CN114014290B - Method and equipment for preparing stable iron phosphate at low cost - Google Patents
Method and equipment for preparing stable iron phosphate at low cost Download PDFInfo
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Abstract
The invention discloses a method and equipment for preparing stable ferric phosphate at low cost, and belongs to the field of preparation of lithium battery anode materials. The method aims to solve the problems that iron phosphate products are difficult to synthesize or the molar ratio of phosphorus to iron in the prepared and synthesized iron phosphate products is not in the market application range under the condition of low phosphorus source iron source raw material ratio during the industrial iron phosphate preparation at present; the method of the invention comprises the following steps: preparing a phosphorus source solution and an iron source solution; continuously stirring and reacting the phosphorus source solution and the iron source solution in three reactors connected in series to finally obtain iron phosphate slurry; and washing, filtering, drying and roasting the obtained iron phosphate slurry to obtain the battery-grade iron phosphate. The invention realizes the synthesis and preparation of the iron phosphate product with stable phosphorus-iron ratio under the condition of less phosphoric acid consumption, is beneficial to further reducing the cost of iron phosphate preparation and synthesis in industry and improving the competitiveness of the product market.
Description
Technical Field
The invention belongs to the field of preparation of lithium battery anode materials, and particularly relates to a method and equipment for preparing stable iron phosphate at low cost.
Background
In the development process of lithium battery materials in recent years, lithium iron phosphate and ternary materials occupy more than 80% of the market, compared with the ternary materials, the lithium iron phosphate material has the advantages of low cost, long cycle life, environmental protection and the like, while iron phosphate as an important raw material of the lithium iron phosphate material determines the physical and chemical parameters of the lithium iron phosphate to a certain extent, at present, many commercial iron phosphate producers exist, the product competition pressure is increasingly severe, the cost reduction becomes a task of striving for core competitiveness of various companies, phosphoric acid as an important component of the iron phosphate production cost occupies 45% of the total cost, and the cost reduction is an important breakthrough, but at present, the P/Fe of the iron phosphate product generated under the high-temperature and high-pressure conditions or special solvents is close to 1.0, and is not in the range (0.960-0.985) required by the P/Fe of the iron phosphate product in the conventional market, so that the prepared iron phosphate product is difficult to be applied to the preparation of lithium phosphate.
According to retrieval, the patent publication number is CN112142025A, the publication date is 2020, 12 and 29 days, the name of the invention is a novel method capable of flexibly increasing the iron-phosphorus ratio, aiming at the production process of iron phosphate by a precipitation method, ferrous sulfate, phosphoric acid, diammonium hydrogen phosphate and hydrogen peroxide are mainly researched as raw materials, the iron-phosphorus ratio of a product is increased through 3 process routes, iron phosphate with different iron-phosphorus ratios is obtained by adjusting the proportion of a first washing filter cake and a second washing filter cake in the route 1, the iron phosphate with the iron-phosphorus ratio of 0.96-0.99 can be obtained theoretically, and the process can effectively increase the iron-phosphorus ratio; in the route 2, ammonia water is added to adjust the pH value of the aged slurry, so as to obtain iron phosphate with high iron-phosphorus ratio; in the route 3, the iron phosphate with low cost and high iron-phosphorus ratio is obtained by improving the first two routes, and the iron-phosphorus ratio of the product is improved to be more than 0.975. The invention discloses a preparation method of iron phosphate with high iron-phosphorus ratio, which is disclosed as CN109205584A and published as 2020, 8 and 21 days, and comprises the following steps: s1, preparing a ferrite solution, adding a phosphoric acid solution and PEG into the ferrite solution to obtain a reaction bottom solution, and adding the reaction bottom solution into a reaction kettle and stirring; s2, preparing a mixed solution of phosphate and hydrogen peroxide, adding the mixed solution of phosphate and hydrogen peroxide into the reaction kettle containing the reaction bottom solution, starting to heat up after ferrous ions are completely converted into ferric ions, heating to 88-92 ℃, keeping the temperature until the reaction materials are completely whitened, starting timing, and continuing to perform heat preservation reaction; and S3, washing the slurry after the heat preservation reaction is finished until the conductivity of the slurry is below 150 mu S/cm, and calcining in a furnace to obtain the iron phosphate with the high iron-phosphorus ratio. Compared with the prior art, the iron phosphate iron-phosphorus ratio prepared by the scheme of the invention can reach 0.98-1.00, and the contents of impurities such as sulfur, manganese and the like are lower. The technology provides a method for regulating the iron-phosphorus ratio, but the phosphorus-iron ratio of the iron phosphate is too high, so that the prepared lithium iron phosphate has low capacity.
In addition, the patent publication No. CN104555975A, the disclosure date is 2015, 4, month, 29, and the name of the invention is a continuous lithium iron phosphate preparation device and a preparation method, which comprises a raw material system, a material conveying system, a tubular reaction device, a kettle-type reaction device, a reaction system pressure regulating system and a discharging system, wherein the raw material system is used for mixing raw material solutions, the material conveying system continuously conveys the mixed raw material solutions into the tubular reaction device, the tubular reaction device enables the materials to be in a plug flow conveying reaction state at a specified time, temperature and pressure, the kettle-type reaction device is arranged behind the tubular reaction device, enables the materials to be in a fully mixed flow reaction state at a specified time, temperature and pressure, and enables products after reaction to be continuously output to the discharging system, the reaction system pressure regulating system fills volatile solvent components into the reaction system, the tubular reaction device and the kettle-type reaction device are maintained at a specified pressure, the kettle-type reaction device is arranged behind the tubular reaction device, but the reaction device has limited reaction intensity, and lithium phosphate preparation can not be easily realized in a short time.
Disclosure of Invention
1. Problems to be solved
Aiming at the problem that iron phosphate with a proper phosphorus-iron molar ratio is difficult to prepare under the condition of low-phosphorus source iron source raw material ratio in the industry at present, the invention provides a method for preparing stable iron phosphate at low cost, and the prepared iron phosphate P/Fe =0.960-0.980, so that the market use requirement is met;
another object of the present invention is to provide an apparatus for preparing stable iron phosphate at low cost by spatially dividing the reaction process by three reactors connected in series to obtain a stable iron phosphate product.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a low-cost method for preparing stable ferric phosphate, comprising the following steps:
(1) Respectively preparing a phosphorus source solution and an iron source solution;
(2) Continuously feeding a phosphorus source solution and an iron source solution to sequentially pass through three reactors connected in series to react to obtain iron phosphate slurry;
(3) And (3) washing, filtering, drying and roasting the iron phosphate slurry obtained in the step (2) to obtain the battery-grade iron phosphate.
Further, in the continuous feeding process of the step (2), the molar ratio of phosphorus in the phosphorus source solution to iron in the iron source solution is 0.98 to 1.04, preferably 0.99 to 1.03.
Furthermore, the mass concentration of phosphorus in the phosphorus source solution in the step (1) is 20-500g/L, and the mass concentration of iron in the iron source solution is 10-100g/L.
Further, the phosphorus source solution in step (1) may be an aqueous solution of a phosphorus source, wherein the phosphorus source is one or more of sodium monohydrogen phosphate, sodium dihydrogen phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate and ammonium phosphate.
Further, the iron source solution in the step (1) is an iron source aqueous solution, and the iron source is one or more of ferric sulfate, ferric hydroxide and ferric chloride.
Furthermore, the series reactor in the step (2) is formed by sequentially connecting a kettle type stirring reactor, a primary tubular reactor and a secondary tubular reactor in series, the reaction temperature of each reactor pair is 70-98 ℃, the average residence time in each reactor is 1-50min, and the stirring speed of each reactor in the reaction process is 100-4500r/min.
Wherein the reaction temperature in the kettle type stirring reactor is 70-80 ℃, the reaction temperature in the first-stage tubular reactor is 75-85 ℃, and the reaction temperature in the second-stage tubular reactor is 80-98 ℃. The reaction temperature is kettle type stirring reactor, primary tubular reactor, secondary tubular reactor. The kettle type stirring reactor plays a role in mixing, the materials are mixed at a certain temperature, but the service life of the kettle type stirring reactor is not prolonged due to the overhigh temperature; the first-stage tubular reactor is used for a high-speed stirring reaction generator, the molar ratio of the phosphorus source to the iron source in the materials is close to 1, and the reaction requires a larger driving force, so that the temperature cannot be too low; the energy required for the iron atom de-intercalation reaction in the secondary tubular reactor is higher, so that the required stirring speed is fastest and the reaction temperature is highest.
Wherein the average residence time of the kettle type stirring reactor is 10-50min, the average residence time of the first-stage tubular reactor is 1-10min, and the average residence time of the second-stage tubular reactor is 5-20min. The reaction residence time is that the kettle type stirred tank reactor, the secondary tubular reactor and the primary tubular reactor. The average residence time of the materials in the kettle type stirring reactor is longer than that of the first-stage tubular reactor and the second-stage tubular reactor, and the reason is that the materials are mixed in the kettle type stirring reactor, and the phosphorus source and the iron source have higher viscosity when being mixed together, so that the materials can be uniformly mixed in a longer time, and the subsequent reaction is facilitated; the reaction process in the first-stage tubular reactor is in a high-speed mixing state, the reaction rate is high, and the time is short; the de-intercalation of iron ions in the secondary tube reactor is more difficult and therefore longer than in the iron phosphate generation stage.
Furthermore, the stirring speed of the kettle type stirring reactor is 100-2000r/min, the stirring speed of the first-stage tubular reactor is 2000-4000r/min, the stirring speed of the second-stage tubular reactor is 3000-4500r/min, the stirring speed of the second-stage tubular reactor is 1000-1500r/min greater than that of the first-stage tubular reactor, and the stirring speed of the first-stage tubular reactor is 1500-2000r/min greater than that of the kettle type stirring reactor. The stirring speed is two-stage tubular reactor, one-stage tubular reactor and kettle type stirring reactor. The reason is that the kettle type stirring reactor has a mixing function, the viscosity of the materials is high, and if the stirring speed is too high, the service life of the stirring equipment is greatly reduced; in the first-stage tubular reactor, the first-stage tubular reactor performs high-speed stirring reaction, the molar ratio of the phosphorus source to the iron source in the material is close to 1, and the reaction requires a larger driving force, so that the stirring speed cannot be too low; the energy required for carrying out the iron atom de-intercalation reaction in the secondary tube reactor is higher, so the stirring speed is required to be fastest.
Further, in the step (3), the drying temperature is 80-150 ℃, the drying time is 1-4h, the roasting temperature is 550-700 ℃, the roasting time is 1-4h, and the obtained iron phosphate slurry is washed by water or ethanol, filtered, dried and roasted to obtain the battery-grade iron phosphate.
Furthermore, the series reactor comprises a kettle type stirring reactor and a tubular reactor, the tubular reactor comprises a first-stage tubular reactor and a second-stage tubular reactor, and the kettle type stirring reactor, the first-stage tubular reactor and the second-stage tubular reactor are sequentially connected through pipelines.
The method utilizes three reactors connected in series to respectively realize a full mixing stage of materials, a reaction stage at a molecular level and a phosphorus-iron ratio adjustment stage of the iron phosphate, and performs spatial segmentation on the reaction process to prepare a stable iron phosphate product with a proper phosphorus-iron ratio. The equipment for preparing stable iron phosphate at low cost is characterized in that a kettle type stirring reactor, a primary tubular reactor and a secondary tubular reactor are sequentially connected in series, wherein the kettle type stirring reactor is provided with a larger volume at first, so that the reaction time can be greatly reduced, the materials are mixed more uniformly, the primary tubular reactor improves the stirring speed through the small volume of the reactor, the materials are quickly fed in and quickly discharged, the reaction intensity of iron phosphate in the generation stage is exponentially increased, iron phosphate white slurry can be generated under the condition of low phosphorus source and iron source raw material ratio, after the iron phosphate white slurry obtained by the primary tubular reactor enters the secondary tubular reactor, iron phosphate with the phosphorus-iron ratio close to 1 starts to be quickly de-embedded in situ under the condition of higher stirring speed, iron ions are partially removed, and a more stable iron phosphate is formed, namely P/Fe =0.960-0.980, so that an iron phosphate product required by the current market is obtained, the preparation cost of the iron phosphate product is reduced, and the phosphorus-iron phosphate ratio of the iron phosphate product is in a proper range.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention provides a method for synthesizing and preparing iron phosphate under the condition of low raw material ratio of a phosphorus source iron source, the prepared iron phosphate is stable, and P/Fe =0.960-0.980, so that the market requirement is met;
(2) The invention provides equipment for preparing stable iron phosphate at low cost, which respectively realizes a full mixing stage of materials, a molecular-level reaction stage and a phosphorus-iron ratio adjustment stage of an iron phosphate product through three reactors connected in series, and prepares the stable iron phosphate product by spatially dividing the reaction process;
(3) According to the method for preparing the iron phosphate, materials are fully mixed in the kettle type stirring reactor, the tubular reaction is quickly carried out, the overall reaction time is greatly shortened by a series reaction mode, and compared with the preparation period of iron phosphate in the traditional process, which is 2.5 hours, the preparation period is 1.0 hour;
(4) The invention reduces the production cost of the iron phosphate product, and simultaneously ensures that the phosphorus-iron ratio of the iron phosphate product is in a proper application range and the product stability is higher.
Drawings
The technical solution of the present invention will be described in further detail with reference to the accompanying drawings and examples, but it should be understood that these drawings are designed for illustrative purposes only and thus are not intended to limit the scope of the present invention. Furthermore, unless otherwise indicated, the drawings are intended to be illustrative of the structural configurations described herein and are not necessarily drawn to scale.
FIG. 1 is an electron micrograph of iron phosphate in example 1 of the present invention;
fig. 2 is a schematic structural diagram of the equipment for preparing stable ferric phosphate.
Detailed Description
The following detailed description of exemplary embodiments of the invention refers to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration exemplary embodiments in which the invention may be practiced. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the invention is not intended to limit the scope of the invention as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the invention, to set forth the best mode of carrying out the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the invention is to be limited only by the following claims.
The iron phosphate is a raw material for preparing the lithium iron phosphate, and the quality of the iron phosphate plays an important role in adjusting the performance of the lithium iron phosphate. However, when the addition amount of the phosphorus source is less, the iron phosphate is difficult to generate, in the prior art, the iron phosphate is generated by using high temperature and high pressure or a special solvent under the condition of less phosphorus source, the P/Fe ratio of the iron phosphate is close to 1.0, and the lithium iron phosphate prepared from the iron phosphate with a high phosphorus-iron ratio is low in capacity, so that the market requirement is difficult to meet. Therefore, in order to prepare the iron phosphate with the proper phosphorus-iron ratio under the condition of low raw material ratio of the phosphorus source iron source, the invention firstly utilizes the large volume of the kettle type stirring reactor to uniformly mix the materials and reduce the reaction time; accelerating the reaction product by a primary tubular reactor to generate iron phosphate white slurry with a phosphorus-iron ratio close to that of the reaction product; the rapid in-situ extraction of iron ions is further accelerated in the secondary tubular reactor, and the iron phosphate in a more stable state is formed. Wherein, the first-order tubular reactor realizes fast-in and fast-out, the volume of the first-order tubular reactor can be smaller so as to realize sufficiently fast stirring speed, the reaction intensity of the iron phosphate in the generation stage is increased, and the schematic diagram of the equipment structure is shown in figure 2. In addition, the stirring speeds of the three reactors connected in series are set to be increased in sequence, namely the stirring speed is that a secondary tubular reactor is larger than a primary tubular reactor and that the stirring speed is that a kettle type stirring reactor is larger than a primary tubular reactor, so that the iron ions can be rapidly in-situ de-intercalated under the condition of vigorous stirring of the generated iron phosphate with the similar phosphorus-iron ratio, and the iron ions are partially removed to prepare stable iron phosphate P/Fe =0.960-0.980, thereby meeting the market requirements.
Example 1
(1) Preparing a ferric sulfate solution with iron content of 75g/L and a ammonium dihydrogen phosphate solution with phosphorus content of 200 g/L;
(2) Continuously introducing the iron source and the phosphorus source in the step (1) into a kettle type stirring reactor according to the molar ratio of the phosphorus source to the iron source of 1.02 for reaction, wherein the stirring speed is 300r/min, the average residence time is 30min, the reaction temperature is 80 ℃, then continuously introducing the reaction material into a primary tubular reactor, the stirring speed is 2300r/min, the residence time is 3min, the reaction temperature is 85 ℃, then continuously introducing the reaction material into a secondary tubular reactor, the stirring speed is 4000r/min, the average residence time is 15min, and the reaction temperature is 90 ℃, and obtaining white iron phosphate slurry as discharged material;
(3) Washing and filtering the white iron phosphate slurry obtained in the step (2), drying at 90 ℃ for 2h, and roasting the dihydrate ferric phosphate material at 680 ℃ for 3h to obtain a stable iron phosphate product, wherein an electron microscope image of the prepared iron phosphate is shown in figure 1.
Example 2
(1) Preparing ferric hydroxide solution with 85g/L of iron content and monoammonium phosphate solution with 250g/L of phosphorus content;
(2) Continuously introducing the iron source and the phosphorus source in the step (1) into a kettle type stirring reactor according to the molar ratio of the phosphorus source to the iron source of 1.01 for reaction, wherein the stirring speed is 500r/min, the average residence time is 49min, the reaction temperature is 78 ℃, then continuously introducing the reaction materials into a primary tubular reactor, the stirring speed is 2500r/min, the average residence time is 2min, the reaction temperature is 80 ℃, then continuously introducing the reaction materials into a secondary tubular reactor, the stirring speed is 3600r/min, the average residence time is 18min, and the reaction temperature is 95 ℃ to obtain white iron phosphate slurry as discharged material;
(3) And (3) washing and filtering the white iron phosphate slurry obtained in the step (2), drying at 100 ℃ for 3h, and roasting the dihydrate ferric phosphate material at 690 ℃ for 2h to obtain a stable iron phosphate product.
Example 3
(1) Preparing ferric chloride solution with iron content of 100g/L and monoammonium phosphate solution with phosphorus content of 500 g/L;
(2) Continuously introducing the iron source and the phosphorus source in the step (1) into a kettle type stirring reactor according to the molar ratio of the phosphorus source to the iron source of 0.98 for reaction, wherein the stirring rate is 1200r/min, the average residence time is 50min, the reaction temperature is 75 ℃, then continuously introducing the reaction materials into a primary tubular reactor, the stirring rate is 3200r/min, the average residence time is 10min, the reaction temperature is 85 ℃, then continuously introducing the reaction materials into a secondary tubular reactor, the stirring rate is 4200r/min, the average residence time is 20min, and the reaction temperature is 98 ℃, thus obtaining white iron phosphate slurry as discharged material;
(3) And (3) washing and filtering the white iron phosphate slurry obtained in the step (2), drying at 120 ℃ for 4h, and roasting the dihydrate iron phosphate material at 700 ℃ for 4h to obtain a stable iron phosphate product.
Comparative example 1
(1) Preparing a ferric sulfate solution with iron content of 75g/L and a ammonium dihydrogen phosphate solution with phosphorus content of 200 g/L;
(2) Continuously introducing the iron source and the phosphorus source in the step (1) into a kettle type stirring reactor according to the molar ratio of the phosphorus source to the iron source of 0.95 for reaction, wherein the stirring speed is 300r/min, the average residence time is 30min, the reaction temperature is 80 ℃, then continuously introducing the reaction material into a primary tubular reactor, the stirring speed is 2300r/min, the average residence time is 3min, the reaction temperature is 85 ℃, then continuously introducing the reaction material into a secondary tubular reactor, the stirring speed is 4000r/min, the average residence time is 15min, and the reaction temperature is 90 ℃ to obtain a discharged white iron phosphate slurry;
(3) And (3) washing and filtering the white iron phosphate slurry obtained in the step (2), drying at 90 ℃ for 2h, and roasting the dihydrate iron phosphate material at 680 ℃ for 3h to obtain a stable iron phosphate product.
Comparative example 2
(1) Preparing a ferric sulfate solution with iron content of 75g/L and a ammonium dihydrogen phosphate solution with phosphorus content of 200 g/L;
(2) Continuously introducing the iron source and the phosphorus source in the step (1) into a kettle type stirring reactor according to the molar ratio of the phosphorus source to the iron source of 1.02 for reaction, wherein the stirring speed is 300r/min, the average residence time is 30min, the reaction temperature is 80 ℃, then continuously introducing the reaction materials into a primary tubular reactor, the stirring speed is 2300r/min, the average residence time is 3min, the reaction temperature is 85 ℃, then continuously introducing the reaction materials into a secondary tubular reactor, the stirring speed is 2000r/min, the average residence time is 15min, and the reaction temperature is 90 ℃ to obtain white iron phosphate slurry as discharged material;
(3) And (3) washing and filtering the white iron phosphate slurry obtained in the step (2), drying at 90 ℃ for 2h, and roasting the dihydrate iron phosphate material at 680 ℃ for 3h to obtain a stable iron phosphate product.
Table 1 shows experimental parameters of examples of the present invention and comparative examples.
TABLE 1 Experimental parameters for each of the examples and comparative examples
The iron phosphates obtained in the above examples and comparative examples were compared, and the results of comparing the physical parameters of the prepared iron phosphates are shown in table 2.
Table 2: physical parameter comparison results of iron phosphate prepared in each example and comparative example
As can be seen from table 2, the method and the apparatus for preparing stable iron phosphate at low cost according to the present invention can obtain iron phosphate products with a phosphorus-iron ratio within a suitable range, and it is noted that the present invention controls the molar ratio of phosphorus in the phosphorus source solution to iron in the iron source solution to be 0.98 to 1.04, and controls the reaction conditions of the three reactors connected in series, compared with the iron phosphate prepared in comparative example 1, in which the molar ratio of phosphorus in the phosphorus source solution to iron in the iron source solution is not within the range of the present invention, the iron phosphate prepared by the present invention has a suitable iron-phosphorus ratio, and D50 is controlled to be in a smaller range, and the rate capability of lithium iron phosphate prepared by using the iron phosphate is significantly improved, and can meet the requirements of battery-grade iron phosphate. In addition, the reaction temperature, the residence time and the stirring speed of the three reactors connected in series are controlled to realize raw material mixing, iron phosphate generation and iron atom de-intercalation, a larger stirring speed is required in the de-intercalation stage, otherwise, iron atoms cannot be de-intercalated, and as shown in comparative example 2, the iron phosphate Fe/P is higher, the particle size is larger, and the rate capability of the prepared lithium iron phosphate is lower. The method for preparing stable iron phosphate at low cost has simple process and mild reaction condition, and is easy for industrial large-scale production.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.
The present invention is not described in detail, but is known to those skilled in the art.
Claims (7)
1. A method for preparing stable ferric phosphate at low cost is characterized by comprising the following steps:
(1) Respectively preparing a phosphorus source solution and an iron source solution;
(2) Continuously feeding the phosphorus source solution and the iron source solution, sequentially passing through three reactors connected in series, and reacting to obtain iron phosphate slurry;
the series reactor is formed by sequentially connecting a kettle type stirring reactor, a primary tubular reactor and a secondary tubular reactor in series,
the reaction temperature in the kettle type stirring reactor is 70-80 ℃, the reaction temperature in the primary tubular reactor is 75-85 ℃, the reaction temperature in the secondary tubular reactor is 80-98 ℃, and the reaction temperature is that the kettle type stirring reactor is smaller than the primary tubular reactor is smaller than the secondary tubular reactor;
the average residence time of the kettle type stirring reactor is 10-50min, the average residence time of the first-stage tubular reactor is 1-10min, the average residence time of the second-stage tubular reactor is 5-20min, and the average residence time is that of the kettle type stirring reactor, the second-stage tubular reactor and the first-stage tubular reactor;
the stirring speed of the kettle type stirring reactor is 100-2000r/min, the stirring speed of the first-stage tubular reactor is 2000-4000r/min, the stirring speed of the second-stage tubular reactor is 3000-4500r/min, the stirring speed of the second-stage tubular reactor is 1000-1500r/min greater than that of the first-stage tubular reactor, the stirring speed of the first-stage tubular reactor is 1500-2000r/min greater than that of the kettle type stirring reactor, and the stirring speed is that the second-stage tubular reactor is greater than that of the first-stage tubular reactor;
(3) And (3) washing, filtering, drying and roasting the iron phosphate slurry obtained in the step (2) to obtain the battery-grade iron phosphate.
2. The method for preparing stable ferric phosphate at low cost according to claim 1, wherein the molar ratio of phosphorus in the phosphorus source solution to iron in the iron source solution in the continuous feeding process in step (2) is 0.98-1.04.
3. The method for preparing stable ferric phosphate at low cost according to claim 2, wherein the phosphorus concentration in the phosphorus source solution in the step (1) is 20-500g/L, and the iron concentration in the iron source solution is 10-100g/L.
4. The method for preparing stable ferric phosphate at low cost according to claim 1, wherein the phosphorus source solution in step (1) is an aqueous solution of phosphorus source, and the phosphorus source is one or more of sodium monohydrogen phosphate, sodium dihydrogen phosphate, ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate and ammonium phosphate.
5. The method for preparing stable ferric phosphate at low cost according to claim 1, wherein the iron source solution in step (1) is an aqueous solution of an iron source, and the iron source is one or more of ferric sulfate, ferric hydroxide and ferric chloride.
6. The method for preparing stable iron phosphate at low cost according to claim 1, wherein the drying temperature in step (3) is 80-150 ℃, the drying time is 1-4h, the roasting temperature is 550-700 ℃, and the roasting time is 1-4h.
7. An apparatus for the low-cost method for preparing stable ferric phosphate according to any one of claims 1 to 6, which comprises a tank type stirring reactor and a tubular reactor, wherein the tubular reactor comprises a primary tubular reactor and a secondary tubular reactor, and the tank type stirring reactor, the primary tubular reactor and the secondary tubular reactor are connected in series in sequence by using pipelines.
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| CN112408351A (en) * | 2020-11-23 | 2021-02-26 | 中钢集团南京新材料研究院有限公司 | Preparation method of high-compaction iron phosphate and lithium iron phosphate |
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2021
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| KR20140069722A (en) * | 2012-11-29 | 2014-06-10 | 주식회사 엘지화학 | Apparatus for continuous hydrothermal synthesis process in super critical condition using switching of mixer |
| CN106876700A (en) * | 2016-11-02 | 2017-06-20 | 杨晓钢 | The method that two step co-precipitation prepare micro-nano porous structure ferric phosphate presoma and lithium iron phosphate positive material |
| CN207361793U (en) * | 2017-08-30 | 2018-05-15 | 山东三秋新能源科技有限公司 | A kind of lithium iron phosphate positive material preparation facilities |
| WO2019200557A1 (en) * | 2018-04-18 | 2019-10-24 | 南通百川新材料有限公司 | Preparation method for iron phosphate |
| CN108862226A (en) * | 2018-08-15 | 2018-11-23 | 南通百川新材料有限公司 | Preparation method of high-purity battery-grade iron phosphate |
| CN111217346A (en) * | 2019-11-22 | 2020-06-02 | 贵州唯特高新能源科技有限公司 | Preparation method of high-performance ferrous phosphate |
| CN112408351A (en) * | 2020-11-23 | 2021-02-26 | 中钢集团南京新材料研究院有限公司 | Preparation method of high-compaction iron phosphate and lithium iron phosphate |
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