JPH0716582B2 - Method for removing gaseous acidic halogen compounds - Google Patents

Description

The present invention relates to a process for the removal of gaseous acidic halogen compounds such as hydrogen fluoride and hydrogen chloride which, if released directly into the surrounding atmosphere, pose a hazard to the human body.

Among these harmful halogen compounds, some gaseous fluorine compounds, especially gaseous fluorides and chlorides, are suitable for the production of various halogen compounds containing elemental halogens such as chlorine and fluorine. Not only by-products, but also in the waste gas formed by many industrial processes. For example, the waste gas resulting from the plasma-etching method and the reactive ion etching method (usually abbreviated as RIE method) used in industrial manufacturing of semiconductors is carbon tetrafluoride (used as a gaseous etching agent). CF ₄ ) and fluoro-hydrocarbons (CxFyHz)
It is known to contain various gaseous acidic fluorine compounds formed by the decomposition of fluorocarbons (CxFy), especially acidic fluorides such as hydrogen fluoride. Further, it is known that when various glass products or metal products are washed with hydrochloric acid or hydrofluoric acid aqueous solution, waste gas containing a gaseous acidic halogen compound such as hydrogen chloride or hydrogen fluoride is produced. It is usually required to remove these harmful gaseous acidic halogen compounds.

In order to detoxify these gaseous acidic halogen compounds before releasing them into the air, the method of removing the gaseous acidic halogen compounds is usually by passing this gas through a shower scrubber, where the gas is washed. A method of washing with an enormous amount of a liquid as an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide is used.
This method is recommended not only for treating waste gases on a large scale, such as those produced in industrial processes for producing halogenated compounds, but also for treating the waste gases that may be produced by etching processes on a smaller scale. . Especially in the semiconductor industry, for example, “Gas utilization technology in the semiconductor industry and safety and health management technical data collection of working environment” (Showa era)
According to page 5 of Fuji Techno System Co., Ltd. (November 57), hydrogen fluoride-containing waste gas generated from the Puyazuma etching method or the RIE method (i) diluted with a large amount of nitrogen gas or abolished It is stated that it is necessary to pass (ii) through a tower scrubber or (iii) through a bubbler containing a neutralizing agent before being released into the air in order to remove halogenated compounds from the gas. ing.

Among the above three methods (i), (ii) and (iii) for treating the waste gas generated from the plasma-etching method or the RIE method, the method of diluting with waste gas nitrogen (i)
Is not a method of removing harmful fluorine compounds from waste gas, so it is meaningless to study. The other two methods, the Syawer scrubber method (ii) and the bubbler method (iii), necessarily use large amounts of water,
Requires large equipment. In particular, the Siwa scrubber method requires a considerable amount of power to operate the scrubber pump, and, in particular, harmful gaseous fluorine compounds at specific concentrations considered acceptable for the prevention of environmental pollution. (For example, it is stipulated by law that hydrogen fluoride should be removed up to the maximum allowable concentration of 3 ppm.) It is necessary to further increase the size. These deficiencies can always occur in the shower scrubber process. For manufacturers that manufacture halogen compounds commercially, it is important to install a large-scale device to treat waste gas innocuous because the large-scale device required for waste gas treatment is a halogen compound such as a fluorine compound. This is acceptable as it is only a fraction of the very large equipment for large scale production of compounds. However, the equipment for waste gas treatment to be used by users who only use halogen compounds must be compact, ie as small as possible but as efficient as possible.

The present inventors have made various studies to eliminate the drawbacks of the conventional method. Accordingly, it is an object of the present invention to provide a novel method capable of effectively removing a gaseous acidic halogen compound, particularly a gaseous acidic chlorine or fluorine compound such as hydrogen chloride or hydrogen fluoride, even when a compact and compact device is used. To provide a simple method.

As a result of various studies by the inventors, the solid adsorbent material containing a reactive group or a drug capable of chemically neutralizing the gaseous acidic halogen compound contains the gaseous acidic halogen compound. It was discovered that it is effective in removing it from waste gas.

Therefore, according to the present invention, by contacting a gaseous acidic halogen compound with at least one solid adsorbent containing a reactive group or a drug capable of chemically neutralizing the acidic halogen compound. Adsorbing a gaseous acidic halogen compound on the solid adsorbent and reacting with the reactive group or agent in the solid adsorbent, thereby converting the gaseous acidic halogen compound to a harmless non-gaseous halogen compound. In the method for removing a gaseous acidic halogen compound, the method comprises impregnating a concentrated aqueous solution of an alkali metal hydroxide as a solid adsorbent containing a chemical agent capable of chemically neutralizing the acidic halogen compound and then reducing the water content. Use asbestos mass compressed to the content and treat the gas to be treated in two or more separate beds or columns. Thus, there is provided a method for removing a gaseous acidic halogen compound, characterized by passing through a bed or column composed of different solid adsorbents, each of which contains said neutralizing group or neutralizing agent. It

Examples of solid adsorbents that can be used in the method of the present invention include asbestos and silica gel.

The solid adsorbent can be a porous synthetic resin made from a nonionic organic polymer such as a styrene-divinylbenzene copolymer. As a chemical agent capable of chemically neutralizing an acidic halogen compound, which is contained in the solid adsorbent, an alkali metal hydroxide such as an aqueous solution of a strong alkali such as sodium hydroxide or potassium hydroxide and an alkali metal hydrogen carbonate. Salts include weakly alkaline aqueous solutions such as sodium hydrogen carbonate. Suitable examples of solid adsorbents containing agents capable of chemically neutralizing acidic halogen compounds include solid adsorbents such as asbestos impregnated with an aqueous solution of alkali metal hydroxide, especially sodium hydroxide. Then, the impregnated adsorbent mass is compressed to allow excess alkaline aqueous solution to flow out of the adsorbent, and a certain amount of the alkaline aqueous solution is absorbed and / or adsorbed in the adsorbent mass.

The solid adsorbent containing a reactive group capable of chemically neutralizing an acidic halogen compound may be a porous synthetic resin containing a basic reactive group such as a quaternary ammonium group. For example, such a porous synthetic resin can be a basic anion exchange resin made from polystyrene or other condensation polymer containing a large number of basic reactive groups as functional anion exchange groups.

The adsorbent is preferably used in the form of granules or particles so that the contact area with the gas can be increased.

Used according to the present invention to simplify the description,
A solid adsorbent containing a reactive group or agent capable of chemically neutralizing an acidic halogen compound is hereinafter referred to as a "reactive adsorbent".

Gaseous acidic halogen compounds which can be removed by the reactive adsorbent in the process of the present invention are compounds which, when dissolved in water, give an acidic solution. This compound is a variety of halogenated compounds such as the following: chlorine compounds, especially chloride and chlorine gases such as hydrogen chloride (HCl) and fluorine compounds, especially fluorides, eg gaseous. Hydrogen Fluoride (HF); Elemental Fluorine Gas (F ₂ ); Silicon Chloride or Silicon Fluoride, eg SiCl ₄ and S
Silicon halides such as iF ₄ ; Chlorine oxides or Fluorine oxides, such as halogen oxides such as Cl ₂ O and F ₂ O;
Chlorinated / oxidized carbon and fluorinated / oxidized carbon, such as CF ₂ O, CO
Halogenated and carbon oxides such as F and CCl ₂ O.

The process of the invention is short enough to remove harmful halogen compounds to the desired level by passing the gaseous halogen compound or waste gas containing it through a single bed or column of reactive adsorbent only once. It is particularly applied when a large amount of cost is required, such as when it is too high or when the initial content of the gaseous acidic halogen compound in the waste gas to be treated is too high. The waste gas is continuously passed through two or more separate beds or columns consisting of two or more different reactive adsorbents. Thus, the use of multiple beds or columns of reactive adsorbent can significantly increase the extent of gaseous acid halide removal from waste gas.

In the process of the present invention, the gas to be treated is passed through a first bed or column of a first reactive adsorbent consisting of a solid adsorbent impregnated with an aqueous solution of a strong alkali such as sodium hydroxide, then Second anion exchange resin or second reactive adsorbent made of silica gel
Preferably through a bed or column. To be more effective, the method of the present invention comprises a first reactive adsorbent comprising a solid adsorbent impregnated with the gas to be treated with an aqueous solution of a weak alkali such as sodium carbonate or sodium hydrogen carbonate. Reactivity consisting of a solid adsorbent which is passed through a bed or column and then a second bed or column consisting of a basic anion exchange resin or silica gel, or alternatively the gas to be treated is impregnated with an aqueous solution of a strong alkali. A second reactive adsorbent comprising a solid adsorbent material that is the same as or different from the first solid adsorbent, passed through a first bed or column of adsorbent and then impregnated with an aqueous solution of a weak alkali. Of the basic anion exchange resin, and finally a third bed or column of basic anion exchange resin.

In the process of the invention, the gaseous acidic halogen compound to be removed is first adsorbed on a solid adsorbent material and then the compound is converted inside the adsorbent mass into a harmless non-gaseous halogen compound, whereby Extremely efficient removal of gaseous acidic halogen compounds. For example, when the method of the present invention is applied to the treatment of waste gas containing a gaseous acidic halogen compound, the halogenated compound is first adsorbed in the solid reactive adsorbent and may pass through the adsorbent mass. I can't
As a result, the gaseous acidic halogen compound is prevented from being released directly into the air. The gaseous acidic halogen compound adsorbed by the reactive adsorbent is then gradually chemically neutralized within the reactive adsorbent mass by the neutralizing agent or reactive group present in the adsorbent, resulting in , Hazardous gaseous acidic halogen compounds can be removed with high efficiency by a small volume of reactive adsorbents without the use of large equipment such as shower scrubbers that use huge amounts of water.

The amount of reactive adsorbent to be used in the process of the present invention will depend on the initial amount of gaseous halogen compounds to be removed, just to effectively and economically remove harmful halogen compounds. It can be appropriately selected according to the degree. The appropriate type and amount or volume of reactive adsorbent to be used can be readily determined by simple preliminary tests. If indicated as an indicator, a reactive adsorbent consisting of asbestos containing a strong alkali as a neutralizing agent, for example, an aqueous solution of sodium hydroxide, is a waste gas containing 1000 ppm or more of a gaseous acidic halogen compound such as a gaseous fluoride. Is suitable for removing the above halogen compounds from this waste gas until the content thereof reaches approximately 100 ppm, and the reactive adsorbent composed of asbestos containing a weak alkaline aqueous solution as a neutralizing agent is , 100p
It is suitable for treating waste gas containing gaseous acidic halogen compounds around pm, such as gaseous fluoride, and removing the above-mentioned halides from this waste gas until the content becomes about 20 to 30 ppm. Further, the reactive adsorbent composed of a basic anion exchange resin is a waste gas containing 100 ppm or less of a gaseous acidic halogen compound, for example, a gaseous fluoride, and the above halogen compound is removed from the waste gas. It has been empirically acknowledged that it is suitable for removal to a level normally accepted as being able to be tailored to prevent environmental pollution. When using a basic anion exchange resin, the gas to be treated is contacted with a reactive adsorbent that is cheaper than the anion exchange resin before reacting with the reactive adsorbent consisting of the anion exchange resin, resulting in the anion. It is economical and convenient to reduce the required amount of exchange resin or delay the depletion of anion exchange resin. In order to save the amount of the anion exchange resin used, for example, it is advantageous to use a reactive adsorbent containing a weak alkaline aqueous solution as a neutralizing agent together with a reactive adsorbent composed of a basic anion exchange resin.

The method of the present invention has the main advantage that gaseous acidic halogen compounds can be removed with high efficiency using relatively small amounts of solid reactive adsorbents; solid reactive adsorbents are easy to handle. And the solid reactive adsorbent once used is
Its relatively low usage allows it to be discarded and has the advantage that it can be regenerated in a simple manner for reuse if desired. In contrast, conventional methods of using shower scrubbers or bubblers necessarily require enormous amounts of wash water and / or water, and therefore various drawbacks resulting from the use of this enormous amount of liquid,
That is, large equipment and containers are required to handle large volumes of liquid, and complete or partial regeneration before discarding or recycling large volumes of used liquid or prior to discharge or disposal in a river. There are drawbacks such as encountering various difficulties in doing so.

For example, when using a shower scrubber that uses an alkaline aqueous solution as a cleaning solution to remove gaseous hydrogen fluoride from waste gas, the number of screen plates installed in the scrubber is much larger than the usual one. By doing so, hydrogen fluoride can be removed up to the maximum allowable concentration of 3 ppm. However, if the number of screen plates in the scrubber is increased, the amount of fine water droplets of the alkaline aqueous solution carried by the treated gas flowing out of the scrubber is increased, and as a result, the treated gas flowing out of the scrubber is removed. In order to remove fine water droplets of the alkaline aqueous solution, it is necessary to carry out the treatment again by the trapping cooler, and if this is not done, the second problem of environmental pollution due to alkali occurs. The increased number of screen plates in the scrubber and the use of trapping coolers have the disadvantage of increasing the size of the device and increasing installation costs.

Even when a large number of shower scrubbers are used in series, gaseous hydrogen fluoride can be removed from the waste gas up to the maximum allowable concentration of 3 ppm. However, in this case too, the same disadvantages as those mentioned for the above-mentioned method of increasing the number of screen plates in one shower scrubber arise.

On the other hand, although the solid reactive adsorbent used in the present invention is small, it shows a great effect in removing the above compounds from the waste gas containing the gaseous acidic halogen compound, and thus the small size Even the reactive adsorbent filled in the vessel is sufficient to carry out the purification treatment of the waste gas containing the gaseous halogen compound to be removed.

Examples of the present invention are shown below, but the present invention is not limited to these examples.

Example 1 This example uses the method of the present invention and is by-produced from a RIE process using carbon tetrafluoride (CF ₄ ) as the gaseous etching agent. And air and the following components: 8.3% by volume
Hydrogen (H ₂ , harmless), 35.6 vol% carbon tetrafluoride (CF ₄ , harmless), 1.6 vol% C ₂ F ₆ (harmless), 2.5 vol% C ₃ H ₈ (harmless), 5880ppm It is a mixture of carbon dioxide (CO ₂ , harmless), 230ppm carbon monoxide (CO) and 4500ppm hydrogen fluoride (HF, harmful), and also traces of silicon tetrafluoride (SiF ₄ , harmful), CF _{The following is} an example of treating waste gas containing 2O, COF (harmful) and other unidentifiable halides produced by decomposition of carbon tetrafluoride.

The extent of gaseous acid fluoride removal achieved in this example was evaluated by the removal of hydrogen fluoride measured by some analyzer. Although carbon monoxide (CO) is harmful to the human body in terms of its toxicity, it is not a gas intended to be removed by the method of the present invention.

A cylindrical pipe (inner diameter 52 mm, length 150 mm) was produced by impregnating asbestos lumps with a 90% aqueous sodium hydroxide solution, compressing until a low water content, and then dividing into granules, so-called 80g of reactive adsorbent consisting of "soda asbestos" was filled. Waste gas having the above composition was passed through a filled pipe containing the above "soda asbestos" at ambient temperature at a flow rate of 40 ml / min. The process gas flowing out of the pipe contained 100 ppm hydrogen fluoride as measured by the detector tube, indicating that the hydrogen fluoride was removed from 4500 ppm to 100 ppm. It is considered that the gaseous hydrogen fluoride was once adsorbed by the adsorbent and then neutralized by the reaction with the aqueous sodium hydroxide solution present in the asbestos as the solid adsorbent material.

The so-called "soda asbestos" mentioned above has a diameter of 2 to 3 mm.
It is a commercially available product in the form of granules.

Example 2 Monoazo type basic dye, metanil yellow To a solution of 0.1 g in 100 ml of water was added 350 g of silica gel, the resulting mixture was allowed to stand at ambient temperature for 1 hour and then dried at 190 ° C. for 90 minutes to charge 50 g of reactive adsorbent. Cylindrical adsorption pipe (diameter 52mm, length
The processing gas obtained in Example 1 and containing 100 ppm of hydrogen fluoride was passed through 150 mm). The further processed gas flowing out of the adsorption pipe is
It contained ppm hydrogen fluoride.

The basic dye present in the reactive adsorbent prepared by the above method can act as a neutralizing agent and when reacted with an acid the hue changes from orange to purple. Therefore, when the gas to be treated is introduced into the adsorption pipe, the reactive adsorbent is close to the inlet for introducing the gas,
It begins to turn purple in the upstream zone of the column. If all parts of the column of reactive adsorbent turned purple, this indicated that the reactive adsorbent was consumed, and thus it was time to replace the reactive adsorbent with a new one. Indicates.

Example 3 "Soda asbestos" 8 identical to that used in Example 1
0 g, 50 g of the same color-changing reactive adsorbent as prepared in Example 3 and 30 g of basic ion exchange resin "Duolite" A101, in this order, into a single cylindrical pipe (diameter 52 mm, 150 mm long) was carefully filled to form different zones or layers in the pipe without mixing different reactive adsorbent materials.

The same waste gas used in Example 1 was passed through the adsorption pipe prepared above from one end of the pipe in which the soda ashes zone was formed at a flow rate of 40 ml / min. The process gas flowing out from the other end of the pipe in which the "duolite" zone is formed contains 1 ppm of hydrogen fluoride, and hydrogen fluoride has a concentration of 4500 ppm. It was shown that it was removed up to the allowable level of 1 ppm, which is less than the maximum allowable concentration of 3 ppm. The treated gas thus obtained is clearly harmless and can be released into the air as it is.

Example 4 The same procedure as in Example 3 was repeated, except that a mixture of air and 1.98% by volume hydrogen fluoride (HF) was used as a sample gas. In the process gas flowing out from the adsorption pipe, the concentration of hydrogen fluoride was reduced to 1 ppm.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01D 53/34 ZAB

Claims (2)

[Claims] 1. A gaseous acidic halogen compound is brought into contact with at least one solid adsorbent containing a reactive group or a chemical capable of chemically neutralizing the acidic halogen compound, to thereby obtain a gaseous gaseous halogen compound. Adsorbing an acidic halogen compound on the solid adsorbent and reacting with the reactive group or agent in the solid adsorbent, thereby converting the gaseous acidic halogen compound to a harmless non-gaseous halogen compound. In the method for removing a gaseous acidic halogen compound, a solid adsorbent containing a chemical agent capable of chemically neutralizing the acidic halogen compound is impregnated with a concentrated aqueous solution of an alkali metal hydroxide and then a low water content is obtained. Using asbestos lumps compressed to a certain extent and using two or more separate beds or columns for the gas to be treated, S contains the neutralizing base or neutralizing agent, and wherein passing a bed or column in comprising different solid adsorbent, a method for removing the gaseous acidic halide. 2. A method according to claim 1 wherein the second bed or column comprises a basic anion exchange resin or silica gel.