JP2006019226A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which, even in the case liquid fuel is used as fuel for combustion, non-burning liquid fuel due to delay of ignition is not discharged to the outside of the fuel cell system with high concentration or is not mixed in recovery water used in the fuel cell system. <P>SOLUTION: The fuel cell system is provided with a fuel processing device 10 that introduces and reforms raw material fuel m1 and produces fuel gas g rich in hydrogen and has a combustion section 11 that introduces and burns liquid combustion fuel m2 for combustion and generates heat necessary for reforming, an adsorption device 20 which is arranged at an exhaust gas leading-out passage 25 for leading out exhaust gas e from the combustion section 11 and is filled with an adsorbent 22 for adsorbing and desorbing the combustion fuel m2 included in the exhaust gas e, and a fuel cell 30 which introduces the fuel gas g and generates power. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system, and in particular, even when a fuel that is burned to obtain reforming heat is used as a liquid fuel, unburned liquid fuel due to ignition delay is discharged out of the fuel cell system at a high concentration or used in the fuel cell system. The present invention relates to a fuel cell system that is not mixed with recovered water.

  A fuel cell is a device that generates electricity by an electrochemical reaction between a hydrogen-rich fuel gas and an oxygen-containing oxidant gas, greatly increasing the emission of harmful gases such as carbon dioxide and nitrogen oxides that cause global warming. It has been attracting attention as a device that can be reduced. The fuel gas to be supplied to the fuel cell is generated by introducing a raw material fuel such as city gas or kerosene and a reforming agent such as reforming water into a fuel processing apparatus, and steam reforming the raw material fuel. Since the steam reforming reaction at this time is an endothermic reaction, it is necessary to supply reforming heat, and the reforming heat is obtained by supplying combustion fuel and air to the combustion section of the fuel processing apparatus and burning it. . The combustion fuel for obtaining the reforming heat is often the same as the raw material fuel to be reformed.

  2. Description of the Related Art A fuel cell system including a fuel cell and a fuel processing device requires humidification water for humidifying an oxidant gas supplied to the fuel cell and water as reforming water introduced into the fuel processing device. A part of the water used in the fuel cell system uses water separated and recovered from the combustion exhaust gas discharged from the combustion section of the fuel processing device, thereby reducing the amount of water brought from outside the fuel cell system.

When the combustion fuel to be introduced into the combustion section of the fuel processor is a gas fuel, there is almost no incomplete combustion even at start-up, and it is used in a fuel cell system because it does not condense even if it is defective and contained in the combustion exhaust gas. In addition, it is not mixed into the recovered water, and even if it is discharged out of the fuel cell system, it is not diffused and does not cause environmental pollution (refer to Patent Document 1, for example).
JP 2003-338304 A (paragraph 0042, FIGS. 1 to 3 etc.)

  In recent years, from the viewpoint of diversification of raw material fuel and economical efficiency, a fuel cell system including a fuel processing device that generates fuel gas using cheap fuel such as kerosene as raw material fuel has been developed. When a liquid fuel is used as a raw material fuel, a liquid fuel is generally used as a fuel for combustion. In a fuel cell system using a liquid fuel as a raw material fuel, combustion air and liquid fuel are used at startup. Is generally vaporized or sprayed, and then ignited to burn the liquid fuel and preheat the fuel processing apparatus. However, the vaporized or sprayed liquid fuel is difficult to avoid the ignition delay at the time of ignition, in which case unburned fuel is contained in the combustion exhaust gas in the form of vapor or mist and discharged outside the fuel cell system. Become.

  If unburned liquid fuel is discharged out of the fuel cell system as it is, there is a risk of causing environmental pollution due to odor, oil stains, and the like. Also, when recovering heat and water from combustion exhaust gas and using them, reforming water and oxidizer for reforming raw material fuel when steam or mist-like unburned liquid fuel condenses and mixes with the recovered water It will be contained in the humidifying water for humidifying the gas, which may reduce the performance of the fuel processor and the fuel cell.

  In view of the above-described problems, the present invention uses unburned liquid fuel due to ignition delay at a high concentration outside the fuel cell system or is used in the fuel cell system even when liquid fuel is used as the fuel for combustion. It is an object of the present invention to provide a fuel cell system that is not mixed with recovered water.

  In order to achieve the above object, a fuel cell system according to the first aspect of the present invention, as shown in FIG. 1, for example, introduces and reforms a raw material fuel m1 to generate a fuel gas g rich in hydrogen. A fuel processing apparatus 10 having a combustion section 11 that introduces combustion liquid m2 as a combustion liquid and combusts to generate heat necessary for reforming; exhaust gas e is derived from the combustion section 11 An adsorbing device 20 that is disposed in the exhaust gas outlet passage 25 and is filled with an adsorbent 22 that adsorbs the combustion fuel m2 contained in the exhaust gas e; and a fuel cell 30 that introduces the fuel gas g and generates electric power.

  If comprised in this way, since it is equipped with the adsorption | suction apparatus with which the adsorbent which adsorb | sucks the combustion fuel contained in waste gas is provided, the high concentration unburned combustion fuel is discharged | emitted out of a system, or the water utilized by a fuel cell system It will not be mixed in. The adsorbent is typically preferably adsorbed and desorbed. Here, “desorption” generally means “attaching / removing”, but in this specification, it means “removing what is attached”.

  Further, in the fuel cell system according to the second aspect of the present invention, for example, as shown in FIG. 1, in the fuel cell system 1 according to the first aspect, the adsorbent 22 is activated carbon.

  In this configuration, the adsorbent is activated carbon, and therefore, due to its physical adsorption characteristics, the combustion fuel is adsorbed when the temperature of the exhaust gas is low, and the combustion fuel is desorbed and self-regenerates when the temperature of the exhaust gas becomes high. The combustion fuel is not discharged out of the system at a high concentration without being exchanged over a long period of time, and is not mixed into the water used in the fuel cell system.

  According to the present invention, since the adsorption device filled with the adsorbent that adsorbs and desorbs the combustion fuel contained in the exhaust gas is provided, the unburned combustion fuel is discharged out of the system at a high concentration or used in the fuel cell system. It is possible to provide a fuel cell system that is not mixed in the water.

Embodiments of the present invention will be described below with reference to the drawings.
First, the configuration of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a fuel cell system 1 according to an embodiment of the present invention. The fuel cell system 1 includes a fuel processing device 10 that reforms a raw material fuel m1 that is introduced by burning a liquid combustion fuel m2 and obtaining reformed heat, and generates a fuel gas g rich in hydrogen, and combusts the combustion fuel m2. Activated carbon packed tower 20 as an adsorbing device that allows the exhaust gas e to pass through, a fuel cell 30 that generates power by introducing the fuel gas g and the oxidant gas a1, a cathode offgas q that is exhausted from the exhaust gas e and the fuel cell An air / water separator 40 that separates and collects water w from the mixed exhaust gas h, which is a mixed gas, water treatment devices 51 and 52 that purify the water w collected from the mixed exhaust gas h, and air that is introduced into the fuel cell 30 a gas-liquid contact tower 60 for humidifying a1.

  The fuel processing apparatus 10 is an apparatus that introduces liquid raw material fuel m1 such as GTL (Gas to Liquid) or kerosene and reforming water s, and generates a fuel gas g rich in hydrogen by a steam reforming reaction. The fuel gas rich in hydrogen is a fuel gas containing 40% or more, particularly about 70% of hydrogen. The fuel processing apparatus 10 has a reforming catalyst packed bed, and is configured to generate a reformed gas rich in hydrogen and to generate a fuel gas g by reducing carbon monoxide from the reformed gas. The fuel processing apparatus 10 includes a vaporizer that vaporizes the introduced liquid raw material fuel m1. Since the steam reforming reaction for reforming the raw material fuel m1 is an endothermic reaction, the fuel processing apparatus 10 has a combustion section 11 for obtaining reforming heat necessary for reforming. The combustion unit 11 has a burner, and is configured to introduce combustion fuel m2 and air a2 and combust it to obtain reforming heat during startup. Further, when the fuel cell 30 is operated, the anode off-gas p containing hydrogen that has not been used for the electrochemical reaction derived from the fuel cell 30 is introduced into the combustion section 11 and burned to obtain reforming heat. It is configured. The fuel processing apparatus 10 has a raw material fuel inlet for introducing the raw material fuel m1, a reformer inlet for introducing the reforming water s, and a fuel gas outlet for deriving the generated fuel gas g. The fuel gas outlet is connected to the fuel electrode 31 of the fuel cell 30 so that the fuel gas g can be supplied to the fuel electrode 31. Further, the combustion unit 11 has an anode off-gas inlet for introducing the anode off-gas p, a combustion fuel inlet for introducing the combustion fuel m2, and an exhaust gas outlet for deriving the burned exhaust gas e. The anode off-gas inlet is connected to the fuel electrode 31 of the fuel cell 30, and the exhaust gas outlet is connected to the activated carbon packed tower 20. Note that “connected” includes the case of being connected by a flow path or the like.

  The same fuel m as the raw fuel m1 reformed into the fuel gas g and the combustion fuel m2 combusted to obtain reforming heat are branched and introduced. The raw fuel m1 and the combustion fuel m2 do not necessarily have to be the same fuel, but in the present invention, at least the combustion fuel m2 is a liquid fuel.

  The activated carbon packed tower 20 introduces the exhaust gas e from the combustion unit 11 of the fuel processing apparatus 10 from above, adsorbs the unburned combustion fuel contained in the exhaust gas e, and the exhaust gas after the unburned combustion fuel is adsorbed. e is discharged from the lower part. The activated carbon packed tower 20 is filled with an activated carbon sheet 22 as an adsorbent inside the packed tower 21. The packed tower 21 is preferably made of stainless steel from the viewpoint of heat resistance and corrosion resistance. The shape of the packed tower 21 is preferably a cylindrical shape from the viewpoint of flowing the exhaust gas e uniformly, but is not limited thereto, and may be a quadrangular prism or other shapes. Moreover, it is preferable that the packed tower 21 is heat-retained with a heat insulating material or the like.

  The activated carbon sheet 22 is made by processing fiber activated carbon into a sheet shape. The activated carbon to be packed in the packed tower 21 may be, for example, granular or raw fiber other than the sheet shape. However, an activated carbon sheet made by processing fiber activated carbon into a sheet shape having a large geometric surface area from the viewpoint of adsorption speed is preferable. Here, the “sheet shape” includes a woven or non-woven fabric or a felt shape of fiber activated carbon. The activated carbon sheet 22 preferably has a property of adsorbing at a temperature of 100 ° C. or less and desorbing at a temperature of 150 ° C. or more. For example, when the combustion fuel m2 is kerosene, the unburned fuel component to be adsorbed is the number of carbons. Since it is about 10-16 hydrocarbons, it is preferable that it is an activated carbon sheet which has the above adsorption / desorption characteristics with respect to such hydrocarbons. Furthermore, the activated carbon sheet 22 is preferably packed into the packed tower 21 by processing into a pleated shape or by stacking a plurality of sheets.

Loading of the activated carbon sheets 22 against the packed tower 21 is preferably superficial velocity is less than or equal to 5000h ^-1 or 50000h ^-1. Furthermore, the lower limit is more preferably 10,000 h ⁻¹ or more from the viewpoint of downsizing the packed tower 21, and the upper limit is more preferably 20000 h ⁻¹ or less from the viewpoint of improving adsorption performance. If comprised in this way, the magnitude | size of the packed tower 21 can be kept to the minimum, ensuring required adsorption | suction performance. Here, the “empty column speed” is defined as a value obtained by dividing the exhaust gas flow rate (m ³ / h) passing through the packed tower by the volume (m ³ ) of the packed tower. The physical meaning is how many times the exhaust gas e for the volume of the packed tower 21 can be treated per unit time.

  The combustion unit 11 of the fuel processing apparatus 10 and the activated carbon packed tower 20 are connected by an exhaust gas passage 25, and the exhaust gas e flows through the exhaust gas passage 25. The position where the activated carbon packed tower 20 is disposed may be upstream of the steam separator 40, but is preferably as close as possible to the fuel processing apparatus 10.

  The fuel cell 30 is a solid polymer fuel cell, and is configured to generate heat by introducing a fuel gas g rich in hydrogen and an oxidant gas a1 containing oxygen and generating an electrochemical reaction. . The fuel cell 30 includes a fuel electrode 31 that introduces a fuel gas g and an air electrode 32 that introduces an oxidant gas a1, and a cooling unit 33 that introduces cooling water c that removes heat generated by power generation. It has. The fuel electrode 31 has a fuel gas inlet for introducing the fuel gas g and an anode offgas outlet for discharging the anode offgas p containing hydrogen that has not been used in the reaction. The air electrode 32 has an oxidant gas inlet for introducing the oxidant gas a1 and a cathode offgas outlet for discharging the cathode offgas q containing oxygen that has not been used in the reaction. The cooling unit 33 has a cooling water inlet for introducing cooling water c having a low temperature and a cooling water outlet for receiving cooling water c that has received heat from the fuel cell 30 and has increased in temperature. The fuel gas inlet of the fuel electrode 31 is connected to the fuel gas outlet of the fuel processing apparatus 10, and the anode offgas outlet is connected to the anode offgas inlet of the combustion unit 11. The cathode offgas discharge port of the air electrode 32 is connected to the flow path 35. The flow path 35 is connected to the exhaust gas flow path 25 and led to the steam separator 40 as a flow path 45.

  The steam separator 40 is configured to condense moisture from the mixed exhaust gas h of the exhaust gas e and the cathode off gas q to separate and recover. The steam separator 40 has a recovered water outlet for extracting the separated recovered water w, and a flow path 44 connected to the gas-liquid contact tower 60 is connected to the recovered water outlet.

  The channel 44 has a makeup water inlet. The makeup water is introduced as necessary to keep the water stored in the lower part of the gas-liquid contact tower 60 at a predetermined water level, and is typically tap water. The recovered water w is stored in the lower part of the gas-liquid contact tower 60 together with the introduced makeup water, and then pumped by the pump 53 through the flow path 54, and the fuel processing apparatus 10 through the flow path 14 and the water treatment apparatus 51. To the gas-liquid contact tower 60 via the flow path 64 and the water treatment device 52.

  The water treatment device 51 is a device that purifies the reforming water s introduced into the fuel treatment device 10. The water treatment device 51 is disposed in the flow path 14 and typically includes an ion exchange resin, and is configured to purify the reforming water s into pure water. The water treatment device 52 is a device that purifies the humidifying water k that humidifies the oxidant gas a <b> 1 introduced into the fuel cell 30. The water treatment device 52 is disposed in the flow path 64 and typically includes an anion exchange resin. The water treatment device 52 is provided with an acidic gas such as NOx and SOx contained in the oxidant gas a1 while keeping the humidifying water k always alkaline. Constructed to effectively remove contaminants.

  The gas-liquid contact tower 60 is configured to humidify the oxidant gas a1 introduced into the fuel cell 30 and remove the pollutants of the acid gas. The gas-liquid contact tower 60 is provided with a humidifying water introduction port for introducing the humidifying water k in the upper portion and an oxidant gas introduction port for introducing the oxidant gas a1 in the lower portion, and is introduced from the oxidant gas introduction port. The oxidizing gas a1 and the humidifying water k introduced and sprayed from the humidifying water inlet are counter-contacted to humidify the oxidizing gas a1. In addition, an oxidant gas outlet from which the humidified oxidant gas a1 is led out toward the fuel cell 30 is provided at the top of the gas-liquid contact tower 60, and a recovered water inlet from which the recovered water w is introduced at the lower part. The bottom is provided with a recovered water outlet for deriving recovered water w containing humidifying water k that has been sprayed and has not been put on the oxidant gas a1. The recovered water outlet is connected to the flow path 54, and the recovered water w derived from the gas-liquid contact tower 60 is pumped by the pump 53 to the water treatment devices 51 and 52.

Next, the operation of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIG.
When the fuel cell system 1 is started, the combustion fuel m2 and the air a2 are introduced into the combustion unit 11 of the fuel processing apparatus 10, and the combustion fuel m2 is combusted by the burner to preheat the fuel processing apparatus 10. The exhaust gas e after combustion of the combustion fuel m2 is led out from the exhaust gas outlet passage 25 toward the activated carbon packed tower 20. The exhaust gas e at the time of start-up includes the vaporized or sprayed liquid fuel m2 remaining without being burned due to the ignition delay at the time of ignition of the burner. The temperature of the exhaust gas e at this time is almost 100 ° C. or less, and the temperature of the exhaust gas e discharged from the combustion unit 11 is relatively low.

  The exhaust gas e containing unburned combustion fuel m2 discharged from the combustion unit 11 is introduced into the activated carbon packed tower 20. The exhaust gas e introduced into the activated carbon packed tower 20 comes into contact with the activated carbon sheet 22 filled in the packed tower 21. Since the exhaust gas e at this time is a relatively low temperature of normal temperature to 100 ° C., the unburned combustion fuel m2 in the exhaust gas e is adsorbed by the activated carbon sheet 22 having a large adsorption capacity in a low temperature range. Thus, the exhaust gas e in which the unburned combustion fuel m2 is adsorbed on the activated carbon sheet 22 is led out from the activated carbon packed tower 20. Therefore, in the exhaust gas e led out from the activated carbon packed tower 20, the concentration of the unburned combustion fuel m2 is sufficiently lowered.

  After ignition of the combustion fuel, the temperature of the exhaust gas e gradually increases. When the temperature of the exhaust gas e rises, the adsorption capacity of the activated carbon sheet 22 for the unburned combustion fuel m2 decreases. However, at this time, the unburned combustion fuel m2 is not substantially present in the exhaust gas e.

  When the preheating of the fuel processing apparatus 10 is completed, the raw material fuel m1 and the reforming water s are introduced into the fuel processing apparatus 10. The raw material fuel m1 introduced into the fuel processing apparatus 10 is vaporized and then guided to the reforming catalyst packed bed, and the reforming water s is converted to steam and then guided to the reforming catalyst packed bed. The raw material fuel m1 and the reformer s guided to the reforming catalyst packed bed obtain reforming heat from the combustion unit 11 and undergo a steam reforming reaction to generate a reformed gas rich in hydrogen. Since the produced reformed gas contains carbon monoxide, the reformed gas is further subjected to a carbon monoxide reduction reaction to produce a hydrogen-rich fuel gas g with reduced carbon monoxide.

  The generated fuel gas g is introduced into the fuel electrode 31 of the fuel cell 30. An oxidant gas a1 humidified by the gas-liquid contact tower 60 is introduced into the air electrode 32. The fuel cell 30 generates water and heat by generating electricity by an electrochemical reaction between hydrogen in the fuel gas g introduced into the fuel electrode 31 and oxygen in the oxidant gas a introduced into the air electrode 32. The fuel gas g that has not been used for the electrochemical reaction is discharged from the fuel electrode 31 as the anode off gas p. The oxidant gas a1 that has not been used for the electrochemical reaction is discharged from the air electrode 32 as the cathode offgas q. The anode off gas p contains about 30 to 40% of hydrogen, and is led to the combustion unit 11 of the fuel processing apparatus 10 to be burned and used for obtaining reforming heat. The cathode offgas q joins with the exhaust gas e discharged from the combustion unit 11, and after the water w is separated and collected by the steam separator 40, the cathode offgas q is discharged outside the fuel cell system 1. On the other hand, the electric power generated by the fuel cell 30 is consumed by a power load such as an electric lamp or an electric device.

  The fuel cell 30 that has generated heat due to power generation is cooled by introducing the cooling water c into the cooling unit 33. The cooling water c is circulated by a cooling water pump (not shown), and the fuel cell 30 is maintained at an appropriate temperature in order to protect the solid polymer film of the cells of the fuel cell 30.

  When the anode off-gas p discharged from the fuel electrode 31 is introduced into the combustion unit 11 of the fuel processing device 10, the supply of the combustion fuel m2 to the combustion unit 11 is stopped, and the anode off-gas p burns instead of the combustion fuel m2. Thus, the heat of reforming necessary for the steam reforming reaction can be obtained. The exhaust gas e after the anode off gas p is combusted is led out from the exhaust gas outlet passage 25 toward the activated carbon packed tower 20. At this time, the fuel processor 10 is in a steady operation. The temperature of the exhaust gas e during steady operation gradually increases from 100 ° C. or lower during ignition to 150 ° C. or higher. When the temperature of the exhaust gas e reaches 150 ° C. or higher, the unburned combustion fuel m2 once adsorbed on the activated carbon sheet 22 is gradually desorbed. However, even if the unburned combustion fuel m2 is desorbed, the concentration of the unburned combustion fuel m2 in the exhaust gas e is relatively low, and even if it is cooled, it is below the saturation concentration at which the unburned combustion fuel m2 is condensed. The unburned combustion fuel m2 is not mixed into the recovered water w used as the reforming water s or the humidifying water k in the fuel cell system 1. Strictly speaking, unburned combustion fuel m2 that is gradually desorbed is included in the exhaust gas e and discharged outside the fuel cell system 1. At this time, it is discharged outside the fuel cell system 1. Since the combustion fuel m2 is extremely small, it hardly affects environmental pollution. On the other hand, the activated carbon sheet 22 from which the combustion fuel m2 is desorbed is regenerated and can be used without being exchanged over a long period of time.

  Here, with reference to FIG. 2, a change with time of the concentration of the combustion fuel m2 in the exhaust gas e at the outlet of the activated carbon packed tower 20 from the start of the fuel cell system 1 according to the embodiment of the present invention to the steady operation. Will be explained. In FIG. 2, C1 is the highest concentration of the unburned combustion fuel m2 component in the exhaust gas e at the outlet of the activated carbon packed tower 20, C2 is the saturation concentration at which the unburned combustion fuel m2 component in the exhaust gas e is condensed, and C3 Indicates the maximum concentration of unburned combustion fuel m2 in the exhaust gas e by desorption at the outlet of the activated carbon packed tower 20. T1 is the temperature of the exhaust gas e at the inlet of the activated carbon packed tower 20 at the time of ignition, T2 is the temperature of the exhaust gas e at the inlet of the activated carbon packed tower 20 when desorption starts, and T3 is the temperature at the inlet of the activated carbon packed tower 20 at the time of steady operation. The temperature of the exhaust gas e is shown.

  When the fuel cell system 1 is started, the concentration of the unburned combustion fuel m2 component in the exhaust gas e is substantially zero, and the temperature of the exhaust gas e is relatively low at T1. When the combustion fuel m2 introduced into the combustion unit 11 of the fuel processor 10 increases and the burner is ignited, the concentration of the combustion fuel m2 in the exhaust gas e rises to C1 with the ignition delay of the combustion fuel m2. Since the maximum concentration C1 is sufficiently lower than the saturation concentration C2 at which the unburned combustion fuel m2 component in the exhaust gas e is condensed, the unburned combustion fuel m2 component is not condensed.

  As time elapses and the temperature of the exhaust gas e rises to a temperature T2 at which desorption of the unburned combustion fuel m2 starts from the activated carbon sheet 22, the concentration of the unburned combustion fuel m2 in the exhaust gas e starts to rise. When the concentration of the unburned combustion fuel m2 in the exhaust gas e gradually increases as the temperature of the exhaust gas e rises, the maximum concentration C3 of the unburned combustion fuel m2 in the exhaust gas e due to desorption is reached. After the concentration of the unburned combustion fuel m2 in the exhaust gas e reaches C3, the remaining amount of undesorbed combustion fuel m2 is still small, so the concentration of the unburned combustion fuel m2 in the exhaust gas e gradually decreases, and the exhaust gas After a while after the temperature of e reaches T3, which is the temperature during steady operation, the concentration of the unburned combustion fuel m2 in the exhaust gas e decreases to substantially zero and thereafter changes stably.

  As a comparative example, referring to FIG. 3, the concentration of the combustion fuel m2 in the exhaust gas e at the outlet of the combustion unit 11 in the conventional fuel cell system in which the exhaust gas outlet passage 25 is not provided with the activated carbon packed tower 20 is determined. Explain the change. In FIG. 3, C4 represents the highest concentration of the unburned combustion fuel m2 component in the exhaust gas e due to the ignition delay, and C2 represents the saturation concentration at which the unburned combustion fuel m2 component in the exhaust gas e is condensed. When the fuel cell system is started, the concentration of the combustion fuel m2 component in the exhaust gas e is substantially zero. However, when the combustion fuel m2 is introduced into the combustion unit 11 of the fuel processing apparatus 10 and the burner is ignited, the ignition delay of the combustion fuel m2 is delayed. Accordingly, the concentration of the combustion fuel m2 in the exhaust gas e rises to C4. The maximum concentration C4 is considerably higher than the saturated concentration C2 at which the component of the combustion fuel m2 in the exhaust gas e is condensed, and when a liquid fuel is used as the combustion fuel m2 in the conventional fuel cell system, the component of the unburned combustion fuel m2 is It is difficult to avoid condensation and mixing with the recovered water.

  From here, it returns to description of the effect | action of the fuel cell system 1 in embodiment of this invention again. The exhaust gas e led out from the activated carbon packed tower 20 merges with the cathode offgas q discharged from the air electrode 32 of the fuel cell 30 to become a mixed exhaust gas h, flows through the flow path 45, and is led to the steam / water separator 40. The mixed exhaust gas h introduced into the steam separator 40 is cooled and the water w is separated and recovered. The mixed exhaust gas h from which the moisture w has been recovered is discharged out of the fuel cell system 1. The mixed exhaust gas h introduced into the steam separator 40 is substantially exhaust gas e itself because no cathode off-gas q is generated when the fuel cell system 1 is started. At this time, the exhaust gas e has a relatively high temperature. Since the temperature is low (100 ° C. or lower), the unburned combustion fuel m2 component due to the ignition delay to the combustion fuel m2 is adsorbed by the activated carbon sheet 22 and the concentration is sufficiently lowered, and is introduced into the steam separator 40 and cooled. However, since the concentration of the combustion fuel m2 component is equal to or lower than the saturation concentration at which condensation occurs, the unburned combustion fuel m2 is not mixed into the recovered water w. Further, as the fuel cell system 1 approaches a steady operation, the unburned combustion fuel m2 desorbed from the activated carbon sheet 22 is included in the mixed exhaust gas h, but the concentration of the unburned combustion fuel m2 in the mixed exhaust gas h. Is lower than the saturation concentration at which the unburned combustion fuel m2 is condensed even if it is cooled, so that the unburned combustion fuel m2 is not mixed into the recovered water w.

  The recovered water w separated and recovered by the steam separator 40 passes through the flow path 44, is supplemented with supplementary water as needed, and is once introduced into the water storage section at the lower part of the gas-liquid contact tower 60 and does not get on the oxidant gas a1. After being mixed with the humidifying water k, the water is introduced into the water treatment devices 51 and 52 through the flow path 54. The recovered water w introduced into the water treatment device 51 is purified into pure water and introduced into the fuel treatment device 10 as reforming water s. The recovered water w introduced into the water treatment device 52 is maintained alkaline and is introduced into the gas-liquid contact tower 60 as humidifying water k.

  The humidifying water k introduced into the gas-liquid contact tower 60 is sprayed from the upper part of the gas-liquid contact tower 60 and humidifies the oxidant gas a1 introduced from the lower part. Part of the humidifying water k is sent to the fuel electrode 32 of the fuel cell 30 on the oxidant gas a1. The humidifying water k not on the oxidant gas a1 is once stored in the lower part of the gas-liquid contact tower 60 and then mixed with the recovered water w, and is introduced to the upstream side of the water treatment devices 51 and 52 through the flow path 54. Then, it is mixed with the recovered water w from the steam separator 40, purified again by the water treatment devices 51 and 52, and used as the reforming water s and the humidifying water k.

  As described above, the present inventors conducted intensive research to put into practical use a fuel cell system that uses an inexpensive liquid fuel as a raw material fuel (combustion fuel). The physical adsorption characteristics of activated carbon exhibiting a large adsorption capability at a relatively low temperature (for example, about 100 ° C. or less), and the adsorption capability decreases as the temperature increases, and the temperature of the exhaust gas e from the combustion unit 11 is determined during ignition ( That is, when the unburned liquid fuel m2 is generated due to the ignition delay, it is relatively low at 100 ° C. or lower, and gradually rises in temperature after ignition and reaches 150 ° C. or higher in steady operation. In view of the above, the present invention was completed through repeated trials on matching of both characteristics.

  In the above description, the adsorbent 22 is described as activated carbon, but unburned combustion fuel m2 such as zeolite, silica gel, activated alumina, etc. is adsorbed at a temperature of 100 ° C. or lower and desorbed at a temperature of 150 ° C. or higher. The material which has the characteristic to do may be sufficient.

  As described above, in the fuel cell system 1 according to the present embodiment, even if there is an ignition delay when the liquid combustion fuel m2 is ignited, the unburned combustion fuel m2 is the recovered water w, in other words, the fuel processing device 10. Since the reforming water s and the oxidant gas a1 introduced into the water are not mixed into the humidifying water k, frequent start and stop such as in DSS operation (operation system in which start / stop is performed at least once a day). Even a liquid fuel fuel cell system that performs the above operation can be stably operated. In addition, it is possible to suppress unburned liquid fuel from being discharged out of the fuel cell system 1 at a high concentration, and it is possible to greatly improve the environmental pollution problem.

1 is a block diagram illustrating a fuel cell system according to an embodiment of the present invention. It is a graph which shows the time-dependent change of the density | concentration of the combustion fuel in the exhaust gas in the activated carbon packed tower exit from the time of starting of the fuel cell system which concerns on embodiment of this invention to a steady operation. It is a graph which shows the time-dependent change of the density | concentration of the combustion fuel in exhaust gas in the combustion part exit from the time of starting of the conventional fuel cell system to a steady operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel processing apparatus 11 Combustion part 20 Adsorber 22 Adsorbent 25 Exhaust gas extraction flow path 30 Fuel cell e Exhaust gas g Fuel gas m1 Raw material fuel m2 Combustion fuel

Claims (2)

A fuel processing apparatus that introduces a raw material fuel and reforms to produce a fuel gas rich in hydrogen, and has a combustion section that introduces and burns a liquid combustion fuel to burn and generates heat necessary for the reforming A fuel processor;
An adsorption device that is disposed in an exhaust gas outlet passage that extracts exhaust gas from the combustion section and is filled with an adsorbent that adsorbs combustion fuel contained in the exhaust gas;
A fuel cell that introduces the fuel gas and generates electric power;
Fuel cell system. The adsorbent is activated carbon;
The fuel cell system according to claim 1.

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