JP5364450B2 - Water treatment device for fuel cell - Google Patents

Description

  The present invention relates to a technology of a water treatment device for a fuel cell using an ion exchange resin.

  A fuel cell requires hydrogen, and in order to produce hydrogen from city gas, natural gas, or the like, water is required in the reforming process, and pure water is used. Pure water is also used for cooling the fuel cell and humidifying the polymer membrane of the polymer electrolyte fuel cell.

  Pure water is usually produced by removing impurity ions using a water treatment apparatus equipped with an ion exchange resin. In addition to the production of pure water from tap water, various techniques for treating condensed water generated by the power generation reaction of the fuel cell and circulating the treated water (pure water) to the fuel cell have been proposed.

  For example, Patent Document 1 discloses a technique for treating carbonate ions and bicarbonate ions (hereinafter referred to as carbonate ions or simply carbonate) in cooling water supplied to a fuel cell with a water treatment device in order to prevent corrosion of the fuel cell. Has been proposed.

JP-A-8-17457

  Here, in order to realize a long-term stable operation of the fuel cell, it is important to remove chloride ions in water supplied to the fuel cell. That is, when water containing chloride ions is supplied to the fuel cell, there is a high risk of corrosion of members used in the fuel cell.

  The objective of this invention is providing the water treatment apparatus for fuel cells which can reduce the chloride ion concentration in the water supplied to a fuel cell effectively.

  The present invention is a water treatment apparatus for a fuel cell using an ion exchange resin, wherein the ion exchange resin includes an anion exchange resin, and chloride ions occupy a total exchange capacity of the anion exchange resin in an initial state. The ratio is set so as to decrease as the concentration of carbonic acid dissolved in the for-treatment water increases and to decrease as the desired chlorine concentration in the for-treatment water decreases.

Further, in the water treatment apparatus for a fuel cell, the anion exchange resin includes a strongly basic anion exchange resin having a trimethylammonium group as an exchange group, and chlorinated in the total exchange capacity of the anion exchange resin in an initial state. It is preferable that the ratio of the product ions is not more than the value obtained by the formula of R _Cl = 4 × C _Cl / CO ₂ ^0.53 . However, _RCl is the ratio (%) of chloride ions (eq / LR) to the total exchange capacity (eq / LR) of the anion exchange resin, and _CCl is the desired chloride ion concentration in the treated water ( ppb) and CO ₂ are CO ₂ concentrations (ppm) obtained by converting carbonic acid dissolved in the water to be treated into CO ₂ .

In the fuel cell water treatment apparatus, the anion exchange resin includes a strongly basic anion exchange resin having a dimethylethanolammonium group as an exchange group, and occupies the total exchange capacity of the anion exchange resin in an initial state. It is preferable that the ratio of chloride ions is not more than the value obtained by the formula of R _Cl = 1.3 × C _Cl / CO ₂ ^0.45 . However, _RCl is the ratio (%) of chloride ions (eq / LR) to the total exchange capacity (eq / LR) of the anion exchange resin, and _CCl is the desired chloride ion concentration in the treated water ( ppb) and CO ₂ are CO ₂ concentrations (ppm) obtained by converting carbonic acid dissolved in the water to be treated into CO ₂ .

  In the water treatment apparatus for a fuel cell, it is preferable that the anion exchange resin in the initial state is a carbonate type by passing carbonate.

  Moreover, in the water treatment apparatus for the fuel cell, it is preferable that the water to be treated be passed through the anion exchange resin in a downward flow.

  Further, in the water treatment apparatus for a fuel cell, the treated water that passes through the anion exchange resin includes condensed water generated by a power generation reaction of the fuel cell, and the treated water is obtained by the anion exchange resin. After being processed, it is preferably reused in the fuel cell.

  ADVANTAGE OF THE INVENTION According to this invention, the water treatment apparatus for fuel cells which can reduce effectively the chloride ion in the water supplied to a fuel cell can be provided.

It is a schematic diagram which shows an example of a structure of the water treatment apparatus of the fuel cell which concerns on this embodiment. It is a diagram showing a relationship between _{R Cl} and _{C Cl} at various CO ₂ concentration in the water to be treated. It is a diagram showing a relationship between _{R Cl} and _{C Cl} at various CO ₂ concentration in the water to be treated.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a water treatment apparatus for a fuel cell according to the present embodiment. The fuel cell water treatment device 10 shown in FIG. 1 includes a cartridge filled with an ion exchange resin. There may be one or more cartridges. The ion exchange resin filled in the cartridge is an anion exchange resin or a mixed bed resin of an anion exchange resin and a cation exchange resin. In addition, the water treatment apparatus 10 of the fuel cell may add a cartridge filled with activated carbon or the like in addition to the cartridge filled with the ion exchange resin.

  The fuel cell water treatment device 10 according to the present embodiment mainly removes impurity ions in water supplied to the fuel cell 12. Examples of water to be treated by the water treatment device 10 of the fuel cell include tap water (city water), pure water, and condensed water generated by the power generation reaction of the fuel cell 12.

  City water such as tap water is supplied to the water treatment device 10 of the fuel cell from the treated water line 14. Further, the condensed water discharged from the fuel cell 12 is temporarily stored in, for example, the condensed water tank 16 and is supplied from the condensed water line 20 to the water treatment device 10 of the fuel cell by the pump 18. And the impurity ion in water is removed by the water treatment apparatus 10 of a fuel cell.

  Examples of impurity ions contained in water include carbonate ions, hydrogen carbonate ions, chloride ions, and sulfate ions. Fuel cell condensate contains a lot of carbonic acid, and removing a small amount of anions (chloride ions, sulfate ions, etc.) from condensate containing a large amount of carbonic acid is a common anion exchange resin. Then it is relatively difficult. In particular, the chloride ion is a monovalent anion, and the adsorption efficiency by the anion exchange resin is poor as compared with a polyvalent anion such as sulfate ion, so it is difficult to reduce the chloride ion in water.

  In the present embodiment, an anion exchange resin is used in which the proportion of chloride ions in the total exchange capacity of the anion exchange resin in the initial state is 10% or less, preferably 1% or less. This makes it possible to effectively reduce chloride ions in water containing a large amount of carbonic acid. When the ratio of chloride ions in the total exchange capacity of the anion exchange resin in the initial state exceeds 10%, the anion exchange resin absorbs impurity ions such as carbonate ions contained in the water instead of chloride ions. Is easily released to the treated water side, and it becomes difficult to effectively reduce chloride ions in the treated water.

When the anion exchange resin includes a strongly basic anion exchange resin having a trimethylammonium group as an exchange group, the ratio of chloride ions to the total exchange capacity of the anion exchange resin in the initial state is expressed by the following formula (1 It is preferable that it is below the value calculated | required by. Thereby, the ratio which discharge | releases a chloride ion to the treated water side in the treated water containing a large amount of carbonic acid falls, and the chloride ion in treated water can be reduced more effectively.
R _Cl = 4 × C _Cl / CO ₂ ^0.53 (1)
R _Cl : Ratio of chloride ion (eq / LR) to the total exchange capacity (eq / LR) of the anion exchange resin (%)
C _Cl : Desired chloride ion concentration in treated water (ppb)
CO ₂ : CO ₂ concentration (ppm) obtained by converting carbonate ions and hydrogen carbonate ions dissolved in the water to be treated into CO ₂

Further, when the anion exchange resin includes a strongly basic anion exchange resin having a dimethylethanolammonium group as an exchange group, the ratio of chloride ions in the total exchange capacity of the anion exchange resin in the initial state is expressed by the following formula: It is preferable that the value is not more than the value obtained by (2). Thereby, the ratio which discharge | releases a chloride ion to the treated water side falls, and the chloride ion in treated water can be reduced more effectively.
R _Cl = 1.3 × C _Cl / CO ₂ ^0.45
R _Cl : Ratio of chloride ion (eq / LR) to the total exchange capacity (eq / LR) of the anion exchange resin (%)
C _Cl : Desired chloride ion concentration in treated water (ppb)
CO _2: CO ₂ concentration of the carbon dioxide which is dissolved in the water to be treated was converted to CO ₂ (ppm)

The above equation (1) is calculated from FIG. 2 showing the relationship between R _Cl and C _Cl at various CO ₂ concentrations in the water to be treated. The above equation (2) is calculated from FIG. 3 showing the relationship between R _Cl and C _Cl at various CO ₂ concentrations in the water to be treated. As can be seen from the above equation, when the desired chloride ion concentration in the treated water is small or the CO ₂ concentration dissolved in the treated water is large, it accounts for the total exchange capacity of the anion exchange resin in the initial state. It is necessary to reduce the ratio of chloride ions.

  Further, anion exchange resins used in water treatment devices for fuel cells have demands for heat resistance, downsizing, etc. in addition to reducing chloride ions. For example, Japanese Patent Application Laid-Open No. 11-204123 discloses an example in which an anion exchange resin having a plurality of hydrocarbon groups is used to improve heat resistance. The publication discloses an example of optimizing the amount of cation exchange resin filled in the mixed bed cartridge in order to reduce the size of the apparatus. Therefore, in the present embodiment, it is preferable to use carbonates such as ammonium bicarbonate that are passed through an anion exchange resin and converted to a carbonate type as an anion exchange resin in an initial state. However, since carbonic acid type anion exchange resin cannot remove carbonic acid, it is desirable to perform decarbonation (decarbonation tower by degassing membrane or air contact) in the latter stage when it is necessary to remove carbonic acid. . The carbonate type anion exchange resin has a small resin volume even with the same exchange capacity as compared with the anion exchange resin such as OH type. That is, the resin volume is reduced by replacing the OH type anion exchange resin with the carbonic acid type. For this reason, the apparatus can be miniaturized. Carbonic acid type anion exchange resins have higher heat resistance than OH type anion exchange resins. Therefore, even when treated water (for example, 40 to 80 ° C.) having a relatively high temperature such as condensed water of a fuel cell is treated, decomposition of the ion exchange resin due to heat is suppressed, and TOC is eluted in the treated water. This can be suppressed.

  In the carbonate type anion exchange resin of the present embodiment, the proportion of chloride ions in the total exchange capacity of the anion exchange resin in the initial state is 10% or less, and the total exchange capacity of the anion exchange resin in the initial state is The proportion of carbonate ions occupied is preferably 70% or more, more preferably 90% or more. In the case of the carbonate type, it is preferable to substitute with bicarbonate ions (bicarbonate ions) instead of carbonate ions. This is because bicarbonate ions are more stable than bicarbonate ions under fuel cell conditions.

  In the water treatment apparatus 10 of the fuel cell according to the present embodiment, it is preferable that water to be treated (for example, tap water, condensed water, etc.) is passed through the anion exchange resin described above in a downward flow. The anion exchange resin filled in the cartridge is consolidated by the downward flow of the water to be treated. As a result, the water to be treated can flow uniformly in the resin and improve the treatment performance.

As described above, treated water (pure water) in which the concentration of impurity ions, particularly chloride ions, is reduced by the water treatment device 10 for a fuel cell according to this embodiment is supplied from the treated water line 22 to the fuel cell 12. . Here, the fuel cell 12 is a solid oxide fuel cell, and in this example, the supplied water reforms city gas or the like into carbon monoxide (CO) and hydrogen gas (H ₂ ). Used for

  In the water treatment apparatus 10 for a fuel cell according to the present embodiment, even if the water contains a large amount of carbonic acid, such as condensed water discharged from a solid oxide fuel cell, a small amount of chloride present in the water. Ions can be effectively removed. Therefore, the condensed water generated by the power generation reaction of the solid oxide fuel cell is processed by the water treatment device 10 of the fuel cell of the present embodiment, and the treated water is supplied to the solid oxide fuel cell and reused. However, stable fuel cell operation is possible over the long term. Further, when the condensed water is circulated and used, tap water or pure water may be supplied at the initial stage of operation of the fuel cell. When the condensed water is circulated and used, it is preferable to discharge the gas contained in the condensed water to the atmosphere, then treat it with the water treatment device 10 and supply it to the fuel cell.

  Note that SUS304, which is one of the general-purpose materials, is known to cause stress corrosion cracking depending on conditions even in the case of ppm level of chloride ions. It is necessary to reduce the chloride ion in water to 100 ppb or less, preferably 50 ppb or less, more preferably 10 ppb or less.

  In the solid oxide fuel cell, fuel gas (for example, city gas) and air (containing oxygen) are supplied to the (solid oxide type) fuel cell 12 from the fuel supply line 24 and the air supply line 26, respectively. Hydrogen gas or carbon monoxide obtained by the fuel reforming reaction reacts with oxygen to generate power. In such a solid oxide fuel cell, since power generation is performed at a high temperature of 600 to 1000 ° C., for example, the heat exchanger 28 heat-exchanges the generated exhaust heat with condensed water and tap water to generate hot water. It is preferable to supply.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

(Examples 1 and 2)
The apparatus shown in FIG. 1 was used to treat the condensed water discharged from the solid oxide fuel cell. The concentration of CO ₂ dissolved in the condensed water was about 250 ppm, and the chloride ion concentration was about 150 ppb. As the ion exchange resin filled in the cartridge, a mixed bed resin of 30 mL of a strongly basic anion exchange resin having a trimethylammonium group as an exchange group and 10 mL of a strongly acidic cation exchange resin was used. The anion exchange resin of Example 1 was converted into an OH type by passing 1500 mL of a 7% NaOH aqueous solution through a strong basic anion exchange resin of the chlorine type (Rohm and Haas, Amberjet 4002C1). The ratio of chloride ions to the total exchange capacity of the ion exchange resin (hereinafter sometimes simply referred to as R _Cl ) is 1% or less. The anion exchange resin of Example 2 is a mixture of the anion exchange resin of Example 1 and an anion exchange resin that has not been converted to OH type, so that _RCl is 10%. The cation exchange resins of Examples 1 and 2 are hydrogen type Amberjet 1024H (Rohm and Haas).

  In both Examples 1 and 2, the water to be treated was passed through the ion exchange resin in a downward flow. Then, after 24 hours of operation, the treated water treated with the ion exchange resin was sampled and the chloride ion concentration was measured. The results are summarized in Table 1.

(Comparative Example 1)
Comparative Example 1 was the same as Example 1 except that the _RCl of the anion exchange resin used was 20%.

As can be seen from Table 1, it was possible to reduce the chloride ion concentration in Example 2 was used R _Cl 10% anion exchange resin to less 50 ppb. Further, in Example 1 using an anion exchange resin having an R _Cl content of 1% or less, the chloride ion concentration could be reduced to less than 10 ppb, and higher chloride ion removal performance than in Example 2 was exhibited. On the other hand, in Comparative Example 1 R _Cl was used 20% of the anion-exchange resin, the chloride ion concentration is 110Ppb, could not be adequately remove chloride ions.

If the CO ₂ concentration of treated water is 250 ppm and the chloride ion concentration of treated water is 50 ppb in the formula of R _Cl = 4 × C _Cl / CO ₂ ^0.53 , R _Cl becomes 10.7%. That is, in order to treat the water to be treated having a CO ₂ concentration of 250 ppm so that the chloride ion concentration in the treated water is 50 ppb or less, the ratio of chloride ions to the total exchange capacity of the anion exchange resin is 10. It is necessary to make it 7% or less. The first and second embodiments satisfy that the value is not more than the value calculated from the above formula. If the chloride ion concentration in the treated water can be reduced to 50 ppb or less, the fuel cell can be stably operated over a long period of time.

(Examples 3 and 4)
The apparatus shown in FIG. 1 was used to treat the condensed water discharged from the solid oxide fuel cell. The concentration of CO ₂ dissolved in the condensed water was about 250 ppm, and the chloride ion concentration was about 150 ppb. As the ion exchange resin filled in the cartridge, a mixed bed resin of 30 mL of strongly basic anion exchange resin having dimethylethanolammonium group as an exchange group and 10 mL of strongly acidic cation exchange resin was used. The anion exchange resin of Example 3 was passed through 1500 mL of a 7% NaOH aqueous solution through a chlorine-type strongly basic anion exchange resin (Amberlite IRA410Cl, manufactured by Rohm and Haas) to convert it to OH type, and R _Cl is 1% or less. The anion exchange resin of Example 4 is a mixture of the anion exchange resin of Example 3 and an anion exchange resin that has not been converted to OH type, so that _RCl is 5%. The cation exchange resin of Examples 3 and 4 is H-type Amberjet 1024H (Rohm and Haas).

  In both Examples 3 and 4, the water to be treated was passed through the ion exchange resin in a downward flow. Then, after 24 hours of operation, the treated water treated with the ion exchange resin was sampled and the chloride ion concentration was measured. The results are summarized in Table 2.

(Comparative Example 2)
Comparative Example 2 was the same as Example 3 except that the _RCl of the anion exchange resin used was 20%.

As can be seen from Table 2, it was possible to reduce the chloride ion concentration in Example 4 using R _Cl 5% anion exchange resin to less 50 ppb. Further, in Example 3 using an anion exchange resin having an _RCl of 1% or less, the chloride ion concentration could be reduced to less than 10 ppb, and the chloride ion removal performance higher than that in Example 4 was exhibited. On the other hand, in Comparative Example 2 R _Cl was used 20% of the anion-exchange resin, the chloride ion concentration is 210Ppb, it could not be almost remove chloride ions.

If the CO ₂ concentration of the treated water is 250 ppm and the chloride ion concentration of 50 ppb in the treated water is applied to the formula of R _Cl = 1.3 × C _Cl / CO ₂ ^0.45 , R _Cl becomes 5.4%. That is, in order to treat the water to be treated having a CO ₂ concentration of 250 ppm so that the chloride ion concentration in the treated water is 50 ppb or less, the ratio of chloride ions to the total exchange capacity of the anion exchange resin is 5. It must be 4% or less. And the said Example 3, 4 is satisfying that it is below the value computed from said formula.

(Examples 5 and 6)
The apparatus shown in FIG. 1 was used to treat the condensed water discharged from the solid oxide fuel cell. As the ion exchange resin filled in the cartridge, a strongly basic anion exchange resin having a trimethylammonium group equivalent to 0.13 eq as an exchange group was used. The anion exchange resins of Examples 5 and 6 were prepared by adding 4 L of ammonium bicarbonate (sodium bicarbonate NaHCO ₃ ) (1 normal) to OH type strongly basic anion exchange resin (Rohm and Haas, Amberjet 4002OH). The ratio of chloride ions occupying the total exchange capacity of the anion exchange resin (R _Cl ) is 1% or less, and the ratio of carbonate ions (hereinafter sometimes simply referred to as R-carbonic acid) is 90% or more. 70%.

  Condensed water (about 60 ° C.) generated in a solid oxide fuel cell having a power generation amount of 1 kW was supplied to the water treatment apparatuses of Examples 5 and 6 and operated for 24 hours. The water to be treated was passed through the ion exchange resin in a downward flow. Table 3 summarizes the results of measuring the volume of the ion exchange resins of Examples 5 and 6 and the TOC concentration in the treated water.

(Comparative Example 3)
Comparative Example 3 was the same as Example 5 except that the R-carbonic acid of the anion exchange resin used was less than 1%.

  As can be seen from Table 3, by making the ion exchange resin into a carbonate type as in Examples 5 and 6, the resin volume can be reduced without impairing the ion exchange capacity compared to the OH type ion exchange resin of Comparative Example 3. I was able to. In particular, in Example 5 in which R-carbonic acid was 90% or more, the resin volume was reduced by 20% compared to Comparative Example 3. In addition, even when the carbonic acid ion exchange resin of Examples 5 and 6 was treated by passing condensed water at 60 ° C., the TOC in the treated water was 0.1 ppm or less, and the resin was decomposed by heat. It was found to be suppressed. On the other hand, when condensed water of 60 ° C. was passed through the OH-type ion exchange resin of Comparative Example 3 and treated, 0.5 ppm of TOC was detected in the treated water, and the resin due to heat was decomposed. It is considered a thing.

  Thus, by making the anion exchange resin in the initial state carbonic acid type in advance, the installation space of the apparatus can be reduced, decomposition of the resin due to heat can be suppressed, and elution of TOC can be reduced.

(Example 7)
Example 7 was the same as Example 1 except that the flow direction of the water to be treated to the ion exchange resin was an upward flow. And the treated water processed with the ion exchange resin was sampled, and the chloride ion concentration was measured. The results are summarized in Table 4 (for comparison, the results of Example 1 are also listed in Table 4).

  In Example 7 in which the water flow direction of the water to be treated was an upward flow, the resin was not consolidated and a slight flow was observed. Therefore, in Example 7, a short circuit flow occurred, and the chloride ion concentration in the treated water slightly increased compared to Example 1 which was a downward flow. Therefore, it is preferable to perform the water treatment in a downward flow as in the first embodiment.

  DESCRIPTION OF SYMBOLS 10 Water treatment apparatus, 12 Fuel cell, 14 To-be-treated water line, 16 Condensed water tank, 18 Pump, 20 Condensed water line, 22 Treated water line, 24 Fuel supply line, 26 Air supply line, 28 Heat exchanger.

Claims (6)

A water treatment apparatus for a fuel cell using an ion exchange resin, wherein the ion exchange resin includes an anion exchange resin, and a ratio of chloride ions to a total exchange capacity of the anion exchange resin in an initial state is A water treatment apparatus for a fuel cell, wherein the water treatment device is reduced in proportion to an inverse proportion according to the concentration of CO ₂ dissolved in the treated water and proportional to a desired chlorine concentration in the treated water. A water treatment device for a fuel cell according to claim 1 Symbol placement, the anion exchange resin comprises a strong basic anion exchange resin to exchange group trimethylammonium group, the anion exchange resin in the initial state all A water treatment apparatus for a fuel cell, characterized in that the ratio of chloride ions in the exchange capacity is not more than the value (R _Cl ) obtained by the following formula (1).
R _Cl = 4 × C _Cl / CO ₂ ^0.53 (1)
(Where R _Cl is the ratio (%) of chloride ions (eq / LR) to the total exchange capacity (eq / LR) of the anion exchange resin, and C _Cl is the desired chloride ion concentration in the treated water. (Ppb), CO ₂ is the CO ₂ concentration (ppm) dissolved in the water to be treated. A water treatment device for a fuel cell according to claim 1 Symbol placement, a water treatment device for a fuel cell using an anion exchange resin, the anion exchange resin to exchange groups dimethylethanolammonium groups strong bases The ratio of chloride ions in the total exchange capacity of the anion exchange resin in the initial state is not more than the value (R _Cl ) obtained by the following formula (2). Fuel cell water treatment device.
R _Cl = 1.3 × C _Cl / CO ₂ ^0.45 (2)
(Where R _Cl is the ratio (%) of chloride ions (eq / LR) to the total exchange capacity (eq / LR) of the anion exchange resin, and C _Cl is the desired chloride ion concentration in the treated water. (Ppb), CO ₂ is the CO ₂ concentration (ppm) dissolved in the water to be treated. The water treatment apparatus for a fuel cell according to any one of claims 1 to 3 , wherein the anion exchange resin in the initial state is converted to a carbonate type by passing carbonate. A fuel cell water treatment device. The fuel cell water treatment device according to any one of claims 1 to 4 , wherein the water to be treated is passed through the anion exchange resin in a downward flow. Water treatment equipment. The water treatment device for a fuel cell according to any one of claims 1 to 5 , wherein the water to be treated that is passed through the anion exchange resin includes condensed water generated by a power generation reaction of the fuel cell. The water treatment apparatus for a fuel cell, wherein the water to be treated is treated with the anion exchange resin and then reused in the fuel cell.

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