JP2006199543A - Operation method of chemical conversion apparatus, operation method of fuel reforming apparatus and operation method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation method of a chemical conversion apparatus, by which chemical conversions such as fuel-reforming or the like can be rapidly performed by quickly raising temperature when a fuel cell is stated. <P>SOLUTION: In the operation method of the chemical conversion apparatus having a reformer burner 28-2 for high temperature combustion using a raw fuel, and a reformer main body 28-1 for chemically converting the raw fuel by successively heating a plurality of chemical conversion sections being different in operation temperature range from a high temperature region to a low temperature region by using a high temperature exhaust gas from a combustion section, an ignition process for igniting the raw fuel at a low air ratio in the combustion section, a first temperature-raising process for raising temperature to a prescribed upper limit temperature in the high temperature region by increasing the air ratio and burning after ignition, and a second temperature-raising process for thereafter raising temperature up to temperature regions except the high temperature region by burning while gradually reducing the air ratio are included. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell power generation system having a high energy effective utilization rate by reducing energy loss when starting a fuel cell, and an operation method thereof.

  A polymer electrolyte fuel cell (hereinafter referred to as PEFC (Polymer Electrolyte Fuel Cell)) uses a solid polymer ion exchange membrane as an electrolyte, and hydrogen (or hydrogen-containing fuel gas) as a fluid. Gas) and oxygen (or oxygen-containing gas), which is an oxidizing gas, are supplied to the fuel electrode (anode) and the air electrode (cathode), respectively, and hydrogen ions move in the solid polymer ion exchange membrane. It generates electricity by causing an electrochemical (battery) reaction. Usually, various measures are taken to supply hydrogen and oxygen to PEFC.

  A fuel cell power generation system having such a fuel cell is attracting attention as a distributed power source in homes and the like. Also, when using city gas other than hydrogen or LPG as the fuel gas, the fuel gas is changed to a hydrogen-rich reformed fuel gas by, for example, a steam reforming method using a fuel reformer, and supplied to the fuel cell. I have to. In the fuel cell, electric power is generated by electrochemically reacting the reformed fuel gas and the oxidizing gas air.

In such a fuel cell, there are the following proposals as startup methods at the initial stage of power generation.
In starting a fuel cell system having a reformer, when the reformer is started, a hydrocarbon containing hydrogen, for example, by a reformer burner provided in a reformer having a fuel reforming section and a CO conversion section The system fuel is combusted, and the temperature is raised to the catalyst operating temperature of the catalyst unit disposed in the reformer. At that time, the flow rates of the injected fuel and the combustion air are controlled by flow rate control means such as a flow rate sensor and a flow rate control valve so that each catalyst temperature falls within a predetermined temperature range (Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 07-282829 Japanese Patent Laid-Open No. 08-111227

  However, when starting up a fuel reformer that incorporates, for example, a reforming section or a CO conversion section in the same container, each catalyst temperature is quickly raised to a predetermined operating temperature range, so that it is highly accurate and reliable. It was necessary to finely control the amount of fuel gas supplied to the reformer burner using a device having a high flow control function. However, the device for controlling the flow rate is expensive and the system is complicated. There is a problem of becoming.

When fuel cells are widely used in general households, there is a demand for a system that is inexpensive, requires reliability of the system, and has quick start-up of the system.
Therefore, a fuel cell power generation system that is inexpensive, compact, and highly reliable by making the device configuration for controlling the catalyst temperature in the fuel reformer at the time of startup within a predetermined temperature range as simple as possible. The appearance of is eagerly desired.

  In view of the above problems, an object of the present invention is to provide a method of operating a chemical conversion apparatus that can quickly raise the temperature and quickly perform chemical conversion such as fuel reforming when starting the fuel cell. To do.

  A first invention of the present invention for solving the above-described problems includes a combustion section that performs high-temperature combustion using raw fuel, and a plurality of chemical conversion sections having different operating temperature ranges using high-temperature exhaust gas from the combustion section. And a chemical conversion device for chemically converting raw fuel from a high temperature range to a low temperature range, and a raw material fuel at a low air ratio in the combustion section. An ignition process for igniting, a first temperature raising process for raising the air ratio of the combustion part after ignition to reach a predetermined upper limit temperature in a high temperature range, and then burning while gradually reducing the air ratio, And a second temperature raising step of raising the temperature to a temperature range other than the high temperature range.

  According to a second aspect of the present invention, in the first aspect of the invention, the chemical conversion device is a fuel reforming device.

  According to a third aspect of the present invention, there is provided the method for operating the fuel reformer according to the second aspect, wherein the chemical conversion section is a catalyst section.

  According to a fourth invention, in the third invention, the catalyst part is arranged in order from the reforming catalyst part, the CO conversion catalyst part, and the CO removal catalyst part, and the high temperature exhaust gas is transferred from the reforming catalyst part to the CO conversion catalyst. The fuel reformer is operated in this order, and the CO removal catalyst unit is heated in order.

  According to a fifth invention, in any one of the second to fourth inventions, after the second temperature raising step is completed, fuel gas is supplied to the polymer electrolyte fuel cell (PEFC) to generate fuel cell power. The fuel cell operating method is characterized.

  According to the present invention, it is possible to raise the temperature of the reformer at the time of start-up with a simple equipment configuration, and a low-cost and simple system is obtained.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment and an Example. In addition, constituent elements in the following embodiments and examples include those that can be easily assumed by those skilled in the art or those that are substantially the same.

[Embodiment]
A fuel cell reforming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of a fuel reformer. As shown in FIG. 1, the fuel reformer 50 according to the present embodiment is a reformer body 28-1 that reforms a raw fuel 29, and a combustion section that burns and heats the reformer body 28-1. When supplying the fuel reformer 28 including the reformer burner 28-2 and the raw fuel 29 from the pipe L10 to the reformer burner 28-2, the shut-off mechanisms 51a and 51b and the throttle mechanism 52a, The pipes L12 and L13 having 52b are provided.

  Then, the supply path of the raw fuel 29 is switched by the shut-off mechanisms 51a and 51b according to the catalyst temperature of various catalyst parts (an example is shown in FIG. 2 described later) built in the fuel reformer 28, and the reformer The amount of fuel gas supplied to the burner is changed, and the amount of air supplied to the reformer burner 28-2 is changed so as to have a flow rate set in advance in accordance with each raw fuel supply path. The amount of combustion at is changed. The throttle mechanisms 52a and 52b may be fixed orifices or the like that provide a predetermined supply amount in addition to the throttle valves.

  Hereinafter, as shown in FIG. 2, as a fuel reformer, the raw fuel 29 supplied to the reformer burner 28-2 is combusted, and the combustion exhaust gas 62 is sent to the reformer main body 28-1, and various catalysts are used. The part is heated indirectly and then exhausted. Here, in the reformer main body 28-1, a reforming catalyst unit 63 that reforms the raw fuel 29 into a gas containing hydrogen and CO, and carbon dioxide gas and hydrogen from the reformed CO and steam. A CO conversion catalyst unit 64 to be generated and a CO removal catalyst unit 65 that removes unreacted CO in the CO conversion catalyst unit 64 are sequentially arranged. Hereinafter, a fuel reformer having a reforming catalyst unit 63, a CO shift catalyst unit 64, and a CO removal catalyst unit 65 will be described as an example of a chemical conversion device. The reforming catalyst is not limited to these.

Here, the reforming of the raw fuel 29 is performed by a steam reforming reaction in the reforming catalyst portion 63 of the reformer body 28-1. That is, the raw fuel 29 and steam are mixed and circulated through the reforming catalyst layer, and the reformer burner 28-2 is used to perform a steam reforming reaction (for example, when city gas is used) at a temperature of 650 to 800 ° C. Is performed by causing CH ₄ + H ₂ O → CO + 3H ₂ ). Examples of the reforming catalyst include Ru / Al ₂ O _3, but are not limited thereto.

  Further, the reformed fuel gas is converted into CO by the CO conversion catalyst unit 64 to generate hydrogen gas and carbon dioxide, and further, a CO removal catalyst unit 65 for removing unreacted CO is provided. By letting it pass, it is a high-quality hydrogen fuel in PEFC.

Next, a method for starting the fuel reformer using the above apparatus will be described.
The reformer burner 28-2 that performs high-temperature combustion using the raw fuel 29 and the high-temperature exhaust heat from the reformer burner 28-2 can be used to reduce a plurality of chemical conversion sections having different operating temperature ranges from the high-temperature range. In the operation method of the fuel reformer 50 having the fuel reformer 28 that sequentially heats over the temperature range and reforms the raw fuel, first, (1) the reformer burner 28- An ignition step of igniting the raw fuel at a low air ratio in (2), and then a first temperature raising step of combusting by increasing the air ratio of the combustion section to reach a predetermined upper limit temperature in a high temperature region, (3) Then, it combusts, reducing an air ratio gradually, and comprises the 2nd temperature rising process heated up to temperature ranges other than a high temperature range.

  Next, a specific method for starting the fuel reformer will be described with reference to FIGS. 3-1 and 3-2. As shown in FIGS. 3A and 3B, the supplied raw fuel 29 is boosted through a booster (not shown) and sent to the downstream line L10. The pipe L10 is branched into a reformer raw material supply pipe L11 and fuel supply pipes L12 and L13 to the reformer burner 28-2. A flow rate control valve 52c is provided in the pipe line L11, and throttle mechanisms 52a and 52b are provided in the pipe lines L12 and L13. Further, blocking mechanisms 51a and 51b that open and close by energization are provided together with the diaphragm mechanisms 52a and 52b.

  The throttle mechanisms 52a and 52b are adjusted to have different Cv values, but may be fixed orifices having the same function, for example. Further, by setting the Cv values of the blocking mechanisms 51a and 51b to a predetermined value, the aperture mechanisms 52a and 52b can be omitted.

  Here, the Cv values of the throttle mechanisms 52a and 52b are determined so as to obtain a desired fuel gas flow rate.

  When the fuel reformer 50 is started, as shown in FIG. 3A, first, the shut-off mechanism 51a is opened, the shut-off mechanism 51b is closed, and the reformer burner 28-2 is connected via the line L12. In addition to supplying fuel gas, an air blower (not shown) is used to supply low air ratio air that ignites raw fuel supplied from the pipe L12, and the reformer burner 28-2 is combusted and ignited. .

  Next, after this ignition is completed, as a first temperature raising step, the shut-off mechanism 51a is opened and fuel gas is supplied to the reformer burner 28-2 via the line L12, and an air blower (not shown). ) Is supplied and burned at a predetermined rotational speed (burner air ratio: for example, 1.2 to 2.0) at which the amount of air necessary for burning the raw fuel supplied from the pipe L12 is obtained.

  Next, as shown in FIG. 3-2, as the second temperature raising step, when the temperature detector installed in the reformer exceeds a certain threshold value, the shut-off mechanism 51b is opened and the shut-off mechanism 51a is closed to make the raw fuel. The 29 supply route is switched to the pipeline L13 side. At the same time, a predetermined rotation speed (burner air ratio: for example, 1.0 to 1.2) at which an air amount necessary for burning the raw fuel 29 supplied from the pipe L13 through an air blower (not shown) is obtained. As air is supplied and burned.

  Furthermore, when there are a plurality of reforming catalysts, if necessary, the number of throttle valves and branch pipes can be increased to provide third and fourth temperature raising steps, and the temperature of the reformer body can be raised. good.

  It is also possible to provide pressure detection means capable of detecting the differential pressure before and after the throttle valve, and to make the combustion air amount variable with reference to the fuel gas amount calculated from the detection signal.

  In the present invention, as shown in the graph of “present invention” in FIG. 4, (1) at a low air ratio by performing the ignition process, the first temperature raising process, and the second temperature raising process as described above. After igniting the raw fuel, (2) In the first temperature raising step, the fuel flow rate is increased (1 to 3 NL / min) and the air ratio is increased (1.2 to 2.0). Burn to the upper limit temperature. Thereafter, (3) the fuel is set to a low flow rate (0.1 to 1.5 NL / min), and the air ratio is gradually lowered while the burner entrainment amount is reduced, so that the steady operation state is achieved. For example, the throttle mechanism 52a has a high fuel flow rate, and the throttle mechanism 52b has a low fuel flow rate.

In this embodiment, in order to ensure combustibility during burner ignition, immediately after igniting at a low air ratio, the air ratio is immediately increased, and the CO shift catalyst portion (temperature 200 to 250 ° C.) 64 and the CO removal catalyst portion (temperature 120). ˜200 ° C.) 65 is increased. Thereby, the temperature increase rate of the reforming catalyst portion (temperature 650 to 700 ° C.) 63 becomes slower than the conventional one.
Thereafter, since the temperature of the reforming catalyst part reaches a predetermined temperature (temperature of 650 to 700 ° C.), the air ratio is gradually lowered while the burner entrainment amount is reduced, and the state is shifted to the steady operation state.

  As a result, although it takes time to raise the temperature to the temperature range of the reforming catalyst portion, the temperature is rapidly raised to the temperature range of the CO conversion catalyst portion and the CO removal catalyst portion, and the fuel reforming apparatus as a whole The start-up completion time can be shortened.

  On the other hand, in the conventional method, as shown in FIG. 4, when the air ratio (1.0 to 1.2) is constant, the fuel flow rate is increased (1 to 3 NL / min), and the reformer When the burner is burned, the reforming catalyst layer temperature immediately reaches a predetermined temperature, so that it is necessary to reduce the burner entrapment amount by a fuel adjustment mechanism or the like. As a result, the CO conversion catalyst part and the CO removal catalyst part installed at the subsequent stage of the reforming catalyst layer did not readily rise in temperature, and as a result, the startup time of the fuel reformer became longer.

  According to the present invention, although it depends on the operating conditions, the startup time can be reduced by approximately 20 to 30% compared to the conventional method.

  As described above, according to the present invention, it is possible to change the fuel supply amount to the reformer burner by providing different throttle mechanisms 52a and 52b for each raw fuel supply path and switching the flow paths to them. At this time, the supply amount from an air blower (not shown) is controlled so that the amount of air supplied to the reformer burner is set in advance for each raw fuel supply path.

  Also, it has a differential pressure measuring mechanism that can calculate the differential pressure before and after the throttle mechanisms 52a and 52b, and has a control function for obtaining the fuel gas supply amount from the differential pressure signal and finely adjusting the air supply amount. It may be.

In the present invention, by using a plurality of raw fuel supply pipes and a simple throttle mechanism and shut-off mechanism interposed in the supply pipes, the fuel reformer can be started quickly and used in a conventional system. The raw fuel flow control device that has been used is no longer necessary.
As a result, when it is installed in a general home, the reliability is improved and the maintenance-free and inexpensive fuel cell system can be provided.

FIG. 5 is a conceptual diagram showing a fuel cell power generation system to which such a fuel reformer is applied.
As shown in FIG. 5, the fuel cell power generation system according to the present embodiment includes the fuel reformer 50 of the fuel cell described above and combustion that burns the fuel gas 12 reformed by the fuel reformer 28. Part 21, first heat exchanger 24 for exchanging heat of refrigerant 23 that cools cooling part 11-3 of fuel cell 11 with high-temperature exhaust gas 22 from combustion part 21, and inlet of cooling part 11-3 of fuel cell 11 And an inlet side temperature measuring device 25-1 for measuring the side refrigerant temperature T 1. The fuel gas 12 is supplied to the fuel electrode 11-1 of the fuel cell 11 and the air electrode 11-2 of the fuel cell 11. The air 13 is supplied to generate electricity. In FIG. 1, reference numeral L1 denotes a cooling line, L2 denotes a discharge line, L3 to L4 denote conduits, and 33-1 and 33-2 denote pumps.

  In the system configured as described above, after fuel reforming is started by the fuel reformer 28, the fuel is generated in the combustion unit 21 that burns the fuel gas 12 at room temperature when generating an electrical output in the fuel cell. The fuel 12 is combusted, and the fuel cell refrigerant 23 is supplied to the first heat exchanger 24 provided downstream of the combustion unit 21 to cool and heat the fuel cell. By recovering the heat from the fuel cell 11, the temperature of the refrigerant 23 of the fuel cell 11 can be quickly raised, which contributes to the heating of the fuel cell 11. Thereby, the energy in the early stage of power generation can be used effectively. Here, as the combustion section 21, the fuel gas 12 may be burned at normal temperature by catalytic combustion, in addition to a normal combustor. Examples of the combustion catalyst include platinum-based monolith catalysts, but the present invention is not limited to this.

The inlet side refrigerant temperature T1 of the cooling section 11-3 is measured by the inlet side temperature measuring device 25-1 in order to maintain the soundness of the fuel cell. When the predetermined set temperature is reached, Control is performed by a control device (CPU), and the supply amount of a heat exchange medium (for example, water or air) is increased to maintain a predetermined temperature.
Moreover, you may make it have the temperature measuring device 25-2 which measures the exit side temperature of the cooling part 11-3 of the said fuel cell 11. FIG.
This enables more accurate control by measuring the temperature on the outlet side. That is, even when the temperature of the refrigerant 23 supplied to the fuel cell is higher than the set temperature, the outlet side temperature may decrease at the initial stage of power generation, and the first heat exchanger is not maintained until the outlet side temperature reaches a predetermined temperature. It is possible to suppress the cooling of the refrigerant heat-exchanged at 24 by the heat dissipating unit 26.
The air supplied to the air electrode 11-2 of the fuel cell 11 is preferably air that has been appropriately humidified by a humidifier (not shown).

  Here, at the initial stage of power generation, the fuel gas 12 is switched to the pipeline L4 side by the switching valve V1 for switching between the pipeline L3 and the pipeline L4, and is entirely combusted in the combustion section 21. Then, when the refrigerant 23 is heated with the high temperature exhaust gas 22 and the temperature of the fuel cell 11 becomes a predetermined operation, the switching valve V1 is switched and the fuel gas 12 is supplied to the pipe line L3 side, whereby the fuel electrode 11 -1 is supplied with fuel for power generation.

  The fuel gas 12 is used by reforming raw fuel 29 by a fuel reformer 28. Here, as the raw fuel 29 of the reformed gas, for example, natural gas (city gas: for example, 13A), gaseous fuel such as LPG, coal gas, alcohol (for example, methanol, etc.), dimethyl ether, kerosene, light oil, naphtha, etc. And liquid fuel.

  Further, the cooling line L1 for the refrigerant 23 is provided with a heat radiating portion 26 using, for example, water or air as a heat exchange medium 27, and radiates heat when heat is generated in fuel cell power generation.

  Moreover, it is preferable that the cooling line L1 is a closed line equipped with a simple water treatment device (for example, an ion exchange resin filling container) not shown. This is because water, which is a refrigerant used in fuel cells, has a low ion concentration, and if it is not a closed line, it requires a huge amount of equipment to remove the ions of water supplied from the outside, generating power costs Is prevented from becoming expensive. The cooling line L1 may be operated to replenish tap water from the outside via a water treatment device (not shown) during operation or stop as necessary.

  In the system of FIG. 1, when the fuel cell power generation is started, the switching valve V <b> 1 is switched so that the fuel gas 12 flows through the pipe L <b> 4, and before the fuel cell generates an electrical output, the fuel gas 12 is supplied to the combustion unit 21. To obtain a high-temperature exhaust gas 22. Then, the coolant 23 of the fuel cell is circulated through the first heat exchanger 24 disposed downstream of the combustion unit 21 and heat exchange with the high-temperature exhaust gas is performed to quickly raise the temperature of the fuel cell circulating water to 60 ° C. or higher. be able to. And after temperature rising is completed, the switching valve V1 is switched to the pipe line L3, the fuel gas 12 is flowed to the fuel electrode 11-1 of the fuel cell 11, and, thereby, a fuel cell load can be applied instantaneously.

  According to the present embodiment, the fuel reformer can be quickly started up, the fuel cell load on the fuel cell body can be applied instantaneously, and energy loss when starting up the fuel cell is reduced. Thus, it is possible to construct a power generation system with a high effective energy utilization rate.

  As described above, the present invention can quickly raise the temperature and perform chemical conversion such as fuel reforming quickly in a fuel reformer for a fuel cell, for example, and can be applied to, for example, a polymer electrolyte fuel cell. Therefore, it is possible to provide a power generation system with a high effective energy utilization rate.

1 is a schematic view of a fuel reformer according to an embodiment. 1 is a configuration conceptual diagram of a fuel reformer according to an embodiment. It is the schematic in the 1st temperature rising process of the fuel reformer which concerns on embodiment. It is the schematic in the 2nd temperature rising process of the fuel reformer which concerns on embodiment. FIG. 4 is a diagram showing the relationship between the temperature rise of each catalyst section inside the reformer and the startup time, and the relationship between the air ratio / fuel flow rate and the startup time. 1 is an overall view of a power generation system of a fuel cell to which the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fuel cell 11-1 Fuel electrode 11-2 Air electrode 11-3 Cooling part 12 Fuel gas 13 Air 21 Combustion part 22 High temperature exhaust gas 24 1st heat exchanger 25-1, 25-2 Temperature measuring device L1 Cooling line L2 discharge | emission Lines L3 to L13 Pipe lines 33-1 and 33-2 Pump 28-1 Reformer body 28-2 Reformer burner 29 Raw fuel

Claims (5)

A combustion section that burns at high temperature using raw fuel;
A chemical conversion device that uses a high-temperature exhaust gas from the combustion section to sequentially heat a plurality of chemical conversion sections having different operating temperature ranges from a high temperature range to a low temperature range, and chemically converts the raw fuel. In the operation method of the reformer device,
An ignition step of igniting raw fuel at a low air ratio in the combustion section;
After ignition, a first temperature raising step for increasing the air ratio of the combustion section to burn and reaching a predetermined upper limit temperature in a high temperature range;
Thereafter, the method for operating the chemical conversion apparatus includes a second temperature raising step of burning while gradually reducing the air ratio and raising the temperature to a temperature range other than the high temperature range. In claim 1,
The method for operating a fuel reformer, wherein the chemical conversion device is a fuel reformer. In claim 2,
A method for operating a fuel reformer, wherein the chemical conversion section is a catalyst section. In claim 3,
The catalyst unit is arranged in order from the reforming catalyst unit, the CO conversion catalyst unit, and the CO removal catalyst unit, and the high temperature exhaust gas is heated in order from the reforming catalyst unit to the CO conversion catalyst unit and the CO removal catalyst unit. A method for operating a fuel reforming apparatus. In any one of Claims 2 thru | or 4,
A fuel cell operating method comprising: supplying a fuel gas to a polymer electrolyte fuel cell (PEFC) and generating fuel cell power after the second temperature raising step is completed.

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