TWI385848B - Reduction method for zno of zinc air fuel cell - Google Patents

Description

Method for reducing zinc oxide of zinc air fuel cell

The present invention relates to a method for reducing zinc oxide, and more particularly to a method for reducing zinc oxide in a zinc air fuel cell.

A metal fuel cell uses oxygen in the air as an oxide in a battery and uses a metal substance as a negative electrode. Such a structure is a high-performance battery having high energy density, long-term storage, and low cost characteristics in various batteries. The research and development of metal fuel cells has received attention from all walks of life. Among them, zinc air fuel cells are the most representative.

Please refer to FIG. 1 , which is a schematic diagram of the structure of a zinc air fuel cell. Generally, the main structure of the zinc air fuel cell includes an air plate 91 as a cathode, a zinc plate 92 as an anode and an electrolyte. 93. The electrolyte 93 is interposed between the air plate 91 and the zinc plate 92 to conduct ions between the air plate 91 and the zinc plate 92.

The cathode reaction performed by the air plate 91 is as shown in the formula (1):

The anode reaction performed by the zinc plate 92 is as shown in the formula (2):

Zn ( s )+2 OH ^- → ZnO + H ₂ O +2 e ^- E ₀ =1.25V........(2)

The net response is shown in equation (3):

The actual open circuit voltage of the zinc air fuel cell is between 1.35 and 1.45 volts (Volt), while the voltage of the actual operation is between 0.9 and 1.2 volts.

As described above, the zinc in the zinc air fuel cell after complete discharge will form a zinc oxide precipitate. At present, zinc oxide in a zinc air fuel cell is usually collected, and zinc oxide is reduced to zinc by solid carbon (C), and the zinc obtained by reduction can be further applied. The reduction reaction of zinc oxide by solid carbon at a temperature of 1200 K is as shown in formula (4):

ZnO _(s) + C _(s) → Zn _(g) + CO _(g) , △ H _1200K = 367.4kJ / mol........(4)

However, the heat absorption of zinc oxide by using solid carbon as a reducing agent is higher than ΔH _1200K , so it is necessary to provide more energy to generate a reaction, resulting in an increase in heat energy consumption for the reduction reaction; further, using the solid carbon as the reducing agent Compared with other liquid and gaseous reducing agents, the reducing agent has a low degree of contact and mixing uniformity with the zinc oxide, which causes a defect that the solid carbon is not completely reacted; further, due to the above reduction reaction The temperature needs to be more than 1200K. At present, it is heated to the high temperature of 1200K by various fuels or gas, which causes the heat source cost to be relatively improved. Moreover, the zinc oxide in the zinc air fuel cell is not recycled and reused in zinc. The method of air fuel cell, therefore, it is necessary to further plan the reduction method of zinc oxide of zinc air fuel cell.

SUMMARY OF THE INVENTION The object of the present invention is to improve the above disadvantages to provide a method for reducing zinc oxide in a zinc air fuel cell, in order to apply zinc obtained by zinc oxide reduction to the manufacture of a zinc air fuel cell.

A second object of the present invention is to provide a method for reducing zinc oxide in a zinc air fuel cell to reduce the heat energy required for the reduction reaction.

Still another object of the present invention is to provide a method for reducing zinc oxide in a zinc air fuel cell to reduce the heat source cost of the overall process.

The method for reducing zinc oxide of a zinc air fuel cell according to the present invention comprises: a recovery step of recovering zinc oxide from a zinc air fuel cell after discharge; and a reducing step of setting the recovered zinc oxide to a solar energy reaction In the apparatus, the zinc oxide is reduced to gaseous zinc by using carbon monoxide as a reducing agent; a cooling step is performed to cool the gaseous zinc to form solid zinc; and an electrode forming step is used to prepare the zinc air fuel cell. Zinc electrode.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The method for reducing zinc oxide in a zinc air fuel cell provided by the present invention reduces the recovered zinc oxide to solid zinc, and then uses the solid zinc to prepare a zinc electrode of a zinc air fuel cell, so that the zinc air fuel cell Zinc oxide can be recycled in a zinc air fuel cell.

Referring to FIG. 2, the zinc oxide reduction method of the zinc-air fuel cell of the present invention comprises a recovery step S1, a reduction step S2, a cooling step S3, and an electrode preparation step S4.

Referring to Fig. 2, the recovery step S1 of the present invention recovers zinc oxide from the discharged zinc air fuel cell. More specifically, since the zinc air fuel cell is in a discharge process, the zinc electrode will chemically react to form zinc oxide (ZnO) and deposit it in the electrode, and the chemical reaction formula is as shown in the formulas (2) to (4). Shown. Therefore, in the present embodiment, the source of the zinc oxide is preferably such that after the zinc air fuel cell is completely discharged, the zinc oxide is recovered from the zinc air fuel cell to reduce the manufacturing cost.

Referring to FIGS. 2 and 3, the reducing step S2 of the present invention comprises disposing the recovered zinc oxide in a solar energy reactor 1 and reducing the zinc oxide to gaseous zinc using carbon monoxide as a reducing agent. More specifically, the zinc oxide recovered in the present embodiment is disposed in the solar energy reaction device 1 and passes carbon monoxide into the solar energy reaction device 1 to provide solar energy as reaction energy through the solar energy reaction device 1 to make the carbon monoxide. The zinc oxide is reduced to gaseous zinc.

For example, as shown in FIG. 4, the solar energy reaction device 1 is provided with a reaction chamber 11, a feed port 12, a discharge port 13, a light input port 14, and a zinc oxide fluidized bed 15. The reaction chamber 11 is disposed in the solar energy reaction device 1; the feed port 12 and the discharge port 13 respectively communicate with the reaction chamber 11; the light input port 14 is opened in the solar energy reaction device 1 for solar energy input The solar energy reaction device 1 heats the reaction chamber 11; the recovered zinc oxide is disposed in the form of a fluidized bed as the zinc oxide fluidized bed 15, and the zinc oxide fluidized bed 15 is disposed in the reaction chamber. Inside the chamber 11. Preferably, the solar energy is concentrated by a concentrating mirror 16 and then input through the light input port 14 to supply heat required for the reaction.

In the present embodiment, the carbon oxide is preferably obtained by the reaction of the formula (5) under a temperature of 973 to 1373 K, or may be mixed with a metal catalyst to facilitate the reaction:

C _(s) +H ₂ O _(g) =CO _(g) +H _2(g) ........(5)

Thus, the generated hydrogen and carbon monoxide can be separated via a catalyst-coated porous stainless steel membrane. The separated hydrogen can be further used as a fuel for a hydrogen fuel cell or as a heat source for other processes subsequent to the gas supply. The obtained carbon monoxide is introduced into the solar reactor 1 so that carbon monoxide oxidizes the recovered zinc oxide into gaseous zinc.

Referring to FIGS. 3 and 4, the recovered zinc oxide is disposed in the solar energy reactor 1 in the form of the zinc oxide fluidized bed 15, and the carbon monoxide is introduced into the feed port 12. The reaction chamber 11 flows through the zinc oxide fluidized bed 15 and is uniformly mixed with zinc oxide to reduce zinc oxide to gaseous zinc at a temperature of 1200 to 1600 K. The reaction is as shown in the formula (6):

ZnO _(s) +CO _(g) =Zn _(g) +CO _2(g) △H _1200K =185.6kJ/mol.....(6)

The product gaseous zinc Zn _(g) and carbon dioxide CO ₂ produced by the reaction can be output from the discharge port 13.

Thus, since the present invention supplies solar energy as reaction energy through the solar energy reaction device 1, the heat source cost due to high temperature can be greatly reduced; and further, the zinc oxide to be reduced is set in the form of the zinc oxide fluidized bed 15. In the solar energy reaction device 1, the gas diffusion rate of carbon monoxide can be increased, so that only a small amount of unreacted carbon monoxide is emitted from the gas output from the discharge port 13; and the heat absorption required for the reaction with carbon monoxide is ΔH _1200K. Lower, it can also reduce the heat energy required to carry out the reaction; further, using the gaseous carbon monoxide as a reducing agent can increase the mixing efficiency of the carbon monoxide and the zinc oxide, thereby increasing the reaction rate.

Referring to Figures 2 and 3, the cooling step S3 of the present invention cools the gaseous zinc to form solid zinc. More specifically, in the present embodiment, the gaseous zinc obtained by the reaction of the formula (6) is discharged from the discharge port 13 and then introduced into a cooler 2 to be cooled into a granular solid zinc. Further application. In addition, the carbon dioxide derived from the feed port 13 can be further cooled to react with calcium oxide (CaO) to form calcium carbonate, and the reaction is as shown in the formula (7):

CaO _(s) +CO _2(g) →CaCO _3(s) ...............(7)

The heat released by the carbon dioxide and gaseous zinc due to cooling can be used as a heat source to preheat other processes.

Wherein, since the particle size of the solid zinc is relatively uneven, as shown in FIG. 3, the solid zinc is preferably subjected to a screening process to obtain a solid zinc having a small particle size and uniform distribution, which is suitable for application to zinc. Production of zinc electrodes in air fuel cells. The screening process of this embodiment introduces the cooled solid zinc into a cyclone 3, through which the larger solid zinc is derived from the bottom, and the smaller solid zinc is derived from the top; The derived solid zinc is further introduced into a dust collector 4 to obtain fine particles of solid zinc of the zinc powder of the optimum particle size, and the electrode preparation step S4 is performed using the sieved solid zinc as a material.

Referring to FIG. 2, in the electrode fabrication step S4 of the present invention, the solid zinc is used to fabricate a zinc electrode in a zinc air fuel cell. More specifically, in this embodiment, the solid zinc obtained by the cooling step S3 is processed into a zinc electrode of a predetermined shape by a method such as powder metallurgy or casting. For example, if the solid zinc is in a powder form, it can be powder metallurgy. It is sintered to form a zinc electrode, and is further disposed on a zinc air fuel cell for application. Thus, the present invention can recover zinc oxide from a zinc air fuel cell and reuse it in a zinc air fuel cell as a zinc electrode to establish a complete zinc oxide fuel cell zinc oxide reduction method.

The invention provides a method for reducing zinc oxide of a zinc air fuel cell to reduce zinc oxide into solid zinc for manufacturing a zinc electrode, so that the zinc oxide can be recycled in a zinc air fuel cell.

The invention provides a method for reducing zinc oxide of a zinc air fuel cell, which reduces the zinc oxide with carbon monoxide to reduce the amount of heat absorption.

The invention provides a method for reducing zinc oxide of a zinc air fuel cell, which uses solar energy to provide heat energy required for the reaction, so as to reduce the heat source cost of the overall process.

The invention provides a method for reducing zinc oxide in a zinc air fuel cell, which is arranged in a fluidized bed manner in the solar energy reaction device to enhance the diffusion efficiency of carbon monoxide and the overall reaction rate.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

[this invention]

1. . . Solar reactor

11. . . Reaction chamber

12. . . Inlet

13. . . Outlet

14. . . Optical input

15. . . Zinc oxide fluidized bed

16. . . Condenser

2. . . Cooler

3. . . Cyclone

4. . . Dust collector

[知知]

91. . . Air plate

92. . . Zinc plate

93. . . Electrolyte

Figure 1: Schematic diagram of a conventional zinc air fuel cell.

Fig. 2 is a flow chart showing a method for reducing zinc oxide in the zinc air fuel cell of the present invention.

Fig. 3 is a schematic view showing the process of the method for reducing zinc oxide in the zinc-air fuel cell of the present invention.

Figure 4: Schematic diagram of the solar energy reactor of the present invention.

Claims (7)

A method for reducing zinc oxide in a zinc air fuel cell comprises: a recovery step of recovering zinc oxide from a discharged zinc air fuel cell; and a reducing step of disposing the recovered zinc oxide in a solar energy reaction device, and The zinc oxide is reduced to gaseous zinc by using carbon monoxide as a reducing agent; a cooling step is performed to cool the gaseous zinc to form solid zinc, and the solid zinc is screened by a screening process; and an electrode forming step is used to prepare the solid zinc A zinc electrode in a zinc air fuel cell is fabricated. The method for reducing zinc oxide in a zinc air fuel cell according to claim 1, wherein in the reducing step, the zinc oxide is disposed in the solar reactor in the form of a fluidized bed, wherein the carbon monoxide flows through The zinc oxide fluidized bed reduces the zinc oxide. The method for reducing zinc oxide of a zinc air fuel cell according to claim 1 or 2, wherein the screening process is to pass the solid zinc into a cyclone, and then pass the solid zinc obtained from the top of the cyclone. A dust collector is used to obtain the solid zinc after screening. The method for reducing zinc oxide of a zinc air fuel cell according to claim 1 or 2, wherein in the electrode forming step, the solid zinc is formed into the zinc electrode by powder metallurgy or casting. The method for reducing zinc oxide of a zinc air fuel cell according to claim 1 or 2, wherein in the reducing step, the carbon monoxide is The zinc oxide is reduced at an ambient temperature of 1200 to 1600K. The method for reducing zinc oxide in a zinc-air fuel cell according to claim 1 or 2, wherein in the reducing step, the carbon monoxide is formed by the reaction of the formula (5), and then the zinc oxide is reduced by the carbon monoxide. , (5) is as follows: C _(s) + H ₂ O _(g) = CO _(g) + H _{2 (g)} (5). The method for reducing zinc oxide in a zinc air fuel cell according to claim 1 or 2, wherein the solar energy provided by the solar energy reaction device is first collected by a condensing mirror and then input into the solar energy reaction device.