JP2016150869A - Method for producing hydrogen chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing hydrogen chloride which is suitable for obtaining high-purity hydrogen chloride by removing impurities efficiently.SOLUTION: A method for producing hydrogen chloride includes: a synthesis step of synthesizing hydrogen chloride from chlorine and hydrogen under a hydrogen excessive condition by a burner combustion device 4; an adsorption removal step of removing a part of impurities in a mixed gas containing hydrogen chloride having undergone the synthesis step using an adsorbent in an adsorber 5; and a pressure swing adsorption-type gas separation step of removing at least a part of impurities contained in crude hydrogen chloride gas having undergone the adsorption removal step by a PSA gas separation device 6.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing hydrogen chloride.

  Hydrogen chloride is used in many chemical industries and is an important industrial intermediate material. In particular, high purity hydrogen chloride is required for semiconductor raw materials. Examples of the method for producing hydrogen chloride include a method by separation / concentration from exhaust gas containing hydrogen chloride by-produced by a synthesis reaction in a chemical facility, or a method of directly synthesizing hydrogen chloride from chlorine and hydrogen.

  As a method for synthesizing hydrogen chloride from chlorine and hydrogen, a combustion method using a burner is known. In the combustion method, in order to reduce unreacted chlorine remaining in the gas after synthesis, combustion is generally performed under hydrogen-excess conditions. For this reason, excessive hydrogen is present in the synthesized gas. Furthermore, impurities other than hydrogen may include nitrogen, oxygen, carbon dioxide, carbon monoxide, bromine, hydrocarbons, moisture, chlorine remaining in trace amounts without being burned, etc., derived from chlorine and hydrogen as raw materials. It is known that this is an obstacle to the high purity of hydrogen chloride.

  For example, Patent Documents 1 and 2 disclose methods for obtaining high-purity hydrogen chloride. Patent Document 1 discloses a method of removing a trace amount of chlorine after burner combustion and excess hydrogen by adding pure water to the hydrogen chloride-containing gas after burner combustion to form hydrochloric acid. In this method, chlorine and hydrogen can be removed significantly, but then, in order to obtain high-purity hydrogen chloride, it is necessary to remove water in hydrochloric acid, which is an azeotropic mixture, requiring a large amount of energy. There was a problem of becoming. In Patent Document 2, as a process in which pure water is not added, a method of using chlorine and hydrogen from which oxygen and moisture have been removed and removing hydrogen by performing distillation after burner combustion to obtain high purity hydrogen chloride is disclosed. Yes. However, in this method, since it is necessary to introduce air at the time of combustion ignition, there is a problem that moisture generated during burner combustion and chlorine that could not be reacted remain.

Japanese Patent No. 2775364 Special table 2013-545704 gazette

  The present invention has been conceived under such circumstances, and mainly aims to provide a method for producing hydrogen chloride suitable for efficiently removing impurities and obtaining high-purity hydrogen chloride. It is an issue.

  The method for producing hydrogen chloride provided by the present invention includes a synthesis step of synthesizing hydrogen chloride from chlorine and hydrogen using a burner combustion apparatus under an excess hydrogen condition, and impurities in a mixed gas containing hydrogen chloride after the synthesis step. An adsorption removal step of removing a part using an adsorbent, and a pressure fluctuation adsorption gas separation step of removing at least part of impurities contained in the crude hydrogen chloride gas that has undergone the adsorption removal step by the PSA method. Including.

  Preferably, the adsorbent used in the adsorption removal step is composed of one or more selected from the group consisting of activated carbon, zeolite, and non-zeolite porous acidic oxide.

  Preferably, in the pressure fluctuation adsorption gas separation step, a plurality of PSA adsorption towers filled with a PSA adsorbent that selectively adsorbs hydrogen chloride are used to bring the PSA adsorption tower into a relatively high pressure state. An adsorption step of introducing the crude hydrogen chloride gas into the PSA adsorption tower, adsorbing hydrogen chloride in the crude hydrogen chloride gas to the PSA adsorbent, and discharging non-adsorbed gas from the PSA adsorption tower; A cleaning gas having a hydrogen chloride concentration higher than that of the crude hydrogen chloride gas is introduced into the PSA adsorption tower, and a cleaning off-gas is discharged from the PSA adsorption tower. A desorption step of desorbing hydrogen chloride and discharging the gas in the tower from the PSA adsorption tower is repeated, and the above-mentioned exhausted from the PSA adsorption tower in the desorption step Obtaining an inner gas as a purification gas.

  Preferably, the PSA adsorbent is composed of one or more selected from the group consisting of zeolite and non-zeolitic porous acidic oxide.

  Preferably, a value obtained by dividing the introduction amount of the cleaning gas introduced into the PSA adsorption tower in the cleaning step by the void volume in the adsorbent packed region in the PSA adsorption tower is 1.85 or more.

  Preferably, before the synthesis step, a distillation step of removing low-boiling components having lower boiling points than chlorine from raw material chlorine containing impurities by distillation is provided.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

1 represents a schematic configuration of a hydrogen chloride production system that can be used to carry out the method for producing hydrogen chloride according to the present invention. The schematic structure of an example of the adsorption | suction apparatus for performing an adsorption | suction removal process is represented. The schematic structure of an example of the PSA gas separation apparatus for performing a pressure fluctuation adsorption type gas separation process is represented. The gas flow state in steps 1-3 of a pressure fluctuation adsorption type gas separation process is represented. The gas flow state in steps 1-3 'of a pressure fluctuation adsorption type gas separation process is represented.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a hydrogen chloride production system X that can be used to carry out the method for producing hydrogen chloride according to the present invention. The hydrogen chloride production system X includes a storage tank 1, a distillation column 2, a vaporizer 3, a burner combustion device 4, an adsorption device 5, a pressure fluctuation adsorption gas separation device (PSA gas separation device) 6, and these A pipe connected to the pipe, and configured to continuously produce hydrogen chloride while supplying raw chlorine and raw hydrogen.

  The storage tank 1 is for storing liquefied chlorine as raw material chlorine. The purity of the liquefied chlorine in the storage tank 1 is not limited as long as it conforms to the Japan Soda Industry Association standard “JISIA05-1998 liquefied chlorine Cl 2”, and preferably 99.4 vol. % Or more. The main impurities contained in the raw material chlorine are nitrogen, oxygen, carbon dioxide, carbon monoxide, hydrogen chloride, bromine, moisture, and hydrocarbons (mainly methane). A pipe 201 provided with an on-off valve 101 is connected to the upper part of the storage tank 1. In a state where liquefied chlorine is stored in the storage tank 1, the storage tank 1 has a gas phase portion. In this gas phase portion, low-boiling components having a boiling point lower than that of chlorine (boiling point -34 ° C.) are concentrated. When the impurity concentration of the low boiling point component in the gas phase is high, the on-off valve 101 is opened and the gas is released through the pipe 201. Thereby, the impurity concentration of the gas phase part in the storage tank 1 can be lowered. The material of the storage tank 1 may be a container having pressure resistance and corrosion resistance. The storage tank 1 may be used at room temperature after being insulated, or a jacket may be installed to stabilize the temperature. For example, when the room temperature is 25 ° C., the internal pressure of the storage tank 1 is about 0.65 MPaG.

  When the storage tank 1 is replenished with liquefied chlorine, for example, the liquefied chlorine in the container of the chlorine transport vehicle is expelled using a purge gas (for example, nitrogen). A part of the expelling gas dissolves in the liquid phase part (liquefied chlorine) and enters the storage tank 1 along with the liquefied chlorine. Therefore, when replenishing liquefied chlorine using nitrogen, the contents of the storage tank 1 may be lower in purity than the standard purity of liquefied chlorine due to excessive nitrogen content.

  A pipe 202 is connected to the lower part of the storage tank 1. The pipe 202 is a flow path for sending liquefied chlorine discharged from the storage tank 1 to the distillation tower 2. The downstream end of the pipe 202 is connected to the distillation tower 2. The pipe 202 is provided with an on-off valve 102 and a flow rate regulator 301. The liquefied chlorine discharged from the storage tank 1 passes through the pipe 202 and the on-off valve 102, is adjusted in flow rate by the flow rate regulator 301, and is introduced into the distillation column 2.

  Although the structure and distillation system of the distillation column 2 are not limited, it is preferably performed by continuous distillation. The inside of the distillation column 2 is maintained at a temperature of about 5 ° C. to 10 ° C. and a pressure of about 0.3 to 0.4 MPaG (gauge pressure). Low boiling point components (gas) are aggregated at the top of the distillation column 2 and purified chlorine (liquefied chlorine) is aggregated at the bottom of the column. A pipe 203 is connected to the top of the distillation column 2, and the pipe 203 is provided with a condenser 410, an on-off valve 103, a pressure regulator 401, and a flow rate regulator 302. The gas containing a large amount of low-boiling components at the top of the column passes through the pipe 203, passes through the condenser 410, is depressurized by the pressure regulator 401, is adjusted in flow rate by the flow rate regulator 302, and is discharged to the outside. A pipe 204 is connected to the lower part of the condenser 410. The pipe 204 is for refluxing the liquid component in the condenser 410 to the distillation column 2. The proportion of chlorine discharged from the top of the column is preferably about 5%, more preferably about 10% with respect to the amount supplied to the distillation column 2, although it depends on the ratio of the reflux ratio to be operated.

  By distillation (distillation step) in the distillation column 2, low boiling point components of nitrogen, oxygen, carbon dioxide, carbon monoxide, and hydrocarbons (mainly methane) are almost completely removed. The impurity concentration of liquefied chlorine after distillation is preferably 10 vol. ppm or less, more preferably 1 vol. ppm or less.

  A pipe 205 is connected to the lower part of the distillation tower 2, and a heater 420 is provided in the pipe 205. The downstream end of the pipe 205 is connected to the vaporizer 3. At the bottom of the column, liquefied chlorine from which low boiling point components have been significantly removed is obtained. The liquefied chlorine at the bottom of the column passes through the pipe 205 and passes through the heater 420 and is then introduced into the vaporizer 3. A pipe 206 is connected to the upper part of the heater 420. The pipe 206 is for returning the gas component in the heater 420 to the distillation column 2.

  In addition, when the raw material chlorine to be used (liquefied chlorine in the storage tank 1) satisfies the above specified purity, purification by distillation of the raw material chlorine may be omitted.

  The vaporizer 3 heats and vaporizes liquefied chlorine. In the vaporizer 3, all or some of the liquefied chlorine is vaporized. A pipe 207 is connected to the upper portion of the vaporizer 3, and the pipe 207 is provided with an on-off valve 104, a pressure regulator 402, and a flow rate regulator 303. The downstream end of the pipe 207 is connected to the burner combustion device 4. A pipe 208 is connected to the lower part of the vaporizer 3, and the on-off valve 105, the pressure regulator 403, and the flow rate regulator 304 are connected to the pipe 208.

  In the vaporizer 3, when all the liquefied chlorine is vaporized, the vaporizer 3 is operated with the on-off valve 105 closed. In the case of full vaporization, the internal temperature of the vaporizer 3 is maintained at 40 to 50 ° C., for example. In the case of partial vaporization, the liquefied chlorine in the vaporizer 3 passes through the pipe 210, the on-off valve 105, and the pressure regulator 403, and is discharged after the flow rate is adjusted by the flow rate regulator 304. Here, the ratio of the liquefied chlorine discharged through the pipe 208 to the liquefied chlorine (including a small amount of impurities) introduced into the vaporizer 3 is preferably about 2%, more preferably about 5%. Even if the liquefied chlorine contains a very small amount of high-boiling components (for example, hydrocarbon components such as C5 and C6) by the operation of discharging the liquefied chlorine through the pipe 208, the high-boiling components Can be removed. Also, the concentration of bromine component can be lowered.

  Chlorine gas obtained by full or partial vaporization passes through the pipe 207, the on-off valve 104, and the pressure regulator 402, the pressure is adjusted to 0.02 MPaG, the flow rate is adjusted by the flow rate regulator 303, and burner combustion is performed. It is introduced into the device 4.

  The burner combustion device 4 synthesizes hydrogen chloride by burning chlorine and hydrogen. A pipe 209 provided with a flow rate regulator 305 is connected to the burner combustion apparatus 4, and raw material hydrogen is supplied to the burner combustion apparatus 4 through this pipe 209. The raw material hydrogen may be purchased and used in a general high-pressure gas container, or may be used after purifying hydrogen generated by, for example, methanol or methane reforming. As a general method for purifying hydrogen, a pressure fluctuation adsorption method (PSA method) is widely known. The purity of the raw material hydrogen used is preferably 99.9 vol. %, More preferably 99.999 vol. % Or more. Similar to the raw material chlorine, the hydrogen gas from which the low-boiling components of nitrogen, oxygen, carbon dioxide, carbon monoxide, and hydrocarbons (mainly methane) are almost completely removed passes through the pipe 209, and the pressure becomes 0.02 MPaG. Then, the flow rate is adjusted by the flow rate regulator 305 and introduced into the burner combustion device 4. The concentration of the impurity component in the hydrogen introduced into the burner combustion apparatus 4 is preferably 10 vol. ppm or less, more preferably 1 vol. ppm or less.

  In the burner combustion apparatus 4, chlorine and hydrogen are combusted to form hydrogen chloride (synthesis process). The ratio of hydrogen to chlorine used for combustion (hydrogen / chlorine) is preferably about 1.1, more preferably 1.2 or more. The reason why hydrogen is made excessive as compared with chlorine is to suppress the residual of chlorine. Moreover, the combustion temperature in the burner combustion apparatus 4 is maintained at about 1200 to 1400 ° C., for example.

  The burner combustion device 4 is made of, for example, graphite, and can be sufficiently used even when exposed to hydrogen chloride, which is a corrosive gas. A heat exchanger is built in the lower part of the burner combustion device 4 (near the outlet), and the gas discharged from the outlet of the burner combustion device 4 is cooled to 40 ° C to 45 ° C. The pressure of the exhaust gas from the burner combustion device 4 is about 0.03 MPaG.

  The gas discharged from the burner combustion device 4 is a mixed gas containing hydrogen chloride synthesized by burner combustion and other impurities (components). Since air is used when the burner combustion device 4 is ignited, oxygen (reacts with hydrogen to become water) and nitrogen are mixed in the burner combustion device 4. Main impurities in the mixed gas discharged from the burner combustion device 4 are residual chlorine, excess hydrogen, nitrogen, bromine, and moisture. A pipe 210 is connected to the lower outlet of the burner combustion device 4. The mixed gas discharged from the burner combustion device 4 is sent to the adsorption device 5 through the pipe 210.

  The adsorption device 5 removes impurities in the mixed gas sent from the burner combustion device 4 using an adsorbent. As shown in FIG. 2, in the present embodiment, the adsorption device 5 includes a first adsorption device unit 51 and a second adsorption device unit 52.

  The first adsorption device section 51 includes two adsorption towers 53A and 53B and pipes 61 to 69 that form gas flow paths. Each of the adsorption towers 53A, 53B has gas passages 54, 55 at both ends, and is filled with an adsorbent for selectively adsorbing chlorine and bromine in the mixed gas between the gas passages 54, 55. Has been. The adsorbent filled in the adsorption towers 53A and 53B is, for example, activated carbon, more preferably coconut shell activated carbon.

  A pipe 61 provided with an on-off valve 61a is connected to the gas passage port 54 of the adsorption tower 53A. A pipe 62 provided with an on-off valve 62a is connected to the gas passage port 54 of the adsorption tower 53B. The pipes 61 and 62 are connected to the pipe 210 in a branched shape. Both ends of the pipe 63 are connected between the pipes 61 and 62. The pipe 63 is provided with on-off valves 63a and 63b. A pipe 64 is connected to the pipe 63 in a branched manner between the on-off valves 63a and 63b.

  A pipe 65 provided with an on-off valve 65a is connected to the gas passage port 55 of the adsorption tower 53A. A pipe 66 provided with an on-off valve 66a is connected to the gas passage port 55 of the adsorption tower 53B. The pipes 65 and 66 are connected to the pipe 67 in a branched manner. Both ends of the pipe 68 are connected between the pipes 65 and 66. The pipe 68 is provided with on-off valves 68a and 68b. A pipe 69 is connected to the pipe 68 in a branched manner between the on-off valves 68a and 68b.

  In the adsorption towers 53A and 53B, the mixed gas from the burner combustion device 4 is allowed to flow through one of them, and the regeneration gas is allowed to flow through the other. In the adsorption towers 53A and 53B, the mixed gas and the regeneration gas are switched alternately. Specifically, when the mixed gas is sent to the first adsorption device 51 via the pipe 210, the mixed gas is ventilated through the pipe 61 (62) to the adsorption tower 53A (53B). Chlorine and bromine are removed by the adsorption tower 53A (53B), and the gas that has passed through the adsorption tower 53A (53B) passes through the pipe 65 (66) and is sent to the second adsorption device section 52 through the pipe 67. The open / close valves 61a, 62a, 63a, 63b, 65a, 66a, 68a, 68b are selected in their open / closed state so that the mixed gas flows through only one of the adsorption towers 53A, 53B.

  Further, for example, heated regeneration gas (such as nitrogen or high-purity hydrogen chloride) is passed through the pipes 69 and 68 to the adsorption tower 53B (53A) where the mixed gas from the burner combustion device 4 is not passed. . By flowing the regeneration gas, with respect to the adsorbent in the tower, the chlorine and bromine components adsorbed by the flow of the mixed gas previously performed are desorbed, and the adsorbent can be regenerated. The gas (regeneration off gas) flowing through the adsorption tower 53B (53A) and discharged from the adsorption tower 53B (53A) is discharged to the outside through the pipe 64. The regeneration temperature (regeneration temperature) of the adsorption towers 53A and 53B is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. When stainless steel is used as the material for the adsorption towers 53A and 53B, the regeneration temperature can be increased to about 250 ° C. However, when glass lining is applied to prevent corrosion, from the viewpoint of protecting the material. The regeneration temperature is preferably about 150 ° C.

  The second adsorption device section 52 includes two adsorption towers 56A and 56B and pipes 71 to 78 that form gas flow paths. Each of the adsorption towers 56A and 56B has gas passage ports 57 and 58 at both ends, and selectively adsorbs moisture in the gas that has passed through the first adsorption device section 51 between the gas passage ports 57 and 58. Of adsorbent. The adsorbent filled in the adsorption towers 56A and 56B is composed of, for example, one or more selected from the group consisting of zeolite and non-zeolitic porous acidic oxide, and more preferably high silica zeolite.

  A pipe 71 provided with an on-off valve 71a is connected to the gas passage port 57 of the adsorption tower 56A. A pipe 72 provided with an on-off valve 72a is connected to the gas passage port 57 of the adsorption tower 56B. The pipes 71 and 72 are connected to the pipe 67 in a branched manner. Both ends of the pipe 73 are connected between the pipes 71 and 72. The pipe 73 is provided with on-off valves 73a and 73b. A pipe 74 is connected to the pipe 73 in a branched manner between the on-off valves 73a and 73b.

  A pipe 75 provided with an on-off valve 75a is connected to the gas passage port 58 of the adsorption tower 56A. A pipe 76 provided with an on-off valve 76a is connected to the gas passage port 58 of the adsorption tower 56B. The pipes 75 and 76 are branched from the pipe 211. Both ends of the pipe 77 are connected between the pipes 75 and 76. The pipe 77 is provided with on-off valves 77a and 77b. A pipe 78 is connected to the pipe 77 in a branched manner between the on-off valves 77a and 77b.

  In the adsorption towers 56 </ b> A and 56 </ b> B, the mixed gas from the first adsorption unit 51 is passed through one of them, and the regeneration gas is passed through the other. In the adsorption towers 56A and 56B, the mixed gas and the regeneration gas are alternately switched. Specifically, when the mixed gas is sent to the second adsorption device section 52 through the pipe 67, the mixed gas is ventilated through the pipe 71 (72) to the adsorption tower 56A (56B). Moisture is removed by the adsorption tower 56A (56B), and the gas that has passed through the adsorption tower 56A (56B) passes through the pipe 75 (76) and is sent to the PSA gas separation device 6 through the pipe 211. The open / close valves 71a, 72a, 73a, 73b, 75a, 76a, 77a, 77b are selected in their open / closed state so that the mixed gas is allowed to flow through only one of the adsorption towers 56A, 56B.

  Further, for example, a heated regeneration gas (such as nitrogen or high-purity hydrogen chloride) is passed through the pipes 78 and 77 to the adsorption tower 56B (56A) through which the mixed gas from the first adsorption unit 51 does not flow. Let it flow. By flowing the regeneration gas, the adsorbent in the tower is desorbed from the water adsorbed by the flow of the mixed gas previously performed, and the adsorbent can be regenerated. The gas (regeneration off gas) flowing through the adsorption tower 56B (56A) and discharged from the adsorption tower 56B (56A) is discharged to the outside through the pipe 74. The regeneration temperature (regeneration temperature) of the adsorption towers 56A and 56B is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. When stainless steel is used as the material for the adsorption towers 56A and 56B, the regeneration temperature can be increased to about 250 ° C. However, when glass lining is applied to prevent corrosion, from the viewpoint of protecting the material. The regeneration temperature is preferably about 150 ° C.

  As shown in FIG. 3, the PSA gas separation device 6 includes adsorption towers 10A, 10B, and 10C (PSA adsorption tower), a compressor 21, a vacuum pump 22, and pipes 31 to 36, and contains hydrogen chloride. It is configured such that hydrogen chloride can be concentrated and separated from gas (crude hydrogen chloride gas) using a pressure fluctuation adsorption method (PSA method). The crude hydrogen chloride gas is a gas that has passed through the adsorption device 5 (the first adsorption device unit 51 and the second adsorption device unit 52), and chlorine, bromine, and moisture are significantly removed. This crude hydrogen chloride gas contains hydrogen and nitrogen as impurities in addition to hydrogen chloride as the main component.

  Each of the adsorption towers 10A, 10B, and 10C has gas passage ports 11 and 12 at both ends, and adsorption for selectively adsorbing hydrogen chloride in the crude hydrogen chloride gas between the gas passage ports 11 and 12. The agent (PSA adsorbent) is filled. Specifically, a space region defined by, for example, a perforated plate (not shown) is formed in each of the adsorption towers 10A, 10B, and 10C, and the region is filled with a PSA adsorbent. Examples of the PSA adsorbent for selectively adsorbing hydrogen chloride include zeolite (synthetic and natural zeolite). Examples of zeolite include A type, X type, Y type, L type, ZSM type, and mordenite, and Y type zeolite or high silica type zeolite is preferably used. Other examples of the PSA adsorbent used include non-zeolite porous acidic oxides such as alumina. These PSA adsorbents need not be added with additives and the like, and are generally commercially available and easily available. The above PSA adsorbents may be used alone or in combination of two or more.

  The compressor 21 is for pumping crude hydrogen chloride gas to the adsorption towers 10A, 10B, and 10C. The vacuum pump 22 is for depressurizing the inside of the adsorption towers 10A, 10B, and 10C.

  The pipe 31 includes a main path 31 ′ connected to the pipe 211 through which the crude hydrogen chloride gas flows through the adsorption device 5, and a branch connected to each gas passage 11 side of the adsorption towers 10 </ b> A, 10 </ b> B, and 10 </ b> C. It has paths 31A, 31B, 31C. A compressor 21 is provided in the main road 31 '. Automatic valves 31a, 31b, and 31c that can switch between an open state and a closed state are attached to the branch paths 31A, 31B, and 31C.

  The pipe 32 includes a main trunk path 32 ′ having a gas discharge end E <b> 1 and branch paths 32 </ b> A, 32 </ b> B, and 32 </ b> C that are connected to the respective gas passage 12 sides of the adsorption towers 10 </ b> A, 10 </ b> B, and 10 </ b> C. The branch paths 32A, 32B, and 32C are provided with automatic valves 32a, 32b, and 32c that can switch between an open state and a closed state.

  The pipe 33 includes a main trunk path 33 ′ having a gas discharge end E <b> 2 and branch paths 33 </ b> A, 33 </ b> B, 33 </ b> C each connected to the gas passage 12 side of the adsorption towers 10 </ b> A, 10 </ b> B, 10 </ b> C. The branch paths 33A, 33B, and 33C are provided with automatic valves 33a, 33b, and 33c that can switch between an open state and a closed state.

  The pipe 34 has a main path 34 ′ to which the vacuum pump 22 is attached and branch paths 34 </ b> A, 34 </ b> B, 34 </ b> C that are connected to the gas passage 11 side of the adsorption towers 10 </ b> A, 10 </ b> B, 10 </ b> C, respectively. The branch paths 34A, 34B, 34C are provided with automatic valves 34a, 34b, 34c capable of switching between an open state and a closed state. The main trunk line 34 'has a product gas extraction end E3 on the downstream side thereof.

  The pipe 35 includes a main path 35 ′ connected to the main path 34 ′ of the pipe 34 and branch paths 35 A, 35 B, 35 C each connected to the gas passage 11 side of the adsorption towers 10 A, 10 B, 10 C. Have The branch paths 35A, 35B, and 35C are provided with automatic valves 35a, 35b, and 35c that can switch between the open state and the closed state. A flow rate adjusting valve 35d (flow rate adjusting means) is attached to the main trunk path 35 '.

  The pipe 36 connects the main path 33 ′ of the pipe 33 and the main path 31 ′ of the pipe 31. The pipe 36 is provided with an automatic valve 36a capable of switching between an open state and a closed state. The pipe 36 sends a later-described cleaning off gas discharged from any of the adsorption towers (10A, 10B, 10C) to the main trunk path 31 'of the pipe 31, and adds it to the crude hydrogen chloride gas flowing through the main trunk path 31'. Is for. In addition, it is good also as a structure which does not comprise this piping 36, and in FIG. 3, the piping 36 and the automatic valve 36a are represented by the dotted line.

  Using the PSA gas separation device 6 having the above-described configuration, a pressure fluctuation adsorption gas separation process (PSA gas separation process) can be performed. When the PSA gas separation device 6 is in operation, the automatic valves 31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 36a, and the flow rate adjustment valve 35d are appropriately switched to obtain desired values in the device. A gas flow state can be realized and one cycle consisting of the following steps 1 to 3 can be repeated. In one cycle of this method, an adsorption process, a cleaning process, and a desorption process are performed in each of the adsorption towers 10A, 10B, and 10C. FIG. 4 schematically shows a gas flow state in the PSA gas separation device 6 in steps 1 to 3.

  In Step 1, a gas flow state as shown in FIG. 4A is achieved, and an adsorption process is performed in the adsorption tower 10A, a desorption process is performed in the adsorption tower 10B, and a cleaning process is performed in the adsorption tower 10C. The operation time for each step in Step 1 is, for example, 120 seconds.

  As can be well understood with reference to FIGS. 3 and 4A together, in step 1, crude hydrogen chloride gas is introduced to the gas passage 11 side of the adsorption tower 10 </ b> A via the pipe 31. The inside of the adsorption tower 10A in the adsorption step is maintained at a predetermined high pressure, hydrogen chloride in the crude hydrogen chloride gas is adsorbed by the PSA adsorbent in the adsorption tower 10A, and the gas passage port 12 of the adsorption tower 10A. Non-adsorbed gas with low hydrogen chloride concentration is discharged from the side. This non-adsorbed gas is discharged from the gas discharge end E1 through the pipe 32 to the outside of the apparatus. More specifically, the composition of the non-adsorbed gas in the adsorption process changes with time. In the initial stage of the adsorption process, the hydrogen chloride concentration in the non-adsorbed gas is relatively low. As the adsorption process proceeds, the adsorption amount of the PSA adsorbent with respect to hydrogen chloride approaches a saturated state, and the adsorption amount of hydrogen chloride decreases, so the composition of the non-adsorbed gas approaches the composition of the crude hydrogen chloride gas.

  Here, the hydrogen chloride concentration in the crude hydrogen chloride gas introduced into the adsorption tower 10A is not particularly limited, but is preferably 80 vol. % Or more, more preferably 95 vol. % Or more. The internal pressure (adsorption pressure) of the adsorption tower 10A in the adsorption process is, for example, 0 to 1 MPaG, and preferably 0 to 0.07 MPaG.

  Since the adsorbing tower 10B has been previously cleaned (see step 3 shown in FIG. 4C), at the start of step 1, hydrogen and nitrogen, which are impurities, are introduced by a cleaning gas having a high hydrogen chloride concentration described later. The impurity concentration of the gas that has been replaced and remains in the tower is low. In step 1, the inside of the adsorption tower 10B is depressurized by the vacuum pump 22, hydrogen chloride is desorbed from the PSA adsorbent in the adsorption tower 10B, and the gas in the tower (mainly desorbed from the gas passage 11 side of the adsorption tower 10B). Gas) is discharged. The discharged gas is taken out from the product gas outlet E3 through the pipe 34 and the vacuum pump 22. The internal pressure (desorption pressure) of the adsorption tower 10B in the desorption step is, for example, −0.1 to −0.01 MPaG, preferably −0.1 to −0.05 MPaG.

  At the same time, in Step 1, a part of the gas from the adsorption tower 10B that has passed through the vacuum pump 22 is connected to the pipe 35 and the gas passage 11 side of the adsorption tower 10C that has already undergone Step 3 (adsorption process) described later. The cleaning off gas is discharged from the gas passage port 12 side of the adsorption tower 10C while being introduced as the cleaning gas through the flow rate adjusting valve 35d. This cleaning off gas is discharged from the gas discharge end E2 to the outside of the apparatus via the pipe 33. In such a step 1, the adsorption tower 10C is cleaned by the gas discharged from the adsorption tower 10B.

  Here, the amount of the cleaning gas introduced into the adsorption tower 10C is adjusted so that the value obtained by dividing the amount of the cleaning gas by the void volume in the adsorbent packed region in the adsorption tower is 1.85 or more, Preferably, the divided value is adjusted to be 2.0 or more. The “adsorbent packed region in the adsorption tower” is a space region that is partitioned by a perforated plate or the like in the adsorption tower and can be filled with the adsorbent. “Void volume in the adsorbent filling area” is a space volume other than the area occupied by the filled adsorbent in the adsorbent filling area, and mainly between adsorbents and adsorbents (between adsorbent particles). ) Is occupied by the space volume. In the case where the entire adsorbent filling region having a constant volume is filled with the granular adsorbent, the “void volume in the adsorbent filling region” can be changed depending on the shape and size of the adsorbent particles themselves.

  In step 2, the gas flow state as shown in FIG. 4B is achieved, and the cleaning process is performed in the adsorption tower 10A, the adsorption process is performed in the adsorption tower 10B, and the desorption process is performed in the adsorption tower 10C. That is, in step 2, the adsorption step is performed in the adsorption tower 10B, as in the adsorption tower 10A in step 1. At the same time, in step 2, the desorption process is performed in the adsorption tower 10C in the same manner as in the adsorption tower 10B in step 1. At the same time, in Step 2, the washing process is performed in the adsorption tower 10A in the same manner as in the adsorption tower 10C in Step 1.

  In step 3, the gas flow state as shown in FIG. 4C is achieved, and the desorption process is performed in the adsorption tower 10A, the cleaning process is performed in the adsorption tower 10B, and the adsorption process is performed in the adsorption tower 10C. That is, in step 3, the adsorption process is performed in the adsorption tower 10C in the same manner as in the adsorption tower 10A in step 1. At the same time, in Step 3, the desorption process is performed in the adsorption tower 10A in the same manner as in the adsorption tower 10B in Step 1. At the same time, in step 3, the washing process is performed in the adsorption tower 10B in the same manner as in the adsorption tower 10C in step 1.

  Then, Steps 1 to 3 described above are repeatedly performed in each of the adsorption towers 10A, 10B, and 10C, whereby the crude hydrogen chloride gas is continuously introduced into any of the adsorption towers 10A, 10B, and 10C, and Gas with high hydrogen chloride concentration (product gas) is continuously acquired. In addition, about the internal temperature of adsorption tower 10A, 10B, 10C at the time of repeating 1 cycle which consists of steps 1-3, the temperature change according to a season is considered and there is no problem if it is about 0-40 degreeC.

  In the PSA gas separation process of the present embodiment, a cleaning process is performed after the adsorption process and before the desorption process for one cycle by the PSA method executed in each of the adsorption towers 10A, 10B, and 10C. The cleaning gas introduced into any of the adsorption towers (10A, 10B, 10C) in the cleaning process is part of the gas discharged from any of the other adsorption towers (10A, 10B, 10C) in the desorption process It is. The gas (cleaning gas) is mainly hydrogen chloride desorbed from the adsorbent and has a high hydrogen chloride concentration. The hydrogen chloride concentration of the cleaning gas is, for example, 99.9 vol. % Or more, depending on conditions, 99.99 vol. It may be more than%.

  In the cleaning step, impurities remaining in a part of the pores of the adsorbent or in the space between the adsorbent and the adsorbent are introduced into the adsorbent by, for example, 99.9 vol. % Pure hydrogen chloride. Then, in the subsequent desorption step, the amount of pure hydrogen chloride desorbed from the PSA adsorbent when the pressure in the column is reduced and the column gas is recovered in the subsequent desorption step is much larger than the amount of cleaning gas introduced in the cleaning step. . For this reason, the impurity component contained in the raw material composition gas (crude hydrogen chloride gas) remaining in the tower at the start of the desorption step is sufficiently diluted to finally have a purity of 99.99 vol. % Of high-purity hydrogen chloride gas (product gas) is recovered.

As described above, the amount of the cleaning gas introduced into the adsorption towers 10A, 10B, and 10C in the cleaning step is a value obtained by dividing the amount of the cleaning gas by the void volume in the adsorbent filling region in the adsorption towers 10A, 10B, and 10C. Is 1.85 or more, preferably 2.0 or more. Thus, by setting the ratio of the cleaning gas amount / the void volume in the adsorbent packed region to 1.85 or more, the gas of the raw material composition remaining in the tower (crude hydrogen chloride gas, as impurities) (Including hydrogen and nitrogen) are appropriately replaced with cleaning gas, and trace impurity components (mainly hydrogen) adsorbed on the surface of the adsorbent and impurity components remaining in the pores of the adsorbent Is considered to be discharged. As a result, the hydrogen chloride concentration in the product gas recovered in the subsequent desorption step can be set to a desired high purity. The void volume varies depending on the shape of the adsorbent and the filling method, but can be easily calculated by the following calculation formula.
<Calculation formula for obtaining void volume: (1) void volume = volume of adsorbent filling region−volume occupied by adsorbent in adsorbent filling region, (2) void volume = volume of adsorbent filling region−unit mass of adsorbent Volume per adsorbent x mass of adsorbent>

  There is no particular upper limit on the ratio of the cleaning gas amount / the void volume in the adsorbent filling region, but it is not appropriate to make the ratio extremely large from a practical viewpoint. That is, if the ratio of the cleaning gas amount / the void volume in the adsorbent filling region becomes excessive, the cleaning gas amount increases more than necessary, and the time required for the cleaning process is extended. As a result, the time for one cycle (cycle time) becomes longer, and the production efficiency of product gas (the amount of product gas obtained per unit time) is lowered, which is not preferable.

  The amount of cleaning gas introduced into the adsorption tower in the cleaning process is adjusted as described above, but the flow rate adjusting valve is also used for the flow rate per unit time and the introduction time of the cleaning gas introduced into the adsorption tower in the cleaning process. It can be appropriately adjusted by operating 35d. The gas discharged from the adsorption tower in the desorption process is recovered as product gas, and a part of the exhaust gas (product gas) is used as cleaning gas, but the chlorination of the product gas discharged outside the tower in the desorption process The hydrogen concentration changes over time. In the initial stage of the desorption process, the gas remaining in the tower is discharged in advance, so the hydrogen chloride concentration is relatively low. As the desorption process proceeds, the gas desorbed from the adsorbent is discharged, so the hydrogen chloride concentration is It gets higher. For this reason, from the viewpoint of increasing the purity of the entire product gas, it is preferable to use the gas discharged from the start of the desorption process to the middle point as the cleaning gas.

  In the case where the gas discharged from the start of the desorption process to the middle point is used as the cleaning gas, in each of the steps 1 to 3 described above with reference to FIG. 4, the cleaning process is performed in parallel with the desorption process. From the start to the middle point, until the subsequent desorption process is completed, the adsorbing tower gas that has been subjected to the cleaning process is blocked from entering and exiting.

  FIG. 5 schematically shows a gas flow state of one cycle in the PSA gas separation device 6 when a standby process is inserted after the cleaning process and before the desorption process is switched. The standby process is inserted as steps 1 ', 2', 3 'immediately after each of steps 1, 2, 3 shown in FIG.

  In step 1 ′, the gas flow state as shown in FIG. 5 (b) is achieved, and the adsorption tower 10A performs the adsorption process subsequent to step 1, and the adsorption tower 10B performs the desorption process subsequent to step 1. A standby process after the cleaning process in step 1 is performed at 10C. In step 2 ′, the gas flow state as shown in FIG. 5 (d) is achieved, and the standby process after the cleaning process in step 2 in the adsorption tower 10A is followed by the adsorption in the adsorption tower 10B after step 2. Following the step 2, the desorption process is performed in the adsorption tower 10C. In step 3 ′, the gas flow state as shown in FIG. 5 (f) is achieved, and the desorption process is continued in the adsorption tower 10A after step 3, and the adsorption tower 10B waits after the cleaning process in step 3. The adsorption process is performed following the step 3 in the adsorption tower 10C.

  As described above, the hydrogen chloride concentration in the crude hydrogen chloride gas is preferably 80 vol. % Or more, more preferably 95 vol. % Or more. If the hydrogen concentration (impurity gas component concentration) in the crude hydrogen chloride gas is high, the amount of cleaning gas introduced until the high-purity hydrogen chloride gas to be recovered increases, and the time required for the cleaning process increases, resulting in an increase in the product gas. This is not preferable because the production efficiency is significantly reduced. In addition, if the time for which the cleaning gas is supplied becomes longer as the introduction amount of the cleaning gas increases, the operation efficiency of the facility is lowered, which is not preferable.

  For the cleaning offgas discharged from the adsorption tower in the cleaning process, the impurity concentration (hydrogen concentration) in the cleaning offgas is lower than the hydrogen concentration in the crude hydrogen chloride gas. Therefore, instead of discharging the cleaning off-gas from the gas discharge end E2 to the outside of the apparatus, the automatic valve 36a of the pipe 36 is opened, and the cleaning off-gas is turned into the crude hydrogen chloride gas on the pipe 31 side via the pipe 36. It may be added and recycled. If the cleaning off gas is recycled to the raw material gas system in this way, the amount of gas discharged to the outside of the apparatus is reduced, so that the yield of the entire recovered product gas can be improved. When the pressure of the cleaning off gas flowing through the pipe 36 is lower than the pressure of the crude hydrogen chloride gas flowing through the pipe 31, a compressor (not shown) for pumping the cleaning off gas toward the pipe 31 is supplied to the pipe 36. It may be provided.

  In addition, hydrogen chloride has a particularly high corrosive action, and the presence of moisture causes deterioration of the materials of the adsorption towers 10A, 10B, and 10C. Therefore, the adsorption towers 10A, 10B, and 10C are sufficiently substituted with an inert gas before use, and the water concentration is 1000 vol. ppm or less, preferably 100 vol. It should be kept below ppm. A dehydrator (not shown) may be installed on the upstream side of the compressor 21 as necessary.

  A high-purity hydrogen chloride gas (product gas) is recovered by the vacuum pump 22 and a part thereof is used as a cleaning gas. A buffer is provided downstream of the vacuum pump 22 in order to suppress pressure fluctuations during supply of the cleaning gas. A tank (not shown) may be installed, and the product gas may be temporarily stored in the buffer tank.

  As described above, in the adsorption process, the washing process, and the desorption process executed in the adsorption towers 10A, 10B, and 10C, the internal pressure of each tower is appropriately changed, but the temperature in the tower is changed along with the pressure fluctuation. May be.

  In the hydrogen chloride production method of the present embodiment, a step of synthesizing hydrogen chloride from chlorine and hydrogen by the burner combustion device 4 under an excess hydrogen condition (synthesis step), and a mixed gas containing hydrogen chloride that has undergone the synthesis step A step of removing a part of the impurities by using the adsorbent in the adsorption device 5 (adsorption removal step), and at least a part of the impurities contained in the crude hydrogen chloride gas that has undergone the adsorption removal step, the PSA gas separation device 6 And a step of removing by pressure (pressure fluctuation adsorption type gas separation step). By executing these series of steps, high-purity hydrogen chloride gas (product gas) can be obtained.

  In this embodiment, before synthesizing hydrogen chloride with the burner combustion apparatus 4, liquefied chlorine (raw material chlorine) containing impurities is distilled, and low-boiling components having a boiling point lower than that of chlorine are removed by distillation. Through the distillation, the impurity concentration of liquefied chlorine is, for example, 10 vol. ppm or less, or 1 vol. Significantly reduced to ppm or less. According to such a configuration, it is possible to greatly reduce the load on the apparatus after the burner combustion (after the synthesis of hydrogen chloride) (adsorption removal process and pressure fluctuation adsorption gas separation process).

  In the process after the burner combustion (adsorption removal process and pressure fluctuation adsorption gas separation process), substantially all impurities are removed by adsorption. Such a purification method using an adsorption process is cost competitive as compared to a distillation process. From the viewpoint of the high-pressure gas safety law, only the storage tank 1, the distillation equipment (distillation tower 2) and the vaporization equipment (vaporizer 3) are subject to the high-pressure gas safety law as the target of high-pressure gas. The downstream of the burner combustion device 4 can be installed only by legal compliance as a general gas facility.

  The use of hydrogen chloride gas (product gas) produced by the above series of steps is not particularly limited. Any high-purity hydrogen chloride gas having a purity of about 99.99% or more may be supplied to the semiconductor material process. Moreover, it may be compressed or liquefied by, for example, a compressor or a condenser, filled in a high-pressure gas container, or stored in a storage tank.

  While specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention. For example, the structure of each part in the hydrogen chloride production system for executing the method for producing hydrogen chloride according to the present invention can be variously changed. A configuration different from that of the above-described embodiment may be adopted for the configuration of the piping forming the gas flow path in the PSA gas separation device 6. The number of PSA adsorption towers is not limited to the three-column type shown in the above embodiment, and the same effect can be expected even when there are two or less towers or four or more towers.

[Example 1]
Hydrogen chloride was produced using the above-described hydrogen chloride production system X. Table 1 shows the raw material chlorine concentration, the raw material hydrogen concentration, and the obtained hydrogen chloride concentration. In this example, the temperature of the storage tank 1 was kept at room temperature (25 ° C.), the distillation tower 2 was kept at a temperature of 10 ° C. and a pressure of 0.4 MPaG, and the vaporizer 3 was vaporized in its entirety. As the raw material hydrogen, commercially available high purity hydrogen was used. The burner combustion apparatus 4 burned with hydrogen / chlorine = 1.1. Activated carbon (manufactured by Kuraray, Kuraray GG) was stacked on the adsorption towers 53A and 53B (dechlorination and debromination tower) of the first adsorption unit 51. High silica zeolite (manufactured by Tosoh, 640HOD1A) was stacked on the adsorption towers 56A and 56B (dehydration tower) of the second adsorption device section 52. In the adsorption towers 10A, 10B, 10C (PSA adsorption tower) of the PSA gas separation device 6, high silica zeolite (manufactured by Tosoh, 385HUD1C) is laminated, the adsorption pressure is 0.1 MPaG, and the amount of cleaning gas / adsorbent is filled. Gas separation by the PSA method was performed under the operating conditions of void volume = 2.2 and desorption pressure −0.09 MPaG.

  Table 1 shows raw material chlorine (including impurities), raw material hydrogen (including impurities), raw material chlorine after the distillation process, mixed gas after burner combustion (synthesis process), and after the adsorption removal process Respective component concentrations in the crude hydrogen chloride gas (after dechlorination / bromine and after dehydration) and the product gas after the PSA gas separation step (after dehydrogenation / denitrogenation) are shown. As shown in Table 1, by using this apparatus, impurity components are significantly removed in each step, and 99.999 vol. % Of high-purity hydrogen chloride (product gas) can be obtained.

X Hydrogen chloride production system 1 Storage tank 2 Distillation tower 3 Vaporizer 4 Burner combustion device 5 Adsorption device 6 PSA gas separation device (pressure fluctuation adsorption gas separation device)
10A, 10B, 10C adsorption tower (PSA adsorption tower)
11, 12 Gas passage port 21 Compressor 22 Vacuum pumps 31-36 Piping 31 ', 32', 33 ', 34', 35 'Main roads 31A-31C, 32A-32C, 33A-33C, 34A-34C, 35A- 35C
Branch paths 31a to 31c, 32a to 32c, 33a to 33c, 34a to 34c, 35a to 35c, 36a Automatic valve 35d Flow rate adjusting valve 51 First adsorber unit 52 Second adsorber unit 53A, 53B Adsorption towers 54 and 55 Gas passage ports 56A, 56B Adsorption towers 57, 58 Gas passage ports 61-69 Piping 61a, 62a, 63a, 63b, 65a, 66a, 68a, 68b On-off valves 71-78 Piping 71a, 72a, 73a, 73b, 75a, 76a , 77a, 77b On-off valves 101 to 105 On-off valves 201 to 211 Pipes 301 to 305 Flow rate regulators 401 to 403 Pressure regulator 410 Condenser 420 Heater

Claims (6)

A synthesis process for synthesizing hydrogen chloride from chlorine and hydrogen using a burner combustion device under hydrogen-excess conditions;
An adsorption removal step of removing a part of the impurities of the mixed gas containing hydrogen chloride through the synthesis step using an adsorbent;
A pressure fluctuation adsorption gas separation step of removing at least a part of impurities contained in the crude hydrogen chloride gas that has undergone the adsorption removal step by a PSA method.   2. The production of hydrogen chloride according to claim 1, wherein the adsorbent used in the adsorption removal step is composed of one or more selected from the group consisting of activated carbon, zeolite, and non-zeolite porous acidic oxide. Method. In the pressure fluctuation adsorption gas separation step, a plurality of PSA adsorption towers filled with a PSA adsorbent that selectively adsorbs hydrogen chloride are used.
In a state where the PSA adsorption tower is at a relatively high pressure, the crude hydrogen chloride gas is introduced into the PSA adsorption tower so that hydrogen chloride in the crude hydrogen chloride gas is adsorbed on the PSA adsorbent, and the PSA adsorption is performed. An adsorption step of discharging non-adsorbed gas from the column, a cleaning step of introducing a cleaning gas having a hydrogen chloride concentration higher than the crude hydrogen chloride gas into the PSA adsorption column, and discharging a cleaning off-gas from the PSA adsorption column; Depressurizing the inside of the PSA adsorption tower to desorb hydrogen chloride from the PSA adsorbent, and repeatedly performing a cycle including a desorption process of discharging the gas in the tower from the PSA adsorption tower,
The method for producing hydrogen chloride according to claim 1 or 2, wherein the gas in the tower discharged from the PSA adsorption tower in the desorption step is obtained as a purified gas.   The method for producing hydrogen chloride according to claim 3, wherein the PSA adsorbent is composed of one or more selected from the group consisting of zeolite and non-zeolitic porous acidic oxides.   The value obtained by dividing the introduction amount of the cleaning gas introduced into the PSA adsorption tower in the cleaning step by the void volume in the adsorbent packed region in the PSA adsorption tower is 1.85 or more. A method for producing hydrogen chloride as described in 1. above.   The method for producing hydrogen chloride according to any one of claims 1 to 5, further comprising a distillation step of removing low-boiling components having lower boiling points than chlorine from raw material chlorine containing impurities by distillation before the synthesis step.

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