JP2005317419A - Ammonia removing method and ammonia removing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove ammonia contained in an hydrogen-rich reformed gas to be supplied to a solid polymer fuel cell 3. <P>SOLUTION: The reformed gas flowing out of a reformer 1 is cleaned by a wash water by an ammonia remover 11, and the ammonia-removed clean reformed gas is supplied to a solid polymer fuel cell 3. The wash water absorbing the ammonia is supplied to a diluting chamber 20 of an electric dialyzer 12, and by electric dialysis, the ammonia is moved to a concentration chamber 21 and the clean wash water removed of ammonia is circulated to the ammonia remover 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for removing ammonia contained in a hydrogen-rich reformed gas supplied to a polymer electrolyte fuel cell, and in particular, removes a small amount of ammonia in the reformed gas by a cleaning method, and further removes ammonia. The present invention relates to a method and an apparatus for removing ammonia by electrodialyzing absorbed washing water.

  Solid polymer fuel cells are promising as power generation fuel cells installed in homes and vehicle-mounted power fuel cells. A solid polymer electrolyte fuel cell is a fuel cell using a polymer membrane, and generates electric power by reacting hydrogen and oxygen supplied as a power generation raw material. In general, a mixture of raw material gas consisting of hydrocarbons such as methane and steam is supplied to a reformer, where it undergoes a reforming reaction in the presence of a steam reforming catalyst, and the resulting hydrogen-rich reformed gas is used as a fuel to produce a solid high Many methods are used to supply the molecular fuel cell.

  The life of a polymer electrolyte fuel cell is determined by the degradation rate of the polymer membrane. Conventionally, the main factor for deteriorating polymer membranes has been attributed to carbon monoxide (CO) contained in the reformed gas in a small amount. As a countermeasure, a CO remover filled with a catalyst on the outlet side of the reformer has been used. It is provided to remove CO contained in a minute amount in the reformed gas. However, according to recent studies, it has been found that the deterioration of the polymer film is influenced by ammonia present in a small amount in the reformed gas in addition to CO.

In general, a hydrocarbon-based raw material gas such as methane or propane used for generating a reformed gas contains a nitrogen component, and the nitrogen reacts with the hydrogen generated in the reformer, and 1 / Ammonia is produced by the reaction formula 2N ₂ + 3 / 2H ₂ = NH ₃ . When the reformed gas containing the generated ammonia is supplied to the solid polymer fuel cell, the polymer membrane deteriorates due to the ammonia.

  Therefore, in order not to damage the polymer membrane, it is required to reduce the concentration of ammonia contained in the reformed gas to 0.1 ppm, preferably about 5 ppb. Therefore, Patent Document 1 proposes a method of removing ammonia contained in the reformed gas to a required level with an ammonia remover and then supplying it to the polymer electrolyte fuel cell.

Japanese Patent Laid-Open No. 2003-31247

  FIG. 2 is a process flow diagram for implementing the method described in Patent Document 1. The hydrogen-rich reformed gas containing ammonia generated in the reformer 1 is blown into the ammonia remover 2 from the pipe a, and then comes into contact with the water sprayed by the water spray nozzle 2a from above to contain the contained ammonia. Is absorbed and removed by water. The reformed gas from which ammonia has been removed is supplied to the polymer electrolyte fuel cell 3 via the pipe b, and the water that has absorbed ammonia is discharged to the storage tank 4 via the pipe c.

  The stored water in the storage tank 4 is supplied to the ion exchange resin tank 6 by a pump 5 provided in the pipe d, and the contained ammonia is adsorbed on the ion exchange resin. Then, the water from which ammonia has been removed is circulated through the pipe e to the watering nozzle 2a of the ammonia remover 2.

  However, in the process described above, it is necessary to periodically regenerate or replace the ion exchange resin that has adsorbed ammonia, the maintenance and management thereof are complicated, and the operation cost increases. Further, new waste is generated with the regeneration of the ion exchange resin. Therefore, an object of the present invention is to solve the problems in the prior art for removing ammonia from the reformed gas.

  The ammonia removal method of the present invention that solves the above problems is a method of removing ammonia contained in a hydrogen-rich reformed gas supplied to a polymer electrolyte fuel cell. In this method, the reformed gas is washed with washing water to remove the ammonia contained in the washing water, and the washing water that has absorbed the ammonia is supplied to the dilution chamber of the electrodialyzer. It is moved to the concentration chamber by electrodialysis, and the wash water from which ammonia flowing out from the dilution chamber is removed is circulated for cleaning the reformed gas (claim 1).

  In the ammonia removal method, chlorine ion-containing water is supplied to the concentration chamber, and hypochlorous acid to be generated reacts with ammonia that has moved to the concentration chamber to be decomposed into nitrogen gas and water (claim 2). ).

  Moreover, the ammonia removal apparatus of the present invention that solves the above problems is an apparatus that removes ammonia contained in a hydrogen-rich reformed gas supplied to a polymer electrolyte fuel cell. The apparatus includes an ammonia remover that absorbs and removes ammonia contained by spraying the wash water on the reformed gas, an electrodialyzer that electrodialyzes the wash water that has absorbed the ammonia, and the ammonia. A supply conduit for supplying the absorbed wash water to the dilution chamber of the electrodialyzer, and a circulation conduit for circulating the wash water from which ammonia has been removed in the dilution chamber of the electrodialyzer to the ammonia remover are provided. (Claim 3).

  According to the ammonia removal method of the present invention configured as described above, the ammonia contained in the reformed gas can be efficiently separated and removed by the cleaning method, so that the clean reformed gas substantially free of ammonia is contained. Can be supplied to the polymer electrolyte fuel cell. In addition, since the wash water that has absorbed ammonia is removed by electrodialysis, troublesome maintenance management such as replacement of ion exchange resin is not required.

  In the method for removing ammonia, as described in claim 2, chlorine ion-containing water is supplied to the concentrating chamber, and the generated hypochlorous acid reacts with ammonia that has moved to the concentrating chamber to react nitrogen gas and water. In the case of decomposition into ammonia, ammonia (ions) moved to the concentration chamber is decomposed into harmless substances, so that industrial waste is not discharged in the ammonia removal process.

  Moreover, the ammonia removal method of the present invention can be suitably carried out by using the ammonia removal apparatus of the present invention.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a process flow diagram of the ammonia removal apparatus of the present invention. The ammonia removal device 10 includes an ammonia removal device 11 and an electrodialysis device 12. The ammonia remover 11 has a tank body 13 and cleaning water spraying means 14 provided above the tank body 13, and the cleaning water spraying means 14 is provided with a spray nozzle at the tip.

  The electrodialysis apparatus 12 includes a dialysis tank 15, an anode 16 and a cathode 17 disposed on both sides of the dialysis tank 15, an anion exchange membrane A disposed on each of the anode 16 side and the cathode 17 side, and a space between these anion exchange membranes A. And a cation exchange membrane C disposed on the surface. The portion on the anode 16 side partitioned by the anion exchange membrane A forms the anode chamber 18, the portion on the cathode 17 side partitioned by the anion exchange membrane A forms the cathode chamber 19, and the anode chamber 18 and the cation exchange membrane A dilution chamber 20 is formed between C and C, and a concentration chamber 21 is formed between the cathode chamber 19 and the cation exchange membrane C. The anion exchange membrane A is an exchange membrane that allows only anion to pass through. For example, an exchange membrane such as model Aciplex-CA2 commercially available from Asahi Kasei Corporation can be used. The cation exchange membrane C is an exchange membrane that allows only cation ions to pass therethrough. Similarly, an exchange membrane such as model Aciplex-CK1 commercially available from Asahi Kasei Corporation can be used.

  The lower part of the ammonia remover 11 and the inlet side of the dilution chamber 20 are connected by a pipe d, and a pump 22 is provided in the pipe d. These supply lines 23 and pumps 22 form a supply line 23 for supplying the wash water that has absorbed ammonia to the dilution chamber 20 of the electrodialysis apparatus 12. Further, the outlet side of the dilution chamber 20 and the washing water spraying means 14 are connected by a circulation pipe 24 constituted by a pipe e.

  A pipe f provided with a pump 25 is connected to the inlet side of the concentrating chamber 21, and the tip of the pipe f communicates with the storage tank 26. The storage tank 26 is supplemented with water containing a small amount of chlorine ions (chlorine ion-containing water) such as tap water from the pipe k and stored. A pipe g is connected to the outlet side of the concentration chamber 21, and the tip of the pipe g communicates with the storage tank 26.

  A pipe h provided with a pump 27 is connected to the inlet side of the anode chamber 18 and the inlet side of the cathode chamber 19, and the tip of the pipe h communicates with the storage tank 16. Furthermore, the pipe i connected to the outlet side of the anode chamber 18 and the tip of the pipe j connected to the outlet side of the cathode chamber 19 communicate with the storage tank 26, respectively. The positive side and the negative side of the power supply device 28 that supplies the DC voltage are connected to the anode 16 and the cathode 17, respectively. As the power supply device 28, an AC / DC conversion device that converts a commercial power source into a direct current using a thyristor, a storage battery device, a system that combines them, a system that combines a storage battery device and a solar battery power generation device, or the like can be used.

  Next, a method for removing ammonia contained in the reformed gas with the apparatus shown in FIG. 1 will be described. The hydrogen-rich reformed gas flowing out from the reformer 1 to the pipe a is supplied below the tank body 13 of the ammonia remover 11. The supplied reformed gas comes into contact with the water droplets of the cleaning water sprayed from the cleaning water spraying means 14 provided above while ascending the inside of the tank body 13, and the contained ammonia is absorbed by the cleaning water. Separated and removed. The reformed gas from which ammonia has been removed by washing flows out of the pipe b and is supplied to the polymer electrolyte fuel cell 3, and the wash water that has absorbed ammonia is stored in the lower part of the tank body 13.

The wash water that has absorbed ammonia stored in the lower part of the tank body 13 is supplied from the pipe d to the dilution chamber 20 of the electrodialyzer 12 by operating the pump 22. On the other hand, chlorine-containing water from the storage tank 26 circulates in the concentration chamber 21, the anode chamber 18, and the cathode chamber 19 of the electrodialysis apparatus 12. Then, by applying a predetermined DC voltage between the anode 16 and the cathode 17 from the power supply device 28, the ammonia ions NH ₄ ^{+ in} the dilution chamber 20 move to the concentration chamber 21 side and are separated and washed without ammonia. Water circulates from the circulation line 24 to the ammonia remover 11.

The ammonia that has moved to the concentrating chamber 21 flows out to the storage tank 26 through the pipe g. Then, when the chlorine-containing water in the storage tank 26 is supplied to the anode chamber 18 through the pipe h, hypochlorous acid is generated by the anode reaction of Cl ⁻ + 2OH ⁻ = ClO ⁻ + H ₂ O + 2e. When this hypochlorous acid circulates again in the storage tank 26, ammonia is decomposed into harmless nitrogen and water by the reaction of 2NH ₃ ⁺ + 3ClO ⁻ = N ₂ + 3Cl ⁻ + 3H ₂ O. The generated nitrogen is diffused from the storage tank 26 through the pipe g, for example.

  The ammonia removal method and the removal apparatus of the present invention can be used when a hydrogen-rich reformed gas is supplied to a solid polymer fuel cell.

The process flow figure of the ammonia removal apparatus of this invention. The process flow figure of the conventional ammonia removal apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reformer 2 Ammonia remover 2a Sprinkling nozzle 3 Polymer electrolyte fuel cell 4 Reservoir 5 Pump 6 Ion exchange resin tank

DESCRIPTION OF SYMBOLS 10 Ammonia removal apparatus 11 Ammonia removal apparatus 12 Electrodialysis apparatus 13 Tank main body 14 Washing water spraying means 15 Dialysis tank 16 Anode 17 Cathode 18 Anode chamber 19 Cathode chamber 20 Dilution chamber

21 Concentration chamber 22 Pump 23 Supply line 24 Circulation line 25 Pump 26 Storage tank 27 Pump 28 Power supply device a to k Pipe

Claims (3)

  In a method of removing ammonia contained in hydrogen-rich reformed gas supplied to a polymer electrolyte fuel cell, the reformed gas is washed with washing water and the contained ammonia is absorbed into the washing water and removed. Then, the wash water that has absorbed ammonia is supplied to the dilution chamber 20 of the electrodialyzer 12, the ammonia is moved to the concentration chamber 21 by electrodialysis, and the wash water from which the ammonia flowing out from the dilution chamber 20 has been removed is used as the reformed gas. A method for removing ammonia, which is circulated for cleaning.   2. The ammonia according to claim 1, wherein chlorine ion-containing water is supplied to the concentration chamber 21, the generated hypochlorous acid reacts with the ammonia that has moved to the concentration chamber 21, and is decomposed into nitrogen gas and water. Removal method. In an apparatus for removing ammonia contained in hydrogen-rich reformed gas supplied to a polymer electrolyte fuel cell, an ammonia remover that absorbs and removes ammonia contained by spraying cleaning water on the reformed gas 11, an electrodialyzer 12 that electrodialyzes the wash water that has absorbed the ammonia, a supply line 23 that supplies the wash water that has absorbed the ammonia to the dilution chamber 20 of the electrodialyzer 12, An ammonia removal apparatus comprising a circulation line (24) for circulating the wash water from which ammonia has been removed in the dilution chamber (20) to the ammonia remover (11).

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