Defluorination device for wastewater

Abstract

The utility model discloses a wastewater defluorination device and belongs to the technical field of phosphorus chemical industry. Comprising a mother liquor buffer tank, a lime slurry supply structure, a mixer, a homogeneous reactor, a slurry buffer tank, a mixing tank, a thickener, a flocculant tank, an overflow buffer tank, a re-slurry tank, a filter press and a filtrate buffer tank, a discharge port of the mixer, the homogeneous reactor, the slurry buffer tank, the mixing tank and the thickener are connected in sequence, and the flocculant tank is connected with the mixing tank; a clear liquid outlet of the thickener is connected with the overflow buffer tank, and an underflow outlet of the thickener is connected with the repulping tank; a feed port of the filter press is connected with the overflow buffer tank, a filtrate outlet of the filter press is connected with the filtrate buffer tank, and a filter residue outlet of the filter press is connected with the re-pulping tank; the filtrate buffer tank is connected with the re-pulping tank, the lime milk preparation tank, the three-washing water tank and the salt dissolving tank; and the repulping tank is connected with the phosphogypsum storage tank. The method is mainly used for removing fluorine and silicon in the sodium fluoride mother liquor and recycling the treated clear water.

Description

Technical Field

[0001] This utility model belongs to the field of phosphorus chemical technology, and specifically relates to a wastewater defluorination device, which is mainly used to remove fluorine and silicon from sodium fluoride mother liquor. The treated water is reused, and the treated waste residue is sent to a phosphogypsum storage tank, thus achieving zero wastewater and solid waste discharge. Background Technology

[0002] The production of phosphoric acid from phosphate rock generates a large amount of fluorine-containing gas. Currently, this gas is absorbed by water to produce fluorosilicic acid (concentration 5-20%), which is then processed into other products, thus recovering the fluorine resources from the phosphate rock. In existing technology, fluorosilicic acid can be reacted with sodium sulfate to obtain sodium fluorosilicate. The production process of sodium fluorosilicate can be found in the description of application number CN201210287774.8, which discloses a production process for sodium fluorosilicate, mainly including the following steps:

[0003] (1) Prepare a sodium sulfate solution with a mass fraction of 26%-32%.

[0004] (2) Add 8%-14% fluorosilicic acid by mass while stirring; The 8%-14% fluorosilicic acid from the fluorosilicic acid settling tank is heated to 35-40℃ by heat exchanger and steam exchange and placed in the fluorosilicic acid storage tank for later use; The prepared sodium sulfate solution is sent from the salting tank to the sodium fluorosilicate synthesis tank by metering pump. When the liquid level of the sodium sulfate solution in the synthesis tank reaches half, the stirrer is started and the speed of the stirrer is maintained at 30-40 r / min. Add the above-mentioned 8%-14% fluorosilicic acid by mass while stirring.

[0005] (3) Control the amount of sodium sulfate solution and adjust the amount of fluorosilicic acid so that the amount of fluorosilicic acid is 3%-6% more than the theoretical amount calculated according to the chemical equation; Under stirring, use a metering pump to send the metered fluorosilicic acid to the synthesis tank and sodium sulfate solution for synthesis reaction. The amount of fluorosilicic acid is added at 3%-6% more than the theoretical mass of the chemical reaction.

[0006] (4) After the reaction of sodium sulfate and fluorosilicic acid is completed, crystal growth is carried out; after the sodium sulfate solution and fluorosilicic acid solution react in the synthesis tank for 20-30 minutes, the sodium fluorosilicate crystal slurry generated by the reaction is put into the first crystal growth tank from the bottom of the synthesis tank for crystal growth; the unreacted sodium sulfate and fluorosilicic acid solution overflows from the top overflow port of the synthesis tank into the first crystal growth tank to continue the reaction; the stirring speed of the agitator in the first crystal growth tank is controlled at 3-6 r / min, and the crystal slurry grown in the first crystal growth tank for 20-40 minutes is put into the second crystal growth tank from the bottom of the first crystal growth tank to continue crystal growth, and the wastewater after the reaction is completed enters the wastewater tank from the top overflow port of the crystal growth tank; the crystal slurry entering the second crystal growth tank continues to grow crystals for 20-40 minutes at a stirring speed of 3-6 r / min, and the crystals after crystal growth are completed are put into the washing tank from the bottom of the second crystal growth tank, and the excess wastewater overflows from the top of the crystal growth tank into the wastewater tank.

[0007] (5) Wash and separate sodium fluorosilicate crystals, and centrifuge and dry them; wash the crystals after crystal growth with an appropriate amount of industrial water until the pH reaches 3-4 to remove excess free acid and ensure crystal quality; after washing, the crystals and washing water are put into a centrifuge for centrifugation; the wastewater after centrifugation is put into a wastewater collection tank, and the product is put into a dryer for drying.

[0008] (6) Recovery of sulfuric acid and fluorosilicic acid: Wastewater from the first crystal growth tank, the second crystal growth tank and the centrifuge is collected and sent to the wastewater tank. The collected wastewater is pumped to the phosphoric acid extraction unit for phosphoric acid production, that is, to recover sulfuric acid and excess fluorosilicic acid.

[0009] The production of sodium fluorosilicate generates a large amount of sodium fluoride mother liquor (collected in a wastewater tank). This mother liquor contains a significant amount of fluorine (F). - If fluorine (such as fluorosilicate ions) and silicon are directly recycled into the phosphoric acid production system, it will lead to the enrichment of F element, resulting in an increase in the fluorine content of phosphoric acid. Summary of the Invention

[0010] To address the aforementioned problems, this utility model provides a wastewater defluorination device, primarily used to remove fluoride and silicon from sodium fluoride mother liquor. The treated water is reused, and the treated waste residue is sent to a phosphogypsum storage tank, achieving zero wastewater and solid waste discharge. The technical solution is as follows:

[0011] This utility model provides a wastewater defluorination device, which includes a mother liquor buffer tank 1, a lime slurry supply structure, a mixer 2, a homogenizing reactor 3, a slurry buffer tank 4, a mixing tank 5, a thickener 6, a flocculant tank 14, an overflow buffer tank 7, a reslurry tank 8, a filter press 9, and a filtrate buffer tank 10. The mother liquor buffer tank 1 and the lime slurry supply structure are both connected to the inlet of the mixer 2 via pipelines. The outlet of the mixer 2, the homogenizing reactor 3, the slurry buffer tank 4, the mixing tank 5, and the thickener 6 are sequentially connected via pipelines. The flocculant tank 14 is connected via... The pipeline is connected to the mixing tank 5; the clear liquid outlet of the thickener 6 is connected to the overflow buffer tank 7 via a pipeline, and its underflow outlet is connected to the re-slurry tank 8 via a pipeline; the feed inlet of the filter press 9 is connected to the overflow buffer tank 7 via a pipeline, its filtrate outlet is connected to the filtrate buffer tank 10 via a pipeline, and its filter residue outlet is connected to the re-slurry tank 8; the filtrate buffer tank 10 is connected to the re-slurry tank 8, the lime slurry preparation tank 13 of the lime slurry supply structure, the three-wash water tank of the phosphoric acid filtration device, and the salt-dissolving tank of the sodium fluoride preparation device via a pipeline; the re-slurry tank 8 is connected to the phosphogypsum storage tank via a pipeline.

[0012] The lime slurry supply structure in this embodiment includes a lime storage tank 11, a lime slurry preparation tank 13, and a lime screw feeder 12. A star-shaped feed valve is provided at the discharge port at the bottom of the lime storage tank 11 and is connected to the lime slurry preparation tank 13 through the lime screw feeder 12. The lime slurry preparation tank 13 is connected to the inlet of the mixer 2 through a pipeline. The filtrate buffer tank 10 is connected to the lime slurry preparation tank 13 through a pipeline.

[0013] Specifically, in this embodiment of the invention, the mother liquor buffer tank 1 is connected to the inlet of the mixer 2 via a pipeline with a mother liquor delivery pump 15; the lime slurry preparation tank 13 is connected to the inlet of the mixer 2 via a pipeline with a lime slurry feed pump 16; the slurry buffer tank 4 is lower than the homogenizing reactor 3 and is connected to the mixing tank 5 via a pipeline with a slurry feed pump 17; and the flocculant tank 14 is connected to the mixing tank 5 via a pipeline with a flocculant feed pump 20. The mixing tank 5 is higher than the thickener 6. The overflow buffer tank 7 is lower than the overflow weir of the thickener 6 and is connected to the feed inlet of the filter press 9 through a pipeline with a filter press feed pump 18. The reslurry tank 8 is lower than the thickener 6 and the filter press 9 and is located directly below the filter press 9. The filtrate buffer tank 10 is lower than the filter press 9 and is connected to the reslurry tank 8, the lime slurry preparation tank 13, the three-wash water tank and the salt dissolving tank through a pipeline with a clear liquid transfer pump 19 and a valve group.

[0014] In this embodiment of the present invention, a stirrer is provided in the lime slurry preparation tank 13, the mother liquor buffer tank 1, the slurry buffer tank 4, the flocculant tank 14, the overflow buffer tank 7, and the re-slurry tank 8. The mixer 2 is an SK-type static mixer, and the filter press 9 is a plate and frame filter press.

[0015] More specifically, in this embodiment of the present invention, the specifications of the mother liquor buffer tank 1 are Φ4000mm*h3200mm, the specifications of the mixer 2 are Φ133mm*h11000mm, the specifications of the homogenizing reactor 3 are Φ1500mm*h5000mm, the specifications of the slurry buffer tank 4 are Φ4000mm*h3200mm, the specifications of the mixing tank 5 are Φ1500mm*h2000mm, the specifications of the overflow buffer tank 7 are Φ3600mm*h3200mm, the specifications of the reslurry tank 8 are Φ2400mm*h2000mm, the filtration area of ​​the filter press 9 is 100㎡, the specifications of the filtrate buffer tank 10 are Φ3600mm*h3200mm, and the specifications of the lime slurry preparation tank 13 are Φ3000mm*h2500mm.

[0016] The beneficial effects of the technical solution provided by this utility model embodiment are as follows: This utility model embodiment provides a wastewater defluorination device, mainly used to remove fluoride and silicon from sodium fluoride mother liquor. The treated water is reused (not directly sent to the phosphoric acid production system, but used as re-slurry water, lime slurry, third wash water, and brine (to dissolve sodium sulfate)). The treated waste residue is sent to a phosphogypsum storage tank, achieving zero wastewater and solid waste discharge. Compared with a reaction vessel, the combination of a mixer and a homogenizing reactor results in a more complete reaction and a shorter reaction time. The use of a thickener reduces the amount of material processed by pressure filtration and facilitates re-slurrying (the density of the underflow itself is easy to transport). Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the entire phosphoric acid production system.

[0018] Figure 2 This is a schematic block diagram of the wastewater defluorination device provided in this embodiment of the utility model;

[0019] Figure 3 This is a schematic diagram of the wastewater defluorination device provided in this embodiment of the utility model.

[0020] In the diagram: 1. Mother liquor buffer tank, 2. Mixer, 3. Homogenizer, 4. Slurry buffer tank, 5. Mixing tank, 6. Thickener, 7. Overflow buffer tank, 8. Reslurry tank, 9. Filter press, 10. Filtrate buffer tank, 11. Lime storage tank, 12. Lime screw feeder, 13. Lime slurry preparation tank, 14. Flocculant tank, 15. Mother liquor transfer pump, 16. Lime slurry feed pump, 17. Slurry feed pump, 18. Filter press feed pump, 19. Clear liquid transfer pump, 20. Flocculant feed pump. Detailed Implementation

[0021] To make the objectives, technical solutions and advantages of this utility model clearer, the utility model will be described in further detail below with reference to the accompanying drawings.

[0022] Example 1

[0023] See Figure 1-3 Example 1 provides a wastewater defluorination device, which includes a mother liquor buffer tank 1, a lime slurry supply structure, a mixer 2, a homogenizing reactor 3, a slurry buffer tank 4, a mixing tank 5, a thickener 6, a flocculant tank 14, an overflow buffer tank 7, a reslurry tank 8, a filter press 9, and a filtrate buffer tank 10. The mother liquor buffer tank 1 stores sodium fluoride mother liquor and is connected to the sodium fluoride preparation device (specifically, a wastewater tank) via pipeline. The lime slurry supply structure provides lime slurry. The lime slurry supply structure includes a lime storage tank 11 (for storing lime), a lime slurry preparation tank 13 (for preparing lime slurry), and a lime screw feeder 12. A star-shaped feed valve is installed at the outlet at the bottom of the lime storage tank 11, and it is connected to the lime slurry preparation tank 13 via the lime screw feeder 12. The lime slurry reacts with the fluorine in the sodium fluoride mother liquor to form calcium fluoride, and the lime slurry reacts with the silicon in the sodium fluoride mother liquor to form calcium fluorosilicate. The amount of lime slurry used is 1.1-1.2 times the calculated value. The mixing of lime slurry and sodium fluoride mother liquor is achieved in mixer 2. The reaction of lime slurry and sodium fluoride mother liquor is carried out in homogenizing reactor 3, resulting in a more complete reaction and a shorter reaction time. Slurry buffer tank 4 is used to store the reacted slurry. Flocculant tank 14 is used to provide flocculant (specifically, PAC, etc.). Mixing tank 5 is used to mix the slurry and flocculant and defoam. Thickener 6 is used to concentrate the slurry. Overflow buffer tank 7 is used to store the concentrated clarified liquid. Filter press 9 is used for pressure filtration. Filtrate buffer tank 10 is used to store the filtrate. Reslurry tank 8 is used to prepare a easily transportable slurry (density 1.3-1.5 g / cm³) by combining the filtrate, filter residue, and underflow from thickener 6. 3 ), and deliver.

[0024] The mother liquor buffer tank 1 is connected to the inlet of the mixer 2 via a pipeline with a mother liquor delivery pump 15. The lime slurry preparation tank 13 is connected to the inlet of the mixer 2 via a pipeline with a lime slurry feed pump 16. The outlet of the mixer 2 is connected to the inlet of the homogenizing reactor 3 via a pipeline. The slurry buffer tank 4 is lower than the homogenizing reactor 3 and is connected to the mixing tank 5 via a pipeline with a slurry feed pump 17. The flocculant tank 14 is connected to the mixing tank 5 via a pipeline with a flocculant feed pump 20. The mixing tank 5 is higher than the thickener 6 and is connected to the central cylinder of the thickener 6 via a pipeline. The overflow buffer tank 7 is lower than the overflow weir of the thickener 6 and is connected to the clear liquid outlet of the thickener 6 (located at the bottom of the overflow weir) via a pipeline. It is also connected to the inlet of the filter press 9 via a pipeline with a filter press feed pump 18. The re-slurry tank 8 is lower than the thickener 6 and the filter press 9. It is connected to the underflow outlet of the thickener 6 via a pipeline and is located directly below the filter press 9 so that the filter cake from the filter press 9 can be directly output to the re-slurry tank 8. The filtrate buffer tank 10 is lower than the filter press 9 and is connected to the filtrate outlet of the filter press 9 via a pipeline. It is connected to the re-slurry tank 8, the lime slurry preparation tank 13, the three-wash water tank of the phosphoric acid filtration unit, and the salt dissolving tank (used to dissolve sodium sulfate) of the sodium fluoride preparation unit via a pipeline equipped with a clear liquid transfer pump 19 and a valve assembly. The re-slurry tank 8 is connected to the phosphogypsum storage tank via a pipeline equipped with a pump.

[0025] Among them, see Figure 3 In this embodiment of the present invention, a stirrer is provided in the lime slurry preparation tank 13, mother liquor buffer tank 1, slurry buffer tank 4, flocculant tank 14, overflow buffer tank 7 and re-slurry tank 8, the mixer 2 is an SK type static mixer, and the filter press 9 is a plate and frame filter press.

[0026] Example 2

[0027] Example 2 provides a wastewater defluorination device, which is basically the same in structure as that in Example 1, except that the specifications of each structure in this example are shown in Table 1:

[0028] Table 1

[0029] .

[0030] Example 3

[0031] See Figure 1Example 3 provides a phosphoric acid production system, which includes a phosphoric acid production unit, a filtration unit (see the description in application CN201910851385.5 for details), a tail gas treatment unit, a phosphogypsum storage tank, a sodium fluoride preparation unit (see the descriptions in application CN201210287774.8, 201210446052.2, or 202221023437.3 for details), and a wastewater defluorination unit as disclosed in Example 1 or 2. The phosphoric acid production unit (including a slurry preparation structure, a beneficiation structure, and an extraction structure, etc.) is connected to the filtration unit via pipelines. The filter residue outlet of the filtration unit (after reslurrying) is connected to the phosphogypsum storage tank via pipelines. The tail gas outlet of the phosphoric acid production unit (outputting silicon- and fluorine-containing tail gas) is connected to the tail gas treatment unit via pipelines. The washing liquid outlet of the tail gas treatment unit is connected to the sodium fluoride preparation unit via pipelines.

[0032] In this patent, pumps, flow meters, or valves may be installed on the pipelines between the various structures as needed.

[0033] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A wastewater defluorination device, characterized in that, The system includes a mother liquor buffer tank (1), a lime slurry supply structure, a mixer (2), a homogenizing reactor (3), a slurry buffer tank (4), a mixing tank (5), a thickener (6), a flocculant tank (14), an overflow buffer tank (7), a reslurry tank (8), a filter press (9), and a filtrate buffer tank (10). The mother liquor buffer tank (1) and the lime slurry supply structure are connected to the inlet of the mixer (2) via pipelines. The outlet of the mixer (2), the homogenizing reactor (3), the slurry buffer tank (4), the mixing tank (5), and the thickener (6) are connected sequentially via pipelines. The flocculant tank (14) is connected to the mixer via a pipeline. The thickener (6) is connected to the overflow buffer tank (7) via a pipeline, and its underflow outlet is connected to the re-slurry tank (8) via a pipeline. The filter press (9) is connected to the overflow buffer tank (7) via a pipeline, and its filtrate outlet is connected to the filtrate buffer tank (10) via a pipeline. Its filter residue outlet is connected to the re-slurry tank (8). The filtrate buffer tank (10) is connected to the re-slurry tank (8), the lime slurry preparation tank (13) of the lime slurry supply structure, the three-wash water tank of the phosphoric acid filtration device, and the salt tank of the sodium fluoride preparation device via a pipeline. The re-slurry tank (8) is connected to the phosphogypsum storage tank via a pipeline.

2. The wastewater defluorination device according to claim 1, characterized in that, The lime slurry supply structure includes a lime storage tank (11), a lime slurry preparation tank (13), and a lime screw feeder (12). The lime storage tank (11) is equipped with a star-shaped feed valve at the bottom outlet and is connected to the lime slurry preparation tank (13) through the lime screw feeder (12). The lime slurry preparation tank (13) is connected to the feed inlet of the mixer (2) through a pipeline. The filtrate buffer tank (10) is connected to the lime slurry preparation tank (13) through a pipeline.

3. The wastewater defluorination device according to claim 2, characterized in that, The mother liquor buffer tank (1) is connected to the inlet of the mixer (2) via a pipeline with a mother liquor delivery pump (15). The lime slurry preparation tank (13) is connected to the inlet of the mixer (2) via a pipeline with a lime slurry feed pump (16). The slurry buffer tank (4) is lower than the homogenizing reactor (3) and is connected to the mixing tank (5) via a pipeline with a slurry feed pump (17). The flocculant tank (14) is connected to the mixing tank (5) via a pipeline with a flocculant feed pump (20). The mixing tank (5) The overflow buffer tank (7) is higher than the thickener (6), and the overflow buffer tank (7) is lower than the overflow weir of the thickener (6) and is connected to the feed inlet of the filter press (9) through a pipeline with a filter press feed pump (18). The reslurry tank (8) is lower than the thickener (6) and the filter press (9) and is located directly below the filter press (9). The filtrate buffer tank (10) is lower than the filter press (9) and is connected to the reslurry tank (8), lime slurry preparation tank (13), three-wash water tank and salt dissolving tank through a pipeline with a clear liquid transfer pump (19) and a valve group.

4. The wastewater defluorination device according to claim 2, characterized in that, Agitators are provided in the lime slurry preparation tank (13), mother liquor buffer tank (1), slurry buffer tank (4), flocculant tank (14), overflow buffer tank (7) and reslurry tank (8). The mixer (2) is an SK type static mixer, and the filter press (9) is a plate and frame filter press.

5. The wastewater defluorination device according to claim 2, characterized in that, The specifications of the mother liquor buffer tank (1) are Φ4000mm*h3200mm, the specifications of the mixer (2) are Φ133mm*l1000mm, the specifications of the homogenizing reactor (3) are Φ1500mm*h5000mm, the specifications of the slurry buffer tank (4) are Φ4000mm*h3200mm, the specifications of the mixing tank (5) are Φ1500mm*h2000mm, the specifications of the overflow buffer tank (7) are Φ3600mm*h3200mm, the specifications of the re-slurry tank (8) are Φ2400mm*h2000mm, the filtration area of ​​the filter press (9) is 100㎡, the specifications of the filtrate buffer tank (10) are Φ3600mm*h3200mm, and the specifications of the lime slurry preparation tank (13) are Φ3000mm*h2500mm.

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