JPH10223244A - Fuel cell electricity generating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably carry out flow rate control for a raw fuel gas to be supplied to a steam reforming apparatus following abrupt electricity output fluctuation, even when the electricity output of a fuel cell is abruptly changed. SOLUTION: In a fuel cell type electricity generating apparatus in which a raw fuel gas is reformed into a hydrogen enriched fuel gas by a desulfurization apparatus 5 and a steam-reforming apparatus 2 and the resultant fuel gas is supplied to a fuel electrode of a fuel cell 1 to generate electricity, an ejector pump 6 is inserted in the rear stage of the desulfurization apparatus in a raw fuel gas supplying route, and a raw fuel gas is sucked, mixed with steam, and supplied to the reforming apparatus, while steam being used as a driving fluid. In this case, the output pressure of the desulfurization apparatus is kept at a set value by connecting a pressure control valve 14 between the raw fuel gas suction inlet of the ejector pump and the output of the desulfurization apparatus, so that excessive suction of the raw fuel gas from the container of the desulfurization apparatus to the elector pump can be prevented at the time, when the output of the fuel cell is abruptly fluctuated and a reverse flow of steam can be avoided. The pressure set value of the pressure control valve is made variable, corresponding to the output fluctuation of the fuel cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses natural gas as raw fuel, reforms the raw fuel gas into a hydrogen-rich fuel gas through a desulfurizer and a steam reformer, and converts the fuel gas into a fuel cell. The present invention relates to a fuel cell power generation device that supplies power to a fuel electrode and generates power, and more particularly to a supply control system for the raw fuel gas.

[0002]

2. Description of the Related Art As is well known, reforming a raw fuel gas into a hydrogen-rich fuel gas to be supplied to a fuel cell (phosphoric acid type fuel cell) using natural gas equivalent to city gas as a raw fuel generally involves the following steps. A steam reforming method is employed. In this case, in order to protect the reforming catalyst from being poisoned by the sulfur component, a desulfurizer is connected to the raw fuel supply passage, and the sulfur component contained in the raw fuel gas is removed as a pretreatment in the steam reforming step. They are removed by a desulfurizer. As a means for mixing the desulfurized raw fuel gas with water vapor and sending it to a reformer at a later stage, an ejector pump which does not require power and is maintenance-free is generally employed.

[0003] FIG. 3 shows a desulfurizer,
FIG. 2 is a system flow diagram of a fuel cell device incorporating an ejector pump. In the figure, 1 is a fuel cell, 2 is a steam reformer, 3 is a raw fuel gas supply source (city gas), 4 is a steam supply source (steam generator), 5 is a desulfurizer, and 6 is steam as a driving fluid. Ejector pumps for sucking the raw fuel gas, mixing it with steam, and sending it to the reformer 2 at the subsequent stage. Numerals 7 and 8 are flow rate control valves connected to the raw fuel gas supply passage and the steam supply passage. Make up the system. On the other hand, the DC output of the fuel cell 1 is converted into AC power by the inverter 9 and supplied to the load 11 via the power system 10.

Further, since the consumption of fuel gas in the fuel cell 1 is proportional to the electric output, a predetermined steam ratio (a mixing ratio of raw fuel gas and steam, and a thermodynamic equilibrium in steam reforming, The output of the inverter 9 is controlled to increase or decrease the supply amount of the raw fuel gas in accordance with the output fluctuation of the fuel cell 1 while maintaining the range of 2 to 5 from conditions such as the properties of the catalyst. (Output current detector) 1 on the side
2 and controller 1 based on the output signal obtained at CT12.
3 controls the flow control valves 7 and 8 connected to the raw fuel gas and steam supply paths. here,
The controller 13 calculates a set value of the flow rate of the raw fuel gas corresponding to the battery output at that time based on the detected value of the CT 12, and the detected value of the flow meter attached to the flow control valves 7, 8 is the same as the flow set value. The valve opening is controlled so as to match.

With this configuration, when the fuel cell 1 is operated, steam is supplied from the steam supply source 4 (the steam source pressure of the steam generator is constant) to the nozzle of the ejector pump 6 through the flow control valve 8 using steam as a driving fluid. The raw fuel gas supplied from the raw fuel gas supply source 3 via the flow control valve 7 and the desulfurizer 5 is sucked into the ejector pump 6, mixed with steam in the pump, and sent to the reformer 2 at the subsequent stage. Here, the fuel gas reformed into a hydrogen-rich gas is supplied to the fuel electrode of the fuel cell 1 to generate power.

Next, the structure of the ejector pump 6 is shown in FIG. That is, the ejector pump 6 is connected to a nozzle 6a for ejecting water vapor as a driving fluid, a suction chamber 6b surrounding the nozzle 6a, a raw fuel gas suction port 6c opened to the suction chamber 6b, and a rear portion of the suction chamber 6b. It is composed of a throat section 6d and a diffuser section 6e. The operating characteristics of the ejector pump 6 having such a structure are well known, and the work amount of the driving fluid ejected from the nozzle 6a is proportional to the square of the ejection speed. If the inlet pressure (steam pressure) of the nozzle 6a is constant, the ejection speed from the nozzle 6a increases as the steam flow rate supplied to the ejector pump 6 increases, and the pressure of the suction chamber 6b in front of the nozzle, that is, the raw fuel The pressure at the gas inlet 6c decreases, and the ability to suck the raw fuel gas into the pump increases. Conversely, when the supply amount of water vapor is reduced, the speed of jetting water vapor from the nozzle 6a is reduced, so that the pressure drop of the raw fuel gas suction port 6c is reduced, and the raw fuel gas suction capability is reduced.

Therefore, by controlling the flow control valves 7 and 8 in accordance with the output fluctuation of the fuel cell 1 as described with reference to FIG. 3 in addition to the operating characteristics of the ejector pump 6, the output of the fuel cell 1 That is, the amount of raw fuel gas corresponding to the amount of fuel gas consumed by the battery can be mixed with steam by the ejector pump 6 and supplied to the reformer 2.

[0008]

However, with the conventional configuration described above, when the electric output of the fuel cell fluctuates rapidly, the following problems arise in terms of the control of the supply of the raw fuel gas. I do. That is, when the electric output of the fuel cell 1 fluctuates rapidly with the increase or decrease of the power load 11 connected to the power supply system 10, the flow control valves 7, 8 respond almost in response to a command from the controller 13 based on the output fluctuation. Operate without delay. As a result, in the ejector pump 6, the flow rate and the speed of the steam ejected from the nozzle 6a greatly change, and accordingly, the pressure of the raw fuel gas suction port of the ejector pump 6 also changes. As shown in FIG. 3, a desulfurizer 5 having a large internal volume is interposed in the raw fuel gas supply path, and the container of the desulfurizer 5 acts as a buffer tank, which causes disturbance. As a result, a response delay occurs in the control system of the raw fuel gas supply, which causes a transient excess or deficiency in the raw fuel gas supply amount or a change in the steam ratio of the raw fuel gas supplied to the reformer 2. In addition to deviating from the allowable range, depending on the situation, there is a possibility that the steam may flow back to the raw fuel gas supply path side via the ejector pump 6.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to solve the above-mentioned problems and to control the flow rate of a raw fuel gas even when the electric output of a fuel cell changes rapidly. To provide a fuel cell power generator that can stably perform the above.

[0010]

According to the present invention, in order to achieve the above object, a raw fuel gas is reformed into a hydrogen-rich fuel gas through a desulfurizer and a steam reformer, and then the fuel gas is reformed. A fuel cell power generator that generates gas by supplying gas to the fuel electrode of the fuel cell. An ejector pump is inserted after the desulfurizer in the raw fuel gas supply path, the raw fuel gas is sucked using steam as the driving fluid, and mixed with the steam. In addition to supplying the raw fuel gas to the reformer, a flow control valve is connected to the raw fuel gas supply path and the water vapor supply path, so that the supply flow rate of the raw fuel gas and water vapor is increased or decreased in accordance with the output fluctuation of the fuel cell. In what
A pressure control valve is connected between the raw fuel gas suction port of the ejector pump and the outlet of the desulfurizer, and the outlet pressure of the desulfurizer is maintained at a predetermined pressure. It is set variably according to the output fluctuation of the battery.

In the above, the pressure control valve is a pressure control valve that functions to keep the outlet pressure of the desulfurizer connected to the ejector pump at a set pressure even when the pressure in the suction chamber of the ejector pump fluctuates rapidly. Thus, even when the supply amount of steam, which is the driving fluid for the ejector pump, changes rapidly due to the rapid output fluctuation of the fuel cell, the desulfurizer does not act as a buffer tank, but remains in the container of the desulfurizer. In addition to preventing the raw fuel gas from flowing out to the ejector pump more than necessary, and conversely, the steam from flowing back from the ejector pump to the desulfurizer side, it is possible to prevent troubles. Similarly, by variably setting the pressure set value of the pressure control valve in accordance with the output fluctuation of the fuel cell, it becomes possible to quickly control the supply of the raw fuel gas by feedforward control, and to control the supply of the raw fuel gas to the reformer. While maintaining the water vapor ratio of the fuel gas, the supply of the raw fuel gas can be controlled without excess or shortage in response to the output fluctuation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the drawings of the embodiment, the same members corresponding to FIG. 3 are denoted by the same reference numerals. That is, although FIG. 1 is basically the same as the configuration of FIG. 3, according to the present invention, a raw fuel gas suction port of an ejector pump 6 for supplying raw fuel gas using steam as a driving fluid, and a raw fuel gas connected thereto. A pressure control valve 14 is additionally provided between the fuel gas desulfurizer 5 and the fuel gas desulfurizer 5. The pressure control valve 14 has a function of operating to maintain the pressure on the primary side (outlet side of the desulfurizer) of the valve at a constant value (a pressure set value). The pressure set value is the same as that of the flow control valves 7 and 8. The calculation is performed by the controller 13 and variably set in accordance with the electric output of the fuel cell 1.

[0013]

As described above, according to the present invention, the desulfurizer is provided in the raw fuel gas supply path, and the raw fuel gas is sucked using steam as a driving fluid, mixed with the steam and supplied to the reformer in the subsequent stage. In a fuel cell power plant equipped with an ejector pump that performs a rapid change in the fuel cell by connecting a pressure control valve between the ejector pump and the desulfurizer to maintain the outlet pressure of the desulfurizer at a set value. Even when the pressure of the raw fuel gas suction port in the raw fuel gas supply ejector pump changes rapidly due to the output fluctuation, the flow rate control of the raw fuel gas can be performed stably.

Further, the pressure set value of the pressure control valve is variably set in accordance with the output fluctuation of the fuel cell, so that the feedforward control enables quick control of the supply of the raw fuel gas. While maintaining the steam ratio of the raw fuel gas supplied to the reformer, the raw fuel gas can be supplied and controlled without excess or shortage in response to the output fluctuation of the fuel cell, and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a system flow diagram of a fuel cell power generator showing a raw fuel gas supply system and a control system according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of the ejector pump shown in FIG.

FIG. 3 is a system flow diagram of a conventional fuel cell power generator.

[Explanation of symbols]

 Reference Signs List 1 fuel cell 2 steam reformer 5 desulfurizer 6 ejector pump 7, 8 flow control valve 12 CT (output current detector of fuel cell) 13 controller 14 pressure control valve

Claims (2)

[Claims] 1. A fuel cell power generator which reforms a raw fuel gas into a hydrogen-rich fuel gas through a desulfurizer and a steam reformer, and supplies the fuel gas to a fuel electrode of a fuel cell to generate power. Yes, an ejector pump is inserted after the desulfurizer in the raw fuel gas supply path, the raw fuel gas is sucked using steam as the driving fluid, mixed with the steam, and supplied to the reformer.
A flow control valve is connected to a raw fuel gas supply passage and a water vapor supply passage to control the supply flow rate of the raw fuel gas and water vapor in accordance with the output fluctuation of the fuel cell. A fuel cell power generator, wherein a pressure control valve is connected between a gas inlet and an outlet of a desulfurizer, and an outlet pressure of the desulfurizer is maintained at a predetermined pressure. 2. The fuel cell power generator according to claim 1, wherein the pressure set value of the pressure control valve is variably set in accordance with the output fluctuation of the fuel cell.