JPH0760691B2 - Fuel cell power generation system - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel cell power generation system.

[Technical background of the invention and its problems]

Conventionally, a fuel cell is known as a device that directly converts the energy of a fuel into electrical energy. A schematic system and circuit configuration of a power generation unit using this fuel cell is shown in FIG. 3 and explained.

The fuel cell 1 is composed of a large number of cells 2 connected in series, oxygen (piping 3) is supplied as an oxidant, and hydrogen (piping 4) is supplied as a fuel, and a direct current power is generated by an electrochemical reaction.

This DC power is converted into AC power by the inverter 6 via the DC circuit breaker 5 and supplied to the power system 10.

Further, 11 is a steam separator, which is in the cooling water system 7 for removing heat generated by the reaction in the fuel cell, and cools the cell and cools itself by heating (hot water or two-phase). A fluid is separated into steam and water (in the case of hot water, pressure is reduced), steam is returned to the reformer 13 described later, and water is returned to the fuel cell 1 as cooling water again.

Immediately before, the steam sent to the reformer 13 is mixed with the raw fuel (generally natural gas) and enters the reactor, where the main component is hydrogen, which is the fuel of the fuel cell 1, due to the action of the catalyst filled inside. Is transformed into a gas that is mostly carbon dioxide.

Since the above action is an endothermic reaction, it is not shown,
The reformer 13 is provided with a combustion chamber, and is supplied with air and hydrogen (battery exhaust fuel or natural gas) from the outside to supply heat for maintaining a reaction equilibrium state.

On the other hand, at the time of start-up, since the heat generation of the fuel cell is small, the electric heater 12 for generating the steam is built in the steam separator 11.

Further, this electric heater 12 is also used during partial load when the heat generation of the fuel cell is insufficient as in the above case.

The curve 21 in Fig. 4 shows the relationship between the amount of insufficient steam and the load of a general fuel cell power generation unit. The amount of steam generated during standby with no load is the smallest, and the amount of steam required as shown by curve 22 in the same figure. It is necessary to generate most of the above by heating the electric heater, and the heat generation of the battery increases as the load increases, so the shortage amount decreases, but it cannot self-sufficient up to about 2/3 of the rated load. On the contrary, since steam is left over, excess steam is cooled and returned to the makeup water tank.

The required capacity of the above electric heater is large and is 20 to 30% of the rated output.
And the more time it takes to shorten the time required for start-up and load change, the larger it becomes. Moreover, this electric heater is used only for a relatively short period of time, such as when starting up and when it is partially loaded, and its equipment cost is one of the factors that hinders economical efficiency.

On the other hand, the fuel cell power generation system has high power generation efficiency even with a small capacity, so even if it is a medium or large capacity power generation system, it is better to have a plurality of small capacity power generation units together for better starting characteristics and avoid technical difficulties. This is also desirable from the standpoint of increasing the reliability of the power generation system, but the conventional system having a plurality of such power generation systems has the drawbacks of having a large number of constituent devices and cost, and of having a complicated control mechanism.

[Object of the Invention]

The present invention provides a fuel cell power generation system that eliminates the uneconomicality and the complexity of the control mechanism in a multi-power generation system or a co-generation system that has a plurality of fuel cell power generation units, and that also improves the reliability of the entire system. The purpose is to do.

[Outline of Invention]

In order to achieve the above object, the present invention comprises a plurality of reformers for reforming raw fuel to produce reformed fuel,
It has a plurality of fuel cells that receive reformed fuel from each of these reformers, and a cell cooling system that recovers the heat generated in these fuel cells to generate steam. There is at least one steam separator for separating steam, and the at least one steam separator is provided with an electric heater, and the steam separated by this steam separator has a plurality of steam generators. In a fuel cell power generation system configured to be supplied to a quality unit, the steam separated by the steam separator is connected so as to be selectively supplied to a part or all of the plurality of reformers. It is characterized by being.

Example of Invention

FIG. 1 is a system and circuit configuration diagram showing an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described here.
That is, in FIG. 1, 15 is a steam pipe that connects the steam separator 11 of each power generation unit, and its branch pipe 16 and a control valve or shutoff valve 17 (including the case where both are installed)
The steam can be supplied to the reformer 13 of the power generation unit, which is required via the. The steam separator 11 in the battery cooling water system 7 is an electric heater for only one unit.
12 built in, no other power generation unit. Of course, the steam separator with built-in electric heater may be in any unit. Fig. 1 shows the state in which the second unit is in the process of starting up after the first unit has been started up. The black parts of valve 17 are closed, and the other valves are open. Is shown.

When the startup of the first power generation unit is completed, the battery cell 2
Electric heater that can cover reforming steam with heat generated by
Is unnecessary. Strictly speaking, the point where the electric heater is not necessary is around the 75% rated load in the curve 21 in FIG. 4, and since this load also differs depending on each power generation system, the electric heater is not necessary in the following explanation. It refers to the state where the load is taken.

In this state, it is not necessary to supply steam to other units, so all valves 17 in the branch pipe 16 are closed except for the first unit, but when starting the second unit, only the second valve opens. Supply the steam required for startup. However, branch pipe from steam separator 11
The valve 19 on the connecting pipe 18 to 16 is closed while the heat generation on the battery side is small, and opened when steam starts to be generated.

In this case, since the surplus steam of the first power generation unit can be used, the power consumption of the electric heater 12 can be reduced as shown by the curve 23 in FIG.

Since the excess steam of the first and second units can be used for starting the third unit, the power consumption of the electric heater 12 can be further reduced, and depending on the number of units installed, a unit that does not require the electric heater may appear.

On the other hand, as the amount of steam generated in the second steam-water separator 11 increases, the valve 17 is throttled to reduce the load on the electric heater 12 and switch to self-replenishment. If the capacity of the electric heater reaches a sufficient load, the activation of the third heater can be started.

Further, in another embodiment of the present invention, as shown in FIG. 2, if the steam-water separator 11 is also integrated into one unit for all the units, a capacity sufficient to perform steam-water separation during operation of all the units is secured. Therefore, the internal volume is slightly larger, but the economic effect is also large,
The system and control mechanism can be further simplified.

〔The invention's effect〕

As described above, according to the present invention, it is not necessary to use a plurality of large-capacity heaters in a multi-generation system or a combined heat and power generation system, and the capacity required for starting one unit and partial load is sufficient. It is possible to provide a fuel cell power generation system in which reliability is greatly improved and reliability is improved by simplifying a control mechanism. Further, since the surplus steam of each unit which has already been started can be used for starting the second and subsequent units, there is an effect of reducing the starting loss.

[Brief description of drawings]

FIG. 1 is a system / circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a system / circuit configuration diagram showing another embodiment of the present invention, and FIG. 3 is a schematic system of a conventional fuel cell power generation unit. -Circuit configuration diagram, FIG. 4 is a graph showing the relationship between the load, the steam shortage in the power generation unit, and the required evaporation amount by the electric heater. 1 ... Fuel cell, 2 ... Fuel cell configuration 6 ... Inverter, 7 ... Battery cooling water system 10 ... Power system, 11 ... Steam separator 12 ... Electric heater, 13 ... Reformer 15 …… Air / water separator communication pipe, 16 …… Branch pipe 17 …… Control valve, stop valve 18 …… Air / water separator-branch pipe connecting pipe 19 …… Control valve, stop valve

Claims (1)

[Claims] 1. A plurality of reformers for reforming a raw fuel to produce a reformed fuel, a plurality of fuel cells supplied with reformed fuel from each of the reformers, and a plurality of fuel cells generated by these fuel cells. Has a battery cooling system that recovers the heat that is generated and generates steam,
This battery cooling system has at least one steam separator for separating the generated steam, and an electric heater is provided in this steam separator, and the steam separator separates the steam. In the fuel cell power generation system configured such that the steam is supplied to the plurality of reformers, the steam separated by the steam-water separator is selectively supplied to some or all of the plurality of reformers. A fuel cell power generation system characterized in that the fuel cell power generation system is connected so as to be supplied to the fuel cell.