JP4314942B2 - Fuel cell power generator and its operation method - Google Patents

Description

The present invention relates to a fuel cell power generation device and an operation method thereof, and more particularly to control of a fuel cell power generation device using liquefied petroleum gas ( hereinafter referred to as LPG or LP gas ) as raw fuel.

The raw fuel of the fuel cell power plant, methane (CH _4), but town gas components mainly are common, there are a number of track record with the LP gas of propane (C ₃ H ₈₎ component mainly. FIG. 5 shows an example of a schematic configuration of a typical LPG fuel cell power generation system described mainly focusing on the raw fuel system.

In FIG. 5, 1 is an electromagnetic on-off valve, 2 is a flow control valve, 3 is a desulfurizer, 4 is a reformer, 5 is a transformer, 6 is a CO remover, 7 is a fuel cell, and 8 is a reformer temperature measurement. thermometer use, 9 L P gas flow meter, LPG flow control unit for controlling the L P gas supply flow rate is 10, 11 cylinder switching control unit, 31 and 32 LPG cylinders, is 33 Pressure gauges 35 and 36 are electromagnetic on-off valves, and 40 and 41 are pressure reducing valves. In addition, 20 of the part enclosed with the dashed-two dotted line shows a fuel cell power generation device package, and includes various peripheral devices not shown.

The general operation of the system of FIG. 5 is as follows. First, a gas whose pressure is reduced to a predetermined pressure, for example, 1 to 3 kPa, by the pressure reducing valve 40 from the LPG cylinder 31 is controlled by the flow rate adjusting valve 2 according to the load of the fuel cell, and passes through the desulfurizer 3 to be a reformer. Sent to 4. The hydrogen-rich reformed gas produced by the reformer 4 is converted into CO ₂ in the reformed gas 5 in the reformer 5 and a part of the remaining CO is removed by the CO remover 6. It is supplied to the fuel cell 7.

  When the primary pressure (10 to 20 MPa) of the LPG in the LPG cylinder 31 decreases as the LPG is consumed and reaches a predetermined pressure, the LPG cylinder 31 is switched to the LPG cylinder 32, and the pressure reducing valve 41 and the flow rate control are switched. Gas is supplied to the reformer 4 through the valve 2 and the desulfurizer 3.

  The fuel cell power generation apparatus using LPG as a raw fuel as described above uses LPG that can be stored as a raw fuel. Therefore, unlike a fuel cell power generation apparatus that uses city gas as a raw fuel, a city gas pipeline caused by a disaster, etc. There is a merit that it is possible to continue power generation even when the power is shut off. On the other hand, since LPG is supplied in a cylinder, the use of fuel requires time and labor for switching and replacing the cylinder.

By the way, the composition of LPG is mainly composed of propane (C ₃ H ₈ ) and butane ((C ₄ H ₁₀ ), a mixture of n-butane and isobutane) as defined in JIS / K2240, and the ratio is Although it differs depending on the type, LPG used as a raw fuel of a fuel cell power generation apparatus usually contains about 3% by volume of butane.

The vapor pressure of butane is 1.275 MPa at 40 # C for propane (C ₃ H ₈ ), 0.278 MPa at 40 # C for n-butane, and 0.427 MPa at 40 # C for isobutane. Butane is less likely to vaporize and tends to remain in the cylinder. For this reason, the gas composition supplied from one cylinder tends to gradually increase the butane concentration ratio.

  In addition, the hydrogen generation capacity per unit volume of butane is 1.3 times that of propane, as shown in the following formula.

Propane: C ₃ H ₈ + 6H ₂ O → 10H ₂ + 3CO ₂
Butane: C ₄ H ₁₀ + 8H ₂ O → 13H ₂ + 4CO ₂
Therefore, as one cylinder approaches the end of use, the butane concentration gradually increases, and the amount of generated hydrogen gradually increases. On the other hand, since the amount of hydrogen consumed in the fuel cell stack is constant, the remaining hydrogen (heat source for reforming reaction) combusted in the reformer burner gradually increases, but this increase gradually changes over time. Therefore, the raw fuel flow rate control in which the temperature of the reformer is taken into the control target functions, and the heat / material balance of the system is maintained by gradually decreasing the raw fuel flow rate.

  As described above, the conventional control can cope with a gradual change in the gas composition in one cylinder. However, when the fuel is switched from an LPG cylinder having an increased butane concentration ratio at the end of the cylinder use to an unused cylinder filled with an initial composition LPG mainly composed of propane, the gas composition changes simultaneously with the switching. That is, for the fuel cell power generation device, the hydrogen generated in the reformer is changed by switching to an unused propane cylinder mainly under the condition that the flow rate of the raw fuel is reduced corresponding to the LPG having an increased butane concentration ratio. The fuel cell stack consumes a certain amount of hydrogen to maintain power generation, and the fuel cell that is the heat source for the reforming reaction has insufficient exhaust hydrogen (residual hydrogen). The temperature will decrease.

  Here, the raw fuel flow rate control detects a temperature drop of the reformer and controls the raw fuel flow rate to increase in order to increase the combustion amount of the burner. This is an increase in the amount of raw fuel that passes through the reactor, which temporarily decreases the temperature of the reformer. As a result, the temperature of the reformer deviates from the operation continuation range, resulting in a case where an emergency stop is forced. In addition, the fuel cell main body may be irreversibly damaged due to a shortage of fuel, for example, the fuel cell may be damaged, and the efficiency may be significantly lowered or the operation may become impossible.

  FIG. 3 is a diagram for explaining a problem of fuel shortage associated with switching of the LPG cylinder. The above phenomenon will be specifically described with reference to FIG. In FIG. 3, LPG having an increased butane concentration is represented as LPG (B), an initial composition LPG mainly composed of propane is represented as LPG (P), and LPG mixed with these is represented as LPG (P + B).

  The fuel cell power generation device before the cylinder switching is operated at a raw fuel flow rate corresponding to LPG (B) having an increased butane concentration (state 1). Here, even when switching to an unused LPG (P) cylinder, the temperature of the reformer does not change immediately after switching, so the raw fuel flow rate is supplied at the same flow rate as before switching (state 2), but desulfurization When LPG (P) begins to be mixed in the space of the reactor (including related piping), the amount of hydrogen generated decreases (states 3, 4, and 5), fuel shortage in the fuel cell body, and reformer Insufficient heat source. The time during this period varies depending on the volume of the desulfurizer and the power generation output, and is about several to several tens of seconds. However, insufficient fuel may cause irreversible damage to the fuel cell body, and the temperature of the reformer will decrease. In some cases, the apparatus is stopped.

  In order to improve this phenomenon, it may be possible to forcibly increase the raw fuel flow for a certain time after switching, but if it is increased without considering gas replacement in the space of the desulfurizer, This time, the amount of generated hydrogen becomes excessive, and the temperature of the reformer rises and the apparatus may be stopped. This phenomenon will be described with reference to FIG. 4 for explaining the problem of excessive fuel accompanying switching of LPG cylinders. In FIG. 4, LPG having an increased butane concentration is represented as LPG (B), LPG having an initial composition mainly composed of propane is represented as LPG (P), and LPG mixed with these is represented as LPG (P + B).

  The fuel cell power generation device before the cylinder switching is operated at a raw fuel flow rate corresponding to LPG (B) having an increased butane concentration (state 1 ′). Here, when the unused LPG (P) cylinder is switched, the raw fuel flow rate control by the temperature of the reformer is canceled, and the raw fuel flow rate is forcibly higher than the flow rate suitable for LPG (P) (LPG (B)) When the gas is supplied at a flow rate), LPG (B) flows into the reformer over an appropriate amount because the LPG (B) is filled in the desulfurizer simple immediately after switching. It becomes a state (state 2 '). After that, when LPG (P) begins to increase in the space such as desulfurizer, the amount of hydrogen generated gradually approaches an appropriate amount (states 3 ', 4', 5 '). There is a risk that the temperature will become high and it may become impossible to continue operation.

  By the way, the applicant of the present application has made stable operation without causing shortage of hydrogen, excessive hydrogen, and S / C abnormality in the fuel cell when the fuel is switched from the fuel A to the fuel B having a different composition without stopping the operation. Japanese Patent Application Laid-Open No. 2004-151858 has filed a fuel cell power generation apparatus having a raw fuel switching facility and an operation method thereof.

Although the prior art which solves the problem in switching of different types of raw fuel gases as in Patent Document 1 is known, the above-described LPG cylinder switching in a fuel cell power generation apparatus using only LPG as raw fuel is known. There is no known device or method for solving the problems involved.
JP 2001-28270 A (page 2-6, Fig. 1-3)

The present invention has been made in view of the above points, and an object of the present invention is to eliminate problems in the conventional driving method. The conventional problems are summarized as follows. That is, in the conventional “control of the raw fuel flow rate according to the temperature of the reformer and the output of the fuel cell”, a gradual change in gas composition such as an increase in butane concentration accompanying gas consumption in one LPG cylinder. However, in the case of a stepwise gas composition change such as a butane concentration sudden decrease (propane composition rapid increase) at the time of cylinder switching, supply at the same flow rate as the end of use of the cylinder before switching. As a result, the amount of hydrogen generated is insufficient, and the temperature response of the reformer is relatively slow, so the temperature of the reformer decreases and deviates from the operation continuation range, thus requiring an emergency stop. There is a problem that will occur. Furthermore, in order to improve this, it releases the flow control of the raw fuel by temporarily reformer temperature at the cylinder switch, forcing, by supplying a gas flow rate corresponding to L P gas composition of unused However, the pre-switching gas remaining in the desulfurizer is excessively supplied, and the temperature of the reformer rises and deviates from the operation continuation range, which may cause an emergency stop. There is.

  Accordingly, an object of the present invention is to provide a fuel cell power generation apparatus and a method for operating the fuel cell power generation apparatus that can stably operate even when the cylinder is switched by appropriately performing fuel flow control when switching the LPG cylinder. There is.

The above-mentioned subject is achieved by the following. That is, according to the invention of claim 1, a fuel cell, a liquefied petroleum gas (LP gas) LP gas supplied from a cylinder to a hydrogen-rich reformed gas reformer to be supplied to the fuel cell, L P method of operating a fuel cell power plant and a gas supply flow rate control means, when switching from the LP gas cylinders use end (cylinder 1) unused new LP gas cylinder (cylinder 2), the cylinder 1 of the L P gas composition, the pressure reducing valve of the preceding gas primary pressure and the LP gas composition provided in the gas outlet portion of the cylinder 1, is calculated based on the correlation obtained in advance, the calculated value of the LP gas composition based, the amount of hydrogen gas in the reformed gas in the reformer outlet so as to be substantially constant, and performs flow control for LP gas supplied from the gas cylinder 2 to the reformer.

As an embodiment of the invention of claim 1, the invention of claim 2 is preferable .

That is, in the operating method according to claim 1, when switching from the cylinder 1 to cylinder 2, L P gas of the L P gas supply flow rate at the time of switching the start of the cylinder 2, the cylinder 1 before the switching as a supply flow rate and the same flow rate, then, the L P gas supply flow rate from the cylinder 2, as the amount of hydrogen gas in the reformed gas in the reformer outlet is substantially the same as before the switching, advance by simulation by changing the predetermined flow rate obtained by supplying L P gas from the cylinder 2, in the reformer outlet, between L P gas from the cylinder 1, L P gas from the cylinder 2 after the gas replacement is completed a predetermined time by, and returning to the LP gas supply flow rate control according to an output of the fuel cell (claim 2).

Further, as an apparatus for carrying out the operation method, the invention of claim 3 below is preferable. That is, a fuel cell power generator for performing the method of operation according to claim 2, a fuel cell, a L P gas supply flow control means having a reformer, a flow meter and control valve, gas a primary pressure measuring means, further wherein L P gas supply flow control means includes a cylinder switching control means, a gas cylinder changeover control valve position calculation means, due to the switching of the cylinder according to claim 2 LP gas flow rate control means for performing flow rate control is provided (claim 3 ).

That is, in the present invention, a signal to be transmitted that switches the LPG cylinder, based on the signal, the L P gas supply flow rate control of the fuel cell power plant, and LPG gas composition, desulfurization of the fuel cell power plant It controls appropriately based on space, such as a container, and the output (load) of a fuel cell power generator.

  According to the present invention, it is possible to provide a fuel cell power generation apparatus capable of continuing stable operation while minimizing disturbance due to gas composition change at the time of LPG cylinder switching, and an operation method thereof.

  Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic system diagram of a fuel cell power generator according to an embodiment of the present invention. In FIG. 1, members having the same functions as those shown in FIG.

1, 2 and main difference is in the L P gas supply flow control means, in that a changeover control valve opening calculation section 12 when the cylinder switch. Further, the LPG flow rate control unit 10 in FIG. 1 has a function of performing flow rate control accompanying the cylinder switching according to claim 2 .

In FIG. 1, the control valve opening calculation unit 12 at the time of switching constantly monitors the primary pressure of the cylinder in use, that is, the residual pressure, and obtains “the residual pressure of the cylinder and the butane in the LPG in advance by a preliminary test or the like. the concentration of the relationship ", a function of calculating the L P gas composition during use. Furthermore, in preparation for switching, and a volume of the desulfurizer or the like and LPG flow during use between L P gas composition during use, to keep the amount of hydrogen generation in the reformer outlet constant, when switching completion The LPG flow rate and the LPG flow rate increase rate are calculated and set to values obtained by simulation in advance, the opening degree of the control valve is obtained based on this, and the LPG flow rate control unit 10 is commanded to control the flow rate control valve 2 Has the function of

  Next, based on FIG. 2, the state change accompanying the LPG cylinder switching of this invention is demonstrated. Also in FIG. 2, LPG having an increased butane concentration is represented as LPG (B), an initial composition LPG mainly composed of propane is represented as LPG (P), and LPG mixed with these is represented as LPG (P + B).

  The fuel cell power generation device before the cylinder switching is operated at the raw fuel flow rate corresponding to LPG (B) having increased butane concentration (state 1 "). In preparation for switching cylinders, LPG is used to keep the hydrogen generation rate at the reformer outlet constant during switching from the volume of the desulfurizer, etc., the flow rate of LPG (B), and the gas composition of LPG (B). The flow rate rise rate of (P) and the flow rate of LPG (P) at the completion of switching are calculated.When switching LPG cylinders, the cylinder switching control unit receives a cylinder switching signal, so that the original due to the reformer temperature is calculated. The fuel flow control is canceled and LPG (P) is supplied at the same flow rate as LPG (B) immediately before switching (state 2 "). Furthermore, based on the flow rate increase rate of LPG (P) calculated in state 1 ", the raw fuel flow rate control valve 2 is operated (states 3" and 4 "). The flow rate of (P) is reached (state 5 "), and thereafter, the normal" flow rate adjustment control according to the reformer temperature and the fuel cell output "is resumed.

  The configuration of the fuel cell power generator and the operation at the time of cylinder switching in FIGS. 1 and 2 enable the operation at the time of LPG cylinder switching, which has been unstable in the past, to be performed in a stable state.

1 is a schematic system diagram of a fuel cell power generator according to an embodiment of the present invention. Explanatory drawing of the state change accompanying the LPG cylinder switching concerning embodiment of this invention. The figure explaining the problem of the fuel shortage accompanying switching of the conventional LPG cylinder. The figure explaining the problem of the fuel excess accompanying the switching of the conventional LPG cylinder. FIG. 6 is a schematic system diagram of a conventional fuel cell power generator.

Explanation of symbols

2 Flow control valve 3 Desulfurizer 4 Reformer 7 Fuel cell 9 Flow meter 10 LPG flow control unit 11 Cylinder switching control unit 12 Switching valve opening calculation unit 31, 32 LPG cylinder 33, 34 Pressure gauge 40, 41 Depressurization valve

Claims (3)

A fuel cell, comprising a liquefied petroleum gas (LP gas) LP gas supplied from a cylinder to a hydrogen-rich reformed gas reformer to be supplied to the fuel cell, and L P gas supply flow control means fuel In the operation method of the battery power generator,
When switching from the LP gas cylinders use end (cylinder 1) unused new LP gas cylinder (cylinder 2), the L P gas composition within said cylinder 1, a pressure reducing valve provided in the gas outlet portion of the cylinder 1 Is calculated based on the correlation between the gas primary pressure and the LP gas composition obtained in advance, and based on the calculated value of the LP gas composition, the amount of hydrogen gas in the reformed gas at the reformer outlet is substantially reduced. A method for operating a fuel cell power generator, wherein the flow rate of LP gas supplied from the cylinder 2 to the reformer is controlled so as to be constant. In operation method of claim 1, when switching from the cylinder 1 to cylinder 2, a L P gas supply flow rate at the time of switching the start of the cylinder 2, and L P gas supply flow rate from the cylinder 1 before the switching as the same flow rate, then the L P gas supply flow rate from the cylinder 2, as the amount of hydrogen gas in the reformed gas in the reformer outlet is switched before and substantially the same in advance by simulation is changed to a predetermined flow rate obtained by supplying L P gas from the cylinder 2, in the reformer outlet, between L P gas from the cylinder 1, the gas by L P gas from the cylinder 2 substituents The fuel cell power generator operating method is characterized by returning to the LP gas supply flow rate control according to the output of the fuel cell after a predetermined time is completed. A fuel cell power generator for performing the method of operation according to claim 2, a fuel cell, a reformer, and L P gas supply flow control means having a flow meter and control valve, the gas primary pressure and a measuring unit, further, the L P gas supply flow control means includes a cylinder switching control means, a gas cylinder changeover control valve position calculation means, the flow control due to the switching of the cylinder according to claim 2 And a LP gas flow rate control means.

Images