JP2003031242A - Polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent condensation of water vapor in a humidity control gas in a feed pipe for supplying a fuel gas or an oxidizing gas adjusted to a target absolute humidity to a gas diffusion electrode. SOLUTION: Humidity adjusting means Ma, Mb for adjusting absolute humidity xa, xb of fuel gas F or oxidant gas A supplied to gas diffusion electrodes 7, 8 to target absolute humidity xas, xbs,
And tube heating means 20a for heating the supply tubes 15a, 15b of the humidity-regulated gases F ', A' to the electrode side.
20b, the temperatures ta ', t of the humidity control gases F', A 'at the downstream ends of the feed pipes 15a, 15b.
b 'end temperature sensors 21a and 21b are provided,
Based on the detected temperatures ta ″ and tb ″, the tube heating means 20
a, 20b by adjusting the heating output of the feed pipes 15a, 15b.
T of the humidity control gas F ', A' at the downstream end of
Heating control means 18 for adjusting a 'and tb' to target end gas temperatures tas 'and tbs' is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell, and more specifically, to supplying a fuel gas to one gas diffusion electrode (fuel electrode) sandwiching a polymer electrolyte membrane and to the other gas. Humidity adjusting means for adjusting the absolute humidity of the fuel gas or the oxidant gas supplied to the gas diffusion electrode to the target absolute humidity in the configuration for supplying the oxygen gas-containing oxidant gas to the diffusion electrode (oxygen electrode), and the humidity thereof. The present invention relates to a polymer electrolyte fuel cell provided with pipe heating means for heating a feed pipe of a humidity-controlled gas whose humidity is adjusted by an adjusting means to an electrode side.

[0002]

2. Description of the Related Art In this type of polymer electrolyte fuel cell,
As shown in FIG. 5, the absolute humidity xa and xb of the fuel gas F and the oxidant gas A supplied to the gas diffusion electrodes 7 and 8 are adjusted to the target absolute humidity xas and xbs according to the operating conditions of the battery by the humidity adjusting means Ma and Mb. By adjusting the temperature of the solid polymer electrolyte membrane 6 to an appropriate wet state to maintain efficient battery operation, the humidity-adjusted gas F'and A'on the electrode side By heating the feed pipes 15a, 15b to the feed pipes 15a, 15b by the pipe heating means 20a, 20b, the water vapor in the humidity control gas F ', A'is radiated to the outside of the feed pipes 15a, Condensation in 15b is prevented to prevent the water content to be supplied to the electrolyte membrane 6 from becoming insufficient due to the condensation in the tube and to hinder the gas supply to the gas diffusion electrodes 7 and 8. I am trying.

As the tube heating means 20a, 20b, an electric heater is wound around the entire length of the feed pipes 15a, 15b, and a jacket or tube through which a high-temperature heat medium passes is attached over the entire length of the feed pipes 15a, 15b. Although various types are adopted, conventionally, the heating output is fixedly set for any type of the tube heating means 20a, 20b, and in that setting, the feeding pipe 15a, 15b ambient temperature and humidity control gas F ',
The condensation of the vapor in the humidity control gas in the pipe is surely prevented regardless of various fluctuation factors and uncertain factors such as the flow rate of A'or the heat transfer characteristics of the feed pipes 15a and 15b to the humidity control gas F'and A'in the pipe. Therefore, in consideration of a corresponding safety factor, the temperature of the feed pipes 15a, 15b is considerably higher than the dew point temperature of the humidity control gas F ', A' (for example, the humidity control gas F ', A'.
The heating output of the tube heating means 20a and 20b is set so that the dew point temperature of the tube is 80 ° C. while the tube output is 100 ° C. or higher (see Japanese Patent Laid-Open No. 2000-67893).

Incidentally, the humidity adjusting means M in the example of FIG.
a and Mb are humidifiers 4 that discharge the gases F and A to be adjusted into the stored water W and send the gases F ′ and A ′ that have floated above the stored water W to the feed pipes 15a and 15b. 5 and the temperatures tm and tn of the stored water W in the humidity controllers 4 and 5 are measured by the sensor 1
The temperatures tm and tn of the stored water W are detected by 6a 'and 16b' and the heating outputs of the heaters 13a and 13b with respect to the stored water W are adjusted based on the detected water temperature.
In the humidity adjusting means Ma and Mb, the target water temperature tms is adjusted by bubbling the gases F and A to be adjusted by the humidity adjusters 4 and 5. , Tns when humidifying to a water vapor saturated state, the dew point temperature tas, t corresponding to the target absolute humidity xas, xbs at the target water temperature tms, tns.
By setting the temperature equal to bs, the absolute humidity xa, xb of the gases F ', A'supplied to the gas diffusion electrodes 7, 8 can be changed to the target absolute humidity xas, in a so-called dew point control adjustment mode. It is adjusted to xbs.

[0005]

However, in the above-mentioned conventional polymer electrolyte fuel cell, the condensation of water vapor in the humidity control gas in the feed pipes 15a and 15b can be prevented. The humidity control gases F ', A'supplied to 8 are heated to a high temperature by the heat applied from the high temperature feed pipes 15a, 15b, and the relative humidity is greatly lowered due to the temperature rise. 'Absolute humidity xa, xb is the target absolute humidity xa
Although the s and xbs are maintained properly, the electrolyte membrane 6 is locally dried at the end of the gas diffusion electrodes 7 and 8 on the side where the humidity control gases F ′ and A ′ are introduced. However, there is a problem in that the battery performance is deteriorated.

Further, the large amount of heat as described above is applied to the in-pipe humidity control gases F'and A '(in other words, the high temperature feed pipe 15).
A large amount of energy is required to heat the feeding pipes 15a and 15b to a high temperature due to the large heat radiation to the inside of the pipes a and 15b) and also to the outside of the high temperature feeding pipes 15a and 15b. Therefore, there is a problem that the energy efficiency of the fuel cell as a whole is lowered.

In view of this situation, the main problem of the present invention is to
When supplying the fuel gas or oxidant gas adjusted to the target absolute humidity to the gas diffusion electrode, it is possible to reliably prevent the condensation of water vapor in the humidity control gas in the feeding pipe without the above problems. In point.

[0008]

[1] The invention according to claim 1 relates to a polymer electrolyte fuel cell, which is characterized in that a fuel gas is supplied to one gas diffusion electrode sandwiching a polymer electrolyte membrane. And, in the configuration for supplying an oxidant gas containing oxygen gas to the other gas diffusion electrode, a humidity adjusting means for adjusting the absolute humidity of the fuel gas or the oxidant gas supplied to the gas diffusion electrode to a target absolute humidity, And a pipe heating means for heating the feed pipe of the humidity-controlled gas whose humidity is adjusted by the humidity adjusting means to the electrode side, while detecting the temperature of the humidity-controlled gas at the downstream end of the feed pipe. The end temperature sensor is provided, and the heating output of the pipe heating means is adjusted based on the temperature detected by the end temperature sensor to adjust the temperature of the humidity control gas at the downstream end of the feed pipe to the target end gas. Heating to adjust the temperature Lies in the fact that is provided with a control means.

That is, according to this structure, the heating output of the pipe heating means is set based on the temperature detected by the end temperature sensor so that the temperature of the humidity control gas at the downstream end of the feed pipe becomes the target end gas temperature. Is adjusted, so if you set a temperature slightly higher than the dew point temperature of the humidity control gas (fuel gas or oxidant gas adjusted to the target absolute humidity) as the target end gas temperature, under that setting By adjusting the heating output according to the above conditions, regardless of fluctuation factors such as the ambient temperature of the feed pipe, the flow rate of the humidity control gas, or the heat transfer characteristics of the feed pipe to the humidity control gas in the pipe, and uncertain factors, Ensure that the temperature of the humidity control gas is kept above the dew point temperature of the feed pipe during the passage through the pipe to the downstream end while avoiding unnecessarily high temperature. Can be delivered by this The condensation of the humidity gas water vapor in the inner can be reliably prevented.

In this way, it is possible to prevent the condensation of the water vapor in the humidity control gas inside the feed pipe while avoiding an excessive temperature rise of the feed pipe, so that the heating output of the pipe heating means is expected to have a high safety factor. The above-mentioned problem that occurs in the conventional type that is fixedly set in, that is, the absolute humidity of the humidity control gas is kept at the target absolute humidity and is proper, but Due to the high temperature and the large decrease in relative humidity due to it, the electrolyte membrane locally tends to dry at the end of the gas diffusion electrode on the side where the humidity control gas is introduced and the battery performance deteriorates. It is possible to effectively avoid the problem that a large amount of energy is required to heat the feed pipe due to the large heat radiation to the pipe inner side and the pipe outer side, and the energy efficiency of the entire fuel cell decreases.
In this respect, it is possible to further prevent the condensation of the water vapor in the humidity control gas in the feed pipe, and further improve the battery performance and energy efficiency as compared with the above-mentioned conventional type.

In the practice of the invention according to claim 1, the above-described configuration is carried out for each of the fuel gas and the oxidant gas, or only for one of the fuel gas and the oxidant gas. Any of the embodiments may be adopted.

Further, in the practice of the invention according to claim 1, the humidity adjusting means is of a type that sends out a humidity control gas having a target absolute humidity to a feed pipe in a water vapor saturated state, or a target in a water vapor unsaturated state. It may be of any type in which the humidity-controlled gas of absolute humidity is delivered to the feed pipe, and the adjustment of absolute humidity by the humidity adjusting means is performed by adjustment by humidification or adjustment by dehumidification according to the state of the gas to be adjusted. Either may be used.

[2] The invention according to claim 2 specifies an embodiment suitable for carrying out the invention according to claim 1, and is characterized in that the heating control means is provided in the end temperature sensor. When the detected temperature is higher than a threshold temperature obtained by adding a predetermined temperature difference to the target end gas temperature, or an evaluation temperature obtained by subtracting the predetermined temperature difference from the detected temperature of the end temperature sensor is the target end gas. When the temperature is higher than the temperature, the heating output of the tube heating means is adjusted to the lower side, and when the temperature detected by the end temperature sensor is lower than the threshold temperature, or
When the evaluation temperature is lower than the target end gas temperature, the heating output of the tube heating means is adjusted to the increasing side.

That is, in the gas temperature detection by the end temperature sensor, the temperature sensing portion of the end temperature sensor is the temperature of the feed pipe or the pipe heating due to the restriction of the sensor mounting structure for the feed pipe having a small diameter. The influence of the output temperature of the means cannot be avoided, and therefore the temperature detected by the end temperature sensor may be constantly higher than the actual temperature of the humidity control gas.

In such a case, the temperature detected by the end temperature sensor is set with a value corresponding to the steady temperature difference between the temperature detected by the end temperature sensor and the actual humidity-adjusted gas temperature being set as the predetermined temperature difference. Depending on the level relation between the above-mentioned threshold temperature (a temperature higher than the target end gas temperature by a predetermined temperature difference), or
If the output of the tube heating means is adjusted as described above according to the level relationship between the evaluation temperature (a temperature lower than the temperature detected by the end temperature sensor by a predetermined temperature difference) and the target end gas temperature, Regardless of whether the temperature sensing part of the end temperature sensor is affected by the pipe temperature of the feed pipe or the output temperature of the pipe heating means,
The temperature of the humidity control gas at the downstream end of the feed pipe can be accurately adjusted to the target end gas temperature.

That is, by this, the expected function of surely preventing the condensation of the water vapor in the humidity control gas in the feed pipe by adjusting the heating output of the pipe heating means based on the temperature detected by the end temperature sensor, Even when the temperature sensing part of the end temperature sensor is affected by the tube temperature of the feed tube or the output temperature of the tube heating means, it can be appropriately exerted, and this facilitates the production of the fuel cell. be able to.

[3] The invention according to claim 3 specifies an embodiment suitable for carrying out the invention according to claim 1 or 2, and is characterized in that the gas to be adjusted is used as the humidity adjusting means. In a configuration in which a humidity controller that discharges water into the stored water and sends a gas that floats above the stored water to the feed pipe, and a water temperature control unit that adjusts the temperature of the stored water in the humidity controller by heating or cooling are provided. A humidity control temperature sensor for detecting the temperature of the floating gas above the stored water in the humidity control device is provided, and the water temperature control means controls the stored water in the humidity control device based on the detected gas temperature of the humidity control temperature sensor. The point is that the temperature is adjusted to adjust the temperature of the floating gas on the stored water to a temperature equal to the dew point temperature corresponding to the target absolute humidity.

In other words, in this configuration, the gas to be adjusted is subjected to a bubbling process in the temperature-controlled reservoir water in the humidity controller to bring the gas to be adjusted into a saturated state of water vapor at a predetermined temperature, thereby adjusting the dew point control mode. The humidity control gas with the target absolute humidity is obtained by using the humidity control method, and the temperature of the stored water in the humidity controller is detected by the sensor as in the conventional method described above, and the temperature of the stored water is detected based on the detected water temperature. When the control method based on the water temperature of adjusting the water temperature to the target water temperature (the temperature equal to the dew point temperature corresponding to the target absolute humidity) is adopted, the following problems are likely to occur.

That is, although the gas floating above the stored water in the humidity controller is saturated with water vapor, the temperature of the floating gas is increased due to heat dissipation to the outside of the device or insufficient heat exchange with the stored water. The target water temperature (the temperature equal to the dew point temperature corresponding to the target absolute humidity) is slightly different, so that the absolute humidity of the levitation gas sent from the humidity controller to the feed pipe as the humidity control gas is the target absolute humidity. As a result, the solid polymer electrolyte membrane cannot be kept in an appropriate wet state even though the condensation of water vapor in the humidity control gas in the feed pipe is prevented as described above. The problem that performance deteriorates easily occurs.

On the other hand, instead of the temperature of the stored water, the temperature of the floating gas on the stored water in the humidity controller is detected by the temperature sensor for humidity control, and the temperature of the floating gas on the stored water is detected based on the detected gas temperature. If the control method based on the gas temperature as described above, in which the temperature of the stored water in the humidity controller is adjusted by heating or cooling the stored water so that the temperature is equal to the dew point temperature corresponding to the target absolute humidity, Compared to the above water temperature control method, the gas that is saturated and floats above the stored water can be adjusted more accurately to the required temperature (temperature equal to the dew point temperature corresponding to the target absolute humidity), and the water temperature control It is possible to effectively prevent the above-mentioned problems that occur in the system, and in this respect, it is possible to further improve the battery performance.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a polymer electrolyte fuel cell, 1 is a cell stack formed by stacking a large number of cells 2.
3 is a reformer for reforming raw fuel Fs to generate reformed gas F, and 4 is reformed gas F which is a mixed gas containing hydrogen gas.
Is a humidity controller on the fuel side for adjusting the humidity of the air, and reference numerals 5 are oxygen-side humidity controllers for adjusting the humidity of the air A as the oxidant gas.

The cells 2 forming the battery stack 1 are shown in FIG.
As shown in FIG. 2, the solid polymer electrolyte membrane 6 is sandwiched between the gas diffusion electrode 7 as a fuel electrode (anode) and the gas diffusion electrode 8 as an oxygen electrode (cathode) to form a membrane sandwiching body 9, and the membrane sandwiching is performed. The body 9 is further configured to be sandwiched by gas-impermeable separators 10 having a large number of grooves 10a and 10b used as reaction gas flow paths formed on both surfaces.

Each of the electrodes 7 and 8 has a structure in which gas-permeable catalyst layers 7b and 8b are provided on the surface of the electrode bodies 7a and 8a made of a porous material on the electrolyte side. As schematically shown in FIG. 3, in the fuel electrode 7, the humidity-modified reformed gas F ′ whose humidity has been adjusted by the humidity controller 4 is passed as a fuel gas to the groove 10a of the separator 10 facing the fuel electrode 7 to improve the modification. The gas F'is diffused to the electrolyte membrane 6 side to cause the catalytic action of the catalyst layer 7b and the proton (H
⁺ ) Under the action of conduction, the anodic reaction shown in the following (Equation 1) is allowed to proceed, and in the oxygen electrode 8, the humidity is adjusted by the humidity controller 5 as an oxidant gas into the groove 10b of the separator 10 facing the oxygen electrode 8. By passing the moist air A ′, the air A ′ is diffused to the side of the electrolyte membrane 6 and the catalytic action of the catalyst layer 8 b and the conduction of protons (H ⁺ ) from the side of the fuel electrode 7 through the electrolyte membrane 6 are conducted. The cathode reaction shown in the following (Equation 2) is advanced below, and electrons e in the external circuit 11 accompanying these reactions
^- power supplied to the load side with a flow.

H ₂ → 2H ⁺ + 2e ⁻ (Equation 1) 1 / 2O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (Equation 2)

Then, the separator 10 for partitioning the flow path of the humidity-controlled reformed gas F'as the fuel gas and the flow path of the humidity-controlled air A'as the oxidant gas is formed of a conductive material (for example, expanded graphite). By stacking a large number of cells 2 with each other, a battery stack 1 in which the cells 2 are electrically connected in series is formed, and a required potential difference on the load side is obtained between both ends of the battery stack 1.

The solid polymer electrolyte membrane 6 has a proton conductivity in a wet state such as a perfluorocarbon sulfonic acid membrane or a polystyrene cation exchange membrane having a sulfonic acid group as a cation conductive membrane. Any of various materials can be used, and a porous carbon thin plate can be cited as a typical example of the electrode bodies 7a and 8a, and a platinum-based catalyst layer can be cited as a typical example of the catalyst layers 7b and 8b. Can be mentioned.

The reformer 3 desulfurizes the raw fuel Fs and then reacts with steam in the presence of a catalyst to produce an intermediate reformed gas rich in hydrogen gas containing carbon monoxide gas (steam reforming treatment). Then, the carbon monoxide gas in the intermediate reformed gas is reacted with steam in the presence of a catalyst to form carbon dioxide gas (CO shift treatment), and further, in the intermediate reformed gas after the CO shift treatment. The carbon monoxide gas remaining in the above is selectively oxidized by a catalytic action to finally produce a reformed gas F mainly composed of hydrogen gas and carbon dioxide gas from which carbon monoxide gas is almost removed. .

Depending on the type of the raw fuel Fs, a small amount of other gas (for example, nitrogen gas) other than hydrogen gas and carbon dioxide gas may exist in the reformed gas F.

The fuel-side and oxygen-side humidity controllers 4 and 5 are respectively
Hermetically-sealed containers 12a and 12b that store water W, heaters 13a and 13b that heat the stored water W in the container, and a cooler 13a 'that cools the stored water W in the container by exchanging heat with the cooling water C. , 13b ', and the container 12
Introducing pipes 14a, 1 for the gas F, A to be adjusted are provided in a, 12b.
4b and feed pipes 15a and 15b for sending the humidity-adjusted gases F'and A'after the humidity adjustment to the electrode side are connected.

Further, the introduction pipes 14a and 14b have their tips opened in the stored water W at the bottom of the container while the spiral structure portion formed therein is immersed in the stored water W. The pipes 15a and 15b have their base ends opened in the space inside the container on the stored water W.

That is, in these humidity controllers 4 and 5, the gases F and A to be adjusted are supplied to the heaters 13a and 13b or the cooler 13.
Stored water W whose temperature is adjusted by a'and 13b 'and an introduction pipe 1
After heat exchange in the course of passage of the spiral structure part in 4a, 14b, the gas to be adjusted F, A is introduced into the introduction pipes 14a, 1
4b is discharged into the stored water W from the tip of 4b to perform a bubbling process, and the bubbling process humidifies or dehumidifies (that is, the stored water Humidification is performed when the temperature of W is higher than the dew point temperature of the adjustment target gases F and A, and dehumidification is performed when the temperature of the stored water W is lower than the dew point temperature of the adjustment target gases F and A. The absolute humidity xa, xb of the adjustment target gas F, A is adjusted. Then, the humidity-adjusted reformed gas F'and the humidity-adjusted air A'after the humidity adjustment, which floats above the stored water W and is stored in the space inside the container, are fed into the supply pipes 15a and 15b.
It is taken out from the containers 12a and 12b through the battery and sent to the battery stack 1.

16a and 16b are floating gas temperatures ta and ta on the stored water W in the fuel-side and oxygen-side humidity controllers 4 and 5, respectively.
A temperature sensor for humidity control that detects tb (that is, the temperature of each of the humidity-controlled reformed gas F ′ and the humidity-controlled air A ′ in the water vapor saturated state), and 17 is the reformed gas F sent from the reformer 3.
Is a concentration sensor for detecting the hydrogen gas concentration d of the humidity controller 18 and a controller 18. The controller 18 is a humidity controlling temperature sensor 16a, 1
6b, the concentration sensor 17, and the following humidity control of (a) to (d) based on the detection information of the voltmeter 19 described later.

(A) The temperatures ta and tb of the floating gases F'and A'existing in the space inside the container above the stored water W in a saturated state of water vapor in the fuel-side and oxygen-side humidity controllers 4 and 5, respectively. Based on the detected gas temperatures ta and tb of the humidity controlling temperature sensors 16a and 16b, the fuel side and the target floating gas temperatures tas and tbs (temperatures equal to dew point temperatures corresponding to target absolute humidity xas and xbs described later) are obtained. Oxygen side humidity controller 4,
The heating output of the heaters 13a and 13b or the cooling output of the coolers 13a 'and 13b' in each of the 5 is adjusted to adjust the temperature of the stored water W in the container in each of the humidity controllers 4 and 5.

In other words, by adjusting the levitation gas temperature, the adjustment target gases F and A are adjusted to the water vapor saturated state of the target levitation gas temperatures tas and tbs in each of the humidity controllers 4 and 5, and thereby the cell 2 is adjusted. Conditioning gas F ', A'supplied to
Absolute humidity xa, xb of the target absolute humidity xas, xbs
(Absolute humidity when the target floating gas temperature tas, tbs is saturated with water vapor).

Va and vb are coolers 13a ', 13
It is a valve for adjusting the supply amount of the cooling water C to b ', and the cooling output of the coolers 13a' and 13b 'to the stored water W in the container is adjusted by adjusting the cooling water supply amount by these valves va and vb.

(B) When the hydrogen gas concentration d of the reformed gas F changes due to a change in the component ratio of the raw fuel Fs (for example, natural gas or biogas), it is supplied to the cell 2 as shown in FIG. 4, for example. In the relationship between the absolute humidity x (xa or xb) of the humidity-controlled reformed gas F ′ or the humidity-controlled air A ′ and the generated voltage V of the cell 2, the optimum absolute humidity xm at which the cell voltage V has a peak.
(That is, the absolute humidity that can prevent both the drying of the electrolyte membrane 6 due to insufficient humidity and the decrease in gas diffusivity of the electrodes 7 and 8 due to excessive humidity to enable the most efficient battery operation) , The humidity-conditioned reformed gas F'and the humidity-controlled air A ', respectively, the hydrogen gas concentration d and the optimum absolute humidity xm.
The relationship K with is stored in advance.

Then, in this memory relation K, the optimum absolute humidity xm corresponding to the hydrogen gas concentration d detected by the concentration sensor 17 is extracted for each of the humidity-controlled reformed gas F'and the humidity-controlled air A ', and the extracted absolute values are extracted. The humidity is set as the target absolute humidity xas, xbs in the humidity adjustment on the fuel-side and oxygen-side humidity controllers 4 and 5, respectively, and along with that, it is equal to the dew point temperature corresponding to the set target absolute humidity xas, xbs. The temperature is set as the target floating gas temperatures tas and tbs in the floating gas temperature adjustment in (a) above.

That is, as a result, the humidity-controlled reformed gas F'and the humidity-controlled air A'supplied to the electrodes 7, 8 of the cell 2 are supplied.
For each of the above, the absolute humidity x (xa or xb) is adjusted to the optimum absolute humidity xm corresponding to the hydrogen gas concentration d of the reformed gas F ′ at that time, thereby obtaining a highly efficient battery operation state. Show high battery performance.

The hydrogen gas concentration d in the reformed gas F is
The correlation between the absolute humidity x and the cell voltage V is not limited to the correlation shown in FIG. 4, and the characteristics of individual fuel cells are different for each fuel cell.

(C) The cell voltage V is detected by the voltmeter 19 as an indicator of the output state of the battery, and based on this detected cell voltage V, the reformed gas supply at that time is corrected as a correction for the control of (b) above. The storage relationship K is modified so that the highest cell voltage V under the control amount and the air supply amount can be obtained in the above control (b).

In 20a and 20b, the water vapor in the humidity control gas F'and A ', the humidity of which has been adjusted by the humidity control units 4 and 5, is fed into the feed pipes 15a and 1.
In order to prevent condensation in 5b, each feed pipe 15a,
A pipe heating means such as an electric heater provided over the entire length of 15b, 21a and 21b are downstream end portions of the feed pipes 15a and 15b (in this example, the humidity control gas F'in the stack 1;
This is an end temperature sensor for detecting the temperatures ta 'and tb' of the humidity control gases F'and A'in the vicinity of the inlet of A '), and the controller 18 is provided in addition to the humidity control described in (a) to (c) above. Then, the following (d) tube heating control is executed based on the detection information of these end temperature sensors 21a and 21b.

(D) Humidified reformed gas F'and humidified air A '
For each of the above, as described below, the target floating gas temperature t
Temperatures higher than as and tbs by the set temperature difference Δt are set as target end gas temperatures tas 'and tbs', and the pipe temperatures of the feed pipes 15a and 15b and the pipe heating means 20 are set.
Under the influence of the output temperatures of a and 20b, the temperatures ta ″ and tb ″ detected by the end temperature sensors are lower than the actual humidity control gas temperatures ta ′ and tb ′ at the downstream ends of the feed pipes 15a and 15b. While the temperature is constantly high, the steady temperature difference Δt
Temperatures higher than the target end gas temperatures tas 'and tbs' by the amount of t are threshold temperatures tas "and tab" for heating output adjustment.
Set as.

The above-mentioned set temperature difference Δt is as follows in order to prevent condensation of water vapor in the feed gas 15a, 15b by adjusting heating output to the tube heating means 20a, 20b as described later. A value that is as small as possible is set within a range in which condensation inside the tubes can be reliably prevented regardless of uneven heating of the feed tubes 15a and 15b.

The steady-state temperature difference Δtt is stored in the controller 18 in advance after the value is determined based on a test.

(Humidity-modified reformed gas F ′ side) Target end gas temperature tas ′ = target floating gas temperature tas +
Set temperature Δt Set threshold temperature tas ″ = target end gas temperature tas ′ + steady temperature difference Δtt (humidified air A ′ side) Target end gas temperature tbs ′ = target floating gas temperature tbs +
Set temperature Δt Set threshold temperature tbs ″ = target end gas temperature tbs ′ + steady temperature difference Δtt

Then, the detected temperatures ta "and tb" of the end temperature sensors 21a and 21b are set to the set threshold temperatures tas "and ta.
When the temperature is higher than b ″, the corresponding tube heating means 20a, 20
When the heating output of b is adjusted to the lower side and the detected temperatures ta ″, tb ″ of the end temperature sensors 21a, 21b are lower than the set threshold temperatures tas ″, tab ″, the corresponding tube heating means 20a, 20b. The heating output of the tube heating means 20a, 20b is adjusted based on the detected temperatures ta ″, tb ″ of the end temperature sensors 21a, 21b in an adjustment mode such that the heating output of the tube heating means is increased. In a situation in which a temperature difference Δtt occurs, the temperature ta ′ of the humidity control gas F ′, A ′ at the downstream end of each feed pipe 15a, 15b,
tb '(actual temperature) is the target end gas temperature tas', tb
Adjust to s'accurately.

That is, in this way, the feeding pipes 15a, 1
The temperature t of the humidity control gas F ', A'at the downstream end of 5b
a ′ and tb ′ are the target floating gas temperatures tas and tb.
s (target absolute humidity xa in the humidity controllers 4 and 5 in this example)
s, xbs, the target end gas temperature tas', which is set higher than the dew point temperature of the humidity-controlled gas F ', A' whose humidity has been adjusted.
By adjusting the heating output of the tube heating means 20a, 20b according to the situation so that tbs', the feed tube 15
irrespective of fluctuation factors such as the ambient temperature of a and 15b, the flow rates of the humidity control gases F'and A'or the heat transfer characteristics of the feed tubes 15a and 15b to the humidity control gases F'and A ', , The temperature ta 'of the humidity control gas F', A ', while avoiding an excessive temperature rise of the feed pipes 15a, 15b.
It is ensured that tb ′ is higher than the dew point temperatures tas, tbs of the feeding pipes 15a, 1b during the passage through the pipes up to the downstream end of the feeding pipes 15a, 15b.
Condensation of water vapor in the humidity-controlled gas within 5b is reliably prevented.

In summary, in the present embodiment, the humidity controllers 4, 5 and the controller 18 change the absolute humidity xa, xb of the fuel gas F and the oxidant gas A supplied to the gas diffusion electrodes 7, 8 from the target absolute humidity xas. , Xbs for adjusting the humidity M
a and Mb, and the humidity adjusting means Ma and Mb.
In the controller 18, the humidity control temperature sensors 16a, 16
By adjusting the temperature of the stored water W in the humidity controllers 4 and 5 based on the detected gas temperatures ta and tb of b, the temperatures ta and tb of the floating gases F ′ and A ′ on the stored water W are set to the target absolute humidity. temperature ta equal to the dew point temperature corresponding to xas, xbs
A water temperature control means for adjusting to s and tbs is configured.

The controller 18 also controls the tube heating means 2
For the output adjustment of 0a and 20b, the end temperature sensor 21
The heating output of the tube heating means 20a, 20b is adjusted based on the detected temperatures ta ", tb" of a, 21b, and the feed tube 15
The temperatures ta 'and tb' of the humidity control gases F'and A'at the downstream end portions of a and 15b are changed to the target end gas temperatures tas' and tb.
A heating control means for adjusting to s'is configured.

[Other Embodiments] Next, other embodiments will be listed.

In the practice of the present invention, various fuels such as natural gas, propane, kerosene, and biogas can be used as the raw fuel Fs, and the oxidant gas A is not limited to air, but oxygen other than air can be used. It may be a gas containing gas or pure oxygen gas.

Although the reformed gas obtained by reforming raw fuel is generally used as the fuel gas F supplied to the fuel electrode 7, in the present invention, the fuel gas F has a hydrogen gas concentration of 100.
The present invention can also be applied to the case of supplying a gas of or close to 100% to the fuel electrode 7 without reforming.

Fuel gas F supplied to the gas diffusion electrodes 7 and 8
And the absolute humidity xa and xb of the oxidant gas A are the target absolute humidity x
The specific humidity adjusting method of the humidity adjusting means Ma, Mb for adjusting to as, xbs is not limited to the bubbling method shown in the above-described embodiment, and for adjusting by humidifying, the humidifying water is sprayed on the target gas. A variety of humidification methods can be adopted, such as a spraying method, a film humidification method that permeates the humidification water to the target gas, and an ultrasonic humidification method that atomizes the humidification water by ultrasonic waves and supplies it to the target gas. Also in the adjustment by, the cooling coil system that cools the target gas with the cooling coil to condense the water content in the gas, the film dehumidification method that removes the water content in the target gas through the membrane, and the water content in the target gas is removed by the hygroscopic material. Various dehumidification methods such as a moisture absorption method can be adopted.

In the above-described embodiment, the absolute humidity xa and xb of the fuel gas F and the oxidant gas A are controlled by the humidity controllers 4 and 5 capable of both adjusting the absolute humidity by humidifying and adjusting the absolute humidity by dehumidifying. Although an example of adjustment is shown, a humidifier that only adjusts the absolute humidity by humidification and a dehumidifier that only adjusts the absolute humidity by dehumidification are separately provided in the supply path of the gas to be adjusted, and they are The absolute humidity of the gas to be adjusted may be adjusted by a humidifier or dehumidifier.

When the absolute humidity of the adjustment target gases F and A before the humidity adjustment is always lower than the optimum absolute humidity change range, only the absolute humidity adjustment by humidification may be performed. Conversely, when the absolute humidity of the adjustment target gases F and A before the humidity adjustment is always on the higher humidity side than the change range of the optimum absolute humidity, only absolute humidity adjustment by dehumidification may be performed.

In the above-described embodiment, the absolute humidity is adjusted by the humidity adjusting means Ma and Mb on the fuel gas side and the oxidant gas side, respectively, and the tube heating means 20a, which is based on the temperature detected by the end temperature sensors 21a, 21b. Although the example of performing the output adjustment of 20b is shown, the adjustment of the absolute humidity by these humidity adjusting means and the output adjustment of the tube heating means based on the temperature detected by the end temperature sensor are performed on the fuel gas side and the oxidant gas side. It is also possible to carry out only one of the above, or in some cases, the humidity adjustment process itself for either one of the fuel gas F and the oxidant gas A may be omitted.

In the above embodiment, the target absolute humidity xas, xbs for the humidity adjustment by the humidity adjusting means Ma, Mb is changed according to the hydrogen gas concentration d in the reformed gas F, but the present invention is not limited to this. Target of humidity adjustment by humidity adjusting means Fixed absolute humidity is set, or target of humidity adjusting by humidity adjusting means according to index values other than hydrogen gas concentration in the reformed gas (for example, cell voltage or battery load). It can also be applied when changing the absolute humidity.

Further, in the above-described embodiment, the feeding pipe 15
Under the influence of the tube temperatures of a and 15b and the output temperatures of the tube heating means 20a and 20b, the temperatures ta ″ and tb ″ detected by the end temperature sensors 21a and 21b are at the downstream ends of the feed tubes 15a and 15b. One example of the case in which the temperature is constantly higher than the actual humidity control gas temperatures ta ′ and tb ′ is shown, but as another example of correspondence, the temperatures ta ″ and tb ″ detected by the end temperature sensors 21a and 21b are shown. The temperature obtained by subtracting the steady-state temperature difference Δtt from the temperature is set as the evaluation temperature, and the evaluation temperature (ta ″ −Δtt), (t
b ″ −Δtt) is the target end gas temperature tas ′, tbs ′.
When the temperature is higher than that, the corresponding tube heating means 20a, 20b
The heating output of the device is adjusted to the lower side, and the evaluation temperature (ta "
-Δtt), (tb "-Δtt) is the target end gas temperature t
When the temperature is lower than as 'and tbs', the heating output of the corresponding tube heating means 20a, 20b may be adjusted to the increasing side.

If the temperature difference between the temperature detected by the end temperature sensor and the actual temperature of the regulated gas at the downstream end of each feed pipe is not so large, the temperature detected by the end temperature sensor itself is A control method of adjusting the heating output of the tube heating means so as to reach the target end gas temperature may be adopted.

As the tube heating means 20a, 20b, various types are adopted, such as winding an electric heater over the entire length of the feed pipe, or attaching a jacket or tube through which the high-temperature heating medium passes for the entire length of the feed pipe. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel cell

FIG. 2 is an exploded perspective view showing a cell structure.

FIG. 3 is a diagram showing a power generation principle of a fuel cell.

FIG. 4 is a graph showing the correlation between hydrogen gas concentration of reformed gas, absolute humidity, and cell voltage.

FIG. 5 is a configuration diagram of a conventional fuel cell

[Explanation of symbols]

4,5 Humidifier 6 Solid polymer electrolyte membrane 7 Gas diffusion electrode (fuel electrode) 8 Gas diffusion electrode (oxygen electrode) 18 Heating control means, water temperature control means 15a, 15b Feeding pipe 16a, 16b Temperature sensor for humidity control 20a, 20b tube heating means 21a, 21b End temperature sensor A Oxidizer gas (adjustable gas) F Fuel gas (adjustable gas) F ', A'Humidity control gas Ma, Mb humidity adjusting means ta, tb Floating gas temperature tas, tbs Dew point temperature corresponding to target absolute humidity ta ', tb' Humidified gas temperature tas ', tbs' target end gas temperature ta ", tb" detection temperature tas ", tbs" threshold temperature Δtt predetermined temperature difference W stored water xa, xb absolute humidity xas, xbs Target absolute humidity

Continued front page    (72) Inventor Hiroshi Yamakawa             1-1-1 Hama, Amagasaki City, Hyogo Prefecture Co., Ltd.             Kubota Technology Development Laboratory (72) Inventor Yasuyuki Kitagawa             1-1-1 Hama, Amagasaki City, Hyogo Prefecture Co., Ltd.             Kubota Technology Development Laboratory F-term (reference) 5H026 AA06                 5H027 AA06 KK00 KK41 MM02 MM12                       MM21

Claims (3)

[Claims] 1. A structure in which a fuel gas is supplied to one gas diffusion electrode sandwiching a solid polymer electrolyte membrane and an oxidant gas containing oxygen gas is supplied to the other gas diffusion electrode, wherein the gas diffusion electrode is provided. Humidity adjusting means for adjusting the absolute humidity of the fuel gas or the oxidant gas to be supplied to the target absolute humidity, and a pipe heating means for heating the feed pipe of the humidity adjusting gas whose humidity is adjusted by the humidity adjusting means to the electrode side. The polymer electrolyte fuel cell is provided with, the end temperature sensor for detecting the temperature of the humidity control gas at the downstream end of the feed pipe is provided, and based on the temperature detected by the end temperature sensor. A polymer electrolyte fuel cell provided with heating control means for adjusting the heating output of the tube heating means to adjust the temperature of the humidity control gas at the downstream end of the feed tube to the target end gas temperature. 2. The heating control means detects when the temperature detected by the end temperature sensor is higher than a threshold temperature obtained by adding a predetermined temperature difference to the target end gas temperature, or when the end temperature sensor detects the temperature. When the evaluation temperature obtained by subtracting the predetermined temperature difference from the temperature is higher than the target end gas temperature, the heating output of the tube heating means is adjusted to the lower side, and the detected temperature of the end temperature sensor is The solid height according to claim 1, wherein the heating output of the tube heating means is adjusted to an increasing side when the temperature is lower than a threshold temperature or when the evaluation temperature is lower than the target end gas temperature. Molecular fuel cell. 3. A humidity controller as the humidity adjusting means, which discharges a gas to be adjusted into stored water and sends the gas floating above the stored water to the feed pipe, and stored water in the humidity controller. In the configuration provided with a water temperature control means for adjusting the temperature by heating or cooling, a humidity control temperature sensor for detecting the temperature of the floating gas on the stored water in the humidity control device is provided, and the water temperature control means is provided for this humidity control temperature. The temperature of the stored water in the humidity controller is adjusted based on the gas temperature detected by the sensor, and the temperature of the floating gas on the stored water is adjusted to a temperature equal to the dew point temperature corresponding to the target absolute humidity. 1. The polymer electrolyte fuel cell according to 1 or 2.