Patent Publication Number: US-9419298-B2

Title: Fuel cell module

Description:
TECHNICAL FIELD 
     The present invention relates to a fuel cell module including a fuel cell stack formed by stacking a plurality of fuel cells for generating electricity by electrochemical reactions of a fuel gas and an oxygen-containing gas. 
     BACKGROUND ART 
     Typically, a solid oxide fuel cell (SOFC) employs a solid electrolyte of ion-conductive solid oxide such as stabilized zirconia. The solid electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (hereinafter also referred to as MEA). The electrolyte electrode assembly is sandwiched between separators (bipolar plates). In use, generally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack. 
     As a system including this type of fuel cell stack, for example, a fuel cell battery disclosed in Japanese Laid-Open Patent Publication No. 2001-236980 (hereinafter referred to as the conventional technique  1 ) is known. As shown in  FIG. 10 , the fuel cell battery includes a fuel cell stack  1   a , and a heat insulating sleeve  2   a  is provided at one end of the fuel cell stack  1   a . A reaction device  4   a  is provided in the heat insulating sleeve  2   a . The reaction device  4   a  includes a heat exchanger  3   a.    
     In the reaction device  4   a , as a treatment of liquid fuel, partial oxidation reforming which does not use water is performed. After the liquid fuel is evaporated by an exhaust gas, the liquid fuel passes through a feeding point  5   a  which is part of the heat exchanger  3   a . The fuel contacts an oxygen carrier gas heated by the exhaust gas thereby to induce partial oxidation reforming, and then, the fuel is supplied to the fuel cell stack  1   a.    
     Further, as shown in  FIG. 11 , a solid oxide fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2010-504607 (PCT) (hereinafter referred to as the conventional technique  2 ) has a heat exchanger  2   b  including a cell core  1   b . The heat exchanger  2   b  heats the cathode air utilizing waste heat. 
     Further, as shown in  FIG. 12 , a fuel cell system disclosed in Japanese Laid-Open Patent Publication No. 2004-288434 (hereinafter referred to as the conventional technique  3 ) includes a first area is having a circular cylindrical shape extending vertically, and an annular second area  2   c  around the first area  1   c , an annular third area  3   c  around the second area  2   c , and an annular fourth area  4   c  around the third area  3   c.    
     A burner  5   c  is provided in the first area  1   c , and a reforming pipe  6   c  is provided in the second area  2   c . A water evaporator  7   c  is provided in the third area  3   c , and a CO shift converter  8   c  is provided in the fourth area  4   c.    
     SUMMARY OF INVENTION 
     In the conventional technique  1 , at the time of reforming by partial oxidation in the reaction device  4   a , heat of the exhaust gas is used for heating the liquid fuel and the oxygen carrier gas. Therefore, the quantity of heat for raising the temperature of the oxygen-containing gas supplied to the fuel cell stack  1   a  tends to be inefficient, and the efficiency is low. 
     Further, in the conventional technique  2 , in order to increase heat efficiency, long flow channels are adopted to have a sufficient heat transmission area. Therefore, considerably high pressure losses tend to occur. 
     Further, in the conventional technique  3 , radiation of the heat from the central area having the highest temperature is suppressed using heat insulation material (partition wall). Therefore, heat cannot be recovered, and the efficiency is low. 
     The present invention has been made to solve the problems of this type, and an object of the present invention is to provide a fuel cell module having simple and compact structure in which it is possible to achieve improvement in the heat efficiency and facilitation of thermally self-sustaining operation. 
     The present invention relates to a fuel cell module including a fuel cell stack formed by stacking a plurality of fuel cells for generating electricity by electrochemical reactions of a fuel gas and an oxygen-containing gas, a reformer for reforming a mixed gas of a raw fuel chiefly containing hydrocarbon and water vapor to produce the fuel gas supplied to the fuel cell stack, an evaporator for evaporating water, and supplying the water vapor to the reformer, a heat exchanger for raising the temperature of the oxygen-containing gas by heat exchange with a combustion gas, and supplying the oxygen-containing gas to the fuel cell stack, an exhaust gas combustor for combusting the fuel gas discharged from the fuel cell stack as a fuel exhaust gas and the oxygen-containing gas discharged from the fuel cell stack as an oxygen-containing exhaust gas to produce the combustion gas, and a start-up combustor for combusting the raw fuel and the oxygen-containing gas to produce the combustion gas. 
     The fuel cell module includes a first area where the exhaust gas combustor and the start-up combustor are provided, an annular second area around the first area and where the reformer and the evaporator are provided, and an annular third area around the second area and where the heat exchanger is provided. Further, the exhaust gas combustor and the start-up combustor are provided coaxially with and separately away from each other. The exhaust gas combustor has a combustion cup member, and a combustion gas hole for supplying the combustion gas produced in the combustion cup member to the second area is formed in an outer circumferential portion of the combustion cup member. 
     In the present invention, the first area including the exhaust gas combustor and the start-up combustor is centrally-located. The annular second area is successively provided around the first area, and the annular third area is then provided around the second area. The reformer and the evaporator are provided in the second area, and the heat exchanger is provided in the third area. 
     In the structure, heat waste and heat radiation are suppressed suitably. Thus, improvement in the heat efficiency is achieved, and thermally self-sustaining operation is facilitated. Further, simple and compact structure is achieved in the entire fuel cell module. The thermally self-sustaining operation herein means operation where the operating temperature of the fuel cell is maintained using only heat energy generated by the fuel cell itself, without supplying additional heat from the outside. 
     Moreover, in the first area, the exhaust gas combustor and the start-up combustor are coaxially with and separated away from each other. Therefore, radiation of the heat of the combustion gas produced in the combustion cup member, due to heat dissipation toward the start-up combustor, is suppressed suitably. Accordingly, the exhaust gas combustor can sufficiently supply the heat to respective components in the second area and third area, i.e., the reformer, the evaporator, and the heat exchanger. 
     The above and other objects features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram schematically showing structure of a fuel cell system including a fuel cell module according to an embodiment of the present invention; 
         FIG. 2  is a perspective view showing FC peripheral equipment of the fuel cell module; 
         FIG. 3  is a cross sectional view showing the FC peripheral equipment; 
         FIG. 4  is a perspective view with partial omission showing the FC peripheral equipment; 
         FIG. 5  is an exploded perspective view showing main components of the FC peripheral equipment; 
         FIG. 6  is an exploded perspective view showing main components of an exhaust gas combustor of the FC peripheral equipment; 
         FIG. 7  is a cross sectional view showing the FC peripheral equipment; 
         FIG. 8  is a view showing an evaporation return pipe of the FC peripheral equipment; 
         FIG. 9  is another cross sectional view showing the FC peripheral equipment; 
         FIG. 10  is a view schematically showing a fuel cell battery disclosed in a conventional technique  1 ; 
         FIG. 11  is a perspective view with partial cutout showing a solid oxide fuel cell disclosed in a conventional technique  2 ; and 
         FIG. 12  is a view schematically showing a fuel cell system disclosed in a conventional technique  3 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     As shown in  FIG. 1 , a fuel cell system  10  includes a fuel cell module  12  according to an embodiment of the present invention, and the fuel cell system  10  is used in various applications, including stationary and mobile applications. For example, the fuel cell system  10  is mounted on a vehicle. 
     The fuel cell system  10  includes the fuel cell module (SOFC module)  12  for generating electrical energy in power generation by electrochemical reactions of a fuel gas (a gas produced by mixing a hydrogen gas, methane, and carbon monoxide) and an oxygen-containing gas (air), a raw fuel supply apparatus (including a fuel gas pump)  14  for supplying a raw fuel (e.g., city gas) to the fuel cell module  12 , an oxygen-containing gas supply apparatus (including an air pump)  16  for supplying the oxygen-containing gas to the fuel cell module  12 , a water supply apparatus (including a water pump)  18  for supplying water to the fuel cell module  12 , and a control device  20  for controlling the amount of electrical energy generated in the fuel cell module  12 . 
     The fuel cell module  12  includes a solid oxide fuel cell stack  24  formed by stacking a plurality of solid oxide fuel cells  22  in a vertical direction (or horizontal direction). The fuel cell  22  includes an electrolyte electrode assembly (MEA)  32 . The electrolyte electrode assembly  32  includes a cathode  28 , an anode  30 , and an electrolyte  26  interposed between the cathode  28  and the anode  30 . For example, the electrolyte  26  is made of ion-conductive solid oxide such as stabilized zirconia. 
     A cathode side separator  34  and an anode side separator  36  are provided on both sides of the electrolyte electrode assembly  32 . An oxygen-containing gas flow field  38  for supplying the oxygen-containing gas to the cathode  28  is formed in the cathode side separator  34 , and a fuel gas flow field  40  for supplying the fuel gas to the anode  30  is formed in the anode side separator  36 . As the fuel cell  22 , various types of conventional SOFCs can be adopted. 
     The operating temperature of the fuel cell  22  is high, that is, several hundred ° C. Methane in the fuel gas is reformed at the anode  30  to obtain hydrogen and CO, and the hydrogen and CO are supplied to a portion of the electrolyte  26  adjacent to the anode  30 . 
     An oxygen-containing gas supply passage  42   a , an oxygen-containing gas discharge passage  42   b , a fuel gas supply passage  44   a , and a fuel gas discharge passage  44   b  extend through the fuel cell stack  24 . The oxygen-containing gas supply passage  42   a  is connected to an inlet of each oxygen-containing gas flow field  38 , the oxygen-containing gas discharge passage  42   b  is connected to an outlet of each oxygen-containing gas flow field  38 , the fuel gas supply passage  44   a  is connected to an inlet of each fuel gas flow field  40 , and the fuel gas discharge passage  44   b  is connected to an outlet of each fuel gas flow field  40 . 
     The fuel cell module  12  includes a reformer  46  for reforming a mixed gas of a raw fuel chiefly containing hydrocarbon (e.g., city gas) and water vapor to produce a fuel gas supplied to the fuel cell stack  24 , an evaporator  48  for evaporating water and supplying the water vapor to the reformer  46 , a heat exchanger  50  for raising the temperature of the oxygen-containing gas by heat exchange with a combustion gas, and supplying the oxygen-containing gas to the fuel cell stack  24 , an exhaust gas combustor  52  for combusting the fuel gas discharged from the fuel cell stack  24  as a fuel exhaust gas and the oxygen-containing gas discharged from the fuel cell stack  24  as an oxygen-containing exhaust gas to produce the combustion gas, and a start-up combustor  54  for combusting the raw fuel and the oxygen-containing gas to produce the combustion gas. 
     Basically, the fuel cell module  12  is made up of the fuel cell stack  24  and FC (fuel cell) peripheral equipment (BOP)  56  (see  FIGS. 1 and 2 ). The FC peripheral equipment  56  includes the reformer  46 , the evaporator  48 , the heat exchanger  50 , the exhaust gas combustor  52 , and the start-up combustor  54 . 
     As shown in  FIGS. 3 to 5 , the FC peripheral equipment  56  includes a first area R 1  where the exhaust gas combustor  52  and the start-up combustor  54  are provided, an annular second area R 2  formed around the first area R 1  and where the reformer  46  and the evaporator  48  are provided, an annular third area R 3  formed around the second area R 2  and where the heat exchanger  50  is provided. A cylindrical outer member  55  constituting an outer wall is provided on the outer peripheral side of the third area R 3 . 
     The start-up combustor  54  is provided at the other end distant from the fuel cell stack  24 , and includes an air supply pipe  57  and a raw fuel supply pipe  58 . The start-up combustor  54  has an ejector function, and generates negative pressure in the raw fuel supply pipe  58  by the flow of the air supplied from the air supply pipe  57  for sucking the raw fuel. 
     The exhaust gas combustor  52  is provided at one end adjacent to the fuel cell stack  24 , and has a combustion cup member  60  at a position spaced away from the start-up combustor  54 . The combustion cup member  60  includes a support portion  61  and a cup portion  62  attached to the support portion  61  in an orientation from the fuel cell stack  24  toward the start-up combustor  54  (first area R 1 ). 
     The support portion  61  includes an attachment plate body  61   a  to which the fuel cell stack  24  is attached, and a cylindrical body  61   b  formed integrally with the attachment plate body  61   a . A plurality of holes (e.g., circular holes or rectangular holes)  62   a , which are combustion gas holes, are formed along the outer circumference of the marginal end of the cup portion  62  on the bottom side. The bottom surface  62   e  of the cup portion  62  is set at a position spaced away from (deviated from) an intermediate position h (see  FIG. 3 ) in the axial direction (indicated by an arrow L) of the FC peripheral equipment  56  toward the fuel cell stack  24 . Alternatively, the bottom surface  62   e  of the cup portion  62  may be set at a position spaced away from the intermediate position h (see  FIG. 3 ) in the axial direction of the FC peripheral equipment away from the fuel cell stack  24 . 
     The combustion cup member  60  has a fixing mechanism  64  for fixing the support portion  61  and the cup portion  62  together such that the support portion  61  and the cup portion  62  are not rotatable with respect to each other. As shown in  FIG. 6 , the fixing mechanism  64  includes recesses  64   b  and a protrusion  64   a  that is engageable with any of the recesses  64   b . The protrusion  64   a  is formed at the other end of the cup portion  62 , which is an open end, so as to protrude radially outwardly. The recesses  64   b  are formed at a lip portion of the inner circumferential surface of the support portion  61 . 
     For the purpose of adjusting the phase between the support portion  61  and the cup portion  62 , at least the recesses  64   b  are provided at a plurality of, e.g., two positions. The protrusion  64   a  may be provided in the support portion  61 , and the recesses  64   b  may be provided in the cup portion  62 . 
     One end of an oxygen-containing exhaust gas channel  63   a  and one end of a fuel exhaust gas channel  63   b  are provided at the combustion cup member  60 . The combustion gas is produced inside the combustion cup member  60  by combustion reaction of the fuel gas (more specifically, fuel exhaust gas) and the oxygen-containing gas (more specifically, oxygen-containing exhaust gas). 
     As shown in  FIG. 1 , the other end of the oxygen-containing exhaust gas channel  63   a  is connected to the oxygen-containing gas discharge passage  42   b  of the fuel cell stack  24 , and the other end of the fuel exhaust gas channel  63   b  is connected to the fuel gas discharge passage  44   b  of the fuel cell stack  24 . 
     As shown in  FIGS. 3 to 5 , the reformer  46  is a preliminary reformer for reforming higher hydrocarbon (C 2+ ) such as ethane (C 2 H 6 ), propane (C 3 H 8 ), and butane (C 4 H 10 ) in the city gas (raw fuel) to produce the fuel gas chiefly containing methane (CH 4 ), hydrogen, and CO by steam reforming. The operating temperature of the reformer  46  is set at several hundred ° C. 
     The reformer  46  includes a plurality of reforming pipes (heat transmission pipes)  66  provided around the exhaust gas combustor  52  and the start-up combustor  54 . Each of the reforming pipes  66  is filled with reforming catalyst pellets (not shown). Each of the reforming pipes  66  has one end (lower end) fixed to a first lower ring member  68   a , and the other end (upper end) fixed to a first upper ring member  68   b.    
     The outer circumferential portions of the first lower ring member  68   a  and the first upper ring member  68   b  are fixed to the inner circumferential surface of a cylindrical member  70  by welding or the like. The inner circumferential portions of the first lower ring member  68   a  and the first upper ring member  68   b  are fixed to the outer circumferential portions of the exhaust gas combustor  52  and the start-up combustor  54  by welding or the like. The cylindrical member  70  extends in an axial direction indicated by an arrow L, and an end of the cylindrical member  70  adjacent to the fuel cell stack  24  is fixed to the attachment plate body  61   a . A plurality of openings  72  are formed in the outer circumference of the cylindrical member  70  in a circumferential direction at predetermined height positions. 
     The evaporator  48  has evaporation pipes (heat transmission pipes)  74  provided adjacent to, and outside the reforming pipes  66  of the reformer  46 . As shown in  FIG. 7 , the reforming pipes  66  are arranged at equal intervals on a virtual circle, concentrically around the first area R 1 . The evaporation pipes  74  are arranged at equal intervals on a virtual circle, concentrically around the first area R 1 . The number of the evaporation pipes  74  is half of the number of the reforming pipes  66 . The evaporation pipes  74  are positioned on the back side of every other position of the reforming pipe  66  (i.e., at positions spaced away from the center of the first area R 1 ). 
     As shown in  FIGS. 3 and 4 , each of the evaporation pipes  74  has one end (lower end) which is fixed to a second lower ring member  76   a  by welding or the like, and the other end (upper end) which is fixed to a second upper ring member  76   b  by welding or the like. The outer circumferential portions of the second lower ring member  76   a  and the second upper ring member  76   b  are fixed to the inner circumferential surface of the cylindrical member  70  by welding or the like. The inner circumferential portions of the second lower ring member  76   a  and the second upper ring member  76   b  are fixed to the outer circumferential portions of the exhaust gas combustor  52  and the start-up combustor  54  by welding or the like. 
     The second lower ring member  76   a  is positioned below the first lower ring member  68   a  (i.e., outside the first lower ring member  68   a  in the axial direction), and the second upper ring member  76   b  is positioned above the first upper ring member  68   b  (i.e., outside the first upper ring member  68   b  in the axial direction). 
     An annular mixed gas supply chamber  78   a  is formed between the first lower ring member  68   a  and the second lower ring member  76   a , and a mixed gas of raw fuel and water vapor is supplied to the mixed gas supply chamber  78   a . Further, an annular fuel gas discharge chamber  78   b  is formed between the first upper ring member  68   b  and the second upper ring member  76   b , and the produced fuel gas (reformed gas) is discharged to the fuel gas discharge chamber  78   b . Both ends of each of the reforming pipes  66  are opened to the mixed gas supply chamber  78   a  and the fuel gas discharge chamber  78   b.    
     A ring shaped end ring member  80  is fixed to an end of the cylindrical member  70  on the start-up combustor  54  side by welding or the like. An annular water supply chamber  82   a  is formed between the end ring member  80  and the second lower ring member  76   a , and water is supplied to the water supply chamber  82   a . An annular water vapor discharge chamber  82   b  is formed between the second upper ring member  76   b  and the attachment plate body  61   a , and water vapor is discharged to the water vapor discharge chamber  82   b . Both ends of each of the evaporation pipes  74  are opened to the water supply chamber  82   a  and the water vapor discharge chamber  82   b.    
     The fuel gas discharge chamber  78   b  and the water vapor discharge chamber  82   b  are provided in a double deck manner, and the fuel gas discharge chamber  78   b  is provided on the inner side with respect to the water vapor discharge chamber  82   b  (i.e., below the water vapor discharge chamber  82   b ). The mixed gas supply chamber  78   a  and the water supply chamber  82   a  are provided in a double deck manner, and the mixed gas supply chamber  78   a  is provided on the inner side with respect to the water supply chamber  82   a  (i.e., above the water supply chamber  82   a ). 
     A raw fuel supply channel  84  is opened to the mixed gas supply chamber  78   a , and an evaporation return pipe  90  described later is connected to a position in the middle of the raw fuel supply channel  84  (see  FIG. 1 ). The raw fuel supply channel  84  has an ejector function, and generates negative pressure by the flow of the raw fuel for sucking the water vapor. 
     The raw fuel supply channel  84  is fixed to the second lower ring member  76   a  and the end ring member  80  by welding or the like. One end of a fuel gas channel  86  is connected to the fuel gas discharge chamber  78   b , and the other end of the fuel gas channel  86  is connected to the fuel gas supply passage  44   a  of the fuel cell stack  24  (see  FIG. 1 ). The fuel gas channel  86  is fixed to the second upper ring member  76   b  by welding or the like, and extends through the attachment plate body  61   a  (see  FIG. 2 ). 
     A water channel  88  is connected to the water supply chamber  82   a . The water channel  88  is fixed to the end ring member  80  by welding or the like. One end of the evaporation return pipe  90  formed by at least one evaporation pipe  74  is provided in the water vapor discharge chamber  82   b , and the other end of the evaporation return pipe  90  is connected to a position in the middle of the raw fuel supply channel  84  (see  FIG. 1 ). 
     As shown in  FIG. 8 , the evaporation return pipe  90  has dual pipe structure  92  in a portion thereof passing through the mixed gas supply chamber  78   a  and the water supply chamber  82   a . The dual pipe structure  92  includes an outer pipe  94 . The outer pipe  94  surrounds the evaporation return pipe  90 , and the outer pipe  94  is positioned coaxially with the evaporation return pipe  90 . The outer pipe  94  is fixed to the first lower ring member  68   a , the second lower ring member  76   a , and the end ring member  80  by welding or the like, and extends in the direction indicated by an arrow L. A gap is provided between the outer circumference of the evaporation return pipe  90  and the inner circumference of the outer pipe  94 . This gap may not be provided. 
     The evaporation return pipe  90  may have dual pipe structure  92   a  in a portion thereof passing through the fuel gas discharge chamber  78   b . The dual pipe structure  92   a  includes an outer pipe  94   a . The outer pipe  94   a  surrounds the evaporation return pipe  90 , and the outer pipe  94   a  is positioned coaxially with the evaporation return pipe  90 . The outer pipe  94   a  is fixed to the first upper ring member  68   b  and the second upper ring member  76   b  by welding or the like, and extends in the direction indicated by the arrow L. A gap is formed between the outer circumference of the evaporation return pipe  90  and the inner circumference of the outer pipe  94   a  as necessary. The lower end of the outer pipe  94   a  is not welded to the first upper ring member  68   b.    
     As shown in  FIGS. 3 and 4 , the heat exchanger  50  includes a plurality of heat exchange pipes (heat transmission pipes)  96  which are provided along and around the outer circumference of the cylindrical member  70 . Each of the heat exchange pipes  96  has one end (lower end) fixed to a lower ring member  98   a , and the other end (upper end) fixed to an upper ring member  98   b.    
     A lower end ring member  100   a  is provided below the lower ring member  98   a , and an upper end ring member  100   b  is provided above the upper ring member  98   b . The lower end ring member  100   a  and the upper end ring member  100   b  are fixed to the outer circumference of the cylindrical member  70  and the inner circumference of the outer member  55  by welding or the like. 
     An annular oxygen-containing gas supply chamber  102   a  to which the oxygen-containing gas is supplied is formed between the lower ring member  98   a  and the lower end ring member  100   a . An annular oxygen-containing gas discharge chamber  102   b  is formed between the upper ring member  98   b  and the upper end ring member  100   b . The heated oxygen-containing gas is discharged to the oxygen-containing gas discharge chamber  102   b . Both ends of each of the heat exchange pipes  96  are fixed to the lower ring member  98   a  and the upper ring member  98   b  by welding or the like, and opened to the oxygen-containing gas supply chamber  102   a  and the oxygen-containing gas discharge chamber  102   b.    
     The mixed gas supply chamber  78   a  and the water supply chamber  82   a  are placed on the radially inward side relative to the inner circumference of the oxygen-containing gas supply chamber  102   a . The oxygen-containing gas discharge chamber  102   b  is provided outside the fuel gas discharge chamber  78   b  at a position offset downward from the fuel gas discharge chamber  78   b.    
     A cylindrical cover member  104  is provided on the outer circumferential portion of the outer member  55 . The center of the cylindrical cover member  104  is shifted downward. Both of upper and lower ends (both of axial ends) of the cover member  104  are fixed to the outer member  55  by welding or the like, and a heat recovery area (chamber)  106  is formed between the cover member  104  and the outer circumferential surface of the outer member  55 . 
     A plurality of holes  108  are formed circumferentially in a lower marginal end portion of the outer member  55  of the oxygen-containing gas supply chamber  102   a , and the oxygen-containing gas supply chamber  102   a  communicates with the heat recovery area  106  through the holes  108 . An oxygen-containing gas supply pipe  110  communicating with the heat recovery area  106  is connected to the cover member  104 . An exhaust gas pipe  112  communicating with the third area R 3  is connected to an upper portion of the outer member  55 . 
     For example, one end of each of two oxygen-containing gas pipes  114  is provided in the oxygen-containing gas discharge chamber  102   b . Each of the oxygen-containing gas pipes  114  has a stretchable member such as a bellows  114   a  between the upper end ring member  100   b  and the attachment plate body  61   a . The other end of each of the oxygen-containing gas pipes  114  extends through the attachment plate body  61   a , and is connected to the oxygen-containing gas supply passage  42   a  of the fuel cell stack  24  (see  FIG. 1 ). 
     As shown in  FIG. 3 , a first combustion gas channel  116   a  as a passage of the combustion gas is formed in the first area R 1 , and a second combustion gas channel  116   b  as a passage of the combustion gas that has passed through the holes  62   a  is formed in the second area R 2 . A third combustion gas channel  116   c  as a passage of the combustion gas that has passed through the openings  72  is formed in the third area R 3 . Further, a fourth combustion gas channel  116   d  is formed as a passage after the exhaust gas pipe  112 . The second combustion gas channel  116   b  forms the reformer  46  and the evaporator  48 , and the third combustion gas channel  116   c  forms the heat exchanger  50 . 
     As shown in  FIG. 1 , the raw fuel supply apparatus  14  includes a raw fuel channel  118 . The raw fuel channel  118  is branched into the raw fuel supply channel  84  and the raw fuel supply pipe  58  through a raw fuel regulator valve  120 . A desulfurizer  122  for removing sulfur compounds in the city gas (raw fuel) is provided in the raw fuel supply channel  84 . 
     The oxygen-containing gas supply apparatus  16  includes an oxygen-containing gas channel  124 . The oxygen-containing gas channel  124  is branched into the oxygen-containing gas supply pipe  110  and the air supply pipe  57  through an oxygen-containing gas regulator valve  126 . The water supply apparatus  18  is connected to the evaporator  48  through the water channel  88 . 
     Operation of the fuel cell system  10  will be described below. 
     At the time of starting operation of the fuel cell system  10 , the air (oxygen-containing gas) and the raw fuel are supplied to the start-up combustor  54 . More specifically, by operation of the air pump, the air is supplied to the oxygen-containing gas channel  124 . By adjusting the opening degree of the oxygen-containing gas regulator valve  126 , the air is supplied to the air supply pipe  57 . 
     In the meanwhile, in the raw fuel supply apparatus  14 , by operation of the fuel gas pump, for example, raw fuel such as the city gas (containing CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 ) is supplied to the raw fuel channel  118 . By regulating the opening degree of the raw fuel regulator valve  120 , the raw fuel is supplied into the raw fuel supply pipe  58 . The raw fuel is mixed with the air, and supplied into the start-up combustor  54  (see  FIGS. 3 and 4 ). 
     Thus, the mixed gas of the raw fuel and the air is supplied into the start-up combustor  54 , and the mixed gas is ignited to start combustion. Therefore, the combustion gas produced in combustion flows from the first area R 1  to the second area R 2 . Further, the combustion gas is supplied to the third area R 3 , and then, the combustion gas is discharged to the outside of the fuel cell module  12  through the exhaust gas pipe  112 . 
     As shown in  FIGS. 3 and 4 , the reformer  46  and the evaporator  48  are provided in the second area R 2 , and the heat exchanger  50  is provided in the third area R 3 . Thus, the combustion gas discharged from the first area R 1  first heats the reformer  46 , next heats the evaporator  48 , and then heats the heat exchanger  50 . 
     Then, after the temperature of the fuel cell module  12  is raised to a predetermined temperature, the air (oxygen-containing gas) is supplied to the heat exchanger  50 , and the mixed gas of the raw fuel and the water vapor is supplied to the reformer  46 . 
     More specifically, as shown in  FIG. 1 , the opening degree of the oxygen-containing gas regulator valve  126  is adjusted such that the flow rate of the air supplied to the oxygen-containing gas supply pipe  110  is increased, and the opening degree of the raw fuel regulator valve  120  is adjusted such that the flow rate of the raw fuel supplied to the raw fuel supply channel  84  is increased. Further, by operation of the water supply apparatus  18 , the water is supplied to the water channel  88 . The air is supplied from the oxygen-containing gas supply pipe  110  to the heat recovery area  106  of the outer member  55 . Thus, the air flows through the holes  108  into the oxygen-containing gas supply chamber  102   a.    
     Therefore, as shown in  FIGS. 3 and 4 , the air flows into the heat exchanger  50 , and the air is temporarily supplied to the oxygen-containing gas supply chamber  102   a . Thereafter, while the air is moving inside the heat exchange pipes  96 , the air is heated by heat exchange with the combustion gas supplied into the third area R 3 . After the heated air is temporarily supplied to the oxygen-containing gas discharge chamber  102   b , the air is supplied to the oxygen-containing gas supply passage  42   a  of the fuel cell stack  24  through the oxygen-containing gas pipes  114  (see  FIG. 1 ). In the fuel cell stack  24 , the heated air flows along the oxygen-containing gas flow field  38 , and the air is supplied to the cathode  28 . 
     After the air flows through the oxygen-containing gas flow field  38 , the air is discharged from the oxygen-containing gas discharge passage  42   b  into the oxygen-containing exhaust gas channel  63   a . The oxygen-containing exhaust gas channel  63   a  is opened to the combustion cup member  60  of the exhaust gas combustor  52 , and the oxygen-containing exhaust gas is supplied into the cup portion  62  of the combustion cup member  60 . 
     Further, as shown in  FIG. 1 , the water from the water supply apparatus  18  is supplied to the evaporator  48 . After the raw fuel is desulfurized in the desulfurizer  122 , the raw fuel flows through the raw fuel supply channel  84 , and moves toward the reformer  46 . 
     In the evaporator  48 , after the water is temporarily supplied to the water supply chamber  82   a , while water is moving inside the evaporation pipes  74 , the water is heated by the combustion gas flowing through the second area R 2 , and vaporized. After the water vapor flows into the water vapor discharge chamber  82   b , the water vapor is supplied to the evaporation return pipe  90  connected to the water vapor discharge chamber  82   b . Thus, the water vapor flows inside the evaporation return pipe  90 , and flows into the raw fuel supply channel  84 . Then, the water vapor is mixed with the raw fuel supplied by the raw fuel supply apparatus  14  to produce the mixed gas. 
     The mixed gas from the raw fuel supply channel  84  is temporarily supplied to the mixed gas supply chamber  78   a  of the reformer  46 . The mixed gas moves inside the reforming pipes  66 . In the meanwhile, the mixed gas is heated by the combustion gas flowing through the second area R 2 , and is then steam-reformed. After removal (reforming) of hydrocarbon of C 2+ , a reformed gas chiefly containing methane is obtained. 
     After this reformed gas is heated, the reformed gas is temporarily supplied to the fuel gas discharge chamber  78   b  as the fuel gas. Thereafter, the fuel gas is supplied to the fuel gas supply passage  44   a  of the fuel cell stack  24  through the fuel gas channel  86  (see  FIG. 1 ). In the fuel cell stack  24 , the heated fuel gas flows along the fuel gas flow field  40 , and the fuel gas is supplied to the anode  30 . In the meanwhile, the air is supplied to the cathode  28 . Thus, electricity is generated in the electrolyte electrode assembly  32 . 
     After the fuel gas flows through the fuel gas flow field  40 , the fuel gas is discharged from the fuel gas discharge passage  44   b  to the fuel exhaust gas channel  63   b . The fuel exhaust gas channel  63   b  is opened to the inside of the combustion cup member  60  of the exhaust gas combustor  52 , and the fuel exhaust gas is supplied into the cup portion  62  of the combustion cup member  60 . 
     Under the heating operation by the start-up combustor  54 , when the temperature of the fuel gas in the exhaust gas combustor  52  exceeds the self-ignition temperature, combustion of the oxygen-containing exhaust gas and the fuel exhaust gas is started inside the cup portion  62 . In the meanwhile, combustion operation by the start-up combustor  54  is stopped. 
     The holes  62   a  are formed in the cup portion  62 . Therefore, the combustion gas supplied into the cup portion  62  passes through the holes  62   a , and flows from the first area R 1  into the second area R 2 . Then, after the combustion gas is supplied to the third area R 3 , the combustion gas is discharged to the outside of the fuel cell module  12 . 
     In the present embodiment, the FC peripheral equipment  56  includes the first area R 1  where the exhaust gas combustor  52  and the start-up combustor  54  are provided, the annular second area R 2  around the first area R 1  and where the reformer  46  and the evaporator  48  are provided, and the annular third area R 3  around the second area R 2  and where the heat exchanger  50  is provided. 
     That is, the first area R 1  is provided at the center, the annular second area R 2  is provided around the first area R 1 , and the annular third area R 3  is provided around the second area R 2 . Heat waste and heat radiation can be suppressed suitably. Thus, improvement in the heat efficiency is achieved, thermally self-sustaining operation is facilitated, and simple and compact structure of the entire fuel cell module  12  is achieved. Thermally self-sustaining operation herein means operation where the operating temperature of the fuel cell  22  is maintained using only heat energy generated in the fuel cell  22  itself, without supplying additional heat from the outside. 
     Moreover, in the first area R 1 , the exhaust gas combustor  52  and the start-up combustor  54  are coaxially with and separated away from each other. Therefore, heat radiation of the combustion gas produced in the combustion cup member  60 , due to heat dissipation toward the start-up combustor  54 , is suppressed suitably. Accordingly, the exhaust gas combustor  52  can sufficiently supply the heat to respective components in the second area R 2  and the third area R 3 , i.e., the reformer  46 , the evaporator  48 , and the heat exchanger  50 . 
     Further, in the present embodiment, as shown in  FIG. 3 , the reformer  46  includes the annular mixed gas supply chamber  78   a , the annular fuel gas discharge chamber  78   b , the reforming pipes  66 , and the second combustion gas channel  116   b . The mixed gas is supplied to the mixed gas supply chamber  78   a , and the produced fuel gas is discharged into the fuel gas discharge chamber  78   b . Each of the reforming pipes  66  has one end connected to the mixed gas supply chamber  78   a , and the other end connected to the fuel gas discharge chamber  78   b . The second combustion gas channel  116   b  supplies the combustion gas to the space between the reforming pipes  66 . 
     The evaporator  48  includes the annular water supply chamber  82   a , the annular water vapor discharge chamber  82   b , the evaporation pipes  74 , and the second combustion gas channel  116   b . The water is supplied to the water supply chamber  82   a , and the water vapor is discharged into the water vapor discharge chamber  82   b . Each of the evaporation pipes  74  has one end connected to the water supply chamber  82   a , and the other end connected to the water vapor discharge chamber  82   b . The second combustion gas channel  116   b  supplies the combustion gas to the space between the evaporation pipes  74 . 
     The heat exchanger  50  includes the annular oxygen-containing gas supply chamber  102   a , the annular oxygen-containing gas discharge chamber  102   b , the heat exchange pipes  96 , and the third combustion gas channel  116   c . The oxygen-containing gas is supplied to the oxygen-containing gas supply chamber  102   a , and the heated oxygen-containing gas is discharged into the oxygen-containing gas discharge chamber  102   b . Each of the heat exchange pipes  96  has one end connected to the oxygen-containing gas supply chamber  102   a , and the other end connected to the oxygen-containing gas discharge chamber  102   b . The third combustion gas channel  116   c  supplies the combustion gas to the space between the heat exchange pipes  96 . 
     As described above, the annular supply chambers (mixed gas supply chamber  78   a , water supply chamber  82   a , and oxygen-containing gas supply chamber  102   a ), the annular discharge chambers (fuel gas discharge chamber  78   b , water vapor discharge chamber  82   b , and oxygen-containing gas discharge chamber  102   b ) and the pipes (reforming pipes  66 , evaporation pipes  74 , and heat exchange pipes  96 ) are provided as basic structure. Thus, simple structure is achieved easily. Accordingly, the production cost of the fuel cell module  12  is reduced effectively. Further, by changing the volumes of the supply chambers and the discharge chambers, and the length, the diameter, and the number of the pipes, a suitable operation can be achieved depending on various operating conditions, and the design flexibility of the fuel cell module can be enhanced. 
     Further, the fuel gas discharge chamber  78   b , the water vapor discharge chamber  82   b , and the oxygen-containing gas discharge chamber  102   b  are provided at the side of one end adjacent to the fuel cell stack  24 , and the mixed gas supply chamber  78   a , the water supply chamber  82   a , and the oxygen-containing gas supply chamber  102   a  are provided at the side of the other end distant from the fuel cell stack  24 . 
     In the structure, the reactant gas immediately after heating and the reactant gas immediately after reforming (fuel gas and oxygen-containing gas) can be supplied to the fuel cell stack  24  promptly. Further, the exhaust gas from the fuel cell stack  24  can be supplied to the exhaust gas combustor  52 , the reformer  46 , the evaporator  48 , and the heat exchanger  50  of the FC peripheral equipment  56  while decrease in the temperature of the exhaust gas from the fuel cell stack  24  due to heat radiation is suppressed as much as possible. Thus, improvement in the heat efficiency is achieved, and thermally self-sustaining operation is facilitated. 
     Further, the exhaust gas combustor  52  is provided at the side of one end adjacent to the fuel cell stack  24 , and the start-up combustor  54  is provided at the side of the other end distant from the fuel cell stack  24 . In the structure, when the exhaust gas from the fuel cell stack  24  is supplied to the exhaust gas combustor  52 , and combusted to produce a combustion gas, decrease in the temperature is suppressed as much as possible. Therefore, improvement in the heat efficiency is achieved, and thermally self-sustaining operation is facilitated easily. 
     Further, since the start-up combustor  54  supplies the combustion gas toward the fuel cell stack  24 , the time required for increasing the temperature of the fuel cell stack  24 , i.e., the time required for starting operation, can be reduced effectively. 
     Further, as shown in  FIG. 3 , the bottom surface  62   e  of the combustion cup member  60  is provided at the position deviated from the intermediate position h of the first area R 1  toward the fuel cell stack  24 . In the structure, the combustion gas maintained at a high temperature can be reliably supplied to the reformer  46  and the evaporator  48  in the second area R 2 . 
     Alternatively, the bottom surface  62   e  of the combustion cup member  60  may be provided at the position deviated from the intermediate position h of the first area R 1  away from the fuel cell stack  24 . In the structure, the combustion gas can be distributed suitably over the entire reformer  46  and the entire evaporator  48  provided in the second area R 2 . 
     Further, as shown in  FIGS. 3, 4, and 6 , the combustion cup member  60  includes the support portion  61  fixed to the first area R 1 , and the cup portion  62  attached to the support portion  61  in an orientation from the fuel cell stack  24  toward the first area R 1 . Thus, the structure of the combustion cup member  60  is simplified, and reduction in the number of assembling steps is achieved. 
     Further, as shown in  FIG. 6 , the combustion cup member  60  has the fixing mechanism  64  for fixing the support portion  61  and the cup portion  62  together such that the support portion  61  and the cup portion  62  are not rotatable with respect to each other. The fixing mechanism  64  includes the recesses  64   b  and the protrusion  64   a  that is engageable with any of the recesses  64   b . At least the recesses  64   b  are provided at a plurality of positions, e.g., at two positions for enabling adjustment of the phase between the support portion  61  and the cup portion  62 . 
     Therefore, simply by providing and arranging the protrusion  64   a  and the recesses  64   b , the phase of the holes  62   a  can be adjusted. That is, in  FIG. 7 , the holes  62   a  are oriented toward positions between the reforming pipes  66  of the reformer  46 . Since the combustion gas supplied from the holes  62   a  to the second area R 2  flows toward the positions between the reforming pipes  66 , the quantity of the heat supplied to the reforming pipes  66  is relatively small. Thus, the heat exchanging efficiency of the reformer  46  is low. 
     In contrast, in  FIG. 9 , the holes  62   a  are oriented toward the reforming pipes  66  of the reformer  46 . Since the combustion gas supplied from the holes  62   a  to the second area R 2  flows toward the reforming pipes  66 , the quantity of heat supplied to the reforming pipes  66  is relatively large. Therefore, improvement in the heat exchanging efficiency in the reformer  46  is achieved. Thus, the quantity of the heat supplied to respective components, in particular the reformer  46 , can be adjusted easily and reliably. 
     Further, as shown in  FIG. 3 , the combustion gas flows from the first area R 1  to the second area R 2 , and then, flows from the second area R 2  to the third area R 3 . Thereafter, the combustion gas is discharged to the outside of the fuel cell module  12 . In the structure, the heat can be effectively supplied to the exhaust gas combustor  52 , the reformer  46 , the evaporator  48 , and the heat exchanger  50  of the FC peripheral equipment  56 . Thus, improvement in the heat efficiency is achieved, and thermally self-sustaining operation is facilitated. 
     Further, the fuel cell module  12  is a solid oxide fuel cell module. Therefore, the fuel cell module  12  is suitable for, in particular, high temperature type fuel cells such as SOFC. 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood that variations and modifications can be effected thereto by those skilled in the art without departing from the scope of the invention as defined by the appended claims.