Abstract:
A reformer includes an evaporation portion for evaporating a raw material, a reforming portion for producing a reformed gas whose principal element is hydrogen from the raw materials, a CO reduction portion for reducing CO involved in the reformed gas, a circulating conduit portion having a storage tank for storing the raw material, a feeding device for feeding the raw material under pressure, a cooling device for cooling the CO reduction portion and a supply device for supplying the raw material to the evaporation portion. The supply device includes a conduit branched from the circulating conduit portion connected to the evaporation portion and a flow control device provided in the conduit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a reformer which is associated with a fuel cell system. 
     2. Description of the Related Art 
     Generally speaking, in fuel cell systems, electric power is generated in a fuel cell stack by using a fuel gas and an oxidizing agent gas. The fuel gas is supplied from a reformer in which a fuel of the hydrocarbon family is reformed into a fuel gas whose principal component is hydrogen. Due to the fact that such a fuel gas involves 0.3-2% CO, it can cause poisoning of the electrode catalyst, thereby considerably lowering the performance of the fuel cell system. 
     To prevent such a drawback, Japanese Laid-open Patent No. Hei.8-100184, published in 1996 without examination, discloses a carbon monoxide removing system in which a raw material to be reformed is first used for cooling the carbon monoxide removing system and thereafter is reformed so as to reduce the CO concentration in a hydrogen-rich fuel gas below 100 ppm. 
     However, if a load of the fuel call system increases, the flow mass of the raw material also increases, which causes an abrupt cooling of the carbon monoxide removing system, thereby unbalancing the same in temperature. Due to the fact that the operation of a reformer is based on the temperature of the carbon monoxide removing system, such an imbalanced condition may cause an unexpected operation of the reformer. 
     SUMMARY OF THE INVENTION 
     It is therefore a principal object of the present invention to provide a reformer which is free from the foregoing drawback. 
     In order to attain the above and other objects, the present invention provides a reformer, especially for fuel cell systems, which comprises an evaporation portion for evaporating a hydrocarbon family fuel and a water as raw materials; a reforming portion for producing a reformed gas whose principal element is hydrogen from the raw materials; a CO-reduction portion for reducing CO involved in the reformed gas; a circulating conduit portion including storage means for storing one of the hydrocarbon family fuel, the water, and a mixture of the hydrocarbon family fuel and the water, a feeding means for feeding one of the raw materials under pressure, and cooling means for cooling the CO reduction portion; and supply means for supplying the raw materials to the evaporation portion, the supply means including a conduit branched from the circulating conduit portion connected to the evaporation portion, and a flow control means provided in the conduit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will be more readily apprehended from the following detailed description when read in connection with the appended drawing, which forms a part of this original disclosure, and wherein: 
     FIG. 1 is a schematic diagram of a reforming system including a reformer in accordance with a first embodiment of the present Invention 
     FIG. 2 is a schematic diagram of a reforming system including a reformer in accordance with a second embodiment of the present invention; 
     FIG. 3 is a schematic diagram of a reforming system including a reformer in accordance with a third embodiment of the present invention; and 
     FIG. 4 is a schematic diagram of a reforming system including a reformer in accordance with a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     With reference to FIG. 1, there is illustrated a schematic diagram of a reforming system including a reformer  1  in accordance with a first embodiment of the present invention. The reforming system includes, in addition to the reformer  1 , a methanol tank  2 , an air compressor  3 , a coolant circulating conduit portion  100  and a water supply portion  200 . The reformer  1  is made up of a combustion portion  11 , an evaporation portion  12 , a reforming portion  13 , and CO reduction portion  14 . 
     The methanol tank  2  is a means for storing therein an amount of methanol which is one of the raw materials of a fuel gas. The methanol tank  2  is connected to the combustion portion  11  and the evaporation portion  12  of the reformer  1  by way of pumps P 1  and P 2 , respectively. The air compressor  3  is connected to the reforming portion  13  and the CO reduction portion  14  of the reformer  1  by way of flow-control valves V 2  and V 3 , respectively. 
     The CO reduction portion  14  of the reformer  1  is designed to reduce CO involved in a reformed gas produced in the reforming portion  13  by using a catalyst (not shown), and has a built-in coolant conduit  15 A for controlling the temperature of the catalyst. The CO reduction portion  14  of the reformer  1  is connected to a fuel cell stack (not shown) which converts chemical energy to electric energy by an electrochemical reaction between hydrogen in the reformed gas and oxygen in an oxidizing agent gas. 
     The coolant circulating conduit portion  100  is provided for cooling the CO reduction portion  14  by circulating an oil therethrough as a coolant. The coolant circulating conduit portion  100  includes a reservoir tank  7 , a pump P 3 , and a heat exchanger  5 . The reservoir tank  7 , which stores therein an amount of oil as the coolant, is connected to the coolant conduit  15 A of the CO reduction portion  14  by way of the pump P 3 . 
     The coolant conduit  15 A of the CO reduction portion  14  is connected to the heat exchanger  5  by way of a coolant conduit  29 . The heat exchanger  5  is also connected to the reservoir tank  7  by way of a coolant conduit  28 . It is to be noted that instead of oil, other fluids which have the same function or effect as oil can be used as the coolant. 
     The water supply portion  200  which supplies water as one of the raw materials of the fuel gas to the evaporation portion  12  is made up of a water tank  4 , a water pump P 4 , the heat exchanger  5 , a radiator  6  having a fan  6 A, and a flow control valve V 1 . 
     The water tank  4  is connected to the pump P 4  and the radiator  6  by way of a conduit  21  and a conduit  25 , respectively. The pump P 4  is connected to the heat exchanger  5  by way of a conduit  22 . The heat exchanger  5  is connected to the radiator  6  by way of conduits  23  and  24 . The water tank  4 , the pump P 4 , the radiator  6 , and the conduits  21  to  25  inclusive constitute a water circulating conduit portion  201 . 
     The heat exchanger  5  is interposed between the coolant circulating conduit portion  100  and the water circulating conduit portion  201  for cooling the coolant which passes through the water circulating conduit portion  201 . 
     The heat exchanger  5  is also connected to the flow control valve V 1  as a flow rate control means by way of the conduits  23  and  26 . That is to say, the water from the conduit  23  is bifurcated into the conduit  24  and a conduit  26 . The flow control valve V 1  is connected to the evaporation portion  12  by way of a conduit  27 . 
     Upon start up of the reforming system, the pump P 1  is turned on, which causes methanol to be supplied from the methanol tank  2  to the combustion portion  11 , thereby burning the supplied methanol. Simultaneously, the pump P 2  supplies the methanol from the methanol tank  2  to the evaporation portion  12 , and the pump P 4  supplies water from the water tank  4  to the evaporation portion  12  by way of the heat exchanger  5  and the flow control valve V 1 . 
     The water and the methanol supplied to the evaporation portion  12  are evaporated by the heat which is generated at the combustion portion  11  and are fed to the reform portion  13 . The resultant water and methanol are mixed with the air supplied from the air compressor  3  by way of the flow control valve V 2  and the resultant mixture is reformed by the catalyst to a hydrogen based reformed gas which involves 0.3-2% CO. In order to reduce the CO to be as small as possible, the reformed gas is fed to the CO reduction portion  14  to which air is supplied from the air compressor  3  by way of the flow control valve V 3  so as to be mixed with the reformed air. The CO is there reduced by using a CO reduction catalyst which oxidizes the CO in a selective fashion. To establish effective oxidation it is important to keep the CO reduction catalyst at a temperature of 110-200° C. 
     The temperature of the CO-reduction catalyst is equal to substantially the ambient temperature so long as the reforming system remains inoperative but increases when the reformed gas is supplied, due to the fact that the CO-reduction reaction generates heat. A quick temperature rise of the CO reduction catalyst to an optimal value can be made by reducing the amount of oil passing through the coolant circulating conduit portion  100 . 
     The CO reduction catalyst is cooled when the coolant conduit  15 A of the CO reduction portion  14  is supplied with the oil from the reservoir tank  7  by the pump P 3 . The oil exhausted from the coolant conduit  15 A is returned to the reservoir tank  7  by way of the conduit  29 , the heat exchanger  5  and the conduit  28 . 
     The oil, while passing through the heat exchanger  5 , is cooled by the water supplied from the water tank  4  to the evaporation portion  12 . The water is thus pre-heated before being supplied to the evaporation portion  12 . Thus, less energy is required to evaporate the water, and the methanol in the evaporation portion  12 . In other words, the temperature of the combustion portion  11  can be made to lower, which permits the amount of methanol to be supplied to the combustion portion  11  to be reduced. 
     The pump P 4  supplies a larger amount of water to the heat exchanger  5  than the amount of water to be supplied to the evaporation portion  12 . The excess water is returned to the water tank  4  by way of the conduits  23  and  24 , the radiator  6 , and the conduit  25 . If the temperature of this water becomes in much excess of a set value, the fan  6 A of the radiator is turned on, which causes forced cooling of the water. 
     The pump P 3  pumps oil at a fixed rate of 10 liters/min, while the pump P 4  pumps water at a fixed rate of 5 liters/min. The fan  6 A is designed to turn on and turn off immediately when the temperature of the water in the water tank  4  becomes not less than 56° C. and not greater than 54° C., respectively. 
     Such an operation mode causes the temperature of the oil stored in the reservoir tank  7  to be kept within a range from 90 to 100° C. Of the pumped water amount of 5 liters/min, only the required amount for the reforming is supplied to the evaporation portion  12  by the control of the flow control valve V 1 . Due to the fact that the water is preheated in the heat exchanger  5 , the amount of the methanol to be burned in the combustion portion  11  can be reduced. This preheating is done by Using the heat generated at the CO reduction portion  14 , which increases the heat efficiency. 
     In the foregoing operation mode, since the fixed flow of oil at a stable temperature cools the CO reduction portion  14  both when the load varies and when the load is steady, the temperature of the catalyst in the CO reduction portion  14  can be kept within a range from 110 to 190° C. independent of the operation condition, thereby reducing the CO in the reformed gas to be not greater than 10 PPM in stable fashion. The resultant reformed gas is fed to the fuel cell stack in a stable fashion independent of load variation. 
     Instead of water as the raw material of the reformed gas, hydrocarbon family fuel or a mixture thereof with water can be used. 
     Second Embodiment 
     With reference to FIG. 2, there is illustrated a schematic diagram of a reforming system including a reformer  1  in accordance with a second embodiment of the present invention. The reforming system includes a reformer  1 , a methanol tank  2 , an air compressor  3 , a water supply portion  300  and a methanol supply portion  400 . The methanol tank  2  is connected to a combustion portion  11  of the reformer  1  by way of a pump P 1 . 
     The water supply portion  300 , which acts as a main raw material supply means, is made up of a water tank  7 A, a pump P 5 , a heat exchanger  5 A, and a flow control valve V 4 . The water tank  7 A is a means for storing therein an amount of water which is one of the raw materials to be reformed. The water also acts as a coolant for cooling a CO reduction portion  14  of the reformer  1 . 
     In the CO reduction portion  14  of the reformer  1 , there is provided a conduit  15 B which is connected to the water tank  7 A by way of the pump P 5 . The conduit  15 B is also connected to the heat exchanger  5 A by way of conduits  34  and  35 . The heat exchanger  5 A is connected to the water tank  7 A by way of the conduit  37 . The water tank  7 A, the pump P 5 , the conduit  15 B, and the heat exchanger  5 A constitute a circulating conduit portion  301 . 
     The conduit  15 B is connected to the flow control valve V 4  by way of the conduit  34  and a conduit  36 . The conduit  34  is bifurcated into the conduits  34  and  35 . The flow control valve V 4  is connected to an evaporation portion  12  of the reformer  1  by way of a conduit  38 . The conduit  15 B is a means for cooling the circulating conduit portion  301  of the water supply portion  300 . 
     The methanol supply portion  400 , which acts as a secondary reforming raw material supply means, is made up of a methanol tank  4 A. a pump P 4 , the heat exchanger  5 A, a radiator  6  with a fan  6 A and a flow control valve V 1 . The methanol tank  4 A stores therein an amount methanol. The pump P 4  feeds the methanol under pressure. 
     The methanol tank  4 A is connected to the pump P 4  and the radiator  6  by way of conduits  21  and  25 , respectively. The pump P 4  is connected to the heat exchanger  5 A by way of a conduit  22 . The heat exchanger  5 A is connected to the radiator  6  by way of conduits  23  and  24 . The methanol tank  4 A, the pump P 4 , the heat exchanger  5 A, the radiator  6  and the conduits  21  to  25 , inclusive, constitute a water circulating conduit portion  401 . 
     The heat exchanger  5 A is interposed between the coolant circulating conduit portion  301  and the water circulating conduit portion  401  for cooling the water circulating conduit portion  401 . 
     The heat exchanger  5 A is also connected to the flow control valve V 1  by way of the conduit  23  and a conduit  26 . The flow control valve V 1  is connected to an evaporation portion  12  of the reformer  1  by way of a conduit  27 . 
     Upon start up of the reforming system, the methanol is fed from the methanol tank  2  to the combustion portion  11  of the reformer  1  by the pump P 1  and is burned at the combustion portion  11 . Methanol is also fed to the evaporation portion  12  of the reformer  1  from the methanol tank  4 A by way of the heat exchanger  5 A and the flow control valve V 1  by the actuation of the pump P 4 . Simultaneously, the pump P 5  feeds water under pressure to the evaporation portion  12  of the reformer  1  from the water tank  7 A by way of the conduit  15 B and the flow control valve V 4 . 
     The water and methanol supplied to the evaporation portion  12  of the reformer  1 , like those in the first embodiment, are evaporated, reformed at the reforming portion  13 , and fed to the CO reduction portion  14 . Due to the fact that the CO reduction reaction at the CO reduction portion  14  is heat generative, it is very important to cool the CO reduction catalyst down to a temperature which is suitable for such a reaction. 
     The water stored in the water tank  7 A is supplied to the conduit  15 B in the CO reduction portion  14  by the actuation of the pump P 5  and cools the CO reduction catalyst while being preheated. The water drained from the conduit  15 B is fed to the evaporation portion  12  by way of the conduits  34  and  36 , the flow control valve V 4  and the conduit  38 . Excess water which is not supplied to the evaporation portion  12  is returned to the water tank  7 A by way of the heat exchanger  5 A and the conduit  37 . 
     The water returned to the water tank  7 A is cooled at the heat exchanger  5 A by the methanol which is being supplied to the evaporation portion  12  from the methanol tank  4 A. The methanol entering the evaporation portion  12  is preheated. Thus, less energy is required to evaporate the water and the methanol at the evaporation portion  12 . In other words, the temperature of the combustion portion  11  can be made lower, which saves the amount of methanol to be supplied to the combustion portion  11 . 
     The amount of methanol which is supplied to the heat exchanger  5 A is larger than the amount of methanol supplied to the evaporation portion  12  and the resultant surplus methanol is returned to the methanol tank  4 A by way of the conduits  23  and  24 , the radiator  6  and the conduit  25 . If the temperature of the returning methanol rises excessively, the fan  6 A is turned on for forcefully cooling the methanol. 
     The pump P 5  discharges the water at a fixed rate of 10 liters/min, while the pump P 4  discharges the methanol at a fixed rate of 5 liters/min. The fan  6 A is turned on and off when the temperature in the methanol tank  4 A becomes not less than 46° C. and not greater than 44° C., respectively. 
     Such a control keeps the temperature of the water in the water tank  7 A within a range from 70 to 80° C. Of the pumped 10 liters/min, the amount of water required by the reformer is supplied to the evaporation portion  12  by controlling the flow control valve V 4 . Of the pumped 5 liters/min, the amount of methanol required by the reformer is supplied to the evaporation portion  12  by controlling the flow control valve V 1 . The preheating of the water at the CO reduction portion  14  and the preheating of the methanol at the heat exchanger  5 A reduce the amount of methanol to be burned at the combustion portion  11 . Due to the fact that each preheating is done by using the heat generated at the CO reduction portion  14 , the heat efficiency of the system is improved. 
     In the foregoing operation mode, since a fixed amount of water at stable temperature cools the CO reduction portion  14  when the load varies and when the load is steady, the temperature of the catalyst in the CO reduction portion  14  can be kept within a range from 110 to 190° C. independent of the operation conditions, thereby reducing the CO in the reformed gas to not greater than 10 PPM in stable fashion. The resultant reformed gas is fed to the fuel cell stack in stable fashion independent of load variations. 
     Instead of the water and the methanol as the primary and secondary raw materials of the reformed gas, a hydrocarbon family fuel and water may be used. 
     Third Embodiment 
     With reference to FIG. 3, there is illustrated a schematic diagram of a reforming system including a reformer  1  in accordance with a third embodiment of the present invention. The reforming system includes the reformer  1 , a methanol tank  2 , an air compressor  3 , and a water supply portion  500 . The water supply portion  500 , which acts as a means for supplying raw material to be reformed, includes a water tank  7 B, a pump P 6 , a radiator  30  with a fan  30 A and a flow control valve V 5 . The water tank  7 B is a means for storing therein an amount of water which is one of the raw materials to be reformed. This water acts as a coolant which is used to control a temperature of a CO reduction portion  14  of the reformer  1 . 
     In the CO reduction portion  14  of the reformer  1 , there is provided a conduit  15 C through which water is passed for cooling a reforming catalyst (not shown). The water tank  7 B is connected by way of the pump P 6  to the conduit  15 C, which is also connected to the radiator  30  by way of conduits  39  and  40 . The radiator  30  is connected to the water tank  7 B by way of a conduit  42 . The water tank  7 B, the pump P 6 , the conduit  15 C and the radiator  30  constitute a water circulating conduit portion  501 . 
     The conduit  15 C is also connected to a flow control valve V 5  by way of the conduit  39  and a conduit  41 . The flow control valve V 5  is connected to an evaporation portion  12  of the reformer  1  by way of a conduit  43 . The conduit  15 C is a means for cooling the water circulating portion of the water supply portion  500 . 
     When the reforming system is started up, the methanol is supplied from the methanol tank  2  to a combustion portion  11  of the reformer  1  by the pump P 1  and is burned at the combustion potion  11 . The methanol is also supplied from the methanol tank  2  to the evaporation portion  12  of the reformer  1  by a pump P 2 . Simultaneously, the water in the water tank  7 B is fed to the evaporation portion  12  of the reformer  1  by pump P 6 , by way of the conduit  15 C and a flow control valve V 5  which controls the flow rate of the water. 
     Similar to the first embodiment, the water and the methanol which are supplied to the evaporation portion  12  of the reformer  1  are evaporated thereat, reformed at a reforming portion  13  and fed to the CO reduction portion  14 . Due to the fact that the chemical reaction at the CO reduction portion  14  is a heat generative one, it is very important to control the temperature of the CO reduction catalyst to a suitable value. 
     The water stored in the water tank  7 B is supplied to the conduit  15 C in the CO reduction portion  14  by the pump P 6 , which simultaneously preheats the water and cools the CO reduction catalyst. The water drained from the conduit  15 C is supplied to the evaporation portion  12  of the reformer  1  by way of the conduit  39 , the conduit  41 , the flow control valve V 5  and the conduit  43 . Excess water which is not supplied to the evaporation portion  12  of the reformer  1  is returned to the water tank  7 B by way of the radiator  30  and a conduit  42 . If the temperature of the returned water exceeds a set value, the fan  30 A is turned on, thereby establishing a forced cooling of the surplus water. 
     Thus, since the CO reduction portion  14  of the reformer  1  is supplied with a fixed amount of water when the load of the system varies, a stable temperature control of the catalyst which matches the chemical reaction independent of the operation condition results, thereby producing the reformed gas in stable fashion in such a manner that the CO in the reformed gas is reduced to not greater than 10 PPM. The resultant reformed gas is fed to the fuel cell stack in stable fashion independent of load variation. 
     Instead of water as the raw material of the reformed gas, a hydrocarbon family fuel or a mixture of hydrocarbon family fuel and water can be used. 
     Fourth Embodiment 
     With reference to FIG. 4, there is illustrated a schematic diagram of a reforming system including a reformer  1  in accordance with a fourth embodiment of the present invention. The reforming system includes the reformer  1 , a methanol tank  2 , an air compressor  3 , a methanol supply portion  600  and a water supply portion  700 . The reformer  1  is made up of a combustion portion  11 , an evaporation portion  12 , a reforming portion  13  and a CO reduction portion  16  which has a first or front part  16 A and a second or rear part  16 B. 
     The methanol supply portion  600  as a means for supplying raw material to be reformed is made up of a methanol tank  7 C which stores therein an amount of methanol as the raw material to be reformed, a pump P 7 , a radiator  31  with a fan  31 A and a flow control valve V 6 . The methanol acts as coolant for cooling the second part  16 B of the CO reduction portion  16 . 
     In the second part  16 B of the CO reduction portion  16 , there is provided a conduit  15 E for the temperature control of the catalyst which is connected to the methanol tank  7 C by way of the pump P 7 . The conduit  15 E is also connected to the radiator  31  by way of conduits  44  and  45 . The radiator  31  is connected to the methanol tank  7 C by way of a conduit  47 . The methanol tank  7 C, the pump P 7 , the conduit  15 E, and the radiator  31  constitute a coolant circulating conduit portion  601 . 
     The conduit  15 E is also connected to the flow control valve V 6  by way of conduits  44  and  46 . The flow control valve V 6  is connected to the evaporation portion  12  of the reformer  1  by way of a conduit  52 . The conduit  15 E is a means for cooling the coolant circulating conduit portion  601  of the methanol supply portion  600 . 
     The water supply portion  700 , which acts as a means for supplying another raw material, is made up of a water tank  7 D, a pump P 8 , a radiator,  32  with a fan  32 A and a flow control valve V 7 . The water tank  7 D acts as a means for storing an amount of water which is one of raw materials to be reformed The water acts as a coolant for controlling of the temperature of the first part  16 A of the CO reduction portion  16 . 
     In the first part  16 A of the CO reduction portion  16 , there is provided a conduit  15 D which is connected to the water tank  7 D by way of the pump P 8 . The conduit  15 D is also connected to the radiator  32  by way,of conduits  48  and  49 . The radiator  32  is connected to the water tank  7 D by way of a conduit  51 . The water tank  7 D, the pump P 8 , the conduit  15 D and the radiator  32  constitute a circulating conduit portion  701 . 
     The conduit  15 D is also connected to a flow control valve V 7  by way of conduits  48  and  50 . The flow control valve V 7  is connected to the evaporation portion  12  of the reformer  1  by way of a conduit  53 . The conduit  15 D is a means for cooling a coolant circulating conduit portion  701  of the water supply means  700 . 
     When the reforming system is driven or turned on, the methanol is supplied from the methanol tank  2  to the combustion portion  11  of the reformer  1  by the pump P 1  and is burned thereat. Simultaneously, the pump P 8  supplies water to the evaporation portion  12  of the reformer  1  from the water tank  7 D by way of the conduit  15 D and the flow control valve V 7 . In addition, the pump P 7  supplies the methanol from the methanol tank  7 C to the evaporation portion  12  of the reformer  1  by way of a conduit  15 E and the flow control valve V 6 . 
     Like in the first embodiment the water and the methanol supplied to the evaporation portion  12  of the reformer  1  is evaporated, reformed at the reforming portion  13  and fed to the CO reduction portion  16 . In the CO reduction portion  16 , CO reduction occurs through a heat generative chemical reaction, which requires that a suitable temperature be maintained by cooling the CO reduction catalyst. 
     The water stored in the water tank  7 D is supplied to conduit  15 D in the first part  16 A of the CO reduction portion  16  by the pump P 8 . The water is thereby simultaneously preheated and the CO reduction catalyst cooled. The water drained from the conduit  15 D is supplied to the evaporation portion  12  of the reformer  1  by way of the conduits  48  and  50 , the flow control valve V 7 , and the conduit  53 . Excess water, which is not supplied to the evaporation portion  12 , is returned to the water tank  7 D by way of the radiator  32  and the conduit  51 . If the temperature of the water exceeds a set value, forced cooling thereof is performed by turning on the fan  32 A. 
     The methanol stored in the methanol tank  7 C is supplied to the conduit  15 E in the second part  16 B of the CO reduction portion  16  by the pump P 7 . In the conduit  15 E, the methanol is preheated and simultaneously cools the CO reduction catalyst. The methanol drained from the conduit  15 E is supplied to the evaporation portion  12  of the reformer  1  by way of the conduits  44  and  46 , the flow control valve V 6 , and the conduit  52 . Excess methanol, which is not supplied to the evaporation portion  12 , is returned to the methanol tank  7 C by way of the radiator  31  and the conduit  47 . In the case where the temperature of the returning methanol exceeds a set value, the fan  31 A is turned on, thereby causing a forced cooling of the methanol. 
     Thus, the first part  16 A and the second part  16 B of the CO reduction portion  16  are cooled by the water and the methanol, each of which has a fixed flow rate and temperature even when the load of the system varies, which permits a stable temperature control of the catalyst which matches the chemical reaction independent of the operation conditions, thereby producing the reformed gas in stable fashion in such a manner that the CO in the reformed gas is reduced to not greater than 10 PPM. 
     It is to be noted instead of the foregoing disclosure, the first part  16 A and the second part  16 B of the CO reduction portion  16  can instead be cooled by the methanol and the water, respectively. 
     The invention has thus been shown and description with reference to specification, however, it should be understood that the invention is in no way limited to the details of the illustrates structures but changes and modifications may be made without departing from the scope of the appended claims.