JPS61222587A - Treatment of waste water containing ammonium nitrate - Google Patents

Abstract

PURPOSE:To efficiently decompose ammonia, org. substance and inorg. substance, by applying wet thermal decomposition treatment to waste water containing ammonium nitrate in the presence of a specific catalyst before performing the wet oxidation of said waste water in an atmosphere containing a specific amount of oxygen. CONSTITUTION:In the treatment of waste water with NH4NO3-concn. of 10% or more discharged from an uranium stock material treatment process, said waste water is at first subjected to wet thermal decomposition in the presence of a supported catalyst containing platinum, gold, ruthenium or rhodium sulfide as catalytically active components under a pH condition of 3-11.5 at 100-370 deg.C. Next, this treated water is subjected to wet oxidation treatment not only in the presence of a supported catalyst containing iron, cobalt, rhodium and compounds thereof as active components but also in the presence of gas containing oxygen in an amount 1-1.5 times a theoretical oxygen amount necessary for decomposing the ammonia, org. substance and inorg. substance in the treated water under a pH condition of 8-11.5 at 100-370 deg.C.

Description

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

In recent years, chemical oxygen demand substances (COD) have been
components) as well as nitrogen components (especially ammonia nitrogen)
The removal of has also become an important rR 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 importance of nuclear power generation in the power generation industry increases, the treatment of NHaNOa-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 attempted to apply the above-mentioned series of ammonia-containing wastewater treatment technologies (hereinafter referred to as prior art) to the treatment of such NHaNOs-containing wastewater. In this attempt, 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 NHaNOs concentration in the wastewater is 1% (100
This is presumed to be due to the fact that it can reach as much as 10% (1000000D■) from 00pp1).

In view of the above-mentioned current situation, the inventor of the present invention has further conducted various studies and determined that the amount of oxygen used is more than the theoretical amount necessary to decompose ammonia, organic substances, and inorganic substances in wastewater. Instead of the prior art in which wet oxidation is carried out using a noble metal and at least one of its insoluble or sparingly soluble compounds, the NHaNOs-containing wastewater is oxidized without substantially supplying oxygen in the presence of a supported catalyst containing at least one of noble metals and its insoluble or sparingly soluble compounds as an active ingredient. It has been found that NO3- ions are decomposed particularly efficiently when wet thermal decomposition is performed. Furthermore, according to the research of the present inventor, when the treated liquid obtained by the above wet pyrolysis treatment is subsequently subjected to the wet oxidation reaction according to the prior art, remaining ammonia, organic substances and inorganic substances are substantially removed. It was found that the upper part was completely decomposed.

That is, the present invention provides the following two types of wastewater treatment methods.

■ Ammonium nitrate-containing wastewater is heated at an OH of approximately 3 to 11.5 mL and a temperature of 100 to 3 mL in the presence of a supported catalyst containing at least one noble metal and its insoluble or sparingly soluble compounds as an active ingredient.
A method for treating wastewater containing ammonium nitrate, characterized by wet thermal decomposition at 70°C; 3-11.5, temperature 100-3
After wet pyrolysis at 70°C, the treatment solution is treated with at least one of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, gold, tungsten and insoluble or sparingly soluble compounds thereof as an active ingredient. pH of approximately 8 in the presence of a supported catalyst and in the presence of a gas containing 1 to 1.5 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances in the treatment liquid. ~11.5. A method for treating wastewater containing ammonium nitrate, characterized by wet oxidation at 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 a NHaNOs concentration of 1% or more. Note that the wastewater may contain both organic substances and inorganic substances. Since the method of the present invention is efficiently carried out at a pH of about 3 to 11.5, more preferably 5 to 11, if necessary, sodium hydroxide,
The pH of the wastewater may be adjusted in advance using an alkaline substance such as sodium carbonate or calcium hydroxide.

Incidentally, when ammonia is added to the NHAN03-containing wastewater for thermal decomposition, the decomposition efficiency is further improved.

In this case, it is preferable that the amount of ammonia added be such that 1.NH3-N/No3-N≦5 (molar ratio).

The catalytically active components used in the present invention include ruthenium,
Examples include rhodium, palladium, osmium, iridium, platinum, gold, and compounds that are insoluble or sparingly soluble in water, and one or more of these may be used. Ruthenium dichloride is an insoluble or poorly soluble compound.

Examples include platinum dichloride, ruthenium sulfide, and rhodium sulfide. These catalytically active components can be prepared using conventional methods such as titania, zirconia, alumina, silica, alumina-silica, activated carbon, or metal porous bodies such as nickel, nickel-chromium, nickel-chromium-aluminum, and nickel-chromium-iron. It is used by supporting it on a carrier. The supported amount is usually 0.05 to 25% of the carrier amount, preferably 0.5 to 3%.
%. The catalyst can be used in various forms such as spherical, pellet, cylindrical, crushed pieces, and powder.

In the case of a fixed bed, the reaction column volume is determined when the space velocity of the liquid is 0.
5 to 10'/, (sky tower standard), more preferably 1 to 5
'/h, (sky tower standard). The size of the catalyst used in the fixed bed is typically from 3 to 50 cm, more preferably from about 5 to 25 cm.

In the case of a fluidized bed, the amount of catalyst that can form a fluidized bed in the reaction column is usually 0.5 to 20311%, more preferably 0.5%.
It is used by suspending 5 to 10% by weight in slurry in waste water. In practical operation in a fluidized bed, the catalyst is supplied to the reaction tower in the form of a slurry suspended in wastewater, and after the reaction is completed, the catalyst is separated from the treated wastewater discharged through appropriate methods such as sedimentation and centrifugation. Separate and recover using appropriate methods and use again. Therefore, considering the ease of catalyst separation from treated wastewater, it is more preferable that the particle size of the catalyst used in the fluidized bed is about 0.15 to about 0.5 m.

The temperature during the thermal decomposition reaction is generally 100 to 370'C1, preferably 200 to 300C. The higher the reaction temperature, the higher the removal rate of NHL ÷ ions and NOs'' ions, and the shorter the residence time of wastewater in the reaction tower. It should be determined by comprehensively considering the type of treatment, the degree of processing required, operating costs, construction costs, etc. Incidentally, in order to maintain the liquid phase, a small amount of gas that exceeds the saturated vapor pressure may be present in the reaction tower, and such gases include air, nitrogen, and the like.

Due to the steam thermal decomposition reaction, NHa+ ions and NO3'' ions, especially NOs- ions, in the wastewater are highly decomposed. If it is necessary to further decompose and remove ammonia, organic substances, and inorganic substances in the treated water, the treated water can be subjected to wet oxidative decomposition using the method of the prior art.

Wet oxidation is carried out at a pH of about 8-11.5, more preferably 9-11.5.
Since the process proceeds efficiently in Step 11, the treated water from the first stage wet pyrolysis is, if necessary, subjected to pHII adjustment in advance using the same alkaline substance as described above.

Catalytic active components used in wet oxidation include iron,
Cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, gold, tungsten, and oxides of these metals, ruthenium dichloride,
Examples include compounds that are insoluble or sparingly soluble in water, such as chlorides such as platinum dichloride, sulfides such as rhodium sulfide, and ruthenium sulfide, and one or more of these may be used. Catalyst carrier, amount of catalytically active component supported on the carrier, shape of catalyst,
The dimensions, method of use, etc. may be the same as in the case of the thermal decomposition process.

The wet oxidation process of NHa÷ion-containing treated water is NHaN
The essential point of thermal decomposition treatment of Os-containing wastewater is that the theoretical amount of 1
~1.5 times more oxygen is required. Gases used as oxygen sources include air, oxygen-enriched air, oxygen,
Further examples include oxygen-containing waste gas containing at least one of hydrogen cyanide, hydrogen sulfide, ammonia, sulfur oxides, organic sulfur compounds, nitrogen oxides, hydrocarbons, and the like as impurities. The amount of supply of these gases is 6, necessary to decompose ammonia, organic substances and inorganic substances in the wastewater (and additionally contained impurities if waste gas is used as an oxygen source) into N2, CO2 and H2O. It is determined based on the theoretical oxygen amount, more preferably 1.05 to 1 of the theoretical oxygen amount.
．． Make sure that twice 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 wet oxidation is also about 100 to 370°C, more preferably about 200 to 300°C. Moreover, the pressure may be a pressure at which the treated water maintains a liquid phase.

If the pH of the liquid after wet oxidation is less than 5, an alkaline substance is supplied into the wet oxidation reactor to adjust the pH of the treated liquid.
is preferably adjusted to about 5 to 8. In this way, exhaustion or deterioration of the catalyst, damage to reactors, piping, heat exchangers, etc. are prevented, and neutralization of the treated liquid prior to discharge is not required.

11 Standing Beans 1 According to the present invention, it is possible to efficiently treat wastewater containing a high concentration of NH4NO2 and to significantly reduce the concentrations of NHa+ ions and NOs- ions. Therefore, for example, wastewater discharged from a uranium raw material processing process or a spent uranium fuel reprocessing process and whose NHANO31 degree may reach 10% or more can be easily treated using simple equipment.

EXAMPLES Examples will be given below to further clarify the features of the present invention.

Example 1 1 volume of wastewater ioom with pH 10 and NH4NO3 concentration 10% (NH3-N/No3-N-1)
It was placed in a 300 m 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 is equivalent to approximately 0.01 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances in wastewater. It contained oxygen. Further, the reactor was filled with 10 g of a catalyst having a diameter of 5 mm and having 2% by weight of ruthenium supported on a titania carrier.

Example 2 shows the decomposition rate of NHa÷, N0s- and total nitrogen components.
It is shown in Table 1 together with the results of 4 to 4.

Example 2 A predetermined amount of NH4OH was added to the same NHaNOs-containing wastewater that was thermally decomposed in Example 1 to produce N83N/N0s-N.
After adjusting the molar ratio, the mixture was subjected to thermal decomposition treatment in the same manner as in Example 1.

Example 3 Thermal decomposition treatment of NHaNOa-containing wastewater was carried out in the same manner as in Example 1, except that a catalyst with a diameter of 5 mm in which 1% by weight of palladium was supported on a titania carrier was used in place of the ruthenium-supported catalyst.

Example 4 NHAN03-containing wastewater was thermally decomposed in the same manner as in Example 3, except that NHaOH was added to adjust the molar ratio of NH3-N/No3-N.

Example 5 NH40)-1 was added to wastewater with a 10% NHa NO3 concentration to adjust the pH to 10, and the space velocity was 1.33'/h.

Thermal decomposition treatment is carried out by supplying air to the lower part of the reactor at a space velocity of 7.01/r (empty tower standard, standard state conversion) while supplying air to the lower part of the reactor at a space velocity of 7.01/r (empty tower standard). I did this. The mass velocity of the liquid is 3.08
ton/m2-hr, and the feed air contained approximately 0.05 times the theoretical amount of oxygen required to decompose ammonia, organic materials, and inorganic materials. In addition, the reactor was filled with a spherical catalyst with a diameter of 5+es in which 2% by weight of palladium was supported on a titania carrier, and thermal decomposition was carried out at a temperature of 250°C and a pressure cuff of 0 kQ/cm2. .

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.

The decomposition rates of NHs%NOs and total nitrogen components in Examples 5 and 6 are shown in Table 2.

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

Example 6 The space velocity of wastewater was 0.517 hr (based on the sky column), the mass velocity was 1.16 ton/m2-hr1, and the space velocity of air was 3.5/h (based on the sky column, converted to standard conditions). , except that the amount of oxygen in the air was approximately 0.05 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances, and the temperature and pressure inside the reactor were 200°C and 45kMc2. The thermal decomposition treatment of NHANO3-containing wastewater was carried out in the same manner as in Example 1.

NOx and SOx were not detected in the gas phase.

Table 2 Example 7 (I) Space velocity of wastewater is 21/, (sky tower standard),
The mass velocity is 4.6 ton/m2-hr, the space velocity of air is 14/, (sky tower standard, standard state conversion), and the amount of oxygen in the air is to decompose ammonia, organic substances, and inorganic substances. The thermal decomposition treatment of τNHZNO@-containing wastewater was carried out in the same manner as in Example 1, except that the temperature and pressure inside the reactor were set to about 0.05 times the theoretical amount of oxygen required for

NOX and SOx were not detected in the gas phase after gas-liquid separation.

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

Table 3 (II) Residual N in treated water obtained in (I) above
HsN was 52091)l, and pH was 7.3.

After adding 1 solution of NaOH to the treated water to adjust the DH to 8.5, air was supplied to the lowest part of the high nickel steel cylindrical reactor at a space velocity of 3/hr (empty column standard), while air was raised to a space velocity of 4/hr. Wet oxidative decomposition was carried out by feeding the reactor to the lower part of the reactor at a rate of .31/h (empty column basis, standard state conversion). The mass velocity of the liquid is 5.9 ton/m2・hr, and the supply air contains ammonia, organic substances, and inorganic substances such as N*, C
It contained oxygen equivalent to about 1.1 times the theoretical amount of oxygen required to decompose it into 02 and H2O.

The reactor was filled with a spherical catalyst having a diameter of 5 cm, in which % palladium 2Ii was supported on a titania carrier, and the temperature during the reaction was 200°C and the pressure was 45 ka/C2.

NOx and SOx were not detected in the gas phase after gas-liquid separation.

On the other hand, the pH of the liquid was 6.7, and NHs -N was not detected.
The total nitrogen content was also less than 1 opp-.

(that's all) Agent Patent Attorney Eiji Mitsuo “Ni No” , -・2

Claims (2)

[Claims] (1) Ammonium nitrate-containing wastewater is heated at a pH of approximately 3 to 11.5 and at a temperature of 100 to 100, in the presence of a supported catalyst containing at least one noble metal and its insoluble or sparingly soluble compounds as an active ingredient.
A method for treating wastewater containing ammonium nitrate, characterized by wet thermal decomposition at 370°C. (2) Ammonium nitrate-containing wastewater is heated at a pH of approximately 3 to 11.5 and at a temperature of 100 to 100, in the presence of a supported catalyst containing at least one noble metal and its insoluble or poorly soluble compounds as an active ingredient.
After wet pyrolysis at 370°C, the treatment solution was used to decompose iron, cobalt,
In the presence of a supported catalyst containing at least one of nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, gold, tungsten, and insoluble or poorly soluble compounds thereof as an active ingredient, ammonia and organic substances in the treatment liquid. and pH in the presence of a gas containing 1 to 1.5 times the theoretical amount of oxygen required to decompose the inorganic substance.
A method for treating wastewater containing ammonium nitrate, characterized by carrying out wet oxidation at a temperature of about 8 to 11.5°C and a temperature of 100 to 370°C.