JP3515588B2 - Wastewater treatment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying wastewater by wet oxidation treatment. More specifically, chemical plant equipment, plating industry equipment, leather manufacturing equipment, metal industrial equipment, metal mining equipment, food manufacturing equipment, pharmaceutical manufacturing equipment, textile industrial equipment, paper pulp industrial equipment, dyeing dye industrial equipment, electronic industrial equipment, Regarding the method for purifying the wastewater discharged from machinery industrial equipment, printing plate making equipment, glass manufacturing equipment, etc. by a wet oxidation treatment method, high chemical oxygen demand (hereinafter,
(Also referred to as “COD”).

[0002]

2. Description of the Related Art Conventionally, an effective treatment for purifying wastewater by oxidizing or oxidatively decomposing COD, TOC, nitrogen compounds, etc. in the wastewater under the condition of high temperature and high pressure under the supply of oxygen-containing gas. A wet oxidation treatment method has been widely studied as a method. The wet oxidation treatment method converts the organic compounds and inorganic compounds of various COD components contained in wastewater into lower molecular weight organic substances, inorganic salts, carbon dioxide gas, nitrogen gas, water and ash, etc., and TOC and COD. , And the amount of nitrogen can be reduced. The low molecular weight organic substance and inorganic salt produced at this time are generally mainly acid compounds, and the pH of the treatment liquid after the treatment is often lower than that of the stock solution.
In order to prevent the deterioration of water, an alkali is often added to wastewater.

However, in the conventional wet oxidation treatment method, no particular measure has been taken for the purpose of strictly controlling pH. For example, even if the amount of alkali added to the reaction is not optimal in the wet oxidation treatment, the treatment is carried out without any measures.

[0004]

The object of the present invention is to strictly control the amount of alkali added in a continuous and strict manner in the case of adding a alkali to purify pollutants such as COD components in wastewater by a wet oxidation treatment method. It is possible to purify pollutants in wastewater with high efficiency even when the wastewater condition changes, and the pH of the discharged treatment liquid.
While controlling the exhaust gas composition as much as possible, control of exhaust gas composition, suppression of scale adhesion to the reaction tower and heat exchanger, improvement of material corrosion resistance, suppression of catalyst deterioration in catalytic wet oxidation treatment,
An object of the present invention is to provide a method for purifying wastewater by a wet oxidation treatment method, which can reduce the load on the secondary treatment equipment and the like after the wet oxidation treatment.

[0005]

In order to solve the above problems, the inventors of the present invention have earnestly studied, and as a result, the waste water retained a liquid phase at a temperature of 140 ° C. to 370 ° C. under the supply of a gas containing oxygen. At the time of performing wet oxidation treatment of wastewater while continuously supplying the alkaline aqueous solution under a pressure to be measured , the oxygen concentration in the exhaust gas after the treatment is measured, and the supply amount of the alkaline aqueous solution is controlled based on the measured value to remove the wastewater. The inventors have found that wet oxidation has been accomplished and completed the invention.

Specifically, the pH of the waste water and the treatment liquid is a very important factor in the wet oxidation treatment reaction.
Items that are affected by, for example, (a) TO
C, COD and BOD High and low treatment efficiency of various indicators such as total nitrogen content, (b) types and concentrations of components remaining in the treatment liquid after wet oxidation treatment, (c) types of components contained in treated exhaust gas And concentration, (d) presence and amount of scale substances adhering to the reaction tower and heat exchanger, etc., (e) corrosion resistance of the material of the wet oxidation reactor, (f) durability of the catalyst in the case of catalytic wet oxidation, (g) Water quality and the like for various post-treatments after wet oxidation treatment, and by controlling these in a predetermined manner, an alkaline aqueous solution is continuously supplied to the wastewater, facilitating the operation, practicality, and economical efficiency. An excellent wastewater treatment method is provided. That is, the present invention is specified as follows.

(1) Under the supply of gas containing oxygen, 14
At the temperature of 0 ° C. to 370 ° C., when the waste water is subjected to wet oxidation treatment while continuously supplying the alkaline aqueous solution under the pressure at which the waste water holds the liquid phase, the oxygen concentration in the exhaust gas after the treatment is measured, and the measurement is performed. A method for treating wastewater, which comprises wet-oxidizing the wastewater by controlling the supply amount of the alkaline aqueous solution based on the value.

(2) The treatment method according to the above 1, wherein the pH of the treatment liquid after the treatment is measured, and the supply amount of the alkaline aqueous solution is controlled based on the measured value.

(3) The temperature inside the reactor is measured, and the amount of the alkaline aqueous solution supplied is controlled based on the measured value.
Alternatively, the processing method described in 2 .

(4) The TOC and / or chemical oxygen demand of the wastewater and / or the treated liquid after the treatment is measured, and the supply amount of the alkaline aqueous solution is controlled based on the measured value.
The method for treating wastewater according to any one of 3 above.

(5) The method for treating wastewater according to any one of the above 1 to 4, wherein the composition of the wastewater and / or the treatment liquid after the treatment is analyzed, and the supply amount of the alkaline aqueous solution is controlled based on the analyzed value. .

As the control method according to the present invention, the oxygen concentration after the wet oxidation treatment is measured, and the alkali supply amount is controlled based on the measured value. According to the studies conducted by the present inventors in this wet oxidation state, the pH of the treatment liquid after the wet oxidation treatment under the following constant treatment conditions is as shown in FIG. It was found that the oxygen concentration increased and decreased in proportion to the oxygen concentration in the subsequent exhaust gas .
That is, as shown in FIG. 1, since the pH after the wet oxidation treatment is almost proportional to the oxygen concentration in the exhaust gas after the wet oxidation treatment,
Proportional to the oxygen concentration variation in the exhaust gas after wet oxidation of an alkali aqueous solution and subjected fed to, by wet oxidation so as to later be pH, it is capable of solving the above problems.

Further, since the change in oxygen concentration in the exhaust gas after the treatment appears in a short time as compared with the change on the liquid side such as the change in pH in the treatment liquid and the change in treatment efficiency, the change in oxygen concentration in the treatment exhaust gas. Controlling the supply amount of the alkaline aqueous solution in proportion to the above makes it possible to control more quickly and accurately than controlling by feeding back from the analysis on the processing liquid side. The measurement of the oxygen concentration in the exhaust gas may be any as long as it can be used for the measurement of normal oxygen, for example, a commercially available oxygen concentration meter, for example, an oxygen concentration meter using an oxygen sensor of zirconia, an oxygen dumbbell type oxygen concentration meter. Etc. can be used, and the method of use is not particularly limited.

The constant reaction treatment conditions described above include, for example, (i) waste water flow rate, (ii) oxygen-containing gas flow rate and oxygen concentration, (iii) waste water composition, and (iv) reaction treatment. Temperature, (v) reaction treatment pressure, (vi) alkali concentration and flow rate of the alkaline aqueous solution are constant, and these conditions can be controlled almost stably during wet oxidation treatment in a normal plant. is there. Regarding the above matters, the usual wet oxidation treatment is performed under certain conditions.

The change in the oxygen concentration after the wet oxidation treatment in such a case is due to the change in the concentration of waste water and the change in the required oxygen amount. In this case, the required amount of alkali also changes, so that the pH after treatment also changes when the alkali concentration and flow rate of the alkaline aqueous solution are constant.

The measurement of the pH of the treatment liquid after the treatment is to confirm whether or not the supply of the alkaline aqueous solution is accurately controlled based on the measured value, and the pH of the treatment liquid after the treatment is measured. Any method can be used as long as it is a commonly used pH measuring device. For example, the pH of the treated liquid after the treatment is measured with a pH meter or the like.

In addition, since the wet oxidation treatment is usually fixed and used, the composition of the wastewater to be purified in the wet oxidation does not change greatly, and the influence of the slight change in the composition of the wastewater on the pH change. Is smaller than the effect of changes in the concentration of wastewater on pH, so if the amount of alkali added is fixed in advance, a slight change in composition is only a change in concentration and can be sufficiently treated. is there.

However, when the plant that discharges the wastewater is a batch-type device, even if it is expected that the composition of the wastewater is large even if it is a continuous-type device, the composition that greatly affects the pH should be measured. It is more effective to perform the wet oxidation treatment after performing the correction and correcting the addition amount of the alkali based on the value. In such a continuous apparatus, when it is expected that the composition of the wastewater will change significantly, for example, when the plant apparatus starts operation, stops, and conditions change.

The pH after the wet oxidation treatment is slightly affected by the reaction temperature of the wet oxidation treatment. Therefore, it is possible to measure the reaction temperature and further correct the supply amount of the alkaline aqueous solution based on the measured value. In the heat removal reactor, the reaction treatment temperature is almost constant, so this reaction treatment temperature change is small.However, when adopting an adiabatic reactor, the reaction treatment temperature depends on the amount of heat generated by treating wastewater and the equipment used. It depends on the balance between the amount of heat radiated from and the amount of heat exchanged. Therefore, when the concentration of wastewater changes and the amount of heat generated by the oxidation or oxidative decomposition of the wastewater changes, the reaction treatment temperature is likely to change after a response delay after a predetermined time. Therefore, in the case of a wet oxidation reactor using an adiabatic reactor, it is effective to measure the reaction treatment temperature and further correct the amount of the alkaline aqueous solution supplied based on the measured value.

Since the response delay after the predetermined time is almost constant when the reaction treatment conditions are constant in the same apparatus, the time from the change in oxygen concentration to the change in reaction temperature is predicted in advance. In addition, since the change in oxygen concentration to the change in calorific value can be predicted, the change in reaction treatment temperature can also be predicted.

The relationship between the reaction temperature and the pH of the treatment liquid after the wet oxidation treatment is as shown in FIG. 2 or FIG. 2 and 3 are in inverse proportion to each other. Generally, what is shown in FIG. 2 is a case where the reaction treatment temperature is as high as about 200 ° C. or higher and the treatment efficiency is relatively high. Under such conditions, in the wet oxidation treatment, various organic substances and the like contained in the raw wastewater are decomposed into organic acids, which are lower than the pH of the raw wastewater. Organic acids such as acetic acid are mainly used as COD components remaining at this time. Therefore, when the reaction treatment temperature rises and the treatment efficiency improves, the oxidative decomposition of this organic acid proceeds, and as a result, the pH rises. This processing efficiency is often about 90% or more as TOC. Also, in general, what is shown in FIG. 3 is contrary to the above,
This is when the reaction treatment temperature is a relatively low temperature of less than about 200 ° C., or when the treatment temperature is a high temperature but the treatment efficiency is relatively low. Under such conditions, in the wet oxidation treatment, various organic substances contained in the raw wastewater are often decomposed or oxidatively decomposed to increase organic acids such as acetic acid.

Further, when lower sulfur compounds and the like are present, sulfate ions tend to increase, and when organic halogen compounds are present, halogen ions tend to increase.
Therefore, when the reaction treatment temperature rises and the treatment efficiency improves, the organic acid such as acetic acid or sulfate ion increases, and as a result, the pH decreases.
This processing efficiency is often less than about 80% as TOC.

In the present invention, it is also possible to measure TOC and / or COD in the wastewater and / or the treatment liquid, and predict the required amount of alkali from the measurement results. It is also possible to grasp the change in the heat value of decomposition almost accurately and predict the amount of change in the reaction treatment temperature. Therefore, although not particularly limited, in the case of a wet oxidation reactor using an adiabatic reactor, TOC and / or
Alternatively, it is effective to measure the COD, predict the change in the reaction treatment temperature, and further correct the supply amount of the alkaline aqueous solution.

The type of alkali used in the present invention is not particularly limited, but NaOH, Na ₂ CO ₃ , KOH, K ₂ CO ₃ or the like is effective in terms of cost. The concentration of these aqueous solutions is not particularly limited, but it is effective to be 0.1% by weight or more so that the amount of the processing liquid after the processing is as small as possible.
More effectively, it is 1% by weight or more. Also, 40% by weight
If it exceeds 10, the viscosity of the aqueous solution rises, and the quantitative supply with a pump or the like tends to be hindered, and it is preferably 30% by weight or less.

The position where the alkaline aqueous solution is added is not particularly limited, but the time loss required for control becomes shorter when the position is added to the latter stage by the wet oxidation treatment.

The pH range controlled in the present invention is not particularly limited, but 3 to 10 is effective, and 5.0 to 8.5 is more effective. . When the pH is less than 3 or more than 10, the merits of the present invention are not so great because the normal wet oxidation treatment rarely requires strict pH control.

In the present invention, the measurement of the oxygen concentration in the treated exhaust gas and the measurement of the treatment liquid pH are not particularly limited as long as they are continuously measured. It is more effective to calculate the amount of change and to control the amount of alkali supplied. Although not particularly limited, similarly, the wet oxidation treatment temperature, TOC and CO in the wastewater and / or the treatment liquid may be used.
Concentrations such as D, composition analysis results in wastewater and / or treated liquid, flow rate of wastewater, flow rate of oxygen-containing gas and oxygen concentration, etc. are calculated automatically using a control device such as a computer, It is more effective to control the supply amount of alkali to be changed.

The composition of the wastewater and / or the treatment liquid after treatment according to the present invention means a substance having a great influence on pH when contained in the wastewater and a product thereof after the wet oxidation treatment, It is not particularly limited as a substance because it cannot be unconditionally determined because it also depends on the amount contained in water. However, when it is contained in wastewater, it is a large substance that affects pH, such as sodium thiosulfate, sodium sulfide, D
There are sulfur-containing compounds such as MSO and PTS, organic halogen compounds such as dichlorobenzene and crotonaldehyde, organic nitrogen compounds such as pyridine and DMF, inorganic nitrogen compounds such as nitrates and nitrous acid, and organic acids such as acetic acid and salicylic acid. . The product after the wet oxidation treatment is, for example, acetic acid, metasulfonic acid, sulfate ion, nitrate ion, thiosulfate ion, nitrite ion, chlorine ion, bromine ion, or the like.

The wastewater purified by the treatment method of the present invention can be discharged directly or subjected to biological treatment or chemical treatment as a post-treatment. In this case, the COD components, etc. are considerably reduced, and the residual COD components, etc. are decomposed into substances that are very easily decomposed in biological treatment and chemical treatment. The burden on is very small.

Further, in the present invention, since the site is small and the apparatus is compact, the treatment equipment is compared with the conventional wastewater treatment equipment such as biological treatment equipment and combustion treatment equipment. Is small, the treatment process is simplified, and it is advantageous in terms of capital investment and running cost.

The concentration of COD in the waste water is effective when it is contained in the range of 1 g / liter to 200 g / liter, and more effective is 5 g / liter to 150 g.
g / liter. When the concentration of COD exceeds 200 g / liter, the heat of oxidation of COD becomes extremely large, which makes it difficult to control the processing apparatus. If it is less than 1 g / liter, the heat of oxidation of COD is small, and in such a case, even if a heat exchange device is used as an auxiliary equipment to recover heat, it becomes difficult to independently operate the wet oxidation treatment device by this heat. It is a thing. In such a case, there is no problem in the wet oxidation itself, but when performing the treatment, a separate heat supply device is required, which is relatively disadvantageous in terms of energy consumption.

As the wet oxidation treatment apparatus used in the present invention, a commonly used one is used, and the wet oxidation reaction tower may be of a single tube type or a multi-tube type.
The components contained in the wastewater, and depending on the amount thereof, the single-tube type and the multi-tubular type can be used alone or in combination to separately treat the components contained in the wastewater under conditions suitable for the treatment.

The wet oxidation reaction tower may be filled with a filler such as metal or ceramic to improve the agitation of the liquid and gas, and the catalyst may be charged to improve the treatment efficiency. it can.

The catalyst described here may be any catalyst as long as it is a solid catalyst and has both activity and durability under the conditions of liquid phase oxidation, such as titanium and iron. , A catalyst containing aluminum, silicon, zirconium, activated carbon, or the like, and preferably an oxide such as titanium, titanium-zirconium, or titanium-iron is used. These catalysts may contain a second component in addition to the above components (hereinafter referred to as the first component).

The second component is at least one metal such as manganese, cobalt, nickel, tungsten, copper, cerium, silver, platinum, palladium, rhodium, gold, iridium or ruthenium, or a component thereof. Can be used. This catalyst is the first
For the component 75 to 99.95% by weight, the second component 25 to
The ratio is preferably 0.05% by weight. In addition, various shapes of the catalyst can be adopted and are not particularly limited.

The treatment pressure of the non-catalytic wet oxidation treatment or the treatment pressure of the catalytic wet oxidation treatment of the present invention is appropriately selected according to the correlation with each treatment temperature, and the pressure is such that the liquid retains the liquid phase.

The treatment temperature of the wet oxidation treatment of the present invention is 11
The temperature is 0 ° C or higher and lower than 370 ° C, and preferably 140 ° C or higher and lower than 300 ° C. When the temperature is 370 ° C or higher, the liquid cannot hold the liquid phase. Further, if the temperature is lower than 110 ° C., the treatment efficiency will decrease.

[0038] In the wet oxidation process, as the space velocity is effective at 0.1hr ~ ¹ ~5hr ~ ^1, and more effectively is 0.5hr ~ ¹ ~3hr ~ ^1. Space velocity 5h
When r ~ ¹ is exceeded, the processing efficiency decreases and the space velocity becomes 0.
This is because if it is less than ¹ hr to less than ¹ , the amount of treatment is reduced and the equipment becomes too large.

In the present invention, the oxygen-containing gas means a gas containing oxygen or ozone. When a gas such as ozone or oxygen is used, it can be appropriately diluted with an inert gas or the like before use. Air is preferably used,
In addition to these gases, oxygen-containing waste gas generated from other plants can also be used as appropriate. In this case, it is preferable that the oxygen concentration supplied be constant.

The amount of this gas used can be appropriately selected depending on the concentration of waste water. In this case, the amount of oxygen required for completely converting the COD component of waste water to water, carbon dioxide gas, inorganic salts, other ash, etc. is 0.5 to 3 times, more preferably 1 to
It is double. When the gas is supplied in excess of the required amount of oxygen, the amount of change in the oxygen concentration after the wet oxidation process will be minimal, so control the pH of the treatment liquid from the measured value of the oxygen concentration in the treated exhaust gas. Will be difficult. Therefore, it is preferable to reduce the amount of oxygen-containing gas supplied as much as possible. Further, if it is less than 0.5 times, the amount of oxygen is not sufficient, and the purification of waste water becomes incomplete. 0.5 times
The 1-fold range is not sufficient as the amount of oxygen required to completely convert the COD component of wastewater into water, carbon dioxide, inorganic salts, and other ash. The reason is that the processing efficiency of COD is usually 100.
Since it is less than 100%, the oxygen supplied is finally 100%.
This is because the COD processing efficiency does not change so much even if the amount of oxygen supplied is reduced to less than 1 time in accordance with the actual processing efficiency in such a case.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0042]

【Example】

(Example 1) Using the wet oxidation treatment apparatus shown in FIG. 4, after the treatment start was stabilized, the wet oxidation treatment was continuously performed for 6 hours. The oxygen concentration in the exhaust gas during the wet oxidation treatment, the reaction temperature, and the pH of the treatment liquid were continuously measured, and the data was loaded into the computer. From the result, the optimum flow rate of the alkaline aqueous solution every 15 minutes was displayed on the computer screen, and the flow rate of the NaOH aqueous solution supply pump 4 was finely adjusted. Also automatic TOC
Using an analyzer, the raw wastewater and the treated water were measured every 15 minutes to determine the concentration and the treatment efficiency.

The detailed method of using this treatment apparatus is as follows. After the waste water sent from the waste water supply line 9 is periodically analyzed for TOC by the automatic TOC analyzer 18, the waste water supply pump 3 is used.
At a flow rate of 1.0 liter / hr, the pressure was increased to 75 kg / cm ² G. In addition, the 10 wt% NaOH aqueous solution sent from the NaOH aqueous solution supply line 10 is
75 kg / cm ² G with aOH solution supply pump 4
The pressure was fed up to. On the other hand, after the pressure of the air supplied from the oxygen-containing gas supply line 11 is increased by the compressor 6, the initial COD (Cr) value is changed to O ₂ / COD (Cr).
(Amount of oxygen in air / chemical oxygen demand) = 1.2 was mixed into the wastewater. The flow rate of the NaOH aqueous solution was adjusted so that the pH of the treatment liquid was 6.0. Early NaO
The flow rate of the H aqueous solution was 55 ml / hr.

The gas-liquid mixture is supplied to the gas-liquid mixture supply line 1
After heating in the heat exchanger 2 through 2, it is introduced into the wet oxidation reaction column (empty column) from the lower part, and the electric heater 2 for heat retention is provided.
A wet oxidation treatment was performed while controlling the treatment temperature to 250 ° C. at 0, and the water to be treated was cooled in the heat exchanger 2 through the treatment liquid line 11 and flowed to the gas-liquid separator 5. The reaction tower was filled with 1.0 liter of a catalyst composed of titanium-zirconium oxide and platinum (0.5% by weight of platinum). The space velocity of this wastewater was 1.0 hr- ¹ . In the gas-liquid separator 5, the liquid level controller (LC) detects the liquid level to operate the liquid level control valve 7 to maintain a constant liquid level, and the pressure controller (PC) detects the pressure. The gas discharged from the exhaust gas discharge line 14 is operated to maintain a constant pressure by operating the pressure control valve 8, the oxygen concentration is measured by the oxygen concentration meter 17, and the gas is discharged from the treatment liquid discharge line 15. After the pH of the treated water is measured by the pH measuring device 16, the TOC is periodically analyzed by the automatic TOC analyzer 18. The waste water used for the treatment has a TOC of 20.8 g / liter to 17.8 g / liter, an average TOC concentration of 19.2 g / liter, and CO
Initially, D (Cr) was 52 g / liter.

The results obtained were that the TOC concentration was 1.6 g / liter to 1.4 g / liter, the average TOC concentration was 1.5 g / liter, and the average TOC treatment efficiency was 92%. The pH of the treatment liquid is 5.7 to 6.2, and the average p
H was 6.0, and the oxygen concentration in the processing gas was 3.7 to 6.3% by volume. The treatment temperature did not change in particular.

Example 2 Using the wet oxidation treatment apparatus shown in FIG. 4, 1.0 liter of a catalyst composed of titanium-iron oxide and ruthenium (ruthenium: 1.5% by weight) was filled in the catalyst. By the same operation as in Example 1, the wet oxidation treatment was continuously performed for 6 hours under the following conditions. The processing solution pH is 8.
The flow rate of the NaOH aqueous solution was adjusted so as to be zero.

The wet oxidation treatment conditions are as follows: the flow rate of the waste water is 1 liter / hr, the NaOH aqueous solution concentration is 10 wt%, and the initial N
The flow rate of the aOH aqueous solution is 135 ml / hr, the space velocity of the waste water is 1.0 hr to ¹ , O2 / COD (Cr) (oxygen content in air / chemical oxygen demand) = 1.9, processing pressure is 9 kg / cm.
² G, treatment temperature 160 ° C. The waste water used for the treatment has a TOC of 9.1 g / liter to 8.0 g / liter, an average TOC concentration of 8.7 g / liter, and CO
Initially, D (Cr) was 33 g / liter.

The obtained results were that the TOC concentration was 3.0 g / liter to 2.7 g / liter, the average TOC concentration was 2.9 g / liter, and the average TOC treatment efficiency was 67%. The pH of the treatment liquid is 7.9 to 8.1, and the average p
H is 8.0, and the oxygen concentration in the processing gas is 12.8 to 13.
It was 9% by volume. The treatment temperature did not change in particular.

(Example 3) Using the wet oxidation treatment apparatus and the catalyst shown in Fig. 4, the process wastewater of Example 1 was stockpiled and the raw wastewater having a constant concentration was subjected to the wet oxidation treatment by the same operation. Then, after the treatment is stabilized, the supplied raw wastewater is added to the raw wastewater 3 by adding water 1 to the raw wastewater (75
(Diluted to wt%). However, the fine adjustment of the optimum flow rate of the alkaline aqueous solution based on the oxygen concentration result in the exhaust gas is 5
It was done every minute.

After switching the waste water, the oxygen concentration in the exhaust gas changed about 15 minutes later, and the amount of the aqueous NaOH solution was finely adjusted after 20 minutes. As a result, the change in oxygen concentration in the exhaust gas after 70 minutes became minute, and the fine adjustment of the supply amount of the NaOH aqueous solution was completed. The wastewater after the treatment showed a pH of 7.5 for 70 to 90 minutes, and after that, 13
After 0 minutes it was stable at 6.0.

Comparative Example 1 A wet oxidation reaction was carried out in the same manner as in Example 1 except that the alkali concentration was not adjusted and the waste water used had the following composition. The composition of the wastewater used for treatment has a TOC concentration of 20.7.
g / liter to 17.9 g / liter, average TOC concentration was 19.3 g / liter, and COD (Cr) was 52 g / liter at the initial stage. As a result, the TOC concentration was 2.0 g / liter to 1.5 g / liter, and the average TOC was
The concentration was 1.7 g / liter, and the average TOC treatment efficiency was 91%. The pH of the wastewater after treatment is 5.
The average pH was 3 to 7.0, and was 6.5. The treatment temperature did not change in particular.

Comparative Example 2 In Example 2, the supply air amount was O ₂ / COD (Cr) (oxygen amount in air / chemical oxygen demand amount) = 7.0, and the following composition was used. The wet oxidation treatment was performed under the same conditions as in Example 2 except that waste water was used.

The composition of the wastewater used for the treatment had a TOC concentration of 9.1 g / liter to 8.3 g / liter and an average TOC.
The concentration was 8.7 g / liter, and COD (Cr) was 33 g / liter in the initial stage.

As a result, the TOC concentration was 3.2 g / liter to 2.8 g / liter, and the average TOC concentration was 3.1.
The TOC treatment efficiency of g / liter was 64% on average. The pH of the wastewater after treatment was 7.8 to 8.3, and the average pH was 8.1. The treatment temperature did not change in particular.

(Comparative Example 3) In Example 3, except that the flow rate of the NaOH aqueous solution was finely adjusted according to the oxygen concentration in the exhaust gas, the supply amount of the NaOH aqueous solution was finely adjusted based on the pH value of the treated waste water. Was wet-oxidized in the same manner as in Example 3. The supply amount of the NaOH aqueous solution was finely adjusted at intervals of 5 minutes.

As a result, the pH changed about 55 minutes after changing the source wastewater. Therefore, after 60 minutes, fine adjustment of the supply amount of the NaOH aqueous solution was started. PH of wastewater after treatment
Is pH between 70 and 130 minutes after the change of wastewater.
Was 7 or more, and the maximum pH was 8.5. It should be noted that it took about 5 hours after changing the wastewater to stabilize the pH of the wastewater after the treatment at 6.0.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the pH of a treatment liquid after treatment and the oxygen concentration in exhaust gas.

FIG. 2 is a graph showing the relationship between the pH of the treatment liquid after treatment and the treatment temperature of wet oxidation. The wet oxidation temperature is 2
The temperature is 00 ° C. or higher and the wet oxidation treatment efficiency is high.

FIG. 3 is a graph showing the relationship between the pH of the treatment liquid after treatment and the treatment temperature of wet oxidation. The wet oxidation temperature is 20
When the temperature is lower than 0 ° C, or the wet oxidation treatment efficiency is low.

FIG. 4 is an apparatus which is one aspect of a wet oxidation processing apparatus according to the present invention.

[Explanation of symbols]

1. Wet oxidation reaction tower 2. Heat exchanger 3. Wastewater supply pump 4. NaOH aqueous solution supply pump 5. Gas-liquid separator 6. compressor 7. Liquid level control valve 8. Pressure control valve 9. Wastewater supply line 10. NaOH aqueous solution supply line 11. Oxygen-containing gas supply line 12. Gas-liquid mixture supply line 13. Processing liquid line 14. Exhaust gas discharge line 15. Process liquid discharge line after processing 16. pH meter 17. Oxygen meter 18. Automatic TOC analyzer 19. Reaction tower thermometer 20. Electric heater for heat retention

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kiichiro Mitsui, No. 992, Nishikioki, Kinohama, Aboshi-ku, Himeji-shi, Hyogo Prefecture, Japan Catalysis Research Institute, Nippon Catalyst Co., Ltd. Nihon Shokubai Co., Ltd. in the catalyst research institute (56) Reference JP-A-4-338285 (JP, A) JP-A-59-55390 (JP, A) JP-A-61-257289 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C23F 1/74 101

Claims (5)

(57) [Claims] 1. A temperature of 140 ° C. under the supply of a gas containing oxygen.
At a temperature of up to 370 ° C., when the wastewater is wet-oxidized while continuously supplying the alkaline aqueous solution under the pressure at which the wastewater holds the liquid phase, the oxygen concentration in the exhaust gas after the treatment is measured,
Control the supply amount of the alkaline aqueous solution based on the measured value,
A method for treating wastewater, which comprises subjecting wastewater to wet oxidation. 2. The treatment method according to claim 1, wherein the pH of the treatment liquid after the treatment is measured, and the supply amount of the alkaline aqueous solution is controlled based on the measured value. Wherein measuring the temperature inside the reactor, according to claim 1 for controlling the supply amount of the aqueous alkaline solution based on the measured value or
Or the processing method described in 2 . 4. TO of the wastewater and / or the treated liquid after the treatment
C. and / or chemical oxygen demand is measured, and the supply amount of the alkaline aqueous solution is controlled based on the measured value.
The method for treating wastewater according to any one of 1 . 5. analyzing the composition of the waste water and / or post-processing of the processing liquid, the processing method of waste water according to claim 1 for controlling the supply amount of the aqueous alkali solution, based on the analysis .