JP3080687B2 - How to concentrate chlorine gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrating chlorine using a pressure swing adsorption method.

[0002]

BACKGROUND OF THE INVENTION Chlorine is a very important industrial intermediate and is used in many chemical industries, and there are facilities for chlorine separation in various places.

Conventionally, as a method for separating chlorine from a mixed gas containing chlorine, a method in which a gas is pressurized and cooled to form liquid chlorine and separated from the gas, or a method in which a chlorine-based organic solvent is used to absorb chlorine is used. A method of separating chlorine by ripping is known. However, the former method uses a high-pressure gas, and therefore requires a gas compressor and a refrigeration facility, which are expensive and troublesome for maintenance, especially when separating chlorine from a gas having a relatively low chlorine concentration. Operation at high pressure or cryogenic temperature increases equipment costs. In the latter method, carbon tetrachloride is usually used as a solvent. However, the use of carbon tetrachloride has been banned due to environmental problems caused by recent chlorofluorocarbon gas, and cannot be said to be an effective method in the future.

[0004]

One of the methods for separating chlorine from a mixed gas containing chlorine is a pressure swing adsorption method. Adsorbents used in this separation method include zeolites, non-zeolitic porous acidic oxides, activated carbon, and molecular sieve carbon. However, at present, chlorine concentration cannot be obtained because of insufficient chlorine selectivity. The present invention performs improvement of adsorbent used in the pressure swing adsorption method, chlorine and
It is to separate and concentrate chlorine more selectively than a mixed gas containing carbon dioxide .

[0005]

Means for Solving the Problems One of the means used as a method for separating chlorine gas is a pressure swing adsorption method. Adsorbents used in this separation method include zeolites, non-zeolitic porous acidic oxides, activated carbon, and molecular sieve carbon. However, at present, there is a problem in chlorine selectivity. Therefore, the present inventors diligently studied whether it is possible to more selectively separate and concentrate chlorine by improving the adsorbent used in the pressure swing adsorption method, and from Ca, Ba, Li The present inventors have found that it is possible to more selectively separate chlorine by including the selected alkali metal and / or alkaline earth metal in the adsorbent, and have reached the present invention.

[0006] The mixed gas containing chlorine to which the method of the present invention is applied includes at least dioxide as a gas other than chlorine.
Contains carbon, oxygen, nitrogen, carbon monoxide, hydrogen,
Hydrocarbons such as argon and methane may be present,
In order to separate chlorine from gases containing these by the pressure swing adsorption method, it is necessary to select one having a sufficiently different adsorption affinity between these gases and the adsorbent as compared with chlorine. Therefore, as the chlorine adsorbent used in the present invention,
Synthetic and natural zeolites bets are selected.

For example, as zeolites, type A, X
Type, Y type, L type, ZSM type, natural mordenite, etc., preferably X type, Y type, L type, ZSM type, and more preferably zeolite containing high silicon.
And particularly preferably zeolite of the Y type and / or the 13X type.
It is.

[0008] The method of the present invention comprises the step of adding Ca,
A material containing an alkali metal ion or an alkaline earth metal ion selected from Ba and Li is used. The method for containing these ions in the adsorbent is an ordinary method, that is, an aqueous solution of a salt of a metal ion to be introduced is brought into contact with the adsorbent, followed by solid-liquid separation, washing, and removal of attached water (drying). Originally, chlorine has a stronger affinity for the above-mentioned adsorbent that does not contain ions than the above-mentioned gas, but the adsorbent containing ions has the ability to further improve the affinity for chlorine. Have.

Since chlorine has a stronger affinity for these ion-containing adsorbents than the above-mentioned gases, a mixed gas containing chlorine is introduced into an adsorption tower filled with these adsorbents. Then, chlorine is adsorbed preferentially over other gases, so that a gas having a low chlorine concentration can be obtained on the gas outlet side of the adsorption tower to such an extent that it is sometimes hardly detected.

The chlorine concentration of the mixed gas containing chlorine adsorbed by the adsorbent is not particularly limited, but usually a chlorine concentration of 5 to 80% is applied. When the chlorine concentration is low, the adsorption time until the regeneration operation by desorption can be long. The operation pressure of this adsorption operation is set to be higher than that of the subsequent chlorine desorption operation. The operating temperature is determined by the type of zeolite to be charged, the type of gas other than chlorine contained in the introduced gas, and economical problems. For example, when Y-type zeolite is used as the adsorbent and carbon dioxide is mixed in the accompanying gas, sufficient chlorine adsorption can be performed even at around normal temperature. On the other hand, in order to prevent the deterioration of the packing material and the material of the equipment, the moisture in the raw material gas is preferably low, and is preferably 1000 ppm or less.

When the adsorption of chlorine into the adsorption tower progresses and the state approaches a saturated state, the supply of the mixed gas containing chlorine as a raw material to the adsorption tower is stopped. Subsequently, the operating pressure of the adsorption tower is lowered to desorb adsorbed chlorine and other gases. At this time, the operation pressure is set to be equal to or lower than the pressure at the time of adsorption, and if necessary, it is also effective to set the pressure to equal to or lower than the atmospheric pressure by using a vacuum pump.

Although the operating temperature is arbitrary, it is basically more economical to set the same temperature as the temperature at the time of adsorption. Of course, if economically effective, a so-called thermal swing method can be adopted. Further, it is a preferable embodiment that a small amount of inert gas, preferably nitrogen gas, is passed during the desorption operation because the desorption of chlorine gas from the adsorbent is promoted.

By this desorption operation, a gas having a higher chlorine concentration than the introduced gas can be obtained, and the adsorbent which has adsorbed chlorine can be regenerated because it is dechlorinated, and the next adsorption operation is repeated. Can be.

Next, the state of implementation in a more specific form on an industrial scale will be described. FIG. 1 shows the configuration.

In FIG. 1, a mixed raw material gas containing chlorine and carbon dioxide is sent from a pipe 1 to a gas compressor 2, where the pressure is raised to a predetermined pressure, and then, through a switching valve 3, three adsorption towers 4a. , 4b and 4c are sent to the first adsorption tower 4a. Each of the three adsorption towers 4a, 4b, and 4c is filled with an adsorbent that preferentially adsorbs the above-mentioned chlorine, and preferentially adsorbs chlorine in the source gas introduced in a pressurized state. At the outlet of the adsorption tower 4a, a gas having a low chlorine content, and sometimes a gas having a chlorine concentration low enough to be hardly detectable (hereinafter referred to as a treated gas) is obtained. The dechlorinated gas is sent to the blower 7 via the switching valve 5 and the valve 6 and discharged (adsorption step).

At this time, in the second adsorption tower 4b, a part of the treated gas discharged from the first adsorption tower 4a is introduced into the second adsorption tower 4b via the flow rate adjusting mechanism 8 and the switching valve 9. In the third adsorption tower 4c, a vacuum pump 10 is connected to the inside of the tower via switching valves 11 and 12a, and a pressure step of increasing the pressure by the treated gas is performed in the tower. A regeneration step is performed in which the adsorbent in the inside is regenerated under reduced pressure.

In the adsorption tower 4a, which has reached a point of saturation by adsorbing a predetermined amount of chlorine, the introduction of the raw material gas is stopped by switching the switching valve 3, and the inside of the tower is switched by the switching of the switching valve 13 to a vacuum pump. The gas is exhausted in step 10 to be in a reduced pressure state, the chlorine adsorbed on the adsorbent is desorbed, and the adsorbent is regenerated (regeneration step). In this regeneration step, a gas having a high chlorine concentration as a product can be obtained from the discharge port of the vacuum pump 10, and the gas containing a high concentration of chlorine is sent to a downstream consumption step.

At this time, in the second adsorption tower 4b, the raw material gas is introduced through the switching valve 14, the treated gas is discharged from the outlet of this tower, and sent to the blower 7 through the switching valve 15 and the valve 6, Further sent to the consumption process. Also, the third adsorption tower 4c
In the above, a part of the treated gas discharged from the second adsorption tower 4b is introduced through the flow rate adjusting mechanism 8 and the switching valve 16, and the pressure in the tower is increased by the treated gas. I have. Thereafter, in the third adsorption tower 4c, the switching valve 17
The raw material gas is introduced through the
It is sent to the blower 7 via the valve 6 and discharged. At the same time, in the first adsorption tower 4a, a part of the treated gas discharged from the third adsorption tower 4c is introduced through the flow rate adjusting mechanism 8 and the switching valve 19, and the pressure in the tower is reduced. A pressure-increasing step is carried out.

At this time, in the second adsorption tower 4b, the switching valve 14
The introduction of the source gas is stopped by switching
By switching the switching valve 20, the inside of the tower is evacuated by the vacuum pump 10 to be in a decompressed state, the chlorine adsorbed by the adsorbent is desorbed, and the adsorbent is regenerated.

In the same manner, by repeating this series of operations alternately for the three adsorption towers 4a, 4b, and 4c, chlorine is separated from the mixed raw material gas containing chlorine and carbon dioxide , and the chlorine concentration in the raw material gas is increased. A gas having a chlorine concentration can be continuously obtained.

[0021]

Next, the present invention will be described in more detail by way of examples.

Example 1 A synthetic Y-type zeolite (manufactured by ZEOCHEM) was brought into contact with a 10% aqueous solution of calcium chloride for 2 hours, followed by solid-liquid separation and washing with water.
Drying and Ca exchanged Y-type zeolite was obtained. Next, the Y-type zeolite was kept at 300 ° C. for 4 hours while being exposed to a nitrogen stream at 200 cc / min. Then, it was cooled to room temperature in a nitrogen stream. At 25 to 30 ° C., chlorine (15
%) / Carbon dioxide (15%) / oxygen (70%) was adjusted to a pressure of 5 atm and aerated at 200 ml / min for 12 minutes. During this time, the gas flowing out of the column was analyzed by gas chromatography to analyze the gas composition. As a result, 100 to 300 ppm of chlorine gas was detected.

After the completion of the ventilation, the supply of the raw material gas was stopped, and the adsorption column was moved to 60 mmHg abs. At a pressure of 5 minutes to desorb chlorine gas. When the desorbed gas was analyzed, the chlorine concentration was 88%. When a gas having the same composition as the first gas was again passed through the adsorption column after the desorption under the same conditions, the chlorine concentration of the gas flowing out for 12 minutes was 100 to 300 ppm.

Example 2 A synthetic Y-type zeolite (manufactured by ZEOCHEM) was brought into contact with a 10% aqueous barium chloride solution for 2 hours, solid-liquid separated, washed with water and dried to obtain a Ba-exchanged Y-type zeolite. Then this Y
The zeolite was kept at 300 ° C. for 4 hours while being exposed to a 200 cc / min nitrogen stream. Then, it was cooled to room temperature in a nitrogen stream. At 25-30 ° C, chlorine (5%)
A gas having a composition of carbon dioxide (15%) and helium (80%) was adjusted to a pressure of 5 atm and aerated for 25 minutes. During this time, the gas flowing out of the column was subjected to gas chromatographic analysis to analyze the gas composition.
00 ppm was detected.

After the completion of the ventilation, supply of the raw material gas was stopped, and the adsorption column was moved to 60 mmHg abs. At a pressure of 5 minutes to desorb chlorine gas. Analysis of the desorbed gas revealed a chlorine concentration of 65%. When a gas having the same composition as the first gas was again passed through the adsorption column after the desorption under the same conditions, the chlorine concentration of the effluent gas was 100 to 300 ppm for 25 minutes.

REFERENCE EXAMPLE 1 A synthetic Y-type zeolite (manufactured by ZEOCHEM) was brought into contact with a 10% aqueous solution of lithium chloride for 2 hours , followed by solid-liquid separation, washing with water and drying.
After drying, Li-exchanged Y-type zeolite was obtained. Then this Y
The zeolite was kept at 300 ° C. for 4 hours while being exposed to a 200 cc / min nitrogen stream. Then, it was cooled to room temperature in a nitrogen stream. A stainless steel adsorption column filled with 40 g of this adsorbent is added with chlorine (15%) at 25 to 30 ° C.
A gas having a composition of nitrogen (15%) and helium (70%) was adjusted to a pressure of 5 atm and aerated at 200 ml / min for 12 minutes. During this time, the gas flowing out of the column was analyzed by gas chromatography to analyze the gas composition. As a result, 100 to 300 ppm of chlorine gas was detected.

After the completion of the ventilation, supply of the raw material gas was stopped, and the adsorption column was moved to 60 mmHg abs. At a pressure of 5 minutes, and nitrogen gas was further passed at 7 ml / min for 3 minutes to desorb chlorine gas. When the desorbed gas was analyzed, the chlorine concentration was 93%. When a gas having the same composition as that of the first gas was again passed through the adsorption column after the desorption under the same conditions, the chlorine concentration of the gas flowing out for 10 minutes also became 10%.
It was 0 to 300 ppm.

Example 3 A synthetic 13X zeolite (manufactured by Fuji Devison) was brought into contact with a 10% aqueous solution of calcium chloride for 2 hours, solid-liquid separated, washed with water and dried to obtain a Ca-exchanged 13X zeolite.
Next, the 13X type zeolite was kept at 300 ° C. for 4 hours while being exposed to a nitrogen stream at 200 cc / min. Then, it was cooled to room temperature in a nitrogen stream. At 60 ° C., chlorine (15%), carbon dioxide (15%), and helium (70) were applied to a stainless steel adsorption column filled with 40 g of the adsorbent.
%) Of a gas having a composition of 200 atm.
It was aerated at 1 / min for 6 minutes. During this time, the gas flowing out of the column was analyzed by gas chromatography to analyze the gas composition. As a result, 200 to 500 ppm of chlorine gas was detected.

After the completion of the ventilation, supply of the raw material gas was stopped, and the adsorption column was moved to 60 mmHgabs. At a pressure of 5 minutes to desorb chlorine gas. When the desorbed gas was analyzed, the chlorine concentration was 82%. When a gas having the same composition as the first gas was again passed through the adsorption column after the adsorption under the same conditions, the chlorine concentration of the gas flowing out for 6 minutes was 200 to 500 ppm.

[0030] Comparative Example 1 Synthesis zeolite Y (ZEOCH
EM (manufactured by EM) in a stainless steel adsorption column filled with 40 g of chlorine (15%) / carbon dioxide (15
%) / Oxygen (70%) gas was adjusted to a pressure of 5 atm and aerated at 200 ml / min for 12 minutes. During this time, the gas flowing out of the column was analyzed by gas chromatography to analyze the gas composition.
0 ppm was detected.

[0031] After completion aeration, the supply of the source gas is stopped, 60 mmHg abs adsorption column with a vacuum pump. At a pressure of 5 minutes to desorb chlorine gas. When the desorbed gas was analyzed, the chlorine concentration was 78%. When a gas having the same composition as the first gas was again passed through the adsorption column after the desorption under the same conditions, the chlorine concentration of the gas flowing out for 12 minutes was 100 to 300 ppm.

[0032]

According to the present invention , a Y type containing an alkali metal and / or an alkaline earth metal selected from Ca, Ba, and Li as an adsorbent used in the pressure swing adsorption method.
And / or 13X-type zeolite, which is improved by using a zeolite and provides a method for more selectively separating chlorine from a mixed gas containing chlorine and carbon dioxide , which is very effective as a measure for improving chlorine concentration.

The present invention is implemented as an accessory in equipment utilizing chlorine.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an installation using a plurality of adsorption towers for performing the present invention particularly continuously.

[Explanation of symbols]

1. Source gas supply pipe 2. Compressor 4a. 4b. 4c. Adsorption tower 6. Valve 7. Blower 8. Flow control mechanism 10. Vacuum pump 3,5,9,11,12a, 12b, 13-20 switching valve

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Ito 30 Asamuta-cho, Omuta-shi, Fukuoka Pref. Inspector in Japan Kenichi Mori (56) Reference US Patent 3029575 (US, A) Soda Handbook (edited and published by Japan Soda Industry Association) (Sho 50-1-30), p.324 (58) .Cl. ⁷ , DB name) B01D 53/04 B01J 20/18 C01B 7/07

Claims (1)

(57) [Claims] 1. A gas containing chlorine and carbon dioxide is introduced into an adsorption tower filled with an adsorbent capable of adsorbing chlorine to selectively adsorb chlorine, and thereafter the gas introduction is stopped. In the method of desorbing under a lower pressure to obtain a gas having a chlorine concentration higher than the chlorine concentration of the introduced gas and regenerating the adsorbent, the adsorbent capable of adsorbing chlorine is C
A method for concentrating chlorine gas, which is a Y-type and / or 13X-type zeolite containing an alkali metal and / or an alkaline earth metal selected from a, Ba, and Li.