WO2019176638A1 - Fuel cell system - Google Patents

Abstract

A fuel cell system (1), provided with: a fuel cell body (2), which generates power by means of a reaction between an oxidant gas fed to a cathode (22) and a fuel gas fed to an anode (21); a reformer (3), which reforms a raw fuel gas and generates the fuel gas; a gas feeding channel (11) for channeling the raw fuel gas fed to the reformer (3); a circulation channel (4) for connecting the gas feeding channel (11) and a gas discharge channel (12) channeling an anode off-gas; an ejector (5) for suctioning the anode off-gas from the circulation channel (4) using the raw fuel gas as a drive flow, and causing the anode off-gas to circulate in the gas feeding channel (11); and a flow rate adjustment unit (6) for adjusting the flow rate of a drive gas, which includes at least some of the raw fuel gas fed from a feeding source (10) of the raw fuel gas to the gas feeding channel (11), and which passes through the ejector (5) and forms a drive flow.

Description

Fuel cell system Cross-reference of related applications

This application is based on Patent Application No. 2018-045914 filed on March 13, 2018, the contents of which are incorporated herein by reference.

This disclosure relates to a fuel cell system.

The fuel cell system includes a fuel cell body that generates electricity by an electrochemical reaction between a fuel gas supplied to an anode and an oxidant gas supplied to a cathode, and steam reforming the raw fuel gas containing hydrocarbon fuel to produce hydrogen. A reformer that generates a fuel gas containing Since the anode off gas discharged from the fuel cell main body contains unused hydrogen fuel, in order to reuse this, for example, a fuel recycling technique for circulating using an ejector is known.

In Patent Document 1, in a fuel cell system using a solid oxide fuel cell (ie, SOFC), an ejector is provided in a fuel gas supply line from a reformer to an SOFC. There has been proposed a system in which an ejector is driven by fuel gas emitted from a mass device, and anode off-gas is recirculated from the suction portion of the ejector to the SOFC. The anode off gas is sucked into the ejector via a circulation line provided with a cooler and a condenser, for example, and the separated water is heated and supplied to the reformer.

JP 2015-43263 A

In the fuel cell system of Patent Document 1, the reformed fuel gas whose total material amount is larger than that of the raw fuel gas is used as the driving flow, so that the volume flow rate of the driving flow is increased to increase the flow velocity, and more anodes are provided. The off-gas can be sucked to increase the fuel circulation rate.

This system is configured so that the total amount of reformed gas with an increased total amount of material always passes through the ejector. Therefore, for example, even when the required power generation output is low and the load is low, the anode off-gas is supplied at a high circulation rate. Will suck. In that case, the power of the blower that is driven to feed the raw fuel gas into the ejector becomes relatively large with respect to the power generation output, and the power generation efficiency, that is, the ratio of the power that can be supplied to the outside may rather decrease. There is.

The purpose of the present disclosure is to make it possible to adjust the circulation rate of the anode off-gas sucked by the drive flow passing through the ejector, and to reduce the electric power necessary for forming the drive flow according to the power generation output, etc. It is an object of the present invention to provide a fuel cell system that can be used.

One aspect of the present disclosure is:
A fuel cell body that generates electricity by an electrochemical reaction between a fuel gas supplied to the anode and an oxidant gas supplied to the cathode;
A reformer that reforms the raw fuel gas to produce the fuel gas;
A gas supply passage through which the raw fuel gas supplied to the reformer flows;
A gas discharge passage through which anode off-gas discharged from the anode flows;
A circulation flow path connecting the gas discharge flow path and the gas supply flow path;
An ejector that draws the anode off-gas from the circulation flow path using the raw fuel gas as a driving flow and circulates the gas to the gas supply flow path;
A flow rate adjusting unit that adjusts the flow rate of the driving gas that forms at least a part of the raw fuel gas supplied from the raw fuel gas supply source to the gas supply flow path and passes through the ejector to form the driving flow; The fuel cell system includes:

In the above configuration, for example, when the power generation output is small, the flow rate adjusting unit reduces the flow rate of the drive gas supplied to the ejector out of the raw fuel gas, and the circulation flow rate of the anode off gas sucked by the drive flow ejected from the ejector Make it smaller. Thereby, power, such as a blower which sends drive gas to an ejector, can be reduced and power consumption can be suppressed. On the other hand, when the power generation output is large, the flow rate adjusting unit can increase the flow rate of the driving gas in the ejector, increase the circulation flow rate of the anode off gas, and increase the fuel reuse rate.

As described above, according to the above aspect, the circulation rate of the anode off-gas sucked by the drive flow passing through the ejector can be adjusted, and the electric power necessary for forming the drive flow can be reduced according to the power generation output, etc. A fuel cell system capable of performing efficient power generation can be provided.

The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
FIG. 1 is a schematic diagram showing the overall configuration of a fuel cell system in Embodiment 1. FIG. 2 is a schematic diagram illustrating the main configuration of the fuel cell system according to Embodiment 1. FIG. 3 is a schematic diagram showing the main configuration of the fuel cell system in Embodiment 1. FIG. 4 is an explanatory diagram of the relationship between load and power generation efficiency in a conventional fuel cell system, FIG. 5 is a diagram illustrating the relationship between the power generation output of the fuel cell system and the circulation rate of the anode off gas in the first embodiment. FIG. 6 is a flowchart executed in the control unit of the flow rate adjustment unit of the fuel cell system in the first embodiment. FIG. 7 is a diagram showing the relationship between the blower power and the flow rate and pressure of raw fuel gas in the first embodiment. FIG. 8 is an explanatory diagram showing the relationship between the circulation flow rate of the anode off gas and the fuel utilization rate of the fuel cell system and the blower operating voltage in the first embodiment. FIG. 9 is a time chart showing the process by the flow rate adjustment unit of the fuel cell system and the time variation of the power generation output and the blower power in Embodiment 1. FIG. 10 is a diagram showing the relationship between the flow rate of raw fuel gas, the fuel concentration, and the fuel flow rate in the ejector of the fuel cell system in the first embodiment. FIG. 11 is an overall schematic configuration diagram of a fuel cell system in Embodiment 2, FIG. 12 is an overall schematic configuration diagram of a fuel cell system in Embodiment 3, FIG. 13 is a time chart showing the process by the flow rate adjustment unit of the fuel cell system and the time variation of the power generation output and the blower power in Embodiment 3. FIG. 14 is an overall schematic configuration diagram of a fuel cell system in Embodiment 4, FIG. 15 is an overall schematic configuration diagram of a fuel cell system in Embodiment 5, FIG. 16 is a flowchart executed in the control unit of the flow rate adjustment unit of the fuel cell system in Embodiment 5, FIG. 17 is an overall schematic configuration diagram of a fuel cell system according to Embodiment 6, FIG. 18 is a flowchart executed in the control unit of the flow rate adjustment unit of the fuel cell system according to the sixth embodiment.

(Embodiment 1)
A first embodiment of the fuel cell system will be described with reference to the drawings.
As shown in FIG. 1, the fuel cell system 1 of the present embodiment includes a fuel cell main body 2 including an anode 21 and a cathode 22, a reformer 3 that generates fuel gas, and a gas supply channel to the reformer 3. 11, a gas discharge passage 12 through which the anode off-gas flows, a circulation passage 4, an ejector 5, and a flow rate adjustment unit 6. The circulation channel 4 connects the gas discharge channel 12 and the gas supply channel 11, and the ejector 5 sucks the anode off-gas from the circulation channel 4 and circulates it to the gas supply channel 11. The fuel cell system 1 is applied to, for example, a power generation system in a fuel cell vehicle or the like, and supplies power to a load such as a motor or a vehicle auxiliary machine that drives the vehicle.

The fuel cell main body 2 has an anode 21 and a cathode 22, and generates power by an electrochemical reaction between a fuel gas supplied to the anode 21 and an oxidant gas supplied to the cathode 22. The fuel cell body 2 is, for example, a solid oxide fuel cell (that is, SOFC), and may be configured as a known cell stack in which a plurality of single cells each having an anode 21 and a cathode 22 disposed on both sides of an electrolyte are stacked. it can. Illustration and description of the detailed configuration of the cell stack are omitted.

The reformer 3 reforms the raw fuel gas to generate fuel gas. A gas supply flow path 11 through which raw fuel gas flows is connected to the upstream side of the reformer 3, and raw fuel gas containing fuel and water (for example, water vapor) is supplied. The reformer 3 reacts the raw fuel gas with the reforming catalyst to generate a fuel gas containing hydrogen. The generated fuel gas is supplied to the anode 21 of the fuel cell main body 2 from the fuel gas flow path 16 connected to the downstream side of the reformer 3.

An oxidant gas flow path 23 for supplying an oxidant gas (for example, air) to the cathode 22 is connected to the upstream side of the cathode 22 of the fuel cell main body 2. The oxidant gas is supplied from the oxidant gas supply source 24 through the oxidant gas flow path 23 to the cathode 22 and causes a power generation reaction together with the fuel gas supplied from the fuel gas flow path 16 to the anode 21. The electric power generated by the fuel cell main body 2 is taken out of the system through a power line (not shown) and used.

A gas discharge passage 12 through which the anode off-gas discharged from the anode 21 flows is connected to the downstream side of the anode 21 of the fuel cell main body 2. A combustor 31 is connected downstream of the gas discharge passage 12 to burn the remaining fuel gas contained in the anode off-gas flowing into the combustor 31. Combustion heat generated in the combustor 31 is used for heating the reformer 3 through a path (not shown), or is introduced into the heat exchanger 25 provided in the oxidant gas flow path 23 to be heat with the oxidant. Used for exchange. One end of the circulation channel 4 is connected to the middle of the gas discharge channel 12, and a part of the anode off gas flows in. The other end of the circulation channel 4 is connected to a gas supply channel 11 via an ejector 5.

The upstream end of the gas supply flow path 11 is connected to the ejector 5, and the raw fuel gas supply source 10 as the supply source arranged on the upstream side of the ejector 5 is passed through the ejector 5 or not. In addition, the raw fuel gas is supplied to the gas supply passage 11. As will be described in detail later, the ejector 5 is configured such that the raw fuel gas passing through the ejector forms a driving flow, sucks the anode off gas from the circulation channel 4, and circulates it to the gas supply channel 11. .

The driving gas that forms the driving flow through the ejector 5 includes at least a part of the raw fuel gas supplied from the raw fuel gas supply source 10. The flow rate of the driving gas can be adjusted by the flow rate adjusting unit 6, and is controlled to an optimal flow rate based on the information of each part of the system taken into the control unit 61.

Specifically, as shown in FIG. 2, the flow rate adjusting unit 6 connects the driving flow path 13 that connects the raw fuel gas supply source 10 and the ejector 5, and connects the driving flow path 13 and the gas supply flow path 11. And a flow rate adjusting valve 15 that adjusts the flow rate of the detour flow that flows through the detour channel 14. The flow rate adjusting valve 15 is, for example, an electric three-way valve having a flow rate adjusting function.

An electric blower 7 is provided between the raw fuel gas supply source 10 and the ejector 5. The raw fuel gas supply source 10 supplies a raw fuel gas containing fuel and water to the drive channel 13 using the blower 7. The bypass channel 14 is a branch channel that branches from the drive channel 13 and is connected to the gas supply channel 11, and supplies the raw fuel gas to the gas supply channel 11 without going through the ejector 5. The flow rate adjusting valve 15 is provided at a branch portion from the drive flow path 13 to the bypass flow path 14, and the drive is controlled by the control section 61.

The control unit 61 changes the flow rate of the bypass gas that branches to the bypass flow path 14 to form the bypass flow by changing the valve opening of the flow rate adjustment valve 15 and the flow rate of the drive gas that passes through the ejector 5. To change. Various information such as required power from a load (not shown), power generation output of the fuel cell main body 2 and power supplied to the blower 7 is input to the control unit 61, and the flow rate adjusting valve 15 is based on the information. By controlling the valve opening degree, it is possible to adjust the bypass gas and the driving gas to have desired flow rates.

As shown in FIG. 3, the ejector 5 includes a nozzle part 51, a suction part 52, a discharge part 53, and a case 54 in which these parts are accommodated. The case 54 has a substantially cylindrical shape, and the nozzle portion 51 is arranged in a double cylinder shape inside thereof. The nozzle portion 51 has an upstream end protruding from the case 54 serving as an inlet 511 communicating with the driving flow path 13 (see FIG. 1), and a portion located inside the case 54 is formed in a tapered shape so that an outlet at the downstream end is formed. A throttle channel that decreases in diameter toward the portion 512 is formed. As a result, the driving gas introduced into the nozzle portion 51 becomes a driving flow whose flow velocity increases toward the downstream end of the nozzle portion 51, and is ejected to the gas supply channel 11 communicating with the outlet portion 512.

The suction part 52 is formed in an annular space formed between the inner peripheral surface of the case 54 and the inner peripheral surface of the nozzle part 51 with an inlet 521 from the circulation channel 4 being opened. In the annular space serving as the suction portion 52, the end portion on the inlet portion 511 side of the nozzle portion 51 is closed, and an annular outlet portion 522 is formed outside the outlet portion 512 of the nozzle portion 51. An end portion of the outlet portion 522 of the suction portion 52 is formed in a tapered shape that is reduced in diameter toward the outlet portion 512. As a result, the anode off-gas is sucked from the inlet portion 521 of the circulation flow path 4 by the driving flow ejected to the gas supply flow path 11 and becomes a suction flow toward the outlet section 512.

The discharge part 53 is configured to include an outlet part 512 of the nozzle part 51 and an outlet part 522 of the suction part 52, and a mixed flow in which the driving flow and the suction flow are mixed at the joining part of the outlet parts 512 and 522. Is discharged into the fuel gas supply path 11.

The flow rate of the anode off-gas sucked from the circulation flow path 4 to the suction part 52 (hereinafter referred to as a circulation flow rate as appropriate) varies depending on the flow rate of the drive flow (hereinafter referred to as the drive flow rate as appropriate). At this time, as the drive flow rate increases, the circulation flow rate also increases (that is, the increase in the drive flow rate≈the increase in the circulation flow rate). Therefore, by changing the valve opening degree of the flow rate adjusting valve 15 to increase or decrease the drive flow rate. The circulation flow rate can be increased or decreased.

In this embodiment, the driving gas that forms the driving flow is the raw fuel gas supplied from the raw fuel gas supply source 10 and includes fuel and water (that is, H ₂ O). The fuel is, for example, city gas containing hydrocarbon fuel such as CH ₄ (ie, CnHm). The raw fuel gas discharged to the fuel gas supply path 11 is steam reformed in the reformer 3 to generate fuel gas.
The reaction in the reformer 3 is shown below (ie, Formula 1: steam reforming reaction; Formula 2: shift reaction).
Formula 1: CnHm + nH ₂ O → nCO + (m / 2 + n) H ₂
Formula 2: CO + H ₂ O → CO ₂ + H ₂

As a result, a fuel gas containing hydrogen (ie, H ₂ ), carbon dioxide (ie, CO ₂ ), and water (ie, H ₂ O) is supplied from the reformer 3 to the fuel cell body 2. In the fuel cell main body 2, H ₂ and CO are consumed by power generation. From the fuel cell main body 2, the anode off-gas containing the remaining H ₂ , CO, and H ₂ O that has not been consumed is discharged.
When the anode off gas is circulated to the fuel gas supply passage 11, the gas composition supplied to the reformer 3 changes according to the circulation flow rate.

Thus, by disposing the ejector 5 upstream of the reformer 3, the anode off-gas containing residual fuel can be sucked from the circulation flow path 4 and circulated to the gas supply flow path 11 for reuse. . At that time, of the raw fuel gas supplied to the reformer 3 by the flow rate adjusting unit 6, the driving gas passing through the ejector 5 from the driving flow path 13 is set to a desired flow rate, and the remainder is bypassed as a bypass gas. It can be branched to the path 14. Accordingly, it is possible to form a desired drive flow and increase or decrease the circulation flow rate from the circulation flow path 4. Accordingly, the power of the blower 7 for sending drive gas that increases or decreases the circulation flow rate to the ejector 5. Can be increased or decreased.

Therefore, for example, based on the power generation output that changes according to the demand from the load, the circulation flow rate can be adjusted to be optimal, and the power generation efficiency can be reduced by preventing the power of the blower 7 from becoming larger than necessary. It can be kept relatively high.

Here, the problem in the conventional system will be described with reference to FIG. When the load is high, the fuel required for power generation increases and the power generation output Q increases (that is, see the left figure in FIG. 4). On the other hand, when the load is low, the fuel required for power generation decreases and the power generation output Q also decreases (that is, FIG. 4 right figure). However, since the entire amount of the raw fuel gas is always supplied to the ejector 5, the drive power W of the blower 7 for supplying the raw fuel gas to the ejector 5 (hereinafter referred to as the blower power W as appropriate) is as follows. It remains relatively large even at low loads. This is because the amount of water supplied to the fuel is relatively large and the total amount of raw fuel gas is kept relatively large.
Therefore, when the load is low, the ratio of the blower power W to the power generation output Q increases, and the power that can be supplied to the user equipment outside the system excluding the blower power W from the power generation output Q (hereinafter referred to as supply power: Q− Since W) becomes smaller, the power generation efficiency (ie, QW / fuel) is lowered.

On the other hand, as shown in FIG. 5, when the flow rate adjustment unit 6 of this embodiment is provided, the drive power W of the blower 7 can be adjusted by adjusting the circulation rate of the anode off gas. Therefore, for example, when the power generation output is small, the circulation rate is reduced, and the raw fuel gas is diverted to the detour channel 14 to reduce the driving gas. As a result, the amount of pressure increase in the blower 7 can be reduced and standby power can be reduced, so that the blower power W with respect to the power generation output can be reduced, and the reduction in power generation efficiency can be suppressed. On the other hand, when the power generation output is large, the power generation efficiency can be further improved by increasing the circulation rate and supplying the raw fuel gas to the drive channel 13 to increase the drive gas.

In this way, the drive of the blower 7 can be adjusted by the flow rate adjusting unit 6 so that the blower power W does not become larger than necessary with respect to the power generation output. Preferably, the increase amount ΔQ of the power generation output Q as the power generation output change amount (hereinafter referred to as power generation output increase amount ΔQ) is the change amount ΔW of the blower power W as the blower power change amount (hereinafter referred to as the blower power increase amount ΔW). The raw fuel gas is supplied to the drive flow path 13 to increase the drive gas within a larger range (that is, ΔQ> ΔW). Thereby, a circulation rate can be enlarged and electric power generation efficiency can be improved.

An example of processing executed in the control unit 61 will be described using the flowchart shown in FIG. For example, this process starts up at a predetermined cycle and is repeatedly executed.
When this process is started, first, in step S1, a blower power increase amount ΔW that is a difference between the previous value and the current value of the blower power W is calculated. The blower power increase amount ΔW takes a positive value when it is in the increasing direction.

As shown in FIG. 7, the blower power W is generally correlated with the flow rate and pressure of the raw fuel gas passing through the blower 7, and the blower power W increases as the flow rate or pressure increases. Therefore, a map corresponding to the blower 7 to be used is stored in the control unit 61 in advance, and the current value of the blower power W is detected by comparing the flow rate and pressure of the raw fuel gas and comparing the previous value. The blower power increase amount ΔW can be calculated by using this.

Subsequently, in step S2, a power generation output increase amount ΔQ that is a difference between the previous value and the current value of the power generation output Q is calculated.
The power generation output Q is generally represented by the following formula 3.
Formula 3: Q = V × I
In Equation 3, V: operating voltage, I: current Here, the current I is a set value, and the operating voltage V is a parameter that varies depending on the temperature of the cell stack, the amount of fuel flowing through the cell stack, the composition, and the sweep current I. Become.

As shown in FIG. 8, generally, as the circulating flow rate increases, the fuel utilization rate decreases and the operating voltage V increases. Accordingly, the power generation output Q increases in proportion to the operating voltage V according to the above equation 3. Therefore, the relationship between the circulation flow rate or fuel utilization rate and the power generation output Q can be stored in advance in a map or the like, and the power generation output increase amount ΔQ can be calculated based on the increase amount of the circulation flow rate or fuel utilization rate. . At that time, correction or the like can be performed with reference to the map for the various parameters described above that affect the operating voltage V. For example, the cell stack temperature can be measured with a thermocouple. The amount and composition of fuel flowing through the cell stack can be mapped from the input fuel, the circulating flow rate, the amount of water, and the reforming rate (≈ reformer temperature).

As a method for calculating the circulation flow rate of the circulation channel 4, a flow meter for measuring the circulation flow rate can be arranged in the circulation channel 4. For example, a plurality of pressure gauges are arranged in the circulation channel 4. A method of calculating based on the pressure drop between any two points of the circulation flow path 4 can also be adopted. Alternatively, the circulation flow rate of the circulation channel 4 can be calculated based on the gas composition of the circulation channel 4. As shown in Equations 1 and 2, the reformer 3 is supplied with raw fuel gas containing, for example, CH ₄ as a fuel. When the circulation flow rate is increased, the gas type in Equations 1 and 2 is increased. Of these, the fact that the ratio of CO, CO ₂ and CH ₄ changes may be used.

In step S3, it is determined whether the power generation output increase amount ΔQ is larger than the blower power increase amount ΔW (that is, ΔQ> ΔW?). If a positive determination is made in step S3, the process proceeds to step S4. If a negative determination is made in step S3, the process proceeds to step S5.

In step S4, the valve opening degree of the flow rate adjusting valve 15 is changed so that the circulating flow rate increases. That is, the opening of the driving flow path 13 is increased to increase the amount of driving gas, while the opening of the bypass flow path 14 is decreased to decrease the amount of bypass gas that branches.

As a result, as shown in FIG. 9, when ΔQ> ΔW at time point A and time point B, a flow rate switching signal in the direction in which the circulation flow rate increases is output, and the flow rate of the drive flow path 13 increases. . At this time, the valve opening may be changed so that the change in the flow rate becomes a constant amount, but the degree of change in the flow rate ratio between the driving gas and the bypass gas is determined each time according to the difference between ΔQ and ΔW. May be. Thereby, for example, the valve opening can be changed so that the difference between ΔQ and ΔW becomes larger, which is desirable for improving the power generation efficiency.

On the other hand, in step S5, the valve opening degree of the flow rate adjusting valve 15 is changed so that the detour flow rate increases. That is, the bypass gas branched by increasing the opening of the bypass channel 14 is increased, while the drive gas is decreased by decreasing the opening of the drive channel 13.

When ΔQ ≦ ΔW is satisfied at time C shown in FIG. 9, a flow rate switching signal is output, and a flow rate switching signal in the direction in which the circulating flow rate increases is indicated (indicated by a dotted line in the figure). Thereby, since the flow volume of the drive flow path 13 reduces and the flow volume of the detour flow path 13 increases, the blower electric power W can be reduced. When there is no change in the blower power W and the power generation output Q (indicated by a solid line in the figure), the flow rate switching signal is not output.

As shown in FIG. 10, for example, if the driving flow rate is suddenly reduced based on the difference between ΔQ and ΔW when the load is suddenly reduced and the power generation output Q is greatly reduced, the passing flow rate passing through the fuel cell body 2 Decreases rapidly and the fuel concentration gradually increases. In this case, when the fuel flow rate represented by the passage flow rate x fuel concentration is suddenly reduced, the power generation output is greatly reduced. For example, the fuel flow threshold TH is set so that the power generation voltage does not fall below a predetermined lower limit value. It is preferable to set and adjust the circulation flow rate within a range that is equal to or greater than the threshold TH.

In step S4 and step S5, when the valve opening degree of the flow rate adjustment valve 15 is changed and the increase process is executed, this process is temporarily ended.
In this way, the circulation flow rate from the circulation channel 4 can be adjusted without changing the flow rates of the fuel and water supplied from the raw fuel gas supply source 10 to the gas supply channel 11.

(Embodiment 2)
Embodiment 2 according to the fuel cell system will be described with reference to FIG.
As shown in FIG. 11, the fuel cell system 1 of the present embodiment has the same basic configuration as that of the first embodiment, the fuel cell main body 2 including the anode 21 and the cathode 22, and the reforming that generates fuel gas. 3, a gas supply flow path 11 to the reformer 3, a gas discharge flow path 12 through which the anode off gas flows, a circulation flow path 4, an ejector 5, and a flow rate adjustment unit 6. The flow path configuration of the flow rate adjustment unit 6 is different from that of the first embodiment, and the following description will focus on the differences.
Of the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-described embodiments represent the same components as those in the above-described embodiments unless otherwise indicated.

The flow rate adjustment unit 6 includes a fuel supply source 10A and a water supply source 10B as supply sources, a drive flow path 13, a bypass flow path 14, and a flow rate adjustment valve 15, and a control unit 61 (not shown). Thus, the valve opening degree of the flow rate adjusting valve 15 can be adjusted. The drive flow path 13 connects the fuel supply source 10 </ b> A and the ejector 5 via the blower 7, and a water supply flow path 131 reaching the water supply source 10 </ b> B is connected downstream of the blower 7. The water supply channel 131 is provided with a water pump 132 and a bypass channel 14 branched from the downstream side of the water pump 132, and is connected to the gas supply channel 11.

The flow rate adjusting valve 15 is provided at a branch portion between the water supply flow path 131 and the bypass flow path 14, and branches into the water flow rate supplied from the water supply flow path 131 to the drive flow path 13 and the bypass flow path 14. Adjust the ratio of the water flow rate that forms a bypass flow. Here, the water delivered from the water pump 132 may be room temperature water, or may be water vapor by exchanging heat with part of the anode off-gas, for example.

In the above configuration, the water supplied from the water supply source 10B from the water supply channel 131 merges with the fuel supplied from the fuel supply source 10A to the drive channel 13 to become the raw fuel gas. This raw fuel gas becomes the driving gas as it is, and a driving flow passing through the ejector 5 is formed. In this embodiment, the controller 61 changes the valve opening of the flow rate adjustment valve 15 to adjust the flow rate of water that bypasses the water supply flow path 131 to the bypass flow path 14, and the drive flow rate that passes through the ejector 5. The circulation flow rate from the circulation channel 4 can be adjusted.

Even in this case, the same effect as in the first embodiment can be obtained. That is, according to the power generation output, the circulation flow rate from the circulation flow path 4 can be increased or decreased to prevent the blower power from increasing more than necessary, and efficient power generation can be performed. Further, in this embodiment, the flow rate adjustment valve 15 is arranged in the water supply flow path 131 and branched to the bypass flow path 14 upstream from joining the drive flow path 13, so that the flow rate adjustment valve 15 is made smaller. Can be reduced.

(Embodiment 3)
A third embodiment of the fuel cell system will be described with reference to FIGS.
As shown in FIG. 12, the fuel cell system 1 of the present embodiment has the same basic configuration as that of the first embodiment, and includes a fuel cell main body 2 including an anode 21 and a cathode 22, and reforming that generates fuel gas. 3, a gas supply flow path 11 to the reformer 3, a gas discharge flow path 12 through which the anode off gas flows, a circulation flow path 4, an ejector 5, and a flow rate adjustment unit 6. The flow path configuration of the flow rate adjustment unit 6 is different from that of the first embodiment, and the following description will focus on the differences.

The flow rate adjustment unit 6 includes a drive flow path 13 that connects the raw fuel gas supply source 10 and the ejector 5 via the blower 7, a gas introduction flow path 17, a flow rate adjustment valve 18, and a control unit 61 (not shown). . One end of the gas introduction channel 17 is connected to the fuel gas channel 16 on the downstream side of the reformer 3, and the other end is connected to the drive channel 13 on the upstream side of the blower 7. Are introduced into the drive channel 13 as an introduction gas. A flow rate adjustment valve 18 is arranged in the middle of the gas introduction flow path 17, and the flow rate of the introduced gas introduced into the drive flow path 13 can be adjusted by changing the valve opening degree. The flow rate adjustment valve 18 is, for example, an electric two-way valve, and the drive is controlled by the control unit 61.

In the above configuration, the raw fuel gas supplied from the raw fuel gas supply source 10 to the drive flow path 13 becomes the drive gas, and a drive flow passing through the ejector 5 is formed. Furthermore, the fuel gas from the gas introduction flow path 17 can be merged into the drive flow path 13 as the introduction gas, and the drive gas can be increased. In the first and second embodiments, the drive flow rate can be increased or decreased by increasing or decreasing the flow rate of the bypass gas that branches from the raw fuel gas. However, as in the present embodiment, the flow rate of the introduction gas that merges with the raw fuel gas is changed. The drive flow rate can also be increased or decreased by increasing or decreasing it.

Also in the present embodiment, the flow rate adjusting valve 18 can be driven by the controller 61 in the same manner as shown in FIG. In this case, as shown in FIG. 13, the opening degree of the flow rate adjusting valve 18 is adjusted in the range from fully closed to fully open, and accordingly, the passing flow rate of the flow rate adjusting valve 18 increases. For example, at time point D and time point E when ΔQ> ΔW, the opening degree of the flow rate adjustment valve 18 increases stepwise, and the drive flow rate increases.

On the other hand, when ΔQ ≦ ΔW at time point E, the opening degree of the flow rate adjustment valve 18 becomes smaller again. Thereby, since the flow volume of the drive flow path 13 decreases and the flow volume of the detour flow path 14 increases, the blower power W can be reduced.

The gas introduction channel 17 may be configured to be connected to the gas supply channel 11 on the upstream side of the reformer 3 instead of being connected to the fuel gas channel 16 on the downstream side of the reformer 3. . In this case, the gas introduced into the gas introduction channel 17 is the raw fuel gas supplied to the gas supply channel 11 or is circulated to the raw fuel gas through the ejector 5 to the gas supply channel 11. The mixed gas is the anode off gas.

As described above, even when the gas downstream of the ejector 5 is introduced into the raw fuel gas and the flow rate is adjusted by the flow rate adjusting valve 18, the same effect as in the first embodiment can be obtained. That is, according to the power generation output, the circulation flow rate from the circulation flow path 4 can be increased or decreased to prevent the blower power from increasing more than necessary, and efficient power generation can be performed. Further, in this embodiment, there is no need to provide a flow path switching means for flow rate adjustment, so that the configuration of the flow rate adjustment valve 18 can be simplified.

(Embodiment 4)
Embodiment 4 which concerns on a fuel cell system is demonstrated with reference to FIG.
As shown in FIG. 14, the fuel cell system 1 of the present embodiment has the same basic configuration as that of the fourth embodiment, the fuel cell main body 2 including the anode 21 and the cathode 22, and the reforming that generates fuel gas. 3, a gas supply flow path 11 to the reformer 3, a gas discharge flow path 12 through which the anode off gas flows, a circulation flow path 4, an ejector 5, and a flow rate adjustment unit 6. The flow path configuration of the flow rate adjusting unit 6 is different from that of the fourth embodiment, and the difference will be mainly described below.

The flow rate adjusting unit 6 of this embodiment has a fuel supply source 10A and a water supply source 10B as supply sources. Among these, the water supply source 10B is a gas downstream of the ejector 5 by a bypass channel 14. The supply channel 11 is connected. The detour channel 14 is provided with a water pump 132 and sends water at a predetermined flow rate from the water supply source 10 </ b> B to the gas supply channel 11.

The fuel supply source 10 </ b> A is connected to the drive flow path 13 through the blower 7 and the ejector 5. Further, the drive flow path 13 on the upstream side of the blower 7 and the fuel gas flow path 16 are connected by a gas introduction flow path 17 including a flow rate adjusting valve 18. The flow rate adjustment valve 18 can adjust the flow rate of the fuel gas as the introduction gas introduced into the drive flow path 13 by adjusting the valve opening degree by the control unit 61 (not shown).

In the above configuration, a driving flow passing through the ejector 5 is formed by the driving gas containing the fuel supplied from the fuel supply source 10A to the driving flow path 13. Furthermore, the fuel gas from the gas introduction channel 17 can be merged into the drive channel 13 as an introduction gas. As a result, the drive flow rate passing through the ejector 5 can be adjusted, and the circulation flow rate of the anode off gas sucked from the circulation flow path 4 can be adjusted. In the gas supply channel 11, the mixed gas of the drive gas and the anode off gas discharged from the ejector 5 is further mixed with water supplied from the water supply source 10 </ b> B via the bypass channel 14, and then the reformer. 3 is supplied.

In this way, a part of the fuel and water contained in the raw fuel gas, for example, all of the fuel is supplied to the drive flow path 13 to be the drive gas, and all of the water is downstream from the ejector 5 from the bypass flow path 14. Can also be introduced. Then, by adjusting the flow rate of the fuel gas introduced from the gas introduction flow path 17 into the driving gas, the circulation flow rate can be adjusted without changing the flow rates of the fuel and water as the raw fuel gas, and the above embodiment The same effect as 4 can be obtained. That is, according to the power generation output, the circulation flow rate from the circulation flow path 4 can be increased or decreased to prevent the blower power from increasing more than necessary, and efficient power generation can be performed. In addition, since it is not necessary to provide flow path switching means for flow rate adjustment, the configuration of the flow rate adjustment valve 18 can be simplified.

(Embodiment 5)
A fifth embodiment of the fuel cell system will be described with reference to FIGS. 15 and 16.
As shown in FIG. 15, the fuel cell system 1 of the present embodiment has the same basic configuration as that of the first embodiment, the fuel cell main body 2 including the anode 21 and the cathode 22, and the reforming that generates fuel gas. 3, a gas supply flow path 11 to the reformer 3, a gas discharge flow path 12 through which the anode off gas flows, a circulation flow path 4, an ejector 5, and a flow rate adjustment unit 6.

The flow rate adjusting unit 6 includes a drive flow path 13, a bypass flow path 14 (not shown), and a flow rate adjustment valve 15, and is configured to be able to circulate anode off gas from the circulation flow path 4 using the ejector 5. Further, the circulation flow rate measuring means 41 is provided in the circulation flow path 4, and the control unit 61 calculates the calculation result of the blower power increase amount ΔW and the power generation output increase amount ΔQ, and further determines the circulation flow rate by the circulation flow rate measurement means 41. The circulating flow rate is adjusted based on the measurement result.

The circulation flow rate measuring means 41 can be a flow meter for measuring the circulation flow rate in the circulation flow path 4 as described above. In that case, it is desirable to arrange a flow meter in consideration of heat resistance. Further, instead of directly measuring the circulation flow rate, a plurality of pressure gauges are arranged in the circulation flow path 4 to calculate based on the pressure drop between any two points of the circulation flow path 4, or the circulation flow path 4 The circulating flow rate measuring means 41 can also be configured so that the circulating flow rate of is calculated based on the gas composition of the circulating flow path 4.

An example of processing executed in the control unit 61 will be described using the flowchart shown in FIG. For example, this process starts up at a predetermined cycle and is repeatedly executed.
When this process is started, first, in step S11, the blower power increase amount ΔW, which is the difference between the previous value and the current value of the blower power W, is calculated. Then, in step S12, the previous value and the current value of the power generation output Q are calculated. The power generation output increase amount ΔQ, which is the difference between the two, is calculated.

In step S13, it is determined whether the power generation output increase amount ΔQ is larger than the blower power increase amount ΔW (that is, ΔQ> ΔW?). If a positive determination is made in step S13, the process proceeds to step S14. If a negative determination is made in step S13, the process proceeds to step S15.

In step S14, the valve opening degree of the flow rate adjusting valve 15 is changed so that the circulating flow rate increases. That is, the opening of the driving flow path 13 is increased to increase the amount of driving gas, while the opening of the bypass flow path 14 is decreased to decrease the amount of bypass gas that branches.

On the other hand, in step S15, the valve opening degree of the flow rate adjusting valve 15 is changed so that the detour flow rate increases. That is, the bypass gas branched by increasing the opening of the bypass channel 14 is increased, while the drive gas is decreased by decreasing the opening of the drive channel 13.

Steps S11 to S15 are the same as steps S1 to S5 in FIG. 6 described above, and details thereof are omitted. In step S14, when the valve opening degree of the flow rate adjustment valve 15 is changed and the increase process is executed, this process is temporarily terminated.

In step S15, when the opening degree of the flow rate adjustment valve 15 is changed and the increase processing is executed, the process proceeds to step S16. In step S16, the circulating flow rate measuring means 41 is used to measure the circulating flow rate and determine whether or not the circulating flow rate is equal to or less than zero (that is, circulating flow rate ≦ 0?).

As shown in FIG. 3, the ejector 5 sucks the anode off gas from the circulation flow path 4 as the driving gas introduced into the nozzle portion 51 is ejected as a driving flow. In that case, by adjusting the flow rate adjustment valve 15 in the direction in which the circulation flow rate decreases, when the flow velocity of the drive flow decreases, a reverse flow occurs in the circulation flow channel 4 and the drive gas burns without passing through the fuel cell body 2. There is a risk of being discharged to the vessel 31. In order to prevent this, it is desirable to determine whether the circulating flow rate is equal to or lower than zero, that is, whether a reverse flow has occurred, and readjust the valve opening degree of the flow rate adjusting valve 15 as necessary.

Therefore, if an affirmative determination is made in step S16, the process returns to step S14, and the valve opening degree of the flow rate adjusting valve 15 is changed so that the circulating flow rate increases. As a result, the circulation flow rate> 0, so that this process is temporarily terminated.

If the determination in step S16 is negative, it is determined that the circulation flow rate is> 0 and there is no possibility of backflow, and this processing is temporarily terminated without adjusting the flow rate.

Even in this case, the same effects as those of the first embodiment can be obtained, and furthermore, the fuel cell system can be made highly reliable by controlling so that the backflow in the circulation flow path 4 is prevented.

(Embodiment 6)
A fifth embodiment of the fuel cell system will be described with reference to FIGS.
As shown in FIG. 17, the fuel cell system 1 of the present embodiment has the same basic configuration as that of the first embodiment, the fuel cell main body 2 including the anode 21 and the cathode 22, and the reforming that generates fuel gas. 3, a gas supply flow path 11 to the reformer 3, a gas discharge flow path 12 through which the anode off gas flows, a circulation flow path 4, an ejector 5, and a flow rate adjustment unit 6.

The flow rate adjusting unit 6 includes a drive flow path 13, a bypass flow path 14 (not shown), and a flow rate adjustment valve 15, and is configured to be able to circulate anode off gas from the circulation flow path 4 using the ejector 5. Moreover, it has the pressure detection means 62 for detecting a blower pressure, and the control part 61 is further using the calculation result of blower electric power increase amount (DELTA) W and electric power generation output increase amount (DELTA) Q, and also the detection result of the pressure detection means 62. Based on this, the circulation flow rate is adjusted.

The pressure detection means 62 can be, for example, a pressure gauge disposed in the drive flow path 13. As the flow rate of the drive gas introduced from the drive flow path 13 into the ejector 5 increases, the load applied to the blower 7 increases. Therefore, in order to prevent the blower 7 from being damaged, it is possible to detect the pressure of the driving gas passing through the nozzle portion 51 of the ejector 5 as the blower pressure and adjust the flow rate so that the detection result does not exceed a predetermined value. desirable.

An example of processing executed in the control unit 61 will be described using the flowchart shown in FIG. For example, this process starts up at a predetermined cycle and is repeatedly executed.
When this process is started, first, in step S21, a blower power increase amount ΔW, which is the difference between the previous value and the current value of the blower power W, is calculated. Then, in step S22, the previous value and the current value of the power generation output Q are calculated. The power generation output increase amount ΔQ, which is the difference between the two, is calculated.

In step S23, it is determined whether the power generation output increase amount ΔQ is larger than the blower power increase amount ΔW (that is, ΔQ> ΔW?). If a positive determination is made in step S23, the process proceeds to step S24. If a negative determination is made in step S23, the process proceeds to step S26.

In step S24, the pressure of the drive channel 13 is detected as the blower pressure using the pressure detection means 62, and the blower pressure is compared with a preset pressure threshold value. The pressure threshold value can be appropriately set according to the blower 7 to be used.

Therefore, in step S24, it is determined whether or not the blower pressure is less than the pressure threshold (that is, blower pressure <pressure threshold?). If an affirmative determination is made in step S24, it is determined that the blower pressure is within the allowable range, the process proceeds to step S25, and the valve opening degree of the flow rate adjustment valve 15 is changed so that the circulation flow rate increases. That is, the opening of the driving flow path 13 is increased to increase the amount of driving gas, while the opening of the bypass flow path 14 is decreased to decrease the amount of bypass gas that branches.

If a negative determination is made in step S24, it is determined that the blower pressure may exceed the allowable range as it is, and the present process is temporarily terminated without performing the flow rate adjustment.

When a negative determination is made in step S23 and the process proceeds to step S26, the valve opening of the flow rate adjustment valve 15 is changed so that the detour flow rate increases. That is, the bypass gas branched by increasing the opening of the bypass channel 14 is increased, while the drive gas is decreased by decreasing the opening of the drive channel 13.

Steps S21 to S23 and S25 to S26 are the same as steps S1 to S5 in FIG. 6 described above, and details thereof are omitted.
In step S25 and step S26, when the opening degree of the flow rate adjustment valve 15 is changed and the increase process is executed, this process is temporarily ended.

Even if it does in this way, the effect similar to the said Embodiment 1 is acquired, and it can control so that the pressure added to the blower 7 may not exceed a pressure threshold value, and it can be set as a reliable fuel cell system.
The processing described in the fifth and sixth embodiments can also be applied to the configurations of the second to fourth embodiments.

The present disclosure is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the disclosure. For example, the fuel cell system can be applied not only to a fuel cell vehicle but also to various industrial and household power generation systems.

Claims (13)

1. A fuel cell body (2) for generating electric power by an electrochemical reaction between a fuel gas supplied to the anode (21) and an oxidant gas supplied to the cathode (22);
   A reformer (3) for reforming raw fuel gas to generate the fuel gas;
   A gas supply channel (11) through which the raw fuel gas supplied to the reformer flows;
   A gas discharge passage (12) through which the anode off-gas discharged from the anode flows;
   A circulation channel (4) connecting the gas discharge channel and the gas supply channel;
   An ejector (5) for sucking the anode off-gas from the circulation flow path using the raw fuel gas as a driving flow and circulating it to the gas supply flow path;
   The flow rate of the driving gas that forms at least one portion of the raw fuel gas supplied from the raw fuel gas supply source (10, 10A, 10B) to the gas supply flow path and forms the driving flow through the ejector. A fuel cell system (1), comprising a flow rate adjustment unit (6) for adjusting the flow rate.
2. The flow rate adjusting unit includes a drive channel (13) that connects the supply source and the ejector, a bypass channel (14) that connects the drive channel and the gas supply channel, and the bypass channel. The fuel cell system according to claim 1, further comprising: a flow rate adjustment valve (15) for adjusting a flow rate of the detour flow that flows through the fuel cell.
3. The raw fuel gas contains fuel and water, the drive flow path is connected to a raw fuel gas supply source (10) as the supply source, and the bypass flow path is branched from the drive flow path. The fuel cell system according to claim 2, wherein the fuel cell system is connected to the gas supply channel.
4. The raw fuel gas contains fuel and water, and the drive channel is connected to a fuel supply source (10A) and a water supply source (10B) as the supply source, and the bypass channel is connected to the water supply source. The fuel cell system according to claim 2, wherein the fuel cell system is branched from a flow path connecting a source and the drive flow path and connected to the gas supply flow path.
5. The fuel cell system according to claim 3 or 4, wherein the flow rate adjusting valve is provided at a branch portion to the bypass flow path.
6. The flow rate adjusting unit includes a drive channel (13) connecting the supply source and the ejector, and the raw fuel gas flowing through the gas supply channel to the drive channel or a fuel gas downstream of the reformer. The gas introduction flow path (17) which introduces the said fuel gas which flows through a flow path (16), and the flow regulating valve (18) which adjusts the flow volume of the introduction gas which flows through the said gas introduction flow path are provided. The fuel cell system described in 1.
7. The raw fuel gas contains fuel and water, and the drive channel is connected to a fuel supply source (10A) as the supply source, and the water supply source (10B) as the supply source and the gas supply flow. The fuel cell system according to claim 6, further comprising a bypass channel (14) connecting the channel.
8. A blower (7) that is provided between the supply source and the ejector and feeds the driving gas into the nozzle portion (51) of the ejector;
   The flow rate adjustment unit detects a power generation output change amount (ΔQ) and a blower power change amount (ΔW) of the fuel cell main body, and a difference (ΔQ−) between the power generation output change amount and the blower power change amount. The fuel cell system according to any one of claims 1 to 7, further comprising a control unit (61) for adjusting a flow rate of the driving gas so that ΔW) becomes larger.
9. The fuel cell system according to claim 8, wherein the control unit adjusts the flow rate of the driving gas so that the circulation flow rate passing through the circulation flow path maintains a circulation flow rate> 0.
10. 10. The fuel cell system according to claim 8 or 9, wherein the control unit adjusts the flow rate of the driving gas so that the pressure of the driving gas passing through the nozzle unit does not exceed a pressure threshold value.
11. 11. The fuel cell system according to claim 8, wherein the control unit calculates the power generation output change amount based on a flow rate of the circulation flow path.
12. 12. The fuel cell system according to claim 11, wherein the control unit calculates the flow rate of the circulation channel based on a pressure drop between any two points of the circulation channel or a gas composition of the circulation channel.
13. The fuel cell system according to any one of claims 8 to 12, wherein the control unit calculates the blower power change amount based on a flow rate and a pressure of a gas passing through the blower.

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