TW202229178A - A method to reduce the fluoride content of wastewater by removing the by-products of the heavy metal process - Google Patents

Abstract

A method for reducing the Fluoride content in wastewater by removing heavy metal by-products, comprising: A reaction step, in which wastewater, calcium chloride slurry and high-salt brine enter a reaction tank for reaction. A mixing control step is used to control the amount of wastewater entering the reaction tank, the ratio of calcium chloride slurry and high-salt brine. A precipitation step, a sedimentation tank is used to receive the treated slurry in the reaction tank; A detection of fluoride ion content Step, to detect when the Fluoride content of the mud is less than the discharge water control standard, return the mud to the reaction tank. A pH adjustment step, the pH value of the mud whose Fluoride content meets the discharge water control standard is further adjusted to an outlet water discharge pool to meet the discharge water standard and then discharged. The aforementioned calcium chloride slurry and high-salt brine involved in the reaction are produced by intelligent processing methods.

Description

Method for reducing fluorine content in wastewater by removing heavy metal process by-products

The present invention mainly relates to a method for reducing the fluorine content of waste water, and particularly relates to a heavy metal removal process that can produce calcium chloride by-products and control the calcium chloride dosage and pH value in real time, so as to achieve high efficiency and reduce the fluorine content of waste water. Methods.

In some contaminated materials, such as fly ash, the composition is mainly composed of suspended particles, dust, bituminous coal or metal particles and oxides generated during the combustion process. In view of the fact that the contaminated fly ash material contains many heavy metal elements , such as calcium (Ca), silicon (Si), aluminum (Al), iron (Fe) and other metal oxides, salts (chloride) and such as cadmium (Cd), chromium (Cr), mercury (Hg), copper (Cu) and lead (Pb) and other harmful heavy metals, so they must be stabilized or detoxified before they can be reused or finally disposed of The material becomes a resource material, thereby creating the reusability of the material, and at the same time, the calcium salt by-product produced in the process can be fully recovered and used.

In the semiconductor manufacturing industry, due to the rapid product update and the rapid advancement of manufacturing technology, the manufacturing process is also changed accordingly, so the types and quantities of various raw materials, chemicals, gases, energy resources used and the wastes they generate are also changing accordingly. Taking the manufacturing process of integrated circuits as an example, on the silicon wafer completed by the fab, the circuit pattern is printed on the photomask, and then the circuit and the components on the circuit are made on the wafer through physical and chemical methods. Provide different functions. Since the circuit design on the IC is a layered structure, it needs to go through Repeat the above procedure several times before completing the complete IC. The wastes that may be generated are waste wafers, waste solvents, waste acids and alkalis, and fluorine-containing sludge. Further explanation: The wafer cleaning process includes removal of particles, organics, ions, metal impurities, etc. The cleaning solvents that may be used in traditional wet cleaning include deionized water, acid solutions (such as hydrofluoric acid, hydrochloric acid, nitric acid, chromic acid, sulfuric acid) etc.) and isopropyl alcohol commonly used for drying, etc. Among them, the thinner ones are usually sent directly to the wastewater treatment plant in the factory for treatment, while those with higher concentrations are cleaned up or reused as waste liquids. The waste generated in the wafer etching process is the etching waste liquid, which is often composed of mixed acids such as hydrofluoric acid, nitric acid, phosphoric acid, hydrochloric acid, and acetic acid. The waste generated after the treatment of the hydrofluoric acid wastewater generated in the cleaning and etching process is wastewater sludge. In the integrated circuit manufacturing process, hydrofluoric acid is generally used in the process of etching and furnace tube cleaning, so fluorine-containing wastewater is generated in the discharged wastewater. At present, most semiconductors use chemical coagulation technology to remove fluorine in water. ions, and the amount of calcium fluoride sludge produced has increased to 89% of the same pollutants.

The object of the present invention is to provide a method for reducing the fluorine content of wastewater by utilizing the calcium chloride by-product derived from the process of removing harmful heavy metals in the material to carry out chemical coagulation.

In order to achieve the above object, the present invention provides a method for reducing the fluorine content of wastewater by removing heavy metal process by-products. Calcium chloride slurry reacts with a high-salt brine; a mixing control step, in order to control the amount of water that this fluorine-containing waste water enters this reaction tank, the ratio of this calcium chloride slurry and this high-salt brine entering this reaction tank; A precipitation step, a sedimentation tank is used to receive the sludge treated by the reaction tank, and insoluble calcium fluoride precipitate is produced; a detection fluoride ion content step is used to detect whether the fluorine content of the sludge in the sedimentation tank is not. is less than the control standard for effluent water, if not, the slurry is returned to the reaction tank; and a pH value adjustment step is to further adjust the pH value of the slurry whose fluorine content meets the control standard for effluent water to an effluent water In the discharge tank, the pH value is detected and recorded to meet the discharge water standard and then discharged; Wherein, the manufacturing process of the calcium chloride slurry and the high-salt brine includes: a setting step, which is based on the pH value of an initial material compared with the pH value of the initial reaction time in a heavy metal dissolution test curve graph, to obtain the maximum A liquid-solid ratio corresponding to the curve close to the pH value, and then according to the liquid-solid ratio through a different liquid-solid ratio viscosity change curve, find out a viscosity value corresponding to the liquid-solid ratio as the initial material In a pickling operation step, the initial material, a water and an acid solution that meet an initial ratio are added to a pickling tank and uniformly stirred to form a slurry, so that the heavy metals in the initial material are mixed with the water. It reacts with the acid solution to elute heavy metals. The ratio of the initial material and water is adjusted to meet the initial viscosity value. The pickling operation step includes a pH control unit for detecting the pH value of the slurry in the pickling tank. , and adjust the pH ratio of the slurry in the pickling tank, so that the corresponding relationship between the pH value of the slurry and the reaction time conforms to the selected curve change of the heavy metal dissolution test curve; a first filtration step, with a first A filter collects the fine particles of carbon particles and heavy metal components in the slurry; an acid-base neutralization step is to transfer the fine particles to a neutralization tank, and add a uniform mixed solution of water and a lime into the and uniformly mixed in the neutralization tank; a second filtration step, collecting a plurality of fine particles containing heavy metal components with a second filter to form the calcium chloride slurry; and a vacuum concentration step, which is The calcium chloride slurry is sent to a vacuum concentration unit for concentrating the calcium chloride slurry into the high-salt brine.

In some embodiments, the fluorine-containing wastewater first flows into a buffer tank, and then the buffer tank provides quantitative output to the reaction tank.

In some embodiments, the fluorine-containing wastewater enters the reaction tank through a first pipeline, the calcium chloride slurry enters the reaction tank through a second pipeline, and the high-salt brine enters the reaction tank through a third pipeline The first pipeline, the second pipeline and the third pipeline are respectively electrically connected and controlled in the mixing control step to open and close the first pipeline, the second pipeline and the third pipeline.

In some embodiments, the sedimentation tank uses a pH value detector to check an instant pH value of the slurry, and controls the fluorine-containing wastewater and the calcium chloride slurry entering the reaction tank according to the instant pH value The reaction ratio of the liquid and the high-salt brine.

In some embodiments, after the pickling operation, the slurry in the pickling tank is input into a first buffer tank, and then quantitatively output from the first buffer tank to the first filter.

In some embodiments, the fine particles collected by the first filter in the first filtering step are collected by a second buffer tank, and the fine particles quantitatively output from the second buffer tank are sent to the medium and inside the slot.

In some embodiments, the slurry in the neutralization tank is collected in a third buffer tank, and then quantitatively output from the third buffer tank to the second filter for collection.

In some embodiments, a fourth buffer tank is used to collect the slurry collected by the second filter of the second filtration step, and output the slurry to the vacuum concentration unit.

In some embodiments, in the pickling operation step, the acid solution added to the pickling tank is waste acid, and the pH control unit is used to control the acid-base ratio of the water and the acid solution It is used to add a controllable amount of pure acid to the pickling tank to adjust the acid value of the pickling tank.

In some embodiments, the fine particles collected by the first filter in the first filtration step are added to the first buffer tank for multiple times to perform multiple cycle filtration.

The characteristics of the present invention are: the present invention can use real empirical data to determine the treatment materials, such as in the pickling stage of fly ash, the solid ratio of fly ash to water and acid solution in the initial stage, and the water and acid solution in the pickling reaction process. and the acid-base value of the pickling solution can be adjusted immediately during the pickling reaction, so as to use the least amount of water and acid, and effectively complete the separation of harmful heavy metals from the fly ash slurry within a predetermined time. , in order to obtain harmless fly ash slag, and further the separated heavy metal slurry can be subjected to acid-base neutralization, filtration, and drying treatment to obtain metal hydroxide, and the slurry obtained by the above-mentioned acid-base neutralization and filtration , carry out the vacuum concentration step to form high-salt brine, and complete the industrial salt product after drying, and then use the calcium chloride slurry obtained by acid-base neutralization and filtration, and the high-salt brine as the chemical coagulation agent. A method for removing/reducing fluorine concentration in fluorine-containing wastewater generated in semiconductor manufacturing processes. The present invention uses controllable wastewater inflow, calcium chloride slurry and high-salt brine ratio to carry out reaction chemistry in a reaction tank, and immediately monitors the pH value of the mud sewage after the reaction, and then immediately conducts the reaction tank according to the pH value. The optimum ratio of wastewater, calcium chloride slurry and high-salt brine is adjusted to achieve high chemical reaction efficiency without excessive dosing, which reduces the amount of sludge produced and saves sludge treatment costs.

1: Method for reducing fluorine content in wastewater

10: Buffer slot

11: Reaction tank

12: Wastewater

13: Calcium chloride slurry

14: High salt brine

2: Hybrid Control Unit

3: sedimentation tank

4: pH adjustment pool

41: Release pool

51: Initial material

52: Water

53: Acid

54: Pickling tank

541: Slurry

542: pH meter

55: pH control unit

56: The first buffer tank

561: Quantitative Slurry

57: First Filter

571: fine particles

58: Second buffer tank

61: Neutralization tank

62: The third buffer tank

63: Second filter

7: Fourth buffer tank

8: Vacuum concentration unit

S11 to S16: the method steps of reducing the fluorine content of wastewater according to an embodiment of the present invention

S21 to S26: the application of an embodiment of the present invention to remove the method steps of heavy metal process by-products

[FIG. 1] is a flow chart of steps of a method for removing by-products of heavy metal process and reducing fluorine content in wastewater according to an embodiment of the present invention;

[FIG. 2] is a system structure diagram of a method for removing by-products of heavy metal process and reducing fluorine content in wastewater according to an embodiment of the present invention;

Fig. 3 is a graph showing a heavy metal dissolution test curve of a method for removing by-products of a heavy metal process and reducing fluorine content in wastewater according to an embodiment of the present invention; and

FIG. 4 is a graph showing the change of liquid-solid specific viscosity at different liquid-solid ratios according to an embodiment of the present invention by applying the method for removing by-products of heavy metal process to reduce fluorine content in wastewater.

Hereinafter, the embodiments of the present invention will be described in detail in conjunction with the drawings. The accompanying drawings are mainly simplified schematic diagrams, and only illustrate the basic structure of the present invention in a schematic manner. Therefore, only the elements related to the present invention are indicated in these drawings. , and the displayed components are not drawn according to the number, shape, size ratio, etc. of the actual implementation. The size of the actual implementation is actually a selective design, and the layout of the components may be more complicated.

Referring to FIG. 1 and FIG. 2 , the method for reducing the fluorine content of wastewater by removing heavy metal process by-products in this embodiment includes: a reaction step S11, a mixing control step S12, a precipitation step A precipitation step S13, a detection fluoride ion content step S14, a pH adjustment step S15, and a discharge step S16.

In the reaction step S11, a reaction tank 11 is used to hold the fluorine-containing waste water 12, and calcium chloride (CaF ₂ ) slurry 13 and a high-salt brine 14 are controlled to enter the reaction tank 11 in an appropriate ratio. Treatment of fluorine-containing wastewater by salt precipitation12. In order to quantitatively supply the fluorine-containing wastewater 12 to the reaction tank 11 , the wastewater 12 can be flowed to a buffer tank 10 , and then a certain amount of wastewater 12 is buffered by the buffer tank 10 , and then injected into the reaction tank 11 .

The mixing control step S12 uses a mixing control unit 2 to control the amount of the wastewater 12 entering the reaction tank 11 and the ratio of the calcium chloride slurry 13 and the high-salt brine 14 entering the reaction tank 11 . It is worth mentioning that, in the calcium salt of the aforementioned treatment of the fluorine-containing wastewater 12, because the solubility of calcium chloride in water is relatively high, and the chemical reaction efficiency produced by the treatment of the fluorine-containing wastewater 12 with calcium chloride is relatively high, Therefore, the treatment effect of calcium chloride is better than that of other types of calcium salts.

In the precipitation step S13, a sedimentation tank 3 is used to receive the treated slurry in the reaction tank 11, and insoluble calcium fluoride precipitates.

The detecting fluoride ion content step S14 is used to detect whether the fluorine content of the mud in the sedimentation tank 3 is less than a discharge water control standard, and if the fluorine content is not less than the discharge water control standard, the mud is sent back to the The reaction tank 11 is used to perform the reaction step S11 again.

In the pH adjustment step S15, in a pH adjustment tank 4, the pH value of the mud in the sedimentation tank 3 whose fluorine content meets the discharge water control standard is further adjusted. In this step, the amount of calcium chloride slurry 13 and high-salt brine 14 is added to the reaction tank 11 to control the solubility of its fluoride. Dissolve 65mg/L of fluoride in water, if the pH value is controlled at 2.5, more than 95% of the fluoride will produce insoluble calcium fluoride precipitation, so control the pH value within the optimum operating range , which can meet the best economic overflow.

In the discharge step S16, the mud waste water adjusted in the pH value adjustment step S15 is sent to a discharge tank 41, and the pH value of the mud waste water in the discharge tank 41 is detected and recorded to meet the discharge water standard and then discharged.

The calcium chloride slurry 13 and the high-salt brine 14 used in the aforementioned reaction step S11 are by-products of a heavy metal removal process, and the preparation steps include: a setting step S21, a pickling operation step S22, a A first quantitative output step S23, a first filtering step S24, a drying and crushing step, and a rotary kiln cracking step S26.

Please refer to Figure 1, Figure 2, Figure 3 and Figure 4 for further details. In this embodiment, the setting step S21 is based on the pH value of an initial material 51 compared with the initial reaction time in a heavy metal dissolution test curve (the horizontal axis is time, and the vertical axis is pH value, as shown in FIG. 3 ). pH value, obtain a liquid-solid ratio corresponding to the curve closest to the pH value, and then according to the liquid-solid ratio through a different liquid-solid ratio viscosity change curve (the horizontal axis is the liquid-solid ratio, and the vertical axis is the viscosity. , as shown in FIG. 4 ), find out a viscosity value corresponding to the liquid-solid ratio as the initial viscosity value of the initial material 51 .

In the pickling operation step S22, the initial material 51, a water 52 and an acid solution 53 in an initial ratio are added to a pickling tank 54 and uniformly stirred into a slurry (for example, a motor stirrer is used), so that the The heavy metals in the initial material 51 react with the water 52 and the acid solution 53 to elute the heavy metals. The ratio of the initial material 51 and the water 52 is adjusted to meet the initial viscosity value. The pickling operation step S22 further includes a The pH value control unit 55 is used to detect the pH value of the slurry 541 in the pickling tank 54, and adjust the pH value ratio of the slurry 541 in the pickling tank 54, so that the pH value of the slurry 541 and the reaction time The corresponding relationship of , conforms to the selected curve change of the heavy metal dissolution test curve diagram, so that the best heavy metal dissolution can be carried out in the same reaction time with a relatively saved amount of water. In the pickling operation step S22, the acid solution added to the pickling tank 54 can utilize the recovered waste acid, and the acid-base value is controlled In the unit 55, the method used to control the acid-base ratio of the water 52 and the acid solution 53 is to add a controllable amount of pure acid to the pickling tank 54 to adjust the acid solution of the pickling tank 54. (for example, adding pure acid can reduce its acid value, adding water 52 can increase its acid value). The pH control unit 55 in the pickling operation step S22 measures the pH value of the slurry 541 in the pickling tank 54 with a pH meter 542 disposed in the pickling tank 54, and adjusts the pH value of the slurry 541 in the pickling tank 54. The value is reported to the pH control unit 55 .

In order to quantitatively output the slurry of the pickling tank 54 to the first filter 57, a first buffer tank 56 can be provided in the output path of the pickling tank 54, and the first buffer tank 56 can provide the function of quantitative output.

In the first filtering step S23 , a first filter 57 is used to collect a plurality of fine particles 571 of carbon particles and heavy metal components in the quantitative slurry 561 output from the first buffer tank 56 .

As shown in FIG. 1, drying and mixing are performed to remove the moisture of the slurry passing through the first filter 57 to form a dry solid, so that the temperature can be controlled more accurately, and then the dry solid is pulverized to A powder with uniform particle size and no agglomeration is formed; it is then heated evenly by a rotary kiln incinerator to crack the powder, and a hopper is used to collect the material slag produced by the cracking, so as to obtain a material that removes harmful substances scum.

In order to provide the first filter 57 with a stable flow to the neutralization tank 61 , the output of the first filter 57 may be connected to the second buffer tank 58 after the first filter 57 . Similarly, in order to stably output the neutralization tank 61 to the second filter 63 , a third buffer tank 62 can be provided between the neutralization tank 61 and the second filter 63 .

Please refer to FIG. 1 and FIG. 2 , and continue to perform an acid-base neutralization step S24, which is to quantitatively output the fine particles 571 from the second buffer tank 58 to the neutralization tank 61, and uniformly mix water and lime. The lime aqueous solution is added into the neutralization tank 61, and is uniformly mixed in the neutralization tank 61 (eg, stirred with a motor stirrer). Then a second filtering step S25 is performed, and the output from the third buffer tank 62 is collected by the second filter 63 The obtained slurry (containing a plurality of fine particles of carbon particles and heavy metal components); and the slurry passing through the second filter 63 is dried and dehydrated to obtain a product of metal hydroxide. Continue to perform a vacuum concentration step S26, which is to quantitatively output the slurry from the fourth buffer tank 7 to a vacuum concentration unit 8, concentrate the slurry into high-salt brine, and dry and dehydrate to prepare an industrial salt.

It can be seen from the above that the present invention applies the calcium salt precipitation method, especially the method for reducing the fluorine content of waste water with calcium chloride, and in the reaction process of calcium chloride, high-salt brine and fluorine-containing waste water, according to the reaction The pH value of the tank can be adjusted to adjust the fluorine content and brine content added to the reaction tank, so as to maintain high efficiency and reduce the fluorine content of wastewater; in addition, the calcium chloride and high-salt brine raw materials participating in the reaction are from the heavy metal removal process. The derived by-products, such as the preparation of metal hydroxides and industrial salts, can be used for each other, and the reaction cost can be greatly reduced.

The embodiments disclosed above are only illustrative of the principles, features and effects of the present invention, and are not intended to limit the scope of the present invention. Modifications and changes are made to the above-described embodiments. Any equivalent changes and modifications made by using the contents disclosed in the present invention should still be covered by the following claims.

1: Method for reducing fluorine content in wastewater

12: Wastewater

13: Calcium chloride slurry

14: High salt brine

S11 to S16: the method steps of reducing the fluorine content of wastewater according to an embodiment of the present invention

S21 to S26: the application of an embodiment of the present invention to remove the method steps of heavy metal process by-products

Claims (10)

A method for reducing the fluorine content of wastewater by removing heavy metal process by-products, comprising: A reaction step is to use a reaction tank for the fluorine-containing waste water to be contained, and to react together with a calcium chloride slurry in an appropriate ratio and a high-salt brine in the reaction tank; A mixing control step, in order to apply a mixing control unit to control the amount of waste water entering the reaction tank, the ratio of the calcium chloride slurry and the high-salt brine entering the reaction tank; In a precipitation step, a sedimentation tank is used to receive the sludge treated by the reaction tank, and insoluble calcium fluoride precipitate is produced; a step of detecting fluoride ion content, for detecting whether the fluorine content of the slurry in the sedimentation tank is less than a discharge water control standard, if not, returning the slurry to the reaction tank, and continuing the reaction step; and a pH value adjustment step, further adjusting the pH value of the mud in the sedimentation tank whose fluorine content meets the discharge water control standard in a pH adjustment tank; In a discharge step, the adjusted mud waste water is sent to a discharge tank, and the pH value of the mud waste water in the discharge tank is detected and recorded to meet the discharge water standard and then discharged; Wherein, the manufacturing process of the calcium chloride slurry and the high-salt brine includes: A setting step is to compare the pH value of an initial material with the pH value of the initial reaction time in a heavy metal dissolution test curve to obtain a liquid-solid ratio corresponding to the curve closest to the pH value, and then according to A viscosity value corresponding to the liquid-solid ratio is found out through a graph of the viscosity change of different liquid-solid ratios, which is used as the initial viscosity value of the initial material; A pickling operation step is to add the initial material, water and acid solution meeting an initial ratio into a pickling tank and uniformly stir to form a slurry, so that the heavy metals in the initial material, the water and the acid solution are reacted For elution of heavy metals, the ratio of the initial material to water is adjusted to meet the initial viscosity value, and the pickling operation step The step includes a pH value control unit for detecting the pH value of the slurry in the pickling tank, and adjusting the pH value ratio of the slurry in the pickling tank to make the corresponding relationship between the pH value of the slurry and the reaction time conforming to the selected curve change of the heavy metal dissolution test curve; a first filtering step, collecting a plurality of fine particles of carbon particles and heavy metal components of the slurry with a first filter; An acid-base neutralization step is to transfer the fine particles to a neutralization tank, and add a uniform mixed solution of water and a lime into the neutralization tank, and mix them uniformly in the neutralization tank; a second filtering step, collecting a plurality of fine particles containing heavy metal components with a second filter to form the calcium chloride slurry; and In a vacuum concentration step, the calcium chloride slurry is transported to a vacuum concentration unit for concentrating the calcium chloride slurry into the high-salt brine. The method for reducing the fluorine content of waste water by removing heavy metal process by-products as described in claim 1, wherein the fluorine-containing waste water first flows into a buffer tank, and then the buffer tank provides quantitative output to the reaction tank. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products as claimed in claim 1 or 2, wherein the fluorine-containing wastewater enters the reaction tank through a first pipeline, and the calcium chloride slurry passes through a second pipeline The high-salt brine enters the reaction tank through a third pipeline, and the mixing control step is to electrically connect and control the first pipeline, the second pipeline and the third pipeline respectively. The opening and closing of the road. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products as described in claim 1, wherein the sedimentation tank uses a pH value detector to check a real-time pH value of the mud, and controls the reaction according to the real-time pH value The reaction ratio of the fluorine-containing wastewater, the calcium chloride slurry and the high-salt brine in the tank. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products according to claim 1, wherein the slurry in the pickling tank after the pickling operation is input into a first buffer tank, and then the first buffer tank is discharged from the first buffer tank. Quantitative output to the first filter. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products according to claim 5, wherein the fine particles collected by the first filter in the first filtering step are collected by a second buffer tank, and the The fine particles quantitatively output from the second buffer tank are placed in the neutralization tank. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products according to claim 6, wherein the slurry in the neutralization tank is collected in a third buffer tank, and then quantitatively output from the third buffer tank to the second filter device collection. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products according to claim 7, wherein a fourth buffer tank is used to collect the slurry collected by the second filter in the second filtration step, and output the slurry to The vacuum concentration unit. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products as described in claim 1, wherein in the pickling operation step, the acid solution added to the pickling tank is waste acid, and in the pH control unit, The method for controlling the acid-base ratio of the water and the acid solution is to add a controllable amount of pure acid to the pickling tank to adjust the acid value of the pickling tank. The method for reducing the fluorine content of wastewater by removing heavy metal process by-products according to claim 1, wherein the fine particles collected by the first filter in the first filtering step are added to the first buffer tank for multiple times inside to perform multiple cyclic filtering.

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