A preparation system for iron phosphate and a preparation method for iron phosphate

Abstract

The present invention relates to the field of preparation of iron phosphate, and specifically, to a preparation system and a preparation method of iron phosphate. The preparation system of iron phosphate includes: a feed pipeline, a main washing water pipeline, a compressed gas tank, a tertiary washing water tank, a secondary washing water tank, a primary washing water tank, a pure water tank, a pressure filtration and washing device, a disc nest mill drying device, and a rotary calcination device. The preparation system of iron phosphate has high equipment utilization rate, can achieve uniform rinsing of the filter cake, shorten the water path travel, and reduce the washing water consumption; by adopting the disc nest mill drying device to remove the free water and surface modification of the iron phosphate filter cake, the processing performance of iron phosphate is improved.

Description

Technical Field

[0001] The present invention relates to the field of preparation of iron phosphate, and in particular, to a preparation system and a preparation method of iron phosphate. Background Art

[0002] The preparation process of iron phosphate mainly uses the reaction of iron salt and phosphate, and obtains iron phosphate slurry through process conditions such as oxidation and aging. Then, the iron phosphate slurry is filtered, rinsed, dried, and calcined to obtain anhydrous iron phosphate. The iron phosphate slurry not only contains iron phosphate products, but often also contains a large amount of impurity anions and cations such as sulfate radicals, ammonium radicals, metal cations, and phosphate radicals. It is necessary to use pure water to rinse and remove a large amount of impurities in the iron phosphate. The existing conventional rinsing method generally uses pure water to enter from the water inlet on one side of the plate and frame filter press and discharge from the outlet on the opposite side to rinse the filter cake. This single-direction washing method for the filter cake has disadvantages such as large consumption of pure water, low washing efficiency, and insufficient rinsing of the filter cake.

[0003] Due to the small particle size of iron phosphate in the iron phosphate filter cake, with D50 only 1 - 10 μm, the filter cake is viscous. Using traditional drying technology has problems such as high energy consumption, uneven drying, and poor processing performance of the dried material. The current mainstream drying method of iron phosphate in the industry is as follows: ① Microwave + roller hearth kiln process. In this drying scheme, the free water of the iron phosphate filter cake is removed by using an industrial microwave oven first, and then the crystal water is removed by using a roller hearth kiln. The entire dehydration process is relatively long, and both the power of the microwave oven and the roller hearth kiln are relatively large, resulting in high drying cost of iron phosphate. At the same time, in the microwave + roller hearth kiln sintering process, the whole process is static sintering, which will have problems such as uneven heating of the material, resulting in impure iron phosphate phase and poor consistency of the inner and outer layer materials; in the microwave + roller hearth kiln process, because the material is loaded in a sagger, the production line length is generally fixed, limited by the loading capacity and site area, the production efficiency of this process is generally low; ② Flash evaporation + rotary kiln process. In this drying scheme, the iron phosphate filter cake is sheared and dispersed and the free water is removed by the blades and high-temperature hot air arranged in the flash evaporator, and then the crystal water is removed by the rotary kiln. Because the process uses natural gas instead of electric energy as the heat source, the energy consumption is significantly reduced compared with the microwave + roller hearth kiln process. At the same time, due to the advantages of high drying efficiency and uniform heating of the flash evaporation + rotary kiln process, it avoids the disadvantages of poor material consistency and low production efficiency caused by the microwave + roller hearth kiln process. However, the iron phosphate prepared by this drying process has problems such as serious material agglomeration, large particle size, and small specific surface area, resulting in poor processing performance of the prepared iron phosphate. Specifically, when used as a precursor of lithium iron phosphate, the sanding time is long, which affects the production efficiency of lithium iron phosphate.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] One aspect of the present invention relates to a preparation system for iron phosphate, comprising: a feed pipeline, a main washing water pipeline, a compressed gas tank, a tertiary washing water tank, a secondary washing water tank, a primary washing water tank, a pure water tank, a pressure filtration and washing device, a disc mill drying device and a rotary calcination device;

[0006] Wherein, the feed pipeline is connected to the fifth pipe orifice of the pressure filtration and washing device; the main washing water pipeline is communicated with the feed pipeline through a first primary branch pipeline; a ninth valve is arranged on the first primary branch pipeline; the main washing water pipeline is connected to the first pipe orifice of the pressure filtration and washing device through a second primary branch pipeline; a seventh valve is arranged at the port of the second primary branch pipeline close to the main washing water pipeline;

[0007] A first secondary branch pipeline is arranged on the second primary branch pipeline; an eighth valve is arranged at the port of the first secondary branch pipeline close to the second primary branch pipeline; a second secondary branch pipeline is arranged on the second primary branch pipeline; the second secondary branch pipeline is connected to the second pipe orifice of the pressure filtration and washing device;

[0008] The first port of the main washing water pipeline is connected to the compressed gas tank, the tertiary washing water tank, the secondary washing water tank, the primary washing water tank and the pure water tank; an eleventh valve is arranged at the second port of the main washing water pipeline; the second port of the main washing water pipeline is connected to a third primary branch pipeline and a fourth primary branch pipeline; the third primary branch pipeline is connected to the third pipe orifice of the pressure filtration and washing device; the fourth primary branch pipeline is connected to the fourth pipe orifice of the pressure filtration and washing device; the first secondary branch pipeline is communicated with the third primary branch pipeline through a first tertiary branch pipeline; a tenth valve is arranged on the first tertiary branch pipeline;

[0009] The discharge port of the pressure filtration and washing device and the feed port of the disc mill drying unit are correspondingly arranged; the disc mill drying device is connected to the rotary calcination device; the squeezing water outlet of the pressure filtration and washing device is connected to a squeezing water pipeline.

[0010] The preparation system of iron phosphate rinses the iron phosphate through an alternating-countercurrent washing process, greatly improving the washing efficiency of iron phosphate and significantly reducing the amount of rinsing water used. In the existing process, the washing method is to wash the filter cake by introducing water on one side of the filter press and discharging water on the other side. This solution has a long water path. The washing effect of the filter cake near the water inlet is good, while the washing effect of the filter cake far from the water inlet is poor. Under the condition that the conductivity of the washing water is qualified, the filter cake near the water inlet often has excessive rinsing, resulting in a large amount of washing water consumption. By adopting the alternating-countercurrent washing solution of the present invention, the uniform rinsing of the filter cake can be achieved by alternately washing through five water inlets on the filter cake. The water path is significantly shorter than the conventional solution, and because each point on the filter cake is evenly rinsed, there is no excessive rinsing, thus reducing the amount of washing water used. The countercurrent washing process can be realized through DCS control on the same filter press, with high equipment utilization rate.

[0011] At the same time, by using a disc nest mill to remove free water and surface modification, and a rotary kiln calcination process route for dehydration of iron phosphate, it not only avoids the large amount of electric energy consumption caused by using a microwave drying and calcination process, reduces the drying cost, and improves the production efficiency, but also avoids the problems of serious material agglomeration, large particle size, and small specific surface area caused by the flash evaporation + rotary kiln process, resulting in poor processing performance of the prepared iron phosphate. At the same time, the natural gas consumption is lower than that of the flash evaporation + rotary kiln.

[0012] The disc nest mill is a production equipment integrating mechanical and pneumatic mills, which is dedicated to the production equipment with strict requirements for particle size distribution. It can simultaneously achieve the depolymerization, drying, and surface treatment of materials. By heating air with natural gas, etc., and then through the large number of turbulent nests formed by the lining plate and grinding disc in the grinding chamber under the high-speed operation of the rotor and the air flow velocity exceeding 200 m / s, the material is quickly and evenly dispersed and ground into ultrafine powder under the action of pressure, shear force, and frictional impact force.

[0013] Preferably, the port of the first and second branch pipelines far from the second and first branch pipelines is connected to a primary wash water collection tank, a secondary wash water collection tank, a tertiary wash water collection tank, a quaternary wash water collection tank, a mother liquor collection tank, and a sampling device.

[0014] Preferably, a blanking flap is arranged below the discharge port of the filter press washing device. It is in a closed state before the filter press washing device discharges materials to prevent the rinsing water from flowing into the next process during the pressure relief process. It is opened when the filter cake in the filter press washing device is discharged.

[0015]

[0016] Preferably, a forced feeding device is arranged at the feeding port of the disc nest mill drying device.

[0017] Preferably, the feeding amount of the disc nest mill drying device is 300 - 2000 kg / h.

[0018] Preferably, a material guiding hopper is arranged above the forced feeding device.

[0019] Preferably, the material guiding hopper is arranged corresponding to the discharge port of the pressure filtration and washing device.

[0020] Preferably, an electric pulse dust collector is arranged between the disc nest mill drying device and the rotary calcination device. The electric pulse dust collector can collect the materials dried by the disc nest mill drying device and transport them to the rotary calcination device for calcination.

[0021] Preferably, a first valve and a seventeenth valve are arranged at the outlet of the compressed gas tank.

[0022] Preferably, a third valve is arranged at the outlet of the three - time washing water tank.

[0023] Preferably, a fourth valve is arranged at the outlet of the two - time washing water tank.

[0024] Preferably, a fifth valve is arranged at the outlet of the one - time washing water tank.

[0025] Preferably, a sixth valve is arranged at the outlet of the pure water tank.

[0026] Preferably, a second valve is arranged between the feed ports of the feed pipeline.

[0027] Preferably, a twelfth valve is arranged at the liquid inlet of the one - time washing water collection tank.

[0028] Preferably, a thirteenth valve is arranged at the liquid inlet of the two - time washing water collection tank.

[0029] Preferably, a fourteenth valve is arranged at the liquid inlet of the three - time washing water collection tank.

[0030] Preferably, a fifteenth valve is arranged at the liquid inlet of the four - time washing water collection tank.

[0031] Preferably, a sixteenth valve is arranged at the liquid inlet of the mother liquor collection tank.

[0032] Another aspect of the present invention also relates to a preparation method of iron phosphate, using the preparation system of iron phosphate as described above, including the following steps:

[0033] (a) Pump the iron phosphate slurry into the pressure filtration and washing device for pressure filtration; alternately wash with the washing water in the three - time washing water tank, two - time washing water tank, one - time washing water tank and pure water tank in sequence;

[0034] When the washing water inlets for the alternate washing are the first pipe orifice and the second pipe orifice, the washing water outlets for the alternate washing are the third pipe orifice and the fourth pipe orifice;

[0035] When the washing water inlets for the alternating washing are the third pipe orifice and the fourth pipe orifice, the washing water outlets for the alternating washing are the first pipe orifice and the second pipe orifice;

[0036] When the washing water inlet for the alternating washing is the fifth pipe orifice, the washing water outlets for the alternating washing are the first pipe orifice, the second pipe orifice, the third pipe orifice and the fourth pipe orifice;

[0037] (b) Open the pressing water pipeline and the compressed gas tank for pressing drainage and blowing to obtain the iron phosphate filter cake; the iron phosphate filter cake is mixed with a surfactant and then dried and calcined to obtain anhydrous iron phosphate.

[0038] The preparation method of the iron phosphate has low preparation cost, less amount of rinsing water, high washing efficiency, less natural gas required for drying the iron phosphate filter cake, and excellent processing performance of the obtained anhydrous iron phosphate. After washing, compressed air is used for blowing to reduce the water content of the filter cake, reducing the natural gas consumption for drying the iron phosphate filter cake.

[0039] Preferably, the time for switching the alternating washing from one set of washing water inlets to the next set of washing water inlets is 100 - 500 s (such as 100 s, 150 s, 200 s, 250 s, 300 s, 350 s, 400 s, 450 s or 500 s).

[0040] Preferably, the water content of the iron phosphate filter cake < 50%.

[0041] Preferably, the conductivity of the washing water collected in the primary washing water collection tank < 300 us / cm (such as 290 us / cm, 280 us / cm, 260 us / cm, 240 us / cm, 220 us / cm, 200 us / cm or 180 us / cm).

[0042] Preferably, the surfactant includes: polyethylene glycol and / or polyacrylamide.

[0043] Preferably, the mass ratio of the surfactant to the iron phosphate filter cake is (0.5 - 2.0):(98 - 99.5) (such as 0.5:99.5, 1.0:99, 1.5:98.5 or 2.0:98).

[0044] Preferably, the inlet air temperature of the dish nest mill drying device is 150 - 300 °C (such as 150 °C, 170 °C, 190 °C, 210 °C, 230 °C, 250 °C, 270 °C or 300 °C).

[0045] Preferably, the calcination temperature is 550 to 680 °C (such as 550 °C, 560 °C, 570 °C, 580 °C, 590 °C, 600 °C, 610 °C, 620 °C, 630 °C, 640 °C, 650 °C, 660 °C, 670 °C or 680 °C).

[0046] Preferably, the calcination time is 2 to 3 h (such as 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h or 3 h).

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] (1) For the preparation system of iron phosphate provided by the present invention, countercurrent washing is carried out on the same pressure filtration and washing device, with high equipment utilization rate; by alternately washing the filter cake crystal form through five water inlets, uniform rinsing of the filter cake can be achieved, the water path travel is shortened, and the washing water consumption is reduced; by using a disc nest mill drying device to remove the free water and surface modification of the iron phosphate filter cake, the processing performance of iron phosphate is improved.

[0049] (2) For the preparation method of iron phosphate provided by the present invention, the preparation cost is low, the amount of rinsing water used is small, the washing efficiency is high, the natural gas required for drying the iron phosphate filter cake is small, and the processed performance of the prepared anhydrous iron phosphate is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 It is a schematic structural diagram of the iron phosphate preparation system provided by the present invention;

[0052] Figure 2 It is a partial structural diagram of the iron phosphate preparation system provided by the present invention;

[0053] Figure 3 It is an SEM result diagram provided by an embodiment of the present invention;

[0054] Figure 4 It is an SEM result diagram provided by a comparative example of the present invention;

[0055] Figure 5 It is an XRD diffraction diagram of iron phosphate sampled from different parts of different packaging bags provided by an embodiment of the present invention;

[0056] Figure 6XRD diffraction pattern of the sampled iron phosphate at different parts of the sagger provided for the comparative example of the present invention.

[0057] Reference numerals:

[0058] 1 - Feed pipeline, 2 - Main washing water pipeline, 3 - Compressed gas tank, 4 - Tertiary washing water tank, 5 - Secondary washing water tank, 6 - Primary washing water tank, 7 - Pure water tank, 8 - Pressure filtration and washing device, 9 - Disc mill drying device, 10 - Rotary calcination device, 11 - Fifth pipe orifice, 12 - First primary branch pipeline, 13 - Ninth valve, 14 - First pipe orifice, 15 - Second primary branch pipeline, 16 - Seventh valve, 17 - First secondary branch pipeline, 18 - Eighth valve, 19 - Second secondary branch pipeline, 20 - Second pipe orifice, 21 - Eleventh valve, 22 - Third primary branch pipeline, 23 - Fourth primary branch pipeline, 24 - Third pipe orifice, 25 - Fourth pipe orifice, 26 - First tertiary branch pipeline, 27 - Tenth valve, 28 - Pressurized water pipeline, 29 - Primary washing water collection tank, 30 - Secondary washing water collection tank, 31 - Tertiary washing water collection tank, 32 - Fourth washing water collection tank, 33 - Mother liquor collection tank, 34 - Sampling device, 35 - Dumping flap, 36 - Forced feeding device, 37 - Feeding hopper, 38 - Electro-pulse dust collection device, 39 - First valve, 40 - Seventeenth valve, 41 - Third valve, 42 - Fourth valve, 43 - Fifth valve, 44 - Sixth valve, 45 - Second valve, 46 - Twelfth valve, 47 - Thirteenth valve, 48 - Fourteenth valve, 49 - Fifteenth valve, 50 - Sixteenth valve. Detailed implementation manners

[0059] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and specific implementation manners. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0060] Example 1

[0061] The preparation system of iron phosphate provided in this example is as Figure 1 and Figure 2 shown, and includes: feed pipeline 1, main washing water pipeline 2, compressed gas tank 3, tertiary washing water tank 4, secondary washing water tank 5, primary washing water tank 6, pure water tank 7, pressure filtration and washing device 8, disc mill drying device 9 and rotary calcination device 10;

[0062] Among them, the feed pipeline 1 is connected to the fifth pipe orifice 11 of the pressure filtration and washing device 8; a first primary branch pipeline 12 is connected and communicated between the wash water main pipeline 2 and the feed pipeline 1; a ninth valve 13 is arranged on the first primary branch pipeline 12; the wash water main pipeline 2 and the first pipe orifice 14 of the pressure filtration and washing device 8 are connected through a second primary branch pipeline 15; a seventh valve 16 is arranged at the port of the second primary branch pipeline 15 close to the wash water main pipeline 2;

[0063] A first secondary branch pipeline 17 is arranged on the second primary branch pipeline 15; an eighth valve 18 is arranged at the port of the first secondary branch pipeline 17 close to the second primary branch pipeline 15; a second secondary branch pipeline 19 is arranged on the second primary branch pipeline 15; the second secondary branch pipeline 19 is connected to the second pipe orifice 20 of the pressure filtration and washing device 8;

[0064] The first port of the wash water main pipeline 2 is connected to the compressed gas tank 3, the tertiary wash water tank 4, the secondary wash water tank 5, the primary wash water tank 6 and the pure water tank 7; an eleventh valve 21 is arranged at the second port of the wash water main pipeline 2; the second port of the wash water main pipeline 2 is connected to a third primary branch pipeline 22 and a fourth primary branch pipeline 23; the third primary branch pipeline 22 is connected to the third pipe orifice 24 of the pressure filtration and washing device 8; the fourth primary branch pipeline 23 is connected to the fourth pipe orifice 25 of the pressure filtration and washing device 8; a first tertiary branch pipeline 26 is connected and communicated between the first secondary branch pipeline 17 and the third primary branch pipeline 22; a tenth valve 27 is arranged on the first tertiary branch pipeline 26;

[0065] The discharge port of the pressure filtration and washing device 8 and the feed port of the disc nest mill drying unit are correspondingly arranged; the disc nest mill drying device 9 and the rotary calcination device 10 are connected; the squeezing water outlet of the pressure filtration and washing device 8 is connected to a squeezing water pipeline 28;

[0066] The port of the first secondary branch pipeline 17 far from the second primary branch pipeline 15 is connected to a primary wash water collection tank 29, a secondary wash water collection tank 30, a tertiary wash water collection tank 31, a quaternary wash water collection tank 32, a mother liquor collection tank 33 and a sampling device 34;

[0067] A blanking flap 35 is arranged below the discharge port of the pressure filtration and washing device 8; a forced feeding device 36 is arranged at the feeding port of the disc nest mill drying device 9; a feeding hopper 37 is arranged above the forced feeding device 36; the feeding hopper 37 is correspondingly arranged with the discharge port of the pressure filtration and washing device 8; an electric pulse dust collector 38 is arranged between the disc nest mill drying device 9 and the rotary calcination device 10.

[0068] Example 2

[0069] The preparation method of iron phosphate provided by this embodiment includes the following steps:

[0070] ① Synthesis of iron phosphate: Prepare a 1mol / L ferrous sulfate solution and a 1mol / L phosphate solution respectively (where the phosphate solution is prepared from 0.95mol ammonium dihydrogen phosphate, 0.18mol phosphoric acid, 20% hydrogen peroxide accounting for the total mass of the phosphate and pure water); use the ferrous sulfate solution as the bottom liquid, and drip the phosphate solution into the ferrous sulfate solution through a peristaltic pump within 25 - 35 minutes. After the dripping is completed, age the slurry at 95°C for 4 hours to obtain an iron phosphate slurry.

[0071] ② Filtration and rinsing of iron phosphate: Open the second valve 45, pump the iron phosphate slurry after the reaction in step ① into the pressure filtration and washing device 8 through the fifth pipe orifice 11 for pressure filtration. Open the eighth valve 18, the tenth valve 27 and the sixteenth valve 50 to discharge the mother liquor into the mother liquor pipeline; after the mother liquor is discharged completely, close the above valves; open the third valve 41 and the fifteenth valve 49, and pump 20m 3 of the third washing water into the pressure filtration and washing device 8 alternately from the third pipe orifice 24 and the fourth pipe orifice 25, the first pipe orifice 14 and the second pipe orifice 20, and the fifth pipe orifice 11 of the pressure filtration and washing device 8 (the time for switching from one group of water inlet pipe orifices to the next group is 100 seconds, controlled by the DCS system); after the third washing water is pumped in completely, close the third valve 41 and the fifteenth valve 49, open the fourth valve 42 and the fourteenth valve 48, and pump 20m 3 of the second washing water into the pressure filtration and washing device 8 alternately from the third pipe orifice 24 and the fourth pipe orifice 25, the first pipe orifice 14 and the second pipe orifice 20, and the fifth pipe orifice 11 of the pressure filtration and washing device 8 (the time for switching from one group of water inlet pipe orifices to the next group is 100 seconds, controlled by the DCS system); after the second washing water is pumped in completely, close the fourth valve 42 and the fourteenth valve 48, open the fifth valve 43 and the thirteenth valve 47, and pump 20m 3 of the first washing water into the pressure filtration and washing device 8 alternately from the third pipe orifice 24 and the fourth pipe orifice 25, the first pipe orifice 14 and the second pipe orifice 20, and the fifth pipe orifice 11 of the pressure filtration and washing device 8 (the time for switching from one group of water inlet pipe orifices to the next group is 100 seconds, controlled by the DCS system); after the first washing water is pumped in completely, close the fifth valve 43 and the thirteenth valve 47, open the sixth valve 44 and the twelfth valve 46, and pump 20m 3Pure water is alternately pumped into the pressure filter washing device 8 from the third pipe orifice 24, the fourth pipe orifice 25, the first pipe orifice 14, the second pipe orifice 20, and the fifth pipe orifice 11 of the pressure filter washing device 8 (the time for switching from one group of water inlet pipe orifices to the next group is 100 seconds, controlled by the DCS system); the conductivity of the washing water collected in the primary washing water collection tank 29 is 230 us / cm; after the alternate washing is completed, the pressing system is started to press and drain the filter cake, and then purged with compressed air. The first valve 39 and the seventeenth valve 40 are opened, and the water content of the obtained iron phosphate filter cake is 47%;

[0072] ③Drying and calcining iron phosphate: The iron phosphate filter cake in step ② is fed into the disc nest mill drying device 9 through the forced feeding device 36. The feeding amount is controlled at 800 kg / h. At the same time, polyethylene glycol (PEG) with a mass fraction of 1.5% of the filter cake is added to the disc nest mill drying device 9. The inlet air temperature of the disc nest mill drying device 9 is 200 °C, and the temperature of the rotary calcining device 10 is 650 °C. The rotation speed of the rotary furnace is controlled so that the iron phosphate is calcined in the rotary furnace for 3 h to obtain powdered anhydrous iron phosphate. The SEM results are as Figure 3 shown.

[0073] Valve control and water flow direction of the alternate washing scheme:

[0074] When the washing water enters from the first pipe orifice 14 and the second pipe orifice 20, the seventh valve 16 and the tenth valve 27 are opened. The washing water enters from the first pipe orifice 14 and the second pipe orifice 20 and flows out from the third pipe orifice 24 and the fourth pipe orifice 25;

[0075] When the washing water enters from the third pipe orifice 24 and the fourth pipe orifice 25, the eleventh valve 21 and the eighth valve 18 are opened. The washing water enters from the third pipe orifice 24 and the fourth pipe orifice 25 and flows out from the first pipe orifice 14 and the second pipe orifice 20;

[0076] When the washing water enters from the fifth pipe orifice 11, the ninth valve 13, the eighth valve 18, and the tenth valve 27 are opened. The washing water enters from the fifth pipe orifice 11 and flows out from the first pipe orifice 14, the second pipe orifice 20, the third pipe orifice 24, and the fourth pipe orifice.

[0077] Example 3

[0078] The preparation method of iron phosphate provided in this example includes the following steps:

[0079] ①Same as Example 2;

[0080] ②Same as Example 2;

[0081] ③Drying and calcining of iron phosphate: Feed the iron phosphate filter cake in step ② into the disc nest mill drying device 9 through the forced feeding device 36, control the feeding rate at 800 kg / h, and at the same time add polyethylene glycol (PEG) with a mass fraction of 0.5% of the filter cake into the disc nest mill drying device 9. The inlet air temperature of the disc nest mill drying device 9 is 300 °C, and the temperature of the rotary calcining device 10 is 680 °C. Control the rotation speed of the rotary furnace to calcine the iron phosphate in the rotary furnace for 2 h to obtain powdered anhydrous iron phosphate.

[0082] Valve control and water flow direction of the alternative washing scheme: The same as in Example 2.

[0083] Example 4

[0084] The preparation method of iron phosphate provided in this example includes the following steps:

[0085] ①The same as in Example 2;

[0086] ②The same as in Example 2;

[0087] ③Drying and calcining of iron phosphate: Feed the iron phosphate filter cake in step ② into the disc nest mill drying device 9 through the forced feeding device 36, control the feeding rate at 800 kg / h, and at the same time add polyethylene glycol (PEG) with a mass fraction of 2% of the filter cake into the disc nest mill drying device 9. The inlet air temperature of the disc nest mill drying device 9 is 150 °C, and the temperature of the rotary calcining device 10 is 550 °C. Control the rotation speed of the rotary furnace to calcine the iron phosphate in the rotary furnace for 3 h to obtain powdered anhydrous iron phosphate.

[0088] Valve control and water flow direction of the alternative washing scheme: The same as in Example 2.

[0089] Comparative Example 1

[0090] The preparation method of iron phosphate provided in this comparative example includes the following steps:

[0091] ①Synthesis of iron phosphate: The same as in Example 2;

[0092] ②Filtration and rinsing of iron phosphate: Pump the iron phosphate slurry after the reaction in step ① into a filter press for filtration, and then rinse with pure water until the conductivity of the rinse water is less than 300 us / cm; after the rinsing is completed, press the filter cake and then blow it with compressed air. The moisture content of the filter cake is 48%;

[0093] ③Drying and calcining of iron phosphate: Feed the iron phosphate filter cake in step ② into the flash + rotary furnace system through a forced feeder, control the feeding rate at 800 kg / h, the inlet air temperature of the flash dryer is 500 °C, and the calcination temperature of the rotary furnace is 650 °C. Control the rotation speed of the rotary furnace to calcine the iron phosphate in the rotary furnace for 3 h to obtain powdered anhydrous iron phosphate. The SEM results are as Figure 4 shown.

[0094] Comparative Example 2

[0095] Use microwave + roller hearth furnace to replace the dish nest mill + rotary furnace in Example 2, without adding surfactant PEG, and the remaining steps are the same as in Example 2.

[0096] Experimental Example

[0097] Measure and statistically analyze the processing performance and energy consumption indicators of the iron phosphate prepared in the examples and comparative examples.

[0098] Table 1 Particle Size Detection Data of Examples and Comparative Examples

[0099] D10 / μm D50 / μm D90 / μm D99 / μm Example 2 2.01 5.51 18.65 60.75 Example 3 2.45 6.02 18.03 70.21 Example 4 1.46 4.57 14.36 65.24 Comparative Example 1 6.17 42.91 138.76 242.93 Comparative Example 2 1.492 3.503 6.831 9.952

[0100] Table 2 Comparison of Various Indicators of Examples and Comparative Examples

[0101]

[0102]

[0103] It can be seen from the data in Table 1 and Table 2 that the anhydrous iron phosphate prepared by the process route of the present invention has a D50 of only 5.51 μm, which is significantly lower than that of the comparative example, and the overall particle size distribution is more concentrated than that of the comparative example. Under the same other test conditions, the specific surface area is significantly larger than that of the comparative example, and the tapped density is significantly lower than that of the comparative example. Judging from the SEM pictures, the microstructure of the example sample has more pores and is more porous than that of the comparative example sample. When the sanding test is carried out under the same preparation process conditions of lithium iron phosphate for the examples and comparative examples, when the same particle size index is reached by sanding, the sanding time of the examples is 2.7 h shorter than that of the comparative example. From the five aspects of particle size, specific surface area, tapped density, microstructure, and sanding time, the processing performance of the anhydrous iron phosphate prepared in the examples is significantly better than that of the comparative example.

[0104] Judging from the rinsing water consumption and rinsing time, the time required for each batch of qualified rinsing in the examples is reduced by more than 32 minutes compared with the conventional washing process, and the pure water consumption per ton of anhydrous iron phosphate is reduced by 28.3 m 3 , and the examples have obvious advantages over the comparative examples in terms of production efficiency and pure water consumption.

[0105] Judging from the natural gas consumption per ton, the average natural gas consumption per ton of the present invention is 38.35 m lower than that of Comparative Example 1 3 , and it has more advantages in terms of energy consumption than Comparative Example 1, and the cost of drying and calcining iron phosphate is lower.

[0106] From Figure 5 and Figure 6It can be seen that from the XRD results of the iron phosphate samples taken from different parts of the example and Comparative Example 2, the XRD tests of the samples from different parts of the example are all pure-phase anhydrous iron phosphate. For the samples from different parts of Comparative Example 2, the crystallinity of the samples in the middle of the sagger is poor and there are impurity diffraction peaks, while the upper layer and the bottom are pure-phase anhydrous iron phosphate. From the XRD test results, the consistency of the iron phosphate prepared in the example is better than that of Comparative Example 2.

[0107] Generally speaking, through the washing, drying and calcination methods of the iron phosphate of the present invention, not only can the production efficiency of iron phosphate be significantly improved, but also the production cost of iron phosphate can be reduced. The iron phosphate prepared has more excellent processing performance, and the iron phosphate prepared by this method is more competitive in the market.

[0108] Although the present invention has been illustrated and described with reference to specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; those of ordinary skill in the art should understand that without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing iron phosphate, characterized in that, A preparation system for iron phosphate, the preparation system for iron phosphate comprising: a feed pipeline, a main washing water pipeline, a compressed gas tank, a tertiary washing water tank, a secondary washing water tank, a primary washing water tank, a pure water tank, a pressure filtration and washing device, a disc nest mill drying device, and a rotary calcination device; Wherein, the feed pipeline is connected to a fifth pipe orifice of the pressure filtration and washing device; the main washing water pipeline and the feed pipeline are connected and communicated through a first primary branch pipeline; a ninth valve is arranged on the first primary branch pipeline; the main washing water pipeline and a first pipe orifice of the pressure filtration and washing device are connected through a second primary branch pipeline; a seventh valve is arranged at a port of the second primary branch pipeline close to the main washing water pipeline; A first secondary branch pipeline is arranged on the second primary branch pipeline; an eighth valve is arranged at a port of the first secondary branch pipeline close to the second primary branch pipeline; a second secondary branch pipeline is arranged on the second primary branch pipeline; the second secondary branch pipeline is connected to a second pipe orifice of the pressure filtration and washing device; A first port of the main washing water pipeline is connected to the compressed gas tank, the tertiary washing water tank, the secondary washing water tank, the primary washing water tank, and the pure water tank; an eleventh valve is arranged at a second port of the main washing water pipeline; the second port of the main washing water pipeline is connected to a third primary branch pipeline and a fourth primary branch pipeline; the third primary branch pipeline is connected to a third pipe orifice of the pressure filtration and washing device; the fourth primary branch pipeline is connected to a fourth pipe orifice of the pressure filtration and washing device; the first secondary branch pipeline and the third primary branch pipeline are connected and communicated through a first tertiary branch pipeline; a tenth valve is arranged on the first tertiary branch pipeline; The discharge port of the pressure filtration and washing device and the feed port of the disc nest mill drying unit are correspondingly arranged; the disc nest mill drying device and the rotary calcination device are connected; the squeezing water outlet of the pressure filtration and washing device is connected to a squeezing water pipeline; An electric pulse dust collection device is arranged between the disc nest mill drying device and the rotary calcination device; The method for preparing iron phosphate comprises the following steps: (a) Pumping an iron phosphate slurry into the pressure filtration and washing device for pressure filtration; alternately washing with washing water in the tertiary washing water tank, the secondary washing water tank, the primary washing water tank, and the pure water tank in sequence; When the washing water inlets for the alternate washing are the first pipe orifice and the second pipe orifice, the washing water outlets for the alternate washing are the third pipe orifice and the fourth pipe orifice; When the washing water inlets for the alternate washing are the third pipe orifice and the fourth pipe orifice, the washing water outlets for the alternate washing are the first pipe orifice and the second pipe orifice; When the washing water inlet for the alternate washing is the fifth pipe orifice, the washing water outlets for the alternate washing are the first pipe orifice, the second pipe orifice, the third pipe orifice, and the fourth pipe orifice; (b) Opening the squeezing water pipeline and the compressed gas tank for squeezing drainage and blowing to obtain an iron phosphate filter cake; mixing the iron phosphate filter cake with a surfactant and then performing drying and calcination to obtain anhydrous iron phosphate; The inlet air temperature of the disc nest mill drying device is 150 - 300 °C; The surfactant includes: polyethylene glycol and / or polyacrylamide.

2. The preparation method of iron phosphate according to claim 1, characterized in that, The port of the first and second stage branch pipelines away from the second first stage branch pipeline is connected to a primary washing water collection tank, a secondary washing water collection tank, a tertiary washing water collection tank, a quaternary washing water collection tank, a mother liquor collection tank and a sampling device.

3. The preparation method of iron phosphate according to claim 1, characterized in that, A blanking flap is arranged below the discharge port of the pressure filtration and washing device.

4. The method for preparing iron phosphate according to claim 1, wherein A forced feeding device is arranged at the feeding port of the disc nest mill drying device.

5. The preparation method of iron phosphate according to claim 4, characterized in that, A material guiding hopper is arranged above the forced feeding device.

6. The preparation method of iron phosphate according to claim 5, wherein, The material guiding hopper is arranged corresponding to the discharge port of the pressure filtration and washing device.

7. The preparation method of iron phosphate according to claim 1, characterized in that, The time for switching the alternative washing from one set of washing water inlets to the next set of washing water inlets is 100 - 500 s.

8. The preparation method of iron phosphate according to claim 2, characterized in that, The water content of the iron phosphate filter cake is < 50%; The conductivity of the washing water collected in the primary washing water collection tank is < 300 us / cm.

9. The preparation method of iron phosphate according to claim 1, characterized in that, The mass ratio of the surfactant to the iron phosphate filter cake is (0.5 - 2.0):(98 - 99.5).

10. The preparation method of iron phosphate according to claim 1, characterized in that, The temperature of the calcination is 550 - 680 °C.

11. The preparation method of iron phosphate according to claim 1, wherein, The time of the calcination is 2 - 3 h.

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