JP2000300937A - Gas treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent gas treatment method capable of removing a target gas component from a gas (exhaust gas) containing an org. gas such as org. solvent gas efficiently, inexpensively and simply by decomposition or the like. SOLUTION: The gas-liquid contact of a gas to be treated containing an org. gas component with a gas treatgment liquid is performed in a gas treatment tower and a part of the gas obtained after the gas-liquid contact in the gas treatment tower is again brought into contact with the gas treatment liquid in the gas treatment tower and the org. gas component dissolved in the gas treatment liquid is decomposed or removed by pref. using a microbiological treatment method to extremely efficiently treat objective gas to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel gas treatment method, more specifically, for example, after contacting an exhaust gas containing an organic solvent, which is an organic gas, preferably with a solution containing activated sludge under specific conditions. And a method for efficiently treating a target gas to be treated by decomposing or removing an organic gas component dissolved in the solution.

[0002]

2. Description of the Related Art For example, as a method of decomposing exhaust gas containing an organic solvent, a method of directly burning, a method of burning using a heat storage type medium (heat storage combustion method), or a method of using an adsorbent such as activated carbon is used. Methods for adsorption and recovery are known.

As a method for removing odors, such as sewage, which is not an organic solvent, a treatment method using microorganisms is known. For example, Japanese Patent Application Laid-Open No. 5-123527 discloses a method for efficiently deodorizing exhaust gas containing odor components using excess sludge.

Further, in a general activated sludge treatment apparatus, a method of feeding air into a sludge tank is adopted. However, in this method, the mixing efficiency of air and a treatment liquid is extremely low and the power cost for the treatment is very large. Disadvantage.

[0005]

Of the above-mentioned conventional methods, the combustion method is expensive and the heat storage combustion method has a gas concentration of 500 ppm.
Use at high concentrations, such as above, requires additional auxiliary fuel and therefore increases running costs. In addition, although the method using sludge is used as a method for deodorizing odors in sewage and the like, its applicability is not known as a method for treating exhaust gas containing an organic gas such as an organic solvent gas. Not yet.

Under these circumstances, there is a need for the development of an excellent method capable of efficiently and practically treating a gas to be treated such as exhaust gas containing an organic gas component, industrially simply and at low cost.

[0007] An object of the present invention is to solve the above-mentioned problems and to apply a microbiological treatment method using sludge or the like to efficiently treat a gas to be treated containing an organic gas component. It is to develop an excellent gas processing method that can perform the above.

[0008]

Means for Solving the Problems The present inventor has solved the above-mentioned problems and made intensive studies to achieve the object of the present invention. As a result, the gas to be treated containing an organic gas component in the gas treatment tower was obtained. Gas-liquid contact between a gas to be treated) and a gas treatment liquid (solution for treating the gas) is performed, and at least a part of the gas obtained after the gas-liquid contact in the gas treatment tower is re-gasified. The organic gas component is decomposed extremely efficiently by contacting it with the gas treatment liquid in the treatment tower and treating the gas component to be treated contained in the resulting gas treatment solution by a microbiological treatment method or the like. The inventors have found that the same processing can be performed, and have completed the present invention. After normal gas-liquid contact, organic gas components remaining in the obtained gas have been found to be remarkably improved by the partial recycling method according to the present invention. At least a part of the gas obtained in one gas processing tower can be treated again by another gas processing tower in gas-liquid contact.

That is, according to the present invention, a gas to be treated (a gas to be treated) containing an organic gas component is brought into gas-liquid contact with a gas treatment liquid in a gas treatment tower, and after gas-liquid contact in the treatment tower, The present invention resides in a gas treatment method in which at least a part of the obtained gas is brought into contact with a gas treatment liquid in a gas treatment tower again to decompose or remove a target organic gas component dissolved in the gas treatment liquid.

[0010] The gas treatment tower is used for gas-liquid contact, which is used for effective gas-liquid contact between a gas component and a liquid component so that a desired gas component is efficiently dissolved in a liquid. Any processing tower having a liquid contact device may be used. Normally, the gas treatment liquid descends from above, while the gas to be treated (the gas to be treated) rises from below, and they come into gas-liquid contact to dissolve the target gas component in the gas treatment liquid.

The present invention also includes the following contents. 1. The gas treatment tower is a gas-liquid contacting device, preferably a plate tower having a perforated plate or the like inside, a packed tower holding a filler inside, or a wet wall tower, and more preferably the gas to be treated and the gas treatment. The above-mentioned processing method performed using an apparatus having a pipe or the like for supplying a liquid to the processing tower.

In the present invention, one gas treatment tower is sufficient, but a plurality of gas treatment towers may be used. When a plurality of contact means are used, the gas-liquid contact system in the tower may be a combination of various contact means such as the above-mentioned tray tower.

2. In the above processing method, a processing method in which at least a part of the gas obtained after the gas-liquid contact in the gas processing tower is mixed with the gas to be processed supplied to the gas processing tower.

The gas after the gas-liquid contact is supplied to the path of the supply pipe of the gas to be treated, for example, to the lower part of the step tower, and the gas is contacted with the gas treatment liquid together with the gas to be treated. Can be dissolved in the gas treatment liquid. For that purpose, it is necessary to provide a pipe capable of performing such processing.

The mixing amount when mixing the gas obtained after the gas-liquid contact to be mixed with the gas to be treated, the type and flow rate of the gas component, the mixing method, the temperature of the gas to be treated and the temperature of the gas to be supplied For example, the mixing ratio needs to be changed depending on the conditions. Usually, the concentration of the organic gas component in the gas to be treated initially supplied is high. On the other hand, since the concentration of the organic gas component present in the gas obtained after the gas-liquid contact is considerably low, if the gas is mixed in a large amount, the concentration of the organic gas component to be treated becomes low, and the treatment efficiency is undesirably reduced. The mixing ratio (volume ratio) is preferably 1 to the gas to be treated.
About 0 to 90%, more preferably about 20 to 80%, and still more preferably about 30 to 50%, and the circulation rate described below is preferably about 20 to 80%, more preferably about 30 to 70%, Preferably 35-60%
The degree can be contacted efficiently.

There is a trade-off between the decomposition rate and the processing air volume, and the mixing ratio and the circulation rate can be appropriately selected and determined from the required decomposition rate and the required processing air volume.

3. The above treatment method in which the gas dissolved in the gas treatment liquid is decomposed by a microbiological treatment method to treat the gas.

As a method for decomposing or removing gas components, known methods and various other methods can be applied, but microbiological methods can be applied to the treatment of many gas components, and are low in cost and cost. It can be easily performed.

4. The above-mentioned treatment method, wherein the gas treatment liquid is present in the activated sludge treatment liquid or the activated sludge treatment liquid or contains a solution containing a usable microorganism.

[5] The above treatment method, wherein the organic gas is at least one kind of organic solvent gas.

6. In the above treatment method, at least a part of the gas obtained after the gas-liquid contact in the treatment tower is converted into a gas treatment liquid and a gas-liquid mixture in a gas treatment tower different from the gas treatment tower that has performed the gas-liquid contact treatment. A treatment method that makes contact.

In the present invention, particularly preferred embodiments of the invention include the following method. I. The organic gas component or a gas containing the same is brought into contact with the gas treatment liquid in one gas-liquid contact device by at least one column-type gas-liquid contact device, and at least one of the gases containing the organic gas component after the gas-liquid contact is obtained. A gas processing method in which the gas is passed through a supply section of the gas to be treated or returned directly to a gas-liquid contact device (the same gas-liquid contact device as described above or another device) or supplied.

B. Above a. In the treatment method, the tower-type gas-liquid contact device includes any one of a tray having a filler layer, a wet wall, a perforated plate, and the like inside.

When a plurality of columns are used, the contact means in the gas-liquid contact device can be changed for each column.

C. In the above treatment method, a gas decomposition treatment method wherein the gas treatment liquid contains an activated sludge treatment liquid or a solution containing microorganisms present in the activated sludge treatment liquid.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that after the above-mentioned characteristic gas-liquid contact between the gas to be treated and the gas treatment liquid, the activated sludge method is preferably used to microbiologically convert the gas treatment liquid by the action of microorganisms. This is a treatment method for decomposing and removing other organic gas components. In the case of the activated sludge method, activated sludge which can decompose or remove organic gas components by contact with the activated sludge to be used can be used. As the treatment method itself in the activated sludge treatment method, a conventionally known method can be used (for example, JP-A-5-123527, JP-A-58-186418, and JP-B-57-52066).
And JP-A-64-2569. ).

The gas treatment liquid used in the method of the present invention may be separated or removed by a method other than microbiological treatment, for example, decomposition or other decomposition of the target gas using a chemical solution or the like without using activated sludge. The available methods can also be used. Further, a decomposition method developed in the future can be used.

As the activated sludge used for the gas treatment by the activated sludge method, a method of aerobic or anaerobic treatment of domestic wastewater or industrial wastewater or immobilized microorganisms obtained from excess sludge generated at this time is used. can do.

The gas component (gas to be treated) that can be treated in the present invention is not particularly limited as long as it is an organic gas component. In the case of microbiological treatment such as an activated sludge treatment method, microorganisms capable of treatment such as decomposition can be appropriately selected and used, so that organic gas can be treated widely.

The organic gas component that can be treated in the present invention is not limited to one type. A mixed gas containing a plurality of components can be similarly treated.

Next, a preferred embodiment will be described with reference to FIG. 1, but of course the present invention is not limited to this.

FIG. 1 is a schematic view showing a typical example of an apparatus for treating exhaust gas in the present invention.

As shown in FIG. 1, as a gas treatment tower, a packed tower capable of gas-liquid contact, a wet wall tower, a plate tower, etc. (gas treatment tower 1)
0), and a gas such as air (solvent gas 1) containing a solvent gas as an organic gas, which is a gas to be treated, is fed from the lower portion thereof. A part of the gas 4 obtained after the gas-liquid contact, which is discharged from the upper part of the gas processing tower after the gas-liquid contact in the gas processing tower 10, is returned to the lower part of the gas processing tower 10 again, and is supplied to the gas processing tower. It is mixed with and merged with the gas to be treated 1 and sent again to the gas treatment tower. The ratio (referred to as “circulation rate”) of the gas 6 returned to the lower part of the gas 4 obtained after the gas-liquid contact treatment may be arbitrary, but it is necessary to increase the circulation rate in order to increase the gas decomposition rate. preferable. On the other hand, if the circulation rate is too high, the processing air volume of the gas to be processed decreases. Usually 20-80%
A degree of circulation rate is employed.

As another embodiment, as shown in FIG. 2, the gas after the treatment in the gas treatment tower can be returned directly to the inside of the gas treatment tower. In this case, the position where the gas obtained after the gas-liquid contact post-treatment is returned is usually preferably as low as possible, but if it is too close to the supply position of the gas 1 to be treated, the gas flow in the gas treatment tower may be reduced. It is not preferable because drift may occur. The number of positions to be returned may be one or more. However, when the circulation rate is high, returning to a plurality of positions is preferable in terms of contact efficiency. When returning to a plurality of places, the distribution of the gas to be returned can be determined by a damper or the like, and the return position can be appropriately changed and adjusted. Also in this case, the circulation rate of the gas obtained after the gas-liquid contact is usually about 20 to 80% as described above.

Further, part of the gas after gas-liquid contact may be returned directly to the lower part of the gas processing tower, and the other part may be mixed with the gas to be processed and supplied to the gas processing tower again. In FIG.
This is possible by piping the dotted line.

A plurality of gas treatment towers can be arranged, and at least part of the gas after gas-liquid contact in one gas treatment tower can be subjected again to gas-liquid contact treatment in another tower. Is included in the present invention.

As described above, in the present invention, the gas components that can be treated (gas components to be treated) present in the gas to be treated are not particularly limited. For example, methyl ethyl ketone, acetone, methyl isobutyl ketone, methanol, ethanol, n-propyl Alcohol, isopropyl alcohol, butanols, ethyl acetate, toluene, xylene,
Ether, methylene glycol, methylene glycol monomethyl acetate, methylene glycol monoethyl acetate, methylene glycol monomethyl ether, methylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and the like. As described above, a gas to be treated including not only a single gas component but also a mixed gas of a plurality of components can be treated in the present invention.

The applicable range of the concentration of the gas to be treated (the gas to be treated 1) varies depending on the type of the gas, but is usually preferably up to about 5000 ppm, more preferably up to about 3000 ppm, further preferably up to about 3000 ppm. It is up to about 2000 ppm.

The average sectional velocity of the gas to be treated (including all gases when returned) in the gas treatment tower is 0.01 to 1
It is about 0 m / sec.

[0040]

The present invention will be described in detail below with reference to examples and comparative examples.

Example 1 Using the gas treatment apparatus shown in FIG. 1, the treatment of methyl ethyl ketone gas was carried out using an activated sludge treatment liquid as the gas treatment liquid.

In FIG. 1, a gas to be treated 1 containing 2000 ppm of methyl ethyl ketone gas in the air is supplied to a gas treatment tower 10. Of the gas 4 obtained after the gas-liquid contact, 35% of the gas 4 (returned gas 6) is returned to the gas to be treated supply unit, merged with the gas to be treated 1, and supplied to the gas treatment tower 10 again.

At this time, the air tower speed is 0.9 m.
/ Sec. The average sectional speed of the gas treatment liquid (activated sludge treatment liquid) is 0.3 m / sec. At this time, the gas concentration of methyl ethyl ketone in the gas 5 discharged from the gas treatment tower 10 was 230 ppm.

(Comparative Example 1) In Example 1, the gas 4 obtained after the gas-liquid contact was returned to the gas treatment tower 10 without
Other processing conditions were the same as in Example 1. At this time, the gas concentration of methyl ethyl ketone in the gas 5 discharged from the gas treatment tower 10 was 390 ppm.

Example 2 Using the gas treatment apparatus shown in FIG. 2, treatment of methanol gas was carried out using activated sludge treatment liquid as the gas treatment liquid.

In FIG. 2, methanol gas 2 was introduced into air.
The gas to be treated 1 containing 500 ppm
To supply. The gas 13 corresponding to 20% of the gas 4 obtained after the gas-liquid contact is supplied to the gas treatment tower 10.

At this time, the air tower speed is 1.1 m.
/ Sec. The average sectional speed of the gas treatment liquid (activated sludge treatment liquid) is 0.4 m / sec. At this time, the gas concentration of methanol in the gas 5 discharged from the gas treatment tower 10 was 92 ppm.

(Comparative Example 2) In Example 2, the gas 4 obtained after the gas-liquid contact was discharged to the outside without returning to the gas processing tower 10, and other processing conditions were the same as in Example 2. Was done. At this time, the gas concentration of methanol in the gas 5 discharged from the gas processing tower 10 was 210 ppm.

As is apparent from the results of the above Examples and Comparative Examples, the activated sludge treatment liquid was used particularly for the gas treatment liquid,
Part of the gas obtained after gas-liquid contact in the gas treatment tower is returned and mixed into the gas to be treated, or supplied directly to the gas treatment tower, further increasing the processing efficiency of the target gas to be treated Can be done.

[0050]

In the gas treatment tower, a gas to be treated (a gas to be treated), for example, a gas containing an organic solvent gas or the like as an organic gas, is brought into contact with a gas treatment liquid. At least a part of the gas component to be treated, which is dissolved in the gas treatment liquid by returning it to the gas treatment tower again, and particularly, the target gas (gas to be treated) is decomposed very efficiently by microbiological treatment ( Gas decomposition rate) or can be eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one typical example of an apparatus for treating exhaust gas in the present invention.

FIG. 2 shows another apparatus for treating exhaust gas in the present invention.
It is a schematic diagram showing an example.

[Explanation of symbols]

 1: Gas to be processed 2: Fan 4: Gas obtained after gas-liquid contact 5: Gas to be exhausted 6: Returned gas 7: Pump 8: Gas processing liquid 9: Processing tank 10: Gas processing tower 11 to 13: Return gas to gas treatment tower 14-17: Damper

Claims (7)

[Claims] A gas-liquid contact between a gas to be treated containing an organic gas component and a gas treatment liquid is performed in a gas treatment tower, and at least a part of the gas obtained after the gas-liquid contact in the gas treatment tower is removed. A gas treatment method comprising contacting the gas treatment liquid again in the gas treatment tower to decompose or remove an organic gas component dissolved in the gas treatment liquid. 2. The processing method according to claim 1, wherein the gas processing tower includes a gas-liquid contact device, and has at least a pipe for supplying the gas to be processed and the gas processing liquid to the gas processing tower. 3. The processing method according to claim 1, wherein at least a part of the gas obtained after the gas-liquid contact is mixed with the gas to be processed supplied into the gas processing tower. 4. The treatment method according to claim 1, wherein the decomposition or removal of the organic gas component is performed by a microbiological treatment method. 5. The treatment method according to claim 1, wherein the gas treatment liquid contains an activated sludge treatment liquid or a solution containing microorganisms usable in the activated sludge treatment liquid. 6. An organic solvent gas comprising at least one organic solvent gas.
The method of claim 1 which is a seed. 7. At least a part of the gas obtained after the gas-liquid contact in the gas treatment tower is separated from the gas treatment liquid in a gas treatment tower different from the gas treatment tower that has performed the gas-liquid contact treatment. The treatment method according to claim 1, wherein liquid contact is performed.