JP2003095607A - Apparatus for estimating reaction in fuel reformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly estimate a rate of reaction of a fuel gas, independently of an individual difference of a reformer and variations with time in reforming characteristics. SOLUTION: A flow rate sensor 31 is mounted on the inlet of a reforming reactor 5 to detect a flow rate of the fuel gas which is a mixture of a reforming gas and the original fuel gas. A flow rate sensor 33 is mounted on the outlet of the reforming reactor 5 to detect a flow rate of the reforming gas. Time series signals detected with the flow rate sensors 31 and 32 are recorded in the memory parts 35 and 37 as the first time series signal and the second time series signal, respectively. An answer calculating part 39 seeks an answering characteristic of a variation in the state of the reforming gas to a variation in the state of the fuel gas based on contents memorized in the memory parts 35 and 37 and a part 41 to estimate reaction quantity seeks a reformed quantity of the fuel gas based on the answering characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel reformer reaction estimation device for estimating a reforming reaction of a fuel reformer that produces hydrogen-rich reformed gas from raw fuel gas.

[0002]

2. Description of the Related Art In recent years, much research has been conducted on fuel cells in which hydrogen gas and oxygen in the air are reacted to directly generate electricity electrochemically. As a method of supplying hydrogen gas to the fuel cell, there are a method of directly supplying stored hydrogen and a method of reforming a raw fuel such as methanol by a reformer to obtain hydrogen gas.

As a conventional fuel reforming technique, for example, there is a technique described in Japanese Patent Laid-Open No. 2000-63104. In the fuel reforming control method disclosed in this publication, the reforming gas outlet temperature of the reforming catalyst portion arranged in the reforming reactor and the supply of the reforming fuel introduced into the reforming reactor. A method for estimating the residual hydrocarbon concentration from the amount and the reaction rate characteristic measured in advance is shown.

[0004]

However, in the above-mentioned conventional technique, the estimated residual hydrocarbon concentration depends on the reaction rate characteristics of the reformer, so that an error due to individual difference of the reformer or There is a problem in that it is impossible to avoid an error due to a change with time of the modification characteristics.

In view of the above problems, an object of the present invention is to provide a fuel reformer capable of accurately estimating the reaction rate of fuel gas, regardless of individual differences in the reformer and changes in the reforming characteristics with time. It is to provide a reaction estimation device of.

[0006]

The invention according to claim 1 is
In order to achieve the above object, a fuel gas in which a raw fuel gas and a reforming gas that reacts with the raw fuel gas to generate hydrogen are mixed is supplied, and the fuel gas is converted into a hydrogen-rich reformed gas. A fuel reformer reaction estimation device for estimating a reforming reaction of a reforming fuel reformer, which is installed at an inlet of a reforming reactor in which a catalyst is arranged, and which controls at least one of a flow rate and a pressure of fuel gas. Detecting fuel gas state detecting means, reforming gas state detecting means installed at the outlet of the reforming reactor and detecting at least one of the flow rate and pressure of the reforming gas, the detected fuel gas state, and detecting Response calculation means for obtaining a response characteristic of the change of the reformed gas state with respect to the change of the fuel gas state from the reformed reformed gas state, and a reforming amount estimation for obtaining the reformed amount of the fuel gas based on the response characteristic. Means and A response estimation unit of the reformer to.

According to a second aspect of the present invention, in order to achieve the above object, in the reaction estimating device for a fuel reformer according to the first aspect, the detected fuel gas state is stored as a first temporary series signal. It has a storage means and a second storage means for storing the detected reformed gas state as a second time-series signal, the response calculation means, the response characteristics of the second time-series signal to the first temporary series signal. The gist is that it is a response calculation means to be obtained.

In order to achieve the above object, the invention according to claim 3 is, in the reaction estimation device for a fuel reformer according to claim 1 or claim 2, whether the operating state of the fuel reformer is a steady state. An operating state determination means for determining whether or not, and when the operating state determination means determines a steady state,
And an operation state changing means for changing the flow rate of the fuel gas, wherein the reforming amount is estimated based on the response characteristics of the change in the reformed gas state when the flow rate of the fuel gas is changed from the steady state. And

[0009]

In order to explain the principle of the present invention, consider a reformer using methanol as a raw fuel. The molecular weight (approximate number) of the composition gas that constitutes the fuel gas is methanol (CH3
OH): 32, oxygen (O2): 32, nitrogen (N2): 2
8, water (H2O): 18.

The molecular weight of the composition gas constituting the reformed gas is
In addition to the residual gas of the above fuel gas, carbon monoxide (C
O): 28, carbon dioxide (CO2): 44, hydrogen (H
2): 2. It can be seen that among these gases, only the molecular weight of hydrogen gas is extremely small as compared with other gases.

FIG. 6 is an example showing the response of the flow rate of the gas flowing out of the orifice to the change of the flow rate of the introduced gas when the gases having different molecular weights are introduced into a container having a constant volume and the orifice is used as the outlet. From this figure, only the reaction of hydrogen gas is extremely fast, and for gases other than hydrogen,
It can be seen that nitrogen gas having a molecular weight of 28 and carbon dioxide having a molecular weight of 44 hardly change. The reaction of fuel gas composed of multiple compositions can be approximated by considering it as an average molecular weight gas. Therefore, in the fuel gas as described above, its response depends largely on the proportion of hydrogen. I understood. Here, since the catalyst is installed inside the reformer, the heat capacity is large and the volume through which the gas passes is small compared to the size of the external appearance, so the rate of temperature change depends on the flow rate and the response speed of pressure. On the other hand, you may think that it is slow enough.

[0012]

According to the first aspect of the present invention, the fuel gas in which the raw fuel gas and the reforming gas that reacts with the raw fuel gas to generate hydrogen are mixed is supplied, and the fuel gas is supplied. A reaction estimation device of a fuel reformer for estimating a reforming reaction of a fuel reformer for reforming into a hydrogen-rich reformed gas, which is installed at an inlet of the reforming reactor in which a catalyst is arranged, Fuel gas state detection means for detecting at least one of the flow rate and pressure, and reformed gas state detection means installed at the outlet of the reforming reactor for detecting at least one of the flow rate and pressure of the reformed gas; Response calculation means for obtaining a response characteristic of the change of the reformed gas state with respect to the change of the fuel gas state from the detected fuel gas state and the detected reformed gas state, and the fuel gas is reformed based on the response characteristic. And a reforming amount estimation means for obtaining the amount By having a, without being influenced by individual differences and aging of the catalyst performance, it is possible to perform a stable modified mass estimation.

According to the second aspect of the present invention, the first storage means for storing the detected fuel gas state as the first temporary series signal and the detected reformed gas state as the second time series signal. A second storage unit is provided, and the response calculation unit is a response calculation unit that obtains a response characteristic of the second time series signal with respect to the first temporary series signal.
In addition to the effects of the invention described, there is an effect that an error is unlikely to occur and the reforming amount can be estimated with high accuracy.

According to the third aspect of the present invention, the operating state determination means for determining whether or not the operating state of the fuel reformer is a steady state, and the operating state determination means determines that the operating state is a steady state. And an operation state changing means for changing the flow rate of the fuel gas, and the reforming amount is estimated based on the response characteristic of the change of the reformed gas state when the flow rate of the fuel gas is changed from the steady state. Therefore, in addition to the effect of the invention according to claim 1 or claim 2, there is an effect that the hydrogen content can be estimated even in a steady state.

[0015]

1 is a block diagram of a fuel cell system to which a first embodiment of a reaction estimating device for a fuel reformer according to the present invention is applied. The fuel cell system is used by changing the amount of power generation, such as a system mounted on a moving body such as a fuel cell vehicle.

In FIG. 1, the fuel reformer 1 which is a fuel reformer comprises a mixer 3, a reforming reactor 5, a shift reactor 7 and a selective oxidation reactor 9. The mixer 3 has a function of uniformly mixing the vapor of raw fuel such as methanol and petroleum-based fuel (here, methanol will be described as an example), water vapor, and air. The reforming reactor 5 has a catalyst layer filled with a reforming catalyst, and a large amount of hydrogen is produced by a partial oxidation reaction and a steam reforming reaction using methanol, water, and oxygen in the air. A reformed gas containing is generated.

The reformed gas produced in the reforming reactor 5 is sent to the shift reactor 7, where carbon monoxide and water remaining in the reformed gas are subjected to a shift reaction to produce carbon dioxide and hydrogen. , To the selective oxidation reactor 9. Selective oxidation reactor 9
Has a catalyst layer filled with a selective oxidation catalyst,
The residual carbon monoxide is selectively oxidized using oxygen in the air supplied from the compressor to produce carbon dioxide that is harmless to the fuel cell stack 11. Then, the reformed gas generated in the fuel reforming section 1 is sent to the fuel cell stack 11.

The fuel cell stack 11 uses the reformed gas from the fuel reforming section 1 and the air from the compressor, specifically, the hydrogen in the reformed gas and the oxygen in the air to cause an electrochemical reaction. Generates DC power. At this time, the hydrogen and oxygen supplied to the fuel cell stack 11 are not all consumed in the fuel cell stack 11, but are partially discharged and burned as excess exhaust reformed gas and exhaust air. Sent to the container 13.

The combustor 13 burns and reacts the surplus exhaust reformed gas discharged from the fuel cell stack 11 with the exhaust air. At this time, although not shown, in some cases, the exhaust reformed gas and the exhaust air from the fuel cell stack 11 are combusted together with the air from the compressor and the fuel methanol.
Then, the exhaust gas generated in the combustor 13 is transferred to the evaporator 1
Sent to 5.

The evaporator 15 recovers the heat of the exhaust gas discharged from the combustor 13 to evaporate methanol and water.
That is, the heat of the combustion reaction in the combustor 13 is carried to the evaporator 15 by the exhaust gas and is reused for evaporating methanol and water. Then, the methanol and water evaporated in the evaporator 15 become methanol vapor and water vapor, respectively, and are sent to the mixer 3 in the fuel reforming section 1, and are uniformly mixed by the mixer 3 to become fuel gas, and the reforming reactor. Sent to 5.

The battery 21 accumulates surplus power generated by the fuel cell stack 11 and regenerative power generated by the drive motor 23 when the fuel cell vehicle is decelerated, and the running power consumed by the drive motor 23 and not shown. When the fuel cell stack 11 does not generate enough power to cover the auxiliary electric power consumed by the air compressor, the fuel reforming section 1, the combustor 13, etc., the fuel cell stack 11 is discharged and the drive motor 23, Auxiliary equipment (compressor, fuel reformer 1, combustor 13
Etc.) to compensate for the power shortage. The distribution of these powers is performed by the power control device 21.

The controller 19 controls the electric power distribution by the electric power control device 21, and at the same time, for example, from the ratio of hydrogen in the reformed gas estimated by the reaction estimation device 17,
Control of a valve (not shown) for adjusting the flow rate of air, methanol, etc. is performed by estimating the amount of residual methanol.

Reaction estimating device 1 for a fuel reformer according to the present invention
7 is a flow rate sensor 31, which is installed at the inlet of the reforming reactor 5 in which a catalyst is arranged, and which detects a flow rate of the fuel gas in which the reforming gas and the raw fuel gas are mixed, and a flow rate sensor 31. A flow rate sensor 33 installed at the outlet of the reforming reactor 5 as a reformed gas state detecting means for detecting the flow rate of the reformed gas, and a time series signal of the flow rate detected by the flow rate sensor 31 as a temporary series signal. From the storage unit 35 that stores the time-series signal of the flow rate detected by the flow rate sensor 33 as the second time-series signal, the detected fuel gas state, and the detected reformed gas state. , A response calculating unit 39 as a response calculating unit that obtains a response characteristic of a change in the reformed gas state with respect to a change in the fuel gas state, and a reforming amount estimation unit that obtains an amount of reformed fuel gas based on the response characteristic Reaction amount estimation unit 4 It has a, and.

The reaction estimation device 17 excluding the flow rate sensors 31 and 33 may be configured as, for example, a one-chip microcomputer or may be integrated with the controller 19.

Next, the operation of the reaction estimation device 17 will be described. Flow rate sensor 31 installed at the inlet of the reforming reactor 5
Measures the flow rate of the fuel gas flowing into the reforming reactor 5. The flow rate sensor 33 installed at the outlet of the reforming reactor 5 measures the flow rate of the reformed gas flowing out of the reforming reactor 5.

The time series data of the flow rate of the fuel gas measured by the flow rate sensor 31 is stored in the storage unit 35. The time series data of the flow rate of the reformed gas measured by the flow rate sensor 33 is stored in the storage unit 37.

The response calculator 39 calculates the response of the reformed gas to the change in the fuel gas from the time series data of the flow rate of the fuel gas and the time series data of the flow rate of the reformed gas.

The reaction amount estimating unit 41 has a relationship between the proportion of hydrogen and the response characteristic of the reformed gas flow rate at the reformer outlet with respect to the change in the fuel gas flow rate at the reformer inlet, which has been previously obtained by experiments. It has the map data and so on, and the ratio of hydrogen contained in the reformed gas is estimated from the response obtained by the response calculation unit 39 with reference to the map.

Next, the operation of the portion particularly related to the present invention in this embodiment, that is, the method of estimating the proportion of hydrogen in the reformed gas will be described. As the time series data of the flow rate of the fuel gas measured by the flow rate sensor 31, for example, n pieces of data measured immediately before are always stored in the storage unit 35, and the time series data is

## EQU1 ## u (1), ..., u (n) ... (1) Shall be represented by.

Similarly, for the time series data of the flow rate of the reformed gas measured by the flow rate sensor 33, for example, n pieces of data measured immediately before are always stored in the storage unit 37, and the time series data thereof is shown. Data is,

## EQU2 ## y (1), ..., Y (n) ... (2) Shall be represented by.

Now, when the response characteristic of the reformed gas to the fuel gas is expressed by the first-order lag characteristic of the gain a and the time constant T, the differential operator s is used and the relation between u and y is as follows. Can be expressed as

[0032]

[Equation 3] Here, the low-pass filter F having a cutoff frequency sufficiently large with respect to the response characteristic of the reformed gas to the fuel gas.
(S) is introduced to obtain the following formula.

[0033]

[Equation 4] The following vectors X, Y and θ are defined. Where k is 1
It is an integer not less than n.

[0034]

[Equation 5] In this way, the response calculator 39 can determine the time constant T indicating the response characteristic.

As shown in FIG. 2, the response characteristic of the flow rate change of the reformed gas when the flow rate of the fuel gas is changed is such that the faster the hydrogen content in the reformed gas, the faster the response speed. Therefore, in this embodiment, the hydrogen content ratio in the reformed gas is estimated by utilizing this response characteristic.

The reaction amount estimating unit 41 has a map showing the relationship between the time constant and the hydrogen content ratio as shown in FIG. 3, which is obtained in advance by experiments or the like, and the hydrogen content ratio can be determined by referring to this map. It is calculated (estimated).

Although the response characteristic is a first-order lag and the parameter representing the response characteristic is a time constant here, the response characteristic may be another characteristic such as a second-order lag, or the response characteristic is representative. The parameter may be the natural frequency as long as it is a secondary delay, and the delay time (the value at the time of establishment is 1
The time may be set to 00% to reach 50%) or the rise time (time to reach 10% to 90%).

Further, since the detection values of the flow rate sensors 31, 33 are temporarily stored in the storage units 35, 37 as time series data, it is easy to compare the data before and after the time series to determine that they are noise data. Therefore, if the determined noise data is excluded, or if it is used after being interpolated or modified by an appropriate interpolation function, the accuracy is further improved.

According to the first embodiment described above, stable reforming amount estimation can be performed without being affected by individual differences in catalyst performance and deterioration over time. In addition, it is possible to estimate the reforming amount with high accuracy without making an error.

FIG. 4 is a configuration diagram of a fuel cell system to which the second embodiment of the reaction estimating device for a fuel reformer according to the present invention is applied. In contrast to the first embodiment shown in FIG.
In the reaction estimation device 17a in the second embodiment of FIG. 4, a flow rate sensor 43 that detects the flow rate at the outlet of the shift reactor 7, and a storage unit 45 that stores the flow rate signal detected by the flow rate sensor 43 as time series data. , The flow rate at the outlet of the reforming reactor 5 stored in the storage unit 37, that is, the time-series data of the flow rate at the inlet of the shift reactor 7, and the time-series data of the flow rate at the outlet of the shift reactor 7 stored in the storage unit 45. Response calculation unit 47 that calculates the response characteristics of the reaction gas to the reformed gas from
And a reaction amount estimation unit 49 that calculates the proportion of hydrogen increased in the shift reactor 7 from the obtained flow rate response characteristics. Since other configurations are similar to those of the first embodiment shown in FIG. 1, the same reference numerals are given to the same components, and duplicated description will be omitted.

Next, the operation of the second embodiment will be described. In this embodiment, the flow rate sensor 4 is also provided at the outlet of the shift reactor 7.
3 is installed and the time series data of the flow rate of the reaction gas output from the shift reactor 7 is stored in the storage unit 45, the flow rate at the outlet of the reforming reactor 5 stored in the storage unit 37, that is, the shift reaction. Combined with the time series data of the flow rate at the inlet of vessel 7,
Time series data of the gas state at the inlet and the outlet of the shift reactor 7 can be obtained.

Then, based on these time-series data, the response calculator 47 can calculate the response characteristics of the reaction gas to the reformed gas in the shift reactor 7,
Based on this response characteristic, the reaction amount estimation unit 49 can calculate the proportion of hydrogen increased in the shift reactor 7.
The calculation method in the response calculation unit 47 and the reaction amount estimation unit 49 is the same as the calculation method in the response calculation unit 39 and the reaction amount estimation unit 41 described in the first embodiment. By adding the estimation of the hydrogen amount in the reaction amount estimation unit 41, the controller 19 can estimate the hydrogen amount obtained in the fuel reforming unit 1 more accurately.

FIG. 5 is a configuration diagram of a fuel cell system to which the third embodiment of the reaction estimating device for a fuel reformer according to the present invention is applied. The difference in the configuration of the reaction estimation device 17b in the third embodiment shown in FIG. 5 from the first embodiment shown in FIG. 1 is whether or not the operating state of the fuel reformer is a steady state. An operating state discriminating unit 51 as an operating state discriminating unit, and an operating state changing unit 53 as an operating state changing unit for varying the flow rate of the fuel gas when the operating state discriminating unit 51 determines that the operating state is a steady state. Has been added.

Then, the response calculation unit 39 and the reaction amount estimation unit 4
In No. 1, since the reforming amount is estimated based on the response characteristic of the change in the reformed gas state when the flow rate of the fuel gas is changed from the steady state, the reformer operating state is the steady state. However, the reforming amount can be estimated. Since other configurations are similar to those of the first embodiment shown in FIG. 1, the same reference numerals are given to the same components, and duplicated description will be omitted.

In this embodiment, the time-series data of the flow rate of the fuel gas supplied to the reforming reactor 5 stored in the storage unit 35 is also fetched in the operation state determination unit 51. The operating state determination unit 51 determines from the captured time series data of the flow rate of the fuel gas whether or not there is a change in the flow rate at which the response can be estimated for a predetermined time, and the steady state is based on this determination. Or not. That is, when there is no change in the flow rate that can be estimated for a predetermined period of time, it is determined that the steady state.

When the operating state discriminating unit 51 determines that the operating state is changing to the steady state, the operating state changing unit 53 obtains a variation amount of the fuel gas flow rate that enables estimation of the reforming amount based on the response of the change in the reformed gas state. , This variation amount is sent to the controller 19. This fluctuation amount is, for example, a pulse-shaped signal that minimizes fluctuations in the state of the fuel reformer 1. The controller 19 adds the fluctuation amount sent from the operation state changing unit 53 to the target flow rate of the fuel gas to calculate a control signal for an actuator (not shown) that actually controls the flow rate. Then, the response calculation unit 39 calculates the response characteristic of the reformed gas state with respect to the fluctuation of the target flow rate of the fuel gas, and the reaction amount estimation unit 4 based on this response characteristic.
1 calculates the hydrogen content ratio in the reformed gas.

In the present embodiment, the signal stored in the storage unit 35 is used to determine whether or not there is a change in the operating state. However, of course, the signal stored in the storage unit 37 is used for the determination. Alternatively, other physical states that represent the operating state of the fuel reformer 1 may be used. Alternatively, the determination may be made from the actuator control signal used in the controller 19 or a target value such as a flow rate.

Further, in the above embodiments, the gas flow rate is used as the state of the fuel gas and the reformed gas, but the gas pressure may be used instead of the gas flow rate. In this case, the flow rate sensor in FIGS. 1, 4 and 5 is replaced with a pressure sensor, the response calculation unit 39 (47) calculates the pressure response, and the horizontal axis of the map in FIG. 3 is used as the time constant of the pressure change. .

Further, a pressure sensor is added to the flow rate sensor in FIGS. 1, 4 and 5, and in the response calculation section 39 (47), as shown in FIG. 3, for each combination of the pressure on the input side and the pressure on the output side. It may be configured to have a map.

It should be noted that the flow rate or pressure may be indirectly estimated by detecting a value having a correlation therewith without directly detecting the flow rate or pressure.

Further, even if the reaction amount estimating means of the present invention is not always used, a simple estimating means as mentioned in the prior art is usually used, and sometimes the reaction amount estimating means of the present invention is used for correction. It may be configured.

[Brief description of drawings]

FIG. 1 is a first embodiment of a reaction estimating device for a fuel reformer according to the present invention.
3 is a configuration diagram of a fuel cell system to which the embodiment of FIG.

FIG. 2 is a diagram showing a response characteristic of a reformed gas flow rate with respect to a fuel gas flow rate in the first embodiment.

FIG. 3 is a diagram showing a relationship between a time constant showing a response characteristic and a hydrogen content ratio in a reformed gas.

FIG. 4 is a second reaction estimating device for a fuel reformer according to the present invention.
3 is a configuration diagram of a fuel cell system to which the embodiment of FIG.

FIG. 5 is a third view of the reaction estimation device of the fuel reformer according to the present invention.
3 is a configuration diagram of a fuel cell system to which the embodiment of FIG.

FIG. 6 is a diagram showing a relationship between a molecular weight of gas and response characteristics.

[Explanation of symbols]

1 ... Fuel reformer 3 ... mixer 5 ... Reforming reactor 7 ... Shift reactor 9 ... Selective oxidation reactor 11 ... Fuel cell stack 13 ... Combustor 15 ... Evaporator 17 ... Reaction estimation device 19 ... Controller 21 ... Power control device 23 ... Drive motor 25 ... Battery 31, 33 ... Flow rate sensor 35, 37 ... Storage unit 39 ... Response calculation unit 41 ... Reaction amount estimation unit

Claims (3)

[Claims] 1. A fuel gas in which a raw fuel gas and a reforming gas that reacts with the raw fuel gas to generate hydrogen are mixed is supplied, and the fuel gas is reformed into a hydrogen-rich reformed gas. A reaction estimation device of a fuel reformer for estimating a reforming reaction of a fuel reformer, which is installed at an inlet of a reforming reactor in which a catalyst is arranged, and detects at least one of a flow rate and a pressure of fuel gas. A fuel gas state detection unit, a reformed gas state detection unit installed at the outlet of the reforming reactor for detecting at least one of the flow rate and pressure of the reformed gas, the detected fuel gas state, and the detected fuel gas state. Response calculation means for obtaining a response characteristic of the change of the reformed gas state with respect to the change of the fuel gas state from the reformed gas state, and reforming amount estimation means for obtaining the reformed amount of the fuel gas based on the response characteristic. Is characterized by Response estimation apparatus charge reformer. 2. A first storage means for storing the detected fuel gas state as a first temporary series signal, and a second storage means for storing the detected reformed gas state as a second time series signal. 2. The reaction estimation device for a fuel reformer according to claim 1, wherein the response calculation unit is a response calculation unit that obtains a response characteristic of the second time series signal with respect to the first temporary series signal. 3. An operating state determination means for determining whether or not the operating state of the fuel reformer is a steady state, and a flow rate of the fuel gas when the operating state determination means determines the steady state. And an operating state changing means for changing the fuel cell flow rate, and estimating the reforming amount based on the response characteristic of the change in the reformed gas state when the flow rate of the fuel gas is changed from the steady state. The reaction estimation device for a fuel reformer according to claim 1 or 2.