JP2012155978A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a desulfurizer from being overheated even when an exhaust gas temperature increases by power generation amount, and aim at improving desulfurization efficiency and extending life of a desulfurization agent, in the case where a fuel cell system such as SOFC and PEFC is so configured that a desulfurizer for removing sulfur component contained in a fuel gas is heated by the exhaust gas exhausted from a power generation module.SOLUTION: To control a temperature of an exhaust gas before introduced into a desulfurizer 6 at a temperature suitable corresponding to characteristics of a desulfurization agent by shunting a part of an oxidant gas and cooling water to be used as a cooling medium and cooling down to a predetermined temperature range by a cooler 7.

Description

  The present invention relates to a fuel cell system including a desulfurizer for removing sulfur components contained in fuel gas.

  Conventionally, as shown in Patent Document 1 below, for example, in a solid oxide fuel cell (SOFC), a sulfur component as an odorant in a fuel gas is removed in order to prevent catalyst deterioration of a reformer. A desulfurizer is provided. Since the performance of the desulfurizing agent enclosed in the desulfurizer varies depending on the ambient temperature, the desulfurizer is heated using high-temperature exhaust gas generated during power generation for those used at high temperatures (patented) Reference 1).

  Patent Document 2 listed below discloses a temperature sensor for detecting the temperature in the vessel of the desulfurizer so that the desulfurizer of the fuel cell power generator can be operated at an appropriate temperature. And a technique for providing a temperature reducing means capable of lowering the temperature of the desulfurizer to a predetermined temperature based on the signal of the temperature sensor is disclosed. This temperature reduction means is comprised from the heat exchanger which cools the desulfurization catalyst layer in a desulfurizer directly, or cools the container outer wall of a desulfurizer.

JP 2006-309982 A Japanese Patent Laid-Open No. 10-214632

  In order to exhibit the desulfurization performance of the desulfurizer, it is necessary to set the desulfurizing agent within a predetermined temperature range that is equal to or higher than the normal temperature according to the characteristics. In the fuel cell system described in Patent Document 1 described above, Since the generated exhaust gas is used as it is for heating the desulfurizer, if the exhaust gas temperature fluctuates due to the power generation capacity (power generation amount), the temperature of the desulfurizing agent also fluctuates greatly, and the desulfurizing agent can be maintained in a suitable temperature range. It will not be possible.

  On the other hand, according to the technique described in Patent Document 2 described above, the temperature of the desulfurizer can be controlled to some extent, but the temperature between the portion close to the refrigerant pipe and the portion away from the refrigerant pipe of the heat exchanger. When there is a difference and very high temperature exhaust gas is supplied to the desulfurizer, the desulfurization catalyst layer will be overheated, resulting in partial deterioration of the desulfurization catalyst and the life of the entire desulfurizer Will be shortened.

  Accordingly, the present invention provides a fuel cell capable of efficiently desulfurizing a fuel gas while maintaining the desulfurizer uniformly within a predetermined temperature range by adjusting the temperature of the exhaust gas for heating the desulfurizer. The purpose is to provide a system.

  In order to achieve the above object, the present invention includes a power generation unit that generates power by a chemical reaction between a fuel gas that has been desulfurized from a sulfur component by a desulfurizer and then reformed to be hydrogen-rich, and an oxidant gas. In the fuel cell system configured to introduce the exhaust gas discharged from the section and heat the desulfurizer, temperature adjusting means for adjusting the temperature of the exhaust gas introduced into the desulfurizer to a predetermined temperature range It is characterized by having (claim 1).

  According to the present invention, the temperature of the exhaust gas introduced into the desulfurizer by the temperature adjusting means can be adjusted to a predetermined temperature range, and the desulfurizer is heated by the temperature-adjusted exhaust gas. When the temperature of the exhaust gas discharged from the power generation unit rises greatly due to the rise, overheating of the desulfurizer is prevented by cooling the exhaust gas, and the desulfurizer is maintained in a predetermined temperature range. Furthermore, since the temperature of exhaust gas as a heating medium for heating the desulfurizer is adjusted before being introduced into the desulfurizer, the entire desulfurizer is heated uniformly and partially overheated. There is no end.

  In the fuel cell system of the present invention, a heat exchanger for condensation for condensing moisture contained in the exhaust gas discharged from the power generation unit, and a circulation for cooling the exhaust gas to the heat exchanger for condensation A cooling water passage to be supplied, and the temperature adjusting means receives at least a part of the cooling water in the cooling water passage as a temperature adjusting refrigerant, thereby exchanging heat with the exhaust gas introduced into the desulfurizer. It is preferable that it is comprised so that it may be made (Claim 2).

  According to this, the exhaust gas can be cooled by using a part or all of the cooling water for condensate recovery as a refrigerant, and compared with the exhaust gas while simplifying the configuration and reducing the cost. Thus, the exhaust gas can be efficiently cooled using the cooling water having a high specific heat.

  The fuel cell system according to the present invention further includes an oxidant gas passage for supplying an oxidant gas to the power generation unit, and the temperature adjusting means is configured to temperature at least a part of the oxidant gas in the oxidant gas passage. It may be configured to exchange heat with the exhaust gas introduced into the desulfurizer by receiving the refrigerant as an adjustment refrigerant.

  According to this, the exhaust gas can be cooled by using a part or all of the oxidant gas flowing in the oxidant gas passage as a refrigerant, and the configuration can be simplified and the cost can be reduced. it can.

  Furthermore, the temperature detecting means for detecting the temperature of the exhaust gas after the temperature adjustment by the temperature adjusting means and before being introduced into the desulfurizer, and the refrigerant according to the detected temperature detected by the temperature detecting means The flow rate adjusting means for adjusting the supply flow rate can be provided (claim 4).

  According to this, it becomes possible to adjust the flow rate of the refrigerant by feedback control based on the exhaust gas temperature after temperature adjustment by the temperature adjusting means, such as fluctuations in exhaust gas temperature and refrigerant temperature before temperature adjustment, etc. Even if this occurs, it is possible to control the exhaust gas temperature supplied to the desulfurizer to be within a predetermined temperature range by adjusting the heat exchange capacity by adjusting the flow rate of the refrigerant.

  As described above, according to the fuel cell system of the first aspect of the present invention, the temperature of the exhaust gas introduced into the desulfurizer can be adjusted to a predetermined temperature range by the temperature adjusting means, and the temperature is adjusted. By heating the desulfurizer with the exhaust gas, when the temperature of the exhaust gas discharged from the power generation unit greatly increases due to an increase in the amount of power generation, overheating of the desulfurizer is prevented by cooling the exhaust gas, The desulfurizer can be maintained in a predetermined temperature range. Furthermore, by adjusting the temperature of the exhaust gas as a heating medium for heating the desulfurizer before being introduced into the desulfurizer, the entire desulfurizer can be heated uniformly and partially overheated. There is no. As a result, the desulfurization agent in the desulfurizer can be maintained uniformly within a predetermined temperature range, and efficient desulfurization can be performed, and deterioration of the desulfurization agent due to overheating can be prevented.

  Further, according to the fuel cell system of the second aspect of the present invention, the exhaust gas can be cooled by using a part or all of the cooling water for collecting condensed water as a refrigerant, and the structure is simplified. In addition, the exhaust gas can be efficiently cooled by using the cooling water having a higher specific heat than the exhaust gas while reducing the cost.

  Further, according to the fuel cell system of claim 3 of the present invention, exhaust gas can be cooled by using a part or all of the oxidant gas flowing in the oxidant gas passage as a refrigerant, Simplification of the configuration and cost reduction can be achieved.

  Furthermore, according to the fuel cell system of claim 4 of the present invention, it becomes possible to adjust the flow rate of the refrigerant by feedback control based on the exhaust gas temperature after the temperature adjustment by the temperature adjustment means. The exhaust gas temperature supplied to the desulfurizer is controlled within a predetermined temperature range by adjusting the heat exchange capacity by adjusting the flow rate of the refrigerant, even if the exhaust gas temperature fluctuation or refrigerant temperature fluctuation occurs. be able to.

1 is a schematic block diagram of a fuel cell system according to a first embodiment of the present invention. It is a schematic block diagram of the fuel cell system which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 shows an example in which a solid oxide fuel cell (SOFC) is used as the fuel cell system according to the first embodiment of the present invention. This fuel cell system includes a power generation module 1 as a power generation unit, a fuel gas passage 2 for supplying a fuel gas such as city gas to the power generation module 1, and a modified fuel gas mixed in the middle of the fuel gas passage 2. A reforming air passage 3 for supplying quality air, an oxidant gas passage 4 for supplying an oxidant gas as power generation air to the power generation module 1, and an exhaust through which high-temperature exhaust gas discharged from the power generation module 1 flows. A gas passage 5, a desulfurizer 6 provided in the middle of the fuel gas passage 2 to remove an odorant containing a sulfur component from raw fuel gas (for example, city gas), and an exhaust gas temperature introduced into the desulfurizer 6 As a temperature adjusting means for adjusting the temperature, a heat exchanger 8 for condensing and recovering moisture contained in the exhaust gas, and various ions by the action of an ion exchange resin from the recovered condensed water Excluding Then, a deionizer 9 for producing pure water, a deionized water tank 10 for storing the produced deionized water, and deionized water for supplying pure water used for steam reforming of fuel gas from the deionized water tank 10 to the power generation module 1 And a supply path 11.

  The power generation module 1 includes a preheater 12 that preheats the fuel gas and the oxidant gas, a reformer 13 that reforms the fuel gas and the oxidant gas into hydrogen-rich fuel gas by steam reforming, and the reformed fuel gas and oxidant gas. A fuel cell main body 14 that generates direct-current power through an electrochemical reaction is built in a housing 15. The housing 15 is a heat insulating container that shields the exhaust gas and heat released from the fuel cell main body 14 and the reformer 13 from the outside. The reformer 13 is disposed above the fuel cell main body 14 and is heated to a high temperature by combustion of off-gas discharged from the fuel cell main body 14. Further, the preheater 12 is disposed above the reformer 13 and is heated by the exhaust gas from the reformer 13.

  The preheater 12 is a heat exchanger that heats the fuel gas and the oxidant gas by exchanging heat between the high-temperature exhaust gas and each of the fuel gas and the oxidant gas. The fuel gas supplied to the power generation module 1 is supplied with pure water from the pure water supply path 11 in the preheater 12, preheated by the preheater 12, and then supplied to the reformer 13 that performs steam reforming. Is done. The oxidant gas supplied to the power generation module 1 is preheated by the preheater 12 and then supplied to the fuel cell main body 14.

  The reformer 13 is a reaction vessel in which a reforming catalyst is enclosed. The reformer 13 is heated to a high temperature by combustion of off-gas from the fuel cell main body 14 and is reformed after steam reforming the fuel gas in a high temperature atmosphere. The fuel gas after quality is supplied to the fuel cell main body 14.

  The fuel cell main body 14 is composed of a SOFC cell stack, and is configured with a plurality of cells separated by a predetermined interval. In each cell, a fuel electrode (anode) and an air electrode (cathode) are integrated with a ceramic film as an electrolyte interposed therebetween. Exhaust gas from the fuel cell main body 14 is discharged from the power generation module 1 to the exhaust gas passage 5 via the reformer 13 and the preheater 12, and the exhaust gas temperature from the power generation module 1 is 250 ° C. to It becomes about 400 ° C.

  The fuel gas passage 2, the reforming air passage 3, and the oxidant gas passage 4 can each be constituted by a pipeline, and each gas is supplied at a predetermined pressure by a blower B provided in each pipeline. . The reforming air passage 3 is joined to the fuel gas passage 2 between the desulfurizer 6 and the preheater 12. Although not shown, each of the passages 2, 3, 4 can be provided with a gas flow sensor or a check valve.

  The exhaust gas passage 5 is preferably mainly composed of piping covered with a heat insulating material, and exhaust gas discharged from the power generation module 1 is supplied in the order of the cooler 7, the desulfurizer 6 and the heat exchanger 8 for condensation, The heat exchange is performed at each of these parts, and then the air is discharged to the atmosphere.

  The desulfurizer 6 is a reaction vessel in which a desulfurizing agent is sealed, and removes sulfur components as odorants contained in fuel gas by adsorption or chemical modification. The desulfurizer 6 is provided in the middle of the fuel gas passage 2 and supplies the fuel gas after the sulfur component is removed to the power generation module 1. Further, the desulfurizer 6 has a built-in heat medium passage connected to the exhaust gas passage 5 so that the desulfurization agent can be heated to a predetermined temperature by the high-temperature exhaust gas flowing through the exhaust gas passage 5.

  In particular, in the present embodiment, a bypass passage 4 a is provided in the middle of the oxidant gas passage 4. The cooler 7 includes a refrigerant flow path to which an oxidant gas as a refrigerant is supplied from the bypass path 4a and an exhaust gas flow path to which an exhaust gas as a cooling target gas is supplied from the exhaust gas path 5. The heat exchanger includes a heat exchanger that cools the exhaust gas to a predetermined temperature range by exchanging heat between the oxidant gas branched into the bypass passage 4a and the exhaust gas exhausted from the power generation module 1. For example, when the suitable operating environment temperature of the desulfurizer 6 is about 150 to 250 ° C., the exhaust gas is heated excessively at the above-described exhaust gas temperature, and therefore the exhaust gas is controlled to a suitable temperature range by the cooler 7.

  Further, the exhaust gas passage 5 is provided with a temperature sensor 16 such as a thermistor for detecting the exhaust gas temperature between the cooler 7 and the desulfurizer 6, and the bypass passage 4a has a temperature sensor. A flow rate adjusting valve 17 is provided for adjusting the flow rate of the oxidant gas as the refrigerant diverted to the bypass passage 4a based on the detected temperature of 16. The flow rate adjusting valve 17 is an electromagnetic control valve, and the operation is controlled by a controller (not shown). As a result, when the temperature detected by the temperature sensor 16 rises so as not to exceed the predetermined temperature range described above, the controller increases the opening of the flow rate adjustment valve 17 to reduce the flow rate of the oxidant gas divided into the bypass passage 4a. On the other hand, when the temperature detected by the temperature sensor 16 decreases, the controller can perform feedback control so as to decrease the flow rate of the oxidant gas diverted to the bypass passage 4a by decreasing the opening of the flow rate adjustment valve 17. Become.

  The condensation heat exchanger 8 also functions as a heat exchanger for exhaust heat recovery in the illustrated embodiment. By performing exhaust heat recovery of the exhaust gas discharged from the power generation module 1, the condensation heat exchanger 8 is not shown in the figure. For example, the water circulated and supplied from the circulation circuit on the hot water storage unit side through the cooling water passage 18 is heat-exchanged and heated. Thus, heat recovery from the exhaust gas is achieved, and the recovered heat is stored in the hot water storage tank in the form of hot water, and the stored hot water is used for hot water supply, hot water filling for the bathtub, and the like. . The condensation heat exchanger 8 collects condensed water because the latent heat of the exhaust gas is taken away during exhaust heat recovery. The recovered condensed water is converted into pure water by the pure water device 9, and the pure water Water is stored in the tank 10.

  According to this embodiment, a part of the oxidant gas supplied via the oxidant gas passage 4 is bypassed, and heat is exchanged between the exhaust gas before being introduced into the desulfurizer 6 by the cooler 7. By doing so, it is possible to cool the exhaust gas temperature to a temperature range adapted to the characteristics of the desulfurizing agent in the desulfurizer 6, prevent overheating of the desulfurizing agent and perform efficient desulfurization, It is also possible to extend the life of the desulfurizing agent. Further, since the bypass channel 4a is provided in the existing oxidant gas passage 4 instead of providing a separate refrigerant supply system for the cooler 7, there is no need to prepare another refrigerant and another refrigerant. A pump mechanism or the like is not required, and the configuration can be simplified and the cost can be reduced. Further, since the bypass passage 4a for returning the oxidant gas after heat exchange to the oxidant gas passage 4 is provided, it is possible to avoid a shortage of the amount of the oxidant gas supplied to the power generation module 1. Further, the temperature of the exhaust gas after being cooled by the cooler 7 and before being introduced into the desulfurizer 6 is detected by the temperature sensor 16, and the flow rate of the oxidant gas divided into the bypass passage 4a based on the detected temperature is determined. Since it is configured to be adjusted by the flow rate adjusting valve 17, even when the temperature of the exhaust gas changes due to the fluctuation of the power generation amount, the flow rate of the oxidant gas that is diverted to the bypass passage 4a is adjusted and controlled. Thus, the temperature of the exhaust gas introduced into the desulfurizer 6 can be more reliably maintained within a predetermined temperature range.

<Second Embodiment>
FIG. 2 shows a fuel cell system according to a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. explain.

  In the present embodiment, the bypass path for the oxidant gas passage is not provided, and a similar bypass passage 18a is provided in the cooling water passage 18 through which the cooling water supplied to the condensation heat exchanger 8 flows. The cooler 7 is provided in the middle of the path 18a. The bypass path 18a is configured to divert cooling water after exhaust heat recovery and supply it to the cooler 7 as a refrigerant, and return it from the cooler 7 to the cooling water passage 18 downstream of the heat exchanger 8 for condensation. Yes. The flow rate adjusting valve 17 for adjusting the flow rate of the refrigerant flowing through the bypass passage 18a is provided in the cooling water passage 18 between the branch point and the return point of the bypass passage 18a.

  According to this embodiment, since the cooling water after exhaust heat recovery is divided, it is introduced into the desulfurizer 6 using the cooling water without reducing the exhaust heat recovery efficiency in the heat exchanger 8 for condensation. The exhaust gas before being discharged can be cooled, and the heat recovery efficiency can be further improved. Further, even after exhaust heat recovery, the temperature of the cooling water is about 60 ° C. to 80 ° C., which is sufficient as a refrigerant for cooling the exhaust gas exceeding 200 ° C. The cooling water is the first embodiment. Because the specific heat is higher than the oxidant gas, which is a refrigerant, it is possible to reliably cool the exhaust gas with higher efficiency than the normal temperature oxidant gas, and the response speed of the exhaust gas temperature when controlling the refrigerant flow rate is also good It will be something.

  The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate. For example, in the above embodiment, the power generation module has a built-in preheater, but the preheater may be provided outside the power generation module. Further, the present invention is not limited to the SOFC, and can be used for other fuel cell systems such as a polymer electrolyte fuel cell (PEFC).

  Moreover, in the said embodiment, although the cooling water with respect to the heat exchanger 8 for condensation is used as a refrigerant | coolant in the cooler 7, not only this but the cooling water for cooling with respect to the fuel cell main body 14 is said cooler 7 said. It may be used as a refrigerant for Further, in the above embodiment, a bypass path is provided in the oxidant gas passage or the cooling water passage, and a part of the oxidant gas or the cooling water is divided and used as a refrigerant for adjusting the temperature of the exhaust gas. The temperature of the exhaust gas may be adjusted by using the whole amount as a refrigerant instead of providing and diverting it.

DESCRIPTION OF SYMBOLS 1 Power generation module 2 Fuel gas passage 4 Oxidant gas passage 5 Exhaust gas passage 6 Desulfurizer 7 Cooler 8 Condensing heat exchanger 16 Temperature detection means 17 Flow rate adjustment means 18 Cooling water passage

Claims (4)

A power generation unit that generates power by a chemical reaction between a fuel gas that has been sulfur-desulfurized by a desulfurizer and then reformed to be rich in hydrogen and an oxidant gas is introduced, and exhaust gas discharged from the power generation unit is introduced to In a fuel cell system configured to heat a desulfurizer,
A fuel cell system comprising temperature adjusting means for adjusting the temperature of exhaust gas introduced into the desulfurizer to a predetermined temperature range. The fuel cell system according to claim 1, wherein
A condensation heat exchanger for condensing moisture contained in the exhaust gas discharged from the power generation unit; and a cooling water passage that is circulated and supplied to cool the exhaust gas to the condensation heat exchanger. The temperature adjusting means is configured to exchange heat with the exhaust gas introduced into the desulfurizer by receiving at least a part of the cooling water in the cooling water passage as a temperature adjusting refrigerant. Battery system. The fuel cell system according to claim 1, wherein
The desulfurizer is provided with an oxidant gas passage for supplying an oxidant gas to the power generation unit, and the temperature adjusting means receives at least a part of the oxidant gas in the oxidant gas passage as a temperature adjusting refrigerant. A fuel cell system configured to exchange heat with the exhaust gas introduced into the. The fuel cell system according to claim 2 or 3,
Temperature detection means for detecting the temperature of the exhaust gas after temperature adjustment by the temperature adjustment means and before being introduced into the desulfurizer, and supply of the refrigerant according to the detected temperature detected by the temperature detection means A fuel cell system comprising a flow rate adjusting means for adjusting a flow rate.

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