System for recovering vanadium from chromium-free underflow of vanadium sodium solution, and method using same

Abstract

A system for recovering vanadium from a chromium-free underflow of a vanadium sodium solution, the system comprising: a sedimentation tank (1), wherein the lower side portion and the bottom of the sedimentation tank (1) are respectively connected to a first pump (3) and a second pump (5); a vanadium removal tank (13), wherein the top of the vanadium removal tank (13) is connected to the second pump (5), a first stirrer (10) and a first steam ring pipe (12) are arranged in the vanadium removal tank (13), and the bottom of the vanadium removal tank (13) is connected to a third pump (15); a slurry making tank (18), wherein a feeding port (23) is provided on the top of the slurry making tank (18), a second stirrer (25) and a second steam ring pipe (19) are arranged in the slurry making tank (18), the bottom of the slurry making tank (18) is connected to a fourth pump (28), and the fourth pump (28) is connected to the top of the vanadium removal tank (13) by means of a first branch pipe; a dilution tank (34), wherein the top of the dilution tank (34) is connected to a second branch pipe, a third stirrer (38) is arranged in the dilution tank (34), and the bottom of the dilution tank (34) is connected to a fifth pump (35); a buffer tank (40), the bottom of which is in communication with the top of the dilution tank (34); and a plate frame (44), which is provided with an inlet and an outlet, wherein the third pump (15) and the fifth pump (35) are both connected to the inlet, and pipes connected at the outlet form cross-shaped pipes, and are in communication with the corresponding tops of the vanadium removal tank (13), the sedimentation tank (1) and the dilution tank (34), respectively. Further provided is a method for recovering vanadium by using the system, thereby reducing the vanadium loss and production costs.

Description

A system and method for recovering vanadium from chromium removal underflow of sodium vanadium solution Technical Field

[0001] The present invention belongs to hydrometallurgical technology, and more particularly relates to a system and method for recovering vanadium from a sodium vanadium solution chromium removal underflow. Background Art

[0002] At present, the process route for producing vanadium-aluminum grade vanadium powder, V2O599.8-P vanadium powder, and battery-grade vanadium powder using sodium vanadium slag leachate as raw material is as follows: the vanadium-containing leachate after purification and impurity removal by calcium chloride is first desiliconized with aluminum sulfate, and then the solution is dechromized. After the silicon and chromium are removed, the solution is subjected to vanadium precipitation to obtain AMV, which is then centrifuged, washed, dried, and then calcined. The obtained vanadium powder meets the V2O599.8-P index in the YB / T 5304-2017 standard and the customer's personalized requirements.

[0003] However, after chromium is removed from the vanadium-containing leachate, a chromium-removed underflow residue is obtained. Due to its fine particle size, filtration is difficult, and the filter cake does not form. As a result, the chromium-removed underflow residue contains approximately 60% water. Testing has revealed that the vanadium content in the chromium-removed underflow residue is approximately 12%, all of which is pentavalent vanadium. Therefore, the vanadium in this underflow residue must be recovered to reduce vanadium losses.

[0004] In the prior art, Wang Xuewen's article "A Comprehensive Recovery Method for Vanadium-Chromium Salt Solutions" proposes adding a reducing agent to a vanadium-chromium salt solution under appropriate pH conditions to reduce pentavalent vanadium and hexavalent chromium to tetravalent vanadium and trivalent chromium. Alkali is then added to adjust the pH to precipitate the vanadium and chromium, which is then filtered to obtain a vanadium-chromium slag. The resulting vanadium-chromium slag is then added to an alkaline solution to selectively leach the vanadium. The leachate is then treated with acid to adjust the pH to precipitate the vanadium, thereby achieving effective separation and recovery of vanadium and chromium. However, this method is unsuitable for treating the chromium-removing underflow slag from the production of high-purity vanadium pentoxide, where the vanadium is pentavalent and the chromium is trivalent.

[0005] Tao Changyuan's paper, "A Method for Separating and Recovering Vanadium and Chromium from Vanadium-Chromium Slag," proposes that the vanadium-chromium slag be impregnated with a sulfuric acid solution, filtered to obtain a filtrate containing vanadium and chromium ions; alkali is added to the filtrate to precipitate and obtain a slurry; an excess of an oxidant is added to the slurry to obtain a mixed solution containing high-valent vanadium ions and high-valent chromium ions; a vanadium precipitant is added under acidic and heated conditions to obtain a vanadium-containing precipitate and a filtrate; the vanadium-containing precipitate is calcined to produce vanadium pentoxide; the filtrate is cooled and allowed to stand to precipitate sodium sulfate crystals and separate a filtrate containing chromium ions; the filtrate containing chromium ions is precipitated under alkaline conditions, and the resulting clear solution is evaporated to obtain sodium chromate crystals. However, this method is complex and lengthy, making it unsuitable for industrial production.

[0006] Therefore, the existing technology needs to be improved.

[0007] Summary of the Invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is as follows: after the lignocellulose is diluted and boiled, it is driven into a plate and frame before the chromium removal bottom flow residue is filtered, so that the lignocellulose forms a thin film on the surface of the filter plate, and the filter cake is easy to fall off; after the lignocellulose is diluted and boiled, it is added to the slurry formed by the chromium removal bottom flow residue as a filter aid and stirred evenly, so that it is easy to filter and the filter cake is easy to form. After the vanadium in the chromium removal bottom flow is diluted and filtered through the plate and frame, the vanadium-containing filtrate is returned directly to the high-purity vanadium pentoxide production line for recovery. After the chromium removal bottom flow is filtered through the plate and frame for the first time, if the vanadium content in the filter cake is ≥3%, the filter cake is returned to the vanadium removal tank again, and after it is slurried again to remove the vanadium, it is pumped into the plate and frame for filter pressing until the vanadium content in the filter cake is <3%, and the filter cake enters the next step.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] According to one aspect of the present invention, a system for recovering vanadium from a sodium vanadium solution underflow for removing chromium is provided, comprising:

[0011] A settling tank, wherein the lower side of the settling tank is connected to the first pump via a flow measuring valve, and the bottom of the settling tank is connected to the second pump via a first underflow valve;

[0012] A vanadium removal tank, the top of which is connected to the second pump via a pipeline. The top of the vanadium removal tank is connected to a first water pipe, a first exhaust pipe, and a buffer hopper. The buffer hopper holds the filter cake returned to the vanadium removal tank for further vanadium reduction. The interior of the vanadium removal tank is equipped with a first agitator and a first steam loop. The bottom of the vanadium removal tank is connected to the third pump via a second underflow valve.

[0013] A pulping tank, the top of which is connected to a second water pipe and a second exhaust pipe and is provided with a feeding port, for adding lignocellulose, a second agitator and a second steam loop are installed inside the pulping tank, the second steam loop and the first steam loop are connected to a common steam pipe, the bottom of the pulping tank is connected to a fourth pump via a third underflow valve, the fourth pump is connected to the top of the vanadium removal tank via a first branch pipe, and the first branch pipe is provided with a first valve;

[0014] a dilution tank, wherein the top of the dilution tank is connected to a second branch pipe connected to the fourth pump, the second branch pipe is provided with a second valve, a third agitator is installed inside the dilution tank, and the bottom of the dilution tank is connected to the fifth pump via a fourth underflow valve;

[0015] A buffer tank, the top of which is connected to a third water pipe, and the bottom of which is connected to the top of the dilution tank via a fifth underflow valve;

[0016] The plate frame has an inlet and an outlet. The third pump is connected to the inlet of the plate frame through a pipeline provided with a third valve. The fifth pump is connected to the inlet of the plate frame through a pipeline provided with a fourth valve. The pipeline connected to the outlet of the plate frame forms a cross pipeline and is connected to the top of the vanadium removal tank, the top of the sedimentation tank and the top of the dilution tank through the fifth valve, the sixth valve and the seventh valve respectively.

[0017] In one embodiment of the present invention, the pipe connected to the bottom of the settling tank is further connected to a first backwash water pipe; the pipe connected to the bottom of the vanadium removal tank is further connected to a second backwash water pipe.

[0018] In one embodiment of the present invention, the top of the vanadium removal tank is also connected to a first liquid level gauge and the lower side of the vanadium removal tank is installed with a first thermometer; the top of the pulping tank is also connected to a second liquid level gauge and the lower side of the pulping tank is installed with a second thermometer; the top of the dilution tank is also connected to a third liquid level gauge; and the top of the buffer tank is also connected to a fourth liquid level gauge.

[0019] In one embodiment of the present invention, the vanadium content in the filter cake returned to the vanadium removal tank for further vanadium reduction is ≥3%.

[0020] In one embodiment of the present invention, the first steam ring pipe is provided with a plurality of evenly distributed small holes toward the bottom center of the vanadium removal tank; the second steam ring pipe is provided with a plurality of evenly distributed small holes toward the bottom center of the pulping tank.

[0021] In one embodiment of the present invention, the diameter of the small holes is 6 mm.

[0022] In one embodiment of the present invention, the first backwash water pipe, the first water pipe, the second backwash water pipe, the second water pipe and the third water pipe are all connected to the pure water main pipe, and the conductivity of the pure water is ≤40uS / cm.

[0023] In one embodiment of the present invention, after the sodium vanadium solution in the settling tank has settled for 48 hours, the flow meter valve and the first pump are opened to carry out vanadium precipitation.

[0024] According to another aspect of the present invention, there is provided a method for recovering vanadium using the aforementioned system for recovering vanadium from the underflow of the sodium vanadium solution after chromium removal, comprising the following steps:

[0025] The chromium slag is settled in the settling tank to obtain the chromium-removed underflow;

[0026] Adding lignocellulose into a pulping tank to prepare a slurry, pumping a portion of the slurry into a vanadium removal tank and a portion of the slurry into a dilution tank;

[0027] The chromium removal underflow is pumped into the vanadium removal tank to be mixed and stirred evenly with the slurry pumped into the vanadium removal tank to obtain chromium slag slurry.

[0028] The liquid in the buffer tank is added to the dilution tank to dilute the slurry, and the diluted slurry is pumped into the plate frame for filtration to form a thin film on the surface of the plate frame, and the filtered clear liquid is returned to the buffer tank;

[0029] The chromium slag slurry is pumped into the plate and frame for filter pressing, the filtrate is returned to the sedimentation tank to recover vanadium, and the filter cake is discharged.

[0030] In one embodiment of the present invention, the method further comprises:

[0031] The vanadium content in the filter cake after discharge is detected. If the vanadium content is less than 3%, the obtained filter cake is sold out. If the vanadium content is ≥3%, the filter cake is transported to a vanadium removal tank and the operation is continued until the vanadium content in the filter cake is less than 3%.

[0032] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0033] (1) The present invention can recover vanadium from the chromium-removing underflow slag in the production process of high-purity vanadium pentoxide, thereby reducing vanadium loss and production costs.

[0034] (2) The present invention mixes wood cellulose with water and boils it for a long time, pumps the boiled wood cellulose slurry into a dilution tank, mixes it with the clear liquid of the previous batch, and then pumps it into a plate and frame to form a thin film on the surface of the filter plate. The chromium-removed bottom flow residue is then driven into the plate and frame for filter pressing, which is conducive to the shedding of the filter cake; the boiled wood cellulose slurry is pumped into the chromium-removed bottom flow residue to re-make the pulp, and then driven into the plate and frame for filter pressing to achieve solid-liquid separation, which is conducive to the formation of the filter cake.

[0035] (3) The present invention adds wood cellulose as a filter aid, which does not introduce new impurities and does not affect the quality of the product vanadium powder.

[0036] (4) The vanadium-containing filtrate recovered by the present invention is directly returned to the high-purity vanadium pentoxide production line for reuse.

[0037] (5) The underflow generated by the present invention can be directly filtered and squeezed using the production plate frame of the existing production line, and the filter cake is easy to form and fall off.

[0038] (6) The equipment integration and technology described in the present invention can be industrialized for production, with low labor intensity, high degree of automation and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 shows a schematic diagram of a system for recovering vanadium from a sodium vanadium solution underflow for removing chromium provided by the present invention;

[0040] FIG2 shows a schematic flow diagram of a method for recovering vanadium from the underflow of sodium vanadium solution for chromium removal provided by the present invention.

[0041] Reference Signs List 1 Settling tank, 2 Flow measuring valve, 3 First pump, 4 First underflow valve, 5 Second pump, 6 First backflushing water pipe, 7 First water pipe, 8 First liquid level gauge, 9 First exhaust pipe, 10 First agitator, 11 Buffer hopper, 12 First steam loop pipe, 13 Vanadium removal tank, 14 Second underflow valve, 15 Third pump, 16 Second backflushing water pipe, 17 First thermometer, 18 Slurry making tank, 19 Second steam loop pipe, 20 Steam pipe, 21 Second water pipe, 22 Second exhaust pipe, 23 Feed port, 24 second liquid level gauge, 25 second agitator, 26 second thermometer, 27 third underflow valve, 28 fourth pump, 29 flow meter, 30 first valve, 31 second valve, 32 third valve, 33 fourth valve, 34 dilution tank, 35 fifth pump, 36 fourth underflow valve, 37 third liquid level gauge, 38 third agitator, 39 fifth underflow valve, 40 buffer tank, 41 fourth liquid level gauge, 42 third water pipe, 43 belt, 44 plate frame, 45 fifth valve, 46 sixth valve, 47 seventh valve. DETAILED DESCRIPTION

[0042] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in the present invention, it is readily apparent to those skilled in the art that various modifications are feasible without departing substantially from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, variations, and deletions may be made to the design, operating conditions, and parameters of the following exemplary embodiments.

[0043] As shown in FIG1 , the present invention provides a system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium, comprising:

[0044] Sedimentation tank 1, the lower side of the sedimentation tank 1 is connected to the first pump 3 through the flow measuring valve 2, and the bottom of the sedimentation tank 1 is connected to the second pump 5 through the first underflow valve 4;

[0045] A vanadium removal tank 13, the top of which is connected to the second pump 5 via a pipeline. The top of the vanadium removal tank 13 is connected to a first water pipe 7, a first exhaust pipe 9, and a buffer hopper 11. The buffer hopper 11 holds the filter cake returned to the vanadium removal tank for further vanadium reduction. A first agitator 10 and a first steam loop 12 are installed inside the vanadium removal tank 13. The bottom of the vanadium removal tank 13 is connected to a third pump 15 via a second underflow valve 14.

[0046] A pulping tank 18 is provided with a second water pipe 21 and a second exhaust pipe 22 connected to the top of the pulping tank 18 and a feeding port 23 for feeding lignocellulose. A second agitator 25 and a second steam loop 19 are installed inside the pulping tank 18. The second steam loop 19 and the first steam loop 12 are connected to a common steam pipe 20. The bottom of the pulping tank 18 is connected to a fourth pump 28 via a third underflow valve 27. The fourth pump 28 is connected to the top of the vanadium removal tank 13 via a first branch pipe. A first valve 30 is provided on the first branch pipe.

[0047] a dilution tank 34, the top of which is connected to a second branch pipe connected to the fourth pump 28, a second valve 31 being provided on the second branch pipe, a third agitator 38 being installed inside the dilution tank 34, and the bottom of the dilution tank 34 being connected to the fifth pump 35 via a fourth underflow valve 36;

[0048] A buffer tank 40 , the top of which is connected to a third water pipe 42 , and the bottom of which is connected to the top of the dilution tank 34 via a fifth underflow valve 39 ;

[0049] The plate frame 44 has an inlet and an outlet. The third pump 15 is connected to the inlet of the plate frame 44 through a pipeline provided with a third valve 32. The fifth pump 35 is connected to the inlet of the plate frame 44 through a pipeline provided with a fourth valve 33. The pipeline connected to the outlet of the plate frame 44 forms a cross-shaped pipeline and is connected to the top of the vanadium removal tank 13, the top of the sedimentation tank 1 and the top of the dilution tank 40 through the fifth valve 45, the sixth valve 46 and the seventh valve 47 respectively.

[0050] In the above system, the bottom of the settling tank 1 is connected to a pipe connected to a first backwash water pipe 6 ; the bottom of the vanadium removal tank 13 is connected to a pipe connected to a second backwash water pipe 16 .

[0051] In the above system, the top of the vanadium removal tank 13 is also connected to the first liquid level gauge 8 and the lower side of the vanadium removal tank 13 is installed with a first thermometer 17; the top of the pulping tank 18 is also connected to the second liquid level gauge 24 and the lower side of the pulping tank 18 is installed with a second thermometer 26; the top of the dilution tank 34 is also connected to the third liquid level gauge 37; the top of the buffer tank 40 is also connected to the fourth liquid level gauge 41.

[0052] In the above system, the vanadium content in the filter cake returned to the vanadium removal tank 13 for further vanadium reduction is ≥3%.

[0053] In the above system, the first steam ring pipe 12 is provided with multiple evenly distributed small holes toward the bottom center of the vanadium removal tank 13; the second steam ring pipe 19 is provided with multiple evenly distributed small holes toward the bottom center of the pulping tank 18.

[0054] In the above systems, the diameter of the small holes is 6 mm.

[0055] In the above system, the first backwash water pipe 6, the first water pipe 7, the second backwash water pipe 16, the second water pipe 21 and the third water pipe 42 are all connected to the pure water main pipe, and the conductivity of the pure water is ≤40uS / cm.

[0056] In the above system, after the sodium vanadium solution in the settling tank 1 has settled for 48 hours, the flow metering valve 2 and the first pump 3 are opened to carry out the vanadium precipitation operation.

[0057] In addition, as shown in FIG2 , the present invention provides a method for recovering vanadium using the system for recovering vanadium from the underflow of the sodium vanadium solution for removing chromium as described above, comprising the following steps:

[0058] The chromium slag is settled in the settling tank to obtain the chromium-removed underflow;

[0059] Adding lignocellulose into a pulping tank to prepare a slurry, pumping a portion of the slurry into a vanadium removal tank and a portion of the slurry into a dilution tank;

[0060] The chromium removal underflow is pumped into the vanadium removal tank and mixed with the slurry pumped into the vanadium removal tank to obtain chromium slag slurry.

[0061] The liquid in the buffer tank is added to the dilution tank to dilute the slurry, and the diluted slurry is pumped into the plate frame for filtration to form a thin film on the surface of the plate frame, and the filtered clear liquid is returned to the buffer tank;

[0062] The chromium slag slurry is pumped into the plate and frame for filter pressing, the filtrate is returned to the sedimentation tank to recover vanadium, and the filter cake is discharged.

[0063] In the above method, the method further comprises:

[0064] The vanadium content in the filter cake after discharge is detected. If the vanadium content is less than 3%, the obtained filter cake is sold out. If the vanadium content is ≥3%, the filter cake is transported to a vanadium removal tank and the operation is continued until the vanadium content in the filter cake is less than 3%.

[0065] The above technical solution of the present invention is described in detail below through specific embodiments.

[0066] As shown in Figure 1-2, after the sodium vanadium solution reacts with the chromium removal agent, it is transferred to settling tank 1 for chromium slag precipitation. After the sodium vanadium solution in settling tank 1 has settled for 48 hours, flow meter valve 2 can be opened and first pump 3 can be started to proceed with vanadium precipitation.

[0067] The chromium-removing underflow in the settling tank 1 requires regular cleaning. Open the first underflow valve 4 and start the second pump 5 to pump the chromium-removing underflow from the settling tank 1 into the vanadium removal tank 13. If opening the first underflow valve 4 and starting the second pump 5 does not successfully discharge the chromium-removing underflow from the settling tank 1, open the first backwash pipe 6 to backwash it and help drain the underflow from the settling tank 1. Once the underflow is successfully discharged, close the first backwash pipe 6.

[0068] Once the liquid level in the vanadium removal tank 13 submerges the lower set of blades of the first agitator 10, the first agitator 10 is activated to agitate the liquid in the vanadium removal tank 13. The chromium removal underflow is pumped into the vanadium removal tank 13. When the liquid level reaches the specified level, the first underflow valve 4 and the second pump 5 are closed. After stopping the pumping of the chromium removal underflow into the vanadium removal tank 13, the first water pipe 7 is opened to add water to the tank. Once the liquid level reaches the specified level, the first water pipe 7 is closed. The third underflow valve 27 and the first valve 30 are opened, the second valve 31 is closed, and the fourth pump 28 is activated to pump the specified amount of lignocellulosic slurry into the vanadium removal tank 13. The valve connecting the steam pipe 20 to the vanadium removal tank 13 is opened. With the first agitator 10 activated, the liquid in the vanadium removal tank 13 is heated to 70°C via the first steam loop 12. The temperature is then maintained constant for ≥0.5 hours. After the constant temperature time is reached, the fourth valve 33 can be opened and closed, the third valve 32 can be opened, the second underflow valve 14 can be opened, and the third pump 15 can be started to pump the slurry in the vanadium removal tank 13 into the plate frame 44 for pressure filtration. If there is a blockage between the bottom of the vanadium removal tank 13 and the third pump 15, the second backwash water pipe 16 can be opened to clear it. The first steam ring pipe 12 is a stainless steel ring pipe connected to the steam pipe 20; the first steam ring pipe 12 has multiple uniformly distributed diameters toward the center of the cone bottom of the vanadium removal tank 13. The first steam loop 12 has a small hole, and the sum of the areas of all the small holes on the first steam loop 12 is larger than the cross-sectional area of ​​the first steam loop 12 to avoid pressure buildup and jetting; the first steam loop 12 is placed on a bracket composed of a plurality of protruding support nails evenly distributed on the same horizontal plane of the inner wall of the vanadium removal tank 13; the distance between the first steam loop 12 and the inner wall of the vanadium removal tank 13 is about 20 mm. The first liquid level gauge 8 is installed on the top of the vanadium removal tank 13 to detect the liquid level in the tank. The first exhaust pipe 9 is connected to the exhaust main pipe and is used to remove the gas generated during the production process in the tank. The buffer hopper 11 is installed on the top of the vanadium removal tank 13 to hold the filter cake returned to the vanadium removal tank 13 for further vanadium reduction. The first thermometer 17 is installed on the lower side of the vanadium removal tank 13 to detect the temperature of the liquid in the tank.

[0069] The second steam loop 19, second exhaust pipe 22, second liquid level gauge 24, second agitator 25, and second thermometer 26 are installed in the same location, manner, and function as the first steam loop 12, first exhaust pipe 9, first liquid level gauge 8, first agitator 10, and first thermometer 17, respectively. The feed port 23 is in the shape of a trumpet and is installed at the top of the pulping tank 18. Open its valve and add cellulose to the pulping tank 18 through the feed port 23. The second water pipe 21 is connected to the top of the pulping tank 18. Open the valve on the second water pipe 21, add a specified amount of water to the pulping tank 18, start the second agitator 25, add a specified amount of cellulose to the pulping tank 18 through the feed port 23, then open the steam valve connecting the steam pipe 20 to the pulping tank 18. The liquid in the tank is heated to boiling and then maintained at a constant temperature through the second steam loop 19 for ≥2 hours. After the constant temperature time is reached, the third underflow valve 27 and the fourth pump 28 can be opened to pump the prepared lignocellulose slurry to the vanadium removal tank 13 or the dilution tank 34 .

[0070] After closing the first valve 30 and opening the second valve 31, the third underflow valve 27 is opened and the fourth pump 28 is started to deliver a specified amount of prepared lignocellulosic slurry to the dilution tank 34. The fifth underflow valve 39 is then opened to discharge a specified amount of clear liquid from the buffer tank 40 into the dilution tank 34. The third agitator 38 is started. After stirring the liquid in the dilution tank 34 for 5 minutes, the fourth underflow valve 36 can be opened and the fifth pump 35 started to pump the diluted lignocellulosic slurry into the plate frame 44. A third liquid level gauge 37 is installed on the top of the dilution tank 34 to monitor the liquid level in the tank.

[0071] After closing the fifth and sixth valves 45 and 46, opening the seventh valve 47, closing the third valve 32 and opening the fourth valve 33, the fourth underflow valve 36 is opened and the fifth pump 35 is activated to pump the diluted wood fiber slurry into the plate frame 44. The swelled wood fiber is trapped on the surface of the plate frame 44, forming a thin film that ensures easy removal of the filter cake during unloading. The filtered clear liquid is returned to the buffer tank 40 and used to prepare the wood fiber solution in the dilution tank 34, reducing wastewater generation and thus production costs. If the amount of clear liquid exceeds the required preparation volume, the fifth valve 45 is opened and the seventh valve 47 is closed, returning the excess clear liquid to the vanadium removal tank 13 to reduce the vanadium concentration in the chromium removal underflow. If the amount of clear liquid is less than the required preparation volume, the third water pipe 42 is opened to meet the required preparation volume. A fourth liquid level gauge 41 is installed at the top of the buffer tank 40 to monitor the liquid level within the tank.

[0072] After a thin film forms on the surface of the plate frame 44, the fifth and seventh valves 45 and 47 are closed, the sixth valve 46 is opened, the fourth valve 33 is closed, the second underflow valve 14 is opened, and the third pump 15 is started. The treated chromium-removed underflow from the vanadium removal tank 13 is pumped to the plate frame 44 for filter pressing. The filtrate then returns to the settling tank for vanadium recovery. After the filter cake is discharged from the plate frame 44, it falls onto the belt 43, where it is sampled and tested for vanadium content. If the vanadium content of the filter cake is less than 3%, the belt 43 rotates in the reverse direction, transporting the filter cake to the next process step. If the vanadium content of the filter cake is ≥3%, the belt 43 rotates forward, transporting the filter cake to the buffer hopper 11. The filter cake then returns to the vanadium removal tank 13, where it is pulped to remove vanadium and then pumped back into the plate frame for filter pressing until the vanadium content is less than 3%. The filter cake returns to the vanadium removal tank 13 without the need for further boiled cellulose.

[0073] Preferably, the first backwash water pipe 6, the first water pipe 7, the second backwash water pipe 16, the second water pipe 21, and the third water pipe 42 are all connected to the pure water main. Pure water is domestic water obtained by removing impurities through two-stage reverse osmosis and EDI. The water quality requirement is conductivity ≤ 40uS / cm.

[0074] In the above system and application operation, specifically, the diameter of the sedimentation tank 1 is 4.4m, the height is 10.0m, the bottom cone height is 2.5m, the diameter of the distribution cylinder is 0.5m, and the depth is 8m. The diameter of the vanadium removal tank 13 is 3.0m, the height is 3.5m, and the bottom is an elliptical arc bottom (height 0.6m). The total liquid volume per single batch is 20m 3 The diameter of the pulping tank 18 is 1.8m, the height is 2.5m, the bottom is an elliptical arc bottom (height 0.5m), and the total liquid volume per time is 5m 3 The dilution tank 34 has a diameter of 1.6m, a height of 2.5m, and an elliptical arc bottom (0.5m high). The total liquid volume per time is 4m 3 The diameter of the buffer tank 40 is 1.6m, the height is 2.5m, the bottom is a cone with a height of 1m, and the volume of clear liquid that can be received at a time is 5m 3 . The frame is 100m 2 .

[0075] In the above system and application operation, specifically, 50 kg of cellulose and 5 m of liquid are added to the pulping tank 18 at a time. 3 The boiled cellulose is pumped into the dilution tank 34 for about 0.5m 3 , and then diluted to 4m in dilution tank 34 3 , the diluted wood cellulose slurry is 4m 3 The boiled cellulose is pumped into the vanadium removal tank 13 for about 2m 3 The chromium removal underflow in the sedimentation tank 1 is pumped into the vanadium removal tank for about 5m at a time. 3 The filter cake after filtration by plate and frame 44 has a water content of about 35%.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. If the present invention is modified or replaced with equivalents without departing from the spirit and scope of the present invention, it should be included in the scope of protection of the claims of the present invention.

Claims

1. A system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium, characterized in that: Include: A settling tank, wherein the lower side of the settling tank is connected to the first pump via a flow measuring valve, and the bottom of the settling tank is connected to the second pump via a first underflow valve; A vanadium removal tank, wherein the top of the vanadium removal tank is connected to the second pump through a pipeline, the top of the vanadium removal tank is connected to a first water pipe, a first exhaust pipe and a buffer hopper, the buffer hopper can hold the filter cake returned to the vanadium removal tank for further vanadium reduction, a first agitator and a first steam loop are installed inside the vanadium removal tank, and the bottom of the vanadium removal tank is connected to a third pump through a second underflow valve; A pulping tank, wherein the top of the pulping tank is connected with a second water pipe and a second exhaust pipe and is provided with a feeding port, wherein wood cellulose is added to the feeding port, a second agitator and a second steam loop are installed inside the pulping tank, wherein the second steam loop and the first steam loop are connected to a common steam pipe, the bottom of the pulping tank is connected to a fourth pump via a third underflow valve, wherein the fourth pump is connected to the top of the vanadium removal tank via a first branch pipe, wherein the first branch pipe is provided with a first valve; a dilution tank, the top of which is connected to a second branch pipeline connected to the fourth pump, the second branch pipeline is provided with a second valve, a third agitator is installed inside the dilution tank, and the bottom of the dilution tank is connected to the fifth pump through a fourth underflow valve; A buffer tank, the top of which is connected to a third water pipe, and the bottom of which is connected to the top of the dilution tank via a fifth underflow valve; A plate frame having an inlet and an outlet, the third pump is connected to the inlet of the plate frame through a pipeline provided with a third valve, the fifth pump is connected to the inlet of the plate frame through a pipeline provided with a fourth valve, a cross-shaped pipeline is formed at the pipeline connected to the outlet of the plate frame and is connected to the top of the vanadium removal tank, the top of the sedimentation tank and the top of the dilution tank through the fifth valve, the sixth valve and the seventh valve respectively.

2. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 1, characterized in that: The pipeline connected to the bottom of the settling tank is also connected to a first recoil water pipe; the pipeline connected to the bottom of the vanadium removal tank is also connected to a second recoil water pipe.

3. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 1, characterized in that: The top of the vanadium removal tank is also connected to a first liquid level gauge and the lower side of the vanadium removal tank is installed with a first thermometer; the top of the pulping tank is also connected to a second liquid level gauge and the lower side of the pulping tank is installed with a second thermometer; the top of the dilution tank is also connected to a third liquid level gauge; the top of the buffer tank is also connected to a fourth liquid level gauge.

4. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 1, characterized in that: The vanadium content in the filter cake returned to the vanadium removal tank for further vanadium reduction is ≥3%.

5. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 1, characterized in that: The first steam ring pipe is provided with a plurality of evenly distributed small holes toward the bottom center of the vanadium removal tank; the second steam ring pipe is provided with a plurality of evenly distributed small holes toward the bottom center of the pulping tank.

6. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 5, characterized in that: The diameter of the small holes is 6 mm.

7. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 1, characterized in that: The first backwash water pipe, the first water pipe, the second backwash water pipe, the second water pipe and the third water pipe are all connected to the pure water main pipe, and the conductivity of the pure water is ≤40uS / cm.

8. The system for recovering vanadium from the underflow of sodium vanadium solution for removing chromium according to claim 1, characterized in that: After the sodium vanadium liquid in the settling tank has settled for 48 hours, the flow measuring valve and the first pump are opened to carry out vanadium settling operation.

9. A method for recovering vanadium using the system for recovering vanadium from the chromium removal underflow of sodium vanadium solution as described in any one of claims 1 to 8, comprising the following steps: The chromium slag is settled in the settling tank to obtain the chromium-removed underflow; Adding lignocellulose into a pulping tank to prepare a slurry, pumping a portion of the slurry into a vanadium removal tank and a portion of the slurry into a dilution tank; The chromium removal underflow is pumped into the vanadium removal tank to be mixed and stirred evenly with the slurry pumped into the vanadium removal tank to obtain chromium slag slurry. Adding the liquid in the buffer tank to the dilution tank to dilute the slurry, pumping the diluted slurry into the plate frame for filtration to form a film on the surface of the plate frame, and returning the filtered clear liquid to the buffer tank; The chromium slag slurry is pumped into the plate and frame for filter pressing, the filtrate is returned to the sedimentation tank to recover vanadium, and the filter cake is discharged.

10. The method according to claim 9, characterized in that The method further comprises: The vanadium content in the filter cake after discharge is detected. If the vanadium content is less than 3%, the obtained filter cake is sold out. If the vanadium content is ≥3%, the filter cake is transported to the vanadium removal tank and the operation is continued until the vanadium content in the filter cake is less than 3%.

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