JP2004067407A - Reforming reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reformer with high efficiency which suppresses temperature gradient in a region where the reforming reaction occurs. <P>SOLUTION: The reformer 3 to reform fuel gas has a reforming part 3a where a reforming catalyst is applied to induce the reforming reaction by passing the fuel gas and has a heating gas passage 18 to supply heat to the reforming part 3a. The calorie supplied from the heating gas passage 18 to the reforming part 3a and the area to be heated by the heating gas passage 18 in the reforming part 3a are controlled depending on the operation conditions. The area of the reforming part 3a to be heated is varied by changing the cross section of the heating gas passage 18 by using control valves 13, 14 or fuel injection valves 24, 25. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a reforming reactor, and more particularly, to a configuration that can appropriately control the temperature of a reforming reactor, thereby improving system efficiency.
[0002]
[Prior art]
As a conventional reforming reactor, a reactor as disclosed in JP-A-9-306533 is known. This is a heat exchange type reforming reactor in which an outer cylinder member is arranged so that an inner cylinder member penetrates, and a combustion gas is supplied to and passed through the outer cylinder member, and a calorie can be supplied inside the inner cylinder member. Is incorporated. The wall material of the inner cylinder member disposed inside the outer cylinder member is formed hollow, and in the case of methanol reforming, LiNO having a melting point in a reaction temperature zone of 200 to 300 ° C. is formed in the hollow portion. ₃ For storing heat storage materials such as. A sufficient amount of heat is supplied to this heat storage material in advance to dissolve it, and the heat storage material is made into a liquid phase.
[0003]
Thereby, even if the supply of heat by the combustion gas supplied from the outer cylinder member is delayed when it becomes necessary to rapidly increase the reformed fuel gas, the latent heat is dissipated when the heat storage material undergoes a phase transition to the solid phase. Thus, the heat required for the reforming can be sufficiently provided.
[0004]
[Problems to be solved by the invention]
However, in a reforming reactor as disclosed in Japanese Patent Application Laid-Open No. 9-306533, the heating gas is appropriately supplied to a reforming reaction section that converts the fuel gas into a reformed gas by heat exchange between the fuel gas and the heating gas. May not be supplied. For example, the heating gas flow rate increases or decreases with an increase or decrease in the fuel gas amount. However, since the volume of the supplied reforming reactor does not change, the heat supplied by the heating gas becomes uneven. As a result, a temperature gradient occurs in the reforming reaction section, and a region where the temperature becomes low or high locally occurs.
[0005]
In the case where steam reforming is performed using methanol as a raw fuel, there is a possibility that the conversion rate may deteriorate due to a decrease in the reforming efficiency in a low temperature region. In addition, H generated by the reforming reaction ₂ , CO, CO ₂ Is exposed to the region where the temperature of the reformed gas containing ₂ And CO ₂ As a result, the reverse shift reaction in which CO is generated is promoted, and the CO in the reformed gas may increase to exceed the allowable range of the fuel cell. In addition, there is a problem in that heat loss increases due to excessive heating and system efficiency deteriorates.
[0006]
Therefore, an object of the present invention is to provide a reforming reactor capable of generating an efficient reaction by equalizing the temperature of a portion where a reforming reaction occurs.
[0007]
[Means for solving the problem]
According to the present invention, in a reforming reactor for reforming a fuel gas, a reforming catalyst is applied, and a fuel gas flow path that causes a reforming reaction when the fuel gas flows is selected from the fuel gas flow path. And a heating unit for supplying heat. Further, a heating state control means for controlling the amount of heat supplied from the heating section to the fuel gas flow path and the range of the fuel gas flow path heated by the heating section according to operating conditions is provided.
[0008]
Alternatively, the fuel cell system includes a fuel gas flow channel for carrying a reforming catalyst for reforming the fuel gas, and a heating gas flow channel for flowing a heating gas for supplying heat to the fuel gas flow channel. The apparatus further includes a channel area changing unit that changes a range of the heating gas flowing through the heating gas channel, and a channel area control unit that controls the channel area changing unit in accordance with an operating condition.
[0009]
[Action and effect]
The amount of heat supplied from the heating section to the fuel gas flow path and the range heated by the heating section in the fuel gas flow path are controlled in accordance with operating conditions. As a result, the range in which the reforming reaction occurs and the amount of heat supplied thereto can be adjusted according to the operating conditions, and the temperature gradient in the portion where the reforming reaction occurs can be reduced, so that an efficient reaction can be produced. be able to.
[0010]
In addition, by controlling the range of the flow of the heating gas, which is the heating source of the fuel gas flow path, the range in which heat is supplied from the heating gas can be controlled, and the range in which the reforming reaction occurs can be controlled, and the range in which the reforming reaction occurs is controlled The amount of heat generated can be adjusted. Thus, the temperature in the range in which the reforming reaction occurs can be controlled, so that an efficient reaction can be generated.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows the configuration of the fuel cell system used in the first embodiment.
[0012]
This embodiment is a fuel reforming type fuel cell system. As the fuel gas, a hydrocarbon-based fuel such as methanol, gasoline, or natural gas can be used. Here, a reformed gas is generated by a steam reforming reaction using methanol.
[0013]
The reformer 3 is a reactor having a reforming section 3a that carries a reforming catalyst that generates a reformed gas richer than fuel gas and air. The reaction occurring here is shown in the following equation.
[0014]
[Formula 1]
CH ₃ OH → CO + 2H ₂ -90.0 (kj / mol) (1)
CO + H ₂ O → CO ₂ + H ₂ +40.5 (kj / mol) (2)
CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ -49.5 (kj / mol) (3)
When steam reforming methanol, the methanol decomposition reaction of the formula (1) and the shift reaction of the formula (2) proceed simultaneously, and an endothermic reaction as a whole proceeds as shown in the formula (3). As described above, since the entire reforming reaction is an endothermic reaction, it is necessary to externally supply heat required for the reaction.
[0015]
Therefore, the combustion unit 2 having the heating gas flow path 18 is formed in the reformer 3, and the combustion catalyst is carried in the heating gas flow path 18. In addition, a combustion air valve 30 for adjusting the flow rate of air in the mixed gas supplied to the combustion section 2 and a fuel injection valve 2a for supplementing insufficient fuel are provided. An exhaust gas from the stack 5 described later, air whose flow rate is adjusted by the combustion air valve 30, and a mixed gas composed of fuel injected from the fuel injection valve 2 are supplied to the heated gas flow channel 18. As a result, a combustion reaction occurs in the heating gas flow path 18, and the reforming reaction is caused by supplying the accompanying heat to the reforming catalyst.
[0016]
Further, the fuel cell system includes an evaporator 1, and uses the combustion gas discharged from the combustion unit 2 to evaporate methanol and water, which are the raw materials of the fuel gas used for the reforming reaction, to generate a fuel gas. This fuel gas is supplied to the reforming section 3a, and a reforming reaction is generated using the heat supplied from the combustion section 2.
[0017]
The reformed gas generated in this manner contains CO that causes deterioration of the stack 5 described later. Therefore, a CO remover 4 for reducing CO is provided, and CO in the reformed gas is reduced to about several tens of ppm before being supplied to the stack 5.
[0018]
The stack 5 is a device that directly converts chemical energy of fuel into electrical energy without passing through mechanical energy or thermal energy. Here, the stack 5 is a polymer electrolyte fuel cell in which the electrolyte membrane is sandwiched between the fuel electrode and the air electrode, and the reformed gas generated in the reformer 3 is used for the fuel electrode, and the oxidant is used for the air electrode. Supplying outside air causes the following electrochemical reaction.
[0019]
[Formula 2]
Fuel electrode: H ₂ → 2H ⁺ + 2e ⁻ ... (4)
Air electrode: (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O ... (5)
Battery whole: H ₂ + (1/2) O ₂ → H ₂ O ... (6)
In order to promote such a reaction, a platinum catalyst is supported on the electrodes of the stack 5. Here, if CO is contained in the reformed gas supplied to the fuel electrode, the CO is adsorbed on the platinum catalyst, and the catalytic function is reduced. Therefore, as described above, the CO remover 4 is provided, and the CO concentration in the reformed gas is reduced to about several tens ppm at which poisoning of the stack 5 can be avoided, and then supplied to the stack 5.
[0020]
Further, the fuel cell system includes a start-up combustor 7 that generates a high-temperature gas for warming up at the time of start-up. At the time of startup, the high temperature gas generated in the startup combustor 7 is supplied to the combustion unit 2 to warm up the combustion catalyst to a temperature at which a combustion reaction can occur.
[0021]
Further, a control unit 6 is provided to control each element constituting the fuel cell system. The reformer 3 is provided with temperature sensors 26 and 27 for measuring the internal temperature, and supplies the output to the controller 6. Here, the startup combustor 7, the evaporator 1, and the reformer 3 are provided with a fuel injection valve for injecting fuel based on a command output from the controller 6 as needed.
[0022]
In such a fuel cell system, if the amount of heat supplied from the combustion unit 2 to the reforming unit 3a is excessive or if the temperature of the reforming unit 3a is locally high, the reforming generated by the equation (3) is performed. The gas is exposed to the hot atmosphere. As a result, a reverse shift reaction, which is the reverse reaction of the equation (2), occurs to generate CO, and the stack 5 may be deteriorated. Excessive heating also increases the heat loss, which may reduce system efficiency. Conversely, if there is a locally low-temperature region in the reforming section 3a, the reaction of the formula (3) does not proceed, and the methanol reforming efficiency decreases.
[0023]
Therefore, in this embodiment, the reformer 3 is configured as shown in FIG.
[0024]
The reforming section 3a includes a first reforming catalyst 15, a second reforming catalyst 16, and a third reforming catalyst 17 (hereinafter, reforming catalysts 15 to 17). They are connected in series by a second duct section 20 (hereinafter, duct sections 19 and 20). The reforming catalysts 15, 16 and 17 are arranged so as to be arranged in a line with a wall therebetween, and the flow of the fuel gas is reversed by the duct portions 19 and 20.
[0025]
Here, in the cross section as shown in FIG. 2, the cross section of the third reforming catalyst 17 is a half of the cross section of the first and second reforming catalysts 15, 16. When the reforming catalysts 15 to 17 are arranged in a line via a wall, one end, here the lower side, is arranged so as to be aligned, so that the first and second reforming catalysts 15, 16 are arranged as shown in FIG. On the other hand, the cross section of the third reforming catalyst 17 has a shape in which the upper half is chipped.
[0026]
Further, a fuel gas inlet 8 serving as a fuel gas supply port and a fuel gas introduction passage 9 for introducing the fuel gas taken in at the fuel gas inlet 8 into the first reforming catalyst 15 are provided. The fuel gas inlet 8 is arranged at an end of the fuel gas introduction passage 9 and is configured to generate a swirling flow in the fuel gas introduction passage 9. Thereby, the fuel gas can be made uniform when the fuel gas is introduced into the first reforming catalyst 15. Further, a reformed gas outlet passage 21 for recovering the reformed gas from the third reforming catalyst 17 and a reformed gas outlet 22 for discharging the reformed gas from the reformed gas outlet passage 21 to the outside of the reformer 3 are provided. Prepare.
[0027]
With this configuration, the fuel gas is supplied from the fuel gas inlet 8 and supplied to the first reforming catalyst 15 via the fuel gas introduction passage 9. Thereafter, a reforming reaction occurs while performing heat exchange with the later-described combustion unit 2, and the first reforming catalyst 15, the first duct unit 19, the second reforming catalyst 16, the second duct unit 20, the third It flows in a meandering manner inside the reformer 3 in the order of the reforming catalyst 17. The reformed gas generated by the reforming reaction passes through the reformed gas outlet passage 21 from the third reforming catalyst 17 and is discharged from the reformed gas outlet 22.
[0028]
Further, the reformer 3 is provided with a combustion section 2 having a circular cross section that penetrates the reformer 3 in a direction in which the reforming catalysts 15 to 17 are arranged. A high-temperature gas or a mixed gas flows as a heating gas for heating the reforming catalyst in the combustion unit 2. Here, a case in which the mixed gas is circulated will be described.
[0029]
The combustion unit 2 is constituted by a heating gas inlet 10, a heating gas flow path 18, and a heating gas outlet 23 along the axial direction. The heating gas flow path 18 carries a combustion catalyst. The heating gas passage 18 is a region adjacent to the reforming catalysts 15 to 17, and the mixed gas taken in from the heating gas inlet 10 flows through the heating gas passage 18 from the first reforming catalyst 15 to the third reforming catalyst. The gas flows in one direction toward the catalyst 17 and is discharged from the heated gas outlet 23. At this time, the combustion reaction, which is an exothermic reaction, proceeds in the heating gas flow path 18 to supply heat required for the reforming reaction in the adjacent reforming catalysts 15 to 17.
[0030]
In addition, a heating gas partition plate 12 that divides a cross section of a heating gas inlet end 11 serving as a mixed gas intake at a predetermined ratio is disposed in the heating gas inlet section 10. Here, as shown in FIG. 2, the volume of the reforming catalysts 15 to 17 along the flow direction of the heating gas is configured to be 2: 3 on the upper side and the lower side, and thus the heating gas inlet end is similarly formed. The cross section 11 is divided into 2: 3 on the upper side and the lower side by the heated gas partition plate 12. Further, the heated gas partition plate 12 is formed so as to divide the cross section of the combustion part 2 in the vertical direction at a ratio of 1: 1 in a portion overlapping the first reforming catalyst 15. Assuming that the upper passage formed by this is an upper heating gas passage 18a and the lower passage is a lower heating passage 18b, when the heating gas inlet end 11 is open, 2/5 of the heating gas flows. The heat is supplied to the upper heating gas flow path 18a to supply heat to the adjacent reforming catalyst (2/5 of the total reforming catalyst). On the other hand, 3/5 of the heating gas is supplied to the lower heating gas passage 18b to supply heat to the adjacent reforming catalyst (3/4 of all reforming catalysts).
[0031]
Further, at the heating gas inlet end 11, a first opening / closing valve 13 that can open and close an upper heating gas channel 18a partitioned by a heating gas partition plate 12, and a lower heating gas channel 18b that can open and close. A second on-off valve 14 is provided. Here, the ratio of the cross-sectional areas of the first on-off valve 13 and the second on-off valve 14 is 2: 3. When the first on-off valve 13 is open, a combustion reaction occurs in the upper heating gas flow path 18b, and the reforming catalyst having a volume of ／ of the whole is heated. On the other hand, when the second on-off valve 14 is open, a combustion reaction occurs in the lower heating gas flow path 18b, and the reforming catalyst having a volume of ／ of the whole is heated.
[0032]
Further, as a temperature sensor for measuring the internal temperature of the reformer 3, an upper temperature sensor 26 is provided at the reforming section 3a adjacent to the upper heating gas flow path 18a, and a temperature sensor is provided at the reforming section 3a adjacent to the lower heating gas flow path 18b. A lower temperature sensor 27 is provided.
[0033]
In a fuel cell system having such a reformer 3, the combustion region of the combustion unit 2 is changed according to the operating conditions of the system. Here, the change of the combustion area is controlled by controlling the opening and closing of the first opening / closing valve 13 and the second opening / closing valve 14 to change the combustion area into three combustion areas corresponding to the amount of fuel gas to be reformed as shown in FIG. Assuming that the amount of fuel gas supplied when performing reforming using the entire reforming catalysts 15 to 17 is 1, the combustion region can be set as follows according to the amount of fuel gas.
[0034]
First, when the amount of fuel gas to be reformed is "small", here, when the amount of fuel gas is larger than 0 and equal to or smaller than 2/5, the first on-off valve 13 is opened as shown in FIG. Then, the second on-off valve 14 is closed. As a result, the mixed gas consisting of the exhaust gas, air, and fuel from the stack 5 is supplied only to the upper heating gas flow path 18a, and a reforming reaction occurs in a 2/5 region of the entire reforming catalyst.
[0035]
At this time, air is mixed with the exhaust gas from the stack 5 through the combustion air valve 30 and fuel is mixed from the fuel injection valve 2a to generate a lean mixed gas. At this time, the exhaust gas from the stack 5 is Since it is small, the flow rate of the lean mixed gas supplied to the combustion unit 2 can also be suppressed. Therefore, when the range for supplying heat is small, useless heating can be suppressed by reducing the flow rate of the mixed gas for generating heat.
[0036]
Next, when the fuel gas amount to be reformed is “medium”, here, when the fuel gas amount is larger than 2/5 and equal to or smaller than 3/5, as shown in FIG. Is opened, and the first on-off valve 13 is closed. As a result, the mixed gas is supplied only to the lower heating flow path 18b, and a reforming reaction occurs in a ３ region of the entire reforming catalyst.
[0037]
At this time, since the flow rate of the exhaust gas discharged from the stack 5 is larger than when the fuel gas is “small”, the flow rate of the generated lean mixed gas is also larger. Thereby, as the supply range of the lean mixed gas becomes wider, the flow rate of the supplied lean mixed gas can be increased.
[0038]
Finally, when the amount of the fuel gas to be reformed is "large", here, when the amount of the fuel gas is larger than 3/5, as shown in FIG. The on-off valve 14 is opened. As a result, the mixed gas is supplied to the entire heating gas flow path 18, so that a reforming reaction occurs in the entire reforming catalyst.
[0039]
At this time, since the exhaust gas from the stack 5 is further increased, the flow rate of the generated lean mixed gas is further increased, and the flow rate can be increased according to the supply range of the lean mixed gas, thereby avoiding insufficient heating. it can.
[0040]
In such control, the amount of heat required by the reforming catalyst is determined according to the flow rate of each fuel gas. Therefore, the air amount of the mixed gas adjusted by the fuel air valve 30 accordingly and the combustion injection valve 2a To adjust the amount of fuel mixed in, and the flow rate of the mixed gas. By adjusting the flow rate of the mixed gas according to the combustion region to be controlled, it is possible to prevent excessive heating or insufficient heat.
[0041]
Next, the control of the use area of the heated gas flow path 18 at the time of startup or cold in such a fuel cell system will be described with reference to FIG. Here, the mixing ratio of the fuel and air of the mixed gas supplied to the heating gas flow path 18 is also controlled in accordance with the control of the use area. These controls are performed by the control unit 6.
[0042]
At the time of startup, air and fuel are supplied to the startup combustor 7 to generate combustion gas. The generated high-temperature combustion gas is supplied to the combustion section 2 of the reformer 3, and the heating gas flow path 18 is heated to raise the combustion catalyst to the activation temperature. At this time, the second opening / closing valve 14 is closed and only the first opening / closing valve 13 is opened to set the state shown in FIG. The combustion gas is supplied only to the upper heating gas flow path 18a, and the minimum amount of the combustion catalyst to be warmed up, that is, the reforming catalyst, is ２ of the total volume here. As described above, since the heat capacity of the region to be heated can be reduced, the temperature can be raised in a short time.
[0043]
Thereafter, the above state is continued until the temperature of the heating gas flow path 18, here the detection value of the upper temperature sensor 26 reaches a predetermined value T1, and when the temperature reaches the predetermined value T1, the mixed gas of fuel and air is supplied to the heating gas flow. Supply to road 18. Here, for example, the predetermined value T1 is set as the lower limit of the activation temperature of the combustion catalyst. That is, since the mixed gas is supplied when the combustion catalyst in the upper heating gas flow path 18a reaches the activation temperature, the ignition can be performed quickly and the heating can be performed smoothly. At this time, since the combustion catalyst carried in the lower heating gas flow path 18b may not reach the activation temperature, the second on-off valve 14 is closed and only the first on-off valve 13 is opened, and the upper heating gas is opened. The mixed gas is supplied only to the flow path 18a. Here, T1 is the lower limit of the activation temperature of the combustion catalyst, but the temperature of the reforming catalyst when the combustion catalyst reaches the activation temperature may be measured in advance by experiments or the like, and the temperature may be set to the predetermined value T1.
[0044]
As described above, the warming-up of the reforming section 3a by the combustion reaction in the upper heating gas flow path 18a is continued, and when the detection value of the upper temperature sensor 26 reaches the predetermined value T2, the first on-off valve 13, the second on-off valve 14 To release. Here, the predetermined value T2 is a temperature detected by the upper temperature sensor 26 when the entire combustion catalyst carried in the heating gas flow path 18 reaches the activation temperature, and is obtained in advance by an experiment or the like. Here, the determination is made based on the output of the upper temperature sensor 26. However, the determination may be made based on whether the output of the lower temperature sensor 27 has reached the activation temperature of the combustion catalyst.
[0045]
In this way, the mixed gas is caused to flow through the entire heating flow path 18 to cause a combustion reaction in the combustion catalyst heated to the active state, thereby quickly warming up the reforming catalyst. When the output of the temperature sensor provided in the reforming section 3a, here, the upper temperature sensor 26 reaches a predetermined value T3, here, the activation temperature of the reforming catalyst, the warm-up operation is ended. Then, the reforming reaction is started, and the region where the combustion reaction occurs is controlled according to the amount of the fuel gas to be reformed.
[0046]
Here, at the time of startup or cold, by making the mixed gas supplied rich in fuel, the combustion temperature is raised in the heating gas flow path 18 and the temperature is raised more quickly. Conversely, after the warm-up, the fuel consumption is suppressed by making the mixed gas fuel-lean. However, this is not always the case when the heating of the reforming catalyst is insufficient, such as when the state in which the amount of fuel gas required for reforming is maximized continues.
[0047]
Next, a method of controlling the reforming region by the control unit 6 will be described with reference to a flowchart shown in FIG.
[0048]
Hereinafter, in steps S601 to S608, a control method of the warming-up operation at the time of startup or cold will be described.
[0049]
In step S601, operating conditions of the fuel cell system are input. Next, proceeding to step S602, it is determined whether or not the temperature of the reforming catalyst detected by the upper temperature sensor 26 is smaller than a predetermined value T1. If it is smaller than T1, it is determined that it is in the initial stage of the start or in the cold state, and the process proceeds to step S603 to supply fuel and air to the start combustor 7. In step S604, the combustion gas generated by the start-up combustor 7 is supplied to the heating gas flow path 18 of the combustion unit 2 to start warming up the combustion catalyst and the reforming catalyst. At this time, as shown in FIG. 3A, the first on-off valve 13 is opened and the second on-off valve 14 is closed.
[0050]
Returning to step S602, the output of the upper temperature sensor 26 is again compared with the predetermined value T1. If it is determined in step S602 that the output of the upper temperature sensor 26 has reached T1 by the warm-up using the combustion gas, the process proceeds to step 605.
[0051]
In step S605, it is determined whether the output of the upper temperature sensor 26 is lower than a predetermined temperature T2. If the temperature of the reformer 3 has not reached T2, the process proceeds to step S606, and only the first on-off valve 13 is opened as shown in FIG. Supply gas. As a result, the combustion catalyst, and eventually the reforming catalyst, is warmed up using the heat accompanying the combustion reaction.
[0052]
Returning to step S605, if it is determined that the output of the upper temperature sensor 26 is equal to or higher than T2, the process proceeds to step S607. In step S607, it is determined whether the output of upper temperature sensor 26 is lower than predetermined temperature T3. If the output from the upper temperature sensor 26 is smaller than T3, it means that the overall warm-up is insufficient, and the process proceeds to step S608. In step S608, the second on-off valve 14 is opened to supply the rich mixed gas to the entire heating gas flow path 18, a combustion reaction occurs in the entire combustion catalyst, and the temperature of the entire reformer 3 is raised.
[0053]
If it is determined in step S607 that the temperature of the reformer 3 has reached T3, the warm-up is ended.
[0054]
Next, in steps S609 to 613, an area where the combustion reaction of the combustion unit 2 occurs is set according to the fuel gas amount.
[0055]
In step S609, it is determined whether the fuel gas amount is “small”. If it is determined that the fuel gas amount is "small", the process proceeds to step S610, where the first on-off valve 13 is opened and the second on-off valve 14 is closed. As a result, as shown in FIG. 3A, the lean mixed gas is supplied only to the upper heating gas flow path 18a to supply heat to a 2/5 region of the entire reforming catalyst, and the reforming reaction is performed in that region. Occurs.
[0056]
On the other hand, if it is not determined in step S609 that the fuel gas amount is “small”, the process proceeds to step S611 to determine whether the fuel gas amount is “medium”. When it is determined that the fuel gas amount is “medium”, the first on-off valve 13 is closed and the second on-off valve 14 is opened. As a result, as shown in FIG. 3B, the lean mixed gas is supplied to the lower fuel gas passage 18b to supply heat to 領域 of the entire reforming catalyst, and a reforming reaction occurs in that region. .
[0057]
On the other hand, if it is not determined in step S611 that the fuel gas amount is “medium”, it is determined that the fuel gas amount is “large”, and the process proceeds to step S613. In step S613, the first on-off valve 13 and the second on-off valve 14 are opened, a lean mixed gas is supplied to the entire heating gas flow path 18, and heat is supplied to the entire reforming catalyst to cause a reforming reaction.
[0058]
As described above, in steps S609 to S613, the combustion area in the heating gas flow path 18 is set according to the fuel gas amount, and the range of the reforming catalyst to be heated is controlled.
[0059]
Next, in step S614, the temperature inside the reformer 3, that is, the temperature of the reforming catalyst is determined by the temperature sensor of the upper temperature sensor 26 or the lower temperature sensor 27 which is installed on the reforming catalyst in which the reforming reaction is occurring. Is detected. In step S615, it is determined whether or not the detected temperature of the reformer 3 is a temperature suitable for the operating conditions. Here, this determination is made beforehand by determining the temperature of the reformer 3 according to the operating conditions by an experiment or the like and determining whether the detected temperature is within an allowable range.
[0060]
If the temperature of the reformer 3 does not meet the operating conditions, the process proceeds to step S616, and the temperature difference is changed by changing the temperature of the reforming fuel gas, the temperature of the mixed gas supplied to the heating gas flow path 18, and the mixing ratio. To correct it. Thereafter, the flow returns to step S614 again, and if it is determined that the temperature of the reformer 3 is in accordance with the operating conditions, the present control is ended.
[0061]
When the flow rate of the reformed gas required in the fuel cell system changes, the control as described above is periodically repeated, so that the combustion unit 2 according to the amount of heat required in the reformer 3. Can generate a combustion reaction. Alternatively, the above control may be performed every time the operating conditions change.
[0062]
Next, effects of the present embodiment will be described.
[0063]
FIG. 4 shows an example of the effect of the present embodiment. Conventionally, a temperature gradient occurs in the reforming reaction section, and when the fuel gas flow rate is small, an increase in CO due to the reverse shift reaction increases. When the fuel gas flow rate increases, an increase in unreacted fuel, that is, deterioration in reforming efficiency, has been observed. Can be On the other hand, in the present embodiment, regardless of the fuel gas flow rate, the amount of heat supplied per unit volume of the portion where the reforming reaction occurs and the reaction rate generated per unit volume can be averaged. And the deterioration of the reforming efficiency can be suppressed.
[0064]
A reforming section 3a that applies a reforming catalyst and causes a reforming reaction using a fuel gas, a heating gas flow path 18 that selectively supplies heat to the reforming section 3a, and a heating gas flow path 18 The amount of heat supplied to the reforming section 3a and the range heated by the heating gas channel 18 of the reforming section 3a are controlled in accordance with operating conditions. Thereby, the reforming unit 3a can be heated with a necessary amount of heat by a capacity necessary for the reforming reaction, so that it is possible to prevent the reforming unit 3a from being excessively heated or shortage of heat. .
[0065]
In addition, a combustion catalyst is applied to the heating gas flow path 18, and the flow rate and the supply range of the mixed gas composed of fuel and air to be supplied to the heating gas flow path 18 are controlled according to the operating conditions. By controlling the flow rate of the mixed gas, the combustion reaction can be controlled, and, consequently, the amount of heat generated accordingly. Thereby, the amount of heat supplied to the reforming section 3a can be easily controlled.
[0066]
When the range in which the mixed gas in the heating gas flow path 18 is supplied increases, the flow rate of the mixed gas is increased. Thus, the amount of heat generated per unit volume of the combustion catalyst can be averaged, and the amount of heat supplied per unit volume in a range in which the reforming reaction occurs can be constant regardless of operating conditions. As a result, the conditions under which the reforming reaction occurs can be made constant. Thereby, excessive heating or insufficient heating of the reforming catalyst can be avoided, and an efficient reforming reaction can be generated.
[0067]
When the flow rate of the fuel gas supplied to the reforming section 3a increases, the range in which the mixed gas in the heating gas flow path 18 is supplied is increased. This makes it possible to change the range in which the reforming reaction occurs according to the supplied fuel gas, so that the reforming reaction generated per unit volume of the reforming catalyst is constant regardless of the supplied fuel gas amount. can do. Thereby, excessive heating or insufficient heating of the reforming catalyst can be avoided, and an efficient reforming reaction can be generated.
[0068]
In particular, by setting the supply range of the mixed gas and the mixed gas flow rate in accordance with the amount of the supplied fuel gas, the amount of heat supplied to the reforming catalyst per unit volume and the reform generated by the reforming catalyst are improved. The quality response can be constant regardless of the operating conditions, here the operating load. Thereby, the amount of heat supplied per unit volume and the amount of heat consumed can be made uniform, so that a local temperature gradient can be suppressed. This avoids the deterioration of the reforming effect due to insufficient heating of the fuel gas and the increase in CO caused by the reverse shift reaction of the reformed gas due to excessive heating, and at the same time, suppresses the increase in heat loss and reduces the system efficiency. It is possible to avoid.
[0069]
A temperature detecting means for detecting or estimating the temperature of at least a part of the reforming section 3a or the heating gas flow path 18 is provided with an upper temperature sensor 26 here. To minimize the range of heating. Thereby, efficient warm-up can be performed and the warm-up time can be shortened, so that, for example, the start-up performance can be improved. In addition, the heating range of the reformer 3 is increased as the temperature of the reformer 3 increases, so that the entire reforming section 3a can be efficiently warmed up.
[0070]
A catalyst temperature detecting means for detecting or estimating the temperature of the combustion catalyst, here an upper temperature sensor 26 is provided. When the combustion catalyst is lower than the activation temperature, it is generated by a high-temperature gas, here the starting combustor 7, at the time of cold or startup. The heated high-temperature gas is supplied to the heated gas channel 18. Thereafter, by supplying the mixed gas from the portion of the heated gas flow path that has reached the activation temperature, the ignitability of the combustion catalyst can be improved, and the startability can be more reliably improved by a smooth temperature increase. it can.
[0071]
Further, by making the mixture ratio of the fuel and air of the mixed gas supplied to the heating gas flow path 18 cold or at the time of startup rich, the combustion temperature of the combustion catalyst can be increased and the temperature can be raised quickly. Further, by making the engine lean after the warm-up is completed, fuel consumption can be suppressed, and startability and system efficiency can be improved.
[0072]
Temperature detecting means for detecting or estimating the temperature of at least a part of the reforming section 3a or the heated gas flow path 18, which is provided with temperature sensors 26 and 27, wherein the temperature detected by the temperature sensor 26 or 27 is lower than a predetermined temperature. If it is higher, the amount of heat supplied to the reforming section 3a is reduced, or the temperature of the fuel gas is lowered. If the temperature is lower than the predetermined temperature, the amount of heat supplied to the reforming unit 3a is increased, or the temperature of the fuel gas is increased. This makes it possible to reliably control the temperature of the portion of the reforming section 3a where the reforming is being performed, thereby suppressing a decrease in system efficiency due to excessive heating or insufficient heating.
[0073]
Further, the fuel gas is caused to flow uniformly into the reforming section 3a. Here, by arranging the fuel gas inlet 8 at the end of the fuel gas introduction passage 9 and generating a swirling flow in the fuel gas introduction passage 9, the fuel gas is made uniform in the reforming section 3a. Supply. By combining the uniform introduction of the fuel gas and the change of the use area of the heating gas flow path 18, the generation of a temperature gradient in the reforming reaction section is further suppressed, and thus the reforming due to the temperature decrease is performed. The effect of avoiding a decrease in efficiency and an increase in CO due to a reverse shift reaction when the temperature rises can be obtained more reliably.
[0074]
Further, a flow area changing means for changing a range of the heating gas, here, a mixed gas or a high-temperature gas flowing through the heating gas flow path 18, here, first and second control valves 13, 14 is provided, and according to operating conditions, Change the flow path area of the heating gas flow path. Thus, the range of the reforming section 3a to which heat is supplied by the heating gas can be changed, so that the range in which the reforming reaction occurs can be changed, and the reforming reaction occurs regardless of the change in the operating conditions. The environment can be stabilized. Therefore, an appropriate reforming reaction can be performed, and the system efficiency can be improved.
[0075]
Here, the heating gas is configured to flow in the heating gas flow path 18 in one direction, and the flow path cross-sectional area is changed by opening and closing the first and second control valves 13 and 14. As a result, the mixed gas can be supplied only to the set region, and a combustion reaction can be caused.
[0076]
Next, a second embodiment will be described. The outline of the fuel cell system is the same as that of FIG. 1 of the first embodiment, and the configuration of the reformer 3 is shown in FIG.
[0077]
In the present embodiment, a region where a combustion reaction occurs in the heating gas flow path 18 is controlled using the first fuel injection valve 24 and the second fuel injection valve 25.
[0078]
The fuel gas generated by the evaporator 1 is supplied from the fuel gas inlet 8 to the reforming catalyst through the fuel gas introduction passage 9. On the other hand, the exhaust gas from the stack 5 and the added air are introduced into the combustion unit 2 from the heating gas inlet 10.
[0079]
The heating gas inlet 10 includes a first fuel injection valve 24 and a second fuel injection valve 25. In FIG. 7, the first fuel injection valve 24 is disposed so as to inject fuel into the upper heating gas flow path 18a adjacent above the first reforming catalyst 15 and the second reforming catalyst 16. That is, when fuel is supplied from the first fuel injection valve 23, a combustion reaction occurs in the upper heating gas flow path 18a, and heat is supplied to a region corresponding to 2/5 of the volume of the entire reforming catalyst. On the other hand, the second fuel injection valve 25 injects fuel into the lower heating gas passage 18b below the first reforming catalyst 15 and the second reforming catalyst 16 and adjacent to the third reforming catalyst 17 in FIG. . That is, when the fuel is supplied from the second fuel injection valve 25, a combustion reaction occurs in the lower heating gas passage 18b, and heat is supplied to a region corresponding to ３ of the entire reforming catalyst. Here, the ratio between the predetermined injection amount of the first fuel injection amount 24 and the predetermined injection amount of the second fuel injection amount 25 is set to 2: 3 similarly to the volume ratio of the reforming catalyst located on the downstream side.
[0080]
The mixed gas generated by mixing the fuel into the exhaust gas and the air supplied to the heating gas inlet 10 using the first or second fuel injection valves 24 and 25 is caused to flow through the heating gas flow path 18. At this time, a combustion catalyst is carried in the heating gas flow path 18, and heat generated by the combustion reaction is supplied to the adjacent reforming catalyst to supplement the heat required for the reforming reaction.
[0081]
Here, the region where the combustion reaction occurs in the heating gas flow path 18 is changed according to the operating conditions of the fuel cell system. Here, the combustion area is set as follows according to the amount of fuel gas supplied to the reformer 3. However, the fuel gas amount when fuel is injected from both the first and second fuel injection valves 24 and 25 is set to 1, and when the fuel gas amount is larger than 0 and equal to or smaller than 2/5, the fuel gas amount is “small”. The case where the fuel gas amount is larger than 5 and 3/5 or less is defined as "medium", and the case where the fuel gas amount is larger than 3/5 is "large".
[0082]
First, when it can be determined that the amount of fuel gas to be reformed is “small”, fuel is injected only from the first fuel injection valve 24 as shown in FIG. As a result, a reforming catalyst is generated in a region that is 2/5 of the total catalyst. Next, when it can be determined that the fuel gas amount to be reformed is “medium”, the fuel is injected only from the second fuel injection valve 25 as shown in FIG. As a result, a reforming catalyst is generated in a region that is ／ of the total catalyst. Further, when it can be determined that the amount of fuel to be reformed is "large", fuel is injected from both the first and second fuel injection valves 24 and 25 as shown in FIG. Thereby, a reforming reaction can be caused in the entire catalyst region.
[0083]
Next, a description will be given of startup or cold operation. Here, it is assumed that the temperature change of the reformer 3 and the combustion region and the mixture ratio of the mixed gas set therewith are the same as those in FIG. Hereinafter, only portions different from the first embodiment will be described.
[0084]
At the time of startup, the heating gas flow path 18 is heated using the combustion gas generated in the startup combustor 7. At this time, the same amount of combustion gas is supplied to the upper heating gas flow path 18a and the lower heating gas flow path 18b, but since the volume to be heated is smaller on the upper heating gas flow path 18a side, the whole is Can be warmed up. Therefore, when the output of the upper temperature sensor 26 installed on the reforming catalyst adjacent to the upper heating gas flow path 18a rises to a predetermined value T1, here, the temperature at which the combustion catalyst is activated, the operation of the startup combustor 7 is stopped. At the same time, fuel is injected by the first fuel injection valve 24 as shown in FIG. At this time, each flow rate is set so that the mixed gas of air and fuel becomes rich. As a result, a combustion reaction occurs in the upper heated gas passage 18a, and the lower combustion catalyst and the reforming catalyst are warmed up.
[0085]
Thus, by supplying the air-fuel mixture at the time when the combustion catalyst is activated, it is possible to ignite quickly, and since the volume to be heated is small and the heat capacity is small, the temperature is quickly raised. Thereby, heating can be performed smoothly.
[0086]
When the temperature further rises and reaches a predetermined temperature T2, injection is performed by the first fuel injection valve 24 and the second fuel injection valve 25. Here, the predetermined temperature T2 is the temperature measured by the upper temperature sensor 26 when the entire combustion catalyst reaches the activation temperature, as in the first embodiment, and is obtained in advance by experiments or the like. As a result, the reformer 3 enters the state shown in FIG. 8C, and a combustion catalyst is generated in the entire fuel gas flow path 18. In this way, by supplying the mixed gas after the temperature of the heating gas flow path 18 has been raised to some extent, it is possible to smoothly perform heating using the entire combustion catalyst.
[0087]
Thereafter, when the temperature further rises to the predetermined temperature T3, it is determined that the warm-up has ended, and the reforming reaction is started. When performing the reforming reaction, the use area of the heating gas flow path 18 is limited according to the amount of the fuel gas to be reformed. At the time of startup, the mixed gas is mixed in a fuel-rich manner as in the first embodiment, and after the warm-up, the fuel is made lean.
[0088]
Next, the control method of the present embodiment will be described with reference to the flowchart of FIG.
[0089]
After detecting the operating condition of the fuel cell system in step S901, it is determined in step S902 whether the temperature in the reformer 3 is equal to or lower than T1. If T1 or less, it is determined that the engine is in the startup or cold state, and fuel and air are supplied to the startup combustor 7 in step S903 to generate combustion gas. In step S904, the combustion gas generated by the starting combustor 7 is supplied to the heating gas flow path 18 to increase the temperature of the heating gas flow path 18, and the temperature is increased in this state until the temperature of the reformer 3 becomes higher than T1. continue.
[0090]
If it is determined in step S902 that the internal temperature of the reformer 3 is higher than T1, the process proceeds to step S905, and it is determined whether the temperature of the reformer 3 is equal to or lower than T2. If T2 or less, in step S906, fuel is injected from the first fuel injection valve 24 to perform warm-up in the state of FIG. That is, a mixed gas of fuel and air is supplied to the upper side of the heating gas flow path 18, and a combustion reaction is performed in this region. The warm-up is performed in such a state, and if it is determined in step S905 that the internal temperature of the reformer 3 is higher than T2, the process proceeds to step S907.
[0091]
In step S907, the temperature of the reformer 3 is detected, and it is determined whether the output is equal to or lower than T3. If the temperature of the reformer 3 is equal to or lower than T3, fuel is injected from the first and second fuel injection valves 24 and 25 in step S908 (the state shown in FIG. Then, the temperature of the reformer 3 is increased to T3 by causing the supply and the combustion reaction. In step S907, if the internal temperature of the reformer 3 is higher than T3, it is determined that the warm-up has ended, and the reforming reaction is started.
[0092]
Next, in steps S909 to S913, a range in which a combustion reaction occurs is set according to the reforming reaction.
[0093]
In step S909, similarly to step S609, it is determined whether or not the amount of fuel gas used for the reforming reaction is "small". If the amount is "small", the process proceeds to step S910 so that a lean mixed gas is obtained. Fuel is injected from the first combustion injection valve 24 (FIG. 8A). As a result, heat generated by the combustion reaction is received in a range of about 2/5 of the volume of the entire reforming catalyst, and a reforming reaction occurs.
[0094]
On the other hand, if it is not determined in step S909 that the fuel gas amount is “small”, the process proceeds to step S910. In step S910, similarly to step S610, it is determined whether or not the fuel gas amount is "medium". If it is determined that the fuel gas amount is "medium", the process proceeds to step S912, and the second process is performed so that the mixed gas becomes lean. Fuel is injected from the fuel injection valve 25 (FIG. 8B). Thereby, the heat generated by the combustion reaction is received in a range of ３ of the volume of the entire reforming catalyst, and the reforming reaction occurs.
[0095]
If the fuel gas amount is not determined to be "medium" in step S910, it is determined to be "large", and the process proceeds to step S913, where the first and second fuel injection valves 24 and 24 are set to have a lean mixed gas. , 25 (FIG. 8 (c)). As a result, heat generated by the combustion reaction is supplied to the entire reforming catalyst, and a reforming reaction occurs.
[0096]
Thereafter, in steps S914 to S916, the temperature inside the reactor 3 is adjusted to a predetermined temperature, as in steps S614 to S616.
[0097]
Next, effects of the present embodiment will be described. Here, only portions different from the first embodiment will be described.
[0098]
A plurality of fuel injection valves are configured so that the heating gas flows in the heating gas flow path 18 in one direction and injects fuel into a part of the cross section of the heating gas flow path when supplied to the heating gas flow path 18. The first fuel injection valve 24 and the second fuel injection valve 25 are provided. The range in which fuel is supplied to the heating gas flow path 18 by the fuel injection valve or a combination of the fuel injection valve is adjusted. By supplying fuel to the heating gas flow path 18 by fuel injection as described above, it is possible to eliminate the influence of the mixed gas adhering to the pipe.
[0099]
Here, the volumes of the reforming catalyst and the heating gas flow path 18 are set to 2: 3 on the upper side and the lower side, but this is not a limitation.
[0100]
As described above, the present invention is not limited to the above embodiment, and it goes without saying that various changes can be made within the scope of the technical idea described in the claims.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a fuel cell system according to a first embodiment.
FIG. 2 is a diagram illustrating a configuration of a reformer according to the first embodiment.
FIG. 3 is an operation diagram of a control valve according to the first embodiment.
FIG. 4 is a diagram illustrating an effect of the first embodiment.
FIG. 5 is a diagram showing a relationship between a reaction volume and a temperature at the time of startup and cold in the first embodiment.
FIG. 6 is a flowchart illustrating a control method according to the first embodiment.
FIG. 7 is a diagram illustrating a configuration of a reformer according to a second embodiment.
FIG. 8 is an operation diagram of a fuel injection valve according to a second embodiment.
FIG. 9 is a flowchart illustrating a control method according to the second embodiment.
[Explanation of symbols]
3 Reformer (reformation reactor)
3a Reforming unit
6 Control unit
8 Fuel gas entrance
12. Heated gas partition plate
13 First control valve (control valve)
14 Second control valve (control valve)
18 Heated gas flow path
24 First Fuel Injection Valve (Fuel Injection Valve)
25 Second fuel injection valve (fuel injection valve)
26 Upper temperature sensor (temperature detecting means, catalyst temperature detecting means)
27 Lower temperature sensor (temperature detecting means, catalyst temperature detecting means)
Heating state control valve S602 to S613, S902 to S913

Claims (12)

In a reforming reactor for reforming fuel gas,
A fuel gas flow path on which a reforming catalyst is applied and which causes a reforming reaction when fuel gas flows,
A heating unit for supplying heat to the fuel gas flow path,
A heating state control unit that controls the amount of heat supplied from the heating unit to the fuel gas flow path and the range of the fuel gas flow path heated by the heating unit according to operating conditions. Characterized reforming reactor. The heating unit is a heating gas flow path coated with a combustion catalyst,
2. The reforming apparatus according to claim 1, wherein the heating state control unit controls a flow rate of a mixed gas including fuel and air supplied to the heating gas flow path and a supply range of the mixed gas according to an operation condition. Reactor. 3. The reforming reactor according to claim 2, wherein the flow rate of the mixed gas is increased when the range of supplying the mixed gas in the heated gas flow path is increased. 4. 4. The reforming reactor according to claim 3, wherein when the flow rate of the fuel gas supplied to the fuel gas flow path is increased, the range of supplying the mixed gas in the heating gas flow path is increased. 5. Temperature detecting means for detecting or estimating the temperature of at least a part of the fuel gas flow path or the heating unit,
At the time of a cold start, at the time of starting, the range heated by the heating part of the fuel gas flow path is minimized, and the range heated is increased as the temperature detected or estimated by the temperature detecting means increases. 2. The reforming reactor according to 1. A catalyst temperature detection unit that detects or estimates the temperature of the combustion catalyst,
The heating unit is a heating gas flow path coated with a combustion catalyst,
At the time of cold or startup, if the combustion catalyst is lower than the activation temperature, a high-temperature gas is supplied to the heating gas flow path, and a portion of the heating gas flow path that has reached the activation temperature is composed of fuel and air. The reforming reactor according to claim 1, wherein a mixed gas is supplied. 7. The reforming reactor according to claim 6, wherein the mixture ratio of fuel and air of the mixed gas supplied to the heating gas flow path at the time of cold or startup is made rich, and after the warm-up is completed, the mixture is made lean. Temperature detecting means for detecting or estimating the temperature of at least a part of the fuel gas flow path or the heating unit,
If the temperature detected or estimated by the temperature detecting means is higher than a predetermined temperature, the heating unit reduces the amount of heat supplied to the fuel gas flow path, or reduces the amount of fuel gas supplied to the fuel gas flow path. The temperature is decreased, and when the temperature is lower than a predetermined temperature, the amount of heat supplied to the fuel gas passage by the heating unit is increased, or the temperature of the fuel gas supplied to the fuel gas passage is increased. 4. The reforming reactor according to 1. The reforming reactor according to any one of claims 1 to 8, wherein the fuel gas to be reformed is caused to flow uniformly into the fuel gas flow path. In a reforming reactor that generates a reformed gas from a fuel gas,
A fuel gas flow path carrying a reforming catalyst for reforming the fuel gas,
A heating gas flow path for flowing a heating gas for supplying heat to the fuel gas flow path,
Flow path area changing means for changing a range of the heating gas flowing through the heating gas flow path,
A flow path area control means for controlling the flow path area changing means in accordance with operating conditions. In the heating gas flow path, the heating gas is configured to flow in one direction,
The reforming reactor according to claim 10, wherein the passage area changing unit is configured by a control valve that limits a passage cross section of the heating gas when supplied to the heating gas passage. In the heating gas flow path, the heating gas is configured to flow in one direction,
The flow path area changing means is configured by including a plurality of fuel injection valves that inject fuel into a part of the cross section of the heating gas flow path when supplied to the heating gas flow path,
The reforming reactor according to claim 10, wherein a range in which fuel is supplied to the heating gas flow path is adjusted by the fuel injection valve or a combination of the fuel injection valve.

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