Treatment system and process method for recovering extraction agent in wet-process phosphoric acid raffinate acid

Abstract

The invention provides a treatment system and a process method for efficiently recovering an extraction agent in wet-process phosphoric acid raffinate, and belongs to the technical field of separation and recovery of the extraction agent in the wet-process phosphoric acid raffinate, the treatment system comprises a pretreatment device and a separation and recovery device, the pretreatment device comprises a cyclone, a first filter, a thickener and a second filter, the separation and recovery device comprises a membrane system, a concentration tank and a buffer tank. The process method realizes effective recovery of the extraction agent in the raffinate acid based on the treatment system. The method provided by the invention can effectively solve the problem that the extraction agent in the raffinate acid is difficult to recycle, saves the process cost, lays a foundation for high-value utilization of the raffinate acid, and has high social and economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of separating and recovering extractants from the raffinate acid of wet-process phosphoric acid, and particularly relates to a treatment system and a process method for efficiently recovering the extractant from the raffinate acid of wet-process phosphoric acid. Background Art

[0002] With the increasing maturity of the solvent extraction purification technology for wet-process phosphoric acid production, the industrial application of wet-process phosphoric acid has gradually replaced thermal phosphoric acid. Moreover, the production of industrial phosphoric acid by solvent extraction purification of wet-process phosphoric acid has become the main development direction for the adjustment of the industrial structure of the wet-process phosphoric acid processing industry.

[0003] The technical core of the solvent extraction method for purifying wet-process phosphoric acid is to separate industrial-grade phosphoric acid from wet-process phosphoric acid with a high impurity content through organic solvent extraction. This process will produce a large amount of by-product raffinate acid. The impurity components in the raffinate acid are complex, including associated impurities and solid contents enriched after extraction and back-extraction. At the same time, there are extractants that are difficult to separate, and most of the extractants are organic solvents, which seriously affect the high-value utilization of the raffinate acid. Patent application CN 116059688 A discloses a purification process for organic solvents and solid contents in raffinate acid, but this solution focuses on the recovery and high-value utilization of acid liquor and cannot effectively recover and utilize the extractant.

[0004] Therefore, developing a treatment process for efficiently recovering the extractant in the raffinate acid and simultaneously solving the low-value utilization of the raffinate acid is of great significance for the adjustment of the industrial structure of the wet-process phosphoric acid processing industry. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present invention provides a treatment system and a process method for efficiently recovering the extractant from the raffinate acid of wet-process phosphoric acid, aiming to solve the technical problems of difficult separation and recovery of the extractant in the raffinate acid of wet-process phosphoric acid.

[0006] In the first aspect, the present invention provides a treatment system for efficiently recovering the extractant from the raffinate acid of wet-process phosphoric acid, which includes a pretreatment device and a separation and recovery device; specifically, The pretreatment device includes a hydrocyclone, a first filter, a thickener, and a second filter. The overflow port of the hydrocyclone is connected to the thickener, the underflow port of the hydrocyclone is connected to the first filter, the underflow port of the thickener is connected to the second filter, and the overflow port of the thickener is connected to the separation and recovery device; The separation and recovery device includes a membrane system, a concentration tank, and a buffer tank. The membrane system includes a circulation tank provided with a silicon carbide membrane module. The concentration tank is provided with a floating oil recovery device including a floating oil tank and a floating oil scraper. The buffer tank is connected to the floating oil recovery device and is used to store the enriched extractant.

[0007] In the above treatment system, the extractant rises to the surface of the acid solution in the concentration tank and aggregates into floating oil or scum, and then is scraped and recovered by the floating oil recovery device; specifically, the floating oil scraper can be made of acid-resistant polytetrafluoroethylene material.

[0008] Preferably, in the above treatment system, the first filter is a vacuum bag filter with a filter cloth mesh number of 500 meshes, and the second filter is a plate and frame filter press with a filter cloth pore diameter ≤ 10 μm.

[0009] Preferably, in the above treatment system, the pretreatment device further includes a diaphragm pump and a dry material tank. The diaphragm pump is used to extract the raffinate acid into the hydrocyclone, and the dry material tank is used to collect the filter cakes discharged from the first filter and the second filter.

[0010] Based on the above treatment system, the second aspect of the present invention provides a process method for efficiently recovering the extractant in the raffinate acid of wet-process phosphoric acid, including the following steps: Pretreatment of raffinate acid: Add the raffinate acid to the hydrocyclone. The overflow of the clear liquid of the hydrocyclone flows into the thickener, and the thick bottom liquid of the hydrocyclone enters the first filter and the obtained filtrate enters the thickener. A flocculant is added to the thickener. The thick bottom liquid of the thickener enters the second filter and the obtained filtrate is refluxed to the thickener. The clear liquid of the raffinate acid overflows to the membrane system; Separation and recovery of the extractant: The clear liquid of the raffinate acid is circulated and filtered through the silicon carbide membrane in the membrane system. The extractant in the filtrate floats to the surface of the acid solution and is scraped and recovered.

[0011] The method of the present invention is applicable to the deep treatment of raffinate acid with P 2 O 5 > 45% and the extractant being phosphoric acid ester and / or fatty alcohol / ketone. For example, in some embodiments of the present invention, when the extractant is tributyl phosphate (TBP) or methyl isobutyl ketone (MIBK), very good recovery effects are achieved.

[0012] Preferably, in the above process method, the bottom flow volume ratio of the hydrocyclone > 15%, which helps to remove the solid content with a size > 40 μm in the raffinate acid.

[0013] Preferably, in the above process method, the flocculant added to the thickener is a combined flocculant, such as a flocculant mainly composed of potassium oxalate and sodium carbonate, or a flocculant mainly composed of sodium carbonate and polyaluminum chloride. Such flocculants are more conducive to the sedimentation of insoluble solid content in the raffinate acid. For example, in some embodiments of the present invention, the flocculant is potassium oxalate and sodium carbonate and the mass ratio of the two is 5:3. In specific applications, those skilled in the art can also add hydrogen peroxide to the clear liquid of the raffinate acid for decolorization according to the actual situation.

[0014] Preferably, in the above process method, the first filter is a vacuum belt filter, and its negative pressure is ≥ 0.05 MPa, the filter cloth has a mesh number of 500 meshes, and the driving speed is < 2 m / min.

[0015] Preferably, in the above process method, the second filter uses plate and frame pressure filtration, and the pore diameter of the filter cloth for plate and frame pressure filtration is ≤ 10 μm, and the operating pressure is 0.4 - 0.6 MPa. The raffinate acid will adsorb and precipitate fine particles such as salts and arsenic insoluble substances under the action of the flocculant to form larger flocs. Plate and frame pressure filtration and the defined filter cloth conditions can effectively complete the pretreatment of the raffinate acid.

[0016] In the pretreatment step of the present invention, the particles in the raffinate acid are first classified by a hydrocyclone, that is, the fine particles are separated from the large particles, thereby effectively removing coarse particles. Then, in a thickener, by adding a suitable flocculant, the particle size of the sedimented solid particles is increased, thereby accelerating the sedimentation speed. At the same time, different filters are used to separate and remove impurities in the hydrocyclone and the thickener. Through the innovative design of the pretreatment process, the present invention selectively and effectively removes impurities such as phosphogypsum, fluorosilicate, and ore particles deposited in solid form in the raffinate acid, thus providing a guarantee for subsequent membrane separation.

[0017] Preferably, in the above process method, the pore diameter of the silicon carbide membrane used in the separation and recovery step is ≤ 0.04 μm; more preferably, in order to ensure the separation efficiency, the acid liquid temperature during the membrane separation process is maintained at 70 - 80 °C (if the temperature is too high, circulating water can be introduced for control), and the pressure range of the silicon carbide membrane is 0.3 - 0.4 MPa, so that the flux of the membrane separation clear liquid is greater than 300 L / (m 2 ·h). Utilizing the hydrophilic and oleophobic properties of silicon carbide and its advantages in the phosphoric acid system, the present invention uses a silicon carbide membrane as the membrane separation material. At the same time, by controlling the pore diameter of the silicon carbide membrane and the acid liquid temperature, a high transmembrane pressure difference and filtrate temperature are used to promote the efficient enrichment of the extractant.

[0018] Preferably, in the above process method, the scraping speed is ≤ 2 m / min.

[0019] Preferably, in the above process method, the following steps are further included: The acid liquid after separating the extractant is subjected to organic nanofiltration and other treatments to obtain higher-quality raffinate phosphoric acid.

[0020] Compared with the prior art, the present invention has the following advantages: (1) A pretreatment device and process are designed according to the composition characteristics of the raffinate acid. On the basis of controlling the overall process flow length, the solid content in the raffinate acid is effectively removed, ensuring the membrane separation efficiency.

[0021] (2) By controlling the pore size of the silicon carbide membrane and the temperature of the acid solution, the present invention realizes the effective separation of the organic phase and suspended solids in the raffinate acid by using a high transmembrane pressure difference and the filtrate temperature, enabling the extractant to be efficiently enriched in the acid solution. The present invention treats the extractant in the raffinate acid by physical methods, which is environmentally friendly, and both the separated raffinate acid and the extractant can be recycled.

[0022] (3) On the basis of the previous separation and enrichment, the extractant floating oil recovery device can scrape off the aggregated extractant from the surface of the raffinate acid, forming a floating oil collection net with a large oil collection area, reducing the difficulty and cost of cleaning and recovering the extractant.

[0023] (4) The pretreatment, separation and recovery in the present invention can be centrally controlled by a DCS control system. The recovery of the extractant is achieved by controlling the opening of the regulating valve and adjusting the flow rate of the terminal filtered permeate, with simple operation and labor efficiency savings. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the present invention, the drawings used in the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of the pretreatment device used in the embodiment of the present invention; Figure 2 It is a schematic diagram of the separation and recovery device used in the embodiment of the present invention.

[0026] In the figure: 1, hydrocyclone; 2, first filter; 3, thickener; 4, second filter; 5, diaphragm pump; 6, dry material tank; 7, membrane system; 8, concentrator; 9, buffer tank; 10, floating oil tank; 11, floating oil scraper. Detailed Embodiments

[0027] The embodiments of the technical solutions of the present invention will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and therefore are only examples and cannot be used to limit the protection scope of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "comprising" in this invention and any of its variations is intended to cover non-exclusive inclusion. The terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. The term "and / or" is only a description of the associated relationship of the associated objects, indicating that three relationships can exist, for example, A and / or B, which can mean: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " indicates that the associated objects before and after are in an "or" relationship. In the description of this invention, unless otherwise clearly specified and limited, terms such as "connected" and "joined" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected or indirectly connected through an intermediate medium; for those of ordinary skill in the art, the specific meanings of the above terms in this invention can be understood according to specific circumstances.

[0029] The raffinate acid is an important by-product in the wet-process phosphoric acid production industry. The extraction acid has a complex composition and contains a large amount of extractant that is difficult to separate, resulting in limited production and utilization value of the raffinate acid. Moreover, existing research mainly focuses on the recycling of acid solutions, and there is less research on the extractant that is difficult to enrich and recycle from the raffinate acid. To solve the technical problem of recycling the extractant in the raffinate acid, the present invention provides a process for efficiently recovering the extractant from the raffinate acid of wet-process phosphoric acid. By means of pretreatment and membrane separation technology, the extractant doped in the raffinate acid is efficiently separated, realizing the recycling of the extractant. At the same time, the low-value utilization of the raffinate acid is solved, and it has high social and economic benefits.

[0030] Please refer to Figure 1 and Figure 2 , the first aspect of the embodiment of the present invention provides a treatment system for efficiently recovering the extractant from the raffinate acid of wet-process phosphoric acid, which includes a pretreatment device and a separation and recovery device. Specifically: The pretreatment device includes a hydrocyclone (1), a first filter (2), a thickener (3), a second filter (4), a diaphragm pump (5) and a dry material tank (6). The overflow port of the hydrocyclone (1) is connected to the thickener (3), the underflow port of the hydrocyclone (1) is connected to the first filter (2), the underflow port of the thickener (3) is connected to the second filter (4), the filtrates obtained from the first filter (2) and the second filter (4) both enter the thickener (3), and the filter cakes obtained from the first filter (2) and the second filter (4) are discharged into the dry material tank (6); among them, the first filter is a vacuum belt filter, and the second filter is a plate and frame filter press; The separation and recovery device includes a membrane system (7), a concentration tank (8) and a buffer tank (9). The membrane system includes a circulation tank provided with a silicon carbide membrane module. The concentration tank (8) is provided with an oil skimming recovery device including an oil skimming tank (10) and an oil skimming scraper (11).

[0031] In a second aspect, based on the above treatment system, an embodiment of the present invention provides a process for efficiently recovering an extractant from the raffinate acid of wet-process phosphoric acid, including the following steps: Pretreatment of the raffinate acid: The raffinate acid is added to the hydrocyclone (1) by a diaphragm pump (5). The overflow of the hydrocyclone is discharged to the thickener, and the underflow thick liquid of the hydrocyclone enters the first filter (2), and the obtained filtrate enters the thickener (3). A flocculant is added to the thickener (3). The underflow thick liquid of the thickener enters the second filter (4), and the obtained filtrate is refluxed to the thickener (3). The clear liquid of the raffinate acid overflows to the membrane system (7). Separation and recovery of the extractant: After the clear liquid of the raffinate acid obtained from the thickener (3) is circulated and filtered through the silicon carbide membrane in the membrane system (7), the extractant in the obtained filtrate floats to the surface of the acid solution and condenses into floating oil or floating slag, and then is scraped and recovered.

[0032] The method of the present invention is applicable to the deep treatment of raffinate acid with phosphoric acid esters and fatty alcohol / ketone as the extractant. The separated raffinate acid and extractant can both be recycled.

[0033] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention. For those without specific techniques or conditions indicated in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0034] Example 1 Using Figure 1 and 2 the treatment system shown, this example provides a process for efficiently recovering an extractant from the raffinate acid of wet-process phosphoric acid, including the following steps: (1) The extractant in the raffinate acid used in this example is tributyl phosphate, the content of the extractant is greater than 3000 ppm, and ω(P 2 O 5 ) of the raffinate acid = 48%. The raffinate acid is pumped to the hydrocyclone by a diaphragm pump. The underflow of the hydrocyclone (the underflow volume flow ratio is 16.24%) enters a vacuum belt filter with a negative pressure of 0.05 MPa, a filter cloth mesh number of 500 meshes, and a driving speed of less than 1.3 m / min. The flocculant selected in the thickener is a combination of potassium oxalate and sodium carbonate (mass fraction ratio 5:3), and 50 kg of potassium oxalate and 30 kg of sodium carbonate are required for each ton of raffinate acid. The filter cloth pore diameter of the plate and frame filter press is 10 μm, and the operating pressure is 0.5 MPa.

[0035] (2) Feed the raffinate acid clear liquid after the treatment in step (1) into the silicon carbide membrane system. The process temperature is 70 - 80 °C, the membrane pore size is 0.04 μm, the operating pressure of the membrane during filtration is 0.35 MPa, and the clear liquid flux is greater than 400 L / (m 2 ·h).

[0036] (3) The upper layer of the extractant enriched in the concentration tank is recycled to the storage tank through the floating oil recovery device, and the scraping speed is 1.5 m / min.

[0037] After the above separation, tributyl phosphate is not detected in the obtained acid liquid, and the content of tributyl phosphate in the product collected by the floating oil recovery device is greater than 130 mg / kg.

[0038] Example 2 Different from Example 1, the extractant in the raffinate acid used in this example is methyl isobutyl ketone, and the content of methyl isobutyl ketone is greater than 4000 ppm.

[0039] After the recovery process, methyl isobutyl ketone is not detected in the obtained acid liquid, and the content of methyl isobutyl ketone in the product collected by the floating oil recovery device is greater than 80 mg / kg.

[0040] Example 3 Different from Example 1, in this example, sodium carbonate and polyaluminum chloride are used as flocculants in the thickener (mass fraction ratio 10:1). 10 kg of polyaluminum chloride and 100 kg of sodium carbonate are required per ton of raffinate acid.

[0041] After the above separation, tributyl phosphate is not detected in the obtained acid liquid, and the content of tributyl phosphate in the product collected by the floating oil recovery device is greater than 130 mg / kg.

[0042] Comparative Example Different from Example 1, in this example, the raffinate acid is not pretreated. The raffinate acid is directly subjected to steps (2) and (3) after natural precipitation (precipitation time > 12 h) in the material tank.

[0043] The experimental results show that the silicon carbide membrane layer is severely polluted, the membrane flux decays significantly, and the membrane flux is lower than 150 L / (m 2 ·h) within 5 minutes, and the recovery effect of the extractant is very poor.

[0044] In summary, the process method and treatment system provided by the present invention can effectively separate the extractant doped in the raffinate acid, achieve the efficient recovery of the extractant, and at the same time solve the problem of low-value utilization of the raffinate acid, having high social and economic benefits.

[0045] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and embodiments having the same constitution and achieving the same effects as the technical idea within the scope of the technical solution of the present invention are all included in the technical scope of the present invention. In addition, within the scope of not departing from the gist of the present invention, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A processing system for recovering an extractant from wet-process phosphoric acid raffinate, characterized in that: It includes a pre-treatment device and a separation and recovery device; The pretreatment device comprises a cyclone (1), a first filter (2), a thickener (3) and a second filter (4); the overflow port of the cyclone (1) is connected to the thickener (3), the underflow port of the cyclone (1) is connected to the first filter (2), the underflow port of the thickener (3) is connected to the second filter (4), and the overflow port of the thickener (3) is connected to a separation and recovery device; The separation and recovery device comprises a membrane system (7), a concentration tank (8) and a buffer tank (9); the membrane system (7) comprises a circulation tank provided with a silicon carbide membrane assembly; the concentration tank (8) is provided with an oil floating recovery device comprising an oil floating tank (10) and an oil floating scraper (11); the buffer tank (9) is connected to the oil floating recovery device and is used to store the enriched extractant.

2. The processing system according to claim 1, characterized in that The first filter (2) is a vacuum bag filter and its filter cloth has a mesh size of 500 meshes, and the second filter (4) is a plate and frame filter press and its filter cloth has a pore size of ≤10 μm.

3. The processing system according to claim 1, characterized in that The pretreatment device further comprises a diaphragm pump (5) for extracting the raffinate acid into the cyclone, and a dry material tank (6) for collecting filter cakes discharged from the first filter and the second filter.

4. A process for recovering an extractant from wet-process phosphoric acid raffinate, characterized in that: The method is carried out using the processing system according to claim 1, and comprises the following steps: The raffinate acid is added to the cyclone (1), the cyclone clear liquid overflows to the thickener (3), the cyclone underflow concentrate enters the first filter (2) and the resulting filtrate enters the thickener (3), a flocculant is added to the thickener (3), the thickener underflow concentrate enters the second filter (4) and the resulting filtrate is refluxed to the thickener (3), and the raffinate acid clear liquid overflows to the membrane system (7); The raffinate acid clear liquid is circulated and filtered through a silicon carbide membrane in the membrane system (7), and the extractant in the filtrate floats to the surface of the acid liquid and is scraped and recovered; The extractant in the raffinate acid is an oily extractant, specifically one or more of phosphates, fatty alcohols / ketones.

5. The process according to claim 4, characterized in that: The underflow volume flow ratio of the cyclone (1) is greater than 15%.

6. The process according to claim 4, characterized in that: The flocculant has potassium oxalate and sodium carbonate as active ingredients, or has sodium carbonate and polyaluminium chloride as active ingredients.

7. The process according to claim 4, characterized in that: The first filter (2) is a vacuum belt filter, and its negative pressure is ≥0.05 MPa, the filter cloth mesh number is 500 mesh, and the transmission speed is <2 m / min.

8. The process according to claim 4, characterized in that: The second filter (4) adopts plate and frame filter pressing, and the filter cloth pore size of the plate and frame filter pressing is ≤10 μm, and the operating pressure is 0.4-0.6 MPa.

9. The process according to claim 4, characterized in that: The pore size of the silicon carbide membrane is ≤0.04 μm, the temperature of the raffinate clear liquid is 70-80° C., and the pressure range of the silicon carbide membrane is 0.3-0.4 MPa.

10. The process according to claim 4, characterized in that: The scraping speed is ≤2m / min.

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