Integrated preparation method of lithium iron phosphate

Abstract

The invention provides an integrated preparation method of lithium iron phosphate, and belongs to the technical field of preparation of lithium iron phosphate materials. The method comprises the following steps: adding a proper amount of FeCl2 solid into FeCl2 waste liquid, mixing, and concentrating; introducing Cl2, oxidizing the FeCl2, and filtering to remove impurities, so as to obtain a high-purity FeCl3 solution; the filter residues are transferred to a building material factory to be manufactured into building materials; the method comprises the following steps: pumping a high-purity FeCl3 solution, a NH4H2PO4 solution and NH3.H2O into an overflow crystallization reaction kettle for reaction, and filtering and countercurrent washing after reaction slurry overflows to obtain a FePO4. 2H2O solution; performing triple-effect evaporative crystallization on the wastewater to obtain an NH4Cl by-product, and transferring the NH4Cl by-product to a chemical fertilizer plant to prepare a fertilizer; transferring the FePO4. 2H2O solution into a turnover tank, and carrying out concentration treatment on the FePO4. 2H2O solution; transferring into a stirring kettle, and adding lithium carbonate and glucose; and carrying out continuous drying, sintering and grading treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium iron phosphate material preparation, and particularly relates to a lithium iron phosphate integrated preparation method. BACKGROUND

[0002] The lithium iron phosphate material is widely applied in the fields of new energy vehicles, high-end UPS, electric tools, photovoltaic power storage devices, wind power generation storage devices, power equipment storage devices and the like, has a long product life cycle, and has a high market demand. With the gradual decline of financial subsidies, the lithium iron phosphate battery which does not develop well in 2018 has a counterattack. At present, the main synthesis route of the lithium iron phosphate material is to prepare the lithium iron phosphate by using iron phosphate as the iron and phosphorus source, lithium carbonate as the lithium source, and glucose as the carbon source through a high-temperature solid-phase method. The traditional route needs to first prepare iron phosphate dihydrate, and then prepare anhydrous iron phosphate through processes such as filtration, washing, drying and dehydration. However, the cost of the iron phosphate raw material is still too high at the present stage, and the cost of only the drying and dehydration process of the iron phosphate dihydrate accounts for more than 10% of the total preparation cost, so it is an urgent need to develop a low-cost integrated preparation method of the lithium iron phosphate. SUMMARY

[0003] The application is carried out to solve the above problems, and aims to provide a lithium iron phosphate integrated preparation method.

[0004] The application provides a lithium iron phosphate integrated preparation method, which has the following characteristics and comprises the following steps: step 1, a proper amount of FeCl2 solid is added to FeCl2 waste liquid for mixing and concentration treatment to obtain FeCl2 concentrated solution; step 2, Cl2 is introduced into the FeCl2 concentrated solution to oxidize FeCl2, and the obtained solution is filtered and impurity-removed to obtain high-purity FeCl3 solution and filter residue respectively; step 3, the filter residue is transferred to a building material factory to be made into building materials; step 4, the high-purity FeCl3 solution, NH4H2PO4 solution and NH3·H2O are pumped into an overflow crystallization reaction kettle to react, the reaction slurry is overflowed out and then filtered and countercurrently washed to obtain FePO4·2H2O solution and collect wastewater; step 5, the wastewater is subjected to three-effect evaporation crystallization to obtain NH4Cl byproduct which is transferred to a chemical fertilizer factory to be made into fertilizer; step 6, the FePO4·2H2O solution is transferred to a turnover tank and concentrated to obtain FePO4·2H2O concentrated solution; step 7, the FePO4·2H2O concentrated solution is transferred to a stirred tank, lithium carbonate and glucose are added to obtain a mixed solution; and step 8, the mixed solution is subjected to continuous drying, continuous sintering and grading to obtain lithium iron phosphate material.

[0005] In the integrated preparation method of lithium iron phosphate provided by the application, the FeCl2 waste liquid in step 1 can be selected from waste liquid of a steel plant or washing liquid of a steel plate plant, and the concentration of FeCl2 in the FeCl2 concentrated solution is 30-60 wt%.

[0006] In the integrated preparation method of lithium iron phosphate provided by the application, the molar ratio of Cl2 to FeCl2 in step 2 is 0.5-0.6:1, the flow control range of Cl2 is 1.5-4 L / min, the reaction temperature of Cl2 and FeCl2 is 30-60℃, and the reaction time is 2-5 h.

[0007] In the integrated preparation method of lithium iron phosphate provided by the application, the molar ratio of FeCl3 to NH4H2PO4 in step 4 is (0.965-0.995):1, and the molar ratio of NH3·H2O to NH4H2PO4 is (2.03-2.05):1.

[0008] In the integrated preparation method of lithium iron phosphate provided by the application, the mass concentration of the pumped NH4H2PO4 solution in step 4 is 40-60 wt%, and the concentration of NH3·H2O is 15-25 wt%.

[0009] In the integrated preparation method of lithium iron phosphate provided by the application, the reaction temperature in step 4 is 60-80℃, and the reaction time is 3-5 h.

[0010] In the integrated preparation method of lithium iron phosphate provided by the application, step 6 further comprises on-line detection of the Fe content in the FePO4·2H2O concentrated solution, and the on-line detection mass content of Fe is 8.5-20.5%.

[0011] In the integrated preparation method of lithium iron phosphate provided by the application, in step 7, the mass ratio of lithium carbonate, glucose and FePO4·2H2O is (0.2-0.22):(0.053-0.065):1, and the addition of lithium carbonate and glucose is directly according to the on-line detection mass content of Fe.

[0012] In the integrated preparation method of lithium iron phosphate provided by the application, in step 8, the continuous drying temperature is 70-100℃, the continuous drying time is 15-30 min, the continuous sintering temperature is 680-750℃, and the sintering holding zone residence time is 6-9 h.

[0013] In the integrated preparation method of lithium iron phosphate provided by the application, the lithium iron phosphate material D50 after the grading treatment in step 8 is 0.9-1.1 um.

[0014] Compared with the prior art, the application has the following beneficial effects: The integrated preparation method of lithium iron phosphate provided by the application uses FeCl2 waste liquid (waste liquid of a steel plant or washing liquid of a steel plate plant) as an iron source, reasonably utilizes waste resources, and reduces costs; uses Cl2 as an oxidizing agent, avoids the introduction of more impurity elements, and improves product quality; uses NH3·H2O as a neutralizing agent, avoids the introduction of more impurity elements, and improves product quality; the product has good particle morphology, moderate particle size, and high tap density; the FePO4·2H2O concentration liquid is directly added with a lithium source and a carbon source according to the Fe content, the FePO4·2H2O drying and dehydration process is removed, and the production cost and time are saved.

[0015] In addition, in the process of preparing the high-purity FeCl3 solution, the impurity-removing filter residue is transported to a building material plant as an environmental protection block raw material, and the NH4Cl byproduct is transported to a fertilizer company as a fertilizer raw material, so that effective resource recycling and utilization can be realized, new added value can be generated, and the production cost is further reduced. The method of the application adopts countercurrent washing and three-effect evaporation, so that water consumption and energy consumption can be effectively saved, and the production cost is further reduced.

[0016] In addition, the method of the application adopts integrated design from the divalent iron source to the lithium iron phosphate product, saves equipment investment and land area, simplifies the process flow, saves production cost, and improves production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a preparation process flowchart of the integrated preparation method of lithium iron phosphate of the application.

[0018] Figure 2 is an SEM image of lithium iron phosphate prepared in Example 1 of the application.

[0019] Figure 3 is an SEM image of lithium iron phosphate prepared by the prior high-temperature solid-phase method. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, purposes and effects realized by the application easy to understand, the following examples combined with the drawings specifically describe the integrated preparation method of lithium iron phosphate of the application.

[0021] Example 1 Figure 1 is a preparation process flowchart of the integrated preparation method of lithium iron phosphate of the application.

[0022] AsFigure 1 As shown, the embodiment provides a lithium iron phosphate integrated preparation method, which comprises the following steps: Step 1, a proper amount of FeCl2 solid is added to FeCl2 waste liquid for mixing and concentration treatment to obtain FeCl2 concentrated solution. The FeCl2 waste liquid is selected from steel plant waste liquid or steel plate plant washing liquid, and the concentration of FeCl2 in the FeCl2 concentrated solution is 30wt%.

[0023] Step 2, Cl2 is introduced into the FeCl2 concentrated solution at a flow rate of 1.5L / min to oxidize the FeCl2 (the molar ratio of Cl2 to FeCl2 is 0.5:1, the reaction temperature is 35℃, and the reaction time is 2.5h), and the obtained solution is filtered to remove impurities to obtain high-purity FeCl3 solution and filter residue.

[0024] Step 3, the filter residue is transferred to a new building material factory to be made into building materials.

[0025] Step 4, the high-purity FeCl3 solution, NH4H2PO4 solution and NH3·H2O (the molar ratio of FeCl3, NH4H2PO4 and NH3·H2O is 0.965:1:2.03, wherein the mass fraction of NH4H2PO4 solution is 43wt%, and the concentration of NH3·H2O is 17wt%) are pumped into an overflow crystallization reactor for reaction (the reaction temperature is 60℃, and the reaction time is 3h), and after the overflow of the reaction slurry, filtration and countercurrent washing are performed to obtain FePO4·2H2O solution and collect wastewater.

[0026] Step 5, the wastewater is subjected to three-effect evaporation crystallization to obtain NH4Cl byproduct and is transferred to a fertilizer factory to be made into fertilizer.

[0027] Step 6, the FePO4·2H2O solution is transferred to a turnover tank and subjected to concentration treatment to obtain FePO4·2H2O concentrated solution (mass concentration is 35%), and the mass content of Fe in the FePO4·2H2O concentrated solution is obtained by online detection (Fe online detection mass content is 10.46%).

[0028] Step 7, the FePO4·2H2O concentrated solution is transferred to a stirred tank, lithium carbonate and glucose are added through an automatic feeding system to obtain a mixed solution. The mass ratio of lithium carbonate, glucose and FePO4·2H2O is 0.2:0.054:1, and the addition of lithium carbonate and glucose is directly proportional to the Fe online detection mass content.

[0029] Step 8, the mixed solution is subjected to continuous drying (drying temperature is 75℃, continuous drying residence time is 15min), continuous sintering (continuous sintering temperature is 680℃, sintering holding zone residence time is 6h), and grading treatment (grading treatment lithium iron phosphate material D50 is 0.9um), to obtain the lithium iron phosphate material.

[0030] Figure 2 is an SEM image of lithium iron phosphate prepared in Embodiment 1 of the present application. Figure 3 is an SEM image of lithium iron phosphate prepared by a prior art high-temperature solid-phase method.

[0031] Figure 3 is lithium iron phosphate prepared by a prior art high-temperature solid-phase method, using ferric orthophosphate as the iron and phosphorus source, lithium carbonate as the lithium source, and glucose as the carbon source. By comparison Figure 2 and Figure 3 it can be seen that, compared with the prior art, the lithium iron phosphate material prepared in the present embodiment has better particle morphology, moderate particle size, higher tap density, and better product quality.

[0032] Embodiment 2 As shown in Figure 1 , the present embodiment provides a one-step preparation method for lithium iron phosphate, comprising the following steps: Step 1, a proper amount of FeCl2 solid is added to FeCl2 waste liquid for mixing and concentration treatment, to obtain FeCl2 concentrated solution. The FeCl2 waste liquid is selected from steel plant waste liquid or steel plate plant washing liquid, and the concentration of FeCl2 in the FeCl2 concentrated solution is 44wt%.

[0033] Step 2, Cl2 is introduced into the FeCl2 concentrated solution at a flow rate of 2.2L / min, to oxidize the FeCl2 (the molar ratio of Cl2 to FeCl2 is 0.55:1, the reaction temperature is 40℃, and the reaction time is 3h), and the obtained solution is filtered to remove impurities, to obtain high-purity FeCl3 solution and filter residue, respectively.

[0034] Step 3, the filter residue is transferred to a new building material factory to be made into building materials.

[0035] Step 4, the high-purity FeCl3 solution, NH4H2PO4 solution, and NH3·H2O (the molar ratio of FeCl3, NH4H2PO4, and NH3·H2O is 0.97:1:2.04, the mass fraction of the NH4H2PO4 solution is 48wt%, and the concentration of NH3·H2O is 20wt%) are pumped into an overflow crystallization reactor for reaction (the reaction temperature is 66℃, and the reaction time is 3.5h), the overflowed reaction slurry is filtered and countercurrently washed, to obtain FePO4·2H2O solution and collect wastewater.

[0036] Step 5, the wastewater is crystallized by three-effect evaporation to obtain NH4Cl by-product and is transferred to a chemical fertilizer plant to be prepared into fertilizer.

[0037] Step 6, the FePO4·2H2O solution is transferred to a turnover tank and is concentrated to obtain FePO4·2H2O concentrated solution (mass concentration of 52%) and the mass content of Fe in the FePO4·2H2O concentrated solution is obtained by online detection (Fe online detection mass content of 15.54%).

[0038] Step 7, the FePO4·2H2O concentrated solution is transferred to a stirred tank, lithium carbonate and glucose are added by an automatic feeding system to obtain a mixed solution. The mass ratio of lithium carbonate, glucose and FePO4·2H2O is 0.21:0.06:1, and the lithium carbonate and glucose are directly added according to the Fe online detection mass content.

[0039] Step 8, the mixed solution is subjected to continuous drying (drying temperature of 80℃, continuous drying residence time of 15min), continuous sintering (continuous sintering temperature of 700℃, sintering holding zone residence time of 7h) and grading treatment (grading treatment lithium iron phosphate material D50 of 0.95um) to obtain lithium iron phosphate material.

[0040] Example 3 As shown in Figure 1 The present embodiment provides a lithium iron phosphate integrated preparation method, comprising the following steps: Step 1, a proper amount of FeCl2 solid is added to FeCl2 waste liquid for mixing and is subjected to concentration treatment to obtain FeCl2 concentrated solution. The FeCl2 waste liquid is selected from steel plant waste liquid or steel plate plant washing liquid, and the concentration of FeCl2 in the FeCl2 concentrated solution is 52wt%.

[0041] Step 2, Cl2 is introduced into the FeCl2 concentrated solution at a flow rate of 3.3L / min to oxidize the FeCl2 (the amount-of-substance ratio of Cl2 to FeCl2 is 0.57:1, the reaction temperature is 51℃, and the reaction time is 3h), and the obtained solution is subjected to filtration and impurity removal treatment to obtain high-purity FeCl3 solution and filter residue, respectively.

[0042] Step 3, the filter residue is transferred to a new building material plant to be prepared into building materials.

[0043] Step 4, the high-purity FeCl3 solution is pumped into an overflow crystallization reaction kettle with a NH4H2PO4 solution and NH3·H2O (the molar ratio of FeCl3, NH4H2PO4, and NH3·H2O is 0.97:1:2.04, the mass fraction of the NH4H2PO4 solution is 55wt%, and the concentration of NH3·H2O is 24wt%) to react (the reaction temperature is 75℃, and the reaction time is 4h), and the reaction slurry is overflowed out and then filtered and countercurrently washed to obtain a FePO4·2H2O solution and collect wastewater.

[0044] Step 5, the wastewater is subjected to three-effect evaporation crystallization to obtain an NH4Cl byproduct and is transferred to a chemical fertilizer factory to be prepared into a fertilizer.

[0045] Step 6, the FePO4·2H2O solution is transferred to a turnover tank and is subjected to concentration treatment to obtain a FePO4·2H2O concentrated solution (the mass concentration is 62%), and the mass content of Fe in the FePO4·2H2O concentrated solution is obtained through online detection (the Fe online detection mass content is 18.5%).

[0046] Step 7, the FePO4·2H2O concentrated solution is transferred to a stirred tank, lithium carbonate and glucose are added through an automatic feeding system to obtain a mixed solution. The mass ratio of lithium carbonate, glucose, and FePO4·2H2O is 0.215:0.055:1, and the lithium carbonate and glucose are directly added according to the Fe online detection mass content.

[0047] Step 8, the mixed solution is subjected to continuous drying (the drying temperature is 90℃, and the continuous drying residence time is 18min), continuous sintering (the continuous sintering temperature is 720℃, and the sintering holding zone residence time is 8h), and grading treatment (the lithium iron phosphate material D50 of the grading treatment is 1.0um) to obtain a lithium iron phosphate material.

[0048] Example 4 As shown in Figure 1 , the present embodiment provides a lithium iron phosphate integrated preparation method, which comprises the following steps: Step 1, a proper amount of FeCl2 solid is added to FeCl2 waste liquid for mixing and concentration treatment to obtain a FeCl2 concentrated solution. The FeCl2 waste liquid is selected from steel plant waste liquid or steel plate plant washing liquid, and the concentration of FeCl2 in the FeCl2 concentrated solution is 30-60wt%.

[0049] Step 2: Cl2 is introduced into the FeCl2 concentrate at a flow rate of 3.8 L / min to oxidize the FeCl2 (the molar ratio of Cl2 to FeCl2 is 0.51:1, the reaction temperature is 46℃, and the reaction time is 4h). The resulting solution is then filtered to remove impurities, yielding a high-purity FeCl3 solution and filter residue.

[0050] Step 3: Transfer the filter residue to a new building materials plant to be manufactured into building materials.

[0051] Step 4: High-purity FeCl3 solution, NH4H2PO4 solution, and NH3·H2O (the molar ratio of FeCl3, NH4H2PO4, and NH3·H2O is 0.985:1:2.0:5, wherein the mass fraction of NH4H2PO4 solution is 48wt% and the concentration of NH3·H2O is 23wt%) are pumped into an overflow crystallization reactor for reaction (reaction temperature is 60℃, reaction time is 5h). After the reaction slurry overflows, it is filtered and washed countercurrently to obtain FePO4·2H2O solution and wastewater is collected.

[0052] Step 5: The wastewater is crystallized through triple-effect evaporation to obtain NH4Cl byproduct, which is then transferred to a fertilizer plant to be processed into fertilizer.

[0053] Step 6: After transferring the FePO4·2H2O solution to a transfer tank and concentrating it, a FePO4·2H2O concentrate (mass concentration of 45%) is obtained. The mass content of Fe in the FePO4·2H2O concentrate is obtained by online detection (the online detection mass content of Fe is 13.45%).

[0054] Step 7: Transfer the FePO4·2H2O concentrate to a stirred tank, and add lithium carbonate and glucose through an automatic feeding system to obtain a mixed solution. The mass ratio of lithium carbonate, glucose, and FePO4·2H2O is 0.22:0.065:1, and the ratio of lithium carbonate and glucose is directly determined based on the online detection of Fe content.

[0055] Step 8: The mixture is subjected to continuous drying (drying temperature is 100℃, continuous drying time is 15min), continuous sintering (continuous sintering temperature is 730℃, sintering heat preservation time is 7.5h), and grading treatment (the graded lithium iron phosphate material has a D50 of 1.1um) to obtain lithium iron phosphate material.

[0056] Example 5 like Figure 1 As shown, this embodiment provides an integrated preparation method for lithium iron phosphate, including the following steps: Step 1, a certain amount of FeCl2 solid is added to FeCl2 waste liquid for mixing and concentration treatment to obtain FeCl2 concentrated solution. The FeCl2 waste liquid is selected from steel plant waste liquid or steel plate plant washing liquid, and the concentration of FeCl2 in the FeCl2 concentrated solution is 55wt%.

[0057] Step 2, Cl2 is introduced into the FeCl2 concentrated solution at a flow rate of 4 L / min for oxidation treatment of FeCl2 (the molar ratio of Cl2 to FeCl2 is 0.54:1, the reaction temperature is 57℃, and the reaction time is 4h), and the obtained solution is filtered to remove impurities to obtain high-purity FeCl3 solution and filter residue, respectively.

[0058] Step 3, the filter residue is transferred to a new building material factory to be made into building materials.

[0059] Step 4, the high-purity FeCl3 solution is pumped into an overflow crystallization reaction kettle together with NH4H2PO4 solution and NH3·H2O (the molar ratio of FeCl3, NH4H2PO4, and NH3·H2O is 0.972:1:2.04, the mass fraction of NH4H2PO4 solution is 44wt%, and the concentration of NH3·H2O is 17wt%) for reaction (the reaction temperature is 60℃, and the reaction time is 5h), and after the reaction slurry overflows, it is filtered and countercurrently washed to obtain FePO4·2H2O solution and collect wastewater.

[0060] Step 5, the wastewater is subjected to three-effect evaporation crystallization to obtain NH4Cl byproduct and is transferred to a chemical fertilizer factory to be made into fertilizer.

[0061] Step 6, the FePO4·2H2O solution is transferred to a turnover tank and subjected to concentration treatment to obtain FePO4·2H2O concentrated solution (mass concentration is 65%), and the mass content of Fe in the FePO4·2H2O concentrated solution is obtained by online detection (Fe online detection mass content is 19.43%).

[0062] Step 7, the FePO4·2H2O concentrated solution is transferred to a stirred tank, lithium carbonate and glucose are added through an automatic feeding system, and a mixed solution is obtained. The mass ratio of lithium carbonate, glucose, and FePO4·2H2O is 0.205:0.06:1, and the addition of lithium carbonate and glucose is directly proportional to the Fe online detection mass content.

[0063] Step 8, the mixed solution is subjected to continuous drying (drying temperature is 90℃, continuous drying residence time is 20min), continuous sintering (continuous sintering temperature is 720℃, sintering holding zone residence time is 9h), and grading treatment (grading treatment lithium iron phosphate material D50 is 0.94um) to obtain lithium iron phosphate material.

[0064] Example 6 Step 1, a certain amount of FeCl2 solid was added to the FeCl2 waste liquid for mixing and concentration treatment to obtain FeCl2 concentrated solution. The FeCl2 waste liquid was selected from steel plant waste liquid or steel plate plant washing liquid, and the concentration of FeCl2 in the FeCl2 concentrated solution was 56wt%.

[0065] Step 2, Cl2 was introduced into the FeCl2 concentrated solution at a flow rate of 3.6 L / min for oxidation treatment of FeCl2 (the molar ratio of Cl2 to FeCl2 was 0.56:1, the reaction temperature was 50℃, and the reaction time was 3.5h), and the obtained solution was filtered to remove impurities to obtain high-purity FeCl3 solution and filter residue, respectively.

[0066] Step 3, the filter residue was transferred to a new building material factory to be made into building materials.

[0067] Step 4, the high-purity FeCl3 solution was pumped into an overflow crystallization reactor together with NH4H2PO4 solution and NH3·H2O (the molar ratio of FeCl3, NH4H2PO4, and NH3·H2O was 0.982:1:2.04, the mass fraction of NH4H2PO4 solution was 47wt%, and the concentration of NH3·H2O was 16wt%) for reaction (the reaction temperature was 60℃, and the reaction time was 5h), and after the reaction slurry overflowed, it was filtered and countercurrently washed to obtain FePO4·2H2O solution and collect wastewater.

[0068] Step 5, the wastewater was treated by three-effect evaporation crystallization to obtain NH4Cl byproduct and was transferred to a fertilizer factory to be made into fertilizer.

[0069] Step 6, the FePO4·2H2O solution was transferred to a turnover tank and concentrated to obtain FePO4·2H2O concentrated solution (mass concentration was 38%), and the mass content of Fe in the FePO4·2H2O concentrated solution was obtained by online detection (Fe online detection mass content was 11.36%).

[0070] Step 7, the FePO4·2H2O concentrated solution was transferred to a stirred tank, lithium carbonate and glucose were added through an automatic feeding system, and a mixed solution was obtained. The mass ratio of lithium carbonate, glucose, and FePO4·2H2O was 0.205:0.06:1, and the addition of lithium carbonate and glucose was directly proportional to the Fe online detection mass content.

[0071] Step 8, the mixture is subjected to continuous drying (drying temperature is 80℃, continuous drying residence time is 24min), continuous sintering (continuous sintering temperature is 710℃, sintering holding zone residence time is 8h), and grading treatment (grading treatment lithium iron phosphate material D50 is 1.06um), to obtain the lithium iron phosphate material.

[0072] The lithium iron phosphate prepared in the above examples is respectively subjected to purity, compaction density and electrical performance testing and cost accounting, and compared with market mainstream lithium iron phosphate products, and the results are shown in Table 1. Among them, market product A, market product B and market product C are respectively three kinds of commercially available lithium iron phosphate materials from different manufacturers.

[0073] Table 1 Serial number Purity / % Compacted density / g-cm -3 ]] 1C capacity exerted / mAh-g -1 ]] Cost accounting / ten thousand yuan per ton Example 1 99.993 2.52 158.5 12.63 Example 2 99.994 2.54 158.7 12.64 Example 3 99.995 2.53 159.1 12.67 Example 4 99.991 2.51 158.6 12.63 Example 5 99.992 2.55 159.2 12.62 Example 6 99.993 2.53 158.8 12.65 Market product A 99.916 2.36 155.6 13.74 Market product B 99.827 2.34 155.4 13.69 Market product C 99.743 2.41 155.9 13.82 As can be seen from the results in Table 1, the lithium iron phosphate material prepared by the method of the present application has high purity, large compaction density, low manufacturing cost and does not lose capacity performance.

[0074] It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for integrated production of lithium iron phosphate, characterized by, The method comprises the following steps: Step 1, a proper amount of FeCl2 solid is added into FeCl2 waste liquid for mixing and concentration treatment to obtain FeCl2 concentrated solution; Step 2, Cl2 is introduced into the FeCl2 concentrated solution to oxidize FeCl2 and the obtained solution is filtered to remove impurities to obtain high-purity FeCl3 solution and filter residue respectively; Step 3, the filter residue is transferred to a building material factory to be made into building materials; Step 4, the high-purity FeCl3 solution, NH4H2PO4 solution and NH3·H2O are pumped into an overflow crystallization reaction kettle to react, the reaction slurry is overflowed and then filtered and countercurrently washed to obtain FePO4·2H2O solution and collect wastewater; Step 5, the wastewater is treated by three-effect evaporation crystallization to obtain NH4Cl byproduct which is transferred to a chemical fertilizer factory to be made into fertilizer; Step 6, the FePO4·2H2O solution is transferred to a turnover tank and concentrated to obtain FePO4·2H2O concentrated solution; Step 7, the FePO4·2H2O concentrated solution is transferred to a stirred tank, lithium carbonate and glucose are added to obtain a mixed solution; Step 8, the mixed solution is continuously dried, continuously sintered and graded to obtain lithium iron phosphate material.

2. The integrated preparation method of lithium iron phosphate according to claim 1, characterized in that: wherein, in step 1, the FeCl2 waste liquid is selected from steel plant waste liquid or steel plate factory washing liquid, the concentration of FeCl2 in the FeCl2 concentrated solution is 30-60wt%.

3. The integrated preparation method of lithium iron phosphate according to claim 1, characterized in that: wherein in step 2, the molar ratio of Cl2 to FeCl2 is 0.5-0.6:1, the flow control range of Cl2 introduction is 1.5-4 L / min, the reaction temperature of Cl2 and FeCl2 is 30-60℃, and the reaction time is 2-5h.

4. The integrated preparation method of lithium iron phosphate according to claim 1, characterized in that: wherein in step 4, the molar ratio of FeCl3 to NH4H2PO4 is (0.965-0.995):1, the molar ratio of NH3·H2O to NH4H2PO4 is (2.03-2.05):

1.

5. The integrated preparation method of lithium iron phosphate according to claim 4, characterized in that: wherein in step 4, the mass concentration of the pumped NH4H2PO4 solution is 40-60wt%, and the concentration of NH3·H2O is 15-25wt%.

6. The integrated preparation method of lithium iron phosphate according to claim 5, characterized in that: wherein in step 4, the reaction temperature is 60-80℃, and the reaction time is 3-5h.

7. The integrated preparation method of lithium iron phosphate according to claim 1, characterized in that: wherein in step 6, it further comprises on-line detection of the content of Fe in the FePO4·2H2O concentrated solution, the on-line detection mass content of Fe is 8.5-20.5%.

8. The integrated preparation method of lithium iron phosphate according to claim 1, characterized in that: wherein In step 7, the mass ratio of the lithium carbonate, the glucose and FePO4·2H2O is (0.2-0.22):(0.053-0.065):1, According to the online detection of Fe content, the lithium carbonate and the glucose are directly added in proportion.

9. The integrated preparation method of lithium iron phosphate according to claim 1, characterized in that: wherein, In step 8, the temperature of the continuous drying is 70-100℃, and the time is 15-30min. The temperature of the continuous sintering is 680-750℃, and the residence time in the sintering holding zone is 6-9h.

10. The integrated preparation method of lithium iron phosphate according to claim 9, characterized in that: wherein In step 8, after the grading treatment, the D50 of the lithium iron phosphate material is 0.9-1.1um.

Images