rate of metallic tungsten is 99.1%. The P in the filtrate is 0.011 g / L, As is 0.048 g / L, and SiO2 is 0.15 g / L. The filter residue is tungsten slag mainly composed of porous calcium carbonate, and the tungsten slag contains 0.45% tungsten.

[0057] Example 2

[0058] A method for decomposing scheelite by saline-alkali according to the present invention includes the following steps:

[0059] (1) The scheelite containing 35 wt% tungsten is ball-milled by a ball mill until more than 95% of the obtained scheelite powder can pass through a 325-mesh vibrating screen. First, clear water is added to the batching tank, then scheelite powder is added, and then sodium carbonate, alumina, and sodium hydroxide are added for mixing. Among them, the addition amount of scheelite powder is controlled so that the tungsten content in the pulp is 0.086 tons / m 3 for configuration. The addition amount of sodium carbonate in the pulp is 200 kg / m 3 , the addition amount of alumina is 8 kg / m 3 , and the addition amount of sodium hydroxide is 4 kg / m 3 . According to the proportion of configuring 1 t of scheelite into 3.5 m 3 of the total volume of pulp, it is diluted to the corresponding volume with clear water to obtain pulp.

[0060] (2) The above-mentioned pulp is fed into a horizontal continuous reaction kettle with a volume of 70 m 3 . This horizontal continuous reaction kettle uses the continuous leaching reaction kettle for scheelite processing disclosed in CN116004980A, as Figure 1As shown in the figure, the reactor is provided with four partition stirring chambers 1, which are the first partition stirring chamber, the second partition stirring chamber, the third partition stirring chamber, and the fourth partition stirring chamber in sequence from left to right. The volumes of the four partition stirring chambers 1 are the same, and each is provided with a stirrer 4. The adjacent partition stirring chambers 1 are separated by a partition 2, and an overflow trough 3 is provided at the top of the partition 2 for the overflow of materials. First, pump the pulp into the first partition stirring chamber of the reactor, and control the pulp speed at 8.5m 3 / h. Pass superheated steam with a temperature of 270°C and a pressure of 1.4MPa into the first partition stirring chamber as the heating medium. Control the heating media distributed in the first partition stirring chamber, the second partition stirring chamber, the third partition stirring chamber, and the fourth partition stirring chamber to account for 85%, 10%, 1.5%, and 3.5% of the total heating medium in all the partition stirring chambers 1 respectively. During the continuous feeding process, quickly raise the temperature in the first partition stirring chamber to above 150°C in a short time to generate porous calcium carbonate in the pulp. The heating time is 0.6min, and the generated porous calcium carbonate is obtained. The heating medium continues to heat, raise the temperature of the first partition stirring chamber in the reactor to 186°C, and raise the temperatures of other chambers to 185°C to make the temperature of the whole system reach the process decomposition temperature, and the corresponding pressure is 1.1MPa for the saline-alkali decomposition reaction. During the reaction process, the stirring speeds of the first, second, third, and fourth partition stirring chambers are 146r / min, 146r / min, 130r / min, and 115r / min respectively. After the reaction, the clinker is obtained. Take the fourth partition stirring chamber as the discharging chamber, continuously discharge the clinker from the fourth partition stirring chamber, and at the same time maintain the pulp inventory in the four chambers of the reactor at 40m 3 . The clinker is filtered to obtain filtrate and tungsten slag. The filtrate is sodium tungstate solution, and the recovery rate of metallic tungsten is 99.07%. The P in the filtrate is 0.010g / L, As is 0.046g / L, and SiO2 is 0.14g / L. The filter residue is tungsten slag mainly composed of porous calcium carbonate, and the tungsten slag contains 0.45% tungsten.

[0061] Example 3

[0062] A method for decomposing scheelite by saline-alkali of the present invention includes the following steps:

[0063] (1) Grind scheelite containing 35wt% tungsten through a ball mill until more than 95% of the obtained scheelite powder can pass through a 325-mesh vibrating screen. First add clear water to the batching tank, then add scheelite powder, and then add sodium carbonate, alumina, and sodium hydroxide for mixing. Among them, the addition amount of scheelite powder is configured to control the tungsten content in the pulp at 0.086 tons / m 3 , the addition amount of sodium carbonate in the pulp is 200kg / m 3 , the addition amount of alumina is 8kg / m 3 , and the addition amount of sodium hydroxide is 4kg / m 3。Configure 1t of scheelite into a slurry with a proportion of 3.5m 3 of the total volume of the slurry, and dilute it with clear water to the corresponding volume to obtain the slurry.

[0064] (2) Feed the above slurry into a horizontal continuous reactor with a volume of 70m 3 . The horizontal continuous reactor adopts the continuous leaching reactor for scheelite processing disclosed in CN116004980A. As Figure 1 shown, the reactor is provided with four partition stirring chambers 1, which are the first partition stirring chamber, the second partition stirring chamber, the third partition stirring chamber, and the fourth partition stirring chamber in sequence from left to right. The volumes of the four partition stirring chambers 1 are the same, and each is provided with a stirrer 4. The adjacent partition stirring chambers 1 are separated by a partition 2, and an overflow trough 3 is provided at the top of the partition 2 for the overflow of materials. First, pump the slurry into the first partition stirring chamber of the reactor, and control the slurry speed at 8.5m 3 / h. Introduce superheated steam with a temperature of 270°C and a pressure of 1.4MPa into the first partition stirring chamber as the heating medium. Control the heating media distributed in the first partition stirring chamber, the second partition stirring chamber, the third partition stirring chamber, and the fourth partition stirring chamber to account for 80%, 15%, 4.5%, and 0.5% of the total heating medium in all the partition stirring chambers 1 respectively. During the continuous feeding process, quickly raise the temperature in the first partition stirring chamber to above 150°C in a short time to generate loose and porous calcium carbonate in the slurry, and the heating-up time is 0.7min. Continue to heat the heating medium, raise the temperature of the first partition stirring chamber in the reactor to 186°C, and the temperatures of other chambers to 185°C to make the temperature of the whole system reach the process decomposition temperature, and the corresponding pressure is 1.1MPa for the saline-alkali decomposition reaction. During the reaction process, the stirring speeds of the first, second, third, and fourth partition stirring chambers are 146r / min, 146r / min, 130r / min, and 115r / min respectively. After the reaction, clinker is obtained. Take the fourth partition stirring chamber as the discharging chamber, continuously discharge the clinker from the fourth partition stirring chamber, and at the same time maintain the slurry inventory in the four chambers of the reactor at 40m 3 . The clinker is filtered to obtain filtrate and tungsten slag. The filtrate is sodium tungstate solution, and the recovery rate of metallic tungsten is 99.04%. The P in the filtrate is 0.010g / L, As is 0.045g / L, and SiO2 is 0.13g / L. The filter residue is tungsten slag mainly composed of loose and porous calcium carbonate, and the tungsten slag contains 0.45% tungsten.

[0065] Comparative Example 1

[0066] A method for saline-alkali decomposition of scheelite, comprising the following steps:

[0067] (1) Grind scheelite containing 35 wt% tungsten in a ball mill until more than 95% of the obtained scheelite powder can pass through a 325-mesh vibrating screen. First, add clear water to the batching tank, then add scheelite powder, and then add sodium carbonate, alumina, and sodium hydroxide for mixing. Among them, the addition amount of scheelite powder is controlled so that the tungsten content in the pulp is 0.086 tons / m 3 is configured, and the addition amount of sodium carbonate in the pulp is 200 kg / m 3 , the addition amount of alumina is 8 kg / m 3 , and the addition amount of sodium hydroxide is 4 kg / m 3 . Prepare it into a slurry with a total volume ratio of 3.5 m 3 for every 1 t of scheelite, and dilute it to the corresponding volume with clear water to obtain the slurry.

[0068] (2) Feed the above slurry into a horizontal continuous reactor with a volume of 70 m 3 . This horizontal continuous reactor uses the continuous leaching reactor for scheelite processing disclosed in CN116004980A. As Figure 1 shown, the reactor is provided with four partition stirring chambers 1, which are the first partition stirring chamber, the second partition stirring chamber, the third partition stirring chamber, and the fourth partition stirring chamber in sequence from left to right. The volumes of the four partition stirring chambers 1 are the same, and each is provided with a stirrer 4. Adjacent partition stirring chambers 1 are separated by a partition 2, and an overflow trough 3 is provided at the top of the partition 2 for the overflow of materials. First, pump the slurry into the first partition stirring chamber of the reactor, and control the slurry speed at 8.5 m 3 / h. Pass superheated steam with a temperature of 270 °C and a pressure of 1.4 MPa into the first partition stirring chamber. Control the heating media distributed in the first partition stirring chamber, the second partition stirring chamber, the third partition stirring chamber, and the fourth partition stirring chamber to account for 15%, 15%, 35%, and 35% of the total heating media in all partition stirring chambers 1 respectively. During the continuous feeding process, the temperature in the first partition stirring chamber reaches above 150 °C within 4 min, and a small amount of loose and porous calcium carbonate is generated. The heating media continue to heat, raise the temperature of the first partition stirring chamber in the reactor to 186 °C, and raise the temperatures of other chambers to 185 °C, so that the temperature of the whole system reaches the process decomposition temperature, and the corresponding pressure is 1.1 MPa, and carry out the saline-alkali decomposition reaction. During the reaction process, the stirring speeds of the first, second, third, and fourth partition stirring chambers are 146 r / min, 146 r / min, 130 r / min, and 115 r / min respectively. After the reaction, clinker is obtained. Take the fourth partition stirring chamber as the discharge chamber, continuously discharge the clinker from the fourth partition stirring chamber, and at the same time maintain the pulp inventory in the four chambers of the reactor at 40 m 3, the clinker is filtered to obtain a filtrate and tungsten slag. The filtrate is a sodium tungstate solution, and the recovery rate of metallic tungsten is 98.5%. In the filtrate, P is 0.011 g / L, As is 0.045 g / L, and SiO2 is 0.14 g / L. The filter residue is tungsten slag, which contains 0.6% tungsten and includes dense calcium carbonate and porous calcium carbonate.

[0069] Comparative Example 2

[0070] A method for decomposing scheelite by saline-alkali includes the following steps using a conventional vertical batch reactor:

[0071] (1) Grind scheelite containing 35 wt% tungsten in a ball mill until more than 95% of the obtained scheelite powder can pass through a 325-mesh vibrating screen. First add clear water to the batching tank, then add the scheelite powder, and then add sodium carbonate, alumina, and sodium hydroxide for mixing. Among them, the addition amount of the scheelite powder is configured to control the tungsten content in the pulp to be 0.086 tons / m 3 The addition amount of sodium carbonate in the pulp is 200 kg / m 3 The addition amount of alumina is 8 kg / m 3 The addition amount of sodium hydroxide is 4 kg / m 3 . According to the proportion of configuring 1 t of scheelite into 3.5 m 3 of the total volume of pulp, dilute it with clear water to the corresponding volume to obtain pulp.

[0072] (2) Open the drain valve and feed valve of the vertical batch reactor in sequence, pump the pulp into a vertical batch reactor with a volume of 10 m 3 , and then close the feed valve and drain valve of the vertical batch reactor.

[0073] (3) Slowly open the steam valve, and introduce superheated steam at 270 °C and 1.4 MPa into the vertical batch reactor. Heat up to 150 °C in 40 min, continue to heat up to 200 °C, and then close the steam valve.

[0074] (4) After holding for 2 - 2.5 h, open the drain valve to relieve pressure, exhaust until the pressure in the reactor is 0.3 MPa, close the drain valve, open the discharge valve, and discharge the slurry in the reactor into the discharge tank and empty it. Wait for the slurry in the next cycle.

[0075] (5) Pump the slurry in the discharge tank into a filter press for filtration. The filtrate is a sodium tungstate solution, and the recovery rate of metallic tungsten is 98.5%. In the filtrate, P is 0.025 g / L, As is 0.0137 g / L, and SiO2 is 0.53 g / L. The filter residue is tungsten slag mainly composed of dense calcium carbonate, and the tungsten slag contains 0.58% tungsten.

[0076] The above are only the preferred embodiments of the present invention and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above in the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes, without departing from the spirit and technical solution of the present invention. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for decomposing scheelite with saline and alkali, comprising the following steps: S1. ball-milling scheelite to obtain scheelite powder, and mixing the scheelite powder, sodium carbonate, aluminum oxide, sodium hydroxide and water to obtain ore slurry; S2, the slurry is fed into a horizontal continuous reactor, wherein the horizontal continuous reactor is provided with more than three partition stirring chambers (1) from left to right, and the adjacent partition stirring chambers (1) are separated by partitions (2), and the partitions (2) are provided with overflow grooves (3), the slurry obtained in step S1 is passed into the first partition stirring chamber (1), the slurry flows through each of the partition stirring chambers (1) through overflow, a heating medium is passed into the partition stirring chamber (1), and the first partition stirring chamber (1) is controlled to heat the slurry. ) accounts for 80% to 90% of the total heating medium in all the partitioned stirring chambers (1), so that loose and porous calcium carbonate is produced in the slurry in the first partitioned stirring chamber (1), and when the temperature in each partitioned stirring chamber (1) rises to 180°C to 200°C, the temperature of the entire system reaches the process decomposition temperature, and after the reaction, clinker is obtained, and the clinker is continuously discharged from the last partitioned stirring chamber (1), and then filtered to obtain filtrate and tungsten slag, wherein the filtrate is a sodium tungstate solution.

2. The method for decomposing scheelite by saline-alkali according to claim 1, characterized in that: In step S2, the heating medium is heat transfer oil, electricity or steam. When the heating medium is steam, the steam pressure corresponding to the reaction temperature is below 1.5 MPa. During the continuous feeding process, the slurry in the first partitioned stirring chamber (1) is heated to above 150° C. in a short time to generate loose and porous calcium carbonate, and the short time is 0.3 min to 1 min. The heating medium allocated in the second partitioned stirring chamber (1) is controlled to account for 5% to 15% of the total heating medium in all the partitioned stirring chambers (1).

3. The method for decomposing scheelite by saline-alkali according to claim 2, characterized in that: In step S2, the reaction temperature in each partitioned stirring chamber (1) is controlled to be 180°C to 190°C. When the heating medium is steam, the steam pressure corresponding to the reaction temperature is 1.05MPa to 1.22MPa.

4. The method for decomposing scheelite by saline-alkali according to claim 1, characterized in that: In step S2, the speed of the slurry is controlled at 7m 3 / h~12m 3 / h, the temperature of the heating medium is 220°C to 350°C, during the reaction, the temperature difference between the first partition stirring chamber (1) and the remaining partition stirring chambers (1) is controlled to be ≤10°C, the slurry in each partition stirring chamber (1) is stirred, the stirring speed of the first partition stirring chamber (1) and the second partition stirring chamber (1) is controlled to be 140r / min to 160r / min, the stirring speed of the remaining partition stirring chambers (1) is controlled to be 110r / min to 140r / min, and the stirring speed of each partition stirring chamber (1) is gradually reduced from the third partition stirring chamber (1) onwards.

5. The method for decomposing scheelite by saline-alkali according to claim 4, characterized in that: In step S2, the speed of the slurry is controlled at 8 m / s. 3 / h~9m 3 / h, the temperature of the heating medium is 250°C to 280°C, and during the reaction, the temperature difference between the first partition stirring chamber (1) and the remaining partition stirring chambers (1) is controlled to be ≤5°C.

6. The method for decomposing scheelite by salt and alkali according to any one of claims 1 to 5, characterized in that: In step S2, the volume of the horizontal continuous reactor is 40m 3 ~90m 3 , keeping the slurry stock in the kettle at 50% to 70% of the volume of the horizontal continuous reactor.

7. The method for decomposing scheelite by salt and alkali according to any one of claims 1 to 5, characterized in that: In step S1, each 1t of scheelite is configured into 3m 3 ~5m 3 The amount of scheelite powder added is controlled by controlling the tungsten content in the slurry to 0.08 tons / m 3 ~0.09 tons / m 3 The amount of sodium carbonate added to the slurry is 180 kg / m 3 ~240kg / m 3 The amount of aluminum oxide added is 8 kg / m 3 ~12.5kg / m 3 The amount of sodium hydroxide added is 4 kg / m 3 ~8kg / m 3 .

8. The method for decomposing scheelite by salt and alkali according to any one of claims 1 to 5, characterized in that: In step S1, the mass fraction of tungsten in the scheelite is 25% to 38%, and more than 95% of the scheelite powder can pass through a 325-mesh vibrating screen.

9. The method for decomposing scheelite by salt and alkali according to any one of claims 1 to 5, characterized in that: In step S2, 3 to 10 partitioned stirring chambers (1) are provided, each of the partitioned stirring chambers (1) has the same volume, each of the partitioned stirring chambers (1) is provided with a stirrer (4), and the overflow tank (3) is provided on the top of the partition (2).

10. The method for decomposing scheelite by salt and alkali according to any one of claims 1 to 5, characterized in that: In step S2, the horizontal continuous reactor adopts the continuous leaching reactor for processing scheelite disclosed in CN116004980A.

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