A method for preparing ferric phosphate by fluidized leaching

Abstract

The present invention relates to the field of new energy technology, and in particular to a method for preparing ferric phosphate by fluidized leaching. The ferric phosphate is directly prepared by fluidized leaching of phosphate ore and converter iron ore mud, which has a simple process flow and low equipment cost, thereby greatly reducing the preparation cost of ferric phosphate.

Description

Technical Field

[0001] The invention relates to the field of new energy technology, and in particular to a method for preparing ferric phosphate by fluidized leaching. Background Art

[0002] Lithium iron phosphate is a new type of lithium-ion battery electrode material, which is characterized by large discharge capacity, low price, non-toxicity, and no environmental pollution. Countries around the world are competing to achieve industrial production. The main use of iron phosphate is to manufacture lithium iron phosphate battery materials. The Chinese invention patent (patent number is CN201210095275.9, and the patent name is a method for preparing iron phosphate for preparing lithium iron phosphate and iron phosphate) discloses a method for preparing iron phosphate for preparing lithium iron phosphate and iron phosphate, which is characterized by comprising the following steps: (1) preparing a cationic surfactant aqueous solution; (2) preparing a soluble iron salt aqueous solution and a soluble phosphate aqueous solution with a concentration of 0.1 to 5 mol / L respectively; (3) mixing the soluble iron salt aqueous solution and the soluble phosphate aqueous solution at 25 to 50°C, ultrasonic and stirring conditions according to Fe:P=1:0.8 to 1.2 (molar ratio); The aqueous solution is slowly added to the cationic surfactant aqueous solution in sequence, and the adding speed is not more than 60 ml / min. After the soluble iron salt aqueous solution and the soluble phosphate aqueous solution are fully added, the concentration of the cationic surfactant in the reaction solution obtained is 1-10 g / L; (4) under 25-50° C., ultrasonic and stirring conditions, ammonia water is added to the reaction solution to adjust the pH of the solution to 0-3, and after the ultrasonic reaction is stopped for a period of time, stirring is continued for 30-180 minutes; (5) The liquid obtained in the step (4) is washed with deionized water or anhydrous ethanol, and then dried at 70-90° C. to obtain powdered iron phosphate.

[0003] The iron and phosphorus sources for preparing ferric phosphate in the prior art are both from industrial reagents, such as the soluble iron salt aqueous solution and the soluble phosphate aqueous solution mentioned above. The above reagents have various impurities due to different mineral sources and synthesis processes. The prior art only proposes to separate and remove different impurities such as Mg and Mg separately. 2+ , Ca 2+ 、Na + , K + 、Al 3+ 、F - , Cl - 、SO4 -, SiO2, etc., their high-purity separation processes overlap, such as mixing, evaporation, crystallization, precipitation, filtration, drying, etc. If each reagent is subjected to a high-purity separation process separately, the cost will be extremely high. If iron phosphate is directly synthesized through phosphate ore beneficiation, and then high-purity iron phosphate is obtained through a high-purity separation process, the cost will undoubtedly be greatly reduced. The existing technology uses cationic surfactants, ultrasound and stirring to make the iron phosphate particle size uniform and less agglomerated, but the introduction of cationic surfactants means the introduction of more foreign ions into the iron phosphate solution, and a new high-purity separation process needs to be added, which undoubtedly increases more costs. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing ferric phosphate by fluidized leaching, which is characterized by: step one, preparing slurry, mixing phosphate ore and converter iron ore mud and wet-grinding them by ball milling to the required particle size, generally 50 to 200 μm, with a moisture content of 28% to 32%, and the prepared slurry can meet the requirements of long-distance pipeline transportation, and the solid particles in the slurry are infiltrated and suspended in the liquid phase by water molecules, so that the solid particles are evenly dispersed and wrapped by a liquid film of water molecules, thereby increasing the effective phase interface area and increasing the mass transfer efficiency of the acid hydrolysis fluidization reaction.

[0005] Step 2: circulating fluidized acid hydrolysis. The slurry is injected into the fluidized reaction column through the slurry inlet and the central tube. The central tube is located at the center of the fluidized reaction column and is fixed with support frames at both ends. The circumferential wall of the central tube outlet is designed to be serrated, so that the slurry fluid diffuses to all sides and generates strong turbulence. The support frame at the lower end of the central tube is designed to be V-shaped and is equipped with a steam distributor. The steam is mixed with the washing return dilute phosphoric acid input from the circulating acid pipe and intersects with the slurry fluid. The steam expands in the solution and then bursts to form countless bubbles that stir and disperse the slurry fluid to make it a suspension. The suspension of solid particles will increase the interphase contact area with the dilute phosphoric acid solution. At the same time, the impact of steam bubbles causes the slurry suspension to generate fluidized turbulence, which reduces the liquid film mass transfer resistance on the surface of the solid particles and is conducive to the chemical reaction. At the same time, the input of steam allows the reaction temperature to reach 80°C. The production efficiency is improved. The input steam makes the fluid in the fluid reaction column a dilute phase and the fluid in the circulation column a dense phase. The density difference between the two is the driving force for the fluid in the circulation column to return to the fluid reaction column. The slurry suspension moves downward due to gravity and continues to react with the sulfuric acid solution input from the sulfuric acid inlet, and the pH value of the suspension in the fluid reaction column is controlled to be 1.2-1.5. The generated heavy component phosphogypsum crystals precipitate, agglomerate and flocculate to the precipitation manifold for precipitation. The generated HF and organic volatile component tail gas are separated by gas and liquid in the liquid foam eliminator and discharged from the tail gas outlet. The generated light component moves upward into the circulation column. The main reactions are: Ca5(PO4)3F+7H3PO4=5Ca(H2PO4)2+HF, 5Ca(H2PO4)2+5H2SO4+5nH2O=5CaSO4·n H2O+10H3PO4,Fe2O3+3H2SO4=Fe2(SO4)3+3H2O; the suspension entering the circulation column is filtered through the filter media to form a filter cake of a certain thickness, the filter cake thickness is 10-12mm, the driving force for filtration comes from the height difference between the circulation column and the liquid level in the middle tank, the clarified liquid is collected in the collecting pipe through the clarified liquid tank and flows to the middle tank, when the filter cake resistance exceeds the design pressure, the backwashing component is started to wash the filter media in sequence to ensure the continuous operation of the circulation column, the filter cake suspension formed by washing is returned to the fluidized reaction column, the coarse solid particles that have not reacted completely continue to react, and the precipitated phosphogypsum crystals are agglomerated and flocculated to the sedimentation collecting pipe for precipitation.

[0006] Step three, leaching and washing, the acid pump sends the clarified liquid from the middle tank into the leaching column, enters the inner cone bucket through the liquid inlet, flows downward into the precipitation bucket, and then flows upward countercurrently to mix with the dilute phosphoric acid solution input from the leaching liquid inlet. The pH value of the solution in the column is controlled to be 2.8-4.0. The generated iron phosphate precipitate is discharged from the precipitation bucket and then centrifuged and filtered. The filter cake is mixed with deionized water and sent to the washing column. The clarified liquid is discharged through the overflow port to recycle the circulating acid. The main reaction is: Fe2(SO4)3+2H3PO4+7H2O=2FePO4·2H2O+3HSO4 - +3H3O +The washing column has the same structure as the leaching column, and is designed with an overflow port, a liquid inlet, a column, an inner cone bucket, a leaching liquid inlet, and a sedimentation collecting bucket. The process flow is also the same, except that the washing liquid is deionized water, and the pH value of the solution in the column is controlled at 6.0. The filter cake after washing is dried to obtain the finished iron phosphate product.

[0007] Compared with the prior art, the present invention has at least the following advantages: the process of directly preparing iron phosphate by fluidized leaching of phosphate ore and converter iron ore mud is simple and the equipment cost is low, thereby greatly reducing the preparation cost of iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the main structure of a method for preparing ferric phosphate by fluidized leaching according to the present invention.

[0009] Figure 2 This is a schematic diagram of the structure of sample A of a method for preparing ferric phosphate by fluidized leaching of the present invention.

[0010] Figure 3 This is a schematic diagram of the B-sample structure of a method for preparing ferric phosphate by fluidized leaching of the present invention.

[0011] Figure 4 This is a schematic diagram of the C-sample structure of a method for preparing ferric phosphate by fluidized leaching according to the present invention.

[0012] Ⅰ-Circulating fluidized column Ⅱ-Leaching column Ⅲ-Washing column

[0013] 1- tail gas outlet 2- liquid foam eliminator 3- ore slurry inlet 4- liquid level meter

[0014] 5 - Fluidized reaction column 6 - Central tube 7 - Circulating acid tube 8 - Steam distributor

[0015] 9- Sulfuric acid inlet 10- Sedimentation header 11- Circulation column 12- Clarifying liquid tank

[0016] 13 - filter media internals 14 - backwash assembly 15 - liquid collecting pipe 16 - middle tank 17 - acid pump

[0017] 18-overflow port 19-liquid inlet 20-column 21-inner cone 22-leaching liquid inlet

[0018] 23-Sedimentation collection bucket. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0020] like Figure 1 , Figure 2 , Figure 3 , Figure 4As shown, a method for preparing ferric phosphate by fluidized leaching is characterized by: step one, preparing slurry, mixing phosphate ore and converter iron ore mud and wet-grinding them by ball milling to the required particle size, generally 50-200 μm, with a moisture content of 28%-32%, and the prepared slurry can meet the requirements of long-distance pipeline transportation, and the solid particles in the slurry are infiltrated and suspended in the liquid phase by water molecules, so that the solid particles are evenly dispersed and wrapped by the water molecule liquid film, thereby increasing the effective phase interface area and increasing the mass transfer efficiency of the acid hydrolysis fluidization reaction.

[0021] Step 2, circulating fluidized acid hydrolysis, the slurry is injected into the fluidized reaction column 5 through the slurry inlet 3 and the central tube 6, the central tube 6 is located at the center of the fluidized reaction column 5, and the upper and lower ends are fixed with support frames. The circumferential wall of the central tube 6 outlet is designed to be serrated, the purpose is to make the slurry fluid diffuse to the surroundings to produce strong turbulence, the lower end support frame of the central tube 6 is designed to be V-shaped, and a steam distributor 8 is arranged; the steam is mixed with the washing return dilute phosphoric acid input from the circulating acid pipe 7 and intersects with the slurry fluid, the steam expands in the solution and then bursts to form countless bubbles that stir and disperse the slurry fluid to make it a suspension, the suspension of solid particles will increase the interphase contact area with the dilute phosphoric acid solution, and at the same time, the impact of steam bubbles causes the slurry suspension to produce fluidized turbulence, reducing the liquid film mass transfer on the surface of the solid particles Resistance is conducive to chemical reaction. At the same time, the input steam makes the reaction temperature reach 80°C, which improves production efficiency. The input steam makes the fluid in the fluid reaction column 5 a dilute phase, and the fluid in the circulation column 11 a dense phase. The density difference between the two is the driving force for the fluid in the circulation column 11 to return to the fluid reaction column 5; the slurry suspension moves downward due to gravity and continues to react with the sulfuric acid solution input from the sulfuric acid inlet 9, and the pH value of the suspension in the fluid reaction column 5 is controlled to be 1.2-1.5. The generated heavy component phosphogypsum crystals are precipitated, agglomerated and flocculated to the precipitation header 10 for precipitation. The generated HF and organic volatile component tail gas are separated by gas and liquid in the liquid foam eliminator 2 and discharged from the tail gas outlet 1. The generated light component moves upward into the circulation column 11. The main reactions are:

[0022] Ca5(PO4)3F+7H3PO4=5Ca(H2PO4)2+HF, 5Ca(H2PO4)2+5H2SO4+5nH2O=5CaSO4·nH2O+10H3PO4, Fe2O3+3H2SO4=Fe2(SO4)3+3H2O; the suspension entering the circulation column 11 is filtered through the filter material internals 13 to form a filter cake of a certain thickness, the filter cake thickness is 10-12mm, the driving force for filtration comes from the height difference between the circulation column 11 and the liquid level of the intermediate tank 16, the clarified liquid is collected into the collecting pipe 15 through the clarified liquid tank 12 and flows to the intermediate tank 16, when the filter cake resistance exceeds the design pressure, the backwashing component 14 is started to wash the filter material internals 13 in sequence to ensure that the circulation column 11 continues to work, the filter cake suspension formed by washing is returned to the fluidized reaction column 5, the coarse solid particles that have not reacted completely continue to react, and the precipitated phosphogypsum crystals are agglomerated and flocculated to the sedimentation collecting pipe 10 for precipitation.

[0023] Step three, leaching and washing, the acid pump 17 sends the clarified liquid from the intermediate tank 16 into the leaching column II, enters the inner cone bucket 21 through the liquid inlet 19, flows downward into the precipitation collection bucket 23, and then flows upward countercurrently to mix with the dilute phosphoric acid solution input from the leaching liquid inlet 22. The pH value of the solution in the column 20 is controlled to be 2.8-4.0. The generated iron phosphate precipitate is discharged from the precipitation collection bucket 23 and then centrifuged and filtered. The filter cake is mixed with deionized water and sent to the washing column III. The clarified liquid is discharged through the overflow port 18 to recycle the circulating acid. The main reaction is: Fe2(SO4)3+2H3PO4+7H2O=2FePO4·2H2O+3HSO4 - +3H3O + The washing column III has the same structure as the leaching column II, and is designed with an overflow port 18, a liquid inlet 19, a column 20, an inner cone bucket 21, a leaching liquid inlet 22, and a sedimentation collection bucket 23. The process flow is also the same, except that the washing liquid is deionized water, and the pH value of the solution in the column 20 is controlled to be 6.0. The filter cake after washing is dried to obtain the finished iron phosphate product.

Claims

1. A method for preparing ferric phosphate by fluidized leaching, characterized in that: First, prepare the slurry, the phosphate ore and the converter iron ore are mixed and wet-milled to the required particle size of 50-200 μm and the moisture content of 28%-32%; second, circulate fluidized acid hydrolysis, the slurry is injected into the fluidized reaction column through the slurry inlet and the central tube, the central tube is located at the center of the fluidized reaction column, and the upper and lower ends are fixed with support frames, the lower end support frame of the central tube is designed to be V-shaped, and a steam distributor is arranged; at the same time, steam is input so that the reaction temperature can reach 80°C, thereby improving the production efficiency; the slurry suspension moves downward due to gravity and is connected with the sulfuric acid inlet. The sulfuric acid solution continues to react, and the pH value of the suspension in the fluid reaction column is controlled to be 1.2-1.

5. The generated heavy component phosphogypsum crystals are precipitated, agglomerated and flocculated to the precipitation header for precipitation. The generated HF and organic volatile component tail gas are separated by gas and liquid in the liquid foam eliminator and discharged from the tail gas outlet. The generated light component moves upward into the circulation column. The main reactions are: Ca5(PO4)3F+7H3PO4=5Ca(H2PO4)2+HF, 5Ca(H2PO4)2+5H2SO4+5nH2O=5CaSO4·nH2O+10H3PO4, Fe 2O3+3H2SO4=Fe2(SO4)3+3H2O; the suspension entering the circulation column is filtered through the filter material internals to form a filter cake of a certain thickness, the filter cake thickness is 10-12mm, the driving force for filtration comes from the height difference between the circulation column and the liquid level in the middle tank, the clarified liquid is collected in the collecting pipe through the clarified liquid tank and flows to the middle tank, when the filter cake resistance exceeds the design pressure, the backwashing component is started to wash the filter material internals in sequence to ensure the continuous operation of the circulation column, the filter cake suspension formed by washing is returned to the fluidized reaction column, the unreacted coarse solid particles continue to react, and the phosphogypsum crystals are precipitated and agglomerated. Flocculation to the sedimentation collection pipe precipitation; Step three, leaching and washing, the acid pump sends the clarified liquid from the middle tank into the leaching column, enters the inner cone bucket through the feed liquid inlet and flows downward into the sedimentation collection bucket, and then flows upward countercurrently to mix with the dilute phosphoric acid solution input from the leaching liquid inlet. The pH value of the solution in the column is controlled to be 2.8-4.

0. The generated iron phosphate precipitate is discharged from the sedimentation collection bucket and then centrifuged and filtered. The filter cake is mixed with deionized water and sent to the washing column. The clarified liquid is discharged through the overflow port to recycle the circulating acid. The main reaction is: Fe2(SO4)3+2H3PO4+7H2O=2FePO4·2H2O+3HSO4 - +3H3O + The washing column has the same structure as the leaching column, and is designed with an overflow port, a liquid inlet, a column, an inner cone bucket, a leaching liquid inlet, and a sedimentation collecting bucket. The process flow is also the same, except that the washing liquid is deionized water, and the pH value of the solution in the column is controlled at 6.

0. The filter cake after washing is dried to obtain the finished iron phosphate product.

2. The method for preparing ferric phosphate by fluidized leaching according to claim 1, characterized in that: The prepared slurry can meet the requirements of long-distance pipeline transportation. The solid particles in the slurry are infiltrated by water molecules and suspended in the liquid phase, so that the solid particles are evenly dispersed and wrapped by the water molecule liquid film, which increases the effective phase interface area and increases the mass transfer efficiency of the acid hydrolysis fluidization reaction.

3. The method for preparing ferric phosphate by fluidized leaching according to claim 1, characterized in that: The circumferential wall of the center tube outlet is designed to be serrated in order to allow the slurry fluid to diffuse in all directions and generate strong turbulence.

4. The method for preparing ferric phosphate by fluidized leaching according to claim 1, characterized in that: Steam mixed with the washing return dilute phosphoric acid input from the circulating acid pipe intersects with the slurry fluid. The steam expands in the solution and then bursts to form countless bubbles that stir and disperse the slurry fluid to make it a suspension. The suspension of solid particles will increase the interphase contact area with the dilute phosphoric acid solution. At the same time, the impact of steam bubbles causes the slurry suspension to produce fluidized turbulence, reducing the liquid film mass transfer resistance on the surface of the solid particles, which is beneficial to the chemical reaction.

5. The method for preparing ferric phosphate by fluidized leaching according to claim 1, characterized in that: In addition, the input steam makes the fluid in the fluid reaction column a dilute phase and the fluid in the circulation column a dense phase. The density difference between the two is the driving force for the fluid in the circulation column to return to the fluid reaction column.

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