JP5439779B2 - Method for producing high pressure and high purity chlorine gas - Google Patents

Description

  The present invention relates to a method for producing chlorine gas having high pressure and high purity.

  As the chlorine gas, various chlorination reactions are known, such as a reaction in which methyl chloride is chlorinated to produce methylene chloride, chloroform, and carbon tetrachloride. When such a chlorination reaction is carried out in a large-scale plant, the supply of chlorine gas as a raw material to the reactor is usually performed by using a reciprocating compressor or the like for the chlorine gas sent from the chlorine gas supply facility. It is common to use it in a high pressure state and press-fit into the reactor.

  However, the supplied chlorine gas usually contains various impurities and often has an adverse effect on the chlorination reaction. For example, the chlorine gas sometimes contains about several ppm of nitrogen trichloride, but the nitrogen trichloride reacts violently with most organic compounds and there is a risk of explosion. In addition, explosion occurs easily when the concentration of nitrogen trichloride is high. In addition, nitrogen trichloride decomposes in the chlorination reaction, and the nitrogen and chlorine generated by this reaction react to generate ammonium chloride scale. For example, when the reaction is carried out by a photochemical reaction. Dirty the surface of the UV lamp, making the reaction unstable. Therefore, it has been desirable to suppress as much as possible the supply of chlorine gas containing nitrogen trichloride to the reactor for the chlorination reaction.

  The chlorine gas is generated from the anode by, for example, electrolysis of an aqueous alkali metal salt solution. At that time, nitrogen trichloride in the chlorine gas is mixed with ammonium ions and nitrogen-containing organic substances in the raw alkali metal salt aqueous solution. It is formed by combining chlorine gas generated from

  As a method for removing this nitrogen trichloride from chlorine gas, for example, in Patent Document 1, when supplying chlorine gas to a reactor, the chlorine gas is once cooled and liquefied as chlorine, and is pumped to the vicinity of the reactor. A method of heating and supplying chlorine gas as a reactor has been proposed. According to this method, it is possible to remove impurities such as nitrogen trichloride, but once the chlorine gas is converted into liquefied chlorine, The process of returning to chlorine gas again is complicated, and nitrogen trichloride is concentrated by liquefying and evaporating to increase the risk of explosion. Therefore, a simpler and safer method for reducing nitrogen trichloride is desired. .

JP-A-8-243376

  The object of the present invention is to provide trichlorinated trichloride which is not desirable for the chlorination reaction contained in the process of increasing the pressure of chlorine gas when supplying high pressure chlorine gas to the chlorine gas supply destination, and easily explodes when the concentration is high. An object is to provide a simple and safe method capable of reducing nitrogen.

  The present inventors have continued intensive studies in view of the above problems. As a result, the chlorine gas produced from the anode chamber of the alkali metal salt aqueous solution electrolytic cell rises in temperature by a one-stage pressure increase, cools via a primary cooler, rises in temperature by a two-stage pressure increase, and passes through a secondary cooler. It has been found that according to the method for producing high-purity chlorine gas that is cooled and fed to the supply destination, nitrogen trichloride in the chlorine gas can be reduced, and the present invention has been completed.

  In particular, it is possible to easily reduce nitrogen trichloride by adjusting the amount of cooling water flowing into the primary cooler so that the temperature after the second stage pressure increase is maintained at a high temperature. Analyzing the concentration of nitrogen trichloride in the chlorine gas after passing through the secondary cooler, and adjusting the flow rate of cooling water into the primary cooler according to the concentration, the temperature at the time of two-stage boosting can be adjusted It can be applied as an automatic adjustment method, and is more preferable.

  In particular, by adjusting the temperature after the two-step pressure increase to 70 ° C. to 100 ° C., the nitrogen trichloride concentration in the chlorine gas can be reliably reduced, which is more preferable.

  Centrifugal blowers are used as devices for boosting and blowing in chlorine gas. Examples of types include turbo fans and turbo blowers. Among them, turbo blowers are widely used.

  As a turbo blower system, there is a single-suction or double-suction system using a single-stage or multi-stage impeller, but when boosting chlorine gas in two stages as in the present invention, a double-suction system is adopted and dried chlorine. In order to target gas, impellers, bearings and casings are made of cast iron (and material equivalent to carbon steel).

The chlorine gas after the two-stage pressurization has a pressure of 1.2 to 1.3 kg / cm ² G.

  As a cooler, a multi-tube heat exchanger is usually used, and cold water at about 10 ° C. is flowed to cool chlorine gas.

  In the present invention, any chlorine gas may be used, but it is particularly effective to apply it to a nitrogen trichloride content of 0.5 to 20 ppm. . In general, it is preferable to apply to chlorine gas which is generated and sent in an electrolysis plant of an alkali metal salt aqueous solution and has the above impurity concentration.

  Specifically, the method for producing high-pressure and high-purity chlorine gas of the present application will be described with reference to FIG.

Chlorine gas is first supplied to the first stage booster (2) of the turbo blower (1) through 12 lines and boosted to 0.4 to 0.5 kg / cm ² G, and 70 to 80 in 13 lines. The temperature rises to ℃. Then, it is supplied to the primary cooler (3) and cooled to 15-40 ° C. Next, it is supplied to the two-stage booster (4) of the turbo blower (1) through 14 lines, and is again boosted to 1.3 to 1.4 kg / cm ² G, and the temperature is increased to 70 to 100 ° C. in 16 lines. To rise.

Finally, it is supplied to the secondary cooler (5) through 16 lines, cooled to 20 to 30 ° C., and chlorine gas is supplied to the supply destination through 17 lines at a pressure of 1.2 to 1.3 kg / cm ² G. To do.

  The primary cooler (3) and the secondary cooler (5) are provided with a cold water supply line (6) and a hot water discharge line (7).

  We have developed a method for producing high-purity chlorine gas that measures the temperature after two-stage boosting and adjusts the temperature after the second-stage boosting by adjusting the amount of cooling water flowing into the primary cooler.

  This method will be specifically described with reference to FIG. The difference from FIG. 1 is that the nitrogen trichloride analysis take-out line (8), the nitrogen trichloride analyzer (9), and the thermometer (10) after two-stage pressurization are linked to the cold water of the primary cooler. The flow control device (11) is attached.

  In conjunction with the thermometer (10), when the temperature becomes lower than the set temperature (usually set at 75 ° C or higher), the control of the chilled water flow rate control device (11) of the primary cooler is adjusted to lower the chilled water flow rate, Raise the temperature at the time of pressurization, and conversely, when the temperature approaches 100 ° C, raise the flow rate of cold water and lower the temperature at the time of two-stage pressurization, and the nitrogen trichloride analyzer (9) determines the nitrogen trichloride concentration. Monitor whether it is within (eg 0.5 ppm or less).

  Conversely, if the nitrogen trichloride exceeds the reference concentration, for example, 0.5 ppm, the nitrogen trichloride analyzer (9) immediately adjusts the control water flow control device (11) of the primary cooler, The flow rate of the cold water in the primary cooler is lowered to increase the temperature at the position 14, and nitrogen trichloride is reduced by thermal decomposition in the two-stage booster (4) of the turbo blower (1).

  Then, after confirming that the concentration of nitrogen trichloride is below the reference concentration, adjust the control valve of the primary cooler control chilled water flow rate control device (11) to gradually increase the chilled water flow rate of the primary cooler. Return to normal operation.

  According to the concentration of nitrogen trichloride, the nitrogen trichloride analyzer (9), the primary cooler chilled water flow rate controller (11), and the thermometer (10) after the two-stage pressurization are connected online according to the above operation. Thus, a method of automatically controlling the concentration of nitrogen trichloride in chlorine gas is preferable in terms of establishing an automatic monitoring system.

  According to the present invention, when chlorine gas is pumped to the user, nitrogen trichloride, an impurity that adversely affects the chlorination reaction, can be reduced, and the danger of explosion and scale generation by the user can be avoided. It is possible to make a significant contribution in terms of quality assurance and safety. In particular, while monitoring the concentration of nitrogen trichloride in the chlorine gas, the nitrogen trichloride concentration in the chlorine gas does not exceed the reference concentration by automatic control. Therefore, it contributes to improving operational efficiency and reducing explosion risk.

  In order to describe the present invention more specifically, examples and comparative examples will be described below, but the present invention is not limited to these examples.

Example 1
Chlorine gas was produced by the process shown in FIG. The chlorine gas supplied from the 12 lines was a chlorine gas obtained by drying chlorine gas produced in a salt electrolysis plant, contained 0.94 ppm of nitrogen trichloride, and the temperature was 24 ° C.

The turbo blower (1) (Ehara centrifugal multistage blower manufactured by Ebara Seisakusho Co., Ltd.) was supplied to the first stage booster (2), boosted to 0.5 kg / cm ² G, and the temperature increased to 75 ° C. in 13 lines. . Thereafter, it is supplied to the primary cooler (3) (multitubular heat exchanger) and cooled to 18 ° C., and then supplied to the two-stage booster (4) of the turbo blower (1) through 14 lines. The pressure was increased again to 4 kg / cm ² G, and the temperature increased to 75 ° C. in 16 lines.

Finally, it is supplied to the secondary cooler (5) (multitubular heat exchanger) through 16 lines, cooled to 21 ° C., and chlorine gas is supplied to the user through 17 lines at a pressure of 1.3 kg / cm ² G. Supplied.

  The nitrogen trichloride content in chlorine gas at 17 lines was reduced to 0.23 ppm.

Example 2
Similarly, chlorine gas was produced by the process shown in FIG. The chlorine gas supplied from the 12 lines contained 1.01 ppm of nitrogen trichloride and had a temperature of 24 ° C. The turbo blower (1) (Ehara centrifugal multistage blower manufactured by Ebara Seisakusho Co., Ltd.) was supplied to the first-stage booster (2), boosted to 0.5 kg / cm ² G, and the temperature increased to 78 ° C. in 13 lines. . Thereafter, it is supplied to the primary cooler (3) (multi-tube heat exchanger) and cooled to 25 ° C., and then supplied to the two-stage booster (4) of the turbo blower (1) through the 14 line. The pressure was increased again to 4 kg / cm ² G, and the temperature increased to 80 ° C. in 16 lines.

Finally, it is supplied to the secondary cooler (5) (multi-tube heat exchanger) through 16 lines, cooled to 22 ° C., and chlorine gas is supplied to the user through 17 lines at a pressure of 1.3 kg / cm ² G. Supplied.

  The nitrogen trichloride content in chlorine gas at 17 lines was reduced to 0.33 ppm.

Example 3
Similarly, chlorine gas was produced by the process shown in FIG. The chlorine gas supplied from the 12 lines contained 0.73 ppm of nitrogen trichloride and the temperature was 24 ° C. The turbo blower (1) (Ehara centrifugal multi-stage blower manufactured by Ebara Seisakusho Co., Ltd.) was supplied to the first-stage booster (2), boosted to 0.5 kg / cm ² G, and the temperature increased to 79 ° C. at 13 lines. . Thereafter, it is supplied to the primary cooler (3) (multi-tube heat exchanger) and cooled to 35 ° C., and then supplied to the two-stage booster (4) of the turbo blower (1) through 14 lines. The pressure was increased again to 4 kg / cm ² G, and the temperature increased to 90 ° C. in 16 lines.

Finally, it is supplied to the secondary cooler (5) (multi-tube heat exchanger) through 16 lines, cooled to 23 ° C., and chlorine gas is supplied to the user through 17 lines at a pressure of 1.3 kg / cm ² G. Supplied.

  The nitrogen trichloride content in chlorine gas at 17 lines was reduced to 0.08 ppm.

Comparative Example 1
Chlorine gas was produced by the process shown in FIG.

The chlorine gas supplied from the 12 lines contained 1.01 ppm of nitrogen trichloride and had a temperature of 24 ° C. The turbo blower (1) (Ehara centrifugal multistage blower manufactured by Ebara Seisakusho Co., Ltd.) was supplied to the pressurizing section (2), and the pressure was increased to 0.5 kg / cm ² G, and the temperature increased to 79 ° C. in 13 lines. Then, it supplied to the primary cooler (3) (multi-tube heat exchanger), cooled to 18 ° C., and supplied chlorine gas to the user through 15 lines.

  The nitrogen trichloride content in chlorine gas at 15 lines remained as high as 0.67 ppm.

One example of the process of the chlorine gas production method of the present invention (used in Examples 1 to 3) An example of the automatic control process of the chlorine gas production method of the present invention Process of chlorine gas production method used in Comparative Example 1

Explanation of symbols

1: Turbo blower 2: First stage pressure booster 3: Primary cooler 4: Second stage pressure booster 5: Secondary cooler 6: Cold water supply line 7: Hot water discharge line 8: Analysis of nitrogen trichloride Extraction line 9: Analysis of nitrogen trichloride Total 10: Thermometer after two-stage pressure increase 11: Chilled water flow rate control device 12 of primary cooler 12: Line 13 for supplying chlorine gas to the first-stage pressure booster of the turbo blower 13: Line 14 for supplying chlorine gas after the first-stage pressure increase to the primary cooler : Line 15 for supplying chlorine gas after primary cooling to the second stage booster of the turbo blower: Line 16 for supplying chlorine gas after primary cooling to the supply destination 16: Supplying chlorine gas after second stage boosting to the secondary cooler Line 17: Line for supplying chlorine gas after secondary cooling to the supplier

Claims (4)

The chlorine gas produced from the anode chamber of the alkaline metal salt aqueous electrolytic cell is heated to 70-80 ° C. by one-stage pressure increase, cooled to 15-40 ° C. via a primary cooler, and temperature is increased by two-stage pressure increase. The method of manufacturing high-purity chlorine gas which raises to 70-100 degreeC , cools temperature to 20-30 degreeC via a secondary cooler, and is supplied to a supply destination.   2. The high-purity chlorine according to claim 1, wherein the temperature after the two-stage boosting is measured by measuring the temperature after the two-stage boosting and adjusting the inflow amount of the cooling water to the primary cooler from the temperature value. A method for producing gas.   Analyzes the nitrogen trichloride concentration in the chlorine gas after passing through the secondary cooler, and adjusts the inflow of cooling water to the primary cooler according to the concentration to adjust the temperature at the second stage pressure increase A method for producing high-purity chlorine gas according to claim 1 or 2. Method of producing high purity chlorine gas of claims 1 to 3, wherein the implementing one stage booster and two-stage boosted by turbo blower

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