JPH0645026B2 - 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 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. Less than the theoretical oxygen amount necessary for decomposing ammonia component, organic substance and inorganic substance by adding COD component to NH ₄ NO ₃ containing wastewater in advance, instead of the prior application technique of performing wet oxidation using oxygen. In the case of performing wet thermal decomposition of the NH ₄ NO ₃ -containing wastewater in the presence of oxygen, not only NH ₄ ⁺ ions but also NO ₃
^- found that ions are efficiently decomposed. Further, according to the research conducted by the present inventor, it was found that the decomposition efficiency is further improved when the NH ₄ NO ₃ -containing wastewater to which the COD component and ammonia are added 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.

In the presence of a supported catalyst containing ammonium nitrate-containing wastewater containing a COD component as an active ingredient, ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, and at least one of these water-insoluble or sparingly soluble compounds. And in the presence of less than the theoretical amount of oxygen necessary to decompose ammonia, organic substances and inorganic substances in the waste water to N ₂ , H ₂ O and CO ₂ , a pH of about 3-11.
5. A method for treating ammonium nitrate-containing wastewater, which is characterized by performing wet thermal decomposition at a temperature of 100 to 370 ° C. In the presence of a supported catalyst containing at least one of these water-insoluble or sparingly soluble compounds as an active ingredient and ammonia, organic substances and inorganic substances in waste water, N ₂ , H ₂ O and CO ₂ PH in the presence of less than the theoretical oxygen required to decompose to
A method for treating ammonium nitrate-containing wastewater, which comprises performing wet pyrolysis at about 3 to 11.5 and 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 present invention is ruthenium,
Examples thereof include rhodium, palladium, osmium, iridium, platinum, gold, and water-insoluble or sparingly soluble compounds thereof, and one or more of these can 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-type and composite-type carriers such as titania, zirconia, titania-zirconia, alumina, and the like, according to a conventional method.
Silica, alumina-silica, activated carbon, or nickel,
Nickel-chrome, nickel-chrome-aluminum,
It is used by being supported on a carrier such as a nickel-chromium-iron porous metal body. The supported amount is usually 0.05 to 25 of the carrier weight.
%, Preferably 0.5 to 3%. The catalyst can be used in various known forms such as a sphere, a pellet, a column, a crushed piece, a powder, and a honeycomb. In the case of a fixed bed, the reaction tower volume is such that the space velocity of the liquid is 0.5 to 10 ¹ / _hr.
(Empty tower standard), more preferably 1 to 5 ¹ / _hr (empty tower standard). The size of the catalyst used in the fixed bed is usually about 3 to 50 mm, more preferably about 5 to 25 mm.
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 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 addition amount of the COD component is equal to or less than 1 mole of NO ₃ ⁻ ions contained in the waste water, and 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.

The amount of the COD component in the case of thermally decomposing the NH ₄ NO ₃ containing wastewater by adding the COD component and ammonia is the same as the above case, and the amount of the ammonia is 1 < ^NH 3 _—N / _NO 3
_The amount is such that _−N ≦ 5 (molar ratio). The wet pyrolysis reaction conditions in this case may be the same as above.

In the present invention, as the COD component source or the COD component and ammonia source, phenol, methanol, aqueous ammonia, and various wastewaters containing these can be used. 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 purification in these plants, wastewater oil-containing wastewaters from a wet desulfurization tower and a wet desocyanation tower. , 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, it is possible to easily treat wastewater discharged from a uranium raw material treatment process or a spent uranium fuel retreatment process and having a NH ₄ NO ₃ concentration of 10% or more with a simple facility. You can do it.

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

Example 1 pH 10 with C ₆ H ₅ OH added so that COD component / _NO 3 _—N = 0.5 (molar ratio), NH ₄ NO ₃ concentration 1% (
^NH3- _N / _{NO3- N} = 1) wastewater 100 ml volume 3
It was placed in a 00 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. 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.

The decomposition rates of NH ₄ ⁺ , NO ₃ ^−, and total nitrogen components are shown in Example 2.
It is shown in Table 1 together with the results of ~ 6.

Examples 2 to 3 ^C 6 _H 5 _OH / _NO 3 was prepared by adding a predetermined amount of C ₆ H ₅ OH to NH ₄ NO ₃ containing wastewater having a pH and concentration different from those in Example 1.
After adjusting _-N (molar ratio), it was subjected to a thermal decomposition treatment in the same manner as in Example 1.

Example 4 Waste water was treated in the same manner as in Example 1 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 instead of the ruthenium-supported catalyst.

Examples 5 to 6 The thermal decomposition treatment of NH ₄ NO ₃ -containing wastewater was performed in the same manner as in Examples 2 to 3 except that the same palladium catalyst as that used in Example 4 was used instead of the ruthenium catalyst.

Examples 7 to 9 C ₆ H ₅ OH and NH ₄ OH were added to the NH ₄ NO ₃ -containing wastewater, and the wastewater was pyrolyzed under the same conditions as in Example 1.

Incidentally, in Examples 7 and 8, the pH of the wastewater was adjusted with sodium hydroxide, and in Example 9, the pH was not adjusted.

The results are as shown in Table 2.

Examples 10 to 12 C ₆ H ₅ OH and NH ₄ OH were added to NH ₄ NO ₃ -containing wastewater, and subjected to thermal decomposition treatment under the same conditions as in Example 4.

In addition, in Examples 10 and 11, the pH of the wastewater was adjusted with sodium hydroxide, and in Example 12,
No pH adjustment was done.

Example 13 _NH 4 NO ₃ concentration ^{_{10% (NH 3 -N / NO}} 3 -N =
Wastewater ^COD / _NO 3 _-N 1.88) = about 0.5 (molar ratio) to become as _C 6 _H 5 OH was added and the pH with NaOH aqueous solution 10 and the liquid space velocity 0.95 ¹ / _Hr
While supplying it to the lower part of the high-nickel copper cylindrical reactor as a (vacant tower standard), air is supplied to the lower part of the reactor as a space velocity of 18.5 ¹ / _hr (vacuum standard, standard state conversion) to perform thermal decomposition Processed. Liquid mass velocity is 2.43ton / m ² · h
r, and the feed air contained about 0.4 times the stoichiometric amount of oxygen required to decompose ammonia, organic substances and inorganic substances. The reactor was filled with a sought-after catalyst having a diameter of 5 mm in which 2% by weight of palladium was supported on a titania carrier, and thermal decomposition was carried out under the conditions of 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 3 shows the decomposition rates of NH ₃ , NO ₃ , total nitrogen components and COD components.

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

Examples 14 to 20 Pyrolysis treatment of waste water was performed in the same manner as in Example 13 except that the catalytically active component and the carrier were changed. The results are as shown in Table 4. The carrier of Examples 14 to 19 is titania, and the carrier of Example 20 is zirconia.

Examples 21 to 24 Pyrolysis treatment of waste water was performed in the same manner as in Example 3 except that the titania carrier was used and the catalytically active component was changed. The results are as shown in Tables 5 to 7.

Claims (2)

[Claims] 1. An ammonium nitrate-containing wastewater containing a COD component is used as an active ingredient of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, and at least one of these water-insoluble or sparingly soluble compounds. A pH of about 3-11 in the presence of a supported catalyst and in the presence of less than the theoretical amount of oxygen required to decompose ammonia, organic and inorganic substances in wastewater to N ₂ , H ₂ O and CO _2. 0.5, wet thermal decomposition at a temperature of 100 to 370 ° C. for treating ammonium nitrate-containing wastewater. 2. An ammonium nitrate-containing wastewater containing a COD component and ammonia is treated with at least one of ruthenium, rhodium, palladium, osmium, iridium, platinum and gold, and a water-insoluble or sparingly soluble compound thereof.
In the presence of a supported catalyst having a seed as an active ingredient and in the presence of oxygen below the theoretical oxygen amount necessary for decomposing ammonia, organic substances and inorganic substances in wastewater to N ₂ , H ₂ O and CO _2. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet pyrolysis at a pH of about 3 to 11.5 and a temperature of 100 to 370 ° C.