JP2899719B2 - Treatment method for wastewater containing ammonium nitrate - Google Patents

Description

The present invention relates to a method for treating wastewater containing ammonium nitrate.

In the present specification, “NH ₃ —N” refers to
Means "ammonia nitrogen", "NO ₃ -N" shall be deemed to be replaced, which means "nitrate nitrogen". Further, “%” means “% by weight”.

Conventional technology and its problems In recent years, chemical oxygen demanding substances (COD
Component) as well as nitrogen components (especially ammonia nitrogen)
Removal has also become an important issue. The present inventors have conducted various studies on a method for treating ammonia-containing wastewater over a long period of time. As a result, the present inventors have conducted a wet oxidation treatment in the presence of a specific catalyst and under specific conditions (temperature, pressure, amount of supplied oxygen, etc.). Completed a method for treating ammonia-containing wastewater that is easy to operate and has practical economic efficiency (Japanese Patent Publication No.
42992, JP-B-57-33320, JP-B-57-42391, JP-B-58-27999, JP-B-59-19757, etc.).

Recently, as the specific gravity of nuclear power generation in the power generation industry increases, the treatment of uranium raw materials and the treatment of NH ₄ NO ₃ containing wastewater discharged from the reprocessing of spent uranium fuel are becoming important technical issues. . The present inventors have proposed such
NH ₄ NO ₃ was in the process of waste water containing tried to apply the above-described series of ammonia-containing wastewater treatment technology (hereinafter referred to as face washing techniques -I). In this attempt, it was found that although NH ₄ ⁺ ions were decomposed at a very high rate, treatment of N ₃ ^- ions did not always give satisfactory results. This is because the concentration of NH ₄ NO ₃ in the wastewater is 1% (10
000 ppm) to as high as 10% (100,000 ppm).

The present inventors have further studied and found that, when implementing the prior application technology, by reducing the amount of oxygen to be added, not only NH ₄ ⁺ ions but also N ₃ ⁻ ions in the NH ₄ NO ₃ containing wastewater. Has been successfully decomposed with high efficiency (Japanese Unexamined Patent Publication No.
See No. 222585: The technology disclosed in the following is applied to the prior invention-
II).

However, in the treatment of NH ₄ NO ₃ -containing wastewater, not only improvement in treatment efficiency but also further cost reduction (reduction of equipment cost and operation cost) is desired from a practical viewpoint.

Means for Solving the Problems The present inventor has conducted various studies in view of the current situation as described above, and as a result, has found that ammonia, organic and inorganic substances in NH ₄ NO ₃ -containing wastewater can be decomposed. An organic substance (COD component) is added to the NH ₄ NO ₃ -containing wastewater instead of the method of the prior application II in which the wet pyrolysis of the NH ₄ NO ₃ -containing wastewater is performed in the presence of oxygen less than the required theoretical oxygen amount, and even when substantially performs the same process in the absence of oxygen, not NH ₄ ⁺ ions only, N ₃ ^-
We have found the unexpected fact that ions can be efficiently decomposed.

Furthermore, according to the inventor of subsequent research, when subjecting the NH ₄ NO ₃ containing waste water were added and the COD components and ammonia with the wet thermal decomposition in the same manner as above, the decomposition efficiency is more improved further Was found.

Furthermore, the NH ₄ NO ₃ containing wastewater may contain salts or ions of alkali metals such as Na and K, and these salts or ions may partially form NH ₄ ⁺ ions during wet pyrolysis.
Promoting action of conversion reaction to NO ₃ ⁺ ions, in order to exert such stabilizing effect of the initial NO ₃ was contained in the waste water ⁺ ions and generate NO ₃ ⁺ ions, total nitrogen component decomposition rate is slightly lower May be. In such a case, the decomposition efficiency is further increased by subjecting the NH ₄ NO ₃ -containing wastewater containing the COD component and the acid or a substance capable of generating an acid under the treatment conditions to wet pyrolysis in the same manner as described above. It has been found that it is further improved.

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

An ammonium nitrate-containing wastewater to which an organic substance is added so that 0.1 <organic substance / NO ₃ −N ≦ 0.5 (molar ratio) is used as an active ingredient at least one selected from the group consisting of a noble metal and its insoluble or hardly soluble compound and a base metal. PH between about 1 and 11.5 in the presence of a supported catalyst and in the substantial absence of oxygen
A method for treating wastewater containing ammonium nitrate, wherein the wastewater is subjected to wet pyrolysis at 100 to 370 ° C.

0.1 <organics / NO ₃ -N ≦ 0.5 (molar ratio) the organics as a plus and _{0.1 <NH 3 -N / NO 3} -N ≦ 2 ammonium nitrate-containing waste water by adding ammonia as a (molar ratio) A pH of about 1 to 11.5 in the presence of a supported catalyst containing at least one selected from the group consisting of a noble metal and its insoluble or hardly soluble compound and a base metal and in the substantial absence of oxygen;
A method for treating wastewater containing ammonium nitrate, wherein the wastewater is subjected to wet pyrolysis at 100 to 370 ° C.

An ammonium nitrate-containing wastewater to which an organic substance is added so that 0.1 <organic substance / NO ₃ −N ≦ 0.5 (molar ratio) and at least one of an acid and an acid-generating substance is added is composed of a noble metal and its insoluble or hardly soluble compound and a base metal. PH of about 1 to 11.5 and a temperature of 100 to 3 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.
A method for treating ammonium nitrate-containing wastewater, comprising performing wet pyrolysis at 70 ° C.

0.1 <organics / NO ₃ -N ≦ 0.5 (molar ratio) and becomes an organic substance as _{addition, 0.1 <NH 3 -N / NO} 3 -N ≦ 2 adding ammonia as a (molar ratio) and acids and acid The ammonium nitrate-containing wastewater to which at least one of the product substances is added is converted into a noble metal and an insoluble or hardly soluble compound and a substantially non-oxygen in the presence of a supported catalyst containing at least one selected from the group consisting of base metals as an active ingredient. PH about 1-11.5 in the presence, temperature 100-3
A method for treating ammonium nitrate-containing wastewater, comprising performing wet pyrolysis at 70 ° C.

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, and a small amount of oxygen is contained in the wastewater to be treated. Is also included.

Wastewater to which the present invention is directed are all wastewater containing NH ₄ NO _3, is particularly preferred NH ₄ NO ₃ high-concentration waste water concentration of 1% or more. In the present invention, such wastewater is treated with organic matter (CO
D)) and subject to thermal decomposition. Examples of the COD component include methanol, ethanol, formic acid, acetic acid, and phenol. Amount of COD components, NO ₃ contained in the waste water ^- equimolar to ion molar number or less, more preferably about 0.1 to 0.5 moles. The reaction when methanol is used as the COD component is represented by the following formula.

NH ₄ NO ₃ + 1 / 3CH ₃ OH → N ₂ + 1 / 3CO ₂ + 8 / 3H ₂ O The method of the present invention is carried out at a pH of about 1 to 11.5, more preferably 3 to 9
Is implemented efficiently.

As the catalytically active component used in the present invention, as a noble metal, ruthenium, rhodium palladium, osmium,
Iridium, platinum and gold, and compounds insoluble or hardly soluble in water such as iron, cobalt, manganese, tungsten, nickel and magnesium are listed as base metals, and one or more of these may be used. Can be used. Examples of the insoluble or hardly soluble noble metal compounds include ruthenium dichloride, platinum dichloride, ruthenium sulfide, and rhodium sulfide. In addition, if necessary, by using a co-catalyst component such as tellurium, selenium, or lanthanum together with these catalytically active components, the activity of the catalytically active component can be increased, and the heat resistance, durability, and mechanical strength of the catalyst can be improved. Improvement can be achieved. These catalytically active components and co-catalyst components are prepared by titania, zirconia, alumina, silica, alumina-silica, activated carbon,
Alternatively, it is used by being supported on a simple substance such as a porous metal such as nickel, nickel-chromium, nickel-chromium-aluminum, nickel-chromium-iron and the like. The loading amount of the catalytically active component is usually about 0.05 to 25% of the loading weight, preferably 0.5 to 25%.
It is about 3%. The amount of the promoter component used is about 0.01 to 30% based on the catalytically active component. The catalyst is spherical,
It is used in a state of being supported on a carrier in various forms such as a pellet, a column, a fragment, a powder, and a honeycomb. When the reaction column volume is a solid bed, the liquid space velocity is 0.5 to 10 ¹ / h
r (superficial basis), more preferably 1 to 5 ¹ / hr (superficial reference)
It is better to be. The size of the catalyst used in the solid bed is usually about 3 to 50 mm, more preferably about 5 to 25 mm. In the case of a fluidized bed, an amount that allows the catalyst to form a fluidized bed in the reaction tower, usually 0.5 to 20%, more preferably 0.5 to 1%, is used by suspending it in a slurry state in wastewater. In practical operation in a fluidized bed, the catalyst is supplied to the reaction tower in a state of being suspended in a slurry state in wastewater, and after the reaction is completed, the catalyst is settled from the treated wastewater discharged and centrifuged. Separation and recovery by a suitable method and reused. Therefore, considering the ease of separating the catalyst from the treated wastewater, the particle size of the catalyst used in the fluidized bed is more preferably about 0.15 to about 0.5 mm.

The temperature during the reaction is usually 100 to 370 ° C., more preferably 20 to 370 ° C.
0-300 ° C. Higher temperature during the reaction, NH ₄ ⁺ ions and NO ₃ ^- but is shortened residence time of the waste water removal rate is increased and reaction column of ion, because equipment costs become large At a contrary, It may be determined by comprehensively considering the type of wastewater, the required degree of treatment, operating costs, construction costs, and the like. Therefore, the pressure during the reaction may be a pressure at which the wastewater keeps a liquid phase at a predetermined temperature.

NH ₄ NO ₃ reaction conditions for the wastewater was the waste water containing ammonia is added to with COD components _{0.1 <NH 3 -N / NO 3} -N ≦ 2 ( molar ratio) decomposing wet heat also may be the same as described above.

NH ₄ NO ₃ in containing waste water by adding a substance which forms an acid to an acid or treated conditions with COD components, also the reaction conditions for wet thermal decomposition of the waste water may be the same as described above.

Examples of the acid to be added include sulfuric acid, nitric acid, and hydrochloric acid.
Sulfuric acid is most preferred. Examples of the acid generating substance include sulfur and sulfur compounds (thiosulfuric acid, thiocyanic acid, thiourea, thioether, thiophenol and the like). Alternatively, a sulfur compound discharged from a coke gas purification device or the like may be used as an acid purification substance source. The amount of the acid or the substance that forms an acid under the treatment conditions with respect to the NH ₄ NO ₃ -containing wastewater is such that the amount corresponds to the total number of moles of salts or ions of alkali metals such as Na and K contained in the wastewater. Amount.

Adding COD components and ammonia to NH ₄ NO ₃ containing waste water
The reaction conditions in the case of 0.1 <NH ₃ -N / NO ₃ -N ≦ 2 (molar ratio) and wet pyrolysis of wastewater to which an acid or an acid-generating substance is added may be the same as the above.

In the present invention, various kinds of wastewater containing these can also be used as the COD component source or the COD component source and the ammonia source. In this case, a gas liquid produced as a by-product in a coke line plant and a coal gasification and liquefaction plant, various wastewaters produced by gas purification in these plants, wastewater oil-containing water from a wet deflow tower and a wet cyan tower,
Activated sludge treated water, settled sludge activity, chemical factory wastewater, petroleum factory wastewater, night soil, sewage, sewage sludge, etc. can be simultaneously treated.

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

Raw wastewater stored in the tank (1) is supplied to the line (3)
Through a line (7) by a pressurizing pump (5) to a heat exchanger (9) and heated by high-temperature treated water from a reaction tower (19) described later, and then through a line (11), It is fed to a heater (15) provided with a boiler (13) and is heated to a predetermined temperature. When the reaction proceeds and reaches a steady state in which a predetermined temperature can be maintained, the heating by the boiler (13) is stopped. The wastewater heated to the predetermined reaction temperature then enters via line (17) the reaction tower (19) containing the supported catalyst and is subjected to a heat treatment in the practical absence of oxygen. The heat-treated high-temperature treated water is sent to a heat exchanger (9) through a line (21), where it is subjected to a preliminary treatment of raw wastewater, and then to a cooler (25) through a line (23). And cooled. Cooler (2
The water supply line (27) and the wastewater line (29) are connected to 5), and the supply of the cooling water and the wastewater are always performed. The treated water leaving the cooler (25) is sent to a gas-liquid separator (33) via a line (31) and is separated into a liquid phase from a line (35) and a gas phase from a line (37). You. Liquid phase pH
If the pH is too low, the pH adjuster (NaOH aqueous solution in the illustrated embodiment) from line (39) is added and then taken out of the system. On the other hand, the gas phase from the line (37) is taken out of the system via the valve (41).

In addition, by attaching a temperature detector (43) to the reaction tower (19), according to the temperature in the reaction tower (19),
The valve (47) is opened and a part of the wastewater passing through the line (7) can be fed directly to the reactor (19) via the bypass line (45).

Prior to the start of the reaction, high-pressure air can be inserted into the gas-liquid separator (33) from the air cylinder via the line (49) in order to increase the inside of the system to a predetermined pressure.

In order to control the pressure in the system during the reaction process,
By attaching the pressure detection device (55) to the gas-liquid separator (33), the opening / closing degree of the valve (41) can be adjusted according to the pressure in the gas-liquid separation gas (33).

In the present invention, when the COD component is added to the wastewater, for example, it may be mixed with the wastewater passing from the line (51) to the line (3). The position at which the COD component is added is not particularly limited, and the COD component can be added at any point up to the reactor.

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

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

According to the present invention, wastewater containing NH ₄ NO ₃ at a high concentration can be treated well, and the concentrations of NH ₄ ⁺ ions and NO ₃ ⁻ ions can be significantly reduced. Accordingly, for example, wastewater discharged from a uranium raw material processing step or a spent uranium fuel reprocessing step and having an NH ₄ NO ₃ concentration of 10% or more can be easily processed with simple equipment. I can do it.

Also, unlike the above-mentioned prior application invention-II which requires the use of oxygen, the equipment for compressing and supplying the oxygen-containing gas and the place for installing it are not required, so that the equipment cost and the operating cost are greatly reduced. And wastewater treatment costs are significantly reduced.

EXAMPLES Examples are shown below to further clarify features of the present invention.

Example 1 pH 6.7 with CH ₃ OH added so that COD component / NO ₃ −N = 0.33 (molar ratio), NH ₄ NO ₃ concentration about 1% (NH ₃ − / NO ₃ −N = 1)
Was placed in a 300 ml stainless steel autoclave and pyrolyzed at 250 ° C. for 90 minutes.

The autoclave contains ruthenium 2 on a titania carrier.
The catalyst was packed with 10 g of a catalyst having a diameter of 5 mm and supporting the weight%.

Table 1 shows the catalytically active components, the pH of the wastewater and the concentration of NH ₄ NO ₃ together with those of Examples 2 to 6, and Table 2 shows the total nitrogen component decomposition rate and the COD and TOC component decomposition rates in Example 2. ~
6 are shown together with the results.

Example 2 A predetermined amount of CH ₃ OH was added to NH ₄ NO ₃ -containing wastewater having a different pH from that treated in Example 1 to obtain CH ₃ OH / NO ₃ —N (molar ratio).
, And subjected to a thermal decomposition treatment in the same manner as in Example 1.

In this example, sulfuric acid (0.013 mol /) corresponding to the number of moles of Na and K ions in the wastewater was added to the wastewater.

Example 3 NH ₄ N different in pH and concentration from the one treated in Example 1
A predetermined amount of CH ₃ OH is added to the O ₃ -containing wastewater to obtain CH ₃ OH / NO ₃ −N
After adjusting (molar ratio), it was subjected to a thermal decomposition treatment in the same manner as in Example 1.

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

Examples 5 to 6 The thermal decomposition treatment of NH ₄ NO ₃ -containing wastewater was carried out in the same manner as in Example 2 except that the same palladium catalyst as used in Example 4 was used instead of the ruthenium catalyst.

Examples 7 to 9 Example 1 was repeated by adding CH ₃ OH and NH ₄ OH to waste water containing NH ₄ NO _3.
The wastewater was thermally decomposed in the same manner as described above.

In Examples 8 and 9, Na and K in the wastewater were used.
Of sulfuric acid (0.013 mol /) corresponding to the number of moles of was added to the wastewater.

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

The CH ₃ OH and NH ₄ OH was added to the Example 10 to 12 NH ₄ NO ₃ containing waste water, Example 4
The wastewater was thermally decomposed in the same manner as described above.

In Examples 11 and 12, Na and K in the wastewater were used.
Of sulfuric acid (0.013 mol /) corresponding to the number of moles of was added to the wastewater.

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

Example 13 CH ₃ OH was added to wastewater (total nitrogen component concentration = 35000 mg /) having an NH ₄ NO ₃ concentration of 10% (NH ₃ —N / NO ₃ —N = 1.0) to obtain CH ₃ OH / N
O ₃ = as well as adjusted to about 0.35 moles, heat is supplied to the high-nickel steel cylindrical reactor strain a solution obtained by the pH to 1.9 by addition of sulfuric acid as a space velocity 3.9 ¹ / hr (superficial reference) Decomposition processing was performed. Mass velocity of the liquid is 2.8ton / m ² · hr,
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 thermal decomposition was performed at a temperature of 250 ° C. and a pressure of 70 kg / cm ² .

After subjecting the gas-liquid mixed phase after the reaction to heat recovery, a gas-liquid separator is led to separate nitrogen gas and the like generated by decomposition of NH ₄ NO ₃ , and the separated gas phase and liquid phase are respectively separated. After indirect cooling, it was taken out of the system. Prior to the start of the reaction, a small amount of air was blown into the gas-liquid separator, and the pressure was reduced to 70 kg / c.
After increasing to m ² , the reaction was started.

Table 5 shows the decomposition rates of NH ₃ , NO ₃ , total nitrogen components, and COD and TOC components.

 NOx and SOx were not detected in the gas phase.

Examples 14 to 30 Wastewater treatment was carried out in the same manner as in Example 13 except that the following wastewater was used and the reaction conditions were adopted, and the catalyst was changed to that shown in Table 6.

 The results are as shown in Table 6.

* Wastewater characteristics and reaction conditions: NH ₄ NO ₃ concentration = 5% total nitrogen concentration = 17500Mg / temperature = 270 ° C. Pressure = 90 kg / cm ² space velocity = 1.5 ¹ / hr of waste water Examples 31 to 34 Wastewater treatment was carried out in the same manner as in Example 13 except that the organic substances and the acids or acidic substances to be added were changed to those shown in Table 7.

 The results are shown in Table 7.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an outline of an example of an embodiment of the method of the present invention. (1) ... Waste water tank (5) ... Pressure pump (9) ... Heat exchanger (13) ... Boiler (15) ... Heating device (19) ... Reaction tower (25) ... Cooler ( 27) Water supply line (29) Drain line (33) Gas-liquid separator (35) Liquid phase line (37) Gas phase line (39) pH adjuster supply line (43 ) Temperature detector (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 Equipment (57)… Ammonia supply line

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C02F 1/00-1/78

Claims (4)

(57) [Claims] 1. An ammonium nitrate-containing wastewater to which an organic substance is added such that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio) is obtained by mixing at least one selected from the group consisting of a noble metal, an insoluble or hardly soluble compound thereof, and a base metal. The pH is about 1 to 1 in the presence of a supported catalyst containing a species as an active ingredient and in the substantial absence of oxygen.
1.5. A method for treating wastewater containing ammonium nitrate, comprising performing wet pyrolysis at a temperature of 100 to 370 ° C. 2. An organic substance is added so that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio), and ammonia is added so that 0.1 <NH ₃ -N / NO ₃ -N ≦ 2 (molar ratio). The added ammonium nitrate-containing wastewater has a pH of about 1 to about 1 in the presence of a supported catalyst containing at least one active component selected from the group consisting of a noble metal and an insoluble or hardly soluble compound and a base metal and in the substantial absence of oxygen. 11.5, temperature
A method for treating wastewater containing ammonium nitrate, wherein the wastewater is subjected to wet pyrolysis at 100 to 370 ° C. 3. An ammonium nitrate-containing wastewater to which an organic substance is added so that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio) and at least one of an acid and an acid-generating substance is added, the noble metal and its insoluble or hardly soluble Wet pyrolysis at a pH of about 1 to 11.5 and a temperature of 100 to 370 ° C. in the presence of a supported catalyst containing at least one selected from the group consisting of compounds and base metals as active ingredients and in the substantial absence of oxygen; A method for treating ammonium nitrate-containing wastewater. 4. An organic substance is added so that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio), and ammonia is added so that 0.1 <NH ₃ -N / NO ₃ -N ≦ 2 (molar ratio). The ammonium nitrate-containing wastewater to which at least one of an acid and an acid-generating substance is added and which is treated with oxygen in the presence of a supported catalyst containing as an active ingredient at least one selected from the group consisting of noble metals and insoluble or hardly soluble compounds thereof and base metals. PH about 1-11.5, temperature 100-3 in the substantial absence of
A method for treating ammonium nitrate-containing wastewater, comprising performing wet pyrolysis at 70 ° C.