JP2003275534A - Method for removing phenols - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for removing phenols which has a sufficiently high removal rate of the phenols, is easily maintained and attains a low running cost in removing the phenols in a waste gas. <P>SOLUTION: The method for removing the phenols is characterized by removing the phenols contained in the gas by bringing the gas containing the phenols into contact with a solid base. The contact between the gas and the solid base is carried out either by passing the gas through a layer filled with granulated solid base or by spraying the solid base into the gas. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing phenols, and more particularly to a method for removing phenols contained in a gas.

[0002]

2. Description of the Related Art Conventionally, a high concentration of phenol resin has been used in the process of manufacturing resin sand using a phenol resin as an adhesive, in the process of applying a phenol adhesive to plywood, laminated boards, etc., the drying process, and the molding process of phenol resin. Since exhaust gas containing phenols is generated, a treatment for removing phenols in the exhaust gas is performed.

As a method for removing phenols, there are an adsorption method, a wet treatment method using an absorbing solution, and the like. The adsorption method removes phenols by adsorbing them onto an adsorbent such as activated carbon.The removal rate of phenols is relatively high, but maintenance management for stable removal of phenol is difficult and running costs are high. . The adsorbent after use was a solid waste.

On the other hand, the wet treatment method is to absorb phenol in an absorbing solution such as sodium hydroxide (Japanese Patent Laid-Open No.
No. 81827, Japanese Patent Laid-Open No. 56-70820). However, the wet treatment method is not always sufficient in terms of the removal rate of phenol, and has a drawback that a large amount of waste liquid is generated during the treatment. Further, there is a problem of equipment corrosion.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art. When removing phenols from exhaust gas, the removal rate of phenols is sufficiently high and maintenance management is performed. It is an object of the present invention to provide a method for removing phenols, which is easy to perform, has a low running cost, and can reduce solid waste.

[0006]

In order to solve the above-mentioned problems, the method for removing phenols of the present invention comprises contacting a gas containing phenols with a solid base so that the phenols are absorbed by the solid base. It is characterized by

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below.

The phenols to be removed in the present invention are not particularly limited as long as they have a phenolic hydroxyl group, and specifically, phenols, alkylphenols (cresol, ethylphenol, 4-t-butylphenol, 2, 4-di-t-butylphenol,
Pentylphenol, octylphenol, nonylphenol, xylenol, etc.), aminophenol, nitrophenol, dinitrophenol, chlorophenol,
Dichlorophenol, trichlorophenol, bromophenol, resorcin, catechol, hydroquinone,
Phloroglucinol, heptylparaben, salicylic acid,
Methyl salicylate, benzyl salicylate, methyl p-oxybenzoate, hydroxybenzaldehyde, vanillin, ethyl vanillin, vanillic acid, butylhydroxytoluene, butylhydroxyanisole, propyl gallate, 4-phenoxyphenol, phenylphenol,
Bisphenol A, 5-hydroxyisophthalic acid, p-
Examples thereof include hydroxyphenylacetic acid, naphthol, and 1,4-dihydroxynaphthalene.

By bringing the gas containing these phenols into contact with the solid base, the phenols in the gas are absorbed by the solid base, so that the phenols can be removed at a sufficiently high removal rate. Further, this absorption is a chemical absorption, and it is presumed that a phenolate compound is produced by this absorption, and this phenolate compound can be discharged out of the system together with the solid base.

Examples of such solid bases include hydrogencarbonates of alkali metals or alkaline earth metals (sodium hydrogencarbonate, calcium hydrogencarbonate, etc.), carbonates (sodium carbonate, sodium sesquicarbonate, potassium carbonate, basic magnesium carbonate (hydroxy). Magnesium carbonate), oxides (magnesium oxide, calcium oxide, etc.), hydroxides (sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide), sodium silicate, soda lime, sodium tripolyphosphate, citric acid Examples thereof include sodium acid salt, and these may be used alone.
You may use it in combination of 2 or more types. It should be noted that sodium carbonate and sodium sesquicarbonate can be used regardless of whether they are natural or synthetic, and sodium carbonate can be used regardless of whether they are light or heavy. Furthermore, the sodium carbonate may be a porous substance (light ash) obtained by firing sodium hydrogen carbonate produced during the process of producing sodium carbonate by the ammonia soda method.

Among the above solid bases, hydrogen carbonate and / or carbonate of alkali metal are preferable, and sodium and / or potassium are preferable as alkali metal constituting hydrogen carbonate and carbonate. By using such a solid base, the removal rate of phenols can be further increased. In addition, sodium hydrogen carbonate is particularly preferable because it has advantages that it is not hygroscopic, easy to handle, and can be obtained in large quantities and at low cost.

The method for bringing the gas containing phenols into contact with the solid base is not particularly limited as long as the two can be brought into sufficient contact with each other, but a preferred embodiment is preferable in terms of the removal rate of phenols, maintenance and running costs. The following two methods can be mentioned as:

That is, according to the first embodiment of the present invention, a gas containing a phenol is passed through a packed bed of a granulated product containing a solid base and having an average particle size of 0.5 mm or more. Thereby, when the gas passes through the packed bed, the gas and the solid base can be sufficiently brought into contact with each other, so that the removal rate of the phenols at a high level can be achieved by the absorption of the phenols in the gas into the solid base. Can be achieved.

More specifically, for example, the granulated product is filled in a predetermined container, and a gas generating facility containing phenols is connected to the front of the container and an absorption blower is connected to the rear of the container via pipes. Then, the gas can be introduced into the container by an absorption blower, and the phenols in the gas can be removed by passing through the packed bed of the granulated material.

The granulated product used in the first embodiment may be composed of only a solid base, and in addition to the solid base, a binder such as sodium silicate, CMC (carboxymethyl cellulose), PVA (polyvinyl alcohol) and the like. The content of the binder is preferably 60% by mass or less based on the total amount of the granulated product, and it is particularly preferred to use the granulated product composed of only the solid base. When the content of the binder exceeds the above upper limit, the removal rate of phenols decreases.

The average particle size of the granulated product is 0.5 mm or more as described above, preferably 0.5 to 5 mm.
Is. As a result, without introducing new equipment,
Phenols can be suitably removed by using the conventional filling type equipment such as activated carbon and zeolite. The average particle size of the granulated product was 0.
If it is less than 5 mm, the pressure loss of the packed bed increases,
In addition, phenomena such as pulverization during filling and processing, accumulation in the pipe, packing of the plates, suction by the decompression pump, and increase in pressure loss when the gas to be processed passes through the packed bed occur. It will be easier. Further, generally, the strength of the granulated product is improved with an increase in the average particle size, but if it exceeds 5 mm, the contact efficiency between the gas and the granulated product is lowered, and the removal rate of phenols tends to be insufficient. It is in.

Here, the hardness can be adopted as an index of the strength of the granulated product. The hardness referred to here is the force [N] at the time of compressing and destroying one particle by applying a force perpendicular to it from above, and this hardness depends on the particle diameter even if it is the same material. Therefore, it is necessary to measure after arranging the particles by sieving.

For example, the average particle size of the granulated product is 0.5 to 2
If it is 0 mm, each particle is sieved to 0.5
It is easy to understand that it is easier to divide by sequentially increasing by 0.5 mm from mm. That is, 0.5 mm, 1.0 mm,
It is 1.5 mm, 2.0 mm, 2.0 mm or more. Here, 5N or more is sufficient to form particles of up to 20 mm in the packed layer, so 5N or more may be defined as 5N as described later. More specifically, for particles having an average particle size of 1.5 mm or more and less than 2.0 mm, sieving is performed using a sieve having a mesh size of 1.5 mm and a sieve having a mesh size of 2.0 mm, and the sieving is performed on the 1.5 mm sieve and Twenty particles under a 2.0 mm sieve may be collected, the hardness of each particle may be measured, and the average value may be adopted as the evaluation standard of the particle strength.

In the present invention, the average hardness of granules having a particle size of 0.5 mm or more and less than 1.0 mm is 0.1 N or more, and the average hardness of granules having a particle size of 1.0 mm or more and less than 1.5 mm. Is 0.5 N or more, and the average hardness of a granulated product having a particle diameter of 1.5 mm or more and less than 2.0 mm is 1 N or more,
The average hardness of the granulated product having a particle diameter of 2.0 mm or more is preferably 5N or more.

The granulated product can be obtained by either a dry method or a wet method. Examples of the granulation method include a compression molding method, a tumbling granulation method, a stirring granulation method, an extrusion molding method, a spray dry method, a fluidized bed method and the like. Among them, a dry compression molding method such as a tablet molding method or a roll pressing method is advantageous for industrial production because the steps such as a drying step are not required and is advantageous for industrial production. It is preferable because a high granulated product can be obtained. In this case, as a method of adjusting the particle size distribution and average particle size of the granulated product, a step of crushing and sieving after molding with a dry compression molding machine can be adopted. Further, as another method of obtaining a granulated product, after kneading a solid base, and optionally water-soluble binder CMC and the like with water, the mixture is molded with a wet extrusion molding machine such as a pelletizer and then dried. Another method is to adjust the particle size distribution and average particle size by sieving. In addition, it is possible to suppress the generation of wear parts of the granulated product and increase the density when packed in the packing layer by making it spherical with a rolling granulator such as a Marumerizer after molding with a pelletizer. it can.

In the above-mentioned molding method, it is preferable to use, as the solid base material, primary particles (single crystal particles of solid base) having an average particle size of 10 to 500 μm. If the average particle size of the primary particles is less than the lower limit, the fluidity is low, and it tends to be difficult to handle. On the other hand, if the average particle size exceeds the upper limit, industrial production of granules becomes difficult, and the cost is also high. It is not preferable because it tends to increase.

In the present invention, the average particle size means that when the average particle size is 70 μm or more, the mass remaining on each sieve and the lowermost pan is measured in the sieving method. A cumulative curve is created with the total mass as 100%, and the particle diameter is the point at which the cumulative mass becomes 50%. On the other hand, when the average particle size is less than 70 μm, the total volume is 100 when measured by a laser diffraction / scattering particle size distribution analyzer.
When the cumulative curve is calculated as%, the cumulative volume is 5
The particle size at the point of 0% is called the average particle size.

The flow rate of the gas passing through the packed bed can be appropriately selected depending on the type and content of phenols, the type of solid base and the average particle size. For example, when sodium hydrogen carbonate or sodium carbonate is used as the solid base, the gas flow rate is preferably 0.1 to 50 m / min.

In the present invention, the temperature at which the gas containing phenols is brought into contact with the solid base is preferably 0 to 90 ° C, more preferably 10 to 60 ° C. If the temperature is below the lower limit, the reaction rate may be slow and the reaction rate of the solid base may be lowered. On the other hand, when the temperature exceeds the upper limit value, not only is it economically disadvantageous because heat resistance is required for the treatment equipment, but when using the one obtained by granulating a hydrogen carbonate as a solid base for use. Since the hydrogen carbonate undergoes thermal decomposition and the granulated product is pulverized, the packed bed may be clogged.

Further, the second embodiment according to the present invention is to spray a gas containing phenols with a solid base having an average particle diameter of 1 to 300 μm.

FIG. 1 is a flow chart showing an example of a processing apparatus used in the second embodiment. In FIG. 1, an exhaust gas generation facility 1, a bag filter 2 having a dust discharge port 7, an exhaust fan 3, and a chimney 4 are arranged in this order from upstream to downstream, and the exhaust gas generation facility 1 and the bag filter 2 are arranged.
Is the first flue 8, the bag filter 2 and the exhaust fan 3 are the second flue 9, and the exhaust fan 3 and the chimney 4 are the third flue 1.
0 are connected to each other. Further, a pulverizer 5 is connected to a predetermined position of the first flue 8, and the pulverizer 5 pulverizes the solid base into an average particle size of 1 to 300 μm, and then the compressed air is injected from the inlet 6 to the first position. It is also possible to inject it into the flue 8.

In the apparatus shown in FIG. 1, when the exhaust gas containing phenols generated in the exhaust gas generation facility 1 is sent to the bag filter 2 through the first flue 8, the average particle diameter is By spraying the solid base contained in the exhaust gas, the exhaust gas comes into contact with the solid base in the first flue 8, and the phenols in the exhaust gas are absorbed by the solid base. Since the solid base that has absorbed the phenols is captured as dust by the bag filter 2 and is discharged out of the system through the discharge port 7, the exhaust gas that has passed through the bag filter 2 has the phenols sufficiently removed. This can be discharged from the chimney 4 by the exhaust fan 3.

Here, the average particle diameter of the solid base according to the second embodiment is 1 to 300 μm, and preferably 2 to 50 μm as described above. The average particle size of the solid base is 3
If it exceeds 00 μm, the contact efficiency between the exhaust gas and the solid base tends to be low, and the removal rate of phenols tends to be insufficient. Further, it is very difficult to inexpensively industrially produce a solid base having an average particle size of less than 1 μm.

In particular, it is preferable to add an anti-caking agent because the finely pulverized solid base is likely to congeal (cake) during storage. The anti-caking agent may be added to and mixed with the solid base of the raw material before the fine pulverization, or may be added after the fine pulverization. Fumed silica can be preferably used as the anti-caking agent. The fumed silica may be either hydrophobic or hydrophilic. For example, when the collected ash discharged from the bag filter is dissolved as described later, it is preferable to use the hydrophilic fumed silica. If the hydrophobic fumed silica is used, the fumed silica and the solid base may float in water and may be difficult to dissolve. It is also possible to grind the solid base in the grinder 5.
Also in this case, when spraying on the first flue 8,
An anti-caking agent may be added to further improve dispersibility and reactivity.

The amount of the solid base sprayed can be appropriately selected depending on the kind of the phenols and the content in the gas, the desired phenol concentration in the gas after the treatment, and the kind of the solid base. For example, when sodium hydrogen carbonate or sodium carbonate is used as the solid base, the amount of spray is 0.1 to 50 m with respect to 1 mol of phenols contained in the exhaust gas.
It is preferably ol.

As described above, the method for removing phenols of the present invention, which is excellent in terms of the removal rate of phenols, maintenance management and running cost, is the process for producing resin sand using a phenol resin as an adhesive, plywood, and lamination. It is very useful in the application of phenolic adhesives to boards and the like, the drying process, the molding process of phenolic resin, etc. Furthermore, in the present invention,
If a water-soluble solid base such as sodium hydrogen carbonate or sodium carbonate is used, the collected ash discharged by the bag filter can be dissolved in water, and if it is biologically processed to decompose organic matter, it can be discharged. Can be reduced.

[0032]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto. In addition, the "double mol" in this example means the molar amount based on 1 mol of phenols contained in the exhaust gas.

[Example 1] (Preparation of sodium hydrogencarbonate granules) 300 kg of sodium hydrogencarbonate powder for food additives (Asahi Glass Co., Ltd.) having an average primary particle size of 98 μm was roll-press compression molded. Machine (manufactured by Turbo Kogyo Co., Ltd., trade name: roller compactor WP type, roll outer diameter 230 mm, roll length 80 mm) is compression molded at a linear pressure of 36.8 kN / cm to obtain flaky sodium hydrogencarbonate powder. A molded body was obtained. The obtained flake-shaped molded body was roughly crushed with a flake breaker, and the mesh of the rotary sizing machine was 4.7.
After setting it to 5 mm and passing it all through, using a rotary sifter (manufactured by Turbo Kogyo Co., Ltd., trade name: Turbo Screener TS type), particles having a particle diameter of 4.0 mm or more and a particle diameter of 1.0 m are used.
Particles of m or less were removed to obtain the target granulated product.

The average particle size of the obtained granulated product was measured by the following procedure. First, using a wire mesh stainless steel standard sieve having an inner diameter of 200 mm, openings of 5.60 mm, 4.75 mm,
4.00 mm, 2.80 mm, 2.00 mm, 1.00
mm pieces were piled up, 100 g of granules were poured on the bottom plate installed at the bottom. Next, low tap shaker type screen shaker (made by Iida Manufacturing Co., Ltd., trade name: I
IDA SIEVE SHAKER, shaking speed 290 revolutions / minute, striking speed 165 times / minute) for 10 minutes, and then the mass of the residue of this granulated product on each standard sieve and the bottom plate is measured, and each eye is measured. The cumulative total of the passing masses with respect to the opening was graphed, and the particle diameter at which the cumulative total of the passing masses was 50% was defined as the average particle diameter. As a result, the average particle size of the obtained granulated product was 2.
It was 2 mm.

Regarding the hardness of the granulated product, the granulated product obtained above is 0.5 mm, 1.0 mm, 1.5 mm,
After sieving with a 2.0 mm or 2.5 mm mesh sieve, 20 hardnesses of each particle size were measured using a Kiya type digital hardness meter KHT-20 manufactured by Fujiwara Seisakusho to obtain an average value. As a result, the average hardness of the particles of 0.5 to 1.0 mm is 6N,
The average hardness of particles of 1.0 to 1.5 mm is 15 N, 1.5
The average hardness of particles of ˜2.0 mm was 28 N, and the average hardness of particles of 2.0 mm or more was 69 N.

(Removal of Phenols Using Packed Bed) Next, a removal test of phenols was conducted according to the following procedure. In this test, the exhaust gas generated when the press machine was opened was used as the gas to be treated during thermoforming with a high-temperature press machine using felt and phenol resin as a curing agent.

First, 60 g of the above granulated material was filled in a filling container made of hard vinyl chloride having an inner diameter of 25 mm and a length of 150 mm to form a filling layer. An electromagnetic air pump (manufactured by Enomoto Micro Pump Co., Ltd.,
A model gas: MV-6005VP, maximum flow rate 4.0 L / min) was connected to suck the gas to be treated and sampled in a gas sampling bag (made of natural rubber, capacity 1 L). In the above process, the temperature of the gas to be treated passing through the filling container was 20 ° C., and the residence time of the gas to be treated in the filling container was 0.7 seconds.

Next, regarding the collected gas to be treated, a phenol gas detector tube No. 60 (manufactured by Gastec Co., Ltd., measurement range of phenol concentration: 0.4 to 187 pp
m) was used to measure the concentration of phenols at a temperature of 20 ° C., the concentration of phenols was below the lower limit of analysis (0.4 ppm or less).

On the other hand, when the gas to be treated collected through an empty filling container not filled with the granulated product was measured with the phenol gas detector tube, the concentration of phenols gas was 1.0 ppm.

[Example 2] (Removal of phenols by spraying sodium hydrogen carbonate) Using the treatment apparatus shown in Fig. 1, a phenols removal test was conducted according to the following procedure.

First, an impact type dry crusher 5 (Hosokawa Micron dry crusher, trade name: ACM) of sodium hydrogencarbonate (made by Asahi Glass Co., Ltd.) having an average particle diameter of 102 μm is used.
Pulverizer) to obtain a sodium hydrogencarbonate powder having an average particle diameter of 9 μm. Here, at the time of pulverization, fumed silica having an average particle diameter of 0.01 μm was previously added and mixed in an amount of 1.0% by mass with respect to the sodium hydrogencarbonate powder. The average particle size is measured by Microtrac FRA.
9220 (manufactured by Nikkiso Co., Ltd.) was used.

Next, when the exhaust gas containing phenols generated in the exhaust gas generation facility 1 is sent to the bag filter 2, the first
In the flue 8 of the above, the sodium hydrogen carbonate powder was sprayed with 20 times mol of phenols using compressed air.
After the dust containing the solid base is captured and removed by the bag filter 2, the exhaust gas passing through the bag filter 2 is discharged to the second flue 9
After being sent to the exhaust fan 3 via the compressor for compression, the third flue 1
It was sent to the chimney 4 through 0 and discharged from the chimney 4. The gas temperature was 20 ° C. between the time when the gas was sucked into the first flue 8 and the time when the gas was discharged from the chimney 4. Also, bug filter 2
The flow velocity of the gas passing through was 1 m / min in the actual gas state.

In the above process, the exhaust gas is sampled from the second flue 9 at the outlet of the bag filter 2 and the JISK0086
The concentration of phenols in the exhaust gas was measured according to the gas chromatographic method specified in 1. In addition, as a blank test, the concentration of phenols in the exhaust gas when sodium hydrogen carbonate was not sprayed was measured, and the residual phenol ratio was obtained from these measured values. The results are shown in Table 1.

[Example 3] A phenols removal test was conducted in the same manner as in Example 2 except that the amount of sodium hydrogen carbonate sprayed was 35 times mol of the phenols. The results obtained are shown in Table 1.

[0045]

[Table 1]

[Example 4] Impact type dry crusher 5 (Hosokawa Micron dry crusher, trade name: A) with sodium hydrogen carbonate (Asahi Glass Co., Ltd.) having an average particle diameter of 93 µm
A removal test of phenols was carried out in the same manner as in Example 2 except that the powder was crushed with a CM pulsarizer) to an average particle size of 9 μm and directly injected into the first flue 8. The obtained results are shown in Table 2. The injection of the crushed sodium hydrogen carbonate did not affect the existing equipment such as the bag filter 2.

[Example 5] A phenols removal test was conducted in the same manner as in Example 4 except that the amount of sodium hydrogen carbonate sprayed was 35 times the mol of the phenols. The obtained results are shown in Table 2.

[0048]

[Table 2]

Example 6 A solid base was prepared in the same manner as in Example 2 except that sodium carbonate having an average particle size of 119 μm (light ash manufactured by Asahi Glass Co., Ltd.) was used in place of the sodium hydrogen carbonate powder of Example 2. Was pulverized to obtain sodium carbonate powder having an average particle diameter of 8 μm. Here, at the time of pulverization, fumed silica having an average particle diameter of 0.01 μm was previously added and mixed in an amount of 1.0% by mass with respect to the sodium carbonate powder.

A phenols removal test was conducted in the same manner as in Example 2 except that the sodium carbonate powder thus obtained was sprayed in an amount of 10 times mol of phenols. The results obtained are shown in Table 3.

Example 7 A phenols removal test was conducted in the same manner as in Example 6 except that the amount of sodium carbonate sprayed was 18 times mol of the phenols. The results obtained are shown in Table 3.

[0052]

[Table 3]

Example 8 The solid base was pulverized in the same manner as in Example 4 except that sodium carbonate having an average particle diameter of 118 μm (made by Asahi Glass Co., Ltd.) was used in place of the sodium hydrogencarbonate powder of Example 4. Then, sodium carbonate powder having an average particle diameter of 8 μm was obtained.

A phenols removal test was conducted in the same manner as in Example 4 except that the sodium carbonate powder thus obtained was sprayed in an amount of 10 times mol of phenols. The results obtained are shown in Table 4.

Example 9 A phenols removal test was conducted in the same manner as in Example 8 except that the amount of sodium carbonate sprayed was 18 times mol of the phenols. The obtained results are shown in Table 2.

[0056]

[Table 4]

[0057]

As described above, according to the present invention, when removing phenols in exhaust gas, the removal rate of phenols is sufficiently high, the maintenance is easy, and the running cost is low. Will be provided.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a processing device used in a second embodiment of the present invention.

[Explanation of symbols]

1 ... Exhaust gas generating equipment, 2 ... Bag filter, 3 ... Exhaust fan, 4 ... Chimney, 5 ... Crusher, 6 ... Inlet, 7 ... Outlet,
8-10 ... Flue.

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Claims (5)

[Claims] 1. A method for removing phenols, which comprises contacting a gas containing phenols with a solid base so that the phenols are absorbed by the solid base. 2. Removal of phenols according to claim 1, characterized in that a gas containing phenols is passed through a packed bed of a granulated product containing a solid base and having an average particle size of 0.5 mm or more. Method. 3. An average particle size of 1 for a gas containing phenols.
Spraying a solid base of ~ 300 μm,
The method for removing phenols according to claim 1. 4. The solid base is a hydrogen carbonate and / or carbonate of an alkali metal.
4. The method for removing phenols according to any one of 3 to 3. 5. The method for removing phenol according to claim 4, wherein the alkali metal is sodium and / or potassium.