Abstract:
Provided is a fuel processing device including: a combustion unit equipped with a heat source; a desulfurization unit for extracting a sulfur component from the source gas; a reforming unit for generating, from the desulfurized source gas, a hydrogen-containing gas having hydrogen as a main component thereof; and a low-temperature conversion unit equipped with an exothermic catalyst for reducing the impurity concentration in the hydrogen-containing gas. The reforming unit and the desulfurization unit are configured so as to surround the combustion unit, and are disposed concentrically in the given order facing outwards from the combustion unit. The present invention further includes a preheating passage which is connected to the desulfurization unit, and which is provided to a bottom part of the combustion unit via a heat insulation material, such that the source gas is preheated by heat from the combustion unit.

Description:
TECHNICAL FIELD 
     The present invention relates to a fuel processing apparatus that generates hydrogen to be supplied to a fuel cell system. 
     BACKGROUND ART 
     A fuel cell system such as a household cogeneration system includes a fuel processing apparatus that generates hydrogen-containing gas and a fuel cell that generates electricity using the hydrogen-containing gas generated by the fuel processing apparatus (for example, see PTL1 and 2). 
     As illustrated in  FIG. 9 , fuel processing apparatus  100  for a conventional fuel cell system includes: combustion section  102  including burner  23 ; desulfurization section  105  provided to surround combustion section  102 , which removes sulfur component from a source gas such as hydrogen carbonate fuel including city gas, LPG, and others; vaporization flow channel  108  in which the source gas and steam are mixed; reforming section  103  that causes a steam reforming reaction of mixed gas at a high temperature of approximately 600° C. and generates hydrogen-containing gas having hydrogen as the main component, conversion section  106  in which the concentration of carbon monoxide which is poisonous to the catalyst of a fuel cell is reduced to approximately 0.5% by the CO shift reaction, and selective oxidation section  110  that further reduces the carbon oxide concentration to approximately 10 ppm or lower by the selective oxidation reaction (for example, see PTL 3). 
     It is preferable that the temperature of desulfurization section  105  is set and maintained to a high temperature of 250° C. to 300° C., which is an optimum temperature for a hydrodesulfurization catalyst. In addition, it is preferable that the source gas provided to desulfurization section  105  is heated to an optimum temperature for the catalyst so as to promote the hydrodesulfurization reaction. Preheating, by the heat of the combustion section, before source fuel is supplied to the desulfurization section has been suggested (see PTL4 and PTL5). 
     However, as illustrated in  FIG. 9 , desulfurization section  105  is provided outside of fuel processing apparatus  100 . Accordingly, desulfurization section  105  is easily affected by an external environment, making it difficult to set and maintain the temperature of the desulfurization section  105  at an optimum temperature. When the desulfurization section  105  is kept operating at a temperature lower than the optimum temperature, activity in hydrodesulfurization catalyst is reduced, shortening the lifetime of the hydrodesulfurization catalyst. Since the lifetime of a fuel processing apparatus is generally considered as 10 years, there has been a request for a method for reducing the influence of the temperature from external environment. 
     Furthermore, since a source gas at room temperature is provided to desulfurization section  105 , there is a problem that the temperature of the source gas is not raised up to a temperature sufficient for hydrodesulfurization reaction. 
     As a means for reducing the influence of the temperature of the external environment, providing a heat insulating section at an outer periphery of fuel processing apparatus  100  (desulfurization section  105 ) has been considered. For example, placing the desulfurization section in a heat insulating section provided around the combustion section has been suggested (see PTL6). However, there is a problem that providing further heat insulation material to the outer periphery of fuel processing apparatus  100  increases the volume of the entire fuel cell system. 
     Alternatively, the amount of hydrodesulfurization catalyst added to desulfurization section  105  may be increased. However, there is a problem that the increased amount of the hydrodesulfurization catalyst added increases the size of the apparatus and the cost for the fuel processing apparatus. Furthermore, PTL7 discloses, for example, a reforming apparatus in which a vaporization section is provided to surround the reforming section. Although the invention disclosed in PTL7 can reduce the amount of heat emitted from the reforming section, an effect that the influence of the temperature on the desulfurization section from the external environment is reduced is not suggested. 
     A fuel processing apparatus housed inside an outer package, with a plurality of reactors closely arranged in parallel has been disclosed in PTL8 as a means for keeping the temperature of the source gas at a high temperature. According to the invention disclosed in PTL8, the reformed gas can be used for preheating the source gas. However, according to the configuration, the influence of the temperature of the external environment is reduced by a granular heat insulating material filling the outer package. Accordingly, it is difficult to miniaturize the size of the apparatus. PTL8 does not suggest that the influence of the temperature on the desulfurization section from the external environment is reduced. Accordingly, a fuel processing apparatus not easily affected by the temperature of the external environment has been needed. 
     Furthermore, as illustrated in  FIG. 9 , in a conventional fuel processing apparatus, there was a region A where no component is arranged around reforming section  103  that reaches a high temperature. Since reforming section  103  is exposed, it was necessary to provide a thick insulating material at an outer periphery of the apparatus in order to prevent the emission of heat to outside of the apparatus. The more the amount of heat insulating material, the more the volume of the apparatus becomes, despite the need for miniaturization of the apparatus. Furthermore, as illustrated in  FIG. 9 , conventional conversion section  106  is provided at one part. Since conversion section  106  is cooled on the inner-rim side contacting vaporization flow channel  108 , exothermic reaction is mainly occurred on the upstream side of the gas. Accordingly, there is a problem that the reaction efficiency of the converter catalyst is reduced due to uneven temperature distribution in the converter catalyst. In response to the problem, a fuel processing apparatus having a catalyst with high reaction efficiency has been needed. 
     CITATION LIST 
     Patent Literature 
     PTL1 
     Japanese Patent Application Laid-Open No. 2008-019159 
     PTL2 
     US Patent Application Publication No. 2009-0317671 
     PTL3 
     WO2009/150792 
     PTL4 
     US Patent Application Publication No. 2009-0087705 
     PTL5 
     US Patent Application Publication No. 2001-0029735 
     PTL6 
     Japanese Patent Application Laid-Open No. 2000-034103 
     PTL7 
     Japanese Patent Application Laid-Open No. 2005-104776 
     PTL8 
     Japanese Patent Application Laid-Open No. 2009-88346 
     SUMMARY OF INVENTION 
     Technical Problem 
     It is an object of the present invention to provide a fuel processing apparatus not easily affected by a temperature of an external environment, and capable of preheating the source gas. It is another object of the present invention to provide a fuel processing apparatus having a catalyst with high reaction efficiency. 
     Solution to Problem 
     According to a first aspect of the present invention, a fuel processing apparatus includes: a combustion section having a heat source; a desulfurization section that removes sulfur component from a source gas; a reforming section that generates hydrogen-containing gas having hydrogen as a main component from the source gas desulfurized; and a low-temperature conversion section having a heat-generating catalyst that reduces an impurity concentration in the hydrogen-containing gas. The reforming section and the desulfurization section are provided surrounding the combustion section, and the reforming section and the desulfurization section are formed in order in concentric circles from the combustion section toward outside. The fuel processing apparatus further comprises a preheat flow channel provided at a bottom of the combustion section with an insulating material interposed in between and in communication with the desulfurization section, such that the source gas is preheated using heat from the combustion section. 
     Advantageous Effects of Invention 
     According to the present invention, a fuel processing apparatus not easily affected by a temperature of an external environment and capable of preheating the source gas is provided. Furthermore, according to the present invention, a fuel processing apparatus having a catalyst with high reaction efficiency is provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of a fuel processing apparatus according to Embodiment; 
         FIG. 2  is a cross-sectional view illustrating the relationship between the first cylinder and the second cylinder as a part of the fuel processing apparatus according to Embodiment; 
         FIG. 3  is a perspective view of a part of fuel processing apparatus (spiral wavy tilted part) according to Embodiment; 
         FIG. 4  is a perspective view of a part of fuel processing apparatus (third cylinder) according to Embodiment; 
         FIG. 5  is an enlarged cross-sectional view of a part of fuel processing apparatus according to Embodiment (vaporization flow channel and high-temperature conversion section); 
         FIG. 6  is a cross-sectional view of main components of a fuel processing apparatus according to a variation of Embodiment; 
         FIG. 7  is a cross-sectional view of main components of a fuel processing apparatus according to a variation of Embodiment; 
         FIG. 8  is a cross-sectional view of main components of a fuel processing apparatus according to a variation of Embodiment; and 
         FIG. 9  is a cross-sectional view of a conventional fuel processing apparatus. 
     
    
    
     DESCRIPTION OF EMBODIMENTS  
     The present invention will be described as follows based on Embodiment. However, the present invention is not limited to the following Embodiment. Components with the same function or similar function are assigned with the same or similar reference numerals, and the description for the components will be omitted. Note that the drawings are schematic. Accordingly, specific dimensions and others will be determined with reference to the following description. Needless to say, relationships of dimensions of the components and ratio may be different between the drawings. 
     &lt;Fuel Processing Apparatus&gt; 
       FIG. 1  is a schematic cross-sectional view of a fuel processing apparatus according to Embodiment. Fuel processing apparatus  1  according to Embodiment includes: combustion section  2  having burner  23  as a heat source; desulfurization section  5  that removes sulfur component from a source gas; reforming section  3  that generates a hydrogen-containing gas having hydrogen as main component from the desulfurized source gas; low-temperature conversion section  6   b  having a exothermic catalyst for reducing impurity concentration in the hydrogen-containing gas; and preheat flow channel  55  provided at the bottom of combustion section  2  via heat insulation material  4  and in communication with desulfurization section  5 , such that the source gas is preheated by the heat at combustion section  2 . 
     Fuel processing apparatus  1  further includes vaporization flow channel  8 . Vaporization flow channel  8  is in communication with reforming section  3 , and obliquely tilted from the upper end of reforming section  3  toward outside, and passes through a region above desulfurization section  5 . The source gas and steam are mixed in vaporization flow channel  8 . 
     Fuel processing apparatus  1  further includes: high-temperature conversion section  6   a  provided above desulfurization section  5  along vaporization flow channel  8 , in communication with reforming section  3  and low-temperature conversion section  6   b , and selective oxidation section  10  in communication with low-temperature conversion section  6   b  provided outside of low-temperature conversion section  6   b  along vaporization flow channel  8 . Fuel processing apparatus  1  includes ammonia decomposition section  9  including an ammonia decomposition catalyst as an exothermic catalyst downstream of low-temperature conversion section  6   b , and a pipe connecting the other end of desulfurization section  5  and one end of vaporization flow channel  8  (not illustrated). 
     In fuel processing apparatus  1 , reforming section  3  and desulfurization section  5  are provided in circle, surrounding combustion section  2 . From combustion section  2  toward outside, reforming section  3  and desulfurization section  5  are arranged in order in concentric circles. In fuel processing apparatus  1 , from combustion section  2  toward outside, reforming section  3 , desulfurization section  5 , and low-temperature conversion section  6   b  are arranged in order in concentric circles. 
     Fuel processing apparatus  1  includes combustion section cylinder  22 , first cylinder to eighth cylinder  21 ,  32 ,  31 ,  41 ,  51 ,  61 ,  62 , and  91 , and bottom section  53 , and the components are provided to surround combustion section  2 . 
     According to fuel processing apparatus  1 , the source gas is supplied to desulfurization section  5  through preheat flow channel  55 . Preheat flow channel  55  is provided next to the bottom of combustion section  2  with an insulating material in between. Accordingly, the source gas flowing through preheat flow channel  55  can be preheated before being supplied to desulfurization section  5 . Accordingly, the desulfurization reaction at desulfurization section  5  proceeds efficiently. 
     In order to preheat the source gas more efficiently, it is preferable that preheat flow channel  55  is provided at the bottom of combustion section  2  and a part of side surface of combustion section  2  (a side surface near the bottom) with insulating material  4  in between. 
     According to fuel processing apparatus  1 , reforming section  3  and desulfurization section  5  are provided in concentric circles from combustion section  2  toward outside. The reforming catalytic reaction at reforming section  3  requires a higher reaction temperature than a reaction temperature for desulfurization catalytic reaction at desulfurization section  5 . Accordingly, in fuel processing apparatus  1 , temperatures suitable for the catalytic reactions are set at reforming section  3  and desulfurization section  5 . 
     Furthermore, according to fuel processing apparatus  1 , low-temperature conversion section  6   b  and ammonia decomposition section  9  having an exothermic catalyst are provided at an outer periphery of desulfurization section  5 . Accordingly, the hydrodesulfurization catalyst housed in desulfurization section  5  is less likely to be affected by the external environment. Accordingly, the amount of insulating material provided at an outer periphery can be reduced. Furthermore, according to fuel processing apparatus  1 , by improving reaction efficiency of the desulfurization catalyst, the amount of catalyst added can be reduced and thus the apparatus can be reduced in size and weight, compared to a conventional apparatus. Furthermore, according to fuel processing apparatus  1  according to Embodiment, the activation efficiency of the reaction catalyst can be maintained at a constant value. Accordingly, it is possible to improve reliability of the apparatus. 
     In the following description, fuel processing apparatus  1  can be described in detail by describing each section. 
     (Combustion Section) 
     Combustion section  2  supplies heat to the entire fuel processing apparatus  1  by operating burner  23  as a heat source of fuel processing apparatus  1 . Combustion section  2  includes combustion section cylinder  22 , first cylinder  21  provided at an outer periphery of combustion section cylinder  22 , and lid section  24  having burner  23  provided at an upper part of combustion section cylinder  22 . 
     Combustion section cylinder  22  includes combustion section cylinder main body  22   a  and funnel-shaped tilted part  22   b  having a diameter widening from an upper opening toward the end of combustion section cylinder main body  22   a . First cylinder  21  includes bottomed first cylinder main body  21   a  in which combustion section  2  is formed, which is provided at the outer circumference of combustion section cylinder main body  22   a , and funnel-shaped (cone-shaped) first tilted section  21   b  having a diameter widening from the opening of first cylinder main body  21   a  toward the outermost periphery of fuel processing apparatus  1 . The upper ends of first cylinder  21  and combustion section cylinder  22  are joined by vacuum welding, for example. Combustion exhaust gas path  25  is provided between first cylinder  21  and combustion section cylinder  22 . 
     (Vaporization Flow Channel, Reforming Section) 
     Vaporization flow channel  8  generates a mixed gas by mixing the source gas desulfurized by desulfurization section  5  and steam obtained by vaporizing the reforming water. Reforming section  3  is in communication with vaporization flow channel  8 , and generates hydrogen-containing gas including hydrogen as a main component from the mixed gas generated at vaporization flow channel  8 . More specifically, when the source gas is a natural gas having methane as main component, steam-methane reforming reaction occurs at reforming section  3  under the heat of approximately 600° C. by combustion section  2 . Subsequently, methane and steam are reformed to gas containing hydrogen, carbon monoxide, and carbon dioxide.
 
CH 4 +H 2 O→CO+3H 2   [Formula 1]
 
CH 4 +2H 2 O→CO 2 +4H 2   [Formula 2]
 
     Vaporization flow channel  8  includes first cylinder  21  and second cylinder  32  provided at an outer periphery of first cylinder  21 . As illustrated in  FIG. 2 , second cylinder  32  includes second cylinder main body  32   a  provided at an outer periphery of first cylinder main body  21   a  and wavy tilted section  32   b  having a diameter widening from upper opening of second cylinder main body  32   a  toward the outermost circumference of fuel processing apparatus  1 . Wavy tilted section  32   b  is a funnel-shaped tilted surface on which a spiral flow channel is formed. More specifically, as illustrated in  FIG. 3 , a spiral flow channel is provided on wavy tilted section  32   b.    
     Upper end  32   e  of second cylinder  32  and upper end  21   c  of first cylinder  21  are joined by vacuum welding, for example. Projections of first tilted section  21   b  and wavy tilted section  32   b  are welded by brazing, for example, without any gap. Accordingly, vaporization flow channel  8  is formed in a space provided between first tilted section  21   b  and projecting parts of wavy tilted section  32   b  by first cylinder  21  and second cylinder  32 . 
     At portions corresponding to the upper end and the lower end of reforming section  3  between second cylinder  32  and first cylinder  21 , stainless steel plates  32   c  and  32   d  are joined, respectively, by welding or another method. Through holes are provided on the main surfaces of stainless steel plates  32   c  and  32   d , allowing the gas to pass through. 
     As described above, reforming section  3  in communication with vaporization flow channel  8  and capable of housing a reformer catalyst is formed in a space between first cylinder main body  21   a  and second cylinder main body  32   a . Note that, it is preferable that the upper ends  32   e  and  21   c  are joined; stainless steel plate  32   c  is joined with the upper end of reforming section  3 . Subsequently, it is preferable that a catalyst is filled in reforming section  3 , and stainless steel plate  32   d  is joined. Other catalyst sections (desulfurization section, conversion section, oxidation section, ammonia decomposition section, and others) can be manufactured by a similar process. 
     By forming spiral vaporization flow channel  8  on the tilted surface of the funnel shape, the length of vaporization flow channel  8  can be made longer than a conventional fuel processing apparatus. By increasing the length of vaporization flow channel  8 , reforming water is more likely to be evaporated, and the reforming water will be mixed more easily with the source gas. 
     In addition, high-temperature conversion section  6   a  and selective oxidation section  10  are provided next to vaporization flow channel  8 . In high-temperature conversion section  6   a , conversion reaction which is exothermic catalytic reaction occurs. The heat generated by the catalytic reaction by high-temperature conversion section  6   a  is effectively absorbed by vaporization flow channel  8 . Accordingly, high-temperature conversion section  6   a  and selective oxidation section  10  are cooled, and the temperatures of the sections are controlled at optimum temperatures. With this, the catalytic reaction proceeds efficiently. 
     By welding the projecting parts of first tilted section  21   b  and wavy tilted section  32   b , a shortcut of vaporization flow channel  8  by reforming water can be prevented. Furthermore, drastic change in the temperature inside vaporization flow channel  8  can be prevented. Conventionally, after a middle cylinder is inserted between an inner cylinder and an outer cylinder, the projecting part of the middle cylinder is lengthened in height by pressing the middle cylinder in the axial direction. With this process, the middle cylinder is attached closely to the outer cylinder and the inner cylinder. However, according to Embodiment, the first tilted section  21   b  and projecting parts of wavy tilted section  32   b  are closely attached. Therefore, vaporization flow channel  8  can be formed easily without a complicated process. 
     Tilt angle θ of first tilted section  21   b  and wavy tilted section  32   b  (see  FIG. 1 ) is approximately 15 degrees to approximately 75 degrees, and is preferably 30 to 50 degrees. 
     Fuel processing apparatus  1  can set the aspect ratio of the entire apparatus (Y/X) in a range approximately from 0.6 to 0.9, and preferably approximately from 0.65 to 0.75 by providing first tilted section  21   b  and wavy tilted section  32   b . Considering that the aspect ratio of the conventional fuel processing apparatus is approximately in a range from 1.6 to 3.0, fuel processing apparatus  1  improves stability of setting when in use. In general, the aspect ratio that makes fuel processing apparatus  1  easy to handle is approximately 1. Accordingly, it is preferable to adjust the tilt angle θ of first tilted section  21   b  and wavy tilted section  32   b  such that the aspect ratio becomes closer to 1. Note that, the aspect ratio (Y/X) of fuel processing apparatus  1  in  FIG. 1  is 235/330=0/71. 
     Various reformer catalysts can be used for the reformer catalyst provided in reforming section  3  without any specific limit. For example, a number of ceramic porous granular material carrying reformer catalyst such as ruthenium, nickel, platinum and others can be filled in a state that allows ventilation. As the reformer catalyst, it is preferable to use platinum catalyst in terms of a viewpoint for not generating gas that affects components or catalysts of the fuel cell at the time of reforming. However, in order to suppress the cost of fuel processing apparatus  1 , it is preferable to use an inexpensive nickel (Ni) catalyst than an expensive platinum catalyst. 
     As the reformer catalyst, using nickel (Ni) catalyst instead of platinum catalyst reduces the cost for the apparatus. However, since ammonia gas may be generated when reforming the source gas into hydrogen gas, ammonia gas may be present in the hydrogen gas, which is problematic. When ammonia gas is present in hydrogen gas, it is likely to degrade components of the fuel cell and to make the catalyst less active. Furthermore, when the fuel cell is used in a household cogeneration system, the odor of ammonia gas may be unpleasant to users. However, according to fuel processing apparatus  1  according to Embodiment, even when the nickel catalyst is used as the reformer catalyst, ammonia gas generated can be decomposed by providing ammonia decomposition section  9 . Accordingly, the problem caused by ammonia gas is solved, and the cost for the entire fuel processing apparatus  1  is reduced. 
     (High-Temperature Conversion Section) 
     High-temperature conversion section  6   a  reduces the carbon monoxide concentration in the hydrogen-containing gas generated by the reforming by reforming section  3 . More specifically, in high-temperature conversion section  6   a , as illustrated in the following formula, carbon dioxide and hydrogen are generated through the reaction of carbon monoxide and steam in the hydrogen-containing gas.
 
CO+H 2 O→CO 2 +H 2   [Formula 3]
 
     High-temperature conversion section  6   a  includes second cylinder  32  and third cylinder  31  provided at the outer periphery of second cylinder  32 . Third cylinder  31  includes a bottomed third cylinder main body  31   a  provided at an outer periphery of second cylinder main body  32   a  and funnel-shaped second tilted section  31   b  having a diameter widening from the opening of third cylinder main body  31   a  toward the end. Reforming section  3  and high-temperature conversion section  6   a  are in communication with each other through a flow channel formed between second cylinder main body  32   a  and third cylinder main body  31   a  and a flow channel formed between spiral wavy tilted section  32   b  and second tilted section  31   b.    
     Flow channel  31   c  illustrated in  FIG. 4  is formed at a part of second tilted section  31   b  in third cylinder  31 . High-temperature conversion section  6   a  is provided in flow channel  31   c , and is adjacent to vaporization flow channel  8  through second tilted section  31   b  ( FIG. 5 ). As illustrated in  FIG. 5 , the gas passed through flow channel  31   c  passes through flow channel  31   d  and high-temperature conversion section  6   a , and turns back to low-temperature conversion section  6   b.    
     As a high-temperature converter catalyst, a copper-based catalyst may be used. 
     (Desulfurization Section) 
     Desulfurization section  5  removes sulfur component from hydrocarbon source gas such as city gas supplied (hydrocarbon raw fuel). 
     Desulfurization section  5  is formed between bottomed fourth cylinder  41  and fifth cylinder  51  provided at an outer periphery of fourth cylinder  41 , and a desulfurization catalyst is provided. Insulating material  4  is provided between fourth cylinder  41  and third cylinder main body  31   a . At portions corresponding to the upper end and the lower end of desulfurization section  5 , stainless steel plates are joined by welding, for example. A through hole is provided on the main surface of the stainless steel plate, allowing gas to pass through. 
     Bottom section  53  includes tabular disc-shaped bottom section main body  53   a  and bottomed cylinder  53   b  provided to surround outer circumference of a bottom of fourth cylinder  41  as a cavity at the center part of the bottom section main body  53   a . Preheat flow channel  55  in communication with desulfurization section  5  is formed between fourth cylinder  41  and cylinder  53   b.    
     As a (hydro) desulfurization catalyst, various desulfurization catalyst can be used without any specific limit. As a desulfurization catalyst, a copper-based catalyst may be used, for example. 
     (Low-Temperature Conversion Section, Ammonia Decomposition Section) 
     Low-temperature conversion section  6   b  is formed between sixth cylinder  61  and seventh cylinder  62 . Sixth cylinder  61  is provided at an outer periphery of fifth cylinder  51 , and the upper end of sixth cylinder  61  is in contact with second tilted section  31   b . Seventh cylinder  62  is provided at an outer periphery of sixth cylinder  61 , and the upper end of seventh cylinder  62  is in contact with second tilted section  31   b . At portions corresponding to the upper end and the lower end of low-temperature conversion section  6   b , stainless steel plates are joined by welding, for example. A through hole is provided on the main surface of the stainless steel plate, allowing gas to pass through. 
     Ammonia decomposition section  9  is formed between sixth cylinder  61  and seventh cylinder  62 , and is provided on a downstream side of low-temperature conversion section  6   b  with regard to the direction of the gas flow. 
     Low-temperature conversion section  6   b  includes a low-temperature conversion catalyst as the exothermic catalyst. Ammonia decomposition section  9  includes an ammonia decomposing catalyst as the exothermic catalyst. As the low-temperature conversion catalyst and the ammonia decomposing catalyst, a copper-based catalyst may be used. 
     (Selective Oxidation Section) 
     Selective oxidation section  10  removes carbon monoxide remaining in the gas converted by high-temperature conversion section  6   a  and low-temperature conversion section  6   b . More specifically, in selective oxidation section  10 , carbon monoxide remaining in the gas converted at a reaction temperature of approximately 100° C. to 200° C. by the catalytic action of ruthenium or others is oxidized by oxygen in added air. 
     Selective oxidation section  10  is provided between eighth cylinder  91  and seventh cylinder  62 . Eighth cylinder  91  is provided at an outer periphery of seventh cylinder  62 , and is in communication with ammonia decomposition section  9  through flow channel  95 . Selective oxidation section  10  is provided along vaporization flow channel  8  and outside of low-temperature conversion section  6   b.    
     (Preheat Flow Channel) 
     Preheat flow channel  55  is formed between first cylinder  41  and bottomed cylinder  53   b . It is preferable that an inlet for the source gas is provided at a part of bottomed cylinder  53   b  corresponding to the center axis of combustion section  2  in the gravity direction. Furthermore, preheat flow channel  55  is formed radially with the center axis of the combustion section in the gravity direction as the center. Accordingly, the source gas supplied from the source gas inlet to preheat flow channel  55  is preheated by the heat from combustion section  2 . Subsequently, the preheated (for example, heated up to approximately 250° C.) source gas is supplied to desulfurization section  5 . Accordingly, the desulfurization reaction at desulfurization section  5  proceeds efficiently. 
     The shape of preheat flow channel  55  is not limited to radial shape, as long as the supplied source gas is preheated. For example, as illustrated in  FIG. 6 , a reversed circular truncated cone-shaped preheat cavity  153   d  may be provided at a part of preheat flow channel  55 . It is preferable that the center axis of combustion section  2  in the gravity direction passes through the center of the bottom surface and the upper surface of the reversed circular truncated cone defining preheat cavity  153   d . Stated differently, circular truncated cone-shaped preheat cavity  153   d  having the center axis of the combustion section  2  in the gravity direction as the center, and a diameter widening from the center toward the outside may be provided at a part of preheat flow channel  55 . Preheat cavity  153   d  is in communication with preheat flow channel  55  having a diameter smaller than preheat cavity  153  at the large-diameter end of the reversed truncated cone in preheat cavity  153   d.    
     With the configuration described above, the source gas supplied from the source gas inlet flows at a low speed in preheat cavity  153   d . Accordingly, the source gas is preheated easily, and the temperature is set at a constant temperature easily. Subsequently, the preheated source gas flows at high flow speed in the small-diameter preheat flow channel  55 , and is supplied to desulfurization section  5 . With this, the source gas is preheated reliably, reducing variation in the temperature of the source gas. 
     In the fuel processing apparatus according to Embodiment, the source gas supplied from the supply inlet is preheated at preheat cavity  153   d , and then provided to desulfurization section  5 . Accordingly, even when the amount of supply of the source gas is changed due to a sudden increase in the supply amount of the source gas or temporary discontinuation of the supply, it is easy to supply the source gas preheated to a desired temperature to desulfurization section  5 . 
     In addition, forming preheat cavity  153   d  allows effective prevention of heat emission from fuel processing apparatus  1 . 
     Furthermore, as illustrated in  FIG. 7 , a part of preheat flow channel  55  may be provided as spiral flow channel  253   d . As illustrated in  FIG. 8 , spiral flow channel  253   d  is formed in a spiral having the center axis of the combustion section  2  in the gravity direction as the center. By forming spiral flow channel  253   d , the source gas is preheated while flowing in the circumferential direction. Accordingly, the source gas is preheated even more reliably. In addition, the variation in the temperature of the source gas can be reduced. Furthermore, the source gas can be preheated without increasing the size of fuel processing apparatus  1 . 
     A material for forming combustion section cylinder  22 , first cylinder to eighth cylinder  21 ,  32 ,  31 ,  41 ,  51 ,  61 ,  62 , and  91 , and bottom section  53  composing fuel processing apparatus  1  is not particularly limited as long as molding can be performed and the material is durable at the highest temperature of the component during processing. Although various materials can be used, stainless steel may be used, for example. 
     Fuel processing apparatus  1  can be manufactured by inserting cylinders made of stainless steel plates formed in cylinder shape with each other. Catalyst sections (reforming section  3 , desulfurization section  5 , high-temperature conversion section  6   a , low-temperature conversion section  6   b , ammonia decomposition section  9 , selective oxidation section  10 , and others) are formed between the cylinders, and combustion section  2  is formed. Reforming section  3  and desulfurization section  5  are provided in concentric circles having combustion section  2  as the center. 
     Furthermore, above desulfurization section  5  and low-temperature conversion section  6   b , vaporization flow channel  8  tilted from the upper end of reforming section  3  toward the outside is provided. With this, vaporization flow channel  8  can be provided without interfering with each catalyst section. 
     Furthermore, pipes for connecting to external apparatuses are provided at the bottom and the side surfaces of fuel processing apparatus  1 . Accordingly, when assembling the apparatus by inserting the cylinders, pipes for connecting with the external apparatuses and each catalyst section do not interfere with each other. As described above, by inserting the cylinders, fuel processing apparatus  1  can be manufactured easily. 
     According to fuel processing apparatus  1 , when the apparatus is in operation, different temperature regions are formed in concentric circles from the combustion section  2  toward outside with combustion section  2  as the center. For example, a temperature region of 600° C., a temperature region from 250° C. to 300° C., a temperature region of 300° C., a temperature region of 200° C., and a temperature region of 150° C. are formed. Reforming section  3  may be provided in the temperature region of 600° C., desulfurization section  5  may be provided in the temperature region from 250° C. to 300° C., high-temperature conversion region  6   a  may be provided in the temperature region of 300° C., low-temperature conversion section  6   b  and ammonia decomposition section  9  may be provided in the temperature region of 200° C., and selective oxidation section  10  may be provided in the temperature region of 150° C. With this, each catalyst section is provided in a preferable temperature region for the catalyst in each catalyst section, improving the reaction efficiency of the catalyst. 
     In the conventional fuel processing apparatus, it is necessary to provide a thick insulating material covering the reforming section at an outer periphery of the apparatus in order to prevent the emission of heat from reforming section to outside of the apparatus. In contrast, according to fuel processing apparatus  1 , ammonia decomposition section  9  and selective oxidation section  10  provided outside of the apparatus also have the insulation effect. Stated differently, according to fuel processing apparatus  1 , it is possible to prevent heat dissipation and to reduce the thickness of the heat insulating material provided at an outer periphery of the apparatus compared to the conventional apparatus, thereby achieving miniaturization of the apparatus. 
     In the conventional fuel processing apparatus, the reaction efficiency of the converter catalyst is reduced due to variation in temperature in the converter catalyst in the conversion section. However, according to fuel processing apparatus  1 , it is possible to effectively prevent the variation in temperature in the conversion catalyst, without increasing the amount of conversion catalyst by separating the conversion section into high-temperature conversion section  6   a  and low-temperature conversion section  6   b.    
     In particular, by providing a high-temperature conversion catalyst in high-temperature conversion section  6   a  provided along vaporization flow channel  8 , and providing a low-temperature conversion catalyst in low-temperature conversion section  6   b , the variation in temperature can be effectively prevented. Since the heat generated by the catalytic reaction at high-temperature conversion section  6   a  is efficiently absorbed in vaporization flow channel  8 , the catalytic reaction proceeds more efficiently. By improving the reaction efficiency of the catalyst, the amount of added catalyst can be reduced. 
     &lt;Fuel Processing Method&gt; 
     Next, the process for processing the source gas into hydrogen-containing gas (gas flow) will be described by describing the fuel processing method. 
     (Desulfurization) 
     First, fuel processing apparatus  1  as illustrated in  FIG. 1  is prepared. Next, a source gas containing methane such as LPG and city gas is supplied from a source gas supply inlet provided at cylinder  53   b  at bottom section  53 . The source gas is supplied to desulfurization section  5  through preheat flow channel  55 . In preheat flow channel  55 , the source gas is heated (preheated). The sulfur component in the source gas reacts with hydrodesulfurization catalyst stored in desulfurization section  5 , and the sulfur component in the source gas is removed. 
     (Reforming) 
     The desulfurized source gas is supplied to vaporization flow channel  8  through a pipe (not illustrated) from an outlet for desulfurized source gas provided at bottom section main body  53   a . At the same time, the reforming water is supplied to vaporization flow channel  8 , and the reforming water is heated and vaporized. Subsequently, the desulfurized source gas and the vaporized reforming water are mixed while passing through vaporization flow channel  8 , generating a mixed gas. The mixed gas obtained is supplied to reforming section  3  filled with reformer catalyst. The hydrogen-containing gas is generated from the mixed gas by the reforming reaction. 
     (High-Temperature Conversion) 
     The gas reformed from the source gas to the hydrogen-containing gas is supplied from the lower end of reforming section  3  to high-temperature conversion section  6   a  provided along vaporization flow channel  8  illustrated in  FIG. 5  through flow channel  35 . Subsequently, the gas is reacted with high-temperature conversion catalyst filling high-temperature conversion section  6   a . The converted gas passed through the lower end of high-temperature conversion section  6   a  is introduced into low-temperature conversion section  6   b.    
     (Low-Temperature Conversion) 
     In low-temperature conversion section  6   b , the gas converted at a high temperature is converted again, reducing carbon monoxide in the hydrogen-containing gas. The gas passed through low-temperature conversion section  6   b  converted at low temperature is introduced into ammonia decomposition section  9  as an optional apparatus. Note that, the low-temperature conversion section  6   b  and high-temperature conversion section  6   a  may be continuously formed integrally. 
     (Ammonia Decomposition) 
     At ammonia decomposition section  9 , remaining ammonia gas is removed from the hydrogen-containing gas. The gas passed through ammonia decomposition section  9  is introduced into selective selection section  10  provided along vaporization flow channel  8  via flow channel  95 . Note that, when it is not necessary to remove ammonia from the hydrogen-containing gas, it is preferable that the same conversion catalyst used for low-temperature conversion section  6   b  is filled at a position of ammonia decomposition section  9 . The purpose of this is to prevent the heat emission to outside of the apparatus. 
     (Selective Oxidation) 
     Carbon monoxide gas remaining in the gas is removed further at selective oxidation section  10 . Selective oxidation section  10  accompanies exothermic reaction, and is provided next to vaporization flow channel  8 . Accordingly, the heat generated by the catalytic reaction at selective oxidation section  10  is efficiently absorbed in vaporization flow channel  8 . Accordingly, the temperature of selective oxidation section  10  is controlled to an optimum temperature, and thus the catalytic reaction proceeds efficiently. 
     The hydrogen-containing gas is generated as described above. The fuel cell system functions by supplying the hydrogen-containing gas to a power generating stack in a fuel cell through pipes (not illustrated). 
     Other Embodiments 
     The present invention has been described above with reference to Embodiment. However, it should not be understood that the description and drawings included as a part of the disclosure has a limiting effect on the present invention. The disclosure articulates various alternative embodiments, examples, and operation technologies for a person skilled in the art. 
     For example, a fuel cell system including fuel processing apparatus  1  described in Embodiment as a part can be manufactured. 
     In fuel processing apparatus  1 , a circular truncated cone shaped space defined by tilted section  22   b  and lid section  24  is formed above combustion section  2 . By providing a tank capable of storing the reforming water in this space allows preheating the reforming water using the heat at combustion section  2 . In addition, since heated reforming water is provided above combustion section  2 , heat emission from fuel processing apparatus  1  can also be prevented. With this, a fuel processing apparatus having smaller influence from external environment and a catalyst having high reaction efficiency can be provided. 
     Conventionally, in vaporization flow channel  8 , the reforming water may not be sufficiently heated, not be evaporated in the vaporization flow channel, and may wet the surface of the reformer catalyst. When the surface of the reformer catalyst is wet, the contact area of the catalyst and the gas is reduced, possibly making the catalyst less active. Furthermore, when the catalyst is wet, the moisture may degrade the catalyst, and may interrupt the reforming of the source gas. However, by preheating the reforming water, the reforming water is sufficiently heated and is evaporated easily. Accordingly, the conventional problem is solved, and the source gas is effectively reformed into hydrogen gas. 
     Needless to say, the present invention includes various embodiments that have not been described herein. Accordingly, the technical scope of the present invention is determined merely by the features of the invention according to the appended claims reasonably arrived based on the description above. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, a fuel processing apparatus capable of preheating the source gas and not easily affected by a temperature of an external environment is provided. Furthermore, according to the present invention, a fuel processing apparatus with a catalyst having high reaction efficiency is provided. 
     REFERENCE SIGNS LIST 
     
         
           1  Fuel processing apparatus 
           2  Combustion section 
           3  Reforming section 
           5  Hydrodesulthrization section 
           6   a  High-temperature conversion section 
           6   b  Low-temperature conversion section 
           8  Vaporization flow channel 
           9  Ammonia decomposition section 
           10  Selective oxidation section 
           23  Burner 
           22  Combustion section cylinder 
           21  First cylinder 
           32  Second cylinder 
           31  Third cylinder 
           41  Fourth cylinder 
           51  Fifth cylinder 
           61  Sixth cylinder 
           62  Seventh cylinder 
           91  Eighth cylinder 
           53  Bottom 
           55  Preheat flow path 
           153   d  Preheat cavity 
           253   d  Spiral flow channel