JP2006105481A - Burner and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vaporizing type burner capable of further shortening ignition delay at the time of ignition with satisfactory ignitability, and further satisfactorily continuing the burning to suppress discharge of unburned combustible components such as carbon monoxide and soot, and a fuel battery system provided with such a burner, which is smoothly startable and can minimize discharge of unburned combustible components. <P>SOLUTION: This burner is used for a burning method for mixing a vaporized liquid fuel with an oxygen-containing gas to form an air-fuel mixture, and burning the air-fuel mixture, using a burner mat for the burning of the air-fuel mixture, performing spark ignition at the time of ignition with an air ratio of the air-fuel mixture of 1.0 or less, and performing ignition control, after confirming the ignition, to increase the air ratio of the air-fuel mixture to 1.2 or more while keeping generation of sparks of the spark ignition. The fuel cell system comprises this burner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a burner that vaporizes and burns liquid fuel such as kerosene. In particular, the present invention relates to a burner suitable for supplying heat necessary for a reformer used in a fuel cell system. The present invention also relates to a fuel cell system including a reformer for reforming a raw material for hydrogen production to obtain a reformed gas containing hydrogen.

  In a small burner that uses liquid fuel as a fuel, such as used in a reformer of a fuel cell system, it is difficult to diffuse and burn the fuel by pressure spraying. For this reason, in such a burner, after the fuel is vaporized, it is mixed with air (primary air) to form an air-fuel mixture, and this air-fuel mixture is burned using a burner head having a plurality of flame holes. It was. In order to vaporize liquid fuel, the liquid fuel is generally supplied dropwise to a cup-like container heated by an electric heater, called a vaporizer, which is heated to a temperature sufficient to vaporize the liquid fuel. In contact with the heated surface (inner wall of the container).

In addition, the burner provided in the reformer used in the fuel cell system has a structure in which a hydrogen electrode off-gas nozzle is provided in the vicinity of the burner head for burning the liquid fuel to burn off the hydrogen electrode off-gas, and the off-gas can also be combusted. Yes. Such a structure of the burner for liquid fuel is described in, for example, Japanese Patent Application Laid-Open No. 7-237902.
JP 7-237902 A

  In such a vaporization type burner, in some cases, immediately after the liquid fuel flow starts, the vaporization of the liquid fuel is not stable because the vaporizer temperature is unstable, and the fuel in the mixture of air and fuel vapor is not stable. The concentration is not stable. If the fuel concentration is not stable, the ignition performance (ignition delay, etc.) is greatly affected by the air ratio. The lower the air ratio at the time of ignition, the easier it is to ignite because the fuel concentration reaches the combustible region earlier. However, if the air ratio is kept low enough to facilitate ignition, after vaporization of the liquid fuel has stabilized, there is a tendency for air to run out and a large amount of unburned carbon monoxide, soot, etc. to be discharged.

  The object of the present invention is to obtain a good ignition performance at the time of ignition and to shorten the ignition delay, while on the other hand, continue the combustion well and suppress the discharge of unburned carbon monoxide and soot. It is to provide a vaporizing burner that can.

  Another object of the present invention is to provide a fuel cell system that has a good ignition performance and has a reformer having a burner that can continue to burn smoothly, and that can be started smoothly and has low unburned emissions. That is.

According to the present invention, in a combustion method in which vaporized liquid fuel is mixed with an oxygen-containing gas to form a mixture, and the mixture is burned.
Burner mat is used for combustion of the air-fuel mixture,
At the time of ignition, spark ignition is performed with the air ratio of the air-fuel mixture being 1.0 or less, and after the ignition is confirmed, the air ratio of the air-fuel mixture is increased to 1.2 or more while the spark ignition spark is generated. A combustion method characterized by performing control is provided.

  In order to increase the air ratio to 1.2 or more, it is preferable to increase the supply amount of the oxygen-containing gas.

In the burner according to the present invention, the vaporized liquid fuel is mixed with an oxygen-containing gas to form an air-fuel mixture, and the air-fuel mixture is burned.
The inlet is an oxygen-containing gas inlet for introducing oxygen-containing gas, and the outlet is provided with a burner mat, and includes a liquid fuel nozzle for flowing down the liquid fuel and a heating surface for vaporizing the liquid fuel that has flowed down. Gas flow path;
An ignition electrode disposed downstream of the burner mat for generating sparks for ignition;
Ignition determination means capable of determining ignition; and, at the time of ignition, until the ignition is confirmed by the ignition determination means, the air ratio of the air-fuel mixture is set to 1.0 or less to generate sparks at the ignition electrode, and the ignition determination means There is provided a burner comprising ignition control means for performing control to increase the air ratio to 1.2 or more while continuing to generate sparks at the ignition electrode when ignition is confirmed by the above.

The burner is a reformer burner for supplying heat for reforming reaction to a reformer used in a fuel cell system to reform a hydrogen production raw material to obtain a reformed gas containing hydrogen. Yes,
The inlet is a hydrogen electrode off-gas inlet for introducing the hydrogen electrode off-gas of the fuel cell, and the outlet can further include a hydrogen electrode off-gas flow path having a hydrogen electrode off-gas nozzle that opens downstream of the burner mat.

According to the present invention, in a fuel cell system comprising a reformer for reforming a raw material for hydrogen production to obtain a reformed gas containing hydrogen, and a fuel cell using the reformed gas as fuel,
A fuel cell system is provided in which the reformer includes the burner.

  According to the present invention, in a burner in which vaporized liquid fuel is mixed with an oxygen-containing gas to form an air-fuel mixture and the air-fuel mixture is burned, good ignition performance can be obtained at the time of ignition, and the ignition delay can be further shortened. On the other hand, it is possible to continue the combustion satisfactorily and to suppress the discharge of unburned components such as carbon monoxide and soot.

  In addition, according to the present invention, there is provided a fuel cell system that has a good ignition performance and has a reformer having a burner that can continue to burn well and can be started smoothly and emit less unburned fuel. .

  As the liquid fuel, a combustible substance that is liquid at normal temperature and normal pressure (25 ° C., 0.101 MPa) can be used as appropriate. For example, compounds having carbon and hydrogen in the molecule such as hydrocarbons and alcohols can be used. Preferable examples that can be obtained inexpensively for industrial use or consumer use include methanol, ethanol, gasoline, kerosene, and light oil. Of these, kerosene is preferable because it is easily available for industrial use and consumer use, and is easy to handle.

  Air (atmosphere) is preferable as the oxygen-containing gas used for combustion in the burner, but oxygen-enriched air with an increased oxygen concentration can also be used, and in the fuel cell system, the air electrode of the fuel cell is used. The cathode off-gas discharged from the (cathode) can also be used.

  Hereinafter, although the form of this invention is demonstrated using drawing, this invention is not limited to these. Further, air will be described as an example of the oxygen-containing gas.

  In the embodiment shown in FIG. 1, primary air and secondary air are used as combustion air, and an air-fuel mixture obtained by mixing vaporized liquid fuel and primary air is burned in the burner mat, and the unburned residue is downstream of the burner mat. Combustion is performed more reliably by the secondary air supplied to the air. However, secondary air is not necessarily required, and a form in which combustion is performed using only primary air is also possible.

  FIG. 1 shows an embodiment of the burner of the present invention. The burner casing 1 is basically a cylinder having a central axis in the vertical direction, and the upper part is a connecting portion 1a for supplying gas or liquid fuel. The casing is not necessarily attached to the burner. When the inner wall of the heating furnace into which the burner is inserted (for example, the inner wall of the furnace of the reformer 102 shown in FIG. 2) can be in close contact with the burner, the inner wall of the heating furnace Can be substituted for the burner casing.

  An inlet of a gas flow path (hereinafter referred to as a combustion gas flow path) 10 to which combustion air (primary air) and liquid fuel are supplied is a primary air supply port 11. The primary air supplied from the primary air supply port is supplied into the vaporizer 2 through the pipe 13 connected to the joint portion 1a.

  The combustion gas flow path is provided with a liquid fuel nozzle 14 facing substantially vertically downward, so that liquid fuel can flow from the liquid fuel supply port 12 into the combustion gas flow path. The heating surface 2a is provided substantially horizontally below the liquid fuel nozzle. The heating surface is formed integrally with the vaporizer 2 and can be heated to a temperature suitable for vaporizing the liquid fuel by heat conduction from the electric heater 9 embedded in the vaporizer. It is not always necessary to use an electric heater for heating the heating surface. Instead of the electric heater or together with the electric heater, the heating surface was heated to a temperature sufficient to heat the heating surface to a predetermined temperature before the burner was introduced. Primary air or secondary air may be used.

  The liquid fuel flowing down from the liquid fuel nozzle comes into contact with the heating surface 2a and vaporizes. The liquid fuel may be dropped intermittently from the nozzle, but it is preferable that the liquid fuel is continuously flowed from the viewpoint of making the concentration of the fuel in the air-fuel mixture more constant. From the viewpoint of stably and continuously flowing down the liquid fuel, it is preferable that the discharge speed of the liquid fuel from the nozzle is 2 cm / second or more. Moreover, it is preferable to set it as 25 cm / sec or less from a viewpoint of the pressure loss of liquid feeding. The discharge speed can be adjusted by appropriately selecting the inner diameter of the liquid fuel nozzle in accordance with a desired combustion amount range.

  Although the liquid fuel nozzle can be provided in a direction other than substantially vertically downward, for example, horizontally, the nozzle itself is substantially vertical from the viewpoint of suppressing the formation of relatively large droplets and making the fuel concentration in the mixture more constant. It is preferable to face downward. “Substantially vertically downward” means that the extending direction of the nozzle does not necessarily have to be strictly vertically downward, and the deviation from the vertically downward is preferably within 10 °, more preferably within 5 °. Preferably, it is more preferably within 3 °.

  It is preferable that at least the tip of the liquid fuel nozzle is in the combustion gas flow path, and the liquid fuel nozzle and the flow direction of the primary air are preferably in the same direction in the portion. More preferably, the path is coaxial. For example, as shown in FIG. 1, the tip of the liquid fuel nozzle faces vertically downward, and the nozzle tip is disposed in a cylindrical combustion gas flow path facing vertically downward. The central axis of the cylinder and the central axis of the nozzle A configuration in which is consistent is preferable. This is because the air flow has the effect of removing the liquid fuel from the nozzle tip, suppresses the large growth of droplets at the nozzle tip, and the liquid fuel concentration in the mixture becomes more constant. .

  The heating surface is preferably substantially horizontal in order for the dropped liquid fuel to diffuse uniformly. Substantially horizontal means that the heating surface does not necessarily have to be exactly horizontal, and the deviation from the horizontal is preferably within 10 °, more preferably within 5 °, and more preferably within 3 °. More preferably. In addition, the heating surface is preferably circular so that the liquid fuel after dripping diffuses uniformly.

  The heating surface can also be formed integrally with the vaporizer. For example, a hollow cylindrical portion that forms the outer wall of the vaporizer and a plate-like portion that forms the heating surface can be formed integrally. Alternatively, for example, a plate member having a surface to be a heating surface can be joined to a hollow cylindrical member or the like by welding or the like. The vaporizer can have a portion for embedding the heater.

  The material of the vaporizer is preferably a metal from the viewpoint of thermal conductivity. For example, aluminum or brass is suitable.

  The temperature of the heating surface can be appropriately set according to the type of liquid fuel to be supplied. For example, when the liquid fuel is kerosene, it is preferably 180 ° C. or higher and 250 ° C. or lower, more preferably 190 ° C. or higher and 220 ° C. or lower. This is disadvantageous in that it is near the initial distillation temperature of kerosene below 180 ° C., so the vaporization rate of the high boiling point component is slow, the fuel concentration in the mixture tends to be unstable, and the flame tends to become unstable. In addition, when the temperature exceeds 250 ° C., the dropped liquid droplet is covered with vaporized fuel vapor, so that a so-called film boiling state occurs, the vaporization speed becomes slow, the fuel concentration in the mixture becomes unstable, and the flame becomes unstable. This is disadvantageous in that it tends to be, and this is to avoid such a situation.

  The primary air introduced into the combustion gas passage is preheated in contact with the burner casing joint heated by heat transfer from the vaporizer and the inner surface of the vaporizer, and mixed with the vaporized liquid fuel. Collides with heated surface. The flow path of the air-fuel mixture of combustion air and liquid fuel turns 90 ° on the heating surface and becomes horizontal along the heating surface, and then turns 90 ° again by the side wall of the carburetor 2. Passes through the gap 15 between the heating surface and the vaporizer sidewall. Changing the flow direction of the air-fuel mixture is preferable in order to promote uniform mixing. It is preferable that the air gap 15 serving as the air-fuel mixture flow path in the carburetor is disposed substantially symmetrically (here, symmetrical with respect to the central axis of the cylindrical carburetor side wall) from the viewpoint of preventing the mixed airflow from drifting.

  The electric heater 9 has a function of supplying heat for preheating the combustion air in addition to supplying heat for vaporizing the liquid fuel. The combustion air is preheated by heat exchange with a vaporizer or the like. In some cases, it is possible to preheat the fuel air separately before supplying it to the burner. If the combustion air is sufficiently preheated separately, it is possible to eliminate the heater for heating the vaporizer, but it is preferable to use an electric heater from the viewpoint of temperature controllability. In order to control the temperature of the heating surface within an appropriate range by operating the output of the electric heater, a thermocouple 3a for measuring the temperature of the vaporizer can be appropriately provided. In the form of FIG. 1, the thermocouple 3 a is attached to the thermocouple well 3.

  The mixture of the vaporized liquid fuel and primary air passes through the rectifier 5 provided at the lower part of the vaporizer and reaches the outlet of the combustion gas flow path provided with the burner mat 6. The rectifier provided on the upstream side of the burner mat is preferably provided in order to adjust the flow of the air-fuel mixture supplied to the burner mat and to make the combustion uniform. In the rectifier, the horizontal cross-sectional area gradually increases toward the bottom, and the opening at the lower end is substantially the same as the shape of the burner mat. The rectifier has a funnel shape as a whole.

  In FIG. 1, a burner mat is provided at the lower end of the vaporizer. However, it is also possible to provide a burner mat spaced below the vaporizer. For example, a communication pipe, which is a hollow cylindrical member for forming a gas mixture flow path, is disposed between the vaporizer and the burner mat, and the gas exiting the vaporizer passes through the communication pipe to be burner. It may be configured to reach the mat. By providing the communication pipe in this manner, the distance between the flame and the vaporizer (particularly the heating surface) can be easily adjusted, and the temperature control of the heating surface may be facilitated.

  In order to improve combustion stability, a flame holder can be provided on the downstream side of the burner mat. The flame holder is generally tubular and prevents the flame from becoming unstable due to the downstream surface of the burner mat forming the flame being exposed to an air flow such as secondary air from the horizontal direction along the burner mat surface.

  The combustible mixed gas derived from the burner mat is ignited and burned by a spark generated by an ignition electrode arranged downstream of the burner mat. Here, an ignition electrode having a ground electrode 7 disposed in contact with the downstream surface of the burner mat and a high voltage electrode 8 is used, and the air-fuel mixture is ignited by a spark generated between the ground electrode and the high voltage electrode. Is done.

  An example of the arrangement of the ground electrode and the high voltage electrode will be described with reference to FIG. FIG. 4 is a view of the burner as viewed from the downstream side of the burner mat (from the lower side of the drawing in FIG. 1). The high-voltage electrode is, for example, a metal rod having a diameter of 1 mm to 3 mm that is insulated by an insulating material such as being placed in an insulator tube, and is insulated from the metal portion of the coupling portion 1a by the insulating material from the coupling portion 1a to the outside. It is taken out and connected to an igniter that generates a high voltage. The tip of the high-voltage electrode opposite to the side of the connecting portion 1a is disposed so that the distance from the ground electrode is, for example, 3 mm or more and 5 mm or less so as to be positioned in the flame formed on the burner mat downstream side. The ground electrode is a metal rod having a diameter of 2 to 3 mm, for example, and is disposed in contact with the burner mat. The ground electrode is electrically grounded, and the high voltage electrode is insulated from the ground line. For example, the ground electrode can be grounded through a burner mat, a burner casing, and the like, and through a device body in which the burner is used. In this case, the high voltage electrode can be insulated from the burner mat, the burner casing or the like by a heat resistant insulating material.

  Both the high-voltage electrode and the ground electrode are preferably made of a metal having high heat resistance. A typical example of a heat-resistant metal is ferritic stainless steel to which aluminum is added.

  When the ground electrode and high voltage electrode are arranged as described above and a high voltage is applied between the igniter and the high voltage electrode and the burner casing (when the ground electrode is electrically connected to the burner casing), the tip of the high voltage electrode and the ground Sparks are generated intermittently between the electrodes, and the air-fuel mixture can be ignited.

  Even when the burner mat is formed of fibers of a non-conductive material such as ceramic, an ignition spark can be formed at a position very close to the flame side surface of the burner mat by the above electrode configuration, and good ignition performance can be obtained. Even when the burner mat is formed of metal fibers, the electrode structure can prevent the metal fibers themselves from being melted and damaged, and can improve long-term reliability.

  The direction in which the mixed gas is derived from the burner mat is preferably vertically downward. In this case, since the flame is also formed vertically downward, the burner can be placed on the upper part of the reformer or the like to which the burner is attached, and the burner is placed on the lower part of the reformer or the like This is because access to the burner is facilitated during maintenance, and space can be saved while ensuring good maintainability as a whole reformer. For this purpose, it is preferable that the burner mat is provided substantially horizontally so that the flame can be formed facing downward, and the air-fuel mixture is supplied from the upper surface of the burner mat.

  On the other hand, secondary air is supplied from the secondary air supply port 21 to the secondary air flow path 20, and then supplied from the secondary air nozzle 22 to the burner mat downstream. The secondary air flow path is annularly provided on the outer periphery of the vaporizer. The secondary air nozzle is provided at a position where the secondary air can be supplied to the flame formation region of the air-fuel mixture. This supply of secondary air promotes complete combustion of the air-fuel mixture.

By using a burner mat for the combustion of the air-fuel mixture, the combustion stability is excellent even if the combustion amount is small. As the burner mat, a non-woven fabric or woven fabric of metal fibers, or a non-woven fabric or woven fabric of fibers made of ceramics such as cordierite, titania, mullite, alumina, silica, and alumina-silica can be used. From the viewpoint of heat uniformity and prevention of backfire, a mat made of woven or non-woven metal fibers is preferable as the burner mat. In addition, when the burner mat is a woven fabric or a non-woven fabric, since the opening ratio is larger than that of a punching plate or the like, the speed of the air-fuel mixture when passing through the burner mat becomes slow. For this reason, for example, in a low combustion region of about 200 kW / m ² , a flame is formed in the vicinity of the burner mat, and the burner mat is immediately red hot by the flame, so that good combustion stability is obtained. In addition, in a high combustion range of, for example, about 4500 kW / m ^2, the speed of the air-fuel mixture passing through the burner mat is relatively slow, so that flame blow-off can be suppressed.

Combustion amount of vaporized liquid fuel per unit area of the burner mat, preferably 200 kW / m ² or more in terms of combustion stability, and more preferably from 600 kW / m ² or more, 1000 kW / m ² or more is more preferable. Further, from the viewpoint of the flame blown off suppression, preferably 4500kW / m ² or less, more preferably 4000 kW / m ² or less, more preferably 3500kW / m ² or less. Therefore, it is possible to provide a burner mat having an area suitable for realizing such a range with respect to a desired combustion amount range.

  The burner of the present invention is particularly suitable for a burner with a small combustion amount. This is because a burner of a type in which liquid fuel is vaporized by a heating surface and burned is suitable for a burner with a small combustion amount, and particularly combustion with a burner mat can be stably burned even with a small combustion amount. This is also because there is a strong demand for compactness in such a small combustion amount burner. Specifically, the effect of the present invention is remarkable in a burner having a maximum combustion amount based on liquid fuel of 8.1 kW (7000 kcal / h) or less, and further in a burner having 5.8 kW (5000 kcal / h) or less. It is.

  The burner of the present invention can be used by being mounted on a reformer in a fuel cell system. From the viewpoint of effectively using the hydrogen electrode off-gas of the fuel cell (the hydrogen electrode of the fuel cell, ie, the combustible gas discharged from the anode), it is preferable to supply the hydrogen electrode off-gas downstream of the burner mat 6 for combustion. The hydrogen electrode off gas is supplied to the burner from a hydrogen electrode off gas supply port 31 that is an inlet of the hydrogen electrode off gas flow path 30. The hydrogen electrode off-gas passes through an annular channel provided on the outer periphery of the secondary air channel, and flows downstream from the hydrogen electrode off-gas nozzle 32 provided at the outlet of the hydrogen electrode off-gas channel (on the flame holding surface side). That is, it is supplied to the surface side opposite to the combustion gas flow path. It is desirable that the burner has a structure in which the hydrogen electrode off-gas can be ignited by the flame of the liquid fuel mixture formed downstream of the burner mat, but this flame may be blown off by excessive off-gas injection during switching. For this reason, it is desirable to install a hydrogen electrode off-gas nozzle at a position where it can be ignited by the electrodes 7 and 8 for igniting the hydrogen electrode off-gas to the liquid fuel mixture. Further, since the hydrogen electrode off gas contains hydrogen that easily forms an explosive mixture, for example, 20 mol% or more and 50 mol% or less, diffusion combustion without premixing with air is preferable, and therefore the hydrogen electrode off gas is directly jetted downstream of the burner mat. A structure is preferred. Primary air and / or secondary air is used as the air for burning the hydrogen electrode off-gas. The aforementioned ignition electrode can also be used to ignite the hydrogen electrode off-gas.

  When burning the hydrogen electrode off-gas, liquid fuel supply to the combustion gas flow path may not be performed, but in some cases, the liquid fuel is supplied to the combustion gas flow path and both the liquid fuel and the hydrogen electrode off-gas are supplied. It can also be burned at the same time.

  Now, an example of a method for performing combustion using such a burner will be described in detail. First, the heater 9 is actuated to heat the heating surface, and air is boosted by a gas boosting means such as a blower as necessary and supplied from the primary air supply port 11, and after the heating surface 2a reaches a predetermined temperature. If necessary, the liquid fuel is boosted by a liquid boosting means such as a pump and supplied to the liquid fuel supply port 12, the liquid fuel is caused to flow down from the liquid fuel nozzle 14, and a spark is generated by the ignition electrode. The air ratio at this time (the air ratio calculated from the supplied liquid fuel amount and the supplied total air amount) is set to 1.0 or less. In addition, the ignition determination means is operated at the start of spark generation by the ignition electrode or before that to monitor the presence or absence of ignition. Here, the thermocouple 3b attached to the thermocouple well and provided downstream of the burner mat is used as the ignition determination means. When ignited, the temperature measured by the thermocouple 3b rises, so that the presence or absence of ignition can be determined. When ignition is confirmed, the air ratio is increased to 1.2 or more.

  By setting the air ratio before ignition to 1.0 or less, preferably 0.9 or less, the fuel concentration of the air-fuel mixture derived from the burner mat quickly reaches the combustible region, so that the ignition delay is extremely short. Good ignition performance can be obtained. On the other hand, from the viewpoint of preventing dust generation, the air ratio is preferably 0.7 or more, more preferably 0.8 or more.

  By setting the air ratio after ignition to 1.2 or more, preferably 1.3 or more, more preferably 1.5 or more, an amount of oxygen suitable for stable combustion is supplied, and carbon monoxide and soot The generation of unburned components such as

  The operation of increasing the air ratio after ignition is preferably performed as quickly as possible after the ignition determining means determines ignition from the viewpoint of suppressing the discharge of unburned matter. In the present invention, since sparks are continuously generated by the ignition electrode while the air ratio is increased, combustion can be stably continued even when the air ratio is rapidly changed.

  In order to increase the air ratio after ignition, it is preferable to increase the air supply amount without changing the liquid fuel supply amount. This is because by increasing the amount of air, vaporization of the liquid fuel is promoted, so that the fuel concentration during the mixing period is stabilized.

  In addition to the thermocouple, a flame rod, a UV (ultraviolet ray) detector, CdS, or the like can be appropriately used as the ignition determination means.

  After ignition is performed as described above, that is, after the air ratio is increased to 1.2 or more, the burner is continuously burned. Here, the combustion air ratio at the time of burning the liquid fuel in the burner will be described with reference to FIG. 3 (FIG. 3 will be described in detail later). In the burner 101, the air ratio calculated from the amount of liquid fuel provided for combustion and the amount of primary air introduced into the burner is preferably 1.8 or less, more preferably 1.3 or less, and 1.0 The following is more preferable. This is because the burner mat is well red hot, the flame is stabilized by the radiant heat from the burner mat, and complete combustion can be performed more reliably. In order to completely burn the liquid fuel, the air ratio calculated from the supplied liquid fuel amount and the supplied total air amount (total amount of primary air and secondary air) is preferably 1.2 or more, It is more preferable to set it as 1.3 or more, and it is still more preferable to set it as 1.5 or more.

  As the means for controlling the air ratio itself, a known flow rate control technique can be used. For example, it is assumed that the flow rate of the liquid fuel is controlled by the flow meter 121, the flow rate regulator 122, and the flow rate control valve 123, and a signal corresponding to the flow rate detected by the flow meter 121 is sent to the arithmetic processing unit 111 such as a computer. The required air flow rate is calculated from the flow rate of the liquid fuel and a preset air ratio, and a signal corresponding to the air flow rate is sent to the flow controller 132 on the air side. The flow control valve 133 can also be used for control.

  Although the combustion air is supplied from one place in FIG. 3, it is only shown as a concept, and may be branched in the middle and supplied to the burner from two or more places. May be branched or may be supplied only as primary air without branching.

  When an oxygen-containing gas other than air is used for combustion, the oxygen-containing gas amount is treated as the air amount and the air ratio is calculated. However, the oxygen-containing gas used here is preferably an oxygen-containing gas having an oxygen content of 18% mol or more from the viewpoint of combustibility.

  When burning the hydrogen electrode off-gas, the hydrogen electrode off-gas can be boosted by a gas booster such as a blower and supplied to the hydrogen electrode off-gas inlet 31 as necessary. If there is a liquid fuel flame, after adjusting the amount of air as appropriate, ignition can be achieved by simply introducing the hydrogen electrode off-gas, but if the hydrogen electrode off-gas amount is unstable, the combustion of the liquid fuel is stopped once, By supplying an air amount suitable for the combustion of the extreme off-gas and then operating the igniter 8 that is the ignition means, the combustion can be stably performed.

[Reformer]
FIG. 2 shows an example in which this burner 101 is mounted on a reformer 102 used in a fuel cell system. The burner is attached to the top of the reformer and is accessible from above.

  The reformer is an apparatus for producing a reformed gas containing hydrogen by reacting a raw material for hydrogen production with water and / or oxygen. In this apparatus, the raw material for hydrogen production is mainly decomposed into hydrogen and carbon monoxide. Usually, carbon dioxide and methane are also contained in the cracked gas. Examples of the decomposition reaction include a steam reforming reaction and an autothermal reforming reaction. The steam reforming reaction involves a large endotherm, and a burner or the like is used to supply heat for this purpose from the outside. Even in the autothermal reforming reaction, heat may be supplied from the outside in some cases. The burner of the present invention can be suitably used for a so-called external heat reformer that supplies heat to the reforming reaction region from the outside. Inside the reformer, a reforming tube 102a containing a catalyst capable of promoting a reforming reaction such as a steam reforming reaction is disposed inside, and the reforming tube is heated by the combustion heat of the burner, and the reforming reaction is performed. Heat is supplied to advance the process.

  The raw material for hydrogen production can be appropriately selected from substances that can obtain a reformed gas containing hydrogen by a steam reforming method or an autothermal reforming method. For example, compounds having carbon and hydrogen in the molecule such as hydrocarbons, alcohols and ethers can be used. Preferable examples that can be obtained inexpensively for industrial use or consumer use include methanol, ethanol, dimethyl ether, city gas, LPG (liquefied petroleum gas), gasoline, kerosene and the like. Of these, kerosene is preferable because it is easily available for industrial use and consumer use, and is easy to handle. The liquid fuel supplied to the burner may be different from the raw material for hydrogen production, but it is preferable to use the same one from the viewpoint of making the entire fuel cell system compact. This is because a storage means such as a tank for these and a supply system such as a pump can be used together.

The steam reforming reaction is a reaction between steam and hydrocarbons, but usually involves heating from the outside because it involves a large endotherm. Usually, the reaction is carried out in the presence of a metal catalyst typified by a Group VIII metal such as nickel, cobalt, iron, ruthenium, rhodium, iridium and platinum. The reaction temperature can be 450 ° C to 900 ° C, preferably 500 ° C to 850 ° C, more preferably 550 ° C to 800 ° C. The amount of steam introduced into the reaction system is defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (steam / carbon ratio), and this value is preferably 0.5-10. Preferably it is 1-7, More preferably, it is 2-5. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is A / B when the flow rate in the liquid state of the raw material for hydrogen production is A (L / h) and the volume of the catalyst layer is B (L). This value is preferably set in the range of 0.05 to 20 h ⁻¹ , more preferably 0.1 to 10 h ⁻¹ , and still more preferably 0.2 to 5 h ⁻¹ .

  Autothermal reforming is a method of reforming while maintaining a balance of reaction heat by advancing the steam reforming reaction with the heat generated at this time while oxidizing part of the raw material for hydrogen production. In recent years, it has attracted attention as a method for producing hydrogen for fuel cells because it has a short start-up time and is easy to control. Also in this case, the reaction is usually carried out in the presence of a metal catalyst, typically a Group VIII metal such as nickel, cobalt, iron, ruthenium, rhodium, iridium and platinum. The amount of steam introduced into the reaction system is preferably 0.3 to 10, more preferably 0.5 to 5, and still more preferably 1 to 3 as a steam / carbon ratio.

  In autothermal reforming, oxygen is added to the raw material in addition to steam. The oxygen source may be pure oxygen, but in many cases air is used. Usually, oxygen is added to such an extent that it can generate an amount of heat that can balance the endothermic reaction accompanying the steam reforming reaction. The amount is preferably from 0.05 to 1, more preferably from 0.1 to 0.75, even more preferably as the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (oxygen / carbon ratio). Is set to 0.2 to 0.6. The reaction temperature of the autothermal reforming reaction is set in the range of 450 ° C. to 900 ° C., preferably 500 ° C. to 850 ° C., more preferably 550 ° C. to 800 ° C., as in the case of the steam reforming reaction. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is preferably selected in the range of 0.1 to 30, more preferably 0.5 to 20, and still more preferably 1 to 10.

  To control the reaction temperature, for example, the temperature of the reaction region is detected by a thermocouple, etc., the amount of liquid fuel supplementarily supplied to the burner is increased, the combustion air is increased, the hydrogen in the fuel cell Means such as increasing or decreasing the amount of hydrogen contained in the hydrogen electrode off-gas by changing the amount used is used.

[Fuel cell system]
Furthermore, an outline of an example of a fuel cell system having a reformer equipped with the burner is shown in FIG. The fuel cell system includes a burner 101, a reformer 102 that performs a steam reforming reaction using the combustion heat of the burner 101, and a fuel in which a reformed gas containing hydrogen obtained by the reformer is supplied to a hydrogen electrode. A battery 103 is included.

  As the fuel cell 103, a fuel cell of a type in which hydrogen is a reactant of electrode reaction at the hydrogen electrode can be appropriately employed. For example, a fuel cell of a solid polymer type, a phosphoric acid type, a molten carbonate type, or a solid oxide type can be employed.

  For example, a solid polymer fuel cell is composed of a hydrogen electrode (anode) 103a and an air electrode (cathode) 103c and a solid polymer electrolyte sandwiched between them, and a reformed gas (hydrogen-containing gas) is placed on the hydrogen electrode side. An oxygen-containing gas such as air is introduced to the pole side after appropriate humidification treatment if necessary. Since a combustible component remains in the hydrogen electrode off-gas discharged from the hydrogen electrode, the hydrogen electrode off-gas is supplied to the burner 101 and burned.

  When the fuel cell system is started, the liquid fuel is vaporized and burned with combustion air, and this heat can be used to warm up the reformer and other devices. After the start-up, the hydrogen off-gas is burned in the burner and the liquid fuel does not have to be burned. In some cases, the hydrogen electrode off-gas and the liquid fuel can be combusted simultaneously.

  Various devices that can be used in the fuel cell system can be provided as appropriate. For example, a reforming gas line between the reformer 102 and the fuel cell 103 can be provided with a CO shift reactor that reduces the CO concentration in the reformed gas and a selective oxidation reactor that further reduces the CO concentration. . A desulfurizer that reduces the concentration of sulfur in the raw material for hydrogen production can also be provided upstream of the reformer. In addition to this, a means for supplying oxygen-containing gas such as air to the air electrode of the fuel cell, a steam generator for generating steam for humidifying the gas supplied to the fuel cell, and various devices such as the fuel cell are cooled. Cooling system, pressurizing means such as pumps, compressors and blowers for pressurizing various fluids, flow regulating means such as valves for regulating the flow rate of fluids, or shutting off / switching the flow of fluids Channel shut-off / switching means, heat exchanger for heat exchange / recovery, vaporizer for vaporizing liquid, condenser for condensing gas, heating / heat-retaining means for externally heating various devices with steam, etc. Examples include storage means, instrumentation air and electrical systems, control signal systems, control devices, and output and power electrical systems.

  The burner of the present invention can be easily miniaturized, and can be suitably used, for example, in a reformer provided in a fuel cell system for a moving body such as an automobile or small-scale power generation.

  Since the fuel cell system of the present invention includes such a burner, it can be easily made compact, and can be suitably applied to the fuel cell system as described above.

It is sectional drawing which shows an example of the burner of this invention. It is typical sectional drawing which shows the example of the reformer with which the burner of this invention was mounted | worn. It is a block diagram which shows the outline of the fuel cell system which has a reformer equipped with the burner of this invention. It is a figure for demonstrating the detail of an ignition electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Burner casing 1a Joint part 2 Vaporizer 2a Heating surface 3 Thermocouple well 3a Vaporized surface temperature control thermocouple 3b Ignition determination thermocouple 5 Rectifier 6 Burner mat 7 Ground electrode 8 High voltage electrode 9 Heater 10 Combustion gas flow Path 11 Primary air supply port 12 Liquid fuel supply port 13 Pipe 14 Liquid fuel nozzle 15 Air gap between heating surface and vaporizer side wall 20 Secondary air flow path 21 Secondary air supply port 22 Secondary air nozzle 30 Hydrogen electrode off gas Flow path 31 Hydrogen electrode off gas supply port 32 Hydrogen electrode off gas nozzle 101 Burner 102 Reformer 102a Reformer tube 103 Fuel cell 103a Hydrogen electrode 103c Air electrode 111 Arithmetic processing unit 121 Flow meter (for liquid fuel)
122 Flow controller (for liquid fuel)
123 Flow control valve (for liquid fuel)
131 Flow meter (for air)
132 Flow controller (for air)
133 Flow control valve (for air)

Claims (5)

In a combustion method in which vaporized liquid fuel is mixed with an oxygen-containing gas to form a mixture, and the mixture is burned,
Burner mat is used for combustion of the air-fuel mixture,
At the time of ignition, spark ignition is performed with the air ratio of the air-fuel mixture being 1.0 or less, and after the ignition is confirmed, the air ratio of the air-fuel mixture is increased to 1.2 or more while the spark ignition spark is generated. A combustion method characterized by performing control.   The method of claim 1, wherein the supply of oxygen-containing gas is increased to increase the air ratio to 1.2 or higher. In a burner in which vaporized liquid fuel is mixed with an oxygen-containing gas to form a mixture, and the mixture is burned,
The inlet is an oxygen-containing gas inlet for introducing oxygen-containing gas, and the outlet is provided with a burner mat, and includes a liquid fuel nozzle for flowing down the liquid fuel and a heating surface for vaporizing the liquid fuel that has flowed down. Gas flow path;
An ignition electrode disposed downstream of the burner mat for generating sparks for ignition;
Ignition determination means capable of determining ignition; and, at the time of ignition, until the ignition is confirmed by the ignition determination means, the air ratio of the air-fuel mixture is set to 1.0 or less to generate sparks at the ignition electrode, and the ignition determination means A burner comprising ignition control means for performing control to increase the air ratio to 1.2 or more while continuing to generate sparks at the ignition electrode when ignition is confirmed by the above. A reformer burner for supplying heat for reforming reaction to a reformer used in a fuel cell system to obtain a reformed gas containing hydrogen by reforming a raw material for hydrogen production,
4. The burner according to claim 3, wherein the inlet is a hydrogen electrode off-gas inlet for introducing a hydrogen electrode off-gas of the fuel cell, and the outlet further has a hydrogen electrode off-gas flow path provided with a hydrogen electrode off-gas nozzle opened downstream of the burner mat. . In a fuel cell system comprising a reformer that reforms a raw material for hydrogen production to obtain a reformed gas containing hydrogen, and a fuel cell that uses the reformed gas as fuel,
A fuel cell system, wherein the reformer comprises the burner according to claim 4.

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