JP4323832B2 - Fuel reformer and operating method of fuel reformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel reformer that generates hydrogen from a hydrocarbon-based reformed fuel using a reforming reaction and an operation method thereof.
[0002]
[Prior art]
As a method of generating hydrogen, a method of generating hydrogen from a hydrocarbon fuel by a reforming reaction is known. For example, Patent Document 1 discloses a technology in which a steam reforming reaction and a partial oxidation reaction are used in combination as a reforming reaction to generate hydrogen from gasoline and supply the generated hydrogen to a fuel cell.
[0003]
[Patent Document 1]
JP-A-11-79703
[Patent Document 2]
JP 2001-139301 A
[0004]
[Problems to be solved by the invention]
However, when reforming a hydrocarbon-based fuel such as gasoline, there is a problem that carbon is deposited on the catalyst that promotes the reforming reaction in the process of proceeding the reforming reaction. If carbon is deposited on the reforming catalyst, the reforming reaction may be inhibited by the deposited carbon, and the efficiency of the reforming reaction may be reduced.
[0005]
The present invention has been made in order to solve the above-described conventional problems. When reforming a hydrocarbon-based fuel to produce hydrogen, the present invention is improved due to the deposition of carbon on the reforming catalyst. The purpose is to suppress a decrease in the efficiency of the quality reaction.
[0006]
[Means for solving the problems and their functions and effects]
In order to achieve the above object, a first fuel reformer of the present invention intermittently supplies a hydrocarbon-based reformed fuel to a reforming catalyst, and utilizes the reforming reaction to perform the reforming. A fuel reformer that generates hydrogen from fuel,
A reformed fuel discharge section for discharging the reformed fuel intermittently;
An oxidant gas supply unit for discharging an oxidant gas containing oxygen at least when the reformed fuel discharge unit stops discharging the reformed fuel;
A fuel introduction chamber into which the reformed fuel discharged from the reformed fuel discharge unit and the oxidant gas discharged from the oxidant gas supply unit are directly introduced;
A catalyst unit provided in connection with the fuel introduction chamber, provided with the reforming catalyst, and supplied with the reformed fuel and the oxidant gas via the fuel introduction chamber;
Each time the reformed fuel discharge unit controls the reformed fuel discharge unit to discharge the reformed fuel in an amount suitable for the reforming reaction, the fuel is discharged each time the reformed fuel discharge unit stops discharging the reformed fuel. A control unit for controlling the oxidant gas supply unit to discharge the oxidant gas in an amount equal to or larger than the volume of the introduction chamber;
It is a summary to provide.
[0007]
According to the first fuel reformer of the present invention configured as described above, the discharge of the reformed fuel is stopped when the operation of discharging the reformed fuel and the operation of stopping the discharge are alternately repeated. In some cases, the carbon deposited on the reforming catalyst can be oxidized and removed by supplying the oxidant gas to the catalyst portion. Here, each time the discharge of the reformed fuel is stopped, an amount of oxidant gas larger than the volume of the fuel introduction chamber is discharged to the fuel introduction chamber. Can be scavenged well. When the scavenging of the fuel introduction chamber is sufficiently performed, a state in which the reformed fuel concentration in the gas supplied to the catalyst section is extremely low is realized, and the deposited carbon can be satisfactorily removed by oxidation.
[0008]
In the first fuel reforming apparatus of the present invention, the control unit is supplied to the catalyst unit through the fuel introduction chamber while the reformed fuel discharge unit stops discharging the reformed fuel. It is preferable to control the discharge amount of the oxidant gas from the oxidant gas supply unit so that the concentration of the reformed fuel in the gas is 1 vol% or less. By adopting such a configuration, the oxidative removal of the carbon deposited on the reforming catalyst can be more reliably performed.
[0009]
In the first fuel reformer of the present invention, the control unit varies the amount of the oxidant gas discharged from the oxidant gas supply unit according to the amount of hydrogen to be generated by the fuel reformer. In addition, the smaller the amount of the oxidant gas discharged from the oxidant gas supply unit, the longer the time for performing the operation of stopping the discharge of the reformed fuel, so that the reformed fuel discharge unit and the oxidant gas are discharged. Control with the agent gas supply unit may be performed.
[0010]
With such a configuration, even when the supply amount of the oxidant gas decreases as the amount of hydrogen to be generated by the fuel reformer decreases, the scavenging of the fuel introduction chamber with the oxidant gas is surely performed. Can do.
[0011]
The second fuel reformer of the present invention intermittently supplies a hydrocarbon-based reformed fuel to the reforming catalyst, and uses a reforming reaction to generate hydrogen from the reformed fuel. Quality device,
A reformed fuel discharge section for discharging the reformed fuel intermittently;
An oxidant gas supply unit that discharges an oxidant gas containing oxygen when at least the reformed fuel discharge unit stops discharging the reformed fuel; and
While the reformed fuel discharged from the reformed fuel discharge unit and the oxidant gas discharged from the oxidant gas supply unit are directly introduced and the reformed fuel discharge unit stops discharging the reformed fuel A fuel introduction chamber formed to have a volume equal to or less than the amount of the oxidant gas discharged by the oxidant gas supply unit;
A catalyst unit provided in connection with the fuel introduction chamber, provided with the reforming catalyst, and supplied with the reformed fuel and the oxidant gas via the fuel introduction chamber;
The reformed fuel discharge unit is controlled to supply the reformed fuel in an amount suitable for the reforming reaction to the catalyst unit, and the amount of the reformed fuel discharged from the reformed fuel discharge unit is controlled. A control unit for controlling the oxidant gas supply unit so as to discharge the oxidant gas in a corresponding amount;
It is a summary to provide.
[0012]
According to the second fuel reformer of the present invention configured as described above, the discharge of the reformed fuel is stopped when the operation of discharging the reformed fuel and the operation of stopping the discharge are alternately repeated. In some cases, the carbon deposited on the reforming catalyst can be oxidized and removed by supplying the oxidant gas to the catalyst portion. Here, since the fuel introduction chamber is formed so as to have a volume equal to or less than the amount of the oxidant gas supplied while stopping the discharge of the reformed fuel, when stopping the discharge of the reformed fuel, the fuel introduction chamber Can be scavenged well by the oxidant gas. When the scavenging of the fuel introduction chamber is sufficiently performed, a state in which the reformed fuel concentration in the gas supplied to the catalyst section is extremely low is realized, and the deposited carbon can be satisfactorily removed by oxidation.
[0013]
In the first or second fuel reformer of the present invention,
The reformed fuel discharge unit sprays the liquid reformed fuel into the fuel introduction chamber,
The oxidant gas supply unit discharges the oxidant gas heated to a predetermined high temperature capable of vaporizing the sprayed reformed fuel also when performing the operation of discharging the reformed fuel,
The fuel introduction chamber may include a heating unit for heating the inner wall surface.
[0014]
With such a configuration, the reformed fuel sprayed into the fuel introduction chamber is vaporized using the heat of the oxidant gas, and the heat of the inner wall surface of the fuel introduction chamber heated by the heating unit is further increased. It can be used to vaporize. Therefore, the reformed fuel can be efficiently vaporized, and the sprayed reformed fuel droplets do not stay in the fuel introduction chamber. Therefore, when stopping the discharge of the reformed fuel, the fuel introduction chamber can be quickly scavenged, and the concentration of the reformed fuel in the gas supplied to the catalyst section can be reduced more reliably, and the efficiency of removing the precipitated carbon can be reduced. Can be improved.
[0015]
In such a fuel reformer, the oxidant gas supply unit may supply the oxidant gas into the fuel introduction chamber so that the oxidant gas forms a swirl flow in the fuel introduction chamber. good. Thereby, the efficiency of vaporizing the sprayed reformed fuel droplets using the heat of the inner wall surface of the fuel introduction chamber can be further improved.
[0016]
In the first or second fuel reformer of the present invention,
The reformed fuel discharge unit sprays the liquid reformed fuel into the fuel introduction chamber,
The oxidant gas supply section is in a turbulent state even when the oxidant gas heated to a predetermined high temperature capable of vaporizing the reformed fuel sprayed is discharged in the reformed fuel. It is good also as supplying in the said fuel introduction chamber.
[0017]
With such a configuration, vaporization of the reformed fuel droplets sprayed into the fuel introduction chamber can be promoted, and the efficiency of scavenging the fuel introduction chamber can be improved.
[0018]
The present invention can be realized in various forms other than the above, and can be realized in the form of, for example, a fuel cell system including a fuel reformer, a method for operating the fuel reformer, and the like.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in the following order based on examples.
A. Overall configuration of the device:
B. Precipitation carbon removal operation:
C. effect:
D. Second embodiment:
E. Variations:
[0020]
A. Overall configuration of the device:
FIG. 1 is a block diagram showing an outline of the configuration of a fuel cell system 15 including a fuel reformer 10 and a fuel cell 17 as an embodiment. The fuel reformer 10 includes an injector 20, a fuel introduction chamber 22, a reformer 24, a heat exchanger 26, a CO reduction unit 28, a heating unit 30, and a control unit 35.
[0021]
The injector 20 injects hydrocarbon-based reformed fuel into the fuel introduction chamber 22. In this embodiment, liquid hydrocarbon is used as the reformed fuel, and the injector 20 includes a nozzle that sprays the liquid reformed fuel in the form of liquid fine particles. The injector 20 can be formed, for example, as an electromagnetic solenoid valve that can control the amount of reformed fuel to be sprayed by opening and closing the valve. The size of the droplet of the reformed fuel to be sprayed can be adjusted by the size of the discharge port provided at the tip of the nozzle. In this embodiment, the injector 20 is controlled to intermittently perform this injection operation when injecting a predetermined amount of reformed fuel.
[0022]
In the fuel introduction chamber 22, in addition to the reformed fuel injected from the injector 20, steam and air (hereinafter, the steam and air supplied to the fuel introduction chamber 22 are collectively referred to as reforming gas). , And supplied through the reforming gas flow path 32. The reforming gas supplied to the fuel introduction chamber 22 is heated in the heating unit 30 prior to supply. In order to adjust the amount of reforming gas supplied from the heating unit 30 to the fuel introduction chamber 22, a valve 31 is provided in the reforming gas flow path 32 connecting the heating unit 30 and the fuel introduction chamber 22. It has been. In the fuel introduction chamber 22, the reformed fuel and the reforming gas are mixed to form a mixed gas, and this mixed gas is sent to the reformer 24. In the fuel reformer 10 of this embodiment, the amount of reforming gas supplied when the injector 20 described above stops the injection of the reformed fuel exceeds the volume of the fuel introduction chamber 22. This will be described in detail later.
[0023]
The reformer 24 includes a reforming catalyst that promotes the reforming reaction. What is necessary is just to select a reforming catalyst suitably according to the reformed fuel to be used. In the reformer 24 of the present embodiment, since steam and air are supplied as described above, a steam reforming reaction and a partial oxidation reaction proceed as reforming reactions. By performing the steam reforming reaction that is an endothermic reaction and the partial oxidation reaction that is an exothermic reaction, at least part of the heat required for the steam reforming reaction can be supplied by the partial oxidation reaction. The reformer 24 may further include a heat source such as a heater, and the temperature in the reformer 24 is controlled so as to be in a predetermined temperature range suitable for the reformed fuel and the reforming catalyst to be used. . In the present specification, a gas containing hydrogen generated by the reformer 24 is referred to as a reformed gas. In the reformer 24, a reaction for oxidizing the carbon deposited on the reforming catalyst also proceeds. This will be described later.
[0024]
The heat exchanger 26 is a device for lowering the temperature of the reformed gas discharged from the reformer 24 by exchanging heat with a predetermined refrigerant. The reformed gas cooled in the heat exchanger 26 is supplied to the CO reduction unit 28. Note that at least one of air and water to be supplied to the fuel introduction chamber 22 may be used as the refrigerant used in the heat exchanger 26.
[0025]
The CO reduction unit 28 is a device that reduces the concentration of carbon monoxide in the reformed gas supplied from the reformer 24. The reformed gas supplied from the reformer 24 usually contains a predetermined amount of carbon monoxide. When the gas containing carbon monoxide is supplied to the fuel cell 17 in this way, the platinum catalyst provided in the fuel cell 17 may be poisoned by the carbon monoxide, and the cell performance may be deteriorated. Therefore, a CO reduction unit 28 is provided to reduce the carbon monoxide concentration in the reformed gas supplied to the fuel cell 17. The CO reduction unit 28 includes a catalyst that promotes a shift reaction that generates carbon dioxide and hydrogen from carbon monoxide and water vapor, and can be a shift unit that reduces the carbon monoxide concentration in the hydrogen-rich gas by the shift reaction. . Alternatively, a carbon monoxide selective oxidation unit that includes a catalyst that promotes a selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen and that reduces the carbon monoxide concentration in the hydrogen-rich gas by the carbon monoxide selective oxidation reaction. Can do. The CO reduction unit 28 may include both the shift unit and the carbon monoxide selective oxidation unit. Alternatively, the CO reduction unit 28 may be a device that selectively extracts hydrogen using, for example, a hydrogen separation membrane containing palladium or the like.
[0026]
The reformed gas whose carbon monoxide concentration is reduced by the CO reduction unit 28 is supplied to the anode of the fuel cell 17 as a fuel gas. Further, air is supplied as an oxidizing gas from the blower 34 to the cathode of the fuel cell 17, and an electrochemical reaction proceeds in the fuel cell 17.
[0027]
The control unit 35 is configured as a logic circuit centered on a microcomputer, and includes a CPU, a ROM, a RAM, or an input / output port for inputting / outputting various signals. The control unit 35 inputs detection signals from various sensors included in the fuel cell system 15 and outputs drive signals to the injector 20 and the valve 31 described above. Thus, the control unit 35 controls the operation state of the entire fuel cell system 15 including the fuel reformer 10.
[0028]
Although the fuel reformer 10 of this embodiment supplies hydrogen to the fuel cell 17, the hydrogen generated by the fuel reformer may be supplied to different types of hydrogen consuming devices. good.
[0029]
B. Precipitation carbon removal operation:
In the fuel reforming apparatus 10 of the present embodiment, the operation of removing precipitated carbon is performed by intermittently injecting reformed fuel into the fuel introduction chamber 22 from the injector 20. That is, when the reforming reaction proceeds, carbon may be deposited on the reforming catalyst, but a period for stopping the fuel injection is provided, and the reforming gas is supplied to the fuel introduction chamber 22 during this period. By supplying only this, the oxidative removal of the carbon deposited on the reforming catalyst is achieved. Further, in the fuel reforming apparatus 10 of the present embodiment, the volume of the fuel introduction chamber 22 is equal to or less than the amount (volume) of the reforming gas supplied to the fuel introduction chamber 22 while the fuel injection is stopped. It is formed as follows. This makes it possible to more reliably remove the precipitated carbon. Hereinafter, control for intermittently injecting fuel will be described.
[0030]
FIG. 2 is a flowchart showing an operation control processing routine that is repeatedly executed at a predetermined timing in the control unit 35 during operation of the fuel reformer 10.
[0031]
When this routine is executed, the control unit 35 first inputs the required hydrogen amount (step S100). The required hydrogen amount is the amount of hydrogen to be generated by the fuel reformer 10, and can be obtained based on the amount of power required for the fuel cell 17, for example.
[0032]
Next, the control unit 35 sets the fuel injection amount and the reforming gas amount based on the required hydrogen amount (step S110). The fuel injection amount is a reformed fuel amount required to generate an amount of hydrogen corresponding to the required hydrogen amount by the reforming reaction, and is set according to the efficiency of the reforming reaction in the reformer 24. Further, the amount of reforming gas (the amount of air and the amount of water vapor) is set to be a predetermined ratio with respect to the amount of reformed fuel to be supplied. In this embodiment, O / C (the ratio of oxygen molecules in the reforming gas to carbon atoms in the reformed fuel) and S / C (in advance) so that the reforming reaction proceeds well in the reformer 24. The ratio of water molecules in the reforming gas to carbon atoms in the reformed fuel) is determined. Then, the reforming gas amount is set based on the reformed fuel amount and O / C and S / C. The reformed fuel amount and reforming gas amount set in step S110 may be calculated each time as described above based on the required hydrogen amount, or the required hydrogen amount and these set amounts may be calculated in advance. It may be set using an associated map.
[0033]
The fuel injection amount and the reforming gas amount may be set in consideration of parameters other than the required hydrogen amount. Examples of such other parameters include the temperature of the reformer 24. Since the efficiency of the reforming reaction varies depending on the temperature of the reformer 24, the amount of reformed fuel necessary to obtain a desired amount of hydrogen can be set more accurately by considering the temperature of the reformer 24. Can do. Further, when the temperature of the reformer 24 is low (for example, when warming up), the amount of water vapor in the reforming gas is reduced and the amount of air is increased to make the oxidation reaction more active in the reformer 24. It is good to make it happen.
[0034]
When the fuel injection amount and the reforming gas amount are set, control unit 35 sets a period for performing fuel injection and a period for stopping fuel injection (step S120). FIG. 3 is an explanatory view illustrating the state of fuel injection in the operation of removing the precipitated carbon. As shown in FIG. 3, the execution cycle T is composed of an injection period t1 in which fuel injection is performed and a stop period t2 in which fuel injection is stopped. In the stop period t2, only the reforming gas is supplied to the fuel introduction chamber 22. In the present embodiment, the execution cycle T is constant, and the time density (hereinafter referred to as duty ratio) between the injection period t1 and the stop period t2 is controlled according to the fuel injection amount set in step S110. Since the flow rate of the reformed fuel injected from the injector 20 is determined by the performance of the injector 20 (for example, the size of the nozzle outlet and the injection pressure), the reformed fuel flow rate and the fuel injection amount set in step S120 are determined. Based on the above, the injection period t1 can be set. FIG. 3A shows a case where the required power amount is larger, that is, a case where the required hydrogen amount is larger, and FIG. 3B shows a case where the required hydrogen amount and the required hydrogen amount are smaller. As shown in FIG. 3, the injection period t1 is set longer as the required hydrogen amount is larger. When actually setting the above periods, the injection period t1 and / or the stop period t2 are determined in advance and stored in the control unit 35 as a map corresponding to the required hydrogen amount or further the reforming catalyst temperature. It is also possible to refer to this map.
[0035]
The control unit 35 controls each unit of the fuel reformer 10 according to the various control amounts set by the above processing (step S130), and ends this routine. Thus, the operation in which the fuel injection is performed for the period t1 and the injection stop is performed for the period t2 is repeated, and the amount of the reformed fuel set in step S110 is supplied as a whole, and hydrogen is generated by the reforming reaction. Further, the reforming gas is supplied in a substantially constant state irrespective of the injection period t1 and the stop period t2 so that the supply amount becomes the amount set in step S110 (hereinafter referred to as the reforming gas flow rate Q). Supplied in. Thereby, in the stop period t2, the oxidized carbon is removed by oxidation using oxygen in the reforming gas.
[0036]
Here, the fuel reformer 10 of the present embodiment is configured such that the amount (volume) of reforming gas supplied during the stop period t2 is equal to or greater than the volume V of the fuel introduction chamber 22. That is, the following equation (1) holds for the reforming gas flow rate Q even when the required hydrogen amount varies and the stop period t2 varies.
Q × t2 ≧ V (1)
[0037]
FIG. 4 is an explanatory view schematically showing the state of the fuel introduction chamber 22 and the reformer 24 when the reformed fuel is intermittently injected from the injector 20. When the injection of the reformed fuel is started from the injector 20 during the injection period t1 (FIG. 4A), the reformed fuel concentration in the fuel introduction chamber 22 increases and is supplied from the fuel introduction chamber 22 to the reformer 24. As a result, the reformed fuel concentration in the gas increases (FIG. 4B). The reforming reaction proceeds in the reformer 24 using the reformed fuel supplied in this way. When the injection period t1 elapses and the stop period t2 is reached, only the reforming gas is supplied to the fuel introduction chamber 22. The amount of the reforming gas supplied to the fuel introduction chamber 22 during the stop period t2 is Q × t2 that is equal to or larger than the volume V of the fuel introduction chamber 22, and therefore the fuel introduction chamber 22 during the stop period t2. The inside is sufficiently scavenged (FIG. 4C). As a result, the reformed fuel concentration in the gas supplied from the fuel introduction chamber 22 to the reformer 24 becomes extremely low, and the reformer 24 oxidizes the precipitated carbon using oxygen in the reforming gas. It is.
[0038]
As described above, when the required hydrogen amount decreases, the stop period t2 is set longer and the reforming gas flow rate Q is set smaller. Conversely, when the required hydrogen amount increases, the stop period t2 is set shorter and the reforming gas flow rate Q is set larger. In this way, even when the required hydrogen amount fluctuates, the size of the fuel introduction chamber 22 is determined so that the above equation (1) always holds. Thus, the fuel introduction chamber 22 is designed so that the above equation (1) always holds when the fuel reformer 10 is operated within the range of the processing capacity set in advance.
[0039]
When designing the fuel introduction chamber 22, for example, a simulation is performed over the entire range of fluctuation of the assumed required hydrogen amount to obtain an expected minimum value of “Q × t 2”. What is necessary is just to make it become the said minimum value or less. Alternatively, the volume of the fuel introduction chamber 22 may be set so as to always be equal to or less than the “Q × t2” in an operation state in which the value of the “Q × t2” is predicted to be particularly small. For example, in the fuel reformer as shown in the present embodiment, since the above Q × t2 generally tends to decrease as the load decreases, a typical operation state at a low load (for example, the fuel cell system 15). In the idling state in which only the power required to maintain the starting state is generated), the volume V of the fuel introduction chamber 22 may be determined so that the expression (1) is satisfied. As long as the above formula (1) is satisfied, it is only necessary to ensure a volume that allows the sprayed reformed fuel to be sufficiently vaporized and mixed with the reforming gas.
[0040]
C. effect:
According to the fuel reforming apparatus 10 of the present embodiment configured as described above, when the reformed fuel is intermittently supplied to oxidize and remove the deposited carbon on the reforming catalyst, during the stop period t2. By setting the amount of reforming gas supplied to be equal to or greater than the volume of the fuel introduction chamber 22, it is possible to more reliably perform the carbon removal. By setting the amount of reforming gas supplied during the stop period t2 to be equal to or greater than the volume of the fuel introduction chamber 22, the inside of the fuel introduction chamber 22 is sufficiently scavenged when the fuel injection is stopped, and supplied to the reformer 24. A state in which the concentration of the reformed fuel in the generated gas is extremely low is realized. Thus, the concentration of the reformed fuel in the gas supplied to the reformer 24 becomes extremely low, so that the deposited carbon of the reforming catalyst is effectively oxidized. And by repeating such an operation, it is possible to prevent deposited carbon from being deposited on the reforming catalyst.
[0041]
FIG. 5 is an explanatory diagram showing the relationship between the fuel injection operation and the reformed fuel concentration in the gas supplied to the reformer 24. As shown in FIG. 5, the reformed fuel concentration in the gas supplied to the reformer 24 increases rapidly when combustion injection is started in the injection period t1, and becomes highest at the end of the fuel injection period t1. Then, the reformed fuel concentration rapidly decreases when the fuel introduction chamber 22 is scavenged by the reforming gas at the stop period t2. Thus, by providing a state in which the reformed fuel concentration in the gas supplied to the reformer 24 is low, it is possible to satisfactorily oxidize and remove the precipitated carbon of the reforming catalyst. Specifically, it is desirable that the time during which the reformed fuel concentration in the gas supplied to the reformer 24 is 1 vol% or less is 50 msec or more. In addition, the efficiency at the time of burning and removing the deposited carbon is not limited to the reformed fuel concentration in the gas supplied to the reformer 24, but the amount of carbon deposited on the reforming catalyst and the reforming gas. It is affected by the amount of oxygen inside and the reforming catalyst temperature.
[0042]
In the stop period t2, as described above, by providing a state in which the reformed fuel concentration in the gas supplied to the reformer 24 is sufficiently low, it is possible to reliably remove the precipitated carbon. . Furthermore, by reducing the reformed fuel concentration in the gas supplied to the reformer 24, it is possible to oxidize the deposited carbon even when the temperature in the reformer 24 is lower. Become. Therefore, the reforming catalyst can be prevented from deteriorating due to the high temperature, and the durability of the reformer 24 can be improved.
[0043]
In the present embodiment, when changing the fuel injection amount, the injector 20 changes the length of the injection period t1 and the stop period t2 while keeping the duty ratio constant. By adopting such a configuration, even when the fuel injection amount is set to be smaller, the scavenging in the fuel introduction chamber 22 is sufficiently performed and the precipitated carbon can be efficiently removed. That is, when the fuel injection amount is small, the reforming gas amount is also set accordingly, and scavenging in the fuel introduction chamber 22 is difficult to be performed, but when the fuel injection amount is small, the stop period t2 is set longer. By doing so, it is possible to sufficiently scavenge the fuel introduction chamber 22 even when the reforming gas flow rate decreases.
[0044]
It should be noted that the same effect can be obtained when changing the period T instead of the duty ratio when changing the fuel injection amount. Even when the period T is changed instead of the duty ratio, when the fuel injection amount is set to be smaller, the stop period t2 becomes longer, so that the fuel introduction chamber 22 can be sufficiently scavenged.
[0045]
In the above-described embodiment, the reformed fuel injection is completely stopped in the stop period t2, but it is also possible to adopt a configuration in which the reformed fuel injection from the injector 20 is not completely stopped. In this embodiment, an electromagnetic solenoid valve is used as the injector 20. However, depending on the type of the injector 20 used, even if the fuel injection signal is turned off, the fuel injection may not stop immediately. Even in such a case, by providing the stop period t2 during which the fuel injection signal is turned off, a state in which the reformed fuel concentration in the gas supplied to the reformer 24 becomes sufficiently low as described above is realized. The same effect can be obtained.
[0046]
D. Second embodiment:
In the first embodiment, the amount of reforming gas supplied during the stop period t2 is set to be equal to or greater than the volume of the fuel introduction chamber 22 so that the fuel introduction chamber 22 is sufficiently scavenged and supplied to the reformer 24. This makes it possible to sufficiently reduce the reformed fuel concentration in the gas. In the second embodiment below, in addition to such a configuration, the structure of the fuel introduction chamber promotes the vaporization of the reformed fuel in the fuel introduction chamber, thereby further improving the efficiency of scavenging in the fuel introduction chamber, The reformed fuel concentration in the gas supplied to the reformer 24 is further reduced.
[0047]
FIG. 6 is an explanatory view showing the state of the cross section of the main part of the fuel reformer of the second embodiment. FIG. 7 is an explanatory diagram showing a state of a section 7-7 in FIG. The fuel reformer of the second embodiment is provided in a system similar to the fuel cell system 15 of the first embodiment. In FIG. 6, the injector 20, the fuel introduction chamber 22 and the reformer in FIG. Only the portion corresponding to 24 is shown. In FIG. 6, the same reference numerals are given to portions common to FIG. 1, and detailed description is omitted.
[0048]
As shown in FIG. 6, in the second embodiment, the fuel introduction chamber 122 and the reformer 24 are each formed in a substantially cylindrical shape. The fuel introduction chamber 122 formed as a cylinder having a larger cross-sectional diameter and the reformer 124 formed as a cylinder having a smaller cross-sectional diameter are connected in series, and the two are integrally formed. Yes.
[0049]
The reforming gas flow path 32 is connected to the fuel introduction chamber 122, but the high-temperature reforming gas introduced from the reforming gas flow path 32 passes through the cylinder inner wall surface in the fuel introduction chamber 122. A swirling flow is formed along The reformed fuel injected from the injector 20 is vaporized while being mixed with the reforming gas forming the swirl flow. A heater 121 is disposed in the wall surface of the fuel introduction chamber 122, and the wall surface of the fuel introduction chamber 122 is heated by the heater 121.
[0050]
A partition wall 123 a is provided between the fuel introduction chamber 122 and the reformer 124. The partition wall 123a is formed in a conical wall shape that protrudes toward the fuel introduction chamber 122, and a communication hole 123b is formed at the center (the top of the head). The mixed gas obtained by mixing the reformed fuel vaporized in the fuel introduction chamber 122 and the reforming gas is introduced into the reformer 124 through the communication hole 123b.
[0051]
A reforming catalyst 125 is provided in the reformer 124. The reforming catalyst 125 can have various shapes such as being carried on a honeycomb carrier or formed into a pellet shape. In this embodiment, a honeycomb carrier is used. When the mixed gas is supplied to the reformer 124, the reforming reaction proceeds on the reforming catalyst, and the generated reformed gas is discharged to the heat exchanger.
[0052]
According to the fuel reforming apparatus of the second embodiment configured as described above, the reforming gas supplied to the fuel introduction chamber 122 forms a swirling flow in the fuel introduction chamber 122, so Among the quality fuel droplets, those having a relatively large particle size and slow vaporization are blown off onto the wall surface of the fuel introduction chamber 122. By blowing off onto the wall surface by the swirl flow, the contact area (heat transfer area) between the reformed fuel droplet and the wall surface of the fuel introduction chamber 122 increases. At this time, since the wall surface of the fuel introduction chamber 122 is heated by the heater 121, the reformed fuel droplets blown off on the wall surface of the fuel introduction chamber 122 are quickly vaporized on the wall surface of the fuel introduction chamber 122. be able to. In this way, by promoting the vaporization of the reformed fuel droplets, the reformed fuel can be prevented from staying in the fuel introduction chamber 122, and the fuel introduction chamber in the stop period t2 during which fuel injection is stopped. The scavenging efficiency in 122 can be improved. Further, by improving the scavenging efficiency of the fuel introduction chamber 122, it is possible to improve the efficiency of oxidizing and removing the deposited carbon in the reforming catalyst. When the wall surface of the fuel introduction chamber 122 is heated by the heater 121 and the wall surface is heated to a temperature at which the Leidenfrost phenomenon occurs on the wall surface, the reformed fuel droplets move around the wall surface. This promotes atomization of the droplets. Thus, vaporization of the reformed fuel can also be promoted by atomizing the reformed fuel droplets.
[0053]
Further, as described above, the reforming gas supplied into the fuel introduction chamber 122 forms a swirling flow in the fuel introduction chamber 122, whereby unvaporized droplets flow into the reformer 124 side, and the reforming gas is improved. The effect of preventing the reformed fuel droplets from adhering to the surface of the catalyst and causing inconvenience is also obtained.
[0054]
Further, in the fuel reforming apparatus of the present embodiment, the diameter of the reforming gas passage 32 is such that the reforming gas introduced from the reforming gas passage 32 into the fuel introduction chamber 122 flows as a turbulent flow. It is preferable to set the diameter (D shown in FIG. 7). Whether the fluid flow is laminar or turbulent can be determined using the Reynolds coefficient Re (Re = Dv / ν, v: flow velocity of the reforming gas, ν: kinematic viscosity coefficient of the fluid). Is possible. Boundary critical Reynolds coefficient Re where fluid flow becomes turbulent _c = About 2000.
[0055]
Thus, by making the reforming gas supplied to the fuel introduction chamber 122 turbulent, vaporization of the sprayed reformed fuel droplets is further promoted, and the efficiency of scavenging from the fuel introduction chamber 122 is improved. be able to. The reason why vaporization of the reformed fuel droplets is promoted by making the reforming gas turbulent is considered as follows. When the atomized reformed fuel droplets evaporate, the reformed fuel droplets are covered with the evaporated reformed fuel vapor layer. As a result, heat conduction to the reformed fuel droplets is hindered, and the efficiency of vaporizing the reformed fuel droplets by the thermal energy of the reforming gas may be reduced. Here, by making the flow of the reforming gas turbulent, an effect of removing the vapor layer covering the reformed fuel droplets can be obtained, and vaporization of the reformed fuel can be promoted.
[0056]
In the second embodiment, the heater 121 is provided to heat the wall surface of the fuel introduction chamber 122, but a different type of heating unit may be provided. When hot gas (for example, combustion gas) is generated in a system including a fuel reformer, the hot gas flow path is routed so that the hot gas can heat the wall surface of the fuel introduction chamber 122. It is also good.
[0057]
E. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0058]
E1. Modification 1:
In the first and second embodiments, the flow rate of the reforming gas is controlled to be substantially constant throughout the injection period t1 and the stop period t2. However, the reforming gas flow rate is changed during the injection period t1 and the stop period t2. You may perform control which changes. In this case as well, the same effect can be obtained if the amount of reforming gas supplied into the fuel introduction chamber during the stop period t2 is equal to or greater than the volume of the fuel introduction chamber.
[0059]
E2. Modification 2:
In the first and second embodiments, the reforming gas composed of air and water vapor is supplied during the stop period t2. However, if an oxidizing gas containing at least oxygen is supplied, the oxidation of the precipitated carbon is performed. Removal can be carried out as well. For example, the supply of water vapor may not be performed during the stop period t2. When air is used as the oxidant gas supplied to the fuel introduction chamber during the stop period t2, the amount of air supplied during the stop period t2 may be equal to or greater than the volume of the fuel introduction chamber.
[0060]
E3. Modification 3:
In the above-described embodiments, air and water vapor are supplied together as reforming gases into the fuel introduction chamber, but both may be supplied separately to the fuel introduction chamber. For example, instead of supplying pre-generated water vapor to the fuel introduction chamber, liquid water may be sprayed into the fuel introduction chamber using a nozzle, and vaporized together with the reformed fuel using heat brought in by heated air. . In this case, when supplying heated air to the fuel introduction chamber during the stop period t2, water spraying may be performed simultaneously, or water spraying may not be performed.
[0061]
Alternatively, at least a part of the air to be supplied may be supplied from the injector 20 instead of supplying the whole amount of air as reforming gas together with water vapor. For example, the reformed fuel may be sprayed by the injector 20 configured as a two-fluid nozzle, and air may be used as the assist gas used in the two-fluid nozzle.
[0062]
E4. Modification 4:
In the above-described embodiments, the fuel introduction chamber and the reformer are distinguished from each other. However, a structure in which the distinction is not provided is also possible. FIG. 8 is an explanatory diagram showing an outline of the configuration of a fuel reformer as a modification. The reformer 224 in the fuel reformer of FIG. 8 includes a reforming catalyst 125 and a spray / mixing unit 222 that is formed as a space having a predetermined area on the upstream side and in which a heater 221 is disposed. ing. The reformed fuel is injected from the injector 220 into the spray / mixing unit 222 and the reforming gas is supplied into the spray / mixing unit 222. The reformed fuel injected from the injector 220 is vaporized by the heat of the heater 221 and the heat of the reforming gas, and is mixed with the reforming gas and guided to the reforming catalyst 225 by the flow of the reforming gas. . In such a fuel reformer, the spray / mixing unit 222 corresponds to a fuel introduction chamber into which the reformed fuel is directly introduced, and the amount of reforming gas supplied during the stop period t2 is the spray / mixing unit. What is necessary is just the volume of 222 or more.
[0063]
E5. Modification 5:
Various liquid hydrocarbon fuels can be used as the liquid reformed fuel injected from the injector 20. For example, those containing gasoline, alcohol, or aldehyde can be used. In the embodiment, liquid fuel is used as the reformed fuel, but gaseous fuel may be used. In this case, instead of spraying the liquid fuel into the fuel introduction chamber, the gaseous fuel may be introduced into the fuel introduction chamber as a gas. If the oxidant gas in an amount larger than the volume of the fuel introduction chamber is supplied into the fuel introduction chamber while the reformed fuel is intermittently discharged into the fuel introduction chamber and the fuel discharge is stopped, the same An effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of a configuration of a fuel cell system 15 including a fuel reformer 10 as an embodiment.
FIG. 2 is a flowchart showing an operation control processing routine.
FIG. 3 is an explanatory diagram illustrating the state of fuel injection in the operation of removing precipitated carbon.
FIG. 4 is an explanatory view schematically showing the state of the fuel introduction chamber 22 and the reformer 24 when the reformed fuel is intermittently injected from the injector 20;
FIG. 5 is an explanatory diagram showing the relationship between the operation of fuel injection and the concentration of reformed fuel in the gas supplied to the reforming catalyst.
FIG. 6 is an explanatory view showing a state of a cross section of a main part of a fuel reformer of a second embodiment.
7 is an explanatory diagram showing a state of a 7-7 cross section in FIG. 6. FIG.
FIG. 8 is an explanatory diagram showing an outline of a configuration of a fuel reformer as a modified example.
[Explanation of symbols]
10 ... Fuel reformer
15 ... Fuel cell system
17 ... Fuel cell
20, 220 ... injector
22, 122 ... Fuel introduction chamber
24, 124, 224 ... reformer
26 ... Heat exchanger
28 ... CO reduction part
30 ... heating unit
31 ... Valve
32 ... Gas flow path for reforming
35. Control unit
121 ... Heater
123a ... partition wall
123b ... Communication hole
125,225 ... reforming catalyst
221 ... Heater
222: Spraying / mixing section

Claims (8)

A fuel reformer that intermittently supplies a hydrocarbon-based reformed fuel to a reforming catalyst and generates hydrogen from the reformed fuel using a reforming reaction,
A reformed fuel discharge section for discharging the reformed fuel intermittently;
An oxidant gas supply unit for discharging an oxidant gas containing oxygen at least when the reformed fuel discharge unit stops discharging the reformed fuel;
A fuel introduction chamber into which the reformed fuel discharged from the reformed fuel discharge unit and the oxidant gas discharged from the oxidant gas supply unit are directly introduced;
A catalyst unit provided in connection with the fuel introduction chamber, provided with the reforming catalyst, and supplied with the reformed fuel and the oxidant gas via the fuel introduction chamber;
Each time the reformed fuel discharge unit controls the reformed fuel discharge unit to discharge the reformed fuel in an amount suitable for the reforming reaction, A fuel reformer comprising: a control unit that controls the oxidant gas supply unit so as to discharge the oxidant gas in an amount equal to or greater than the volume of the introduction chamber. The fuel reformer according to claim 1, wherein
The control unit is configured such that the concentration of the reformed fuel in the gas supplied to the catalyst unit via the fuel introduction chamber is 1 vol while the reformed fuel discharge unit stops discharging the reformed fuel. %. A fuel reformer that controls a discharge amount of the oxidant gas from the oxidant gas supply unit so as to be less than or equal to%. The fuel reformer according to claim 1 or 2, wherein
The control unit varies the amount of the oxidant gas discharged from the oxidant gas supply unit according to the amount of hydrogen to be generated by the fuel reformer, and the oxidant gas supply unit discharges the oxidant gas supply unit. Fuel reforming that controls the reformed fuel discharge unit and the oxidant gas supply unit such that the smaller the amount of the oxidant gas is, the longer the time for performing the operation of stopping the discharge of the reformed fuel is. apparatus. A fuel reformer that intermittently supplies a hydrocarbon-based reformed fuel to a reforming catalyst and generates hydrogen from the reformed fuel using a reforming reaction,
A reformed fuel discharge section for discharging the reformed fuel intermittently;
An oxidant gas supply unit that discharges an oxidant gas containing oxygen when at least the reformed fuel discharge unit stops discharging the reformed fuel; and
While the reformed fuel discharged from the reformed fuel discharge unit and the oxidant gas discharged from the oxidant gas supply unit are directly introduced and the reformed fuel discharge unit stops discharging the reformed fuel A fuel introduction chamber formed to have a volume equal to or less than the amount of the oxidant gas discharged by the oxidant gas supply unit;
A catalyst unit provided in connection with the fuel introduction chamber, provided with the reforming catalyst, and supplied with the reformed fuel and the oxidant gas via the fuel introduction chamber;
The reformed fuel discharge unit is controlled to supply the reformed fuel in an amount suitable for the reforming reaction to the catalyst unit, and the amount of the reformed fuel discharged from the reformed fuel discharge unit is controlled. A fuel reformer comprising: a control unit that controls the oxidant gas supply unit so as to discharge a corresponding amount of the oxidant gas. The fuel reformer according to any one of claims 1 to 4,
The reformed fuel discharge unit sprays the liquid reformed fuel into the fuel introduction chamber,
The oxidant gas supply unit discharges the oxidant gas heated to a predetermined high temperature capable of vaporizing the sprayed reformed fuel also when performing the operation of discharging the reformed fuel,
The fuel introduction chamber is a fuel reformer provided with a heating unit for heating the inner wall surface thereof. The fuel reformer according to claim 5, wherein
The oxidant gas supply unit is a fuel reformer that supplies the oxidant gas into the fuel introduction chamber so that the oxidant gas forms a swirl flow in the fuel introduction chamber. The fuel reformer according to any one of claims 1 to 4,
The reformed fuel discharge unit sprays the liquid reformed fuel into the fuel introduction chamber,
The oxidant gas supply section is in a turbulent state even when the oxidant gas heated to a predetermined high temperature capable of vaporizing the reformed fuel sprayed is discharged in the reformed fuel. A fuel reformer for supplying the fuel into the fuel introduction chamber. A method of operating a fuel reformer that generates hydrogen from a hydrocarbon-based reformed fuel using a reforming reaction,
(A) a step of intermittently repeating the operation of discharging the reformed fuel into a predetermined fuel introduction chamber;
(B) leading the reformed fuel discharged in the step (a) to a reforming catalyst that promotes the reforming reaction, and generating hydrogen from the reformed fuel by the reforming reaction;
(C) supplying an oxidant gas containing oxygen in an amount equal to or larger than the volume of the fuel introduction chamber to the fuel introduction chamber when the operation of discharging the reformed fuel is stopped When,
(D) The operation of the fuel reformer including the step of guiding the oxidant gas supplied in the step (c) to the reforming catalyst and oxidizing and removing carbon deposited on the reforming catalyst. Method.

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