JP2001293487A - Waste water treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water treating method capable of suppressing the activity deterioration of a solid catalyst containing activated carbon in the case when the waste water containing an organic and/or inorganic oxidizable material is treated at a treating temperature below 170 deg.C and under a pressure at which the waste water keeps the liquid phase, which are relatively low temperature/low pressure, by using a solid catalyst containing activated carbon and when the temperature of the device is raised and the device is started and/or the device is cooled and stopped. SOLUTION: In the waste water treating method in which the waste water containing the organic and/or inorganic oxidizable material is subjected to oxidation and/or oxidative decomposition by using the catalyst, the waste water is treated while supplying oxygen-containing gas by using the solid catalyst at a treating temperature of >=50 deg.C and below 170 deg.C and under a pressure at which the waste water keeps the liquid phase. A catalyst protective solution containing a readily decomposable oxidizable material is also supplied in the case when the device temperature is raised to start and/or cooled to stop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying waste water. More specifically, the present invention relates to a method for performing wet oxidation treatment of waste water containing organic and / or inorganic oxidizable substances using a solid catalyst while supplying an oxygen-containing gas, and particularly by appropriately performing a catalyst protection treatment. The present invention relates to a method capable of suppressing a decrease in catalytic activity when the apparatus is heated and started and / or cooling and stopping the apparatus, and capable of stably treating wastewater for a long period of time.

[0002]

2. Description of the Related Art As a method for treating wastewater containing organic or inorganic oxidizable substances, for example, a biological treatment method and a wet oxidation method are known. Of these, biological treatment takes a long time to decompose oxidizable substances in wastewater, and can only treat low-concentration substances, so when wastewater contains high-concentration oxidizable substances, It is necessary to dilute to an appropriate concentration, which has the disadvantage that the equipment area of the processing facility becomes large. Moreover, since the microorganisms used are greatly affected by the temperature and the like, it has been difficult to continue stable operation.

[0003] On the other hand, in the wet oxidation method, wastewater is treated at high temperature and high pressure in the presence of oxygen, and oxidizable substances in the wastewater are oxidized and / or decomposed (hereinafter abbreviated as "oxidation / decomposition treatment"). Is sometimes done). In this method, as a means for increasing the reaction rate and relaxing the reaction conditions, for example, a catalyst wet oxidation method using a catalyst using an oxide or a catalyst combining these oxides with a noble metal element or the like has been proposed.

However, in order to purify the wastewater by oxidizing and decomposing various oxidizable substances contained in the wastewater by this method, it is necessary to treat the wastewater at a treatment temperature of 170 ° C. or more. In many cases, a pressure exceeding 1 MPa (Gauge) was required. For example, JP
No. 1-347574 describes a method of performing wet oxidation treatment of acetic acid at a treatment temperature of 170 ° C. using a catalyst supporting platinum on titania, but this technique still requires relatively high temperature treatment conditions. Further, development of a wastewater treatment method capable of performing advanced treatment under low-temperature and low-pressure conditions of less than 170 ° C. is desired.

[0005] From the above, the present inventors have conventionally studied a novel catalyst and a novel treatment method. As a result, as one of the means that can reduce the reaction conditions,
When using a solid catalyst containing activated carbon, 170 ° C
Under low-temperature and low-pressure processing conditions of less than 3, it was confirmed that the compound has high activity specifically for organic and inorganic oxidizable substances.

However, when a solid catalyst containing activated carbon is used, there is a problem that the activated carbon itself burns under conventional wet oxidation conditions, and it is necessary to use the activated carbon stably as a catalyst for wet oxidation for a long period of time. Was impossible. Therefore, the present inventors have proposed that by maintaining the oxygen concentration in the exhaust gas after treatment using a solid catalyst containing activated carbon at 0 to 5%, combustion of the activated carbon itself can be suppressed, and wastewater can be treated efficiently. Since the heading and its technical significance were recognized, the application was filed earlier (Japanese Patent Application No. 12-5198).

The development of such technology has made it possible to treat wastewater containing organic and / or inorganic oxidizable substances to a high degree even under low temperature and low pressure conditions. However, when the apparatus is heated and started up and / or when the apparatus is cooled and stopped, as in the case of the conventional catalyst system, if the operation is performed in an oxidizing atmosphere, the combustion of the activated carbon itself is likely to occur, and the catalytic activity is increased. Was sometimes reduced.

In the wet oxidation treatment, the wastewater is often heated and pressurized so that the wastewater retains a liquid phase. For this reason, it is common to supply an oxygen-containing gas even when no oxidizable substance is present in order to maintain the pressure in the apparatus when starting up the apparatus. Due to this situation, the activity of the catalyst containing activated carbon may be degraded when starting up equipment that has not yet started wastewater treatment, or when shutting down the equipment by stopping the supply of wastewater. It has become. For this reason, when starting up the apparatus and / or when stopping the apparatus, there is a method in which a gas containing no oxygen, for example, nitrogen gas, is supplied into the apparatus, but it is preferable from the viewpoint of cost and complexity of operation. It was not something. Further, even when the oxygen-containing gas was not supplied, the catalytic activity sometimes decreased due to the oxygen remaining in the apparatus or the oxygen adsorbed on the catalyst.

Conventionally, as a technique for starting or stopping a wet oxidation treatment apparatus using a solid catalyst, Japanese Patent Application Laid-Open No. 4-300696 discloses, for example, the equipment required for preheating at start-up is omitted or simplified, and oxidation is rapidly performed. There are technologies that can start the reaction and technologies that highly treat wastewater even when the device is stopped. However, a technology for preventing the activity of the catalyst from being reduced has not been proposed yet.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wastewater containing organic and / or inorganic oxidizable substances.
When the wastewater is treated using a solid catalyst containing activated carbon at a treatment temperature of less than 170 ° C., which is a relatively low temperature and low pressure, and the pressure at which the wastewater retains a liquid phase, when the equipment is heated and started up Another object of the present invention is to provide a wastewater treatment method capable of suppressing the activity deterioration of a solid catalyst containing activated carbon when cooling and stopping the apparatus.

[0011]

SUMMARY OF THE INVENTION The wastewater treatment method of the present invention, which has achieved the above object, comprises the steps of oxidizing and / or oxidizing organic and / or inorganic oxidizable substances contained in wastewater using a catalyst. Alternatively, in a method for treating wastewater to be subjected to oxidative decomposition, a wastewater is supplied using a solid catalyst containing activated carbon by supplying an oxygen-containing gas at a treatment temperature of 50 ° C. or more and less than 170 ° C. under a pressure at which the wastewater maintains a liquid phase. When the apparatus is heated and started up and / or when the apparatus is cooled and stopped, a catalyst protection liquid containing an easily decomposable oxidizable substance is supplied to the solid catalyst layer to operate the apparatus. The point is to have a gist.

In carrying out the method of the present invention, the operation is preferably performed such that the catalyst protective liquid remains at the outlet of the catalyst layer. The temperature at which the catalyst protection liquid is supplied is
The temperature is preferably lower than the wastewater treatment temperature. Further, examples of the catalyst protection liquid used in the present invention include a liquid containing alcohols. In addition, when the apparatus is heated and started and / or when the apparatus is cooled and stopped,
Oxygen concentration in the exhaust gas passing through the catalyst layer is 0 to 5 vol
%, It is preferable to operate in the range.

In the method of the present invention, when supplying the catalyst protective liquid to the catalyst layer, an oxygen-containing gas or an oxygen-free gas is supplied, and the amount of oxygen in these supply gases is [oxygen in supply gas] / It is desirable to set the amount of oxygen required of the catalyst protection solution when the processing efficiency of the catalyst protection solution is maximized to be in the range of 0 to 1.3. Further, in the present invention, it is desirable that the gas-liquid circulation method in the catalyst layer filled with the solid catalyst is a gas-liquid downward co-current flow.

The solid catalyst used in the present invention basically contains activated carbon, and further contains Pt, Pd, R
It is desirable that the material contains at least one element selected from the group consisting of h, Ru, Ir, Ag and Au. In practicing the present invention, it is preferable that the oxygen-containing gas is supplied from the downstream side of the catalyst layer in the flow direction of the liquid, and the pressure is controlled so as to maintain the pressure in the apparatus. It is listed as.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have developed wastewater containing organic and / or inorganic oxidizable substances at a relatively low temperature.
In treating wastewater using a solid catalyst containing activated carbon under low pressure conditions, when the apparatus is heated to start up and / or when the apparatus is cooled and stopped, the solid catalyst containing activated carbon is not used. Various studies have been made on a method capable of suppressing the activity deterioration. As a result, when the apparatus is heated and started up and / or when the apparatus is cooled and stopped, if the catalyst protection liquid containing the easily decomposable oxidizable substance is supplied to the catalyst layer and operated, The inventor has found that the above-mentioned object has been accomplished brilliantly, and completed the present invention. It has also been found that it is more effective to operate the system so that the catalyst protective solution containing the easily decomposable oxidizable substance remains at the outlet of the catalyst layer.

In the present invention, it is necessary to supply a catalyst protective solution containing a readily decomposable oxidizable substance to the solid catalyst layer. More effectively, the catalyst protection liquid is left at the outlet of the catalyst layer. When oxygen in the gas phase or oxygen adsorbed on the catalyst is present in the catalyst layer, the easily decomposable oxidizable substance in the catalyst protection solution is oxidized and decomposed from a low temperature, and therefore exists in the catalyst layer. The generated oxygen is used for the reaction, and the catalyst layer becomes oxygen-deficient. Therefore, combustion of the catalyst hardly occurs, and a decrease in the activity of the catalyst can be suppressed. It is also considered that when the catalyst protective liquid is present in the catalyst layer, it is possible to suppress the thermal deterioration of the catalyst containing activated carbon.
Furthermore, after the temperature rise when starting up the device, when the catalyst protection liquid is switched to the wastewater to be treated, if the catalyst protection liquid remains in the catalyst layer, the initial reaction of the catalyst is likely to occur, and the normal reaction occurs smoothly. Wastewater treatment can be carried out.

However, if there is no catalyst protection liquid, the combustion of the catalyst is apt to occur due to the excess oxygen, and it is difficult to smoothly shift to the normal wastewater treatment. Further, when the apparatus is stopped, if the waste water is switched to the catalyst protection liquid, the waste water can be highly purified to the end, and it is difficult to discharge harmful substances in the waste water. Furthermore, if the catalyst is not switched to the catalyst protection solution, the activity of the catalyst is reduced, and the wastewater cannot be highly purified to the end, and the wastewater treatment cannot be smoothly performed when the wastewater treatment is started next time. Sometimes.

Even under the condition that the catalyst protection liquid does not remain at the outlet of the catalyst layer, if the easily decomposable substance of the catalyst protection liquid and the solid catalyst can come into contact with most of the solid catalyst layer, considerable catalyst protection is achieved. Is what you can do. This is because even if the entire catalyst of the solid catalyst is not protected, if the residual oxygen amount in the latter half of the solid catalyst layer in which the easily decomposable substances have disappeared is very small, the catalyst does not deteriorate much.

The method for protecting the catalyst of the present invention is carried out when the apparatus which is normally stopped is heated to start up and / or when the apparatus which performs the treatment of waste water is cooled and stopped. However, in treating wastewater,
It can also be applied when heating and maintaining the device. That is, the present invention can be applied to holding the apparatus that has been performing the wastewater treatment in a heated state and holding the apparatus until the wastewater treatment is restarted. Therefore, in the present invention, the term “when the apparatus is heated and started up and / or when the apparatus is cooled and stopped” includes the case where the apparatus is heated and held.

In the method of the present invention, the temperature at which the catalyst protective solution is supplied is not particularly limited. However, as can be understood from the object of the present invention for protecting the catalyst, the catalyst layer is heated. It is desirable to supply a catalyst protection liquid when the system is in operation. Further, since the catalyst protection of the present invention is performed when the apparatus is heated and started and / or when the apparatus is cooled and stopped, the temperature at the time of supplying the catalyst protection liquid is reduced when the wastewater is treated. Often lower than the temperature. Specifically, it is preferable to supply the catalyst protection liquid at 50 ° C. or higher, and in many cases at 60 ° C. or higher. At a temperature lower than the normal temperature of wastewater treatment by less than 5 ° C., it is often sufficient to change the catalyst protection liquid to wastewater treatment. For this reason, when starting up the apparatus by heating, 5
It is desirable that the supply of the catalyst protection liquid be started at 0 ° C. or lower, in many cases at 60 ° C. or lower, and then supplied until switching to wastewater treatment. When cooling and stopping the equipment, switch from wastewater treatment to supply of catalyst protection liquid immediately,
It is desirable to keep supplying the catalyst protection liquid until the temperature becomes 50 ° C. or lower, and often 60 ° C. or lower.

The processing pressure may be any pressure at which the catalyst protection liquid maintains a liquid phase. However, 1 MPa (Gaug
Pressures above e) are not preferred from an economic point of view.
Further, when the processing pressure is excessively increased, as in the case where the processing temperature is increased, the problem of combustion of the activated carbon itself is likely to occur. In addition, the activity of the catalyst may be reduced. Therefore, when pressurizing, it is desirable to provide a pressure control valve on the exhaust gas outlet side of the wet oxidation treatment apparatus and adjust the pressure appropriately according to the processing conditions so that the wastewater can maintain the liquid phase in the reaction tower. Further, in order to improve the durability of the catalyst, it is desirable to control the processing pressure within ± 20%, more preferably ± 10%, and still more preferably ± 5% of the processing pressure.

In the present invention, it is also possible to start or stop the apparatus by supplying only the catalyst protection liquid without supplying gas to the catalyst layer. If the gas is not supplied, it is often difficult to control the pressure, and the pressure change at that time often adversely affects the catalyst. In such a case, by supplying gas from the rear of the catalyst layer and maintaining the pressure in the apparatus, not only stable pressure control is possible, but also the activity of the catalyst is reduced because oxygen is not supplied to the catalyst layer. It can be suppressed effectively. Since the present invention relates to a method for treating wastewater by a wet oxidation method, it is desirable to use an oxygen-containing gas used for wastewater treatment in this case in terms of operability and economy.

When a catalyst containing activated carbon is used,
When the apparatus is stopped or when the catalyst is stored, it is desirable that the atmosphere of the catalyst is in a state of low oxygen concentration. For this reason, when the apparatus is stopped and stored in a state where the catalyst is filled in the reaction tower, it is desirable that the oxygen concentration in the catalyst layer be low when the apparatus is stopped, Further, it is desirable that the catalyst protection liquid is present in the catalyst layer.

The solid catalyst used in the present invention only needs to contain at least activated carbon as a catalyst component.
The type of the activated carbon is not particularly limited, and examples thereof include those made from charcoal, coconut shell, coal, coke, peat, lignite, pitch, and the like, and acrylonitrile-based activated carbon fiber and phenol-based. Activated carbon fibers such as activated carbon fibers, cellulose-based activated carbon fibers, and pitch-based activated carbon fibers may be used. Regarding the shape of the solid catalyst, various shapes such as a spherical shape, a granular shape, a pellet shape, a ring shape, a crushed shape, and a honeycomb shape can be used.

In the present invention, even if a solid catalyst consisting only of activated carbon is used, depending on the type and concentration of the oxidizable substance, the substance exhibits the oxidizing activity necessary for oxidizing and decomposing the substance. As the solid catalyst used in the present invention, Pt, P
It is also effective to further include one or more elements selected from the group consisting of d, Rh, Ru, Ir, Ag, and Au, whereby a catalyst having higher catalytic activity can be obtained. This is desirable because the efficiency of oxidizing and decomposing the oxidizable substance contained in the wastewater can be improved and the processing temperature can be further reduced.
The content of these elements is not particularly limited, but is desirably contained in the solid catalyst at a ratio of preferably 0.01 to 5% by mass, more preferably 0.05 to 2% by mass. The solid catalyst includes titanium, zirconium,
Aluminum, silicon, iron, manganese, chromium, cobalt, nickel, copper, zinc, cerium, praseodymium,
One or more elements selected from the group consisting of tellurium and bismuth can also be contained.

The physical properties of the catalyst containing activated carbon in the present invention are not particularly limited, but preferably, the total volume of the pores having a pore diameter of 0.1 to 10 μm is 0.1 to 0. 0.8 ml / g and a specific surface area of 100 to
Those having 2,500 m ² / g are preferred. Also, 0.1 to 10
The total volume of the pores having a pore diameter of μm is 0.15 to
0.7 ml / g is more desirable, and even more preferably 0.2 to 0.6 ml / g. The specific surface area, more preferably those 500~2,000m ² / g, more preferably is of 800~1,700m ² / g, and most desirably is of the 900~1,500m ² / g . The reasons for these provisions are as follows.

In the wet oxidation treatment of wastewater of the present invention, the macropore diameter of the catalyst pores of 0.1 to 10 μm greatly affects the diffusion of oxidizable substances and oxygen contained in the wastewater.
Therefore, in a catalyst having a large pore diameter of 0.1 to 10 μm,
Since the diffusion of the oxidizable substance and oxygen is facilitated, the reaction proceeds easily. That is, the processing efficiency at low temperature and low pressure is improved. In contrast, a catalyst having a small pore diameter of 0.1 to 10 μm has poor diffusion of oxidizable substances and oxygen. This makes it difficult for the oxidizable substance to be adsorbed to the catalytically active sites, and the reaction does not proceed efficiently. In addition, oxygen is not used efficiently for the decomposition of the oxidizable substance, and the activated carbon itself is generated by excess oxygen. It becomes easy to burn. On the other hand, a catalyst having a very large pore diameter of 0.1 to 10 μm has a problem that the mechanical strength of the catalyst is reduced. For this reason, a catalyst having a total pore volume having a pore volume in the above range having a pore diameter of 0.1 to 10 μm is desirable.

Also, the larger the specific surface area of the catalyst, the more the adsorbable substances contained in the wastewater are adsorbed, and accordingly the efficiency of the wastewater treatment tends to be improved. For this reason,
Catalysts with a low specific surface area are undesirable. However, in the case of a catalyst having a very large specific surface area, there is a problem that the mechanical strength of the catalyst is reduced. For these reasons,
A catalyst having a specific surface area of the catalyst within the above range is desirable.

In general, it has been known that, when activated carbon is subjected to a treatment such as an oxidation treatment or a reduction treatment, a polar group is introduced into the surface or, conversely, the activated carbon is removed, and the physical properties thereof are significantly changed. Similarly, in the catalyst according to the present invention,
Depending on the amount of the polar group in the catalyst, the catalyst performance changes remarkably. In particular, the relationship between the amount of the polar group and the catalytic activity greatly changes depending on the component to be treated (oxidizable substance) in the wastewater. For example, components to be treated (oxidizable substances)
Is an organic substance or an anionic inorganic substance, it is necessary that the catalyst containing activated carbon has a small amount of polar groups and is a highly hydrophobic catalyst (activated carbon). For this reason, the catalyst which has been subjected to the reduction treatment tends to show higher activity. Conversely, in the case of a cationic inorganic substance such as ammonia or hydrazine, the amount of polar groups in the catalyst containing activated carbon needs to be large. Therefore, the more the catalyst is oxidized, the higher the activity may be.

It is considered that the reason for this is that the ease with which the component to be treated is adsorbed on the catalyst has a large effect. Many of the polar groups in catalysts containing activated carbon are oxygen-containing functional groups such as hydroxyl groups and carboxyl groups. Therefore, in the catalyst containing activated carbon in the present invention, although not particularly limited, the amount of oxygen / the amount of carbon (hereinafter also referred to as O / C ratio) in the catalyst is correlated with the amount of the polar group in the catalyst. In a relationship. Therefore, the catalyst having a small amount of the polar group is O /
A catalyst having a small C ratio and a large amount of a polar group has a large O / C ratio. In the catalyst according to the present invention, a preferable catalyst and a non-preferable catalyst for the component to be treated can be classified by O / C ratio. Specifically, when the component to be treated (oxidizable substance) is an organic substance or an anionic inorganic substance, a desirable catalyst has an O / C ratio of 0 to 0.12.
And more preferably 0 to 0.10, and still more preferably 0 to 0.08. Conversely, when the component to be treated (oxidizable substance) is a cationic inorganic substance such as ammonia or hydrazine, a desirable catalyst has an O / C ratio of 0.08.
０．３0.30, more preferably 0.10 to 0.25
And more preferably 0.12 to 0.20. However, a catalyst having an excessively large O / C ratio causes a problem that the mechanical strength of the catalyst is reduced.

As described above, the catalyst containing activated carbon in the present invention is not particularly limited. However, in producing the catalyst, the catalyst is subjected to various treatments and the O / C ratio is adjusted to various treatment purposes. It is desirable to do. Specifically, in order to reduce the O / C ratio in the catalyst and to reduce the amount of the polar group, the catalyst is preferably subjected to various reduction treatments. For example, a method using a gas phase reduction using hydrogen or a liquid phase reduction using a reducing substance such as sodium sulfite or hydrazine may be used. By this treatment, it is considered that the active component of the catalyst is reduced and / or the activated carbon (the activated carbon surface) is hydrogenated, so that a catalyst highly active against organic substances and anionic inorganic substances can be produced. Further, it can be carried out by various activation treatments usually performed in the step of producing activated carbon. For example, it can be carried out by contacting with steam, carbon dioxide, or nitrogen gas at a high temperature. Conversely, in order to increase the O / C ratio in the catalyst and increase the amount of the polar group, it is desirable to perform various oxidation treatments on the catalyst.
For example, gas phase oxidation or oxidation using various gases such as oxygen-containing gas, ozone, and NOx, hydrogen peroxide, ozone aqueous solution, bromine water, permanganate, dichromate, hypochlorite, nitric acid And a method using liquid phase oxidation using a chemical such as phosphoric acid. By this treatment, the active component of the catalyst is oxidized and / or a polar group such as an oxygen-containing functional group is introduced into the activated carbon (activated carbon surface), and a highly active catalyst for cationic inorganic substances such as ammonia and hydrazine is obtained. It can be manufactured. Further, the catalyst containing activated carbon in the present invention may be subjected to treatments such as nitration, sulfonation, and amination, and treatment with an alkali metal compound.

As described above, in the catalyst containing activated carbon according to the present invention, a catalyst having excellent adsorption performance for a component to be treated (oxidizable substance) tends to be a catalyst having high catalytic activity. Therefore, the physical property value of the catalyst containing activated carbon in the present invention is defined as the component to be treated (oxidizable substance).
Can also be mentioned. For example, when the component to be treated (oxidizable substance) in the wastewater is an organic substance, not only the adsorption performance of the organic substance itself but also the adsorption performance of the oxidizable substance generated by oxidizing and decomposing the organic substance. You can also. Further, when an organic substance having 2 or more carbon atoms is a component to be treated, the acetic acid is generally, but not limited to, easily remaining in the treatment liquid after the wet oxidation treatment. Therefore, a catalyst prepared using activated carbon having excellent acetic acid adsorption performance tends to be a catalyst having high catalytic activity for organic substances. Conversely, when the component to be treated (oxidizable substance) is a cationic inorganic substance such as ammonia or hydrazine, a catalyst prepared using activated carbon having excellent ammonia adsorption performance has a catalytic activity against these. It tends to be a high catalyst. Although not particularly limited, activated carbon used for a catalyst having excellent adsorption performance for a component to be treated tends to be an activated carbon having excellent adsorption performance for a component to be treated. For this reason, in producing the catalyst according to the present invention, it is desirable to use, as the activated carbon to be used, activated carbon having excellent adsorption performance for the component to be treated.

In the present invention, "excellent in adsorption performance" means, for example, the amount of saturated adsorption of a target component per unit amount of activated carbon under a specific condition. It is. In addition, it is expressed by the adsorption rate of the target component per unit amount of activated carbon under a specific condition, and the higher the rate, the better the adsorption performance. This adsorption speed can be expressed by an initial adsorption speed or an arbitrary post-adsorption speed, and is not particularly limited. However, preferably, it is expressed by the initial adsorption rate. Particularly, when activated carbon having a high initial adsorption rate is used, the activity of the catalyst is high, and when it is converted into a catalyst, the catalyst tends to have excellent adsorption performance. .

The catalyst containing activated carbon in the present invention is
It can be defined by various physical property values as described above. However, the range of the physical property values not described above does not limit the range of the catalyst containing activated carbon according to the present invention. Other various physical property values include, for example, the amount of various functional groups, the amount of ash and impurities, the structural form of carbon, the acidity, the volume of pores other than macropores (mesopores, micropores, submicropores), and the like. There are ratios, values of the external specific surface area and the internal specific surface area, and those relating to the ratio.

The term "oxidizable substance" as used in the present invention means an organic and / or inorganic compound that can be purified by oxidizing and decomposing treatments, and may also be expressed as an organic compound, a sulfur compound, a nitrogen compound, or the like. Although not particularly limited, an organic halogen compound or an organic phosphorus compound may be used. Specifically, for example, methanol, ethanol, acetaldehyde, formic acid, acetone, acetic acid, propionic acid, tetrahydrofuran (TH
F), organic compounds such as phenol; ammonia, hydrazine, nitrite, dimethylformamide (DM
F), nitrogen compounds such as pyridine; and sulfur compounds such as thiosulfate ion, sodium sulfide, dimethyl sulfoxide, and alkylbenzene sulfonate. These may be dissolved in water or may be present as suspended substances.

In the method of the present invention, the temperature is basically 50 ° C. or higher and 17
Although the wastewater is treated at a temperature lower than 0 ° C, if the temperature is lower than 50 ° C, it is difficult to efficiently oxidize and decompose organic and / or inorganic oxidizable substances. Become. The treatment temperature is preferably higher than 80 ° C, more preferably higher than 100 ° C, and still more preferably higher than 110 ° C. Even when the treatment temperature is 110 ° C. or lower, advanced treatment of organic compounds such as methanol, formic acid, and formaldehyde is possible. However, for advanced treatment of organic compounds having 2 or more carbon atoms, the temperature exceeds 100 ° C. Often a reaction temperature is required. If the treatment temperature is 170 ° C. or higher, the activated carbon itself tends to burn, which is not practical. For this reason, the processing temperature is preferably 1
The temperature is preferably 60 ° C. or lower, more preferably 150 ° C. or lower, and still more preferably 140 ° C. or lower.

On the other hand, the pressure at which the wastewater is treated may be any pressure at which the wastewater retains a liquid phase at the above-mentioned treatment temperature, but is usually from atmospheric pressure to about 1 MPa (Gauge). For example, when the treatment temperature is 50 to 90 ° C., the wastewater is often in a liquid state even at atmospheric pressure, and therefore may be at atmospheric pressure from the viewpoint of economy, but in order to improve the treatment efficiency, It is preferable to apply pressure. Further, when the treatment temperature exceeds 95 ° C., the wastewater often evaporates under the atmospheric pressure. Therefore, it is preferable to pressurize to about 0.2 to 1 MPa (Gauge). However, 1 MPa (Gau
Pressures above ge) are not preferred from an economic point of view. In addition, when the processing pressure is increased, as in the case where the processing temperature is increased, the problem of combustion of the activated carbon itself is likely to occur. Further, the activity of the catalyst may be reduced.

The catalyst protective solution used in the present invention is not particularly limited as long as it contains a readily decomposable oxidizable substance. Specifically, an easily decomposable oxidizable substance is a substance that can be easily oxidized and decomposed using a solid catalyst containing activated carbon under wet oxidation treatment conditions of 50 ° C. or more and less than 170 ° C. good. The substance must be at
It is preferably a substance that can be easily oxidized and decomposed at a temperature of less than 0 ° C., more preferably a substance that can be easily oxidized and decomposed at a temperature of 50 ° C. to less than 120 ° C. It is more preferable that the substance be easily oxidized and decomposed at a temperature lower than 50 ° C., and it is most preferable that the substance be easily oxidized and decomposed at a temperature of 50 to 90 ° C.

Further, p of an aqueous solution containing a readily decomposable substance
It is desirable that H is neutral, and it is not desirable that H is acidic or alkaline because it causes corrosion or deterioration of the device or catalyst. As such a catalyst protection liquid, for example, a liquid containing alcohols is desirable. In particular,
A liquid containing methanol, ethanol, propanol and the like can be mentioned, and a liquid containing glycol and glycerin may be used. Also, effectively, it has 1 to 1 carbon atoms.
Alcohols 4 are desirable because of their easy decomposability and the like, more preferably methanol, ethanol, and propanol, and most preferably methanol. Therefore, the normal wastewater to be treated may contain methanol or the like, or may further contain methanol or the like added to the wastewater. However, the catalyst protection liquid is not limited to this, and an aqueous solution containing various easily decomposable substances can be used. For example, organic substances such as acetaldehyde, formaldehyde, acetone, tetrahydrofuran, phenol, and formic acid, and inorganic substances such as sodium sulfite and sodium bisulfite can be used.

In the present invention, the concentration of the catalyst protective solution is not particularly limited, but the COD (Cr) concentration is preferably 0.1 to 50 g / liter, more preferably 0.5 to 30 g. / Liter. If this concentration is less than 0.1 g / liter, the catalyst protection effect of the catalyst protection solution will be low. On the other hand, if it exceeds 50 g / liter, a large amount of oxidizable substances for the catalyst protection liquid is required, which increases the cost, and is therefore not preferable.

In the present invention, the concentration of the catalyst protection solution at the outlet of the catalyst layer is not particularly limited, and the catalyst protection effect can be enhanced as long as the catalyst protection solution remains. But preferably at the exit of the catalyst layer
The OD (Cr) concentration is preferably 0.05 to 50 g / liter, more preferably 0.1 to 30 g / liter. When the concentration is less than 0.05 g / liter, the effect of protecting the catalyst near the outlet of the catalyst layer is reduced. 5
If it exceeds 0 g / liter, not only is the cost increased, but also the post-treatment of the remaining catalyst protective solution becomes complicated, which is not preferable.

In the present invention, the method of adding the catalyst protection solution when the apparatus is heated to start up is not particularly limited, and a readily decomposable substance dissolved in water is pumped (for example,
The wastewater may be supplied directly to the wet oxidation treatment apparatus using a wastewater supply pump 5) shown in FIG. 1 described later, or an easily decomposable substance may be added to a wastewater tank and supplied together with the wastewater. Further, as a method of adding the catalyst protection liquid when the apparatus is stopped, after the supply of the wastewater is stopped, the easily decomposable substance dissolved in water may be supplied by the same pump as the wastewater. Furthermore, when supplying the catalyst protection liquid using a pump different from the pump that supplies wastewater,
You may make it supply from just before a reaction tower.

The space velocity of the catalyst protective solution in the catalyst layer is not particularly limited, and may be the same as that of ordinary wastewater treatment conditions.
r ^{-1 to} 10 hr ^-1 , more preferably 0.1 hr ^{-1 to 5} h
r ^-1, even more preferably may be such that the 0.1hr ^-1 ~3hr ^-1. When the space velocity is less than 0.1 hr ^-1 , it takes a long time to obtain a sufficient catalyst protection effect, which is not practical. On the other hand, when it exceeds 10 hr ^-1 , a large amount of the catalyst protection liquid is required, which is not preferable.

In the apparatus for carrying out the present invention, the number, type, shape and the like of the reaction tower are not particularly limited.
A single-tube reaction tower or a multi-tube reaction tower used for ordinary wet oxidation treatment can be used.

Since the spent catalyst protective solution discharged by the practice of the present invention often contains easily decomposable oxidizable substances, it is not preferable to directly discharge it into rivers, seas, etc. There are many. Therefore, it is preferable that the used catalyst protection liquid is returned to the drain tank, the catalyst protection liquid or the catalyst protection liquid and the wastewater are both subjected to wet oxidation treatment and purified, and it is also preferable to repeatedly use the catalyst protection liquid. Further, after a biological treatment, a chemical treatment, or the like is performed as a post-treatment, the water may be directly discharged to a river, the sea, or the like.

In the present invention, the oxygen concentration in the exhaust gas passing through the catalyst layer is 0 to 5 vol% when the apparatus is heated to start up and / or when the apparatus is cooled and stopped.
It is desirable to maintain within the range. This oxygen concentration is 0 to
By setting the content to 5 vol%, the effect of suppressing a decrease in the activity of the catalyst becomes more remarkable when the apparatus is started by raising the temperature and / or when the apparatus is stopped by cooling. However, if the oxygen concentration in the exhaust gas exceeds 5 vol%, combustion of activated carbon due to excess oxygen is not preferred. Therefore, the treatment is preferably performed in a state where oxygen is insufficient. From such a viewpoint, it is desirable that the oxygen concentration in the exhaust gas is closer to 0 vol%, and most preferably, it is 0 vol% in which no oxygen remains. Therefore, the oxygen concentration in the exhaust gas is preferably maintained in the range of 0 to 4 vol%, more preferably 0 to 2 vol%, and still more preferably 0 to 1 vol%. That is, as long as the pressure inside the device can be maintained during operation of the device, from the viewpoint of suppressing the catalyst activity from decreasing, the smaller the supply amount of the oxygen-containing gas, the more desirable. However, if the supply amount is too small, the operation operation may become complicated when the apparatus is started up and the operation state is switched to the drainage treatment. Further, when the apparatus is stopped, the treatment of the drainage is not completely performed to the end, which is not preferable.

In the present invention, when the apparatus is heated and started or when the apparatus is cooled and stopped, the temperature at which the catalyst protection liquid is supplied is significantly lower than the temperature at which the wastewater is treated. In the case of temperature, even if oxygen is present in the catalyst layer, the activity of the catalyst is not suddenly reduced. Therefore, when the temperature is lower than 50 ° C., and in many cases, lower than 60 ° C., particularly, oxygen may be present in an amount exceeding 5 vol%, and the catalyst protective liquid may not be required in the catalyst layer in many cases. If the temperature of the wastewater exceeds 90 ° C,
If the temperature is as low as not less than 80 ° C. and oxygen is 5 vol.
Even if the amount exceeds 1%, the activity of the catalyst does not decrease as long as it is within a short time, for example, within 24 hours, more preferably within 12 hours, and when the catalyst protective solution is present in the catalyst layer. Often.

In the present invention, in order to maintain the oxygen concentration in the exhaust gas in the range of 0 to 5 vol%, the oxygen concentration in the exhaust gas is measured using an oxygen concentration meter 16 as shown in FIGS. However, it is desirable to adjust or control the supply amount of the oxygen-containing gas or the oxygen-free gas based on the measured value. The oxygen concentration meter used for measuring the oxygen concentration in the exhaust gas may be any one that can be used for ordinary oxygen measurement, and a commercially available oxygen concentration meter can be used. Examples of such an oxygen concentration meter include an oxygen concentration meter using an oxygen sensor made of zirconia, an oxygen dumbbell type oxygen concentration meter, a gas chromatograph, and the like, and these are not particularly limited by the method of use.
Also, the method of adjusting or controlling the supply amount of the oxygen-containing gas is not particularly limited. For example, the method can be adjusted or controlled by the oxygen-containing gas flow rate control valve 9 or the like, but it goes without saying that other means may be used. is there.

In the present invention, the term "oxygen concentration in the exhaust gas" refers to the gaseous phase immediately after passing through the catalyst layer when the apparatus is heated and started and / or when the apparatus is cooled and stopped. Means the oxygen concentration in the gas, usually the oxygen concentration in the exhaust gas generated when the gas-liquid after the treatment with the catalyst protection liquid is subjected to the gas-liquid separation treatment as shown in FIG. .

The catalyst protection treatment in the present invention can be carried out either with or without supply of an oxygen-containing gas, but it is desirable to carry out with a small amount of oxygen-containing gas supplied. Usually, the wet oxidation treatment is often performed under pressure, so that when the apparatus is heated and started up and / or when the apparatus is cooled and stopped, the pressure in the wet oxidation treatment apparatus is maintained to some extent. There is a need. At this time, the pressure in the apparatus can be stably maintained by supplying a small amount of gas.

Further, instead of the oxygen-containing gas, an inert gas such as a nitrogen gas or a gas containing no oxygen can be used. However, since the present invention relates to a method for treating wastewater by a wet oxidation method, it is desirable to use an oxygen-containing gas used for wastewater treatment in terms of operability and economy.

In the present invention, it is preferable that the operation is performed while maintaining the oxygen concentration in the exhaust gas in the range of 0 to 5 vol% during the catalyst protection treatment. [Amount of oxygen in the medium] / [Oxygen demand of the catalyst protection liquid when the treatment efficiency of the catalyst protection liquid is maximized] (hereinafter, this ratio may be referred to as “D value”) = 0
To 1.3.
That is, by, for example, adjusting or controlling the gas supply amount so that the D value represented by the above ratio is in the range of 0 to 1.3, it is possible to suppress a decrease in the activity of the catalyst. In the present invention, as described later in detail, it is more preferable that the easily decomposable oxidizable substance remains at the outlet of the catalyst layer. However, when the D value becomes about 1.0 to 1.3, The easily decomposable oxidizable substance may not remain at the outlet of the catalyst layer. From these facts, the D value is 1.0, especially 1.
If it exceeds 3, the amount of oxygen supplied becomes larger than the amount of oxygen required for the oxidation / decomposition treatment of the catalyst protection liquid, and the activated carbon itself tends to burn due to excess oxygen. From such a viewpoint, the D value is preferably about 0 to 0.8, more preferably about 0 to 0.6, and still more preferably 0 to 0.
It is better to be about 4.

In the present invention, the “oxygen demand of the catalyst protection solution when the treatment efficiency of the catalyst protection solution is maximized” means the temperature of the wastewater treatment, the treatment pressure, the LHSV, the air flow distribution system, the catalyst used, and the like. With the processing conditions of
When only the supply amount of oxygen is changed, it means the required amount of oxygen of the catalyst protection liquid when the processing efficiency of the catalyst protection liquid is maximized. The treatment efficiency of the catalyst protection liquid changes depending on the processing temperature. However, in the method according to the present invention, the processing temperature of the catalyst protection liquid changes. For this reason, the processing temperature at the time of calculating the D value is a value at the highest temperature at which the catalyst protection liquid is supplied. Usually, in the method of the present invention, at the highest temperature, the processing efficiency also increases. Therefore, the D value is an index indicating the excess rate of the oxygen supply amount in performing the catalyst protection treatment. More specifically, the chemical oxygen demand (COD (Cr)) treatment efficiency when the solid catalyst is treated with the catalyst protection solution while changing the oxygen supply amount under a given treatment condition is 9 or less.
0%, the oxygen-containing gas becomes O ₂ / COD (C
If supplied at r) = 0.9, the D value is 1.0. When the oxygen-containing gas is supplied at a ratio of O ₂ /COD=1.0, the D value is 1.11. However,
The denominator of the D value, “the oxygen demand of the catalyst protection liquid when the treatment efficiency of the catalyst protection liquid is maximum” is “the oxygen amount in the supply gas when the treatment efficiency of the catalyst protection liquid is maximum”. It is not always the same. That is, the “denominator of the D value” and the “oxygen supply amount when the treatment efficiency of the catalyst protection liquid is maximized” are not necessarily the same. The oxygen supply amount exemplified above is O ₂ / COD
If the processing efficiency of COD (Cr) is 90% and the maximum when (Cr) = 0.9, the oxygen supply amount and the "denominator of D value" are the same. However, when the oxygen supply is O ₂ / CO
When D (Cr) = 2.0, the COD (Cr) processing efficiency may be 90% and the maximum. The D value at this time is 2.
22.

The “treatment efficiency of the catalyst protection solution” described in the “Oxygen demand of the catalyst protection solution when the treatment efficiency of the catalyst protection solution is maximized” according to the present invention means, for example, C
OD processing efficiency, TOC processing efficiency, nitrogen processing efficiency, BOD
Various processing efficiencies, such as processing efficiency, TOD processing efficiency, or specific substance processing efficiency, can be employed depending on the catalyst protection solution, and are not particularly limited. However, the catalyst protection liquid is a liquid containing a readily decomposable oxidizable substance, and in this case, the amount of oxygen consumed is particularly important. Is desirable.

In the present invention, the method of flowing gas and liquid in the catalyst layer filled with the catalyst is not particularly limited, but a more preferable method is a method of flowing gas and liquid downward in parallel. By flowing gas and liquid downward in parallel, the gas-liquid contact efficiency is improved and the amount of dissolved oxygen is increased,
Further, it is considered that the treatment efficiency is improved because the contact efficiency between the liquid and the catalyst is improved. Further, when gas-liquid is caused to flow in parallel, the liquid containing a large amount of the oxidizable substance comes into contact with the gas having a high oxygen concentration at the inlet portion of the catalyst layer, so that the combustion of the activated carbon itself is considered to be suppressed.

In the present invention, the method of gas-liquid circulation in the catalyst layer filled with the catalyst for protecting the solid catalyst is not particularly limited. However, a preferred method is to make it the same as the gas-liquid flow direction in the wastewater treatment. By making the flow direction the same as the gas-liquid flow direction in the wastewater treatment, it can be more easily implemented in terms of operability and the like. For this reason, as a preferable method, there is a method of flowing in a gas-liquid downward co-current flow as shown in FIG. 1 described later. Also,
As shown in FIG. 2 to be described later, gas and liquid can be caused to flow in an upward flow, or a fluidized bed type can be used. In addition, it is possible to flow in a gas-liquid countercurrent, but a gas-liquid cocurrent is more preferable. When gas and liquid are caused to flow in parallel, a liquid containing a large amount of oxidizable substance and a gas with high oxygen concentration come into contact with each other at the catalyst layer inlet,
It is considered that the combustion of the activated carbon itself is suppressed.

In the wastewater treatment method according to the present invention, the type of the solid catalyst layer of the wastewater treatment device may be a fluidized bed type (fluidized bed type). In the wet oxidation treatment using a solid catalyst, when using a catalyst containing activated carbon according to the present invention,
A fluidized-bed wastewater treatment apparatus can be more easily employed than in the case where a conventional solid catalyst is used. The fluidized-bed type wastewater treatment apparatus is less likely to generate a hot spot due to the reaction, and thus can perform a higher-concentration wastewater treatment than a fixed-bed type (fixed-bed type) apparatus. In addition, the treatment of waste water, which tends to cause deterioration of the catalyst containing activated carbon, is facilitated by the characteristics of the apparatus. This is because a fluidized bed type wastewater treatment apparatus can add a new catalyst or a recycled catalyst while extracting a deteriorated waste catalyst. Conventionally, in the wet oxidation treatment using a solid catalyst, as a cause of catalyst deterioration, there has been a problem that an active component in the solid catalyst moves behind a fixed bed. This problem can also be solved in a fluidized bed apparatus because the solid catalyst itself moves. In the case of fluidized bed type,
Since a fixed catalyst having a smaller particle diameter than a solid catalyst generally used can be employed, and the contact efficiency with gas and liquid can be further improved, the processing performance can be improved. In addition, in the case of a fluidized bed type, even a wastewater containing a small amount of solids, which was difficult to treat in a fixed bed type, can be treated because it is unlikely to cause a problem of clogging of a reaction tower. The range can be further expanded.

In the case of this fluidized bed type apparatus, although not particularly limited, the reaction tower may be a single column or a plurality of columns, and in view of operability and equipment cost. Is preferably one tower. Further, although not particularly limited, the inside of the reaction tower may be one chamber, but the processing performance is more improved when divided into a plurality of chambers (multistage),
It is also desirable from the viewpoint of operation control.

In the present invention, “oxidation / decomposition treatment” means
Oxidative decomposition treatment of acetic acid to carbon dioxide and water, decarboxylation treatment of acetic acid to carbon dioxide and methane, hydrolysis treatment of urea to ammonia and carbon dioxide, oxidative decomposition treatment of ammonia and hydrazine to nitrogen gas and water Examples include oxidation and oxidative decomposition treatment of dimethyl sulfoxide to carbon dioxide, water, and ash such as sulfate ions, and oxidation treatment of dimethyl sulfoxide to dimethyl sulfone and methane sulfonic acid. Processing to decompose to nitrogen gas, carbon dioxide, water, ash, etc.,
Various oxidation and / or oxidation treatments such as decomposition treatment to reduce the molecular weight of hardly decomposable organic substances and nitrogen compounds, or oxidation treatment to oxidize.
Or the meaning including decomposition.

The type of wastewater to be treated in the present invention is not particularly limited. For example, various types of equipment such as chemical plants, electronic parts manufacturing equipment, food processing equipment, metal processing equipment, metal plating equipment, printing and plate making equipment, photographic equipment, and the like. It may be wastewater from an industrial plant, or wastewater from power generation equipment such as thermal power generation or nuclear power generation. Specifically, wastewater from an EOG production facility, an alcohol production facility such as methanol, ethanol, higher alcohols, etc., particularly, an aliphatic carboxylic acid such as acrylic acid, acrylic ester, methacrylic acid, methacrylic acid ester or its ester, or terephthalic acid Organic matter-containing wastewater discharged from a process for producing an aromatic carboxylic acid or an aromatic carboxylic acid ester such as an acid and a terephthalate is exemplified. Further, the wastewater may contain a nitrogen compound such as amine, imine, ammonia and hydrazine. Further, the wastewater may contain a sulfur compound such as thiosulfate ion, sulfide ion, and dimethyl sulfoxide. It may also be domestic wastewater such as sewage or human waste. Alternatively, wastewater containing harmful substances such as organic halogen compounds such as dioxins, fluorocarbons, diethylhexyl phthalate, and nonylphenol, and environmental hormone compounds may be used.

Hereinafter, the operation and effect of the present invention will be described more specifically with reference to examples. However, the following examples do not limit the present invention, and may be changed without departing from the spirit of the preceding and following examples. All are included in the technical scope of the present invention.

[0062]

EXAMPLE 1 Waste water treatment was carried out using the apparatus shown in FIG. The reaction tower 1 has a cylindrical shape with an inner diameter of 26 mmφ and a length of 3,000 mm, and contains therein 1 liter of a 4 mmφ pellet-shaped solid catalyst containing activated carbon and platinum as main components and containing 0.3% by mass of platinum. 390 g) and a catalyst layer length of 1880 mmH.

The startup in this apparatus was performed in the following procedure. First, 15,000 mg / L of COD (Cr) containing 10 g / L of methanol is sent to a drainage supply pump 5 through a drainage supply line 6, and a booster feed is performed at a flow rate of 1 L / h by the drainage supply pump 5. did. Air (oxygen-containing gas) introduced from the oxygen-containing gas supply line 8 was pressurized by the compressor 7 and then supplied to the catalyst protection liquid before the heater 3. At this time, the supply amount of the supply air was controlled by the oxygen-containing gas flow control valve 9. The supply amount was adjusted so that the D value became 0.3 when the internal temperature of the reaction tower 1 was 120 ° C. The gas-liquid mixture that has passed through the heater 3 is
The gas was supplied from the upper part of the reaction tower 1 so as to be in a gas-liquid downward parallel flow.
The internal temperature of the reaction tower 1 at the start of gas-liquid supply was 20 ° C. Note that when the internal temperature of the reaction tower 1 was 120 ° C., the treatment efficiency of the catalyst protection liquid became the maximum because of the O ₂ / COD
(Cr) = 0.99 when air was supplied, and the COD (Cr) treatment efficiency at this time was 100%.

The reaction tower 1 is filled with a catalyst layer.
After passing through the catalyst layer, the catalyst protective liquid and the like are discharged from the lower part of the reaction tower 1, cooled in the cooler 4, released from the pressure control valve 12 and discharged, and then discharged in the gas-liquid separator 11. separated. In the pressure control valve 12, the pressure in the reaction tower 1 was detected by a pressure controller PC provided on the gas-liquid outlet side of the reaction tower 1, and the pressure was controlled to maintain a pressure of 0.6 MPa (Gauge). For this reason, at the start of the air supply, the pressure was atmospheric pressure, but gradually increased, and the temperature in the reaction
When the temperature exceeds 0 ° C., 0.6 MPa (Gauge)
The pressure was stable. The oxygen concentration in the exhaust gas in the gas-liquid separator 11 was measured using an oxygen concentration meter 16, and the exhaust gas was discharged from a gas discharge line 13.

In this manner, the supply of the catalyst protection liquid is started,
After confirming that the catalyst protection liquid was discharged from the pressure control valve 12, the heating was started using the heater 3 and the electric heater 2. During the heating, the catalyst protection liquid was always supplied to the catalyst layer so that the activity of the catalyst did not decrease. In this case, the catalyst protection liquid was always left at the catalyst outlet (in the discharged liquid). The start-up of the apparatus by the supply of the catalyst protection liquid is performed when the internal temperature of the reaction
This was performed until the temperature reached 0 ° C. The concentration of the catalyst protective solution at the outlet of the catalyst layer (in the gas-liquid separation liquid 11) at 120 ° C. was 10,400 mg / liter. Further, the oxygen concentration of the exhaust gas at the time of raising the temperature is 60
It was always 0% by volume from around over ℃.

After the internal temperature of the reaction tower 1 reached 120 ° C., the supply of the catalyst protection liquid was stopped, and the supply was immediately switched to the supply of the wastewater to be treated. The wastewater to be treated was discharged from the wastewater supply line 6 as in the case of the catalyst protection liquid. The wastewater to be treated at this time is wastewater discharged from a fatty acid carboxylic acid and aliphatic carboxylic acid ester production facility and contains organic compounds having 2 or more carbon atoms such as alcohol, aldehyde, and carboxylic acid, and COD (Cr) is reduced. 15,000 mg / liter, pH 2.8. Also, 40% of the total TOC component was acetic acid.

In the treatment of waste water, the internal temperature of the reaction
The heater 3 and the electric heater 2 were controlled so as to reach 30 ° C. The supply amount of air was controlled by the oxygen-containing gas flow control valve 9 such that the oxygen concentration in the exhaust gas in the gas-liquid separator 11 was 0.2 vol%. The air supply amount at this time is O
_The ratio ₂ / COD (Cr) [the amount of oxygen in the supply gas / the amount of chemical oxygen required in the wastewater] was 0.96. Further, the processing liquid in the gas-liquid separator 11 was detected by using a liquid level controller LC, and the processing liquid discharge pump 14 was controlled so as to have a constant liquid level. Other than these, processing was performed according to the method of starting up the apparatus. The processing liquid discharged from the processing liquid discharge pump 14 was discharged through a processing liquid discharge line 15, and the processing liquid was sampled as needed to measure the COD (Cr) concentration. COD (Cr) when 50 hours have passed since the start of operation and the treatment became stable
The processing efficiency was 96%.

COMPARATIVE EXAMPLE 1 The procedure of Example 1 was repeated, except that the apparatus shown in FIG. 1 was used to start up using water instead of 15,000 mg / L of COD (Cr) containing 10 g / L of methanol. The treatment was carried out according to 1. The supply amount of the oxygen-containing gas (air) was the same as the amount of air supplied in Example 1. Therefore, the gas-liquid separator 1 at the time of temperature rise
The oxygen concentration in the exhaust gas in No. 1 was always 21 vol%.

After the temperature rise to 120 ° C. is completed, the supply liquid is switched from water to waste water in the same manner as in Example 1.
Treatment of wastewater started. The wastewater used at this time was the same as in Example 1. Also, as in Example 1, the internal temperature of the reaction tower 1 was set to 130 ° C., and the amount of supplied air was adjusted so that the oxygen concentration of the exhaust gas in the gas-liquid separator 11 became 0.2 vol%. 9 was controlled.

As a result, 50 minutes after the start of the supply of wastewater.
After the elapse of time, the COD (Cr) treatment efficiency was 65%. At this time, the supply amount of air is O ₂ / COD (C
r) Ratio was 0.65.

[0071]Examples 2 to 6 Contains 10 g / l of methanol as catalyst protection liquid
Instead of using the solution shown in Table 1 below,
Others are the same processing method and the same processing conditions as in the first embodiment.
The treatment was carried out by the method according to 1. Wastewater to be treated
The same wastewater as in Example 1 was used. In addition, each catalyst protection
The COD (Cr) concentration of the solution is 15,000 mg / lit.
It was. The results are shown in Table 1 below. Also implemented
In Example 6, the wastewater to be treated is used as it is as a catalyst protection liquid.
Was. That is, the liquid used as the catalyst protection liquid is treated after the temperature is raised.
It was wastewater to be treated. The internal temperature of the reaction tower 1 was 120 ° C.
In Example 2, the treatment efficiency of the catalyst protection liquids of Examples 2 to 5 was maximized.
What became O_Two/ COD (Cr) = about 1.0 and air
The COD (Cr) treatment effect at this time
The rate was 100%. When the internal temperature of the reaction tower 1 is 12
At 0 ° C., the catalyst protective solution of Example 6 (the wastewater to be treated)
The processing efficiency was maximized by O_Two/ COD (Cr) =
0.82 when air was supplied, and CO 2
The D (Cr) treatment efficiency was 82%. Therefore, the embodiment
In the case of No. 6, O _Two/ COD (C
Air was supplied at r) = about 0.25.

[0072]

[Table 1]

Examples 7 to 10 and Comparative Examples 2 and 3 Example 1 was repeated except that the D value was changed to the value shown in Table 2 below.
The treatment was carried out using the same catalyst protective solution, the same waste water, the same catalyst, the same treatment conditions, and the same equipment. The results are shown in Table 2 below.

[0074]

[Table 2]

Example 11 The apparatus shown in FIG. 1 was used, except that the following conditions were satisfied.
Wastewater treatment was carried out in the same manner as described above. Inside the reaction tower 1, 1 liter (440 g) of a 5 mm diameter pellet solid catalyst containing activated carbon and palladium as main components and containing 0.5% by mass of palladium, and a catalyst layer length of 1880 mm
H-filled. As the catalyst protection liquid, a liquid of 10,000 mg / L of COD (Cr) containing 6 g / L of methanol was used.
The pressure was fed at a flow rate of h. The pressure control valve 12 is
Control was performed so as to maintain a pressure of 0.5 MPa (Gauge).

The amount of supplied air is controlled so that the D value becomes 0.4 when the internal temperature of the reaction tower 1 is 110 ° C., and until the internal temperature of the reaction tower 1 becomes 110 ° C. by this catalyst protection liquid. Done. The concentration of the catalyst protective solution at the catalyst layer outlet (in the gas-liquid separator) at 110 ° C. was 5,800 mg /
Liters. The oxygen concentration in the exhaust gas at the time of the temperature rise was always 0 vol% from around the time when the internal temperature of the reaction tower 1 exceeded 60 ° C. When the internal temperature of the reaction tower 1 was 110 ° C., the treatment efficiency of the catalyst protection liquid became maximum when O ₂ /COD(Cr)=0.99 and air was supplied. (Cr) The processing efficiency was 100%.

Immediately thereafter, the supply of the catalyst protection liquid is stopped,
We immediately switched to supplying wastewater to be treated. The wastewater to be treated used at this time was a solvent-based wastewater containing a large amount of alcohols such as ethyl alcohol and propyl alcohol, and the COD (Cr) of the wastewater was 30,000 mg / liter and the pH was 7.1. . The wastewater did not contain alkali metal ions, ammonium ions, and inorganic salts.

In the treatment of the waste water, the heater 3 and the electric heater 2 were controlled such that the internal temperature of the reaction tower 1 became 115 ° C. The supply amount of air was controlled by the oxygen-containing gas flow control valve 9 such that the oxygen concentration of the exhaust gas in the gas-liquid separator 11 was 0.5 vol%. Amount of air supplied at this time _was 0.97 O 2 / COD (Cr) ratio.

As a result, 50 minutes after the start of the supply of wastewater.
The COD (Cr) treatment efficiency at the time when the treatment passed and the treatment became stable was 95%.

Comparative Example 4 The apparatus was started up in the same manner as in Example 11 except that water was used without supplying the catalyst protection liquid when the temperature of the apparatus was raised. The amount of air supplied was the same as the amount of air supplied in Example 11. Therefore, the gas-liquid separator 1 at the time of temperature rise
The oxygen concentration in the exhaust gas in No. 1 was always 21 vol%.

After the temperature was raised to 110 ° C., the wastewater treatment was continued by switching to the solvent-based wastewater containing a large amount of alcohols such as ethyl alcohol and propyl alcohol as in Example 11. At this time, similarly to the eleventh embodiment, the oxygen-containing gas flow control valve 9 was controlled such that the oxygen concentration of the exhaust gas in the gas-liquid separator 11 was 0.5 vol%.

As a result, 50 minutes after the start of the supply of wastewater.
After the elapse of time, the COD (Cr) treatment efficiency was 55%. The air supply amount at this time is O ₂ / COD (C
r) The ratio was 0.56.

Example 12 The apparatus shown in FIG. 2 was used. The basic configuration of the apparatus shown in FIG. 2 is similar to that of the apparatus shown in FIG. 1, and corresponding parts are denoted by the same reference numerals. In the apparatus shown in FIG. 2, the waste water heated by the heater 3 is supplied from the bottom of the reaction tower 21 (22 is an electric heater), and the treatment liquid after the oxidation and decomposition treatment is supplied to the reaction tower 21. 21
It is configured to be discharged from the upper part of. That is, in the reaction tower 21 shown in FIG. 2, the gas-liquid circulation system in the catalyst layer is of the gas-liquid upward co-current flow type.

The above-mentioned reaction column 21 has a cylindrical shape with an inner diameter of 26 mmφ and a length of 3,000 mm.
The same amount of the same solid catalyst as indicated by was charged. Then, wastewater treatment was performed in the same manner as in Example 1 (the same wastewater, the same treatment method, and the same treatment conditions).

The temperature was raised using a catalyst protective solution, and
The catalyst protective solution concentration at the catalyst layer outlet (in the gas-liquid separator 11) when the internal temperature of Sample No. 1 reached 120 ° C. was 10, 40
It was 0 mg / liter. The oxygen concentration in the exhaust gas at the time of temperature rise was always 0 vol% from around the time when the internal temperature of the reaction tower 21 exceeded 60 ° C.

As a result, 50 minutes after the start of the supply of wastewater.
The COD (Cr) treatment efficiency when the time passed and the treatment became stable was 88%. The amount of air supplied during the wastewater treatment is such that the oxygen concentration in the exhaust gas in the gas-liquid separator 11 is 0.2
The oxygen-containing gas flow rate control valve 9 was controlled so as to be vol%. The air supply amount at this time is O ₂ / COD (Cr)
The ratio was 0.89.

Example 13 The waste water treatment was carried out using the apparatus shown in FIG. FIG.
1 has the same configuration as the apparatus shown in FIG. 1 except that an air supply position for maintaining the pressure in the apparatus at the time of startup is separately provided behind the reaction tower 1.
That is, in the apparatus shown in FIG. 3, an oxygen-containing gas supply line 31 is connected between the reaction tower 1 and the pressure control valve 12 in addition to the apparatus configuration shown in FIG. The gas from the oxygen-containing gas supply line 8 is supplied to the oxygen-containing gas flow control valve 32 by the gas supply line 31.
Through the pressure control valve 12.

Then, the processing was performed in the same manner as in Example 1 except that air was supplied from the oxygen-containing gas supply line 31 at startup. That is, the supply air at the time of startup is controlled by the oxygen-containing gas flow control valve 32 so that the D value becomes 1.5 and the supply position of the air is changed according to the first embodiment. Processing was performed. Therefore, the oxygen concentration in the exhaust gas at the time of startup was always 21 vol%. However, after the pressure is increased, no air is supplied to the inside of the reaction tower 1 (solid catalyst layer), so that the oxygen concentration in the gas phase inside the reaction tower 1 is 0 V
ol% (that is, the D value is 0). The catalyst protective solution concentration at the outlet of the catalyst layer (in the gas-liquid separator 11) was 14,800 mg / liter.

When the wastewater treatment immediately after the start-up was performed in accordance with Example 1, the wastewater treatment
The D (Cr) treatment efficiency was 96%.

Example 14 After the wastewater treatment shown in Example 1 was performed, the apparatus was subsequently cooled according to the following method. In this cooling method, first, heating by the electric heater 2 and the heater 3 is stopped, and cooling of the apparatus is started, and at the same time, the oxygen supply amount is reduced to O ₂ /
COD (Cr) was set to 0.82. Immediately after the internal temperature of the reaction tower 1 reached 120 ° C., the catalyst protection liquid used for startup in Example 1 was switched to drainage and supplied so that the activity of the catalyst did not decrease. At the same time, D
The oxygen-containing gas was reduced so that the value became 0.3.
At this time, the catalyst protection liquid was made to remain at the outlet of the catalyst layer.

As a result, the oxygen concentration in the exhaust gas was 0.2 vol% at the time of the wastewater treatment, but gradually decreased, and was constantly 0 vol% until the temperature of the reaction tower 1 dropped to about 60 ° C.
%Met.

After the temperature of the apparatus dropped to 30 ° C., the temperature was raised in the same manner as in Example 1. Further, the treatment of the waste water was restarted in the same manner as in Example 1. as a result,
50 hours after the start of the supply of the wastewater, the COD (Cr) treatment efficiency when the treatment was stabilized was 96%.

Comparative Example 5 COD (Cr) containing 10 g / l of methanol
The treatment was carried out according to Example 14, except that cooling was carried out using water instead of the 15,000 mg / l catalyst protection liquid. The oxygen concentration in the exhaust gas in the gas-liquid separator 11 at the time of cooling, immediately after switching from waste water to the catalyst protection liquid,
It was about 0.2 vol%, but increased rapidly,
At a temperature of about 110 ° C. exceeded 20 vol%.

Then, after the temperature of the apparatus was lowered to 30 ° C., the temperature was raised in the same manner as in Example 1, and the wastewater treatment was resumed in the same manner as in Example 1. As a result, 50 hours had elapsed since the start of the supply of the wastewater, and the COD (Cr) treatment efficiency when the treatment was stabilized was 71%.

Examples 15 to 19 Using the various catalyst protecting liquids shown in Table 3 below,
Following the treatment of the wastewater, the apparatus of Example 15 described below was cooled. Similarly, following the wastewater treatment of the third embodiment, the cooling of the apparatus of the following sixteenth embodiment is performed in the same manner as in the fourth embodiment.
Following the treatment of the wastewater of Example 17, the cooling of the apparatus of Example 17 described below, the treatment of the wastewater of Example 5 described above, and the cooling of the apparatus of Example 18 described below were performed following the treatment of the wastewater of Example 6 described below. The cooling of the device of Example 19 was carried out in each case. The cooling method at this time was carried out in the same manner as in Example 14. In addition, all the catalyst protection liquids were the same liquids as in Examples 2 to 6.

Then, after the temperature of the apparatus has dropped to 30 ° C., each of the embodiments continues to correspond to the above-described embodiments 2 to 6.
The temperature was increased in the same manner as in Example 1, and the wastewater treatment was restarted by the method according to Example 1. 5 since we started supplying wastewater
Table 3 below shows the COD (Cr) treatment efficiency when 0 hour has passed and the treatment has stabilized.

[0097]

[Table 3]

Example 20 The same catalyst protection liquid, the same drainage, the same treatment conditions as in Example 14 were used, except that the supply amount of the oxygen-containing gas at the time of cooling the apparatus in Example 14 was changed to D value 1.1. Processing was performed using the same equipment.

As a result, the oxygen concentration of the exhaust gas gradually increases, and the oxygen concentration of the exhaust gas at 110 ° C. becomes about 2 vol.
1%. Further, the residual COD of the catalyst protection liquid in the gas-liquid separator 11 at 110 ° C. and 80 ° C. (C
r) The concentration was less than 100 mg / l. Then, the result of the treatment of the waste water performed according to Example 1 is CO 2
The D (Cr) treatment efficiency was 88%.

[0100]

The present invention is configured as described above, and can be started by raising the temperature of the processing apparatus or by cooling the apparatus so as to prevent the performance of the solid catalyst from deteriorating.
The durability of the solid catalyst can be greatly improved. Further, according to the present invention, it is possible to stably purify wastewater for a long period of time, and it is possible to reduce wastewater treatment costs.

Further, the method for treating wastewater by the wet oxidation method which is basically adopted in the present invention is an excellent method capable of reducing the cost of wastewater treatment equipment and wastewater treatment, and capable of treating wastewater to a high degree. Processing method. Therefore, by adding the effect of the catalyst protection of the present invention to such a wet oxidation method, the effect of the method can be remarkable.

Further, the treated liquid of the wastewater treated according to the present invention can be reused as water for other uses.
It is also excellent in terms of resource recycling, which can be expected to have effects such as cost reduction and effective use of resources.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing one configuration example of an apparatus configured to carry out the present invention.

FIG. 2 is a schematic explanatory diagram showing another configuration example of an apparatus configured to carry out the present invention.

FIG. 3 is a schematic explanatory diagram showing still another configuration example of an apparatus configured to carry out the present invention.

[Explanation of symbols]

 1,21 Reaction tower 2,22 Electric heater 3 Heater 4 Cooler 5 Drain supply pump 6 Drain supply line 7 Compressor 8,31 Oxygen-containing gas supply line 9,32 Oxygen-containing gas flow control valve 10 Treatment liquid line 11 Gas-liquid Separator 12 Pressure control valve 13 Gas discharge line 14 Processing liquid discharge pump 15 Processing liquid discharge line 16 Oxygen concentration meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Miyanosaki ▼ Kunichi, Hyogo Prefecture 1 F-term in Nippon Shokubai Co., Ltd. (reference) 4D050 AA12 AB11 AB14 AB16 AB17 AB18 AB19 BB01 BC01 BC05 CA01 4G069 AA03 AA12 BA08A BA08B BB02A BB02B BC32A BC33A BC71A BC72A BC72B BC74A BC75A BC75B CA05 EC02 EC03 EC05 EC02

Claims (9)

[Claims] 1. A wastewater treatment method for oxidizing and / or oxidatively decomposing organic and / or inorganic oxidizable substances contained in wastewater using a catalyst, comprising: a treatment temperature of 50 ° C. or more and less than 170 ° C. Under a pressure at which the wastewater retains a liquid phase, the wastewater is treated using a solid catalyst containing activated carbon by supplying an oxygen-containing gas, and when the apparatus is heated to start up and / or the apparatus is cooled. To stop
A method for treating wastewater, comprising supplying a solid catalyst layer with a catalyst protective solution containing a readily decomposable oxidizable substance to operate the solid catalyst layer. 2. The method according to claim 1, wherein the operation is performed such that the catalyst protection liquid remains at the outlet of the catalyst layer. 3. The method according to claim 1, wherein the temperature at which the catalyst protection liquid is supplied is lower than the wastewater treatment temperature. 4. The method according to claim 1, wherein the catalyst protection liquid is a liquid containing alcohols. 5. The method according to claim 1, wherein the oxygen concentration in the exhaust gas passing through the catalyst layer is maintained in a range of 0 to 5 vol% when the apparatus is heated and started and / or when the apparatus is cooled and stopped. The method according to any one of claims 1 to 4. 6. An oxygen-containing gas or a non-oxygen-containing gas is supplied when the catalyst protective liquid is supplied to the catalyst layer, and the amount of oxygen in the supply gas is [oxygen amount in the supply gas] / [catalyst protection]. The method according to any one of claims 1 to 5, wherein the amount of oxygen required of the catalyst protection liquid when the treatment efficiency of the liquid is maximized] is set in the range of 0 to 1.3. 7. The method according to claim 1, wherein the gas-liquid flowing method in the catalyst layer filled with the solid catalyst is a gas-liquid downward co-current flow. 8. The solid catalyst further comprises Pt, Pd, Rh,
The method according to any one of claims 1 to 7, comprising one or more elements selected from the group consisting of Ru, Ir, Ag, and Au. 9. The method according to claim 1, wherein the oxygen-containing gas is supplied from a downstream side of the catalyst layer in the flow direction of the liquid, and the pressure is controlled so as to maintain the pressure in the apparatus. The described method.