Method of controlling operation of fuel gas production apparatus

Abstract

An ECU detects various conditions of a home fuel gas refining system before starting operation of the home fuel gas refining system using pressure sensors and temperature sensors. Then, it is determined whether the detected conditions are abnormal or not. If abnormal conditions are determined, a self-repair process is performed for a predetermined abnormal condition among the conditions determined as abnormal.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of controlling operation of a fuel gas production apparatus for reforming a hydrogen-containing fuel, which contains, for example, hydrocarbon or alcohol, into a reformed gas, and refining the reformed gas to produce a hydrogen-rich fuel gas.

2. Description of the Related Art

For example, hydrogen production apparatuses (fuel gas production apparatuses) for reforming a hydrocarbon fuel such as natural gas or a hydrogen-containing fuel such as an alcohol (e.g., methanol) into a hydrogen-containing gas (reformed gas), and refining the hydrogen-containing gas to produce a fuel gas supplied to a fuel cell or the like are adopted conventionally.

For example, Japanese Laid-Open Patent Publication No. 2002-20102 discloses a hydrogen production apparatus shown in FIG. 15. The hydrogen production apparatus includes a compressor 1, a hydrodesulfurization unit 2, a steam reformer 3, a catalyst combustor 4, a gas shift reactor 5, and a PSA (Pressure Swing Adsorption) unit 6. A fuel gas such as a city gas is supplied to the hydrodesulfurization unit 2. After desulfurization of the fuel, the steam reformer 3 reforms the fuel by steam reforming to produce a hydrogen-containing gas (hydrogen rich gas). The catalyst combustor 4 is provided around the steam reformer 3, and combusts the hydrogen and oxygen in the air using catalyst. The gas shift reactor 5 induces a shift reaction for converting carbon monoxide in the hydrogen-containing gas into carbon dioxide and hydrogen. After the gas shift reaction, the PSA unit 6 refines the hydrogen-containing gas into highly pure hydrogen by pressure adsorption.

A hydrogen storage tank 8 and an off gas holder 9 are connected to the PSA unit 6. The hydrogen storage tank 8 temporarily stores the highly pure hydrogen before it is supplied to a polymer electrolyte fuel cell (PEFC) 7. The off gas holder 9 temporarily stores the off gas (impurities) removed by pressure adsorption in the PSA unit 6. The off gas holder 9 supplies the off gas to the catalyst combustor 4 as a fuel for heating the steam reformer 3.

The PSA unit 6 has a plurality of adsorption towers filled with adsorbent material for selectively adsorbing impurities (components other than hydrogen) under high pressure, and desorbing the adsorbed components under low pressure. A series of steps comprising adsorption of impurities, desorbing of impurities, replacement of the gas, and pressurization are performed in a cyclic manner in each of the adsorption towers for obtaining the highly pure hydrogen, and discharging the other gas components as the off gas.

Operation of the hydrogen production apparatus described above is subject to unscheduled, urgent interruption for some reasons. For example, an abnormal condition may occur during operation of the hydrogen production apparatus, and a user may stop operation of the hydrogen production apparatus externally. Further, operation of the hydrogen production apparatus may be restarted after a long period of suspension period.

However, in some situations, it is not possible to start operation of the hydrogen production apparatus due to the condition of the hydrogen production apparatus itself or failures in some devices. Though operation of the hydrogen production apparatus may be started if the problem can be eliminated by simple maintenance operation, it is not suitable to force the user to engage in the maintenance operation. Therefore, in particular, in the hydrogen production apparatus for household use, the burden of the maintenance operation on the user should be reduced as much as possible.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a method of controlling a fuel gas production apparatus in which conditions of the fuel gas production apparatus can be detected before starting operation of the fuel gas production apparatus to perform a process for a predetermined condition of the apparatus, and the burden of the maintenance operation on the user is reduced as much as possible.

The present invention relates to a method of controlling operation of a fuel gas production apparatus. The fuel gas production apparatus reforms a hydrogen-containing fuel to obtain a reformed gas, and removes impurities from the reformed gas to refine the reformed gas into a hydrogen-rich fuel gas. The term “hydrogen-containing fuel” herein means any fuel which contains hydrogen element, such as hydrocarbon or alcohol.

Firstly, when a start up signal of the fuel gas production apparatus is inputted, various conditions of the fuel gas production apparatus are detected. It is determined whether the detected conditions are abnormal. A self-repair process is performed for a predetermined abnormal condition among conditions determined as abnormal.

It is preferable that the method comprises the step of displaying information about an abnormal condition which has been determined after the self-repair process.

Further, according to another aspect of the present invention, when a start up signal of the fuel gas production apparatus is inputted, an abnormal condition of the fuel gas production apparatus is detected. Then, it is determined whether the detected abnormal condition should be handled by a process according to a stop pattern among a plurality of predetermined stop patterns, and operation of the fuel gas production apparatus is stopped according to the process of the determined stop pattern.

Further, it is preferable that the method further comprises the step of outputting a signal indicating the abnormal condition if the abnormal condition cannot be eliminated by self-repair. For example, the signal indicating the abnormal condition is transmitted to a maintenance service company. Thus, the maintenance operation of the fuel gas production apparatus is carried out promptly.

According to the present invention, if an abnormal condition of a fuel gas production apparatus is detected before starting operation of the fuel gas production apparatus, a self-repair process is performed in correspondence with a predetermined abnormal condition. Therefore, no undue burden of the maintenance operation is imposed on the user. Therefore, even if the fuel gas production apparatus is stopped in the abnormal condition, with the simple steps, it is possible to start normal operation of the fuel gas production apparatus rapidly and reliably. Further, it is possible to reduce the burden of the user's maintenance operation as much as possible.

Further, according to the present invention, since a plurality of stop patterns are determined in advance, by stopping operation of the fuel gas production apparatus according to a stop pattern in correspondence with the detected abnormal condition, if operation of the gas production apparatus can be started again, the suitable stop process is performed. Thus, no undue burden of the maintenance operation is imposed on the user. With the simple steps, it is possible to start normal operation of the fuel gas production apparatus reliably and rapidly. Further, it is possible to reduce the burden of the user's maintenance operation as much as possible.

The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a home fuel gas refining system for carrying out a control method according to a first embodiment of the present invention;

FIG. 2 is a diagram showing main components of a PSA mechanism of the home fuel gas refining system;

FIG. 3 is a timing chart showing operation of the PSA mechanism;

FIG. 4 is a flow chart showing upstream operation of a control method;

FIG. 5 is a flowchart showing downstream operation of the control method;

FIG. 6 is a diagram schematically showing a home fuel gas production system for carrying out a control method according to a second embodiment of the present invention;

FIG. 7 is a diagram showing system operation modes and stop patterns;

FIG. 8 is a flowchart showing operation according to a first stop pattern;

FIG. 9 is a flowchart showing operation according to a second stop pattern;

FIG. 10 is a flowchart showing operation according to a third stop pattern;

FIG. 11 is a flowchart showing operation according to a fourth stop pattern;

FIG. 12 is a flowchart showing operation according to a fifth stop pattern;

FIG. 13 is a flowchart showing operation according to a PSA normal stop pattern;

FIG. 14 is a table showing an abnormal condition determination criterion by a pressure sensor 104a and stop modes; and

FIG. 15 is a block diagram schematically showing a conventional system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagram schematically showing a home fuel gas refining system (fuel gas production apparatus) 10 for carrying out a control method according to a first embodiment of the present invention.

The home fuel gas refining system 10 includes a reforming unit 12, a refining unit 14, and a storage unit 16. The reforming unit 12 reforms a hydrogen-containing fuel, e.g., a fuel containing hydrocarbon such as methane or propane (hereinafter also referred to as the “reforming fuel”) to obtain a hydrogen-rich gas (hereinafter also referred to as the “reformed gas”). The refining unit 14 refines the hydrogen rich gas to produce a highly pure hydrogen gas (hereinafter also referred to as the “fuel gas”). The storage unit 16 stores the fuel gas.

The reforming unit 12 includes an evaporator 18 for evaporating the reforming fuel using combustion catalyst. A combustor (heating unit) 20 such as a burner is provided for the evaporator 18. A water supply tank 21 is connected to the evaporator 18 through a water compressor 23.

A reactor 22 for obtaining a reformed gas by reforming the reforming fuel is provided at a position downstream of the evaporator 18. A cooling unit 24 for cooling the reformed gas is provided at a position downstream of the reactor 22. Further, a gas liquid separator 26 for separating the reformed gas into gas components and liquid components is provided at a position downstream of the cooling unit 24. The water removed by the gas liquid separator 26 is supplied to the water supply tank 21.

The reforming unit 12 has an air supply mechanism 28. The air supply mechanism 28 includes an air compressor 30. A reforming air supply passage 32, a combustion air supply passage 34, and an off gas discharging air supply passage 36 are connected to the air compressor 30. The reforming air supply passage 32 is connected to the evaporator 18 through an ejector 37 for sucking the reformed gas by the reforming air. The combustion air supply passage 34 is connected to an intermediate position of the off gas discharging air supply passage 36 through valves 37a, 37b and a burner 35 for supplying a hot air to the reactor 22. The off gas discharging air supply passage 36 is connected to the combustor 20 through a PSA (Pressure Swing Adsorption) mechanism 42 as described later. The reforming air supply passage 32, the combustion air supply passage 34, and the off gas discharging air supply passage 36 are connectable to the air compressor 30 through valves 38a, 38b, and 38c.

The PSA mechanism 42 of the refining unit 14 is connected to the downstream side of the gas liquid separator 26 through a reformed gas supply passage 40. After the removal of moisture, the reformed gas is supplied to the PSA mechanism 42. A branch passage 46 is connected to the reformed gas supply passage 40 through a three-way valve 44. A compressor 48 and a cooling unit 50 are provided at positions downstream of the three-way valve 44.

As shown in FIG. 2, the PSA mechanism 42 comprises a tri-tower pressure swing adsorption apparatus, for example. The pressure swing adsorption apparatus has adsorption towers 60a, 60b, 60c which are connectable to the compressor 48. The adsorption towers 60a through 60c have pressure sensors 62a through 62c for detecting the pressures in the adsorption towers 60a through 60c. The adsorption towers 60a through 60c have inlet/outlet ports at lower positions, and valves 66a through 66c are provided at the lower inlet/outlet ports of the adsorption towers 60a through 60c. The adsorption towers 60a through 60c are connected to the off gas discharge passage 68 through the valves 66a through 66c.

Flow rate control valves 70, 72 are provided in parallel in the off gas discharge passage 68. The off gas discharge passage 68 is connected to the burner 35 and the combustor 20 through a start up fuel supply passage 74. Further, the off gas discharge passage 68 is connected to an intermediate position of the off gas discharging air supply passage 36 through an ejector 76.

Further, the adsorption towers 60a through 60c have inlet/outlet ports at upper positions, and fuel gas discharge valves 80a through 80c and pressure equalization (cleaning) valves 82a through 82c are provided at the upper inlet/outlet ports of the adsorption towers 60a through 60c. The adsorption towers 60a through 60c are connectable to a fuel gas passage 84 through the fuel gas discharge valves 80a through 80c.

As shown in FIG. 1, a flow rate control valve 86 and a pressure regulator valve 88 are provided in parallel, and a compressor 90 and a valve 92 are provided in parallel in the fuel gas passage 84. A filling tank 96 as part of the storage unit 16 is connected to the fuel gas passage 84 through a valve 94. A branch fuel gas passage 98 is connected to an intermediate position of the fuel gas passage 84. A buffer tank 102 is connected to the branch fuel gas passage 98 through a valve 100.

The filling tank 96 supplies the fuel gas to a vehicle (not shown) equipped with a fuel cell. The buffer tank 102 supplies the fuel gas to a stationary fuel cell (not shown) to generate electricity for home use in the stationary fuel cell, and supplies a start up fuel to the start up fuel supply passage 74 through a valve 37c.

The home fuel gas refining system 10 has various sensors for detecting various operating conditions of the home fuel gas refining system 10. Specifically, a pressure sensor 104a is provided near the air compressor 30, and a pressure sensor 104b is provided in the off gas discharging air supply passage 36. Further, a pressure sensor 104c is provided near the water compressor 23.

Temperature sensors 106a, 106b, 106c, 106dd are provided at the combustor 20, the burner 35, the reactor 22, and the cooling unit 24, respectively. Further, a temperature sensor 106e is provided between the evaporator 18 and the reactor 22.

In the reformed gas supply passage 40, a temperature sensor 106f is provided near the gas liquid separator 26 and a temperature sensor 160g is provided near the cooling unit 50. In the off gas discharging air supply passage 36, a temperature sensor 106h is provided at a position downstream of the PSA mechanism 42.

The home fuel gas refining system 10 communicates with and controls auxiliary devices. In particular, in the first embodiment, various conditions of the home fuel gas refining system 10 are detected based on detection signals from the pressure sensors 104a through 104c and the temperature sensors 106a through 106h. The home fuel gas refining system 10 includes, e.g., an ECU (Electric Control Unit) 108 as a control unit for determining whether the detected condition is abnormal or not, and performing a self-repair process corresponding to a predetermined abnormal condition.

If the ECU 108 detects any abnormal condition after the self-repair process, the ECU 108 sends information about the abnormal condition to a control panel 110 for displaying an alarm on the control panel 110.

Next, operation of the home fuel gas refining system 10 will be described below.

In the home fuel gas refining system 10, the ECU 108 operates the air compressor 30 for supplying the reforming air, the combustion air, and the off gas discharging air to the reforming air supply passage 32, the combustion air supply passage 34, and the off gas discharging air supply passage 36, respectively.

The reforming air flows through the reforming air supply passage 32, and is supplied to the evaporator 18. Further, a reforming fuel such as a natural gas and water are supplied to the evaporator 18. The combustion air is supplied to the combustor 20, and hydrogen or the like is supplied to the combustor 20 as necessary for combustion to evaporate the reforming fuel and water at the evaporator 18.

The evaporated reforming fuel is supplied to the reactor 22. In the reactor 22, a fuel gas in the reforming fuel such as methane and oxygen and vapor in the air are used to induce oxidation reaction CH₄+2O₂→CO₂+2H₂O (exothermic reaction) and fuel reforming reaction CH₄+2H₂O→CO₂+4H₂ (endothermic reaction) simultaneously (autothermal reforming).

As described above, the reformed gas produced by the reactor 22 is cooled by the cooling unit 24, and supplied to the gas liquid separator 26. After the moisture is removed by the gas liquid separator 26, the reformed gas is supplied toward the PSA mechanism 42 through the reformed gas supply passage 40, and compressed by the compressor 48. Then, the reformed gas is supplied selectively to the adsorption towers 60a through 60c of the PSA mechanism 42 (see FIG. 2).

At this time, as shown in FIG. 3, in the PSA mechanism 42, for example, an adsorption step is performed in the adsorption tower 60a, a purging step is performed in the adsorption tower 60b, and a pressure reduction step is performed in the adsorption tower 60c simultaneously. Therefore, in the adsorption tower 60a, gas components other than hydrogen are removed from the reformed gas by adsorption, and the reformed gas is refined to produce a fuel gas (hydrogen rich gas) having high hydrogen concentration. The fuel gas is supplied to the fuel gas passage 84. As shown in FIG. 1, the fuel gas is selectively stored in the filling tank 96 and the buffer tank 102 by the action of the compressor 90.

Then, as shown in FIG. 3, after the adsorption step in the adsorption tower 60a, and a pressure equalization step in the adsorption tower 60b and the adsorption tower 60c are performed, the adsorption step in the adsorption tower 60a, a pressure increasing step in the adsorption tower 60b, and a blowing down step in the adsorption tower 60c are performed. Therefore, in the blowing down step in the adsorption tower 60c, the off gas (impurities) is discharged into the off gas discharge passage 68 when the valve 66c is opened.

As shown in FIG. 1, the off gas discharge passage 68 is connected to the off gas discharging air supply passage 36. The off gas discharged into the off gas discharge passage 68 flows toward the combustor 20 by the off gas discharging air flowing along the off gas discharging air supply passage 36. The off gas is used as a combustion fuel in the combustor 20.

As described above, in the adsorption towers 60a through 60c, the adsorption step, the pressure reduction step, the pressure equalization step, the blowing down step, and the purge step are performed successively in a cyclic manner for constantly refining the reformed gas into the fuel gas in the PSA mechanism 42. The fuel gas is supplied from the fuel gas passage 84 to the storage unit 16.

The home fuel gas refining system 10 is operated to meet the requirements of energy consumption for home use. Therefore, operation of the home fuel gas production system 10 is started, and stopped repeatedly. The operating period and suspension period are not constant. Further, operation of the home fuel gas refining system 10 may be stopped abnormally for some reasons.

In view of the above, in the first embodiment, operation of the home fuel gas refining system 10 is started according to a flow chart shown in FIG. 4.

Firstly, when an unillustrated start up switch (ignition switch) is turned on for inputting an ON signal to the ECU 108, the ECU 108 starts checking the status of the home fuel gas refining system 10. Specifically, the ECU 108 controls the pressure sensors 104b, 104c for pressure detection, and determines whether the detected pressures are lower than a predetermined pressure of P1 kPa (e.g., 10 kPa) (step S1).

If it is determined that the pressure detected by the pressure sensor 104b is not lower than P1 kPa (NO in step S1), it is determined that there is an obstacle in the off gas discharging air supply passage 36. If it is determined that the pressure detected by the pressure sensor 104c is not lower than P1 kPa, it is determined that there is an obstacle in a water supply passage. The ECU 108 displays an abnormal position on the control panel 110 to notify the occurrence of the abnormal condition to the user. Therefore, the user can replace the parts required at the abnormal position displayed on the control panel 110.

If it is determined that the pressures detected by the pressure sensors 104b, 104c are lower than P1 kPa (YES in step S1), the routine proceeds to step S2 for determining whether the temperature detected by the temperature sensor 106dd is lower than a predetermined temperature of T1*C. If it is determined that the temperature detected by the temperature sensor 106dd is not lower than the predetermined temperature of T1° C. (NO in step S2), the routine proceeds to steps S3 and S4 to perform a self-repair process of the cooling unit 24.

Specifically, a long life coolant (LLC) as a cooling liquid is circulated through the cooling unit 24 for a predetermined time to decrease the temperature of the cooling unit 24. If it is determined that the temperature detected by the temperature sensor 106dd is not lower than T1° C. after the predetermined time (N1 minutes) of circulation of the LLC (NO in step S4), the routine proceeds to step S5 to stop circulation of the LLC, and display an abnormal condition on the control panel 110. For example, as the abnormal condition, the control panel 110 displays a failure of a device of the cooling water system such as a failure of a radiator fan of the cooling unit 24, a failure of a water pump, shortage of the cooling water, or clogging of the cooling water.

If it is determined that the temperature detected by the temperature sensor 106dd is lower than the predetermined temperature of T1° C. (YES in step S2), the routine proceeds to step S6 to determine whether the pressure detected by the pressure sensor 104a is lower than P2 kPa or not. If it is determined that the pressure detected by the pressure sensor 104a is not lower than P2 kPa (NO in step S6), the routine proceeds to perform a self-repair process, and set a valve position of the valve 38c to M1%.

Under the condition, if it is determined that the pressure detected by the pressure sensor 104a is not lower than P2 kPa after a predetermined time (N2 minutes) (YES in step S8), an abnormal condition is displayed on the control panel 110. For example, as the abnormal condition, the control panel 110 displays an abnormal pressure in the system or a failure of a device.

In step S6, if it is determined that the pressure detected by the pressure sensor 104a is lower than P2 kPa (YES in step S6), the routine proceeds to step S9 to determine whether the temperatures detected by the temperature sensors 106a, 106h are lower than predetermined temperatures of T2° C., T3° C., respectively. If it is determined that the temperatures detected by the temperature sensors 106a, 106h are not lower than the predetermined temperatures of T2° C., T3° C., respectively (NO in step S9), the routine proceeds to step S10 to turn on the air compressor 30.

Then, the valve position of the valve 38c is adjusted to 100% (step S11), and the off gas discharging air is supplied through the off gas discharging air supply passage 36 toward the combustor 20 for the predetermined time (N2 minutes). Then, if it is determined that the temperatures detected by the temperature sensors 106a, 106h are not lower than the predetermined temperatures of T2° C., T3° C., respectively (NO in step S12), the routine proceeds to step S13 to turn off the air compressor 30, adjust the valve position of the valve 38c to M2%, and display an abnormal condition on the control panel 110. For example, as the abnormal condition, the control panel 110 displays an abnormal temperature of the catalyst of the evaporator 18 or a failure of the air compressor 30.

If it is determined that the temperatures detected by the temperature sensors 106a, 106h are lower than the predetermined temperatures of T2° C., T3° C., respectively (YES in step S9), the routine proceeds to step S14 to determine whether the temperatures detected by the temperature sensors 106b, 106c, 106e, 106f, and 106g are lower than predetermined temperatures of T4° C., T5° C., T6° C., T7° C., and T8° C., respectively.

If at least one of the temperatures detected by the temperature sensors 106b, 106c, 106e, 106f, and 106g is not lower than the predetermined temperature (NO in step S14), a warming up process of the evaporator (CBN) 18 is started (step S15). If any of the temperatures detected by the temperature sensors 106b, 106c, 106e, 106f, and 106g is not lower than the predetermined temperature after the warming up process for a predetermined time (N3 seconds) (YES in step S16), an abnormal condition is displayed on the control panel 110. For example, as the abnormal condition, the control panel 110 displays a failure of a warming up device.

If it is determined that all of the temperatures detected by the temperature sensors 106b, 106c, 106e, 106f, and 106g are lower than the predetermined temperatures, respectively (YES in step S14), the routine proceeds to step S17 to check the status of the PSA mechanism 42. Specifically, the pressure sensors 62a through 62c detect pressures in the adsorption towers 60a through 60c of the PSA mechanism 42. The ECU 108 stores normal starting positions of the adsorption towers 60a through 60c, e.g., predetermined starting pressures at positions T1 through T3 in FIG. 3 in advance. It is determined whether the detected pressures P of the adsorption towers 60a through 60c are within a range between predetermined pressures of P3 kPa and P4 kPa (step S18).

For example, if it is determined that the pressure in the adsorption tower 60b is lower than the predetermined pressure of P3 kPa, the routine proceeds to step S19 to open the valve 94 for releasing the fuel gas (hydrogen gas) stored in the filling tank 96 to the PSA mechanism 42. The valve 80b of the PSA mechanism 42 is opened. Therefore, under the action of the valve 92, the fuel gas is supplied into the adsorption tower 60b. The amount of the fuel gas supplied into the adsorption tower 60b is limited to a predetermined amount by the flow rate control valve 86.

Likewise, if the detected pressures in the adsorption towers 60a, 60c are lower than the predetermined pressures of P3 kPa, respectively, the valves 80a, 80c are opened to supply a predetermined amount of the fuel gas to the adsorption towers 60a, 60c.

If it is determined that the pressures in the adsorption towers 60a through 60c are lower than the predetermined pressures of P3 kPa after the supply of the fuel gas for a predetermined time (N4 seconds) (YES in step S20), an abnormal condition is displayed on the control panel 110. For example, as the abnormal condition, the control panel 110 displays a failure of the PSA mechanism 42.

In step S18, for example, if it is determined that the pressure in the adsorption tower 60b is higher than the predetermined pressure of P4 kPa, the routine proceeds to step S21 to open the valves 66b, 70. Thus, the off gas (remaining gas) corresponding to the excessive pressure in the adsorption tower 60b is supplied to the combustor 20. The off gas is combusted in the combustor 20, and discharged as an exhaust gas.

If it is determined that the pressures in the adsorption towers 60a through 60c are higher than the predetermined pressure of P4 kPa after a predetermined time (N5 seconds) (YES in step S22), an abnormal condition is displayed on the control panel 110. For example, as the abnormal condition, the control panel 110 displays a failure of the PSA mechanism 42.

When checking of the status of the PSA mechanism 42 is finished, the routine proceeds to step S23 to adjust the valve positions of the valves 38a, 38b to M3%. Then, operation of the fuel gas refining system 10 is started.

As described above, in the first embodiment, even if operation of the home fuel gas refining system 10 is stopped abnormally, prior to starting operation of the home fuel gas refining system 10 again, it is determined whether various conditions of the home fuel gas refining system 10 are abnormal. If a predetermined abnormal condition is detected, a self-repair process is performed.

Therefore, no undue burden of the maintenance operation is imposed on the user. With the simple steps, it is possible to start operation of the home fuel gas refining system 10 rapidly and reliably. Further, the burden of the maintenance operation on the user is reduced as much as possible.

Further, if any abnormal condition is detected after the self-repair process, the ECU 108 sends information about the abnormal condition to the control panel 110 to display an alarm including the abnormal position and the information about the abnormal condition. Therefore, the user can learn the details of the abnormal condition reliably. For example, the frequency of the user's part replacement operation is minimized, and the burden on the user is reduced as much as possible.

FIG. 6 is a block diagram schematically showing a home fuel gas production system (HRS) 210 as a fuel gas production apparatus for carrying out a control method according to a second embodiment of the present invention. The constituent components that are identical to those of the home fuel gas refining system 10 according to the first embodiment are labeled with the same reference numeral, and description thereof is omitted.

The water supply tank 21 is connected to the evaporator 18 through the water compressor 23 and a valve 212a. The supply of the reforming fuel to the ejector 37 can be stopped by a valve 212b.

A start up fuel supply passage 214 is connected to the combustor 20. Valves 38d, 38e are provided in the start up fuel supply passage 214. A branch air supply passage 36a branched from the off gas discharging air supply passage 36 is connected to the start up fuel supply passage 214 at a position between the valves 38d, 38e. A valve 38f is provided in the branch air supply passage 36a.

A branch passage 52 is provided in the reformed gas supply passage 40 at a position upstream of the compressor 48. The branch passage 52 and the off gas discharging air supply passage 36 are connected by a bypass passage 54. A valve 56 is provided in the bypass passage 54. A back pressure regulator valve 58 is provided in the branch passage 52.

The home fuel gas production system 210 has various sensors for detecting various abnormal conditions of the home fuel gas production system 210. Specifically, a pressure sensor 104a is provided near the air compressor 30, and a pressure sensor 104b is provided in the off gas discharging air supply passage 36. Further, a pressure sensor 104c is provided in the reforming fuel supply passage 105.

A pressure sensor 104d is provided at the evaporator 18, and a pressure sensor 104e is provided at the reactor 22. Further, a pressure sensor 104f is provided near the gas liquid separator 26 at a position downstream of the gas liquid separator 26, and a pressure sensor 104g is provided near the compressor 48 at a position downstream of the compressor 48. Temperature sensors 106a, 106h, 106c are provided at the combustor 20, the evaporator 18, and the reactor 22, respectively.

The home fuel gas production system 210 communicates with and controls auxiliary devices. In particular, in the second embodiment, various abnormal conditions of the home fuel gas production system 210 are detected based on detection signals from the pressure sensors 104a through 104g and the temperature sensors 106a, 106c, and 106h. The home fuel gas production system 210 includes, e.g., an ECU (Electric Control Unit) 108 as a control unit for determining whether the detected abnormal condition corresponds to a stop pattern among a plurality of predetermined stop patterns, and performing a stop process according to the corresponding predetermined stop pattern.

The ECU 108 sends various items of information such as information about an abnormal condition to the control panel 110. If it is determined that the problem of the abnormal condition cannot be eliminated by the self-repair process, the abnormal position and information about the abnormal condition are notified to a maintenance service company 216. Therefore, information about the serious failure which requires part replacement is provided for the maintenance service company 216.

Next, a method of stopping operation of the fuel gas production system 210 in an abnormal condition according to the second embodiment will be described.

The home fuel gas production system 210 stores a plurality of predetermined stop patterns in various system operation modes in advance. Specifically, as shown in FIG. 7, when the home fuel gas production system (HRS) 210 is stopped (block 218), an unillustrated start up switch (ignition switch) is turned on to start a system check (block 220). In the system check (block 220), if an abnormal condition is detected, the routine proceeds to a stop process according to a first stop pattern (block 222a). If the condition is normal, the routine proceeds to perform a status check (block 224).

If an abnormal condition is detected in the status check (block 224), the routine proceeds to the stop process according to the first stop pattern (block 222a). If no abnormal condition is detected, the routine proceeds to perform a PSA status check (block 226). Also in the PSA status check (block 226), if an abnormal condition is detected, the routine proceeds to the stop process according to the first stop pattern (block 222a). If no abnormal condition is detected, the routine proceeds to a process before burner ignition for warming up (block 228).

In the process before burner ignition for warming up (block 228), if an abnormal condition such an ignition failure is detected, the routine proceeds to a stop process according to a second stop pattern (block 222b). If no abnormal condition is detected, the routine proceeds to a process after burner ignition for warming up (block 230). If an abnormal condition such as an accidental fire is detected, the routine proceeds to the second stop pattern (block 222b). If no abnormal condition is detected, combustion catalyst warming up is performed (block 232).

The combustion catalyst warming up is performed for warming up the evaporator 18. If an abnormal condition such as an accidental fire in the combustor 20 or an accidental fire in the evaporator 18 is detected, the routine proceeds to a stop process according to a third stop pattern (block 222c). If combustion catalyst warming up (block 232) is performed normally, the routine proceeds to start reforming operation in the reactor 22 and start PSA operation (block 234). Depending on the abnormal condition at the time of starting operation (block 234), the routine proceeds selectively to a stop process according to a fourth stop pattern (block 222d), a stop process according to a fifth stop pattern (block 222e) or a stop process according to a sixth stop pattern (block 222f).

The time from the start of PSA operation is counted. After reforming operation and PSA operation are performed for a predetermined time (block 236), depending on the abnormal condition, the routine proceeds selectively to the stop process according to the fourth stop pattern (block 222d), the stop process according to the fifth stop pattern (block 222e) or the stop process according to the sixth stop pattern (block 222f). If operation after the predetermined time (block 236) is performed normally, and a stop switch is turned on, the routine proceeds to a stop process according to a PSA normal stop pattern (block 238), and then, the routine proceeds to stop the home fuel gas production system (HRS) 210 (block 218).

Next, these stop processes in the respective stop patterns will be described in detail. According to the first stop pattern (block 222a), if an abnormal condition is detected in the system check (block 220), as shown in FIG. 8, an abnormal lamp is turned on (step S101), and the ignition switch is turned off (step S102). The ECU 108 notifies the failure to the maintenance service company (step S103), and the maintenance service company 216 carries out the required repair operation of the abnormal position by part replacement or the like.

According to the second stop pattern (block 222b) in FIG. 7, for example, at the time of the accidental fire or abnormal combustion in the combustor 20, the failure is detected by the temperature sensor 106a of the combustor 20, the temperature sensor 106c of the reactor 22, and the pressure sensor 104e of the reactor 22. Under the condition, in the all circulation mode (the three-way valve 44 is opened to establish connection to the branch passage 46), the combustion air in the combustor 20 is discharged together with the warming up air from the evaporator 18.

At this time, it is necessary to prevent the unconsumed start up fuel from remaining in the circulation line. It is because the excessive fuel may enter the evaporator 18 at the time of starting operation, and the catalyst temperature may increase sharply.

In view of the above, firstly, the valves 38d, 38e are closed to interrupt the flow in the start up fuel supply passage 214, and the valve 38a is fully opened (100%) to discharge the start up fuel in the circulation line by the large amount of scavenging air (step S111 in FIG. 9). At the time of warming up the system, the three-way valve 44 is always open. The three-way valve 44 is kept opened.

In step S112, after the scavenging process is performed for a predetermined time (T1 seconds), all operation in the supply system is stopped. That is, in step S113, the air compressor 30 is turned off, the valves 38b, 38c are closed, and the ignition switch is turned off. The valve 38a is fully closed (0%).

According to the third stop pattern (block 222c), a failure of warming up due to the accidental fire in the evaporator 18 and/or the combustor 20 is detected based on the temperature of the reactor 22 detected by the temperature sensor 106c and the temperature of the evaporator 18 detected by the temperature sensor 106h. As shown in FIG. 10, the valves 38d, 38e, and 38f are closed, and the valve 38a is fully opened (100%). Further, in the same manner as the steps S112 and S113, the steps S122 and S123 are performed to stop all operation in the supply system.

According to the fourth stop pattern (block 222d), as shown in FIG. 11, after operation of the PSA mechanism 42 is stopped normally (step S131), operation of the entire home fuel gas production system 210 is stopped normally (step S132).

The stop process according to the fifth stop pattern (block 222e) is performed when generation of the fuel gas is started by reforming of the PSA mechanism 42. If any of the detection values of the temperature sensor 106c of the reactor 22, the temperature sensor 106h of the evaporator 18, and the pressure sensors 104a through 104g increases or decreases to reach a threshold, the routine proceeds to the stop process according to the fifth stop pattern (block 222e).

For example, if the air compressor 30 and the valve 38c are malfunctioning, the flow rate of the air supplied to the system is decreased. In particular, if the air is not supplied to the evaporator 18, the catalyst temperature may increase excessively by the off gas of the PSA mechanism 42, and the evaporator 18 may be damaged undesirably.

Therefore, in order to prevent the off gas from being discharged from the PSA mechanism 42, as shown in FIG. 12, operation of the PSA mechanism 42 and operation of the compressor 48 are stopped, and supply of the reforming fuel and supply of the water are stopped not to refine the reformed gas(OTHER: OFF in step S141). Further, in order to increase the flow rate of the air supplied to the evaporator 18, the valve 38c is fully opened (100%), and the ON state of the air compressor 30 is maintained. Further, in order to stop operation of the compressor 48, the three-way valve 44 is kept opened, and in order to decrease the temperature of the evaporator 18, the valve 38a is fully opened (100%).

Then, after the above condition is maintained for a predetermined time (T2 seconds) (YES in step S142), the routine proceeds to step S143. In step S143, the three-way valve 44 is closed and the valve 56 is opened for scavenging of the gas on the upstream of the PSA mechanism 42. Thus, the scavenging gas flows into the evaporator 18.

After a predetermined time (T3 seconds) has passed (YES in step S144), the routine proceeds to step S145 to stop cooling by the air compressor 30, the valve 38a, and the cooling water. Then, after a predetermined time (T4 seconds) has passed (YES in step S146), the routine proceeds to step S147 to close the valve 38c for preventing the increase of the internal pressure by the air.

The stop process according to the sixth stop pattern (block 222f) is performed in the same manner as the stop process according to the first stop pattern (block 222a). The power supply is stopped rapidly.

In the stop process according to the PSA normal stop pattern (block 238), as shown in FIG. 13, operation of the home fuel gas production system 210 is stopped normally (step S151). At this time, predetermined amounts of the fuel gas are filled in the filling tank 96 and the buffer tank 102, respectively. Then, the routing proceeds to step S152 to stop operation of the PSA mechanism 42. In the PSA mechanism 42, the adsorption towers 60a through 60c are stopped at normal starting positions, i.e., at one of the positions T1 through T3 in FIG. 3. Then, stop sequence of the reactor 22 is started (step S153).

Detection of the abnormal condition in various system operation modes is performed based on the detection signals from the pressure sensors 104a through 104g, and the temperature sensors 106a, 106c, 106h. The thresholds in the detected values of the sensors used as criterion for determination of the abnormal conditions vary depending on the system operation mode. Some sensors may have upper and lower limit values in the same system operation mode. That is, with the small number of sensors having the upper and lower limit values, it is possible to set the thresholds required for determination of various abnormal conditions such as failures of various devices used in the home fuel gas production system 210.

For example, criterion (thresholds) used for determining the abnormal condition by the pressure sensor 104a and the stop patterns are set as shown in FIG. 14. The thresholds are expressed by the relationship “A kPa<B kPa<C kPa”. Using the pressure sensor 104a, for example, pressure losses in the exhaust gas line including the air compressor 30, the valve 38c, and the off gas discharging air supply passage 36, and the combustion line including the start up fuel supply passage 214, and clogging in the ejector 76 can be monitored.

Further, in the various system operation modes and abnormal conditions, it is possible to determine the failure position, and determine whether the failure is critical or not. Even if an abnormal signal is generated, operation is continued for a short period of time after detection of the abnormal condition, and a stop mode (b, c, d and e) is selected to stop operation of the system in the normal stop mode. Therefore, it is possible to prevent system failures at the time of starting operation in the next time. If it is determined that a critical failure occurs which cannot be handled by self-repair, an urgent stop mode (a, f) for immediately stopping operation of the system is selected.

In the second embodiment, as shown in FIG. 7, a plurality of stop patterns, e.g., the first through sixth stop patterns (blocks 222a through 222f) are determined in advance in correspondence with the system operation modes of the home fuel gas production system 210. Therefore, for example, by stopping operation of the home fuel gas production system 210 in accordance with the stop pattern in correspondence with the abnormal condition detected by the pressure sensors 104a through 104g and the temperature sensors 106a, 106c, 106h, if operation of the system can be started again, a suitable stop process can be performed.

In summary, in the second through fifth stop patterns (blocks 222b through 222e), if an abnormal condition is detected, operation is continued for a short period of time, and operation is stopped in a normal operation mode for preventing the system failure at the time of starting operation again. Therefore, no undue burden for the maintenance operation is imposed on the user.

If a critical failure which does not allow the continuation of operation occurs, i.e., if operation according to the first stop pattern or operation according to the sixth stop pattern (block 222a or block 222f) is performed, operation of the system is stopped immediately. The failure information and the failure position are notified to the maintenance service company 216. Therefore, the maintenance service company 216 can suitably carry out the repair such as part replacement.

Thus, with the simple steps, it is possible to start operation of the home fuel gas production system 210 rapidly and reliably. The burden of the user's maintenance operation is reduced as much as possible advantageously.

While the invention has been particularly shown and described with reference to preferred embodiments, it will be understood that variations and modifications can be effected thereto by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method of controlling a fuel gas production apparatus for reforming a hydrogen-containing fuel into a reformed gas, and refining the reformed gas to produce a hydrogen-rich fuel gas, the method comprising the steps of: detecting various conditions of said fuel gas production apparatus when a start up signal of said fuel gas production apparatus is inputted; and performing a predetermined process for a predetermined condition among said detected conditions.

2. A control method according to claim 1, wherein the various conditions of said fuel gas production apparatus are determined by measuring pressure and temperature.

3. A control method according to claim 1, further comprising the steps of: determining whether the detected conditions are abnormal; and performing a self-repair process for a predetermined abnormal condition among conditions determined as abnormal.

4. A control method according to claim 3, further comprising the step of displaying information about an abnormal condition which has been determined after the self-repair process.

5. A control method according to claim 1, wherein the various conditions of said fuel gas production apparatus comprise an abnormal condition, and the method further comprises the steps of: determining whether the detected abnormal condition should be handled by a process according to a stop pattern among a plurality of predetermined stop patterns; and stopping operation of said fuel gas production apparatus according to the process of the determined stop pattern.

6. A control method according to claim 5, further comprising the step of outputting a signal indicating the abnormal condition if the abnormal condition cannot be eliminated by self-repair.

7. A control method according to claim 5, further, comprising the step of notifying the abnormal condition to a maintenance service company if the abnormal condition cannot be eliminated by self-repair.