JP3166549B2 - Method and apparatus for wet removal of hydrogen phosphide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for wet removal of hydrogen phosphide, and more particularly to a method for removing hydrogen phosphide from a fumigation warehouse when a gas containing hydrogen phosphide (hereinafter referred to as hydrogen phosphide containing gas) is used for fumigation. The present invention relates to a method and an apparatus for wet removal of hydrogen phosphide for removing hydrogen phosphide from a high-concentration and large-volume hydrogen phosphide-containing gas discharged.

[0002]

2. Description of the Related Art Hydrogen phosphide is an agent in semiconductor manufacturing,
Alternatively, it is used as a fumigation gas for fumigating cereals and the like. Since this hydrogen phosphide is toxic, it is necessary to remove hydrogen phosphide from the hydrogen phosphide-containing gas before discharging the gas containing hydrogen phosphide into the atmosphere. In particular,
When using hydrogen phosphide-containing gas as a fumigation gas, in order to quickly work in the fumigation warehouse after fumigation, discharge the highly concentrated hydrogen phosphide-containing gas in the fumigation warehouse from the fumigation warehouse in a short time. It is necessary, and it is important to reliably remove hydrogen phosphide from hydrogen phosphide-containing gas with high concentration and large air flow.

Conventionally, a method for removing a hydrogen phosphide-containing gas has been a solid phase adsorption method in which hydrogen phosphide in a hydrogen phosphide-containing gas is adsorbed and removed by an adsorbent mainly containing an oxidizing agent such as potassium permanganate. The law is mainly adopted. Also,
It is also possible to remove hydrogen phosphide by a catalytic catalytic oxidation method or a direct combustion method. However, the solid-phase adsorption method is a simple and reliable method for removing hydrogen phosphide from a hydrogen phosphide-containing gas having a low concentration and a small amount of air, but it is a method of removing hydrogen phosphide from a gas having a high concentration and a large amount of air such as fumigation. In order to remove hydrogen phosphide from a hydrogen phosphide-containing gas in a short time, an enormous amount of adsorbent is required, which is disadvantageous in that it is not economical. In addition, the catalytic catalytic oxidation method and the direct combustion method can process high-concentration, large-air-volume hydrogen phosphide-containing gas.
There is a disadvantage that it is not practical because the risk of explosion increases as the wind volume increases.

[0004] From such a background, attention has been paid to a wet absorption method capable of treating a hydrogen phosphide-containing gas having a high concentration and a large air flow in a short time without danger of explosion. This method is a method of removing hydrogen phosphide by contacting and absorbing a hydrogen phosphide-containing gas with a chemical solution using a scrubber device or the like.

[0005]

However, in the wet absorption method, the technology such as the chemical solution to be used and the optimum use conditions of the chemical solution have not been established, and the hydrogen phosphide contained in the hydrogen phosphide-containing gas is highly removed. There is a disadvantage that it cannot be removed stably at a high rate. The present invention has been made in view of such circumstances, and a wet removal of hydrogen phosphide capable of stably removing hydrogen phosphide in a high-concentration, large-volume hydrogen phosphide-containing gas at a high removal rate. It is an object to provide a method and an apparatus.

[0006]

In order to achieve the above object, the present invention provides a wet removal of hydrogen phosphide in which a gas containing hydrogen phosphide is brought into contact with a chemical solution to remove the hydrogen phosphide in the gas. In the method, a sodium hypochlorite solution is used as the chemical solution, the redox potential of the sodium hypochlorite solution is maintained at 1030 to 1120 mV, and the pH value of the sodium hypochlorite solution is 8 to The method is characterized in that the gas is brought into contact with the gas while maintaining the gas pressure at 9.

Further, in order to achieve the above object, the present invention provides a method for producing hydrogen phosphide, which comprises contacting a gas containing hydrogen phosphide with a chemical solution so that the hydrogen phosphide in the gas is absorbed by the chemical solution and removed. in the wet removal device, a contact device for contacting the hydrogen phosphide-containing gases in the sodium hypochlorite solution, the redox potential of the sodium hypochlorite solution
Control and ORP control system to control said and a pH control system for controlling the pH value of the sodium hypochlorite solution, the redox potential controlled by controlling and the pH value 1030~1120mV to 8-9 It is characterized by doing.

[0008]

According to the present invention, the hydrogen phosphide in the hydrogen phosphide-containing gas is oxidized to phosphoric acid by contacting the hydrogen phosphide-containing gas with the sodium hypochlorite solution. Is absorbed by In this oxidation and absorption,
The oxidation-reduction potential indicating the oxidizing power of the sodium hypochlorite solution is 1
Since the hydrogen phosphide-containing gas is brought into contact with the gas while maintaining the pressure at 030 to 1120 mV, the hydrogen phosphide in the hydrogen phosphide-containing gas can be stably removed at a high removal rate.

According to another aspect of the present invention, the redox potential of the sodium hypochlorite solution is from 1030 to 1120 m
V, and the pH value of the sodium hypochlorite solution was adjusted to 8 to 9 by adding a pH adjuster. As a result, hydrogen phosphide in the hydrogen phosphide-containing gas can be stably removed at a high removal rate, and the pH value decreases due to the accumulation of phosphoric acid in the sodium hypochlorite solution by the oxidation reaction. As a result, the generation of chlorine gas due to the generation can be suppressed as much as possible. In addition, by adjusting the pH value to the above range, the ORP value of the sodium hypochlorite solution can be quickly raised from the initial aeration stage when the hydrogen phosphide-containing gas is brought into contact with the sodium hypochlorite solution.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method and apparatus for wet removal of hydrogen phosphide according to the present invention will be described in detail below with reference to the accompanying drawings. Before describing the method and apparatus for wet removal of hydrogen phosphide of the present invention, the theoretical basis of the present invention will be described in order to facilitate understanding of the present invention.

When a hydrogen phosphide-containing gas containing hydrogen phosphide (PH ₃ ) is brought into contact with a sodium hypochlorite solution (NaClO), the phosphide in the hydrogen phosphide-containing gas is expressed as shown in equation (1). Hydrogen is oxidized to harmless phosphoric acid (H ₃ PO
₄ ) It is absorbed in sodium hypochlorite solution. On the other hand, sodium hypochlorite becomes sodium chloride (NaCl) and is rendered harmless.

PH ₃ + 4NaClO → H ₃ PO ₄ + 4NaCl (1) In order for the reaction of the formula (1) to proceed reliably, it is essential that the sodium hypochlorite solution has a sufficient oxidizing power. Yes, the effective chlorine concentration is usually used as an index of the oxidizing power. Then, as the hydrogen phosphide is oxidized and absorbed by the sodium hypochlorite solution by the reaction of the formula (1), the available chlorine in the sodium hypochlorite solution is consumed, thereby removing the hydrogen phosphide. Is generally thought to gradually decrease.

However, according to a batch experiment carried out by the inventors, a sodium hypochlorite solution having an effective chlorine concentration of 1.5% was added to a redox potential (hereinafter referred to as O) of the sodium hypochlorite solution.
When the hydrogen phosphide-containing gas is brought into contact with the RP without any control of the hydrogen ion concentration (hereinafter referred to as pH), the cumulative treatment amount of hydrogen phosphide, the hydrogen phosphide removal rate, ORP value and p of sodium hypochlorite solution
It was found that there was the following relationship with the H value. That is,
In the initial aeration phase when the hydrogen phosphide-containing gas begins to come into contact with the sodium hypochlorite solution, the ORP is reduced even though the available chlorine in the sodium hypochlorite solution is almost consumed.
Values were low, indicating a low rate of hydrogen phosphide removal.
In addition, although the effective chlorine concentration of the sodium hypochlorite solution decreases as the cumulative amount of treated hydrogen phosphide increases, the ORP value of the sodium hypochlorite solution increases and phosphatization occurs. It was found that hydrogen could be stably removed at a high removal rate. This is because the sodium hypochlorite solution pH decreases due to the phosphoric acid accumulated in the sodium hypochlorite solution as the cumulative amount of hydrogen phosphide increases, and the oxidizing power of the sodium hypochlorite solution decreases. Was thought to increase. This means that the sodium hypochlorite solution shown in FIG.
This was also demonstrated from the relationship between the H value and the ORP value.

That is, sodium hypochlorite undergoes the reactions shown in the formulas (2) and (3) in water to give hypochlorous acid (HCl).
O) and hypochlorite ion (ClO ⁻ ) are produced and evaluated as available chlorine which is an index of oxidizing power. NaClO + H ₂ O = HClO + 4NaOH (2) HClO = ClO ⁻ + H ⁺ (3) However, both hypochlorous acid (HClO) and hypochlorite ion (ClO ⁻ ) are measured as the same available chlorine. There is a great difference in oxidizing power, and hypochlorous acid has stronger oxidizing power. Then, the equilibrium relationship of the equation (3) is left, that is, in order to generate a lot of hypochlorous acid, the hydrogen ion (H ⁺ ) concentration in the sodium hypochlorite solution may be increased. From this, by adding a pH adjuster such as hydrochloric acid to the sodium hypochlorite solution to lower the pH of the sodium hypochlorite solution, and by maintaining the oxidation-reduction potential of the sodium hypochlorite solution high, Hydrogen phosphide in the hydrogen phosphide-containing gas can be stably removed at a high removal rate from the initial aeration stage.

However, the ORP of sodium hypochlorite solution
By maintaining the value at a high value, hydrogen phosphide can be stably removed at a high removal rate. On the other hand, as shown in FIG. ₂ ) began to occur, and the concentration also increased with an increase in the accumulated processing amount, and reached a concentration of several tens of ppm. The reason for this is that, as shown by the equations (4) and (5), as the phosphoric acid is accumulated in the sodium hypochlorite solution due to the oxidation and absorption and the pH value decreases, the by-products are reduced. It was considered that chlorine gas was generated.

2HClO + NaOH + H ₃ PO → NaH ₂ PO + 2H ₂ O + 1 / 2O ₂ + Cl ₂ (4) 2HClO + NaOH + H ₃ PO → Na ₂ HPO + 3H ₂ O + O ₂ + Cl ₂ (5) Similarly, even if hydrogen phosphide can be stably removed at a high removal rate, there is a problem if the chlorine gas concentration is increased. From these facts, the inventors have studied conditions under which a high hydrogen phosphide removal rate can be obtained and the generation of chlorine gas can be suppressed.

FIG. 3 shows that when the effective chlorine concentration of the sodium hypochlorite solution is kept constant and the pH value of the sodium hypochlorite solution is changed to 7, 8, 8.5, 9, 10, And maintaining the pH value of the sodium hypochlorite solution constant so that the effective chlorine concentration of the sodium hypochlorite solution is within a practical range of 0.5.
%, 1.0%, 1.5%, and 2.0%, the hydrogen phosphide removal rate when treating a hydrogen phosphide-containing gas having a hydrogen phosphide inlet concentration of 1000 ppm, O
It summarizes the results of the RP value and the generation status of chlorine gas. In the view of FIG. 3, the hydrogen phosphide removal rate and the chlorine gas generation status are indicated by ○, Δ, and × for each measurement point, the hydrogen phosphide removal rate is shown on the left side of the figure, and the chlorine generation amount is shown on the right side of the figure. . As for the hydrogen phosphide removal rate, ○ indicates 99% or more, Δ indicates 98% or more and less than 99%, and X indicates less than 98%.
, Δ indicates 1 ppm or more and less than 5 ppm, and X indicates 5 ppm or more.

The present inventors have obtained the following findings from the results shown in FIG. If the pH value of the sodium hypochlorite solution is less than 8, chlorine gas is likely to be constantly generated regardless of the effective chlorine concentration of the sodium hypochlorite solution. If the pH value of the sodium hypochlorite solution exceeds 9, the redox potential of the sodium hypochlorite solution does not increase even though the available chlorine of the sodium hypochlorite solution is sufficient. If the ORP value of the sodium hypochlorite solution is less than 1030 mV, the removal rate of hydrogen phosphide is reduced. If the ORP value of the sodium hypochlorite solution exceeds 1120 mV, chlorine gas is likely to be generated when the effective chlorine concentration is high even if the pH value of the sodium hypochlorite solution is 8 or more.

To summarize the above findings, the phosphatization is achieved by maintaining the ORP value of the sodium hypochlorite solution at 1030 to 1120 mV and maintaining the pH value of the sodium hypochlorite solution at 8 to 9. Hydrogen phosphide in the hydrogen-containing gas can be stably removed at a high removal rate, and generation of chlorine gas can be suppressed as much as possible. In this case, it is more effective to set the pH value higher when the ORP value is set lower, and to set the pH value lower when the ORP value is set higher.

FIG. 4 is an overall configuration diagram showing an example of the wet hydrogen phosphide removal apparatus of the present invention constructed based on the above findings (1) to (4). Hereinafter, the method for wet removal of hydrogen phosphide of the present invention will be described while describing the apparatus configuration. As shown in FIG. 4, the hydrogen phosphide-containing gas discharged from the fumigation warehouse or the like is sent to the first washing tower 10. The hydrogen phosphide-containing gas sent into the first washing tower 10 rises through the filler layer 12 filled with a filler such as a Racheling. During this ascent, a sodium hypochlorite solution as an absorbing liquid is ejected from a nozzle 14 above the filler layer 12, and the hydrogen phosphide-containing gas and the sodium hypochlorite solution come into contact. First washing tower 10
An absorption liquid reservoir 16 for storing sodium hypochlorite solution is provided at the bottom of the inside, and the sodium hypochlorite solution in the absorption liquid reservoir 16 is circulated to the nozzle 14 by a pump 18.

The ORP value and the pH value of the sodium hypochlorite solution that comes into contact with the hydrogen phosphide-containing gas in the first washing tower 10 are measured by the ORP meter 20 and the pH meter 22. Then, the measured ORP value is transmitted to the chemical liquid pump 28 of the absorbing liquid tank 26 via the signal cable 24,
The measured pH value is transmitted to the chemical liquid pumps 36 and 38 of the sodium hydroxide liquid tank 32 and the hydrochloric acid tank 34 via the signal cable 30. Then, the ORP value of the sodium hypochlorite solution in the absorption liquid reservoir 16 is 1030 to
The supply amount of the chemical supplied from each of the tanks 26, 32, and 34 to the absorption liquid reservoir 16 is controlled so that the pH is maintained in the range of 1120 mV and the pH value is maintained in the range of 8 to 9.

[0022] Thereby, the hydrogen phosphide in the hydrogen phosphide-containing gas can be stably removed at a high removal rate from the initial aeration stage in which the hydrogen phosphide-containing gas is brought into contact with the sodium hypochlorite solution, In addition, generation of chlorine gas due to the phosphoric acid being accumulated in the sodium hypochlorite solution and the pH of the sodium hypochlorite solution being too low can be suppressed as much as possible.

Next, the processing gas from which the hydrogen phosphide-containing gas has been contacted with the sodium hypochlorite solution to remove the hydrogen phosphide is passed through a mist separator 40 provided in the upper part of the first washing tower 10. After the moisture is removed, the gas is sent to the second washing tower 42. The second cleaning tower 42 completely removes a trace amount of chlorine gas that may be generated in the first cleaning tower 10,
When chlorine gas is generated due to troubles such as operating conditions in the first washing tower 10, the chlorine gas is removed. That is,
The hydrogen phosphide-containing gas sent into the second washing tower 42 is
As it rises through the filler layer 44, it comes into contact with the sodium hydroxide solution ejected from the nozzle 46 above the filler layer 44. The ejected sodium hydroxide is circulated by a pump 53 between an alkali reservoir 48 formed at the bottom of the second washing tower 42 and a nozzle 46, and the second washing tower 42
Sodium hydroxide is replenished from the sodium hydroxide solution tank 50 provided outside to the alkali reservoir 48 by the chemical solution pump 52. The pH of the alkali reservoir 48 is measured by a pH meter 54 for the second washing tower 42, and the measured value is transmitted to the chemical pump 52 via a signal cable 56.
Then, the final processing gas processed in the second cleaning tower 42 is dehumidified by the mist separator 58 and discharged to the atmosphere from the top of the second cleaning tower 42.

In the above-described embodiment, during the operation of the first washing tower 10, the sodium hypochlorite solution and the pH adjusting agent are replenished to the absorbing solution reservoir 16, and the OR of the sodium hypochlorite solution is performed.
Although the P value and the pH value are controlled within the predetermined ranges, the operation of the first washing tower 10 may be performed as follows when discharging the hydrogen phosphide-containing gas from the fumigation warehouse. In other words, the hydrogen phosphide concentration of the hydrogen phosphide-containing gas discharged from the fumigation warehouse has a high curve at the beginning of evacuation, but sharply decreases by the air purge, and thereafter gradually decreases. Therefore, when the hydrogen phosphide concentration has decreased to some extent, the sodium hypochlorite solution and the pH adjuster supplied to the absorption liquid reservoir 16 are stopped,
After that, the ORP value of the sodium hypochlorite solution is 1030 to 1120 mV by the ORP meter 20 and the pH meter 22.
And that the pH value is in the range of 8-9. By stopping the supply, the effective chlorine concentration of the sodium hypochlorite solution is consumed and decreases, but the pH value in the sodium hypochlorite solution decreases due to the accumulation of phosphoric acid, and the ORP value increases. Act on. As a result, the ORP value and the pH value of the sodium hypochlorite solution can be maintained within the above-mentioned predetermined range for a certain period of time unless the effective chlorine concentration of the sodium hypochlorite solution becomes extremely low. When this operation method is continued, as can be seen from the relationship between the pH value and the amount of chlorine gas generation described with reference to FIG. 1, the amount of chlorine gas increases as the pH value decreases and shifts to the acidic side. In this case, the pH value is slightly increased by slightly adding sodium hydroxide as a pH adjuster to the alkali side.
As a result, the amount of the sodium hypochlorite solution and the pH adjuster used can be reduced, so that the running cost can be reduced, and the available chlorine in the sodium hypochlorite solution at the end of the operation of the first washing tower 10 can be reduced. Since the concentration becomes low, it becomes easy to treat the waste liquid of the sodium hypochlorite solution.

In the present embodiment, sodium hydroxide and hydrochloric acid were used as pH adjusters, but the present invention is not limited to this. Potassium hydroxide, calcium hydroxide, sulfuric acid,
A common alkali or acid such as nitric acid may be used. Also,
In the second washing tower, chlorine is absorbed into sodium hydroxide to form sodium hypochlorite or sodium chloride. Therefore, it is used as a pH adjuster for the first washing tower of the absorbing solution of the second washing tower. As a result, the running cost can be further reduced.

[0026]

As described above, according to the method and apparatus for wet removal of hydrogen phosphide of the present invention, a sodium hypochlorite solution is used as a chemical solution, and the oxidation-reduction potential of the sodium hypochlorite solution is 1030. Since the pressure is maintained at １1120 mV or more, hydrogen phosphide in the hydrogen phosphide-containing gas can be stably removed at a high removal rate.

According to the present invention, the redox potential of the sodium hypochlorite solution is maintained at 1030 to 1120 mV, and the pH value of the sodium hypochlorite solution is maintained at 8 to 9. Therefore, hydrogen phosphide in the hydrogen phosphide-containing gas can be stably removed at a high removal rate from the initial aeration stage where the hydrogen phosphide-containing gas is brought into contact with the sodium hypochlorite solution, and chlorine is removed. Generation of gas can be suppressed as much as possible.

Therefore, the present invention is extremely useful as a hydrogen phosphide removing device in the case where a high-concentration, large-volume hydrogen phosphide-containing gas is discharged into the atmosphere from a fumigation warehouse or the like.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the accumulated amount of hydrogen phosphide, the hydrogen phosphide removal rate, the ORP value and the pH value of sodium hypochlorite solution, and the concentration of chlorine gas.

FIG. 2 is a diagram showing a relationship between an ORP value and a pH value of a sodium hypochlorite solution.

FIG. 3 is an experimental result diagram in which a condition under which a high hydrogen phosphide removal rate is obtained and the generation of chlorine gas is suppressed is examined.

FIG. 4 is an overall configuration diagram showing an example of a hydrogen phosphide wet removal apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... 1st washing tower 12, 44 ... Filler layer 14, 46 ... Nozzle 16 ... Absorbing liquid reservoir 20 ... ORP measuring instrument 22, 54 ... pH measuring instrument 26 ... Absorbing liquid tank 32, 50 ... Sodium hydroxide liquid tank 34 ... Hydrochloric acid tank 40,58 ... Mist separator 42 ... Second washing tower

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Teruyuki Tsutsumi 1-6-21 Nishi-Shimbashi, Minato-ku, Tokyo Inside Teijin Chemicals Co., Ltd. (72) Inventor Tetsuro Niiyama 1-6-1-21, Nishi-Shimbashi, Minato-ku, Tokyo Teijin Chemicals Co., Ltd. (56) References JP-A-50-95104 (JP, A) JP-A-1-262930 (JP, A) JP-A-5-220345 (JP, A) (58) Fields surveyed ( Int.Cl. ⁷ , DB name) B01D 53/34-53/96

Claims (2)

(57) [Claims] 1. A method for removing hydrogen phosphide in a gas by bringing a gas containing hydrogen phosphide into contact with a chemical solution, the method comprising the steps of: removing sodium phosphite solution as the chemical solution; Use and
The redox potential of the sodium hypochlorite solution was 1030
1120 mV and the sodium hypochlorite solution
A method for wet removal of hydrogen phosphide , wherein the gas is contacted while maintaining the pH value at 8 to 9 . 2. A hydrogen phosphide wet-removing apparatus, wherein a gas containing hydrogen phosphide is brought into contact with a chemical solution to absorb the hydrogen phosphide in the gas with the chemical solution and remove the hydrogen phosphide. a contact device for contacting the gas containing the sodium hypochlorite solution, O for the oxidation-reduction potential control of the sodium hypochlorite solution
And RP control system, it said and a pH control system for the pH value control of sodium hypochlorite solution, and controlling the oxidation reduction potential 1030~1120mV且
Wherein the pH value is controlled to 8 to 9 ;