JP4733479B2 - Fuel cell system equipped with liquid hydrocarbon desulfurization device - Google Patents

Description

The present invention relates to a fuel cell system of a fuel reforming type comprising a desulfurization equipment for liquid hydrocarbons.

  In recent years, a fuel reforming type fuel cell system has been studied as a power generation system with a small environmental load. In a fuel reforming type fuel cell system, hydrocarbons are reformed together with water by a reforming catalyst to generate hydrogen, and this hydrogen is introduced into the anode of the fuel cell to generate electricity through an electrochemical reaction with oxygen in the air. To do.

  As the hydrocarbon, liquid hydrocarbons made from petroleum such as kerosene can be used. However, liquid hydrocarbons made from petroleum contain sulfur as an impurity. Since sulfur mixed in liquid hydrocarbons degrades the reforming catalyst, removal of sulfur contained in liquid hydrocarbons is one of the issues to improve the efficiency and life of fuel cell systems. It has become one.

Removal of sulfur contained in the liquid hydrocarbon is performed by a desulfurizer using a desulfurization catalyst. For example, Patent Document 1 discloses a desulfurization apparatus that uses a cartridge-type desulfurization catalyst, vaporizes desulfurized liquid hydrocarbon, and supplies the vaporized liquid hydrocarbon to a reformer.
JP 2001-279256 A (paragraph 0006, FIG. 3)

  By the way, the liquid hydrocarbons that have passed through such a desulfurizer contain a small amount of light hydrocarbons (hereinafter simply referred to as hydrogen) such as hydrogen and methane, which are by-products when desulfurizing with a catalyst. If a gas such as hydrogen is contained in the liquid hydrocarbon after desulfurization, the indicated value of the flow meter that controls the supply amount of the liquid hydrocarbon to the reformer fluctuates, which causes the control to be disturbed. Furthermore, hydrogen is a flammable gas that requires careful handling and must be managed safely.

In view of the above problems, the present invention can prevent hydrogen mixed in liquid hydrocarbons after desulfurization from entering the flowmeter, and can safely manage hydrogen mixed in liquid hydrocarbons. and an object thereof is to provide a fuel cell system comprising a desulfurization equipment.

The fuel cell system according to claim 1, which has solved the above problems, includes a desulfurizer that desulfurizes liquid hydrocarbons, a storage tank that is connected downstream of the desulfurizer and stores the liquid hydrocarbons after desulfurization, and the storage tank A fuel cell system comprising: a liquid hydrocarbon desulfurization device comprising: a pump connected to a tank for delivering the liquid hydrocarbon from the storage tank; and generating electricity using hydrogen obtained by reforming the liquid hydrocarbon with a reformer The supply position of the liquid hydrocarbon after desulfurization to the storage tank is disposed above a suction port connected to the pump, and the storage tank collects hydrogen mixed in the liquid hydrocarbon after desulfurization. e Bei the hydrogen recovery unit, hydrogen recovered by said hydrogen recovery unit, and a configuration, characterized in that feeding and burning the burner of the reformer.

In the desulfurization apparatus according to the fuel cell system according to claim 1, since the supply position of the liquid hydrocarbon after desulfurization is disposed above the suction port connected to the pump, the desulfurization apparatus is mixed in the liquid hydrocarbon after desulfurization. Hydrogen does not float up to reach the suction port of the pump, and it is possible to prevent hydrogen from entering a flow meter downstream of the pump. In addition, since hydrogen recovery means for recovering hydrogen mixed in the liquid hydrocarbon is provided, hydrogen can be safely managed as will be described later.
Further, according to the fuel cell system of claim 1, hydrogen does not enter the flow meter of the liquid hydrocarbon after desulfurization, and the indicated value does not fluctuate, and the liquid hydrocarbon reformer after desulfurization is supplied. The supply amount of is stable. In addition, hydrogen can be stored safely under a certain pressure and managed safely.
Moreover, hydrogen can be safely treated by supplying the hydrogen recovered by the hydrogen recovery means to the burner of the reformer and burning it. In addition, by using hydrogen as a byproduct for heating the reformer, energy can be effectively used.

The fuel cell system according to claim 2 is a desulfurizer for desulfurizing liquid hydrocarbons, a storage tank connected downstream of the desulfurizer to store the liquid hydrocarbons after desulfurization, and a liquid tank connected to the storage tank. A liquid cell desulfurization device comprising a pump for delivering hydrocarbons from the storage tank, and a fuel cell system for generating electricity using hydrogen obtained by reforming the liquid hydrocarbons with a reformer, The supply position of the liquid hydrocarbon after desulfurization to the storage tank is disposed above a suction port connected to the pump, and the storage tank includes a hydrogen recovery means for recovering hydrogen mixed in the liquid hydrocarbon after desulfurization. When the reformer is stopped, the kerosene supply passage leading to the reformer and the reformed gas passage of the reformer are purged with the hydrogen recovered by the hydrogen recovery means. It was.

In the desulfurization apparatus according to the fuel cell system according to claim 2, since the supply position of the liquid hydrocarbon after desulfurization is disposed above the suction port connected to the pump, the desulfurization apparatus is mixed in the liquid hydrocarbon after desulfurization. Hydrogen does not float up to reach the suction port of the pump, and it is possible to prevent hydrogen from entering a flow meter downstream of the pump. In addition, since hydrogen recovery means for recovering hydrogen mixed in the liquid hydrocarbon is provided, hydrogen can be safely managed as will be described later.
Further, according to the fuel cell system of claim 2, hydrogen does not enter the flow meter of liquid hydrocarbon after desulfurization and the indicated value does not fluctuate, and the liquid hydrocarbon reformer after desulfurization is supplied. The supply amount of is stable. In addition, hydrogen can be stored safely under a certain pressure and managed safely.
In addition , when the reformer is stopped, coking by hydrocarbons remaining in the kerosene supply channel and reformed gas channel leading to the reformer occurs, the kerosene supply channel is blocked, the activity of the reforming catalyst decreases, or Inactivation can be prevented. Moreover, hydrogen can be safely treated by using the hydrogen recovered by the hydrogen recovery means for purging the reformed gas flow path .

The fuel cell system according to claim 3, wherein the hydrogen recovery means includes a space formed in an upper portion of the liquid level of the liquid hydrocarbon after the desulfurization in the storage tank, and a portion in which the space of the storage tank is formed. And a valve that opens and closes according to the pressure of the gas occupying the space.

According to the fuel cell system of the third aspect, since hydrogen can be stored in the space of the storage tank, there is no need to newly provide a container for storing the recovered hydrogen and a valve associated therewith. Can be configured. Moreover, since the valve opened and closed according to the pressure of the gas which has hydrogen as a main component is provided, hydrogen can be stored safely below a fixed pressure and can be managed safely.

According to the present invention, it is possible to prevent the hydrogen mixed in the liquid hydrocarbon enters the flowmeter also comprises a desulfurization equipment of liquid hydrocarbons that can safely manage the hydrogen mixed in the liquid hydrocarbon A fuel cell system can be provided.

  Next, a first embodiment of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a diagram for explaining the configuration of the fuel cell system 10, and FIGS. 2 and 3 are diagrams showing hydrogen flow paths recovered by the desulfurization apparatus 1 and the hydrogen recovery means 5.

  As shown in FIG. 1, a fuel cell system 10 according to this embodiment includes a reformer 11 that reforms liquid hydrocarbons such as kerosene with a reforming catalyst to generate hydrogen, and the hydrogen and oxygen in the air. The fuel cell stack 30 that generates electric power by the electrochemical reaction is used as a main component.

  The reformer 11 is supplied with water and liquid hydrocarbons desulfurized by the desulfurization apparatus 1. In the reformer 11, hydrogen, carbon dioxide, and a small amount of carbon monoxide are generated by the reforming reaction using the reformed catalyst using vaporized water and liquid hydrocarbon as raw materials. The reformer 11 is supplied with heat energy for continuing the reforming reaction by the burner 12. As the fuel for the burner 12, liquid hydrocarbons that are not desulfurized are mainly used, and hydrogen that has not been used for power generation at the anode (not shown) of the fuel cell stack 30 is also used for the fuel. The waste heat of the combustion gas of the burner 12 can be recovered and used for hot water supply.

  The carbon monoxide mixed in the hydrogen produced by the reformer 11 passes through the shift reactor 13 and the CO selective oxidizer 14 in order to inhibit the electrochemical reaction of the fuel cell stack 30 and reduce the power generation efficiency. And refine. The purified hydrogen-based gas is supplied to the anode (not shown) of the fuel cell stack 30.

  In the fuel cell stack 30, electric power is generated by an electrochemical reaction between humidified air (oxygen) supplied to the cathode (not shown) and humidified hydrogen supplied to the anode. Further, the cooling water can be circulated through the fuel cell stack 30 to recover the heat generated by the power generation and can be used for hot water supply. Hydrogen that is not used for power generation in the fuel cell stack 30 is sent to the burner 12 as off-gas and incinerated.

  When the fuel cell system 10 is stopped, if liquid hydrocarbons remain in the reforming catalyst inside the reformer 11, the liquid hydrocarbons are carbonized on the surface of the reforming catalyst during the stop to cause coking, There arises a problem that the activity of the reforming catalyst is lowered or deactivated. In order to prevent this, when the fuel cell system 10 is stopped, the reformer 11 is steam purged by first stopping the liquid hydrocarbons and supplying only water to the reformer 11, and then nitrogen from a nitrogen cylinder or the like. Can be purged. In FIG. 1, combustion air is supplied by a blower, and the entire fuel cell system 10 is controlled by a control device (not shown).

Next, the desulfurization apparatus 1 according to the first embodiment will be described with reference to FIG. Here, it is assumed that kerosene is used as the liquid hydrocarbon and the hydrogen recovered by the hydrogen recovery means 5 is incinerated by the burner 12 for supplying thermal energy to the reformer 11.
The desulfurization apparatus 1 includes a desulfurizer 2, a storage tank 3, and a pump 4, and further includes a space 6 above the kerosene liquid level 8 inside the storage tank 3 constituting the hydrogen recovery means 5, and a valve 7. Note that the piping including the first gate valve 22 and the second gate valve 23 is used in the second embodiment to be described later, and is not essential to the present embodiment.

Hereinafter, the details of each device constituting the desulfurization apparatus 1 will be described.
The desulfurizer 2 receives undesulfurized kerosene sent from a kerosene storage tank 15, which is a liquid hydrocarbon, by a liquid feeding means 18 such as a pump, and kerosene by a desulfurizing agent and a desulfurization catalyst filled therein. Is for desulfurization. The desulfurizer filled in the desulfurizer 2 is a nickel-based adsorptive desulfurizer, and the desulfurization catalyst is a cobalt-molybdenum-based, nickel-aluminum-based or nickel-tungsten-based hydrodesulfurization catalyst, or these and zinc oxide A combined catalyst system can be used.

  The desulfurizer 2 may be provided with heating means such as an electric heater in order to raise the temperature of the catalyst to a temperature at which activity is manifested. The desulfurizer 2 is formed of a pressure-resistant casing made of a material resistant to liquid hydrocarbons, for example, a metal such as stainless steel, and can have a structure disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-15543. .

  The storage tank 3 is for storing kerosene after desulfurization (hereinafter referred to as desulfurized kerosene), and a known kerosene container such as a metal tank can be used. In the present embodiment, the top plate of the storage tank 3 is extended with a pressure sensor 16 for detecting the pressure of the gas occupying the space 6 and a pipe reaching the burner 12 via the valve 7. Further, in the storage tank 3, the desulfurized kerosene supply position F is disposed above the suction port SC of the pipe leading to the pump 4.

  Further, an upper limit level sensor LH and a lower limit level sensor LL for controlling the amount of desulfurized kerosene stored in a certain range are provided on the side wall of the storage tank 3. When the control device (not shown) of the fuel cell system 10 detects that the liquid level 8 of the desulfurized kerosene in the storage tank 3 is below the lower limit level sensor LL, the desulfurizer is removed from the storage tank 15 by the liquid feeding means 18. The operation of transferring kerosene to the storage tank 3 through 2 is performed, and when it is detected that the liquid level 8 of the desulfurized kerosene has reached the upper limit level sensor LH, the transfer is stopped.

  The desulfurized kerosene stored in the storage tank 3 is sent to the reformer 11 by the pump 4 and reformed to generate hydrogen. Here, the amount of desulfurized kerosene to be supplied from the storage tank 3 to the reformer 11 is determined by the amount of hydrogen corresponding to the required power generation amount to the fuel cell stack 30. For this reason, the control device of the fuel cell system 10 calculates the amount of hydrogen necessary for the fuel cell stack 30 to satisfy the power generation requirement, and based on this value, the desulfurized kerosene to be supplied to the reformer 11 Find the amount. Then, the output value to the pump 4 is adjusted according to the capacity curve of the pump 4 determined in advance by experiments or the like, and the actual flow rate is detected by the flow meter 17 on the discharge side of the pump 4 to perform feedback control.

  Here, in the desulfurization apparatus 1, when desulfurization of kerosene is performed by the desulfurization catalyst in the desulfurizer 2, hydrogen is generated as a by-product, and bubbles are mixed into the desulfurized kerosene. When desulfurized kerosene mixed with bubbles enters the flow meter 17 via the pump 4, the indicated value of the flow meter 17 fluctuates, causing control of the power generation amount of the fuel cell system 10.

  However, in the present embodiment, the supply position F of desulfurized kerosene in the storage tank 3 is disposed above the suction port SC connected to the pump 4, so that the bubbles float upward from the supply position F. The suction port SC connected to the pump 4 is not reached, and bubbles can be effectively prevented from entering the flow meter 17. Note that the desulfurized kerosene supply position F is preferably disposed below the lower limit level sensor LL. This is because if the supply position F is above the lower limit level sensor LL, the desulfurized kerosene supplied to the storage tank 3 falls on the liquid surface 8 and entrains bubbles.

  The hydrogen bubbles rising upward from the supply position F reach the space 6 formed above the liquid surface 8 of the kerosene, and hydrogen gradually accumulates in the space 6. Since the storage amount of desulfurized kerosene in the storage tank 3 is controlled within a certain range, the pressure of a gas containing hydrogen as a main component (hereinafter simply referred to as hydrogen) occupying the space 6 varies slightly, but gradually It rises.

  The control device of the fuel cell system 10 monitors the pressure of hydrogen in the space 6 with the pressure sensor 16, and when detecting that the predetermined upper limit pressure PH has been reached, the valve 7 is opened to transfer the hydrogen in the space 6 to the burner 12. Send out and incinerate. Then, the valve 7 is closed when the pressure sensor 16 detects that the pressure is lower than the predetermined lower limit pressure PL. Thereby, hydrogen can be stored at a certain pressure or lower and incinerated by the burner 12, which can be managed safely.

  The predetermined upper limit pressure PH can be determined in consideration of the design pressure resistance of the storage tank 3 and legal regulations such as the high-pressure gas safety law. The predetermined lower limit pressure PL is set to the atmospheric pressure considering that the volume of the space 6 changes as the amount of desulfurized kerosene varies in the range between the upper limit level and the lower limit level in the storage tank 3. It is preferable to set so as not to be a negative pressure.

  When the reformer 11 is stopped, that is, when the fuel cell system 10 is stopped, the control device opens the valve 7 to send the hydrogen in the space 6 of the storage tank 3 to the burner 12 for incineration. At this time, in order to minimize the amount of hydrogen retained in the stopped space 6, the hydrogen is burned until the pressure in the space 6 becomes lower than the lower limit pressure PL and higher than the atmosphere while monitoring with the pressure sensor 16. It is preferable to set to send to 12. By doing in this way, the hydrogen in the space 6 can be managed safely.

  Even when the burner 12 and the heater for heating the desulfurization catalyst of the desulfurizer 2 to the activation temperature are stopped at the same time, hydrogen gas can be combusted by the residual heat of the burner 12 and the reformer 11. Moreover, although the burner 12 became low temperature, when the temperature of the desulfurizer 2 is equal to or higher than the activation temperature of the desulfurization catalyst, hydrogen can be burned using the igniter of the burner 12.

Next, a second embodiment will be described with reference to FIG.
In the second embodiment, when the reformer 11 is stopped, the kerosene supply channel 24 and the reformed gas channel 21 communicating with the reformer 11 are purged with hydrogen recovered by the hydrogen recovery means 5. Different from the first embodiment. The configuration of the desulfurization apparatus 1 is different from the first embodiment in that a pipe downstream of the valve 7 is branched and the first gate valve 22 and the second gate valve 23 are used. Since the other configuration is the same, the description is omitted.

  In the present embodiment, during rated operation of the fuel cell system 10, as in the first embodiment, hydrogen is sent to the burner 12 by the valve 7 and the first gate valve 22, and the pressure in the space 6 is kept below a certain value. Keep it safe to manage. When the fuel cell system 10 is stopped, the kerosene supply flow path 24 that leads to the reformer 11 with hydrogen and the reformed gas flow path 21 in the reformer 11 are provided by the valve 7 and the second gate valve 23. Purging to prevent clogging of the kerosene supply passage 24 and reduction of the activity of the reforming catalyst due to coking, and to safely treat the hydrogen recovered by the hydrogen recovery means 5.

  The purge operation of the reformed gas passage 21 with hydrogen will be described in more detail. When stopping the reformer 11, first, the supply of desulfurized kerosene to the kerosene supply passage 24 and the reformed gas passage 21 leading to the reformer 11 is stopped. Next, the reformed gas passage 21 is purged with dry steam, and the kerosene supply passage 24 and the reformed gas passage 21 leading to the reformer 11 by opening the valve 7 and the second gate valve 23 are purged with hydrogen. To do. Then, when the pressure of the pressure sensor 16 is lower than the lower limit pressure PL and higher than atmospheric pressure, the second gate valve 23 is closed. Thereby, the usage-amount of nitrogen used for the purge of the reformer 11 can be reduced or made zero. In addition, since the desulfurized kerosene remaining in the kerosene supply channel 24 leading to the reformer 11 is also purged by the hydrogen stored in the space 6, the kerosene supply flow leading to the reformer 11 due to the residual heat of the reformer 11. It is possible to prevent the passage 24 from being blocked by kerosene coking.

  In the present embodiment, the volume of the space 6 is preferably set to a volume that can secure an amount of hydrogen necessary for purging the kerosene supply channel 24 and the reformed gas channel 21 leading to the reformer 11. Further, in order to minimize the amount of hydrogen held in the stopped space 6, the pressure in the space 6 becomes slightly higher than the atmospheric pressure while monitoring with the pressure sensor 16 as in the first embodiment. It is preferable that the kerosene supply flow path 24 and the reformed gas flow path 21 leading to the reformer 11 are purged. When purging the reformed gas flow path 21, the gas that has passed through the flow path does not pass through the fuel cell stack 30, but directly enters the burner 12. However, the flow path and switching valve for this purpose are not shown in the figure. It is omitted.

  Next, a third embodiment will be described with reference to FIG. In this embodiment, the hydrogen recovery means 5 is provided on a pressure sensor 16 provided in the storage tank 3, a valve 7, a reservoir 41, a pressure gauge 42 provided in the reservoir 41, and a pipe from the reservoir 41 to the burner 12. The valve 43 is controlled by a control device (not shown) that controls the entire fuel cell system.

In the present embodiment, hydrogen mixed in desulfurized kerosene is recovered as follows.
During rated operation of the fuel cell system 10, the valve 7 and the valve 43 are closed, and the reservoir 41 is isolated from the storage tank 3 and the burner 12. When the hydrogen mixed in the desulfurized kerosene accumulates in the space 6 in the same manner as described above and the indicated value of the pressure sensor 16 exceeds the first set value X, the control device keeps the valve 43 closed and the valve 7 And hydrogen is introduced into the reservoir 41.

  The control device repeats this operation and accumulates hydrogen in the reservoir 41. As a result, the pressure in the reservoir 41 increases stepwise. When the indicated value of the pressure gauge 42 exceeds the second set value Y, the control device opens the valve 43 to send hydrogen to the burner 12 for incineration. Then, when the indicated value of the pressure gauge 42 becomes the third set value Z or less, the valve 43 is closed. At this time, the relationship is set value X> set value Y> set value Z> atmospheric pressure.

  When stopping the fuel cell system 10, the control device first opens the valve 43 to send the hydrogen in the reservoir 41 to the burner 12 for incineration. When the indicated value of the pressure gauge 42 becomes lower than the indicated value of the pressure sensor 16, the valve 7 is opened and the hydrogen in the space 6 of the storage tank 3 is sent to the burner 12 via the valve 43 and incinerated. Thereby, when hydrogen is incinerated with the burner 12, it can prevent that hydrogen flows backward from the reservoir 41 to the storage tank 3, and can manage hydrogen safely.

In this embodiment as well, it is preferable to incinerate hydrogen with the burner 12 until the indicated value of the pressure sensor 16 is slightly higher than the atmospheric pressure.
In the present embodiment, the reformed gas flow path 21 of the reformer 11 may be purged with hydrogen stored in the reservoir 41 as in the second embodiment.

  Next, a fourth embodiment will be described with reference to FIG. In this embodiment, a relief valve that opens and closes by the force of a spring according to the pressure is used as the valve 7 that is connected to a portion where the space 6 of the storage tank 3 is formed and is opened and closed according to the pressure of the gas occupying the space 6. ing.

  In the present embodiment, when hydrogen accumulates in the storage tank 3 during the rated operation of the fuel cell system 10 and the pressure of hydrogen occupying the space 6 becomes higher than the blowing pressure of the valve 7, the hydrogen is directed toward the burner 12. Sent and incinerated. When the pressure in the space 6 becomes a certain value or less, the valve 7 is closed by the spring force. Thereby, the hydrogen in the space 6 can be managed safely.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, in order to minimize the amount of hydrogen retained in the storage tank 3, the diameter of the portion that forms the space 6 in the storage tank 3 can be made smaller than the diameter of the portion that stores desulfurized kerosene.

It is a block diagram of a fuel cell system. It is a figure of the desulfurization apparatus and fuel cell system which concern on 1st and 2nd embodiment. It is a figure of the desulfurization apparatus and fuel cell system which concern on 3rd Embodiment. It is a figure of the desulfurization apparatus and fuel cell system which concern on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Desulfurization apparatus 2 Desulfurizer 3 Storage tank 4 Pump 5 Hydrogen recovery means 6 Space 7 Valve 11 Reformer 10 Fuel cell system 21 Reformed gas flow path 24 Kerosene supply flow path F Supply position SC Suction port

Claims (3)

A desulfurizer for desulfurizing liquid hydrocarbons;
A storage tank connected downstream of the desulfurizer and storing the liquid hydrocarbon after desulfurization;
A pump connected to the storage tank for delivering the liquid hydrocarbon from the storage tank;
A liquid hydrocarbon desulfurization apparatus comprising:
A fuel cell system for generating electricity with hydrogen obtained by reforming the liquid hydrocarbon with a reformer ,
The supply position of the liquid hydrocarbon after the desulfurization to the storage tank is disposed above the suction port connected to the pump,
The reservoir example Bei hydrogen recovery means for recovering the hydrogen mixed in the liquid hydrocarbon after the desulfurization,
A fuel cell system, wherein hydrogen recovered by the hydrogen recovery means is supplied to a burner of the reformer and burned. A desulfurizer for desulfurizing liquid hydrocarbons;
A storage tank connected downstream of the desulfurizer and storing the liquid hydrocarbon after desulfurization;
A pump connected to the storage tank for delivering the liquid hydrocarbon from the storage tank;
A liquid hydrocarbon desulfurization apparatus comprising:
A fuel cell system for generating electricity with hydrogen obtained by reforming the liquid hydrocarbon with a reformer ,
The supply position of the liquid hydrocarbon after the desulfurization to the storage tank is disposed above the suction port connected to the pump,
The reservoir example Bei hydrogen recovery means for recovering the hydrogen mixed in the liquid hydrocarbon after the desulfurization,
A fuel cell , wherein when the reformer is stopped, the kerosene supply passage leading to the reformer and the reformed gas passage of the reformer are purged with hydrogen recovered by the hydrogen recovery means. system. The hydrogen recovery means includes
A space formed above the liquid surface of the liquid hydrocarbon after the desulfurization in the storage tank;
A valve connected to a portion of the storage tank where the space is formed and opened and closed according to the pressure of the gas occupying the space;
The fuel cell system according to claim 1 , wherein the fuel cell system is configured to include:

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