JPH074505B2 - Exhaust gas purification cylinder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas purifying column, and more specifically, to a gas containing a toxic component discharged from a semiconductor manufacturing process or the like by passing the gas through the gas. The present invention relates to a purification cylinder for exhaust gas for purification.

In recent years, with the development of the optoelectronics industry, which is a semiconductor manufacturing industry, the use amount of extremely toxic hydride gases such as arsine, phosphine, diborane, and hydrogen selenide has been increasing.

These toxic components are substances that are indeterminate as a raw material or a doving gas in the silicon semiconductor or compound semiconductor manufacturing industry or the optical fiber manufacturing industry.

In many cases, unreacted toxic components are contained in the exhaust gas discharged from the semiconductor process or the optical fiber manufacturing process. Each of these components is extremely toxic to living organisms, and the allowable concentration for occupational health is 0.05 ppm for arsine, 0.3 ppm for phosphine, and 0.1 pp for diborane.
m and hydrogen selenide are 0.05 ppm. Therefore, it is necessary to remove these toxic components prior to the emission of gas in order not to destroy the environment.

[Conventional technology and problems to be solved]

As a method of removing these toxic components, a method of removing the toxic components by passing a gas containing the toxic components through a purifying cylinder filled with an adsorbent is known.

For example, a method in which nitrates such as silver nitrate are supported on a porous carrier or those in which a metal chloride such as ferric chloride is impregnated into a porous carrier are used as an adsorbent (JP-A-56).
No. 89837), a method using three kinds of adsorbents obtained by impregnating an inorganic silicate with an alkali aqueous solution, an oxidizing agent aqueous solution or an alkaline and oxidizing agent aqueous solution (JP-A-59-4982).
No. 2) and a method using an adsorbent obtained by impregnating activated carbon with a copper compound and other metal compounds (JP-A-59-16).
No. 0535). However, the former two have the problem that the entire apparatus is complicated because it is necessary to pre-moisten the treated gas, and the latter has a problem that the removal capacity is relatively low and the air after absorbing arsine If you touch it, it will generate heat and the activated carbon may be ignited. Therefore, there are problems such as limited use conditions. In order to solve these problems in the prior art, the inventors of the present invention have disclosed in JP-A-61-209030 that (1) cupric oxide and (2) silicon oxide, aluminum oxide and zinc oxide. A method of using a purifying agent prepared by compounding and molding at least one metal oxide selected from the group consisting of:

This method is a completely dry method, and has an excellent feature that the maximum amount of toxic components removed per unit weight and unit volume (hereinafter referred to as the amount of saturation) of the cleaning agent is significantly larger than that of conventional cleaning agents. have. However, if a purifying cylinder filled with this purifying agent alone is used at a low temperature of, for example, 10 ° C. or lower, sufficient activity may not always be obtained depending on the conditions. That is, under the conditions of high load at low temperature, such as when such a purification column is used outdoors in winter, the purification column breaks in a relatively short time, and at the outlet of the purification column, a low concentration but toxic There is a problem that the component is detected.

[Means and actions for solving problems]

The present inventors have conducted extensive studies in order to further improve the method in JP-A-61-209030, and as a result, by adding manganese dioxide to the above components, the maximum removal amount per unit volume, that is, While finding that the amount of saturated purification decreases somewhat, it is found that a purifying agent that can rapidly and reliably remove toxic components even at low temperatures can be obtained.
The present invention has been completed, focusing on the use of this in combination with the purifying agent disclosed in JP-A-61-209030.

That is, the present invention is an exhaust gas purifying cylinder having a gas inlet and an outlet and filled with a purifying agent for purifying a gas containing one or more of arsine, phosphine, diborane and hydrogen selenide as toxic components. A first purification agent, which is a molded body of a composition of (1) cupric oxide and (2) at least one metal oxide selected from the group consisting of silicon dioxide, aluminum oxide and zinc oxide. On the gas inlet side, a composition of (1) cupric oxide, (2) manganese dioxide, and (3) at least one metal oxide selected from the group consisting of silicon dioxide, aluminum oxide and zinc oxide. The exhaust gas purifying cylinder is characterized in that a second purifying agent, which is a molded body, is filled in each of the gas outlet sides.

The exhaust gas purifying cylinder of the present invention is applied to purifying a gas containing nitrogen, hydrogen, argon, helium, air and the like, and one or more of arsine, phosphine, diborane and hydrogen selenide as toxic components.

The first purifying agent and the second purifying agent used in the present invention are different from mere absorption and adsorption, and the toxic components in the gas are fixed and removed to the purifying agent mainly by the chemical reaction with the purifying agent. It is a thing. Further, even if these purifying agents generate heat by contact with air after use, there is no risk of ignition and the safety is high.

In the present invention, the first is filled in the gas inlet side of the purifying cylinder
The purifying agents are (1) cupric oxide, and (2) silicon dioxide,
A purification agent which is a molded product of a composition of at least one metal oxide selected from the group consisting of aluminum oxide and zinc oxide, and has a purification rate at a low temperature slightly higher than that of the second purification agent described below. Although inferior, the amount of saturated purification is large.

On the other hand, the second purifying agent filled in the gas outlet side of the purifying cylinder is a purifying agent that is a molded body that further contains manganese dioxide as a component in addition to the components of the first purifying agent, and the saturation purification amount is the first purifying agent. However, it has a high purification rate and can reliably remove harmful components even at low temperatures.

The composition of the first purifying agent is usually 0.02 to 0.7, preferably 0.03 to 0.55 when expressed by the atomic ratio M / (M + Cu) of the metal. The composition of the second purifying agent is the atomic ratio of metal M / (M + Cu
+ Mn) is usually 0.02 to 0.7, preferably
The ratio of copper to manganese is usually 0.1 to 0.9, preferably 0.2 to 0.8 in terms of metal atomic ratio Cu / (Cu + Mn). In the above, Cu and Mn represent the numbers of atoms of copper and manganese, respectively, and M represents the number of atoms of silicon, aluminum or zinc (when these components are used at the same time, the total number of those atoms).

The cleaning agent can be prepared by various methods. Copper or zinc is oxidized by adding alkali salts such as caustic soda, caustic potassium, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate and ammonia to metal salts such as nitrates, sulfates, chlorides and organic acid salts. The intermediate product may be precipitated, and the resulting precipitate may be calcined to form an oxide of copper or zinc, which may be mixed with another metal oxide so as to have a specific composition, and molded. Is added as a precipitate to obtain a hydroxide or basic carbonate in the form of a mixture with other metal oxides so as to have a specific composition, and the mixture is baked in a molded state to oxidize copper or zinc. However, at least the second purifying agent is preferably prepared by the latter method using copper or zinc hydroxide or basic carbonate after molding and then firing. In this case, it is most preferable to use basic copper carbonate or a subsalt obtained by using sodium carbonate, potassium carbonate, sodium bicarbonate or potassium bicarbonate as the alkali.

Further, as the oxides of aluminum and silicon, for example, alumina sol and silica sol are used. These are sodium salts of mineral acid produced by neutralizing an aqueous solution of sodium aluminate or sodium silicate with mineral acid by electrodialysis. Can be obtained or a method of treating an aqueous solution of sodium aluminate and sodium silicate with a cation exchange resin.

Further, regarding manganese dioxide used as the second purifying agent, for example, a method of decomposing potassium permanganate in nitric acid, a method of oxidizing manganese sulfate with potassium permanganate,
Various methods such as a method of treating inert manganese dioxide with hot concentrated nitric acid can be used.

In addition, cupric oxide, basic copper carbonate, manganese dioxide, zinc oxide, basic lead carbonate, alumina sol and silica sol are commercially available in various varieties, so use one appropriately selected from them. Good.

If the size of the molded product is spherical, the diameter is about 2 mm to 12 mm,
If it is cylindrical, the diameter is 2 mm to 12 mm and the height is about 2 mm to 12 mm. Also, the density of the particles of the molded product is not particularly limited,
It is preferable to make the density of the second purifying agent smaller than that of the first purifying agent, and normally 1.5 to 3.5 g / m 2 for the first purifying agent.
It is preferable to use the first and second purifying agents that are molded to have a concentration of about 0.6 to 1.5 g / ml.

In the present invention, the first side is provided on the inlet side of a cylinder made of metal, quartz glass, hard plastic, etc., having a gas inlet and outlet.
The purifying agent is filled with the second purifying agent on the outlet side.
The ratio of the first purifying agent and the second purifying agent filled in the purifying cylinder differs depending on the flow rate of gas, the concentration of toxic components, the contact temperature between the purifying agent and the gas, etc., but cannot be specified unconditionally. From the viewpoint, it is preferable that the amount of the second purifying agent is smaller than that of the first purifying agent. Usually, the filling length of the second purifying agent is 2 to 40%, preferably the total filling length of the purifying agent. Is 5 to 30
%.

The size of the purifying cylinder is not particularly limited, but in practice, the inner diameter is usually 50 to 1,000 mm, and the purifying agent filling length is 200 to 2,000 mm.

In the present invention, it is preferable to provide a detection agent layer together with the purification agent layer in order to detect or predict breakthrough of the purification column due to a toxic component. The detection agent layer may be interposed between the first purification agent layer and the second purification agent layer or in the middle of the second purification agent layer, or may be provided in contact with the downstream side end of the second purification agent layer. Usually, it is preferable to interpose it in the middle of the second cleaning agent layer. For example, when the total filling length of the purifying agent and the detecting agent is 2,000 mm, the first purifying agent layer is 1,500 to 1,940 mm, the second purifying agent layer is 10 to 200 mm, and the detecting agent layer is in order from the gas inlet side to the outlet side. 20 to 100 mm and the second cleaning agent layer are filled in the range of 30 to 200 mm.

The shape of the purifying cylinder is usually a single cylinder, but it may be composed of a plurality of cylinders depending on the installation space or the like. For example, a first cylinder filled with the first purifying agent and a single cylinder. The second cylinder filled with the second purifying agent and the detecting agent may be connected in series with a pipe or the like.

The detection agent may be any as long as it can detect a toxic component in gas with high sensitivity, for example, obtained by supporting basic copper carbonate on a carrier as a discoloring component disclosed by the applicant in JP-A-61-296268. The detection agents that are suitable are common to arsine, phosphine, diborane, and hydrogen selenide and are preferable because they can be detected with high sensitivity.

There is no particular limitation on the concentration of the toxic component in the gas to be treated and the gas flow velocity applied to the exhaust gas purifying cylinder of the present invention,
Generally, the higher the concentration, the smaller the flow velocity. That is, the empty cylinder linear velocity at which exhaust gas passes through the purification cylinder is
When acm / sec and the concentration of the toxic component are b vol%, it is preferable to operate in the range of the following formula with the operation parameter as y.

0.0005 <y <200 However, under the condition that y = a × by is less than 0.0005, the size of the purification column becomes too large, which is economically disadvantageous. As it becomes larger, it becomes necessary to use a cooler or the like.

For example, when the gas to be treated is hydrogen-based, if the concentration of the toxic gas contained is 10% or more and the flow rate is 20 cm / sec or more, heat generation causes the reduction of the purifying agent by hydrogen and the activity is lost. In such a case, it is preferable to take measures such as cooling the purifying cylinder for operation.

The gas to be treated that can be applied to the purification column of the present invention is usually in a dry state, but even in a wet state, it does not have to be wet enough to cause dew condensation in the purification column.

The exhaust gas purifying cylinder of the present invention is usually used at room temperature to room temperature, but in practice, it has a sufficient ability at −20 to 100 ° C. and does not particularly require heating or cooling.

The pressure of the gas passed through the purification column may be normal pressure, reduced pressure, or increased pressure, but it is usually 20 kg / cm ² ahs or less, preferably 0.001 to 10 kg / cm ² ash.

Next, one example of the exhaust gas purifying cylinder of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a vertical sectional view of an exhaust gas purifying cylinder. In FIG. 1, a stainless steel cylindrical container 3 having a gas inlet 1 and a gas outlet 2 is seen from the top in order of a first layer 4 filled with a first purifying agent, and a first layer 4 filled with a second purifying agent. A second layer 5, a third layer 6 filled with a detecting agent, and a fourth layer 8 filled with a second purifying agent and the lower end of which is supported by a perforated plate 7 are respectively provided, and the third layer on the side surface of the container 3 is provided. A sight glass 9 made of tempered glass is provided at a corresponding position of the layer 6, that is, the detection agent layer, and serves as an exhaust gas purifying cylinder.

The purifying cylinder is used by connecting it to an exhaust gas exhaust pipe introduced from a semiconductor process or the like. A gas containing a toxic component introduced from a semiconductor process or the like through a pipe enters the purification layer from the gas inlet 1, and this gas first comes into contact with the first purification agent having a large saturated purification amount in the first layer 4. As a result, most of the toxic components in the gas are removed. However, under low temperature conditions such as in winter, the gas reaches the second layer 5 without being sufficiently purified, and by contacting the second purification agent having a high removal rate, the toxic components remaining in the gas are almost eliminated. Since it is completely removed, breakthrough in a short time is prevented. In this way, the gas is purified and further exits the outlet 2 via the third and fourth layers. With the passage of time, the amount of toxic components removed increases, the purifying agent approaches saturation, the first layer 4 and the second layer 5 break through, and the toxic components become third.
The sensing agent becomes colored when it begins to mix in the gas passing through layer 6. At this point, even if the toxic component passes through the detection agent layer,
It is not discharged to the outside because it is removed by the second purifying agent of the layer 8. By switching to another purification tube during this time,
It is possible to prevent the discharge of toxic components to the outside.

〔The invention's effect〕

Since the exhaust gas purifying column of the present invention is filled with the first purifying agent having a large amount of toxic components removed and the new second purifying agent having a large removal rate even at low temperature, it has a large purifying ability and is installed outdoors in winter. Excellent purification performance can be obtained even in cases such as when

Further, when the purifying cylinder of the present invention is used, no moistening treatment of the gas to be treated (treatment by a bubbler usually provided in front of the purifying cylinder) is required, and therefore, the gas is not provided on the upstream side of the vacuum pump for sucking the gas to be treated. A purification tube can be installed, in which case it is possible to process under reduced pressure. By doing so, the toxic components are removed before they pass through the vacuum pump, and the oil of the pump is not polluted by the toxic components, so that maintenance is facilitated.

〔Example〕

(1) Each component used for the purifying agent was prepared by the following method.

Cupric oxide; 20 wt% aqueous solution of copper sulfate and 20 wt% of sodium carbonate
% Aqueous solution until pH 9 to 10 was added to precipitate crystals of basic copper carbonate. This crystal was repeatedly filtered and washed to obtain basic copper carbonate. A part of this was used as a raw material for the second purifying agent, the rest was dried in air at 130 ° C, and then calcined at 300 ° C for 5 hours. Cupric oxide was used as a raw material for the first purifying agent.

Manganese dioxide: A 10 wt% aqueous solution of barium chlorate was mixed with a 10 wt% aqueous solution of manganese sulfate in a stoichiometric amount. After removing the precipitated barium sulfate by filtration, the solution is
Evaporation at 50 ° C. for 10 hours gave crude manganese dioxide. The crude manganese dioxide was stirred in hot concentrated nitric acid for 5 hours, washed with ion-exchanged water, and then dried at 120 ° C. for 5 hours to obtain active manganese dioxide.

Alumina sol; Cataloid-AS- manufactured by Catalyst Chemical Industry Co., Ltd.
2 was used.

Silica sol: Snowtex manufactured by Nissan Kagaku Co., Ltd. was used.

Zinc oxide; 20 wt% aqueous solution of zinc sulfate and 20 wt% of sodium carbonate
% Aqueous solution was added until the pH reached 9 to 10 to precipitate crystals of basic zinc carbonate. The crystals were filtered, washed, dried at 130 ° C., and calcined at 300 ° C. for 5 hours to obtain zinc oxide.

(2) Preparation of first purifying agent; (1) Cupric oxide, (2) Alumina sol, silica sol, and zinc oxide are mixed in a ratio of the atomic ratio M / (M + Cu) of predetermined metals, and kneaded with a kneader. After that, it is baked for 3 hours at 350 ° C, and then it is tableted to form pellets with a diameter of 5 mm and a length of 4 mm, and the grain density is about
Various first clarifiers with 2.55 g / ml and packing density of about 1.66 g / ml were prepared.

(3) Preparation of second purifying agent; (1) basic copper carbonate, (2)
Manganese dioxide, (3) alumina sol, and silica sol are each provided with a predetermined metal atom ratio M / (M + Cu + Mn) and Cu / (C
u + Mn), and after kneading with a kneader,
Various purifying agents having a diameter of 2 mm and a length of 3 to 10 mm and a packing density of about 0.67 g / ml were prepared by extrusion molding and then firing at 250 ° C. for 2 hours.

(4) Preparation of detection agent: A 20% by weight aqueous solution of sodium carbonate was added dropwise while stirring an aqueous solution of 20% copper sulfate to form a precipitate of basic copper carbonate. The precipitate was filtered, washed, and dried at 100 ° C. to obtain a basic copper carbonate powder showing blue color.

This powder was sprinkled on α-alumina having a specific surface area of 0.005 to 0.040 m ² / g (SA5218, Norton Co.) and supported (about 4 wt%) to prepare a detection agent.

(5) Purifying cylinder: The following purifying cylinder for exhaust gas was manufactured by filling the first purifying agent, the second purifying agent and the detecting agent in the same form as shown in FIG.

A cylinder with an inner diameter of 110.1 mm and a length of 800 mm, which is made of stainless steel and has a tempered glass viewing window on the side wall of the detection agent and a perforated plate for supporting the purification agent layer at the bottom, and a fourth layer in order from the bottom. The second purifying agent is 0.32 kg (filling length 50 mm), the third layer is detecting agent 0.39 kg (filling length 40 mm), the second purifying agent is 0.32 kg (filling length 50 mm) and the first layer is 4.1 kg of the first purifying agent (filling length 265 mm) was filled into each to make a purifying cylinder. In this way, the purification tubes filled with the cleaning agent as shown in Table 1 were manufactured.

(6) Measurement of purification capacity A purification tube was installed in the chamber at 5 ° C, and 0.5 to 1
Hydrogen or nitrogen containing 2% toxic components is circulated at 28.5 l / min (vacuum linear velocity 5 cm / sec), the time until the detection agent changes color, the amount of toxic components removed and the toxic gas at the purification cylinder outlet The time until detection was measured. To detect toxic components at the outlet of the purifying cylinder, an absorptiometer (HD-1 manufactured by Nippon Oxygen Co., Ltd.) based on the cold atomic absorption method of mercury is used, which allows the toxic components to be clearly confirmed. Concentration: 25 ppm for arsine, 3 for phosphine
The detection reference points were 1 ppm and 27 ppm for diborane. Also, for hydrogen selenide, the standard is not specified in the above measuring instruments, so the outlet gas was monitored using the same detection agent (detection limit 50 ppb) that was filled in the purification column. The results of each test are shown in Table 2.

As described above, the exhaust gas purifying cylinder of the present invention has an excellent purifying ability even at a low temperature such as 5 ° C.

[Comparative example]

Instead of filling the first purifying agent and the second purifying agent in combination,
Purifying agent (CuO + Al ₂ O ₃ ; atomic ratio of metal M / (M + Cu) = 0.0
7) Only or second purifying agent (CuO + MnO ₂ + Al ₂ O ₃ ; atomic ratio of metal M / (M + Cu + Mn) = 0.30, Cu / (Cu + Mn) = 0.42)
Purification cylinders similar to those of the example were manufactured except that only the first layer, the second layer, and the fourth layer were filled, and the purification ability of each was measured under the same conditions as described in the example. The respective results are shown in Table 3.

As described above, each of them has a smaller purification capacity than the purification column of the present invention.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an exhaust gas purifying cylinder of the present invention filled with a first purifying agent and a second purifying agent. The numbers in the drawings are as follows. 1 ... Gas inlet, 2 ... Gas outlet, 3 ... Container, 4 ... First
Layer, 5 ... Second layer, 6 ... Third layer, 8 ... Fourth layer, and 9 ...
Peep window

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 20/06 B 7202-4G B01D 53/34 ZAB

Claims (1)

[Claims] 1. An exhaust gas purifying cylinder having a gas inlet and outlet and filled with a purifying agent for purifying a gas containing one or more of arsine, phosphine, diborane and hydrogen selenide as toxic components. A first purification agent, which is a molded body of a composition of (1) cupric oxide and (2) at least one metal oxide selected from the group consisting of silicon dioxide, aluminum oxide and zinc oxide. On the gas inlet side, a composition of (1) cupric oxide, (2) manganese dioxide, and (3) at least one metal oxide selected from the group consisting of silicon dioxide, aluminum oxide and zinc oxide. An exhaust gas purifying cylinder characterized by being filled with a second purifying agent, which is a molded body, at each of the gas outlet sides.