JPS61245883A - Treatment of waste water containing ammonium nitrate - Google Patents

Abstract

PURPOSE:To lower the concns. of an NH4<+> ion and a NO3<-> ion to a large extent, by applying wet thermal decomposition treatment to waste water containing ammonium nitrate, to which ammonia was added if necessary, in the presence of a specific catalyst and a specific amount of oxygen under a specific condition. CONSTITUTION:Wet thermal decomposition treatment is applied to NH4NO3- containing waste water not only in the presence of a catalyst comprising at least one of a noble metal, a noble metal ion and a soluble noble metal compound but also in presence of oxygen in an amount below a theoretical oxygen amount necessary for decomposing the ammonia component, org. substance and inorg. substance in the NH4NO3-containing waste water. Further, at this time, pH is adjusted to about 3-11.5 and reaction is performed at 100-370 deg.C and ammonia is preliminarily added so as to satisfy 1<NH3-N/NO2-N<=5 (mol ratio). Whereupon, decomposition efficiency is enhanced further and an NH4<+> ion and a NO3<-> ion are efficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Benefits 1 The present invention relates to a method for treating wastewater containing ammonium nitrate.

Prior art and its problems In recent years, chemical oxygen demand substances (COD) have been increasing from the viewpoint of water quality regulation.
Ingredients) as well as benign elements (especially ammonia nitrogen)
Removal of this has also become an important issue.

As a result of long-term research on various methods for treating ammonia-containing wastewater, the present inventors have discovered that wet oxidation treatment can be carried out in the presence of a specific catalyst and under specific conditions, making it easy to operate and practical and economical. Completed a method for treating ammonia-containing wastewater with
No., Special Publication No. 56-42992, Special Publication No. 57-4239
1, Special Publication No. 58-27999, Special Publication No. 57-333
2O etc.).

Recently, as the importance of nuclear power generation in the power generation industry increases, the treatment of NHaNOs-containing wastewater discharged from the processing of uranium raw materials and the reprocessing process of spent uranium fuel is becoming an important technical issue. The present inventor has developed the above-mentioned series of ammonia for the treatment of such NH4N03-containing wastewater.

An attempt was made to apply the treatment technology for wastewater containing Nia (hereinafter referred to as the prior application technology). In this trial, it was found that although NHa+ ions were decomposed with extremely high efficiency, the decomposition of NO3- ions was not always satisfactory.

This is NHaNOai in the wastewater mentioned above! degree is 1% (10
000pE) to 10% (100000EIEIm)
).

In view of the above-mentioned current situation, the inventor of the present invention has conducted various researches to solve the same problem, and as a result, has developed a method for decomposing ammonia, organic substances, and inorganic substances in wastewater in the presence of supported catalysts. Required theoretical oxygen ω
Instead of the prior art in which wet oxidation is performed using oxygen, ammonia components, organic substances, and inorganic substances in the N84NO3-containing wastewater are used in the presence of a catalyst consisting of at least one of a noble metal, a noble metal ion, and a soluble noble metal compound. When performing wet pyrolysis of the NHaNOs-containing wastewater in the presence of less than the theoretical amount of oxygen required to decompose the
It has been found that not only Ha÷ ions but also NO3- ions are efficiently decomposed. Furthermore, according to the research of the present inventor, when NHANO3-containing wastewater to which ammonia has been added so that 1〈NH3-N/N03-N≦5 (molar ratio) is subjected to wet pyrolysis in the same manner as above, It was found that the decomposition efficiency was further improved. That is, the present invention provides the following two types of wastewater treatment methods.

■ Theory necessary for decomposing ammonia, organic substances, and inorganic substances in wastewater containing ammonium nitrate into N2, H2O, and CO2 in the presence of a catalyst consisting of at least one of a noble metal, a noble metal ion, and a soluble noble metal compound. In the presence of less than 1 hour of oxygen, the pH is about 3-11.
5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet thermal decomposition at a temperature of 100 to 370°C.

■ Ammonium nitrate-containing wastewater to which ammonia has been added so that 1〈NH3-N/N)≦5 (molar ratio) is
Presence of oxygen in the presence of a catalyst consisting of at least one of noble metal ions and soluble noble metal compounds and less than the theoretical amount of oxygen necessary to decompose ammonia, organic substances and inorganic substances in the wastewater to N2, H2O and CO2. pH below
A method for treating wastewater containing ammonium nitrate, characterized by carrying out wet pyrolysis at a temperature of about 3 to 11.5°C and a temperature of 100 to 370°C.

The present invention targets all wastewater containing NH4NO2, and is particularly suitable for treating high-concentration wastewater with NHLNO3Fk1 degree of 1% or more.

Note that the wastewater may contain both organic substances and inorganic substances. Since the method of the present invention is carried out efficiently at a pH of about 3 to 11.5, more preferably 5 to 11, if necessary, the pH of the wastewater can be adjusted by adding an alkaline substance such as sodium hydroxide, sodium carbonate, calcium hydroxide, etc. Adjustments may be made in advance.

Examples of the catalyst component used in the present invention include noble metals such as platinum, ruthenium, Odium, palladium, osmium, and iridium, ions of these noble metals, and compounds of water-soluble noble metals. Two or more types can be used. Examples of noble metals include ruthenium black and palladium black, and examples of noble metal ions include ammonia, chlorine, cyanide, sodium,
Examples include those in the form of complex compounds using potassium etc. as a ligand. Examples of complex compounds include (NH4)2 (RuCQs (H2O)), (R
u (NH3) s ) CQ 2, (RuCQ (
NH3))5CQ.

Na2(PdCQ&), (NH4)2(PdCQa), (Pd(NH3)A)C122, K2(Pd(NO2)4)2H2O, K2
(Pd(CN)A)3H2O etc. are exemplified.It6° water-soluble compounds include RuCQ3, RLIC
Qt ・5H2O%PtCQt, RuCQ2, RuC
Q2 ・2H2O%RhCQ3 ・3H2O, QSC(
Examples include It, IrC (12, etc.) The catalyst component is usually 0.0 cc per 500 cc of wastewater for a while after the start of treatment.
It is supplied to the reaction tank at a rate of about 1 to 0.2 a. In order to increase the contact area and make the reaction proceed uniformly, the reaction tank contains titania, zirconia, alumina, silica, alumina-silica, activated carbon, or iron, nickel, nickel-chromium, nickel-chromium-aluminum, It may be filled with spherical or powdered metal porous bodies such as nickel-chromium-iron (pulverized pieces, powder, granules, pellets, cylindrical bodies, etc.).

As the reaction progresses, noble metal black is deposited on the inner surface of the reaction vessel or on the surface of the spheres or powder, and this begins to act as a catalyst, so it is sufficient to stop supplying the catalyst at this point. Furthermore, if the catalytic activity of the noble metal black decreases with the passage of time, the supply of the catalyst component is restarted.

When the reaction is carried out batchwise, it is preferable to use about 3 to 5 times the amount of the catalyst component as described above.

The gas used as an 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,
Examples include oxygen-containing waste gas containing at least one of nitrogen oxides, hydrocarbons, and the like. These gas supply ports are determined based on the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances present in wastewater.
Usually less than the theoretical oxygen port, preferably 0.2 of the theoretical M
~0.6 times as much oxygen is present in the reaction system. When oxygen-containing waste gas is used as an oxygen source, harmful components in the gas are also decomposed and rendered harmless. The oxygen-containing gas may be supplied at once, or may be supplied in multiple doses.

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 H4÷ ions and N0a- ions increases and the residence time of wastewater in the reaction tower is shortened, on the other hand, the equipment cost increases, so the type of wastewater and the degree of treatment required are , operating costs, construction costs, etc. should be comprehensively considered.

Therefore, the pressure during the reaction may be any pressure at which the wastewater remains in a liquid phase at a minimum predetermined temperature.

Adding ammonia to NHANO3-containing wastewater produces 1〈NH3
-N/No, -N≦5 (molar ratio), the reaction conditions for wet thermal decomposition of wastewater may be the same as above.

Effects of the Invention According to the present invention, wastewater containing a high concentration of NH4NO2 can be efficiently treated, and the concentrations of NHa÷ ions and NO3- ions can be significantly reduced. Therefore, for example, wastewater discharged from the uranium raw material processing process or the spent uranium fuel reprocessing process and whose NHa N0331 degree can reach 10% or more can be easily treated using simple equipment. .

Tomo-Kou-1 Below, an actual travel example will be shown to further clarify the features of the present invention.

Example 1 1) HIO%NHzNOsllFK1% ("" -N/
Capacity: 100m12 of wastewater (N0s-N-1) ff1300
- housed in a stainless steel autoclave with 2
Thermal decomposition treatment was carried out at 50°C for 60 minutes. The reactor is filled with air prior to treatment, which contains oxygen equivalent to approximately 0.2 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances. Was. RUC (130,50) was dissolved in the wastewater.

The decomposition rates of NHs, NOs and total nitrogen components were measured in Example 2~
Table 1 shows the results of Comparative Example 10 and Comparative Example 1.

Examples 2 to 5 A predetermined amount of NHaOH was added to the same NH4NO3-containing wastewater as that treated in Example 1 to adjust the NH3N/N0a-N (molar ratio). Served.

Example 6 Wastewater was treated in the same manner as in Example 1 except that PdC (12) was used as a catalyst instead of RuCQ3.

Examples 7 to 10 NHaNO3-containing wastewater was thermally decomposed in the same manner as Examples 2 to 5 except that PdCQ2 was used instead of RuCQ3.

Comparative Example 1 NHa was produced in the same manner as in Example 3 except that no catalyst was used.
Thermal decomposition treatment of NOa-containing wastewater was carried out.

Examples 11-14 NH-N'03 Example 1 except that 11 degrees and pH were changed
The wastewater was thermally decomposed in the same manner as above.

The results are shown in Table 2.

Examples 15 to 17 The thermal decomposition treatment of wastewater was carried out in the same manner as in Example 6 except that the temperature and pH were changed.

The results are shown in Table 2.

Example 18 Lower part of a high nickel steel cylindrical reactor with pH 10 and NHaNOsle degree 10% (NH3-N/N0a-N-'1.88) with space velocity of JR water 0.92/, (based on sky column) Thermal decomposition treatment was carried out by supplying air to the lower part of the reactor at a space velocity of 17°7/hr (empty column standard, standard state conversion). The mass velocity of the liquid is 1.2 ton/m2・h, and the supplied air contains oxygen equivalent to approximately 0.24 times the theoretical oxygen Ω required to decompose ammonia, organic substances, and inorganic substances. It contained.

The reactor is filled with titania spheres with a diameter of 5-1, and RuC (13o, 55Q) is supplied per hour, and thermal decomposition is performed at a temperature of 250°C and a pressure cuff of 0 k!J/C12
It was carried out under the conditions of G.

After the gas-liquid mixed phase that had completed the reaction was subjected to heat recovery, it was led to a gas-liquid separator, and the separated gas and liquid phases were each indirectly cooled and then taken out of the system.

Table 3 shows the decomposition rates of NH3, NO3 and total nitrogen components.

Note that NOx and SOx were not detected in the gas phase.

Example 19 Wastewater was treated in the same manner as in Example 18, except that PCjCQ2 was used as a catalyst instead of RuCQ3. Table 3 shows the results.

Note that NOx and SOx were not detected in the gas phase.

Table 3 Example 2O pH 10, NH-NO3 11 degrees 10% (N83 N7N), 100 - volume of waste water from 2)
The sample was placed in a No. 011 stainless steel autoclave and subjected to thermal decomposition treatment at 250°C for 60 minutes.

The reactor is filled with air prior to treatment, which contains oxygen equivalent to approximately 0.2 times the theoretical oxygen Ω required to decompose ammonia, organic substances, and inorganic substances. Was. Ruthenium black 0.2o for wastewater
was added as a catalyst.

Table 4 shows the decomposition rates of NH3, NO3 and total nitrogen components.゛

Claims (2)

[Claims] (1) Necessary for ammonium nitrate-containing wastewater to be decomposed into N_2, H_2O, and CO_2 in the presence of a catalyst consisting of at least one of a noble metal, a noble metal ion, and a soluble noble metal compound. In the presence of less than the theoretical amount of oxygen, the pH is about 3~
11.5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet thermal decomposition at a temperature of 100 to 370°C. (2) 1<(NH_3-N)/(NO_3-N)≦5(
Ammonium nitrate-containing wastewater with ammonia added thereto in the presence of a catalyst consisting of at least one of a noble metal, a noble metal ion, and a soluble noble metal compound, and ammonia, organic substances, and inorganic substances in the wastewater were mixed with N_2, H
In the presence of less than the theoretical amount of oxygen required to decompose to _2O and CO_2, at a pH of about 3 to 11.5 and a temperature of 100
A method for treating ammonium nitrate-containing wastewater, characterized by wet pyrolysis at ~370°C.