JPS61257291A - Treatment of waste water containing ammonium nitrate - Google Patents

Abstract

PURPOSE:To treat waste water effectively and to reduce the concn. of NH4<+> ion, etc., remarkably by the oxidative decomposition of waste water contg. ammonium nitrate by the wet process in the presence of a catalyst comprising a noble metal, etc. and a specified amt. of O2 at a specified pH and temp. CONSTITUTION:Waste water contg. ammonium nitrate is oxidatively decomposed by the wet process in the presence of a catalyst comprising at least one kind among noble metal, noble metal ion, and soluble noble metal compd. and O2 corresponding to 1-1.5 times theoretically necessary for decomposing NH3, org. substances, and inorg. substances in the waste water to N2, H2O, and CO2 at ca. 3-11.5pH, and 100-370 deg.C. As the result, waste water contg. NH4NO3 at high concn. is treated effectively and the NH4<+> ion concn. and NO3<-> ion concn. are reduced remarkably. Accordingly, treatment of waste water which has sometimes as high as 10% NH4NO3 concn., for example, those discharged from a treating stage of raw material for uranium, etc., can be performed easily with a simple apparatus.

Description

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

Next come.

In recent years, chemical oxygen demand substances (COD) have been
components) as well as nitrogen components (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
No. 20, etc.).

Recently, as the proportion of nuclear power generation in the power generation industry has increased, the treatment of NHhNOs-containing wastewater discharged from the processing of uranium raw materials and the reprocessing of spent uranium fuel is becoming an important technical issue. The present inventor attempted to apply the above-mentioned series of ammonia-containing wastewater treatment technologies (hereinafter referred to as prior art) to the treatment of such NHANO3-containing wastewater. 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 means that the NH4N0311 degree in the wastewater is 1%cio
This is presumed to be due to the fact that it can reach as much as 10% (100,000 pp■) from ooopp■).

In view of the above-mentioned current situation, the inventors of the present invention have conducted various studies, and as a result, instead of the leading technology of performing wet oxidation at pH 8 or higher in the presence of a supported catalyst, the present inventor has developed a method in the presence of an unsupported catalyst 1(1). ni p
When performing wet oxidative decomposition of NHa NOs-containing wastewater at H3~11.5, not only NHa+ ions but also N0
It has been found that s-ions are also efficiently decomposed. Furthermore, according to the research of the present inventor, NH to which a COD component has been added in advance
It has been found that when aNOs-containing wastewater is subjected to wet oxidative decomposition in the same manner as described above, the decomposition efficiency is 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, H20, 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. pH in the presence of 1 to 1.5 times the amount of oxygen
A method for treating wastewater containing ammonium nitrate, characterized by carrying out wet oxidative decomposition at a temperature of about 3 to 11.5°C and a temperature of 100 to 370°C.

■ Ammonium nitrate-containing wastewater to which a COD component has been added is treated 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 the ammonia in the wastewater,
Organic and inorganic substances with N2, H20 and CO2
In the presence of 1 to 1.5 times the theoretical amount of oxygen required for decomposition to
A method for treating wastewater containing ammonium nitrate, characterized by wet oxidative decomposition at 0°C.

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

Note that the wastewater may contain both organic substances and ammonium substances. In this case, the pH of the wastewater may be adjusted in advance using an alkaline substance such as sodium hydroxide, sodium carbonate, or calcium hydroxide.

Catalyst components used in the present invention include noble metals such as platinum, ruthenium, rhodium, palladium, osmium, and iridium, their ions, and compounds of these noble metals that are soluble in water. 2
More than one species can be used. More specific examples of the noble metal include ruthenium black, palladium black, and the like. Examples of noble metal ions include those in the form of complex compounds with ammonia, chlorine, cyanide, sodium, potassium, etc. as ligands, and complex compounds include (NHA)t (RuCQs (HaO)),
(Ru(NHs)a)C(12,(RuCQ)
(NHs ))s CQa 1N Q e (
P d CQ & ), (NHa )2 (PdC
Qa), (Pd(NHa)&)CQ
2, K2 (Pd (Not)a)2
Examples include H20°Kg (Pd (CN)4)3820.

Water-soluble compounds include RLJC (Is, RuC
Qt ・5H20, PtCQt, PCJC; Qe, P
d CQ 2 ・2Ha O, RhCQs ・3H2
Examples include 0,05CQ A and I r CQ a. The catalyst component is 500cc of waste water that has been washed for a while after the start of treatment.
It is usually supplied to the reaction system at a ratio of about 0.01 to 0.2Q. Inside the reaction tank, titania, zirconia, alumina,
Silica, alumina-silica, activated carbon, or metal porous bodies such as iron, nickel, nickel-chromium, nickel-chromium-aluminum, nickel-chromium-iron, etc. 9 spheres or powders (crushed pieces, granules, pellets, cylinders) body, etc.) may be filled. 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. The supply amount of these gases is determined based on the theoretical amount of oxygen necessary to decompose ammonia, organic substances, and inorganic substances present in wastewater.
Generally, oxygen is present in the reaction system in an amount of 1 to 1.5 times the theoretical amount of oxygen, preferably 1.05 to 1.2 times the theoretical amount of oxygen. 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 HA÷ ions and N0s- 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.

When adding a COD component to NHaNOs-containing wastewater, the COD component is added to 1 mol or less, more preferably about 0.1 to 0.5 mol, per mol of Nosl in the wastewater. In this case, the wet oxidation conditions may be similar to those described above.

According to the present invention, wastewater containing a high concentration of NH4NO3 can be efficiently treated and the concentrations of NHa" ions and NOs- ions can be significantly reduced. Therefore, for example, it is possible to treat uranium raw materials. It is possible to easily treat wastewater and the like discharged from processes or spent uranium fuel reprocessing processes, where the concentration of NHLNOs can reach 10% or more, using simple equipment.

Sadness-1-1 Examples will be shown below to further clarify the characteristics of the present invention.

Example 1 Wastewater ioom with pH 5.3 and NHaNOsl 1 degree 1% (NHs-N/NOs-N, 1)
was placed in a 300-capacity stainless steel autoclave and subjected to oxidation treatment at 250° C. for 60 minutes. still,
The reactor is filled with air prior to treatment, containing approximately 1.1 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances. Ta. Furthermore, RuC950,50 was dissolved in the wastewater.

The decomposition rates of NHs, NOs and total nitrogen components were measured in Example 2~
The results are shown in Table 1 along with the results of No. 6.

Example 2 A predetermined amount of Cs Hs OH was added to the same NHa NOs-containing wastewater as treated in Example 1 to produce COD/. 5-N
- A solution with a pH of 5.3, adjusted to about 0.5 (molar ratio), was subjected to wet oxidation treatment in the same manner as in Example 1.

Example 3 N
Wet oxidation treatment of HANO3-containing wastewater was performed. Example 4 Wet oxidation treatment of wastewater was carried out in the same manner as in Example 1 except that PdCQ2 was used as a catalyst instead of RucQs.

Examples 5-6 Wet oxidation treatment of NHaNOs-containing wastewater was carried out in the same manner as in Examples 2-3 except that PdCQt was used instead of Ru CQ s.

Example 7 Wastewater with a pH of 10 and a NHaNO* concentration of 10% <NHs -N/No, -N-1-0) was processed into a high-nitrogen steel cylindrical type with a space velocity of 0.92'/(sky column standard). Wet oxidation treatment was carried out by supplying air to the lower part of the reactor at a space velocity of 92/h (on a superficial basis, standard state conversion).The mass velocity of the liquid was 2.12/h. ton/m'・hr,
The feed air contained approximately 1.1 times the theoretical amount of oxygen required to decompose ammonia, organic materials, and inorganic materials. RuC (!s) was supplied to the reactor at a rate of 0.55 a per hour, and the wet oxidation was carried out at a temperature of 250°C.
It was carried out under the conditions of pressure cuff 0 ko/C11I-G. The reactor was also filled with titania spheres having a diameter of 5 liters.

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 2 shows the NHs in this example and Examples 8 to 10.
, shows the decomposition rate of NOs and total nitrogen components.

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

Example 8 06 so that COD/No3-N (molar ratio) is 0.5
Add H50H and increase the space velocity of air to 99'/h
Wet oxidation treatment of N84NO3-containing wastewater was carried out in the same manner as in Example 7 except that the temperature was changed to r. Example 9 Wet oxidation treatment of NHgNOx-containing wastewater was carried out in the same manner as in Example 7 except that PdCQg was used instead of RuCQs.

Example 10 Wet oxidation treatment of N84NO3-containing wastewater was carried out in the same manner as in Example 8, except that pdcQ2 was used in place of RuC9s.

Example 11 1001 fi of wastewater with a pH of 10 and a NHANO3 concentration of 10% (NH2'N0s-N=1) was placed in a stainless steel autoclave with a capacity of 300 m and subjected to oxidation treatment at 250°C for 60 minutes. The reactor is filled with air prior to treatment, which contains oxygen equivalent to approximately 1.1 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances. Was. Further, ruthenium black 0.20 was added to the wastewater.

Table 3 shows NHs, N in this example and Example 12.
The decomposition rate of Os and total nitrogen components is shown.

Example 12 A wet oxidation treatment of NHa NOs-containing wastewater was carried out in the same manner as in Example 11, except that Ce Hs OH was added so that the COD/No, -N (molar ratio) was about 0.5.

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. A method for treating wastewater containing ammonium nitrate, which comprises carrying out wet oxidation decomposition at a temperature of 100 to 370°C at a pH of about 3 to 11.5 in the presence of 1 to 1.5 times the theoretical amount of oxygen. (2) Ammonium nitrate-containing wastewater to which a COD component has been added is treated 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 are removed by N_2, H_2O, and C.
1 to 1.5 of the theoretical amount of oxygen required to decompose to O_2
In the presence of double the amount of oxygen, the pH is approximately 3 to 11.5, and the temperature is 100.
A method for treating wastewater containing ammonium nitrate, characterized by wet oxidative decomposition at ~370°C.