JP6687822B1 - Method and system for treating volatile organic compounds - Google Patents

Abstract

When an organic solvent containing a highly flammable flammable solvent is concentrated and burned, there is a risk of ignition at the time of concentrating. A step of adsorbing a raw gas containing a volatile organic compound to a catalyst, reforming and releasing a part of the raw gas with the catalyst, and passing steam through the catalyst to remove an adsorbed component of the catalyst from the catalyst. A method for treating a volatile organic compound, which comprises a step of desorbing and a step of burning a mixed gas of the adsorbing component and the vapor, desorbs the adsorbing component of the catalyst together with the vapor from the catalyst, so that ignition occurs. The danger of is reduced.

Description

  The present invention relates to a treatment method and a system for carrying out the method, in which a powder and an organic solvent are made into a slurry state and an organic solvent used as a binder is a flammable volatile organic compound in a manufacturing process of a multilayer ceramic capacitor. Is. In particular, a mixed solvent of mineral spirits and terpineol is vaporized in the manufacturing process and has a pungent odor. It can be suitably used when treating the exhaust gas including deodorization.

  Among organic compounds, volatile organic compounds (hereinafter referred to as “organic solvent”) are used in various fields (for example, Patent Document 1) and have a useful effect. However, the organic solvent is finally volatilized. Then, the discharged organic solvent has a large environmental load with respect to the natural environment.

  On the other hand, the “Environmental Standard” is set in the Basic Environmental Law as a standard that should be maintained in order to protect human health and preserve the living environment. Air pollution is set with the goal of achieving this environmental standard. Regulations are implemented based on the Prevention Law. The Air Pollution Control Act stipulates emission standards for volatile organic compounds.

  Mineral spirit is an organic solvent and has an irritating odor, but is used for dissolving various solutes. For example, as in the case described in the present invention, it can be used for screen printing in the manufacturing process of a laminated ceramic capacitor. Further, when it has an offset printing step, it is used in combination with a high boiling point solvent.

  This mineral spirit, except for some components such as benzene, does not have a clear detailed component content. However, it is necessary to perform a final treatment as an organic solvent (VOC) by burning or the like and release it to the natural world at an emission standard value or less.

  In order to treat an organic solvent having such an irritating odor, a method of adsorbing, concentrating, and burning is used. For the adsorption, a concentrating device such as a porous material such as activated carbon, a chelating material, a wet scrubber, or a honeycomb rotor concentrating device (Patent Document 2) is used. In this method, a raw gas containing an organic solvent is passed through a rotor containing an adsorbent (for example, zeolite), the organic solvent is adsorbed by the adsorbent, and it is desorbed and recovered using dry hot air.

  When such a concentrating device is used, even a raw gas having a low content of organic solvent is desorbed after being concentrated by a concentrator, so that a gas to be treated having a high content concentration can be obtained, which is efficient. Combustion disposal can be performed.

JP, 2005-160952, A JP, 2016-159233, A

  However, when an organic solvent containing a highly flammable substance (hereinafter referred to as "flammable solvent") is treated, there is a problem in that, if the concentration is carried out by a concentrating device, it is ignited for some reason. For example, Mineral Spirit is a mixed solvent of petroleum hydrocarbons (Terpen / Mineral Spirit) equivalent to JIS Industrial Gasoline No. 4 and corresponds to the Class 3 organic solvent of the Organic Solvent Poisoning Prevention Regulations (Occupational Safety and Health Act). The characteristics of the flammable solvent are that it has an irritating odor, has a low flash point (43 ° C.), an upper limit of explosion limit of 0.6 Vol% and an upper limit of explosion limit of 8.0 Vol%. Mineral spirits are a mixture of several ingredients, not all of which have been identified. However, trimethylbenzene and nonane are the main raw materials. Therefore, there is also a problem that the odor is strong.

  The present invention has been conceived in view of the above problems, and is a method for treating a volatile organic compound that can concentrate and treat a raw gas containing a flammable solvent without fear of ignition.

Specifically, the method for treating a volatile organic compound according to the present invention,
Adsorbing a raw gas containing a volatile organic compound on a catalyst, and reforming and releasing a part of the raw gas with the catalyst,
Passing vapor through the catalyst to desorb the adsorbed components of the catalyst from the catalyst;
A step of burning a mixed gas of the adsorption component and the vapor,
The volatile organic compound is a mixed solvent of mineral spirits and terpineol,
The catalyst is formed of alumina, and the catalyst modifies trimethylbenzene and nonane into harmless substances .

  In the method for treating a volatile organic compound according to the present invention, the volatile organic compound in the raw gas is adsorbed on the catalyst to concentrate the volatile organic compound. Then, when desorbing the adsorbed component adsorbed on the catalyst, desorption is performed using high temperature steam. Therefore, the adsorbed component desorbed from the catalyst is a mixed gas with vapor. This mixed gas is a gas that is difficult to ignite because the amount of heat is absorbed by the moisture in the surrounding steam as heat of vaporization. Since this mixed gas is sent to the combustion device as it is for combustion, the volatile organic compounds in the raw gas can be concentrated and the volatile organic compounds can be burned without fear of ignition.

  Further, the raw gas that cannot be completely adsorbed by the catalyst is partially or wholly reformed by the catalyst into harmless organic matter and then released. Therefore, the residual amount of the volatile organic compound in the raw gas in the released gas is reduced by the amount of the reformed gas, and the residual amount of the volatile organic compound in the raw gas in the atmospheric release can be sufficiently reduced. .

  In particular, trimethylbenzene and nonane, which are the cause of the irritating odor in the raw gas, are converted into other substances by the modification, and the irritating odor of the released gas is reduced to an unnoticeable level.

It is a figure which shows the structure of the volatile organic compound processing system which implement | achieves the processing method of the volatile organic compound which concerns on this invention. It is a figure which shows the internal structure of a reformer. It is a graph which shows the measurement result of the odor sensor of the discharge gas B which left the reformer. It is a figure which shows the result investigated by the gas chromatograph mass spectrometry (TD-GC / MS method) of the discharge gas B which left the reformer.

  The method for treating a volatile organic compound according to the present invention will be described below. The following description describes one embodiment of the present invention, and the present invention is not limited to the following description. The following embodiments can be modified without departing from the spirit of the present invention.

  The flammable solvent (volatile organic compound) to be treated in the present invention has a flash point of 40 ° C to 50 ° C. A raw gas containing 10% by mass to 40% by mass of a flammable solvent is a suitable processing target. When the concentration of the flammable solvent is high, it is not necessary to concentrate the raw gas, and the raw gas may be burned as it is. Further, if the content ratio of the flammable solvent is small, there is no fear of ignition in the first place, and the concentrated gas may be obtained as in the prior art.

  Next, the manufacturing process of the monolithic ceramic capacitor according to the present invention will be briefly described. A plurality of ceramic green sheets containing a ceramic material powder containing Ba and Ti as main components are prepared, and a conductive paste containing Ni as a main component of a conductive component is applied to the ceramic green sheets by screen printing.

  In this screen printing process, a mineral paste, which is an organic solvent, is used to form a conductive paste film serving as an internal electrode. At this time, the mineral spirit, which is a flammable solvent, has a role as a conductive paste, but volatilizes and is collected in an exhaust duct in a factory (hereinafter also referred to as “on-site”).

  Further, in the manufacturing process of the laminated ceramic capacitor, the ceramic green sheets on which the conductive paste film is not formed are laminated so as to have a predetermined outer layer thickness. Next, a predetermined number of ceramic green sheets having the conductive paste film formed thereon are stacked. Further, by stacking the ceramic green sheets on which no conductive paste is formed so as to have a predetermined outer layer thickness, a mother block in a raw state from which a plurality of component bodies can be taken out is obtained.

  This mother block is cut, a plurality of chip-shaped parts are taken out, and these parts are fired in a batch furnace in a reducing atmosphere to obtain sintered chip-shaped parts. Also during this firing, the mineral spirit which is the solvent in the conductive paste is evaporated and collected in the exhaust duct.

  On the other hand, a mixture of copper powder having an average particle size of about 1.0 μm, an organic solvent containing terpineol as a main component with respect to the glass frit, and a mixture containing a varnish in which an acrylic binder is dissolved in this organic solvent, The conductive paste for external electrodes is prepared in advance by dispersing and mixing this.

  The conductive paste for external electrodes is formed into a film with a predetermined thickness. After immersing the end of the above-mentioned chip-shaped component held by the holder in this conductive paste film, the conductive paste serving as an external electrode is applied to both end faces of the component body by taking out from the conductive paste film. . In this process, terpineol produces volatile components, which are collected in the exhaust duct.

  Next, in order to bake the conductive paste to be the external electrodes, the component body is heat-treated in a furnace and kept at a temperature of about 900 ° C. for 10 minutes. Then, the temperature is lowered to obtain a monolithic ceramic capacitor. During this heat treatment, terpineol in the conductive paste for external electrodes is evaporated and collected in an exhaust duct.

  Thus, the exhaust gas containing mineral spirits (flash point: 43 ° C.) and terpineol (flash point: 82 ° C.) is mixed in the exhaust duct. This is called “raw gas A”. Even in this mixed state, the vaporized gas of mineral spirit is flammable. Therefore, the raw gas A having high flammability is safely treated by the method for treating a volatile organic compound according to the present invention. Thus, the volatile organic compounds in raw gas A include mineral spirits and terpineol.

  In the method for treating a volatile organic compound of the present invention, the volatile organic compound in the raw gas A is adsorbed on the catalyst and the flammable solvent is adsorbed on the catalyst to be removed. At this time, the volatile organic compounds are concentrated on the catalyst. Then, some volatile organic compounds are modified.

  The adsorbed component C adsorbed on the catalyst is desorbed from the catalyst with steam. This steam is called regeneration steam R in the sense that it regenerates the catalyst. The adsorption component C contains a volatile organic compound and a harmless substance modified with a catalyst as described later. Here, the harmless substance is a substance having low flammability and strong odor, and even if the flammability and the odor are not confirmed, it is sufficient if the substance can be burned without causing a problem such as ignition.

  Since the adsorbed component C is desorbed from the catalyst by the regenerating steam R, a large amount of mist-like water is present in the surroundings when desorbed. Therefore, if there is a rapid increase in the amount of heat, it will easily evaporate and take away the amount of heat. That is, the waste mixed gas D of the adsorbed component C and the regeneration vapor R is a gas that is difficult to ignite. In this way, even if the solvent is flammable, it can be safely treated by once adsorbing it on the catalyst and desorbing it with steam. The waste mixed gas D is burned in the combustion device as it is.

  On the other hand, some volatile organic compounds of the raw gas A cannot be completely adsorbed by the catalyst. Even if there is a volatile organic compound that cannot be completely adsorbed, it can be released into the atmosphere as a safe gas if the concentration is below the specified level. Therefore, in the method for treating a volatile organic compound of the present invention, a catalyst is used for adsorption, and the volatile organic compound that could not be adsorbed is reformed to be converted into an odorless and harmless substance and then released.

  Explaining in a more specific example, it is assumed that the amount of the volatile organic compound that is not completely absorbed by the catalyst (this amount is referred to as “unabsorbed amount”) is M. Of course, this M is a small amount in view of the total amount of the volatile organic compounds in the raw gas A, and most of the volatile organic compounds are adsorbed by the catalyst. Therefore, even if all of the unabsorbed amount is the volatile organic compound, the amount is less than the specified amount.

  More specifically, assuming that 50% of the unabsorbed amount becomes a harmless gas reformed with a catalyst, the unabsorbed amount of the volatile organic compound relative to the total amount of the volatile organic compound in the raw gas A is: It can be M / 2. In this way, by using the catalyst as the adsorbent of the volatile organic compound in the raw gas A, the residual amount of the volatile organic compound in the gas that has passed through the catalyst can be reduced. The gas that has passed through the catalyst is called "release gas B". The release gas B can be released into the atmosphere as it is.

  The catalyst for adsorption and reforming is not particularly limited. A single substance, a mixture, or an alloy of typical catalytic substances such as platinum, ruthenium, palladium, rhodium, alumina and manganese can be used. The catalyst is only required to be able to modify at least a part of the flammable solvent so that the substance has a higher flash point. This is because it suffices if ignition in the concentration step can be suppressed.

  In particular, in the raw gas A containing mineral spirits and terpineol as volatile organic compounds, a honeycomb shape of alumina can be preferably used as a catalyst.

  The reason is that the honeycomb shape of alumina and the honeycomb shape of manganese are effective as a metal having a catalytic function without raising the temperature of the catalyst surface. Platinum and palladium do not activate their catalytic functions unless the surface temperature of the catalyst is raised. On the other hand, alumina and manganese can be reformed at a catalyst surface temperature of 180 ° C. or higher and 300 ° C. or lower by utilizing a chemical reaction (oxidation action) with air in exhaust gas.

It has long been known that alumina (γ-Al ₂ O ₃ ) has a high activity for the dehydration reaction of alcohol. Alumina is used not only for dehydration of alcohols but also for elimination of polar molecules, isomerization of hydrocarbons, and hydrogen exchange reaction. Alumina can also be suitably used for the isomerization (reduction of molecular weight) of hydrocarbons in the mixed solvent this time.

  FIG. 1 shows the configuration of a volatile organic compound treatment system 1 for carrying out the volatile organic compound treatment method according to the present invention. At the site 10, the mixed solvent in which the medium is dissolved is evaporated to become the raw gas A. The raw gas A is specifically a mixed gas containing mineral spirits and terpineol. The site 10 communicates with the reformer 20 and the reformer 22 via a duct or the like. A blower 31 for supplying wind pressure may be provided on the way.

  Further, the raw gas A may be provided with a cold air mixer 34 for mixing the outside air Wc. This is to prevent the temperature from rising when the raw gas A flows into the reforming device 20 and the reforming device 22 and to reduce the concentration of the raw gas A per volume. A cooler may be provided in the duct through which the raw gas A is blown. The coolers may be provided individually in the reformer 20 and the reformer 22. These are called cooling means for cooling the raw gas A. By cooling the raw gas A, it is possible to make it difficult to catch fire when the raw gas A is absorbed and concentrated by the catalyst.

  A switching device 41 is arranged on the site 10 side of the reformer 20 and the reformer 22. The switching device 41 may be a motor damper or a valve. A switching device 42 is provided on the outlet side of the reformer 20 and the reformer 22. The switching device 42 may be a motor damper or a valve. The movements of the switching device 41 and the switching device 42 are interlocked. That is, the raw gas A is passed through either the reforming device 20 or the reforming device 22 and is discharged as the discharge gas B. In addition, three or more reformers may be provided. In that case, the portions of the switching device 41 and the switching device 42 are further branched, and the raw gas A is sent to any of the reforming devices and released as the release gas B.

  The reforming device 20 and the reforming device 22 are containers filled with a catalyst, and are connected to a steam supply source 18 for supplying a catalyst regeneration steam R. Further, a valve 43 is arranged between the steam supply source 18 and the reformer 20 and the reformer 22, so that the regeneration steam R can be supplied to either the reformer 20 or the reformer 22.

  FIG. 2 shows the internal structure of the reformer 20 (the reformer 22 may have the same structure). 2A shows a state where the raw gas A is being reformed, and FIG. 2B shows a state where the catalyst 26 is being regenerated. A catalyst 26 is filled in the reformer 20. An inlet 23i for the raw gas A is formed below the reformer 20, and an outlet 23o for the released gas B is provided above the reformer 20.

  Further, a jet port 24 i of the regeneration steam R is formed in the upper portion of the inner surface of the reformer 20. Further, a discharge port 24o is provided below the reformer 20.

  Referring again to FIG. 1, the emission gas B is emitted to the atmosphere from the emission ports 23o of the reformer 20 and the reformer 22. Further, the outlets 24o of the reformer 20 and the reformer 22 communicate with the combustion device 16. The exhaust gas from the combustion device 16 is directly discharged to the atmosphere.

  The operation of the volatile organic compound processing system 1 having the above configuration will be described with reference to FIGS. 1 and 2. The raw gas A generated at the site 10 is sent to the reformer 20 (or the reformer 22) in the subsequent stage by the blower 31. At this time, the raw gas A may be cooled by adding cold air Wc to the raw gas A or cooling the duct.

  The volatile organic compound in the raw gas A introduced into the reformer 20 through the intake port 23i is adsorbed to the catalyst 26 by passing between the catalysts 26. In addition, a part of the gas is reformed to change the structure of the substance, resulting in a high flash point and odorless and harmless gas. The raw gas A that has passed through the catalyst 26 becomes the released gas B. The discharge gas B is composed of air, a volatile organic compound, and a modified volatile organic compound. The volatile organic compound and the modified volatile organic compound become a sufficiently small amount (amount equal to or less than the emission reference value) with respect to the emission gas B. The release gas B is released as it is.

  All the volatile organic compounds in the raw gas A that have passed through the catalyst 26 are not adsorbed, and some pass through the catalyst 26 depending on the state of the catalyst 26. However, by partially modifying it, the substantial amount of volatile organic compounds emitted can be reduced.

  Next, the reformer 22 will be described. Since the catalyst 26 in the reforming device 20 and the reforming device 22 is a porous body, it also performs an adsorption action as well as a catalytic action. Therefore, the volatile organic compound in the raw gas A is adsorbed by the catalyst 26 by this adsorption action. As a result, the surface of the catalyst 26 is covered and the catalytic action is hindered.

  Therefore, the reforming device 20 and the reforming device 22 are replaced at regular intervals, and the reforming device whose surface of the catalyst 26 is covered is desorbed by the regeneration steam R from the surface of the catalyst 26 to remove the adsorbed component C. Let go. Switching between the reforming device 20 and the reforming device 22 is performed by the switching device 41 and the switching device 42 that operate in conjunction with each other. Further, the switching of the switching device may be switched at regular intervals, or may be switched depending on the concentration of the flammable solvent in the discharge gas B by providing an organic sensor at the discharge port 23o.

  With reference to FIG. 2B, the regeneration steam R supplied from the steam supply source 18 is blown onto the catalyst 26 from the ejection port 24i to desorb the adsorbed component on the surface of the catalyst 26. The desorbed adsorbent component C becomes a waste mixed gas D in which vapor and adsorbent component C are mixed and is discharged from the discharge port 24o. Since mist is present in the vapor in the waste mixed gas D, the amount of heat is easily absorbed and it is difficult to catch fire. Therefore, even if the concentrated volatile organic compound remains in the adsorbent component C, it can be desorbed and discharged without fear of ignition.

  The reformer from which the adsorbed component C on the surface of the catalyst 26 is removed is replaced after the surface of the catalyst 26 of the other reformer is covered with the solvent component by use. That is, the treatment of the volatile organic compound can be continuously continued. Note that the waste mixed gas D is sent to the combustion device 16 and burned.

  As described above, in the volatile organic compound treatment system 1 according to the present invention, a plurality of reformers are prepared, and when the catalytic function deteriorates, the reformer is replaced with a new reformer to maintain the treatment capacity. The replaced reformer catalyst is regenerated separately and used again.

  The effects of the volatile organic substance treatment method and treatment system according to the present invention will be described below with reference to examples.

Processing amount of released gas B of about 45 m ³ / min using the processing system having the configuration of FIGS. 1 and 2 (when the exhaust duct is 50 cm × 50 cm and the surface wind velocity of the processing device is 3.0 m / sec) Is. By increasing the surface wind speed to 3.0 m / sec and triple the wind speed rather than the commonly used 1.0 m / sec, the time taken for the exhaust gas to be sent to the reformer can be shortened.

  FIG. 3 shows the measurement results of the odor sensor, showing the results of the raw gas A and the released gas B that has exited the reformer 20. Since the released gas B was measured at two different positions, it was indicated by the symbols B1 and B2. The horizontal axis represents elapsed time (days), and the vertical axis represents the count value of the odor sensor.

  If the count is 500 or less, even if the air is released to the atmosphere as it is, no odor will be felt at a distance of 50 m or more from the system. In the state of original gas A, a pungent odor is felt even if the distance from the system is more than 200 m.

  As shown in FIG. 3, by using the processing system according to the present invention, irritating odor can be removed from the released gas B. Raw gas A is a mixed gas of mineral spirits and terpineol. Among these, trimethylbenzene and nonane are considered to be the main causes of the pungent odor. That is, from the result of FIG. 3, it is considered that the treatment system significantly reduces trimethylbenzene and nonane in the released gas B.

  Further, since terpineol is contained in a large amount in the steam regeneration gas at the time of regeneration of the catalyst, it is easily adsorbed to the catalyst, mixed and diluted at the time of steam regeneration, and the pungent odor is also reduced.

  In FIG. 4, the result of having investigated the released gas B by the gas chromatograph mass spectrometry (TD-GC / MS method) is shown. FIG. 4A shows the result of the released gas B, and FIG. 4B shows the result of the inspection of the waste mixed gas D accompanied by the regeneration vapor R and the adsorbed component C. In the figure, trimethylbenzene is indicated by a triangle (▲), nonane is indicated by a square (■), and terpineol is indicated by a circle (●).

  With reference to FIG. 4A, trimethylbenzene, nonane, and terpineol are detected in the released gas B. These are the components of the raw gas A that have passed through the reformer 20. Although trimethylbenzene and nonane, which cause odor, remain, the results shown in FIG. 3 indicate that if the leakage is to this extent, it may be released into the atmosphere as it is, and the concentration is below the so-called specified value.

  On the other hand, referring to FIG. 4B, terpineol was detected in the waste mixed gas D, but trimethylbenzene and nonane were not present. Since the raw gas A has a strong irritating odor, it is considered that a large amount of trimethylbenzene and nonane are present. In the released gas B, trimethylbenzene and nonane remained only to the extent that no odor could be detected. Then, the remaining trimethylbenzene and nonane are considered to be trapped in the reformer 20, but did not exist in the waste mixed gas D.

  That is, it is considered that the trimethylbenzene and nonane captured by the reforming device 20 were reformed into other substances. It is considered that the substance X surrounded by a dotted line in FIG. These are substances (peaks) that were not originally contained in the raw gas A. Although the substance X is not specified, it can be said to be a harmless substance because it burns with terpineol without any problem.

The method for treating a volatile organic compound according to the present invention can be suitably used for concentrating a solvent having a low flash point.

1 Volatile Organic Compound Treatment System 10 Site 16 Combustor 18 Steam Supply Source 20 Reformer 22 Reformer 23i Inlet 23o Outlet 24i Jet 24o Outlet 26 Catalyst 31 Blower 41 Switch 42 Switch 43 Valve A Raw gas B Released gas D Waste mixed gas R Regeneration steam

Claims (5)

Adsorbing a raw gas containing a volatile organic compound on a catalyst, and reforming and releasing a part of the raw gas with the catalyst,
Passing vapor through the catalyst to desorb the adsorbed components of the catalyst from the catalyst;
A step of burning a mixed gas of the adsorption component and the vapor,
The volatile organic compound is a mixed solvent of mineral spirits and terpineol,
The method for treating a volatile organic compound is characterized in that the catalyst is formed of alumina, and the catalyst modifies trimethylbenzene and nonane into harmless substances .   The method for treating a volatile organic compound according to claim 1, further comprising the step of cooling the raw gas before contacting the raw gas with the catalyst. A reforming device for adsorbing a raw gas containing a volatile organic compound on a catalyst and reforming and releasing a part of the raw gas by the catalyst,
Regeneration steam supply device for supplying steam to the catalyst in the reformer, and desorbing adsorbed components of the catalyst from the catalyst,
A combustion device for burning the waste mixed gas of the adsorption component and the vapor,
The volatile organic compound is a mixed solvent of mineral spirits and terpineol,
The treatment system for a volatile organic compound, wherein the catalyst is formed of alumina, and the reformer reforms trimethylbenzene and nonane into harmless substances . The volatile organic compound treatment system according to claim 3 , further comprising a plurality of the reformers, and a switching device that switches the reformers. Processing system of claim 3 or volatile organic compounds according to any one of 4, characterized in that it comprises a cooling means for cooling prior to adsorbing the raw gas to the catalyst.

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