阅读说明：本技术 低浓度含氟废水制备氟化铝的方法和设备 (Method and equipment for preparing aluminum fluoride from low-concentration fluorine-containing wastewater ) 是由 许新芳 李长明 刘正锋 于 2020-05-28 设计创作，主要内容包括：一种低浓度含氟废水制备氟化铝的方法,包括四级合成槽生产氟化铝步骤,四级合成槽生产氟化铝步骤具体为,将低浓度含氟洗涤废水依次通入采用串联方式连接的第一合成槽、第二合成槽、第三合成槽、第四合成槽,并在第一合成槽、第二合成槽、第三合成槽、第四合成槽内分别加入氢氧化铝,并控制相应的氢氟酸酸度,本发明方法中生产氟化铝与现有的气固反应生产氟化铝的工艺根本不同,其反应在液体态环境下进行,既能将低浓度含氟废水中的氟元素回收利用,得到附加值较高的氟化铝产品,还能回收氟化铝生产过程中产生的微小氟化铝颗粒物,可有效降低氟化铝生产成本,本发明还提供了一种实现低浓度含氟废水制备氟化铝的方法的设备。(A method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater comprises a step of producing aluminum fluoride by a four-stage synthesis tank, wherein the step of producing aluminum fluoride by the four-stage synthesis tank is specifically that low-concentration fluorine-containing washing wastewater is sequentially introduced into a first synthesis tank, a second synthesis tank, a third synthesis tank and a fourth synthesis tank which are connected in series, aluminum hydroxide is respectively added into the first synthesis tank, the second synthesis tank, the third synthesis tank and the fourth synthesis tank, and the acidity of corresponding hydrofluoric acid is controlled. The invention also provides equipment for realizing the method for preparing the aluminum fluoride from the low-concentration fluorine-containing wastewater.)

1. A method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater is characterized by comprising the following steps: the method comprises the steps of producing aluminum fluoride by a four-stage synthesis tank, wherein the step of producing aluminum fluoride by the four-stage synthesis tank specifically comprises the following steps:

introducing low-concentration fluorine-containing washing wastewater into a first synthesis tank, adding aluminum hydroxide into the first synthesis tank to form a first treatment waste liquid, stirring the first treatment waste liquid, and controlling the temperature of the first treatment waste liquid at 70-80 ℃;

overflowing the first treatment waste liquid in the first synthesis tank into a second synthesis tank, adding aluminum hydroxide into the second synthesis tank to form a second treatment waste liquid, stirring the second treatment waste liquid, and controlling the temperature of the second treatment waste liquid to be 70-80 ℃;

overflowing the second treatment waste liquid in the second synthesis tank into a third synthesis tank, adding aluminum hydroxide into the third synthesis tank to form a third treatment waste liquid, stirring the third treatment waste liquid, and controlling the temperature of the third treatment waste liquid to be 70-80 ℃;

overflowing the third treatment waste liquid in the third synthesis tank into a fourth synthesis tank, adding aluminum hydroxide into the fourth synthesis tank to form a fourth treatment waste liquid, stirring the fourth treatment waste liquid, controlling the temperature of the fourth treatment waste liquid to be 70-80 ℃, controlling the acidity of hydrofluoric acid to be 0.5g/L at the reaction end point of the fourth treatment waste liquid, discharging the fourth treatment waste liquid from the bottom of the fourth synthesis tank, feeding the fourth treatment waste liquid into a plate-and-frame filter, separating out mother liquid and filter cake, and feeding the filter cake into a flash evaporation dryer for drying to obtain aluminum fluoride.

2. The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claim 1, wherein the method comprises the following steps: the acidity of hydrofluoric acid at the end of the reaction of the first treated waste liquid is 5-10 g/L.

3. The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claim 1, wherein the method comprises the following steps: the acidity of the hydrofluoric acid at the end of the reaction of the second treated waste liquid is controlled to be 1-2 g/L.

4. The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claim 1, wherein the method comprises the following steps: the acidity of the hydrofluoric acid at the end of the reaction of the third treated waste liquid is controlled to be 0.5-1 g/L.

5. The method for producing aluminum fluoride from low-concentration fluorine-containing wastewater according to any one of claims 1 to 4, characterized in that: and methyl orange is adopted as a hydrofluoric acid acidity indicator in the first treated waste liquid, the second treated waste liquid, the third treated waste liquid and the fourth treated waste liquid.

6. The method for producing aluminum fluoride from low-concentration fluorine-containing wastewater according to any one of claims 1 to 4, characterized in that: the first, second, third and fourth treated waste liquids were controlled to 80 ℃.

7. The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claim 1, wherein the method comprises the following steps: the method also comprises a tail gas washing step before the step of producing the aluminum fluoride in the four-stage synthesis tank, wherein the tail gas washing step specifically comprises the following steps:

and (3) introducing tail gas discharged from the top of the secondary fluidized bed into a Venturi scrubber for cooling and washing, and obtaining low-concentration fluorine-containing washing wastewater after cooling and washing by the Venturi scrubber.

8. The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claim 7, wherein the method comprises the following steps: and returning the mother liquor to the Venturi scrubber to be used as a scrubbing liquid of tail gas discharged from the top of the secondary fluidized bed.

9. The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claim 7, wherein the method comprises the following steps: the method also comprises a step of producing aluminum fluoride by a double fluidized bed before the step of washing the tail gas, wherein the step of producing the aluminum fluoride by the double fluidized bed comprises the following steps:

charging wet aluminum hydroxide into a reaction chamber of the secondary fluidized bed;

tail gas generated by the main fluidized bed enters the auxiliary fluidized bed through the primary airflow reactor, and wet aluminum hydroxide in a reaction cavity of the auxiliary fluidized bed forms a fluidized state under the action of the tail gas generated by the main fluidized bed and is dried;

the dried aluminum hydroxide flows downwards from the secondary fluidized bed into the primary gas flow reactor and is preheated by reversely contacting with the ascending tail gas generated by the main fluidized bed;

the aluminum hydroxide preheated by the primary gas flow reactor enters a reaction cavity of the main fluidized bed, and forms a fluidized state under the action of hydrogen fluoride gas in the reaction cavity of the main fluidized bed to react with hydrogen fluoride to produce aluminum fluoride and tail gas.

10. An apparatus for implementing the method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater according to claims 1 to 9, which is characterized in that: the device comprises a double fluidized bed aluminum fluoride production device, a tail gas washing device and a four-stage synthesis tank aluminum fluoride production device, wherein the double fluidized bed aluminum fluoride production device comprises a side fluidized bed, a main fluidized bed, a first-stage airflow reactor, a second-stage airflow reactor and a third-stage airflow reactor, the tail gas washing device comprises a Venturi scrubber, the four-stage synthesis tank aluminum fluoride production device comprises a first synthesis tank, a second synthesis tank, a third synthesis tank, a fourth synthesis tank, a plate and frame filter and a flash evaporation dryer, a solid phase outlet at the side part of the side fluidized bed is connected with a solid phase inlet at the top part of the first-stage airflow reactor, a solid phase outlet at the bottom part of the first-stage airflow reactor is connected with a solid phase inlet at the top part of the main fluidized bed, a gas phase outlet at the side part of the first-stage airflow reactor is connected with a gas phase inlet at the side part of the second-stage airflow reactor, a solid phase outlet, the gas phase outlet at the top of the secondary gas flow reactor is connected with the gas phase inlet at the side of the tertiary gas flow reactor, the solid phase outlet at the bottom of the tertiary gas flow reactor is connected with the solid phase reflux inlet at the side of the main fluidized bed, the gas phase outlet at the top of the tertiary gas flow reactor is connected with the gas phase inlet at the bottom of the secondary fluidized bed, the gas phase outlet at the top of the secondary fluidized bed is connected with the gas phase inlet at the top of the venturi scrubber, the liquid phase outlet at the bottom of the venturi scrubber is connected with the liquid phase inlet at the top of the first synthesis tank, the overflow port at the top of the first synthesis tank is connected with the liquid phase inlet at the top of the second synthesis tank, the overflow port at the top of the second synthesis tank is connected with the liquid phase inlet at the top of the third synthesis tank, the overflow port at the top of the third synthesis tank is connected with the liquid phase inlet at the top of the fourth synthesis, and a liquid phase outlet of the plate and frame type filter is connected with a liquid phase inlet at the top of the Venturi scrubber, and a solid phase outlet of the plate and frame type filter is connected with an inlet of the flash evaporation dryer.

Technical Field

The invention relates to the technical field of anhydrous aluminum fluoride production, in particular to a method and equipment for preparing aluminum fluoride from low-concentration fluorine-containing wastewater.

Background

The fluorine chemical industry is a sub-industry of the chemical industry, and the industry becomes an important industry with rapid development due to multiple product varieties, excellent performance and wide application field. While the industry is continuously developing and advancing, the industry at present generally adopts calcium oxide to neutralize or produce high-purity cryolite from fluorine-containing wastewater generated in the production process.

The fluorine-containing wastewater is treated by utilizing the low-valent calcium oxide to perform neutralization reaction, and the generated calcium fluoride with lower main content is directly discharged for treatment, wherein the main content of the calcium fluoride is about 70 percent, so that the waste of fluorine resources and the increase of production cost are caused.

The high-purity cryolite is produced by utilizing the sodium hydroxide, the aluminum hydroxide and the fluorine-containing wastewater, and the market of the high-purity cryolite is in a low state, so that a large amount of high-ice inventory is accumulated, the high-ice inventory cannot be sold, and a large amount of labor and capital are occupied.

Disclosure of Invention

In view of the above, it is necessary to provide a method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater.

It is also necessary to provide equipment for preparing aluminum fluoride from low-concentration fluorine-containing wastewater.

The method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater comprises the step of producing aluminum fluoride in a four-stage synthesis tank, wherein the step of producing aluminum fluoride in the four-stage synthesis tank specifically comprises the following steps:

introducing low-concentration fluorine-containing washing wastewater into a first synthesis tank, adding aluminum hydroxide into the first synthesis tank to form a first treatment waste liquid, stirring the first treatment waste liquid, and controlling the temperature of the first treatment waste liquid at 70-80 ℃;

overflowing the first treatment waste liquid in the first synthesis tank into a second synthesis tank, adding aluminum hydroxide into the second synthesis tank to form a second treatment waste liquid, stirring the second treatment waste liquid, and controlling the temperature of the second treatment waste liquid to be 70-80 ℃;

overflowing the second treatment waste liquid in the second synthesis tank into a third synthesis tank, adding aluminum hydroxide into the third synthesis tank to form a third treatment waste liquid, stirring the third treatment waste liquid, and controlling the temperature of the third treatment waste liquid to be 70-80 ℃;

overflowing the third treatment waste liquid in the third synthesis tank into a fourth synthesis tank, adding aluminum hydroxide into the fourth synthesis tank to form a fourth treatment waste liquid, stirring the fourth treatment waste liquid, controlling the temperature of the fourth treatment waste liquid to be 70-80 ℃, controlling the acidity of hydrofluoric acid to be 0.5g/L at the reaction end point of the fourth treatment waste liquid, discharging the fourth treatment waste liquid from the bottom of the fourth synthesis tank, feeding the fourth treatment waste liquid into a plate-and-frame filter, separating out mother liquid and filter cake, and feeding the filter cake into a flash evaporation dryer for drying to obtain aluminum fluoride.

Preferably, the acidity of hydrofluoric acid at the end of the reaction of the first treated waste liquid is 5-10 g/L.

Preferably, the acidity of the hydrofluoric acid at the end of the reaction of the second treated waste liquid is controlled to be 1 to 2 g/L.

Preferably, the acidity of the hydrofluoric acid at the end of the reaction of the third treated waste liquid is controlled to be 0.5 to 1 g/L.

Preferably, methyl orange is adopted as the hydrofluoric acid acidity indicator in the first treated waste liquid, the second treated waste liquid, the third treated waste liquid and the fourth treated waste liquid.

Preferably, the first treated waste liquid, the second treated waste liquid, the third treated waste liquid, and the fourth treated waste liquid are all controlled to 80 ℃.

Preferably, a tail gas washing step is further included before the step of producing aluminum fluoride in the four-stage synthesis tank, and the tail gas washing step specifically comprises:

and (3) introducing tail gas discharged from the top of the secondary fluidized bed into a Venturi scrubber for cooling and washing, and obtaining low-concentration fluorine-containing washing wastewater after cooling and washing by the Venturi scrubber.

Preferably, the mother liquor is recycled to the venturi scrubber as a scrubbing liquid for the off-gas discharged from the top of the secondary fluidized bed.

Preferably, the method further comprises a step of producing aluminum fluoride by a double fluidized bed before the step of washing the tail gas, and the step of producing aluminum fluoride by the double fluidized bed comprises the following steps:

charging wet aluminum hydroxide into a reaction chamber of the secondary fluidized bed;

tail gas generated by the main fluidized bed enters the auxiliary fluidized bed through the primary airflow reactor, and wet aluminum hydroxide in a reaction cavity of the auxiliary fluidized bed forms a fluidized state under the action of the tail gas generated by the main fluidized bed and is dried;

the dried aluminum hydroxide flows downwards from the secondary fluidized bed into the primary gas flow reactor and is preheated by reversely contacting with the ascending tail gas generated by the main fluidized bed;

the aluminum hydroxide preheated by the primary gas flow reactor enters a reaction cavity of the main fluidized bed, and forms a fluidized state under the action of hydrogen fluoride gas in the reaction cavity of the main fluidized bed to react with hydrogen fluoride to produce aluminum fluoride and tail gas.

The equipment for realizing the method for preparing the aluminum fluoride from the low-concentration fluorine-containing wastewater comprises a double fluidized bed aluminum fluoride production device, a tail gas washing device and a four-stage synthesis tank aluminum fluoride production device, wherein the double fluidized bed aluminum fluoride production device comprises a secondary fluidized bed, a main fluidized bed, a first-stage gas flow reactor, a second-stage gas flow reactor and a third-stage gas flow reactor, the tail gas washing device comprises a Venturi scrubber, the four-stage synthesis tank aluminum fluoride production device comprises a first synthesis tank, a second synthesis tank, a third synthesis tank, a fourth synthesis tank, a plate and frame filter and a flash evaporation dryer, a solid phase outlet at the side part of the secondary fluidized bed is connected with a solid phase inlet at the top part of the first-stage gas flow reactor, a solid phase outlet at the bottom part of the first-stage gas flow reactor is connected with a solid phase inlet at the top part of the main fluidized bed, a gas phase outlet at the side part of the first-stage, the solid phase outlet at the bottom of the secondary gas flow reactor is connected with the solid phase reflux inlet at the side part of the main fluidized bed, the gas phase outlet at the top of the secondary gas flow reactor is connected with the gas phase inlet at the side part of the tertiary gas flow reactor, the solid phase outlet at the bottom of the tertiary gas flow reactor is connected with the solid phase reflux inlet at the side part of the main fluidized bed, the gas phase outlet at the top of the tertiary gas flow reactor is connected with the gas phase inlet at the bottom of the secondary fluidized bed, the gas phase outlet at the top of the secondary fluidized bed is connected with the gas phase inlet at the top of the venturi scrubber, the liquid phase outlet at the bottom of the venturi scrubber is connected with the liquid phase inlet at the top of the first synthesis tank, the overflow port at the top of the first synthesis tank is connected with the liquid phase inlet at the top of the second synthesis tank, the overflow port at the top of the second synthesis tank is connected with the liquid phase inlet at the, and a liquid phase outlet at the bottom of the fourth synthesis tank is connected with a liquid phase inlet of the plate-and-frame filter, a liquid phase outlet of the plate-and-frame filter is connected with a liquid phase inlet at the top of the Venturi scrubber, and a solid phase outlet of the plate-and-frame filter is connected with an inlet of the flash evaporation dryer.

The process for producing the aluminum fluoride in the method is fundamentally different from the existing process for producing the aluminum fluoride by gas-solid reaction, the reaction is carried out in a liquid environment, the fluorine element in the low-concentration fluorine-containing wastewater can be recycled, the aluminum fluoride product with higher added value can be obtained on the basis of meeting the standard discharge and green circulation of the wastewater, the micro aluminum fluoride particles generated in the aluminum fluoride production process can be recycled, and the production cost of the aluminum fluoride can be effectively reduced.

Drawings

FIG. 1 is a schematic structural diagram of a device for preparing aluminum fluoride from low-concentration fluorine-containing wastewater.

In the figure: the device comprises a double fluidized bed aluminum fluoride production device 10, a side fluidized bed 11, a main fluidized bed 12, a first-stage gas flow reactor 13, a second-stage gas flow reactor 14, a third-stage gas flow reactor 15, a tail gas washing device 20, a Venturi scrubber 21, a four-stage synthesis tank aluminum fluoride production device 30, a first synthesis tank 31, a second synthesis tank 32, a third synthesis tank 33, a fourth synthesis tank 34, a plate and frame filter 35 and a flash dryer 36.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Referring to fig. 1, the embodiment of the invention provides a method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater, which comprises a step of producing aluminum fluoride in a four-stage synthesis tank, wherein the step of producing aluminum fluoride in the four-stage synthesis tank specifically comprises the following steps:

introducing low-concentration fluorine-containing washing wastewater into a first synthesis tank 31, adding aluminum hydroxide into the first synthesis tank 31 to form a first treatment waste liquid, stirring the first treatment waste liquid, and controlling the temperature of the first treatment waste liquid to be 70-80 ℃;

overflowing the first treated waste liquid in the first synthesis tank 31 into a second synthesis tank 32, adding aluminum hydroxide into the second synthesis tank 32 to form a second treated waste liquid, stirring the second treated waste liquid, and controlling the temperature of the second treated waste liquid to be 70-80 ℃;

overflowing the second treated waste liquid in the second synthesis tank 32 into a third synthesis tank 33, adding aluminum hydroxide into the third synthesis tank 33 to form a third treated waste liquid, stirring the third treated waste liquid, and controlling the temperature of the third treated waste liquid to be 70-80 ℃;

overflowing the third treated waste liquid in the third synthesis tank 33 into the fourth synthesis tank 34, adding aluminum hydroxide into the fourth synthesis tank 34 to form a fourth treated waste liquid, stirring the fourth treated waste liquid, controlling the temperature of the fourth treated waste liquid to be 70-80 ℃, controlling the acidity of hydrofluoric acid to be 0.5g/L at the end point of the reaction of the fourth treated waste liquid, discharging the fourth treated waste liquid from the bottom of the fourth synthesis tank 34, feeding the fourth treated waste liquid into a plate-and-frame filter 35, separating mother liquid and filter cake, and feeding the filter cake into a flash dryer 36 to be dried to obtain aluminum fluoride.

The method for treating the fluorine-containing wastewater can avoid the problem of crystallization of pipelines of a production system.

In the method, the mode of connecting four-stage synthesis tanks in series is adopted, which is beneficial to realizing the continuous treatment of the low-concentration fluorine-containing wastewater.

The process for producing the aluminum fluoride in the method is fundamentally different from the existing process for producing the aluminum fluoride by gas-solid reaction, the reaction is carried out in a liquid environment, the fluorine element in the low-concentration fluorine-containing wastewater can be recycled, the aluminum fluoride product with higher added value can be obtained on the basis of meeting the standard discharge and green circulation of the wastewater, the micro aluminum fluoride particles generated in the aluminum fluoride production process can be recycled, and the production cost of the aluminum fluoride can be effectively reduced.

Referring to FIG. 1, the acidity of hydrofluoric acid at the end of the reaction of the first treated waste liquid is controlled to be 5-10 g/L.

Referring to FIG. 1, the acidity of hydrofluoric acid at the end of the reaction of the second treated waste liquid is further controlled to be 1-2 g/L.

Referring to FIG. 1, the acidity of hydrofluoric acid at the end of the reaction of the third treated waste liquid is further controlled to be 0.5-1 g/L.

Referring to fig. 1, further, methyl orange is used as a hydrofluoric acid acidity indicator in the first treated waste liquid, the second treated waste liquid, the third treated waste liquid, and the fourth treated waste liquid.

Referring to fig. 1, further, the first treated waste liquid, the second treated waste liquid, the third treated waste liquid, and the fourth treated waste liquid were all controlled at 80 ℃.

Referring to fig. 1, further, before the step of producing aluminum fluoride in the fourth-stage synthesis tank, a tail gas washing step is further included, and the tail gas washing step specifically includes:

and tail gas discharged from the top of the secondary fluidized bed 11 enters a Venturi scrubber 21 for cooling and washing, and low-concentration fluorine-containing washing wastewater is obtained after cooling and washing by the Venturi scrubber.

Referring to fig. 1, further, the mother liquor is recycled to the venturi scrubber 21 as a scrubbing liquid for the off-gas discharged from the top of the secondary fluidized bed 11.

Referring to fig. 1, further, the step of producing aluminum fluoride by a dual fluidized bed is included before the step of washing the tail gas, and the step of producing aluminum fluoride by a dual fluidized bed specifically includes:

charging wet aluminum hydroxide into the reaction chamber of the secondary fluidized bed 11;

tail gas generated by the main fluidized bed 12 enters the secondary fluidized bed 11 through the primary airflow reactor 13, and wet aluminum hydroxide in a reaction cavity of the secondary fluidized bed 11 forms a fluidized state under the action of the tail gas generated by the main fluidized bed 12 and is dried;

the dried aluminum hydroxide flows downwards from the secondary fluidized bed 11 into the primary gas flow reactor 13 and is preheated by being in reverse contact with the ascending tail gas generated by the main fluidized bed 12;

the aluminum hydroxide preheated by the primary gas flow reactor 13 enters the reaction chamber of the main fluidized bed 12, and forms a fluidized state under the action of the hydrogen fluoride gas in the reaction chamber of the main fluidized bed 12 to react with the hydrogen fluoride to produce aluminum fluoride and tail gas.

Tests show that in the drying process, the temperature is unstable, so that the moisture removal cannot meet the requirements, a single fluidized bed is adopted, the drying process of the aluminum hydroxide and the reaction of the aluminum hydroxide and the hydrogen fluoride are carried out simultaneously, the drying process of the aluminum hydroxide is an endothermic reaction, the reaction of the aluminum hydroxide and the hydrogen fluoride is an exothermic reaction, so that the temperature in the fluidized bed is not constant, the drying of the aluminum hydroxide is influenced, the reaction of the aluminum hydroxide and the hydrogen fluoride is influenced, the final yield of the aluminum fluoride is influenced, and the loss of the hydrogen fluoride in tail gas is increased.

The method adopts a single fluidized bed, the drying temperature of the aluminum hydroxide and the reaction temperature of the aluminum hydroxide and the hydrogen fluoride are contradictory, the temperature is too low, the reaction kinetics of the aluminum hydroxide and the hydrogen fluoride are insufficient, the particle size of the wet aluminum hydroxide is crushed to be too fine under the condition of high temperature, the reaction of the aluminum hydroxide and the hydrogen fluoride is influenced, the final yield of the aluminum fluoride is influenced, and the loss of the hydrogen fluoride in tail gas is increased.

The beneficial effects of the embodiment are as follows:

(1) the wet aluminum hydroxide directly enters the secondary fluidized bed 11 without additionally building drying equipment; surface water and crystal water of aluminium hydroxide are got rid of through the reaction heat that utilizes aluminium fluoride, play energy saving and consumption reduction's effect, fluidized bed equipment characteristic has decided aluminium hydroxide and is in fluidized state, and aluminium hydroxide water content is even, avoids getting into that local water content is too high or lead to its inside reaction temperature unstable after low aluminium hydroxide gets into mainstream fluidized bed 12.

(2) After directly entering the secondary fluidized bed 11, the wet aluminum hydroxide is not contacted with high-temperature air flow (the temperature is about 550-650 ℃) but contacted with medium-temperature air flow (the temperature is about 320 ℃), so that the cracking phenomenon of the aluminum hydroxide is avoided and the generation of superfine aluminum hydroxide micropowder is avoided, the quality and the yield of aluminum fluoride products are improved, and the granularity and the fluidity of the products are better.

(3) After the tail gas that the mainstream fluidized bed 12 produced gets into side fluidized bed 11, when heating wet aluminium hydroxide, self temperature reduces, improves heat utilization rate, because the tail gas temperature reduces, the active ingredient in the tail gas is absorbed more easily, and absorbing device just can become simpler, and it is easier to reach standard and discharge, has still reduced the energy consumption.

(4) After entering the secondary fluidized bed 11, the tail gas generated by the main fluidized bed 12 reacts with the aluminum hydroxide while heating the wet aluminum hydroxide, so that the aluminum hydroxide is transformed, the reaction activity is improved, the content of unreacted hydrogen fluoride in the tail gas is reduced, and the reaction rate of the hydrogen fluoride is improved.

(5) By adopting the mode of combining the main fluidized bed 12 and the auxiliary fluidized bed 11, the dehydration of the aluminum hydroxide and the reaction of the aluminum hydroxide and the hydrogen fluoride are respectively and independently carried out without mutual influence, the respective temperature stable control is easily realized, the reaction temperature in the main fluidized bed 12 can be independently improved, the reaction efficiency is improved, the temperature of the auxiliary fluidized bed 11 is independently reduced, and the generation of the ultra-fine aluminum hydroxide micro powder is reduced.

(6) Most of the heat of the tail gas is absorbed by the aluminum hydroxide in the secondary fluidized bed 11, and the heat released by the aluminum hydroxide and the hydrogen fluoride in the main fluidized bed 12 is added, so that the whole system does not need to supplement heat from the outside during operation, and the energy consumption is reduced.

(7) After the aluminum hydroxide dried by the secondary fluidized bed 11 enters the primary gas flow reactor 13, the aluminum hydroxide flows from top to bottom in the primary gas flow reactor 13, the tail gas generated by the main fluidized bed 12 flows from bottom to top through the primary gas flow reactor 13, the aluminum hydroxide and the tail gas flow in the reverse direction, the tail gas is cooled, the aluminum hydroxide is heated to a transition temperature, the aluminum hydroxide is stably transited from the secondary fluidized bed 11 with lower temperature to the main fluidized bed 12 with higher temperature, and the aluminum hydroxide can be prevented from bursting due to temperature shock to generate superfine aluminum hydroxide micro powder.

(8) The wet aluminum hydroxide is dried by the auxiliary fluidized bed 11, the concentration of hydrogen fluoride in the tail gas for drying the aluminum hydroxide is much smaller than that of the hydrogen fluoride in the main fluidized bed 12, the dried aluminum hydroxide is in a high-expansion state in the auxiliary fluidized bed 11, the mobility is good, the aluminum hydroxide can be fully contacted with the low-content hydrogen fluoride in the tail gas, and compared with the existing disc type drying equipment, the cooling effect on the tail gas and the absorption effect on the hydrogen fluoride in the tail gas are better.

Referring to fig. 1, further, the temperature of the tail gas entering the reaction chamber of the secondary fluidized bed 11 is controlled to be 300-400 ℃.

Referring to fig. 1, further, the temperature of the off-gas entering the reaction chamber of the secondary fluidized bed 11 is controlled at 320 ℃.

Referring to fig. 1, further, in the reaction chamber of the main fluidized bed 12, the reaction temperature of the aluminum hydroxide and the hydrogen fluoride is controlled to be 480 to 520 ℃.

Referring to fig. 1, further, the tail gas generated from the main fluidized bed 12 contains hydrogen fluoride gas.

Referring to fig. 1, the embodiment of the present invention further provides an apparatus for implementing a method for preparing aluminum fluoride from low-concentration fluorine-containing wastewater, including a dual fluidized bed aluminum fluoride production apparatus 10, a tail gas washing apparatus 20, and a four-stage synthesis tank aluminum fluoride production apparatus 30, where the dual fluidized bed aluminum fluoride production apparatus 10 includes a secondary fluidized bed 11, a main fluidized bed 12, a first-stage gas flow reactor 13, a second-stage gas flow reactor 14, and a third-stage gas flow reactor 15, the tail gas washing apparatus 20 includes a venturi scrubber 21, the four-stage synthesis tank aluminum fluoride production apparatus 30 includes a first synthesis tank 31, a second synthesis tank 32, a third synthesis tank 33, a fourth synthesis tank 34, a plate and frame filter 35, and a flash dryer 36, a solid phase outlet on a side of the secondary fluidized bed 11 is connected to a solid phase inlet on a top of the first-stage gas flow reactor 13, a solid phase outlet on a bottom of the first-stage gas flow reactor 13 is connected to a solid phase inlet, a gas phase outlet of the first-stage gas flow reactor 13 is connected with a gas phase inlet at the side part of the second-stage gas flow reactor 14, a solid phase outlet at the bottom part of the second-stage gas flow reactor 14 is connected with a solid phase backflow inlet at the side part of the main fluidized bed 12, a gas phase outlet at the top part of the second-stage gas flow reactor 14 is connected with a gas phase inlet at the side part of the third-stage gas flow reactor 15, a solid phase outlet at the bottom part of the third-stage gas flow reactor 15 is connected with a solid phase backflow inlet at the side part of the main fluidized bed 12, a gas phase outlet at the top part of the third-stage gas flow reactor 15 is connected with a gas phase inlet at the bottom part of the auxiliary fluidized bed 11, a gas phase outlet at the top part of the auxiliary fluidized bed 11 is connected with a gas phase inlet at the top part of the venturi scrubber 21, a liquid phase outlet at the bottom part of the venturi scrubber 21 is connected with a liquid phase inlet at, an overflow port at the top of the third synthesis tank 33 is connected with a liquid phase inlet at the top of the fourth synthesis tank 34, a liquid phase outlet at the bottom of the fourth synthesis tank 34 is connected with a liquid phase inlet of the plate and frame filter 35, a liquid phase outlet of the plate and frame filter 35 is connected with a liquid phase inlet at the top of the venturi scrubber 21, and a solid phase outlet of the plate and frame filter 35 is connected with an inlet of the flash dryer 36.

The main fluidized bed 12 and the auxiliary fluidized bed 11 have the same structure, the main fluidized bed 12 comprises a tank body and a bottom bed arranged in the tank body, the tank body is divided into a bottom cavity and a reaction cavity which are relatively independent by the bottom bed, the reaction cavity is positioned above the bottom cavity, a hood is arranged on the bottom bed, an inlet of the hood is communicated with the bottom cavity, and an outlet of the hood is communicated with the reaction cavity.

The main fluidized bed 12 or the sub-fluidized bed 11 is preferably constructed in the same manner as in "intermediate cyclone recycle fluidizing device" of utility model having grant publication No. CN 208661080U.

In a specific embodiment, the first synthesis tank 31, the second synthesis tank 32, the third synthesis tank 33 and the fourth synthesis tank 34 are respectively provided with a stirring component, a heating component, an acidity sensor and a microprocessor, the heating component is a spiral pipe, the equipment for realizing the method for preparing the aluminum fluoride from the low-concentration fluorine-containing wastewater further comprises an aluminum hydroxide storage tank, outlets of the aluminum hydroxide storage tank are respectively connected with inlets of four electromagnetic vibration feeders, outlets of the four electromagnetic vibration feeders are respectively correspondingly connected with inlets of the first synthesis tank 31, the second synthesis tank 32, the third synthesis tank 33 and the fourth synthesis tank 34, the microprocessor can adopt a single chip microcomputer, the acidity sensors of the first synthesis tank 31, the second synthesis tank 32, the third synthesis tank 33 and the fourth synthesis tank 34 are respectively connected with the microprocessor, and the microprocessor is respectively connected with the first synthesis tank 31, the second synthesis tank 32, the third synthesis tank 33, the fourth synthesis tank 34, The electromagnetic vibration feeder of the fourth synthesis tank 34 is connected, the acidity sensor in the first synthesis tank 31 detects the acidity of hydrofluoric acid in the liquid in the first synthesis tank 31, when the detected acidity value of the hydrofluoric acid is not within the range of 5-10 g/L, the microprocessor starts the electromagnetic vibration feeder in the first synthesis tank 31 to add aluminum hydroxide into the first synthesis tank 31, when the detected acidity value of the hydrofluoric acid is within the range of 5-10 g/L, the microprocessor closes the electromagnetic vibration feeder in the first synthesis tank 31, and the control of the acidity of the hydrofluoric acid in the second synthesis tank 32, the third synthesis tank 33 and the fourth synthesis tank 34 is consistent with that of the first synthesis tank 31, but the control range of the acidity of the hydrofluoric acid is different.

In a specific embodiment, a plurality of first guide plates and a plurality of second guide plates are arranged in the reaction cavity of the secondary fluidized bed 11 from top to bottom, the first guide plates and the second guide plates are arranged in a staggered manner in the vertical direction, one end of each first guide plate is in contact with the left side wall of the reaction cavity of the secondary fluidized bed 11, the other end of each first guide plate extends downwards at a certain angle, one end of each second guide plate is in contact with the right side wall of the reaction cavity of the secondary fluidized bed 11, the other end of each second guide plate extends downwards at a certain angle, and the plurality of first guide plates and the plurality of second guide plates form a zigzag flow channel in the reaction cavity of the secondary fluidized bed 11. Through holes are preferably densely distributed on the first guide plate and the second guide plate.

Above-mentioned side fluidized bed 11's inner structure, can guarantee hydrogen fluoride gas and aluminium hydroxide fully contact, and can guarantee aluminium hydroxide homodisperse, good mobility has, especially aluminium hydroxide humidity after the drying is even, can prevent to lead to the fact the temperature in the fluidized bed invariable because of aluminium hydroxide local humidity is too high or low excessively, the flow direction and the developments behind hydrogen fluoride gas entering side fluidized bed 11, after guaranteeing to contact the aluminium hydroxide material, hydrogen fluoride gas flow dead angle can not appear and arouse local too high, local hardening can not appear, the corruption that causes equipment can not appear ponding more.

The steps in the method of the embodiment of the invention can be sequentially adjusted, combined and deleted according to actual needs.

The modules or units in the device of the embodiment of the invention can be combined, divided and deleted according to actual needs.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.