JP6101653B2 - Combustor ignition method - Google Patents

Description

Embodiments described herein relate generally to a combustor ignition method applied to a reformer for a fuel cell power generation system.

  In polymer electrolyte fuel cell systems using commercially available gas fuels such as city gas and LPG as raw materials, there are various methods for purifying hydrogen from hydrocarbon-based raw fuel gases. Often used.

_{C n H m + nH 2 O} → nCO + (m / 2 + n) H 2 ... (1)
This reaction is generally an endothermic reaction, and heat is applied from the outside in order to advance the reaction.

As a heat source, hydrogen gas exhausted without reacting at the anode of the battery cell stack of the polymer electrolyte fuel cell system (anode off gas), city gas of raw fuel or LPG is burned, and the heat of combustion is used. There are many cases. That is,
C _n H _m + (n + m / 4) · O ₂ → nCO ₂ + m / 2 · H ₂ O (2)
The combustion reaction of hydrocarbons represented by the reaction formula of H ₂ + 1 / 2O ₂ → H ₂ O (3)
It is necessary to cause the hydrogen combustion reaction represented by the reaction formula of

In order to start the combustion cell system, it is necessary to preheat the reformer to about 600 ° C. to 800 ° C., which is the temperature at which the reaction of the reaction formula (1) occurs efficiently, but at the time of startup, hydrogen is still Therefore, it is necessary to transfer the heat generated only by the combustion reaction of the reaction formula (2) to the reformer. Further, during power generation, the anode unreacted hydrogen gas that has passed through the anode is burned to obtain heat, and this reaction gas contains a large amount of CO ₂ purified by the reformer and H ₂ O generated by the anode reaction. In many cases, the flammability is different from that of pure hydrogen. If the anode offgas alone does not provide the heat necessary for reforming, evaporation of reformed water, or increase in steam temperature, the anode offgas or combustion air is mixed with a small amount of hydrocarbons to generate heat generated by combustion. Take a way to increase.

  In this way, the anode off gas and hydrocarbons are burned with the same nozzle in the form of complete premixed combustion at startup, anode offgas diffusion combustion and hydrocarbon premixed combustion during operation, Conventionally, partial premixed combustion, a method of diffusing and burning anode off-gas during operation, a method of diffusing and burning hydrocarbons only during ignition, and a method of diffusing and burning anode off-gas during temperature rise and power generation are proposed. ing.

  In any case, the reformer burner of the fuel cell system employs an ignition method in which a high voltage is applied to the spark plug when the ignition is performed for the first time. In addition, for detection of misfire, a method of detecting misfire by providing a detection means for detecting a decrease in combustion gas temperature or a minute flame current is adopted.

Japanese Patent Laid-Open No. 2004-6111 JP 2004-182489 A JP 2002-63926 A Japanese Patent No. 3880372 JP 2013-87037 A

  However, when adopting an ignition method that uses discharge, it is necessary to properly manage the discharge distance, and the tolerances such as the axial blurring and protrusion length of the spark plug that determine the positional relationship between the spark plug and the nozzle are considerably narrow. There is a need to. If this is neglected, the optimum amount of energy will not be transmitted to the optimum position of the premixed gas blown out from the nozzle, and ignition will not occur. Strict management of this tolerance is a major design constraint. In addition, the combustion control method in which the spark plug as described in Patent Document 5 is also used for flame detection is a method often used for purposes other than the fuel cell reformer. Special relays and circuits are required to switch instantly.

The problem to be solved by the present invention is to provide a method for igniting a combustor capable of performing ignition without depending on discharge.

An ignition method of a combustor according to an embodiment is a combustor of a reformer for a fuel cell power generation system that burns fuel by igniting a fuel or a mixture of fuel and air blown from a nozzle with an igniter, the igniter However, in the ignition method of the combustor configured by an ignition heater including a heat generating portion made of an electric resistor that generates heat when energized, in a step of flowing only air to the nozzle for a certain period of time, and in a state where nothing flows to the nozzle, Energizing the ignition heater, and flowing a mixture of air and fuel gas through the nozzle .

  According to the present invention, ignition can be performed without depending on discharge.

The longitudinal cross-sectional view which shows the structure of the reformer incorporating the combustor which concerns on one Embodiment. The longitudinal cross-sectional view and cross-sectional view which expand and show the structure of the nozzle block and ignition heater which comprise the combustor of the embodiment. The perspective view which shows the external appearance of the nozzle block which comprises the combustor of the embodiment. The circuit diagram which shows the structure of the electric circuit connected to the ignition heater which comprises the combustor of the embodiment. The block diagram which shows the whole structure of the polymer electrolyte fuel cell power generation system using the reformer 80 incorporating the combustor of the embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing the configuration of a reformer incorporating a combustor according to an embodiment. FIG. 2A is a longitudinal sectional view showing an enlarged configuration of a nozzle block and an ignition heater constituting the combustor of the embodiment, and FIG. 2B is a view in FIG. 1 and FIG. It is a cross-sectional view which shows the cross-sectional shape of the part shown by arrow A of FIG. FIG. 3 is a perspective view showing an external appearance of a nozzle block constituting the combustor of the same embodiment.

  The combustor according to the present embodiment is a combustor of a reformer for a fuel cell power generation system that burns fuel by igniting a fuel blown from a nozzle or a mixture of fuel and air with an igniter. The vessel is composed of an ignition heater having a heat generating portion made of an electric resistor that generates heat when energized. The structure of the reformer 80 to which the combustor is applied is shown in FIG.

  The reformer 80 includes a reformer 90, a first cylindrical member 91, a second cylindrical member 92, a third cylindrical member 93, a combustor block 94, a combustion exhaust gas block 95, a reforming catalyst layer. 96, thermocouple 97, and the like. Among these elements, the combustor according to the present embodiment includes at least the nozzle block 10, first to third cylindrical members 91 to 93 disposed on the side surface of the nozzle block 10, the combustor block 94, and ignition. A heater 20 is used. As shown in FIG. 2A, the ignition heater 20 includes a heat generating portion 21 made of an electric resistor that generates heat when energized. The position of the heat generating portion 21 in the ignition heater 20 is limited to a predetermined region that is a fixed distance away from the lower end of the combustor nozzle, for example, a region that is about 10 mm away from the lower end position of the combustor nozzle.

  As shown in FIGS. 2A and 2B, the nozzle block 10 includes first to third nozzles 11 to 13 constituting a combustor nozzle. For example, the first nozzle 11 is configured by a space having an annular cross section formed between a hole drilled in the center of the nozzle block 10 and the ignition heater 20 therein, and the cross section of the first nozzle 11 is Concentric with the center, the second is formed by twelve holes with a diameter of several millimeters drilled in the nozzle block 10 at equal intervals in a circumferential manner so that the PCD is about 1.5 times the diameter of the first nozzle. The third nozzle is composed of 24 holes of several millimeters in diameter, with the PCD on the outside of the nozzle 12 being formed at equal intervals around the circumference of about 2 to 3 times the diameter of the first nozzle. 13 is configured.

  Further, as shown in FIG. 1, a fuel header is formed in a space constituted by the first cylindrical member 91, the second cylindrical member 92, and the nozzle block 10, and the second cylindrical member 92 A space formed by the third cylindrical member 93 and the nozzle block 10 constitutes a premixed fuel header. The nozzle block 10 has a hole connected to the first nozzle 11, a hole connected to the fuel header, and a hole connected to the premixed fuel header.

  FIG. 4 is a circuit diagram showing a configuration of an electric circuit connected to the ignition heater 20 constituting the combustor of the present embodiment.

  An electric circuit 30 for applying a 100 V AC voltage to the ignition heater 20 and an electric circuit 40 for passing a constant current and measuring the voltage of the ignition heater 20 are selectively connected via the switch circuit 50. Configured to be connected. The electric circuit 30 includes an AC power supply 31, and the electric circuit 40 includes a constant current power supply 41 and a voltmeter 42.

  The switch circuit 50 includes switches S <b> 1 and S <b> 2, and switching control thereof is performed by the control device 60. When the switches S <b> 1 and S <b> 2 are connected to the contact 1, a 100 V AC voltage is applied to the ignition heater 20 by the electric circuit 30. On the other hand, when the switches S1 and S2 are respectively connected to the contact 2, the voltage is measured in a state in which a constant current is flowing to the ignition heater 20 by the electric circuit 40.

  The combustor configured in this manner is attached to the upper part of the reforming unit 90 including the combustion exhaust gas header and the four cylindrical members below the combustion exhaust gas header.

  FIG. 5 is a configuration diagram showing an overall configuration of a polymer electrolyte fuel cell power generation system using a reformer 80 incorporating a combustor according to the present embodiment.

  The fuel cell power generation system includes a fuel processor 100 including a reformer 80, an evaporator 81, a desulfurizer 82, a shift reactor 83, and a methanation reactor 84, a fuel cell anode 85, and the like. In addition, an air blower 61, a fuel blower 62, a valve 71, a valve 72, a valve 73, orifices 74 and 75, a three-way valve 76, and the like are disposed around the fuel processing apparatus 100.

  The operations of the fuel processor 100 and the auxiliary machines such as various blowers and valves arranged in the vicinity thereof are controlled by the controller 60. The control device 60 has various functions such as a function for igniting the combustor in a predetermined procedure, a function for controlling the flow rate of fuel flowing to the reformer 80, and a function for detecting misfiring of the combustor.

  For example, in order to ignite the combustor, the control device 60 flows only the air through the combustor nozzle for a certain period of time as the first stage, and energizes the ignition heater in a state where nothing flows through the combustor nozzle as the second stage. Then, as a third stage, ignition is performed by a three-stage procedure in which a mixture of air and fuel gas is supplied to the combustor nozzle.

  Further, the control device 60 controls the flow rate of the fuel that flows to the reformer 80 based on the voltage measured by flowing a constant current through the ignition heater 20 during off-gas combustion.

  The control device 60 detects misfire by measuring the electrical resistance of the ignition heater 20 during off-gas combustion in order to detect misfire in the combustor.

  Next, an example of the operation of the fuel cell power generation system by the control device 60 according to the present embodiment will be described with reference to FIGS. 1 to 4 and FIG.

  When starting the fuel processing apparatus 100 shown in FIG. 5, first, the air blower 61 is started with the valve 73 open, and the combustion air passes through the orifice 75 and the first nozzle 11 and the third nozzle 13. So that the combustion space of the reformer 80 is in an air-only state.

  Next, the air blower 61 is temporarily stopped, the switches S1 and S2 of the switch circuit 50 (see FIG. 4) are connected to the contact 1, respectively, and an AC voltage is applied to the ignition heater 20 to generate heat. As a result, the temperature of the heat generating portion 21 (see FIG. 2A) of the ignition heater 20 rises to 800 ° C. or more after a predetermined time has elapsed.

  Next, the air blower 61 and the fuel blower 62 are started simultaneously. At this time, the valve 73 is closed so that air flows only through the third nozzle 13. In addition, the raw fuel is initially set to a closed state so that the raw fuel flows only to the reformer 80 side via the three-way valve 76 and the orifice 74 and does not flow to the process inlet. . As a result, the raw fuel flowing to the reformer 80 side is mixed with a part of the air supplied by the air blower 61 and supplied to the air pipe of the combustor in the reformer 80 in a premixed state. To the third nozzle 13. The mixture of fuel and air blown out from the third nozzle 13 absorbs the radiant heat from the ignition heater 20 heated to 800 ° C. or more and ignites to form a premixed flame.

  After the flame is formed, by switching the switches S1 and S2 of the switch circuit 50 (see FIG. 4) from the contact 1 to the contact 2, respectively, the AC voltage application to the ignition heater 20 is stopped and at the same time the ignition heater 20 is constant. A current is passed to measure the voltage, and a resistance value is obtained from the applied constant current and the measured voltage.

  The air-fuel mixture reacted with the flame becomes combustion exhaust gas and flows into the combustion space in the reformer 80 shown in FIG. 1, and turns back to a temperature of about 900 ° C. at the lowermost end of the reforming unit 90. The reforming catalyst layer 96 having a cross-sectional shape is heated and heated through a heat transfer cylinder, exits the reformer 80, enters the evaporator 81, heats the reforming water to evaporate, and is exhausted.

  The steam generated in the evaporator 81 enters the reforming catalyst layer 96 through the raw fuel pipe of the reformer 80, and the process gas flow path is filled with steam. During this temperature increase, the valve 73 can be opened, air can be passed through the first nozzle 11, and air can be passed around the ignition heater 20.

  When the indicated value of the thermocouple 97 attached to the lower end of the reforming catalyst layer 96 is approximately 700 ° C. or higher, the valve 71 is opened and the raw fuel is allowed to flow to the desulfurizer 82. As a result, the amount of fuel supplied to the third nozzle 13 is decreased, and at the same time, a mixture of raw fuel and water vapor is supplied to the reforming catalyst layer 96 to start hydrogen generation. At this time, the air supply to the third nozzle 13 and the first nozzle 11 is not stopped, and the flow rate is adjusted by adjusting the rotational speed of the air blower 61. The flame may disappear once during this flow rate adjustment process.

  As shown in FIG. 5, the gas containing hydrogen generated in the reforming catalyst layer 96 is subjected to valve removal after CO is removed by the shift reactor 83 having a shift catalyst and the methanation reactor 84 having a methanation catalyst. 72 and supplied to the second nozzle 12 of the combustor through the fuel pipe.

  The hydrogen rich gas supplied to the second nozzle 12 is mixed with the air blown out from the first nozzle 11 and the third nozzle 13 after leaving the nozzle. At this time, since the combustion space is at a high temperature of 700 ° C. or higher, it spontaneously ignites as the hydrogen rich gas flow rate gradually increases, and a diffusion flame is formed at the outlet of the second nozzle 12. The raw fuel gas slightly mixed with the air of the third nozzle 13 is also burned by the diffusion flame.

  A part of the hydrogen-rich gas after leaving the methanation reactor 84 flows to the fuel blower 62 inlet and flows to the desulfurizer 82 together with the raw fuel, causing a hydrodesulfurization reaction to remove the sulfur content of the raw fuel. On the other hand, the combustion gas after transferring heat to the reforming catalyst layer 96 in the reformer 80 enters the evaporator 81 and evaporates the reforming water. The evaporated vapor is mixed with the raw fuel exiting the desulfurizer 82 and supplied to the reforming catalyst layer 96.

  After a certain period of time, the valve 72 is closed, a hydrogen rich gas is caused to flow to the fuel cell anode 85, and power generation is started. Thereby, 80% to 90% of hydrogen in the hydrogen rich gas is consumed, and the anode off gas having a reduced hydrogen concentration flows to the second nozzle 12 and continues combustion and reforming. At this time, the diffusion air flows through the first nozzle 11.

  During operation, the resistance value of the ignition heater 20 is monitored, and the fuel flow rate and the reforming water flow rate are set to appropriate values using the resistance value. If the resistance value of the ignition heater 20 decreases during operation and falls below a set threshold value, it is determined that misfire has occurred and operation is stopped.

  Thus, according to the present embodiment, since the ignition heater 20 is used as the igniter instead of the ignition plug, the distance between the burner nozzle position and the ignition plug electrode is within a narrow range suitable for discharge as in the prior art. Even if it does not do, since the temperature of all the premixed gas jetted from the 3rd nozzle 13 by the ignition heater 20 heated to 800 degreeC or more can be made high by radiant heat transfer, burner nozzle position and It is not necessary to manage the control tolerances such as the shaft shake of the igniter more strictly than the normal manufacturing tolerances.

  Further, by installing the heat generating part 21 only at a position downstream from the combustor outlet, the radiant heat transfer to the burner nozzle can be reduced, so that the heat generated by the ignition heater 20 can be efficiently transmitted to the premixed gas. it can.

  Also, at the start-up, after the air purge is performed, once the air is stopped so that there is no forced flow in the combustion air state, the ignition heater 20 will not be cooled, and gas and air will flow. When this is done, the temperature of 800 ° C. or higher necessary for ignition can be maintained.

  Also, electric circuits 30 and 40 as shown in FIG. 4 are provided, and when the ignition operation is performed by the control device 60, the switches S1 and S2 are respectively set to the contact 1 to apply an AC voltage to the ignition heater 20, while the operation is performed. During this time, the switches S1 and S2 are respectively switched to the contact point 2, and the voltage is measured while applying a constant current to the ignition heater 20, so that the electric resistance value of the ignition heater 20 is known from the applied constant current and the measured voltage. Can be obtained. For example, if the correspondence table obtained by measuring the relationship between the metal resistance and the temperature in advance is created by utilizing the property that the electrical resistance of the metal increases as the temperature rises, it can be obtained by measuring the voltage of the ignition heater 20. The temperature of the ignition heater 20 can be obtained from the obtained electrical resistance value. Thereby, since the temperature in the combustor can be obtained through the ignition heater 20, the fuel flow rate can be controlled without additionally installing a measuring device such as a thermocouple or a flame current measuring device. This makes it possible to make a misfire determination.

  As described above in detail, according to the above embodiment, ignition can be performed without depending on discharge.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Nozzle block, 11 ... 1st nozzle, 12 ... 2nd nozzle, 13 ... 3rd nozzle, 20 ... Ignition heater, 21 ... Heat generating part, 30, 40 ... Electric circuit, 31 ... AC power supply, 41 ... Constant current power source, 42 ... Voltmeter, 50 ... Switch circuit, 60 ... Control device, 71-73 ... Valve, 74,75 ... Orifice, 76 ... 3-way valve, 61 ... Air blower, 62 ... Fuel blower, 81 ... Evaporator , 82 ... desulfurizer, 83 ... shift reactor, 84 ... methanation reactor, 85 ... fuel cell anode electrode, 90 ... reforming section, 91 ... first cylindrical member, 92 ... second cylindrical member, 93 ... third cylindrical member, 94 ... combustor block, 95 ... combustion exhaust gas block, 96 ... reforming catalyst layer, 97 ... thermocouple, 100 ... fuel treatment device, S1, S2 ... switch.

Claims (1)

A combustor of a reformer for a fuel cell power generation system that combusts a fuel blown from a nozzle or a mixture of fuel and air by igniting with an igniter, wherein the igniter is an electric resistor that generates heat when energized. In an ignition method of a combustor configured by an ignition heater provided with a heat generating part ,
Flowing only air through the nozzle for a certain period of time;
Energizing the ignition heater in a state where nothing flows through the nozzle;
And a step of flowing a mixture of air and fuel gas through the nozzle.