JPH0647101B2 - 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 has tried to apply the above-mentioned series of ammonia-containing wastewater treatment technology (hereinafter referred to as prior application technology) 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% (10000 ppm) to 10% (100000 pp).
It is presumed that this is due to the fact that it may reach up to m).

Means for Solving the Problems The present inventor has carried out various studies further in view of the above-mentioned current situation, and as a result, the theoretical oxygen amount equal to or more than the theoretical oxygen amount required for decomposing ammonia, organic substances and inorganic substances in wastewater is obtained. Instead of the prior-art technique of performing wet oxidation using oxygen, the theoretical oxygen required for decomposing ammonia components, organic substances and inorganic substances in the liquid by previously adding ammonia to NH ₄ NO ₃ -containing wastewater The NH ₄ NO in the presence of 1 to 1.5 times the amount of oxygen.
It was found that not only NH ₄ ⁺ ions but also NO ₃ ⁻ ions are efficiently decomposed when wet-oxidative decomposition of _3- containing wastewater is performed. Further, according to the research by the present inventor, it was found that when the NH ₄ NO ₃ -containing wastewater to which ammonia and COD components were added in advance was subjected to wet oxidative decomposition in the same manner as described above, the decomposition efficiency was further improved. It was That is, the present invention provides the following two methods for treating ammonium nitrate-containing wastewater.

(1) Wastewater containing ammonium nitrate containing ammonia in the presence of a supported catalyst containing at least one of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold and insoluble or sparingly soluble compounds thereof as an active ingredient. PH 3 to 11 in the presence of 1 to 1.5 times the theoretical amount of oxygen necessary for decomposing ammonia, organic substances and inorganic substances into nitrogen, water and carbon dioxide.
5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet oxidation at a temperature of 100 to 370 ° C.

(2) Existence of a supported catalyst containing ammonium nitrate-containing wastewater containing ammonia and COD components as an active ingredient of at least one of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, and insoluble or sparingly soluble compounds thereof. PH 3 to 11. In the presence of 1 to 1.5 times the stoichiometric amount of oxygen necessary to decompose ammonia, organic substances and inorganic substances in the waste water into nitrogen, water and carbon dioxide gas. 5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet oxidation at a temperature of 100 to 370 ° C.

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

The catalytically active component used in the wet oxidative decomposition of the present invention includes ruthenium, rhodium, palladium, osmium,
Examples thereof include iridium, platinum, gold, and water-insoluble or sparingly soluble compounds thereof, and one or more of these may be used. Examples of the insoluble or sparingly soluble compound include ruthenium dichloride, platinum dichloride, ruthenium sulfide and rhodium sulfide. These catalytically active components are known single-system or composite-system carriers such as titania, zirconia, titania-zirconia, alumina, silica, alumina-silica, activated carbon, or nickel, nickel-chromium, nickel. It is used by supporting it on a carrier such as a porous metal body of chromium-aluminum, nickel-chromium-iron or the like. The supported amount is usually 0.05 to 25% of the weight of the carrier, preferably 0.5 to 3%. The catalyst can be used in a state of being supported on a carrier having a known form such as a sphere, a pellet, a column, a crushed piece, a powder, and a honeycomb. In the case of a fixed bed, the volume of the reaction tower is such that the space velocity of the liquid is 0.5 to 101 / hr (empty tower standard), and more preferably 1 to 51 / hr (empty tower standard). good. The size of the catalyst used in the fixed bed is usually about 3-5.
It is 0 mm, more preferably about 5 to 25 mm. In the case of a fluidized bed, an amount capable of forming a fluidized bed in the reaction tower, usually 0.5 to 20% by weight, more preferably 0.5 to 10% by weight, is suspended in waste water in a slurry form, use. For practical operation in a fluidized bed, the catalyst is suspended in slurry in a state of slurry and supplied to the reaction tower, and after the reaction is completed, the catalyst is appropriately settled from the treated wastewater discharged by centrifugal separation or the like. Separate and collect by various methods, and reuse. Therefore, considering the ease of separating the catalyst from the treated wastewater, the particle size of the catalyst used in the fluidized bed is more preferably about 0.15 to about 0.5 mm.

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 on the basis of the theoretical oxygen amount necessary for wet oxidative decomposition of ammonia, organic substances and inorganic substances existing in the wastewater containing ammonia or ammonia and COD components, and is usually set. 1 to 1.5 times the stoichiometric amount of oxygen, more preferably 1.05 to 1.2 times the stoichiometric amount of 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 amount of the COD component added is equal to or less than 1 mole of NO ₃ ions contained in the waste water, more preferably 0.1 to 3.
It is about 0.5 mol.

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.

Reaction conditions for wet pyrolysis of waste water containing NH ₄ NO ₃ containing COD components at the above ratio and adding ammonia to 1 <NH ₃ −N / NO ₃ −N ≦ 5 (molar ratio). May be the same as above.

In the present invention, phenol, methanol, aqueous ammonia, and various wastewaters containing these can be used as the COD component source or the COD component and ammonia source. In this case, a gas liquid produced as a by-product in a coke oven plant and a coal gasification and liquefaction plant, various wastewaters generated by gas refining in these plants, wastewaters from wet desulfurization towers and wet decyanization towers, oil-containing oils. Wastewater, activated sludge treated water, sedimented activated sludge, chemical factory wastewater, oil factory wastewater, night soil, sewage, sewage sludge, etc. can be treated at the same time.

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 Hereinafter, examples and comparative examples will be shown to further clarify the features of the present invention.

Comparative Example 1 100 m of waste water having a pH of 10 and an NH ₄ NO ₃ concentration of 10% (NH ₃ —N / NO ₃ —N = 1) was placed in a stainless steel autoclave having a capacity of 300 m, and wet oxidation treatment was performed at 250 ° C. for 60 minutes. The reactor is filled with air prior to the treatment, which contains about 1.1 times the theoretical amount of oxygen required for decomposing ammonia, organic substances and inorganic substances. Was. Further, the reactor was filled with 10 g of a catalyst having a diameter of 5 mm and having 1 wt% of ruthenium supported on a titania carrier.

The decomposition rates of NH ₄ ⁺ , NO ₃ ^−, and total nitrogen components are shown in Example 1.
2 and the results of Comparative Example 2 are shown in Table 1.

Example 1 After adjusting the NH ₃ —N / NO ₃ —N (molar ratio) by adding a predetermined amount of NH ₄ OH to the same NH ₄ NO ₃ containing wastewater as that treated in Comparative Example 1, the comparative example 1 and Similarly, it was subjected to a wet oxidation treatment.

Comparative Example 2 Waste water was treated in the same manner as in Comparative Example 1 except that a catalyst having a diameter of 5 mm in which 1% by weight of palladium was supported on a titania carrier was used instead of the ruthenium-supported catalyst.

Example 2 The same procedure as in Example 1 was repeated except that the same palladium catalyst as that used in Comparative Example 2 was used instead of the ruthenium catalyst.
Wet oxidation treatment of H ₄ NO ₃ -containing wastewater was performed.

Example 3 NH ₄ OH was added to waste water having a NH ₄ NO ₃ concentration of 10% to obtain N.
_{H 3 -N / NO 3 -N =} 2 ( molar ratio) and liquid (pH 1
0) is supplied to the lower part of the high nickel steel cylindrical reactor at a space velocity of 1.331 / hr (empty tower standard), while the air is at a space velocity of 1921 / hr (empty tower standard, standard state conversion). It was supplied to the lower part and a wet oxidation treatment was performed. The mass velocity of the liquid is 3.08 ton / m ² · hr, and the supply air contains ammonia, which corresponds to about 1.15 times the theoretical oxygen amount necessary to decompose the organic substance and the inorganic substance. Contained. Further, the reactor was filled with a spherical catalyst having a diameter of 5 mm in which 2% by weight of palladium was supported on a titania carrier, and the heat treatment was carried out at a temperature of 250 ° C. and a pressure of 70 kg / cm ² .

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 2 shows the decomposition rates of NH ₃ , NO ₃ and total nitrogen components together with the results of Example 4.

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

Example 4 NH ₄ OH was added to waste water having a NH ₄ NO ₃ concentration of 10% to obtain N _{4.
H 3 -N / NO 3 -N =} 2 ( molar ratio) and liquid (pH 1
0) is supplied to the lower part of the high nickel steel cylindrical reactor at a space velocity of 0.51 / hr (empty tower standard), while the air is at a space velocity of 721 / hr (empty tower standard, standard state conversion). It was supplied to the lower part and a wet oxidation treatment was performed. The mass velocity of the liquid is 1.16 ton / m ² · hr, and the supply air contains ammonia, which is equivalent to about 1.1 times the theoretical oxygen amount required to decompose organic substances and inorganic substances. Contained.
Further, the reactor was filled with a spherical catalyst having a diameter of 5 mm in which 2% by weight of palladium was supported on a titania carrier, and the wet oxidation treatment was carried out under the conditions of a temperature of 200 ° C. and a pressure of 45 kg / cm ² . .

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.

No NO _x and SO _x were detected in the gas phase.

Comparative Example 3 pH ₄ NH ₄ NO ₃ -containing wastewater (NH ₃ —N / NO ₃ —N = 1) to which C ₆ H ₅ OH was added so that COD component / NO ₃ —N = 0.5 (molar ratio). ) 100m capacity 30
It was housed in a 0 m stainless steel autoclave and subjected to wet oxidation treatment at 250 ° C. for 60 minutes. The reactor was filled with air containing oxygen equivalent to about 1.1 times the theoretical amount of oxidation required to decompose ammonia, organic substances and inorganic substances. Further, the reactor was filled with 10 g of a catalyst having a diameter of 5 mm in which 2% by weight of ruthenium was supported on a titania carrier.

Table 3 shows NH ₃ , N in the present Comparative Example and Example 5.
O _3, shows the degradation rate of the COD components and total nitrogen components.

Example 5 The same amount of NH ₄ NO ₃ containing wastewater as in Comparative Example 3 was used.
_After adding ₄ OH to adjust NH ₃ —N / NO ₃ —N (molar ratio), it was subjected to a wet oxidation treatment in the same manner as in Comparative Example 3.

Comparative Example 4 Waste water was treated in the same manner as in Comparative Example 3 except that a catalyst having a diameter of 5 mm in which 2% by weight of palladium was supported on a titania carrier was used in place of the ruthenium-supported catalyst.

Example 6 NH ₄ NO ₃ was used in the same manner as in Comparative Example 4 except that the same palladium catalyst as that used in Comparative Example 4 was used instead of the ruthenium catalyst and the NH ₃ —N / NO ₃ —N molar ratio was changed.
Wet oxidation treatment of contained wastewater was performed.

Examples 7 to 13 Wet oxidative decomposition of ammonium nitrate-containing wastewater was carried out in the same manner as in Example 1 except that the combination of the catalytically active component and the carrier shown in Table 4 was used instead of the palladium-titania catalyst.

Table 5 shows the decomposition rates of NH ₃ , NO _3, and total nitrogen components (denoted by TN).

Continuation of the front page (72) Inventor Yasushi Doi 5-1, Hirano-cho, Higashi-ku, Osaka-shi, Osaka (Osaka Gas Co., Ltd.) (56) (JP, B2) Japanese Patent Publication Sho 58-27999 (JP, B2)

Claims (2)

[Claims] 1. In the presence of a supported catalyst containing ammonium nitrate-containing wastewater containing ammonia as an active ingredient, at least one of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, and insoluble or sparingly soluble compounds thereof. In addition, pH 3 in the presence of 1 to 1.5 times the theoretical amount of oxygen required to decompose ammonia, organic substances and inorganic substances in waste water into nitrogen, water and carbon dioxide gas.
~ 11.5, a method of treating ammonium nitrate-containing wastewater, characterized by performing wet oxidation at a temperature of 100 to 370 ° C. 2. A supported catalyst comprising ammonium nitrate-containing wastewater containing ammonia and COD components as an active ingredient of at least one of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold and insoluble or sparingly soluble compounds thereof. Ammonia in the presence of and in the wastewater,
At a pH of 3 to 11.5 and a temperature of 100 to 370 ° C. in the presence of 1 to 1.5 times the theoretical oxygen amount necessary to decompose organic substances and inorganic substances into nitrogen, water and carbon dioxide gas. A method for treating ammonium nitrate-containing wastewater, which comprises wet oxidation.