A system and method for impurity removal from a wet-process phosphoric acid slurry

Abstract

The application relates to a wet-process phosphoric acid slurry impurity removal device system and method, the impurity removal device system comprising a reaction unit, an impurity removal unit and a flow control unit; part of the slurry of the reaction unit is transported to the impurity removal unit through the flow control unit; and the part of the slurry after the impurities are removed is returned to the reaction unit through the flow control unit. The impurity removal device system provided by the application can meet the continuous production requirements of the phosphate ore, simultaneously perform the reaction of the phosphate ore and the external circulation extraction of the impurities, and thus simultaneously remove the phosphoric acid and the phosphogypsum impurities at the source.

Description

Technical Field

[0001] This invention belongs to the field of phosphoric chemical technology and relates to a purification device system and method, specifically to a purification device system and method for wet-process phosphoric acid slurry. Background Technology

[0002] Wet-process phosphoric acid production is a method that uses inorganic acids to decompose phosphate rock to obtain phosphoric acid. After wet processing, metallic impurities such as iron, magnesium, aluminum, sodium, potassium, and silicon from the phosphate rock enter the phosphoric acid and the byproduct phosphogypsum, severely affecting the quality of the phosphoric acid and the resource utilization of the phosphogypsum. Current methods for removing impurities from phosphoric acid include crystallization, chemical precipitation, ion exchange, and solvent extraction. Methods for removing impurities from phosphogypsum include water washing, lime neutralization and heat treatment, sieving, calcination, and organic solvent extraction. However, these methods suffer from high energy consumption, high costs, environmental pollution, and equipment corrosion.

[0003] CN 204873847U discloses a wet-process phosphoric acid purification system, comprising an extraction system, a desulfurization and defluorination device, a sedimentation and washing device, and a back-extraction system connected in series. This novel wet-process phosphoric acid purification system adjusts the connection relationships in traditional wet-process phosphoric acid purification systems, changing the traditional four-tank, one-tower, five-stage extraction and single-stage back-extraction to a four-tank, four-stage extraction and two-stage back-extraction system. This increases the extraction rate by more than 10% without changing the extraction tower structure or adding new equipment. However, this purification system only treats phosphoric acid and requires multi-stage extraction to achieve the purification effect, neglecting the issue of residual phosphogypsum impurities, which is detrimental to the resource utilization of phosphogypsum.

[0004] CN 111943156A discloses a process for optimizing phosphoric acid reaction and separation using activated silica, comprising: S1: mixing activated silica; S2: re-slurrying activated silica and dilute phosphoric acid; S3: mixing and aging in a digester; S4: filtration using a vacuum drum filter; and S5: a dilute phosphoric acid tube cleaning system. This process can achieve the harmless treatment of fluorinated silica, improve the recovery rate of fluorosilicic acid from phosphate rock, and simultaneously achieve efficient separation of phosphogypsum and dilute phosphoric acid by mixing an additive into the phosphoric acid digester. However, this invention only solves the separation and purification of phosphoric acid and the harmless treatment of fluorinated raw materials, without considering the impurities remaining in phosphogypsum and phosphoric acid after phosphate rock acid hydrolysis, which is not conducive to the resource utilization of purified phosphoric acid and phosphogypsum.

[0005] CN 204675835U discloses a wet-process phosphoric acid impurity removal device. This device effectively removes magnesium ions and sulfate ions from wet-process phosphoric acid production. The removed phosphoric acid meets the requirements for industrial-grade and feed-grade phosphates, with a sulfate removal rate of over 85%, a magnesium ion removal rate of over 50%, and a phosphoric acid loss rate of 1.2-1.5%. However, this device can only selectively remove some impurities from phosphoric acid, and the removal rate is not high, thus having certain limitations.

[0006] In view of the shortcomings of existing technologies, there is an urgent need to provide a cleanliness removal device system that is efficient, simple, and inexpensive. Summary of the Invention

[0007] The purpose of this invention is to provide a purification device system and method for wet-process phosphoric acid slurry. The purification device system can simultaneously perform acid hydrolysis of phosphate rock and external circulation extraction of impurities, thereby achieving simultaneous removal of phosphoric acid and phosphogypsum impurities. It has high production efficiency and is suitable for wet-process phosphoric acid production.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a purification device system for wet-process phosphoric acid slurry, the purification device system comprising a reaction unit, an impurity removal unit, and a flow control unit;

[0010] Part of the slurry from the reaction unit is transported to the impurity removal unit via a flow control unit.

[0011] After impurities are removed, the slurry is returned to the reaction unit via the flow control unit.

[0012] The impurity removal system for wet-process phosphoric acid slurry provided by this invention, through the inclusion of a reaction unit, can meet the requirements of continuous phosphate rock production. Impurities from the phosphate rock are continuously released in the reaction unit. When the impurity release is at its maximum, the slurry is transported to the impurity removal unit, where it undergoes countercurrent extraction with the extractant to remove impurities, thus reducing the problem of impurity entrainment at the source. A flow control unit allows for precise control based on production capacity and extraction efficiency. The reaction unit, impurity removal unit, and flow control unit work synergistically to simultaneously carry out the reaction of the phosphate rock and the external circulation extraction of impurities, thereby achieving the simultaneous removal of phosphoric acid and phosphogypsum impurities and solving the problem of high impurity content in wet-process phosphoric acid slurry from the source.

[0013] Preferably, the reaction unit includes a premixing device, an acid hydrolysis device, and a crystallization device connected in sequence along the material flow direction; the slurry discharged from the crystallization device is separated and the resulting acid is reused in the premixing device.

[0014] In the premixing device, phosphate rock is mixed with acid to achieve pre-decomposition of phosphate rock; the slurry in the premixing device flows to the acidolysis device, where the phosphate rock is acidolyzed under the action of acid; the slurry in the acidolysis device flows to the crystallization device to complete the crystal growth of phosphogypsum in the slurry.

[0015] Preferably, the top of the premixing device is provided with a raw material inlet and a return acid inlet.

[0016] Preferably, the acidolysis device is provided with an acid inlet at the top.

[0017] Preferably, the crystallization device has a discharge port at the bottom.

[0018] Preferably, the premixing device, the acid hydrolysis device, and the crystallization device are each equipped with 1-3 reaction tanks, and each reaction tank is equipped with a stirring device.

[0019] The premixing device, acidolysis device, and crystallization device are each equipped with 1-3 reaction tanks, for example, 1, 2, or 3.

[0020] The premixing device, acidolysis device, and crystallization device are each equipped with a reaction tank, and a stirring device is installed inside the reaction tank to promote thorough mixing of the slurry, which is beneficial to the reaction.

[0021] Preferably, the reaction tank is connected via an arch and / or an overflow port.

[0022] The present invention uses an arch and / or overflow port to connect the reaction tank, which enables continuous feeding and discharging of slurry and improves production efficiency.

[0023] Preferably, the centroid of the overflow port is 50-90% of the height of the reaction tank, for example, 50%, 60%, 70%, 80% or 90%, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the height of the arch is 50-90% of the height of the reaction tank, for example, it can be 50%, 60%, 70%, 80% or 90%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the flow control unit includes a feeding control unit, a slurry return device, and an organic phase conveying control unit;

[0026] The feeding control unit is used to transport a portion of the slurry from the reaction unit to the impurity removal unit.

[0027] The slurry return device is used to return a portion of the slurry, after impurities have been removed, to the reaction unit.

[0028] The organic phase transport control unit is used for transporting the organic phase in the impurity removal unit.

[0029] Preferably, the feeding control unit includes a feeding device, a slurry pressure stabilizing device, and a first flow monitoring device connected sequentially along the material flow direction.

[0030] The feeding device delivers a portion of the slurry from the reaction unit to the slurry stabilizing device, which then sends it into the impurity removal unit. The first flow monitoring device is used to monitor the flow rate of the slurry entering the impurity removal unit from the slurry stabilizing device.

[0031] Preferably, the feeding device includes a feeding pump.

[0032] Preferably, the slurry pressure stabilizing device includes a high-level slurry pressure stabilizing tank.

[0033] Preferably, the first flow monitoring device includes a first electromagnetic flow meter.

[0034] The first flow monitoring device is used to monitor the flow rate of the slurry.

[0035] Preferably, the inlet of the feeding device is connected to any one of the reaction tank outlets of the premixing device, the acidolysis device, or the crystallization device.

[0036] The inlet of the feeding device can be selected from the outlet of different reaction tanks of the premixing device, acidolysis device, or crystallization device. However, when the amount of impurities released in the phosphate rock is the largest, the slurry enters the impurity removal unit through the inlet of the feeding device, and the impurity removal effect is the best. If the slurry is delivered to the impurity removal unit too early, the amount of impurities released in the phosphate rock reaction process is too small, and it is difficult to remove impurities effectively. If the slurry is delivered to the impurity removal unit too late, the reaction product phosphogypsum will coat a large number of impurities, which will also lead to a decrease in the impurity removal effect.

[0037] Preferably, the organic phase conveying control unit includes an organic phase conveying device, an organic phase pressure stabilizing device, and a second flow monitoring device connected sequentially along the material flow direction.

[0038] The organic phase conveying device conveys the organic phase to the organic phase stabilizing device, and then the organic phase stabilizing device enters the impurity removal unit; the second flow monitoring device is used to monitor the flow rate of the organic phase entering the impurity removal unit from the organic phase stabilizing device.

[0039] Preferably, the organic phase transport device includes an organic phase pump.

[0040] Preferably, the organic phase voltage stabilizing device includes an organic phase high-level voltage stabilizing tank.

[0041] Preferably, the second flow monitoring device includes a second electromagnetic flow meter.

[0042] The second flow monitoring device is used to monitor the flow rate of the organic phase.

[0043] Preferably, the impurity removal unit includes an extraction tower, a pulse device, and an organic phase storage device.

[0044] The top of the extraction tower is provided with a slurry inlet and a loaded organic phase outlet, and the bottom of the extraction tower is provided with a slurry outlet, an organic phase inlet, and a connection port for connecting to a pulse device.

[0045] The organic phase storage device is connected to the organic phase inlet via the organic phase delivery control unit.

[0046] The reaction unit is connected to the slurry inlet via the feeding control unit.

[0047] The slurry outlet is connected to the reaction unit via the slurry return device.

[0048] The extraction tower in the impurity removal unit of the present invention can mix the organic phase and the slurry and make the slurry uniformly dispersed in the organic phase. The metal impurities, soluble phosphorus, fluorine and organic impurities in the slurry are extracted by the organic phase and discharged from the loaded organic phase outlet. The slurry with impurities removed is discharged from the slurry outlet and returned to the reaction unit through the slurry return device.

[0049] Preferably, the slurry return device is connected to the next-stage reaction tank adjacent to the inlet of the feeding device; the next-stage reaction tank includes any one of the reaction tanks of the premixing device, the acid hydrolysis device, or the crystallization device.

[0050] Preferably, the extraction tower includes a sieve plate extraction tower.

[0051] Preferably, the pulse device includes a pulse pump.

[0052] This invention, by incorporating a pulse device, facilitates an increase in the contact area between the slurry and the organic phase, extends the extraction time of the slurry, and thereby improves the extraction rate of impurities in the slurry.

[0053] Preferably, the organic phase storage device includes an organic phase storage tank.

[0054] This invention introduces an extraction tower and a pulse device to perform liquid-liquid-solid three-phase extraction in synergy, which can simultaneously realize the reaction of phosphate rock and the external circulation extraction of impurities, thus solving the problem of high impurity content in wet-process phosphoric acid and phosphogypsum from the source.

[0055] In a second aspect, the present invention provides a method for using a purification device system for wet-process phosphoric acid slurry as described in the first aspect, the method comprising the following steps:

[0056] Phosphate rock is subjected to pre-decomposition treatment, acid hydrolysis treatment and crystallization treatment in sequence. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0057] When at least one of the pre-decomposition treatment, acid hydrolysis treatment or crystallization treatment is performed, impurity removal treatment is performed simultaneously.

[0058] The slurry generated from the impurity removal process is returned to any one of the pre-decomposition treatment, acid hydrolysis treatment, or crystallization treatment.

[0059] The slurry produced by the impurity removal process is returned to the next stage of processing for further treatment.

[0060] The present invention provides a method for a wet-process phosphoric acid slurry impurity removal device system. By controlling the feed rate and stirring process parameters of the reaction unit, the method promotes the acid hydrolysis of phosphate rock and the full crystallization and growth of phosphogypsum in the reaction unit. The reaction slurry is fully extracted by the organic phase, and the slurry with impurities removed is returned for pre-decomposition treatment, acid hydrolysis treatment or crystallization treatment, thus solving the problem of high impurity content of phosphoric acid and phosphogypsum from the source.

[0061] Preferably, the mass ratio of acid reversion to phosphate rock is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] Preferably, the acid used in the acidolysis treatment includes sulfuric acid.

[0063] Preferably, the mass ratio of sulfuric acid to phosphate rock is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] Preferably, the mass ratio of the slurry discharged after the crystallization treatment to the phosphate rock is (0.1-1):1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] Preferably, at least one of the pre-decomposition treatment, acid hydrolysis treatment, or crystallization treatment is carried out by stirring.

[0066] Preferably, the stirring speed is 100-500 rpm, for example, it can be 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] Preferably, the stirring time is 3-10 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] Preferably, the reagents used in the impurity removal treatment include organic extractants, which include neutral extractants and / or acidic extractants.

[0069] Preferably, the neutral extractant comprises any one or a combination of at least two of the following: dibutyl butylphosphonate, tributyl phosphate, 2,2′-dibutoxydiethyl ether, methyl isobutyl ketone, tributylphosphine oxide, di(2-ethylhexyl) sulfoxide, thiophenecarboxyltrifluoroacetone, petroleum sulfoxide, diisobutyl ketone, or 2-octanol. Typical but non-limiting combinations include the combination of dibutyl butylphosphonate and tributyl phosphate, and 2,2′-dibutoxydiethyl ether and methyl isobutyl ketone. Combinations of methyl ketones, combinations of thiophenecarboxyltrifluoroacetone and petroleum sulfoxide, combinations of methyl isobutyl ketone, tributylphosphine oxide and di(2-ethylhexyl) sulfoxide, combinations of dibutyl butylphosphonate, tributyl phosphate, 2,2′-dibutoxydiethyl ether, methyl isobutyl ketone and tributylphosphine oxide, or combinations of methyl isobutyl ketone, tributylphosphine oxide, di(2-ethylhexyl) sulfoxide, thiophenecarboxyltrifluoroacetone, petroleum sulfoxide, diisobutyl ketone and 2-octanol.

[0070] Preferably, the acidic extractant comprises any one or a combination of at least two of di(2-ethylhexyl)phosphoric acid, monododecyl phosphoric acid, 2-ethylhexyl phosphate mono(2-ethylhexyl) ester, styrenephosphonate mono(2-ethylhexyl) ester, naphthenic acid, tert-carbonic acid, di(2,2,4-trimethylpentyl)phosphonic acid, or 5,8-dinonyl-2-naphthalenesulfonic acid. Typical but non-limiting combinations include the combination of di(2-ethylhexyl)phosphoric acid and monododecyl phosphoric acid, 2-ethylhexyl phosphate mono(2-ethylhexyl) ester, and styrenephosphonate mono(2-ethylhexyl) ester. Combinations of esters and naphthenic acids, combinations of di(2-ethylhexyl)phosphonic acid, monododecyl phosphate, 2-ethylhexyl phosphate mono(2-ethylhexyl) ester and styrenephosphonic acid mono(2-ethylhexyl) ester, styrenephosphonic acid mono(2-ethylhexyl) ester, naphthenic acid, tertiary carbonate, di(2,2,4-trimethylpentyl)phosphonic acid and 5,8-dinonyl-2-naphthalenesulfonic acid, or combinations of di(2-ethylhexyl)phosphonic acid, monododecyl phosphate, styrenephosphonic acid mono(2-ethylhexyl) ester, naphthenic acid, tertiary carbonate and 5,8-dinonyl-2-naphthalenesulfonic acid.

[0071] Preferably, the volumetric flow rate ratio of the slurry to the organic extractant in the impurity removal process is 1:(0.5-50), for example, it can be 1:0.5, 1:1, 1:10, 1:20, 1:30, 1:35, 1:40 or 1:50, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] When the volumetric flow rate ratio of the organic extractant to the slurry is too small, the slurry flows downward quickly, the extraction time is short, and the impurity removal effect is poor. When the volumetric flow rate ratio is too large, the slurry flows downward slowly, making it difficult for the slurry and extractant to separate at the top of the extraction tower, resulting in a long extraction time. The phosphogypsum crystals grow in the impurity removal unit, carrying impurities and a large amount of extractant, which is not conducive to the impurity extraction process. Therefore, this invention controls the ratio of the two within a reasonable range to obtain a good impurity removal effect.

[0073] Preferably, the pulse frequency of the impurity removal process is 10-60 times / minute, for example, it can be 10 times / minute, 20 times / minute, 30 times / minute, 40 times / minute, 50 times / minute or 60 times / minute, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0074] As a preferred embodiment of the method provided in the second aspect of the present invention, the method includes the following steps:

[0075] Phosphate rock is subjected to pre-decomposition treatment, acid hydrolysis treatment and crystallization treatment in sequence. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0076] The mass ratio of acid reversion to phosphate rock is (1-5):1; the acid used in the acidolysis treatment includes sulfuric acid; the mass ratio of sulfuric acid to phosphate rock is (1-10):1; the mass ratio of the slurry discharged after the crystallization treatment to phosphate rock is (0.1-1):1; at least one of the pre-decomposition treatment, acidolysis treatment, or crystallization treatment is carried out by stirring; the stirring speed is 100-500 rpm, and the time is 3-10 h;

[0077] When at least one of the pre-decomposition treatment, acid hydrolysis treatment or crystallization treatment is performed, impurity removal treatment is performed simultaneously.

[0078] The reagents used in the impurity removal treatment include organic extractants; the volume flow ratio of the slurry to the organic extractant in the impurity removal treatment is 1:(0.5-50); the pulse frequency of the impurity removal treatment is 10-60 times / minute.

[0079] The slurry generated from the impurity removal process is returned to any one of the pre-decomposition treatment, acid hydrolysis treatment, or crystallization treatment.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] (1) The wet phosphoric acid slurry purification device system provided by the present invention can meet the continuous production requirements of phosphate rock by setting up a reaction unit, an impurity removal unit and a flow control unit, and can also simultaneously carry out the reaction of phosphate rock and the external circulation extraction of impurities, thereby achieving the simultaneous removal of phosphoric acid and phosphogypsum impurities.

[0082] (2) The present invention strictly controls the timing of impurity removal in the slurry, ensuring that the slurry enters the impurity removal unit when the release of impurities in the phosphate rock is at its maximum, thereby achieving excellent impurity removal effect.

[0083] (3) By controlling the feed ratio and stirring process parameters of the reaction unit, this invention promotes the acid hydrolysis of phosphate rock and the full crystallization and growth of phosphogypsum in the reaction unit; by controlling the volume flow ratio of slurry and organic extractant, the reaction slurry is fully extracted by the organic phase, and the slurry with impurities removed is returned to the reaction unit. The residual P2O5 content of the obtained phosphogypsum is as low as 0.75%, the Al2O3 content is 0.22%, the Fe2O3 content is as low as 0.12%, and the SiO2 content is 1.8%; the Mg, Al and Fe contents of the obtained phosphoric acid are as low as 0.11%, 0.16% and 0.05%, respectively, thus solving the problem of high impurity content in wet-process phosphoric acid slurry from the source. Attached Figure Description

[0084] Figure 1 This is a schematic diagram of the impurity removal device system for wet-process phosphoric acid slurry provided in Example 1.

[0085] The components are: 1. Premixing device; 2. Acid hydrolysis device; 3. Crystallization device; 4. Return pump; 5. Feed pump; 6. High-level slurry stabilizing tank; 7. First electromagnetic flowmeter; 8. Organic phase pump; 9. High-level organic phase stabilizing tank; 10. Second electromagnetic flowmeter; 11. Sieve plate extraction tower; 12. Pulse pump; 13. Organic phase storage tank. Detailed Implementation

[0086] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0087] Example 1

[0088] This embodiment provides a system for removing impurities from wet-process phosphoric acid slurry, such as... Figure 1 As shown, the impurity removal device system includes a reaction unit, an impurity removal unit, and a flow control unit; a portion of the slurry from the reaction unit is conveyed to the impurity removal unit via the flow control unit; the portion of the slurry after impurity removal is returned to the reaction unit via the flow control unit.

[0089] The reaction unit includes a premixing device 1, an acid hydrolysis device 2, and a crystallization device 3 connected sequentially along the material flow direction. The slurry discharged from the crystallization device 3 is separated and the resulting acid is reused in the premixing device 1. The premixing device 1 has a raw material inlet and an acid return inlet at its top. The acid hydrolysis device 2 has an acid feed inlet at its top. The crystallization device 3 has a discharge outlet at its bottom. Each of the premixing device 1, acid hydrolysis device 2, and crystallization device 3 has three independently configured reaction tanks, each containing a stirring device. The reaction tanks are connected by an arch and an overflow port. The centroid of the overflow port is 70% of the height of the reaction tank from the bottom. The height of the arch is 70% of the height of the reaction tank. The three reaction tanks are designated as the first reaction tank, the second reaction tank, and the third reaction tank.

[0090] The flow control unit includes a feeding control unit, a return pump 4, and an organic phase conveying control unit. The feeding control unit is used to convey a portion of the slurry from the reaction unit to the impurity removal unit. The return pump 4 is used to return the portion of the slurry after impurity removal to the reaction unit. The organic phase conveying control unit is used for conveying the organic phase in the impurity removal unit. The feeding control unit includes a feeding pump 5, a high-level stabilizing tank 6, and a first electromagnetic flowmeter 7 connected sequentially along the material flow direction. The inlet of the feeding pump 5 is connected to the outlet of the third reaction tank of the acid hydrolysis device 2. The organic phase conveying control unit includes an organic phase pump 8, an organic phase high-level stabilizing tank 9, and a second electromagnetic flowmeter 10 connected sequentially along the material flow direction.

[0091] The impurity removal unit includes a sieve plate extraction tower 11, a pulse pump 12, and an organic phase storage tank 13. The top of the sieve plate extraction tower 11 is provided with a slurry inlet and a loaded organic phase outlet, and the bottom of the sieve plate extraction tower 11 is provided with a slurry outlet, an organic phase inlet, and a connection port for connecting to the pulse pump 12. The organic phase storage tank 13 is connected to the organic phase inlet through the organic phase conveying control unit. The reaction unit is connected to the slurry inlet through the feeding control unit. The slurry outlet is connected to the reaction unit through the return slurry pump 4. The return slurry pump 4 is connected to the inlet of the first reaction tank of the crystallization device 3.

[0092] Example 2

[0093] This embodiment provides a system for removing impurities from wet-process phosphoric acid slurry. The difference from Embodiment 1 is that the impurity removal unit is not equipped with a pulse pump 12, but all other aspects are the same as in Embodiment 1.

[0094] Example 3

[0095] This embodiment provides a purification device system for wet-process phosphoric acid slurry. The difference from Embodiment 1 is that the flow control unit does not have a return pump 4, but all other aspects are the same as in Embodiment 1.

[0096] Example 4

[0097] This embodiment provides a purification device system for wet-process phosphoric acid slurry. The difference from Embodiment 1 is that the sieve plate extraction tower 11 is replaced with an extraction tank, while the rest is the same as Embodiment 1.

[0098] Example 5

[0099] This embodiment provides a purification device system for wet-process phosphoric acid slurry. The difference from Embodiment 1 is that the inlet of the feed pump 5 is connected to the outlet of the first reaction tank of the premixing device 1, and the return pump 4 is connected to the inlet of the second reaction tank of the premixing device 1. The rest are the same as in Embodiment 1.

[0100] Example 6

[0101] This embodiment provides a purification device system for wet-process phosphoric acid slurry. The difference from Embodiment 1 is that the inlet of the feed pump 5 is connected to the outlet of the second reaction tank of the crystallization device 3, and the return pump 4 is connected to the inlet of the third reaction tank of the crystallization device 3. The rest are the same as in Embodiment 1.

[0102] Comparative Example 1

[0103] This comparative example provides a wet phosphoric acid purification device disclosed in CN 204675835U. The wet phosphoric acid purification device includes a main body, a first feed cylinder and a second feed cylinder are provided at the top of the main body; a liquid inlet hole is provided on the side wall of the main body, and a liquid inlet device is installed in the liquid inlet hole; a liquid outlet device is provided at the bottom of the main body; the liquid outlet device includes a filter cylinder and a liquid outlet pipe, and a liquid outlet switch and a filter layer are provided inside the filter cylinder.

[0104] Application Example 1

[0105] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Example 1. The method includes the following steps:

[0106] Phosphate rock is subjected to pre-decomposition treatment, sulfuric acid acidolysis treatment and crystallization treatment in sequence by stirring. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0107] The mass ratio of acid to phosphate rock is 3:1; the mass ratio of sulfuric acid to phosphate rock is 5:1; the mass ratio of the slurry discharged after crystallization to phosphate rock is 0.5:1; the stirring speed is 300 rpm and the time is 7 hours.

[0108] During the pre-decomposition treatment and sulfuric acid acid hydrolysis treatment, dibutyl butyl phosphonate is used simultaneously for impurity removal treatment; the slurry generated from the impurity removal treatment is returned for crystallization treatment.

[0109] The volumetric flow ratio of the slurry to the dibutyl butyl phosphonate in the impurity removal process is 1:20; the pulse frequency of the impurity removal process is 30 times / minute.

[0110] Application Example 2

[0111] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Example 1. The method includes the following steps:

[0112] Phosphate rock is subjected to pre-decomposition treatment, sulfuric acid acidolysis treatment and crystallization treatment in sequence by stirring. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0113] The mass ratio of acid to phosphate rock is 2:1; the mass ratio of sulfuric acid to phosphate rock is 8:1; the mass ratio of the slurry discharged after crystallization to phosphate rock is 0.8:1; the stirring speed is 200 rpm and the time is 8 hours.

[0114] During the pre-decomposition treatment and sulfuric acid acid hydrolysis treatment, dibutyl butyl phosphonate is used simultaneously for impurity removal treatment; the slurry generated from the impurity removal treatment is returned for crystallization treatment.

[0115] The volumetric flow ratio of the slurry to the dibutyl butyl phosphonate in the impurity removal process is 1:10; the pulse frequency of the impurity removal process is 20 times / minute.

[0116] Application Example 3

[0117] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Example 1. The method includes the following steps:

[0118] Phosphate rock is subjected to pre-decomposition treatment, sulfuric acid acidolysis treatment and crystallization treatment in sequence by stirring. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0119] The mass ratio of acid to phosphate rock is 4:1; the mass ratio of sulfuric acid to phosphate rock is 3:1; the mass ratio of the slurry discharged after crystallization to phosphate rock is 0.2:1; the stirring speed is 400 rpm and the stirring time is 5 hours.

[0120] During the pre-decomposition treatment and sulfuric acid acid hydrolysis treatment, dibutyl butyl phosphonate is used simultaneously for impurity removal treatment; the slurry generated from the impurity removal treatment is returned for crystallization treatment.

[0121] The volumetric flow ratio of the slurry to the dibutyl butyl phosphonate in the impurity removal process is 1:35; the pulse frequency of the impurity removal process is 50 times / minute.

[0122] Application Example 4

[0123] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Example 1. The method includes the following steps:

[0124] Phosphate rock is subjected to pre-decomposition treatment, sulfuric acid acidolysis treatment and crystallization treatment in sequence by stirring. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0125] The mass ratio of the acid to the phosphate rock is 1:1; the mass ratio of the sulfuric acid to the phosphate rock is 10:1; the mass ratio of the slurry discharged after crystallization to the phosphate rock is 1:1; the stirring speed is 100 rpm and the time is 10 h.

[0126] During the pre-decomposition treatment and sulfuric acid acid hydrolysis treatment, dibutyl butyl phosphonate is used simultaneously for impurity removal treatment; the slurry generated from the impurity removal treatment is returned for crystallization treatment.

[0127] The volumetric flow ratio of the slurry to the dibutyl butyl phosphonate in the impurity removal process is 1:0.5; the pulse frequency of the impurity removal process is 10 times / minute.

[0128] Application Example 5

[0129] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Example 1. The method includes the following steps:

[0130] Phosphate rock is subjected to pre-decomposition treatment, sulfuric acid acidolysis treatment and crystallization treatment in sequence by stirring. The acid obtained after crystallization treatment is used for pre-decomposition treatment.

[0131] The mass ratio of acid to phosphate rock is 5:1; the mass ratio of sulfuric acid to phosphate rock is 1:1; the mass ratio of the slurry discharged after crystallization to phosphate rock is 0.1:1; the stirring speed is 500 rpm and the time is 3 hours.

[0132] During the pre-decomposition treatment and sulfuric acid acid hydrolysis treatment, dibutyl butyl phosphonate is used simultaneously for impurity removal treatment; the slurry generated from the impurity removal treatment is returned for crystallization treatment.

[0133] The volumetric flow ratio of the slurry to the dibutyl butyl phosphonate in the impurity removal process is 1:50; the pulse frequency of the impurity removal process is 60 times / minute.

[0134] Application Example 6

[0135] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 1. The difference between this method and Application Example 1 is that, except for adjusting the volume flow ratio of the slurry to dibutyl butyl phosphonate to 1:60, all other aspects are the same as in Application Example 1.

[0136] Application Example 7

[0137] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 1. The difference between this method and Application Example 1 is that, except for adjusting the volume flow ratio of the slurry to dibutyl butyl phosphonate to 1:0.1, all other aspects are the same as in Application Example 1.

[0138] Application Example 8

[0139] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 1. The difference from Application Example 1 is that the stirring speed is adjusted to 50 rpm, while the rest are the same as in Application Example 1.

[0140] Application Example 9

[0141] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 1. The difference from Application Example 1 is that the stirring speed is adjusted to 600 rpm, while the rest are the same as in Application Example 1.

[0142] Application Example 10

[0143] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 2. The steps of the method are the same as those in Application Example 1.

[0144] Application Example 11

[0145] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 3. Except for the direct discharge of the slurry generated from the impurity removal process, the rest is the same as in Application Example 1.

[0146] Application Example 12

[0147] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 4. The steps of the method are the same as those in Application Example 1.

[0148] Application Example 13

[0149] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 5. The difference from Application Example 1 is that, during the pre-decomposition treatment, dibutyl butyl phosphonate is used simultaneously for impurity removal treatment; the slurry produced by the impurity removal treatment is returned to continue the pre-decomposition treatment, and the rest is the same as in Application Example 1.

[0150] Application Example 14

[0151] This application example provides a method for removing impurities from wet-process phosphoric acid slurry using the impurity removal device system described in Application Example 6. The difference from Application Example 1 is that dibutyl butyl phosphonate is used simultaneously for impurity removal during the pre-decomposition treatment, sulfuric acid acid hydrolysis treatment, and crystallization treatment. The slurry produced by the impurity removal treatment is returned to continue the crystallization treatment. The rest is the same as in Application Example 1.

[0152] Comparative Application Example 1

[0153] This comparative application example provides a method for removing impurities using the wet phosphoric acid removal device described in Comparative Example 1, the method comprising the following steps:

[0154] S1. Add oyster shell powder and sodium carbonate, two impurity removal materials, to the first feed cylinder and the second feed cylinder respectively;

[0155] S2. Add the wet-process phosphoric acid to be purified into the main body through the liquid inlet device, turn on the stirrer, and at the same time turn on the heating tube to heat the wet-process phosphoric acid to be purified to 50-70℃. Monitor the temperature of the solution inside the main body in real time through the temperature monitoring device.

[0156] S3. Open the feed switches of the first feed cylinder and the second feed cylinder respectively, and add two impurity removal raw materials in a specific mass ratio according to the scale on the first feed cylinder and the second feed cylinder to carry out a chemical precipitation impurity removal reaction on phosphoric acid;

[0157] S4. After the reaction is complete (about 20-40 minutes), turn off the stirrer to stop stirring. After the mixed solution has settled and precipitated, turn on the liquid outlet switch and receive the purified wet-process phosphoric acid product from the liquid outlet pipe.

[0158] The slurry discharged from corresponding use cases 1-14 and comparative application example 1 was separated. XRF was used to analyze the content of residual P2O5, Al2O3, Fe2O3 and SiO2 impurities in phosphogypsum, and the results are shown in Table 1. ICP was used to analyze the content of Mg, Al and Fe impurities in phosphoric acid, and the results are shown in Table 2.

[0159] Table 1

[0160] <![CDATA[P2O5(%)]]> <![CDATA[Al2O3(%)]]> <![CDATA[Fe2O3(%)]]> <![CDATA[SiO2(%)]]> Application Example 1 0.75 0.22 0.12 1.8 Application Example 2 0.91 0.25 0.18 2.4 Application Example 3 0.85 0.23 0.15 2.5 Application Example 4 1.68 0.29 0.20 3.1 Application Example 5 1.45 0.28 0.23 3.0 Application Example 6 1.88 0.29 0.24 4.4 Application Example 7 1.76 0.38 0.29 5.5 Application Example 8 4.30 0.33 0.24 4.3 Application Example 9 3.60 0.31 0.26 4.7 Application Example 10 1.75 0.30 0.23 4.4 Application Example 11 1.87 0.34 0.26 5.1 Application Example 12 2.40 0.26 0.20 3.5 Application Example 13 4.50 0.37 0.28 5.7 Application Example 14 2.60 0.29 0.21 3.6 Comparative Application Example 1 - - - -

[0161] Table 2

[0162]

[0163]

[0164] As can be seen from Tables 1 and 2, the wet-process phosphoric acid slurry removal device system and method provided by the present invention removes impurities simultaneously during the acid hydrolysis and crystallization process of phosphate rock. After the slurry with impurities removed is discharged, analysis shows that the impurity content of phosphogypsum and phosphoric acid is low, thus solving the problem of removing impurities from the source.

[0165] A comparison of Application Examples 1, 6, and 7 shows that when the volumetric flow ratio of the slurry to dibutyl butyl phosphonate is too small, phase separation between the slurry and extractant at the top of the extraction tower is difficult, the extraction time is long, and phosphogypsum crystallizes and grows in the impurity removal unit, which is detrimental to the impurity extraction process. Conversely, when the volumetric flow ratio is too large, the slurry flows downwards quickly, the extraction time is short, and the impurity removal effect is poor. A comparison of Application Examples 1, 8, and 9 shows that the stirring speed of the pre-decomposition treatment, acidolysis treatment, and crystallization treatment in the reaction unit has a significant impact on the impurity removal effect. If the stirring speed is too low, phosphogypsum will grow and agglomerate, and the P2O5 content will increase. If the speed is too high, the phosphogypsum particles will be broken, the system viscosity will increase sharply, the slurry will become viscous, and impurities will be difficult to separate in the extraction tower. A comparison of Application Examples 1 and 8 shows that the stirring speed of the pre-decomposition treatment, acidolysis treatment, and crystallization treatment in the reaction unit has a significant impact on the impurity removal effect. If the stirring speed is too low, phosphogypsum will grow and agglomerate, and the P2O5 content will increase. If the speed is too high, the phosphogypsum particles will be broken, the system viscosity will increase sharply, the slurry will become viscous, and impurities will be difficult to separate in the extraction tower. The comparison shows that the impurity removal unit lacks a pulse pump, resulting in insufficient mixing of the slurry within the sieve plate extraction tower and relatively high impurity residue. A comparison between Application Example 1 and Application Example 11 reveals that the flow control unit lacks a return pump, causing the impurity-removed slurry to be discharged directly from the bottom of the sieve plate extraction tower. This results in insufficient crystallization and growth of phosphogypsum crystals, leading to high P2O5 and impurity content in the discharged phosphogypsum. A comparison between Application Example 1 and Application Example 12 shows that using a conventional extraction tank reduces the impurity removal efficiency compared to the sieve plate extraction tower. A comparison between Application Example 1 and Application Examples 13 and 14 shows that delivering the slurry to the impurity removal unit too early results in insufficient impurity release during the phosphate rock reaction process, hindering effective impurity removal. Delivering it too late results in the reaction product phosphogypsum encapsulating a large amount of impurities, also reducing the impurity removal efficiency.

[0166] As can be seen from the comparison between Application Example 1 and Comparative Application Example 1, the wet phosphoric acid purification device disclosed in the prior art only has a certain removal effect on magnesium ions and the removal rate is low. However, there are many types of metal impurities in the wet phosphoric acid slurry, so the purification device has certain limitations in application.

[0167] In summary, the wet-process phosphoric acid slurry impurity removal device system provided by the present invention, by setting up a reaction unit, an impurity removal unit and a flow control unit, can meet the continuous production requirements of phosphate rock, and can also simultaneously carry out the reaction of phosphate rock and the external circulation extraction of impurities, thereby achieving the simultaneous removal of phosphoric acid and phosphogypsum impurities.

[0168] This invention strictly controls the timing of impurity removal from the slurry, ensuring that the slurry enters the impurity removal unit when the release of impurities in the phosphate rock is at its maximum, thereby achieving excellent impurity removal effect.

[0169] This invention promotes the acid hydrolysis of phosphate rock and the full crystallization and growth of phosphogypsum within the reaction unit by controlling the feed ratio and stirring process parameters. By regulating the volumetric flow rate ratio of the slurry and the organic extractant, the reaction slurry is fully extracted by the organic phase, and the slurry with impurities removed is returned to the reaction unit. The resulting phosphogypsum has a residual P2O5 content as low as 0.75%, an Al2O3 content as low as 0.22%, an Fe2O3 content as low as 0.12%, and a SiO2 content as low as 1.8%. The resulting phosphoric acid has Mg, Al, and Fe contents as low as 0.11%, 0.16%, and 0.05%, respectively, thus solving the problem of high impurity content in wet-process phosphoric acid slurry from the source.

[0170] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A system for removing impurities from wet-process phosphoric acid slurry that simultaneously performs acid hydrolysis of phosphate rock and external circulation extraction of impurities, characterized in that, The impurity removal device system includes a reaction unit, an impurity removal unit, and a flow control unit; Part of the slurry from the reaction unit is transported to the impurity removal unit via a flow control unit. The slurry, after impurities have been removed, is returned to the reaction unit via a flow control unit. The flow control unit includes a feeding control unit, a slurry return device, and an organic phase conveying control unit; The impurity removal unit includes an extraction tower, a pulse device, and an organic phase storage device; The feeding control unit is used to transport a portion of the slurry from the reaction unit to the impurity removal unit; The slurry return device is used to return a portion of the slurry, after impurities have been removed, to the reaction unit.

2. The impurity removal device system according to claim 1, characterized in that, The reaction unit includes a premixing device, an acid hydrolysis device, and a crystallization device connected in sequence along the material flow direction; the slurry discharged from the crystallization device is separated and the resulting acid is reused in the premixing device.

3. The impurity removal device system according to claim 2, characterized in that, The premixing device is equipped with a raw material inlet and a return acid inlet at the top.

4. The impurity removal device system according to claim 2, characterized in that, The acidolysis device is equipped with an acid inlet at the top.

5. The impurity removal device system according to claim 2, characterized in that, The crystallization device is provided with a discharge port at the bottom.

6. The impurity removal device system according to claim 2, characterized in that, The premixing device, acidolysis device, and crystallization device are each equipped with 1-3 reaction tanks, and each reaction tank is equipped with a stirring device.

7. The impurity removal device system according to claim 6, characterized in that, The reaction tank is connected by an arch and / or an overflow port.

8. The impurity removal device system according to claim 7, characterized in that, The centroid of the overflow port is 50-90% of the height of the reaction tank from the bottom of the reaction tank.

9. The impurity removal device system according to claim 7, characterized in that, The height of the arch is 50-90% of the height of the reaction tank.

10. The impurity removal device system according to any one of claims 2-9, characterized in that, The organic phase transport control unit is used for transporting the organic phase in the impurity removal unit.

11. The impurity removal device system according to claim 1, characterized in that, The feeding control unit includes a feeding device, a slurry pressure stabilizing device, and a first flow monitoring device connected sequentially along the material flow direction.

12. The impurity removal device system according to claim 11, characterized in that, The inlet of the feeding device is connected to any one of the following: the outlet of the reaction tank of the premixing device, the outlet of the reaction tank of the acidolysis device, or the outlet of the reaction tank of the crystallization device.

13. The impurity removal device system according to any one of claims 2-9, characterized in that, The organic phase conveying control unit includes an organic phase conveying device, an organic phase pressure stabilizing device, and a second flow monitoring device connected sequentially along the material flow direction.

14. The impurity removal device system according to any one of claims 2-9, characterized in that, The top of the extraction tower is provided with a slurry inlet and a loaded organic phase outlet, and the bottom of the extraction tower is provided with a slurry outlet, an organic phase inlet, and a connection port for connecting to a pulse device. The organic phase storage device is connected to the organic phase inlet via the organic phase delivery control unit; The reaction unit is connected to the slurry inlet via the feeding control unit; The slurry outlet is connected to the reaction unit via the slurry return device.

15. The impurity removal device system according to any one of claims 6-9, characterized in that, The slurry return device is connected to the next-stage reaction tank adjacent to the inlet of the feeding device; the next-stage reaction tank includes any one of the reaction tanks of the premixing device, the acid hydrolysis device, or the crystallization device.

16. A method for using the impurity removal device system according to any one of claims 1-15, characterized in that, The method includes the following steps: Phosphate rock is subjected to pre-decomposition treatment, acid hydrolysis treatment and crystallization treatment in sequence. The acid obtained after crystallization treatment is used for pre-decomposition treatment. When at least one of the pre-decomposition treatment, acid hydrolysis treatment or crystallization treatment is performed, impurity removal treatment is performed simultaneously. The slurry produced by the impurity removal process is returned to any one of the pre-decomposition treatment, acid hydrolysis treatment, or crystallization treatment.

17. The method according to claim 16, characterized in that, The mass ratio of acid reversion to phosphate rock is (1-5):

1.

18. The method according to claim 16, characterized in that, The acid used in the acidolysis treatment includes sulfuric acid.

19. The method according to claim 18, characterized in that, The mass ratio of sulfuric acid to phosphate rock is (1-10):

1.

20. The method according to claim 16, characterized in that, The mass ratio of the slurry discharged after the crystallization treatment to the phosphate rock is (0.1-1):

1.

21. The method according to claim 16, characterized in that, At least one of the pre-decomposition treatment, acid hydrolysis treatment, or crystallization treatment is carried out by stirring.

22. The method according to claim 21, characterized in that, The stirring speed is 100-500 rpm.

23. The method according to claim 21, characterized in that, The stirring time is 3-10 hours.

24. The method according to any one of claims 16-23, characterized in that, The reagents used in the impurity removal process include organic extractants, which include neutral extractants and / or acidic extractants.

25. The method according to claim 24, characterized in that, The neutral extractant includes any one or a combination of at least two of the following: dibutyl butylphosphonate, tributyl phosphate, 2,2'-dibutoxydiethyl ether, methyl isobutyl ketone, tributylphosphine oxide, di(2-ethylhexyl) sulfoxide, thiophenecarboxyltrifluoroacetone, petroleum sulfoxide, diisobutyl ketone, or 2-octanol.

26. The method according to claim 24, characterized in that, The acidic extractant includes any one or a combination of at least two of the following: di(2-ethylhexyl)phosphoric acid, monododecyl phosphoric acid, 2-ethylhexyl phosphate mono(2-ethylhexyl) ester, styrenephosphonic acid mono(2-ethylhexyl) ester, naphthenic acid, tert-carbonic acid, di(2,2,4-trimethylpentyl)phosphonic acid, or 5,8-dinonyl-2-naphthalenesulfonic acid.

27. The method according to claim 24, characterized in that, In the impurity removal process, the volumetric flow rate ratio of the slurry to the organic extractant is 1:(0.5-50).

28. The method according to any one of claims 16-23, characterized in that, The pulse frequency for the impurity removal process is 10-60 times / minute.

29. The method according to any one of claims 16-23, characterized in that, The method includes the following steps: Phosphate rock is subjected to pre-decomposition treatment, acid hydrolysis treatment and crystallization treatment in sequence. The acid obtained after crystallization treatment is used for pre-decomposition treatment. The mass ratio of acid reversion to phosphate rock is (1-5):1; the acid used in the acidolysis treatment includes sulfuric acid; the mass ratio of sulfuric acid to phosphate rock is (1-10):1; the mass ratio of the slurry discharged after the crystallization treatment to phosphate rock is (0.1-1):1; at least one of the pre-decomposition treatment, acidolysis treatment, or crystallization treatment is carried out by stirring; the stirring speed is 100-500 rpm, and the time is 3-10 h; When at least one of the pre-decomposition treatment, acid hydrolysis treatment or crystallization treatment is performed, impurity removal treatment is performed simultaneously. The reagents used in the impurity removal treatment include organic extractants; the volume flow ratio of the slurry to the organic extractant in the impurity removal treatment is 1:(0.5-50); the pulse frequency of the impurity removal treatment is 10-60 times / minute. The slurry produced by the impurity removal process is returned to any one of the pre-decomposition treatment, acid hydrolysis treatment, or crystallization treatment.

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