JP2017182943A - Method for controlling fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of inhibiting fuel gas from being wastefully discharged during discharge from a gas-liquid separator even when there are individual differences in the amount of waste water through an exhaust drain valve in a fuel cell system using the exhaust drain valve.SOLUTION: In a method for controlling a fuel cell system, a control device performs the steps of: calculating the exhaust gas amount of the exhaust drainage valve per unit time from the volume of a gas-liquid separator and a circulation passage, and the pressure drop amount in the circulation passage during opening of the exhaust drainage valve when there is no water in the gas-liquid separator and the circulation passage; estimating the amount of waste water per unit time of the exhaust drainage valve based on the calculated exhaust gas amount; estimating the amount of water stored in the gas-liquid separator from the power generation amount of the fuel cell; and draining water by controlling opening/closing of the exhaust drainage valve based on the amount of waste water per unit time of the estimated exhaust drainage valve when the estimated amount of waste water is equal to or more than the specified amount.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control method for a fuel cell system.

  For example, as described in Patent Document 1, the fuel cell system includes a circulation channel that circulates the fuel gas contained in the anode off gas to the fuel cell. Since the anode off gas contains impurities such as produced water and nitrogen, the fuel cell system described in Patent Document 1 uses the exhaust drain valve to discharge impurities out of the circulation flow path.

JP 2008-181811 A

  In the fuel cell system, when discharging generated water, water is separated from gas using a gas-liquid separator. At this time, the amount of water discharge varies depending on the individual difference of the exhaust drainage valve. Therefore, even if the water discharge amount is determined in advance so that the gas is not discharged, more than the expected amount of water is discharged, and the fuel In some cases, gas containing gas is wasted. When fuel gas is discharged, fuel efficiency deteriorates. Therefore, in a fuel cell system using an exhaust drainage valve, there is a technology that can suppress wasteful discharge of fuel gas when draining from a gas-liquid separator. It was desired.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a method for controlling a fuel cell system is provided. The control method of the fuel cell system includes a circulation flow path for circulating an anode off-gas of the fuel cell to the fuel cell; an air gas connected to the circulation flow path and separating generated water from the anode off-gas in the circulation flow path. A fuel comprising: a liquid separator; an exhaust drain valve for draining the produced water separated by the gas-liquid separator; and exhausting the anode off-gas discharged from the gas-liquid separator; and a control device A control method for a battery system, wherein: (a) the control device includes a volume of the gas-liquid separator and the circulation channel, and the exhaust drainage when there is no water in the gas-liquid separator and the circulation channel. The amount of exhaust gas discharged from the exhaust drain valve per unit time is calculated from the amount of pressure drop in the circulation flow path when the valve is opened. (B) After the step (a), the control device calculates Said exhaust gas Based on the amount, the amount of drainage per unit time of the exhaust drainage valve is estimated. (C) After the step (b), the control device accumulates in the gas-liquid separator from the power generation amount of the fuel cell. (D) after the step (c), when the estimated amount of water is greater than or equal to a specified amount, the control device is based on the estimated amount of discharged water per unit time of the exhaust drain valve. Drainage is performed by controlling the opening and closing of the exhaust drain valve. According to the control method of the fuel cell system of this embodiment, even if there is an individual difference in the amount of drainage by the exhaust drainage valve by performing steps (a) to (d), the fuel gas is discharged during drainage from the gas-liquid separator. Can be prevented from being discharged in vain. As a result, deterioration of fuel consumption can be suppressed.

  It should be noted that the present invention can be realized in various modes, such as a vehicle equipped with a fuel cell, a fuel cell system mounted on the vehicle, a control device that executes a control method for the fuel cell system, and the like. Can be realized.

It is the schematic which shows schematic structure of a fuel cell system. It is a flowchart of drainage capacity estimation processing. It is a flowchart showing a waste water treatment.

A. Embodiment:
FIG. 1 is a schematic diagram showing a schematic configuration of a fuel cell system 100 according to an embodiment of the present invention. The fuel cell system 100 includes a fuel cell 10, a control device 20, an oxidizing gas channel system 30, and a fuel gas channel system 50.

  The fuel cell 10 is a polymer electrolyte fuel cell that generates electricity by receiving supply of hydrogen (fuel gas) and air (oxidizing gas) as reaction gases. The fuel cell 10 has a stack structure in which a plurality of cells 11 are stacked. Each cell 11 has a membrane electrode assembly (not shown) in which electrodes are arranged on both surfaces of an electrolyte membrane (not shown), and a set of separators that sandwich the membrane electrode assembly. The electric power generated by the fuel cell 10 is stored in the battery 92 via the DC / DC converter 90. Various loads 93 are connected to the battery 92. Electric power is supplied from the fuel cell 10 or the battery 92 to the air compressor 32, the circulation pump 64, and various valves, which will be described later, and is driven.

  The oxidizing gas flow path system 30 includes an oxidizing gas pipe 31, an air compressor 32, an on-off valve 33, a cathode offgas pipe 41, and a regulator 42. The oxidizing gas flow path system 30 includes a flow path on the cathode side in the fuel cell 10.

  The air compressor 32 is connected to the fuel cell 10 via the oxidizing gas pipe 31. The air compressor 32 compresses air taken from outside in accordance with a control signal from the control device 20 and supplies the compressed air to the fuel cell 10 as an oxidizing gas.

  The on-off valve 33 is provided between the air compressor 32 and the fuel cell 10 and opens and closes according to the flow of supply air in the oxidizing gas pipe 31. Specifically, the on-off valve 33 is normally in a closed state and opens when air having a predetermined pressure is supplied from the air compressor 32 to the oxidizing gas pipe 31.

  The cathode offgas pipe 41 discharges the cathode offgas discharged from the cathode of the fuel cell 10 to the outside of the fuel cell system 100. The regulator 42 adjusts the cathode offgas pressure (back pressure on the cathode side of the fuel cell 10) in the cathode offgas piping 41 in accordance with a control signal from the control device 20.

  The fuel gas passage system 50 includes a fuel gas pipe 51, a hydrogen tank 52, an on-off valve 53, a regulator 54, an injector 55, an exhaust / drain valve 60, an anode offgas pipe 61, a pressure sensor 62, and a circulation. A pipe 63, a circulation pump 64, and a gas-liquid separator 70 are provided. The fuel gas channel system 50 includes an anode-side channel in the fuel cell 10. Hereinafter, the fuel gas pipe 51 includes a downstream side of the injector 55, an anode-side flow path in the fuel cell 10, an anode offgas pipe 61, a circulation pipe 63, and a gas-liquid separator 70. The flow path is also referred to as a circulation flow path 65. The circulation channel 65 is a channel for circulating the anode off gas of the fuel cell 10 to the fuel cell 10. A pressure sensor 62 for detecting the pressure in the circulation channel 65 is connected to the circulation channel 65.

  The hydrogen tank 52 is connected to the anode of the fuel cell 10 through the fuel gas pipe 51, and supplies the hydrogen filled inside to the fuel cell 10. The on-off valve 53, the regulator 54, and the injector 55 are provided in the fuel gas pipe 51 in this order from the upstream side, that is, the side close to the hydrogen tank 52.

  The on-off valve 53 opens and closes in response to a control signal from the control device 20 and controls the inflow of hydrogen from the hydrogen tank 52 to the upstream side of the injector 55. When the fuel cell system 100 is stopped, the on-off valve 53 is closed. The regulator 54 adjusts the hydrogen pressure on the upstream side of the injector 55 in accordance with a control signal from the control device 20. The injector 55 is an electromagnetically driven on / off valve in which the valve element is electromagnetically driven in accordance with the driving cycle and valve opening time set by the control device 20. The control device 20 controls the amount of hydrogen supplied to the fuel cell 10 by controlling the drive cycle and valve opening time of the injector 55.

  The anode off-gas pipe 61 is a pipe connecting the outlet of the anode of the fuel cell 10 and the gas-liquid separator 70. The anode off gas pipe 61 guides the anode off gas containing fuel gas, nitrogen gas, etc., which has not been used for the power generation reaction, to the gas-liquid separator 70.

  The gas-liquid separator 70 is connected between the anode off-gas pipe 61 and the circulation pipe 63 of the circulation flow path 65. The gas-liquid separator 70 separates the generated water from the anode off gas in the circulation channel 65 and stores the separated water.

  The circulation pipe 63 is connected downstream from the injector 55 of the fuel gas pipe 51. The circulation pipe 63 is provided with a circulation pump 64 that is driven in accordance with a control signal from the control device 20. The anode off gas from which the generated water has been separated by the gas-liquid separator 70 is sent out to the fuel gas pipe 51 by the circulation pump 64. Thus, in this fuel cell system 100, the anode off gas containing hydrogen is circulated and supplied to the fuel cell 10 again, thereby improving the utilization efficiency of hydrogen.

  The exhaust drain valve 60 is provided in the lower part of the gas-liquid separator 70. The exhaust / drain valve 60 drains the generated water stored in the gas-liquid separator 70 and exhausts the anode off gas in the gas-liquid separator 70. During operation of the fuel cell system 100, the exhaust drain valve 60 is normally closed and opens and closes in response to a control signal from the control device 20. In the present embodiment, the exhaust drain valve 60 is connected to the cathode offgas pipe 41, and the generated water and anode offgas discharged by the exhaust drain valve 60 are discharged to the outside through the cathode offgas pipe 41.

  The control device 20 is configured as a computer including a CPU, a memory, and an interface circuit to which the above-described components are connected. The CPU executes various control processes, which will be described later, as a control method of the fuel cell system 100 by executing a control program stored in the memory, and controls the operation of the fuel cell system 100.

  FIG. 2 is a flowchart of the drainage capacity estimation process. This process is a process executed by the control device 20 when the fuel cell system 100 is started, and is a process for estimating the amount of drainage per unit time of the exhaust drainage valve 60. When starting this process, the control device 20 first fills the circulation passage 65 with the fuel gas from the hydrogen tank 52, and opens the exhaust / drain valve 60 with the open / close valve 53 and the injector 55 closed (step). S300). After opening the exhaust / drain valve 60, the control device 20 calculates the pressure drop amount in the circulation passage 65 caused by the gas being discharged from the gas-liquid separator 70 using the pressure sensor 62, and the pressure Is detected (step S310). If no pressure drop is detected (step S310: NO), water has been discharged from the gas-liquid separator 70, so the control device 20 stands by until a pressure drop is detected.

  On the other hand, when a pressure drop is detected (step S310: YES), the gas is discharged from the gas-liquid separator 70. In this case, the control device 20 calculates the exhaust gas amount per unit time (step S320). The control device 20 determines the unit of the exhaust / drain valve 60 based on the volume of the circulation channel 65 obtained in advance and the amount of pressure drop in the circulation channel 65 when the exhaust / drain valve 60 is detected as detected by the pressure sensor 62. The amount of exhaust gas per hour can be calculated.

  Subsequently, the control device 20 estimates the drainage amount per unit time of the exhaust / drain valve 60 based on the calculated exhaust gas amount per unit time (step S330). The control device 20 can estimate the drainage amount per unit time by referring to a map in which the relationship between the exhaust gas amount per unit time and the drainage amount per unit time is associated in advance. In this embodiment, the waste water treatment mentioned later is implemented based on the estimated amount of waste water per unit time.

  FIG. 3 is a flowchart showing the waste water treatment in the present embodiment. This process is a process repeatedly executed by the control device 20 during the operation of the fuel cell system 100. It is assumed that the exhaust / drain valve 60 is closed at the start of this process. When this process is started, the control device 20 first estimates the amount of water stored in the gas-liquid separator 70 based on the amount of power generated by the fuel cell 10 (step S400). The control device 20 can estimate the amount of stored water based on a map or function in which the relationship between the current value of the fuel cell 10 and the amount of water generated is defined.

  Next, the control device 20 determines whether or not the estimated amount of stored water has exceeded a specified amount stored in the gas-liquid separator 70 (step S410). When the estimated amount of stored water is greater than the specified amount (step S410: YES), the control device 20 opens the exhaust / drain valve 60 (step S420). On the other hand, when the estimated amount of stored water is equal to or less than the specified amount (step S410: NO), the control device 20 stands by until the estimated amount of stored water reaches the specified amount.

  After opening the exhaust drain valve 60, the control device 20 multiplies the amount of drainage per unit time estimated by the drain capacity estimation process (FIG. 2) by the time elapsed since the exhaust drain valve 60 was opened. The amount of water discharged from the exhaust / drain valve 60 is estimated, and it is determined whether or not the amount of water has reached the desired amount of drainage (step S430). The desired amount of drainage is the limit amount of drainage from which gas is not discharged from the gas-liquid separator 70, and is almost the same or slightly smaller than the above-mentioned prescribed amount. If the amount of water obtained by multiplying the estimated amount of drainage per unit time has not reached the desired amount of drainage (step S430: NO), the controller 20 multiplies the estimated amount of drainage per unit time by time. The controller 20 waits until the determined amount of water reaches the desired amount of drainage, and if the amount of water determined by multiplying the estimated amount of drainage per unit time by time reaches the desired amount of drainage (step S430: YES), the control device 20 Then, the exhaust / drain valve 60 is closed (step S440). In step S440, the control device 20 resets the water storage amount estimated in the next step S400 and the value of the water amount estimated in the next step S430. According to the wastewater treatment described above, the control device 20 can perform drainage by controlling the opening and closing of the exhaust drainage valve 60 so that gas is not discharged from the exhaust drainage valve 60.

  According to the control method of the fuel cell system 100 of the present embodiment described above, the gas per unit time is calculated from the pressure drop amount in the absence of the initial water in the gas-liquid separator 70 by the drainage capacity estimation process described above. The exhaust gas amount of the liquid separator 70 is calculated, and the drainage amount per unit time of the exhaust drain valve 60 can be obtained from the calculated exhaust gas amount. Therefore, since the drainage capacity according to the individual difference of the exhaust drainage valve 60 can be estimated, for example, even if there is individual variation in the orifice diameter of the exhaust drainage valve 60 and the stroke amount of the valve, the drainage amount in the drainage treatment described above Can be adjusted to such an amount that the gas is not discharged from the gas-liquid separator 70, and it is possible to suppress the wasteful discharge of the fuel gas from the gas-liquid separator 70. As a result, according to the present embodiment, it is possible to prevent the fuel consumption of the fuel cell system 100 from deteriorating.

B. Variations:
<First Modification>
In the embodiment described above, a map in which the relationship between the amount of exhaust gas per unit time and the amount of drainage per unit time is associated in advance is used for estimating the amount of drainage per unit time. However, instead of the map, a function representing the relationship between the amount of exhaust gas per unit time and the amount of drainage per unit time may be used.

<Second Modification>
In the above embodiment, the waste water treatment for draining from the gas-liquid separator 70 has been described in detail, but the control device 20 separately performs a process for exhausting impurities such as nitrogen from the circulation flow path 65, In the exhaust process, the exhaust drain valve 60 may be opened and closed at a timing different from the above-described drain process.

<Third Modification>
In the wastewater treatment of the above embodiment, the exhaust drainage valve 60 is controlled to be opened and closed so that the gas is not exhausted from the exhaust drainage valve 60. However, the exhaust drainage valve 60 is configured so that a small amount of gas is exhausted from the exhaust drainage valve 60. Opening and closing may be controlled.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the column of the summary of the invention are intended to solve the above-described problems or to achieve a part or all of the above-described effects. In order to achieve, it is possible to replace and combine as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 11 ... Cell 20 ... Control apparatus 30 ... Oxidation gas flow path system 31 ... Oxidation gas piping 32 ... Air compressor 33 ... On-off valve 41 ... Cathode off-gas piping 42 ... Regulator 50 ... Fuel gas flow path system 51 ... Fuel gas Pipe 52 ... Hydrogen tank 53 ... On-off valve 54 ... Regulator 55 ... Injector 60 ... Exhaust drain valve 61 ... Anode off-gas pipe 62 ... Pressure sensor 63 ... Circulation pipe 64 ... Circulation pump 65 ... Circulation flow path 70 ... Gas-liquid separator 80 ... Drainage exhaust gas map 90 ... DC / DC converter 92 ... Battery 93 ... Load 100 ... Fuel cell system

Claims (1)

A circulation flow path for circulating the anode off gas of the fuel cell to the fuel cell;
A gas-liquid separator connected to the circulation channel and separating generated water from the anode offgas in the circulation channel;
An exhaust drain valve for draining the generated water separated by the gas-liquid separator and exhausting the anode off-gas discharged from the gas-liquid separator;
A control method of a fuel cell system comprising:
(A) The control device is configured so that the volume of the gas-liquid separator and the circulation channel, and the circulation flow when the exhaust drain valve is opened when there is no water in the gas-liquid separator and the circulation channel. Calculating the exhaust gas amount of the exhaust drain valve per unit time from the pressure drop in the road;
(B) After the step (a), the control device estimates a drainage amount per unit time of the exhaust drainage valve based on the calculated exhaust gas amount;
(C) after the step (b), the control device estimates the amount of water accumulated in the gas-liquid separator from the power generation amount of the fuel cell;
(D) After the step (c), when the estimated amount of water is equal to or greater than a specified amount, the control device determines the amount of the exhaust drain valve based on the estimated amount of drain per unit time of the exhaust drain valve. And a step of draining by controlling opening and closing.

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