DE1771446A1 - Method for metering liquid reactants in fuel elements - Google Patents

Description

Method for dosing liquid reactants in fuel elements

In the case of fuel elements that have liquid dissolved in the electrolyte Reactants work, the metering of the reactants is more difficult than with fuel elements that use gaseous fuels and oxidizing agents are operated. In the latter case, the fuel, e.g. hydrogen and the oxidizing agent, e.g. oxygen, can be fed to the fuel element under constant pressure. For fuel elements with liquid fuel, e.g. hydrazine, or liquid oxidizing agent e.g. hydrogen peroxide, the liquid reactant must dem Electrolytes added either continuously or intermittently will. While with continuous addition of the liquid

109887/0565 bad orig _INal

By / Or

PLA 68/1242

Reactants in the electrolyte can be kept constant changes the concentration increases periodically with discontinuous addition.

Are now fuel elements under variable conditions, with, e.g. operated with changing load and temperature, so the fuel elements do not work under optimal conditions even if the concentration of the liquid reactant is kept constant. operating conditions. With optimal operation of the Brennatofffe elements, the concentration must be adjusted to the temperature and load fluctuations. If the concentration is too high of the liquid reactant, there is above all the risk that the counter electrode and the potential of this will be adversely affected Electrode is diminished or even collapses * A * u low Concentration, on the other hand, leads to a deterioration of the electrodes »

The object of the present invention is therefore to provide a method % vat : ^ Dosing of liquid reactants in fuel elements tu findent in which the liquid reactant is continuously in the

of the fuel element is promoted and where the of the liquid reactant in each case to the variable operating conditions

is adjusted. ' _t

The solution to the task at hand is to feed the cell voltage via a controller to the motor of a metering pump controls liquid reactants in such a way that when the cell is removed voltage increases the delivery rate of the pump and as it rises

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109887/0565

BATH ORIGINAL

PLA Cβ / 12 A 2

S 1771U6

Cell voltage is reduced, with the fuel element in a concentration range works in which an increase in concentration of the liquid reactant brings about an increase in the cell voltage with the same list and the fuel element contains at least one electrode, the current-voltage behavior of which increasing concentration of the dissolved reactants is improved.

The inventive method is primarily for the operation of Fuel elements suitable in which in alkaline electrolyte dissolved hydrazine is used. Of course, other liquid substances such as methanol, Boranate or hydrogen peroxide can be used. When operating a fuel element with 6 η KOH and hydrazine, the concentration range is in which an increase in concentration cleo hydrazine zu.einer increase in cell voltage at the same load leads to about 0.01 mol to 2 mol / l 6 η KOH, provided that oxygen is used as Oxidizing agent is used. If the load on the fuel element is now increased, the cell voltage drops, as a result of which in accordance with According to the invention, the amount of hydrazine delivered is increased to the extent that the voltage preset for the regulator is maintained. One additional electronic equipment to keep the voltage constant is therefore not required.

Another advantage of the invention is that overdosing of the liquid reactant and thus a deterioration of the counter electrode is avoided. Also the losses are due

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109887/0565 bad ori _{G} Nal}

PLA 68/1242

177U46

chemical short-circuit and self-decomposition of the hydrazine pressed down to a minimum.

The method will now be based on the following figures and examples the invention will be explained in more detail.

In Fig. 1, 1 represents a fuel element whose electrolyte ' space is connected to the electrolyte reservoir 5 via the lines 2 and 3 and the pump 4. The storage vessel for the fuel or the oxidizing agent is shown in the schematic drawing

6 designated. The reactants are fed in via the pump

7 through line 8 into the electrolyte circuit. The motor 9, which drives the metering pump 7, is electrical with the controller 10 tied together. Electrical lines lead from the electrodes of the fuel element to the controller 10 and the drive motor 11 of the pump 4. The load connected to the fuel element iot shown in the figure with 12.

If the cell voltage of the fuel element now falls below a predetermined value, the drive current of the motor 9 is increased via the controller 10, and thus the amount of the liquid reactant, the one at 13 in the. Electrolyte cycle is fed. This increases the cell voltage, so that the drive current of the Motor 9 is reduced via the controller. At the same time, the delivery rate of the pump 7 is reduced.

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109887/0565

BATH ORIGINAL

PLA 68/1242

'The motor 11, which is provided for the electrolyte circulation

Pump 4 drives is operated independently of the cell voltage.

The regulator 10 shown in FIG. 1, which is used to control the pump motor 9, is adjusted to the number of fuel elements and their cell voltage or battery voltage. In the case of fuel batteries "in which a large number of individual cells are connected in series, a sufficiently high DC voltage is available so that normal amplifiers can be used" In this case, the van will control the hot or the pump via a set-actual value comparison . ^v

In Fig * 2 the structure of a controller is shown, which can be used for bineel cells and batteries. The lowest voltage at which the bowler is still working is 0.5 V. In this regulator, the threshold voltage dft transistor 14 is used as the SblJ value for regulation. As the cell voltage decreases, the actual value, an optimal portion of the! Rope tension, on the 100-ohm fider and 15 »! Gripped» becomes smaller. PNTe * »0hreitet this actual value the threshold voltage of the transistor 14 _t eo is this high impedance ujld locked so * As a result, the transistor 16 likewise da0

ill * high resistance and transistor ITj is low. The current can now flow through the transistor t7 «u to the Hotor 18 and drive the Puape. When the rope tension increases, the process is reversed and the transistors 14 and 16 become low-resistance. The transistor 17 has a high resistance and thus the power supply to the motor

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109887/0565

PIA 68/1242

locked and the delivery of the reactant stopped. The point at which the motor should start can be set at the tap of the 100 ohm resistor *

A fuel element operated with liquid hydrazine and gaseous oxygen is shown schematically in FIG. 3. The anode consists of a platinum- coated nickel mesh and the cathode consists of powdery Baney silver. » 21 denotes an asbestos diaphragm, 22 a fine- meshed wire mesh and 23 a coarse-meshed wire mesh. The electrolyte containing the hydrazine is fed into the asbeetfree layer at 24 °. At a given cell voltage of 0.7 V , the following hydrazine concentrations are established in this fuel element, depending on the load. At 5 mA / cm the H ₂ HcOH concentration is 0.03 to 0.05 mol, at 10 mA / cm ² load 0.1 Hol and at 1 mA / oja ² 0.25 mol.

t '

2 claims

3 figures

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109887/0585

BATH ORIGINAL

Claims (2)

177H46 claims f 1. Method of dosing liquid reactants in fuel elements, in which the liquid reactant is continuously fed into the electrolyte of the fuel element and in which the concentration of the liquid reactant is adapted in each case to the variable operating conditions, characterized in that that the cell voltage controls the motor of a metering pump for the liquid reactant via a cone in such a way that that when the cell voltage decreases, the delivery rate of the pump increases and when the cell voltage increases, it is reduced, with the fuel element works in a concentration range, in which an increase in the concentration of the liquid reactant results in an increase in the cell voltage with the same load and the fuel element contains at least one electrode, whose current-voltage behavior is improved with increasing concentration of the dissolved reactant. 2. The method according to claim 1, characterized in that the liquid reactant is hydrazine, methanol, boranate or hydrogen peroxide is used. - '/ _ By / Or 109887/0565 ** » Blank page