JPH08108172A - Treatment of waste water containing oxide form nitrogen - Google Patents

Abstract

PURPOSE: To perfectly decompose and detoxify waste water containing oxide form nitrogen in high concn. by spraying waste water containing oxide form nitrogen into an incinerator to incinerate the same at predetermined temp. in the presence of a denitrating agent. CONSTITUTION: Waste water containing oxide form nitrogen is sprayed toward the high temp. flame in an incinerator main body 1 from a waste water spray nozzle 6 through piping 5. At this time, the incineration temp. in the main body 1 is set to 850 deg.C or higher. However, the incineration temp. is pref. 1100 deg.C or lower, more pref. 1000 deg.C or lower from a viewpoint such that the generation of NOx becomes much as temp. becomes high and from the aspect of the conservation of fuel and the material quality of the incinerator main body. By this constitution, water is rapidly evaporated from waste water and nitrogen oxide is decomposed. In the case of the coexistence of org. matter, the incineration of the org. matter is performed. At the time of incineration, a denitrating agent such as ammonia is supplied to be ejected into the incinerator main body along with waste water from the waste water spray nozzle 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a treatment method for decomposing / detoxifying wastewater containing oxidized nitrogen. More specifically, it relates to a method for incinerating wastewater containing oxidized nitrogen.

[0002]

2. Description of the Related Art Nitrogen / Phosphorus drainage regulations have been implemented for the conservation of the aquatic environment, and waste liquids / wastewater containing nitrogen / phosphorus-containing compounds generated in various industries are appropriately treated and then stipulated by law. It is compulsory to discharge it as wastewater below a certain concentration.

Regarding the nitrogen content present in the wastewater, reduced nitrogen containing free ammonia and various ammonium salts and ammonia of an amine group organic substance, nitrate nitrogen such as ammonium nitrate and sodium nitrate, and the above-mentioned nitrate nitrogen. It is known that it can be roughly classified into oxidized nitrogen including nitro group-containing organic substances, etc., and a treatment method suitable for each treatment target has been developed.

As a technique for treating nitrogen content, a biological denitrification method using denitrifying bacteria has been performed so far for a dilute liquid having a nitrogen content concentration of several hundred ppm or less in wastewater.

Recently, Japanese Patent Publication No. 6-45035, Japanese Patent Publication No. 6-49196, and the like have combined treatment of waste water containing organic matter and nitrogen compounds such as human waste by a biological denitrification method using denitrifying bacteria with membrane separation. A method of processing is disclosed. In the case of concentrated wastewater in which reduced nitrogen and nitrate nitrogen are mixed, it has been proposed to treat by combining the ammonia stripping method + electrodialysis method + biological denitrification method using denitrifying bacteria.

In order to treat the same wastewater, in addition to the above, a wet catalytic oxidation method using an oxidation catalyst has been proposed in JP-A-6-91280 and the like. Also in the treatment of ammonium nitrate-containing wastewater, as a pretreatment, there is known a method of thermally decomposing at a temperature of 100 to 370 ° C. in the presence of a specific catalyst and then combining it with an existing treatment (Japanese Patent Publication No. 6-4).
No. 7100, Japanese Patent Publication No. 6-47101, etc.).

However, each of the above-mentioned various methods uses a low concentration waste liquid having a nitrogen content of several thousands ppm or less, dilutes to the above-mentioned concentration before the treatment, or treats only the nitrogen component. Since the treatment is carried out after reduction by pretreatment, the process as a whole is complicated, a large site is required, equipment costs are high, and there are problems such as sludge generation.

Further, a method for incinerating a waste liquid containing an organic nitrogen compound is also described in JP-B-55-39725 and JP-A-4-283309. These are two-stage incineration treatments in which an organic nitrogen compound is burned at a higher temperature in the latter stage than in the former stage, thereby suppressing the production of nitrogen oxides.

[0009]

An object of the present invention is to provide a treatment method for completely decomposing / detoxifying wastewater containing oxidized nitrogen. Moreover, it is a method that enables treatment of wastewater containing oxidized nitrogen at a high concentration.

Another object of the present invention is not a method of combining a plurality of methods proposed so far as a method of treating wastewater containing oxidized nitrogen, but a simple, simple and inexpensive process. This is a processing method.

[0011]

The present invention is characterized in that waste water containing oxidized nitrogen is spray-supplied into an incinerator, a denitrifying agent is present, and incinerated at 850 ° C. or higher. It is a method of treating wastewater containing water. When the concentration of oxidized nitrogen contained in the wastewater is low, it is desirable to concentrate the wastewater containing oxidized nitrogen as much as possible before incineration before supplying.

[0012]

In the present invention, the waste water containing oxidized nitrogen is completely decomposed by incineration at high temperature in the incinerator, and nitrogen oxides (hereinafter referred to as NO _x ) generated by the decomposition are spray-supplied in the present invention. In addition, a denitration agent (De-NO _x agent) is allowed to exist and burned to suppress it.

Although the details of the reaction mechanism of the denitrification agent are unknown, the denitrification agent is used in the incinerator with respect to NO _x generated from oxidized nitrogen,
It is considered that they react as H ₃ , and as a result, the NO _x concentration in the combustion exhaust gas discharged from the furnace can be reduced to below the regulated value.

According to the present invention, the above object can be achieved by a single combustion in the incinerator without combining a plurality of methods and applying a multi-stage combustion as in the past.

The wastewater targeted by the present invention is molybdenum,
Derived from the vanadium compound manufacturing process, chemical manufacturing process, semiconductor manufacturing process, nuclear reprocessing process, etc., and containing nitrate nitrogen such as ammonium nitrate, sodium nitrate, etc., including nitro group, nitroso group It includes a compound or a compound having a NO bond in its structure. In the present invention, the wastewater as described above is generically called wastewater containing oxidized nitrogen.

The concentration of oxidized nitrogen in waste water is generally several hundred ppm to several thousand ppm, and it is considered that a waste liquid of tens of thousands ppm may be rarely generated from the reprocessing step of the nuclear industry. However, in the present invention, it is desirable that these wastewaters are concentrated to a concentration of 100,000 ppm (10%) or more before being supplied to incineration. this is,
When incinerating wastewater as in the present invention, by simultaneously evaporating a large amount of water contained in the wastewater to a high temperature,
This is to save the fuel required for this and to react in a relatively short reaction area in the incinerator in a short time. Furthermore, by increasing the concentration of wastewater to be incinerated, the treatment volume can be reduced and the equipment can be downsized, so that the entire equipment including incidental equipment can be made compact.

In addition to oxidized nitrogen, the wastewater may contain organic substances that can be incinerated or compounds that can be thermally decomposed, or organic substances that can be incinerated generated from other processes,
It may be mixed with a waste liquid containing a compound capable of being thermally decomposed and then supplied into the incinerator.

The wastewater containing oxidized nitrogen cannot be discarded as it is to a river or the like due to the nitrogen regulation in the wastewater, and therefore it is required to be decomposed and rendered harmless before being discharged. In the present invention, the wastewater containing oxidized nitrogen is incinerated, but it is possible to reduce the exhaust gas generated thereby to the exhaust gas regulation value (NO _x 250 ppm based on 12% oxygen).

The contents of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of an incinerator that can be used in the method of the present invention. The incinerator body 1 in the figure has a burner 4 having a fuel inlet 2 and an air inlet 3 at the top of the furnace, the outside being covered with a metal plate and the inside being formed of refractory material.
Is provided. As the burner, it is preferable to use a high-load, short-flame burner in order to make the incinerator small and achieve a stable combustion state at a high temperature. It is desirable to use LPG or kerosene, which is a clean fuel that can be completely burned and does not generate acid gas and dust components required for post-treatment.

In the present invention, in order to decompose the oxidized nitrogen and completely incinerate the organic matter even in the presence of the organic matter, and to accelerate the reaction with the denitration agent, the incineration temperature is 850 ° C.
It is necessary to do the above.

Although the flame temperature of the above-mentioned high-load short-flame burner may be as high as 1600 ° C. or higher, the higher the upper limit temperature of the region for incinerating wastewater, the higher the NO
1100 ° C or less, more preferably 1000 ° C, due to the increase in _x , fuel saving, and problems with the material of the furnace material.
The following is recommended.

The waste water is sprayed from the waste water spray nozzle 6 through the pipe 5 toward the high temperature flame in the furnace, whereby rapid evaporation of water and decomposition of oxidized nitrogen, and when organic matter coexists. Combustion of organic matter is performed.

The present invention requires the presence of a denitration agent when burning wastewater. Therefore, the denitration agent is supplied from the pipe 7 and ejected from the wastewater spray nozzle 6 together with the wastewater into the furnace, and the wastewater is burned in the state where the denitration agent is present.
Incidentally, a separate spray nozzle may be provided to supply the denitration agent, and the denitration agent may be jetted toward the high temperature flame in the furnace and supplied at the same time when the waste water is sprayed from the waste water spray nozzle 6 into the furnace. Good.

Examples of the denitration agent used in the present invention include ammonia water and compounds that generate ammonia by thermal decomposition of ammonium chloride, ammonium carbonate, ammonium formate, ammonium oxalate, urea and the like. Among these, the use of urea is preferable from the viewpoint of easy handling and economy.

When ammonia water is by-produced from another process, it can be used, and it may be used alone or in combination with another denitration agent.

Assuming that NH ₃ is generated from the denitrification agent, the amount of the denitrification agent added is ₃ to 10 times, preferably 5 to 8 times the NO _x amount from the oxidized nitrogen present in the wastewater to be treated. .

If the oxidized nitrogen present in the wastewater and the amount thereof are known, the NO _x produced by decomposition is predicted from the rational formula, structural formula, etc. of the oxidized nitrogen, and based on this, the NOx removal agent Although the amount to be added may be set, in most cases it is an emission from factories, etc., and there are unclear parts in the composition, components, etc. of wastewater, so incinerate a small amount of the wastewater in advance. , The exhaust gas is analyzed, and N contained in the exhaust gas
It is desirable to determine the amount of denitration agent from O _x amount.

Waste water supplied to the incinerator decomposes and
Due to the reaction and detoxification, the flue gas discharged from the outlet 8 of the incinerator contains only a small amount of NO _x below the legally specified limit value.

The incineration exhaust gas is cooled and dust-removed by a conventional method through a water scrubber or a detoxification tower, and when acid gases such as HCl and SO ₂ are present, they are absorbed and removed before being released into the atmosphere. be able to. As one example, as shown in FIG. 1, an in-liquid combustion can 9 is installed following the outlet 8 of the incinerator, and the combustion exhaust gas passes through the downcomer tube 10 and enters the liquid in the in-liquid combustion can. It can indicate the type of cooling and dust removal by blowing.

The wastewater containing oxidized nitrogen, which is to be treated in the present invention, may be sent to the treatment step as a dilute aqueous solution of several thousand to tens of thousands of oxidized nitrogen to be treated as described above. It is normal. Therefore, in the case of incineration as in the present invention, in order to save fuel and make the equipment compact, wastewater containing oxidized nitrogen is concentrated in advance, and the concentration of oxidized nitrogen is 10% or more, more preferably. Is 15
It is a good idea to keep it above%.

The upper limit of the concentration of oxidized nitrogen does not exist in principle, but it is more efficient to make the concentration as high as possible, and therefore the concentration of precipitates and the viscosity increase due to concentration, and the concentration in the incinerator is increased. It may be adjusted within a range that does not interfere with spraying.

Among oxidized nitrogen, nitrate nitrogen, compounds containing a nitro group and a nitroso group, and the like have explosive properties, and therefore, in such a case, extreme caution is required in concentrating. . In the case of previously concentrating the wastewater containing oxidized nitrogen that may cause an explosion when concentrating as described above, the concentration of oxidized nitrogen should be kept at 30% or less, and the temperature should be 100 ° C or lower, preferably 100 ° C or lower. Keep it below 80 ° C.

Further, in the step of concentrating the waste liquid, care should be taken to avoid mixing of organic substances such as oil from a pump and the like, and to prevent contact with metal powder.

[0034]

【Example】

Example 1 Waste water (component NaNO ₃ 11.2%, Na ₂ SO ₄ 17.
0%, cresol 0.8%, sodium acetate 3.4%,
The balance of water, all by weight, is 9% by using the incinerator of FIG.
It was incinerated under the conditions of 00 ° C and residual oxygen of 2 to 5 Vol% Dry.

The waste water was sprayed from the waste water spray nozzle 6 into the incinerator. The waste water was preliminarily burned at 900 to 950 ° C. in advance and the exhaust gas was analyzed to find that NO _x 1800 to 21
00 ppm was detected. This was 28 to 30% as the NO _x generation rate with respect to the NO ₃ roots in the wastewater. Based on this result, ammonium chloride (NH
₄ Cl) and urea (H ₂ NCONH ₂ ) respectively
_A total of 3 times the _x amount and 6 times the NO _x amount were used and sprayed into the incinerator together with the waste water.

Separately, amonium chloride is added to the NO _x amount of 6
The same amount of waste water was used for incineration using double amount.

As shown in Table 1, the results show that in all cases, the NO _x in the exhaust gas is the regulated value (NO _{x on the} basis of 12% oxygen).
It can be seen that it became less than 250 ppm).

[0038]

[Table 1]

Example 2 An aqueous solution containing 10% by weight of ammonium nitrate (NH ₄ NO ₃ ) was evaporated under reduced pressure at 70 ° C. or lower and concentrated to prepare an aqueous solution containing 25% by weight. Using this as waste water at 950 ° C., Example 1
It was incinerated as in.

Since the NO _x generation rate to the NO ₃ roots in the waste liquid was about 15% in the preliminary combustion, urea as a denitration agent was used in an amount 6 times the NO _x amount.

The results are shown in Table 1, and when incinerated without using the denitration agent, 2000 to 2200 ppm of NO _x was observed, but the reduction rate was about 93% due to the addition of the denitration agent.
Thus, NO _x could be significantly reduced.

Further, part of the denitration agent is ammonia water (29
wt%), urea was set to 4 times the NO _x amount, ammonia water was set to 2 times the NO _x amount, and a total of 6 times the NO _x amount was used. When supplied and subjected to the same incineration process as described above, the NO _x generation amount was almost the same.

Example 3 Wastewater (component NH ₄ NO ₃ 25%, ethyl alcohol 1
4.5%, the balance water, all weight%) was incinerated using the incinerator of FIG. 1 under the conditions of 900 ° C. and oxygen 3-4%. Urea was added as a denitration agent in an amount of 8 times the amount of NO _x based on the result of preliminary combustion and supplied to the furnace.

As shown in Table 1, the results show that N in the exhaust gas is
It was confirmed that O _x was reduced.

In any of Examples 1 to 3, no residual organic matter and no generation of dust were observed.

[0046]

Industrial Applicability According to the present invention, it is possible to provide a treatment method for decomposing / detoxifying wastewater containing a high concentration of oxidized nitrogen such as nitrate nitrogen, for which an appropriate treated method has not been established. Further, it is a method that is simple as an apparatus and extremely easy to operate as compared with various treatment methods that have been proposed so far.

In the case of waste water containing a mixture of ammonia nitrogen and nitrate nitrogen, it has been proposed to treat it by combining an ammonia stripping method + an electrodialysis method + a biological denitrification method using denitrifying bacteria. However, this method requires complicated steps, high equipment costs, and a large area for installation. Although the economic efficiency of this method has been estimated, even if only the part of the biological denitrification method using denitrifying bacteria is taken out, it is estimated that the equipment cost is 1 billion yen in the case of treated water volume of 100 m ³ / day, Naturally, the treatment cost per unit wastewater is also expected to be as high as 30 to 45 yen / kg. Compared with these, in the present invention, both the equipment cost and the operating cost are several times less, and the treatment cost is expected to be 15 to 20 yen / kg / waste water, and the economy is excellent.

[Brief description of drawings]

1 shows an example of an incinerator for carrying out the present invention.

[Explanation of symbols]

 1 Incinerator main body 2 Fuel inlet 3 Air inlet 4 Burner 5 Piping 6 Waste water spray nozzle 7 Piping 8 Incinerator outlet 9 Submerged combustion can 10 Downcomer tube

Claims (3)

[Claims] 1. A method for treating wastewater containing oxidized nitrogen, comprising spraying wastewater containing oxidized nitrogen into an incinerator, allowing a denitrifying agent to be present, and incinerating the wastewater at 850 ° C. or higher. 2. The method for treating wastewater containing oxidized nitrogen according to claim 1, wherein the wastewater containing oxidized nitrogen is concentrated in advance and supplied. 3. The method for treating wastewater containing oxidized nitrogen according to claim 1, wherein the oxidized nitrogen is ammonium nitrate or sodium nitrate.