JP2003292304A - Method for manufacturing pure chlorine gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a large quantity of pure chlorine gas from hydrogen chloride and oxygen using less energy. <P>SOLUTION: Hydrogen chloride and oxygen are reacted in a reactor (10) at a pressure of ≥0.6 MPa to obtain a high-pressure crude chlorine gas containing unreacted oxygen. The high-pressure crude chlorine gas is cooled by a cooling means (20) without elevating the pressure to liquefy chlorine in the gas, giving high-pressure liquefied crude chlorine. The unreacted oxygen is separated from the high-pressure liquefied chlorine by a chlorine purifying means (30), giving high-pressure liquefied pure chlorine. The unreacted oxygen is recovered by a recovering means (40) and used for the reaction with hydrogen chloride in the reactor (10). The high-pressure liquefied pure chlorine is decompressed in a decompressing means (50) to obtain liquefied pure chlorine, which is then vaporized to give a pure chlorine gas. The cooling means (20) is a heat exchanger, where a latent heat generated by liquefying chlorine is used for vaporizing the liquefied pure chlorine. The chlorine concentration of the high-pressure crude chlorine gas is ≥45% as mole fraction and the high- pressure liquefied pure chlorine is decompressed to ≤0.3 MPa. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing pure chlorine gas.

[0002]

2. Description of the Related Art Pure chlorine gas, which is gaseous chlorine (Cl ₂ ) containing no oxygen (O ₂ ), is useful as an industrial chemical. As a method for producing it, hydrogen chloride (HCl) is reacted with oxygen. It is known how to do this. Such a method is represented by the formula (1)

[Chemical 1] In order to obtain chlorine in good yield, the reaction is usually carried out under pressure, and an excess amount of oxygen of more than 0.25 mol times hydrogen chloride is used.
Therefore, high-pressure crude chlorine gas, which is gaseous chlorine containing unreacted oxygen, is generated at the same pressure as in the reaction system and at high pressure. To obtain the target pure chlorine gas from the high-pressure crude chlorine gas, for example, as shown in FIG. 2, unreacted hydrogen chloride is obtained from the high-pressure crude chlorine gas obtained by reacting hydrogen chloride with oxygen in the reactor (10). ,
After removing water (H ₂ O) and the like produced as a by-product in the absorption tower (60) and the drying tower (70), it is cooled by the cooling means (20) to liquefy the chlorine in the high-pressure crude chlorine gas to liquefy the high-pressure liquid crude. Chlorine is obtained, and unreacted oxygen is separated from this high-pressure liquid crude chlorine by the chlorine refining means (30) to obtain high-pressure liquid pure chlorine.
After decompressing at 0) to form liquid pure chlorine, it may be vaporized by heating at a heat exchanger (20) or the like. The unreacted oxygen separated from the high-pressure liquid crude chlorine by the chlorine refining means (30) can be recovered and used for the reaction with hydrogen chloride, and the separated unreacted oxygen is directly used in the reactor (10) without pressurization. And can be used for reaction with hydrogen chloride.

In order to obtain a larger amount of pure chlorine gas in such a method, it is preferable to cool the high-pressure crude chlorine gas under a higher pressure to liquefy a large amount of chlorine. In JP-A-275001, for example, a high pressure crude chlorine gas of 0.5 MPa in absolute pressure is used for a compressor (80).
Then, the pressure is further increased to 2.6 MPa and then cooled to liquefy chlorine.

However, such a conventional manufacturing method has a problem that when the high-pressure crude chlorine gas is further compressed, the unreacted oxygen contained in this gas also needs energy for compressing it.

[0005]

Therefore, the present inventor has diligently studied in order to develop a method capable of producing a large amount of pure chlorine gas from hydrogen chloride and oxygen with less energy, and as a result, 0.6 MPa or more has been obtained. When hydrogen chloride and oxygen are reacted under pressure, not only the reaction yield of chlorine improves and more pure chlorine gas is obtained, but when the reaction is carried out at such a reaction pressure, the high-pressure crude gas obtained by the reaction is obtained. The inventors have found that energy for pressurizing the high-pressure crude chlorine gas is unnecessary because even if the chlorine gas is cooled without further pressurization, a sufficient amount of chlorine can be liquefied, and the present invention has been completed.

[0006]

Means for Solving the Problems That is, according to the present invention, hydrogen chloride and oxygen are reacted under a pressure of 0.6 MPa or more to obtain a high-pressure crude chlorine gas containing unreacted oxygen, and the obtained high-pressure crude chlorine gas is obtained. Is cooled without pressurizing, chlorine in the high-pressure crude chlorine gas is liquefied to obtain high-pressure liquid crude chlorine, and unreacted oxygen is separated from the obtained high-pressure liquid crude chlorine to obtain high-pressure liquid pure chlorine, which is then separated. The unreacted oxygen is recovered and used in the reaction with hydrogen chloride.The obtained high-pressure liquid pure chlorine is decompressed into liquid pure chlorine, which is then vaporized into pure chlorine gas. A manufacturing method is provided.

FIG. 1 schematically shows an example of a pure chlorine gas production apparatus (1) for producing pure chlorine gas by the production method of the present invention. This production apparatus (1) comprises a reactor (10) for reacting hydrogen chloride and oxygen under a pressure of 0.6 MPa or more to obtain high-pressure crude chlorine gas containing unreacted oxygen, and a high pressure obtained in the reactor. Cooling the crude chlorine gas to liquefy the chlorine in the high-pressure crude chlorine gas to obtain high-pressure liquid crude chlorine, and cooling means (20) to separate the unreacted oxygen from the high-pressure liquid crude chlorine obtained by the cooling means. Chlorine refining means (30) for obtaining liquid pure chlorine, recovery means (40) for recovering oxygen separated by the chlorine refining means and supplying it to the reactor, and depressurizing high-pressure liquid pure chlorine obtained by the chlorine refining means It is provided with a decompression means (50) for making liquid pure chlorine, and the high pressure crude chlorine gas obtained in the reactor (10) is configured to be cooled by the cooling means (20) without being pressurized. ing.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the production method of the present invention, hydrogen chloride and oxygen are reacted. In the device (1) shown in FIG. 1, hydrogen chloride and oxygen are reacted in a reactor. The amount of oxygen used is
It is usually more than 0.25 mol times, preferably 0.4 mol times or more, and usually 0.6 mol times or less with respect to hydrogen chloride. The reaction temperature is usually 300 ° C or higher and 500 ° C or lower. The reaction is usually performed in the presence of a catalyst. The reaction is 0.
6 MPa or more, preferably 0.8 MPa or more 2.0 MP
Since it is carried out under a pressure (P0) of a or less, chlorine is produced in a good reaction yield. In order to carry out the reaction at such a pressure, for example, hydrogen chloride and oxygen may be supplied to the reactor after adjusting the pressure within the above range. By such a reaction,
Water (H ₂ O) is produced as a by-product. By the reaction, ideally all the amount of hydrogen chloride (100%) reacts with oxygen, but usually 80% or more reacts with oxygen to become chlorine.

Since the excess oxygen remains unreacted as unreacted oxygen, high-pressure crude chlorine gas containing unreacted oxygen can be obtained. Such high-pressure crude chlorine gas usually contains unreacted hydrogen chloride and by-produced water. Further, as an impurity, an inert gas such as nitrogen gas, argon gas or carbon dioxide gas may be contained, and if a small amount, a gaseous impurity brought from hydrogen chloride or oxygen used as a raw material is contained. Good. The pressure of the high-pressure crude chlorine gas obtained from the reactor (10) is the reaction pressure (P0) in the reactor (10).
Is substantially equal to.

The high-pressure crude chlorine gas thus obtained contains unreacted hydrogen chloride, by-produced water and the like, but it is preferable to cool them after removing them. In the apparatus (1) shown in FIG. 1, unreacted hydrogen chloride is removed by the absorption tower (60) and water is removed by the drying tower (70).

The high-pressure crude chlorine gas obtained in the reactor (10) is continuously introduced into the absorption tower (60), and the unreacted hydrogen chloride contained in the high-pressure crude chlorine gas is converted into water in the absorption tower (60). It is absorbed and removed. In such an absorption tower (60), the high-pressure crude chlorine gas may be usually supplied from the tower bottom (61) of the absorption tower and adjusted in temperature by the cooler (C1) before being supplied. Water is supplied from the tower top (62) and sprayed inside the absorption tower. Hydrogen chloride contained in the high-pressure crude chlorine gas comes into contact with water in the absorption tower (60) and is absorbed by this water.Therefore, the high-pressure crude chlorine gas continuously extracted from the tower top (62) contains hydrogen chloride. Is not included. Also,
The pressure of the extracted high-pressure crude chlorine gas is substantially equal to the pressure when it is supplied to the absorption tower. The high-pressure crude chlorine gas obtained in the reactor (10) is cooled to the extent of the temperature of the water used for absorption by coming into contact with water in the absorption tower (60).

The absorption tower (60) has two or more stages, an upper stage and a lower stage, and a part of the effluent water supplied from the tower top (62) and flowing down toward the tower bottom (61) is in the upper stage. It was pulled out from the middle and the tower top (6
2) It may be configured to be supplied to the absorption tower from the vicinity. Water extracted from the middle of the upper stage may be temperature-controlled by a cooler (C2) or the like and then supplied to the absorption tower.

Water absorbs hydrogen chloride of high-pressure crude chlorine gas inside the absorption tower (60) to become hydrochloric acid (hydrogen chloride aqueous solution),
It is withdrawn from the bottom of the tower (61). From the thus extracted hydrochloric acid, hydrogen chloride can be obtained by distillation or the like, and the obtained hydrogen chloride may be supplied to the reactor (10) as a raw material.
Further, the hydrochloric acid extracted from the bottom of the tower is usually capable of further absorbing hydrogen chloride, so part or all of it may be supplied to the absorption tower (60) from the lower stage, with a cooler (C3) or the like. It may be supplied after the temperature is adjusted.

The high-pressure crude chlorine gas continuously obtained from the top (62) of the absorption tower includes water produced as a by-product and water brought into contact with water in the absorption tower (60). Has been. In the production apparatus (1) shown in FIG. 1, the water containing the high-pressure crude chlorine gas is absorbed by concentrated sulfuric acid (H ₂ SO ₄ ) in the drying tower (70).
The high-pressure crude chlorine gas is continuously supplied from the bottom (71) of the drying tower. Concentrated sulfuric acid is supplied from the tower top (72) and sprayed inside the drying tower. The water contained in the high-pressure crude chlorine gas is stored in the drying tower (7
Since it comes into contact with concentrated sulfuric acid at 0) and is absorbed by this concentrated sulfuric acid, the high pressure crude chlorine gas continuously withdrawn from the tower top (71) does not contain water. The pressure of this high-pressure crude chlorine gas is
It is substantially equal to the pressure when it is supplied to the drying tower.

The concentrated sulfuric acid absorbs the water of the high pressure mixed gas inside the drying tower (70) to become sulfuric acid containing water, and the tower bottom (7
Extracted from 1). Since the extracted sulfuric acid can further absorb water, a part thereof may be supplied to the drying tower (70), or the temperature may be adjusted with a cooler (C4) or the like and then supplied to the drying tower. Good.

The high-pressure crude chlorine gas is cooled without increasing the pressure. To cool without boosting pressure, for example,
As shown in, the high pressure crude chlorine gas obtained from the drying tower (70) or the like may be directly supplied to the cooling means (20). In this manufacturing apparatus (1), a heat exchanger is used as the cooling means (20). By cooling the high-pressure crude chlorine gas, chlorine in the high-pressure crude chlorine gas is liquefied. Liquefaction is carried out while maintaining the pressure of the high-pressure crude chlorine gas almost at all, and high-pressure liquid crude chlorine having a pressure substantially equal to the pressure of the high-pressure crude chlorine gas before cooling can be obtained. High-pressure liquid crude chlorine is obtained by liquefying chlorine in high-pressure crude chlorine gas, and usually contains unreacted oxygen in an unliquefied state. The temperature of the obtained high-pressure liquid crude chlorine is usually about -35 ° C to -5 ° C, preferably -20 ° C to-.
It is in the range of about 10 ° C. Liquefaction of high-pressure crude chlorine gas is usually performed continuously.

Unreacted oxygen is separated from the obtained high-pressure liquid crude chlorine. To separate unreacted oxygen, a distillation column may be used as the chlorine purification means (30) as shown in FIG. 1, and high-pressure liquid crude chlorine may be introduced into this distillation column. Since the liquefaction temperature of oxygen is much lower than the liquefaction temperature of chlorine, by performing distillation for separating high-pressure liquid crude chlorine into a gas phase and a liquid phase,
It is possible to separate oxygen in a gaseous state as a gas phase and to obtain liquid pure chlorine as a liquid phase. In this production apparatus (1), a distillation column is used as the chlorine refining means (30), and by introducing liquid crude chlorine into the distillation column (30), unreacted oxygen remains in the gaseous state at the top (32 It can be obtained by extracting high-pressure liquid pure chlorine from the column bottom (31). Distillation tower
The inside of (30) is usually about the same pressure (P
0). The separated unreacted oxygen may contain a slight amount of unliquefied chlorine, but such unliquefied chlorine is liquefied by cooling the unreacted oxygen with a cooler (C5), and a distillation column ( It can be returned to 30).

The separated unreacted oxygen is recovered and used for the reaction with hydrogen chloride. The unreacted oxygen recovered is usually part of the separated unreacted oxygen. Recovery is a means for collecting unreacted oxygen extracted from the top of the distillation column (32) (40)
You can collect it at. In the production apparatus (1) shown in FIG. 1, a pump (compressor) for introducing unreacted oxygen from the top (32) of the distillation column to the reactor (40) is used as the recovery means (40). Although the pressure (P0) of the reactor (10) is 0.6 MPa or more, in the production method of the present invention, since unreacted oxygen is separated from high-pressure liquid crude chlorine having a pressure substantially the same as the pressure, The pressure of the separated unreacted oxygen is also substantially equal to the pressure of the reactor, and is usually low enough to correspond to a slight pressure loss in the piping, absorption tower, drying tower, cooling means, etc. Therefore, by raising the pressure by a pump (compressor) by a pressure corresponding to such a slight pressure loss, unreacted oxygen can be recovered and led to the reactor (10), and can be used again for the reaction with hydrogen chloride.

On the other hand, the high-pressure liquid pure chlorine obtained is supplied to the bottom (31) of the distillation column after a part of the temperature is adjusted by a heater (B1) or the like in order to adjust the temperature of the distillation column. May be.
Liquid crude chlorine is supplied to the distillation column (30), high-pressure liquid pure chlorine is extracted from the distillation column, and oxygen is usually extracted continuously.

The obtained high-pressure liquid crude chlorine is decompressed into liquid pure chlorine and then vaporized. To reduce the pressure, for example, as shown in FIG. 1, a pressure reducing means (50) may be used. In this production apparatus (1), as a pressure reducing means, a pressure adjusting valve provided in a pipe for extracting high-pressure liquid pure chlorine from the column bottom (31) is used, and the pressure was extracted from the column bottom (31). The high-pressure liquid pure chlorine is reduced in pressure by passing through the pressure control valve (50) to become liquid pure chlorine.

The pressure (P1) of the high-pressure liquid pure chlorine immediately after being withdrawn from the column bottom (31) is substantially the same as the reaction pressure (P0), but it must pass through the pressure reducing control valve (50). It is decompressed with. The pressure (P2) after depressurization is usually 0.3MP in absolute pressure.
a or less, preferably 0.25 MPa or less, and may be atmospheric pressure (0.1 MPa) or lower. The difference (ΔP12 = P1-P2) between the pressure (P2) of liquid pure chlorine after depressurization and the pressure (P1) of high-pressure liquid pure chlorine is preferably 0.3 MPa or more, more preferably 0.5 M.
Pa or higher. High-pressure liquid pure chlorine is reduced to the above pressure by decompression, and part or all of it may be vaporized,
The liquid pure chlorine thus obtained usually contains chlorine vaporized by being depressurized.

In the production method of the present invention, such liquid pure chlorine is vaporized. In order to vaporize, for example, liquid pure chlorine may be heated by externally applying energy, but the high-pressure crude chlorine gas is cooled without pressurization, and latent heat generated by liquefying chlorine in the gas is generated. Then, it is preferable to vaporize the liquid normal chlorine because the latent heat can be effectively utilized and pure chlorine gas can be obtained with less energy. To vaporize with such latent heat, for example, as shown in FIG. 1, a heat exchanger may be used as the cooling means (20). The heat exchanger (20) exchanges heat between high-pressure crude chlorine gas and liquid pure chlorine. By exchanging heat with a heat exchanger, the high-pressure crude chlorine gas is cooled and the chlorine in the high-pressure crude chlorine gas is liquefied into high-pressure liquid crude chlorine, and liquid pure chlorine is heated and vaporized into pure chlorine gas. be able to. The temperature of the obtained pure chlorine gas may be further adjusted with a heater (B2) or the like.

[0023]

According to the production method of the present invention, since hydrogen chloride and oxygen are reacted under a pressure of 0.6 MPa or more,
Chlorine can be obtained in good yield. Further, since it is possible to liquefy a sufficient amount of chlorine from the high-pressure crude chlorine gas obtained by the reaction, it is not necessary to pressurize the high-pressure crude chlorine gas and also pressurize unreacted oxygen contained in the high-pressure crude chlorine gas. No energy is needed for it. Since the reaction yield is high and a sufficient amount of chlorine can be liquefied from the high-pressure crude chlorine gas, a large amount of pure chlorine gas can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an example of a pure chlorine gas production apparatus for producing pure chlorine gas by the method of the present invention.

FIG. 2 is a diagram schematically showing an example of a pure chlorine gas production device for producing pure chlorine gas by a conventional method.

[Explanation of symbols]

1: Pure chlorine gas production equipment 10: Reactor 60: Absorption tower 20: Heat exchanger (cooling means) 61: Bottom of tower 30: Distillation tower (chlorine refining means) 62: Tower top 31: Tower bottom 70: Drying tower 32: Tower top 71: Tower bottom 40: Compressor (collection means) 72: Tower top 50: Pressure control valve (pressure reducing means) 80: Compressor (collection means) B1-B2: Heater C1-C5: Cooler

Claims (6)

[Claims] 1. A high pressure crude chlorine gas containing unreacted oxygen is obtained by reacting hydrogen chloride and oxygen under a pressure of 0.6 MPa or more, and the obtained high pressure crude chlorine gas is cooled without pressurization to obtain a high pressure. The chlorine in the crude chlorine gas is liquefied to obtain high-pressure liquid crude chlorine, unreacted oxygen is separated from the obtained high-pressure liquid crude chlorine to obtain high-pressure liquid pure chlorine, and the separated unreacted oxygen is recovered and chlorinated. A method for producing pure chlorine gas, which is characterized in that the obtained high-pressure liquid pure chlorine used for the reaction with hydrogen is decompressed into liquid pure chlorine and then vaporized into pure chlorine gas. 2. The method according to claim 1, wherein liquid pure chlorine is vaporized by latent heat generated by liquefying chlorine in the high-pressure crude chlorine gas. 3. The chlorine concentration of high-pressure crude chlorine gas is 4 in terms of mole fraction.
The production method according to claim 1, wherein the high-pressure liquid pure chlorine is reduced to 0.3 MPa or less by 5% or more. 4. A reactor for reacting hydrogen chloride and oxygen under a pressure of 0.6 MPa or more to obtain high-pressure crude chlorine gas containing unreacted oxygen, and cooling the high-pressure crude chlorine gas obtained in the reactor. Cooling means for liquefying chlorine in high-pressure crude chlorine gas to obtain high-pressure liquid crude chlorine, and chlorine purification means for separating unreacted oxygen from the high-pressure liquid crude chlorine obtained by the cooling means to obtain high-pressure liquid pure chlorine A recovery means for recovering the oxygen separated by the chlorine refining means and supplying it to the reactor, and a decompression means for decompressing the high-pressure liquid pure chlorine obtained by the chlorine refining means into liquid pure chlorine, An apparatus for producing pure chlorine gas, characterized in that the high-pressure crude chlorine gas obtained in the reactor (10) is configured to be cooled by a cooling means without being pressurized. 5. The cooling means heat-exchanges high-pressure crude chlorine gas with liquid pure chlorine to cool the high-pressure crude chlorine gas and liquefy chlorine in the high-pressure crude chlorine gas to obtain high-pressure liquid crude chlorine. The apparatus for producing pure chlorine gas according to claim 4, which is a heat exchanger that heats and vaporizes liquid pure chlorine to produce pure chlorine gas. 6. The chlorine concentration of high-pressure crude chlorine gas is 4 in terms of mole fraction.
5% or more, and the decompression means uses 0.3M of high-pressure liquid pure chlorine.
The manufacturing apparatus according to claim 5, wherein the pressure is reduced to Pa or less.