Fluorine gypsum residue gas washing waste acid recycling system

Abstract

The invention discloses a fluorine gypsum residue gas washing waste acid recycling system which comprises an absorption tower, a lower-section circulating tank, a lower-section circulating pump, an upper-section circulating tank, an upper-section spraying pump, a side line treatment unit, an acid regeneration separation unit and a fluorine resource recycling unit. A gas-liquid distribution isolation structure is arranged between the lower-section trapping region and the upper-section fine absorption region for receiving upper-section backflow and guiding the upper-section backflow back to the upper-section circulating tank; and the upper-section circulating tank is provided with an overflow port for reflowing to the lower-section circulating tank. A bypass side line is arranged at an outlet of the lower-section circulating pump, solids are removed through a cyclone separator and a self-cleaning filter, and then the obtained regenerated acid enters a diffusion dialysis membrane, so that regenerated acid is recycled for upper-section spraying and salt-rich liquid; a salt-rich solution enters a precipitation reaction tank, a calcium source is added to generate calcium fluoride, a solid product is obtained through centrifugal solid-liquid separation, and a mother solution is reused in a lower-section circulating tank; and the rotational flow underflow, the filtering sewage and the lower-section sewage converge into a sludge discharge header pipe. The system can realize stable purification of slag gas, reduce discharge of waste acid and recover fluorine resources.

Description

Technical Field

[0001] This invention relates to the field of fluorine-containing tail gas scrubbing and absorption and waste acid resource recovery and utilization technology, specifically to a fluorinated gypsum slag gas scrubbing waste acid recovery and utilization system. Background Technology

[0002] Fluoropyrogypsum slag is usually a by-product of anhydrous hydrogen fluoride production lines. During the transportation, temporary storage, and filling (loading) of gypsum, gypsum dust carries acidic fluorine-containing components to form slag gas. This slag gas is characterized by strong corrosiveness, high dust content, and significant fluctuations in operating conditions, and requires purification through washing and absorption to achieve compliant emissions.

[0003] In existing projects, spray absorption towers are often used to directly wash and absorb the aforementioned slag gas. A circulating spray loop is formed through a circulating tank and a circulating pump, allowing the absorbent liquid to be reused to improve absorption efficiency. However, under direct washing and absorption conditions, solid particles such as gypsum powder entrained in the slag gas, as well as dissolved salt impurities, will enter and gradually accumulate in the circulating absorbent liquid. This leads to an increase in the solid load and salt load of the circulating liquid, which in turn causes problems such as nozzle wear or blockage, increased pressure drop in the demister, and scaling on the tower and pipelines. This results in fluctuations in purification effect, frequent maintenance and cleaning, and even the need for shutdown, affecting the continuous and stable operation of the system.

[0004] On the other hand, the absorbent obtained after washing and absorption is usually an acidic fluoride-containing absorbent, which, in addition to the usable acidic and fluoride components, also contains solid dust and various impurity ions. Current practices often involve direct reuse after sedimentation or simple solid-liquid separation, or maintaining system operation through periodic discharge and replenishment of water and acid. This approach is insufficient to fundamentally suppress the accumulation of salts and impurities, resulting in large volumes of waste acid and high treatment costs. Furthermore, the usable acid and fluoride resources in the absorbent are difficult to effectively separate and recover, typically ending up in subsequent neutralization treatment as fluoride-containing wastewater or fluoride-containing sludge, leading to resource waste and the risk of secondary pollution. Summary of the Invention

[0005] This invention proposes a waste acid recovery and utilization system for fluorogypsum sludge gas scrubbing. The system aims to ensure stable tail gas purification while achieving continuous stripping of solid impurities and controlled transfer of salt load in the circulating absorbent. It also regenerates and reuses acidic components in the absorbent and recovers fluorine-rich streams, thereby reducing the risk of scaling and clogging and minimizing waste acid emissions. This improves the system's continuous operation capability and fluorine resource utilization efficiency. The technical solution adopted is as follows: A waste acid recovery and utilization system for fluorogypsum sludge gas scrubbing includes an absorption tower, a lower circulation tank, a lower circulation pump, an upper circulation tank, an upper spray pump, a side-stream treatment unit, an acid regeneration and separation unit, and a fluorine resource recovery unit. The absorption tower is equipped with a slag gas inlet and a purified gas outlet. The absorption tower is divided into a lower collection zone and an upper fine absorption zone from bottom to top. The lower collection zone is equipped with a lower spray assembly, the upper fine absorption zone is equipped with an upper spray assembly, and a demister is installed at the purified gas outlet. The absorption tower is provided with a gas-liquid distribution isolation structure between the lower collection zone and the upper fine absorption zone. The gas-liquid distribution isolation structure is used to receive the upper spray return liquid and allow slag gas to pass through into the upper fine absorption zone. The gas-liquid distribution isolation structure is connected to the upper circulation tank. The lower circulation tank is connected to the bottom of the lower collection area, the suction port of the lower circulation pump is connected to the lower circulation tank, and the outlet of the lower circulation pump is connected to the lower spray assembly through the lower spray pipeline to form a lower circulation spray circuit. The suction inlet of the upper spray pump is connected to the upper circulation tank, and the outlet of the upper spray pump is connected to the upper spray assembly through the upper spray pipeline to form an upper circulation spray circuit. The inlet of the side-stream treatment unit is connected to the outlet of the lower circulation pump via a bypass pipe to extract a portion of the lower circulation absorbent as a side stream. The outlet of the side-stream treatment unit is connected to the inlet of the acid regeneration separation unit. The acid regeneration separation unit is equipped with a regenerated acid outlet and a salt-rich solution outlet. The regenerated acid outlet is connected to the upper circulation tank to provide regenerated acid to the upper circulation spray circuit. The salt-rich solution outlet is connected to the fluorine resource recovery unit. The fluorine resource recovery unit is used to recover fluorine resources from salt-rich solutions and is equipped with a mother liquor reuse outlet, which is connected to the lower circulation tank.

[0006] Furthermore, the gas-liquid distribution isolation structure includes a liquid collection tray with vent holes and a chimney cap above the vent holes; the liquid collection tray is provided with a liquid guide port and is connected to the upper circulation tank through a liquid guide pipe.

[0007] Furthermore, the side-line treatment unit sequentially includes a hydrocyclone separator and a self-cleaning filter. The inlet end of the hydrocyclone separator is connected to the bypass pipe, the overflow port of the hydrocyclone separator is connected to the inlet end of the self-cleaning filter, the underflow port of the hydrocyclone separator is connected to the sludge discharge main pipe, and the sewage outlet of the self-cleaning filter is connected to the sludge discharge main pipe.

[0008] Furthermore, the acid regeneration separation unit includes a diffusion dialysis membrane, the feed liquid side inlet of the diffusion dialysis membrane is connected to the outlet end of the self-cleaning filter, the feed liquid side inlet of the diffusion dialysis membrane is connected to the outlet end of the side-line treatment unit, the feed liquid side outlet is the salt-rich solution outlet; the dialysis water side outlet of the diffusion dialysis membrane is the regenerated acid outlet.

[0009] Furthermore, the upper circulation tank is provided with an overflow port, which is connected to the lower circulation tank through an overflow pipe, so that when the liquid volume of the upper circulation spray circuit exceeds the set liquid level, it flows back to the lower circulation spray circuit.

[0010] Furthermore, the fluorine resource recovery unit includes a precipitation reaction tank, a calcium source dosing device, and a solid-liquid separation device. The inlet of the precipitation reaction tank is connected to the outlet of the salt-rich solution. The calcium source dosing device is used to add calcium source to the precipitation reaction tank to generate calcium fluoride precipitate. The solid-liquid separation device is used to separate the calcium fluoride solid product from the mother liquor. The mother liquor reuse outlet is connected to the liquid phase outlet of the solid-liquid separation device.

[0011] Furthermore, the calcium source dosing device includes a lime slurry storage tank and a metering pump. The precipitation reaction tank is equipped with an online pH detection instrument, and the metering pump adjusts the calcium source dosing amount according to the signal from the online pH detection instrument.

[0012] Furthermore, the solid-liquid separation device is a centrifuge.

[0013] Furthermore, the lower circulation tank is provided with a drain outlet, and a drain valve is installed on the drain outlet. The drain outlet is connected to the sludge discharge main pipe, and the drain valve is installed on the drain outlet for controlled discharge of the lower circulation liquid.

[0014] Furthermore, the demister is a two-stage demister structure, including a baffle demister layer and a wire mesh demister layer, and differential pressure monitoring points are set before and after the demister to monitor entrainment and blockage conditions.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves independent collection and return of the upper reflux liquid by setting up a lower collection zone and an upper fine absorption zone in the same absorption tower, and by cooperating with a gas-liquid distribution isolation structure. This allows the lower circuit to bear the load of dust entrained in the slag gas, while the upper circuit uses regenerated acid for fine absorption. This reduces the probability of the upper nozzles and demisters being contaminated by solids and salts, thereby improving the stability of the exhaust gas purification effect.

[0016] This invention continuously strips solid particles from the circulating absorbent by setting a bypass side line at the outlet of the lower circulating pump and configuring a combination of cyclone separation and self-cleaning filtration, thereby reducing the accumulation of solids in the circulating system, reducing the risk of clogging and scaling of nozzles, pipelines and demisters, improving the system's continuous operation capability and reducing the frequency of downtime for cleaning.

[0017] This invention achieves the separation of acidic components and salts in the absorbent through diffusion dialysis, allowing the regenerated acid to be reused in the upper spray stage to maintain the absorption driving force. At the same time, the salt-rich solution is concentrated and discharged for subsequent resource recovery, thereby ensuring absorption efficiency while inhibiting the unlimited accumulation of salt load in the circulation loop, reducing waste acid emissions and treatment costs.

[0018] The salt-rich solution enters the fluorine resource recovery unit, where calcium fluoride is generated through precipitation and then separated into solid and liquid products. The mother liquor is reused in the next circulation tank, which not only realizes the recovery and utilization of fluorine-containing resources, but also reduces the risk of fluorine-containing wastewater discharge and secondary pollution. Attached Figure Description

[0019] Figure 1 This is a system schematic diagram according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the absorption tower in an embodiment of the present invention.

[0020] Among them, 1-Absorption tower; 2-Lower circulation tank; 21-Drain outlet; 3-Lower circulation pump; 4-Upper circulation tank; 5-Upper spray pump; 6-Side line treatment unit; 61-Cyclone separator; 62-Self-cleaning filter; 7-Acid regeneration separation unit; 71-Rich salt solution outlet; 72-Regenerated acid outlet; 8-Fluorine resource recovery unit; 81-Precipitation reaction tank; 82-Calcium source dosing device; 83-Solid-liquid separation device; 9-Overflow outlet; 11-Slag gas inlet; 12-Purified gas outlet; 13-Lower collection zone; 131-Lower spray assembly; 14-Upper fine absorption zone; 141-Upper spray assembly; 15-Demister; 16-Gas-liquid distribution isolation structure; 161-Collection tray; 162-Ventilation hole; 163-Chimney cap. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments. It should be understood that the present invention is not limited to the parameters and conditions listed in the following embodiments. Without departing from the essence of the technical solution of the present invention, those skilled in the art can make appropriate adjustments or equivalent substitutions to the process conditions, all of which should fall within the protection scope of the present invention.

[0022] Example 1: Reference Figures 1-2This embodiment provides a waste acid recovery and utilization system for fluorogypsum slag gas scrubbing, including an absorption tower 1, a lower circulation tank 2, a lower circulation pump 3, an upper circulation tank 4, an upper spray pump 5, a side-stream treatment unit 6, an acid regeneration and separation unit 7, and a fluorine resource recovery unit 8. The absorption tower 1 is provided with a slag gas inlet 11 and a purified gas outlet 12. The tower is divided into a lower collection zone 13 and an upper fine absorption zone 14 from bottom to top. The lower collection zone 13 is equipped with a lower spray assembly 131, and the upper fine absorption zone 14 is equipped with an upper spray assembly 141. A demister 15 is provided at the purified gas outlet 12. Preferably, in this embodiment, the demister 15 is a two-stage demister structure, including a baffle demister layer and a wire mesh demister layer, to reduce liquid entrainment in the purified gas and improve exhaust stability. A gas-liquid distribution isolation structure 16 is provided between the lower collection zone 13 and the upper fine absorption zone 14. The gas-liquid distribution isolation structure 16 includes a liquid collection plate 161 with vent holes 162. A chimney cap 163 is provided above the vent holes 162 to receive the upper spray return liquid and allow slag gas to pass through into the upper fine absorption zone 14. The return liquid after the upper spray falls into the liquid collection plate 161 and returns to the upper circulation tank 4 through the liquid guide, thereby forming an upper circulation spray loop.

[0023] The lower circulation tank 2 is connected to the bottom of the lower collection zone 13 of the absorption tower 1, and is used to collect the lower washing liquid. The suction port of the lower circulation pump 3 is connected to the lower circulation tank 2, and its outlet is connected to the lower spray assembly 131 through the lower spray pipeline, thus forming a lower circulation spray circuit. The upper circulation tank 4 is connected to the gas-liquid distribution isolation structure 16, and is used to receive the upper return liquid collected by the collection tray 161. The suction port of the upper spray pump 5 is connected to the upper circulation tank 4, and its outlet is connected to the upper spray assembly 141 through the upper spray pipeline, thus forming an upper circulation spray circuit. To achieve liquid balance between the upper and lower circuits, the upper circulation tank 4 is equipped with an overflow port 9, which is connected to the lower circulation tank 2 through an overflow pipeline. When the liquid level in the upper circulation tank 4 exceeds the set height, some of the upper circulation liquid enters the lower circulation tank 2 through the overflow port 9.

[0024] The side-stream treatment unit 6 is used for continuous purification of the lower-stage circulating absorbent. Its inlet is connected to the outlet pipe of the lower-stage circulating pump 3 via a bypass pipe to draw a portion of the circulating absorbent from the lower-stage circulating loop as a side-stream. The side-stream treatment unit 6 includes a hydrocyclone separator 61 and a self-cleaning filter 62. The hydrocyclone separator 61 is used to preferentially separate coarser solid particles in the side-stream, and its overflow enters the self-cleaning filter 62. The self-cleaning filter 62 further traps fine particles and suspended solids, reducing the solid load of the side-stream effluent and facilitating its entry into the subsequent acid regeneration separation unit 7. The underflow from the hydrocyclone separator 61 and the sludge from the self-cleaning filter 62 both flow into the sludge discharge main pipe. At the same time, the lower-stage circulating tank 2 is equipped with a sludge discharge port 21, which is connected to the sludge discharge main pipe. The lower-stage circulating liquid is discharged in a controlled manner through a sludge discharge valve to centrally remove the solids and part of the salt load accumulated during system operation, achieving controlled transfer of salt and impurities.

[0025] The acid regeneration separation unit 7 is used for acid / salt separation of the side-stream purification solution. In this embodiment, the acid regeneration separation unit 7 includes a diffusion dialysis membrane. The feed side (acid side) inlet of the diffusion dialysis membrane is connected to the outlet of the side-stream treatment unit 6, and the feed side (acid side) outlet forms a salt-rich solution outlet 71; the dialysis water side (water side) outlet of the diffusion dialysis membrane forms a regenerated acid outlet 72. During operation, after the side-stream purification solution enters the feed side of the diffusion dialysis membrane, the acidic components migrate to the dialysis water side under the selective action of the membrane, so that the dialysis water side obtains regenerated acid that can be used for spray absorption. The regenerated acid is returned to the upper circulation tank 4 through the regenerated acid outlet 72 as the source of spray liquid for the upper fine absorption zone 14; while the feed side outlet obtains a relatively salt-rich solution, which enters the fluoride resource recovery unit 8 through the salt-rich solution outlet 71.

[0026] The fluorine resource recovery unit 8 includes a precipitation reaction tank 81, a calcium source dosing device 82, and a solid-liquid separation device 83. The salt-rich solution enters the precipitation reaction tank 81 through the salt-rich solution outlet 71. The calcium source dosing device 82 adds calcium source to the precipitation reaction tank 81, causing the fluorine-containing components in the salt-rich solution to react with the calcium source to form calcium fluoride precipitate. Preferably, in this embodiment, the calcium source dosing device 82 includes a lime slurry storage tank and a metering pump. The precipitation reaction tank 81 is equipped with an online pH monitoring instrument. The metering pump adjusts the lime slurry dosing amount according to the signal from the online pH monitoring instrument, thereby maintaining suitable reaction conditions for calcium fluoride formation and sedimentation in the precipitation reaction tank 81. The slurry after the precipitation reaction enters the solid-liquid separation device 83 for separation to obtain solid calcium fluoride product. Preferably, in this embodiment, the solid-liquid separation device 83 uses a centrifuge for solid-liquid separation to improve the separation efficiency of the solid product and the continuous operation capability. The liquid phase of the solid-liquid separation device 83 is recycled as mother liquor to the lower circulation tank 2, enabling closed-loop recycling of system liquid and materials and reducing external discharge.

[0027] The working process of this embodiment is as follows: The slag gas containing dust, acid mist and fluorinated acid components enters the lower collection zone 13 of the absorption tower 1 through the slag gas inlet 11. Under the action of the lower spray assembly 131, it comes into full contact with the lower circulating liquid. The dust particles are wetted and captured and enter the liquid phase. The acid mist droplets are washed and incorporated into the circulating liquid. Some of the fluorinated acid components are absorbed, so that the slag gas completes the main load collection and washing in the lower section. The gas continues to rise and enters the upper fine absorption zone 14 through the vent 162 of the gas-liquid distribution isolation structure 16. Under the action of the regenerated acid sprayed by the upper spray assembly 141, it is further finely absorbed and polished. The fine droplets carried by the gas are removed at the demister 15 and discharged from the purified gas outlet 12. Meanwhile, the lower circulation loop undertakes "dirt-resistant capture". Its side stream, after being continuously stripped of solids by the hydrocyclone separator 61 and the self-cleaning filter 62, enters the diffusion dialysis membrane to achieve the separation of regenerated acid and salt-rich solution: the regenerated acid returns to the upper circulation tank 4 through the regenerated acid outlet 72 for fine absorption, and the salt-rich solution enters the precipitation reaction tank 81 through the salt-rich solution outlet 71 and generates calcium fluoride precipitate under the action of the calcium source dosing device 82. The precipitate is separated by the solid-liquid separation device 83 to obtain calcium fluoride solid product, and the mother liquor is recycled to the lower circulation tank 2. Through the centralized discharge of the sludge discharge main pipe and the controlled discharge of the lower circulation tank sludge outlet 21, the solids and part of the salt load are effectively removed, thereby maintaining the long-term stable operation of the system.

Claims

1. A system for recovering and utilizing waste acid from fluorogypsum slag gas scrubbing, characterized in that, It includes an absorption tower (1), a lower circulation tank (2), a lower circulation pump (3), an upper circulation tank (4), an upper spray pump (5), a side-stream treatment unit (6), an acid regeneration and separation unit (7), and a fluorine resource recovery unit (8). The absorption tower (1) is provided with a slag gas inlet (11) and a purified gas outlet (12). The absorption tower (1) is formed from bottom to top into a lower collection zone (13) and an upper fine absorption zone (14). The lower collection zone (13) is provided with a lower spray assembly (131), and the upper fine absorption zone (14) is provided with an upper spray assembly (141). A demister (15) is provided at the purified gas outlet (12). The absorption tower (1) has a gas-liquid distribution isolation structure (16) between the lower collection zone (13) and the upper fine absorption zone (14). The gas-liquid distribution isolation structure (16) is used to receive the upper spray return liquid and allow slag gas to pass through into the upper fine absorption zone (14). The gas-liquid distribution isolation structure (16) is connected to the upper circulation tank (4). The lower circulation tank (2) is connected to the bottom of the lower collection area (13), the suction port of the lower circulation pump (3) is connected to the lower circulation tank (2), and the outlet of the lower circulation pump (3) is connected to the lower spray assembly (131) through the lower spray pipeline to form a lower circulation spray circuit. The suction port of the upper spray pump (5) is connected to the upper circulation tank (4), and the outlet of the upper spray pump (5) is connected to the upper spray assembly (141) through the upper spray pipeline to form an upper circulation spray circuit. The inlet of the side-stream processing unit (6) is connected to the outlet of the lower circulation pump (3) via a bypass pipe to extract a portion of the lower circulation absorbent as a side-stream. The outlet of the side-stream processing unit (6) is connected to the inlet of the acid regeneration separation unit (7). The acid regeneration separation unit (7) is provided with a regenerated acid outlet (72) and a salt-rich solution outlet (71). The regenerated acid outlet (72) is connected to the upper circulation tank (4) to provide regenerated acid to the upper circulation spray circuit. The salt-rich solution outlet (71) is connected to the fluorine resource recovery unit (8). The fluorine resource recovery unit (8) is used to recover fluorine resources from salt-rich solution and is equipped with a mother liquor reuse outlet, which is connected to the lower circulation tank (2).

2. The system according to claim 1, characterized in that, The gas-liquid distribution isolation structure (16) includes a liquid collection plate (161), a vent hole (162) is provided on the liquid collection plate (161), and a chimney cap (163) is provided above the vent hole (162); the liquid collection plate (161) is provided with a liquid guide port and is connected to the upper circulation tank (4) through a liquid guide pipe.

3. The system according to claim 1, characterized in that, The side-line treatment unit (6) includes a hydrocyclone separator (61) and a self-cleaning filter (62) in sequence. The inlet of the hydrocyclone separator (61) is connected to the bypass pipe, the overflow port of the hydrocyclone separator (61) is connected to the inlet of the self-cleaning filter (62), the underflow port of the hydrocyclone separator (61) is connected to the sludge discharge main pipe, and the sewage outlet of the self-cleaning filter (62) is connected to the sludge discharge main pipe.

4. The system according to claim 1, characterized in that, The acid regeneration separation unit (7) includes a diffusion dialysis membrane. The feed liquid side inlet of the diffusion dialysis membrane is connected to the outlet of the self-cleaning filter (62). The feed liquid side inlet of the diffusion dialysis membrane is connected to the outlet of the side-line treatment unit. The feed liquid side outlet is the salt-rich solution outlet (71). The dialysis water side outlet of the diffusion dialysis membrane is the regenerated acid outlet (72).

5. The system according to claim 1, characterized in that, The upper circulation tank (4) is provided with an overflow port (9), which is connected to the lower circulation tank (2) through an overflow pipe so that when the liquid volume of the upper circulation spray circuit exceeds the set liquid level, it flows back to the lower circulation spray circuit.

6. The system according to claim 1, characterized in that, The fluorine resource recovery unit (8) includes a precipitation reaction tank (81), a calcium source addition device (82), and a solid-liquid separation device (83). The inlet of the precipitation reaction tank (81) is connected to the outlet of the salt-rich solution. The calcium source addition device (82) is used to add calcium source to the precipitation reaction tank (81) to generate calcium fluoride precipitate. The solid-liquid separation device (83) is used to separate the calcium fluoride solid product and the mother liquor. The mother liquor recycling outlet is connected to the liquid phase outlet of the solid-liquid separation device (83).

7. The system according to claim 6, characterized in that, The calcium source dosing device (82) includes a lime slurry storage tank and a metering pump. The precipitation reaction tank (81) is equipped with an online pH detection instrument. The metering pump adjusts the calcium source dosing amount according to the signal from the online pH detection instrument.

8. The system according to claim 6, characterized in that, The solid-liquid separation device (83) is a centrifuge.

9. The system according to claim 1, characterized in that, The lower circulation tank (2) is provided with a drain outlet (21), which is connected to the sludge discharge main pipe, and a drain valve is provided on the drain outlet (21).

10. The system according to claim 1, characterized in that, The demister (15) is a two-stage demister structure, including a baffle demister layer and a wire mesh demister layer.

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