DE1596304A1 - Fuel element for hydrazine - Google Patents

Description

\ J \ J VJ \ J \ J

Registration number. EDUP 85 Prankfurt / Main, September 30, 1966

Kth / Seh

VARTA AKTIENGESELLSCHAFT Prankfurt / Main, Neue Mainzerstraße 54

Fuel element for hydrazine

The invention relates to a fuel element with a multilayer porous gas diffusion electrode as Fuel electrode in connection with a control device for the supply of hydrazine.

From the U.S. It is already in patent specification No. 3,121,031 known from a storage container in a fuel electrode to introduce a mixture of hydrazine and potassium hydroxide. Due to the catalyst material, which is in Form of a coarse powder as a layer between two finely porous sieves are located, the hydrazine liquid is converted into the electrochemically usable hydrogen gas and into Nitrogen gas implemented. The nitrogen gas and remnants of Hydrogen gas or ammonia escape into the electrolyte at a given electrode surface and must then be drained from the fuel element.

In German Patent No. 1,189,168, a process is described in which, for example, hydrazine is introduced as a more easily dehydratable additional fuel into the working area of a multi-fuel fuel electrode and the hydrazine is fed through

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the voltage level of the fuel element is determined.

British patent specification Kr. 1.014.232 describes a method for operating a fuel cell with hydrazine known, in which a mixture of hydrazine and electrolyte is introduced into an electrode, which consists of only one single working layer containing the catalyst and from the counter electrode through an ion exchange membrane is separated. The supply of the hydrazine liquid is regulated so that the hydrazine is almost completely implemented at the fuel electrode.

The object was to provide a device using multilayer gas diffusion electrodes find which the advantageous operation of a fuel cell using the in the decomposition of hydrazine released hydrogen. The device should also create the possibility of the implementation of Hydrazine to discharge nitrogen released from the electrode without disturbing the operation of the fuel element.

This device should also make full use of what is produced by the decomposition of hydrazine Allow hydrogen gas for the electrochemical conversion. It should also enable a suitable adaptation of the hydrazine supply to the load on the fuel cell.

This problem is solved by a fuel element with a multi-layer porous gas diffusion electrode in which the electrode has fine-pore outer layers

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iind has a coarse-pored working layer, the Working shift the catalyst for the decomposition of the hydrogen gas used as fuel from the hydrazine and to the work shift a discharge line with a pressure relief valve for the resulting nitrogen gas and a feed line for the hydrazine fluid connected is, which via a valve controlled by the voltage level of the fuel element with a Reservoir is connected.

The use of an electrode that has one work shift or two work shifts and one in between arranged gas conducting layer and finely porous basin layers on the outer surfaces, makes it possible through the connection of a pressure relief valve of the gas from the work shift into the electrolyte liquid to prevent. The middle, coarse-pored layer is blown free by the gas pressure that forms and that Gas cannot escape into the electrolyte as long as the gas pressure is lower than the capillary pressure of the electrolyte in the fine pores of the top layer, increased by the hydrostatic pressure in the electrolyte space. At a The hydrazine liquid enters the middle electrode layer and the hydrazine is passed through the material the working layer is decomposed into hydrogen gas and nitrogen gas.

The gas mixture of hydrogen and nitrogen flows through the middle layer to the exhaust pipe and is thereby

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depleted as a result of the electrochemical conversion of the hydrogen gas in the catalyst of the working shift. With a suitable dosage of the hydrazine feed, the hydrogen gas is practically completely converted, and over only the remaining nitrogen gas escapes from the exhaust pipe and the pressure relief valve. Because of the constant current of the gas mixture prevents inert gas cushions from forming in the coarse pores of the working layer. When a higher electrical power is drawn from the fuel element or the fuel battery at a With an equally strong supply of hydrazine, a polarization voltage is created by the inert gas cushions that are created on the electrode. This voltage is used via an amplifier to control the solenoid valve or other Dosing devices and thus for regulating the hydrazine supply used.

The control of the hydrazine supply by the voltage level of the fuel element can also be done without interposition an automatic facility. One can according to the fuel element or the fuel battery taken power, measured by the amperage, a manual valve in the supply line for the hydrazine press and set to an empirically determined value.

A fuel battery is particularly advantageous which, in addition to hydraein, is also a liquid fuel Oxidizing agents - for example, hydrogen peroxide is used. The hydrogen peroxide is then made from a

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Reservoir Into the coarse-pored working shift of the Multilayer oxygen electrode introduced, whereby the The valve is controlled according to the voltage level of the fuel element.

FIG. 1 shows one form of the fuel element system according to the invention. The fuel electrode with the working layer 1 and the two Deokschichten 2 works as Gas diffusion electrode with an aqueous about 6 i. '· Potassium hydroxide solution. The working layer 1 is about the Connection line 3 and a manual valve 11 with the storage container 10 for the mixture of hydrazine and potassium hydroxide tied together. The work shift is also connected to the outlet line 4 for the gaseous nitrogen which escapes via the pressure relief valve 12. A branch is connected to the line 4, which creates an overpressure generated above the liquid in the reservoir 10. The oxygen electrode with the working layer 5 and the cover layer 6 separates the electrolyte space from the gas space 71 which is supplied with oxygen gas via line 8. The electrical power of the fuel element is drawn off via the connecting lines 9.

FIG. 2 shows a similar device which is equipped with an automatic control of the metering valve 25, which replaces the manual valve of FIG. The setting of the valve «25 is controlled by the voltage» -

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controlled position of the fuel element. For this purpose, the input of a measuring amplifier 23 is connected to the connecting lines 9 connected via lines 22. The output signal of the Heß amplifier is via the lines 24 to the Switching coil of valve 25 given.

Figure 3 shows a similar device to Figure 2. The fuel element is now instead of oxygen gas supplied with a hydrogen peroxide solution. The oxygen electrode now consists of the coarse-pored one Working layer 29 and the two cover layers 28. The supply of the hydrogen peroxide solution from the storage container 30 is also controlled by the voltage level of the fuel element. This is what the two of them will do Connecting lines 9 connected via lines 32 to the input of the measuring amplifier 33, which via the output lines 34 actuates the switching coil of the automatic valve 35. According to the setting of the solenoid valve the working layer 29 of the oxygen electrode is supplied with hydrogen peroxide from the storage container 30 via the feed lines 31 and through the catalyst material of the Working shift 29, the oxygen is released to operate the electrode.

The device according to the invention enables the advantageous use of hydrazine as fuel. The liquid one Fuel can be stored much more easily than hydrogen gas.

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The device according to the invention allows the fuel almost completely for the electrochemical Utilize sales without losses, since the finely porous cover layers allow the hydrogen gas generated to escape is avoided from the work shift into the electrolyte space and when the gas mixture flows through the work shift of the electrode with a suitable setting of the metering valve complete conversion of the hydrogen gas contained in the mixture is achieved. The nitrogen gas does not form any inert gas cushions in the working layer of the electrode because there is a gas flow from the point of entry of the Hydrazine is generated to the outlet line and to the pressure relief valve.

Setting the overpressure can effectively prevent the electrolyte from entering the working layer of the electrode penetrates from the electrolyte compartment as long as there is enough hydrazine

is supplied to build up the necessary gas pressure. On the other hand, if the gas pressure is too high, the gas is prevented from being pressed through the cover layer into the electrolyte and the electrode does not supply any electrical power for a short time.

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Claims (2)

Claims 1. Fuel element with at least one multilayer porous Gas diffusion electrode, which has finely porous cover layers and a coarsely porous working layer, the Working shift the catalyst for the decomposition of the hydrogen gas used as fuel from the hydrazine contains, characterized in that a discharge line with overpressure valve for the resulting work shift Nitrogen gas and the feed line for the hydrazine liquid is connected, which via a through the electrode potential controlled valve is connected to a storage container. 2. Fuel element according to claim 1, characterized in that the multilayered oxygen diffusion electrode finely porous cover layers and a coarse-porous working layer having, the working layer the catalyst for the decomposition of the oxygen gas used as the oxidizing agent from which contains hydrogen peroxide and a supply line for the hydrogen peroxide liquid to the work shift is connected, which via a valve controlled by the electrode potential with a storage container connected iet. 109823/0101 Blank page jf ...