JPS6168867A - Fuel cell plant controller - Google Patents

Abstract

PURPOSE:To prevent temperature increase caused by remaining heat by putting out a burner of heat source of a reformer when operation stopped, and continuously supplying fuel and steam to a reforming line to utilize endothermic action of reformation. CONSTITUTION:A reformed fuel control valve 11 controls flow rate of reformed fuel. The reformed fuel is supplied to a hydrogen electrode of a fuel cell 5 and part of it is consumed to generate electric energy, and the rest is burned with a main burner 12 of a reformer 4. A heat controller of a controller 100 closes the valve 11 by receiving a stop signal to put out the burner, and opens a valve 20 to cool with nitrogen. When received a stop signal, a fuel stop controller opens a reforming steam valve 19 and a reforming fuel valve 10 only for a specified time by operation of a single shot timer to continue reformation, and temperature increase is prevented by the endothermic action.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell power generation plant control device that prevents a temperature rise in a reformer tube when the plant is stopped.

[Technical background of the invention and its problems]

Electric power is normally generated by rotating it with a prime mover such as a steam turbine in a generator and sending it to the demand side as AC. Most of the electricity systems in Japan are AC systems.

On the other hand, the steam that drives a steam turbine, etc. is extracted as thermal energy by burning fuel such as oil or gas in a boiler, etc., and it is disadvantageous in terms of efficiency to convert the steam energy C: and then extract it as electrical energy. In recent years, the fuel cell system has been adopted as an energy-saving power generation method, which involves chemically changing the fuel and extracting electrical energy directly from the flow of electrons generated during this chemical change. Ta.

This fuel cell generates electricity by chemically changing the supplied fuel, but the output is direct current, and if it is consumed in a specific area, it will be consumed as direct current, and as part of energy conservation policy, large amounts of electricity will be generated. In the case where electric power is supplied, the AC is converted to AC using a DC/AC converter and connected to the power grid.

By the way, in a plant using this fuel cell,
From plant start-up to main burner ignition, the reforming reaction is maintained using only the pilot burner as the heat source. and,
While the plant is operating, the main burner is ignited, the pilot burner is kept at a level that will not extinguish the fire, and the reforming reaction is maintained using the heat source of the main burner. Note that reforming refers to heating raw fuel under a catalyst to produce reformed fuel with a high hydrogen content.

When shutting down a plant while it is in operation (second), the reformer that performs the reforming reaction must be cooled with nitrogen. This is done by closing the valve and letting nitrogen for cooling flow into the reformer.In other words, the inlet valve to the reformer is the raw fuel control valve;
There is a reforming steam control valve and a reformed fuel control valve as an outlet valve, so these control valves are closed and the cooling nitrogen control valve is opened to allow nitrogen to flow in.

However, in such a cooling system, if the plant were to stop at time t0 as shown in Figure 8C-2, the temperature of the catalyst layer, which had been kept low due to the endothermic reaction caused by the reforming of the raw fuel, would exceed the raw fuel. Cutting may cause a temporary increase and exceed the limit value.

If something like this happens, the catalyst and tubes will deteriorate more quickly and may be damaged.

[Purpose of the invention]

The object of the present invention is to cool the catalyst and tubes of the reformer, which is the main device for obtaining reformed fuel with a high hydrogen content from fuel, by maintaining a constant temperature reduction rate when the plant is stopped. An object of the present invention is to provide a fuel cell plant control device that can protect a fuel cell plant.

[Summary of the invention]

In the present invention, when the plant is stopped (2. The burner, which is the heat source of the reformer, is extinguished and NG and steam are continuously flowed into the reforming line, the reforming 1. This is to prevent the temperature of the layer from rising.

[Embodiments of the invention]

FIG. 1 is a block diagram in which a fuel cell plant control device 100 of the present invention is applied to a fuel cell plant. The raw fuel enters the reformer 4 with its flow rate controlled by a reforming fuel control valve 101, where it is heated under a catalyst and becomes a reforming material with a high hydrogen content. The reformed fuel is then transferred to the high temperature shift converter 8.
Carbon monoxide is then removed through the low temperature shift converter 9. The reformed fuel has a flow rate controlled by a reformed fuel control valve 11, flows into the five hydrogen electrodes of the fuel cell 5, and is partially consumed as electrical energy, and the rest is burned in the main burner 2 of the reformer 4. The high-temperature gas for heating in the reformer 4 joins the exhaust gas from the oxygen electrode 5B of the fuel cell 5, flows through the combustor 7 into the turbine 2 of the turbo compressor, and drives the humbretsner 3 connected thereto.

The air discharged from the compressor 3 is controlled in flow rate by an air control valve 131, and flows into the oxygen electrode 5 of the fuel cell 5. After seven days, part of the oxygen reacts with hydrogen at the hydrogen electrode 5A and is consumed, and the rest is exhausted from the oxygen electrode 5B.

Then, it joins with the exhaust gas from the main burner 12 of the reformer 4, and is used to drive the turbine 2 of the turbo compressor via the combustor 7.

The fuel cell 5 generates electrical energy through a catalytic reaction between hydrogen in the hydrogen electrode 5A and oxygen in the oxygen electrode 5B, so that the oxygen electrode 5B becomes a positive electrode and the hydrogen electrode 5A becomes a negative electrode, and is connected between the two electrodes. supply that electrical energy to an electrical load.

In the fuel cell plant, the DC output of the fuel cell 5 is supplied to a converter 6, where it is converted into AC power, and sent to the power grid as AC power.

Next, in the fuel cell plan) 1, the reforming steam control valve 10. Tube 14 inside the reformer 4. High temperature transformer8. Low temperature transformer9. Reformed fuel control valve 11. Then, the reformer 4, which is the main component of the line up to the hydrogen electrode 5A inlet of the fuel cell 5 (hereinafter referred to as the twisted material reforming system), is connected to the main burner 12 from the outside through a double-tube structure tube 14 filled with catalyst. Alternatively, it is heated by a pilot bar f15 to supply the heat necessary for the reforming reaction.

Figure 2 shows that raw fuel is supplied to the reforming line of the reformer for a preset period of time after the plant shuts down.
FIG. 2 is a control diagram of a control device whose purpose is to introduce steam, continue reforming, and measure temperature drop by its endothermic action. FIG. 3 is a characteristic diagram of the operation of each pulp and catalyst temperature when the control is activated. The part surrounded by the dashed line marked as ``in'' in Figure 2 is the heating control section, and when it receives a stop signal, the pulp 11
Fully close the burner, extinguish the burner, stop heating, and reduce the pulp to 20
Fully open the tank and cool with nitrogen. The part surrounded by the broken line shown in (B) shows the operation of the single shot timer when the raw fuel stop control unit receives a stop signal; pulp 19 and pulp 10 are fully opened for the set time (- The time it takes for the temperature to drop sufficiently is constant,
If known, this method can easily accomplish two purposes:

Figure 4 shows that after the plant shuts down, and while the catalyst layer temperature is higher than the preset temperature, raw fuel and steam are introduced into the reforming line of the reformer to continue reforming and absorb heat. FIG. 2 is a control diagram of a control device whose purpose is to measure temperature drop through action. The planton stem configuration may be the same as in FIG. FIG. 5 is a diagram showing the operation of each pulp when the control shown in FIG. 4 is activated. In FIG. 4, the part surrounded by the wavy line labeled (4) is a heating control section, and the control configuration and pulp operation are the same as those in FIG. 2. The part surrounded by the wavy line (B) is the raw fuel stop control section. When the stop signal is received, the comparator operates to fully open the pulp 19 and the pulp 10 only while the catalyst bed temperature is higher than the set temperature to continue reforming.

This method 12 can achieve the objective when the plant is in various states during shutdown and the time required to lower the temperature to the desired temperature is not constant.

Figure 6 shows the amount of raw fuel and steam introduced into the reforming line of the reformer after the plant shuts down as the temperature of the catalyst bed decreases due to the endothermic effect of reforming. FIG. 3 is a control diagram of a control device that gradually decreases the amount of water. The plant system configuration may be the same as in Figure 1, but the pulp 19
It is necessary for the pulp 1o and the pulp 1o to be control valves that can adjust the opening degree.

FIG. 7 is a diagram showing the operation of each pulp when the control shown in FIG. 6 is activated. In FIG. 6, the part surrounded by the wavy line labeled (4) is the heating control section, and the control configuration and pulp operation are the same as in FIG. 2. When the part surrounded by the wavy line labeled (B) receives a stop signal from the raw fuel stop control unit, the function generator's operation manual is set in advance based on the relationship between temperature and reformed amount according to the temperature drop in the catalyst layer. As the pulp 10 closes at the same rate, the temperature decreases, and raw fuel for carrying out the necessary amount of reforming flows into the reforming line of the reformer. The opening degree of the pulp 19 is determined according to the opening degree of the pulp 10 so that the necessary amount of steam flows for the raw fuel currently flowing.

In this way, as the temperature of the catalyst layer decreases, the raw fuel and steam flowing into the reforming line of the reformer are reduced, and at a preset temperature C2, the inflow into the reforming line is stopped. : It has become.

According to this method, consumption of raw fuel can be suppressed to the necessary minimum.

〔Effect of the invention〕

By applying the control method of the present invention, it is possible to suppress the temperature rise of the catalyst bed when the plant is stopped.

In this way, if the temperature of the catalyst layer inside the reformer is controlled by the endothermic reaction of the raw fuel, deterioration and damage of the tube 14 due to temperature rise can be eliminated, and the cooling time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a system configuration diagram in which the control device of the present invention is used in a fuel cell power generation plant≦2 speed, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is an explanatory diagram of its operation, and Fig. 4 is a block diagram showing another embodiment, FIG. 5 is a diagram explaining its operation, FIG. 6 is a block diagram showing another embodiment, FIG. 7 is a diagram explaining its operation, and the eighth factor is the conventional one. It is an explanatory diagram of operation in an example. 1... Fuel cell plant 2... Turbine 3...
Compressor 4...Reformer 5...Fuel cell
5A... Hydrogen electrode 5B... Oxygen electrode
6... Converter 7 - Combustor 8... High temperature shift converter 9... Low temperature shift converter 10... Raw fuel control valve for reforming 11... Reformed fuel control valve 12... Main・Burner 13...Air control valve 14...Tube 15...Pilot parner 16...
- Pilot burner fuel control valve 17 - Pilot burner air control valve 18 - Main burner air control valve 19 - Reforming steam control valve Addition - Cooling N2 control valve 21 - Catalyst layer Temperature Detector (7317) Agent Patent Attorney Nori Kei Chika (and 1 others)
Figure 7 Figure 8

Claims (1)

[Claims] In a fuel cell plant that heats raw fuel under a catalyst to obtain reformed fuel with a high hydrogen content and generates electricity based on the reformed fuel, a heating control unit that heats the raw fuel to obtain the reformed fuel. and a raw fuel stop control unit that continues supplying some or all of the raw fuel and then stops the heating after the heating control unit stops heating when the plant is stopped.