JP5802479B2 - Fuel cell system and control method thereof - Google Patents

Description

  The present invention relates to a fuel cell system including a conduit for supplying reformed water obtained from, for example, exhaust gas discharged from a fuel cell to a reformer of the fuel cell, and a control method thereof.

  Conventionally, in a fuel cell system using, for example, a solid oxide fuel cell (SOFC: hereinafter simply referred to as a fuel cell), an oxidant gas (normal air) and a fuel gas (city gas, etc.) are supplied to the fuel cell. Power generation.

  In this type of fuel cell system, for example, when a fuel cell is operated using city gas, pure water for fuel reforming (reformed water) is used to reform the city gas and extract hydrogen. Is required.

  However, since the fuel cell system is installed outdoors, when the operation is stopped when the outside air temperature is low such as in winter, the pure water for fuel reforming is frozen in the fuel cell system, There is a risk of damage to the pure water generating device and the pure water supply device.

  For this reason, as a general technique for preventing freezing of the water in the fuel cell system, a method of preventing freezing by attaching a heat source such as a heater to a part that is not desired to be frozen and directly warming that part, There is a method of not freezing by removing.

  Or there exists a technique of preventing freezing by circulating the water warmed by the thermal storage part or the heating part like the following patent document 1. FIG. Further, as described in Patent Document 2 below, there is a technique in which, by blowing air heated by a heat source provided in the fuel cell system, a portion that may be frozen indirectly is heated to prevent freezing.

JP 2008-91096 A JP 2009-266613 A

  However, among the above-described conventional techniques, the method of directly warming a part that is not to be frozen is effective, but more heaters are required when there are many parts that may be frozen.

Moreover, in the method of draining water, when there is a part where water cannot be completely removed, such as a pure water generator, the method itself cannot be selected.
Furthermore, in the method of circulating water, a bypass path for circulation is required separately. In order to circulate without freezing, it is necessary to warm not only the portion that is not desired to be frozen but also the entire path including the bypass path. Because it is, it needs more heat.

In addition, the method of indirectly heating with heated air has a problem that energy utilization efficiency is poor because part of the heated air is exhausted as it is.
The present invention has been made in view of these problems, and an object of the present invention is to provide a fuel cell system and a control method thereof that can efficiently warm a portion to be warmed and prevent freezing of water with a simple configuration.

(1) The present invention, which has been made to solve such a problem, includes, as a first aspect, a water tank that stores water from the upstream side of a flow path that supplies water to the reformer , and a first pipeline. A pump for flowing the water along the flow path, a second pipe, a filter for purifying the water, a third pipe, and the reformer in order , and the temperature of the water is directly or indirectly a temperature sensor for detecting, in the reformer fuel cell system including a fuel cell for generating electric power using an oxidizing agent gas and the fuel gas downstream of the front Stories second tube Michi及 beauty the third A heater for heating the water is provided on at least one of the pipes, and the pump is configured by a pump capable of switching the direction of flowing the water to the first pipe line side or the second pipe line side. The temperature of the water detected by the temperature sensor A control unit that controls the heater and the pump so that the heater is energized and reciprocated along the flow path when the heater is below a predetermined determination value set to stop. Features.

In this embodiment, at least one of the second tubular Michi及 beauty third conduit provided with a heater for heating water, as a pump, the direction of flow of water in the first tube roadside or second tube roadside When a switchable pump is used and the temperature of the water is equal to or lower than a predetermined determination value set to prevent freezing of the water, the heater is energized and water is reciprocated by the pump.

  In other words, when there is a risk of freezing due to a drop in the temperature of the water, the heater is energized to heat the water and the water heated by the pump (warm water) is reciprocated, so local heating by the heater is prevented. It has a remarkable effect that it can prevent water freezing effectively.

  In addition, since the water is reciprocated by the pump, the heated water can be sent to a section where it is not desired to freeze without providing an unnecessary bypass path, so that the system can be downsized.

  Furthermore, by controlling the heater, water can be heated only when there is a risk of freezing. From this point, the heater can be efficiently energized and wasteful power consumption can be suppressed.

That is, in this aspect, with a simple configuration, there is a remarkable effect that the part to be warmed can be efficiently warmed and water can be prevented from freezing.
Here, the “predetermined determination value set in order to prevent freezing of water” is not limited to 0 ° C., and is not frozen in consideration of, for example, sensor measurement errors or local temperature variations. Considering the safety side, the “temperature higher than 0 ° C. (temperature at which water can be frozen)” set by experiments or the like can be adopted (the same applies hereinafter).

  (2) In the present invention, as a second aspect, the heater is provided in both the water tank and the second pipeline, or in both the water tank and the third pipeline. It is characterized by that.

  In this aspect, a preferred heater arrangement is illustrated. In other words, the heater is disposed at the above-described location to heat the water, and the water is reciprocally flowed by the pump, thereby reliably heating the water (range of reciprocating flow) and preventing its freezing. .

  (3) As a third aspect of the present invention, in the fuel cell system control method for controlling a fuel cell system according to claim 1 or 2, the step of detecting the temperature of the water via the temperature sensor. And when the temperature of the water detected by the temperature sensor is equal to or lower than a predetermined determination value set to prevent freezing of the water, the step of energizing the heater and heating the water, And a step of reciprocating the water along the flow path by the pump in a state where the water is not frozen.

  In this aspect, when the temperature of the water is equal to or lower than a predetermined determination value set to prevent freezing of the water, the heater is energized to heat the water, and the water is not frozen by the pump. Since the water is reciprocated, the effect of being able to efficiently prevent the water from being frozen can be obtained with a simple configuration as in the first embodiment.

Note that the operation timing of the pump may be a period before the heater is energized, in addition to the period during which the heater is energized.
(4) As a fourth aspect of the present invention, when the operation of the fuel cell is stopped, the pump is driven to draw the water from the third pipeline side to the water tank. It is characterized by.

  In this embodiment, when the operation of the fuel cell is stopped, the pump is driven to perform the operation of drawing water from the third pipeline side to the water tank. There is no water. Therefore, even when the temperature decreases, the water does not freeze.

The stop of the operation of the fuel cell is the stop of power generation in the fuel cell.
(5) As a fifth aspect of the present invention, the water is reciprocated by the pump before energizing the heater.

In this aspect, since water is reciprocated by the pump before energizing the heater, there is an advantage that the water hardly freezes even if the heater is not energized when the water temperature decreases.
Further, by performing freeze prevention operation with this pump and then energizing the heater (which consumes a lot of power), the power consumption can be suppressed.

  (6) As a sixth aspect of the present invention, the heater is energized when the temperature of the water detected by the temperature sensor is equal to or lower than a predetermined heater drive determination value (T2a).

In this aspect, since the heater is energized when the temperature of the water is equal to or lower than the heater drive determination value (T2a), water freezing can be prevented.
As the heater drive determination value (T2a), in addition to the water freezing temperature (0 ° C.), the “temperature at which water can be frozen” that exceeds 0 ° C. by a predetermined value can be adopted.

  (7) The present invention provides, as a seventh aspect, when the temperature of the water detected by the temperature sensor is equal to or higher than a predetermined heater stop determination value (T2b) higher than the predetermined heater drive determination value (T2a). It is characterized in that energization of the heater is stopped.

  In this aspect, when the temperature of the water is equal to or higher than the heater stop determination value (T2b), the energization of the heater is stopped assuming that the temperature of the water is sufficiently high so that there is no possibility of freezing. Can be reduced.

  (8) As an eighth aspect of the present invention, the temperature sensor includes environmental temperature detection means (for example, a sensor that detects outside air temperature) that detects an environmental temperature of the environment around the flow path, and the environmental temperature detection means When the environmental temperature detected in step (b) is equal to or lower than a predetermined pump drive determination value (T1a), the pump performs a reciprocating flow operation.

  In this aspect, when the environmental temperature is equal to or lower than the pump drive determination value (T1a), it is assumed that the water may freeze, and the reciprocating flow operation is performed by the pump. Can do.

As the pump drive determination value (T1a), in addition to the water freezing temperature (0 ° C.), the “temperature at which water can be frozen” that exceeds 0 ° C. by a predetermined value can be adopted.
(9) In the ninth aspect of the present invention, as the ninth aspect, the environmental temperature detected by the environmental temperature detection means is equal to or higher than a predetermined pump stop determination value (T1b) higher than the predetermined pump drive determination value (T1a), and When energization of the heater is stopped, the reciprocating flow operation by the pump is stopped.

  In this aspect, when the environmental temperature is equal to or higher than the pump stop determination value (T1b) and the heater is turned off, the water temperature is sufficiently high so that there is no possibility of freezing. Since it stops, the power consumption of the pump can be reduced.

  The present invention described above includes a heat exchanger that obtains water by heat exchange from exhaust gas discharged from a fuel cell, and a reformer that reforms fuel gas using water obtained by heat exchange. A fuel cell system that supplies water obtained by heat exchange to a reformer through a water tank, a first pipe, a pump, a second pipe, a water filter, and a third pipe Applicable to.

  Here, the reformer is a device for reforming a composition suitable for power generation (for example, reforming city gas or the like into a gas having a higher hydrogen component) when supplying fuel gas to the fuel cell. That is.

1 is an explanatory diagram schematically showing a fuel cell system of Example 1. FIG. 1 is a block diagram showing an electrical configuration of a fuel cell system of Example 1. FIG. 2 is a flowchart illustrating reforming water pump control in the fuel cell system according to the first embodiment. 3 is a flowchart illustrating antifreeze heater control in the fuel cell system according to the first embodiment. 3 is a flowchart illustrating exhaust fan control in the fuel cell system according to the first embodiment. It is explanatory drawing which shows the fuel cell system of Example 2 typically. FIG. 5 is an explanatory diagram schematically showing a fuel cell system of Example 3.

  Hereinafter, embodiments of a fuel cell system to which the present invention is applied and a control method thereof will be described with reference to the drawings.

a) First, the fuel cell system of this embodiment will be described.
As schematically shown in FIG. 1, the fuel cell system 1 of this embodiment includes a fuel cell 3 that generates power by receiving supply of a fuel gas (for example, city gas) and an oxidant gas (for example, air), and a fuel. A reformer 5 for reforming the fuel gas supplied to the battery 3 into a hydrogen-rich gas is provided, and these are housed in a heat insulating container 7.

  Further, outside the heat insulating container 7, an air pump 9 that sends air to the fuel cell 3, a fuel pump 11 that sends fuel gas to the fuel cell 3 (via the reformer 5), and exhaust gas from the fuel cell 3 A heat exchanger 13 for recovering moisture (reformed water) from the water, a condensed water tank (reformed water tank) 15 for storing the reformed water recovered by the heat exchanger 13, and reforming in the reformed water tank 15 A first antifreeze heater 17 that heats water, a pure water supply pump (reformed water pump) 19 that sends reformed water to the reformer 5 side, and a water filter 21 that removes impurities contained in the reformed water. And a second antifreeze heater 23 for heating the reformed water sent to the reformer 5, an exhaust fan 25 for exhausting the gas in the fuel cell system 1 to the outside, and the like.

Hereinafter, each configuration will be described in detail.
Although not shown, the fuel cell 3 is a stack in which a plurality of plate-like fuel cells serving as power generation units are stacked. This fuel cell is a so-called fuel electrode support membrane type fuel cell, which is a well-known fuel electrode (disposed so as to be in contact with the fuel flow path), a solid electrolyte body, and (as it is in contact with the air flow path). And an air electrode).

  The reformer 5 is a plate-like device that reforms the fuel gas supplied to the fuel cell 3 into a hydrogen-rich fuel gas (reformed gas). Although not shown, a vaporizer for vaporizing the reformed water is provided on the upstream side of the reformer 5.

Here, as the fuel gas used for reforming, in addition to city gas, there are LPG, kerosene, methanol, biomethanol, and the like.
The heat exchanger 13 is a device that cools the exhaust gas (after power generation) discharged from the fuel cell 3 and condenses and recovers moisture from the exhaust gas. Is introduced and discharged.

  The reforming water tank 15 is a water tank that can store the reforming water generated by the heat exchanger 13, and the bottom of the reforming water tank 15 prevents freezing of the reforming water stored in the reforming water tank 15. In order to do this, the first antifreeze heater 17 is arranged.

The first antifreeze heater 17 and the second antifreeze heater 23 are electric heaters that generate heat when energized.
The reforming water pump 19 can send the reforming water to the reformer 5 side (right direction in the figure), and the reforming water can be sent to the reforming water tank 15 side in the reverse direction (in the figure) according to a control signal. It is a pump that can be sent in the left direction, that is, a pump that can reciprocate.

  The water filter 21 is a filter using an ion exchange resin or the like in order to remove impurities and metal ions contained in the modified water. By using this water filter 21, it is possible to prevent impurities from accumulating in the reformer 5 and the components of the fuel cell 3 from deteriorating due to reaction with metal ions.

  In particular, in this embodiment, a reforming water pipe (reforming water line) 27 is provided so that reforming water can be supplied from the reforming water tank 15 to the reformer 5. The line 27 includes a first pipeline 27a, a second pipeline 27b, and a third pipeline 27c from the upstream side.

  A first temperature sensor (water temperature sensor) 29 for detecting the temperature of the reforming water is attached to the first pipe line 27a, and between the first pipe line 27a and the second pipe line 27b. The reforming water pump 19 is disposed, the water filter 21 is disposed between the second pipe line 27b and the third pipe line 27c, and the second pipe line 27c is provided with the second pipe line 27c. A freeze prevention heater 23 is arranged.

A second temperature sensor (air temperature sensor) 33 that detects the temperature is disposed in the vicinity of the vent 31 of the fuel cell system 1.
b) Here, an electrical configuration for controlling the fuel cell system 1 will be described.

As shown in FIG. 2, the operation of the fuel cell system 1 of the present embodiment is controlled by a control device 35 such as a well-known microcomputer.
The control device 35 includes a signal indicating the temperature of the reformed water detected by the first temperature sensor 29 (pure water temperature for fuel reforming) and the temperature of the outside air detected by the second temperature sensor 33 (outside the system). A signal indicating the temperature is input.

  Further, the control device 35 outputs control signals for controlling the operations of the fuel pump 11, the air pump 9, the reforming water pump 19, the first antifreeze heater 17, the second antifreeze heater 23, and the exhaust fan 25. .

c) Next, the operation of the fuel cell system 1 will be described.
As shown in FIG. 1, in the fuel cell 3, the reaction between the hydrogen gas in the reformed gas reformed by the reformer 5 and the oxidant gas in the air sent by the air pump 9, Generate electricity.

The hydrogen gas and the oxidant gas used for the power generation reaction in the fuel cell 3 are converted into water vapor by the reaction and discharged to the outside of the fuel cell 3 through the exhaust gas line 37.
The water vapor that has passed through the exhaust gas line 37 is cooled by passing through the heat exchanger 13, becomes condensed water (used as reformed water), and is stored in the reformed water tank 15.

  By the way, as described above, the fuel cell 3 requires hydrogen gas for its power generation reaction. For example, in the fuel cell system 1 for general households, fuel such as city gas supplied by the fuel pump 11 is used. The hydrogen gas necessary for power generation is taken out by steam reforming using reformed water in the reformer 5.

Further, when the reformer 5 performs steam reforming of city gas as a fuel, so-called pure water from which metal ions as impurities in the water are removed must be used as reforming water.
That is, in the water containing the metal ions, impurities are accumulated in the reformer 5 and deterioration occurs due to the reaction of the constituent members of the fuel cell 3 with the metal ions. 27, a water filter 21 for generating pure water using an ion exchange resin or the like is mounted.

However, the water filter 21 using an ion exchange resin cannot completely drain water in the water filter 21 due to its nature.
Therefore, when the fuel cell system 1 is stopped, when the ambient temperature decreases and the temperature inside the system reaches below freezing point, water remaining in the water filter 21 is frozen, and this is repeated, There is a risk of causing the performance of the filter 21 to deteriorate.

  Further, if the reformed water is frozen by the reformed water pump 19 or the reformed water line 27, the reformed water cannot be normally supplied to the fuel cell system 1 at the next start-up, and the steam reforming of the fuel gas is performed. May not be possible.

  Therefore, in this embodiment, as will be described in detail later, “reforming water drawing operation by the reforming water pump 19 after the operation of the fuel cell 3 is stopped”, “reciprocating operation of the reforming water pump 19”, “first By performing control such as “heating by the second antifreeze heaters 17 and 23”, freezing of the reformed water is prevented.

d) Next, the control performed by the control device 35 of the fuel cell system 1 will be described.
<Reformed water pump control>
This reforming water pump control is performed every control cycle, for example, every 10 ms.

  As shown in FIG. 3, in this reformed water pump control, first, in step (S) 100, it is determined whether or not an instruction to stop the operation of the fuel cell 3 (that is, stop generation) is issued. Specifically, for example, when it is determined that the temperature of the fuel cell body (for example, the stack portion) has been sufficiently cooled, for example, when it is determined that “temperature of the fuel cell body <100 ° C.” or the like, 3 is determined to be stopped. Note that this determination temperature can be changed.

If an affirmative determination is made here, the process proceeds to step 110. If a negative determination is made, the present process is temporarily terminated.
In step 110, since the operation of the fuel cell 3 is stopped, the reforming water pump 19 is driven in reverse. That is, contrary to the normal operation of supplying the reforming water from the water tank 15 side to the reformer 5 side (the operation of sending the reforming water in the forward direction), the reforming water is drawn into the water tank 15 side. Operation (operation to send reforming water in the reverse direction) is performed. As a result, the reforming water present in the third conduit 27 c from the second antifreeze heater 23 to the reformer 5 is transferred to the open end 23 a on the reformer 5 side of the second antifreeze heater 23. Pull in. Note that the operation of the reforming water pump 19 is stopped after the drawing-in is completed.

As a result, water does not exist in the third conduit 27c from the second antifreeze heater 23 to the reformer 5, so that the reformed water does not freeze at that position.
In addition, since it is known in advance how much reforming water can be drawn by the operation time of reverse rotation driving of the reforming water pump 19, the reforming water is supplied to the reformer of the second antifreeze heater 23. The reforming water pump 19 may be reversely driven for a predetermined time so as to be drawn to the end portion 23a on the 5 side.

  In the following step 120, based on the signal from the second temperature sensor 33, whether the outside air temperature is equal to or lower than a predetermined pump drive determination value (that is, a determination value for determining whether or not the reforming water pump 19 is reciprocated). Determine whether or not. That is, it is determined whether or not there is a possibility that the outside air temperature is lowered and the reforming water is frozen. If an affirmative determination is made here, the process proceeds to step 130, whereas if a negative determination is made, the present process is temporarily terminated.

  In step 130, since the outside air temperature has decreased, the reforming water pump 19 is driven as usual, and control is performed so as to send the reforming water in the forward direction for a predetermined time. As a result, the reforming water is sent to the reformer 5 side by a certain amount (and therefore a certain distance).

  In the subsequent step 140, the reforming water pump 19 is driven in reverse to control to draw the reforming water in the reverse direction for a predetermined time. As a result, the reformed water is drawn into the water tank 15 by a certain amount (and therefore by a certain distance).

  In the subsequent step 150, based on the signal from the second temperature sensor 33, the outside air temperature is a predetermined pump stop determination value (that is, a determination value for determining whether or not to stop the reciprocating drive of the reforming water pump 19) T1b. It is determined whether (T1a <T1b) or less. That is, it is determined whether or not the outside air temperature has increased and the possibility of freezing of the reformed water has decreased. If an affirmative determination is made here, the process proceeds to step 160, whereas if a negative determination is made, the process returns to step 130.

  That is, when the outside air temperature is a low temperature at which the reforming water is likely to be frozen by the processing of steps 130 to 150, the reciprocating operation of the reforming water pump 19 is repeated, and the forward and reverse directions of the reforming water are performed. Repeat the water flow in the direction.

In this way, by allowing the reformed water to flow back and forth, freezing of the reformed water can be effectively prevented even when the outside air temperature is low.
In step 160, it is determined whether or not energization of the first and second antifreeze heaters 17 and 23 is stopped by antifreeze heater control described later. If an affirmative determination is made here, the process proceeds to step 170, whereas if a negative determination is made, the process returns to step 130 and the reciprocating operation of the reforming water pump 19 is repeated.

That is, the reciprocating operation of the reforming water pump 19 is repeated in order to prevent freezing at a low temperature such that the first and second antifreezing heaters 17 and 23 are energized (turned on).
When the first and second antifreeze heaters 17 and 23 are on, the warm water heated by the first and second antifreeze heaters 17 and 23 is repeated by repeating the reciprocating operation of the reforming water pump 19. Since the reformed water flows through the water tank 15, the reformed water pump 19, and the water filter 21, freezing of the reformed water is effectively prevented.

  In step 170, since the first and second antifreeze heaters 17 and 23 are not energized (off), it is assumed that the temperature of the reforming water is sufficiently high so that there is no possibility of freezing. The reciprocating operation of the pump 19 is stopped, the freeze prevention operation is stopped, and this processing is once ended.

<Antifreeze heater control>
This anti-freezing heater control is performed every control cycle, for example, every 10 ms.
As shown in FIG. 4, in the present freeze prevention heater control, first, in step 200, it is determined whether or not an instruction to stop the operation of the fuel cell 3 (that is, stop power generation) has been issued. If an affirmative determination is made here, the process proceeds to step 210. If a negative determination is made, the present process is temporarily terminated.

  In step 210, since the operation of the fuel cell 3 is stopped, the reforming water temperature is set to a predetermined heater drive determination value (that is, the first and second antifreeze heaters 17, based on the signal from the first temperature sensor 29). 23 is a determination value for determining whether or not to energize). That is, it is determined whether or not there is a possibility that the reforming water temperature is lowered and the reforming water is frozen. If an affirmative determination is made here, the process proceeds to step 220. If a negative determination is made on the other hand, the present process is temporarily terminated.

In step 220, since the reforming water temperature has decreased, energization of the first and second antifreezing heaters 17 and 23 is started to warm the reforming water.
In the following step 230, based on the signal from the first temperature sensor 29, the reforming water temperature is a predetermined heater stop determination value (that is, whether or not to stop energization of the first and second antifreeze heaters 17 and 23). It is determined whether or not it is equal to or less than a determination value T2b (where T2a <T2b). That is, it is determined whether the reforming water temperature has risen and the possibility of freezing of the reforming water has disappeared. If an affirmative determination is made here, the process proceeds to step 240. If a negative determination is made, the process returns to step 220. In addition, there exists a relationship of T2a <T1a <T2b <T1b between each determination value.

That is, when the reforming water temperature is a low temperature at which the possibility of freezing is low due to the processing in steps 220 to 230, energization of the first and second antifreezing heaters 17 and 23 is continued.
In step 240, since the reforming water temperature has risen sufficiently, energization of the first and second antifreeze heaters 17 and 23 is stopped, and the present process is temporarily terminated.

  Therefore, in this antifreezing heater control, when the reforming water temperature is low, the reforming water is heated by the first and second antifreezing heaters 17 and 23, so that the reforming water is effectively prevented from freezing. The

  The stoppage of energization in step 240 is stored by, for example, a flag, and the reciprocating operation of the reforming water pump 19 in step 160 of FIG. 3 is determined based on the state of the flag. That is, when energization to the first and second antifreeze heaters 17 and 23 is stopped, the reciprocating operation of the reforming water pump 19 is stopped. The reciprocating operation of the reforming water pump 19 is always performed during energization.

<Exhaust fan control>
This exhaust fan control is performed every control cycle, for example, every 10 ms.
As shown in FIG. 5, in the exhaust fan control, first, in step 300, it is determined whether or not an instruction to stop the operation of the fuel cell 3 (that is, stop power generation) is issued. If a positive determination is made here, the process proceeds to step 310, whereas if a negative determination is made, the present process is temporarily terminated.

In step 310, since the operation of the fuel cell 3 is stopped, the operation of the exhaust fan 25 is also stopped. Note that the exhaust fan 25 is operated as the fuel cell 3 starts operating.
In this exhaust fan control, since the operation of the exhaust fan 25 is stopped when the operation is stopped, the inflow of the outside air into the fuel cell system 1 is suppressed, so that the temperature change in the fuel cell system 1 is moderate as compared with the outside air temperature. Become.

  Thereby, the start of the freeze prevention control can be delayed, and it becomes possible to reduce the power consumption when the fuel cell system 1 is stopped at the low temperature (by performing the freeze prevention control).

e) Next, the effect by the control of the fuel cell system of the present embodiment will be described.
In the present embodiment, the water tank 15 is provided with the first antifreeze heater 17, and the third conduit 27 c is provided with the second antifreeze heater 23.

  In this embodiment, when the operation of the fuel cell 3 is stopped, the reforming water pump 19 is driven in the reverse direction so as to draw the reforming water into the water tank 15 side. Thereby, since the reforming water does not exist in the third conduit 27c from the second antifreeze heater 23 to the reformer 5, the reforming water at that position is prevented from freezing.

  Further, when the operation of the fuel cell 3 is stopped, when the outside air temperature is equal to or lower than the pump drive determination value (T1a), the reforming water pump 19 performs a reciprocal flow operation, so that the reforming water is prevented from freezing. Can do.

  Further, in this embodiment, when the temperature of the reforming water is equal to or lower than the heater drive determination value (T2a), the first and second antifreeze heaters 17 and 23 are energized to warm the reforming water. Water freezing can be prevented.

  That is, in this embodiment, when the temperature of the reforming water is equal to or lower than the heater drive determination value (T2a), the reforming water is heated by the first and second antifreeze heaters 17 and 23 and the reforming water pump 19 is used. Since the reciprocating flow of the reformed water heated by is simultaneously performed, local heating by both heaters 17 and 23 is suppressed, and the necessary heating range (water tank 15, water filter 21, etc.) is effectively heated. Thus, freezing of the reforming water can be prevented.

  Further, in this embodiment, since the temperature determination values for determining the operation of the reforming water pump 19 and the first and second antifreezing heaters 17 and 23 are different, the reforming water pump 19 has a lower temperature when the outside air temperature decreases. A reciprocal operation is started to prevent freezing, and when the temperature of the reforming water drops to near freezing point, the heaters 17 and 23 are energized. it can.

  Further, the reformed water is reciprocated by the reformed water pump 19 so that the heated reformed water can be sent to a section where it is not desired to be frozen without providing an unnecessary bypass path. Is possible.

  In addition, by controlling the first and second antifreeze heaters 17 and 23, the reforming water can be heated only when there is a risk of freezing, so that both heaters 17 and 23 can be energized efficiently. Thus, wasteful power consumption can be suppressed. In addition, since it is only necessary to heat only the range in which the reforming water is reciprocated, both heaters 17 and 23 having a small amount of heat may be used. Also in this respect, power consumption can be reduced.

  That is, in the present embodiment, with a simple configuration, there is a remarkable effect that it is possible to efficiently warm a portion to be warmed and prevent the reforming water from freezing.

Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
As shown in FIG. 6, in the fuel cell system 41 of this embodiment, the fuel cell 43 and the reformer 45 are housed in a heat insulating container 47 as in the first embodiment.

  Similarly, outside of the heat insulating container 47, an air pump 49, a fuel pump 51, a heat exchanger 53, a reforming water tank 55, a first antifreezing heater 57, a reforming water pump 59, a water filter 61, a first filter, 2 A freezing prevention heater 63 and an exhaust fan 65 are provided, and a first temperature sensor 67 and a second temperature sensor 69 are also provided.

Particularly in the present embodiment, the second antifreeze heater 63 is disposed in the second pipeline 71 b between the reforming water pump 59 and the water filter 61 in the reforming water line 71.
Also in the present embodiment, the same control as in the first embodiment is performed, so that the same effect can be obtained.

When the operation is stopped and the control for drawing in the reforming water is performed, the reforming water is drawn into the opening end 61 a on the reformer 45 side of the water filter 61.
Further, when the reforming water is reciprocated, control is performed so that the reforming water heated by the second antifreezing heater 63 reaches the water filter 61.

Next, the third embodiment will be described, but the description of the same contents as the second embodiment will be omitted.
As shown in FIG. 7, in the fuel cell system 81 of the present embodiment, the fuel cell 83 and the reformer 85 are housed in a heat insulating container 87 as in the second embodiment.

  Similarly, outside of the heat insulating container 87, an air pump 89, a fuel pump 91, a heat exchanger 93, a reforming water tank 95, a reforming water pump 97, a second antifreeze heater 99, a water filter 101, an exhaust gas. In addition to the fan 103, the first temperature sensor 105 and the second temperature sensor 107 are also provided.

In particular, in this embodiment, the first antifreeze heater is not disposed in the water tank 95, and the reforming water is heated by the single second antifreeze heater 99.
Also in the present embodiment, since the same control as in the second embodiment is performed, there are advantages that the same effect can be obtained and the configuration can be simplified.

When the reforming water is reciprocated, control is performed so that the reforming water heated by the second antifreeze heater 99 reaches the water tank 95 or the water filter 101.
Alternatively, the second antifreezing filter may be disposed in the first pipe line 109a (of the reforming water line 109) between the water tank 95 and the reforming water pump 97.

  As a result, the reformed water in the water tank 95 can also be heated at the same time, so that the effect of preventing freezing can be sufficiently obtained without the first antifreeze heater.

Next, the fourth embodiment will be described, but the description of the same contents as the first embodiment will be omitted.
Although not shown, the fuel cell system of the present embodiment, like the first embodiment, turns on / off the (first and second) antifreeze heaters based on the reforming water temperature detected by the first temperature sensor. The anti-freeze heater is controlled to be turned on / off by using a mechanical thermostat using bimetal instead of controlling the heat.

  Specifically, for example, the thermostat is configured to turn on and off the electric circuit from the anti-freezing heater to the power source according to the reforming water temperature (in the first pipe), and the reforming water temperature decreases. In this case, the anti-freezing heater is turned on, and the anti-freezing heater is turned off when the reforming water temperature rises.

This has the advantage that the configuration can be simplified.
However, in the case of the above-described method, since the energization state to the antifreezing heater cannot be determined, there is a problem in the control for reciprocating the reforming water pump.

  Therefore, in the case of the above-described method, a sensor for monitoring energization (for example, a clamp-type current sensor for measuring a current in a path) is attached to an electric circuit between the thermostat and the antifreeze heater, and the antifreeze heater is actually installed. A signal indicating whether or not power is supplied to the control device is taken into the control device.

  Alternatively, by making the pump stop determination value T1b for determining the stop of the reciprocating operation of the reforming water pump sufficiently higher (for example, about 15 ° C.) than the heater stop determination value T2a for determining the energization stop of the freeze prevention heater, Local heating as described above can be prevented. In addition, it can be made higher than the variation range (for example, +/- 10 degreeC) of a general thermostat.

As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, A various aspect can be taken.
For example, the anti-freezing heater may be disposed in at least one place among the water tank, the first pipeline, the second pipeline, and the third pipeline.

DESCRIPTION OF SYMBOLS 1, 41, 81 ... Fuel cell system 3, 43, 83 ... Fuel cell 5, 45, 85 ... Reformer 13, 53, 93 ... Heat exchanger 15, 55, 95 ... Water tank 17, 57 ... First freezing Prevention heater 19, 59, 97 ... reforming water pump (pure water supply pump)
21, 61, 101 ... water filters 23, 63, 99 ... second antifreeze heaters 25, 65, 103 ... exhaust fans 27, 71, 109 ... reformed water lines 27a, 109a ... first conduits 27b, 71b ... 2nd pipe line 27c ... 3rd pipe line 29, 67, 105 ... 1st temperature sensor (water temperature sensor)
33, 69, 107 ... second temperature sensor (air temperature sensor)

Claims (9)

From the upstream side of the flow path for supplying water to the reformer ,
A water tank for storing water, a first pipe, a pump for flowing the water along the flow path, a second pipe, a filter for purifying the water, a third pipe, and the reformer. In order,
A temperature sensor for directly or indirectly detecting the temperature of the water ;
In a fuel cell system including a fuel cell that generates power using an oxidant gas and a fuel gas on the downstream side of the reformer ,
At least one of the previous SL second tube Michi及 beauty said third conduit provided with a heater for heating the water,
The pump is composed of a pump capable of switching the direction of flowing the water to the first pipeline side or the second pipeline side,
When the temperature of the water detected by the temperature sensor is equal to or lower than a predetermined determination value set to prevent freezing of the water, the heater is energized and the water reciprocates along the flow path. A fuel cell system comprising a control unit that controls the heater and the pump.   2. The fuel according to claim 1, wherein the heater is provided in both the water tank and the second pipeline, or in both the water tank and the third pipeline. 3. Battery system. In the control method of the fuel cell system for controlling the fuel cell system according to claim 1 or 2,
Detecting the temperature of the water via the temperature sensor;
When the temperature of the water detected by the temperature sensor is equal to or lower than a predetermined determination value set to prevent freezing of the water, energizing the heater and heating the water;
A step of reciprocating the water along the flow path by the pump in a state where the water is not frozen;
A control method for a fuel cell system, comprising:   4. The fuel cell according to claim 3, wherein when the operation of the fuel cell is stopped, the pump is driven to draw the water from the third conduit side to the water tank. 5. How to control the system.   The method for controlling a fuel cell system according to claim 3 or 4, wherein the water is reciprocated by the pump before energizing the heater.   The fuel according to any one of claims 3 to 5, wherein the heater is energized when the temperature of the water detected by the temperature sensor is equal to or lower than a predetermined heater drive determination value (T2a). Battery system control method.   The energization of the heater is stopped when the temperature of the water detected by the temperature sensor is equal to or higher than a predetermined heater stop determination value (T2b) higher than the predetermined heater drive determination value (T2a). Item 7. A control method for a fuel cell system according to Item 6.   The temperature sensor includes environmental temperature detection means for detecting the environmental temperature of the environment surrounding the flow path, and when the environmental temperature detected by the environmental temperature detection means is equal to or lower than a predetermined pump drive determination value (T1a), The control method of the fuel cell system according to any one of claims 3 to 7, wherein a reciprocating flow operation is performed by the pump.   When the environmental temperature detected by the environmental temperature detection means is equal to or higher than a predetermined pump stop determination value (T1b) higher than the predetermined pump drive determination value (T1a), and when the energization of the heater is stopped, 9. The control method for a fuel cell system according to claim 8, wherein the reciprocating operation is stopped.

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