JP2969477B2 - 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 the top technology -I). In this attempt, it was found that NH ₄ ⁺ ions are decomposed with very high efficiency, but that the treatment of NO ₃ ^- ions may 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 as a result of further investigation, when carrying out the prior application techniques, by reducing the amount of oxygen to be added, NH ₄ NO ₃ not only NH ₄ ⁺ ions in the wastewater containing NO ₃ ^- ions 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, NO 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, the initial NO ₃ ⁺ ions and product contained in the wastewater NO ₃ ^- in order to exert and stabilizing action of 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 mixed with a substantial amount of oxygen in the presence of a catalyst comprising at least one of a noble metal, a noble metal ion and a soluble noble metal compound. A method for treating wastewater containing ammonium nitrate, wherein the wastewater is subjected to wet pyrolysis at a pH of about 1 to 11.5 and a temperature of 100 to 370C in the absence.

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) Is subjected to wet pyrolysis in the presence of a catalyst comprising at least one of a noble metal, a noble metal ion and a soluble noble metal compound at a pH of about 1 to 11.5 and a temperature of 100 to 370 ° C. in the substantial absence of oxygen. A method for treating wastewater containing ammonium nitrate.

An ammonium nitrate-containing wastewater to which an organic substance is added and at least one of an acid and an acid-generating substance is added so that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio) is mixed with at least one of a noble metal, a noble metal ion, and a soluble noble metal compound PH of about 1 to 1 in the presence of a catalyst consisting of
1.5. A method for treating wastewater containing ammonium nitrate, comprising performing wet pyrolysis at a temperature of 100 to 370 ° 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 has been added is subjected to a pH of about 1 to 1 in the presence of a catalyst comprising at least one of a noble metal, a noble metal ion and a soluble noble metal compound 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.

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.

Examples of the catalytically active component used in the present invention include noble metals such as platinum, ruthenium, rhodium, palladium, osmium, and iridium, and ions of these noble metals and noble metal compounds soluble in water.
More than one species can be used. Examples of the noble metal include ruthenium black and palladium black. Examples of the noble metal ion include those in the form of a complex compound using ammonia, chlorine, cyan, sodium, potassium, and the like as ligands. Examples of the complex compound include (NH ₄ ) ₂ (RuCl ₅ (H ₂ O)) , (Ru (NH ₃ ) ₆ ) Cl ₂ , (RuCl (NH ₃ )) ₅ Cl, Na ₂ (PdCl ₄ ), (NH ₄ ) ₂ (PdCl ₄ ), (Pd (NH ₃ ) ₄ ) Cl ₂ , K ₂ (Pd (NO ₂ ) ₄ ) 2 H ₂ O, K ₂ (Pd (CN) ₄ ) 3 H ₂ O and the like are exemplified. As soluble compounds in _{water, RuCl 3, RuCl 4 · 5H} 2 O, PtCl 4, PdCl 2, Pb
_{Cl 2 · 2H 2 O, RhCl} 3 · 3H 2 O, etc. OsCl _4, IrCl ₂ are exemplified. The catalyst component is usually supplied to the reaction tank at a rate of about 0.01 to 0.2 g with respect to 500 cc of wastewater for a while after the treatment is started.
In the reaction vessel, in order to increase the contact area and promote the reaction uniformly, titania, zirconia, alumina, silica, alumina-silica, activated carbon, or iron, nickel,
Nickel-chromium, nickel-chromium-aluminum,
A sphere such as a porous metal such as nickel-chromium-iron or powder (crushed pieces, powder, pellets, cylinders, etc.) may be filled in advance. With the progress of the reaction, noble metal black is formed on the inner surface of the reaction tank and starts to exert its effect as a catalyst. At this point, the supply of the catalyst may be stopped. If the catalytic activity of the above-mentioned noble metal black decreases over time, supply of the catalyst component is restarted. When the reaction is carried out batchwise, it is preferable to use about 3 to 5 times the amount of the catalyst component described above.

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 the acid generating 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, gas liquid by-produced in a coke oven plant and a coal gasification and liquefaction plant, various wastewaters generated by gas purification in these plants, wastewater oil-containing water from a wet desulfurization 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. The catalyst is added into the tank (1) or at any position up to the reaction tower (19). 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 a line (17) a reaction tower (19) filled with spheres or powders of porous metal and substantially in the presence of a catalyst and substantially oxygen. It is subjected to a heat treatment in the absence. The heat-treated high-temperature treated water is sent to a heat exchanger (9) through a line (21), where a pre-heat treatment of the wastewater is performed, and then a cooler (25) is passed through a line (23). And cooled. A water supply line (27) and a drainage line (29) are connected to the cooler (25), and supply and drainage of the cooling water are constantly performed. The treated water leaving the cooler (25) is sent to a gas-liquid separator (33) via a line (31), and is sent to a line (35)
And the gas phase from line (37).
If the pH of the liquid phase is too low, a pH adjuster (in the illustrated embodiment, an aqueous NaOH solution) is added from the line (39) 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 may be fed 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 detecting 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 separator (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-generating substance (sulfuric acid in the illustrated apparatus) is added to the wastewater, for example, the acid 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.

Effects of the Invention According to the present invention, wastewater containing NH ₄ NO ₃ at a high concentration can be efficiently treated, 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 in which the use of oxygen is essential, the equipment for compressing and supplying the oxygen-containing gas and the equipment location 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 —N / NO ₃ —N = 1 )
Was placed in a 300 ml stainless steel autoclave and pyrolyzed at 250 ° C. for 90 minutes.

To the wastewater in the autoclave, 0.5 g of RuCl ₃ was added as a catalyst.

Table 1 also shows the reaction conditions of Examples 1 to 6, and
The table also shows the total nitrogen component decomposition rate and the COD component decomposition rate of each example.

Examples 2 to 3 The wastewater treated in Example 1 was subjected to a thermal decomposition treatment in the same manner as in Example 1 except for the wastewater containing different pH and NH ₄ NO ₃ concentration.

In Examples 2 and the Examples below 5, the amount of sulfuric acid to meet the concentration of Na ions and K ions in the waste water (0.03 mol /) was added to the previously waste water, in place of Example 4 RuCl ₃ PdCl _A waste water pyrolysis treatment was performed in the same manner as in Example 1 except that ₂ was used as a catalyst.

It was subjected to thermal decomposition treatment of waste water but using PdCl ₂ as a catalyst in place of Example 5 to 6 RuCl ₃ in the same manner as in Example 2-3.

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.

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

In Examples 8 to 9 and Examples 11 to 12 described later, sulfuric acid (0.013 mol /) in a mole number corresponding to the mole number of Na and K in the wastewater was added to the wastewater.

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.

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

Example 13 CH ₃ was added to wastewater having an NH ₄ NO ₃ concentration of 10% (NH ₃ −N / NO ₃ −N = 1.0).
OH was added to adjust CH ₃ OH / NO _{3 to} about 0.35 mol, and sulfuric acid was added to adjust the pH of the solution to 1.9.
^It was supplied to the lower part of a high nickel steel cylindrical reactor as ¹ / hr (based on an empty tower) to perform a thermal decomposition treatment. The mass velocity of the liquid is
A 1.1ton / m ² · hr, the reactor has titania spheres is filled, pyrolysis, while supplying per hour RuCl ₃ 0.63 g, temperature 250 ° C., under a pressure of 70 kg / cm ² Performed below.

After subjecting the gas-liquid mixed phase after the reaction to heat recovery, it is led to a gas-liquid separator to separate nitrogen gas, carbon dioxide gas, etc. generated by decomposition of NH ₄ NO ₃ and added CH ₃ OH, and separation. The vapor phase and liquid phase thus obtained were each taken out of the system after indirect cooling. Prior to the start of the reaction, a small amount of air was fed into the gas-liquid separator to increase the pressure to 70 kg / cm ^2, and then the reaction was started.

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

 NOx and SOx were not detected in the gas phase.

Example 14 A waste water heat separation treatment was performed in the same manner as in Example 13 except that PdCl ₂ was used instead of RuCl ₃ .

 The results are shown in Table 5.

 NOx and SOx were not detected in the gas phase.

Example 15 pH10, NH ₄ NO ₃ concentration of about _{1% (NH 3 -N / NO} 3 -N = 2) of the waste water 100ml to as the COD components / NO ₃ -N = 0.50 (molar ratio)
After adding CH ₃ OH and adjusting the pH to 1.9 by adding sulfuric acid,
It was placed in a 300 ml stainless steel autoclave and decomposed at 250 ° C. for 90 minutes.

The wastewater in the autoclave is
0.2 g had been added as catalyst.

Table 6 shows the decomposition rates of NH ₃ , NO ₃ , total nitrogen components and COD components.

[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 (56) References JP-A-61-222587 (JP, A) JP-A-61-257292 (JP, A) JP-A-4-48988 (JP, A) (58) Fields investigated (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 so that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio) is produced by adding an organic substance to a catalyst containing at least one kind of a noble metal ion and a soluble noble metal compound. A method for treating wastewater containing ammonium nitrate, wherein the wastewater is subjected to wet pyrolysis at a pH of about 1 to 11.5 and a temperature of 100 to 370 ° C in the substantial absence. 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). Wet pyrolysis of the added ammonium nitrate-containing wastewater in the presence of a catalyst comprising at least one noble metal ion and a soluble noble metal compound and in the substantial absence of oxygen at a pH of about 1 to 11.5 and a temperature of 100 to 370 ° C. A method for treating wastewater containing ammonium nitrate. 3. An ammonium nitrate-containing wastewater to which an organic substance is added and at least one of an acid and an acid-generating substance is added so that 0.1 <organic substance / NO ₃ -N ≦ 0.5 (molar ratio), and the noble metal ion and the soluble noble metal compound A pH of about 1 to 1 in the presence of at least one catalyst and in the substantial absence of oxygen
11.5. A method for treating ammonium nitrate-containing wastewater, comprising performing wet pyrolysis at a temperature of 100 to 370 ° C. 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). Ammonium nitrate-containing wastewater to which at least one of an acid and an acid-generating substance has been added and which has a pH of about 1 to 11.5 in the presence of a catalyst comprising at least one noble metal ion and a soluble noble metal compound and in the substantial absence of oxygen; A method for treating ammonium nitrate-containing wastewater, comprising performing wet pyrolysis at a temperature of 100 to 370 ° C.