Patent Publication Number: US-2007111052-A1

Title: Method of treating reformate, apparatus for treating reformate and fuel cell electric power generating system

Description:
TECHNICAL FIELD  
      This invention relates to a method of treating a reformate in which carbon monoxide in the reformate, which contains hydrogen and which is formed from a hydrocarbon fuel and a water component by the steam reforming reaction, is removed by the selective oxidation thereof, to an apparatus for treating a reformate, and to a fuel cell electric power generating system having the apparatus for treating a reformate.  
     BACKGROUND ART  
      In a fuel cell electric power generating system, a reformate containing a large amount of hydrogen is utilized as a fuel. The reformate is generally obtained by the steam reforming reaction of a hydrocarbon fuel with a water component. The reformate formed by the steam reforming reaction contains several % of carbon monoxide which poisons an electrode catalyst of a fuel cell. Therefore, it is necessary to reduce the concentration of carbon monoxide in the reformate before it is fed to the fuel cell.  
      Among the fuel cells, a proton-exchange membrane fuel cell is particularly promising for sale on the market such as for a power source of automobiles and for domestic uses (supply of high temperature heat) because the start-up time is reduced due to its low operation temperature of as low as below 100° C. and because the material costs can be suppressed to a low level. However, since the operation temperature of the proton-exchange membrane fuel cell is low as described above, the activity of the electrode catalyst is low and the catalyst is poisoned by carbon monoxide in the reformate. Therefore, it is necessary to reduce the carbon monoxide concentration in the reformate to several 10 ppm or less.  
      The reformate obtained from a hydrocarbon fuel by the steam reforming reaction using a reforming catalyst contains several % of carbon monoxide. As a consequence, a transforming reaction using a transformation catalyst is often conducted after the steam reforming reaction. In this manner, the carbon monoxide concentration in the reformate may be reduced to several thousands ppm. Even with this method, however, the carbon monoxide concentration is still high in the case of the solid polymer type fuel cell. Thus, a carbon monoxide removing apparatus having a selective oxidation catalyst is disposed downstream of the transformation catalyst to perform selective oxidation reaction of carbon monoxide with oxygen in air. By this method, the carbon monoxide concentration in the reformate may be reduced to several tens ppm or less.  
     DISCLOSURE OF THE INVENTION  
     Problems to be Solved by the Invention  
      However, in a fuel cell system which is provided with a fuel cell and which uses a Ru-based or Pt-based catalyst as a selective oxidation catalyst, when air for selective oxidation is supplied to the fuel cell simultaneously with the supply of a reformate at the time of start of the system, the carbon monoxide concentration in the reformate gradually increases during continuous operation beyond several hours so that the electrode catalyst of the fuel cell is occasionally poisoned. Thus, there is a problem in reliability of the fuel cell system. In the course of the commercialization for, for example, automobiles or domestic uses, the reliance and stability for a long term are highly desired in the fuel cell system.  
      Thus, it is an object of the present invention to provide a method of treating a reformate which can remove carbon monoxide in the reformate for a long period of time in a stable and reliable manner, to provide an apparatus for treating a reformate, and to provide a fuel cell electric power generating system having such an apparatus for treating a reformate.  
     Means for Solving the Problem  
      In order to achieve the above object, a method for treating a reformate according to claim  1  comprises, as shown in  FIG. 1  for example, a temperature elevating step of heating a selective oxidation catalyst  19  to elevate temperature thereof, the selective oxidation catalyst  19  being for selectively oxidizing carbon monoxide in the reformate  44  with air  34  for selective oxidation; a selective oxidation catalyst activating step of, after the temperature of the selective oxidation catalyst  19  has been elevated in the temperature elevating step, supplying the reformate  44 , formed in a reforming step of forming the reformate  43  from a hydrocarbon fuel  42  by steam reforming reaction, to the selective oxidation catalyst  19  for a predetermined time, without supplying the air  34  for selective oxidation, to activate the selective oxidation catalyst  19 ; and a carbon monoxide removing step of removing carbon monoxide in the reformate  44 , formed in the reforming step, by the selective oxidation thereof with the air  34  for selective oxidation using the activated selective oxidation catalyst  19 .  
      In the above construction which has the temperature elevating step, the selective oxidation catalyst activating step, and the carbon monoxide removing step, temperature of the selective oxidation catalyst  19  is elevated, without supplying the air  34  for selective oxidation, so as to allow the reduction reaction of the selective oxidation catalyst  19  to easily take place. The reformate  44  is supplied for a predetermined period of time to reduce the selective oxidation catalyst  19  with hydrogen so that the catalyst is activated. Using the activated selective oxidation catalyst  19 , carbon monoxide in the reformate  44  is selectively oxidized and removed therefrom. Therefore, carbon monoxide in the reformate  44  can be removed in a stable and reliable manner for a long period of time.  
      In a method of treating a reformate according to claim  2 , as recited in claim  1 , as shown in  FIG. 1  for example, the heating in the temperature elevating step is carried out using a heat generated by an electric heater  21 .  
      In the above construction in which the temperature elevating step is carried out using a heat generated by an electric heater  21 , the temperature of the selective oxidation catalyst  19  can be elevated in a reliable manner by supplying an electric power to the electric heater  21  without being influenced by conditions in other steps.  
      In a method of treating a reformate according to claim  3 , as recited in claim  1  or claim  2 , as shown in  FIG. 2  for example, the heating in the temperature elevating step is carried out using a heat of oxidation generated by oxidation of combustible gas components in the reformate  144 , formed in the reforming step, by the air  134  for selective oxidation using the selective oxidation catalyst  119 .  
      Since the carbon monoxide removing step, in which carbon monoxide in the reformate  144  is oxidized, accompanies the oxidation of combustible gas components in the reformate  144  by the air  134  for selective oxidation using the selective oxidation catalyst  119 , the heat of oxidation is utilized for heating without waste and, therefore, the heating is carried out efficiently. Thus, the treatment process can be simplified because it is not necessary to add a heating step.  
      In a method of treating a reformate according to claim  4 , as recited in any one of claim  1  to claim  3 , as shown in FIG.  3  for example, the heating in the temperature elevating step is carried out using a heat of combustion generated in a combustion step of combusting a combustion fuel  230  using a combustion catalyst  222 .  
      Since the heating in the temperature elevating step is typically carried out by appropriation of a large amount of heat of combustion which is mainly utilized for heating the reforming catalyst  220  used for the formation of the reformate  243 , the heating may be performed within a short period of time.  
      In order to achieve the above object, an apparatus  1  for treating a reformate according to claim  5 , as shown in  FIG. 1  for example, comprises: carbon monoxide removing means  15 , filled with a selective oxidation catalyst  19 , for removing carbon monoxide in the reformate  44 , formed in reforming means  11  for forming the reformate  43  from a hydrocarbon fuel  38  by the steam reforming reaction, by selective oxidation thereof with air  34  for selective oxidation; temperature elevating means  21  for elevating temperature of the selective oxidation catalyst  19 ; and control means  25  for performing a control such that the temperature of the selective oxidation catalyst  19  is elevated by the temperature elevating means  21 , that the reformate  44  is supplied in a predetermined amount to the selective oxidation catalyst  19 , whose temperature has been elevated, without supplying the air  34  for selective oxidation, and that, after the reformate  44  has been supplied in the predetermined amount, supply of the air  34  for selective oxidation to the selective oxidation catalyst  19  is started.  
      In the above construction which includes the carbon monoxide removing means  15 , the temperature elevating means  21 , and the control means  25 , control can be made so that the temperature of the selective oxidation catalyst  19  filled in the carbon monoxide removing means  15  is elevated by the temperature elevating means  21 . To the thus temperature-elevated selective oxidation catalyst  19 , a reformate  44  is supplied in a predetermined amount without supplying the air  34  for selective oxidation thereto. After the supply of the predetermined amount has been completed, the supply of the air  34  for selective oxidation to the selective oxidation catalyst  19  is started. Thus, the selective oxidation catalyst  19  can be activated by the hydrogen reduction with the reformate  44  to enable the removal of carbon monoxide in the reformate  44  by selective oxidation thereof. Accordingly, the removal of carbon monoxide in the reformate  44  can be carried out in a stable and reliable manner for a long period of time.  
      In order to achieve the above object, a fuel cell electric power generating system  301  according to claim  6 , as shown in  FIG. 4  for example, comprises: the reforming means  111 ; the apparatus  101  for treating a reformate  145  as recited in claim  5 ; and a fuel cell  106  for generating an electric power by electrochemical reaction of the reformate  145 , from which carbon monoxide has been removed, with an oxidizing agent gas  135 .  
      In the above construction, there can be provided a fuel cell electric power generating system  301  in which the apparatus  101  for treating a reformate can supply the reformate  145 , from which carbon monoxide has been removed and which has a low content of carbon monoxide, in a stable manner for a long period of time. Thus, the fuel cell  106  can supply an electric power in a stable manner for a long period of time.  
     Effect of the Invention  
      Since the temperature elevating step, the selective oxidation catalyst activating step, and the carbon monoxide removing step are provided, the temperature of the selective oxidation catalyst is elevated, without supplying the air for selective oxidation, so as to allow the reduction reaction of the selective oxidation catalyst to easily take place. The reformate is supplied for a predetermined period of time to reduce the selective oxidation catalyst with hydrogen so that the catalyst is activated. Using the activated selective oxidation catalyst, carbon monoxide in the reformate is selectively oxidized and removed therefrom. Therefore, carbon monoxide in the reformate can be removed in a stable and reliable manner for a long period of time.  
      The present application is based on the Japanese Patent Application No. 2003-280618 filed on Jul. 28, 2003. This Japanese Patent Application is hereby incorporated in its entirety by reference into the present application.  
      The present application will become more fully understood from the detailed description given hereinbelow. However, the detailed description and the specific embodiment are illustrated of desired embodiments of the present invention and are described only for the purpose of explanation. Various changes and modifications will be apparent to those ordinary skilled in the art of the basic of the detailed description.  
      The applicant has no intention to give to public any disclosed embodiment. Among the disclosed changes and modifications, those which may not literally fall within the scope of the patent claims constitute, therefore, a part of the present invention in the sense of doctrine of equivalents.  
     PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION  
      Embodiments of the present invention will be described below with reference to the drawings. In each of the Figures, the same reference numerals designate the similar or corresponding parts and overlapped description will be omitted.  
       FIG. 1  is a block diagram illustrating the construction of a fuel treating apparatus  1 , as an apparatus for treating a reformate, according to a first embodiment of the present invention. The fuel treating apparatus  1  includes a fuel gas feeding blower  2 , a pump  3  for supplying process water for reforming, an air feeding blower  5  for selective oxidation, a reforming section  11  as reforming means, filled with are forming catalyst  20 , a transforming section  12  filled with a transformation catalyst  14 , a selective oxidation section  15  as carbon monoxide removing means, filled with a selective oxidation catalyst  19 , a combustion section  10 , a boiler  16 , a selective oxidation section heater  21  as temperature elevating means or an electric heater, a reforming section temperature detector  26 , a selective oxidation section temperature detector  27 , and a controlling device  25  as controlling means. A flow passage  13  extends within the transforming section  12  for heating a fuel gas  38  passing through the transformation catalyst  14  before being fed to the reforming section  11  without contact with the transformation catalyst  14 . Also, a flow passage  18  extends within the selective oxidation section  15  for heating the fuel gas  38  passing through the selective oxidation catalyst  19  before being fed to the reforming section  11  without contact with the selective oxidation catalyst  19 .  
      The fuel gas feeding blower  2  feeds the fuel gas  38  as a hydrocarbon fuel to the reforming section  11  through the flow passage  18  and the flow passage  13 . The pump  3  for supplying process water for reforming supplies process water  39  for reforming to the flow passage  18 , disposed with the selective oxidation section  15 , through the boiler  16 . The air feeding blower  5  for selective oxidation feeds the air  34  for selective oxidation to the selective oxidation catalyst  19  contained in the selective oxidation section  15 . The selective oxidation catalyst  19  is typically a supported catalyst containing, as a catalyst, a noble metal such as Pt or Ru supported on a carrier such as alumina.  
      In the reforming section  11 , the reformate  43  is produced by a steam reforming reaction (for example, CH 4 +H 2 O→3H 2 +CO) of the fuel gas  42  as a reforming fuel supplied to the reforming section  11  through the flow passage  18  and the flow passage  13  with the process water  41  for reforming using the reforming catalyst  20 . In the transforming section  12 , carbon monoxide in the reformate  43  supplied to the transforming section  12  is removed by a transforming reaction (CO+H 2 O→CO 2 +H 2 ) of the carbon monoxide with the process water  41  for reforming which remains present in the reformate  43  using the transformation catalyst  14 . In the selective oxidation section  15 , carbon monoxide remaining in the reformate  44  supplied to the selective oxidation section  15  is removed by the selective oxidation reaction (CO+(½)O 2 →CO 2 ) using the selective oxidation catalyst  19 .  
      In the combustion section  10 , a raw material  30  for combustion introduced into the combustion section  10  is combusted using the air  31  for combustion. The combustion section  10  is provided with a combustion burner (not shown) by which the raw material  30  for combustion is combusted.  
      In the boiler  16 , the process water  39  for reforming fed to the boiler  16  is heated and evaporated by the heat supplied from the transforming section  12 , the selective oxidation section  15 , and the reforming section  11 . The evaporated process water  40  for reforming is passed, together with the fuel gas  38 , to the reforming section  11  through the flow passage  18  and the flow passage  13 .  
      The selective oxidation section heater  21  is wound around the outer periphery of the selective oxidation section  15  and is disposed in the fuel treatment apparatus  1 . The selective oxidation section heater  21  is supplied with an electric power from the controlling device  25  to generate a heat by which the selective oxidation catalyst  19  in the selective oxidation section  15  is heated so that the temperature of the selective oxidation catalyst  19  is elevated.  
      The reforming section temperature detector  26  measures the temperature of the reforming catalyst  20  in the reforming section  11  and outputs a temperature signal i 1  to the controlling device  25 . The selective oxidation section temperature detector  27  measures the temperature of the selective oxidation catalyst  19  in the selective oxidation section  15  and outputs a temperature signal i 2  to the controlling device  25 .  
      The controlling device  25  receives the temperature signal i 1  from the reforming section temperature detector  26  and the temperature signal i 2  from the selective oxidation section temperature detector  27 . The controlling device  25  conducts the control of the entire fuel treatment device  1  and is adapted to control, for example, the supply of the fuel gas  38 , process water  39  for reforming, the air  34  for selective oxidation, raw material  30  for combustion, and the air  31  for combustion.  
      Next, the description will be made of the method for treating the reformate according to the above first embodiment in the normal operation stage using the controlling device  25 . The fuel gas  38  as the raw material to be reformed is fed to the reforming section  11  of the fuel treatment apparatus  1  by the fuel gas feeding blower  2 , while the process water  39  for reforming is fed thereto by the pump  3  for supplying the process water for reforming. The process water  39  for reforming is heated by the boiler  16  to form the evaporated process water  40  for reforming. The heating of the process water  39  for reforming in the boiler  16  is performed by the transfer of the heat of the selective oxidation reaction (exothermic reaction) from the selective oxidation section  15  as well as by the transfer of the heat of the transforming reaction (exothermic reaction) from the transforming section  12 . As a result of the heating by the boiler  16 , the temperature of the process water  39  for reforming increases from the ambient temperature to 80 to 100° C.  
      The evaporated process water  40  for reforming is mixed with the fuel gas  38  and the mixture is fed to the reforming section  11  through the flow passage  18  in the selective oxidation section  15  and the flow passage  13  in the transforming section  12 . The fuel gas  38  and the evaporated process water  40  for reforming are directly heated in the flow passage  18  by the selective oxidation section  15  and further directly heated in the flow passage  13  by the transforming section  12 . The temperature of fuel gas  38  and the evaporated process water  4 . 0  for reforming which exit from the flow passage  18  has increased to 100 to 120° C., while the temperature of fuel gas  38  and the evaporated process water  40  for reforming which exit from the flow passage  13  has increased to 200 to 300° C.  
      The fuel gas  42  exiting from the flow passage  13  and the evaporated process water  41  for reforming which exit from the flow passage  13  are subjected to a steam reforming reaction in the reforming section  11  to form a reformate  43  which is rich in hydrogen. The reformate  43  contains carbon monoxide in an amount of about 10%. The reformate  43  exiting from the reforming section  11  is introduced into the transforming section  12 . In the transforming section  12 , carbon monoxide in the reformate  43  is removed by a transforming reaction, so that the concentration of carbon monoxide in the reformate  43  is reduced to about 0.5 to 2%. The typical composition of the reformate  44  exiting from the transforming section  12  includes 75% of hydrogen, 21% of carbon dioxide, 3% of methane, and 1% of carbon monoxide, in terms of mol % on the dry base. The reformate  44  existing from the transforming section  12  is introduced into the selective oxidation section  15 , carbon monoxide in the reformate  44  is removed by the selective oxidation reaction in the selective oxidation section  15 , and the carbon monoxide concentration is reduced to several tens ppm or less. The reformate  45  exiting from the selective oxidation section  15  is supplied from the fuel treating apparatus  1  to a device (not shown in  FIG. 1 ) adapted to utilize the reformate  45 .  
      Next, the description will be made of the method for treating the reformate according to the above first embodiment at the start of the operation using the controlling device  25 . The raw material  30  for combustion and the air  31  for combustion are fed to the combustion section  10  and the combustion burner (not shown) is ignited to start the combustion thereof. The temperature of the reforming catalyst  20  in the reforming section  11  detected by the reforming section temperature detector  26  is maintained at 400° C. or less. The fuel gas  42  is supplied to the reforming section  11 . The control of the temperature of the reforming section  11  is made by stopping the combustion in the combustion section  10  as soon as the temperature has exceeded 400° C. The reason for the control of the temperature of the reforming section  11  at a temperature of 400° C. or less is to prevent the fuel gas  42  from being carbonized in the state where no water is present.  
      After the initiation of the combustion in the combustion section  10 , an electric power is supplied to the selective oxidation section heater  21  so that the heater generates a heat for heating the selective oxidation section  15 . Thus, the temperature of the selective oxidation section  15  is elevated (temperature elevating step). When the temperature of the selective oxidation section  15  exceeds 100° C., the supply of the process water  39  for reforming is started. The reason for starting the supply after the temperature has exceeded 100° C. is to prevent the condensation of the process water  39  for reforming in the fuel treatment apparatus  1 . Since the reforming section  11  and transforming section  12  are typically disposed at positions nearer to the combustion section  10  than the selective oxidation section  15  is, there is no fear of occurrence of dew condensation as long as the temperature of the selective oxidation section  15  exceeds 100° C.  
      After the start of the supply of the process water  39  for reforming, the flow rate of the fuel gas  38  and the flow rate of the raw material  30  for combustion are increased, and the temperature of the reforming section  11  is increased to 650° C. By increasing the temperature of the reforming section  11  to 650° C., it is possible to produce the reformate  44  which is rich in hydrogen. Next, the amount of heat generated by the selective oxidation section heater  21  is controlled so that the temperature of the selective oxidation section  15  measured by the selective oxidation section temperature detector  27  is adjusted to 140° C.  
      In this state, the hydrogen rich reformate  44  is streamed through the selective oxidation section  15  in an amount of 25 L (predetermined amount) for 10 minutes (predetermined period of time), so that the selective oxidation catalyst  19  is subjected to hydrogen reduction and activated (selective oxidation catalyst activating step). Since the temperature of the selective oxidation catalyst  19  has been raised to 140° C. and is within the temperature range of not lower than 120° C. and not higher than 200° C., the reduction treatment of the selective oxidation catalyst  19  can be conducted efficiently. Next, the supply of the electric power to the selective oxidation section heater  21  is stopped and the air  34  for selective oxidation is supplied to the selective oxidation section  15  (carbon monoxide removing step). By this, carbon monoxide in the reformate  44  is efficiently selectively oxidized and removed. Therefore, the fuel treatment apparatus  1  can supply the reformate  45  which is small in the carbon monoxide content (the content is several tens ppm or less).  
      As described in the foregoing, according to the fuel treatment apparatus  1  of the first embodiment, the controlling device  25  performs a control such that the selective oxidation catalyst  19  is heated at the start of the operation to 140° C. using the selective oxidation section heater  21  and that the reformate  44  is supplied to the selective oxidation catalyst  19 , without feeding the air for selective oxidation, to reduce the selective oxidation catalyst  19 , thereby to permit the activation of the selective oxidation catalyst  19 .  
       FIG. 2  is a block diagram illustrating the construction of a fuel treating apparatus  101  according to a second embodiment of the present invention. The same reference numerals plus 100 are used to denote the component parts in the second embodiment which correspond to those in the first embodiment. The following description will be mainly made of the structure different from the fuel treatment apparatus  1  of the first embodiment. Those points which are not described below are the same as those of the fuel treatment apparatus  1  of the first embodiment. The fuel treating apparatus  101  is not provided with the selective oxidation section heater  21  ( FIG. 1 ). Therefore, a controlling device  125  is not configured to supply an electric power to the selective oxidation section heater  21 .  
      A method for treating the reformate according to the second embodiment in the normal operation stage using the controlling device  125  is the same as the method for treating the reformate according to the above first embodiment in the normal operation stage using the controlling device  25 .  
      Next, the description will be made of the method for treating the reformate according to the second embodiment at the start of the operation using the controlling device  125 . A raw material  130  for combustion and air  131  for combustion are fed to a combustion section  110  and a combustion burner (not shown) is ignited to start the combustion thereof. Next, a fuel gas  142  is supplied to a reforming section  111 . When the temperature of a reforming catalyst  120  in the reforming section  111  detected by a reforming section temperature detector  126  exceeds 400° C., the combustion in the combustion section  110  is stopped, and the temperature of the reforming catalyst  120  is maintained at 400° C. or less. The fuel gas  142  fed to the reforming section  111  is heated in the reforming section  111  by the reforming catalyst  120 . The heated fuel gas  142  heats a selective oxidation section  115  during its passage through the selective oxidation section  115 .  
      When the temperature of the selective oxidation section  115  exceeds 100° C., the supply of process water  139  for reforming is started. After the start of the supply of the process water  139  for reforming, the flow rate of a fuel gas  138  and the flow rate of the raw material  130  for combustion are increased, and the temperature of the reforming section  111  is increased to 650° C. By increasing the temperature of the reforming section  111 , it is possible to produce are formate  144  which is rich in hydrogen. After the temperature of 650° C. has been reached in the reforming section  111 , air  134  for selective oxidation is supplied to the selective oxidation section  115  by an air feeding blower  105  for selective oxidation. As a result, a combustion reaction of combustible gas components such as hydrogen in the reformate  144  takes place in the selective oxidation section  115  to increase the temperature of the selective oxidation catalyst  119  (temperature elevating step). In this case, since the selective oxidation catalyst  119  has not yet been subjected to a reduction treatment, the carbon monoxide removing efficiency may be reduced after operation for a long period of time. However, it is possible to elevate the temperature by the combustion reaction of combustible gas components such as hydrogen. When the temperature of the selective oxidation section  115  is elevated to 140° C., the supply of the air  134  for selective oxidation is stopped.  
      In this state, the hydrogen rich reformate  144  is streamed through the selective oxidation section  115  in an amount of 25 L (predetermined amount) for 10 minutes (predetermined period of time), so that the selective oxidation catalyst  119  is subjected to hydrogen reduction and activated (selective oxidation catalyst activating step) Since the temperature of the selective oxidation catalyst  119  has been raised to 140° C., the reduction treatment of the selective oxidation catalyst  119  can be conducted efficiently. When the temperature of the selective oxidation section  115  decreases to below 120° C. during the activation of the selective oxidation catalyst  119 , the supply of the air  134  for selective oxidation is again started and continued until the temperature of the selective oxidation section  115  returns to 140° C. When the temperature of the selective oxidation section  115  returns to 140° C., the supply of the air  134  for selective oxidation is stopped and the reduction treatment of the selective oxidation catalyst  119  is restarted. A total of 25 L of the hydrogen rich reformate  144  is streamed without supplying the air  134  for selective oxidation.  
      Next, the air  134  for selective oxidation is supplied to the selective oxidation section  115  (carbon monoxide removing step). By this, carbon monoxide in the reformate  144  is efficiently selectively oxidized and removed. Therefore, the fuel treatment apparatus  101  can supply the reformate  145  which is small in the carbon monoxide content (the content is several tens ppm or less)  
      In the second embodiment, the air feeding blower  105  for selective oxidation serves as temperature elevating means for elevating the temperature of the selective oxidation catalyst  119 .  
      According to the fuel treatment apparatus  101  of the second embodiment, the controlling device  125  performs a control such that the air  134  for selective oxidation is supplied by the air feeding blower  105  for selective oxidation to the selective oxidation section  115  at the start of the operation to combust the combustible gas components such as hydrogen in the reformate  144  in the selective oxidation section  115  and to heat the selective oxidation catalyst  119  to 140° C. and that the reformate  144  is supplied to the selective oxidation catalyst  119 , without feeding the air  134  for selective oxidation, to reduce the selective oxidation catalyst  119 , thereby to permit the activation of the selective oxidation catalyst  119 .  
       FIG. 3  is a block diagram illustrating the construction of a fuel treating apparatus  201  according to a third embodiment of the present invention. The same reference numerals plus 200 are used to denote the component parts in the third embodiment which correspond to those in the first embodiment.  
      The following description will be mainly made of the structure different from the fuel treatment apparatus  1  of the first embodiment. Those points which are not described below are the same as those of the fuel treatment apparatus  1  of the first embodiment. The fuel treating apparatus  201  is not provided with the selective oxidation section heater  21  ( FIG. 1 ). Therefore, a controlling device  225  is not configured to supply an electric power to the selective oxidation section heater. The fuel treating apparatus  201  is provided with a combustion catalyst section  217 , filled with a combustion catalyst  222 , connected to a line through which a combustion exhaust gas  233  is discharged from a combustion section  210 . The combustion catalyst section  217  is disposed adjacent to a transforming section  212  and a selective oxidation section  215 . The combustion catalyst section  217  is capable of combusting hydrogen and a hydrocarbon fuel.  
      A method for treating the reformate according to the third embodiment in the normal operation stage using the controlling device  225  is the same as the method for treating the reformate according to the above first embodiment in the normal operation stage using the controlling device  25 .  
      Next, the description will be made of the method for treating the reformate according to the third embodiment at the start of the operation using the controlling device  225 . A raw material  230  for combustion and air  231  for combustion are fed to the combustion section  210  and a combustion burner (not shown) is ignited to start the combustion thereof. After the start of the combustion in the combustion section  210 , a fuel gas  238  is supplied to a reforming section  211 . When the temperature of a reforming catalyst  220  in the reforming section  211  detected by a reforming section temperature detector  226  has arrived at 400° C., the combustion in the combustion section  210  is stopped. When the combustion in the combustion section  210  is stopped, however, the feed of the raw material  230  for combustion and the air  231  for combustion to the fuel treatment device  201  is continued. Thus, the raw material  230  for combustion and the air  231  for combustion are passed to the combustion catalyst section  217  to start the combustion in the combustion catalyst section  217 .  
      The temperatures of the transforming section  212  and the selective oxidation section  215  increase by the heat of the combustion generated in the combustion catalyst section  217 . When the temperature of the reforming section  211  becomes lower than 300° C., the feed of the raw material  230  for combustion is stopped and the combustion section  210  is purged once by air  231  for combustion. Thereafter, the feed of the raw material  230  for combustion is restarted and the burner (not shown) is again ignited to start the combustion in the combustion section  210 . Incidentally, the combustion catalyst section  217  serves as heating means in the present invention.  
      When the temperature of the selective oxidation section  215  exceeds 100° C., the supply of process water  239  for reforming is started. After the start of the supply of the process water  239  for reforming, the flow rate of the fuel gas  238  and the flow rate of the raw material  230  for combustion are increased, and the temperature of the reforming section  211  is increased to 650° C. By the increase of the temperature of the reforming section  211  to 650° C., it is possible to produce a reformate  244  which is rich in hydrogen. Next, the combustion in the combustion section  210  is stopped and the combustion of combustible components (such as H 2 , CH 4  and CO) of a combustible gas is started in the combustion catalyst section  217 . As a result of the combustion, the temperature of the selective oxidation catalyst  219  increases (temperature elevating step). When the temperature of the selective oxidation section  215  reaches at 140° C., the feed of the raw material  230  for combustion is stopped and the combustion section  210  is purged once by air for combustion. Thereafter, the feed of the raw material  230  for combustion is restarted and the burner (not shown) is again ignited to start the combustion in the combustion section  210 .  
      In this state, the hydrogen rich reformate  244  is streamed through the selective oxidation section  215  in an amount of 25 L (predetermined amount) for 10 minutes (predetermined period of time), so that the selective oxidation catalyst  219  is subjected to hydrogen reduction and activated (selective oxidation catalyst activating step). Since the temperature of the selective oxidation catalyst  219  has been raised to 140° C., the reduction treatment of the selective oxidation catalyst  219  can be conducted efficiently. When the temperature of the selective oxidation section  215  decreases to below 120° C., the procedure including the commencement of the combustion in the combustion catalyst section  222  by the termination of the combustion in the combustion section  210  and the restarting of the combustion in the combustion section  210  when the temperature of the selective oxidation section  215  reaches at 140° C. is repeated to increase the temperature of the selective oxidation section  215  to 140° C. Then, the reduction treatment of the selective oxidation catalyst  219  is continued. When the reduction treatment is over, the air  234  for selective oxidation is supplied to the selective oxidation section  215  (carbon monoxide removing step). By this, carbon monoxide in the reformate  244  is efficiently selectively oxidized and removed. Therefore, the fuel treatment apparatus  201  can supply the reformate  245  which is small in the carbon monoxide content (the content is several tens ppm or less).  
      According to the fuel treatment apparatuses  1 ,  101 , and  201  of the first to third embodiments, the temperature of the selective oxidation catalysts  19 ,  119 , and  219  is elevated at the start of the operation to 140° C. by heating the selective oxidation catalysts  19 ,  119 , and  219  before introducing the air  34 ,  134 , and  234  for selective oxidation to the selective oxidation section  15 ,  115 , and  215 , respectively. The reformates  44 ,  144  and  244  are then introduced to the selective oxidation section  15 ,  115 , and  215 , respectively, to reduce and activate the selective oxidation catalysts  19 ,  119 , and  219 . Therefore, when the reformates  45 ,  145 , and  245  produced in the fuel treatment apparatuses  1 ,  101 , and  201  are each fed to a fuel cell stack  106  (see  FIG. 4 ) to generate electric power, it is possible to suppress the concentration of carbon monoxide in each of the reformates  45 ,  145 , and  245  fed to the fuel cell stack  106  to 38 ppm after the lapse of 24 hours from the commencement of the electric power generation. When the reduction activation treatment is not conducted, the concentration of carbon monoxide increases to 90 ppm after the lapse of 4 hours from the commencement of the electric power generation.  
      A fuel cell electric power generating system  301  according to the fourth embodiment of the present invention will be described with reference to  FIG. 4  and, if necessary, also to  FIG. 2 . The fuel cell electric power generating system  301  includes a fuel treatment apparatus  101  according to the second embodiment, a fuel cell stack  106  as a fuel cell, a reformate feeding line  128 , an off-gas feeding line  129 , a reformate bypass line  124 , a three way solenoid valve  122  as a three way valve, and a check valve  123 .  
      The reformate feeding line  128  is adapted to feed the reformate  145 , produced in and supplied from the fuel treatment apparatus  101 , to the fuel cell stack  106 . The off-gas feeding line  129  is adapted to convey an off-gas  132  discharged from the fuel cell stack  106  to the combustion section  110  of the fuel treatment apparatus  101 . The reformate bypass line  124  is adapted to feed the reformate  145  from the reformate feeding line  128  to the off-gas feeding line  129 , while bypassing the fuel cell stack  106 . The three way solenoid valve  122  is adapted to introduce the reformate  145  from reformate feeding line  128  to the fuel cell stack  106  when it is in the position “a” and to introduce the reformate  145  from the reformate feeding line  128  to the off-gas feeding line  129  while bypassing the fuel cell stack  106 , when it is in the position “b”. Whether the three way solenoid valve  122  is in the position “a” or in the position “b” is controlled by the controlling device  125 .  
      The three way solenoid valve  122  forms a part connecting the reformate feeding line  128  and the reformate bypass line  124 . The check valve  123  is placed in the off-gas feeding line  129  and disposed upstream of a part connecting the off-gas feeding line  129  and the reformate bypass line  124  with respect to the direction of the flow of the off-gas  132 . The check valve  123  allows the flow of the off-gas  132  from the fuel cell stack  106  to the combustion section  110  as described hereinafter and prevents the flow from the combustion section  110  to the fuel cell stack  106  as described hereinafter.  
      The controlling device  125  controls the entire fuel cell electric power generating system  301  and controls the supply of the fuel gas  138 , the process water  139  for reforming, the air  134  for selective oxidation and the air  131  for combustion as well as the supply of a stack electric current Is to electric power loads.  
      The fuel cell stack  106  has a multi-stack structure in which solid polymer membranes (not shown) and separators (not shown) are alternately stacked. The fuel cell stack  106  is adapted to generate an electric power by the electrochemical reaction of the fed reformate  145  and the fed air  135  for stack as an oxidizing gas and to produce the off-gas  132  (unused reformate). The off-gas  132  here is a superfluous reformate remaining after the hydrogen in the reformate  145  has been utilized for generating the electric power in the fuel cell stack  106 . When, for example, 80% (mol %) of the hydrogen contained in the reformate  145  has been utilized for generating the electric power, the off-gas is a so-called hydrogen rich gas containing the remainder 20% (mol %) or equivalent amount of hydrogen. The fuel cell stack  106  is electrically connected to an electric power load  107  so that the stack current Is is fed to the electric power load  107 .  
      Next, the description will be made of a method for operating the fuel cell electric power generating system  301  according to the fourth embodiment of the present invention including a method for treating a reformate in the normal operation stage using the controlling device  125 . To the reforming section  111  of the fuel treatment apparatus  101 , the fuel gas  138  is fed and the process water  139  for reforming is also fed. The boiler  116  heats the process water  139  for reforming to form vaporized process water  140  for reforming.  
      The fuel gas  138  and the vaporized process water  140  for reforming are mixed and thereafter passed to the reforming section  111  through the flow passage  118  of the selective oxidation section  115  and the flow passage  113  of the transforming section  112 . The fuel gas  138  and the vaporized process water  140  for reforming are directly heated in the flow passage  118  by the selective oxidation section  115  and further directly heated in the flow passage  113  by the transforming section  112 .  
      The fuel gas  138  and the evaporated process water  140  for reforming which exit from the flow passage  113  are subjected to a steam reforming reaction in the reforming section  111  to form the reformate  143  which is rich in hydrogen. The reformate  143  exiting from the reforming section  111  is introduced into the transforming section  112 . In the transforming section  112 , carbon monoxide in the reformate  143  is removed by a transforming reaction, so that the concentration of carbon monoxide in the reformate  143  is reduced. The reformate  114  existing from the transforming section  112  is introduced into the selective oxidation section  115 , where carbon monoxide in the reformate  144  is removed by the selective oxidation reaction so that the concentration of carbon monoxide is reduced to below several tens ppm in the selective oxidation section  115 .  
      The reformate existing from the selective oxidation section  115  of the fuel treatment apparatus  101  is fed through the reformate feeding line  128  to the fuel cell stack  106 . In this case, the three way solenoid valve  122  is in the position “a”. In the fuel cell stack  106 , an electric power is generated by the electrochemical reaction of the fed reformate  145  fed and air fed for stack (not shown) and is supplied to the electric power load  107 .  
      The fuel cell stack  106  discharges the off-gas  132 . The off-gas  132  is fed through the off-gas feeding line  129  to the combustion section  110  of the fuel treatment apparatus  101 . To the combustion section  110 , the air  131  for combustion and, if necessary, the raw material  130  for combustion are supplied to perform the combustion. The combustion heat generated in the combustion section  110  is mainly utilized for steam reforming reaction (endothermic reaction) in the reforming section  111 .  
      Next, the description will be made of the method for operating the fuel cell electric power generating system  301  according to the fourth embodiment at the start of the operation including the method for treating the reformate. Before starting the operation, the three way solenoid valve  122  is set in the position “b”. Next, the raw material  130  for combustion and the air  131  for combustion are fed to the combustion section  110 . The combustion burner (not shown) is ignited to start the combustion. Thereafter, the fuel gas  142  is fed to the reforming section  111 . When the temperature of the reforming catalyst  120  in the reforming section  111  exceeds 400° C., the combustion in the combustion section  110  is stopped and the temperature of the reforming catalyst  120  is decreased to 400° C. or less. The fuel gas  142  is passed from the reformate feeding line  128  through the three way solenoid valve  122 , reformate bypass line  124  and off-gas feeding line  129 , while bypassing the fuel cell stack  106 , to the combustion section  110  and is combusted in the combustion section  110 . The fuel gas  142  supplied to the reforming section  111  is heated by the reforming catalyst  120  in the reforming section  111 . The heated fuel gas  142  heats the selective oxidation section  115  during its passage through the selective oxidation section  115 .  
      When the temperature of the selective oxidation section  115  exceeds 100° C., the supply of the process water  139  for reforming is started. Thereafter, the flow rate of the fuel gas  138  and the flow rate of the raw material  130  for combustion are increased, so that the temperature in the reforming section  111  is increased to 650° C. By increasing the temperature of the reforming section  111  to 650° C., it is possible to produce a reformate  144  which is rich in hydrogen. After the temperature of the reforming section  111  has been reached to 650° C., the air  134  for selective oxidation is supplied to the selective oxidation section  115 . As a result, a combustion reaction takes place in the selective oxidation section  115  to increase the temperature of the selective oxidation catalyst  119  (temperature elevating step). When the temperature of the selective oxidation section  115  is reached to 140° C., the supply of the air  134  for selective oxidation is stopped.  
      In this state, the hydrogen rich reformate  144  is streamed through the selective oxidation section  115  in an amount of 25 L for 10 minutes, so that the selective oxidation catalyst  119  is subjected to hydrogen reduction and activated (selective oxidation catalyst activating step). When the temperature of the selective oxidation section  115  decreases to below 120° C. during the activation of the selective oxidation catalyst  119 , the supply of the air  134  for selective oxidation is again started and continued until the temperature of the selective oxidation catalyst  119  returns to 140° C. When the temperature of the selective oxidation section  115  returns to 140° C., the supply of the air  134  for selective oxidation is stopped. The reduction treatment of the selective oxidation catalyst  119  is restarted and the hydrogen rich reformate  144  is streamed without the feed of the air  134  for selective oxidation. A total of 25 L of the hydrogen rich reformate  144  is streamed for a total of 10 minutes without the feed of the air  134  for selective oxidation.  
      Next, the air  134  for selective oxidation is supplied to the selective oxidation section  115 . Then the three way solenoid valve  122  is shifted to the position “a” and the hydrogen rich reformate  144  is fed to the fuel cell stack  106  to start the generation of the electric power. By this, carbon monoxide in the reformate  144  is efficiently selectively oxidized and removed. Therefore, it is possible to supply the reformate  145  which is small in the carbon monoxide content (the content is several tens ppm or less) to the fuel cell stack  106 .  
      According to the fuel cell electric power generating system  301  of the fourth embodiment, the controlling device  125  performs a control such that the air  134  for selective oxidation is supplied to the selective oxidation section  115  by the air feeding blower  105  for selective oxidation at the start of the operation to combust the combustible gas components such as hydrogen in the reformate  144  in the selective oxidation section  115  and to heat the selective oxidation catalyst  119  to 140° C. and that the reformate  144  is supplied to the selective oxidation catalyst  119 , without the feed of the air  134  for selective oxidation, to reduce the selective oxidation catalyst  119 , thereby to permit the activation of the selective oxidation catalyst  119 . Therefore, the reformate which is small in the content of carbon monoxide can be supplied to the fuel cell stack  106  for a long period of time. Therefore the electrode catalyst (not shown) of the fuel cell stack  106  can be prevented from being poisoned with carbon monoxide. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram showing the construction of a fuel treatment apparatus according to a first embodiment of the present invention.  
       FIG. 2  is a block diagram showing the construction of a fuel treatment apparatus according to a second embodiment of the present invention.  
       FIG. 3  is a block diagram showing the construction of a fuel treatment apparatus according to a third embodiment of the present invention.  
       FIG. 4  is a block diagram showing the construction of a fuel cell electric power generating system according to a fourth embodiment of the present invention. 
    
    
     DESCRIPTION OF REFERENCE NUMERALS  
     
         
           1 , 101 , 201  fuel treating apparatus  
           10  combustion section  
           11  reforming section  
           12  transforming section  
           14  transformation catalyst  
           15  selective oxidation section  
           19  selective oxidation catalyst  
           20  reforming catalyst  
           21  selective oxidation section heater  
           25  controlling device  
           34  air for combustion  
           38  fuel gas  
           43 , 44  reformate  
           106  fuel cell stack  
           135  air for stack  
           145  reformate  
           217  combustion catalyst section  
           222  combustion catalyst  
           301  fuel cell electric power generating system