JP2000051871A - Method for treating drainage containing hydrogen peroxide and ammonia - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat hydrogen peroxide and ammonia in drainage safely and efficiently in operation conditions of a relatively low temperature and a low pressure by a method in which after the drainage being contacted with a catalyst to decompose hydrogen peroxide in the drainage, ammonia is evaporated and removed. SOLUTION: Drainage containing hydrogen peroxide (H2O2) and ammonia (NH3) is introduced into a hydrogen peroxide decomposition apparatus 1 to conduct the catalytic decomposition of the hydrogen peroxide. As the apparatus 1, a fluidized bed type reaction is preferable, conditions of a relatively low temperature and a low pressure can be adopted, the hydrogen peroxide in the drainage is decomposed into water and oxygen, and the oxygen gas is discharged outside a system. Next, the treated water is introduced into an ammonia evaporation column 2, and the ammonia is evaporated at a low temperature and under a low pressure to be removed. The treated water after the evaporation of ammonia is discharged outside the system, and the ammonia gas is condensed as required to be recovered and used effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for efficiently treating wastewater containing hydrogen peroxide and ammonia discharged from a semiconductor factory or the like.

[0002]

2. Description of the Related Art Waste water containing hydrogen peroxide and ammonia is discharged from a semiconductor manufacturing process. Hydrogen peroxide in this wastewater is applied to COD _Mn and needs to be decomposed. Ammonia causes eutrophication in rivers, lakes and seas, and must be treated.

Hitherto, as a method for removing only ammonia in wastewater, there is a method using biological treatment. However, the method using biological treatment generates sludge; it is difficult to maintain and control; Requires equipment footprint;
There are disadvantages such as.

[0004] Hydrogen peroxide in wastewater is decomposed by adding a chemical such as catalase. However, in this method, it is difficult to control the injection amount of the chemical and to obtain a stable water quality.

As a method for solving the above problems and simultaneously efficiently decomposing and removing hydrogen peroxide and ammonia in wastewater, the present applicant has previously proposed a method for decomposing both components using a noble metal-supported catalyst. (JP-A-5-269475).
No.).

[0006]

Problems to be Solved by the Invention
The catalytic cracking method using a noble metal-supported catalyst disclosed in Japanese Patent No. 5 requires operation at high temperature and high pressure, and has a problem of high initial cost.

[0007] The present invention solves such a problem, and provides hydrogen peroxide and ammonia which can safely and efficiently treat hydrogen peroxide and ammonia in wastewater under relatively low temperature and low pressure operating conditions. It is an object of the present invention to provide a method for treating wastewater containing.

[0008]

According to the method for treating wastewater containing hydrogen peroxide and ammonia according to the present invention, the wastewater containing hydrogen peroxide and ammonia is brought into contact with a catalyst to decompose the hydrogen peroxide in the wastewater. After that, ammonia is volatilized and removed.

In the method of the present invention, only hydrogen peroxide in the waste water is catalytically decomposed (2H ₂ O ₂ → 2H ₂ O + O ₂ ), so that a high temperature and high pressure operating condition is not required and the temperature is 100 ° C. Lower temperature, less than normal pressure,
Catalytic cracking can be performed under low pressure operating conditions.

Ammonia remaining in the waste water after decomposing and removing hydrogen peroxide can be easily removed by volatilization. The volatilized ammonia may be condensed, collected and reused, or may be decomposed by catalytic air oxidation.

When ammonia is volatilized prior to catalytic decomposition of hydrogen peroxide in order to catalytically decompose only hydrogen peroxide in the wastewater, oxygen gas is simultaneously generated by decomposition of hydrogen peroxide, and thermal efficiency And a gas-explosive mixed gas of oxygen gas and ammonia gas is generated.

According to the present invention, safe and efficient processing can be performed by removing ammonia by catalytic decomposition and removing ammonia by volatilization.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of a method for treating wastewater containing hydrogen peroxide and ammonia according to the present invention.

[0015] Hydrogen peroxide (H ₂ O ₂ ) and ammonia (N
The wastewater (raw water) containing H ₃ ) is first introduced into the hydrogen peroxide decomposer 1 to perform catalytic decomposition of hydrogen peroxide.

As the catalytic cracking apparatus 1, it is preferable to use a fixed bed type reaction tower filled with a catalyst.

In the present invention, examples of the catalyst include activated carbon, and other than that, platinum, palladium, ruthenium, rhodium, indium,
Iridium, silver, gold, cobalt, copper, nickel and tungsten, and water-insoluble or poorly water-soluble compounds of these metals, specifically, cobalt monoxide, cobalt peroxide, nickel monoxide, ruthenium dioxide, rhodium trioxide , One or more oxides selected from oxides such as palladium monoxide, iridium dioxide, cupric oxide, and tungsten dioxide are supported on a carrier such as alumina, activated carbon, titanium oxide, zirconia, zeolite, and other synthetic resins. There is also a thing that did. The amount of the metal and / or its compound supported in the supported catalyst is usually 0.05 to 25% by weight, preferably 0.5 to 10% by weight of the weight of the carrier. Such activated carbons and supported catalysts can be used in various forms such as spherical, pellet, columnar, crushed pieces, honeycomb, powder, and the like. The particle size is usually preferably 0.2 to 10 mm, particularly preferably about 0.5 to 5 mm.

The conditions for passing the liquid through the fixed bed type reaction tower vary depending on the concentration of hydrogen peroxide in the waste water and the catalyst used.
In the present invention, since only hydrogen peroxide is decomposed without decomposing ammonia, the following relatively low temperature and low pressure conditions can be employed.

[Liquid passing conditions] Temperature: less than 100 ° C., preferably 20 to 90 ° C. Pressure: Normal pressure or less (a pressure that can maintain the liquid phase is sufficient) Flow rate: SV1 to 100 hr ⁻¹ , preferably 10 to 10 50
hr ^{-1 Further} , if the pH of the waste water is acidic below 7, the decomposition rate of hydrogen peroxide is reduced, so that the pH is 7 or more, especially pH 7 to
It is preferably 13.

In the hydrogen peroxide decomposition apparatus 1, hydrogen peroxide in raw water is decomposed into water and oxygen, and oxygen gas is discharged out of the system.

The treated water of the hydrogen peroxide decomposing apparatus 1 contains almost no hydrogen peroxide and remains ammonia. In the present invention, this water is introduced into the ammonia volatilization tower 2 and the ammonia in the water is removed. Is stripped off.

As the method for stripping off and removing ammonia, all known methods such as a stripping method and an evaporation method (including a distillation method) can be employed. The operating conditions are as follows: less than 100 ° C., normal pressure It is preferable to employ the following low-temperature and low-pressure conditions, and specifically, the following method can be employed.

(I) The gas-liquid ratio (G /
L) Stripping is performed at 1000 to 5000 times with air, nitrogen gas or the like. (ii) At a water temperature of 60 ° C. or more, a steam amount / processing amount ratio of 5 to 20.
Strip with steam in%. (iii) At a water temperature of 60 ° C. or more, a steam amount / processing amount ratio of 5 to 6
Distill at 0%, reflux ratio 1-7.

The treated water from which the ammonia has been volatilized and removed in this way is discharged out of the system.

The vaporized ammonia gas can be condensed and collected as needed, and can be effectively used for wafer cleaning and the like.

This ammonia gas may be decomposed and removed by catalytic air oxidative decomposition.

As the catalyst used for the catalytic air oxidative decomposition, the same catalyst (except for activated carbon) similar to the above-mentioned hydrogen peroxide decomposition catalyst can be used.

[0028]

The present invention will be described more specifically with reference to the following examples.

Example 1 Ammoniacal nitrogen: 1250 mg / L, hydrogen peroxide: 6
000 mg / L, synthetic wastewater having a pH of 10.5 was prepared, and this was used as raw water. First, a column packed with 60 mL of a zeolite catalyst carrying cobalt peroxide (cobalt carrying amount 2.5% by weight, average particle diameter 2 mm) was packed into a column filled with The solution was passed under the conditions.

[Pouring conditions] Temperature: 20 ° C. Pressure: normal pressure Flow rate: 370 mL / hr (SV = 6 hr ⁻¹ ) The concentration of hydrogen peroxide in the effluent is 2 mg / L or less, and the concentration of ammonia nitrogen is 1200 mg / L. Met.

1000 mL of this effluent was used for an inner diameter of 50 m.
m, 3m diameter on 1500mm height acrylic resin column
m into a volatilization tower filled with glass beads, and blow air from the bottom through a diffuser at a rate of 50 NL / min (G /
(L = 3000 times) for 1 hour (water temperature 60 ° C.). The concentration of ammonia nitrogen remaining in the water after the treatment is 60
mg / L.

On the other hand, the average concentration of ammonia in the volatilized gas generated in the volatilization treatment was 600 ppm (volume ratio).

After the gaseous gas was heated to 330 ° C., it was placed in a stainless steel reaction tower having an inner diameter of 50 mm.
After aerating velocity (SV) of 20,000 hr ^-1 , a vanadium-titania-based reduction catalyst was passed through a stainless steel reaction tower having an inner diameter of 50 mm. A reaction tower filled with 500 mL) was aerated at a superficial velocity (SV) of 6000 hr ^-1 .

The ammonia concentration of the obtained processing gas is 1 p
pm (volume ratio) or less, NO _X concentration was less than 10 ppm (by volume).

Example 2 Ammoniacal nitrogen: 2000 mg / L, hydrogen peroxide: 6
000 mg / L, SiO ₂ : 2 mg / L, pH 11.0
Of synthetic wastewater, and this was used as raw water.
The solution was passed through a column packed with 60 mL of a weight-% platinum-supported titania catalyst (average particle size: 1.5 mm) under the following conditions.

[Pouring conditions] Temperature: 60 ° C. Pressure: normal pressure Flow rate: 1200 mL / hr (SV = 30 hr ⁻¹ ) The concentration of hydrogen peroxide in the effluent is 2 mg / L or less, and the concentration of ammonia nitrogen is 1800 mg / L. Met.

The treated solution (1000 mL) was concentrated 1.8-fold by simple distillation at 100 ° C. using a 2-L branched flask.

The concentration of ammonia nitrogen in the obtained condensed water was 3900 mg / L, and the concentration of SiO ₂ was 1 mg / L or less. The ammonia nitrogen concentration in the concentrated water is 60
mg / L.

[0039]

As described above in detail, according to the method for treating wastewater containing hydrogen peroxide and ammonia according to the present invention, the hydrogen peroxide and ammonia in the wastewater can be treated at a relatively low temperature.
Safe and efficient processing under low pressure operating conditions. It is easier to maintain and manage than biological treatment, and the equipment installation area can be reduced, and no sludge is generated. No drug addition is required. Ammonia can be recovered and used effectively. And the like.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a method for treating wastewater containing hydrogen peroxide and ammonia according to the present invention.

[Explanation of symbols]

 1 Hydrogen peroxide decomposition equipment 2 Ammonia volatilization tower

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C02F 1/58 C02F 1/58 PF term (reference) 4D037 AA13 AB11 AB12 BB06 BB09 CA09 CA11 4D038 AA08 AB26 AB29 BA02 BB02 BB03 BB15 BB16 BB20 4D050 AA13 AB33 AB35 BA08 BB09 BC01 BC06 CA02 CA03 4G069 AA02 AA03 BA01B BA04B BA07B BB02B BB04B BB20B BC50B BC54B BC67B BC75B CA05 CA07 CA08 CA11 CA17 DA06 EA02

Claims (3)

[Claims] 1. After contacting a waste water containing hydrogen peroxide and ammonia with a catalyst to decompose hydrogen peroxide in the waste water,
A method for treating wastewater containing hydrogen peroxide and ammonia, which comprises stripping and removing ammonia. 2. After contacting a wastewater containing hydrogen peroxide and ammonia with a catalyst to decompose hydrogen peroxide in the wastewater,
A method for treating wastewater containing hydrogen peroxide and ammonia, wherein ammonia is volatilized, condensed, and recovered. 3. After contacting a wastewater containing hydrogen peroxide and ammonia with a catalyst to decompose hydrogen peroxide in the wastewater,
A method for treating wastewater containing hydrogen peroxide and ammonia, wherein ammonia is volatilized, and the ammonia after volatilization is brought into contact with a catalyst to be decomposed.