JPH07328654A - Treatment of ammoniacal nitrogen-containing waste water - Google Patents

Abstract

PURPOSE:To make a waste water harmless by wet oxidizing the waste water containing ammoniacal nitrogen in the presence of a solid catalyst to convert inclusion in the waste water into gaseous nitrogen, carbon dioxide, water and ash. CONSTITUTION:The ammoniacal nitrogen-containing waste water is wet oxidized at the treating temp. of 100-180 deg.C and the treating pressure of <=11kg/cm<2> in the presence of the solid catalyst by supplying a gas containing oxygen >=1.8 times theoretical oxygen demand to the waste water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of subjecting wastewater containing ammonia nitrogen to wet oxidation treatment in the presence of a solid catalyst to convert the substances contained in the wastewater into nitrogen, carbon dioxide, water and ash, and to It relates to a method of detoxification. More specifically, the present invention treats various wastewater containing ammonia nitrogen represented by industrial wastewater at a specific treatment temperature and treatment pressure in the presence of a solid catalyst and an oxygen-containing gas. The present invention relates to a method of converting substances contained in wastewater into nitrogen, carbon dioxide gas, water and ash by performing a wet oxidation treatment to render the wastewater harmless.

[0002]

2. Description of the Related Art In sea areas, lakes, rivers, etc., red tides and musty odor substances have been a problem for a long time due to eutrophication. It is caused by nutrients such as nitrogen and phosphorus. For this reason, wastewater regulations on nitrogen and phosphorus are enforced, and these nutrient salts cannot be sufficiently treated only by performing the secondary treatment by the conventional activated sludge method. Therefore, it is necessary to newly provide a denitrification step.

Conventionally, as methods for removing nitrogen, methods such as denitrification treatment by living organisms, stripping method by aeration, ion exchange method, and oxidative denitrification by oxidizers such as hypochlorous acid and ozone have been used. The denitrification process by organisms is a method of nitrifying ammonia nitrogen to nitrate nitrogen, and then anaerobically treating the nitrate nitrogen to produce nitrogen gas, but it is inevitable because it requires a long treatment time. However, there is a problem that the device scale becomes large. The stripping method is a method of injecting a gas into the liquid phase and releasing the dissolved ammonium nitrogen into the gas phase.However, the contaminants simply migrate from the liquid phase to the gas phase, and Since it is not a fundamental solution, some step is required to remove ammonia in the gas phase. In the ion exchange method, in wastewater containing a large amount of ions other than nitrogen-containing ions, it is necessary to frequently regenerate the ion exchange base material, and the durability of the ion exchange base material is significantly impaired. Further, the denitrification method using hypochlorous acid has a risk of producing organic chlorine, which has been a problem in recent years, and the presence of bromine ion is indispensable as a catalyst in the denitrification method using ozone. Is required, resulting in high cost, which is not preferable in actual implementation.

On the other hand, as a method for treating waste water containing ammonia, a method of treating by catalytic wet oxidation has been proposed (Japanese Patent Publication No. 56-42992, Japanese Patent Publication No. 57-57).
42391, Japanese Patent Publication 58-27999, Japanese Patent Publication 59-19757, Japanese Patent Publication 59-29317.
No. These are 100 to 100 in the presence of a specific catalyst.
It is a method of performing wet oxidation treatment at a temperature of 370 ° C. and under a pressure condition in which waste water maintains a liquid phase. As described in these examples, these methods have relatively high wastewater treatment temperature and pressure, and under these conditions, ammonia in the wastewater is easily oxidized to nitric acid, which is a sufficient wastewater treatment method. It is something that cannot be said to be naive.

[0005]

Usually, when the wastewater containing ammonia nitrogen is subjected to the wet oxidation treatment, the treatment temperature and pressure of the wastewater are relatively high, and under these conditions, the equipment used for the treatment is heat-resistant. Properties, pressure resistance, etc., increase the cost of the equipment, and also impose a great deal of restrictions when setting the operating conditions of the wet oxidation device, which may cause an undesirable case. . More specifically, for example, depending on the composition of the components in the wastewater, ammonia in the wastewater is easily oxidized to nitric acid by the wet oxidation treatment, and when the treatment temperature is high, especially when the temperature is 180 ° C. or higher, fluctuations in the wastewater concentration and It was confirmed that the processing efficiency greatly fluctuated due to the fluctuation of the equipment itself.
That is, when treating wastewater containing ammonia nitrogen by the catalytic wet oxidation method, if the supplied oxygen amount is less than the theoretical oxygen demand of the wastewater, ammonia remains in the treated water, and if the supplied oxygen amount becomes excessive. Ammonia nitrogen is oxidized to nitrate nitrogen and remains in the treated water at a high concentration as it is. Therefore, it has been clarified that simple and stable highly efficient treatment cannot be performed unless the amount of oxygen supplied is always kept optimal with respect to the concentration of wastewater.

Further, the processing temperature of the wet oxidation is simply 180 ° C.
Under the following treatment conditions, depending on the wastewater treatment conditions, the composition and concentration of the wastewater, if the oxygen supply amount is less than 1.5 times the theoretical oxygen demand of the wastewater, ammonia will remain in the treated water at a high concentration. However, it was also found that satisfactory processing could not be performed.

Further, in an actual device, the concentration of waste water is not constant but constantly fluctuates, and accordingly, it is not preferable to change the wet oxidation treatment condition as needed in a practical specification. Is.

Therefore, an object of the present invention is to treat wastewater containing ammonia nitrogen under conditions that are milder than normal treatment conditions, for example, under low-temperature low-pressure treatment conditions and with high efficiency. To provide.

[0009]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive studies, and as a result, in treating the ammonia-nitrogen-containing wastewater by the catalytic wet oxidation method, 10
It has been found that even under the temperature condition of 0 to 180 ° C., ammonia can be removed by making the supplied oxygen amount excessive. It was also found that under treatment conditions of 180 ° C or lower, the proportion of nitric acid that is oxidized to form nitric acid is significantly reduced, and that the lower the pressure during treatment, the less nitric acid remains in the treated water. The present invention has been completed. The present invention is specified as follows.

(1) Wastewater containing ammonia nitrogen is treated at a treatment temperature of 100 to 180 ° C. and a treatment pressure of 11 kg / c.
A wastewater characterized by supplying to the wastewater a gas containing less than m2 and containing 1.8 times or more of the theoretical oxygen demand of the wastewater in the presence of a solid catalyst, and subjecting the wastewater to wet oxidation treatment. Processing method.

(2) The solid catalyst is titanium, silicon, aluminum, zirconium, manganese, iron, cobalt,
A solid catalyst containing a water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium. A certain method of treating wastewater according to the above item 1.

(3) The solid catalyst is insoluble in water of at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component. Or a solid catalyst containing a sparingly soluble compound and a water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of titanium, silicon and zirconium as the component B of the catalyst. Wastewater treatment method.

(4) The solid catalyst is insoluble in water of at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component. Or a sparingly soluble compound, and manganese as a catalyst C component,
At least one selected from the group consisting of iron and cobalt
2. The method for treating wastewater according to the above 1, which is a solid catalyst containing a compound of a certain element that is insoluble or sparingly soluble in water.

(5) The solid catalyst is insoluble in water of at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component. Or a sparingly soluble compound, a water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of titanium, silicon and zirconium as a catalyst B component, and a group consisting of manganese, iron and cobalt as a catalyst C component 2. The method for treating wastewater according to the above 1, which is a solid catalyst containing a water-insoluble or sparingly soluble compound of at least one element selected from the above.

[0015]

The present invention will be described in detail below. The ammonia nitrogen-containing wastewater according to the present invention contains ammonia nitrogen and may further contain COD components, inorganic salts and the like.

The term "ammonia nitrogen" in the present invention means a general term for ammonia and ammonium ions which are dissolved in the liquid phase. As an example, dissolved salts such as ammonium sulfate and ammonium chloride, aqueous ammonia, etc. However, the present invention is not limited to these as long as they are generally called ammonia and ammonium ions. The concentration of ammonia nitrogen in the waste water to be treated is not limited as long as it is dissolved in the aqueous solution.

The COD component in the present invention is a substance measured as COD, whether organic or inorganic, and specific examples thereof include methanol, ethanol, acetaldehyde, formic acid, acetone, styrene, phenol and methyl. Organic compounds represented by amines, trimethylamine, aniline, acetonitrile, acrylonitrile, benzenethiol, organophosphorus compounds and the like; nitrogen compounds such as nitrous acid; sulfur compounds such as hydrogen sulfide, sulfurous acid and thiosulfuric acid. It is not limited. The concentration of COD components in wastewater is 100,0
It is preferably 00 mg / l or less. Total COD
When the amount of the component exceeds 100,000 mg / l, the amount of heat generated during the oxidation treatment becomes too large, and it becomes impossible to control the amount of heat unless there is a device that recovers the amount of heat generated by some method. The cost is high.

The inorganic salts in the present invention include metal ions such as sodium, potassium, calcium, iron, aluminum and magnesium, halogen ions such as fluorine, chlorine and bromine, carbonate ions, phosphorus and silicon ions. Be done. The concentration of the inorganic salts contained in the wastewater may be within a range that does not precipitate as a salt under the treatment conditions, but when the salt concentration of the wastewater becomes high, the dissolution rate of oxygen in the gas phase into the liquid phase decreases, It is preferable that the salt concentration is low.

The processing temperature according to the present invention is 100 to 180 ° C.
And preferably 130 to 170 ° C. 100
When the temperature is lower than ℃, it is not possible to sufficiently remove ammonia nitrogen, and when the temperature is higher than 180 ℃, the reaction of ammonia with oxygen to form nitric acid is much faster than other reactions. Therefore, a large amount of nitric acid is generated under the condition that oxygen is excessively present, and the nitric acid remains at a high concentration in the treated water. On the other hand, the treatment temperature of wastewater is 1
In the case of 00 to 180 ° C, the production rate of nitric acid becomes slow,
Nitric acid is less likely to be generated even if oxygen is present in excess, and ammonia nitrogen can be decomposed into nitrogen or the like.

In the present invention, the processing temperature is 100 to 180.
If the temperature is ° C, the effect of the invention is not produced, but the effect is produced depending on the other factors, that is, the relationship with the oxygen concentration and the pressure during the treatment. This relationship indicates that when removing ammoniacal nitrogen by the catalytic wet oxidation method, the ammoniacal nitrogen reacts with oxygen to form nitrogen gas, and the ammoniacal nitrogen reacts with oxygen to oxidize to nitrate nitrogen. This is because there are two cases in which the nitrogen gas is reacted with ammonia nitrogen after being treated.

That is, at 100 to 180 ° C., the catalytic activity is weaker than that at 180 ° C. or higher, and sufficient oxygen is oxidized at an oxygen supply of less than 1.5 times the theoretical oxygen demand. I can't do it. Therefore, the supplied oxygen amount is 1.8 times or more of the theoretical oxygen demand, preferably 2 times.
It is necessary to double or more, more preferably triple or more. If the theoretical oxygen demand is less than 1.8 times, high concentration of ammonia will remain in the treated water. Further, the upper limit of the amount of oxygen supplied is preferably less than 15 times, more preferably less than 12 times, when the nitrogen treatment efficiency of 90% or more is targeted. The upper limit of the amount of oxygen supply varies greatly depending on the salt concentration in the wastewater, the catalyst used, and the target treatment efficiency.In each case, the amount of gas is such that the salt in the wastewater does not precipitate, and the nitrogen in the wastewater is The upper limit of the range in which the compound is sufficiently removed is set. For example, when the catalyst prepared in Catalyst Preparation Example 2 described below is used, it is 10 times or less the theoretical oxygen demand of waste water. When the amount of oxygen supplied exceeds the upper limit, nitrate nitrogen will remain in the treated water at a high concentration. In addition, if the catalyst composition is other than the above, the preferable supply amount of oxygen may have different upper limit values.

In the catalytic wet oxidation treatment method, since oxygen dissolved in the liquid is used for the oxidation of ammonia, the transfer rate of oxygen from the gas phase to the liquid phase, that is, the dissolution rate of oxygen has a great influence on the treatment. give. That is, if the pressure at the time of treatment is increased, the oxidation of ammonia proceeds rapidly. However, conversely, by lowering the pressure, the oxidation rate of ammonia is slightly slowed down, and it becomes possible to suppress the production of nitric acid even under the processing conditions in which the supply oxygen amount is large excess. That is, if the pressure is lowered and the amount of oxygen supplied is set under the condition that the treatment of ammonia at the maximum concentration of wastewater can be performed, as a result, a more stable treatment can be performed against fluctuations in wastewater concentration. It will be possible.

The oxygen-containing gas in the present invention is a gas containing oxygen, and specifically, various ones such as air, oxygen-enriched air, and exhaust gas containing oxygen can be mentioned. The oxygen concentration in the oxygen-containing gas is 5 vo
It is 1% or more, preferably 15 vol% or more. When the oxygen concentration in the oxygen-containing gas is 5 vol% or less, the oxygen partial pressure in the device becomes low, the oxygen in the gas phase is not sufficiently dissolved in the liquid, and the treatment speed becomes slow, so sufficient treatment is performed. It may disappear. Furthermore, as the oxygen-containing gas, the oxygen concentration is 2
You may use 5 vol% or more of gas. When oxygen-enriched air is used, the partial pressure of oxygen is increased and the dissolution rate of oxygen from the gas phase to the liquid phase is increased, and as a result, the removal rate of ammonia can be increased. That is, the processing time can be shortened and the apparatus can be made compact, but nitric acid is easily generated as compared with the case where a gas having a low oxygen concentration is supplied, so that the optimum range of the supplied oxygen amount is slightly narrow. In some cases As the gas having an oxygen concentration of 25% or more, oxygen enriched air obtained by a method such as PSA method (pressure swing adsorption method) or selective oxygen permeable membrane method, or pure oxygen produced by liquid oxygen However, the method for producing oxygen-enriched air in the present invention is not limited to these. Oxygen-enriched air with an oxygen concentration of about 25-35% is used as a blowing gas by passing it through a selective oxygen-permeable membrane such as polysiloxane-based, cellulose acetate-based, polypropylene-based, polyether-based, etc. under suction with a blower. In this case, the pressurized state of the blower can be used as it is, which is very advantageous. In order to improve the utilization efficiency of the oxygen-containing gas, part or all of the exhaust gas from the reaction or the like may be recycled in the case where it is advantageous in terms of operation and economy. The oxygen concentration of the supply gas is preferably 95% or less from the viewpoint of equipment durability and reaction safety due to high concentration oxygen, but considering the treatment characteristics as described above, the fluctuation range of the wastewater concentration, the target It may be appropriately set in consideration of the processing efficiency, processing equipment cost, running cost, construction cost, etc.

In the present invention, the oxygen-containing gas is continuously introduced into the apparatus and used for treating waste water. If it is introduced intermittently, an anaerobic part appears in the waste water and the treatment is not performed, and as a result, the treatment efficiency may be low, which is not preferable.

The theoretical oxygen demand in the present invention is calculated from the concentration of ammonia nitrogen in the wastewater, assuming that the reaction proceeds at a ratio of 3 moles of oxygen molecules to 4 moles of ammonia molecules in the wastewater. When other COD components are contained in the waste water, those values are added to the theoretical oxygen demand amount due to ammonia.

Next, the treatment pressure according to the present invention is preferably not less than the pressure at which the waste water holds the liquid phase and less than 11 kg / cm 2. If it exceeds 11 kg / cm2,
As described above, the reaction rate of ammonia is improved, but a state in which a large excess of oxygen is present in the wastewater is likely to occur, so that ammonia is easily oxidized to nitric acid, and the purification of the wastewater is difficult. This can be disadvantageous in.

As described above, the temperature of 100 to 180 ° C.,
The concentration of the wastewater is maintained by supplying a gas containing oxygen at 1.8 times or more of the theoretical oxygen demand of the wastewater under a pressure condition of less than 11 kg / cm 2 while maintaining the liquid phase of the wastewater and carrying out catalytic wet oxidation. The influence of fluctuations is small, and the residual amount of nitrate nitrogen is also minimized, so that it is possible to perform wastewater treatment exhibiting excellent efficiency in total nitrogen treatment. Further, the wastewater treatment can be performed with higher efficiency by using a specific catalyst.

As the catalyst used in the present invention, any catalyst may be used as long as it is a solid catalyst having durability and activity under wet oxidation reaction conditions, but titanium, silicon, aluminum, zirconium and manganese are preferable. ,
Iron, cobalt, nickel, cerium, tungsten,
At least one selected from the group consisting of copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium.
It is a solid catalyst containing a compound of a certain element that is insoluble or sparingly soluble in water. More preferably, (1) the solid catalyst comprises cerium, tungsten, copper as the catalyst A component,
A water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of silver, gold, platinum, palladium, rhodium, ruthenium and iridium, and a catalyst B component selected from the group consisting of titanium, silicon and zirconium. A solid catalyst containing a compound of at least one element which is insoluble or sparingly soluble in water, or (2) the solid catalyst contains cerium, tungsten, copper, silver, gold, platinum or palladium as the catalyst A component. ,rhodium,
A water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of ruthenium and iridium, and at least one element selected from the group consisting of manganese, iron and cobalt as a catalyst C component A solid catalyst containing an insoluble or sparingly soluble compound, most preferably (3) the solid catalyst comprises cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component. A water-insoluble or sparingly soluble compound of at least one element selected from the group, and a water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of titanium, silicon and zirconium as the catalyst B component. , And a small amount selected from the group consisting of manganese, iron and cobalt as the catalyst C component. Both a solid catalyst comprising an insoluble or poorly soluble compounds in water one element.

Of the components of catalyst A, platinum is preferably used because the ammonia nitrogen treatment is most efficiently performed.

When the catalyst A component and the catalyst B component which are solid catalysts of the above (1) are contained, the catalyst A component is 0.1% by weight to 20% by weight, preferably 0.1% by weight to 15% by weight.
Is. When the catalyst A component is less than 0.1% by weight,
If the activity of the catalyst is not sufficient and exceeds 20% by weight,
The cost of the catalyst is high, and the catalytic activity corresponding to it is not expected.

When the catalyst A component and the catalyst C component which are solid catalysts of the above (2) are contained, the catalyst A component is 0.1% by weight to 20% by weight, preferably 0.1% by weight to 15% by weight.
Is. When the catalyst A component is less than 0.1% by weight,
If the activity of the catalyst is not sufficient and exceeds 20% by weight,
The cost of the catalyst is high, and the catalytic activity corresponding to it is not expected.

A catalyst A component which is the solid catalyst of (3) above,
When the catalyst B component and the catalyst C component are contained, the catalyst A component is 0.1% by weight to 20% by weight, preferably 0.1% by weight to 15% by weight. When the content of the catalyst A component is less than 0.1% by weight, the activity of the catalyst is not sufficient, and when it exceeds 20% by weight, the cost of the catalyst becomes high, and the corresponding catalyst activity cannot be expected. . Catalyst B
The component is 1.0% to 79.9% by weight, preferably 5.0% to 59.9% by weight. When the content of the catalyst B component is less than 1.0% by weight, the physical strength of the catalyst is relatively weak and no superiority to the catalyst of the above (2) is obtained, and it exceeds 79.9% by weight. In this case, the effect of adding the C component is hardly obtained. The content of the catalyst C component is 20% by weight to 98.9% by weight, preferably 40% by weight to 94.9% by weight. When the catalyst C component is less than 20% by weight, the effect of adding the C component is hardly obtained, and when it exceeds 98.9% by weight, the physical strength of the catalyst is relatively weak, and No advantage over the catalyst).

The catalyst used in the present invention preferably has the composition specified as described above.
Various materials such as granules, pellets, and integral structures such as honeycombs can be used.

The catalyst according to the present invention produces an effect by any of the preparation methods as long as the composition is within the above range, but a preparation example in which the effect of the present invention is easily produced is described below. However, it is not limited to these preparation methods as long as the composition is within the above range.

(1) An aqueous solution of each of the catalyst A component, the catalyst B component and the catalyst C component is mixed, and the pH is made slightly alkaline with aqueous ammonia to obtain a precipitate. This is filtered and washed, and the obtained cake is dried and calcined to obtain a powder. A molding aid such as starch is added to this powder and molded into a predetermined shape to obtain a finished catalyst.

(2) The respective aqueous solutions of the catalyst B component and the catalyst C component are mixed, and the pH is made slightly alkaline with aqueous ammonia to obtain a precipitate. This is filtered, washed,
The cake obtained is dried and baked to obtain a powder. A molding aid is added to this powder, and the powder is molded into a predetermined shape and dried.
After calcination, the catalyst A component aqueous solution is impregnated, dried and calcined again to obtain a finished catalyst.

(3) The catalyst B component oxide and the catalyst C component oxide are thoroughly mixed, and then an aqueous solution of the catalyst A component is added and mixed, and then a molding aid is added to form a desired shape. Then, it is dried and calcined to obtain a finished catalyst.

(4) The catalyst B component oxide and the catalyst C component oxide are thoroughly mixed, and a molding aid is added to the mixture to obtain a predetermined shape, followed by drying and firing. The molded product is impregnated with an aqueous solution of the catalyst component A, dried and calcined to obtain a finished catalyst.

(5) An oxide of the catalyst B component and an aqueous solution of the catalyst C component are mixed to make the pH weakly alkaline to obtain a precipitate. This is filtered and washed, and the obtained cake is dried and calcined to obtain a powder. A molding aid is added to this powder to mold it into a predetermined shape, which is dried and calcined, then impregnated with an aqueous solution of the catalyst component A, and dried and calcined again to obtain a carrier-type completed catalyst.

(6) The catalyst B component oxide and the catalyst C component aqueous solution are mixed to make the pH weakly alkaline to obtain a precipitate. This is filtered and washed, and the obtained cake is dried and calcined to obtain a powder. After adding and mixing an aqueous solution of the component A of the catalyst, a molding aid is added, the mixture is molded into a predetermined shape, dried and fired to obtain a finished catalyst.

The temperature during the wastewater treatment in the present invention is 100.
To 180 ° C, preferably 130 ° C to 170 ° C. If the temperature at the time of wastewater treatment is less than 100 ° C, ammonia nitrogen cannot be sufficiently removed, and 180 ° C
When it exceeds, the tendency of ammonia nitrogen to be oxidized and become nitrate nitrogen to remain in the treated water remarkably appears, and the total nitrogen treatment efficiency decreases, which is not preferable. Pressure is
At the treatment temperature, the wastewater retains the liquid phase and is 11 kg /
less than cm2, preferably 8 kg / cm2 to 11 kg / c
The m2 is preferable from the viewpoint of stable processing and the cost of the apparatus. If it exceeds 11 kg / cm @ 2, ammoniacal nitrogen may be oxidized to nitric acid as described above and may remain in the treated water at a high concentration.

The inflow velocity of the waste water in the present invention is preferably in the range of 0.2 to 10 / hr in space velocity (LHSV) with respect to the catalyst. If the LHSV is less than 0.2 / hr, the treatment efficiency does not increase with respect to the amount of catalyst and the cost increases, which is not preferable. If LHSV exceeds 10 / hr, the treatment efficiency of ammonia nitrogen is not sufficient, which is not preferable.

The catalytic wet oxidation reactor according to the present invention is usually used as a wet oxidation reactor, for example, single-tube type, multi-tube type, vertical type, horizontal type, etc.
Although any device such as a combination thereof may be used, a single tube vertical type reaction device is preferably used. In the single-tube vertical reactor, not only the control of the apparatus becomes simple, but also the probability that the waste water and the oxygen-containing gas will flow unevenly in the apparatus is low, and uniform and stable treatment can be easily performed. Any material may be used as the material of the device as long as it has durability against the wastewater to be treated. For example, if halogen is not contained in the waste water and the pH is maintained within the range of 6 to 12 over the entire apparatus, an apparatus made of stainless steel is used.

In the present invention, when sulfur or halogen is contained in the waste water, it is desirable to adjust the pH by supplying an alkaline component before or during the treatment.
This is because the presence of halogen ions and sulfate ions under acidic conditions may significantly impair the durability of the material of the reaction tube.

[0045]

By applying the present invention to the treatment of wastewater containing ammonia nitrogen, the treatment efficiency greatly varies due to the fluctuation of the wastewater concentration, which is a problem when treating under the condition of 180 ° C or higher. The problem is completely solved, and stable and highly efficient processing becomes possible. In addition, since the wet oxidation treatment of wastewater can be performed at low temperature and low pressure, the operating conditions of the treatment device become simpler,
As for the material of the processing equipment, more general-purpose materials can be used. Therefore, both the initial investment and the operating cost of the treatment facility can be greatly reduced, and the facility cost can be reduced.

[0046]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

(Catalyst Preparation Example 1) Titanyl sulfate was dissolved in water, palladium nitrate was added, ammonia water was added to adjust the pH to 9, and this was filtered and washed to obtain a cake, which was dried to 700 ° C. After firing in, it is pulverized and oxide powder of titanium-palladium (weight ratio TiO2: Pd = 99.5:
0.5) was obtained.

Starch was added to the oxide powder thus obtained.
After adding water and mixing well, it was molded into a pellet shape (cylindrical shape, average diameter 5 mm, length 6 mm), dried and calcined at 500 ° C. for 3 hours to obtain a finished catalyst.

(Catalyst Preparation Example 2) Ferric nitrate was dissolved in water, zirconyl nitrate was added, an aqueous sodium hydroxide solution was added to adjust the pH to 9, and this was filtered and washed to dry the cake obtained. After firing at 700 ° C, it is pulverized and powdered with iron-zirconium oxide powder (weight ratio Fe2O3: ZrO2: P
t = 60: 40) was obtained. Starch in this oxide powder,
After water was added and mixed well, it was molded into a pellet shape (cylindrical shape, average diameter 5 mm, length 6 mm), dried and baked at 400 ° C. for 4 hours to obtain a molded product.

The molded product thus obtained was impregnated with a chloroplatinic acid aqueous solution, dried at 120 ° C., and then baked at 400 ° C. for 4 hours. The composition of the obtained finished catalyst was iron-zirconium oxide: platinum = 99.6: 0.4 by weight.

(Catalyst Preparation Example 3) Iron oxide powder and titanium oxide powder were thoroughly mixed, starch and water were added and further mixed, and then pelletized (cylindrical shape, average diameter 5 mm, length 6 m).
m), dried and calcined at 500 ° C. for 4 hours to obtain a molded product (weight ratio Fe2O3: TiO2 = 70: 30).

The molded product thus obtained was impregnated with a ruthenium nitrate aqueous solution, dried at 120 ° C., and then baked at 400 ° C. for 4 hours. The composition of the obtained finished catalyst was iron-
Titanium oxide: ruthenium = 99: 1.

(Catalyst Preparation Example 4) An aqueous rhodium nitrate solution was added to cobalt oxide powder and mixed well, and starch and water were added and further mixed, and then pelletized (cylindrical shape, average diameter 5 mm, length 6 mm). ), Dried and calcined at 500 ° C. for 4 hours to obtain a finished catalyst. The composition of the obtained finished catalyst is cobalt oxide: rhodium = 99.5: by weight.
It was 0.5.

(Catalyst Preparation Example 5) Titanium oxide powder was added to an aqueous solution of manganese nitrate, and an aqueous solution of sodium hydroxide was added thereto with vigorous stirring until the pH became 9, to coprecipitate manganese, and after filtration and washing, 500 ° C. Titanium-manganese oxide powder (weight ratio TiO2: MnO2 = 5)
0:50) was obtained. Starch and water were added to this powder, and they were mixed well, molded into granules (diameter 5 mm), dried and fired to obtain a molded product.

The molded product thus obtained was impregnated with a chloroplatinic acid solution, dried and calcined to obtain a finished catalyst (weight ratio titanium-manganese oxide: platinum = 99.5: 0.5).

(Catalyst Preparation Example 6) A palladium nitrate solution and zirconium oxide powder were added to an aqueous solution of ferric nitrate, and ammonia water was added to the solution until the pH reached 9 with vigorous stirring to coprecipitate iron and filtration. After washing, it is baked at 500 ° C. and pulverized to produce iron-zirconium-palladium oxide (weight ratio Fe.
2O3: ZrO2: Pd = 70: 29.5: 0.5) was obtained. To the powder thus obtained, starch and water were added and mixed well, and after molding into granules (diameter 5 mm), drying and firing were carried out to obtain a finished catalyst.

Example 1 Waste water having a composition shown in Table 1 was treated according to the flow shown in FIG. First of all, the drainage sent from the tank 5 is 1 by the pump 3.
The pressure was increased to 9 kg / cm 2 at a flow rate of liter / hr and the pressure was supplied into the apparatus. Further, a 10 wt% sodium carbonate aqueous solution was pressurized and supplied by the pump 4 through the line 11 at a flow rate of 100 ml / hr, and was mixed into the waste water. on the other hand,
The air supplied from the line 12 was pressurized by the compressor 7, and then mixed into the mixed solution at a flow rate of 48 Nl / hr (corresponding to 4 times the theoretical oxygen demand of 10000 mg / l ammonium sulfate solution). This gas-liquid mixture was heated to 160 ° C. in the heat exchanger 2 and the heater 10 via the line 13, and then introduced into the wet oxidation tower 1. The wet oxidation tower 1 is filled with 1 liter of the catalyst obtained in Catalyst Preparation Example 1, the waste water is treated in the wet oxidation tower 1, the treated water is cooled in the heat exchanger 2 through the line 14, and the gas-liquid is used. Pour into separator 6. In the gas-liquid separator 6,
The liquid level is detected by the liquid level controller (LC), the liquid level control valve 8 is operated to maintain a constant liquid level, and the pressure is detected by the pressure controller (PC) to operate the pressure control valve 9. It is operated to maintain a constant pressure.

According to the above-mentioned flow, the wastewater concentration was varied within the range of Table 1 every 24 hours, and a continuous treatment test for 100 hours was conducted.

FIG. 2 shows changes over time in the concentration of ammonia in waste water and the concentrations of ammonia and nitric acid in treated water.

Example 2 A treatment test was conducted under the same conditions as in Example 1 except that the catalyst obtained in Catalyst Preparation Example 2 was used. The results are shown in Fig. 3.

Comparative Example 1 A treatment test was conducted under the same conditions as in Example 1 except that the treatment temperature was 80 ° C. and the treatment pressure was 6 kg / cm 2. The results are shown in Fig. 4.

Comparative Example 2 A treatment test was conducted under the same conditions as in Example 1 except that the treatment temperature was 200 ° C., the treatment pressure was 40 kg / cm 2, and the catalyst was the catalyst obtained in Catalyst Preparation Example 2. It was Results are shown in FIG.

(Comparative Example 3) The flow rate of the supplied air was 13.3 Nl / hr (ammonium sulfate 10000 mg / hr).
The treatment test was carried out under the same conditions as in Example 1 except that the amount was 1.1 times the theoretical oxygen demand of the solution. Results are shown in FIG.

(Example 3) The gas supplied to the reaction tube was changed from air to oxygen-loaded air having an oxygen concentration of 50 vol%.
Equivalent to 9.5 times the theoretical oxygen demand of 0 mg / l solution)
A treatment test was conducted under the same conditions as in Example 1 except for the above. The results are shown in Fig. 7.

(Embodiment 4) The drainage flow rate is 0.2 liter /
hr, the flow rate of sodium carbonate is 20 ml / hr, and the supply air amount is 4.3 N liter / hr (ammonium sulfate 10
A treatment test was carried out under the same conditions as in Example 1 except that the catalyst obtained in Catalyst Preparation Example 3 was used as the catalyst) (corresponding to 2.25 times the theoretical oxygen demand of a 000 mg / l solution). The results are shown in Fig. 8.

[0066]

[Table 1]

[Brief description of drawings]

FIG. 1 is an example of an apparatus used in a processing method according to the present invention. 1. Wet oxidation reactor 2. Heat exchanger 3. Drainage feed pump 4. Sodium carbonate feed pump 5. Drainage tank 6. Gas-liquid separator 7. Air compressor 8. Liquid level control valve 9. Pressure control valve 10. Electric heater 11. Carbonate soda feed line 12. Air feed line

FIG. 2 shows the results obtained in Example 1. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

FIG. 3 shows the results obtained in Example 2. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

FIG. 4 shows the results obtained in Comparative Example 1. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

FIG. 5 shows the results obtained in Comparative Example 2. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

FIG. 6 shows the results obtained in Comparative Example 3. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

FIG. 7 shows the results obtained in Example 3. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

FIG. 8 shows the results obtained in Example 4. The vertical axis represents ammonia nitrogen in wastewater and treated water,
The nitrate nitrogen concentration is shown, and the horizontal axis shows the elapsed time.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location B01J 23/44 M 23/656 23/89 M C02F 1/58 ZAB P (72) Inventor Kiichiro Mitsui 1 992 Nishi-oki, Okihama, Aboshi-ku, Himeji-shi, Hyogo, Japan Catalysis Research Institute

Claims (5)

[Claims] 1. A wastewater containing ammonia nitrogen is treated at a treatment temperature of 100 to 180 ° C. and a treatment pressure of 11 kg / cm 2.
A gas containing less than 1.8 times the theoretical oxygen demand of the wastewater in the presence of a solid catalyst to the wastewater,
A method for treating wastewater, which comprises subjecting the wastewater to wet oxidation treatment. 2. The solid catalyst is selected from the group consisting of titanium, silicon, aluminum, zirconium, manganese, iron, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium. The method for treating wastewater according to claim 1, wherein the solid catalyst comprises a compound of at least one element which is insoluble or sparingly soluble in water. 3. The solid catalyst is insoluble in water of at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component, or A sparingly soluble compound and at least one selected from the group consisting of titanium, silicon and zirconium as the component B of the catalyst.
The method for treating wastewater according to claim 1, wherein the solid catalyst is a solid catalyst containing a water-insoluble or sparingly soluble compound of a certain element. 4. The solid catalyst is insoluble in water of at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component, or A solid catalyst comprising a sparingly soluble compound and a water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of manganese, iron and cobalt as a catalyst C component. Wastewater treatment method. 5. The solid catalyst is insoluble in water of at least one element selected from the group consisting of cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium as the catalyst A component, or A sparingly soluble compound, a water-insoluble or sparingly soluble compound of at least one element selected from the group consisting of titanium, silicon and zirconium as the catalyst B component, and a group consisting of manganese, iron and cobalt as the catalyst C component The method for treating wastewater according to claim 1, which is a solid catalyst comprising a compound of at least one selected element which is insoluble or hardly soluble in water.