JPS5913915B2 - How to treat organic wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating organic matter-containing wastewater, that is, organic wastewater, by wet oxidation.

More specifically, the present invention relates to a catalytic wet oxidation treatment method in which organic wastewater is brought into contact with an oxygen-containing gas in the presence of a catalyst under pressure or normal pressure to oxidize and decompose organic substances in the wastewater.

Treatment methods for organic wastewater include microbial treatment methods such as activated sludge method, sprinkling p-bed method, and rotating disk method, as well as physicochemical treatment methods such as activated carbon adsorption method, ozone oxidation method, and ultrafiltration method. Among them, the present invention relates to a physicochemical treatment method, particularly a wet oxidation method.

Wet oxidation methods for organic wastewater are well known, particularly at 200-300°C and 30-100°C, known as the Chin-Normand method.
A method of oxidizing organic wastewater using oxygen or an oxygen-containing gas under high temperature and high pressure of C4 is known, but it takes a long time for decomposition and requires a large reactor, which increases equipment costs. It also had the disadvantage of high operating costs.

Recently, as an improvement to this method, research has been conducted on a method of treating organic wastewater at low temperature and low pressure using various catalysts in a short contact time.
No. 7469, No. 49-48153, No. 49-9415
No. 7, No. 49-95462, etc. disclose a method using metal oxides such as oxidized steel, manganese dioxide, and cobalt oxide as a catalyst, and JP-A No. 49-44556, etc. disclose a method using noble metals such as palladium and platinum as a catalyst. It has been known.

Furthermore, Japanese Patent Publication No. 44-22275, Japanese Patent Publication No. 52-1492
A wet oxidation method using a copper compound as a catalyst has been proposed in No. 61 and Japanese Patent Application Laid-Open No. 53-60877.

However, in wet oxidation methods of organic wastewater using metal oxides and copper or copper compounds as catalysts, temperatures of 170 to 2
At present, high temperature and high pressure treatment conditions of 20 DEG C. and a pressure of 14 to 35/4/cd are required, and the supported metals elute into the treatment water, so improvements are currently being sought.

The present invention relates to an improvement of the conventionally proposed wet oxidation method for organic matter. Organic wastewater can be effectively treated by bringing it into contact with organic wastewater.

According to the method of the present invention, the decomposition efficiency is high, so the process can be carried out using a small reactor, and it can be carried out at a lower temperature and lower pressure than the conventional method, so the equipment cost can be reduced, and the operating cost is also low.
There is no elution of supported metals into the treated water, and it is possible to treat organic matter from low concentrations to high concentrations, and the range of application can be expanded.

The organic wastewater treated according to the present invention includes activated sludge-treated supernatant, cyanide-containing wastewater, phenol-containing wastewater, polymer-containing wastewater, 9 industrial wastewater such as petrochemical factory wastewater, 9 food factory wastewater, and sewage wastewater such as human waste sewage. It means something.

The catalyst used in the present invention is reduced copper itself which has been subjected to reduction treatment,
Alternatively, those supported on a carrier and subjected to a reduction treatment, or those obtained by reducing a copper alloy, etc. are used.

Copper is supported on a carrier using the usual deposition method or coprecipitation method.

A copper compound may be supported on a carrier by a dipping method, an impregnating method, a spraying method, or the like, and then reduced in a reducing atmosphere to obtain reduced copper.

Further, since reduced copper increases the specific surface area and adsorption sites, the reactivity can be further improved by using it in a porous form.

Although the details of the oxidation mechanism by reduced copper in the present invention are not clear, it is thought to be due to a type of transmitter action.

According to the inventors, when copper metal is used without reduction treatment, it exhibits only the same activity as copper oxide, but its activity can be significantly increased by pre-reduction treatment to form reduced copper. This seems to be due to

For example, the above-mentioned Japanese Patent Publication No. 44-22275 discloses a wet oxidation method in the presence of metallic copper or a copper compound, which is proposed on the basis that the copper plate and copper oxide have substantially the same activity.

This result can be inferred that the surface of the copper plate has changed to copper oxide, and not only is the reduction pretreatment of the present invention not disclosed in the above publication, but it can also be considered to support its effectiveness. .

Furthermore, by using porous reduced copper as the reduced copper in the present invention, the activity is more improved than that of ordinary reduced copper, so that the wastewater treatment conditions can be further relaxed.

The porous state usually has a specific surface area of o, lrr? /
It is sufficient if it is at least 1.0 i/r, preferably at least 1.0 i/r.

The method of the present invention can be carried out at room temperature (20° C.) or above, and may be appropriately selected depending on the type of wastewater to be treated.

For example, in the case of general organic wastewater such as wastewater from a fluid catalytic cracker (hereinafter referred to as FCC wastewater), it is treated at a temperature of 100°C or higher, but PVA (polyvinyl alcohol)
Polymer-containing waste water such as waste water can be treated at a relatively low temperature of 100°C or less.

On the other hand, in the method of the present invention, there is no change in processing efficiency even if the temperature is raised to 150°C or higher;
The treatment may be carried out at a temperature of 150° C. or lower, but depending on the type of wastewater and treatment conditions, the treatment can be carried out at a temperature of 150° C. or higher if necessary.

The pressure of the reaction system is usually 10; it may be the autogenous pressure that keeps the reaction system in the liquid phase at t/c4 or less, or a slightly higher pressure. There is no need to maintain high pressure.

There is no particular limit to the amount of air fed, but it may be within the theoretical amount of air in the wet oxidation method, that is, the amount of oxygen consumed by potassium dichromate, or 20 units in excess thereof.

The method of the present invention can be carried out in either a fixed bed or a fluidized bed, so in the case of a fixed bed, a catalyst with a large shape such as granules or plates is used, and in the case of a fluidized bed, a catalyst in the form of a powder, etc. is used.
Fine particles or the like may be used.

The oxygen-containing gas used in the present invention may be pure oxygen, air, or oxygen-enriched gas.

The pH of the reaction system is neutral to alkaline, usually 5 to 5.
A liquid of about 1O is used.

If the pH of the wastewater is on the acidic side, use it after neutralizing it.
It is normal for the pH of the treatment liquid to decrease somewhat as oxidation progresses, but this does not cause any particular problem when the pH of the raw wastewater is around 7.0.

Catalysts whose activity has decreased can be re-reduced and used, and in the case of obtaining reduced copper used as a catalyst and in the case of the above-mentioned re-reduction, reduction is performed using hydrogen gas or hydrogen-containing gas, carbon monoxide, flue gas, generated Usually using gas etc. at a temperature of about 150 to 40
Dry or wet catalytic reduction at 0° C., space velocity 2-5, contact time 1-4 hours, or methanol, formalin, formic acid.

Reduction may be carried out by a conventional method using a reducing agent such as hydrazine.

The reduced state is usually measured using an X-ray microanalyzer (EPM).
It is analyzed by A) and used as a catalyst in a state where almost no oxygen is detected on the surface.

In addition, the decrease in catalyst activity will reduce the COD removal rate and TOC of the treated water.
Check in advance when the removal rate starts to drop sharply, and
The reproduction process may be performed accordingly.

As for the regeneration method, in the case of a fluidized bed, a reducing atmosphere zone may be provided in the catalyst cycle, and in the case of a fixed bed, multiple reaction columns may be switched and used to sequentially regenerate the deactivated products. good.

As described above, according to the method of the present invention, unlike the conventional wet oxidation method which requires high temperatures, the oxidation treatment conditions can be relaxed by using reduced copper, so the pressure resistance of the reactor can be reduced and construction costs can be saved. Its effects, such as the ability to reduce power costs and the like due to the reduction in reaction pressure, are outstanding.

Furthermore, according to the method of the present invention, 64 to 94 inches of COD in the waste water is oxidized and decomposed, although it varies somewhat depending on the type and amount of organic matter contained in the waste water.

On the other hand, as will be shown later in Examples, when copper oxide is used as a catalyst, only 15 to 82% of the waste water is decomposed when the same waste water is treated under the same conditions.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 Catalytic wet oxidation was carried out on FCC wastewater using the apparatus shown in FIG.

After putting the waste water into the raw water tank 1, it is sent to the reactor 3 in a fixed amount by the raw water pump 2, and the air is injected from the air cylinder 4 through the pressure reducing valve 5 into the discharge line of the raw water pump 2, mixed with the raw water, and then sent to the reactor 3. Sent to.

The inside of the reaction tower is heated to a predetermined temperature by a reaction tube heater 6 using a nichrome wire, and the treated water, steam, and waste gas are led to a condenser 7, where the steam is condensed and stored together with the treated water in the condenser 1, where it is kept for a certain period of time. Each sample was sampled and analyzed.

After exiting the condenser 7, the exhaust gas was discharged via an integrating flow meter 8.

The reactor is made of 5US304 and has an outer diameter of 40#φ and a diameter of 14mφ.
, using a stainless steel tube with a height of 720 m, and a catalyst 5 in the reactor.
Fill the reactor with 0 cc of hydrogen, flow hydrogen into the reactor in advance, and set the temperature to 30 cc.
The mixture was reduced at 0°C for 2 hours, confirmed with EPMA, and used at 0°C.

As catalysts, a copper particle catalyst having the shape and properties shown in Table 1 and a porous copper catalyst manufactured by Hanka Kagaku Yakuhin ■ were used.

Further, as a comparative example, a porous copper catalyst was used without being subjected to reduction treatment.

The results are shown in Table 1.

As is clear from the results in Table 1, the porous copper catalyst subjected to reduction treatment (hereinafter referred to as porous reduced copper catalyst).

) is not reduced (hereinafter referred to as porous copper oxide catalyst).

), it has superior COD and TOC removal rates.

Furthermore, among the metal steel catalysts that were similarly subjected to reduction treatment, the porous copper catalyst having pores with a large specific surface area was 7 times more excellent in terms of COD and TOC removal rates.

Example 2 By the same method as in Example 1, using the same porous reduced copper catalyst and porous copper oxide catalyst as used in Example 1, four types of FCC wastewater, phenol-containing wastewater, sanitary wastewater, and PVA wastewater were prepared. The waste water was subjected to catalytic wet oxidation.

The results are shown in Table 2.

As is clear from Table 2, the COD and TOC removal rate of the porous reduced copper catalyst subjected to the reduction operation is much higher than that of the porous copper oxide catalyst.

In addition, in an experiment using FCC wastewater, when the concentration of copper ions in the treated water in condenser 7 was analyzed, it was found that the average concentration of copper ions in the treated water of the porous reduced copper catalyst was 13.3 ppm of copper ions were confirmed.

Therefore, when a porous copper oxide catalyst is used, it is necessary to remove copper ions from the treated water before release.

Example 3 In the same manner as in Example 2, using the same porous reduced copper catalyst and porous copper oxide catalyst, the reaction temperature and reaction pressure were changed to perform FCC.
Catalytic wet oxidation was performed on wastewater.

The results are shown in Table 3.

As is clear from Table 3, even if the reaction temperature and reaction pressure are changed, under the same conditions, the porous reduced copper catalyst is superior to the porous copper oxide catalyst in terms of COD and TOC removal rates.

In the case of a still porous copper oxide catalyst, COD below 150℃
Since the TOC removal rate was extremely low, it was omitted from Table 3.

Also, as is clear from Table 3, the treatment temperature was 200°C.

Even if the reaction pressure was changed to 30Ky/cr&, it still remained at 150℃ and 10
No change was observed in the COD and TOC removal rates compared to the case of Kg/ca.

Example 4 In the same manner as in Example 1, catalytic wet oxidation was performed on PvA wastewater using the same porous reduced copper catalyst and changing the reaction temperature.

The results are shown in Table 4.

These results show that for polymer-containing wastewater such as PVA wastewater, the method of the present invention provides extremely high treatment efficiency at temperatures below 100°C, and furthermore, treatment at room temperature (20°C) and normal pressure is sufficient. It was recognized that the effect was obtained.

Example 5 Using the apparatus shown in Figure 1, FCC wastewater was continuously wet oxidized using the same porous reduced copper catalyst as in Example 1, and CO
Changes in the removal rate of D and TOC were observed.

The reaction conditions were a temperature of 150°C and a pressure of 10V4/Cm.
g Air flow rate 36 Nl/Ftj e Raw water flow rate 100 (1
17 temples.

LH8v=2.0.

As is clear from Table 5, if the water flow time is 9 hours,
Under these conditions, the quality of treated water deteriorated rapidly.

This is thought to be due to deterioration of the metal copper catalyst as it is oxidized to copper oxide.

Example 6 The porous reduced copper catalyst degraded by the wet oxidation method of FCC wastewater in Example 2 was regenerated with hydrogen gas at a temperature of 300°C and a space velocity of 2 for 2 hours under normal pressure.

The reducing gas flowed in from before the pressure reducing valve, and the pump 2 stopped.

After the regeneration, the CODMn and TOC removal rates before and after the regeneration of the FCC wastewater and air were again measured by the method of Example 2.

The results obtained are shown in Table 6.

From Table 6, it was confirmed that even if the catalyst deteriorated considerably, it could be reactivated by regeneration and could be regenerated sufficiently.

Example 7 As in Example 6, a deteriorated porous reduced copper catalyst was pumped into pump 2 at a temperature of 200°C using an aqueous formalin solution (5 parts concentration).
A formalin solution was passed through the reaction tower at a space velocity of 2. An L1 nitrogen cylinder was used as the cylinder 4, and nitrogen gas was passed through the reactor at a flow rate of 36 Nt 1 hour for treatment for 3 hours.

After regeneration, the F'CC wastewater and air were passed through the reactor to perform wet oxidation.

The results are shown in Table 7.

From Table 7, it was confirmed that the deterioration of the catalyst was sufficiently regenerated by reduction and the original activity could be fully recovered.

[Brief explanation of drawings]

The drawing is a 70-sheet schematic illustration of the apparatus used in the examples. 1: raw water tank, 2: pump, 3: reaction tower, 4: cylinder,
5: Pressure reducing valve, 6: Heater, 1: Condenser, 8: Integrating flow meter, X mark: Sampling point.

Claims (1)

[Claims] 1. A method for wet oxidizing wastewater containing organic matter with an oxygen-containing gas, characterized in that the treatment is carried out in the presence of reduced copper or a reduced copper-supported catalyst that has been pre-reduced. How to treat organic wastewater. 2. The method according to claim 1, wherein the reduced copper is porous. 3. The method according to claim 1 or 2, wherein the processing pressure is 10 kg/crA or less.