JP2007048698A - Humidification system of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a humidification system of a fuel cell in which quick responsiveness is obtained, in which stable dew point control is made regardless of variations in a gas flow rate, and of high or low target dew point, and, a compact-sized humidification system is realized. <P>SOLUTION: The humidification system is constituted so as to supply steam from a common steam generating source 3 to respective gas supply lines L1, L2 for supplying the steam to the fuel cell, steam flow rate regulating means 41, 42 regulating steam amount are installed on those steam supply lines SL1, SL2 respectively, and the steam flow rate regulating means 41, 42 are made to be respectively controlled by open loop control based on a prescribed environmental parameter so that each gas temperature may become equal to the set dew point temperature, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is particularly preferably applied to a solid polymer electrolyte fuel cell, and relates to a fuel cell humidification system that can favorably maintain a humidified state of a solid polymer membrane used as an electrolyte.

  A fuel cell is a device that directly converts chemical energy of a fuel into electrical energy by electrochemically reacting a fuel such as hydrogen with an oxidant such as air. Among them, the solid polymer electrolyte fuel cell using the solid polymer membrane having ionic conductivity has characteristics such as high output density, simple structure, and relatively low operating temperature. Expectations for further technological development are increasing.

  By the way, the solid polymer membrane needs to keep the moisture content in an appropriate range because it is easy to dry in the reaction process, and the membrane resistance easily changes according to its moisture content. The gas (anode gas and cathode gas) supplied to the battery is appropriately humidified by a humidifier.

And as a humidifier for that, conventionally, a so-called bubbling method in which fine gas bubbles are passed through the liquid phase and humidified (Patent Document 1), water is evaporated by heating to vapor, An injection system that mixes with gas (Patent Document 2) is known.
JP 2002-252011 A JP 2004-220868 A

  However, in the bubbling method, when the gas dew point is changed, the temperature of the water in the tank needs to be changed, so the response speed is very slow in the first place. For example, the load on the fuel cell suddenly fluctuates. There is a problem that it is difficult to deal with when it is necessary to quickly change the gas dew point. Further, when the gas flow rate is low especially at a low dew point, there is a problem that it is difficult to stably supply a gas having a desired dew point.

  On the other hand, the injection method is generally said to have the advantage that the dew point can be changed quickly. However, since the feedback control (hereinafter also referred to as FB control) is actually performed, until the desired dew point is settled. In addition, it takes time not much different from the bubbling method.

  In addition, in any method, when the dew point is FB-controlled, a dew point meter capable of continuous measurement of the dew point is required. Currently, such a dew point meter is only a capacitance type, and this capacitance type Since it is difficult to keep the dew point meter at a condition that can be measured with high accuracy, for example, when applied to a fuel cell evaluation system, a test that greatly changes the dew point cannot be performed, and the dynamic range is wide with high accuracy. The failure of being unable to do so can occur.

  In addition, conventionally, humidifiers are separately provided for each of the anode gas and the cathode gas, but there is a problem in that compactness cannot be achieved. If these humidifiers are simply used in common, the effect of control on one gas supply system is affected by the other gas supply system due to problems such as poor control response as described above and a small dynamic range. It is easy to cause interference and may cause instability.

  The present invention has been made in view of such a situation, and is capable of obtaining quick response, stable dew point control regardless of the gas flow rate, the target dew point level, and more compact. The main object of the present invention is to provide a new and useful fuel cell humidification system.

  In order to achieve this object, the present invention takes the following measures.

  That is, the fuel cell humidification system according to the present invention includes a common steam generation source for generating steam, and an anode gas supply line and a cathode gas supply line extending from the steam generation source and connected to the fuel cell. A pair of steam supply lines, a steam flow rate adjusting means provided on each of the steam supply lines and capable of adjusting the amount of steam flowing through each of the steam supply lines, and an anode gas and a cathode gas after steam mixing A steam flow rate control unit that performs open loop control of each of the steam flow rate adjusting means based on a predetermined environmental parameter so as to set each dew point to a predetermined set dew point.

  If it is such, since a steam generation source is made common, it can attain compactness, and since the same quality steam is supplied, dew point setting and temperature control can be performed under the same conditions. In addition, the steam flow rate control means that controls the amount of steam supplied to each gas supply line is controlled by open-loop control of the steam flow rate control unit from predetermined environmental parameters so that a desired dew point can be obtained. Very early. Moreover, because open loop control is used to speed up the response, etc., even if the steam generation source is shared, interference between the gas supply lines hardly occurs, and stable dew point control is possible. It becomes possible. Furthermore, since it is open-loop control, dew point measurement is not necessary, and problems caused by the ability of the dew point meter (for example, the above-described point that the dynamic range is small) can be prevented. In addition, since the control stability is high, even when the gas flow rate is low at a low dew point, it is possible to stably supply a gas having a desired dew point.

  In the case where the steam flow rate adjusting means adjusts the steam flow rate by expansion / contraction of the internal flow path using a valve, the environmental pressures include the respective fluid pressures upstream and downstream of the steam flow rate adjusting means, and the anode before steam mixing. If the respective flow rates of the gas and the cathode gas and the fluid temperature in the vapor flow rate adjusting means can be acquired, the dew point can be controlled.

  The fluid pressure downstream of the steam flow rate adjusting means may be obtained by providing a pressure detecting means on the steam supply line, but the downstream side of the junction with the steam supply line in the gas supply line (gas introduction of the fuel cell) You may acquire by the output signal from the pressure detection means provided in the port vicinity especially preferable. The fluid pressure downstream of the steam flow control means is on the steam supply line and on the gas supply line, unless there are special circumstances such as extremely long pipes or narrow parts in the flow path. This is because the values are almost the same. If the pressure is acquired from the gas supply line in this way, a pressure monitor installed at the gas introduction port of the fuel cell can be used as the pressure detection means, saving parts and reducing the costs associated therewith. , Compactness and easy maintenance can be promoted.

  When the gas flow rate adjusting means for controlling the flow rate of the anode gas and the cathode gas before steam mixing to be close to the target flow rate setting value like a mass flow controller is provided, it is necessary to actually measure the gas flow rate. For example, the flow rate setting value may be used as the flow rate among the environmental parameters. Thereby, the gas flow rate detecting means can be omitted.

  If the steam generation source is made common as described above, an unexpected flow from one steam supply line to the other steam supply line may occur, and the anode gas and the cathode gas may be mixed. For this, it is preferable that each steam supply line is provided with a check valve for preventing the return of fluid.

  As described above, according to the present invention, since the steam generation source is shared, it is possible to reduce the size and to supply the same quality steam, so that the dew point can be set and the temperature can be adjusted under the same conditions. . In addition, in order to obtain the desired dew point, the steam flow rate adjustment means is open-loop controlled from environmental parameters, so the responsiveness is very good. Interference is unlikely to occur and stable control is possible. Furthermore, since a dew point meter is not required for the control, it is possible to prevent a problem that the dynamic range due to the capability of the dew point meter is small and to obtain a large dynamic range.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The fuel cell 1 shown in FIG. 1 is not shown in its internal structure. For example, the fuel cell 1 is of a solid polymer type, and includes a solid polymer film having ionic conductivity and two sheets sandwiching the solid polymer film from both sides. Anode (fuel electrode [negative electrode]) and cathode (air electrode [positive electrode]) which are parallel plate electrodes, and anode gas (fuel gas) AG containing hydrogen and cathode gas (oxidizing gas) CG containing oxygen are brought into contact with these electrodes. It is comprised by the cell provided with the fuel electrode flow path and the air electrode flow path for making it.

  The introduction ports 11 and 12 of the fuel electrode flow path and the air electrode flow path are connected to the anode gas supply line L1 and the cathode gas supply line L2, and the anode gas AG is connected to each of these through the gas supply lines L1 and L2. Then, the cathode gas CG is sent to each of the electrodes so that the fuel cell 1 generates power.

  By the way, the anode gas AG and the cathode gas CG are sent to the gas supply lines L1 and L2 in a dry state from a cylinder (not shown) or the like, and the flow rate of the dry gas is the mass flow controller 21, which is a gas flow rate adjusting unit, 22 to control the flow rate to a predetermined value. Further, since it is necessary to replenish moisture to the solid polymer film, in this embodiment, a humidification system WS for adding water vapor (hereinafter also referred to as steam) to each gas supply line L1, L2 is provided. ing. In the following description, when it is necessary to distinguish between a gas in a dry state and a gas in a wet state due to the addition of water vapor, D and W are added to the subscripts, respectively.

Next, the humidification system WS will be described.
As shown in FIG. 1, this humidification system WS is connected to the common steam generation source 3 for generating steam and the anode gas supply line L1 and the cathode gas supply line L2 extending from the steam generation source 3. a pair of steam supply line SL1, SL2 that is, the steam flow rate adjusting means 41 for adjusting the steam supply line SL1, SL2 amount steam flowing through each anode gas AG _W and the cathode gas CG _W is predetermined respectively And a control device 5 that performs open-loop control so as to obtain a dew point.

Each part will be described.
The steam generation source 3 includes a sealed tank 31 that stores water and a heater 32 that heats the water. By heating the water with the heater 32, the space portion of the sealed tank 31 is It is configured to be filled with steam (gas phase water) above atmospheric pressure. Further, a steam outlet port 3a is provided in the space portion of the sealed tank 31, and the steam is connected to the steam supply lines SL1 and SL2 by connecting the base ends of the steam supply lines SL1 and SL2 to the port 3a. It is configured to be supplied.

  Each of the steam supply lines SL1 and SL2 has a common base end, and is branched from the middle, and ends at the cathode gas supply lines L1 and L2 and the anode gas supply lines L1 and L2, respectively. It is connected to junctions J1 and J2 provided in the middle. On the other hand, in the steam supply lines SL1 and SL2, the check valves CV1 and CV2 for preventing the steam from returning to the upstream side in order from the branch portion S, and the steam flow rate adjusting means for adjusting the flow rate of the steam. 41 and 42 are provided. Each of the steam supply lines SL1, SL2 and the gas supply lines L1, L2 has a temperature adjusting mechanism (not shown) such as a hot hose, and the pipe temperature is controlled so as to be equal to or higher than a predetermined temperature where no condensation occurs inside. Has been.

The steam flow rate adjusting means 41 and 42 are of a remote operation type in which the valve opening degree is controlled by a signal from the outside and the internal flow path can be adjusted. Temperature control mechanisms T1 and T2 are attached to the steam flow rate adjusting means 41 and 42, and the FB control is performed locally so that the temperature is detected and the temperature becomes a predetermined constant value. Pressure sensors P _C , P 1 and P 2 are provided upstream and downstream of the steam flow rate adjusting means 41 and 42, respectively. The primary pressure (upstream fluid pressure) and the secondary pressure of the steam flow rate adjusting means 41 and 42 are provided. (Downstream fluid pressure) can be detected. Primary pressure sensor P _C that detects the primary pressure, is provided with the branch portion S of the steam supply line SL1, SL2, the primary pressure of the steam flow rate adjustment means 41 and 42 in this single primary pressure sensor P _C Detect in common. The secondary pressure sensors P1 and P2 for detecting the secondary pressure are provided on the downstream side of the gas supply lines L1 and L2 from the junctions J1 and J2 (in the vicinity of the gas introduction ports 11 and 12 of the fuel cell). The secondary pressure sensors P1 and P2 have a display unit, and also serve as pressure monitors at the gas introduction ports of the fuel cell.

  The control device 5 uses a general purpose or dedicated computer, and includes an internal bus 501, a CPU 502, a memory 503, an I / O channel 504, an A / D converter 505, and the like, as shown in FIG. Then, when the CPU 502 operates according to a predetermined program stored in the memory 503 in advance, as shown in FIG. 3, the control device 5 has a data receiving unit 51, a vapor pressure control unit 52, a gas flow rate setting unit 53, The dew point setting unit 54, the gas flow rate control unit 55, the steam flow rate control unit 56, and the like are configured to exhibit their functions.

Thus, the data receiving unit 51 receives various data. Here, some of the data relating to environmental parameters, i.e., the primary pressure data and the secondary pressure data of the primary pressure sensor P _C and the secondary pressure sensor P1, coming output from P2 the steam flow rate adjustment means 41 and 42 At least the set temperature data of the temperature adjusting mechanism attached to the steam flow rate adjusting means 41, 42 is received. As other environmental parameters, there are flow rate setting values of each gas, which will be described later, and data relating to these environmental parameters is stored in the environmental parameter data storage unit D1 set in a predetermined area of the memory 503.

  The vapor pressure control unit 52 compares the primary pressure, which is also the vapor pressure at the vapor generation source 3, with a predetermined target vapor pressure, and the heater of the vapor generation source 3 to bring the primary pressure close to the target vapor pressure. 32 is FB-controlled. More specifically, the primary pressure data is acquired from the environmental parameter data storage unit D1, and if the value is lower than the target vapor pressure, the output of the heater 32 is increased, and if higher, the output of the heater 32 is decreased. The target vapor pressure does not have to be a single value and may have a range.

  The gas flow rate setting unit 53 sets a target flow rate of each gas before steam mixing based on an input from an operator, a signal from another computer, or the like, and sets flow rate data indicating the value to a predetermined flow rate in the memory 503. The data is stored in the setting data storage unit D2 provided in the area.

  The dew point setting unit 54 sets a target dew point of each gas based on an input from an operator, a signal from another computer, or the like, and stores set dew point data indicating the value in the setting data storage unit D2. Is.

The gas flow rate control unit 55 outputs a command signal such that the flow rates of the gases AG _D and CG _D flowing through the mass flow controllers 21 and 22 become set values. Specifically, the flow rate setting data of each gas AG _D , WG _D is acquired from the setting data storage unit D2, respectively, a predetermined calculation is performed on those values (gas flow rate setting values), and the value of each command signal is obtained. Calculate. The gas flow rate control unit 55 in this embodiment calculates the valve opening degree from the differential pressure of the mass flow controllers 21 and 22 so that the actual gas flow rate becomes the gas flow rate set value, and becomes the valve opening degree. Such a command signal is output. Some mass flow controllers perform FB control locally inside as long as flow rate setting data is provided, and adjust the valve opening by themselves so that the flow rate setting value is obtained. In this case, the gas flow rate setting is performed. The data may be output as a command signal as it is.

Vapor flow rate control unit 56, the anode gas AG _W and the cathode gas after the steam mixing, a CG _W of each dew point, in order to set the dew point (the value of the set dew point data), each of said steam flow rate adjustment means 41 and 42 Each is open-loop controlled based on environmental parameters. Hereinafter, the operation will be described in detail with reference to FIG.

  First, from the set dew point (value of the set dew point data), the gas pressure in the dry state (value of the secondary pressure data) and the gas flow rate in the dry state (value of the set flow rate data), the moisture weight flow rate (the value of the set dew point) ( kg / h).

  More specifically, after calculating the moisture content (%) from the set dew point and the dry gas pressure (step S1), the moisture flow rate (L / min) is changed to the dry gas flow rate (NL / min) and the moisture content (% ) (Step S2), and finally, the water weight flow rate (kg / h) is calculated from the water flow rate (L / min) (step S3).

  Next, the valve opening which becomes the moisture weight flow rate (kg / h) is calculated, and a valve opening command signal for maintaining the valve opening is output to the steam flow rate adjusting means 41 and 42.

  More specifically, a predetermined coefficient indicating the nature of the valve is obtained from the moisture weight flow rate (kg / h), primary pressure, secondary pressure, differential pressure, and steam temperature (degree of superheat) (step S4), and the coefficient Is extracted from a coefficient-valve opening relationship characteristic table stored in advance (step S5). This characteristic table is unique to each valve, and is obtained by testing in advance. Then, a valve opening command signal for achieving the valve opening is output to the steam flow rate adjusting means 41, 42 (step S6).

That is, according to the humidification system WS configured in this way, it is possible to supply steam that can independently achieve a desired dew point to the anode gas AG and the cathode gas CG supplied to the fuel cell 1. For example, if the flow rate of the anode gas AG _D and the cathode gas CG _D are different, if the same other conditions such as setting the dew point, the respective gas AG _D, steam at a ratio corresponding to the flow rate ratio of CG _D Will be supplied.

  In addition, since the steam generation source 3 is shared, it is possible to reduce the size of the steam generation source 3. In addition, the steam temperature can be easily managed.

  Moreover, since each dew point is controlled by open loop, the response is very good.

  Furthermore, since the open loop control is used to improve the responsiveness, it is difficult to cause interference between the gas supply lines L1 and L2 even though the steam generation source 3 is shared. Dew point control becomes possible. In particular, in this embodiment, since the pressure (primary pressure) of the steam generation source 3 is locally controlled and kept as constant as possible, the stability is further improved.

  In addition, since it is open loop control, dew point measurement is not necessary, and problems caused by the ability of the dew point meter (for example, a small dynamic range) can be prevented.

  Further, since the control stability is high, even when the gas flow rate is low at a low dew point, the gases AG and CG having the desired dew point can be stably supplied.

The present invention is not limited to the above embodiment. For example, a plurality of steam flow rate adjusting means may be provided in parallel so that the flow rate adjustment range can be increased.
Other configurations can be variously modified without departing from the spirit of the present invention.

1 is a schematic circuit diagram showing an embodiment of the present invention. The equipment block diagram of the control apparatus in the embodiment. The functional block diagram of the control apparatus in the embodiment. The flowchart which shows operation | movement of the control apparatus in the embodiment.

Explanation of symbols

WS: Humidification system 1 ... Fuel cell 21, 22 ... Gas flow rate adjusting means (mass flow controller)
DESCRIPTION OF SYMBOLS 3 ... Steam generation source 41, 42 ... Steam flow rate control means 56 ... Steam flow rate control part L1 ... Anode gas supply line L2 ... Cathode gas supply line SL1, SL2 ... Steam supply line P1, P2 ... Pressure detection means (secondary pressure sensor)
CV1, CV2 ... Check valve

Claims (5)

A common steam source that generates steam; and
A pair of steam supply lines extending from the steam generation source and connected to an anode gas supply line and a cathode gas supply line for the fuel cell,
A steam flow rate adjusting means provided on each of the steam supply lines and capable of adjusting the amount of steam flowing through each of the steam supply lines;
A steam flow rate control unit that performs open loop control of each of the steam flow rate adjusting means based on predetermined environmental parameters so that the dew points of the anode gas and the cathode gas after steam mixing are set to predetermined dew points. Fuel cell humidification system.   In the case where the steam flow rate adjusting means adjusts the steam flow rate by expansion / contraction of an internal flow path by a valve, as the environmental parameters, respective fluid pressures upstream and downstream of the steam flow rate adjusting means, and anode gas before steam mixing 2. The humidification system for a fuel cell according to claim 1, wherein at least the flow rates of the cathode gas and the cathode gas and the fluid temperature in the vapor flow rate adjusting means are used.   3. The fuel cell according to claim 2, wherein the fluid pressure downstream of the steam flow rate adjusting means is acquired from an output signal from a pressure detecting means provided downstream of a junction with the steam supply line in the gas supply line. Humidification system.   A gas flow rate adjusting means for adjusting the flow rates of the anode gas and the cathode gas before vapor mixing is provided on each gas supply line, and a flow rate setting value for the gas flow rate adjusting means is set as a flow rate among the environmental parameters. 4. The fuel cell humidification system according to claim 2, wherein the humidification system is used as a fuel cell. The fuel cell humidification system according to claim 1, 2, 3, or 4, wherein each of the steam supply lines is provided with a check valve for preventing return of fluid.