Patent Publication Number: US-8974647-B2

Title: Gas generation device

Description:
TECHNICAL FIELD 
     The present invention relates to a gas generation device that generates a gas. 
     BACKGROUND ART 
     Conventionally, fluorine gas is used in the semiconductor manufacturing process and so on for material cleaning, surface modification, and other purposes. While the fluorine gas itself is used in some cases, a variety of fluorine-based gases synthesized based on the fluorine gas, such as NF 3  (nitrogen trifluoride) gas, NeF (neon fluoride) gas, and ArF (argon fluoride) gas, may also be used in other cases. 
     For supplying fluorine gas stably in such sites, a fluorine gas generation device that generates fluorine gas by electrolysis of HF (hydrogen fluoride), for example, is used. 
     The fluorine gas generation device disclosed in Patent Document 1 includes an electrolyzer. The interior of the electrolyzer is divided by a partition wall into a cathode chamber and an anode chamber. In the electrolyzer, an electrolytic bath is formed with a KF-HF-based mixed molten salt. A cathode is disposed in the cathode chamber, and an anode is disposed in the anode chamber. HF is supplied through an HF supply line to the electrolytic bath in the electrolyzer for electrolysis of HF, whereby hydrogen gas is generated from the cathode and fluorine gas is generated from the anode in the electrolyzer. 
     At the top of the cathode chamber, an outlet for hydrogen gas is provided. The hydrogen gas generated in the cathode chamber exits from the outlet and is discharged through a hydrogen gas line on the cathode side. The hydrogen gas line is provided with an automatic valve and an HF adsorption column. The HF adsorption column is packed with granular NaF (sodium fluoride) pellets. This enables HF mixed in the hydrogen gas to be adsorbed by the NaF pellets in the HF adsorption column and, thus, removed from the hydrogen gas. 
     At the top of the anode chamber, an outlet for fluorine gas is provided. The fluorine gas generated in the anode chamber exits from the outlet and is discharged through a fluorine gas line. The fluorine gas line is provided with an HF adsorption column and an automatic valve. As in the hydrogen gas line, HF mixed in the fluorine gas is adsorbed by the NaF pellets in the HF adsorption column and, thus, removed from the fluorine gas. 
     On the fluorine gas line, a compressor unit is provided on the downstream of the HF adsorption column and the automatic valve. 
     In each of the cathode chamber and anode chamber, a pressure gauge for measuring the pressure in the corresponding chamber is provided. The automatic valves disposed on the hydrogen gas line and fluorine gas line open/close in accordance with the pressure values measured by the pressure gauges. 
     The automatic valve on the fluorine gas line opens when the pressure inside the anode chamber is higher than atmospheric pressure, causing the fluorine gas in the anode chamber to be sucked through the fluorine gas line into the compressor unit. On the other hand, the automatic valve on the fluorine gas line closes when the pressure inside the anode chamber is lower than atmospheric pressure. 
     [Patent Document 1] JP 2004-52105 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     When NaF pellets adsorb HF excessively, the NaF pellets decompose into powder, which in turn agglutinates. In this case, the interior of HF adsorption columns or piping connected to the HF adsorption columns may be clogged with the agglutinated NaF. This raises the need to replace the NaF pellets in the HF adsorption columns at regular intervals, which requires troublesome work as well as cost. 
     An object of the present invention is to provide a gas generation device capable of reducing work burden and cost. 
     Solution to Problem 
     (1) According to an aspect of the present invention, a gas generation device that generates a first gas and a second gas by electrolysis includes an electrolyzer divided into a first chamber and a second chamber and containing therein an electrolytic bath including a compound to be electrolyzed, a first discharge path through which the first gas generated in the first chamber is discharged, a second discharge path through which the second gas generated in the second chamber is discharged, first and second adsorbers that each include an adsorbent for adsorbing a third gas mixed in the first gas, third and fourth adsorbers that each include an adsorbent for adsorbing the third gas mixed in the second gas, a connector configured to be switchable between a first state and a second state, the first state being the state where the first and third adsorbers are connected to the first and second discharge paths, respectively, and the second and fourth adsorbers are disconnected from the first and second discharge paths, respectively, the second state being the state where the second and fourth adsorbers are connected to the first and second discharge paths, respectively, and the first and third adsorbers are disconnected from the first and second discharge paths, respectively, a first heater that heats the adsorbents in the first and third adsorbers, a second heater that heats the adsorbents in the second and fourth adsorbers, and a controller that controls the connector, the first heater, and the second heater, wherein the controller switches the connector between the first state and the second state, and when the connector is in the first state, the controller controls the first and second heaters such that the third gas is adsorbed by the adsorbents in the first and third adsorbers and the third gas is desorbed from the adsorbents in the second and fourth adsorbers, and when the connector is in the second state, the controller controls the first and second heaters such that the third gas is adsorbed by the adsorbents in the second and fourth adsorbers and the third gas is desorbed from the adsorbents in the first and third adsorbers. 
     In this gas generation device, electrolysis of the compound included in the electrolytic bath takes place, so that the first gas is generated in the first chamber and the second gas is generated in the second chamber. The first gas generated in the first chamber is discharged through the first discharge path, while the second gas generated in the second chamber is discharged through the second discharge path. 
     In the case where the connector is in the first state, the first and third adsorbers are connected to the first and second discharge paths, respectively, and the second and fourth adsorbers are disconnected from the first and second discharge paths, respectively. As a result, the first gas generated in the first chamber is guided to the first adsorber, while the second gas generated in the second chamber is guided to the third adsorber. 
     In this case, the adsorbents in the first through fourth adsorbers are heated by the first and second heaters such that the third gas is adsorbed by the adsorbents in the first and third adsorbers and that the third gas is desorbed from the adsorbents in the second and fourth adsorbers. 
     In the case where the connector is in the second state, the second and fourth adsorbers are connected to the first and second discharge paths, respectively, and the first and third adsorbers are disconnected from the first and second discharge paths, respectively. As a result, the first gas generated in the first chamber is guided to the second adsorber, while the second gas generated in the second chamber is guided to the fourth adsorber. 
     In this case, the adsorbents in the first through fourth adsorbers are heated by the first and second heaters such that the third gas is adsorbed by the adsorbents in the second and fourth adsorbers and that the third gas is desorbed from the adsorbents in the first and third adsorbers. 
     As a result, when the connector is in the second state, the third gas adsorbed to the adsorbents in the first and third adsorbers is desorbed from the adsorbents. On the other hand, when the connector is in the first state, the third gas that was adsorbed by the adsorbents in the second and fourth adsorbers while the connector was in the second state is desorbed from the adsorbents. 
     Therefore, by switching the connector alternately between the first and second states, it is possible to prevent the third gas from being excessively adsorbed to the adsorbents in the first through fourth adsorbers, without the need to replace the adsorbents in the first through fourth adsorbers. As a result, the work burden as well as cost can be reduced. 
     Further, in both cases where the connector is in the first state and in the second state, the first and second gases of high purity, with the third gas removed therefrom, are discharged through the first and second discharge paths. This allows the first and second gases to be supplied continuously, while preventing the third gas from being excessively adsorbed to the adsorbents in the first through fourth adsorbers. 
     (2) The gas generation device may further include a first circulation path through which the third gas desorbed from the adsorbent in the second adsorber is guided to the first chamber when the connector is in the first state, and through which the third gas desorbed from the adsorbent in the first adsorber is guided to the first chamber when the connector is in the second state, and a second circulation path through which the third gas desorbed from the adsorbent in the fourth adsorber is guided to the second chamber when the connector is in the first state, and through which the third gas desorbed from the adsorbent in the third adsorber is guided to the second chamber when the connector is in the second state. 
     In this case, the third gas desorbed from the adsorbents in the first and second adsorbers is guided to the first chamber, while the third gas desorbed from the adsorbents in the third and fourth adsorbers is guided to the second chamber. This enables the third gas desorbed from the adsorbents to be used again as the material for electrolysis. As a result, the cost can further be reduced. 
     (3) The gas generation device may further include a first gas supplier that supplies a fourth gas to the second adsorber when the connector is in the first state, and that supplies the fourth gas to the first adsorber when the connector is in the second state, and a second gas supplier that supplies a fifth gas to the fourth adsorber when the connector is in the first state, and that supplies the fifth gas to the third adsorber when the connector is in the second state. 
     In this case, when the connector is in the first state, the fourth and fifth gases are supplied from the first and second gas suppliers to the second and fourth adsorbers, so that the third gas desorbed from the adsorbents in the second and fourth adsorbers is pushed out of the second and fourth adsorbers. Further, when the connector is in the second state, the fourth and fifth gases are supplied from the first and second gas suppliers to the first and third adsorbers, so that the third gas desorbed from the adsorbents in the first and third adsorbers is pushed out of the first and third adsorbers. This prevents the third gas desorbed from the adsorbents from being re-adsorbed in the first through fourth adsorbers. 
     (4) The first gas supplier may include a storage that stores part of the first gas discharged through the first discharge path, and a gas supply path through which the first gas stored in the storage is guided as the fourth gas to the second adsorber when the connector is in the first state, and through which the first gas stored in the storage is guided as the fourth gas to the first adsorber when the connector is in the second state. 
     In this case, part of the first gas generated in the first chamber is supplied to the first and second adsorbers, so that the third gas desorbed from the adsorbents in the first and second adsorbers is pushed out of the first and second adsorbers without the use of another gas. This can prevent the third gas from being re-adsorbed by the adsorbents in the first and second adsorbers without an increase in cost. 
     (5) Of the first gas discharged through the first discharge path, an excess over a required amount may be stored in the storage. In this case, the excess of the first gas is used to push the third gas out of the first and second adsorbers. This can prevent the third gas from being re-adsorbed by the adsorbents in the first and second adsorbers, while securing the required amount of first gas. 
     (6) The first gas may be fluorine gas, the second gas may be hydrogen, the third gas and the compound may be hydrogen fluoride, the adsorbents may be sodium fluoride, the first chamber may be an anode chamber, and the second chamber may be a cathode chamber. 
     In this case, hydrogen fluoride that is mixed in the fluorine gas and hydrogen generated by electrolysis of hydrogen fluoride can reliably be adsorbed by sodium fluoride. Further, hydrogen fluoride adsorbed to sodium fluoride can readily be desorbed from sodium fluoride. 
     Advantageous Effects of Invention 
     It is possible to prevent the third gas from being excessively adsorbed to the adsorbents in the first through fourth adsorbers, without the need of replacing the adsorbents in the first through fourth adsorbers. As a result, the work burden as well as cost can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram showing the configuration of a fluorine gas generation device according to an embodiment of the present invention. 
         FIG. 2  is a diagram illustrating a first operating state. 
         FIG. 3  is a diagram illustrating a second operating state. 
         FIG. 4  is a block diagram showing a part of a control system in the fluorine gas generation device in  FIG. 1 . 
         FIG. 5  is a flowchart illustrating, by way of example, processing for switching supply paths of fluorine gas and others performed by a control device in the fluorine gas generation device according to the present embodiment. 
         FIG. 6  is a flowchart illustrating, by way of example, the processing for switching the supply paths of fluorine gas and others performed by the control device in the fluorine gas generation device according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A gas generation device and a gas generation method according to an embodiment of the present invention will now be described with reference to the drawings. In the following embodiment, a fluorine gas generation device for generating fluorine gas will be described as an example of the gas generation device. 
     (1) Configuration of the Fluorine Gas Generation Device 
       FIG. 1  is a schematic diagram showing the configuration of the fluorine gas generation device according to an embodiment of the present invention. As shown in  FIG. 1 , the fluorine gas generation device  100  includes an electrolyzer  1 . The electrolyzer  1  is formed, for example, of Ni (nickel), Monel, pure iron, stainless steel, or other metal or alloy. The interior of the electrolyzer  1  is divided by a partition wall  2  into a cathode chamber  3  and an anode chamber  4 . The partition wall  2  is made of Ni or Monel, for example. 
     In the electrolyzer  1 , an electrolytic bath  1   a  of KF-HF-based mixed molten salt is formed. A cathode  5  of Ni (nickel), for example, is disposed in the cathode chamber  3 , and an anode  6  of carbon with low polarizability, for example, is disposed in the anode chamber  4 . When a voltage is applied across the cathode  5  and the anode  6 , electrolysis of HF (hydrogen fluoride) takes place. As a result, in the electrolyzer  1 , hydrogen gas is primarily generated from the cathode  5  and fluorine gas is primarily generated from the anode  6 . 
     At the top of the cathode chamber  3 , a cathode outlet  20   a  is provided. Connected to the cathode outlet  20   a  is an (upstream) end of a pipe  20 . The other end of the pipe  20  is connected to an end of each of pipes  21 ,  22 . The pipe  21  has open/close valves V 1 , V 2  provided in this order from the upstream side. The pipe  22  has open/close valves V 3 , V 4  provided in this order from the upstream side. 
     The pipe  21  has the other end connected to a gas inlet of an HF adsorption column  60 . The pipe  22  has the other end connected to a gas inlet of an HF adsorption column  61 . The interiors of the HF adsorption columns  60 ,  61  are packed with cylindrical NaF (sodium fluoride) pellets. 
     The HF adsorption column  60  has a gas outlet to which an end of a pipe  23  is connected. The pipe  23  has open/close valves V 5 , V 6  provided in this order from the upstream side. The HF adsorption column  61  has a gas outlet to which an end of a pipe  24  is connected. The pipe  24  has open/close valves V 7 , V 8  provided in this order from the upstream side. 
     The pipes  23  and  24  have their other ends connected to an end of a pipe  25 . The other end of the pipe  25  is connected, for example, to a gas cylinder or a manufacturing line in a factory. 
     A portion of the pipe  21  located between the open/close valves V 1 , V 2  and a portion of the pipe  22  located between the open/close valves V 3 , V 4  are connected to each other via a pipe  26 . The pipe  26  has open/close valves V 9 , V 10  provided in this order from the pipe  21  side. A portion of the pipe  26  located between the open/close valves V 9 , V 10  is connected to an end of a pipe  27 . The pipe  27  has the other end connected to an inert gas tank  53 . The inert gas tank  53  stores therein an inert gas, such as N 2  (nitrogen), Ar (argon), or He (Helium), at high pressure. 
     A portion of the pipe  23  located between the open/close valves V 5 , V 6  and a portion of the pipe  24  located between the open/close valves V 7 , V 8  are connected to each other via a pipe  28 . The pipe  28  has open/close valves V 11 , V 12  provided in this order from the pipe  23  side. A portion of the pipe  28  located between the open/close valves V 11 , V 12  is connected to an end of a pipe  29 . The pipe  29  is provided with an open/close valve V 13 . The pipe  29  has the other end connected to an end of each of pipes  30  and  31 . The pipe  30  has the other end configured to be located in the electrolytic bath  1   a  in the cathode chamber  3 . 
     The pipe  31  is provided with an open/close valve V 14 . The pipe  31  has the other end connected to an HF supply source  51 . The liquid level of the electrolytic bath  1   a  is detected, for example, by a liquid level detector (not shown). When the detected liquid level is lower than a prescribed value, the open/close valve V 13  is closed while the open/close valve V 14  is opened. This causes HF to be supplied from the HF supply source  51  via the pipes  31 ,  30  into the electrolytic bath  1   a.    
     At the top of the anode chamber  4 , an anode outlet  40   a  is provided. Connected to the anode outlet  40   a  is an (upstream) end of a pipe  40 . The pipe  40  has the other end connected to an end of each of pipes  41 ,  42 . The pipe  41  has open/close valves V 15 , V 16  provided in this order from the upstream side. The pipe  42  has open/close valves V 17 , V 18  provided in this order from the upstream side. 
     The pipe  41  has the other end connected to a gas inlet of an HF adsorption column  62 . The pipe  42  has the other end connected to a gas inlet of an HF adsorption column  63 . The HF adsorption columns  62 ,  63  are packed with cylindrical NaF pellets. 
     The HF adsorption column  62  has a gas outlet to which an end of a pipe  43  is connected. The pipe  43  has open/close valves V 19 , V 20  provided in this order from the upstream side. The HF adsorption column  63  has a gas outlet to which an end of a pipe  44  is connected. The pipe  44  has open/close valves V 21 , V 22  provided in this order from the upstream side. The pipes  43  and  44  have their other ends connected to an end of a pipe  45 . The pipe  45  is provided with a compressor  45   a.    
     A portion of the pipe  41  located between the open/close valves V 15 , V 16  and a portion of the pipe  42  located between the open/close valves V 17 , V 18  are connected to each other via a pipe  46 . The pipe  46  has open/close valves V 24 , V 25  provided in this order from the pipe  41  side. A portion of the pipe  46  located between the open/close valves V 24 , V 25  is connected to an end of a pipe  47 . The pipe  47  is provided with an open/close valve V 26 . The pipe  47  has the other end connected to a buffer tank  52 . In the buffer tank  52 , fluorine gas generated in the anode chamber  4  is stored at high pressure, as will be described later. The buffer tank  52  is connected to an end of a pipe  50 . The pipe  50  is provided with an open/close valve V 27 . The pipes  45  and  50  have their other ends connected to an end of a pipe  46   a . The pipe  46  is provided with an open/close valve V 23 . The other end of the pipe  46   a  is connected, for example, to a gas cylinder or a manufacturing line in a factory. 
     A portion of the pipe  43  located between the open/close valves V 19 , V 20  and a portion of the pipe  44  located between the open/close valves V 21 , V 22  are connected to each other via a pipe  48 . The pipe  48  has open/close valves V 28 , V 29  provided in this order from the pipe  43  side. A portion of the pipe  48  located between the open/close valves V 28 , V 29  is connected to an end of a pipe  49 . The pipe  49  has the other end configured to be located in the upper space within the anode chamber  4 . 
     In the fluorine gas generation device  100  according to the present embodiment, heating furnaces  80 ,  81  are provided for heating the NaF pellets packed in the HF adsorption columns  60 - 63 . The HF adsorption columns  60 ,  62  are disposed in the heating furnace  80 , while the HF adsorption columns  61 ,  63  are disposed in the heating furnace  81 . The members constituting the heating furnaces  80 ,  81  are formed, for example, of stainless steel (SUS316L), nickel, Monel, copper, Inconel-based alloy, or Incoloy-based alloy. 
     (2) Operation 
     An operation of the fluorine gas generation device  100  will now be described. The fluorine gas generation device  100  operates alternately in a first operating state and a second operating state as described below. 
       FIG. 2  is a diagram illustrating the first operating state.  FIG. 3  is a diagram illustrating the second operating state. 
     In the first operating state shown in  FIG. 2 , the open/close valves V 1 , V 2 , V 4 , V 5 , V 6 , V 7 , V 10 , V 12 , V 13 , V 15 , V 16 , V 18 , V 19 , V 20 , V 21 , V 23 , V 25 , V 26 , and V 29  are opened, while the open/close valves V 3 , V 8 , V 9 , V 11 , V 14 , V 17 , V 22 , V 24 , V 27 , and V 28  are closed. In this state, the compressor  45   a  is driven, and a voltage is applied across the cathode  5  and the anode  6  by a voltage applier  70  (see  FIG. 4 , which will be discussed later). 
     Further, the HF adsorption columns  60 ,  62  are heated at a first temperature by the heating furnace  80 , while the HF adsorption columns  61 ,  63  are heated at a second temperature by the heating furnace  81 . Here, the second temperature is higher than the first temperature. The first temperature may be 80° C. to 90° C., for example, and the second temperature may be 300° C., for example. 
     In this case, the hydrogen gas generated in the cathode chamber  3  is supplied through the pipes  20 ,  21 , the HF adsorption column  60 , and the pipes  23 ,  25 , to a gas cylinder or a manufacturing line in a factory. In the HF adsorption column  60 , HF mixed in the hydrogen gas is adsorbed by the NaF pellets and, thus, removed from the hydrogen gas. 
     Further, the fluorine gas generated in the anode chamber  4  is supplied through the pipes  40 ,  41 , the HF adsorption column  62 , and the pipes  43 ,  45 ,  46   a , to a gas cylinder or a manufacturing line in a factory. In the HF adsorption column  62 , HF mixed in the fluorine gas is adsorbed by the NaF pellets and, thus, removed from the fluorine gas. 
     Furthermore, the inert gas stored at high pressure in the inert gas tank  53  is fed through the pipes  27 ,  26 ,  22  to the HF adsorption column  61 , while the fluorine gas stored at high pressure in the buffer tank  52  is fed through the pipes  47 ,  46 ,  42  to the HF adsorption column  63 . 
     It is noted that in the first operating state and in the second operating state described later, the open/close valve V 23  is temporarily closed and, at the same time, the open/close valve V 27  is opened, so that the fluorine gas generated in the anode chamber  4  is guided to the buffer tank  52  for storage therein. In this case, of the fluorine gas generated in the anode chamber  4 , an excess over the required amount (for example, the amount to be used in the manufacturing line in a factory) is stored in the buffer tank  52 . 
     As the HF adsorption columns  61 ,  63  are heated at high temperature (second temperature), in the HF adsorption columns  61 ,  63 , HF adsorbed to the NaF pellets is desorbed therefrom. 
     HF desorbed within the HF adsorption column  61  is pushed out of the HF adsorption column  61  by the inert gas fed from the inert gas tank  53 , and is returned through the pipes  24 ,  28 ,  29 ,  30  into the electrolytic bath  1   a.  HF desorbed within the HF adsorption column  63  is pushed out of the HF adsorption column  63  by the fluorine gas fed from the buffer tank  52 , and is returned through the pipes  44 ,  48 ,  49  to the upper space in the anode chamber  4 . 
     It is noted that the heating of the HF adsorption columns  61 ,  63  by the heating furnace  81  is stopped after a lapse of certain time from the start of operation in the first operating state. Further, the open/close valves V 4 , V 7 , V 10 , V 12 , and V 13  are closed, so that the supply of the inert gas from the inert gas tank  53  to the HF adsorption column  61  is stopped, and the open/close valves V 18 , V 21 , V 25 , V 26 , and V 29  are closed, so that the supply of the fluorine gas from the buffer tank  52  to the HF adsorption column  63  is stopped. Hereinafter, the open/close valves V 4 , V 7 , V 10 , V 12 , V 13 , V 18 , V 21 , V 25 , V 26 , and V 29  will be called a first valve group. 
     In the second operating state shown in  FIG. 3 , the open/close valves V 2 , V 3 , V 4 , V 5 , V 7 , V 8 , V 9 , V 11 , V 13 , V 16 , V 17 , V 18 , V 19 , V 21 , V 22 , V 23 , V 24 , V 26 , and V 28  are opened, while the open/close valves V 1 , V 6 , V 10 , V 12 , V 14 , V 15 , V 20 , V 25 , V 27 , and V 29  are closed. In this state, the compressor  45   a  is driven, and a voltage is applied across the cathode  5  and the anode  6  by the voltage applier  70  (see  FIG. 4 , which will be discussed later). 
     Further, the HF adsorption columns  61 ,  63  are heated at the first temperature by the heating furnace  81 , while the HF adsorption columns  60 ,  62  are heated at the second temperature by the heating furnace  80 . 
     In this case, the hydrogen gas generated in the cathode chamber  3  is supplied through the pipes  20 ,  22 , the HF adsorption column  61 , and the pipes  24 ,  25 , to a gas cylinder or a manufacturing line in a factory. In the HF adsorption column  61 , HF mixed in the hydrogen gas is adsorbed by the NaF pellets and, thus, removed from the hydrogen gas. 
     Further, the fluorine gas generated in the anode chamber  4  is supplied through the pipes  40 ,  42 , the HF adsorption column  63 , and the pipes  44 ,  45 ,  46   a , to a gas cylinder or a manufacturing line in a factory. In the HF adsorption column  63 , HF mixed in the fluorine gas is adsorbed by the NaF pellets and, thus, removed from the fluorine gas. 
     Furthermore, the inert gas stored at high pressure in the inert gas tank  53  is fed through the pipes  27 ,  26 ,  21  to the HF adsorption column  60 , while the fluorine gas stored in the high pressure state in the buffer tank  52  is fed through the pipes  47 ,  46 ,  41  to the HF adsorption column  62 . 
     As the HF adsorption columns  60 ,  62  are heated at high temperature (second temperature), in the HF adsorption columns  60 ,  62 , HF adsorbed to the NaF pellets is desorbed therefrom. 
     HF desorbed within the HF adsorption column  60  is pushed out of the HF adsorption column  60  by the inert gas fed from the inert gas tank  53 , and is returned through the pipes  23 ,  28 ,  29 ,  30  into the electrolytic bath  1   a.  HF desorbed within the HF adsorption column  62  is pushed out of the HF adsorption column  62  by the fluorine gas fed from the buffer tank  52 , and is returned through the pipes  43 ,  48 ,  49  to the upper space in the anode chamber  4 . 
     It is noted that the heating of the HF adsorption columns  60 ,  62  by the heating furnace  80  is stopped after a lapse of certain time from the start of operation in the second operating state. Further, the open/close valves V 2 , V 5 , V 9 , V 11 , and V 13  are closed, so that the supply of the inert gas from the inert gas tank  53  to the HF adsorption column  60  is stopped, and the open/close valves V 16 , V 19 , V 24 , V 26 , and V 28  are closed, so that the supply of the fluorine gas from the buffer tank  52  to the HF adsorption column  62  is stopped. 
     Hereinafter, the open/close valves V 2 , V 5 , V 9 , V 11 , V 13 , V 16 , V 19 , V 24 , V 26 , and V 28  will be called a second valve group. 
     (3) Adsorption and Desorption of HF 
     As described above, in the first operating state, HF mixed in the hydrogen gas and the fluorine gas is adsorbed by the NaF pellets in the HF adsorption columns  60 ,  62  and, thus, removed from the hydrogen gas and the fluorine gas. Further, in the second operating state, HF mixed in the hydrogen gas and the fluorine gas is adsorbed by the NaF pellets in the HF adsorption columns  61 ,  63  and, thus, removed from the hydrogen gas and the fluorine gas. 
     As HF is removed from the fluorine gas and the hydrogen gas, hydrogen and fluorine gases of high purity can be supplied to manufacturing lines in a factory and so on. Further, the removal of highly corrosive HF can prevent corrosion of the pipes constituting the supply paths for the hydrogen gas and the fluorine gas. 
     If HF is excessively adsorbed to the NaF pellets in the HF adsorption columns  60 - 63 , however, the NaF pellets will decompose into powder, which will then agglutinate. In such a case, the interiors of the HF adsorption columns  60 - 63  or the pipes  21 - 24 ,  41 - 44  connected to the HF adsorption columns  60 - 63  may be clogged with the agglutinated NaF. 
     In view of the foregoing, in the present embodiment, the HF adsorption columns  61 ,  63  are heated at the second temperature in the first operating state, so that HF is desorbed from the NaF pellets in the HF adsorption columns  61 ,  63 . Further, the HF adsorption columns  60 ,  62  are heated at the second temperature in the second operating state, so that HF is desorbed from the NaF pellets in the HF adsorption columns  60 ,  62 . 
     As the fluorine gas generation device  100  operates alternately in the first and second operating states, HF adsorbed by the NaF pellets in the HF adsorption columns  60 ,  62  in the first operating state is desorbed from the NaF pellets in the second operating state. Further, HF adsorbed by the NaF pellets in the HF adsorption columns  61 ,  63  in the second operating state is desorbed from the NaF pellets in the first operating state. This can prevent HF from being excessively adsorbed to the NaF pellets in the HF adsorption columns  60 - 63 . 
     Here, in order to efficiently and reliably prevent excessive adsorption of HF to the NaF pellets, it is preferable to appropriately control the time for continuing the first operating state and the time for continuing the second operating state. Hereinafter, the time during which the first operating state is continued and the time during which the second operating state is continued will each be called the operation-continuing time T 1 . 
     Further, if the temperature and time for heating the NaF pellets for making HF desorbed therefrom are inappropriate, the NaF pellets may decompose into powder and the powder may agglutinate, as in the case where the NaF pellets adsorb HF excessively. It is thus preferable to appropriately control the second temperature, the heating time of the HF adsorption columns  61 ,  63  in the first operating state, and the heating time of the HF adsorption columns  60 ,  62  in the second operating state. Hereinafter, the time during which the HF adsorption columns  61 ,  63  are heated in the first operating state and the time during which the HF adsorption columns  60 ,  62  are heated in the second operating state will each be called the heating time T 2 . 
     The composition of the NaF pellet to which HF is adsorbed is expressed as: NaF•nHF (n&gt;0). The present inventors have found, through experiments and investigation as will be described later, that the NaF pellet remains in a certain shape when the above “n” is within the range of not less than 0.01 and not more than 0.5. In the present embodiment, the operation-continuing time T 1 , the second temperature, and the heating time T 2  are set in advance, through experiments and simulation, such that the NaF pellets in the HF adsorption columns  60 - 63  have the composition of: Na•nHF (0.01≦n≦0.5). 
     (4) Relation between the Adsorbed Amount of HF and the Shape of the NaF Pellet 
     In order to investigate the relation between the amount of HF adsorbed to the NaF pellet and the shape of the NaF pellet, the following experiment was carried out. 
     Fluorine gas having HF mixed therein was supplied to the HF adsorption columns  60 - 63  packed with a plurality of cylindrical NaF pellets. The total weight of the NaF pellets before supplying the fluorine gas was 15 kg, and the total weight of the NaF pellets after supplying the fluorine gas was 15.31 kg. This means that the amount of HF adsorbed to the NaF pellets was 0.31 kg. 
     After the supply of the fluorine gas, the NaF pellets were collected from a plurality of locations in the HF adsorption columns  60 - 63 . In this case, in the HF adsorption columns  60 - 63 , a greater amount of HF was adsorbed to the NaF pellet located at a more upstream side (at a location closer to the gas inlet). More specifically, the compositions of the collected NaF pellets were, from the upstream side, NaF•1.15HF, NaF•0.78HF, NaF•0.24HF, NaF•0.19HF, NaF•0.15HF, NaF•0.14HF, NaF•0.18HF, NaF•0.18HF, and NaF•0.22HF. 
     The NaF pellets with the compositions of NaF•1.15HF and NaF•0.78HF decomposed into powder and then agglutinated; they were unable to maintain the cylindrical form. In contrast, the NaF pellets with the compositions of NaF•0.24HF, NaF•0.19HF, NaF•0.15HF, NaF•0.14HF, NaF•0.18HF, and NaF•0.22HF experienced no decomposition into powder or agglutination; they remained in the cylindrical form. 
     From the above, it was found that the NaF pellet remains in the cylindrical form when the NaF pellet has the composition of: NaF•nHF (0.01≦n≦0.5). 
     (5) Control System in the Fluorine Gas Generation Device 
       FIG. 4  is a block diagram showing a control system in the fluorine gas generation device  100 . The fluorine gas generation device  100  in  FIG. 1  includes a control device  90  shown in  FIG. 4 . The control device  90  includes a central processing unit (CPU) and a memory, or a microcomputer. The control device  90  also has a timer  90   a.    
     The control device  90  controls the operations of the voltage applier  70 , the heating furnaces  80 ,  81 , the open/close valves V 1 -V 29 , and the compressor  45   a,  to thereby control the timing for applying a voltage across the cathode  5  and the anode  6 , the heating times and heating temperatures of the HF adsorption columns  60 - 63 , the opening and closing of the open/close valves V 1 -V 29 , and the driving and stopping of the compressor  45   a.    
     (6) Supply Path Switching Processing 
     In the present embodiment, during the operation of the fluorine gas generation device  100 , the control device  90  carries out the supply path switching processing as described below.  FIGS. 5 and 6  show a flowchart illustrating, by way of example, the supply path switching processing by the control device  90 . It is noted that the open/close valves V 1 -V 29  are all closed in the initial state. Further, in this example, the fluorine gas generation device  100  initially operates in the first operating state. 
     First, when the start of electrolysis of HF is instructed by an input device (not shown) or the like, the control device  90  resets the elapsed time that was counted while the fluorine gas generation device  100  was previously operating, and starts the operation of counting the elapsed time by the built-in timer  90   a  (step S 1 ). 
     Then, the control device  90  controls the voltage applier  70 , the heating furnaces  80 ,  81 , the open/close valves V 1 -V 29 , and the compressor  45   a  so as to cause the fluorine gas generation device  100  to operate in the first operating state shown in  FIG. 2  (step S 2 ). 
     More specifically, the control device  90  opens the open/close valves V 1 , V 2 , V 4 , V 5 , V 6 , V 7 , V 10 , V 12 , V 13 , V 15 , V 16 , V 18 , V 19 , V 20 , V 21 , V 23 , V 25 , V 26 , and V 29 , and closes the open/close valves V 3 , V 8 , V 9 , V 11 , V 14 , V 17 , V 22 , V 24 , V 27 , and V 28 . Further, the control device  90  drives the compressor  45   a,  and causes the voltage applier  70  to apply a voltage across the cathode  5  and the anode  6 . Furthermore, the control device  90  causes the heating furnace  80  to heat the HF adsorption columns  60 ,  62  at the first temperature, and causes the heating furnace  81  to heat the HF adsorption columns  61 ,  63  at the second temperature. 
     Next, the control device  90  detects the elapsed time since when the counting was started in step S 1  by the built-in timer  90   a  (step S 3 ). Then, the control device  90  determines whether the detected elapsed time from the start of counting by the timer  90   a  has reached a preset heating time T 2  (step S 4 ). 
     If the elapsed time from the start of counting by the timer  90   a  has not reached the heating time T 2 , the control device  90  repeats the processing in steps S 3 , S 4  until the elapsed time from the start of counting reaches the heating time T 2 . 
     If the elapsed time from the start of counting by the timer  90   a  has reached the heating time T 2 , the control device  90  stops the operation of the heating furnace  81  (step S 5 ), and closes the first valve group described above (step S 6 ). This causes the heating of the NaF pellets in the HF adsorption columns  61 ,  63  to be stopped, and also causes the supply of the inert gas and the fluorine gas to the HF adsorption columns  61 ,  63  to be stopped. 
     Next, the control device  90  detects the elapsed time since when the counting was started in step S 1  by the built-in timer  90   a  (step S 7 ). Then, the control device  90  determines whether the detected elapsed time from the start of counting by the timer  90   a  has reached a preset operation-continuing time T 1  (step S 8 ). 
     If the elapsed time from the start of counting by the timer  90   a  has not reached the operation-continuing time T 1 , the control device  90  repeats the processing in steps S 7 , S 8  until the elapsed time from the start of counting reaches the operation-continuing time T 1 . 
     If the elapsed time from the start of counting by the timer  90   a  has reached the operation-continuing time T 1 , the control device  90  once resets the elapsed time counted by the timer  90   a  (step S 9 ), and starts the operation of counting the elapsed time (step S 10 ). 
     Then, the control device  90  controls the voltage applier  70 , the heating furnaces  80 ,  81 , the open/close valves V 1 -V 29 , and the compressor  45   a  so as to cause the fluorine gas generation device  100  to operate in the second operating state shown in  FIG. 3  (step S 11 ). 
     More specifically, the control device  90  opens the open/close valves V 2 , V 3 , V 4 , V 5 , V 7 , V 8 , V 9 , V 11 , V 13 , V 16 , V 17 , V 18 , V 19 , V 21 , V 22 , V 23 , V 24 , V 26 , and V 28 , and closes the open/close valves V 1 , V 6 , V 10 , V 12 , V 14 , V 15 , V 20 , V 25 , V 27 , and V 29 . Further, the control device  90  drives the compressor  45   a,  and causes the voltage applier  70  to apply a voltage across the cathode  5  and the anode  6 . Furthermore, the control device  90  causes the heating furnace  81  to heat the HF adsorption columns  61 ,  63  at the first temperature, and causes the heating furnace  80  to heat the HF adsorption columns  60 ,  62  at the second temperature. 
     Next, the control device  90  detects the elapsed time since when the counting was started in step S 10  by the built-in timer  90   a  (step S 12 ). Then, the control device  90  determines whether the detected elapsed time from the start of counting by the timer  90   a  has reached a preset heating time T 2  (step S 13 ). 
     If the elapsed time from the start of counting by the timer  90   a  has not reached the heating time T 2 , the control device  90  repeats the processing in steps S 12 , S 13  until the elapsed time from the start of counting reaches the heating time T 2 . 
     If the elapsed time from the start of counting by the timer  90   a  has reached the heating time T 2 , the control device  90  stops the operation of the heating furnace  80  (step S 14 ), and closes the second valve group described above (step S 15 ). This causes the heating of the NaF pellets in the HF adsorption columns  60 ,  62  to be stopped, and also causes the supply of the inert gas and the fluorine gas to the HF adsorption columns  60 ,  62  to be stopped. 
     Next, the control device  90  detects the elapsed time since when the counting was started in step S 10  by the built-in timer  90   a  (step S 16 ). Then, the control device  90  determines whether the detected elapsed time from the start of counting by the timer  90   a  has reached a preset operation-continuing time T 1  (step S 17 ). 
     If the elapsed time from the start of counting by the timer  90   a  has not reached the operation-continuing time T 1 , the control device  90  repeats the processing in steps S 16 , S 17  until the elapsed time from the start of counting reaches the operation-continuing time T 1 . 
     If the elapsed time from the start of counting by the timer  90   a  has reached the operation-continuing time T 1 , the control device  90  once resets the elapsed time counted by the timer  90   a  (step S 18 ), and starts the operation of counting the elapsed time (step S 19 ). Thereafter, the control device  90  repeats the processing in steps S 2  through S 19 . 
     (7) Effects 
     In the fluorine gas generation device  100  according to the present embodiment, HF that was adsorbed by the NaF pellets in the HF adsorption columns  60 ,  62  in the first operating state is desorbed from the NaF pellets in the second operating state. Further, HF that was adsorbed by the NaF pellets in the HF adsorption columns  61 ,  63  in the second operating state is desorbed from the NaF pellets in the first operating state. This can prevent HF from being excessively adsorbed to the NaF pellets in the HF adsorption columns  60 - 63 , without the need of replacing the NaF pellets in the HF adsorption columns  60 - 63 . As a result, work burden on the workers as well as cost can be reduced. 
     Further, in the fluorine gas generation device  100  according to the present embodiment, hydrogen and fluorine gases of high purity, with HF removed therefrom, can be supplied in both of the first and second operating states. This enables the hydrogen gas and the fluorine gas to be supplied continuously, while preventing HF from being excessively adsorbed to the NaF pellets in the HF adsorption columns  60 - 63 . 
     Further, in the fluorine gas generation device  100  according to the present embodiment, HF desorbed from the NaF pellets in the HF adsorption columns  60 - 63  is returned into the electrolyzer  1 . This enables HF desorbed from the NaF pellets to be used again as the material for electrolysis. As a result, the cost can further be reduced. 
     Further, in the fluorine gas generation device  100  according to the present embodiment, the operation-continuing time T 1 , the second temperature, and the heating time T 2  are set such that the NaF pellets in the HF adsorption columns  60 - 63  have the composition of: Na•nHF (0.01≦n≦0.5). This reliably prevents the decomposition and agglutination of the NaF pellets, and reliably prevents the clogging of the interiors of the HF adsorption columns  60 - 63  as well as the clogging of the pipes  21 - 24 ,  41 - 44  connected to the HF adsorption columns  60 - 63 . 
     Further, in the fluorine gas generation device  100  according to the present embodiment, the HF adsorption columns  60 - 63  can be used continuously, even if the HF adsorption columns  60 - 63  are small in size, without the need to replace the NaF pellets in the HF adsorption columns  60 - 63 . This can further reduce the device cost and transport cost. It is noted that the HF adsorption columns  60 - 63  are made to have the volumetric capacities of 0.5 L to 2 L, for example. 
     (8) Other Embodiments 
     While the timing of switching between the first and second operating states is controlled on the basis of the time counted by the timer  90   a  in the above embodiment, not limited thereto, the timing of switching between the first and second operating states may be controlled in another way. 
     For example, the timing of switching between the first and second operating states may be controlled on the basis of the generated amounts of hydrogen gas and fluorine gas in the cathode chamber  3  and anode chamber  4 . In this case, a sensor for detecting the generated amount of fluorine gas or hydrogen gas is provided in the electrolyzer  1 , for example. Further, the amounts of generation of fluorine gas and hydrogen gas are set in advance such that the NaF pellets in the HF adsorption columns  60 - 63  have the composition of: NaF•nHF (0.01≦n≦0.5). At the time point when the generated amount of fluorine gas or hydrogen gas detected by the sensor has reached a preset value, the operating state is switched between the first and second operating states. In this manner, it is possible to efficiently and reliably prevent HF from being excessively adsorbed to the NaF pellets in the HF adsorption columns  60 - 63 . 
     Further, while fluorine gas is generated in the anode chamber  4  and hydrogen gas is generated in the cathode chamber  3  in the above embodiment, oxygen or another gas may be generated in each of the anode chamber  4  and the cathode chamber  3 . 
     Further, while fluorine gas stored in the buffer tank  52  is fed to the HF adsorption columns  62 ,  63  to cause HF desorbed from the adsorbents to be pushed out of the HF adsorption columns  62 ,  63  in the above embodiment, HF desorbed from the adsorbents may be pushed out of the HF adsorption columns  62 ,  63  in another way. For example, a gas tank storing an inert gas such as nitrogen, argon, or helium may be additionally provided, and the inert gas may be fed from the gas tank to the HF adsorption columns  62 ,  63 , to thereby cause HF desorbed from the adsorbents to be pushed out of the HF adsorption columns  62 ,  63 . 
     Further, while the switching between the first and second operating states, the stopping of the heating furnace  81  in the first operating state, and the stopping of the heating furnace  80  in the second operating state are performed automatically by the control device  90  in the above embodiment, an operator may perform the switching between the first and second operating states, stop the heating furnace  81  in the first operating state, and stop the heating furnace  80  in the second operating state. 
     (9) Correspondences between the Elements recited in the Claims and Those Described in the Embodiments 
     In the following paragraphs, non-limiting examples of correspondences between various elements recited in the claims below and those described above with respect to various preferred embodiments of the present invention are explained. 
     In the embodiments described above, the fluorine gas generation device  100  is an example of the gas generation device, the anode chamber  4  is an example of the first chamber, the cathode chamber  3  is an example of the second chamber, fluorine gas is an example of the first gas, hydrogen gas is an example of the second gas, the pipe  40  is an example of the first discharge path, hydrogen fluoride is an example of the third gas, the pipe  20  is an example of the second discharge path, the HF adsorption column  62  is an example of the first adsorber, the HF adsorption column  63  is an example of the second adsorber, the HF adsorption column  60  is an example of the third adsorber, and the HF adsorption column  61  is an example of the fourth adsorber. 
     Further, the open/close valves V 1 -V 4 , V 15 -V 18  are an example of the connector, the states of the open/close valves V 1 -V 4 , V 15 -V 18  in the first operating state shown in  FIG. 2  are an example of the first state, the states of the open/close valves V 1 -V 4 , V 15 -V 18  in the second operating state shown in  FIG. 3  are an example of the second state, the heating furnace  80  is an example of the first heater, the heating furnace  81  is an example of the second heater, the control device  90  is an example of the controller, the pipe  49  is an example of the first circulation path, the pipes  29 ,  30  are an example of the second circulation path, fluorine gas is an example of the fourth gas, the buffer tank  52  and the pipe  47  are an example of the first gas supplier, the inert gas such as nitrogen, argon, or helium is an example of the fifth gas, the inert gas tank  53  and the pipe  27  are an example of the second gas supplier, the buffer tank  52  is an example of the storage, and the pipe  47  is an example of the gas supply path. 
     As the elements recited in the claims, a variety of other elements having the configuration or function recited in the claims may be used as well. 
     [Industrial Applicability] 
     The present invention is applicable to the supply of gases to a variety of processing equipment.