JP2006147194A - Waste liquid disposal method, waste liquid disposal device, and hydrogen generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain an increase in the size of a vessel for containing waste a liquid through by restraining a degree of the increase of the waste liquid caused by a neutralizing agent, in performing the neutralization treatment of the waste liquid after an alkaline water solution of, that is, a hydrogenated complex compound of boron is used for a fuel cell or for the generation of hydrogen. <P>SOLUTION: There is used for an alkaline water solution a solid organic acid whose pH is 3 or less when formed into a saturated solution, which is for example, a powdery citric acid, a tartaric acid, and an acetic acid. The waste liquid disposal device or the hydrogen generator is so constituted that the neutralizing agent is stored in a manner isolated from a container containing the waste liquid, and the neutralization agent and the waste liquid are mixed when the isolation is released. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a waste liquid treatment method, a waste liquid treatment apparatus, and a used alkaline aqueous solution for neutralizing a waste aqueous solution that is a waste liquid after using an alkaline aqueous solution of a borohydride complex compound for fuel cell or hydrogen generation. The present invention relates to a hydrogen generator that can be used.

  Metal hydride complex compounds such as tetrahydroborate such as sodium borohydride (NaBH4) are stable in an alkaline aqueous solution such as sodium hydroxide (NaOH), and therefore, borohydride fuel cells (hereinafter referred to as fuel cells). (See, for example, Patent Document 1), or as a liquid hydrogen generator for generating hydrogen by contacting the catalyst body (see, for example, Patent Document 2). .) As this type of fuel cell or hydrogen generator, a small and easy-to-use one is required. For fuel cells, the fuel liquid is usually circulated between the fuel cell main body and the container outside the fuel cell, but the waste liquid that has become unusable due to the reaction is collected in the container, and a container containing new fuel liquid. To be exchanged. As for the hydrogen generator, a compact disposable hydrogen generator in which a storage part for storing an alkaline aqueous solution and a catalyst body storage part are combined has been studied.

  By the way, an alkaline aqueous solution, which is a waste liquid discharged from a fuel cell using an alkaline aqueous solution of borohydride complex as a fuel, and an alkaline aqueous solution of borohydride complex compound were brought into contact with the catalyst body to generate hydrogen by a hydrolysis reaction. The later waste liquid composed of alkaline aqueous solution is a hazardous substance, requires care in handling and storage, and is subject to the regulations of poisonous and deleterious substances in its disposal as waste. Therefore, these alkaline aqueous solutions are generally neutralized with a neutralizing solution such as hydrochloric acid and sulfuric acid and discarded.

  However, neutralization with a neutralizing solution such as hydrochloric acid and sulfuric acid requires that the neutralizing solution be added at a considerably high ratio to the used alkaline aqueous solution, which increases the amount of neutralized waste liquid. . For this reason, since the above-mentioned container which stores the fuel of a fuel cell will enlarge, miniaturization of a fuel cell (what consists of a fuel cell main part and a fuel cell circulation system) will be prevented. In addition, the disposable hydrogen generator must be designed in consideration of the injection amount of the neutralization solution as the volume of the storage portion for storing the alkaline aqueous solution of the borohydride complex compound. And not only in the problem in such equipment, but also in the case where, for example, the waste liquid in the container and the storage unit is separately transferred to a storage container and neutralized for example, the amount of waste liquid after neutralization increases. The storage container becomes large, requires a large installation space, and is inconvenient in handling such as movement. The above problems are derived from the high injection ratio of the neutralization solution to the waste solution. Furthermore, neutralization solutions such as hydrochloric acid and sulfuric acid have the disadvantage that they are inconvenient to handle because they tend to spill.

JP 2002-246039 (Claim 1, Claim 2, Paragraphs 0025 to 0029) JP2001-19401 (paragraph 0005, paragraph 0015, paragraphs 0025-0026)

  The present invention has been made in view of such circumstances, and its purpose is, for example, in neutralizing the waste liquid after using an alkaline aqueous solution of a borohydride complex compound in a fuel cell or a hydrogen generator. An object of the present invention is to provide a waste liquid treatment method and a waste liquid treatment apparatus that are easy to handle and have a small degree of increase in waste liquid due to neutralization. Another object of the present invention is to provide a hydrogen generator that generates hydrogen gas by bringing an alkaline aqueous solution of a borohydride complex into contact with a catalyst. The hydrogen generator is compact and can be easily neutralized in the hydrogen generator. Is to provide.

  The waste liquid treatment method of the present invention is a solid organic acid having a pH of 3 or less when an alkaline aqueous solution, which is a waste liquid discharged from a fuel cell using an alkaline aqueous solution of a borohydride complex compound as a fuel liquid, is used as a saturated solution. It is characterized by neutralization treatment.

  Further, the waste liquid treatment method of the present invention comprises a solid organic acid having a pH of 3 or less when the waste liquid composed of the alkaline aqueous solution after generating hydrogen from the alkaline aqueous solution of the borohydride complex is used as a saturated solution. It is characterized by sum processing.

  The waste liquid treatment apparatus of the present invention is a solid organic container that contains the waste liquid described in the above-described waste liquid treatment method, and is separated from the storage container, and has a pH of 3 or less when a saturated solution is obtained. An organic acid storage unit for storing an acid; and a release means for releasing the isolation between the storage container and the organic acid in order to bring the waste liquid and the organic acid into contact with each other to neutralize the waste liquid. It is characterized by.

Furthermore, the hydrogen generator of the present invention is provided in an airtight container, and an aqueous solution storage part for storing an alkaline aqueous solution of a borohydride complex compound,
A catalyst storage unit that is provided in the sealed container so as to be partitioned from the aqueous solution storage unit, and stores a catalyst that generates hydrogen in contact with the alkaline aqueous solution;
Switching means for switching between a state in which the aqueous alkali solution and the catalyst are brought into contact with each other to generate hydrogen, and a state in which the aqueous alkaline solution and the catalyst are isolated from each other;
A hydrogen outlet for releasing the generated hydrogen;
An organic acid storage unit that is provided in the sealed container separately from the aqueous solution storage unit and the catalyst storage unit, and stores a solid organic acid having a pH of 3 or less when a saturated solution is formed;
In order to neutralize the waste liquid consisting of the alkaline aqueous solution after bringing the alkaline aqueous solution and the catalyst into contact with each other to generate hydrogen, the organic acid medium storage unit is separated from the aqueous solution storage unit. Release means for releasing. In addition, the organic acid mentioned above can mention at least 1 sort (s) chosen from a citric acid, tartaric acid, and an acetic acid, for example.

  According to the present invention, in neutralizing an alkaline aqueous solution, which is a waste liquid after using an alkaline aqueous solution of a borohydride complex compound for fuel cell or hydrogen generation, a solid having a pH of 3 or less when a saturated solution is obtained. Organic acid, such as powdered citric acid, is easier to handle than liquid neutralizers, and the amount of neutralizer is less than that of waste liquid. The degree of increase is small, and thus the increase in the size of the container for storing the waste liquid is suppressed.

  Since the amount of the neutralizing agent is small and the increase in the amount of waste liquid due to the neutralization treatment can be suppressed in this way, a small waste liquid treatment apparatus is provided by attaching a storage portion (organic acid storage portion) for storing the neutralizing agent to the waste liquid container. Thus, the waste liquid treatment operation is simplified. Furthermore, a configuration in which a portable hydrogen generator is provided with an organic acid storage unit can be adopted, and since the waste liquid can be neutralized in the hydrogen generator, a disposable hydrogen generator can be realized.

  An embodiment of a waste liquid treatment method according to the present invention will be described. The embodiment described here relates to waste liquid treatment of an alkaline aqueous solution of a used borohydride complex compound used as a fuel for a borohydride fuel cell (hereinafter referred to as a fuel cell). . FIG. 1 shows the basic configuration of the fuel cell. Reference numeral 2 in FIG. 1 denotes a rectangular case body made of, for example, an insulating material. Inside the case body 2, an oxidant (positive electrode) chamber 30 and a fuel electrode (negative electrode) chamber 40 are formed by a permeable membrane 21 made of a polymer electrolyte membrane. It is divided into and. In the oxidant electrode chamber 30, a plate-like oxidant electrode 31 is provided so that one surface side thereof is in contact with the permeable membrane 21, and between the other surface side of the oxidant electrode 31 and the case body 2. A space forming the oxidant channel 32 is formed. An oxidant supply path 33 and a discharge path 34 are connected to the flow path section 32. The oxidant supply path 33 is connected to the oxidant supply path 33 from the upstream side by an oxidant supply source 35, a supply pump 36, a humidifying unit 37, and a heating unit. 38 are provided in this order.

  A plate-like fuel electrode 41 is provided in the fuel electrode chamber 40 so that one surface side thereof is in contact with the permeable membrane 21, and between the other surface side of the fuel electrode 41 and the case body 2, A space forming the flow path portion 42 is formed. Connected to one end side of the flow path portion 42 is a fuel circulation path 45 in which a waste liquid treatment device 5, a valve 43 and a supply pump 44 are interposed.

  As the fuel supplied to the fuel electrode 41 (flowing through the flow path portion 42), an alkaline aqueous solution of a borohydride complex compound is used. Specifically, the borohydride complex compound is sodium borohydride (NaBH4). , Potassium borohydride (KBH4), or lithium borohydride (LiBH4). As the alkaline aqueous solution, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide can be used. If the concentration of the aqueous alkali solution is too high, the borohydride complex compound is difficult to dissolve. Therefore, it is preferably selected within the range of 30% by weight, for example, 20% by weight. The borohydride complex compound is preferably used at a concentration of, for example, 0.1 to 50% by weight in consideration of the intended power generation capacity and solubility in an alkaline aqueous solution.

  Next, the waste liquid treatment apparatus 5 will be described in detail with reference to FIG. The waste liquid treatment apparatus includes a metal storage container 50 that forms a cylindrical sealed container, and a metal organic acid that forms a cylindrical sealed container smaller than the storage container 50 provided on the upper surface side of the storage container 50. It is comprised from the accommodating part 51. FIG. An outer edge portion of a partition member 52 made of a diaphragm such as rubber or a resin plate is formed in the organic acid storage portion 51 so as to be fixed to a side wall of the organic acid storage portion 51. The storage container 50 and the organic acid storage part 51 are partitioned by the diaphragm 52 made of rubber, for example. The storage container 50 stores an alkaline aqueous solution 53 of a borohydride complex compound, which is a fuel liquid to be supplied to the fuel cell. The organic acid storage unit 51 has a pH of 3 or less when a saturated solution is used. A solid organic acid 54 is stored.

  A cylindrical tube 55 is inserted in the center of the upper end surface of the organic acid storage unit 51, and the tip of the cylindrical tube 55 is located in the vicinity of the diaphragm 52. In the cylindrical tube 55, a flexible portion 56 that is bent by pressing is formed, and a cylindrical needle member 57 is closely fitted through the portion. A protective cap 58 is attached to the upper end surface of the organic acid storage part 51 so as to close the needle member 57. That is, in this example, the storage container 50 and the organic acid storage part 51 are separated by the diaphragm 52 that partitions the storage container 50 and the organic acid storage part 51, the flexible portion 56 provided in the cylindrical tube 55, and the needle member 57. Release means for releasing isolation is configured.

  In addition, a hydrogen discharge unit (not shown) is formed on the upper surface of the storage container 50 for releasing hydrogen gas generated by the reaction between the solid organic acid and the alkaline aqueous solution of the used borohydride complex compound. In addition, for example, a hydrogen discharge pipe connected to a processing facility equipped with a device for sucking and exhausting the hydrogen gas may be connected to the hydrogen discharge portion so that the hydrogen gas is not released into the atmosphere during the neutralization process. .

  Further, connection members 59 and 60 are provided on the upper surface of the storage container 50, a fuel liquid supply pipe 61 is connected to the connection member 59, and a fuel liquid discharge pipe 62 is connected to the connection member 60. ing. The fuel liquid supply pipe 61 and the fuel liquid discharge pipe 62 are part of the circulation path 45. Further, a suction pipe 63 is connected to a portion located in the connection member 59 in the storage container 50, and a tip end portion of the suction pipe 63 is provided close to the bottom surface of the storage container 50. In this way, the waste liquid treatment apparatus 5 can be attached to and detached from the circulation path 45 by the connection members 59 and 60 formed on the upper surface portion of the storage container 50.

  The solid organic acid 54 having a pH of 3 or less when the saturated solution stored in the organic acid storage unit 51 is specifically exemplified by powdered citric acid, tartaric acid, and acetic acid. it can. Acetic acid is a liquid at normal temperature, but can be used as a solid because it becomes crystalline at 16.6 ° C. or lower. In this case, use in a cold region seems to be effective. Further, these solid organic acids may be stored in the organic acid storage unit 51 in a desired shape such as pellets according to the purpose of use.

  Next, the operation of the above-described embodiment will be described. An oxidant such as air from the oxidant supply source 35 is supplied to the flow path portion 32 of the oxidant electrode chamber 30 by the supply pump 36. Here, before supplying the oxidant to the flow path portion 32, the humidifier 37 humidifies the absolute temperature to, for example, about 30 to 70%, and further the heater 38 heats to a necessary temperature, for example, 40 to 90 ° C. The air that has flowed through the flow path portion 32 is discharged from the discharge path 34.

  On the other hand, in the waste liquid treatment apparatus 5, a fuel liquid 53 obtained by dissolving a predetermined amount of sodium borohydride stored in the storage container 50 in a sodium hydroxide aqueous solution is sucked up through a suction pipe 63 by a supply pump 44 and fuel is discharged. It supplies to the flow path part 42 of the polar chamber 40. In this example, the used aqueous solution of sodium borohydride discharged from the flow path portion 42 is returned to the storage container 50 and circulated until the aqueous alkaline solution cannot be used as fuel for the fuel cell. That is, the waste liquid of the alkaline aqueous solution is stored in the storage container 50 of the waste liquid treatment apparatus 5 after use. The fuel liquid permeates into the fuel electrode 41, which is a porous body. At this time, an 8-electron reaction represented by the following formula (1) mainly occurs, and a 4-electron reaction represented by the formula (2) also occurs. It is thought that there is.

NaBH4 + 8NaOH → NaBO2 + 6H2O + 8Na ⁺ + 8e ⁻ (1)
NaBH 4 +4 NaOH → NaBO 2 + 2H 2 O + 2H 2 + 4Na ⁺ + 4e ⁻ (2)
In this way, electrons are taken out from the fuel electrode 41 to a circuit connected to the outside, and sodium ions in the fuel move to the oxidant electrode chamber 30 side through the permeable membrane 21, and the following equation (3) As shown, sodium hydroxide is generated from sodium ions, oxygen and moisture.

2O 2 + 4H 2 O + 8Na ⁺ + 8e ⁻ → 8 NaOH (3)
Next, neutralization of the alkaline aqueous solution that is the waste liquid stored in the storage container 50 of the waste liquid treatment apparatus 5 is performed. First, the used waste liquid treatment device 5 is removed from the circulation path 45. At this time, the connection members 59 and 60 are closed by an on-off valve provided in the connection members 59 and 60. Then, for example, the above-described hydrogen discharge pipe is connected to a hydrogen discharge portion (not shown) formed on the upper surface portion of the storage container 50. Subsequently, the protective cap 58 provided on the upper end surface of the organic acid storage unit 51 is removed, and the needle member 57 is pushed downward with a human finger, for example, to pierce the diaphragm 52. Since the rubber is a shrinkable rubber, the torn central film is pulled outward, and a hole is opened in the central part of the diaphragm 52. A predetermined amount of solid organic acid 54 stored in the organic acid storage unit 51, such as powdered citric acid, falls by gravity from this hole, and the waste liquid stored in the storage container 50 is neutralized to neutralize the reaction. As a result, hydrogen gas is generated. The hydrogen gas is sucked and discarded to the processing facility through a hydrogen discharge pipe (not shown). The waste liquid treatment apparatus 5 subjected to the neutralization treatment is collected by, for example, a collection trader and recycled, for example. Then, a new waste liquid treatment apparatus 5 is attached to the circulation path 45, and the fuel liquid is supplied to the fuel cell in the same manner.

  According to this embodiment, a solid organic acid having a pH of 3 or less when an alkaline aqueous solution, which is a waste liquid discharged from a fuel cell using an alkaline aqueous solution of sodium borohydride as a fuel solution, is used as a saturated solution. Since neutralization is performed with powdered citric acid, it is more convenient to handle than neutralization solutions such as hydrochloric acid and sulfuric acid, which are conventionally used, as shown in the examples described later, and neutralizes waste liquid. Since the amount of the neutralizing agent is smaller than that, the degree of increase in the waste liquid by the neutralization treatment is small, so that the increase in the size of the container in which the waste liquid is stored can be suppressed.

  Since the amount of the neutralizing agent is small and the increase in the amount of the waste liquid due to the neutralization treatment is suppressed in this way, the storage unit for storing the neutralizing agent (solid organic acid) in the waste liquid container (organic acid storage unit 51) Can be configured as a small waste liquid treatment apparatus 5. This simplifies the waste liquid treatment operation and is very convenient for collection by, for example, a collection company.

  In the above-described embodiment, the organic acid storage unit 51 for storing the solid organic acid is attached in the waste liquid treatment apparatus 5, but the organic acid storage part is not attached in the waste liquid treatment apparatus. The processing apparatus may be separately transferred to a storage tank, and an operator may directly input a solid organic acid into the storage tank for neutralization. Even if it does in this way, since it is the same effect as the above-mentioned and is a solid neutralizer, neutralization work is very convenient for an operator compared with a liquid neutralizer.

  Next, an embodiment of the hydrogen generator according to the present invention will be described. First, an outline of the fuel cell system 7 incorporating the hydrogen generator will be described with reference to FIG. The fuel cell system 7 includes a hydrogen electrode (negative electrode) to which hydrogen is supplied and an oxidant electrode (positive electrode) to which an oxidant such as oxygen or hydrogen peroxide is supplied, and obtains electric energy by an electrode reaction. A fuel cell 71 capable of generating electricity, a hydrogen generator 72 that supplies hydrogen to the hydrogen electrode, and an air supply means that is an oxygen supply means that supplies oxygen to the oxidant electrode of the fuel cell 71 by supplying air, for example. 73, for example, the fuel cell 71 and the hydrogen generator 72, and the fuel cell 71 and the air supply means 73 are connected to each other through a flow path 74 such as a pipe. The fuel cell system 7 is configured to be detachable as a power source of an electric device, for example, and the hydrogen gas generated by the hydrogen generator 72 is supplied to the hydrogen electrode of the fuel cell 71 via the flow path 74 and air supply means. The air from 73 is supplied to the positive electrode of the fuel cell 71, and the electrode reaction proceeds to cause the fuel cell 71 to generate electricity and supply electricity to the electrical equipment.

  Next, a hydrogen generator according to an embodiment of the present invention will be described with reference to FIGS. In the figure, 8 is a stainless steel reaction vessel having a cylindrical sealed vessel having a diameter and a height of 60 mm and 100 mm, for example, and in this reaction vessel 8, the hydrogen generation reaction of the borohydride complex compound is promoted. For example, a catalyst storage portion 81 is provided which is filled (contained) with a catalyst which is a reaction aid of, for example, a vertically extending cylindrical body. Further, a gas permeable film 82, which is a gas permeable member that allows gas to pass but not liquid, is provided in the reaction vessel 8 as a partition wall so as to surround the catalyst housing portion 81, and this gas permeable film 82. The inner region partitioned by is filled with an alkaline aqueous solution of a predetermined amount of the borohydride complex described above to form an aqueous solution storage portion 83. That is, the catalyst storage unit 81 is provided so as to be immersed in the alkaline aqueous solution.

  In addition, an organic acid storage portion 84 is provided on the bottom surface of the aqueous solution storage portion 83. The organic acid storage portion 84 stores solid organic acid having a pH of 3 or less when a saturated solution is used. The upper surface portion of the organic acid storage portion 84 is formed by a partition member 85 made of, for example, shrinkable rubber or a resin plate. In addition, flexible portions 86 and 86 that are bent by pressing are formed on the upper end surface of the reaction vessel 8 located in the aqueous solution storage portion 83, and cylindrical needle members 87 and 87 are inserted through the portions. The tip portions of the needle members 87 and 87 are located in the vicinity of the surface of the partition member 85. Further, protective caps 88 and 88 are attached to the upper end surface of the reaction vessel 8 so as to close the needle members 87 and 87. That is, in this example, the partition member 85 that partitions the aqueous solution storage portion 83 and the organic acid storage portion 84, the flexible portions 86 and 86 provided on the upper end surface of the reaction vessel 8, and the needle members 88 and 88 store the aqueous solution. Release means for releasing isolation between the portion 83 and the organic acid storage portion 84 is configured.

  In addition, a space region outside the aqueous solution storage portion 83 and the organic acid storage portion 84 is formed as a hydrogen generation space 92, and the upper surface of the reaction vessel 8 is a hydrogen with a cap that can be taken out, for example, for discharging hydrogen. The discharge port 93 is provided at a position corresponding to the hydrogen generation space 92.

  As shown in FIGS. 5 and 6, the catalyst storage unit 81 includes an inner cylinder 94 and an outer cylinder 95 surrounding the peripheral surface of the inner cylinder 94, and one end side of the inner cylinder 94 is While being fixed to one end side of the reaction vessel 8, the other end side is closed by a side end face of the outer cylindrical body 95. A rotation shaft 96 is provided on the side end surface, and the rotation shaft 96 protrudes outside through the organic acid storage portion 84 and the reaction vessel 8, and the rotation shaft 96 rotates to cause the outer cylinder body 95 to rotate. The inner cylinder 94 is configured to be rotatable around the central axis.

  More specifically, as shown in FIGS. 5 and 6, the outer peripheral surface of the inner cylindrical body 94 is filled with a catalyst by being divided in the circumferential direction in a semicircular region extending from one end edge to the other end edge in a cross section, for example. In addition, a plurality of, for example, four groove-shaped catalyst filling portions 98 extending in the longitudinal direction are provided side by side, and each catalyst filling portion 98 is filled with, for example, a solid rod-shaped catalyst to form a catalyst layer. A net body 99 that is formed and further covers the surface of the catalyst layer to prevent the catalyst from falling off is provided. Further, an opening 100 is formed on the surface of the outer cylinder 95 leaving both ends of the cylinder, and the outer cylinder 95 rotates with respect to the surface of the catalyst filling part 98 by rotating. The state in which the aqueous solution storage part 83 and the catalyst storage part 81 communicate with each other by overlapping the projection area, that is, the state in which the catalyst storage part 81 is opened into the alkaline aqueous solution, and the aqueous solution storage part 83 and the catalyst storage part 81 are not overlapped. It is configured as an open / close member so that it can be switched between the isolated state and the isolated state.

  Further, the catalyst is selected from, for example, metals such as nickel and cobalt having hydrogen catalytic activity, hydrogen storage alloys, and fluorinated products thereof.

  Next, a method for generating hydrogen gas with the above-described hydrogen generator will be described by taking an example of mounting the fuel cell system 7 shown in FIG. 3 as an example. First, the hydrogen discharge port 93 of the hydrogen generator 72 of the present invention and the fuel cell 71 are connected via the flow path 74. For example, the outer cylinder 95 is rotated by a predetermined angle around the central axis of the inner cylinder 94 manually or by a drive mechanism (not shown), and the projection region is projected onto the opening 100 of the outer cylinder 95 with respect to the surface of the catalyst filling unit 98. As a result, the catalyst storage unit 81 is opened in the alkaline aqueous solution. For example, the aqueous alkaline solution flows into the catalyst storage unit 81 by water pressure, and the alkaline aqueous solution and the catalyst come into contact with each other. At this time, the boron hydride complex compound reacts with the water of the alkaline aqueous solution due to the active action of the catalyst. For example, the hydrolysis reaction shown in the following reaction formula (4) is promoted to generate hydrogen gas. As a result, a metal oxide is generated and the alkaline aqueous solution deteriorates.

NaBH4 + 2H2O → NaBO2 + 4H2 (4)
The hydrogen gas generated in the reaction vessel 8 rises in the aqueous solution storage portion 83 in the form of bubbles, for example, and passes through the gas permeable membrane 82 so that the alkali mist is separated and supplied to the hydrogen generation space 92. At this time, the alkaline aqueous solution in the aqueous solution container 83 is agitated by the gas lift effect, and the concentration distribution of the alkaline aqueous solution is suppressed from occurring. The hydrogen gas discharged to the outside through the hydrogen discharge port 93 is supplied to the hydrogen electrode of the fuel cell 71 through the flow path 74 and used as a power generation fuel.

  Next, neutralization treatment of the waste liquid composed of the alkaline aqueous solution after hydrogen is generated from the alkaline aqueous solution of the borohydride complex compound stored in the aqueous solution storage portion 83 of the hydrogen generator 72 is performed. First, the used hydrogen generator 72 is removed from the fuel cell system 7. Subsequently, the protective caps 88, 88 provided on the upper end surface of the reaction vessel 8 are removed, and the needle members 87, 87 are pushed downward with a human finger, for example, to break through the partition member 85, for example, the partition member If 85 is a shrinkable rubber, the torn central film is pulled outwards and ruptured, or if it is a resin plate, it is crushed to open a hole. The waste liquid stored in the aqueous solution storage unit 83 falls from the hole by gravity and is neutralized by a predetermined amount of solid organic acid stored in the organic acid storage unit 84, for example, powdered citric acid. Since a little hydrogen gas is generated by the neutralization reaction, for example, it is preferable to connect the above-described hydrogen discharge pipe to the hydrogen discharge port 93 and discard it to the processing facility. The neutralized hydrogen generator 72 is recovered by, for example, a recovery contractor and discarded, for example. A new hydrogen generator 72 is attached to the flow path 74 and hydrogen gas is supplied to the hydrogen electrode of the fuel cell 71 in the same manner.

  According to this embodiment, the above-described solid organic acid is stored in the organic acid storage portion 84 provided in the hydrogen generator 72, so that the neutralization treatment can be easily performed in the hydrogen generator 72. Since the solid organic acid has a smaller volume (volume) of the neutralized waste liquid than the neutralized solution, the hydrogen generator 72 can be designed to be small and very convenient for use as a portable hydrogen generator. is there.

  Next, an experiment conducted for confirming the effect of the present invention will be described.

A. Experimental Example (Example 1)
To a 130 ml reaction vessel containing 0.5 g of Raney Ni powder having an average particle diameter of 5 μm, 100 ml of a 10 wt% sodium hydroxide aqueous solution in which 1.4 g of sodium borohydride having an average particle diameter of 300 μm was dissolved was dropped. Hydrogen gas generated by the decomposition reaction was supplied as a fuel for the polymer electrolyte fuel cell.

  After hydrogen gas generation, 2.4 g of a product remaining in the reaction vessel, 10 wt% aqueous sodium hydroxide solution (waste liquid) containing NaBO2 having an average particle size of 500 μm, and powdered citric acid having an average particle size of 100 μm 20.5 g was added to neutralize the pH of the solution in the reaction vessel to about 7. The volume (volume) of the solution in the reaction vessel after the neutralization treatment was 125 ml. The amount of citric acid added was set based on the results of Example 3 described later.

(Example 2)
Neutralization was performed under the same conditions as in Example 1 except that 21 g of powdered tartaric acid having an average particle size of 100 μm was added to the reaction vessel. The volume (volume) of the solution in the reaction container after neutralization was 128 ml. In addition, the addition amount of tartaric acid was set based on the result of Example 4 mentioned later.

(Example 3)
In a reaction vessel containing 100 ml of a 10% by weight aqueous sodium hydroxide solution in which 5.0 g of sodium metaborate (NaBO2) was dissolved, powdered citric acid was added until the alkaline aqueous solution in the reaction vessel was neutralized, that is, pH. Was added little by little until approximately 7 was obtained. The result is shown in FIG. The vertical axis in FIG. 7 is pH, and the horizontal axis is the amount of citric acid added. As shown in FIG. 7, by adding 20.5 g of citric acid, the alkaline aqueous solution in the reaction vessel could be changed to a neutralizing aqueous solution. In this example, a solution obtained by adding NaBO2 to an NaOH solution is used, but it is understood that the solution is equivalent to an actual waste liquid used in a fuel cell or a hydrogen generator.

Example 4
The experiment was performed under the same conditions as in Example 1 except that powdered tartaric acid was added to the reaction vessel. The result is shown in FIG. The vertical axis in FIG. 8 is pH, and the horizontal axis is the amount of tartaric acid added. As shown in FIG. 8, by adding 21 g of tartaric acid, the aqueous alkali solution in the reaction vessel could be changed to a neutralizing aqueous solution.

(Comparative Example 1)
After generating hydrogen gas under the same conditions as in Example 1, 10% by weight of HCl was added to 10% by weight aqueous sodium hydroxide solution (waste liquid) containing 2.4 g of NaBO 2 as the product remaining in the reaction vessel. An aqueous solution was added for neutralization. The volume (volume) of the solution in the reaction vessel after neutralization was 195 ml, which exceeded the 130 ml reaction vessel.

B. Results and Discussion As described above, according to the above experimental results, the waste liquid consisting of an alkaline aqueous solution is neutralized with powdered citric acid or tartaric acid, thereby significantly increasing the volume (volume) of the waste liquid after neutralization. It can be understood that it can be suppressed. In this way, since powdered citric acid or tartaric acid has a smaller volume (volume) of neutralized waste liquid than HCl aqueous solution, for example, when neutralizing in a waste liquid treatment apparatus and a hydrogen generator as described above, It turns out that it is extremely effective.

It is a schematic block diagram which shows one Embodiment of the waste-liquid processing method which concerns on this invention. It is a schematic sectional drawing which shows the waste liquid processing apparatus which concerns on the said embodiment. It is explanatory drawing which shows the battery system incorporating the hydrogen generator of this invention. It is the longitudinal cross-sectional view and side view which show the hydrogen generator which concerns on embodiment of this invention. It is a perspective view which shows the catalyst storage part of the said hydrogen generator. It is sectional drawing which shows the catalyst accommodating part of the said hydrogen generator. It is a characteristic view which shows the result of the experiment example performed in order to confirm the effect of this invention. It is a characteristic view which shows the result of the experiment example performed in order to confirm the effect of this invention.

Explanation of symbols

5 Waste liquid treatment apparatus 50 Storage container 51 Organic acid storage section 52 Diaphragm 53 Fuel liquid 54 Solid organic acid 55 Cylindrical tube 57 Needle member 58 Protective cap 8 Reaction container 81 Catalyst storage section 82 Gas permeable membrane 83 Aqueous solution storage section 84 Organic acid storage Part 92 Hydrogen generation space

Claims (6)

  Characterized by neutralizing an alkaline aqueous solution, which is a waste liquid discharged from a fuel cell using an alkaline aqueous solution of a borohydride complex compound as a fuel liquid, with a solid organic acid having a pH of 3 or less when the saturated aqueous solution is used. Waste liquid treatment method.   A waste liquid treatment characterized by neutralizing a waste liquid comprising an aqueous alkali solution after generating hydrogen from an alkaline aqueous solution of a boron hydride complex compound with a solid organic acid having a pH of 3 or less when the saturated liquid is obtained. Method.   The waste liquid treatment method according to claim 1 or 2, wherein the organic acid is at least one selected from citric acid, tartaric acid, and acetic acid.   A storage container for storing the waste liquid according to claim 1 or 2, and an organic acid storage section that is provided separately from the storage container and stores a solid organic acid having a pH of 3 or less when a saturated solution is used. And a releasing means for releasing the separation between the storage container and the organic acid storage unit in order to neutralize the waste liquid by bringing the waste liquid and the organic acid into contact with each other. apparatus.   The waste liquid treatment apparatus according to claim 4, wherein the organic acid is at least one selected from citric acid, tartaric acid, and acetic acid. An aqueous solution storage unit that is provided in an airtight container and stores an alkaline aqueous solution of a borohydride complex compound;
A catalyst storage unit that is provided in the sealed container so as to be partitioned from the aqueous solution storage unit, and stores a catalyst that generates hydrogen in contact with the alkaline aqueous solution;
Switching means for switching between a state in which the aqueous alkali solution and the catalyst are brought into contact with each other to generate hydrogen, and a state in which the aqueous alkaline solution and the catalyst are isolated from each other;
A hydrogen outlet for releasing the generated hydrogen;
An organic acid storage unit that is provided in the sealed container separately from the aqueous solution storage unit and the catalyst storage unit, and stores a solid organic acid having a pH of 3 or less when a saturated solution is formed;
Release the isolation between the aqueous solution storage unit and the organic acid storage unit in order to neutralize the waste solution consisting of the alkaline aqueous solution after bringing the alkaline aqueous solution and the catalyst into contact with each other to generate hydrogen. A hydrogen generator comprising: release means for performing the operation.

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