JP2007123107A - Fuel cell power generation system and fuel treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To satisfy both shortening of starting time and enhancing of power generation efficiency in a fuel cell power generation system having a fuel treatment device and a fuel cell. <P>SOLUTION: In a fuel cell system comprising the fuel treatment device having a reforming catalyst and the fuel cell, in starting, the fuel treatment device is operated by an inner heat method in which a part of fuel to be reformed is oxidized to make a reformed heat source, and in a stationary operation, the fuel treatment device is operated by an outer heat method in which a reforming catalyst is heated by an outside heat source. Advantages of both of the inner heat type fuel treatment device having quick starting time and low efficiency and the outer heat type fuel treatment device having slow starting time and high efficiency can be exhibited. If an inner heat burner and an outer heat burner are used in starting, starting time can be more shortened than use of only the inner heat burner. When a combustion catalyst is used in the inner heat burner and a cluster burner is used in the outer heat burner, since metal is not heated to the unnecessary temperature, inexpensive metal can be used, and a system having quick starting time, high efficiency, and low cost can be provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power generation system using a fuel cell as a main power source and a main heat source, and more particularly to a fuel cell power generation system and a fuel processing apparatus suitable for home use.

  Generally, household electricity demand is high in the morning and evening and low at night. For this reason, it is efficient and economical for a fuel cell for home use to perform partial load operation following power demand, and it is reasonable to stop it at night when demand is low.

  A polymer electrolyte fuel cell equipped with a fuel reforming system is usually operated by an external heating system in which a reforming catalyst layer is heated using an external heat source. In the case of the external heating method, the reforming catalyst layer is indirectly heated through the catalyst layer wall, so that it takes 1 hour for the reforming catalyst layer to rise to a temperature suitable for the reforming reaction at the start-up in the morning. There is a problem that it takes time and cannot answer a part of demand. In order to shorten the start-up time, if an internal heating method is adopted in which air is added and a part of the fuel to be reformed is burned as a heat source, the rate of temperature rise increases, but it is an oxidant in the reformed gas. Since nitrogen in the air remains, the hydrogen concentration is lowered, resulting in a decrease in power generation efficiency. In addition, in the case of the internal heat method, nitrogen is added even if the hydrogen flow rate is the same as in the external heat method, so that there is a problem that the amount of reformed gas increases and auxiliary power increases.

  As a processing device for fuel supplied to the fuel cell, there is a type of apparatus in which an external heat burner is provided at the center, and the reforming catalyst layer is indirectly heated by the combustion exhaust gas of the external heat burner through the tube wall. For example, it is described in Patent Documents 1 and 2. This method is very excellent in reducing heat dissipation loss. In addition, the heat capacity is minimized and the start-up is quick.

JP 2003-321206 A (summary) JP 2002-187705 A (summary)

  The fuel processing device that is provided around the external heat burner and indirectly heats the reforming catalyst layer with the combustion exhaust gas of the burner has the above-mentioned advantages, but the heat of the exhaust gas is transferred to the reforming catalyst layer through the tube wall. Therefore, there is a limit in shortening the start-up time in terms of heat capacity.

  An object of the present invention is to provide a fuel cell power generation system and a fuel processing apparatus that can be rapidly started and that can be operated with high efficiency.

  The present invention employs an internal heat system in which a part of the fuel to be reformed is burned at the start of the fuel cell and used as a heat source for the reforming catalyst layer, and the return gas from the fuel cell is burned at other times of normal operation. It adopts an external heat system that indirectly heats the reforming catalyst layer by generating high-temperature combustion exhaust gas, and realizes rapid start-up and high-efficiency operation by a hybrid of internal heat system and external heat system.

  Further, in a preferred aspect of the present invention, the internal heat method and the external heat method are used together at the time of starting the fuel cell, and the external heat method is adopted at the steady state. In this case, as a general merit, since both burners can be used at the time of startup, the temperature of the reforming catalyst layer can be increased from the inside and the outside, and the startup time can be further shortened.

  In the present invention, a fuel cell power generation system and a fuel processing apparatus provided with the aforementioned internal heat system and external heat system are provided. The fuel processing apparatus of the present invention includes a reforming catalyst layer for steam reforming a hydrocarbon-based fuel, an external heat combustor for generating combustion exhaust gas used as a heating source of the reforming catalyst layer, An internal heat combustor for combusting a part of the hydrocarbon-based fuel supplied to the reforming catalyst layer and heating the reforming catalyst layer from the inside is provided.

  According to the present invention, it is possible to provide a fuel cell power generation system that can be rapidly started when the fuel cell is started and that can perform high-efficiency operation during steady operation other than the start time.

  In the present invention, the internal heat system is a system in which a part of the reformed fuel is reformed as a reforming heat source by oxidizing a part of the reformed fuel while supplying the reformed fuel to the reforming catalyst layer. Say. In addition, the external heat system refers to a system in which the fuel to be reformed supplied to the portion where the reforming catalyst is provided is heated from the outside based on a high-temperature gas.

  In the present invention, it is most desirable to employ both an internal heat system and an external heat system for rapid start-up when the fuel cell is started. However, in both types, if a burner is used, the temperature will rise too rapidly, and the metal constituting the fuel processor will be heated above the endurance temperature before the reforming catalyst layer rises to the temperature required for reforming. I'm worried. Therefore, in the internal heat system, it is desirable to burn using a combustion catalyst that burns at a low temperature except mainly for ignition. A combination of a combustion catalyst and a ring-shaped cluster burner is very preferable in constructing an internal heat type combustor.

  The fuel processing apparatus of the present invention includes an internal heat combustor and an external heat combustor. The internal heat combustor is preferably a combination of the above-described combustion catalyst and a ring-shaped cluster burner, and the external heat combustor is preferably a cluster burner. In a fuel processor for a household fuel cell having a power generation output of 1 kW, the gas flow rate of the external heat combustor is extremely small and misfire is likely to occur. Therefore, it is desirable to use a cluster burner that is excellent in stable combustibility at a low flow rate. In the case of external heat, combustion is performed by adding auxiliary fuel in addition to the anode return gas, thereby maintaining the reforming temperature at 630 ° C. or higher to increase the fuel utilization rate of the fuel cell, thereby improving power generation efficiency. . For this reason, a cluster burner having a wide combustion stable air ratio region is extremely effective.

  We recommend a system configuration that uses a cluster burner with a hula seal in the external heat combustor and a combustion catalyst in the internal heat combustor as a fuel processor for the fuel cell power generation system incorporating the above measures. However, the internal heat combustor is initially ignited by the ring-shaped cluster burner. Conventionally, either the internal heat type or the external heat type is used, and there is no combination of both.

  Also, when trying to increase the power generation efficiency by increasing the fuel utilization rate of the fuel cell in a steady state, the high hydrogen conversion efficiency cannot be maintained only with the anode return gas, and the hydrogen in the anode return gas can be reduced due to fluctuations in the fuel utilization rate. The flow rate fluctuates. When the anode return gas hydrogen flow rate fluctuates, it also leads to variations in fuel utilization. In order to solve this problem, it is effective to increase the stability and efficiency by adding auxiliary fuel to keep the reforming catalyst layer temperature constant.

  In a very preferred example of the present invention, a cluster burner is used for the external heat combustor, a ring-shaped cluster burner and a combustion catalyst are used for the internal heat combustor. While stably heating, the ring-shaped burner is ignited by the internal heat combustor and heated to a temperature at which it can be burned by the combustion catalyst. When the fuel to be reformed is heated to a temperature at which it can be combusted by the combustion catalyst, the ring-shaped cluster burner is turned off, and thereafter, rapid combustion is performed within a range in which the metal is burned by the combustion catalyst and no burden is placed on the metal.

  In another preferred example, an evaporator is provided in the externally heated combustion exhaust gas system, a CO shift catalyst and a CO gas cooling unit are provided in the reformed gas system, and controllability is not independently impaired, and Create water vapor that is not flowing.

  In a domestic fuel cell power generation system, since the so-called DSS (Daily Start and Shutdown), which stops operation at midnight when demand is low and operates at other times, is reasonable, it is becoming a normal operation mode. In this case, if it takes about an hour to start in the early morning, it is difficult to answer the short-term power and hot water demand in the early morning. When the internal heat type fuel processing device is adopted mainly for rapid start-up, the start-up becomes quick and can be made 15 minutes or less, but the efficiency during steady operation is lowered. According to the present invention, rapid start-up and high-efficiency operation can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings. However, it is not limited to these examples.

  A configuration of a fuel cell power generation system centering on the inside of the fuel processing apparatus is shown in FIG. The power generation system of FIG. 1 includes a combustion exhaust gas system having an external heat combustor, and a reformed gas system having an internal heat combustor and a reforming catalyst. Description will be made in the order of the combustion exhaust gas system and the reformed gas system of the external heat combustor.

  The combustion exhaust gas system of the external heat combustor uses the auxiliary fuel 1-1 such as city gas and the return gas 3 from the fuel cell 33 or the reformed gas system, and the air 10 heated in the heat exchange unit 34 An external heat combustor 2 that generates heat by burning is provided. In addition, the reforming catalyst layer heat exchanging portion 9 that gives heat to the reforming catalyst layer 36 by the combustion exhaust gas 25 from the external heat combustor 2, and the reforming catalyst layer heat exchanging portion 9 gives heat to the reforming catalyst layer 36. A heat exchanging unit 24 that heats the mixed gas 43 by heat-exchanging the combustion exhaust gas 26 after that with a mixed gas 43 of a hydrocarbon-based fuel such as city gas and water vapor is provided. Furthermore, an evaporation unit 38 that evaporates and superheats the water 11-1 with the combustion exhaust gas 27 that exits the heat exchange unit 24, and a heat exchange unit 34 that heats the air 4-1 with the combustion exhaust gas 28 that exits the evaporation unit 38 are provided. It has been.

  In the reformed gas system, the reformed raw material gas 7 composed of a mixed gas of hydrocarbon fuel and steam heated in the heat exchange section 24 of the flue gas system of the external heat combustor 2 is supplied to the partial oxidation air 4 An internal heat combustor 6 for partial oxidation at -2 is provided. Further, the partial combustion reforming raw material gas 35 that has been partially oxidized and heated in the internal heat combustor 6 is subjected to a reforming reaction by heat from the reforming catalyst layer heat exchange part 9 of the combustion exhaust gas system of the external heat combustor 2. The reforming catalyst layer 36 for generating the reformed gas is provided. Further, heat is recovered from the reformed gas 8 that has been reformed by the reforming catalyst layer 36 and has become hydrogen-rich, and the heat exchange unit 5 that heats the mixed gas 23 from the mixing unit 22 and the reforming from the heat exchange unit 5 A CO shift catalyst layer 17 is provided for causing the gas 16 to undergo a CO shift reaction. In the CO shift catalyst layer 17, a CO shift cooling unit 42 is provided that maintains the temperature of the CO shift catalyst within the temperature range suitable for the shift reaction with the water 11-2. In addition, a heat exchange unit 19 using water 11-3 is provided to cool the reformed gas 18 from the CO shift catalyst layer 17 to a temperature suitable for the downstream first stage CO selective oxidation unit. In addition, a first-stage CO selective oxidation section 15 that supplies air 4-3 and water 11-4 to the reformed gas 20 from the heat exchange section 19 to perform selective oxidation reaction and cooling, and a first-stage CO selective oxidation section A second-stage CO selective oxidation unit 31 is provided that performs selective oxidation reaction and cooling by supplying air 4-4 and water 11-5 to the reformed gas 30 from 15.

  Electric power is generated in the fuel cell 33 using the reformed gas 32 from the second-stage CO selective oxidation unit 31. As for connecting the flue gas system of the external heat combustor and the reformed gas system, there are the reforming catalyst layer heat exchanging section 9 and the mixing section 22 which have already been explained. In the mixing unit 22, water or water vapor 12 from the heat exchange unit 19, water or water vapor 21 from the CO shift cooling unit 42, water vapor 39 from the evaporator 38, and hydrocarbon-based fuel 1 such as city gas not heated. -2 is mixed. These constitute the fuel cell power generation system of the present invention.

  The operation of the fuel cell power generation system configured as described above will be described first in the order of normal operation and then of startup. Note that the steady state refers to the time of fuel cell operation after startup.

  Normally, in the external heat combustor 2, the auxiliary fuel 1-1 and the return gas 3 from the fuel cell 33 are combusted by using the air 10 whose temperature has been raised in the heat exchanging section 34, and the adiabatic flame temperature is 1,200 ° C. or higher. As a result, a high-temperature combustion exhaust gas 25 of 900 to 1,000 ° C. is generated. Using this high-temperature combustion exhaust gas 25, the reforming catalyst layer heat exchanging section 9 performs heat transfer including radiation to the reforming catalyst layer 36, and the reforming reaction is performed on the partial combustion reforming raw material gas 35 before reforming. Inject necessary heat to ensure the reforming temperature is 630 ℃ or higher. Combustion exhaust gas 26, which is heated to about 800 ° C. by applying heat to the reforming catalyst layer 36 in the reforming catalyst layer heat exchanging section 9, is converted into hydrocarbons by the heat exchanging section 24, the evaporator 38 and the heat exchanging section 34 Heat is applied to the mixed gas 23 of fuel and water vapor, water 11-1 and air 4-1, to recover the heat, and finally, it is discharged as a combustion exhaust gas 29 at about 130 ° C. The preheated raw material gas 7 to be reformed does not supply the partial oxidation air 4-2 in a steady state, so it passes through the internal heat combustor 6 and the reforming catalyst layer 36 in the reforming catalyst layer heat exchange section. Under the heat of 9, the reforming catalyst causes the reforming reaction shown in the following formula (1) and the CO shift reaction shown in the formula (2). Then, the reformed gas 8 rich in hydrogen is generated.

C _m H _n + mH ₂ O⇔mCO + (m + n / 2) H ₂ (1)
CO + H ₂ O⇔CO ₂ + H ₂ (2)
The reformed gas 8 is recovered to about 280 ° C. at which the heat-recovered reformed gas 16 can be supplied to the CO shift catalyst layer 17 while recovering heat by the mixed gas 23 in the heat exchange section 5. The reformed gas 16 is subjected to a CO shift reaction in the CO shift catalyst layer 17 according to the equation (2). At this time, in order to keep the temperature range appropriate for the CO shift reaction, heat recovery is performed while the water is cooled by the CO shift cooling unit 42. Thereafter, in order to obtain a reformed gas temperature suitable for sending the reformed gas 18 after the CO shift reaction to the first-stage CO selective oxidation section 15 and the second-stage CO selective oxidation section 31, the heat exchange section 19 The heat of the reformed gas 18 is recovered by the water 11-3. Then, in the two-stage CO selective oxidation section consisting of the first-stage CO selective oxidation section 15 and the second-stage CO selective oxidation section 31, CO is reduced using air 4-3 and 4-4, and finally Reduces the CO concentration to 10 ppm or less. At this time, water 11-4 and 11-5 are supplied to the CO selective oxidation unit to advance the oxidation reaction shown in the equations (3) and (4) with CO and hydrogen to remove heat.

2CO + O ₂ ⇒ 2CO ₂ (3)
2H ₂ + O ₂ ⇒2H ₂ O (4)
In addition, when it becomes 320 degreeC or more, since the methanation reaction shown to the following (5) formula arises, maintenance of temperature is important.

CO + 3H ₂ ⇔CH ₄ + H ₂ O (5)
The obtained reformed gas 32 is supplied to the anode of the fuel cell 33 to generate power, and hydrogen in the reformed gas is consumed. The return gas 3 after the hydrogen component is consumed by the amount of current is directed to the external heat combustor 2 and becomes a heat source for the reforming reaction.

  In order to increase the power generation efficiency at regular times, it is necessary to increase the current in the fuel cell. However, since more hydrogen is consumed in the reformed gas, the hydrogen concentration in the return gas exiting the fuel cell is Lower. When the return gas having a low hydrogen concentration is combusted in the external heat combustor, the calorific value is reduced, the proper reforming temperature cannot be maintained in the reforming catalyst layer, and the generated hydrogen concentration decreases. If the fuel cell is supplied with a low hydrogen concentration, hydrogen deficiency occurs in the fuel cell and damages the fuel cell. For this reason, it is effective to supply the auxiliary fuel 1-1 such as city gas at the normal time, and to burn the auxiliary fuel 1-1 and the return gas 3 in the external heat combustor 2. The amount of generated hydrogen can be increased by increasing the amount of heat entering the reforming catalyst layer 36 from the layer heat exchanger 9. Thereby, the reforming process efficiency exceeding the supply amount of the auxiliary fuel 1-1 by increasing the fuel utilization rate can be obtained.

  At the time of start-up, the external heat combustor 2 is started, and at the same time, the internal heat combustor 6 that partially oxidizes a part of the reforming raw material is also operated by injecting the partial oxidation air 4-2. The porous catalyst layer 36 is heated from the inside and is also heated from the outside by the reforming catalyst layer heat exchanging section 9. Due to the heating of both, the startup time can be shortened. Note that the reformed gas 32 bypasses the fuel cell 33 during startup.

  FIG. 2 shows the reforming process efficiency when the reforming temperature is set to 630 ° C. As can be seen from this, reforming process efficiency is improved by increasing the fuel utilization rate. Between the fuel utilization rate of 70% and 75%, the external heat burner adiabatic flame temperature due to the combustion of the return gas 3 and the city gas that is the auxiliary fuel 1-1 is branched according to 1200 ° C, 1320 ° C and 1400 ° C. This is because the auxiliary fuel 1-1 is injected into the return gas 3 at the time of branching. Conventionally, when auxiliary fuel 1-1 is added, it has been considered that the denominator increases from the relational expression shown in the following equation (6) and the efficiency decreases.

Reforming process efficiency = (calorific value of reformed gas 32-calorific value of return gas 3) / (auxiliary fuel 1-1 + hydrocarbon fuel 1-2) (6)
For this reason, it has been attempted to generate hydrogen by heating the fuel processor only with the return gas 3 without adding the auxiliary fuel 1-1. With return gas 3 alone, a fuel utilization rate of around 70% is the limit for maintaining the thermal mass balance of a polymer electrolyte fuel cell (PEFC) power generation system. However, in practice, even if auxiliary fuel 1-1 is added, the reforming temperature and the heat and mass balance can be maintained, and the amount of hydrogen produced can be increased, so that the reforming process efficiency as shown in FIG. It becomes possible to improve the power generation efficiency. It can be seen that this system has little variation in the reforming process even when the adiabatic flame temperature changes, that is, it is robust. This is a very important effect for the fuel processor.

  FIG. 3 shows the fuel utilization when the reforming temperature is set to 630 ° C. and the ratio of the auxiliary fuel 1-1 in the supplied city gas. As can be seen in contrast to FIG. 2, the reforming process efficiency and the auxiliary fuel 1-1 are in a proportional relationship with the fuel utilization rate as the medium. FIG. 3 shows that the amount of the auxiliary fuel 1-1 cannot be reduced unless the adiabatic flame temperature of the external heat burner, that is, the external heat combustor is increased, that is, the reforming process efficiency cannot be increased. However, if the adiabatic flame temperature is raised, the surrounding metal temperature will rise, so in order to use low-cost stainless steel for the metal, the metal temperature must be selected to be 850 ° C. or lower. In addition, as the fuel utilization rate increases, the reforming process efficiency increases, but on the other hand, the auxiliary power required for supplying auxiliary fuel and supplying air to the cathode of the fuel cell increases. Is the optimum operating point.

  FIG. 4 is a result of examining the characteristics at the time of starting with a normal burner, and shows a temperature distribution in the reforming catalyst layer after 5 minutes from ignition. The horizontal axis indicates the position from the inlet to the outlet of the reforming catalyst layer, and the vertical axis indicates the temperature in the reforming catalyst layer after 5 minutes of ignition at that position. When a normal burner is used for an internal heat combustor and an external heat combustor, although the temperature rises quickly, a portion exceeding 850 ° C. is generated upstream. For this reason, stainless steel cannot be used for the metal.

  FIG. 5 shows the temperature distribution in the reforming catalyst layer when a normal burner is used for the external heat combustor and a combustion catalyst (normal burner only at the time of ignition) is used for the internal heat combustor. The maximum temperature was 850 ° C. and the downstream temperature also increased, and the problem in FIG. 4 could be solved.

  FIG. 6 shows the configuration of a cylindrical fuel processor for implementing the fuel cell power generation system of FIG. The air 10 heated through the air conduit 53 and the return gas 3 or the return gas 3 and the auxiliary fuel 1-1 supplied through the gas conduit 55 are configured by a cluster burner provided in the center of the apparatus. Burn with external heat combustor 2. The ignition in the external heat combustor 2 is performed by the spark plug 49 of the spark plug conduit 54. The high-temperature combustion exhaust gas 25 generated in the external heat combustor 2 is guided to the return channel 60 through the descending channel 56 that guides the combustion exhaust gas to the bottom of the apparatus. In addition, a plurality of holes 58 are provided in the pipe wall of the descending flow path so that a part of the combustion exhaust gas 25 flows out to the return flow path 60 having a high flow velocity, and the temperature of the combustion exhaust gas flowing through the return flow path 60 decreases. To prevent. Heat is applied to the reforming catalyst layer 36 of the adjacent honeycomb structure through the tube wall by the combustion exhaust gas flowing through the folded flow path 60. The reforming catalyst layer 36 is not limited to a honeycomb structure, but a honeycomb structure is preferable in order to shorten the start-up time. Thereafter, the combustion exhaust gas passes around the reforming raw material preheating layer 52 and the evaporator 38, heats the reforming fuel gas and water 11-1, and is discharged from the combustion exhaust gas discharge pipe 59. The reforming material preheating layer 52 can be formed of a steel wool filling layer or the like. A heat insulating material 61 is provided around the air conduit 53, the spark plug conduit 54, and the gas conduit 55 so that the reformed material preheating layer 52 can be sufficiently heated by the heat of the combustion exhaust gas.

  Air 4-1 is supplied to the fuel processing apparatus from the bottom, travels around the apparatus surface, recovers heat, and creates heated air 10. The heated air 10 is sent to the external heat combustor 2 composed of a cluster burner through the air conduit 53 to produce a high-temperature combustion exhaust gas 25.

  Water contained in the reformed raw material gas 7 is supplied from three locations. The water 11-1 is fed into the evaporator 38 through the steam supply pipe 64 from the upper part of the cylinder. The water 11-2 is sent to the CO shift cooling unit 42 adjacent to the CO shift catalyst layer 17, and recovers heat from the reformed gas to generate water and wet steam. Water 11-3 is supplied to the heat exchanging unit 5 above the CO shift cooling unit 42, and heat is recovered from the reformed gas to generate water and wet steam. The CO shift cooling unit 42 and the heat exchange unit 5 recover heat from the reformed gas, respectively, and adjust and control the amount of water so that the temperature is suitable for the CO shift reaction. Steam generated from the water 11-2 and the water 11-3 is fed into a section where the mixing unit 22 is located through a plurality of holes 65. Further, the steam generated by the evaporator 38 is also supplied to the mixing unit 22 through the steam supply pipe 66. These steams are mixed with the hydrocarbon-based fuel 1-2 in the mixing unit 22 to become the reformed raw material gas 7.

  At the time of start-up, the reformed raw material gas 7 is mixed with the partial oxidation air 4-2 by the ring-shaped cluster burner 50 in the internal heat combustor 6, ignited by the spark plug 51, and under oxygen-deficient conditions. Partial oxidation combustion. When the temperature of the partially oxidized combustion gas exceeds 300 ° C., the partial oxidation reaction proceeds by the combustion catalyst of the internal heat combustor 6. At this point, the spark plug 51 is stopped and partial oxidation combustion is performed using only the combustion catalyst. At this time, the ring-shaped cluster burner 50 functions as a high-performance mixer. The temperature of the gas before reforming exiting the internal heat combustor 6 becomes 300 to 800 ° C.

  If the partial oxidation air 4-2 is no longer supplied due to steady operation, combustion in the internal heat combustor 6 stops, and the combustion catalyst functions as a high-performance rectifier. Thereby, the deviation of the flow rate distribution of the raw material gas to be reformed is corrected. Thereafter, the reforming material gas flows into the reforming material preheating layer 52 and is heated by the combustion exhaust gas flowing through the folded flow path 60. Thereafter, the raw material gas to be reformed enters the reforming catalyst layer 36 and is heated by the combustion exhaust gas that also flows through the folded flow path 60 to cause a reforming reaction, thereby generating a hydrogen-rich reformed gas 8. At this time, the temperature of the reformed gas is monitored by the temperature detector 72 at the outlet, and the supply amount of the auxiliary fuel 1-1 is adjusted so as to become a predetermined temperature or higher. The reformed gas 8 is folded twice and adjusted to an appropriate temperature with water 11-3 and enters the CO shift catalyst layer 17. The CO shift catalyst layer 17 also absorbs heat of reaction from the outside by the water 11-2 in order to maintain an appropriate temperature at which the CO shift reaction proceeds. By the CO shift reaction, the reformed gas 8 becomes a hydrogen-rich reformed gas. This reformed gas enters the first-stage CO selective oxidation unit 15, and the CO concentration is reduced by the air 4-3. The heat generated at that time is absorbed by water 11-4. Thereafter, the reformed gas enters the second-stage CO selective oxidation section 31, reduces the CO concentration with air 4-4, absorbs the heat generated at that time with water 11-5, and finally the CO concentration Becomes the reformed gas 32 of 10 ppm or less.

  In this embodiment, the heat insulating material 62 is provided inside the CO shift catalyst layer 17, the first stage CO selective oxidation unit 15, and the second stage CO selective oxidation unit 31, so that the reforming catalyst layer 36 is not overcooled. I am doing so. In addition, a cluster burner in which a plurality of small burners are arranged on the surface is arranged as the external heat combustor 2 to improve the ignitability and flame holding performance in the minimum flow as in the 1 kW system. As a result, even if the gas flow velocity is close to natural convection, even if a small flow of fuel and air occurs and one of the small burners misfires, it can be re-ignited by the other small burners, so that stable operation is possible. There is an effect.

  Using a combustion catalyst for the internal heat combustor 6 and burning at about 300-500 ° C at start-up and operating at the same time as the external heat combustor 2 consisting of a cluster burner, raise the metal temperature to 850 ° C or higher In addition, the effect of shortening the start-up time can be obtained by using low-cost stainless steel. In this embodiment, a ring-shaped cluster burner 50 is used as a burner for heating the reforming raw material gas to a temperature at which the combustion catalyst can react. The ring-shaped cluster burner 50 works effectively as a mixer for steam and hydrocarbon fuel except during combustion, thereby contributing to improvement in reforming efficiency.

  If the folded flow path 60 in which the heat of the combustion exhaust gas of the external heat combustor 2 configured by the cluster burner enters the reforming catalyst layer 36 is folded as it is, a low temperature section is formed at the center, and the reforming catalyst layer As a result, the hydrogen conversion efficiency tends to decrease. Further, uneven heat transfer is likely to occur in the circumferential direction. For this reason, in this embodiment, a plurality of holes 58 are provided in the folded flow path, and the internal high-temperature gas and radiant light are taken out to improve the efficiency. In addition, spacers 71-1, 71-2, 71-3 that keep the width of the flow path constant are inserted in the folded flow path to achieve a uniform flow. Furthermore, the reforming catalyst, the combustion catalyst, and the CO shift catalyst use a honeycomb structure catalyst to shorten the startup time. In addition, air 4-1 is introduced from the bottom of the fuel processing apparatus to recover the heat dissipation loss from the apparatus surface. Although not described in the present embodiment, at the time of start-up, until the reformed gas 32 returns to the external heat combustor 2, the auxiliary fuel 1-1 is combusted by the external heat combustor, and the reforming catalyst A heat source for heating the layer 36 may be obtained. Further, the external heat combustor 2 is provided at a level equal to or lower than the inlet of the reforming catalyst layer 36, so that the reforming catalyst layer is effectively heated with the combustion exhaust gas. Desirable for.

  FIG. 7 shows another embodiment of the fuel processor. The difference from FIG. 6 is that an inlet for water 11-6 is provided at the lower part to recover the heat at the lower part to generate steam, and the water 11-2 and 11-3 become steam through the hole 70. It is the point where it merges with the one. Thereby, there exists an effect that hydrogen conversion efficiency is raised.

  In FIG. 7, the reforming catalyst layer 36 is also provided in the return path of the reformed gas. Thereby, the heat of the bottom plate heated by the radiant heat of the combustion exhaust gas 25 can be recovered to promote the reforming reaction, and the hydrogen conversion rate can be improved. Further, with such a configuration, the height of the reforming catalyst layer can be reduced.

  FIG. 8 shows another embodiment of the fuel cell power generation system according to the present invention. The difference from FIG. 1 is that the air 4-1 is heated in the heat exchanging section 5 and the hydrocarbon-based fuel 1-2 is heated in the heat exchanging section 34. This configuration is robust because the CO shift temperature is controlled by the amount of air without phase change. According to the present embodiment, it is possible to shorten the startup time and to provide a system with high power generation efficiency and controllability.

The system block diagram which shows one Example of the fuel cell power generation system of this invention. The figure which showed the relationship between a fuel utilization rate and a reforming process efficiency. The figure which showed the fuel utilization rate and the ratio of the auxiliary fuel gas in supply city gas. The figure which showed the temperature distribution at the time of starting by a prior art example. The figure which showed the temperature distribution of the external heat cluster burner and the internal heat combustion catalyst at the time of starting. The block diagram which showed one Example of the fuel processing apparatus which concerns on this invention. The block diagram which showed the other Example of the fuel processing apparatus which concerns on this invention. The system block diagram which showed the other Example of the fuel cell power generation system which concerns on this invention.

Explanation of symbols

  1-1 ... auxiliary fuel, 1-2 ... hydrocarbon reforming fuel, 2 ... external heat combustor, 3 ... return gas, 4-1 ... air, 4-2 ... partial oxidation air, 4-3 ... air , 4-4 ... air, 5 ... heat exchange section, 6 ... internal heat combustor, 7 ... reforming raw material gas, 8 ... reformed gas, 9 ... reforming catalyst layer heat exchange section, 10 ... air, 11- 1 ... water, 11-2 ... water, 11-3 ... water, 11-4 ... water, 11-5 ... water, 11-6 ... water, 12 ... water or steam, 15 ... first stage CO selective oxidation part, 16 ... reformed gas, 17 ... CO shift catalyst layer, 18 ... reformed gas, 19 ... heat exchange part, 20 ... reformed gas, 21 ... water or steam, 22 ... mixing part, 23 ... mixed gas, 24 ... heat Exchange part, 25 ... Combustion exhaust gas, 26 ... Combustion exhaust gas, 27 ... Combustion exhaust gas, 28 ... Combustion exhaust gas, 29 ... Combustion exhaust gas, 30 ... Reformed gas, 31 ... Second stage CO selective oxidation part, 32 ... Reformed gas, 33 ... Fuel cell, 34 ... Heat exchange section, 35 ... Partial combustion reforming raw material gas, 36 ... Reforming catalyst layer, 38 ... Evaporator, 39 ... Steam, 42 ... CO shift cooling section, 43 ... Mixing 49 ... Spark plug, 50 ... Ring cluster burner, 51 ... Spark plug, 52 ... Reforming raw material preheating layer, 53 ... Air conduit, 54 ... Spark plug conduit, 55 ... Gas conduit, 56 ... Downstream , 58 ... hole, 59 ... combustion exhaust gas exhaust pipe, 60 ... folded flow path, 61 ... heat insulating material, 62 ... heat insulating material, 64 ... steam supply pipe, 65 ... hole, 66 ... steam supply pipe, 70 ... hole, 71- 1 ... Spacer, 71-2 ... Spacer, 71-3 ... Spacer, 72 ... Temperature detector.

Claims (19)

  A fuel processing device for producing a hydrogen-rich reformed gas by reforming a reformed raw material gas containing a hydrocarbon fuel and steam with a reforming catalyst, and the reformed gas produced by the fuel processing device as an anode In a fuel cell power generation system comprising a fuel cell for supplying and generating power, at the time of startup, partial oxidation air is added to the reformed raw material gas, and the reformed raw material gas is provided by a combustion catalyst provided in the fuel reforming system. The fuel processor is operated by an internal heating method in which a part of the fuel is burned and the reforming catalyst is heated from the inside, and in the steady state, the return gas from the fuel cell is burned to generate combustion exhaust gas. A fuel cell power generation system, wherein the fuel processor is operated by an external heating method for heating the reforming catalyst.   A fuel processing device for producing a hydrogen-rich reformed gas by reforming a reformed raw material gas containing a hydrocarbon fuel and steam with a reforming catalyst, and the reformed gas produced by the fuel processing device as an anode In a fuel cell power generation system including a fuel cell that supplies power to generate electricity, an internal heat system that heats the reforming catalyst from the inside by burning a part of the reformed raw material gas and the reforming catalyst at the outside during startup A fuel cell power generation system, wherein the fuel processing apparatus is operated by an external heat system that uses a combustion exhaust gas to heat and the fuel processing apparatus is operated by the external heat system in a steady state.   3. The external heat system according to claim 2, wherein the return gas from the fuel cell or the reformed gas produced by the fuel processing apparatus is combusted to generate combustion exhaust gas, and the reforming catalyst is heated by the combustion exhaust gas. Thus, at the time of startup, the reformed gas manufactured by the fuel processing apparatus is burned to generate the combustion exhaust gas, and in the steady state, the return gas from the fuel cell is burned to generate the combustion exhaust gas. A fuel cell power generation system characterized by the above.   4. The fuel cell power generation system according to claim 3, wherein combustion gas is generated by burning auxiliary fuel in addition to the return gas from the fuel cell in a steady state.   3. The internal heat combustor for performing partial oxidation combustion by adding partial oxidation air to the reformed raw material gas, and the reformed gas or the fuel produced by the fuel processing apparatus according to claim 2 A fuel cell power generation system comprising an external heat combustor that burns return gas from a battery to generate combustion exhaust gas.   6. The fuel cell power generation system according to claim 5, wherein a cluster burner is provided as the external heat combustor.   6. The fuel cell power generation system according to claim 5, wherein an ignition plug and a combustion catalyst are provided as the internal heat combustor.   6. The auxiliary fuel is burned in the external heat combustor at the start-up until the reformed gas manufactured by the fuel processing device and bypassing the fuel cell returns to the external heat combustor. A fuel cell power generation system that generates combustion exhaust gas for heating a porous catalyst.   5. The fuel cell power generation system according to claim 4, wherein the supply amount of the auxiliary fuel is controlled so as to become a predetermined temperature or higher while monitoring the temperature of the outlet of the reforming catalyst.   In the fuel processing apparatus comprising: a reforming catalyst layer for steam reforming a hydrocarbon-based fuel; and an external heat combustor for generating combustion exhaust gas used as a heating source for the reforming catalyst layer. A fuel processor comprising an internal heat combustor for combusting a part of the hydrocarbon-based fuel supplied to the porous catalyst layer and heating the reforming catalyst layer from the inside.   11. The fuel processing apparatus according to claim 10, wherein the internal heat combustor includes an ignition plug and a combustion catalyst.   11. The fuel processor according to claim 10, wherein the internal heat combustor includes a ring-shaped cluster burner and a combustion catalyst for ignition.   The fuel processing apparatus according to claim 10, further comprising a cluster burner as the external heat combustor.   In Claim 10, the flue gas channel which distributes the flue gas generated with the external heat combustor, the reforming raw material gas which consists of the hydrocarbon fuel and water vapor is led to the reforming catalyst layer, reforming A reforming gas passage for guiding the reformed gas to the outlet is provided so as to surround the external heat combustor, and the combustion exhaust gas passage and the reforming gas passage are adjacent to each other through a pipe wall. A fuel processing apparatus characterized by being configured as described above.   15. The fuel processing apparatus according to claim 14, wherein the reforming catalyst layer is installed in the middle of the reforming system gas flow path.   16. The combustion catalytic internal heat combustor according to claim 15, wherein partial combustion is performed by adding partial oxidation air to the reformed raw material gas upstream of the reforming catalyst layer in the reforming gas flow path. A fuel processing apparatus characterized by comprising:   15. The fuel processing apparatus according to claim 14, wherein a CO shift catalyst layer and a CO selective oxidation unit are provided downstream of the reforming catalyst layer in the reforming system gas flow path.   15. The descending flow path according to claim 14, further comprising: a descending flow path that guides the combustion exhaust gas generated in the external heat combustor to the bottom of the apparatus; and a return flow path that converts the combustion exhaust gas guided to the apparatus bottom to an upward flow. A fuel processing apparatus characterized in that a plurality of holes are provided in a tube wall forming a gas and a part of the flue gas flowing in the descending flow path toward the bottom of the apparatus flows out to the return flow path.   In Claim 17, water or water vapor | steam which raised the temperature by collect | recovering heat | fever from reformed gas in the said CO shift catalyst layer and the said CO selective oxidation part, and hydrocarbon-type fuel are mixed, and to-be-reformed raw material gas A fuel processing apparatus comprising: a reforming gas passage provided with a mixing unit that performs the above-described operation.

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