JP6908820B2 - Formic acid treatment method and formic acid treatment equipment - Google Patents

Description

The present invention relates to a method and an apparatus for detoxifying a gas containing formic acid vapor by a dry treatment.

Formic acid is used in a wide range of fields such as agriculture, textile industry, synthetic organic chemistry, and semiconductor device manufacturing. In recent years, in vacuum reflow soldering equipment, a method using formic acid for reducing oxides on the solder surface has been developed and is rapidly developing. Generally, the exhaust of a vacuum reflow soldering device contains 1% by volume or more of formic acid. However, formic acid vapor is harmful to the eyes and skin, and the recommended permissible exposure concentration (TLV) is 5 volume ppm. Therefore, the gas containing formic acid vapor needs to be detoxified before being discharged to the atmosphere. Further, in order to prevent the corrosion of pipes due to formic acid and the prevention of foul odors in the surrounding environment, it has been required to further reduce the concentration of formic acid in the exhaust gas, for example, 0.5 volume ppm or less.

Until now, as a method for treating the vapor of formic acid in the exhaust, a method of circulating it in a burner for combustion aggravation, a method of heating in the presence of a catalyst for thermal decomposition treatment, and a method of performing thermal decomposition treatment at 200 ° C. or higher without using a catalyst. There is a method of thermal decomposition treatment by heating (Patent Document 1), but all of them require a large-scale device, which hinders a small-scale business operator from introducing a vacuum reflow soldering device.

Further, as a method for treating formic acid vapor, there is also a method in which exhaust gas containing formic acid vapor is brought into contact with water or alcohol to dissolve formic acid for wet treatment (Patent Document 2). Furthermore, if the concentration of formic acid in the aqueous solution exceeds 90% by mass, it is classified as a deleterious substance, and therefore the handling of waste liquid may be restricted, which is also not suitable for small businesses.

As an easy-to-handle acid gas abatement method, a dry treatment method using adsorption to a solid is known. For example, hydroxides of alkali metals and alkaline earth metals are widely used as a dry treatment method for acidic gases such as sulfur oxides and hydrogen chloride, and calcium hydroxide is mainly used because of its cost and ease of handling. It is used (Patent Document 3). Examples of treatment targets for halogen-based gas and acid gas include an adsorbent made of granulated material of slaked lime (Patent Document 4), and a mixture of soda lime, zeolite and activated carbon for treatment of oxidizing gas and acid gas. Examples thereof include a treatment agent made of the granulated material (Patent Document 5). In Patent Document 5, formic acid vapor is treated in Examples and Comparative Examples, but not below TLV. Further, the concentration of formic acid vapor in the gas is treated from 100 ppm to 10 ppm by using activated carbon containing _{K 2} CO _{3 (Patent Document 6).}

For the solid material used in the dry treatment, the acid gas contained in the gas is fixed by physical adsorption or chemical adsorption and removed from the gas. Physical adsorption is a state in which acid gas is adsorbed on a solid material by van der Waals force, and the bond is relatively weak, and adsorption / desorption occurs reversibly by controlling temperature and pressure. Chemisorption is a state in which an acid gas is adsorbed by a chemical reaction with a solid material, and the bond is strong, and it is difficult to desorb the once adsorbed gas.

JP-A-2007-125578 Japanese Unexamined Patent Publication No. 2001-244618 Japanese Unexamined Patent Publication No. 2002-029738 Japanese Unexamined Patent Publication No. 2005-177576 Japanese Unexamined Patent Publication No. 2004-181300 Japanese Unexamined Patent Publication No. 9-86914

However, as a result of examining various existing treatment agents, the present inventors have found that the amount of formic acid treated in the exhaust gas is not sufficient, or the concentration of formic acid in the exhaust gas is reduced to 0.5 volume ppm or less. There was a problem that it was difficult.

When only calcium hydroxide is used as an exhaust gas treatment agent as described in Patent Documents 3 and 4, formic acid is sufficiently adsorbed when a gas containing a high concentration of formic acid having a concentration of several volume% is circulated. However, the phenomenon that the adsorbent was immediately broken was observed.

Further, when a treatment agent containing a combination of activated carbon and soda lime as described in Patent Document 5 was used, formic acid could be adsorbed to some extent when a gas containing a high concentration of formic acid was circulated. The concentration of formic acid in the exhaust gas after that exceeded 0.5 volume ppm.

The present invention is a dry treatment method for formic acid, which can treat a large amount of formic acid as compared with a conventional treatment agent even through a gas containing vapor of formic acid, and can reduce the concentration of formic acid after treatment to 0.5 volume ppm or less. The purpose is to provide.

As a result of intensive research to solve the above problems, the present inventors first treated the gas containing formic acid vapor with a treatment agent using a carbonaceous adsorbent and calcium hydroxide in combination, and then subjected to porous adsorption. The present invention was completed by finding that the amount of treatment per unit volume of the treatment agent can be increased and formic acid can be removed to a formic acid concentration of 0.5 volume ppm or less by performing the secondary treatment using the agent. I came to let you.

That is, the present invention is a treatment method for removing formic acid from a gas containing formic acid, wherein the formic acid contained in the gas is treated with a first treatment agent containing a carbonaceous adsorbent and calcium hydroxide. Provided is a method for treating formic acid, which comprises one treatment step and a second treatment step of further treating the gas after the first treatment step with a porous adsorbent.

INDUSTRIAL APPLICABILITY The present invention provides a dry treatment method for formic acid, which can treat a large amount of formic acid as compared with a conventional treatment agent and can reduce the concentration of formic acid to 0.5 volume ppm or less even through a gas containing vapor of formic acid. be able to.

It is a figure which shows the formic acid processing apparatus 1 which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a formic acid treatment apparatus 11 according to the present invention. The formic acid treatment device 11 has a first treatment unit 13 that treats the exhaust gas from the formic acid-using device 17, and a second treatment unit 15 that further treats the gas treated by the first treatment unit 13. The first treatment unit 13 and the second treatment unit 15 are composed of a treatment agent-filled container having a gas inlet and a gas outlet, respectively.

The concentration of formic acid contained in the exhaust gas treated by the formic acid treatment apparatus 11 is not particularly limited, but usually exceeds at least 5 volume ppm, which is TLV. Further, the formic acid treatment apparatus 11 can deal with a gas having a formic acid concentration of 1% by volume or more. On the other hand, the concentration of formic acid contained in the exhaust gas treated by the formic acid treatment apparatus 11 is usually considered to be 10% by volume or less. However, according to the method of the present invention, the upper limit is not particularly limited, and practically, it may be about 20% by volume.
The exhaust gas treated by the formic acid treatment apparatus 11 is not 100% formic acid vapor but a gas containing a predetermined concentration of formic acid. The gases other than formic acid that make up the exhaust gas are not only air, but also inert gases such as nitrogen gas, argon gas, neon gas, and helium gas, reducing gases such as hydrogen gas and carbon monoxide gas, and a mixture thereof. It is possible that it was done.

In the first treatment unit 13, the exhaust gas comes into contact with the first treatment agent, and formic acid in the exhaust gas is removed by the first treatment agent. For example, the first treatment unit 13 is a tubular reactor or the like in which the first treatment agent is filled. In addition, a stirring blade or a baffle plate may be provided in the first processing unit 13 to make the gas uniform.

The first processing unit and the second processing unit do not need to be particularly heated. Further, in the first treatment section and the second treatment section, the temperature of the exhaust gas introduced is preferably 0 to 100 ° C., and is usually around room temperature.

The first treatment agent contains a carbonaceous adsorbent and calcium hydroxide. The carbonaceous adsorbent is not particularly limited as long as it is a porous carbon material, but its BET specific surface area ^{is preferably 500 m 2} / g or more, more preferably 1000 m ² / g or more, and 1500 m ² It is more preferably / g. For example, activated carbon can be used as the carbonaceous adsorbent. As the activated carbon, an activated carbon containing a metal component, a so-called metal-impregnated activated carbon, can be used. For example, an activated carbon impregnated with copper oxide and zinc oxide can be used. The metal-impregnated activated carbon has a metal or a compound thereof attached to the surface of the activated carbon, and the concentration of the metal with respect to the activated carbon is about 1 to 10% by mass in terms of metal.

As the first treatment agent, it is preferable to use soda lime as a material containing calcium hydroxide. Soda lime, also called soda lime, is a material containing calcium hydroxide as a main component, alkali metal hydroxide and water. The soda lime preferably contains 50% by mass or more of calcium hydroxide, and more preferably 70% by mass or more. As the soda lime, powdery or granular soda lime having a particle size of 100 μm to 5 mm and a specific surface area of ^{about 1 to 100 m 2} / g can be used.

The form of the first treatment agent is not particularly limited as long as it contains both calcium hydroxide and a carbonaceous adsorbent, and a mixed product of calcium hydroxide and a carbonaceous adsorbent can be used. The ratio of calcium hydroxide to carbonaceous adsorbent contained in the first treatment agent is preferably calcium hydroxide: carbonaceous adsorbent = 1: 0.1 to 0.5 in terms of mass ratio, preferably 1: 0. .2 to 0.4 is more preferable.

In the first treatment step, by using calcium hydroxide and a carbon adsorbent in combination, a large amount of formic acid can be treated as compared with using calcium hydroxide and a carbon adsorbent alone. Calcium hydroxide reacts with formic acid to generate calcium formate, which can fix formic acid to the treatment agent. Only calcium could be used effectively. Further, the carbonaceous adsorbent can retain gaseous formic acid in the pores by physical adsorption, but the amount of adsorption per unit volume is less than that of calcium hydroxide which can be fixed as calcium formate. By using calcium hydroxide and a carbonaceous adsorbent together, the carbonic acid adsorbent with a high adsorption rate first adsorbs formic acid, and then calcium hydroxide fixes the formic acid gradually released from the carbonic acid adsorbent. It is considered that a large amount of formic acid can be adsorbed.

In addition, since calcium hydroxide chemically adsorbs formic acid and fixes it as calcium formate, it does not release formic acid even in the air after use, and formic acid is removed from the used treatment agent during the treatment agent replacement work. Does not leak. Further, since calcium hydroxide does not deteriorate its adsorption capacity even if it absorbs moisture, there is no problem even if the inlet gas contains moisture or if it absorbs moisture in the environment.

In the second treatment unit 15, the outlet gas of the first treatment unit 13 comes into contact with the porous adsorbent, and formic acid in the outlet gas is removed by the porous adsorbent. For example, the second processing unit 15 is a tubular reactor or the like filled with a porous adsorbent. In addition, a stirring blade or a baffle plate may be provided in the second processing unit 15 so as to make the composition of the gas uniform.

The porous adsorbent is not particularly limited as long as it is a porous material capable of physically adsorbing formic acid and having a high specific surface area, but a carbonic adsorbent or an inorganic adsorbent can be used. Activated carbon, zeolite, and silica gel can be used.

The zeolite and silica gel that can be used as the porous adsorbent ^{preferably have a BET specific surface area of 100 m 2} / g or more, more preferably 200 m ² / g or more, and more preferably 300 m ² / g or more. More preferred. For example, as the zeolite, zeolite having various structures such as A type, B type, X type, and Y type can be used. When zeolite is used, a pH indicator may be added to the zeolite. The pH of the zeolite can be visually confirmed and the replacement time can be confirmed by the discoloration of the pH indicator due to the adsorption of formic acid.

The activated carbon used as the porous adsorbent preferably has a BET specific surface area of 500 m ² / g or more, more preferably 1000 m ² / g or more, and further preferably 1500 m ² / g. As the activated carbon, an activated carbon impregnated with a metal component, for example, an activated carbon impregnated with copper oxide and zinc oxide can be used so as to easily adsorb formic acid, which is an acid gas. The metal-impregnated activated carbon has a metal or a compound thereof attached to the surface of the activated carbon, and the concentration of the metal with respect to the activated carbon is about 1 to 10% by mass in terms of metal.

Since the second treatment unit 15 treats formic acid by utilizing physical adsorption capable of adsorbing formic acid at a high speed even if the concentration of formic acid is low, the formic acid can be reduced to 0.5 volume ppm or less. Further, since the concentration of formic acid in the outlet gas of the first treatment unit 13 is lowered to the ppm level, even if carbon monoxide derived from formic acid is generated in the second treatment unit 15, the amount is very small. No particular problem occurs. Further, the porous adsorbent of the second treatment unit 15 only needs to adsorb a small amount of formic acid, and the adsorbing ability can be maintained for a long period of time.

The shape of both the first treatment agent used in the first treatment unit 13 and the porous adsorbent used in the second treatment unit 15 is not particularly limited, and the shape is not particularly limited, and the pellet form is granulated in either powder or granular form. It may be.

Further, since the formic acid treatment apparatus 11 processes the gas containing the vapor of formic acid in a dry manner, it does not require a heat source required for combustion abatement or catalyst heating abatement, which saves energy and makes the apparatus smaller. It is possible. Further, the treatment agent used is an inexpensive material that is generally used, it is not necessary to use an expensive precious metal catalyst or the like, the formic acid treatment apparatus 11 is inexpensive, and the running cost is also low. Is.

Although only one first processing unit 13 and one second processing unit 15 are provided in the apparatus in FIG. 1, a plurality of each may be provided. When there are a plurality of gas, the gas may be circulated to the plurality at the same time, and even when one is exchanged, the gas is circulated to the other so that the processing is not interrupted.

The formic acid-using device 17 is not particularly limited as long as it is a device that uses formic acid for some treatment and contains formic acid in the exhaust gas, but is a vacuum reflow soldering device that uses formic acid as a gas for reducing the oxide on the solder surface. It is preferable to have. As the gas used in the vacuum reflow soldering device, use an inert gas such as nitrogen gas, argon gas, neon gas, or helium gas, or formic acid diluted with a reducing gas such as hydrogen gas or carbon monoxide gas. Can be done. Further, in addition to formic acid, the gas may contain carboxylic acids such as acetic acid, propionic acid and butyric acid, and alcohols such as methanol and ethanol.

In addition to the exhaust gas of the formic acid-using device 17, the formic acid treatment device 11 removes formic acid from a gas in which formic acid generated unintendedly as a by-product or the like is mixed, or formic acid is added to the gas used for some purpose. It can also be used to remove formic acid from the gas if it gets mixed.

Hereinafter, the present invention will be described in more detail with reference to Reference Examples and Examples, but the scope of the present invention is not limited to the following Examples.

First, the present inventors performed Reference Examples 1 to 11 in order to investigate the formic acid adsorption ability of a general treatment agent.

[Reference Examples 1 to 6]
A stainless steel pipe having an outer diameter of 1 inch was filled with a treatment agent at a filling height of 200 mm. A treatment gas having a formic acid concentration of 5% by volume diluted with nitrogen gas was circulated there at a rate of 1 L / min. The formic acid concentration in the outlet gas was monitored, the treatment was terminated when the volume exceeded 5 volume ppm, the treatment time from the start of the treatment to the end of the treatment was measured, and the amount of formic acid treated was calculated. The results are shown in Table 1.

Zeolite A: X type, cation = Ca, shape = 1.5 mmΦ, pellet-shaped moisture-absorbing zeolite A: Zeolite A with 25% by mass of water added
Soda lime: 79% by mass of calcium hydroxide, 2% by mass of potassium hydroxide, 1% by mass of sodium hydroxide, other water)
Dried soda lime: The above-mentioned soda lime is dried to reduce the water content to 1% by mass or less. Activated carbon A: Granular activated carbon, crushed, particle size = 8 to 24 mesh (2.36 mm to 0.7 mm)
Soda lime with activated carbon: Soda lime containing 20% by mass of powdered activated carbon, pelletized

In Reference Example 1 in which zeolite was used as the treatment agent, a certain degree of formic acid treatment ability was exhibited. The carbon monoxide in the outlet gas was less than the permissible exposure concentration of 25 parts by volume ppm. However, assuming that the exhaust gas of the vacuum reflow soldering apparatus contains moisture or absorbs moisture in the atmosphere, in Reference Example 2 using the hygroscopic zeolite A, formic acid could hardly be treated. From the above, it is considered that when zeolite alone is used as a formic acid treatment agent, it is vulnerable to moisture and is not suitable for the purpose of treating the exhaust gas of a vacuum reflow soldering device.

In Reference Example 3 using soda lime, the expected formic acid processing capacity was not obtained. Analysis of the treatment agent after the treatment revealed that calcium formate was produced, but calcium hydroxide also remained. On the other hand, in Reference Example 4 in which soda lime was dried and used, formic acid could hardly be treated, and it was found that soda lime was vulnerable to drying. When the gas is circulated, the water content in the soda lime may evaporate and the soda lime may be dried. Therefore, when the soda lime alone is used, the treatment may not be possible due to the drying.

In Reference Example 5 using activated carbon, a larger amount of formic acid could be treated than with zeolite or soda lime, but carbon monoxide of 25% by volume or more was detected in the outlet gas. It is considered that carbon monoxide was generated by the reduction of formic acid by the carbon constituting the activated carbon and the decomposition of formic acid (for example, HCOOH → CO + H _{2 O) by the catalytic effect of a trace amount of metal impurities contained in the activated carbon.} Be done. In addition, since activated carbon adsorbs formic acid by physical adsorption, there is a problem that formic acid may be released due to changes in the environment, and formic acid may leak out when the temperature changes or the treatment agent is replaced. .. Therefore, when activated carbon is used as the first treatment section, it is necessary to treat carbon monoxide in the second treatment section, and the activated carbon breaks down relatively quickly, so it is necessary to replace it frequently. It ends up.

In Reference Example 6 using soda lime containing activated carbon, a large amount of formic acid could be treated as compared with Reference Examples 1 to 5 having the same volume. However, 0.5 to 4 parts by volume of formic acid remained in the outlet gas, and it was difficult to obtain an outlet gas having a formic acid concentration of less than 0.5 parts by volume. In order to further reduce the formic acid concentration, we decided to search for a second-stage treatment method.

[Reference Examples 7 to 11]
A treatment agent was placed in a stainless steel pipe having an outer diameter of 1/2 inch with a filling height of 40 mm. A treatment gas having a formic acid concentration of 0.2% by volume diluted with nitrogen gas was circulated there at a rate of 10 L / min. The formic acid concentration in the outlet gas was monitored, the treatment was terminated when the volume exceeded 5 volume ppm, the treatment time from the start of the treatment to the end of the treatment was measured, and the amount of formic acid treated was calculated. The results are shown in Table 2.

Zeolite A: X type, cation = Ca, shape = 1.5 mmΦ, pellet form Zeolite B: X type, cation = Na, shape = 1.6 mmΦ, pellet form Zeolite C: pH indicator (bromocresol) for zeolite B Green) is added.
Activated carbon A: Granular activated carbon, crushed, particle size = 8 to 24 mesh (2.36 mm to 0.7 mm)
Moisture-absorbing activated carbon: 20% by mass of water added to the above activated carbon A.

In Reference Examples 7 to 11, since the outlet gas of the first treatment section was assumed and the gas having a formic acid concentration of 0.2% by volume was introduced, both the zeolite and each activated carbon exhibited a certain level of adsorption capacity. In addition, each outlet gas was initially 0.5 volume ppm or less. Further, in Reference Example 9, a pH indicator was added, but formic acid can be treated without any particular problem, and when the formic acid concentration of the outlet gas exceeds 5 parts by volume ppm, the zeolite is already discolored and the pH is changed. It was possible to confirm visually.

[Examples 1 to 3 and Comparative Examples 1 to 4]
Formic acid was treated with the treatment agents shown in Table 3 in the first treatment section and the second treatment section.
As the first treatment section, a treatment agent was placed in a stainless steel pipe having an outer diameter of 1 inch with a filling height of 200 mm. Further, as the second processing portion, a processing agent was put into a stainless steel pipe having an outer diameter of 1/2 inch with a filling height of 40 mm. A treatment gas having a formic acid concentration of 5% by volume diluted with nitrogen gas was circulated through the first treatment section at a rate of 1 L / min. The outlet gas of the first treatment section is circulated to the second treatment section, the formic acid concentration of the outlet gas of the second treatment section is monitored, the treatment time at the time when it exceeds 0.5 volume ppm is measured, and 5 volume ppm is further measured. The treatment was terminated when the above amount was exceeded, and the amount of formic acid processed was calculated from the treatment time from the start of the treatment to the end of the treatment. The results are shown in Table 3.

Activated carbon-containing soda lime: Soda lime containing 20% by mass of powdered activated carbon, pelletized dry activated carbon-containing soda lime: The above-mentioned activated carbon-containing soda lime dried to a water content of 1% by mass or less Activated carbon A: Granular activated carbon, crushed , Particle size = 8 to 24 mesh (2.36 mm to 0.7 mm)
Zeolite A: X type, cation = Ca, shape = 1.5 mmΦ, pelletized soda lime: calcium hydroxide 79% by mass, potassium hydroxide 2% by mass, sodium hydroxide 1% by mass, other moisture)

[Example 4]
Formic acid treatment was carried out in the same manner as in Example 1 except that a gas having a formic acid concentration of 5% by volume diluted with hydrogen gas was used as the treatment gas.

As shown in Table 3, in Examples 1 to 3, by combining the first treatment with soda lime containing activated carbon and the second treatment with zeolite or activated carbon, only soda lime containing activated carbon was used in both the first treatment and the second treatment. Compared with Comparative Example 1, the processable time can be extended by 5 volumes ppm or less even with the same volume, a large amount of formic acid can be processed, and a clean outlet gas having a fore acid concentration of 0.5 volume ppm or less can be obtained for a long period of time. Was done.

Further, in Comparative Examples 2 and 4, since both the first treatment and the second treatment were treated with activated carbon or zeolite utilizing physical adsorption, it was possible to treat up to 0.5 volume ppm or less, but the treatment agent having the same volume. In spite of the use of, the foric acid concentration of the outlet gas exceeded 0.5 volume ppm in a short period of time, and the processable time was 5 volume ppm or less, which was shorter than that of Examples 1 to 3, and the processable amount. Was few. Further, in Comparative Example 2, it was confirmed that carbon monoxide was produced by contacting high-concentration formic acid with activated carbon.

Further, in Comparative Example 1 and Comparative Example 3, since soda lime containing activated carbon and soda lime that utilize chemisorption are used in both the first treatment and the second treatment, foric acid is added to a low concentration of 0.5 volume ppm or less. Since the treatment could not be performed, the treatment time of 0.5 volume ppm or less was 0 minutes.

Therefore, in Comparative Example 5 in which the first treatment with activated carbon and the second treatment with soda lime containing activated carbon were combined, the formic acid concentration of the outlet gas exceeded 0.5 volume ppm in a short period of time, unlike Examples 1 to 3. In addition, the processable time of 5 volumes ppm or less was short, and the processable amount was small. In addition, it was confirmed that carbon monoxide was produced when high-concentration formic acid came into contact with activated carbon.

The soda lime containing activated carbon used in Examples and Comparative Examples contains powdered activated carbon, but since the proportion of activated carbon is as small as 20% by mass, chemical adsorption is dominant over physical adsorption by activated carbon. In No. 1, it is considered that the formic acid could not be treated to a low concentration of 0.5 volume ppm or less.

In Example 4 in which the diluting gas of formic acid was hydrogen, the same formic acid treatment as in Example 1 in which the diluting gas was nitrogen could be performed.

11 Formic acid treatment equipment 13 First treatment unit 15 Second treatment unit 17 Formic acid treatment equipment

Claims (7)

A treatment method for removing formic acid from a gas containing 1% by volume or more of formic acid to reduce the formic acid concentration to 0.5% by volume or less.
Formic acid contained in the gas is fixed as calcium formate using a first treatment agent in which calcium hydroxide and activated carbon are used in a mass ratio of calcium hydroxide: activated carbon = 1: 0.1 to 0.5. The first processing process to be performed and
A second treatment step of adsorbing formic acid in the gas after the first treatment step using a porous adsorbent composed of activated carbon, zeolite, or silica gel.
Processing method of formic acid, characterized that you have a. The method for treating formic acid according to claim 1 , wherein the activated carbon contained in the first treatment agent is a metal-impregnated activated carbon. Wherein the first treatment agent, treatment method formic acid according to claim 1 or 2, characterized in that the activated charcoal soda lime. The method for treating formic acid according to any one of claims 1 to 3, wherein the activated carbon used in the second treatment step is a metal-impregnated activated carbon. The method for treating formic acid according to any one of claims 1 to 3, wherein the zeolite used in the second treatment step is a zeolite containing a pH indicator. Exhaust containing 1% by volume or more of formic acid is supplied from the device using formic acid, and has a first treatment agent in which calcium hydroxide and activated carbon are used in combination in a mass ratio of calcium hydroxide: activated carbon = 1: 0.1 to 0.5. First processing unit and
The outlet gas of the first treatment section is supplied, and the second treatment section having a porous adsorbent made of activated carbon, zeolite, or silica gel, and the second treatment section.
Have,
A device for treating formic acid in an exhaust gas that removes formic acid from the exhaust gas to reduce the formic acid concentration to 0.5 volume ppm or less. The formic acid processing apparatus according to claim 6 , which is provided in the vacuum reflow soldering apparatus.

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