JP2000333307A - Fuel storage device of electric car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate formic acid that causes the corrosion of a fuel container and the deterioration of reforming equipment by equipping an ion exchange resin in a fuel tank accommodating methanol. SOLUTION: An ion exchange resin cartridge 6 is provided in a fuel container 1 for storing methanol while the cartridge 6 is dipped into the methanol, and at the same time an ion exchange resin column 7 is provided in a circulation channel pipe 4. Also, a conductivity sensor 8 for detecting the conductivity of fluid in the container is provided through one side wall surface of the fuel container 1, and a measurement value is inputted to a judgment control part 9. The judgment control part 9 controls a circulation pump 5 based on a judgment result. In normal operation, formic acid being generated by passing the fuel in the fuel container 1 through the circulation channel pipe 4 and the ion exchange resin column 7 by a circulation pump 5 is eliminated. For example, in the case of a methanol concentration of 50 vol.%, a methanol quantity of 50 ml, a formic acid concentration of 0.005 wt.%, 0.001 wt.%, and 0.03 wt.%, and an ion exchange resin quantity of 20 ml, the formic acid is eliminated by one filtering (approximately 1 minute) and the conductivity decreases to a pure water level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel storage device for an electric vehicle equipped with a fuel cell using methanol as a power source.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a fuel cell having excellent characteristics with little noise and exhaust gas as a power source for an electric vehicle. As fuel for this fuel cell,
Because of the need to supply hydrogen, coal, natural gas,
Alcohols and the like are used as a source of hydrogen. In particular, among alcohols, methanol has a larger number of hydrogen atoms relative to the number of carbon atoms in the molecule than other hydrocarbons, and is an excellent source of hydrogen. In addition, when mounted on an automobile, methanol that can be used as a liquid at room temperature is advantageous in terms of ease of handling.

[0003] For the above reasons, the use of methanol as a fuel for fuel cells of automobiles has been studied. In this case, it is necessary to store methanol in the fuel container, but the methanol is oxidized by oxygen in the air to produce formaldehyde and formic acid. Formic acid has a strong corrosive property among organic acids, and accordingly, the generation of formic acid may cause corrosion of the fuel container and the fuel passage during storage of the fuel.

Therefore, as a measure for preventing corrosion of the fuel container and the fuel flow path, the inner surface of the fuel container is subjected to a surface treatment such as plating or painting to improve corrosion resistance.

[0005]

However, in the case of a corrosion-resistant film produced by surface treatment, if the surface treatment is incomplete and a defect is present from the beginning, corrosion occurs from that point and a hole is formed in the fuel container. This may cause fuel to leak from this hole. In addition, even when the surface-treated portion is damaged due to some physical or chemical damage during manufacturing or processing, the underlying metal may be exposed and corrosion may progress.

[0006] Similarly, as a method of improving the corrosion resistance of a fuel container, use of a corrosion-resistant material for the container can be cited, but the corrosion-resistant material is generally expensive, which leads to an increase in cost.

The present invention provides a fuel storage device for an electric vehicle which can solve the above-mentioned problems and can reduce the corrosion of the fuel container without taking measures to improve the corrosion resistance by changing the material of the material or taking a surface treatment. The purpose is to do.

[0008]

In order to achieve the above object, the present invention provides an ion exchange resin for removing formic acid generated by the oxidation of methanol in a fuel container.

In addition, an ion exchange resin for positively adding a corrosion inhibitor to the fuel to enhance the corrosion inhibitory effect and removing the corrosion inhibitor and formic acid in a fuel supply passage from the fuel container to the reformer. Is provided.

Next, a fuel storage device for an electric vehicle according to the present invention will be described in detail.

When methanol is used as fuel for a fuel cell, it is mixed with water and supplied to a reformer to generate hydrogen by the following reforming reaction.

CH ₃ OH + H ₂ O = CO ₂ + 3H ₂ Methanol stored in the fuel container is oxidized by oxygen contained in the air in the container and converted into formic acid via formaldehyde. The corrosiveness of methanol to metals is mainly due to the dissociation of formic acid, which is an oxidation product, in water,
This is because it acts as an acid.

However, since formic acid is an ionic substance,
It can be removed by ion exchange resin.

When formic acid is removed by an ion exchange resin, a solution containing formic acid must pass through the ion exchange resin. Even in the stationary state, formic acid can be removed by installing ion-exchange resin in a part of the fuel container because natural convection may cause circulation in the fuel in the fuel container. It is.

Further, by providing a means for circulating the fuel, it is possible to circulate the fuel in the fuel container and increase the amount of liquid passing through the ion exchange resin, thereby improving the formic acid removal efficiency. Further, by installing a circulation channel having a column filled with an ion exchange resin and circulating the fuel, the removal efficiency is further improved.

The fuel circulation by the circulation means is desirably performed only when the formic acid concentration in the fuel is high, from the viewpoint of reducing excess energy consumption and extending the life of the circulation means. Therefore, a sensor for detecting the production of formic acid is provided in the fuel container to monitor the formic acid concentration and determine the start and stop of the circulation based on the measured value.

Regarding the physical property values to be measured, it is possible to use a conductivity sensor by utilizing the fact that formic acid is an ionic substance and the conductivity increases with the generation of formic acid. The conductivity sensor has a relatively simple structure and can be expected as an inexpensive and robust sensor. In addition, since formic acid exhibits properties as an acid, it is possible to detect the formation of formic acid also by a change in pH value. Then, it is also possible to apply a pH sensor. The pH sensor can be expected to detect the presence of formic acid with higher sensitivity than the conductivity sensor.

According to the above method, the formic acid concentration in the fuel container can be maintained at a level that does not affect the material of the container and piping.

However, when used as fuel for a fuel cell, it is converted to hydrogen by a reformer before being supplied to the fuel cell body. At this time, if formic acid is mixed as an impurity into the fuel supplied to the reformer, it causes troubles such as a decrease in reforming efficiency and deterioration of the catalyst metal. Therefore, by providing the ion exchange resin in the fuel supply flow path from the fuel container to the reformer, it is possible to prevent formic acid from reaching the reformer.

The above method is a method based on a policy of removing generated formic acid with an ion exchange resin. However, a corrosion inhibitor is added to the fuel during storage so that the corrosion of the fuel container can be prevented even when formic acid is generated. A suppression method is also possible.

In this case, when the fuel to which the corrosion inhibitor is added is supplied to the reformer as it is, there is a possibility that problems such as a decrease in the reforming efficiency and a deterioration of the catalytic metal occur as in the case where formic acid is mixed. high. Therefore, an ion exchange resin is provided in the fuel supply flow path from the fuel container to the reformer to remove the corrosion inhibitor and formic acid.

Also in the case of adding a corrosion inhibitor, it is desirable that the addition amount be as small as possible from the viewpoint of economy. for that reason,
In the same manner as determining the start and stop of circulation to the ion exchange resin column, the determination and adjustment of the availability and the amount of addition of the corrosion inhibitor are performed based on the conductivity and the pH. At this time,
Regarding the selection of a corrosion inhibitor, when the target metal is iron or aluminum, the anticorrosive effect of sodium silicate is large, and it is promising for corrosion inhibition. Sodium silicate has little effect on the human body, and is also advantageous in terms of environmental problems.

Further, the anticorrosive effect of sodium silicate is p
It is effective in the range of H10 or more. Therefore, by measuring the pH of the fuel with a pH sensor and adding sodium silicate based on the result to control the pH to 10 or more, the corrosiveness of the fuel can always be kept low.

In the above method, the ion exchange resin is provided in the fuel container, in the circulation channel connected to the fuel container, or in the fuel supply channel to the reformer. The ion exchange capacity of the ion exchange resin decreases with use time. The ion exchange resin having the reduced exchange capacity can be reused by performing a regeneration treatment.

However, it is difficult to regenerate in a vehicle, because an acid and an alkali aqueous solution are used for the regenerating, which may damage the fuel container and the piping. Therefore, the ion exchange resin is taken out and regenerated. At this time, by storing the ion exchange resin in a cartridge that can be taken out from the outside,
Workability is significantly improved.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a first embodiment of a fuel storage device for an electric vehicle according to the present invention.

In FIG. 1, reference numeral 1 denotes a fuel container for storing methanol, and a fuel supply port 2 is provided on an upper surface of the fuel container 1.
A fuel supply pipe 3 for supplying fuel to a reformer (not shown) is connected to a front wall surface. A circulation flow pipe 4 for circulating methanol in the fuel container is connected to a rear wall surface of the fuel container 1, and a circulation pump 5 is provided in the middle of the pipe.

In an electric vehicle equipped with a fuel cell having such a configuration, an ion exchange resin cartridge 6 is provided in a fuel container 1 for storing methanol by immersing the cartridge in methanol, and an ion exchange resin cartridge 6 is A resin column 7 is provided.

Further, a conductivity sensor 8 for detecting the conductivity of the liquid in the container by penetrating one side wall of the fuel container 1 is provided, and the measured value of the conductivity of the liquid detected by the conductivity sensor 8 is provided. Is input to the determination control unit 9.

The determination control section 9 controls the circulation pump 5 based on the determination result of the measured value of the conductivity.

Next, the operation of the fuel storage device for an electric vehicle configured as described above will be described.

During normal operation, the fuel in the fuel container 1 is circulated by the circulation pump 5 to the circulation flow path pipe 4 and the ion exchange resin column 7.
To remove generated formic acid.

FIGS. 2 and 3 show changes in conductivity and pH when a 50 vol% methanol aqueous solution containing formic acid was filtered through a column filled with an ion exchange resin. Here, the test conditions are as follows.

Methanol concentration: 50 vol% Methanol amount: 50 ml Formic acid concentration: 0.005 wt%, 0.01 wt%, 0.03 wt% Ion exchange resin: Mixing cation exchange resin and anion exchange resin in equal amounts of ion exchange capacity Ion exchange resin In this case, the contact time with the ion exchange resin required for one filtration is about 1 minute, but the conductivity is almost lowered to the level of pure water (1 μS / cm). It can be seen that formic acid has been removed. When the added formic acid concentration is low, the pH is 6 or more in two contacts,
It is almost neutral. Even if the initial addition amount is large,
Further, by repeating the contact, formic acid can be removed up to the neutral region.

It is more efficient to carry out the above-mentioned circulation of the fuel only when the formic acid concentration in the fuel is higher than the concentration of concern. Therefore, the conductivity of the fuel is monitored by the conductivity sensor 8, and a start or stop command for the operation of the circulation pump 5 is issued to the circulation pump 5 by the judgment control unit 9 based on the result, thereby reducing unnecessary circulation operation. .

Here, instead of the conductivity sensor 8, p
It is also possible to use an H sensor. In this case, the start and stop of the circulation operation are determined based on the monitored pH value.

The above-described fuel circulation can be performed when the vehicle is operating, but cannot be performed when the operation is stopped. It is also conceivable that the vehicle is left unattended for a long time with the fuel installed.

In such a case, formic acid is removed by the ion exchange resin cartridge 6 in the fuel container 1. In order to examine the effect of formic acid removal of the fuel containing formic acid by the ion-exchange resin in the state of standing in this way, the ion-exchange resin was put in an aqueous methanol solution to which formic acid was added, and the conductivity and the pH of the standing state were measured. The changes were examined.

FIG. 4 and FIG. 5 show the results. Here, the test conditions are as follows.

Methanol concentration: 50 vol% Methanol amount: 50 ml Formic acid concentration: 0.01 wt% Ion exchange resin: Mixing cation exchange resin and anion exchange resin in equal amounts of ion exchange capacity Ion exchange resin amount: 20 ml It is possible to remove formic acid without circulating fuel.

FIG. 6 is a side view showing a second embodiment of the fuel storage device for an electric vehicle according to the present invention.

In FIG. 6, reference numeral 1 denotes a fuel container for storing methanol, and a fuel supply port 2 is provided on the upper surface of the fuel container 1.
A fuel supply pipe 3 for supplying fuel to the reformer 15 is connected to a front lower wall surface, and a fuel supply pump 14 is provided in the middle thereof.

A corrosion inhibitor adding device 10 is provided at the rear of such a fuel container 1, and its supply pipe is disposed so as to penetrate the wall of the container. A pH sensor 11 for measuring a liquid pH is provided, and a pH value measured by the pH sensor 11 is input to a determination control unit 12.

The determination control unit 12 controls the amount of the corrosion inhibitor supplied into the fuel container 1 based on the pH value measured by the pH sensor 11.

In the fuel storage device for an electric vehicle having such a structure, the corrosion inhibitor adding device 10 adds sodium silicate as a corrosion inhibitor to the fuel in the fuel container 1 based on the pH value measured by the pH sensor 11. As a result of studying fuel containers made of iron or aluminum by adding iron, sodium silicate showed an excellent corrosion inhibiting effect.

FIG. 7 shows the results of an iron corrosion test in a solution obtained by adding sodium silicate as a corrosion inhibitor to a methanol aqueous solution containing formic acid. here,
The test conditions are as follows.

Methanol concentration: 50 vol% Formic acid concentration: 0.1 wt% Target metal: iron Even when formic acid having a high concentration of 0.1 wt% is contained, by adding a certain amount or more of sodium silicate, It can be seen that the occurrence of corrosion can be suppressed.

It is considered that the actual fuel does not always contain a high concentration of formic acid from the beginning, but that formic acid is gradually generated and the concentration increases.

FIG. 8 shows the results of an iron corrosion test in a solution obtained by adding various concentrations of formic acid to a 50 vol% methanol aqueous solution containing 0.1 wt% of sodium silicate.

As described above, the addition of formic acid increases the corrosivity, and the change due to the corrosion of the sample and the test solution is increased. Attention is paid to the change in pH at this time. At 10 or less, the occurrence of corrosion is remarkable, while at 10 or more, the corrosion of iron is suppressed.

Therefore, the pH of the fuel is detected by the pH sensor 11.
Is monitored, and the pH value is monitored by instructing the corrosion inhibitor adding apparatus 10 to add sodium silicate by the judgment control unit 12 based on the result.
By adding sodium silicate as described above, it is possible to prevent the occurrence of corrosion and to prevent the addition of excessive sodium silicate.

On the other hand, if the fuel containing sodium silicate is supplied to the reformer 15 as it is, it causes a reduction in the reforming efficiency and a deterioration of the catalyst metal. Since sodium silicate is an ionic substance,
Removal is possible. Therefore, when fuel is supplied to the reformer 15 through the fuel supply pipe 3 by the fuel supply pump 14, the ion exchange resin column 13 is provided in the fuel supply pipe 3, so that sodium silicate can be removed. .

FIGS. 9 and 10 show the conductivity and the conductivity when a 50 vol% methanol aqueous solution to which sodium silicate was added was filtered through a column filled with the ion exchange resin in order to examine the sodium silicate removal performance by the ion exchange resin. Shows the change in pH. Here, the test conditions are as follows.

Methanol concentration: 50 vol% Methanol amount: 50 ml Sodium silicate concentration: 0.05 wt%, 0.1 wt%, 0.3 wt% Ion exchange resin: Mixing cation exchange resin and anion exchange resin in equal amounts of ion exchange capacity Exchange resin amount: 20 ml Thus, sodium silicate was almost completely removed by two filtrations. Therefore, even if sodium silicate is added to the fuel, the influence on the reformer 15 can be removed by the ion exchange resin.

When actually applied, the contact time with the ion exchange resin before flowing into the reformer 15 is also important.
Therefore, the shape of the ion exchange resin column needs to be considered in advance.

[0056]

As described above, according to the fuel storage device for an electric vehicle according to the present invention, when methanol as a fuel is stored in the fuel container, corrosion of the fuel container and the fuel flow pipe and deterioration of the reformer occur. With regard to the above, it is possible to remove formic acid which causes corrosion of a fuel container, which is an oxidation product of methanol, and causes deterioration of a reformer by using an ion exchange resin.

Further, even if a corrosion inhibitor is added to the fuel stored in the fuel container and the corrosion inhibitor is removed by an ion exchange resin before the fuel is supplied to the reformer, corrosion or reforming of the fuel container may be performed. It is possible to suppress the deterioration of the container.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a fuel storage device for an electric vehicle according to the present invention.
FIG. 2 is a plan view showing the embodiment.

FIG. 2 is a diagram showing a change in conductivity when a methanol aqueous solution containing formic acid is passed through an ion exchange resin in the embodiment.

FIG. 3 is a diagram showing a change in pH when a methanol aqueous solution containing formic acid is passed through an ion exchange resin.

FIG. 4 is a diagram showing a change in conductivity when an ion-exchange resin is placed in a methanol aqueous solution containing formic acid and allowed to stand.

FIG. 5 is a diagram showing a change in pH when an ion exchange resin is put in a methanol aqueous solution containing formic acid and allowed to stand still.

FIG. 6 shows a second embodiment of the fuel storage device for an electric vehicle according to the present invention.
The side view which shows embodiment of FIG.

FIG. 7 is a diagram showing the results of an iron corrosion test in a solution obtained by adding sodium silicate as a corrosion inhibitor to a methanol aqueous solution to which formic acid is added in the embodiment.

FIG. 8: 50% with addition of 0.1 wt% sodium silicate
The figure which shows the result of the corrosion test of iron in the solution which added various concentrations of formic acid to the aqueous solution of vol% methanol.

FIG. 9 is a diagram showing a change in conductivity when an aqueous methanol solution to which sodium silicate is added is passed through an ion exchange resin in the embodiment.

FIG. 10 is a graph showing a change in pH when an aqueous methanol solution to which sodium silicate is added is passed through an ion exchange resin.

[Explanation of symbols]

 1: fuel container 2: fuel supply port 3: fuel supply pipe 4: circulation channel pipe 5: circulation pump 6: ion exchange resin cartridge 7, 13: ion exchange resin column 8: conductivity sensor 9, 12: judgment control unit 10: Corrosion inhibitor addition device 11: pH sensor 14: Fuel supply pump 15: Reformer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10L 1/02 C10L 1/02 5H115 // H01M 8/06 H01M 8/06 A (72) Inventor Satoshi Haraguchi No. 1, Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu plant, Toshiba Corporation (72) Inventor Sadao Ida No. 1, Toshiba-cho, Fuchu-shi, Fuchu-shi, Tokyo Inside the Fuchu plant, Toshiba Corporation (72) 2-4 cho-cho F-term in Toshiba Keihin Plant (reference) 3D038 CA06 CB01 CC06 3E062 AA06 AB03 BA20 BB05 BB09 KA09 KC01 4H006 AA02 AD32 DA66 FE11 4H013 BA01 5H027 BA01 BA16 5H115 PG04 PI18 PI29 TO30

Claims (10)

[Claims] 1. A fuel storage device for an electric vehicle equipped with a fuel cell as a power source, wherein an ion exchange resin is provided in a fuel container containing methanol. 2. The fuel storage device for an electric vehicle according to claim 1, wherein a circulation flow path for circulating methanol in the fuel container is formed, and an ion exchange resin column filled with the ion exchange resin in the circulation flow path is provided. And a fuel circulation pump for supplying methanol in the fuel container to a circulation flow path. 3. The fuel storage device for an electric vehicle according to claim 2, wherein a conductivity sensor for detecting the formation of formic acid due to oxidation of methanol in the fuel container, and the fuel based on a measurement value of the conductivity sensor. A fuel storage device for an electric vehicle, comprising a control means for instructing a circulation pump to start or stop a methanol circulation operation. 4. The fuel storage device for an electric vehicle according to claim 2, wherein a pH sensor for detecting generation of formic acid due to oxidation of methanol in the fuel container, and the fuel circulation pump based on a measured value of the pH sensor. A fuel storage device for an electric vehicle, further comprising control means for instructing start or stop of the methanol circulation operation. 5. The electric vehicle fuel storage device according to claim 1, wherein an ion exchange resin is provided in a fuel supply passage from the fuel container to the reformer. Fuel storage device. 6. A fuel storage device for an electric vehicle equipped with a fuel cell as a power source, wherein a corrosion inhibitor adding device for adding a corrosion inhibitor to methanol in a fuel container is provided, and a fuel inhibitor is supplied from the fuel container to the reformer. A fuel storage device for an electric vehicle, characterized in that an ion exchange resin is provided in the fuel supply flow path of (1). 7. The fuel storage device for an electric vehicle according to claim 6, wherein a pH sensor for detecting a corrosion inhibiting effect of ethanol in the fuel container is detected, and a corrosion value is measured from the measured value of the pH sensor. Control means for determining the addition amount of the inhibitor and controlling the addition amount of the corrosion inhibitor supplied into the fuel container from the corrosion inhibitor adding device. . 8. The fuel storage device for an electric vehicle according to claim 6, wherein sodium silicate is used as a corrosion inhibitor to be added. 9. The fuel storage device for an electric vehicle according to claim 8, wherein the range of the pH value to be controlled is 10 or more. 10. The fuel storage device for an electric vehicle according to claim 1, wherein the ion exchange resin is housed in an externally replaceable cartridge. .