Process method for producing titanium-doped iron phosphate through continuous reaction

Abstract

The invention relates to the technical field of titanium-doped iron phosphate preparation, and particularly discloses a process method for producing titanium-doped iron phosphate through continuous reaction, which comprises the following steps: S1, continuously adding iron-phosphorus mixed liquor, titanyl sulfate, ammonia water and hydrogen peroxide into a primary reaction kettle in a parallel flow manner, starting a delivery pump to pump the material into a secondary reaction kettle after the reaction time reaches 1 hour, reacting in the second-stage reaction kettle for 1 hour, and then outputting slurry; s2, the slurry is filtered and washed with deionized water until the conductivity of washing water is lower than 1000 [mu] s / cm, and a filter cake is obtained; s3, aging the filter cake with 0.05 mol / L dilute phosphoric acid until the color is changed from yellow to white, carrying out heat preservation for 0.5-1.5 hours, and then carrying out secondary filtering and washing until the conductivity of washing water is lower than 150 [mu] s / cm, so as to obtain an iron phosphate filter cake; and S4, drying the iron phosphate filter cake at 100-120 DEG C for 8-12 hours, and calcining at 580-620 DEG C for 3-5 hours to obtain the anhydrous iron phosphate. According to the invention, continuous reaction and continuous feeding and discharging are adopted, so that the problems of non-uniform titanium doping, large product difference and high input cost caused by the existing intermittent reaction and solid-phase preparation method are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of titanium-doped iron phosphate preparation, in particular to a process method for continuously reacting to produce titanium-doped iron phosphate. BACKGROUND

[0002] Under the background of continuous development in the new energy field, lithium iron phosphate has become the core material of power and energy storage systems due to its low cost and high safety. However, with the shortage of high-quality production capacity in the industry, the intensification of competition and the decline of profits, titanium-doped iron phosphate technology innovation is particularly urgent, especially to meet the performance requirements of the third, fourth and above lithium iron phosphate products, continuously react to prepare titanium-doped anhydrous iron phosphate, make the titanium element uniformly doped, the target titanium content is 5000+ / -500mg / kg, and the titanium element is uniformly distributed in the crystal lattice, and high compaction density lithium iron phosphate is prepared, and the iteration upgrading target of the iron phosphate product is realized.

[0003] In the known titanium-doped iron phosphate technology, the titanium element doping node can be: 1. introduced during the preparation of lithium iron phosphate by a solid phase method, as shown in the authorized patent CN201010602891.X Preparation method of lithium iron phosphate composite material, the lithium source, iron source, titanium source and phosphorus source are added to the ball mill together, then the dried material is calcined under the protection of inert gas. But this reaction process needs a lot of heat energy and uninterrupted mechanical grinding, and the titanium dioxide particles are not uniform in size during the grinding process, and it is difficult to obtain uniformly doped lithium iron phosphate. 2. introduced during the preparation of iron phosphate, as shown in the patent CN202411223959.1 Method for preparing titanium-doped iron phosphate by using metatitanic acid and titanium dioxide by-product, the titanium sulfate solution is prepared and mixed with the prepared ferrous sulfate solution to react, then aged, washed, dried and calcined. Such production process is mostly intermittent reaction, which needs to control many nodes and devices, and the operation is frequent, which increases the use of manpower and material resources, and the intermittent reaction process has large fluctuation, and the batch difference of the obtained anhydrous iron phosphate is large. Some processes such as the patent CN202311785880.3 Titanium-doped anhydrous iron phosphate material and preparation method and application show that the ferrous sulfate containing titanium liquid is mixed with the ferrous sulfate not containing titanium liquid, and then the iron phosphate is synthesized by oxidation. This method also leads to uneven distribution of titanium.

[0004] The application adopts continuous reaction, continuously feeds in and out in the reaction stage, has few constant control points of reaction conditions, needs few input devices and costs, has stable reaction operation, the titanium source is uniformly doped, and the product has no batch difference, and is suitable for large-scale industrial production. SUMMARY

[0005] The application aims to provide a process method for continuously reacting to produce titanium-doped iron phosphate, and solves the problems of uneven titanium doping, large equipment investment and cost, and large product difference caused by the existing batch reaction and solid-phase preparation method.

[0006] To solve the above problems, the technical scheme adopted by the application is as follows: a process method for continuously reacting to produce titanium-doped iron phosphate, comprising the following steps: S1 continuous reaction: continuously input iron-phosphorus mixed solution, titanyl sulfate, ammonia water and hydrogen peroxide into a first-stage reaction kettle, and when the reaction time reaches 1 hour, start a conveying pump to pump the material into a second-stage reaction kettle, and output the slurry after 1 hour of reaction in the second-stage reaction kettle; wherein, the titanyl sulfate is pre-mixed with the hydrogen peroxide, then contacts with the iron-phosphorus mixed solution, and enters the reaction system, and the pH of the continuous reaction system is controlled to be 1.8-2.2 through the ammonia water flow; S2 washing: filter the slurry and wash it with deionized water until the washing water conductivity is lower than 1000 us / cm, to obtain a filter cake; S3 aging: age the filter cake with 0.05 mol / L dilute phosphoric acid until the color changes from yellow to white, and after 0.5-1.5 hours of incubation, filter and wash the filter cake again until the washing water conductivity is lower than 150 us / cm, to obtain an iron phosphate filter cake; S4 drying and calcination: dry the iron phosphate filter cake at 100-120 DEG C for 8-12 hours, and then calcine it at 580-620 DEG C for 3-5 hours to obtain anhydrous iron phosphate.

[0007] Further, the preparation step of the iron-phosphorus mixed solution in S1 is as follows: dissolve a titanium white by-product in deionized water, add ammonia water to adjust the pH to 3.7-4.1, and then flocculate and filter to obtain a ferrous sulfate clear solution, and mix the ferrous sulfate clear solution with a pH=2-3 ammonium phosphate solution according to the iron-phosphorus ratio of 0.95-0.97.

[0008] Further, the aging temperature in S3 is 90-98 DEG C.

[0009] Further, the drying in S4 is carried out in a negative pressure environment, and the calcination is carried out in an air atmosphere.

[0010] The beneficial effects of the embodiment are as follows: 1. No obvious batch difference: the reaction method of the application is continuous reaction, and the material is continuously fed in and out in the reaction stage, so that the produced product has no obvious batch difference.

[0011] 2. Low cost: the reaction kettle adopted by the application is 30 cubic meters, and the reaction kettle cannot be too large otherwise the stirring is uneven, and cannot be too small otherwise the yield is low, and 3 million tons of production capacity only needs 2 30m 3The reaction kettle has small investment and occupies small area, compared with six reaction kettles required by the batch method, the equipment cost is reduced, and the reaction is stable and runs smoothly, the reaction condition is constant, and only relevant indexes need to be detected by sampling at fixed time.

[0012] 3. Titanium source uniform doping: the application forms a stable complex by premixing titanyl sulfate and hydrogen peroxide, avoids local titanium precipitation, uniformly dopes the titanium source in the iron phosphate preparation stage, is beneficial to improving the lattice stability of the calcination process, and thus can obtain higher compaction density and electrochemical performance in the iron lithium stage.

[0013] 4. Stable quality: the titanium content of the product fluctuates by less than or equal to 1.5% within 12 hours of continuous reaction.

[0014] 5. Performance meets requirements: the compaction density of the current mainstream commercial product of lithium iron phosphate is 2.4-2.5 g / cm 3 , the fourth-generation high-compaction product can reach 2.6-2.7 g / cm 3 , the compaction density of the lithium iron phosphate obtained by the application reaches 2.59-2.60 g / cm 3 , and meets the requirements of power batteries.

[0015] 6. High practical performance: the application continuously runs for 12 hours, the continuous reaction is stable, the production capacity data support industrial application, and the traditional batch reaction is operated in steps, single batch output, and low efficiency. DETAILED DESCRIPTION

[0016] Figure 1 A continuous reaction production process of titanium-doped iron phosphate is shown in the flow chart. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0018] Referring to Figure 1 , the continuous reaction production process of titanium-doped iron phosphate includes the following steps: S1 continuous reaction: continuously input the iron-phosphorus mixed solution, titanyl sulfate, ammonia water, and hydrogen peroxide into the first-stage reaction kettle in parallel, start the delivery pump to pump the material into the second-stage reaction kettle when the reaction time reaches 1 hour, and output the slurry after 1 hour of reaction in the second-stage reaction kettle; wherein, the titanyl sulfate is premixed with the hydrogen peroxide, then contacts the iron-phosphorus mixed solution, and enters the reaction system, and the pH of the continuous reaction system is controlled to be 1.8-2.2 by the ammonia water flow rate; S2 washing: the slurry is filtered and washed with deionized water until the wash water conductivity is less than 1000 μs / cm, to obtain a filter cake; S3 aging: the filter cake is aged with 0.05 mol / L dilute phosphoric acid until the color changes from yellow to white, and after 0.5-1.5 hours of incubation, the filter cake is filtered and washed again until the wash water conductivity is less than 150 μs / cm, to obtain a filter cake of iron phosphate; S4 drying and calcination: the filter cake of iron phosphate is dried at 100-120 °C for 8-12 hours, and then calcined at 580-620 °C for 3-5 hours to obtain anhydrous iron phosphate.

[0019] The preparation method of the present application will be described in detail below in conjunction with specific examples: Example 1 S1: titanium white by-products are dissolved in deionized water, and ammonia water is added to adjust the pH to 3.7-4.1. After adding a small amount of flocculant, a ferrous sulfate clear liquid is obtained by filtration. The ferrous sulfate clear liquid is mixed with ammonium phosphate with a pH of 2-3 at an iron-phosphorus ratio of 0.95-0.97 to obtain an iron-phosphorus mixed solution. The iron-phosphorus mixed solution, titanyl sulfate, ammonia water, and hydrogen peroxide materials are simultaneously and continuously fed into a reaction kettle and continuously reacted. The titanyl sulfate is first mixed with hydrogen peroxide, then mixed with the iron-phosphorus mixed solution, and then fed into the reaction system. Ammonia water is continuously added to adjust the pH to 2±0.2. After 1 hour of reaction in the primary reaction kettle, the material is continuously pumped into the secondary reaction kettle by a pump. After 1 hour of reaction in the secondary reaction kettle, the material is pumped into a reaction material storage tank for standby.

[0020] S2: 1000 ml of material at 3 hours, 6 hours, 9 hours, and 12 hours is filtered, and the filter cake is washed until the conductivity is less than 1000 μs / cm.

[0021] S3: the washed filter cake is placed in a 0.05 mol / L dilute phosphoric acid solution and is beaten and heated to 95 °C for aging. After the filter cake is aged and turns white, it is filtered, and then washed with deionized water again until the conductivity is less than 150 μs / cm.

[0022] S4: the filter cake after the second washing is placed in a 100 °C negative pressure drying oven for 10 hours, and then calcined at 600 °C in an air atmosphere for 4 hours to obtain titanium-doped anhydrous iron phosphate.

[0023] The detection data of anhydrous iron phosphate at four sampling times are as follows:

[0024] In this example, the titanium content is 4908-4970 ppm, the iron-lithium tap density is 2.59-2.60 g / cm 3 , the tap density is 0.81-0.84 g / cm 3 , and there is no obvious difference between batches of products.

[0025] In this embodiment, the liquid level in the reactor is controlled at approximately 80%, which is achieved through the discharge rate of the feed liquid. If the liquid level is too low, the reaction yield will be low; if the liquid level is too high, or even the reactor is full, the slurry may enter the heat exchanger, fan, or other equipment, causing an accident. Titanium oxysulfate is premixed with hydrogen peroxide to form a complex. Because the flow rate of titanium ions is relatively low, it is first mixed evenly with hydrogen peroxide to avoid uneven mixing in the reactor.

[0026] Comparative Example 1 S1: Take 1000ml of ferrous sulfate from the apparatus and add titanium oxysulfate to the reaction vessel and mix well. Add hydrogen peroxide, ammonium phosphate and ammonia water to the reaction vessel simultaneously and in parallel. Adjust the ammonia water flow rate to control the pH of the reaction system to 1.8±0.2, with no ferrous iron residue.

[0027] S2: After filtering the reaction material, the filter cake is washed with deionized water until the conductivity is below 1000 μs / cm.

[0028] S3: The washed filter cake is aged with 0.05 mol / L dilute phosphoric acid. After turning white, it is filtered and washed for 30 minutes until the conductivity is below 150 μs / cm.

[0029] S4: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain titanium-doped anhydrous ferric phosphate.

[0030] The detection data of anhydrous ferric phosphate in Comparative Example 1 are shown in the table below:

[0031] Results analysis: As can be seen from the above data, there is no significant difference in data between the titanium-doped iron phosphate prepared by the continuous reaction of this invention and the titanium-doped iron phosphate prepared by the traditional batch reaction. Furthermore, the data obtained from the continuous reaction of this invention after 12 hours show no significant difference. The anhydrous iron phosphate obtained exhibits excellent properties, and the prepared lithium iron phosphate has high compaction, fully meeting the requirements of power lithium iron phosphate batteries. However, based on production calculations, the continuous reaction of this invention only requires two 30m³ cycles. 3 The reactor can meet the reaction requirements of 30,000 tons, while batch reactions would require 6 reactors. This invention reduces equipment investment and maintenance, greatly reducing cost investment. It has profound significance for the subsequent expansion of titanium-doped iron phosphate production capacity, large-scale production, stable operation of production lines, and quality improvement.

[0032] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A continuous reaction process for producing titanium-doped iron phosphate, characterized in that, Includes the following steps: S1 Continuous Reaction: Iron-phosphorus mixture, titanium oxysulfate, ammonia, and hydrogen peroxide are continuously fed into the primary reactor in a parallel flow. After 1 hour of reaction, the transfer pump is started to pump the material into the secondary reactor. After 1 hour of reaction in the secondary reactor, the slurry is output. Among them, titanium oxysulfate is premixed with hydrogen peroxide first, and then enters the reaction system after contacting with the iron-phosphorus mixture. The pH of the continuous reaction system is controlled by the flow rate of ammonia to be 1.8-2.

2. S2 Washing: The slurry is filtered and washed with deionized water until the conductivity of the wash water is less than 1000 μs / cm to obtain a filter cake; S3 aging: The filter cake is aged with 0.05 mol / L dilute phosphoric acid until the color changes from yellow to white. After keeping it at this temperature for 0.5-1.5 hours, it is filtered and washed a second time until the conductivity of the wash water is less than 150 μs / cm to obtain ferric phosphate filter cake. S4 Drying and Calcination: The ferric phosphate filter cake is dried at 100-120℃ for 8-12 hours and then calcined at 580-620℃ for 3-5 hours to obtain anhydrous ferric phosphate.

2. The process for continuous reaction production of titanium-doped iron phosphate according to claim 1, characterized in that: The preparation steps of the iron-phosphorus mixture described in S1 are as follows: dissolve the titanium dioxide by-product in deionized water, add ammonia to adjust the pH to 3.7-4.1, flocculate and filter to obtain ferrous sulfate clear solution, and mix the ferrous sulfate clear solution with ammonium phosphate solution with pH=2-3 at an iron-phosphorus ratio of 0.95-0.

97.

3. The process for continuous reaction production of titanium-doped iron phosphate according to claim 1, characterized in that: The aging temperature described in S3 is 90-98℃.

4. The process for continuous reaction production of titanium-doped iron phosphate according to claim 1, characterized in that: The drying described in S4 is carried out in a negative pressure environment, while the calcination is carried out in an air atmosphere.

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