阅读说明：本技术 一种利用磷酸亚铁制备正磷酸铁的方法 (Method for preparing ferric orthophosphate by using ferrous phosphate ) 是由 吕天宝 徐岩岭 张占儒 张云 于文刚 谯凌峰 马文国 张盛强 张绍伟 孙瑞军 于 2020-07-24 设计创作，主要内容包括：本发明公开了一种利用磷酸亚铁制备正磷酸铁的方法,将磷酸亚铁浆料进行研磨,控制好研磨后的物料粒径；将磷酸亚铁浆料和磷酸及微过量的双氧水混合,充分反应后升温熟化；将冷却后的磷酸铁浆料通过板框压滤机过滤洗涤；将洗涤后的滤饼通过闪蒸干燥机干燥得到二水磷酸铁,再通过新式回转窑脱去结晶水,获得正磷酸铁。本发明提供的方法可制备出粒径为2-4μm的正磷酸铁,制备出的正磷酸铁材料具有较高的堆积密度,合成的磷酸铁锂具有较好电化学性能,在锂离子电池领域具有很好的应用前景。(The invention discloses a method for preparing ferric orthophosphate by utilizing ferrous phosphate, which comprises the steps of grinding ferrous phosphate slurry, and controlling the particle size of the ground material; mixing the ferrous phosphate slurry, phosphoric acid and a small excess of hydrogen peroxide, fully reacting, and heating for curing; filtering and washing the cooled iron phosphate slurry by using a plate-and-frame filter press; and drying the washed filter cake by a flash dryer to obtain ferric phosphate dihydrate, and removing crystal water by a novel rotary kiln to obtain the ferric orthophosphate. The method provided by the invention can be used for preparing ferric orthophosphate with the particle size of 2-4 mu m, the prepared ferric orthophosphate material has higher bulk density, and the synthesized lithium iron phosphate has better electrochemical performance and good application prospect in the field of lithium ion batteries.)

1. A method for preparing ferric orthophosphate by ferrous phosphate is characterized in that: the method comprises the following process flows:

step S1: grinding the ferrous phosphate slurry, sending the ground slurry into a storage tank after sanding, and cooling the slurry through a cold water coil for later use;

step S2: pumping ferrous phosphate slurry and phosphoric acid into a weighing and metering tank respectively, adding quantitative ferrous phosphate slurry into a reaction kettle through the weighing and metering tank, adding quantitative water, phosphoric acid and hydrogen peroxide respectively, heating and curing through outer half-pipe steam after full reaction, discharging to a cooling tank, cooling, and pumping to a water washing feeding tank;

step S3: removing phosphate radicals in the cooled iron phosphate slurry through solid-liquid separation by a filter press, washing for five times until the conductivity is qualified, pulping a filter cake, and pumping to a kiln tail storage tank; pumping the filtrate to a CN filter for sedimentation separation, overflowing supernatant into a clear liquid tank, feeding thick slurry into a thick slurry tank, and pumping to a water washing feed tank;

step S4: removing part of free water in the iron phosphate solution through a diaphragm pressing plate frame, and improving the solid content of the iron phosphate; the flash dry feed rate was controlled.

Step S5: drying the iron phosphate filter cake of the filter plate frame by a flash evaporation main machine to remove water, after flash drying and feeding in a bin are completed, according to the discharging time of the rotary kiln, after a thick material layer reaches a final temperature region, increasing the rotating speed of the rotary kiln to be more than 13Hz, simultaneously switching on a draught fan to the maximum frequency, and rapidly conveying out a thin material layer by negative pressure air conveying;

step S6: and (3) removing crystal water from the iron phosphate dihydrate which is dried by flash evaporation until free water is removed at the temperature of 580-.

2. The method for preparing ferric orthophosphate from ferrous phosphate as claimed in claim 1, characterized in that: and S1 and S2, grinding the ferrous phosphate until the particle size is less than 4 microns, calculating the adding amount of phosphoric acid and hydrogen peroxide according to the iron content and the phosphoric acid content in the slurry, and pumping the mixture into an iron phosphate synthesis kettle.

3. The method for preparing ferric orthophosphate from ferrous phosphate as claimed in claim 1, characterized in that: in step S3, the iron phosphate is separated by a filter press and washed five times until the conductance is acceptable.

4. The method for preparing ferric orthophosphate from ferrous phosphate as claimed in claim 1, characterized in that: in the steps S4 and S5, partial water of the iron phosphate is removed through a diaphragm press frame, the solid content is improved, and the iron phosphate is dried through a flash evaporation host machine to remove the water.

5. The method for preparing ferric orthophosphate from ferrous phosphate as claimed in claim 2, characterized in that: in step S6, the iron phosphate dihydrate which is flash-dried to have no free water is subjected to 580-600 ℃ to remove crystal water.

Technical Field

The invention relates to the technical field of chemical industry, in particular to a method for preparing ferric orthophosphate by utilizing ferrous phosphate.

Background

The iron phosphate is used as a raw material of lithium iron phosphate serving as a positive electrode material of a lithium battery, the demand of the iron phosphate is more and more increased along with the development and utilization of new energy in China, and the iron phosphate can also be used as a catalyst, for manufacturing ceramics and the like.

After a large number of searches, the following results are obtained: the invention has the following patent: the invention discloses an application number (CN 201110072970.9) and a publication number (CN 102153061A) of a synthetic method of an iron orthophosphate material, and relates to a synthetic method of an iron orthophosphate material. The invention belongs to the technical field of lithium ion anode materials. A synthetic method of an iron orthophosphate material comprises the following steps: 1) manufacturing a hollow sphere template: stirring oil with carbon-hydrogen bond and water-soluble surfactant without metal ions in water solution for 0.1-10 hr to form emulsion; the weight ratio of oil to surfactant is 1: 1-9, accounting for 0.1-5% of the total weight of the solution; 2) and (3) ferric orthophosphate precipitation: adjusting the pH value of the solution in an acidic solution containing phosphate and ferric salt to form ferric phosphate precipitate; the precipitate is attached to the emulsion microsphere to form a structure with the outer part being iron phosphate and the core being the emulsion microsphere; 3) treating ferric phosphate microspheres: filtering and drying the emulsion microspheres, and then calcining at high temperature to form the hollow/shell structure microsphere ferric orthophosphate material. The invention has the advantages of simple process, convenient operation, stable ferric orthophosphate microspheres, large rate discharge capacity, low temperature capacity and the like

The existing production process of iron phosphate is a method for synthesizing iron salt and phosphate or directly producing iron powder and phosphoric acid, and has the defects of high production cost and energy consumption, complex production process, high impurity content and the like, so that the product quality stability is poor.

Disclosure of Invention

The invention aims to provide a method for preparing ferric orthophosphate by using ferrous phosphate, which solves the problems in the background art.

In order to achieve the purpose, the invention provides the following technical scheme: a method for preparing ferric orthophosphate by ferrous phosphate comprises the following process flow:

step S1: grinding the ferrous phosphate slurry, sending the ground slurry into a storage tank after sanding, and cooling the slurry through a cold water coil for later use;

step S2: pumping ferrous phosphate slurry and phosphoric acid into a weighing and metering tank respectively, adding quantitative ferrous phosphate slurry into a reaction kettle through the weighing and metering tank, adding quantitative water, phosphoric acid and hydrogen peroxide respectively, heating and curing through outer half-pipe steam after full reaction, discharging to a cooling tank, cooling, and pumping to a water washing feeding tank;

step S3: removing phosphate radicals in the cooled iron phosphate slurry through solid-liquid separation by a filter press, washing for five times until the conductivity is qualified, pulping a filter cake, and pumping to a kiln tail storage tank; pumping the filtrate to a CN filter for sedimentation separation, overflowing supernatant into a clear liquid tank, feeding thick slurry into a thick slurry tank, and pumping to a water washing feed tank;

step S4: removing part of free water in the iron phosphate solution through a diaphragm pressing plate frame, and improving the solid content of the iron phosphate; the flash dry feed rate was controlled.

Step S5: drying the iron phosphate filter cake of the filter plate frame by a flash evaporation main machine to remove water, after flash drying and feeding in a bin are completed, according to the discharging time of the rotary kiln, after a thick material layer reaches a final temperature region, increasing the rotating speed of the rotary kiln to be more than 13Hz, simultaneously switching on a draught fan to the maximum frequency, and rapidly conveying out a thin material layer by negative pressure air conveying;

step S6: and (3) removing crystal water from the iron phosphate dihydrate which is dried by flash evaporation until free water is removed at the temperature of 580-.

Preferably, in the steps S1 and S2, ferrous phosphate is sanded to a particle size of less than 4 microns, the addition amount of phosphoric acid and hydrogen peroxide is calculated according to the iron content and the phosphoric acid content in the slurry, and the slurry is pumped into an iron phosphate synthesis kettle.

Preferably, the iron phosphate is separated by a filter press in step S3 and washed five times until the conductivity is acceptable.

Preferably, in steps S4 and S5, the iron phosphate is partially dehydrated by a diaphragm press frame to increase the solid content, and is dried by a flash evaporation main machine to remove the moisture.

Preferably, the iron phosphate dihydrate which is flash-dried to have no free water in step S6 is subjected to 580-600 ℃ to remove crystal water.

Compared with the prior art, the invention has the following beneficial effects:

in the grinding process, the particle size of the ground ferrous phosphate is controlled, so that the controllability of the oxidation process of the final iron phosphate product and the uniform particle size are ensured. The complete reaction in the oxidation process is ensured by adding the hydrogen peroxide in a slight excess manner, so that the iron-phosphorus ratio of the iron phosphate product is stable. The iron phosphate prepared by the method has controllable particle size and high iron-phosphorus ratio stability, and the produced lithium iron phosphate has the advantages of excellent processing performance, stable electrical performance and the like; the invention fully utilizes ferrous sulfate resources, removes ions such as titanium, calcium, magnesium, zinc, manganese and the like with low cost, has impurity removal efficiency of more than 90 percent, and obtains high-purity food-grade ferric orthophosphate with the content of more than 99.9 percent.

Drawings

FIG. 1 is a schematic view of the process flow for the preparation of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the present invention provides a technical solution of a method for preparing ferric orthophosphate from ferrous phosphate: a method for preparing ferric orthophosphate by ferrous phosphate comprises the following process flow:

step S1: grinding the ferrous phosphate slurry, sending the ground slurry into a storage tank after sanding, and cooling the slurry through a cold water coil for later use;

step S2: pumping ferrous phosphate slurry and phosphoric acid into a weighing and metering tank respectively, adding quantitative ferrous phosphate slurry into a reaction kettle through the weighing and metering tank, adding quantitative water, phosphoric acid and hydrogen peroxide respectively, heating and curing through outer half-pipe steam after full reaction, discharging to a cooling tank, cooling, and pumping to a water washing feeding tank;

step S3: removing phosphate radicals in the cooled iron phosphate slurry through solid-liquid separation by a filter press, washing for five times until the conductivity is qualified, pulping a filter cake, and pumping to a kiln tail storage tank; pumping the filtrate to a CN filter for sedimentation separation, overflowing supernatant into a clear liquid tank, feeding thick slurry into a thick slurry tank, and pumping to a water washing feed tank;

step S4: removing part of free water in the iron phosphate solution through a diaphragm pressing plate frame, and improving the solid content of the iron phosphate; the flash dry feed rate was controlled.

Step S5: drying the iron phosphate filter cake of the filter plate frame by a flash evaporation main machine to remove water, after flash drying and feeding in a bin are completed, according to the discharging time of the rotary kiln, after a thick material layer reaches a final temperature region, increasing the rotating speed of the rotary kiln to be more than 13Hz, simultaneously switching on a draught fan to the maximum frequency, and rapidly conveying out a thin material layer by negative pressure air conveying;

step S6: and (3) removing crystal water from the iron phosphate dihydrate which is dried by flash evaporation until free water is removed at the temperature of 580-.

In the embodiment of the invention, further, in the steps S1 and S2, ferrous phosphate is ground to a particle size of less than 4 microns, the adding amount of phosphoric acid and hydrogen peroxide is calculated according to the iron content and the phosphoric acid content in the slurry, and the mixture is pumped into an iron phosphate synthesis kettle.

In the embodiment of the present invention, in step S3, the iron phosphate is separated by the filter press and then washed five times until the conductance is qualified.

In the embodiment of the invention, in steps S4 and S5, part of water in the iron phosphate is removed by a diaphragm press frame to increase the solid content, and the iron phosphate is dried by a flash evaporation host machine to remove the water.

In the embodiment of the invention, further, in step S6, the iron phosphate dihydrate that is flash-dried to have no free water is subjected to 580-600 ℃ to remove crystal water.

Simultaneously provides a flash drying method of the ferric phosphate, which comprises the following specific process steps:

(1) grinding the ferrous phosphate slurry, conveying the ground slurry to a storage tank after sanding, and cooling the slurry through a cold water coil for later use.

(2) And (2) respectively pumping the ferrous phosphate slurry and the phosphoric acid into a weighing and metering tank, adding quantitative ferrous phosphate slurry into the reaction kettle through the weighing and metering tank, respectively adding quantitative water, phosphoric acid and hydrogen peroxide, heating and curing through outer half-pipe steam after full reaction, discharging to a cooling tank, cooling, and pumping to a washing feeding tank.

(3) Taking the head tank slurry under the stirring condition before batching to analyze the Fe content.

(4) Removing phosphate radicals in the cooled iron phosphate slurry through solid-liquid separation by a filter press, washing for five times until the conductivity is qualified, pulping a filter cake, and pumping to a kiln tail storage tank; and pumping the filtrate to a CN filter for settling separation, overflowing the supernatant into a clear liquid tank, feeding the thick slurry into a thick slurry tank, and pumping to a water washing feeding tank.

(5) Removing part of free water in the iron phosphate solution through a diaphragm pressing plate frame, and improving the solid content of the iron phosphate; and drying the iron phosphate filter cake of the filter plate frame by a flash evaporation host machine to remove water.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.