A fluorine-containing wastewater treatment system

Abstract

The utility model relates to a kind of fluorine-containing wastewater treatment systems, belong to fluorine-containing wastewater treatment technical field, the utility model includes crystallization fluidized bed and carbon dioxide blast device;Crystallization fluidized bed includes the flow guide cylinder of concentric setting, crystallization cylinder and outer tube;The upper end of flow guide cylinder is inserted into crystallization cylinder;Carbon dioxide aeration device includes carbon dioxide gas supply system and gas distributor;Carbon dioxide gas supply system and gas distributor are connected by carbon dioxide gas supply pipe between;Gas distributor is set in the bottom of flow guide cylinder;The utility model can be realized using carbon dioxide gas adjustment sewage's acid-base adjustment, realizes the stable control of sewage pH, can effectively intervene the growth of calcium fluoride crystallization, increase calcium fluoride crystalline particle, reduce the separation difficulty of calcium fluoride;Meanwhile, the intervention of carbon dioxide to calcium fluoride crystallization process, calcium fluoride also can reduce or avoid the wrapping of calcium hydroxide, reduce the dosage of defluorination agent, and improve the purity of calcium fluoride crystallization.

Description

Technical Field

[0001] This utility model belongs to the field of fluoride-containing wastewater treatment technology, specifically, it relates to a fluoride-containing wastewater treatment system. Background Technology

[0002] Fluoride-containing wastewater typically requires chemical precipitation and coagulation-sedimentation methods to remove fluoride ions. The most commonly used precipitant in chemical precipitation is calcium salts, such as lime, calcium chloride, calcium carbonate, and carbide slag. Calcium salts are effective at removing fluoride, but in practice, a drawback is that the calcium fluoride formed by the reaction of calcium salts and fluoride tends to coat the surface of calcium hydroxide, hindering the complete reaction. This results in high calcium salt dosages (often 3-4 times the theoretical value), high sludge yield with complex composition, low calcium fluoride content, and low reuse value. Furthermore, effluent from simple chemical precipitation often fails to meet discharge requirements, generally necessitating additional deep defluorination, which increases production and operating costs.

[0003] Studies have shown that using crystallization fluidized bed equipment can improve the defluorination effect of chemical precipitation. For example, patent CN101941752B discloses a method and device for treating fluoride-containing wastewater, proposing a process idea of ​​using a solid-liquid two-phase fluidized bed as a crystallization reactor and calcium chloride as a seed crystal to extract calcium fluoride from fluoride-containing wastewater. This method is mainly aimed at fluoride-containing wastewater from industries such as chemical engineering, non-ferrous metal smelting, glass, electronics, and photovoltaics. The pH of this type of wastewater is mostly between 1 and 2. Before entering the fluidized bed for calcium fluoride crystallization and precipitation, a large amount of NaOH or KOH reagents need to be added for neutralization, which is costly. In addition, the crystallization fluidized bed usually uses mechanical stirring to make the calcium fluoride crystal nuclei fluidized. During the mechanical stirring process, the crystal particles collide with each other, which makes it impossible for the crystals to grow stably, affecting the subsequent solid-liquid separation and screening process and reducing the production efficiency of the equipment. Furthermore, in the existing technology, when adding calcium salt defluorinating agents, the pH value of the wastewater fluctuates, resulting in small calcium fluoride crystals that easily encapsulate the calcium salt defluorinating agent, leading to an increase in the amount of defluorinating agent used, low purity of calcium fluoride crystals, and difficulty in recycling. Summary of the Invention

[0004] To overcome the problems existing in the background technology, this utility model provides a fluoride-containing wastewater treatment system. By setting a carbon dioxide aeration device at the bottom of the guide tube of the crystallizing fluidized bed, carbon dioxide gas is introduced into the crystallizing fluidized bed at the same time as defluorination, which can effectively improve the particle size of calcium fluoride crystals and reduce the consumption of defluorinating agent.

[0005] To achieve the above objectives, this utility model is implemented through the following technical solution:

[0006] The fluoride-containing wastewater treatment system includes a crystallizing fluidized bed and a carbon dioxide aeration device; the crystallizing fluidized bed includes a concentrically arranged guide tube, a crystallizing tube, and an outer tube; the upper end of the guide tube is inserted into the crystallizing tube; the carbon dioxide aeration device includes a carbon dioxide supply system and a gas distributor; the carbon dioxide supply system and the gas distributor are connected by a carbon dioxide supply pipe; the gas distributor is located at the bottom of the guide tube.

[0007] Preferably, the fluoride-containing wastewater treatment system further includes a defluorinating agent addition device; the defluorinating agent addition device includes a defluorinating agent storage tank, a defluorinating agent delivery pump, and a defluorinating agent delivery pipe; the defluorinating agent storage tank is connected to a guide cylinder through the defluorinating agent delivery pump and the defluorinating agent delivery pipe; a flow meter is provided on the defluorinating agent delivery pipe.

[0008] Preferably, the fluoride-containing wastewater treatment system further includes a seed crystal addition device; the seed crystal addition device includes a seed crystal storage tank, a seed crystal delivery pump, and a seed crystal delivery pipe; the seed crystal storage tank is connected to a guide tube through the seed crystal delivery pump and the seed crystal delivery pipe; and a flow meter is provided on the seed crystal delivery pipe.

[0009] Preferably, the gas distributor is made of 316L stainless steel sintered plate, with aeration holes having a diameter of 0.1-0.5mm and an opening ratio of 1-3%.

[0010] Preferably, the carbon dioxide supply pipe is equipped with a flow regulating valve, a pressure gauge, and a flow meter.

[0011] Preferably, the guide tube is equipped with an online pH meter and a temperature monitoring instrument.

[0012] Preferably, the bottom of the crystallization cylinder is conical, and a crystallization discharge port is provided at the bottom of the cone; a sewage inlet is provided at the bottom of the guide cylinder.

[0013] Preferably, the top of the crystallization cylinder is provided with an exhaust port.

[0014] Preferably, the top of the outer cylinder is provided with an overflow weir, and the overflow weir is provided with a drainage outlet.

[0015] The beneficial effects of this utility model are:

[0016] This invention introduces carbon dioxide into the fluidized bed by setting a gas distributor at the bottom of the guide tube. This eliminates the need to add large amounts of acid-base adjusting reagents to adjust the pH of the wastewater. The pH of the influent wastewater can be controlled at 12-13, which greatly reduces the amount of acidic agents such as hydrochloric acid or sulfuric acid required to neutralize alkaline wastewater, thereby reducing the increase of impurity ions in the wastewater caused by the addition of neutralizing agents.

[0017] This invention utilizes a gas distributor installed at the bottom of the guide tube of a crystallizing fluidized bed to introduce carbon dioxide into the bed, thereby achieving acid-base regulation of wastewater using carbon dioxide gas. This results in stable pH control of the wastewater, effectively interfering with the growth of calcium fluoride crystals, increasing the size of the calcium fluoride crystals, and reducing the difficulty of separating calcium fluoride. Simultaneously, the intervention of carbon dioxide in the calcium fluoride crystallization process can also reduce or prevent calcium fluoride from coating calcium hydroxide, reducing the amount of defluorinating agent required and improving the purity of the calcium fluoride crystals.

[0018] This invention effectively overcomes the problems of small calcium fluoride crystal particles and difficult separation in the existing crystallization fluidized bed defluorination process, reduces the cost of defluorination treatment, reduces the amount of acid-base neutralization reagent used, and achieves efficient and low-cost treatment of fluoride-containing wastewater. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model;

[0020] In the diagram, 1-guide tube, 2-crystallization tube, 3-outer tube, 4-carbon dioxide supply system, 5-gas distributor, 6-spiral guide plate, 7-exhaust port, 8-overflow weir, 9-drain outlet, 10-pH online detector, 11-defluorinating agent storage tank, 12-defluorinating agent transfer pump, 13-seed crystal storage tank, 14-seed crystal transfer pump, 15-flow regulating valve, 16-crystallization discharge port, 17-sewage inlet. Detailed Implementation

[0021] To make the objectives, technical solutions, and beneficial effects of this utility model clearer, the preferred embodiments of this utility model will be described in detail below with reference to the accompanying drawings, so as to facilitate the understanding of those skilled in the art.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "equipped with" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] like Figure 1 As shown, the fluoride-containing wastewater treatment system includes a crystallizing fluidized bed, a carbon dioxide aeration device, and a defluorinating agent addition device. The main improvement of this invention lies in the addition of a carbon dioxide aeration device to the existing crystallizing fluidized bed. By introducing carbon dioxide into the crystallizing fluidized bed, the crystallization process of calcium fluoride is interfered with, increasing the particle size of the calcium fluoride crystals and reducing the difficulty of separating the calcium fluoride crystals.

[0024] This invention can be implemented by introducing carbon dioxide into any existing solid-liquid two-phase crystallization fluidized bed, without limiting the specific structure of the crystallization fluidized bed. Furthermore, carbon dioxide can be introduced from the bottom of the guide tube 1 or the bottom of the crystallization tube 2, preferably from the bottom of the guide tube 1. An example of the crystallization fluidized bed structure in this embodiment is as follows:

[0025] The crystallization fluidized bed is cylindrical and includes a guide tube 1, a crystallization tube 2, and an outer tube 3 arranged concentrically. The upper end of the guide tube 1 is inserted into the crystallization tube 2, and a necessary material channel is left between the top of the guide tube 1 and the crystallization tube 2 (this channel is common knowledge of crystallization fluidized beds).

[0026] The guide tube 1 is equipped with an online pH meter 10 for monitoring the pH value of the wastewater online, so as to adjust the carbon dioxide flow rate in a timely manner and thus regulate the acidity or alkalinity of the wastewater. The crystallization tube 2 is also equipped with a temperature monitoring instrument for monitoring the wastewater temperature. This invention can achieve fluoride removal at a lower temperature, so the thermometer is not a necessary instrument.

[0027] The bottom of the crystallization cylinder 2 is conical, and a crystallization discharge port 16 is opened at the bottom of the cone. A sewage inlet 17 is opened at the bottom of the guide cylinder 1, and the sewage is sent to the crystallization fluidized bed for defluorination reaction from the sewage inlet 17.

[0028] The top of the crystallization cylinder 2 is provided with an exhaust port 7 to allow unreacted carbon dioxide to be discharged in a timely manner.

[0029] Preferably, the top of the outer cylinder 3 is provided with an overflow weir 8, and the overflow weir 8 is provided with a drainage outlet 9.

[0030] The carbon dioxide aeration device includes a carbon dioxide supply system 4 and a gas distributor 5. The carbon dioxide supply system 4 and the gas distributor 5 are connected by a carbon dioxide supply pipe; the carbon dioxide supply pipe is equipped with a flow regulating valve 15, a supply fan, a pressure gauge, and a flow meter to control the carbon dioxide inlet pressure and inlet volume. The gas distributor 5 is located at the bottom of the guide tube 1.

[0031] The defluorinating agent addition device includes a defluorinating agent storage tank 11, a defluorinating agent delivery pump 12, and a defluorinating agent delivery pipe. The defluorinating agent storage tank 11 is connected to the guide cylinder 1 through the defluorinating agent delivery pump 12 and the defluorinating agent delivery pipe. A flow meter is installed on the defluorinating agent delivery pipe to measure the amount of seed crystals added.

[0032] As a preferred embodiment, this utility model also includes a seed crystal adding device, which includes a seed crystal storage tank 13, a seed crystal delivery pump 14, and a seed crystal delivery pipe. The seed crystal storage tank 13 is connected to the guide cylinder 1 through the seed crystal delivery pump 14 and the seed crystal delivery pipe, and a flow meter is provided on the seed crystal delivery pipe. By adding seed crystals into the guide cylinder 1 through the seed crystal adding device, the crystallization rate is improved and the particle size of the crystals is further increased.

[0033] As a preferred option, the gas distributor 5 is made of 316L stainless steel sintered plate, with aeration holes having a diameter of 0.1-0.5mm and an opening ratio of 1-3%.

[0034] Application examples of this utility model:

[0035] A chemical industry wastewater with high concentration of alkaline fluoride has an fluoride content of 580 mg / L.

[0036] The wastewater was added to a crystallization fluidized bed with an influent pH of 13.1, an influent temperature of 24°C, a carbon dioxide supply system pressure of 0.25 MPa, and a carbon dioxide flow rate of 1.8 m³ / (m³·h). A 20% CaCl2 aqueous solution was used as the defluorinating agent, and the dosage was controlled at 1.3 times the theoretical value (molar ratio of calcium to fluoride ions in the wastewater).

[0037] For the first 45 minutes, control the wastewater pH to 9.0-9.5, start the calcium chloride dosing device, and continuously add defluorinating agent into the flow guide tube. After 45 minutes, control the wastewater pH to 7.8-9.0, add calcium fluoride seed crystals into the flow guide tube at a dosage of 0.8 g / L, and continuously purge with carbon dioxide to adjust or maintain the pH value throughout the entire reaction process. The entire reaction process is maintained for 2.5 hours.

[0038] After the reaction was completed, the crystals discharged from the crystal outlet were analyzed. The average particle size was 2.2 mm, the calcium fluoride purity was 90.4%, the effluent pH was 7.8, the fluoride content was 9.2 mg / L, and the fluoride removal rate was 98.41%. The effluent met the discharge requirements of the national standard GB30484-2013.

[0039] Under the same conditions, using a conventional crystallization fluidized bed (which can be understood as removing the carbon dioxide aeration device and spiral guide plate from the fluidized bed of this utility model, while retaining the agitator of the existing crystallization fluidized bed), the wastewater pH is first adjusted to 8.0±0.5 with hydrochloric acid, and the same amount of calcium chloride and seed crystals and crystallization reaction time are maintained. The effluent fluoride concentration is 15.5 mg / L, which does not meet the discharge standard and requires further treatment by a deep treatment module. The average size of the calcium fluoride particles is 1.1 mm, and the purity is 82.6%, resulting in low product utilization value.

[0040] Application results show that the device of this invention can obtain calcium fluoride crystals with larger particle size, and the calcium fluoride crystals are large in size, easy to separate, and have improved purity.

[0041] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of this utility model.

Claims

1. A fluoride-containing wastewater treatment system, characterized in that, It includes a crystallization fluidized bed and a carbon dioxide aeration device; the crystallization fluidized bed includes a guide tube (1), a crystallization tube (2) and an outer tube (3) arranged concentrically; the upper end of the guide tube (1) is inserted into the crystallization tube (2); the carbon dioxide aeration device includes a carbon dioxide supply system (4) and a gas distributor (5); the carbon dioxide supply system (4) and the gas distributor (5) are connected by a carbon dioxide supply pipe; the gas distributor (5) is located at the bottom of the guide tube (1).

2. The fluoride-containing wastewater treatment system according to claim 1, characterized in that, It also includes a defluorinating agent addition device; the defluorinating agent addition device includes a defluorinating agent storage tank (11), a defluorinating agent delivery pump (12) and a defluorinating agent delivery pipe; the defluorinating agent storage tank (11) is connected to the guide tube (1) through the defluorinating agent delivery pump (12) and the defluorinating agent delivery pipe; a flow meter is provided on the defluorinating agent delivery pipe.

3. The fluoride-containing wastewater treatment system according to claim 1, characterized in that, It also includes a seed crystal adding device; the seed crystal adding device includes a seed crystal storage tank (13), a seed crystal delivery pump (14) and a seed crystal delivery pipe; the seed crystal storage tank (13) is connected to the guide tube (1) through the seed crystal delivery pump (14) and the seed crystal delivery pipe; the seed crystal delivery pipe is equipped with a flow meter.

4. The fluoride-containing wastewater treatment system according to any one of claims 1 to 3, characterized in that, The gas distributor (5) is made of 316L stainless steel sintered plate, with aeration holes of 0.1-0.5mm in diameter and an opening rate of 1-3%.

5. The fluoride-containing wastewater treatment system according to any one of claims 1 to 3, characterized in that, The carbon dioxide supply pipe is equipped with a flow regulating valve (15), a pressure gauge and a flow meter.

6. The fluoride-containing wastewater treatment system according to any one of claims 1 to 3, characterized in that, The flow guide tube (1) is equipped with an online pH detector (10).

7. The fluoride-containing wastewater treatment system according to claim 1, characterized in that, The bottom of the crystallization cylinder (2) is conical, and a crystallization discharge port (16) is opened at the bottom of the conical crystallization cylinder (2); a sewage inlet (17) is opened at the bottom of the guide cylinder (1).

8. The fluoride-containing wastewater treatment system according to claim 1, characterized in that, The top of the crystallization cylinder (2) is provided with an exhaust hole (7).

9. The fluoride-containing wastewater treatment system according to claim 1, characterized in that, The top of the outer cylinder (3) is provided with an overflow weir (8), and a drainage outlet (9) is provided on the overflow weir (8).

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