JPH0645027B2 - Method of treating wastewater containing ammonium nitrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for treating ammonium nitrate-containing wastewater.

Conventional technology and its problems In recent years, from the viewpoint of water quality regulation, chemical oxygen demand substances (COD
Component) as well as nitrogen component (especially ammonia nitrogen)
The removal of is also an important issue. The present inventors have conducted various studies over a long period of time on a method for treating ammonia-containing wastewater, and as a result, by carrying out a wet oxidation treatment in the presence of a specific catalyst and under specific conditions, the operation is facilitated and the economic efficiency is reduced. A method for treating wastewater containing ammonia with properties was completed (Japanese Patent Publication No. 59-19757 and Japanese Patent Publication No. 56-4).
No. 2992, Japanese Patent Publication No. 57-42391, Japanese Patent Publication No. 58-
No. 27999, Japanese Examined Patent Publication No. 57-33320).

Recently, as the specific gravity of nuclear power generation in the power generation industry has increased, the treatment of NH ₄ NO ₃ -containing wastewater discharged from the treatment of uranium raw materials and the retreatment of spent uranium fuel has become an important technical issue. . The present inventor tried to apply the above-mentioned series of ammonia-containing wastewater treatment techniques (hereinafter referred to as prior application techniques) to the treatment of such NH ₄ NO ₃ -containing wastewater. In this attempt, it was found that NH ₄ ⁺ ions are decomposed with extremely high efficiency, but NO ₃ ⁻ ions are not always satisfactory. This is because the NH ₄ NO ₃ concentration in the wastewater is 1% (10,000
It is presumed that this is due to the fact that it may reach as high as 10% (100,000 ppm) from 10 ppm (ppm).

Means for Solving the Problems The present inventor has conducted various researches in view of the above-mentioned current situation, and as a result, in decomposing ammonia, organic substances and inorganic substances in wastewater in the presence of a supported catalyst, In place of the prior-art technique of performing wet oxidation using oxygen in an amount equal to or larger than the required theoretical oxygen amount, (a) a complex compound of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, (b) water of these metals Oxygen necessary for decomposing ammonia components, organic substances and inorganic substances in NH ₄ NO ₃ -containing wastewater in the presence of a water-soluble compound and a catalyst consisting of at least one of (c) ruthenium black and palladium black if the presence of oxygen than an amount performing wet thermal decomposition of the _NH 4 NO ₃ containing waste water not only _NH ^{4 +} ions, NO ₃ ^- ions efficiently min It was found to be the difference. Further, according to the study by the present inventor, 1 < ^NH3-N /
It was found that the decomposition efficiency is further improved when the NH ₄ NO ₃ -containing wastewater to which ammonia is added so that NO _{3 −N} ≦ 5 (molar ratio) is subjected to wet thermal decomposition in the same manner as above. . That is, the present invention provides the following two types of wastewater treatment methods.

The ammonium nitrate-containing wastewater is composed of (a) a complex compound of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, (b) a water-soluble compound of these metals, and (c) at least one of ruthenium black and palladium black. Ammonia, organic substances and inorganic substances in the presence of a catalyst and wastewater are treated with N ₂ , H ₂ O.
And a pH of about 3 to 11.5 and a temperature of 100 to 370 ° C. in the presence of less than the theoretical amount of oxygen required for decomposition to CO _2.
A method for treating ammonium nitrate-containing wastewater, which comprises performing wet pyrolysis with.

Ammonium nitrate-containing wastewater added with ammonia so that 1 < ^NH3-N / _NO3-N≤5 (molar ratio) is (a) a complex compound of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, (b) In the presence of a water-soluble compound of these metals and a catalyst consisting of at least one of (C) ruthenium black and palladium black, ammonia, organic substances and inorganic substances in waste water are treated with N ₂ , H ₂ O and CO ₂ PH in the presence of less than the theoretical amount of oxygen required to decompose to about 3-11.
5. A method for treating ammonium nitrate-containing wastewater, characterized by performing wet pyrolysis at a temperature of 100 to 370 ° C.

The present invention is intended to treat all wastewater containing NH ₄ NO ₃ , and is particularly suitable for treating high-concentration wastewater having an NH ₄ NO ₃ concentration of 1% or more. The wastewater may contain both organic substances and inorganic substances. The method of the present invention is efficiently carried out at a pH of about 3 to 11.5, more preferably 5 to 11. Therefore, if necessary, the pH of the waste water is adjusted with an alkaline substance such as sodium hydroxide, sodium carbonate or calcium hydroxide. May be performed in advance.

Examples of the catalyst component used in the present invention include noble metals such as platinum, ruthenium, rhodium, palladium, osmium and iridium, ions of these noble metals, and compounds of noble metals soluble in water, and one or two of these may be used. More than one species can be used. Examples of the noble metal include ruthenium black and palladium black, and examples of the noble metal ion include those in the form of complex compounds with ammonia, chlorine, cyanide, sodium, potassium, etc. as ligands. NH ₄ ) ₂ [RuCl ₅ (H ₂ O)], [Ru (NH ₃ ) ₆ ] Cl ₂ , [RuCl (NH ₃ )] ₅ Cl, Na ₂ [PdCl ₄ ], (NH ₄ ) ₂ [PdCl ₄ ], [Pd _{(NH 3) 4] Cl} 2, _{K 2} [Pd _{(NO 2) 4] 2H} 2 O, _{K 2} [Pd _{(CN 4)} 4] 3H ₂ O and the like.

Examples of water-soluble compounds include RuCl ₃ and RuCl _{4
· 5H 2 O, PtCl 4,} PdCl 2, PdCl 2 · 2
H ₂ O, RhCl ₃ .3H ₂ O, OsCl ₄ , IrCl
₂ etc. are illustrated. The catalyst component is usually supplied to the reaction tank at a rate of about 0.01 to 0.2 g with respect to 500 cc of waste water for a while after the treatment is started. In the reaction vessel, titania, zirconia, titania-zirconia, alumina, silica, alumina-silica, activated carbon, or iron, nickel, nickel-
Chrome, Nickel-Chromium-Aluminum, Nickel-
A known honeycomb body such as a porous metal body of chromium-iron or the like, a sphere or a powder (crushed pieces, powder particles, pellets, columnar bodies, etc.) may be filled. As the reaction progresses, noble metal blacks are adhered and formed on the inner surface of the reaction tank or on the surface of the sphere or powder, and this starts to act as a catalyst. Therefore, the supply of the catalyst may be stopped at this point. When the catalytic activity of the above-mentioned noble metal black is further stopped with the lapse of time, the supply of the catalyst component is restarted. When the reaction is carried out in a batch system, it is preferable to use the catalyst component in an amount of about 3 to 5 times the above amount.

The gas used as the oxygen source in the present invention includes air, oxygen-enriched air, oxygen, and hydrogen cyanide as an impurity.
Hydrogen sulfide, ammonia, sulfur oxides, organic sulfur compounds,
An oxygen-containing waste gas containing at least one kind of nitrogen oxides, hydrocarbons and the like can be mentioned. The supply amount of these gases is determined based on the theoretical oxygen amount necessary for decomposing ammonia, organic substances and inorganic substances present in wastewater,
Usually less than the theoretical oxygen amount, more preferably 0.2 of the theoretical oxygen amount.
Ensure that ~ 0.6 times more oxygen is present in the reaction system. When an oxygen-containing waste gas is used as an oxygen source, harmful components in the gas are decomposed and rendered harmless at the same time. The oxygen-containing gas may be supplied at once, or may be supplied in multiple times.

The temperature during the reaction is usually 100 to 370 ° C, more preferably 200 to 300 ° C. The higher the temperature during the reaction, the more N
Although the removal rate of H ₄ ⁺ ions and NO ₃ ⁻ ions is increased and the retention time of waste water in the reaction tower is shortened, on the other hand, the equipment cost is large, so the type of waste water and the required treatment It should be determined by comprehensively considering the degree, operating cost, construction cost, etc. Therefore, the pressure at the time of reaction may be a pressure at which the wastewater maintains a liquid phase at a minimum predetermined temperature.

Add ammonia to NH ₄ NO ₃ -containing wastewater and
The reaction conditions for wet thermal decomposition of wastewater with ^NH3-N / _NO3-N≤5 (molar ratio) may be the same as above.

EFFECTS OF THE INVENTION According to the present invention, wastewater containing NH ₄ NO ₃ at a high concentration can be efficiently treated, and the NH ₄ ⁺ ion and NO ₃ ⁻ ion concentrations can be significantly reduced. Therefore, for example, the waste water discharged from the uranium raw material processing step or the spent uranium fuel reprocessing step and having an NH ₄ NO ₃ concentration of 10% or more can be easily treated with simple equipment. You can

Examples The following examples are given to further clarify the features of the present invention.

Example 1 pH10, _NH 4 NO ₃ concentration ^{1% (NH3-N} /
100 ml of _NO3-N = 1) wastewater was placed in a 300 ml stainless steel autoclave and pyrolyzed at 250 ° C for 60 minutes. The reactor is filled with air prior to the treatment, which contains ammonia and oxygen equivalent to about 0.2 times the theoretical oxygen amount required for decomposing organic substances and inorganic substances. Was. R for wastewater
0.5 g of uCl ₃ was dissolved.

The decomposition rates of NH ₃ , NO _3, and total nitrogen components are shown in Examples 2-1.
The results are shown in Table 1 together with the results of 0 and Comparative Example 1.

Examples 2 to 5 After adding a predetermined amount of NH ₄ OH to the same NH ₄ NO ₃ containing wastewater as that treated in Example 1 to prepare ^{NH 3 —N} / _{NO 3 —N} (molar ratio), Similarly, it was subjected to a thermal decomposition treatment.

Example 6 Waste water was treated in the same manner as in Example 1 except that PdCl ₂ was used as a catalyst instead of RuCl ₃ .

Examples 7 to 10 The thermal decomposition treatment of NH ₄ NO ₃ -containing wastewater was performed in the same manner as in Examples 2 to 5 except that PdCl ₂ was used instead of RuCl ₃ .

Comparative Example 1 NH ₄ N was prepared in the same manner as in Example 3 except that no catalyst was used.
Pyrolysis treatment of O ₃ -containing wastewater was performed.

Examples 11 to 14 Thermal decomposition of waste water was performed in the same manner as in Example 1 except that the NH ₄ NO ₃ concentration and pH were changed. The results are as shown in Table 2.

Examples 15 to 17 The waste water was thermally decomposed in the same manner as in Example 6 except that the NH ₄ NO ₃ concentration and pH were changed. The results are as shown in Table 2.

Example 18 pH10, _NH 4 NO ₃ concentration ^{10% (NH3-N} /
_NO3-N = 1.88) wastewater with a space velocity of 0.92 ¹ /
_While supplying to the lower part of the high nickel copper cylindrical reactor as _hr (empty tower standard), air is supplied to the lower part of the reaction as space velocity of 17.7 ¹ / _hr (empty tower standard, standard state conversion) to perform thermal decomposition treatment. Was done. Liquid mass velocity is 1.2ton / m ² · h
The feed air contained ammonia, oxygen equivalent to about 0.24 times the theoretical amount of oxygen required for decomposing organic substances and inorganic substances. Also, the reactor has a diameter of 5
filled with mm titania spheres, and RuC per hour
supplies l ₃ 0.55 g, pyrolysis temperature 250 ° C., was carried out under a pressure of 70kg / cm ² · G.

The gas-liquid mixed phase that had undergone the reaction was subjected to heat recovery and then introduced into a gas-liquid separator, and the separated gas phase and liquid phase were indirectly cooled and then taken out of the system.

Table 3 shows the decomposition rates of NH ₃ , NO _3, and total nitrogen components.

In addition, NO _x and SO _x were not detected in the gas phase.

Example 19 Waste water was treated in the same manner as in Example 18 except that PdCl ₂ was used as a catalyst instead of RuCl ₃ .
The results are shown in Table 3.

In addition, NO _x and SO _x were not detected in the gas phase.

Example 20 pH10, _NH 4 NO ₃ concentration ^{10% (NH3-N} /
100 ml of waste water of _NO3−N = 2) was placed in a stainless steel autoclave having a volume of 300 ml, and pyrolyzed at 250 ° C. for 60 minutes. The reactor is filled with air prior to the treatment, which contains ammonia and oxygen equivalent to about 0.2 times the theoretical oxygen amount required for decomposing organic substances and inorganic substances. Was. 0.2 g of ruthenium black was added to the waste water as a catalyst.

Table 4 shows the decomposition rates of NH ₃ , NO ₃ and total nitrogen components.

Claims (2)

[Claims] 1. An ammonium nitrate-containing wastewater containing (a) a complex compound of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold (b) a water-soluble compound of these metals and (c) at least ruthenium black and palladium black. Ammonia, organic substances and inorganic substances in the wastewater in the presence of a catalyst consisting of one kind
₂ , in the presence of less than the stoichiometric amount of oxygen required to decompose to H ₂ O and CO ₂ , pH about 3 to 11.5, temperature 100.
A method for treating ammonium nitrate-containing wastewater, characterized by performing wet pyrolysis at 370C. 2. An ammonium nitrate-containing wastewater, to which ammonia is added so that 1 <NH ₃ —N / NO ₃ —N ≦ 5 (molar ratio), is added to (a) ruthenium, rhodium, palladium, osmium, iridium, platinum and gold. Complex compound (b) water-soluble compounds of these metals and (c) ammonia in the wastewater in the presence of a catalyst comprising at least one of ruthenium black and palladium black, organic substances and inorganic substances, N ₂ , A pH of about 3 to 1 in the presence of less than the theoretical oxygen required to decompose to H ₂ O and CO _2.
A method for treating ammonium nitrate-containing wastewater, which comprises performing wet pyrolysis at a temperature of 100 to 370 ° C.