JPS61257290A - Treatment of waste water containing ammonium nitrate - Google Patents

Abstract

PURPOSE:To reduce the concn. of NH4<+> ion and NO3<-> ion remarkably thermally decomposing waste water contg. NH4NO3 by the wet process in the presence of catalyst contg. a noble metal, etc., as active components at a specified pH, and specified temp. CONSTITUTION:Waste water contg. NH4NO3 is thermally decomposed by the wet process in the presence of a catalyst contg. at least one among noble metal, noble metal ion, and soluble noble metal compd. as active components, at ca. -11.5pH and 100-370 deg.C. As the result, waste water contg. NH4NO3 at high concn. is treated effectively, and the concn. of NH4<+> ion and NO3<-> ion are reduced remarkably. Accordingly, treatment of waste water having frequently above 10% NH4NO3, which, for example, discharged from a treating stage of raw material of uranium, or retreating stage of used uranium fuel, can be easily performed with a simple apparatus.

Description

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

Conventional techniques and their issues In recent years, chemical oxygen demand substances (CODs) 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. Special Publication No. 59-19757 to complete the treatment method of 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 increases, the treatment of NHaNO3-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 NHANO3-containing wastewater. In this trial, it was found that although NH + ions were decomposed with extremely high efficiency, the decomposition of NO3 - ions was not always satisfactory.

This means that NHzNOs 11 degrees in the wastewater is 1% (10
0001)+)■) to 10% (100000pp■)
It is assumed that this is due to the fact that it may even reach a certain degree.

As a result of further various studies in view of the current situation as described above, the inventor of the present invention has determined that the amount of oxygen exceeds 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 oxygen, the N
When performing wet pyrolysis of wastewater containing HLNOa, N
It has been found that O3~ ions are decomposed particularly efficiently. Furthermore, according to the research of the present inventor, when the treated liquid obtained by the above-mentioned wet pyrolysis treatment is subsequently subjected to a wet oxidation reaction, remaining ammonia, organic substances and inorganic substances are substantially completely removed. It was found that it was decomposed. That is,
The present invention provides the following three types of wastewater treatment methods.

■ Ammonium nitrate-containing wastewater is heated to a pH of about 3 to 11.5 and a temperature of 100 in the presence of a catalyst containing at least one of a noble metal, a noble metal ion, and a soluble noble metal compound as an active ingredient.
A method for treating ammonium nitrate-containing wastewater, characterized by wet pyrolysis at ~370°C.

■ Ammonium nitrate-containing wastewater is heated to a pH of about 3 to 11.5 and a temperature of 100 to 100 in the presence of a catalyst containing at least one of a noble metal, a noble metal ion, and a soluble noble metal compound as an active ingredient.
After wet pyrolysis at 370°C, the treatment solution was used to decompose iron, cobalt,
Ammonia and organic substances in the treatment liquid 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. 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 514m ammonium, characterized by wet oxidative decomposition at a temperature of about 8 to 11.5°C and a temperature of 100 to 370°C.

■ Ammonium nitrate-containing wastewater is heated to a pH of about 3 to 11.5 and a temperature of 100 to 100 in the presence of a catalyst containing at least one of a noble metal, a noble metal ion, and a soluble noble metal compound as an active ingredient.
After wet pyrolysis at 370°C, the treatment solution is treated in the presence of a catalyst containing at least one of a noble metal, a noble metal ion, and a soluble compound as an active ingredient. 1 of the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances in liquid
pH approximately 8 in the presence of ~1.5 times the amount of oxygen-containing gas
~11.5, a method for treating ammonium nitrate-containing wastewater, characterized by wet oxidative decomposition at a temperature of 100 to 370°C.

The present invention targets all wastewater containing NHzNO3, and is particularly suitable for treating high-temperature wastewater with an NHzNO3 temperature of 1% or higher.

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 is ! ! ! Adjustments may be made in advance.

Furthermore, by adding ammonia to the N Ht N O3-containing wastewater,
In the case of thermal decomposition, the decomposition efficiency is further improved.

In this case, the amount of ammonia added is 1 NH3-
It is preferable that N/No, -N≦5 (molar ratio).

Catalyst components used in the present invention include noble metals such as ruthenium, rhodium, palladium, osmium, iridium, platinum, and gold, their ions, and water-soluble compounds of these noble metals, and one or more of these metals may be used. Two or more types can be used. Examples of noble metals include ruthenium black and palladium black. 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 > 2
(RuC95(H2O)), (RLJ (NHs
)6)CQ2, (RuC12(NH3))s
CQlN a a (P d CQ t ),
(NHa)2 (PdCQt), (Pd
(NH3)A )CQ2 ,K2 (Pd
(NO2)t )2H20,K2 (Pd (ON
)a) 3820 etc. are exemplified.

As water-soluble compounds, Ru CQ 3, RLI
CQt ・5H20, PtC9t, PdCQ2, Pd
CQ2・2 H20, Rh CQ 3・3H20,0
Examples include 5CQz and IrC92. The catalyst component is usually 0.0% per 500cc of water for a while after the start of treatment.
It is supplied to the reaction tank at a rate of about 1 to 0.2 g. 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 spheres or powder (crushed pieces, granules, pellets, cylinders, etc.) such as porous metal bodies such as nickel-chromium-iron.

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, steps 3 to 5 above
It is preferable to use approximately double the amount of the catalyst component.

The temperature during the thermal decomposition reaction is usually 100 to 370°C, more preferably 200 to 300°C. The higher the reaction temperature, the higher the removal rate of NH&+ ions and NO3- ions, and the shorter the residence time of wastewater in the reaction tower, but on the other hand, the equipment cost increases, so the type of wastewater , should be determined by comprehensively considering the level of processing required, operating costs, construction costs, etc. Note that a saturated lid is placed inside the reaction tower to maintain the liquid phase.

A small amount of gas that exceeds the atmospheric pressure may be present, and such gases include air, nitrogen, and the like.

The above thermal decomposition reaction decomposes NH&+ ions and NO3- ions, particularly NO3- ions, in the wastewater to a high degree. If it is necessary to further decompose and remove ammonia, organic substances, and inorganic substances in the treated water, the treated water can be further subjected to wet oxidative decomposition according to the method of the prior art.

Wet oxidation involves: l) H about 8 to 11.5, more preferably 9
Since the process proceeds efficiently in steps 1 to 11, the treated water from the first stage wet pyrolysis is subjected to pHII adjustment in advance using the same alkaline substance as described above, if necessary.

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. These catalytically active components can be prepared using conventional methods such as titania, zirconia, alumina, silica, alumina-silica, activated carbon, or porous metals such as iron, nickel, nickel-chromium, nickel-chromium-aluminum, and nickel-chromium-iron. It is used by supporting it on a carrier such as The amount supported is usually 0.05 to 25%, preferably 0.5 to 3% of the weight of the carrier.

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 by a liquid space velocity of 0.5 to 10'/h, (
It is preferable to set the ratio to be 1 to 5/1 (based on the empty tower), and more preferably 1 to 5/1 (based on the empty tower). The size of the catalyst used in the fixed bed is typically 3 to 50 III, preferably about 5
~251m1. In the case of a fluidized bed, the amount of catalyst that can form a fluidized bed in the reaction column, usually 0.5 to 20% by weight,
More preferably, 0.5 to 10% by weight is suspended in waste water in the form of a slurry and used. 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, the particle size of the catalyst used in the fluidized bed is approximately 0.1
More preferably, it is about 5 to about 0.5 Il.

Further, when the catalyst in wet oxidation is used in the form of an unsupported catalyst, the same noble metal, noble metal ion or soluble noble metal compound as mentioned above is used.

The wet oxidation process of treated water containing NHA+ ions is performed using NHzN
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 supply amount of these gases is based on ammonia in wastewater,
It is determined based on the theoretical amount of oxygen necessary to decompose organic substances and inorganic substances (I! When waste gas is used as a source, further containing impurities) to N2, CO2 and H2O, and is more preferable. is the theoretical oxygen amount of 1°05 to 1.
Make sure that twice as much oxygen is present in the reaction system. When oxygen-containing waste gas is used as a scattering 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 100-370°C, more preferably about 200-jOO°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.

According to the present invention, wastewater containing NHaNOa at high temperature can be efficiently treated, and the temperatures of NHa+ ions and NO3- ions can be significantly lowered. Therefore, for example, wastewater discharged from a uranium raw material treatment process or a spent uranium fuel reprocessing process and whose NHANO3 temperature can reach 10% or more can be easily treated using simple equipment.

Tomo-LJW Examples will be shown below to further clarify the features of the present invention.

Example 1 10C1 of wastewater with pH 10 and NHt NO3 temperature 10% ("H3-N/No, -N-1) was placed in a stainless steel autoclave with a capacity of 300 mG and thermally decomposed at 250°C for 60 minutes. The reactor is filled with air prior to treatment, which contains oxygen equivalent to approximately 0.01 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances. Additionally, 5 g of RuQQ3o was added to the reactor as a catalyst.

The decomposition rates of NH3, NO3 and total nitrogen components were measured in Examples 2 to 4.
The results are shown in Table 1.

Example 2 NHLNO3-containing wastewater IC similar to that treated in Example 1
Predetermined 1t (7) NHA OH! In addition, NH3-N/NO
After adjusting the 3N (mole ratio) to 2, it was subjected to thermal decomposition treatment in the same manner as in Example 1.

Example 3 Wastewater was treated in the same manner as in Example 1 except that PdCQt was used in place of RuCQ3.

Example 4 The thermal decomposition treatment of NH4NO3-containing wastewater was carried out in the same manner as in Example 2 except that PdCe2 was used instead of RuCQ3.

Example 5 NHA OH was added to 10% NHA NO3ml wastewater to adjust the pH to 10 and NH3-N/No3-N=2, and then the space velocity was set to 1.33/h (sky column standard).
While supplying it to the lower part of the high nickel steel cylindrical reactor,
Thermal decomposition treatment was carried out by supplying air to the lower part of the reactor at a space velocity of 7.0'/h (on the basis of the sky column, in terms of standard conditions). The mass velocity of the liquid is 3.08 ton/m2-h
rt" 1. The supply air is approximately 0.2 of the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances.
It contained four times as much oxygen. Also, in the reactor,
Filled with titania spheres with a diameter of 5 cm, Ru CQ
s was added to the wastewater at a rate of 0.8 g per hour, and thermal decomposition was carried out at a temperature of 250°C and a pressure cuff of 0 k<1/ci2.

After the reaction, the gas-liquid mixed phase was subjected to heat recovery and 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 decomposition rates of NH3, NO3 and total nitrogen components.

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

Example 6 NHANO3-containing wastewater was thermally decomposed in the same manner as in Example 5 except that P d CQ 2 was used in place of RuC123.

The results are shown in Table 2. NOx and SOx were also not detected in the gas phase.

Table 2 Example 7 Treated liquid obtained by thermal decomposition in Example 5 (residual NH3-N 3150g1pm, I) 88.1
) was adjusted to pH 8.5 with a sodium hydroxide solution, and air was then supplied to the lower part of a high nickel m cylindrical reactor at a space velocity of 41/h (based on the sky column) while air was adjusted to a space velocity of 3/h.
Wet oxidative decomposition was carried out by supplying the reactor to the lower part of the reactor at a rate of 0.6/h (empty column basis, standard state conversion). The mass velocity of the liquid is 9.3 ton/m2·hr, and the supply air is a mixture of ammonia, organic substances, and inorganic substances with N2
It contained about 1.1 times the theoretical amount of oxygen required to decompose it into , CO2 and H2O.

The reactor was filled with a spherical catalyst with a diameter of 5 mm in which 42% by weight of Schifnira was supported on a titania carrier, and the temperature during the reaction was 250° C. and the pressure cuff was Q kg/cra2.

Air-liquid valve lI! NOx and SOx were not detected in the subsequent gas phase.

On the other hand, the pH of the solution is 6.8, and N) I3-N is detected.
Total nitrogen content was also less than 20 ppg+.

Example 8 Residual NHs-N in the treated water obtained in Example 6 was 24
501) El■, pH was 7.9. A NaOH solution was added to the treated water to adjust the pH to 8.5, and then air was supplied to the lower part of a high nickel W4 cylindrical reactor at a space velocity of 4/, C (based on the empty column), while air was Wet oxidative decomposition was carried out by feeding the reactor to the lower part of the reactor at a rate of 24.41/hr (empty column basis, standard state conversion). The mass velocity of the liquid is 9.3 ton/m2·hr,
The feed air contained approximately 1.1 times the theoretical amount of oxygen required to decompose ammonia, organic materials, and inorganic materials to N2, CO2, and N20.

The reactor was filled with a spherical catalyst having a diameter of 5 mm in which 2% by weight of ruthenium was supported on a titania carrier, and the temperature during the reaction was 250° C. and the pressure cuff was 0 kill/CI2.

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

On the other hand, the pH of the liquid was 6.5, NH3N was not detected, and the total nitrogen content was less than ioppm.

Example 9 After adding NH4OH to NHa NOa 11 degrees 10% waste water to make the pH 10 and NH3-N/No3-N-2, this was made into a high nickel steel cylinder with a space velocity of 21/, r (sky tower standard). Thermal decomposition treatment was carried out by supplying air to the lower part of the reactor at a space velocity of 141/hr (empty column standard, standard state conversion). The mass velocity of the liquid was 4.5 ton/I2·h, and the supplied air contained oxygen equivalent to approximately 0.05 times the theoretical amount of oxygen required to decompose ammonia, organic substances, and inorganic substances. The reactor was filled with titania spheres with a diameter of 5 mm, and RuC11a was fed at 1.8Q per hour.
In addition to wastewater at a rate of
The test was carried out under conditions of 5 kMc12.

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 rate of NH3, NO3 and total nitrogen components is 90% each.
, 99% or more and 99% or more.

Further, NOx and SOx were not detected in the gas phase.

Example 10 Residual NH3-N in the treated liquid obtained in Example 9 was 35
00pp■, pH was 8.9. While supplying the treated water to the lower part of the high nickel steel cylindrical reactor at a space velocity of 21/hr (sky column standard), air was supplied at a space velocity of 17.1/hr.
Wet oxidative decomposition was carried out by supplying the reactor to the lower part of the reactor at a rate of '/h (empty column standard, standard state conversion). The mass velocity of the liquid is 4.6 ton/m2 hr, and the supply air contains ammonia, organic substances, and inorganic substances with N2, C
It contained oxygen equivalent to about 1.1 times the theoretical amount of oxygen required to decompose it into O2 and N20.

The reactor was filled with a spherical catalyst having a diameter of 5 cm, in which 2% by weight of palladium was supported on a titania carrier, and the temperature during the reaction was 200°C and the pressure was 45 kg/cm2.

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

On the other hand, the pH of the liquid was 6.5, NH3-N was not detected, and the total nitrogen content was less than 10 ppII+.

Example 11 Treated liquid obtained by thermally decomposing wastewater containing NH4NO3 in the same manner as in Example 5 (residual N83 N3150p1)
After adjusting pf-18,1) to p)18.5 with a sodium hydride solution, RuC was added instead of the supported catalyst.
Wet oxidative decomposition was carried out in the same manner as in Example 7 except that 1.2 Q of Qa was supplied per hour.

NOx and SOx were not detected in the gas phase after gas-liquid separation, while the pH of the liquid was 6.9, NH3-N was not detected, and the total nitrogen component was 25 ppm or less.

Example 12 Fruit! I! F! Treated liquid obtained by thermally decomposing wastewater containing NHtNOs in the same manner as in 46 (residual NHa NN24
50pp, pH 7.9) was adjusted to pH 8.5 with sodium hydroxide solution, and PdCQ was added instead of the supported catalyst.
Wet oxidative decomposition was carried out in the same manner as in Example 8, except that 1.20% of 2 was fed per hour.

NOx and SOx were not detected in the gas phase after gas-liquid separation, while the pH of the liquid was 6.6, NH3-N was not detected, and the total nitrogen component was less than 20 ppm.

Example 13 Treated liquid (residual NHs -N35001) obtained by thermally decomposing wastewater containing NH4NO3 in the same manner as in Example 9
)■, pH 8,9) using RuCQa instead of the supported catalyst.
It was subjected to wet oxidative decomposition in the same manner as in Example 10, except that 0.6Q of was supplied per hour.

NOx and SOx were not detected in the gas phase after gas-liquid separation, while the pH of the liquid was 6.6, N83N was not detected, and the total nitrogen component was 25E)l)1 or less.

(that's all)

Claims (3)

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