JPH0448988A - Treatment of waste water containing ammonium nitrate - Google Patents

Abstract

PURPOSE:To improve treatment efficiency and to reduce cost by subjecting ammonium nitrate-containing waste water in which org. matter is contained to wet thermal decomposition in the presence of a supported catalyst containing a noble metal and one kind of a base metal as active components in an atmosphere substantially containing no oxygen under a specific pH and temp. condition. CONSTITUTION:Ammonium nitrate-containing waste water in which org. matter is contained so as to become 0.1 < org. matter/NO3-N <=0.5 (mol. ratio) is subjected to wet thermal decomposition in the presence of a supported catalyst containing a noble metal and at least one component selected from a group consisting of an insoluble or hardly soluble compound of a noble metal and a base metal as active components in an atmosphere substantially containing no oxygen under such a condition that pH is about 1 - 11.5 and temp. is 100 - 370 deg.C. Waste water containing NH4NO3 in high concn. is efficiently treated and the concns. of an NH4 ion and an NO3 ion can be reduced to a large extent. Therefore, for example, waste water discharged from a treatment process of an uranium raw material or a reprocessing plant of used uranium fuel and wherein the concn. of NH4NO3 reaches about 10% or more can easily be treated by simple equipment.

Description

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

In addition, in this specification, "NH3-N" means
"Ammonia nitrogen" means "NO3~N" means "nitrate nitrogen". Also, "%" means "wt%".

Prior art and its problems In recent years, chemical oxygen demand substances (COD) have been increasing from the viewpoint of water quality regulation.
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 (temperature, pressure, amount of oxygen supplied, etc.). , completed a method for treating ammonia-containing wastewater that is easy to operate and has practical economic efficiency (Special Publication No. 56-42992, Japanese Patent Publication No. 57-333)
No. 20, Special Publication No. 57-42391, Special Publication No. 58-27
No. 999, Special Publication No. 59-19757, etc.).

Recently, as the importance of nuclear power generation in the power generation industry increases, the treatment of NH4No3-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 inventors attempted to apply the above-mentioned series of ammonia-containing wastewater treatment techniques (hereinafter referred to as "prior application technology-I") to the treatment of such NH4No3-containing wastewater. In this trial, it was found that although NH4'' ions were decomposed with extremely high efficiency, it was not always possible to obtain satisfactory results in the treatment of NO3- ions. The concentration is from 1% (10000ppm) to 1
This is presumed to be due to the fact that it can reach as much as 0% (100,000 ppm).

As a result of further research, the present inventors found that by implementing the prior art technology, by reducing the amount of oxygen added, not only NH4+ ions but also NO3- ions in NH4N O3-containing wastewater can be removed with high efficiency. (Refer to Japanese Patent Application Laid-Open No. 61-222585 (2), hereinafter the technology disclosed therein is referred to as the prior invention - (2)).

In the treatment of N H4N O3-containing wastewater, particularly from a practical point of view, it is desired not only to improve treatment efficiency but also to reduce costs (reduction in equipment costs and operating costs).

Means for Solving the Problems In view of the current situation as described above, the present inventor has further conducted various studies, and as a result, the present inventor has determined that it is necessary to decompose ammonia components, organic substances, and inorganic substances in N H4N O3-containing wastewater. Instead of the method of the prior application-n in which the wet pyrolysis of the N H4N O3-containing wastewater is carried out in the presence of less than the theoretical oxygen n,
Even when adding organic matter (COD component) to 4No3-containing wastewater and performing the same treatment in the substantial absence of oxygen,
We have discovered an unexpected fact that not only NH4 ions but also NO, - ions can be efficiently decomposed.

Furthermore, according to the inventor's subsequent research, it was found that when NH4No3-containing wastewater to which COD components and ammonia were added was subjected to wet pyrolysis in the same manner as above, the decomposition efficiency was further improved. .

Furthermore, NH4NO3-containing wastewater may contain salts or ions of alkali metals such as Na and K, and some of these salts or ions are converted into NH4 during wet thermal decomposition.
Promotion of the conversion reaction of a+ ions to NO3+ ions,
NO3+ ions contained in the original wastewater and generated N
In order to exert the stabilizing effect of O,+ ions, the total nitrogen component decomposition rate may decrease slightly. In such cases, the decomposition efficiency can be further improved by subjecting the NH4NO3-containing wastewater to which COD components and acid or a substance capable of producing acid under treatment conditions to wet pyrolysis in the same manner as above. I discovered that.

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

■ Ammonium nitrate-containing wastewater to which organic matter has been added so that 0.1<organic matter/NO3-N≦0.5 (molar ratio) is mixed with at least one species selected from the group consisting of noble metals and their insoluble or poorly soluble compounds, and base metals. in the presence of a supported catalyst containing as an active ingredient and in the substantial absence of oxygen at a pH of about 1.
~11.5, a method for treating ammonium nitrate-containing wastewater, characterized by carrying out wet thermal decomposition at a temperature of 100 to 370°C.

■ Add organic matter so that 0.1<organic matter/NO3-N≦0.5 (molar ratio) and add ammonia so that 0.1<NH3-N/NO3-N≦2 (molar ratio). The ammonium nitrate-containing wastewater is brought to pH in the presence of a supported catalyst containing at least one active ingredient selected from the group consisting of noble metals, their insoluble or sparingly soluble compounds, and base metals, and in the substantial absence of oxygen.
1 to 11.5 and a temperature of 100 to 370°C.

■ Ammonium nitrate-containing wastewater to which organic matter is added and at least one acid and acid-generating substance is added so that 0.1<organic matter/NO3-N≦0.5 (molar ratio) is mixed with precious metals and their insoluble or sparingly soluble compounds. and a supported catalyst containing at least one selected from the group consisting of base metals as an active ingredient and in the substantial absence of oxygen to a pH of about 1 to 11.
65. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet thermal decomposition at a temperature of 100 to 370°C.

■ Add organic matter so that 0.1<organic matter/NO3-N≦0.5 (molar ratio), and add ammonia so that 0.1<NH3-N/NO3-N≦2 (molar ratio). Ammonium nitrate-containing wastewater to which at least one acid and acid-generating substance has been added is treated in the presence of a supported catalyst containing at least one active ingredient selected from the group consisting of noble metals, insoluble or poorly soluble compounds thereof, and base metals, and in the presence of oxygen. pH of about 1 to 1 in the substantial absence of
11.5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet thermal decomposition at a temperature of 100 to 370°C.

In addition, in the present invention, the expression "in the substantial absence of oxygen" means that oxygen is not actively supplied to the wastewater to be treated; This also includes cases where is dissolved.

The wastewater targeted by the present invention is all wastewater containing NH4No3, and particularly high-concentration wastewater with an NH4NO3 concentration of 1% or more is suitable. In the present invention, organic matter (COD component) is added to such wastewater and subjected to thermal decomposition treatment. Examples of COD components include methanol, ethanol, formic acid, acetic acid, and phenol. The amount of COD component added is equal to or less than the number of moles of N O3- ions contained in the wastewater, and more preferably about 0.1 to 0.5 moles. The reaction when methanol is used as a COD component is expressed by the following formula.

NH4NOB +1/3 CH30H→N2 +1/3
C02+8/3 H20 The method of the present invention has a pH of about 1 to 1.
1.5, more preferably 3 to 9 for efficient implementation.

The catalytic active components used in the present invention include ruthenium, rhodium, palladium, osmium,
Iridium, platinum, gold, and compounds that are insoluble or poorly soluble in water, and base metals such as iron, cobalt, manganese, tungsten, nickel, and magnesium, and one or more of these. can be used. Examples of insoluble or poorly soluble noble metal compounds include ruthenium dichloride, platinum dichloride, ruthenium sulfide, and rhodium sulfide. In addition, if necessary, co-catalyst components such as tellurium, selenium, and lanthanum can be used in combination with these catalytic active components to increase the activity of the catalytic active components and improve the heat resistance, durability, and mechanical strength of the catalyst body. Improvements can be made. These catalytically active components and co-catalyst components can be prepared using conventional methods such as titania, zirconia, alumina, silica, alumina-silica, activated carbon,
Alternatively, it may be supported on a carrier such as a porous metal material such as nickel, nickel-chromium, nickel-chromium-aluminum, nickel-chromium-iron, or the like. The amount of the catalytically active component supported is usually about 0.05 to 25%, preferably about 0.5 to 3% of the weight of the carrier. Further, the amount of the co-catalyst component used is about 0.01 to 30% based on the catalytically active component.

The catalyst is used in a state in which it is supported on carriers in various forms such as spheres, pellets, cylinders, crushed pieces, powders, and nicums. In the case of a fixed bed, the reaction column volume is set so that the space velocity of the liquid is 0. It's good. The size of the catalyst used in a fixed bed is usually about 3-5
0), more preferably about 5 to 25 mm.

In the case of a fluidized bed, gold that allows the catalyst to form a fluidized bed in the reaction column, usually 0.5 to 20%, more preferably 0.5 to 1
% is suspended in waste water as 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 preferably about 0.15 to about 0.5 mm.

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 NO3- 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.

The reaction conditions for wet pyrolysis of wastewater containing NH4NCh by adding ammonia together with the COD component to obtain a molar ratio of 0.1<NH3-N/NO3-N≦2 may be the same as those described above.

The reaction conditions may be the same as those described above when wet thermal decomposition of wastewater is performed by adding an acid or a substance that forms an acid under treatment conditions to the NH4NO3-containing wastewater together with the COD component.

Examples of the acid to be added include sulfuric acid, nitric acid, and hydrochloric acid, with sulfuric acid being the most preferred. Examples of acid-generating substances include sulfur and sulfur compounds (thiosulfuric acid, thionic acid, thiourea, 1,000-onythyl, thiophenol, etc.). Alternatively, sulfur compounds discharged from a coke path gas purification device or the like may be used as the acid generating substance source. The amount of acid or a substance that forms an acid under the treatment conditions for the NH4NO3-containing wastewater is:
The amount should be approximately equivalent to the total number of moles of alkali metal salts or ions such as Na and Ni contained in the wastewater.

The reaction conditions are also for wet pyrolysis of wastewater in which COD components and ammonia are added to NH4NO3-containing wastewater to achieve a molar ratio of 0.1 <NH3-N/NO3-N≦2, and an acid or an acid-generating substance is added. Same as above is fine.

In addition, in the present invention, various wastewaters containing these can be used as a COD component source or a COD component source and ammonia source. In this case, gas liquid by-produced in coke oven plants and coal gasification and liquefaction plants, various wastewaters generated during gas purification in these plants, wastewater from wet desulfurization towers and wet cyanide towers, oily water, and activated sludge. It can simultaneously treat treated water, activated sludge, chemical factory wastewater, petroleum factory wastewater, human waste, sewage, sewage sludge, etc.

FIG. 1 shows a flowchart of one embodiment of the method of the invention.

The wastewater raw water stored in the tank (1) passes through the line (3) and is sent to the heat exchanger (9) via the line (7) by the booster pump (5), and is then fed to the heat exchanger (9) from the reaction tower (19), which will be described later. After being heated by high temperature treated water, it passes through line (11),
It is fed to a heater (15) attached to a boiler (13) and heated to a predetermined temperature. When the reaction progresses and reaches a steady state in which the predetermined temperature can be maintained, heating by the boiler (13) is stopped. The waste water heated to the predetermined reaction temperature then enters the reaction column (19) containing the supported catalyst via line (17) and is subjected to heat treatment in the substantial absence of oxygen. The heat-treated high-temperature treated water passes through the line (21) to the heat exchanger (9).
After preliminary treatment of the raw wastewater is carried out, the wastewater is sent to the cooler (25) via the line (23) and cooled. A water supply line (27) and a drainage line (29) are connected to the cooler (25), and cooling water is constantly supplied and drained. The treated water exiting the cooler (25) is sent to the gas-liquid separator (33) via the line (31), where it is separated into a liquid phase from the line (35) and a gas phase from the line (37). Ru. If the pH of the liquid phase is too low, a pHM adjuster (in the illustrated embodiment, an aqueous NaOH solution) from line (39) is added and then removed from the system. On the other hand, the gas phase from the line (37) is transferred to the valve (4).
1) and then taken out of the system.

In addition, by attaching a temperature detection device (43) to the reaction tower (19), the valve (47) is opened depending on the temperature inside the reaction tower (technical unit 9), and the temperature that passes through the line (7) is A portion of the waste water can be fed directly to the reactor (19) via a bypass line (45).

Prior to the start of the reaction, high-pressure air can be fed into the gas-liquid separator (33) from an air cylinder through the line (49) in order to raise the pressure in the system to a predetermined level.

In addition, in order to control the pressure inside the system during reaction processing, a pressure detection device (55) is attached to the gas-liquid separator (33), so that the pressure inside the gas-liquid separator (33) can be adjusted. depending on,
The degree of opening and closing of the valve (41) can be adjusted.

In the present invention, when a COD component is added to wastewater, it may be mixed with the wastewater passing through line (3) from line (51), for example. The COD component can be added at any point up to the reactor without particular limitations.

Furthermore, in the present invention, when adding an acid or an acid-generating substance (sulfuric acid in the illustrated apparatus) to wastewater, it may be mixed with the wastewater passing through line (3) from line (53), for example. The addition position of the acid or acid-generating substance is also not particularly limited, and can be added at any point up to the reactor.

Furthermore, in the present invention, when ammonia is added to wastewater, it may be mixed into the wastewater passing from line (57) to line (3), for example. The position of adding ammonia is not particularly limited either, and it can be added at any point up to the reactor.

Effects of the Invention According to the present invention, wastewater containing a high concentration of NH4No3 can be efficiently treated and the concentrations of NH4'' ions and NO3- ions can be significantly reduced. Alternatively, wastewater discharged from the spent uranium fuel reprocessing process and whose NH4NO3 concentration may reach 10% or more can be easily treated using simple equipment.

In addition, unlike the case of the prior invention-n, which requires the use of oxygen, equipment for compressing and supplying oxygen-containing gas and its installation location are not required, so equipment costs and operating costs are significantly reduced. This significantly reduces wastewater treatment costs.

EXAMPLES Hereinafter, examples will be shown to further clarify the features of the present invention.

Example I CH30H was added so that C0D component/NO3N = 0.33 (molar ratio), pH 6.7, NH4NO3 concentration approximately 1
% (NH3~N/NO3-N=1) capacity of 100ml of wastewater! It was placed in a 300 ml stainless steel autoclave and subjected to thermal decomposition treatment at 250° C. for 90 minutes.

The autoclave was filled with 10 g of a catalyst having a diameter of 5III11 and having 2% by weight of ruthenium supported on a titania carrier.

Table 1 shows catalyst active components, wastewater pH and NH4No3.
are shown together with those of Examples 2 to 6, and
The table shows the total nitrogen component decomposition rate and the COD and TOC component decomposition rates together with the results of Examples 2 to 6.

Example 2 NH4NO3 with a different pH than that treated in Example 1
Add a predetermined amount of CH30H to the wastewater containing CH30H/
After adjusting NO3-N (molar ratio), it was subjected to thermal decomposition treatment in the same manner as in Example 1.

In this example, sulfuric acid (0,013 mol/Q) corresponding to the number of moles of Na and ions in the wastewater was also added to the wastewater.

Example 3 NH with different pH and concentration from that treated in Example 1
4No. Add a predetermined amount of CH30H to the wastewater containing CH
, OH/NO3-N (molar ratio) was adjusted, and then subjected to thermal decomposition treatment in the same manner as in Example 1.

Example 4 The thermal decomposition treatment of wastewater was carried out in the same manner as in Example 1, except that a catalyst with a diameter of 5 mm in which 2% by weight of palladium was supported on a titania carrier was used in place of the ruthenium-supported catalyst.

Examples 5 to 6 Thermal decomposition treatment of NH4NO3-containing wastewater was carried out in the same manner as in Example 2, except that the same palladium catalyst used in Example 4 was used in place of the ruthenium catalyst.

Example Catalyst active component I Ru 2 Ru 3 Ru 4 Pd 5 Pc1 6 Pd H of wastewater 6,7 1,9 5,0 6,7 1,9 5,0 1TableNH4NO3 1f (%) CH30) 1/ N03 (molar ratio) 0.33 0.33 0.50 0.33 0.33 0.50 Table 2 Examples Total nitrogen component decomposition rate (%) 5 〉99 6 〉99COD, TOC
Component decomposition rate (%) > 99 > 99 > 99 > 99 > 99 > 99 Examples 7 to 9 CH30H and NH4OH were added to the NH4N03-containing wastewater, and the wastewater was thermally decomposed in the same manner as in Example 1.

In addition, in Examples 8 and 9, Na and K in wastewater
of sulfuric acid (0,013 mol/I
2) was added to the wastewater.

Tables 3 and 4 show the conditions and results, respectively.

Examples 10 to 12 CH30H and NH4OH were added to NH4NO3-containing wastewater, and the wastewater was thermally decomposed in the same manner as in Example 4.

In Examples 11 and 12, sulfuric acid (0,013 mol/[1) was added to the wastewater in an amount corresponding to the number of moles of Na and K in the wastewater.

Tables 3 and 4 show the conditions and results, respectively.

Actual catalyst NH4NO3 Activity Concentration example Component (W/V%) Table 3 NO3-N N (h -N (molar ratio) COD O3 (molar ratio) u u u d d d Example Table 4 Total nitrogen component decomposition Rate (%) COD, TOC component decomposition rate (%) 8 〉99 9 〉99 11 > 99 12 >99 〉99 〉99 〉99 〉99 〉99 〉99 Example 13 NHa NO3 concentration 10% (NH3-N/ NO3-N=
1.0) wastewater (total nitrogen component concentration = 35000a+g/
Add CH30)1 to Q) to adjust CH30H/NO3 = approximately 0.35 mol, and add sulfuric acid to adjust the pH to 1.9.
It was supplied to the lower part of a high nickel steel cylindrical reactor (based on the empty column) and subjected to thermal decomposition treatment. The purchasing speed of liquid is 2
．． 8 ton/m2 ・hr, and the reactor was equipped with a 5II diameter 2% ruthenium carrier supported on a titania carrier.
Packed with 1 m of spherical catalyst, thermal decomposition is carried out at a temperature of 25
The test was carried out under the conditions of 0°C and cuff pressure of 0 kg/cff12.

After the gas-liquid mixed phase after the reaction is subjected to heat recovery, NH4NO3
In order to separate nitrogen gas etc. generated by the decomposition of
The mixture was introduced into a gas-liquid separator, and the separated gas and liquid phases were each indirectly cooled and then taken out of the system. Before starting the reaction, a small amount of air is fed into the gas-liquid separator to reduce the pressure to 70%.
kg/cm”, the reaction was started.

Table 5 shows NH3, No3, total nitrogen components, COD, T
It shows the decomposition rate of OC components.

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

Table 5 NH3NO3 total nitrogen components COD, TOC component decomposition rate
Decomposition rate Decomposition rate Decomposition rate Examples 14 to 30 Using the following wastewater and adopting the reaction conditions,
Wastewater was treated in the same manner as in Example 13, except that the catalyst was replaced with one shown in Table 6.

The results are shown in Table 6.

*Properties of wastewater and reaction conditions: N Ha N O3 concentration = 5% Total nitrogen concentration = 17500 mg/Q Temperature - 270°C Pressure - 90 kg/cd Waste water space velocity - 1,5'/hr Table 6 of Examples Catalytic activity Ingredients 10 Supports 2%Pd-TiO2 2%Pd-ZrO2 1%RtrTi02 1%0s-TiO□ 1%Ir-TiO2 0.3%Pt(io2 1%Au-TiO2 5%Fe-TiO2 5%Nj4i02 5%W (io2 10% product - TiCh 5%) 4n・5%Ce-TiO2 Total nitrogen component decomposition rate (%) 〉 99 〉 99 〉 99 Table 6 (continued) Example Catalytic active component Pork horse mackerel decomposition rate 10 Support
(%) 26 5%Cu-TiO2832710%Co
TiO292 285%Ce・5%Ce-Ti029829 5%
Ce・1%Te-TiO2983015%Mg-TiO
289 Examples 31 to 34 Wastewater was treated in the same manner as in Example 13, except that the organic substances and acids or acidic substances to be added were replaced with those shown in Table 7.

The results are shown in Table 7.

Table 7 Example Organic substance Acid or acid generating substance Total nitrogen component decomposition rate COD, TOC decomposition rate (%)
(%) 31 Mt Sulfur >99 >99B2
Et Hydrochloric acid 99 >9933
Fa Sulfuric acid 99 >9934 ph
Sulfuric acid >99 >99 Note: Mt = methanol, Et = ethanol, Fa = formic acid, ph = phenol

[Brief explanation of the drawing]

FIG. 1 is a flowchart outlining an example of an embodiment of the method of the present invention. (1)...Wastewater tank (5)...Booster pump (9)...Heat exchanger (13)...Boiler (15)...Heater (19)...Reaction tower (25 )... Cooler (27)... Water supply line (29)... Drainage line (33)... Gas-liquid separator (35)... Liquid phase line (37)... Gas phase line (39)...pH adjuster supply line (43)...Temperature detection device (45)...Bypass line (49)...High pressure air supply line (51)...COD component supply line (53)... )...Acid or acid generating substance supply line (55)
...Pressure detection device (57) ...Ammonia supply line (and above)

Claims (1)

[Claims] [1] Ammonium nitrate-containing wastewater to which organic matter has been added so that 0.1<organic matter/NO_3-N≦0.5 (molar ratio) is made of precious metals and their insoluble or sparingly soluble compounds, and base metals. pH in the presence of a supported catalyst containing at least one selected from the group as an active ingredient and in the substantial absence of oxygen.
1 to 11.5 and a temperature of 100 to 370°C. [2] Add organic matter so that 0.1<organic matter/NO_3-N≦0.5 (molar ratio) and add ammonia so that 0.1<NH_3-N/NO_3-N≦2 (molar ratio). ammonium nitrate-containing wastewater to which pH is adjusted in the presence of a supported catalyst containing at least one active ingredient selected from the group consisting of noble metals, their insoluble or sparingly soluble compounds, and base metals and in the substantial absence of oxygen.
1 to 11.5 and a temperature of 100 to 370°C. [3] Ammonium nitrate-containing wastewater to which organic matter is added and at least one acid and acid-generating substance is added so that 0.1<organic matter/NO_3-N≦0.5 (molar ratio) is mixed with precious metals and their insoluble or poorly soluble wastewater. In the presence of a supported catalyst containing at least one active ingredient selected from the group consisting of soluble compounds and base metals and in the substantial absence of oxygen, the pH is about 1 to 1.
11.5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet thermal decomposition at a temperature of 100 to 370°C. [4] Add organic matter so that 0.1<organic matter/NO_3-N≦0.5 (molar ratio), and add ammonia so that 0.1<NH_3-N/NO_3-N≦2 (molar ratio). ammonium nitrate-containing wastewater to which at least one acid and an acid-generating substance have been added in the presence of a supported catalyst containing at least one selected from the group consisting of noble metals, insoluble or poorly soluble compounds thereof, and base metals as an active component. pH around 1 in the substantial absence of oxygen
11.5. A method for treating ammonium nitrate-containing wastewater, which comprises performing wet thermal decomposition at a temperature of 100 to 370°C.