DE1496363C - Fuel element - Google Patents

Description

1 2

The invention relates to a fuel element with consist essentially of iron oxide and aluminum

a chamber for the fuel, one of them minium oxide or iron oxide, magnesium oxide and

separated chamber for the oxidizing agent, an aluminum oxide. One serves as the solid electrolyte

Melt-flow electrolytes and two alternating with the mixture of sodium carbonate, tungsten oxide, sodium

Fuel or the oxidizing agent in connection 5 trium silicate and monazite.

bringable electrodes. The fuel element according to the invention works. In the known fuel elements, a so-called three-phase reaction does not always take place like the known elements with a three. There is phase reaction. Rather, it is necessary in the gas phase that the gaseous oxidizing agent, ie when the electrodes come into contact with the oxidizing agent, the liquid electrolyte and the solid ionizing agent or reducing agent, the electrode oxidizes the electrode at one point. The or reduced and then when the electrode is immersed serves as a catalyst in this case. The electrode in the electrolyte, these reversely redu-used electrodes, are generally decorated or oxidized. The electrode is therefore subject to sintered metal powders of very high purity. Therefore a permanent redox process,
They generally have to be heated under vacuum or under protective conditions. The porosity of the electrode is heated without essential gas, which of course makes the manufacture of the electrodes complicated. Another disadvantage of the three-low pore proportion, ie a high mechanical phase reaction, is that the reaction can generate strength. At the same time, depending on the weakest reaction participant, there is no risk that the performance of the element will be directed as a result, whereby the efficiency is considerably restricted under certain circumstances by contamination or clogging of the pores. Furthermore, the number is falling significantly. In the inventive sintering of the known mixtures of metal oxides for the production of an electrode, materials suitable for mixed fuel elements are obtained in the oxides of bivalent and trivalent metals, which, as is generally known, have semiconducting properties to have. Micropores limited. Above all, nickel is found, 25 This is used for the electrodes of the fuel elements made of silver and high-purity carbon. Probably a special advantage, since under these circumstances the most serious disadvantage of the known fuel elements at the operating temperatures of the fuel elements is ultimately to be seen in the fact that sufficient conductivity of the electrodes ensures that the porous electrodes are only satisfied for a relatively short time.

hiring work. On the one hand, the electrodes have a 30 They are also galvanic elements

such low mechanical strength that they are often known to be made of metal or carbon

destroyed and thus useless. Existing electrode is oxidized or with oxygen

In addition, there is also the risk that the pores will become loaded and then reduced again in the electrolyte.

add so that the effective surface of the electrons or the oxygen is released. This known

however, the capacitance of the burning galvanic element cannot be stimulated.

fabric element is reduced. give in the direction of the invention, since a reduction

This fact is particularly well-known among the. tion of those made of metal or carbon

th fuel elements disadvantageously noticeable, not possible with electrodes of the known elements,

which the electrodes alternate with burning - thus their use as fuel electrodes -

substance or oxidizing agent and the electrolyte would be adjustable in 1 °. ,

Be associated. It has proven to be particularly advantageous when

such a fuel element clogs the pores or the fuel electrode is made of a mixture of ZnO,

if the electrode is destroyed, the gaseous Cr ₂ O ₃ and Al ₂ Oj in a molar ratio of 1: 1: 0.3

The fuel or the oxidizing agent is not sintered and partially has a spinel structure.

Electrode deposited and the three-phase reaction 45 With such a fuel electrode can be a

are fed. achieve considerable performance of the element.

• The aim of the invention is therefore to avoid the positive electrode according to the invention with

of these disadvantages to create a fuel element, preference from a mixture of NiO, Co ₂ O ₃ , Al ₂ O ₁₁

whose electrodes are easy to manufacture, a high and additionally MgO in a molar ratio of

have mechanical strength and moreover 5 ° 1: 1: 1: 1 sintered. The use of such

The electrode, which guarantees a long service life for the element, also has a considerable effect

Afford. 'j ■ ^{: increase in} performance.

According to the invention, this object is achieved with a further details, features and advantages of

The fuel element of the training invention described above emerges from the following description

This solution is achieved in that the electrodes are made from a number of preferred embodiments with the aid of the

sintered mixture of zinc oxide and / or aluminum drawing. Here shows

minium oxide with oxides of iron, cobalt, nickel, F i g. 1 consist of a longitudinal section through a according to the chromium and / or copper, the elec-
medium reducible or oxidizable, on contact with 60 FIG. 2 a section corresponding to FIG. 1 with electrodes immersed in the electrolyte, however, oxidizable or reducible,
are. . 3 shows a longitudinal section through another electrode guide form of a fuel element consisting of several metal oxides,
are for fuel elements of the F i g mentioned at the outset. 4 a longitudinal section through a fuel type known, in which the electrodes on one side 65 element in the conventional design,
are in contact with the electrolyte, while F i g. 5 shows in a diagram the dependence on which the reaction gas is supplied on the other side. Voltage (V) and the current density (mA / cm ² ) at The electrodes of this known fuel cell in a fuel element according to the invention

Comparison with a conventional fuel element according to FIG. 4 and

F i g. 6 is a diagram showing a comparison of the voltage and the operating time between a Allows fuel element according to the invention and a conventional fuel element.

The fuel element according to FIG. 1 and 2 has a housing 1, the lower half of which molten electrolyte 2 is filled. The part of the remaining above the electrolyte 2 Housing 1 is through the partition wall 5, which is at least partially immersed in the electrolyte, into the chamber 6 divided for the fuel and the chamber 7 for the oxidizing agent. In the fuel chamber 6 the liftable and lowerable fuel electrode 3 is arranged. The positive electrode 4 is located in the Chamber 7 for the oxidizing agent. The fuel is supplied to the chamber 6 via the inlet channel 8, while excess or oxidized fuel can escape through the outlet channel 9. In the same way, on the chamber 7 there is an inlet channel 10 and an outlet channel 11 for an oxidizing agent intended. The electrodes 3, 4 are each attached to a rod 12 or 13, which in the exemplary embodiment consists of stainless steel. The rods 12, 13 also serve as connecting terminals. The bars 12, 13 are through an insulating insert 14 made of quartz electrically isolated from the cell vessel 1.

A molten mixture of sodium, potassium and lithium carbonates is preferably used as the electrolyte 2 in a molar ratio of 3: 3: 4 use. In addition, alkali hydroxides, alkali oxides, Alkali halogen salts, sulfides, phosphates and their mixtures can be used as the electrolyte.

The electrodes 3, 4 consist of a sintered mixture of zinc oxide and / or aluminum oxide with Oxides of iron, cobalt, nickel, chromium and / or copper.

An electrode made of a mixture of zinc oxide, Chromium oxide and aluminum oxide used in a molar ratio of 1: 1: 0.3. The making of this Electrode is done in the following way:

50 g of zinc sulphate, 140 g of chromium sulphate and 49 g of potassium alum are dissolved in 1 liter of water and neutralized in 800 ecm of diluted ammonia water (approximately IN). The metal hydroxides obtained in this way are washed with water, dried and then ^{baked for 5 hours at a temperature of about 1000 °} C., as a result of which the metal oxides ZnO and Cr ₂ O ₃ are formed. An X-ray analysis of these metal oxides showed that they at least partially have a spinel structure. The metal oxide powder is placed in an iron mold - for example 4 cm long, 2 cm wide and 0.2 cm high - together with 5 stainless nets (sieve number 0.30 according to DIN 1171) and pressed. The nets are distributed evenly in the powder layer. The pressure is about 500 kg per cm ² . The solid electrode thus obtained is then _{sintered in an H 2} atmosphere at a temperature of 1050 ° C. for 5 hours. The electrode obtained in this way is gray and mechanically strong.

The positive electrode, which preferably consists of NiO, Co ₂ O ₃ , Al ₂ O ₃ and MgO in a molar ratio of 1: 1: 1: 1, is also produced in a similar manner. In the case of the positive electrode, however, the final sintering takes place in air.

Hydrogen, carbon monoxide, hydrocarbons, such as methane, ethane, propane, etc., or other flammable gases. As an oxidizing agent, which are present in the chamber 7, find z. B. Air or oxygen and carbon dioxide use.

In the position of the F i g. 1 becomes the fuel electrode 3 is reduced by the fuel, while the positive electrode is oxidized by the oxidizing agent. If the electrodes are then shown in FIG. 2 lowered and immersed in the electrolyte 2, so oxidation occurs in an electrochemical reaction of the fuel electrode 3 and a reduction of the positive electrode 4. During this process a tension can be picked up on the rods 12, 13. This changes that of the fuel element Removable amount of current proportional to the speed at which the lifting process is carried out and lowering is repeated. In an experiment, the results are shown in Table 1 below contained results:

Table 1

Cycles / min.

1
2
3
4th
5

Current density (mA / cm ² ),
at a voltage of 0.5 V.

100
125
175
200
165

In Fig. 3 is another embodiment of the Fuel element shown according to the invention. In this element, the electrodes 3 ', 4' are disk-shaped trained and circulate continuously. The disc-shaped electrodes 3 ', 4' are on the Rods 12, 13 mounted corresponding shafts 12 ', 13', which also serve to connect the consumer. The shafts 12 ', 13' are isolated from the housing 1 of the element by means of the insulating body 14 '. Table 2 shows the results of an experiment in which the current density as a function was measured by the speed of rotation of the electrodes. It can be seen that the highest current density at a Speed of 10 revolutions per minute is reached, at higher speeds, however, a drop in Current density was observed.

Table 2

In the tests according to Tables 1 and 2 electrodes of the type were used, their production above is explained in detail. In the case of the element with electrodes moved up and down, the elec-

Speed (rpm) Current density (mA / cm ² )
at 0.5 V voltage 1 50 2 90 4th 175 6th 220 8th 260 10 275 12th 250 14th 215

Claims (3)

5 6 Troden 5 cm long, 3 cm wide and 0.1 cm thick and penetrates through the electrodes, since difficulties persisted a grid made of stainless steel mesh. That rides out the pressure between electrolyte and gas-fuel element, with which the experiments are similar. However, this increases the efficiency Table 2, had disc-feeding electrodes degraded and their lifespan diminished Electrodes with a radius of 5 cm and a 5 shortens. Thickness of 0.15 cm. In the case of both fuel elements, the fact that this is true is shown by a comparison of the propane commercially available as fuel, as oxy diagrams in FIG. 5 and 6, where the corresponding dationsmittel a mixture of CO ₂ with O _{2 is used} in a characteristic curve for the fuel element volume ratio of 1: 1 according to the invention. A _{mixture of Na 2} CO ₃ , K ₂ CO ₃ , Li ₂ CO ₃ in material element B is shown as the electrolyte element A and a corresponding conventional fuel element. Use the data for the distillation in a 3: 3: 4 molar ratio. The fabric element according to the invention were at a distribution temperature of 58O ⁰ C. Search arrangement according to FIG. 3 with rotating elec- This results in the following trode measured in the fuel cell. Reactions: In Fig. 5 is the dependence of the current density on 15 the voltage for both elements A, B is shown. The propane gas makes the fuel _{electrode D} j _e electrode reaction surface of the conventional one reduced: element B was 25 cm ² , the cell temperature C ₃ H ₈ + 10MO "-> 10MO _n -! + 3CO ₂ + 4H, O ⁶²⁵ ° ^C - ^The voltage was increased at the moment /] \ measure than the current density by supplying pro- 20 pan to the fuel electrode and a gas mixture When the thus reduced fuel _{from air and} carbon dioxide to the positive electrode electrode comes into contact with the electrolyte, the electrode will begin _{to rise.} The electrode reaction area of the again oxidized: element according to the invention Λ was 45 cm ² , the 10MO _n -, + 10 (CO ₃ -) -> 10MO "+ 10CO ₀ cell temperature 595 ° C. The gas chamber for the combustion 4- 2Oe ~ (2) ² 5 fabric electrode was made with propane, the gas chamber for the positive electrode with carbon dioxide containing So the following overall reaction results: _air fed. Both elements were used as electrical CH 4- 10 (CO -) - »■ 13 CO, + 4 HO 4- 20 e ~ ' ^{vt e} ' ^ne mixture of sodium, potassium and lithium ^{38 3 2 2} (3) carbonate is used in a molar ratio of 3: 3: 4. 30 The diagram of FIG. 5 clearly shows that the Due to the oxidizing agent, the positive element is formed according to the invention with the same Electrode oxidized: voltage to deliver a significantly higher current M'O _m + V ₂ O ₂ -J- MO _{7n + 1} (4) is capable. The diagram of FIG. 6 enables a The oxidized positive electrode is _{reduced on contact 35 due to the} dependence of the operating time on that with the electrolyte: voltage at the elements according to the diagram M'O _{m + 1} 4- CO ₂ 4- 2e ~ ->M'O _m 4- CO ₃ - (5) of FIG. 5. Both elements were with a constan th current density of 100 mA / cm ² operated. It is Thus, for the positive electrode, the following results _from FIG. 6 it can be seen that the state of the beginning overall reaction: ₄₀ knew element B due to the rigid electrodes, CO ₂ 4- V2 O ₂ 4- 2e ~ - »CO ₃ - (6) whose pores gradually close with the electrolyte set, so deteriorated that the electrodes after The overall reaction of the element results so after 200 hours have been inoperable. By summarizing equations (3) and by contrast, such a deterioration in (6) was as follows: ₄₅ Fuel element A according to the invention cannot be C ₃ H ₈ 4- 5O ₂ -> ■ 3CO ₂ 4- 4H ₂ O (7) observe what its cause in the difference in Reaction mechanism has. So it is with the burning In the above equations, the substance cell according to the invention means a long service life Symbols M and M 'each represent a metal atom. expected. In Fig. 4 is for comparison with the fuel 5 ° elements according to the invention, as shown in FIG. 1 to 3 are shown, a fuel element conventional claims Type shown. 15 denotes the cell vessel, 16 the electrolyte, 17 the fuel electrode, 18 the positive electrode, 19 the fuel chamber, 20 the 55 Chamber for the oxidizing agent, 21 or 22 A 1. Fuel element with a chamber for the and outlet channels for the fuel, 23 and 24 the fuel, a separate chamber for the corresponding channels for the oxidizing agent and oxidizing agent, a fusible electrolyte 25 a seal to prevent gas leakage. and two alternating with the fuel and the In the known fuel element according to FIG. 4 60 oxidizing agents connectable electrolyte takes place a three-phase reaction, namely where troden, characterized in that Electrolyte, an electrode and gas meet. the electrodes are made from a sintered mixture of So there is a reaction between the individual zinc oxide and / or aluminum oxide with oxides of the Partners only in a very limited spatial iron, cobalt, nickel, chromium and / or copper Area possible, whereby the elements are removed from the element, with the electrodes from the focal point Electricity is also severely limited. Reducible resp. With the oxidizing agent. nuier operation of the known fuel element oxidizable, on contact with the electrolyte there is the further disadvantage that the electrolyte can be oxidized or reduced. 7 8 2. Fuel element according to claim 1, characterized 3. Fuel element according to claim 1 or 2, characterized in that the fuel electrode is characterized in that the positive electrode a sintered mixture of ZnO, Cr ₂ O ₃ and a sintered mixture of NiO, Co ₂ O ₃ , Al ₂ O ₃ in a molar ratio of 1 :. 1: 0.3 be Al ₂ O ₃ and additionally MgO in a molar ratio and partially has a spinel structure. 5 of 1: 1: 1: 1 consists. 1 sheet of drawings