WO2008001656A1

WO2008001656A1 - Method for starting fuel cell system

Info

Publication number: WO2008001656A1
Application number: PCT/JP2007/062374
Authority: WO
Inventors: Susumu Hatada
Original assignee: Nippon Oil Corporation
Priority date: 2006-06-28
Filing date: 2007-06-20
Publication date: 2008-01-03
Also published as: JP5065627B2; TW200820481A; JP2008010260A

Abstract

Disclosed is a method for starting a fuel cell system using a hydrocarbon fuel. This starting method enables to suppress deposition of carbon from the hydrocarbon fuel. Specifically disclosed is a method for starting a fuel cell system comprising a line for flowing a mixed gas of a hydrocarbon fuel gas and water vapor, and a fuel cell connected to the downstream of the line. In this starting method, water vapor is supplied to the line before the hydrocarbon fuel gas is supplied to the line.

Description

Specification

Starting method of fuel cell system

Technical field

The present invention relates to a method for starting a fuel cell system that generates power using a reformed gas obtained by reforming a hydrocarbon fuel such as kerosene.

Background art

[0002] In a fuel cell system, a hydrocarbon-based fuel such as kerosene or city gas is usually reformed to produce a reformed gas containing hydrogen, and the resulting reformed gas and air are supplied to the fuel cell. And generate electricity by electrochemical reaction.

[0003] When starting up a fuel cell system, particularly when using a fuel cell that operates at a high temperature, such as a solid acid fuel cell, the anode electrode of the fuel cell is oxidized and the reforming catalyst is oxidized. A reducing gas such as hydrogen is circulated through the fuel cell anode and the reforming catalyst so that the reforming performance does not deteriorate.

[0004] Various reforming reactions such as steam reforming, partial oxidation reforming, and autothermal reforming (performing both steam reforming and partial oxidation reforming) are used for reforming. When steam reforming is performed (including autothermal reforming), hydrocarbon fuel gas and water vapor are mixed and supplied to the reformer. At this time, if the hydrocarbon fuel is liquid, vaporize it beforehand.

[0005] Generally, when using a hydrocarbon-based fuel, particularly when using a hydrocarbon-based fuel having a high carbon composition ratio in the molecule such as kerosene, the hydrocarbon-based fuel is used in a high-temperature atmosphere of, for example, about 400 ° C or higher. Force Carbon may be deposited. Carbon deposition causes channel blockage in piping and reformers. In particular, when a reforming catalyst is used in the reformer, carbon deposition is likely to occur on the reforming catalyst.

[0006] It is known that carbon deposition can be suppressed even in a high temperature atmosphere by mixing water vapor with a hydrocarbon fuel. Therefore, for example, in a fuel cell system using kerosene, steam and kerosene steam are mixed at about 300 ° C to 400 ° C, and this mixed gas is supplied to the reformer. . [0007] Note that, regardless of the type of reforming reaction, carbon may also be deposited in the hydrocarbon fuel power in the line where the hydrocarbon fuel to the reformer flows. Therefore, water vapor is not required for reforming! Even in the case of partial oxidation reforming, steam is mixed with hydrocarbon fuel.

Such a hydrocarbon fuel supply method is described in Patent Document 1.

Patent Document 1: Patent Publication 2005-213057

Disclosure of the invention

Problems to be solved by the invention

[0009] In order to perform power generation with a fuel cell system that reforms and uses a hydrocarbon-based fuel, it is suitable for warming up the equipment constituting the system to a desired temperature and for performing an electrochemical reaction in the fuel cell. A start-up operation is performed to enable generation of a gas having a composition.

[0010] In the start-up operation, carbon deposition as described above may occur, and there is a demand for a start-up method that can more reliably suppress carbon deposition.

[0011] An object of the present invention is to provide a start-up method capable of suppressing the deposition of hydrocarbon-based fuel-powered carbon in a fuel cell system using a hydrocarbon-based fuel.

Means for solving the problem

[0012] The present invention provides the following method.

[0013] (1) Activation of a fuel cell system that activates a fuel cell system having a line for flowing a mixed gas of hydrocarbon fuel gas and water vapor, and a fuel cell connected downstream of the line In the method

A method for starting a fuel cell system, comprising: supplying water vapor to the line before supplying hydrocarbon fuel gas to the line.

(2) a) Before supplying the hydrocarbon-based fuel gas and water vapor to the line, oxygen is supplied to the fuel cell power sword and hydrogen is supplied to the fuel cell anode. A step of generating a voltage by an electrochemical reaction in a battery;

b) after step a, supplying water vapor to the line while monitoring the voltage of the fuel cell while continuing the oxygen supply and hydrogen supply; and c) After step b, after detecting a drop in the voltage of the fuel cell, supplying hydrocarbon fuel gas to the line

(1) The method of description.

(3) In the step b, the supply flow rate of water vapor is set to a desired flow rate of water vapor at the completion of the start-up operation,

The method according to (2), wherein in step c, the supply flow rate of the hydrocarbon-based fuel gas is set to a desired flow rate of the hydrocarbon-based fuel gas when the start-up operation is completed.

(4) In the step b, the supply flow rate of water vapor is a part of the desired flow rate of water vapor when the start-up operation is completed,

In step c, the supply flow rate of the hydrocarbon fuel gas is a part of the desired flow rate of the hydrocarbon fuel gas at the completion of the start-up operation,

After step c

d) increasing the flow rate of water vapor supplied to the line while monitoring the voltage of the fuel cell while continuing the oxygen supply and hydrogen supply; and

e) After step d, after detecting a decrease in the voltage of the fuel cell, increasing the flow rate of hydrocarbon fuel gas supplied to the line

The method according to (2), further comprising:

[0017] (5) A hydrocarbon-based fuel supplied by repeating the combination of steps d and e a plurality of times so that the flow rate of water vapor supplied to the line is the desired flow rate of water vapor at the completion of start-up operation and supplied to the line (4) The method according to (4), wherein the flow rate of the gas is set to a desired flow rate of the hydrocarbon-based fuel gas at the completion of the startup operation.

[0018] (6) A fuel cell system having a predetermined time interval between a time point at which an operation for supplying water vapor to the line and a time point at which an operation for supplying a hydrocarbon-based fuel gas to the line is performed. A startup method,

The predetermined time interval is set in advance by a preliminary start operation for starting the fuel cell system in advance,

The method of the preliminary start-up operation is

i) Before supplying hydrocarbon fuel gas and water vapor to the line, Performing oxygen supply to the fuel cell power sword and hydrogen supply to the fuel cell anode to generate a voltage due to an electrochemical reaction in the fuel cell;

ii) after step i, performing the operation of supplying water vapor to the line while monitoring the voltage of the fuel cell while continuing the oxygen supply and hydrogen supply; and

iii) After step ii, a step of detecting a decrease in the voltage of the fuel cell

Have

In Step ii, the time from when the operation of supplying water vapor is performed until the time when the voltage drop is detected in Step iii is measured, and this measured time is defined as the predetermined time interval. Ru

(1) A method for starting the fuel cell system according to (1).

The invention's effect

[0019] According to the present invention, in a fuel cell system using a hydrocarbon-based fuel, a start-up method capable of suppressing the deposition of hydrocarbon-based fuel power carbon is provided.

Brief Description of Drawings

FIG. 1 is a flowchart showing an outline of an embodiment of a fuel cell system capable of implementing the present invention.

FIG. 2 is a flow chart for explaining an embodiment of a starting method of the fuel cell system of the present invention.

FIG. 3 is a flowchart partially showing the periphery of a pump in another embodiment of a fuel cell system in which the present invention can be implemented.

Explanation of symbols

[0021] 1 pump (for kerosene)

2 Vaporizer (for kerosene)

3 Pump (for water)

4 Vaporizer (for water)

5 Mixer

6, 7, 8

9, 11 Three-way valve 10 Reformer

20 Fuel cell

101 Line through which a mixed gas of kerosene gas and water vapor flows

102, 103 Circulation line around the pump

A Fuel cell anode

C Fuel cell power sword

BEST MODE FOR CARRYING OUT THE INVENTION

[0022] The present invention includes a line for flowing a mixed gas of a hydrocarbon-based fuel gas and water vapor (hereinafter referred to as a fuel's water vapor mixed gas line) and a fuel cell connected downstream of this line. The present invention relates to a fuel cell system activation method for activating a fuel cell system having the fuel cell system. More specifically, the fuel cell anode is connected downstream of this line. There is no need to connect a fuel cell directly downstream of this line. When hydrocarbon fuel is modified by a reformer, the fuel cell is connected downstream of the fuel vapor mixed gas line via the reformer. In this case, the reformer is connected to the fuel / water vapor mixed gas line, the reformed gas line for flowing the reformed gas is connected to the downstream of the reformer, and the fuel cell is downstream of the reformed gas line. Is connected. Sarakuko installed a shift reactor (CO + H0 → H + CO) and a carbon monoxide selective oxidation reactor (2CO + 0 → 2CO) between the reformer and the fuel cell anode.

2 2 2 2 2 May be. Alternatively, when the hydrocarbon fuel can be reformed inside the fuel cell, the fuel cell anode can be directly connected downstream of the fuel-water vapor mixed gas line.

In the present invention, before supplying the hydrocarbon-based fuel gas to the fuel / steam mixed gas line, steam is supplied to this line. As a result, it is possible to more reliably prevent carbon from being deposited from the hydrocarbon-based fuel during startup.

[0024] At this time, it is preferable to supply steam having a steam Z carbon ratio (SZC) of 3 or more in a mixed gas of hydrocarbon-based fuel gas and steam. SZC is a water vapor (H 2 O) molecule relative to the number of moles of carbon (C) atoms in the hydrocarbon fuel contained in this mixed gas.

2 is the ratio of moles.

[0025] The following describes the present invention with reference to the drawings. The present invention is not limited thereto. FIG. 1 shows a schematic configuration of one form of a fuel cell system that can implement the starting method of the present invention. Here, kerosene is used as the hydrocarbon fuel, and the fuel cell is connected downstream of the fuel / steam mixed gas line via a reformer.

[0027] [Temperature rise]

First, the equipment that needs to be heated, in this case, kerosene vaporizer 2, water vaporizer 4, reformer 10, and fuel cell 20 is heated. If necessary, the piping is also heated. This heating can be appropriately performed by a method employed in a known start-up operation of the fuel cell system. As a heat source for the calorie heat, combustion heat obtained by burning a combustible material such as a hydrocarbon fuel prepared for use in power generation by a combustion means such as a burner can be used. Alternatively, it can be heated by an electric heater.

[0028] [Reducing gas supply]

In order to prevent oxidation of the reforming catalyst accommodated in the anode electrode reformer of the fuel cell, a reducing gas can be supplied to the reformer and the anode of the fuel cell. Open the valve 8 and start supplying the reducing gas until the anode electrode reaches the temperature range where there is a risk of acidification.

In FIG. 1, the force for supplying the reducing gas (hydrogen) to the reformer 10 via the mixer 5 is not necessarily required. The reducing gas can be supplied separately to the reformer (reforming catalyst layer) and the fuel cell anode, respectively, but when a reformer is present, the reformer (reforming catalyst layer). Then, the fuel cell anode can be supplied.

[0030] Hydrogen can be used as the reducing gas. Hydrogen may be pure hydrogen, but may be accompanied by another gas that does not impair the reducibility, such as nitrogen. A cylinder can be used as the source of the reducing gas.

[0031] [Hydrocarbon fuel 'steam supply]

When the reformer is ready for reforming, gas obtained by vaporizing kerosene (kerosene gas) can be supplied to the reformer. For example, when kerosene is steam reformed, the reaction proceeds at 550 ° C to 750 ° C, so after the reforming catalyst layer in the reformer reaches this temperature range, kerosene gas is added to the reforming catalyst layer. Can be supplied. For this purpose, kerosene is boosted by a pump 1 as a boosting means and vaporized by a vaporizer 2. A pump and a vaporizer may be provided as necessary. example For example, when methane gas having a desired pressure is used as a hydrocarbon-based fuel, neither a booster nor a vaporizer is required.

[0032] At this time, water vapor is mixed with kerosene gas in order to suppress carbon deposition. In the present invention, water vapor is supplied to the line through which the mixed gas of kerosene gas and water vapor flows before the kerosene gas is supplied. . This makes it possible to more reliably suppress carbon deposition.

[0033] Specifically, the valve 7 is opened, the pressure of the water is increased by the pump 3, and the vaporizer 4 vaporizes the water. The obtained water vapor is supplied from the mixer 5 to a line (fuel / water vapor mixed gas line) 101 through which a mixed gas of kerosene gas and water vapor flows. Noreb 7 may be opened before the temperature rises. In addition, valve 7 need not be installed. In this case, opening of valve 7 does not occur. As shown in Fig. 3, when there is a circulation line 103 connecting the upstream of the pump 3 and between the pump 3 and the vaporizer 4 (in this case, a three-way valve 11 between the pump 3 and the vaporizer 4). The three-way valve 11 is switched to the upstream side of the pump 3 in advance before the supply of water vapor is started, the pressure of the water is increased by the pump 3, and the water is circulated through the circulation line to vaporize the three-way valve 11. Switch to vessel side 4 and vaporize water with vaporizer 4. The obtained water vapor is supplied from the mixer 5 to a line (fuel “water vapor mixed gas line) 101 through which a mixed gas of kerosene gas and water vapor flows.

[0034] After that, the valve 6 is opened, the kerosene pressure is increased by the pump 1, the kerosene gas obtained from the air heater 2 is guided to the mixer, and mixed with the water vapor to flow to the line 101. Valve 6 may be opened before the temperature rises. In this case, it is not necessary to install the valve 6. In this case, the operation to open the valve 6 does not occur. As shown in Fig. 3, when there is a circulation line 102 connecting the upstream of pump 1 and between pump 1 and vaporizer 2 (in this case, there is a three-way solenoid 9 between pump 1 and vaporizer 2). Before the start of kerosene supply, switch the three-way valve 9 to the upstream side of the pump 1, boost the kerosene with the pump 1, and circulate the kerosene through the circulation line, and set the three-way valve 9 to the vaporizer. Switch to 2 side, vaporize kerosene with vaporizer 2, introduce the resulting kerosene gas to the mixer, mix with water vapor, and flow to line 101.

[0035] Next, the timing of water vapor supply and kerosene gas supply to the fuel / water vapor mixed gas line will be described.

[0036] Based on the volume of the flow path and the flow rate of the supply gas, operate the operating end of the kerosene supply (starting the pump, opening the valve, etc.) Mixed gas line 1 The time to reach 01 can be estimated. The same applies to the water supply. Based on these estimated times, after operating the operating end of the steam supply, operating the operating end of the kerosene supply for a time interval, the steam reaches the line 101 after the steam reaches the line 101. The system can be controlled to reach However, because there are uncertain factors such as the liquid filling state in the flow path before starting and bubbles, it is not always easy to estimate the above time accurately. It is preferable to set longer than the estimated time.

[0037] On the other hand, the fuel cell voltage reacts sensitively to the partial pressure of electrochemically reactive chemical species such as hydrogen and oxygen. The lower the hydrogen partial pressure, the lower the voltage. For example, when hydrogen (a mixed gas containing hydrogen) is supplied to the anode and water vapor is added thereto, the hydrogen partial pressure is lowered by the addition of water vapor, and the fuel cell The voltage drops immediately. Therefore, by detecting this voltage drop, it is possible to know that water vapor has reached the anode. If the water vapor reaches the anode, the water vapor flows into the fuel-water vapor mixed gas line 101 located upstream of the anode, so that the kerosene gas may be supplied to the line 101.

[0038] When starting the fuel cell system using such a principle, it is preferable to perform the following steps a to c from the viewpoint of more reliably suppressing carbon deposition.

[Step a]

Before supplying the hydrocarbon fuel gas and water vapor to the fuel / water vapor mixed gas line, supply oxygen to the fuel cell power sword and hydrogen to the fuel cell anode to supply the fuel cell. To generate voltage by electrochemical reaction.

[0040] In order to supply hydrogen to the anode, pure hydrogen may be used, but as long as it is not limited to this, a gas containing hydrogen can be appropriately used. For example, a mixed gas of inert gas such as hydrogen and nitrogen can be used.

[0041] Hydrogen supply to the anode can be performed at an appropriate timing before the hydrocarbon fuel is supplied to the fuel / steam mixed gas line. As described above, if hydrogen (or a mixed gas containing hydrogen) is supplied to the anode as a reducing gas for preventing acidification of the anode electrode or the like, by continuing this supply, in step a Hydrogen supply to the anode It can be carried out.

[0042] In order to supply oxygen to the force sword, pure oxygen may be used, but a gas containing oxygen that is not limited thereto may be used as appropriate. For example, if you supply air to a power sword,

[0043] The oxygen supply to the power sword may be performed at an appropriate timing before the hydrocarbon fuel is supplied to the fuel / steam mixed gas line.

[0044] When the fuel cell reaches a temperature at which a voltage can be generated by an electrochemical reaction, hydrogen is supplied to the anode and oxygen is supplied to the power sword, a voltage is generated in the fuel cell.

[0045] It should be noted that at this time, it is preferable that the current of the fuel cell power is not extracted. This is because the amount of hydrogen supplied to the anode may be small as long as no current is taken out. At this time, oxygen supply to the power sword is also small. At this time, the voltage is an open circuit voltage.

[Step b]

After step a, steam is supplied to the fuel / steam mixed gas line while monitoring the voltage of the fuel cell while continuing the oxygen supply and hydrogen supply.

[0047] For the oxygen supply and the hydrogen supply, it is preferable to keep the oxygen concentration and the hydrogen concentration as constant as possible. This is to eliminate the voltage fluctuation factor as much as possible and to make it easier to observe the voltage drop due to the arrival of water vapor at the anode. For example, a cylinder can be used as a supply source of hydrogen (or a mixed hydrogen gas), and air can be used as an oxygen supply source. The fuel cell may be in the process of being heated. This is because the voltage changes with temperature, but the magnitude and speed of the voltage change due to the change in gas composition is much faster than the voltage change due to temperature rise.

[0048] The cell voltage of the fuel cell can be estimated using the following Nernst equation. Ε, ΔG, F, R, and T are cell voltage, Gibbs free energy, Faraday constant, gas constant, and temperature, respectively. ρ, ρ, ρ

Η2 02 Η20 are the hydrogen partial pressure, oxygen partial pressure, and water vapor partial pressure at the reaction interface, respectively.

[0049] [Equation 1]

The cell voltage drop of the fuel cell due to the arrival of water vapor at the anode can be estimated from the change in partial pressure due to the addition of water vapor using the following equation. —Δ で is the cell voltage drop. “” Represents after the arrival of water vapor.

[Equation 2]

f H i to PH _I0 , ^F

\ ^{2F 2} PH I ^2F AAV Especially when the temperature and oxygen partial pressure do not change before and after the arrival of water vapor, the cell voltage drop of the fuel cell can be estimated using the following formula. In a stack with n cells connected in series, the voltage drop is 1 η Δ Ε.

[Equation 3]

—

By supplying water vapor, p 'H20 Zp H20 becomes larger than 1, so RTZ2F X ln (p H2

It is desirable to adjust the flow rate so that ZP ') x n is large enough to be detected by a voltmeter.

H2

. For example, in the process of increasing the temperature of a stack of 100 cells connected in series, hydrogen 4NLM (NLM is 0 ° C, 0. lOlMPa converted to liter Z) converted to the anode and air 50NLM Begins to be supplied to the power sword. At this time, supply of hydrogen to at least the anode is started until the anode electrode reaches a temperature range in which oxidation is likely to occur. If 6NLM of steam is supplied to the anode in step b and the stack temperature does not change to 800 ° C before and after steam supply, the voltage drops by at least 3.2V, and a voltage drop can be detected with a general voltmeter. In order to obtain the voltage drop in more detail, the relationship between the hydrogen's water vapor partial pressure and the voltage at the anode reaction interface or the relationship between the supplied hydrogen Z water vapor mixing ratio and the voltage may be obtained by preliminary experiments or simulations.

[Process c]

After step b, after the fuel cell voltage drop is detected, the hydrocarbon fuel gas is supplied to the fuel / steam mixed gas line. [0053] A voltage drop means that water vapor has reached the anode. Therefore, supply hydrocarbon fuel gas to the fuel's steam-mixed gas line.

FIG. 2 arranges the above steps a to c as a flowchart. In step a, hydrogen and oxygen are supplied to the fuel cell to generate voltage, and in step b, water vapor is supplied to the fuel / steam mixed gas line. The voltage is monitored, and if a voltage drop is detected in step c, supply of hydrocarbon fuel gas to this line is started.

[Supply amount of water vapor and hydrocarbon fuel]

In step b, the amount of water vapor supplied is the desired flow rate of water vapor at the completion of startup operation, and in step c, the amount of hydrocarbon fuel gas supplied is the desired flow rate of hydrocarbon fuel gas at the time of completion of startup operation. It can be. This method is a simple method that can supply desired amounts of water vapor and hydrocarbon fuel gas at a time.

[0056] Alternatively, in step b, the flow rate of water vapor is a part of the desired flow rate of water vapor at the completion of start-up operation, and in step c, the flow rate of hydrocarbon-based fuel gas is changed to the hydrocarbon-based flow rate at the time of completion of start-up operation. As part of the desired flow rate of the fuel gas, and after step c,

d) a step of increasing the flow rate of water vapor supplied to the fuel 'water vapor mixed gas line while monitoring the voltage of the fuel cell while continuing the oxygen supply and hydrogen supply; and e) the fuel after step d The process of increasing the flow rate of hydrocarbon fuel gas supplied to the fuel / steam mixed gas line after detecting a drop in battery voltage

May be performed.

[0057] With this method, the supply amount of water vapor and hydrocarbon fuel can be increased stepwise.

[0058] For example, when the start-up operation is completed, the desired flow rate of water vapor is represented as F, and the start-up operation is completed.

St

When the desired flow rate of hydrocarbon fuel gas at the time is expressed as F, the fuel in step b

HC

The flow rate of steam supplied to the steam mixture gas line is (F Z2) and

St

The flow rate of the hydrocarbon-based fuel gas supplied to this line is (F / 2), and

HC

Increase the flow rate of water vapor supplied to this line to F and use this line in step e. The flow rate of hydrocarbon fuel to be supplied can be increased to F.

HC

[0059] Further, by repeating the combination of steps d and e a plurality of times, the supply flow rates of water vapor and hydrocarbon fuel can be increased in three or more stages, and finally the desired flow rates can be obtained. For example, in the case of 3 steps, (F / 3) in steps b and c respectively

Supply the steam of St and gas of hydrocarbon fuel of (F Z3), then the first step d

HC

And (2F Z3) water vapor and (2F Z3) hydrocarbon fuel gas in and

St HC

And in the second step d and e, (F) water vapor and (F)

St HC hydrocarbon fuel gas can be supplied.

[0060] In this way, by supplying the hydrocarbon-based fuel gas step by step while confirming the presence of water vapor, a smoother start-up operation becomes possible.

[0061] The supply of the hydrocarbon-based fuel gas to the fuel / steam mixed gas line can be suitably performed by an operation of starting a booster such as a pump or a blower or a compressor, or an operation of opening a valve. Increasing the flow rate of the hydrocarbon-based gas can be appropriately performed by an operation for increasing the rotation speed of the pressurizing means or an operation for increasing the opening of the valve.

[0062] The supply of water vapor to the fuel / water vapor mixed gas line can be appropriately performed by an operation of starting a pressure increasing means such as a pump or an operation of opening a valve. The increase in the flow rate of water vapor can be appropriately performed by an operation for increasing the number of rotations of the pressure increasing means or an operation for increasing the opening of the valve.

[0063] Alternatively, it is set in advance by a preliminary start-up operation from the time when the operation of supplying water vapor to the fuel / water vapor mixed gas line to the time of performing the operation of supplying gas of hydrocarbon-based fuel to this line. By setting the predetermined time interval, it is possible to supply water vapor to this line before supplying hydrocarbon fuel gas to this line.

[0064] In the preliminary start-up operation, the following steps i to iii can be performed.

i) Supplying hydrocarbon fuel gas and water vapor to the fuel / steam mixed gas line j

Performing oxygen supply to the fuel cell power sword and hydrogen supply to the fuel cell anode to generate a voltage due to an electrochemical reaction in the fuel cell; ii) After step i, the step of supplying steam to the fuel's steam mixing line while monitoring the voltage of the fuel cell while continuing the supply of oxygen and hydrogen, and iii) of step ii And a step of detecting a decrease in the voltage of the fuel cell.

[0065] The time from when the operation of supplying water vapor in step ii to the time when the voltage drop is detected in step iii can be measured, and this measured time can be set as the predetermined time interval.

[0066] The operation of supplying water vapor to the fuel / water vapor mixed gas line is an operation that finally completes necessary preparation such as preheating of the vaporizer and finally allows water vapor to flow through the line, such as opening a valve. Means that. In addition, the operation of supplying hydrocarbon fuel gas to the fuel / steam mixed gas line means that it is possible to flow hydrocarbon fuel gas through the line after completing the necessary preparations such as preheating the vaporizer. For example, opening a valve.

[0067] This fuel cell system activation method is simple.

[After supplying hydrocarbon fuel gas]

As described above, after a mixed gas of a desired amount of hydrocarbon fuel gas and water vapor is supplied to the fuel-water vapor mixed gas line, each device has a predetermined temperature as necessary. The temperature can continue to rise. The supply of hydrogen to the anode can be stopped when it is no longer necessary to detect the aforementioned voltage drop. If a reformer is present, reforming can be started in the reformer.

[0069] When the start-up operation is completed, the normal operation can be started. Normal operation includes not only rated operation but also partial load operation. The reformed gas obtained from the reformer 10 is supplied to the anode of the fuel cell 20 as an anode gas. An oxygen-containing gas such as air is supplied to the power sword of the fuel cell as a power sword gas. In the fuel cell, hydrogen contained in the anode gas and oxygen contained in the power sword gas react electrochemically to generate power. Since the anode off-gas discharged from the anode contains combustible components, the amount of heat can be appropriately used by combustion. Moreover, the sensible heat of the anode off gas or the force sword off gas discharged from the force sword can be used as appropriate.

[0070] [Hydrocarbon-based fuel] As the hydrocarbon-based fuel, a compound or a mixture thereof containing carbon and hydrogen (including other elements such as oxygen) known in the field of fuel cell systems as a raw material for reformed gas may be used. And compounds having carbon and hydrogen in the molecule, such as hydrocarbons and alcohols, can be used. For example, hydrocarbon fuels such as methane, ethane, propane, butane, natural gas, LPG (liquid petroleum gas), city gas, gasoline, naphtha, kerosene, light oil, alcohols such as methanol and ethanol, dimethyl ether, etc. Such as ether. Of these, kerosene is preferable because it is easily available for industrial use and for consumer use, and is easy to handle.

[Components of Fuel Cell System]

When using a liquid hydrocarbon fuel, a vaporizer is used to vaporize the fuel. As the vaporizer, a known vaporizer capable of vaporizing the hydrocarbon fuel to be used can be used. For example, a vaporizer having a structure capable of heating a pipe through which a liquid flows from the outside and evaporating the liquid in the pipe. In addition, a vaporizer having a structure in which a heating member such as an evaporating dish or an evaporation container is heated and a liquid can be brought into contact with the heating member to evaporate can also be exemplified. For these heating, an electric heater or a combustion gas can be used as a heat source. As the water vaporizer, a known vaporizer capable of vaporizing water can be used.

[0072] In order to detect the voltage drop of the fuel cell and automatically control the supply of the hydrocarbon-based fuel gas to the fuel / steam mixed gas line or increase the flow rate thereof, the same line is used. A computer or a sequencer can be used to automatically perform the operation of supplying the water vapor to the water and supplying the hydrocarbon fuel gas at predetermined time intervals.

[0073] In the fuel cell system, the reformed gas obtained from the reformer can be subjected to a sacrificial treatment as necessary. For example, a shift reaction (CO + H 0 → CO + H) to reduce the concentration of carbon monoxide and increase the hydrogen concentration, and a selective acid reaction (2) to reduce the concentration of carbon monoxide.

2 2 2

CO + O → 2CO), humidification or dehumidification can be performed.

twenty two

[0074] Further, if necessary, desulfurization for reducing the concentration of sulfur contained in the hydrocarbon-based fuel can be performed. [0075] The reformer is a known reformer capable of performing steam reforming, partial acid reforming or autothermal reforming (performing both water steam reforming reaction and partial acid reforming reaction). The instrument can be used as appropriate. When a heat source is required in the reformer, for example, an available high temperature gas can be appropriately used. As a specific example, a combustion gas obtained by burning a hydrocarbon-based fuel node off gas can be used as a heat source.

[0076] As the fuel cell, a fuel cell that electrochemically reacts hydrogen can be used as appropriate. For example, solid polymer, phosphoric acid, molten carbonate, or solid oxide fuel cells can be employed.

[0077] In addition to the above devices, known constituent elements of the fuel cell system can be appropriately provided as necessary. Specific examples include cooling systems for cooling various devices such as fuel cells, pumps for pressurizing various fluids, boosting means such as compressors and blowers, adjusting the flow rate of fluids, Flow control means such as a valve for switching the flow Z, etc., flow path shutoff, Z switching means, heat exchanger for heat exchange and heat recovery, condenser for condensing gas, steam, etc. Heating Z Z heat retention means, storage means for various fluids, instrument air and electrical systems, control signal systems, control devices, output and power electrical systems.

Industrial applicability

The start-up method of the fuel cell system of the present invention can be used for, for example, a stationary or mobile power generation system, and a fuel cell system used for a cogeneration system.

Claims

The scope of the claims

[1] In a fuel cell system start-up method for starting a fuel cell system comprising a line for flowing a mixed gas of hydrocarbon-based fuel gas and water vapor, and a fuel cell connected to the downstream of the line,

[2] a) Before supplying the hydrocarbon fuel gas and water vapor to the line,

Performing oxygen supply to the fuel cell power sword and hydrogen supply to the fuel cell anode to generate a voltage due to an electrochemical reaction in the fuel cell;

b) after step a, supplying water vapor to the line while monitoring the voltage of the fuel cell while continuing the oxygen supply and hydrogen supply; and

c) After step b, after detecting a drop in the voltage of the fuel cell, supplying hydrocarbon fuel gas to the line

The method of claim 1 comprising:

[3] In step b, the supply flow rate of water vapor is the desired flow rate of water vapor at the completion of the start-up operation,

3. The method according to claim 2, wherein, in step c, the supply flow rate of the hydrocarbon-based fuel gas is set to a desired flow rate of the hydrocarbon-based fuel gas when the start-up operation is completed.

[4] In step b, the supply flow rate of water vapor is a part of the desired flow rate of water vapor when the start-up operation is completed,

After step c

The method of claim 2 further comprising:

[5] The hydrocarbon fuel to be supplied to the line by repeating the combination of the steps d and e a plurality of times so that the flow rate of water vapor supplied to the line becomes the desired flow rate of water vapor when the start-up operation is completed. 5. The method according to claim 4, wherein the flow rate of the gas is set to a desired flow rate of the hydrocarbon-based fuel gas when the start-up operation is completed.

[6] A method for starting a fuel cell system having a predetermined time interval between a time point at which an operation for supplying water vapor to the line and a time point at which an operation for supplying a hydrocarbon-based fuel gas to the line is performed. Because

The method of the preliminary start-up operation is

i) Before supplying the hydrocarbon-based fuel gas and water vapor to the line, supply oxygen to the fuel cell power sword and supply hydrogen to the fuel cell anode, and perform an electrochemical reaction in the fuel cell. Generating a voltage according to

Have

The method for starting the fuel cell system according to claim 1.