JPH08112513A - Method for deodorizing waste gas generated in coating work and deodorizing device - Google Patents

Abstract

PURPOSE: To effectively deodorize waste gas by removing dust from waste gas generated in a coating process before bringing it into contact with a porous mineral adsorbent carrying hydrazine salts and passing it through an active carbon filter. CONSTITUTION: The temperature of waste gas is adjusted to <=100 deg.C. At first, after dust is removed by a dust collecting filter 41, the waste gas is passed through a bed 42 packed with porous mineral foil carrying hydrazine salts. Then almost all the malodorous materials of aldehydes and a part of the other malodorous materials are adsorbed and removed. Furthermore, when it is passed through a bed 43 packed with granular active carbon, the remaining malodorous materials are adsorbed and removed. After that, it is dissipated in the air as clean air 23 by a suction fan 33. Malodor is removed from waste gas generated in a coating work is inexpensively and surely removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a deodorizing apparatus for deodorizing exhaust gas generated in a painting process for automobiles and the like.

[0002]

2. Description of the Related Art In a coating booth, a setting booth, and a (baking) drying section coating process in an automobile coating process, various odors are generated from a solvent volatilized for forming a coating film and a resin mixed with the coating film. . For example, when coating is performed using a coating material containing an acrylic resin, a commonly used solvent such as toluene or xylene is discharged as coating exhaust gas. Further, raw material monomers such as acrylic acid ester and decomposition products thereof are volatilized from the coating material. Therefore, the exhaust gas generated from the coating booth using the coating material containing acrylic resin also has a tearing property due to the acrylic ester.

Further, when coating is performed using a paint containing a melamine resin, formaldehyde used as a polycondensation agent is volatilized from the paint. Therefore,
Exhaust gas generated from a coating process using a paint containing a melamine resin has an irritating odor caused by formaldehyde.

Although the formaldehyde itself is not included in the regulated substances of the Odor Control Law, it is suspected to be carcinogenic, so the working environment standard is defined as 0.5 ppm or less according to the Japan Society for Occupational Health standards. Further, since the irritation to the eyes is remarkable, there is a demand for a method for surely removing this from the coating exhaust gas. It is stipulated that the standard of working environment of toluene and xylene, which are usually contained in paint exhaust gas, and the standard of Japan Society for Occupational Health is 100 ppm or less. From this figure, formaldehyde removal is much lower than removal of the above solvent. I know what is required.

As for the acrylic resin, which is a polymer resin containing a derivative of acrylic acid or methacrylic acid as a main component, there are a great variety of acrylic resins depending on the type and combination of acrylic monomers. These are originally used for natural drying, but they are also used for baking coating by reinforcing them with melamine resin, and it is estimated that the aldehydes decomposed and generated at that time have a unique burning odor and become the main component of the malodor. ing.
Most of the main components of the monomer have rather a pungent odor.

According to a survey conducted by the Environment Agency and the like, high molecular weight aldehydes such as isovaleraldehyde, normal valeraldehyde, and normal butyraldehyde are included in the aldehydes formed by the reaction in the baking process, and their threshold values are extremely low. It has been pointed out that special attention is required because it smells even at low concentrations. For example, since isovaleraldehyde can smell even at a low concentration of 0.003 ppm, delicate deodorization is required.

By the way, in order to deodorize exhaust gas generated in the painting process, a conventional direct combustion method in which the exhaust gas is introduced into a high temperature combustion furnace for oxidative decomposition, and catalytic combustion for oxidative decomposition at a relatively low temperature have been used. Deodorizing treatment was carried out by using a method, an adsorption method of adsorbing on activated carbon and removing it.

[0008]

However, the above direct combustion method has a problem that the fuel cost is high and the energy consumption is large. The above-mentioned catalytic combustion method has a problem that the replacement cost of the catalyst is high when the catalyst is poisoned and it takes a long time to replace the catalyst. In addition, the adsorption method using activated carbon has a relatively high adsorption capacity for high-molecular gas, but it has a small adsorption capacity for formaldehyde, acetaldehyde, etc., and requires frequent replacement of the activated carbon, leading to an increase in cost. It was In view of the above situation, it is an object of the present invention to provide a method and a deodorizing device for effectively deodorizing exhaust gas generated in a coating process at low cost.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object. As a result, the exhaust gas generated in the coating process was removed, and then contacted with a porous mineral adsorbent carrying hydrazine salts. The present invention has been found to significantly reduce the frequency of exchanging activated carbon by allowing the activated carbon to pass through an activated carbon filter after that.

That is, the present invention includes a collecting step for collecting exhaust gas generated in the coating step, and a filtering step for removing fine particles from the exhaust gas by passing the exhaust gas collected in the collecting step through a filter, A method for deodorizing a coating exhaust gas, which comprises a step of removing odorous substances such as formaldehyde and acetaldehyde by contacting the exhaust gas from which fine particles have been removed in the filtering step with a porous mineral adsorbent supporting hydrazine salts. And a deodorizing device. Hereinafter, the present invention will be described in detail.

In the present invention, first, the exhaust gas generated in the painting step is sucked by the suction means (collecting step). The exhaust gas sucked by the suction means passes through the dust filter, and the particulates are removed from the exhaust gas here (filtering step).

The exhaust gas from which the fine particles have been removed by the dust filter is brought into contact with a porous mineral adsorbent carrying hydrazine salts to remove odorous substances such as aldehydes such as formaldehyde, acetaldehyde and other alkyl aldehydes. It will be (odorous substance removal process).

It is preferable that the temperature of the exhaust gas passing through the porous mineral adsorbent in the step of removing the malodorous substance is 100 ° C. or less by introducing cold air. This increases the function of the porous mineral adsorbent.

Among the coating exhaust gases, some of the organic solvent components such as toluene and xylene are deodorized by the above-mentioned coating exhaust gas deodorizing method of the present invention, and then, if necessary,
Furthermore, most of the malodorous substances can be removed by adsorption removal with activated carbon. Also, among the paint exhaust gases,
For odorous substances such as formaldehyde and acetaldehyde, which inhibit the adsorption capacity of activated carbon, they are removed in advance by a hydrazine salt-supporting porous mineral adsorbent by the deodorizing method of the coating exhaust gas of the present invention. Therefore, even if the treatment with activated carbon is performed after the method for deodorizing the coating exhaust gas of the present invention, the life of the activated carbon can be significantly extended.

The mechanism by which the aldehydes can be adsorbed and removed by the porous mineral adsorbent supporting the hydrazine salts has not been elucidated in detail. However, basically, hydrazine salts are deposited in the interstices of layered crystals of porous minerals, which keeps hydrazine chemically stable, and when aldehydes in the coating exhaust gas come into contact with it, aldazine is formed. It is presumed that it causes chemisorption.

The deodorizing method of the present invention and the deodorizing device of the present invention will be described with reference to the drawings (FIG. 1). The deodorizing device 11 includes an exhaust gas intake port 31, a cool air intake amount adjusting valve 32, and a suction fan 3.
3 and sucks the coating exhaust gas 21 from the suction port 31, and when the exhaust gas temperature exceeds 100 ° C., the cool air suction adjusting valve 32 is opened to mix the cool air 22 to bring the exhaust gas temperature to 100. Adjust so that it is below ℃.

Exhaust gas adjusted to a temperature of 100 ° C. or lower is dust-removed by a dust collecting filter 41, passes through a layer 42 filled with a porous mineral foil carrying a hydrazine salt, and most of odorous substances such as aldehydes and other malodorous substances are discharged. After part of the substance is adsorbed and removed, in order to adsorb and remove the remaining malodorous substance, the layer 43 filled with the granular activated carbon is passed through. Then, the suction fan 33 disperses the deodorizing device as clean air 23 into the atmosphere.

The granular activated carbon 43 is not particularly limited as long as it is a material capable of adsorbing a malodorous substance having a relatively weak adsorption performance for a porous mineral supporting a hydrazine salt such as toluene or xylene, and silica gel, zeolite or the like. But good.
Hydrophobic synthetic zeolite having an increased silica composition may be used.

[0019]

The present invention will be described in more detail below with reference to examples of the present invention, but the present invention is not limited to these examples.

Example 1 In the case of melamine resin A part of the exhaust gas of a coating factory that actually used the melamine resin was sucked directly into the test device without any treatment to evaluate the deodorizing performance. There was no problem with the initial performance, and the test was continued for one month. Table 1 shows the measurement results of the final day of the test of 8 hours / day × 24 days when the test was actually performed.

As the evaluation device, the device having the basic structure shown in FIG. 1 was used. The cross-sectional area of the apparatus was 0.7 m ² , the filling amount of the hydrazine salt-supporting porous mineral foil was 30 kg, and the filling amount of the granular activated carbon was 15 kg. Gas flow rate in the deodorizer is 0.2m
/ Sec, there is no problem such as flooding, and there is no problem such as uneven filling layer. As the activated carbon and the dust collecting filter, commercially available products were used. The hydrazine salt-supporting porous mineral foil was formed by kneading zeolite fine powder with a mixed aqueous solution of aluminum sulfate and hydrazine and rolling into a foil having a thickness of 0.5 mm. Dry it in the microwave and crush it to 20m.
The product produced by sieving with a m-square and 3 mm-square mesh and sizing was used.

The evaluation was carried out by measuring the four components of formaldehyde, acetaldehyde, toluene and xylene using a detector tube, and the sensory evaluation was conducted by a panel of 6 people. In the sensory evaluation, the odor intensity of 2.5 or less was evaluated as ◯, 3.5 or more as x, and the middle was evaluated as Δ. At least 8 hours / day ×
In a 24-day test, no odor or eye irritation was observed in the exhaust gas after deodorization, and it was confirmed that the exhaust gas had long-term durability.

Example 2 Acrylic Resin A part of the exhaust gas of a coating factory using an acrylic resin that was actually in operation was directly sucked into the test device without treatment to evaluate the deodorizing performance. There was no problem with the initial performance, and the test was continued for one month. Table 2 shows the measurement results of the final day of the test of 8 hours / day × 24 days when the test was actually performed.

As the evaluation apparatus, the apparatus having the basic structure shown in FIG. 1 was used, but an apparatus smaller than the one used in the factory experiment of melamine resin was prepared, and an activated carbon packed bed was prepared for the purpose of lowering the gas temperature before activated carbon. Cooling was performed through a water cooling pipe before. The cross-sectional area of the device was 0.04 m ² , the filling amount of the hydrazine salt-supporting porous mineral foil was 2 kg, and the filling amount of the granular activated carbon was 1 kg. The gas flow rate in the deodorizing device was 0.2 m / sec, there were no problems such as flooding, and there were no problems such as nonuniformity of the packed bed. As the activated carbon and the dust collecting filter, commercially available products were used. The hydrazine salt-supporting porous mineral foil was formed by kneading zeolite fine powder with a mixed aqueous solution of aluminum sulfate and hydrazine and rolling into a foil having a thickness of 0.5 mm. It was dried in a microwave oven, crushed, sieved through a 20 mm square and a 3 mm square mesh, and sized to prepare a product. The evaluation was performed in the same manner as in Example 1. In a test of at least 8 hours / day × 24 days, no odor or eye irritation was observed in the exhaust gas after deodorization, and it was confirmed that the exhaust gas after long-term durability was durable.

Example 3 In the case of other paints As another evaluation example, an example in which a deodorization test of exhaust gas from a coating booth of a factory for coating metal with an alkyd resin paint was conducted was shown. There was a lot of mist in the exhaust air of the painting booth, and the clogging of the dust collection filter was large, so the evaluation was terminated in one week, but there was no problem with the deodorizing efficiency during that period. The exhaust air from the coating booth was low, and it was not necessary to introduce clean air to lower the temperature. There was no problem with the initial performance, and the test was continued for one week. Table 3 shows the measurement results of the final day of the test of 8 hours / day × 6 days that were actually operated.

As the evaluation apparatus, the apparatus having the basic structure shown in FIG. 1 was used, and the same small apparatus used in the acrylic resin factory experiment was used for evaluation. The water-cooled pipe installed before the activated carbon packed bed used in the acrylic resin factory experiment was not used because the exhaust gas temperature was low. The cross-sectional area of the device is 0.04
m ² , filling amount of hydrazine salt-supporting porous mineral foil is 2 k
g, and the filling amount of granular activated carbon was 1 kg. The gas flow rate in the deodorizing device was 0.2 m / sec, there were no problems such as flooding, and there were no problems such as nonuniformity of the packed bed. As the activated carbon and the dust collecting filter, commercially available products were used. The hydrazine salt-supporting porous mineral foil has a thickness of 0.5 m obtained by kneading zeolite fine powder with a mixed aqueous solution of aluminum sulfate and hydrazine.
m foil was rolled and molded. It was dried in a microwave oven, crushed, sieved through a 20 mm square and a 3 mm square mesh, and sized to prepare a product. Evaluation is Example 1
I went in the same way. In a test of at least 8 hours / day × 6 days, no odor or eye irritation was observed in the exhaust gas after deodorization, and it was confirmed that it had a deodorizing effect.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

According to the present invention, the bad odor of the coating exhaust gas can be removed inexpensively and reliably, and the maintenance of the apparatus can be easily performed. Further, it is also possible to deodorize exhaust gas in a printing plant, a woodworking plant, a food processing plant or the like, which is particularly problematic with aldehydes.

[Brief description of drawings]

FIG. 1 is a schematic view of a coating exhaust gas deodorizing apparatus of the present invention.

[Explanation of symbols]

 11 Paint Exhaust Gas Deodorizer 21 Paint Exhaust Gas 22 Cold Air 23 Exhaust Gas after Deodorization 31 Intake Port 32 Cool Air Intake Volume Control Valve 33 Suction Fan 41 Dust Collection Filter 42 Hydrazine Salt-Supporting Porous Mineral Foil 43 Granular Activated Carbon

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/81 // B05B 15/12 7310-4F B01D 53/34 117 A (72) Inventor Mukai Tatsuo 2-6-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (72) Inventor Katsumi Hirano 5-5-15 Nishinakajima, Yonagawa-ku, Osaka City Japan Paint Plant Engineering Co., Ltd. (72) Inventor Takahiro Yamato 5-5-15 Nishinakajima, Yodogawa-ku, Osaka Japan Paint Plant Engineering Co., Ltd.

Claims (3)

[Claims] 1. A collecting step of collecting exhaust gas generated in a coating step, a filtering step of removing fine particles from the exhaust gas by passing the exhaust gas collected in the collecting step through a filter, and the filtering step. And a step of contacting the exhaust gas from which the fine particles are removed with a porous mineral adsorbent carrying a hydrazine salt to remove a malodorous substance, and a deodorizing method for a coating exhaust gas. 2. A suction means for sucking the exhaust gas generated in the coating step, a dust collecting filter for removing fine particles from the exhaust gas sucked by the suction means, and a porous mineral adsorbent carrying hydrazine salts. A paint exhaust gas deodorizing device characterized by including and. 3. The coating according to claim 2, wherein the porous mineral adsorbent supporting hydrazine salts has a function of introducing cold air so that the temperature of the exhaust gas passing therethrough becomes 100 ° C. or lower. Exhaust gas deodorizer.