JPH11128930A - Apparatus for concentrating dilute hydrofluoric acid waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the concentration and volume reduction of diluted hydrofluoric acid waste liquid by passing a dilute hydrofluoric acid waste liquid which is sent from a dilute hydrofluoric acid waste liquid recovery tank and has a hydrofluoric acid concentration not exceeding a specified value through an RO column having reverse osmosis membranes. SOLUTION: In concentration treatment, dilute hydrofluoric acid waste liquid discharged from a washing device is passed through an RO column 11 filled with RO membranes, divided into concentrated water, filtrate, and circulating water, and discharged. The concentrated water is recovered in a dilute hydrofluoric acid water liquid concentration tank 1b and the circulation water is recovered in a dilute hydro fluoric acid waste liquid recovery tank 5. The filtrate is discharged into a neutralization tank 17 and treated. It is also possible to treat the filtrate by recycling pure water. Since the concentration capacity of the RO membrane is lowered when a fluorine ion concentration is 1000 ppm or above, it is necessary to keep the concentration not exceeding 1000 ppm in the tank 5. Accordingly, the upper limit setting value of a hydrofluoric acid concentration meter 2 set in a hydrofluoric acid concentration measuring tank 1 is set up in consideration of dilution in the tank 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste liquid treatment apparatus, and more particularly to a concentrated treatment apparatus for dilute hydrofluoric acid waste liquid containing 1000 ppm or less of fluoride ions.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, various kinds of chemicals are used in large quantities. In particular, in the wafer cleaning step, it is common to perform cleaning using an acid and an alkali chemical, and to perform treatment using hydrofluoric acid as final cleaning. Recently, the use of a large amount of hydrofluoric acid having a very low concentration has become very large. In the past, the circulation method that used the chemical solution entering the treatment tank while circulating it was the mainstream, but a new cleaning method was devised, and the method of disposing of the chemical solution using a spray type or one bath method has become the mainstream. Because it is. Therefore, the fact is that the amount of dilute hydrofluoric acid waste liquid is much larger than before. Usually, the waste liquid and waste water containing hydrofluoric acid ions are collected in a collecting tank or the like regardless of the concentration. For the subsequent treatment of the diluted hydrofluoric acid waste liquid, a fluoride precipitation treatment method is often used. For processing, a factory that has a waste liquid treatment facility is in the factory, and a factory that does not have a waste liquid treatment facility is a method that entrusts the treatment to an industrial waste contractor. However, since there is no method for reducing the amount of waste liquid before the above-mentioned fluoride precipitation treatment is performed, if the amount of wafer treatment due to the disposable use of a chemical solution increases, dilute hydrofluoric acid at a factory level of 10 tons or more / day is required. Waste liquid will be discharged. In that case, the cost of semiconductor devices will increase due to the expansion of industrial waste treatment facilities and the increase in disposal costs.

[0003]

By simply performing the above-mentioned conventional waste liquid treatment, the amount of waste liquid will continue to increase due to the increase in the amount of wafer treatment, thereby increasing the size of waste liquid treatment equipment and the cost of waste liquid treatment. As a result, the cost of the device is increased.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a dilute hydrofluoric acid concentrating treatment apparatus in which the amount of dilute hydrofluoric acid waste liquid is greatly reduced and the volume thereof is reduced.

[0005]

According to a first aspect of the present invention, there is provided a dilute hydrofluoric acid waste liquid concentration treatment apparatus comprising an RO tower having a reverse osmosis membrane, wherein 1000 pp sent from a dilute hydrofluoric acid waste liquid recovery tank is provided.
By diluting dilute hydrofluoric acid waste liquid of m or less through this RO tower, the dilute hydrofluoric acid waste liquid is concentrated and reduced in volume.

As described above, the pH of the diluted hydrofluoric acid waste liquid used in a large amount in the final cleaning in the cleaning etching process is adjusted in the recovery tank, and then the diluted hydrofluoric acid waste liquid having a reverse osmosis membrane (hereinafter abbreviated as an RO membrane) is removed.
By passing water through the O tower, the dilute hydrofluoric acid waste liquid is concentrated and reduced in volume, and at the same time, the waste liquid can be significantly reduced.

A second aspect of the present invention is a dilute hydrofluoric acid waste liquid concentration treatment apparatus, wherein the RO tower of the treatment apparatus according to the first aspect is provided in series and in parallel.

Thus, by providing the RO towers in series and in parallel, it is possible to immediately cope with a change in the concentration of fluorine ions in the waste liquid, and it is possible to surely concentrate the dilute hydrofluoric acid waste liquid by improving the concentration efficiency. Significant reduction and volume reduction of dilute hydrofluoric acid waste liquid.

According to a third aspect of the present invention, the concentrated dilute hydrofluoric acid waste liquid is passed through the RO tower of the processing apparatus according to the first aspect, and the concentrated water discharged from the RO tower is removed. It is characterized by a circulation system in which circulating water is again passed through an RO tower by a liquid sending pump and continuously concentrated in water and circulating water.

[0010] As described above, the dilute hydrofluoric acid waste liquid passed through the RO tower having the RO membrane is separated into concentrated water, permeated water, and circulating water, and is discharged. Is collected in a neutralization tank. The circulating water is collected in a dilute hydrofluoric acid waste liquid recovery tank, where
H adjustment is performed, and thereafter, the wastewater is treated by a circulation type continuous concentration treatment method in which water is again passed to the RO tower by a liquid sending pump, so that the amount of dilute hydrofluoric acid waste liquid can be significantly reduced and volume reduced.

The dilute hydrofluoric acid waste liquid concentration treatment apparatus according to claim 4 is a hydrofluoric acid concentration measuring tank having a hydrofluoric acid concentration meter before the dilute hydrofluoric acid waste liquid is passed through the RO tower of the processing apparatus according to claim 1. In this case, the fluoride ion concentration is measured in advance, and when a measured value exceeding a certain concentration occurs, the valve is automatically opened and closed to collect the dilute hydrofluoric acid waste liquid having a high fluoride ion concentration in the dilute hydrofluoric acid waste liquid concentration tank. Features.

The dilute hydrofluoric acid waste liquid recovered from various cleaning apparatuses is not only a waste liquid having a constant fluorine ion concentration,
Waste liquids having different fluorine ion concentrations are collected in the dilute hydrofluoric acid waste liquid recovery tank. Therefore, when a dilute hydrofluoric acid waste solution having a high fluoride ion concentration exceeding the processing limit of the RO film is recovered, the concentration is measured with a hydrofluoric acid concentration meter, and a valve linked to the hydrofluoric acid concentration meter is operated. By automatically opening and closing, the RO film is protected and only the dilute hydrofluoric acid waste liquid can be recovered.

According to a fifth aspect of the present invention, the dilute hydrofluoric acid waste liquid concentrating treatment apparatus is characterized in that before the dilute hydrofluoric acid waste liquid is passed through the RO tower of the processing apparatus according to the first aspect of the present invention, the dilute hydrofluoric acid waste liquid recovery tank is supplied with a pump from a NaOH storage tank. The pH of the dilute hydrofluoric acid waste liquid is automatically adjusted by the NaOH liquid sent in step (1).

As described above, the pH meter is automatically controlled by the injection pump of the NaOH storage tank, and when the PH value is out of a certain range, the NaOH liquid is automatically injected so that the PH value becomes neutral. Is what you do.

According to this invention, the amount of dilute hydrofluoric acid waste liquid can be greatly reduced by continuously concentrating a large amount of dilute hydrofluoric acid waste liquid.

[0016]

FIG. 1 shows a dilute hydrofluoric acid waste liquid concentration apparatus according to an embodiment of the present invention. The dilute hydrofluoric acid waste liquid discharged from the cleaning apparatus is concentrated by passing water through an RO tower 11 filled with an RO membrane, and is separated into concentrated water, permeated water, and circulating water and discharged. The concentrated water is diluted hydrofluoric acid waste liquid concentration tank 16
Then, the circulating water is recovered in the dilute hydrofluoric acid waste liquid recovery tank 5. The permeated water is discharged to the neutralization tank 17 for treatment. In addition, the permeated water can be treated by being recycled to pure water.

In this embodiment, a used RO membrane that has been used and used in purification of ultrapure water or the like is filled in the RO tower 11 without using a new RO membrane. In semiconductor manufacturing, many RO membranes are used in a purification system to produce ultrapure water. The fact is that they are exchanged regularly. Therefore, many replaced RO films remain. Therefore, there is an advantage that no initial cost is required because the used RO film which has been replaced is used.

Further, an RO tower 11 filled with an RO film for concentrating a dilute hydrofluoric acid waste liquid is provided in series and in parallel. Valves 12 are provided at the entrance and exit of the upper and lower RO towers 11, respectively.
13, 14, and 15. When dilute hydrofluoric acid waste water is passed, valves 12 and 13 are used in one of the upper and lower RO towers 11.
Alternatively, the valves 14 and 15 are opened and closed for use.

By using the RO tower 11 filled with the RO membrane in series, it is possible to cope with a change in the concentration of fluorine ions, and a stable concentration treatment can be performed. In addition, by providing the RO tower 11 in parallel in the upper and lower stages, the enrichment process can be performed in a continuous operation without stopping the enrichment device due to RO membrane exchange or the like.

Further, the dilute hydrofluoric acid waste liquid passed through the RO tower 11 filled with the RO membrane is concentrated, and the circulating water discharged therefrom is collected in the dilute hydrofluoric acid waste liquid recovery tank 5 and again returned to the RO tower 11.
A liquid sending pump 9 is provided to allow water to flow. The circulating water discharged from the RO tower by the liquid feed pump is continuously
It is possible to control the concentration ratio and the processing time by controlling the amount of concentrated water or permeated water discharged by passing the water through the tower 11.

The dilute hydrofluoric acid waste liquid discharged from each cleaning device is first sent to a hydrofluoric acid concentration measuring tank 1 in which a hydrofluoric acid concentration meter 2 is always installed. The hydrofluoric acid concentration measuring tank 1 has switching valves 3 and 4, and the hydrofluoric acid concentration meter 2 and the switching valves 3, 4 are interlocked according to measured values.

In this case, the dilute hydrofluoric acid waste liquid is first sent to the hydrofluoric acid concentration measuring tank 1 and the fluoride ion concentration is measured by the hydrofluoric acid concentration meter 2. When the measured fluorine ion concentration exceeds the value, for example, by setting the upper limit to 1%, the valves 3 and 4 are automatically switched to be collected in the dilute hydrofluoric acid waste liquid concentration tank 16. RO film itself has a fluorine ion concentration of 1000 ppm
When the concentration becomes higher, the concentration treatment capacity is reduced, so that it is necessary to suppress the fluoride ion concentration in the dilute hydrofluoric acid waste liquid recovery tank 5 to 1000 ppm or less. Therefore, the upper limit set value of the hydrofluoric acid concentration meter 2 installed in the hydrofluoric acid concentration measuring tank 1 needs to be set in consideration of mixing and dilution in the dilute hydrofluoric acid waste liquid collecting tank 5. Further, even if the concentrated hydrofluoric acid waste liquid is erroneously flowed, the hydrofluoric acid concentration meter 2 catches an abnormal value and opens and closes the valve, so that an emergency response can be taken immediately.

A NaOH storage tank 7 for adjusting the pH of the dilute hydrofluoric acid waste liquid collected in the dilute hydrofluoric acid waste liquid recovery tank 5 and its N
a charging pump 8 for charging an aOH solution into the dilute hydrofluoric acid waste liquid collecting tank 5
Having. By adjusting the pH of the dilute hydrofluoric acid waste liquid, it is possible to minimize the influence on each component in the concentrator, particularly on the RO membrane. In addition, since pure permeated water is obtained, pure water recycling becomes possible.

[0024]

As described above, according to the present invention, the volume of waste liquid having a fluoride ion concentration of 1000 ppm or less in dilute hydrofluoric acid waste liquid can be concentrated and reduced to 1/5 to 1/10. The quantity can be significantly reduced. Since the RO film is not new and can be used, there is an advantage that no initial cost is required. Also, permeated water can be environmentally resource-saving because pure water can be recycled.

[Brief description of the drawings]

FIG. 1 is a diagram showing a dilute hydrofluoric acid waste liquid concentration treatment apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 1 Hydrofluoric acid concentration measurement tank 2 Hydrofluoric acid concentration meter 3 Valve 4 Valve 5 Dilute hydrofluoric acid waste liquid recovery tank 6 PH measurement meter 7 NaOH storage tank 8 Input pump 9 Liquid sending pump 10 Filter 11 RO tower 12 Valve 13 Valve 14 Valve 15 Valve 16 Dilute hydrofluoric acid waste liquid concentration tank 17 Neutralization tank

Claims (5)

[Claims] A dilute hydrofluoric acid waste liquid having a fluoride ion concentration of 1000 ppm or less is passed through an RO tower filled with a reverse osmosis membrane to reduce the concentration of dilute hydrofluoric acid waste liquid and reduce the amount of dilute hydrofluoric acid waste liquid. Hydrofluoric acid waste liquid concentration treatment equipment. 2. A dilute hydrofluoric acid waste liquid is passed through the RO tower, which is provided in series and in parallel, to discharge concentrated water containing fluoride ions, circulating water, and permeated water having reduced fluorine ions at the outlet of the RO tower. The dilute hydrofluoric acid waste liquid concentration treatment apparatus according to claim 1, wherein 3. The concentrated water and circulating water containing fluoride ions discharged from the RO tower are collected in a dilute hydrofluoric acid waste liquid recovery tank and a dilute hydrofluoric acid waste liquid concentrator tank, respectively. 3. The dilute hydrofluoric acid waste liquid concentrating treatment device according to claim 1, wherein water is passed through and continuously concentrated. 4. Before the dilute hydrofluoric acid waste liquid is sent to the RO tower, the dilute hydrofluoric acid waste liquid is once sent to a hydrofluoric acid concentration measuring tank provided with a hydrofluoric acid concentration meter, and the value of the hydrofluoric acid concentration meter is measured. 4. The dilute hydrofluoric acid according to claim 1, wherein the diluent hydrofluoric acid has a function of automatically operating a valve when the concentration exceeds a certain concentration value and switching from a dilute hydrofluoric acid waste liquid recovery tank to a dilute hydrofluoric acid waste liquid concentration tank. Waste liquid concentration treatment equipment. 5. When the diluted hydrofluoric acid waste liquid is collected in the dilute hydrofluoric acid waste liquid collecting tank before the dilute hydrofluoric acid waste liquid is sent to the RO tower, the NaOH liquid is introduced into the dilute hydrofluoric acid waste liquid collecting tank. 5. The dilute hydrofluoric acid waste liquid concentration treatment device according to claim 1, wherein the treatment device has a pH adjustment function.