DE102007032807A1 - Mixer for direct methanol gas cell system in mobile electronic device, has measuring points formed symmetrically in proximity of center of gas separating device away from center, and are provided on same symmetry plane of device - Google Patents

Abstract

The mixer has a tank (100), a gas or liquid inlet, a liquid outlet (103) formed on one side of an integrated gas separating device (200), and a gas outlet (104) formed by a gas-selective membrane that covers another side of the device. A fill level measuring system (107) arranged in the tank has a pair of measuring points determining liquid level for ensuring that more than half of inner volume of tank is filled with liquid. The points are formed symmetrically in the proximity of the center of the device away from the center, and are provided on the same symmetry plane of the device.

Description

The This invention relates to a combined mixer and gas / liquid separator for the separation of a gas / liquid mixture a direct methanol fuel cell (DMFC) and a corresponding Level measurement system.

Technical background and State of the art

A Fuel cell is a galvanic cell, which is the chemical reaction energy a continuously supplied fuel and a Oxidizing agent converts into electrical energy. A fuel cell usually consists of two electrodes passing through a membrane or an electrolyte are separated from each other. The anode will with the fuel, for example hydrogen, methane or methanol, lapped and the fuel is oxidized there. The cathode is lapped with the oxidizing agent, for example oxygen, Hydrogen peroxide or potassium thiocyanate, which reduces at the electrode becomes. The ones used to realize the individual components Materials vary depending on the fuel cell type choose.

compact Direct methanol fuel cell systems (DMFC) are currently in focus the development in many electronics companies. It is expected, that they power the power of mobile electronic devices replace or change because they have longer service times and allow faster charging. Direct methanol fuel cells (DMFC) are low-temperature fuel cells, even at temperatures in the range of approx. 60-120 ° C work. As the electrolyte, this cell type uses a polymer membrane. Methanol (CH3OH) is combined with water without prior reforming supplied directly to the anode and oxidized there. At the anode arises as exhaust gas carbon dioxide (CO2). The cathode as the oxidant supplied oxygen reacts with H + ions and electrodes to water. The advantage of DMFC lies in the use of a liquid, very easily storable and extremely cheap energy source, which can be disseminated for example in plastic cartridges. moreover There is a widely branched infrastructure for methanol already in many areas, for example by using as Antifreeze additive in windshield wiper water for motor vehicles. This fuel cell type can - depending on the design - services ranging from a few mW to a few 100 KW. DMFCs are suitable especially for portable use in electronic Equipment as a replacement and supplement to conventional Accumulators. Typical applications are in telecommunications and the power supply of notebooks.

The Oxidation of the methanol at the catalyst of the anode takes place stepwise, being multiple reaction pathways with different intermediates in the discussion. To uphold the efficiency of the fuel cell, It is necessary to rapidly remove the reaction products from the environment remove the electrode. Due to the prevailing temperatures and the underlying chemistry creates a liquid / gas mixture from CO2, water, water vapor and unreacted methanol. Out this liquid / gas mixture, the CO2 must be separated, after adjustment of the methanol concentration, the liquid Re-fuel mixture to the anode. The separation The gases are produced with the help of a CO2 separator.

At the cathode is formed from unused air, water and water Water vapor also a liquid / gas mixture. To one To achieve long autarky of the system, one must as possible much of the water is separated from the air and in be returned to the anode circuit. To this The purpose is a heat exchanger behind the cathode outlet the fuel cell arranged to cool the mixture and to achieve a condensation of the water vapor.

the Downstream heat exchanger is arranged an air separator, which separates the air flow from the liquid water to the Return water back to the anode circuit. Accordingly, the separators are primarily used for water management and the removal of CO2 from the equilibrium. conventional Separators separate the phase mixture from liquid and gas or vapor components, wherein the Gas or vaporous components to the environment be delivered.

The separators or separators are thus primarily the water management and the removal of CO2 out of balance. They are usually realized as separate facilities, which is connected to the actual fuel cell in each case via a common for the liquid / gas mixture supply line. This spatial distance also causes a temperature gradient and from the slowly cooling liquid / gas mixture condenses water. Conventional separators separate the phase mixture from liquid and gas or vapor components, wherein the gaseous or vaporous components are released to the environment. The present invention also starts here.

Known is a separator for separating the liquid / gas mixture equipped with a porous membrane. The porous one Membrane is with its inside the liquid / gas mixture facing and its outside communicates with the environment in Contact. Furthermore, such membranes are usually hydrophobic Materials coated or consist of these. From the inside the membrane extend diffusion channels to the outside, which are dimensioned so that on the inside (liquid) Water does not penetrate, but diffuse gas to the outside can.

at the separators or separators of the prior art is the Liquid / gas mixture spent in a cavity at the the gas-permeable membrane is adjacent. One volume of the cavity and one relative position of the membrane depend on the orientation of the Separators in operation and the expected volumes of liquid / gas mixture. The volume of the cavity is set so that the liquid / gas mixture after entering the cavity into a gas and liquid phase can separate and then over the entire volume of the cavity are separated from each other. The membrane will be like this arranged to abut an upper side of the cavity, the is in regular operation with the gas phase in contact. At the Bottom, the liquid phase is discharged. A however, sufficient functionality of such separators is only if the orientation of the separator in the room is taken into account becomes. At most, the separator may be out of its upright position by a few degrees Be pivoted position, so that the gas phase continues at the Membrane rests. Especially for the mobile use of fuel cells However, this circumstance is limiting.

A possible embodiment of a combined CO ₂ and water separator is in US 6,110,613 shown. The Stapelbrennstoffauslaßstrom consisting of a fuel mixture and CO ₂ and the Stapelluftauslaßstrom consisting of air and water are fed into a common separator. The liquid components of both streams leave the separator at the bottom thereof and are fed into the stack fuel inlet after admixing concentrated fuel. The gaseous components are directed to a recycle device that transfers water and fuel components from the exhaust stream into the intake air stream through a permeable unit.

Of the The disadvantage of this solution is that it is not orientation-independent is because liquid through the gas outlet of the separation space would be lost if turned upside down would. Furthermore, the structure is very complicated, as a Fuel / water recovery device needed downstream is going to be a high water level and fuel loss in the system to avoid.

Another embodiment of a combined CO ₂ and water separation device is in EP 1 383 191 A1 disclosed. Here, CO ₂ separation is achieved in a fuel-filled space having an inlet connected to a stack fuel outlet and an outlet connected to a circulation pump. The CO ₂ bubbles are separated from the fuel mixture by gravity during the residence time of the fuel mixture within the separation space. About this separation space a water separator is arranged. There are openings between the CO2 separation space and the water separator, which results in a supply of separated CO2 to the vent and a return of separated water to the CO2 separation device (back to the anode loop), both through the action of gravity. The main disadvantage of this embodiment is the strong dependence on the orientation of the device, ie the device operates substantially only in an upright position. This can also lead to problems when the separation device in a flat system structure, as z. As required in notebook charging stations, must be integrated.

Further are for the operation of mobile electronic devices compact DMFC systems necessary in addition to different Orientations must work.

It is therefore an object of the invention, a gas / liquid separator of a DMFC system indicating the function of the system in a wider range of orientations of the Systems allowed.

These The object is solved by the features of claim 1.

Accordingly, there is a mixer with integrated gas separation device ( 200 ) for a direct metha nol fuel cell (DMFC), the device comprising:
a tank, a gas / liquid inlet for receiving a gas / liquid stream, a liquid outlet disposed on a first side of the apparatus, a gas outlet formed by a gas-selective membrane covering a second side of the apparatus, an inner wall disposed over the liquid outlet between the gas / liquid inlet and the liquid outlet such that gas bubbles are prevented from reaching the liquid outlet directly, characterized in that a level measuring system is arranged in the tank comprising at least one pair of Measuring points for determining a liquid level comprises, so as to ensure that more than half of the internal volume of the tank is filled with liquid, the measuring points are arranged in the vicinity of the center of the device symmetrically away from said center, and on the same plane of symmetry Device are provided.

advantageously, makes the placement of the level measurement system symmetrical away from the center of the device the work of the system in one wider range of orientations, d. H. up to 90 ° from the vertical upright orientation.

Of the Fluid outlet can be on the opposite Side of the page, which includes the gas outlet. Of the Fluid outlet may also be at the bottom of the device be arranged, the gas outlet at the top of the device, and the gas / liquid inlet may be in an upper Part of a side surface of the device attached be. The liquid outlet can be in the center of the soil be arranged of the device.

Prefers said membrane is made of PTFE and can have a thickness of 100 to 300 microns have.

A inner wall can between the inlet and the level measuring system be arranged, wherein the inlet stream against the said inner Wall is guided to a stable level measurement to ensure.

The Level measuring system can be used as a conductive level measuring device be formed, which provides a measurement signal only if both measuring points of the at least one pair of measuring points in Liquid are immersed. The level measuring system may comprise two conductive tubes, each correspondingly have a contact point, wherein the tubes are parallel extend to and away from a first plane of symmetry of the tank and the contact points symmetrically away from a second plane of symmetry of the tank and symmetrically away from a third plane of symmetry of the tank are arranged. The contact points can be be arranged at the ends of the respective tubes.

The first plane of symmetry may be the horizontal plane of symmetry in the xy plane, the second plane of symmetry the vertical plane of symmetry in the yz plane, and the third plane of symmetry is the plane of the xz plane.

The symmetrical removal of the contact points from the third plane of symmetry can be achieved by connecting the tubes with a different length are formed.

Of the Gas / liquid flow may be supplied from a DMFC anode become.

additionally is according to the invention, a conductive level measuring system for determining a filling level in a prismatic Container specified. The system includes at least a few of measuring points for determining a level, wherein the measuring points are arranged in the vicinity of the center of the device are symmetrically away from said center, and on the same Symmetry plane of the device.

The Level gauge can have two conductive tubes comprise, each corresponding to a contact point, wherein the tubes are parallel to and away from a first Symmetrieebene of the tank extend and the contact points symmetrical away from a second symmetry plane of the tank and symmetrically are arranged away from a third plane of symmetry of the tank.

The Konktaktpunkte can at the ends of the respective tubes be arranged.

The first plane of symmetry may be the horizontal plane of symmetry in the xy plane, the second plane of symmetry the vertical plane of symmetry in the yz plane, and the third plane of symmetry the plane of symmetry x-z plane.

The symmetrical removal of the contact points from the third plane of symmetry can be achieved by connecting the tubes with a different length are formed.

Brief description of the drawings

The Invention will be described below with reference to exemplary embodiments the invention and the corresponding drawings in more detail to be discribed.

1 shows a DMFC system of the prior art;

2 shows an embodiment of a mixer with integrated Gasabscheidevorrichtung according to the prior art;

3 shows a schematic 3D side view of an embodiment of the combined mixer and Gasabscheidevorrichtung according to the invention.

4 shows a plan view of the invention as in 3 shown under operating conditions;

5 shows the embodiment 4 rotated by + 90 °, where the x-axis is the axis of rotation;

6 shows the embodiment 4 rotated by -90 ° relative to the x-axis;

7 shows the level measuring system according to the invention;

8th . 9 show the orientation independence of the level measuring system according to the invention.

A DMFC system is as in 1 shown, built. A fuel cell stack 10 has an air inlet 11 and an air outlet 13 on. An air pump or a fan 12 Lead reaction air of the stack cathode through the air inlet 11 to. The DMFC fuel cell stack works with a so-called fuel stream consisting of water and methanol on the anode side and with a so-called oxidant stream, ie air and oxygen, on the cathode side. The DMFC stack directly produces electricity through an electrochemical reaction. The membrane 14 of the stack is permeable to water and thus the operation of the stack produces a transfer of water from the anode side to the cathode side by an electro-osmotic suction. To use a concentrated fuel and the volume of the fuel tank 30 To minimize this, recovering this water is essential to the system. The heat exchanger 50 is used to condense water from the cathode air outlet 13 used. This water must be in a water separator 60 be separated and in the so-called Anodenzuleitung 18 to be led back. The air leaves the separator at the vents 61 , The liquid outlet 62 of the water separator 60 is with the main anode cycle 18 connected. The anode fuel cycle includes a circulation pump 23 introducing the fuel mixture to the stack anode inlet 15 leads, a CO ₂ separation device 20 , and a mixer 122 in which the concentrated fuel and the recovered water from the heat exchanger are circulated through their respective water connection 64 and fuel connection 32 be guided. A driving force is necessary for the supply of the recovered water. Therefore, the scheme has a pump 63 for water recovery.

2 shows an embodiment of the mixer with integrated gas separation device of the prior art. The inlet flow of water / air 101 is located in the upper part of the device. The liquid water gets through by gravity 106 separates and falls towards the bottom of the device. The inlet fuel stream is in the bottom of the device 102 isolated, which works as a liquid retention tank. The gate of the incoming stream leaves the device through a vent 104 , which consists of a gas-permeable membrane. The liquid mixture exits the device through the fuel outlet 103 to be led back to the pile. The prior art combined CO ₂ separator mixer uses gravity as the principle of separation and is therefore limited to operation in an upright position or possibly with a small inclination of up to 30 ° from the vertical. The storage and transport of the system is also limited by a leaking mixer when the mixer is not in an upright position.

3 shows a schematic drawing of an embodiment of the combined mixer with integrated gas-separating device according to the invention. The device according to the invention comprises a tank or a container 100 to contain a fluid, a gas-selective membrane 202 , a river inlet 101 , a liquid flow outlet 103 , a gas outlet 104 , an inner wall at the upper part 200 , an inner wall at the bottom 201 and a level gauge 107 ,

The flow or stream enters the combined mixer and gas separation apparatus in the upper part of the apparatus. The inner wall 201 , which is located at the bottom, prevents gas bubbles from the liquid outlet 103 , which is preferably placed in the center of the bottom plate of the device, directly reach. The gas outlet 104 , here preferably a CO2 outlet, is arranged at the top of the device, the gas passing through a hydrophobic membrane 202 flows.

This membrane 202 not only allows the venting of gas to the environment, but also prevents the outflow of liquid through the gas outlet 104 , The membrane used is usually made of PTFE and usually has a thickness of 100 to 300 μm.

The liquid content of the tank is through a level gauge 107 regulated. The normal level must be greater than half of the total internal volume of the tank to ensure that only liquid through the liquid outlet 103 flows out, as shown in the following figures. To prevent large fluctuations in the level due to the incoming current is a wall 200 between the inlet and the level measuring device 107 arranged, preferably close to the inlet 101 , The wall includes a portion that is substantially parallel to the side wall that surrounds the inlet 101 includes, is arranged, but may also have a second portion which is formed substantially parallel to the bottom surface to a direct contact of the level measuring device 107 to prevent with the liquid.

4 shows a side elevational view of the invention under working conditions as in 3 shown. The mixture enters the mixer through the inlet 101 one. The incoming stream is biphasic, ie gaseous and liquid, and therefore generates gas bubbles 301 in the liquid contents. The inner wall 201 prevents the bubbles directly from the liquid outlet 103 to take. She is slightly averse to the liquid inlet 101 in the direction of the outlet 103 and close to the outlet 103 arranged. The level 300 is through the two level sensors 107 , which are arranged in the tank, regulated.

5 shows the embodiment of the 4 rotated by + 90 °, where the x-axis is the axis of rotation. In other words, in this configuration, the bottom surface is a side surface that is the opposite side of the side that is the inlet 101 having. 6 shows the embodiment of the 4 rotated by -90 ° relative to the x-axis, ie, the bottom surface is now the side that the liquid inlet 101 having. 5 and 6 illustrate the orientation independence of the device.

Since the liquid level is designed to be greater than half the volume contained in the mixer, the liquid outlet is 103 still below the liquid level 300 that is, in contact with the liquid. Further, part of the surface of the membrane 202 not covered by the liquid, in 5 the upper area so that gas can be released through the membrane to the environment. The level sensor 107 , which operates on the principle of conductivities, is arranged so that this level is maintained in rotated positions. Although the device is not in an upright position, the diaphragm stops 202 Make sure that the contained liquid remains in the mixer and there is still plenty of surface available to gas the mixer 104 leave.

The level measuring system 107 is in more detail in 7 shown. It consists of two carrying tubes 400 , which each have a contact point at their ends 401 and 402 exhibit. The actual measurement is based on the difference between the conductivity of a gas and a liquid. When the two contact points are both immersed in the liquid, a current can flow through the conductive liquid. The current will be lower depending on whether one or both contact points are surrounded by gas.

Orientation independence is in 8th and 9 shown. In 8th the device is rotated 90 ° about the X-axis. It can be seen that the contact points are at the same distance from the axis of symmetry 500 the device are placed. The level gauge detects liquid only when both contacts 401 and 402 immersed in the liquid. If this is not the case, more liquid will enter the tank 100 introduced. Because the contacts removed. are positioned from the symmetry axis, the liquid level remains 300 above the liquid outlet 103 ,

In 9 the device is shown in a -90 ° rotated position about the Y-axis. To ensure that the level 300 above the liquid outlet 103 remains, you can see that the tubes, the contacts 401 and 402 carry, have a different length, so that the contact points with a given distance from the axis of symmetry 500 are arranged away. Since both contact points are to be immersed in liquid, this arrangement ensures that the liquid level 300 above the liquid outlet 103 remains.

The two conductive tubes 400 are arranged so that they are parallel to and away from a first plane of symmetry 700 of the tank 100 extend as in 7 shown. The contact points 401 . 402 are in the tank 100 arranged so that it is symmetrically away from a second plane of symmetry 800 of the tank 100 and symmetrically away from a third plane of symmetry 900 of the tank 100 are. The contact points 401 . 402 are preferred at the ends of the respective tubes 400 arranged, but can also be arranged differently. As in 7 without limitation, the first plane of symmetry is the horizontal plane of symmetry 700 in the XY plane, the second plane of symmetry is the vertical plane of symmetry 800 in the YZ plane, and the third plane of symmetry 900 is the level in the XZ plane.

LIST OF REFERENCE NUMBERS

10 DMFC fuel cell stack 11 air intake the stacked cathode 12 air pump 13 air outlet the stacked cathode 14 membrane 15 inlet the stack anode 16 outlet the stack anode 18 Anode circuit 20 CO ₂ separator 21 Gas outlet of the CO ₂ separator 22 Liquid outlet of the CO ₂ separator 23 circulation pump 30 fuel tank 31 fuel pump 32 fuel connection to the mixer 40 mixer 50 heat exchangers 52 Heat exchanger outlet 55 Fan 60 water separator 61 air outlet of the water separator 62 liquid outlet of the water separator 63 pump for water recovery 70 Water recirculation pump 100 Tank / container which contains a liquid 101 inlet a water / air stream (from the heat exchanger) 102 inlet a fuel stream (from the stack outlet) 103 outlet a fuel 104 Vent outlet for gases (CO ₂ and air) 105 Fuel mixture level 106 Water, which falls by gravity 107 level sensor 200 Inner wall 201 Inner wall 202 gas Selective membrane 300 liquid Level 301 gas bubbles 400 supporting roar 401 contact point 402 contact point 500 axis of symmetry 600 axis of symmetry 700 plane of symmetry 800 plane of symmetry 900 plane of symmetry

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 6110613 [0010]
• - EP 1383191 A1 [0012]

Claims (18)

Mixer with integrated gas separation device ( 200 ) for a direct methanol fuel cell (DMFC), comprising: a tank ( 100 ), a gas / liquid inlet ( 102 ) for receiving a gas / liquid stream, a liquid outlet ( 103 ) located on a first side of the device ( 200 ), a gas outlet ( 104 ), formed by a gas-selective membrane ( 801 ), which is a second side of the device ( 200 ), an inner wall ( 801 ), located above the liquid outlet ( 103 ) between the gas / liquid inlet ( 102 ) and the liquid outlet ( 103 ), such that gas bubbles are prevented from leaving the liquid outlet ( 103 ), characterized in that a level measuring system ( 107 ) in the tank ( 100 ), which comprises at least one pair of measuring points for determining a liquid level, so as to ensure that more than half of the internal volume of the tank ( 100 ) is filled with liquid, wherein the measuring points in the vicinity of the center of the device ( 200 ) are arranged symmetrically away from said center, and on the same plane of symmetry of the device ( 200 ) are provided. Mixer with integrated gas separation device ( 200 ) according to claim 1, wherein the liquid outlet ( 103 ) is arranged on the opposite side of the side, the gas outlet ( 104 ). Mixer with integrated gas separation device ( 200 ) according to claim 1 or 2, wherein the liquid outlet ( 103 ) at the bottom of the device ( 200 ), the gas outlet ( 104 ) at the top of the device ( 200 ), and wherein the gas / liquid inlet ( 102 ) in an upper portion of a side surface of the device ( 200 ) is attached. Mixer with integrated gas separation device ( 200 ) according to at least one of the preceding claims, wherein the liquid outlet ( 103 ) is arranged in the center of the bottom of the device. Mixer with integrated gas separation device ( 200 ) according to at least one of the preceding claims, wherein said membrane ( 801 ) consists of PTFE. Mixer with integrated gas separation device ( 200 ) according to at least one of the preceding claims, wherein said membrane ( 801 ) has a thickness of 100 to 300 microns. Mixer with integrated gas separation device ( 200 ) according to at least one of the preceding claims, wherein an inner wall ( 800 ) between the inlet ( 102 ) and the level measuring system ( 107 ), wherein the inlet flow against said inner wall ( 800 ) is guided to ensure a stable level measurement. Mixer with integrated gas separation device ( 200 ) according to at least one of the preceding claims, wherein the level measuring system ( 107 ) is a conductive level measuring device which provides a measuring signal only when both measuring points of the at least one pair of measuring points are immersed in liquid. Mixer with integrated gas separation device ( 200 ) according to at least one of the preceding claims, wherein the level measuring system ( 107 ) two conductive tubes ( 400 ), each corresponding to a contact point ( 401 ) and ( 402 ), wherein the tubes are parallel to and remote from a first plane of symmetry (FIG. 700 ) of the tank ( 100 ) and the contact points ( 401 . 402 ) symmetrically away from a second plane of symmetry ( 800 ) of the tank and symmetrically away from a third plane of symmetry ( 900 ) of the tank are arranged. Mixer with integrated gas separation device ( 200 ) according to claim 9, wherein the Konktaktpunkte ( 401 . 402 ) at the ends of the respective tubes ( 400 ) are arranged. Mixer with integrated gas separation device ( 200 ) according to claim 9, wherein the first plane of symmetry is the horizontal plane of symmetry ( 700 ) in the xy plane, the second plane of symmetry is the vertical plane of symmetry ( 800 ) in the yz plane, and the third plane of symmetry ( 900 ) is the level of the xz plane. Mixer with integrated gas separation device ( 200 ) according to claim 9, wherein the symmetrical distance of the contact points ( 401 . 402 ) is achieved from the third plane of symmetry by the tubes ( 400 ) are formed with a different length. Mixer with integrated gas separation device ( 200 ) according to one of the preceding claims, wherein the gas / liquid stream is supplied from a DMFC anode. Conductive level measuring system for determining a level in a prismatic container ( 100 ) comprising at least a few of measuring points for determining a filling level, wherein the measuring points in the vicinity of the center of the device ( 200 ) are arranged symmetrically away from said center, and on the same plane of symmetry of the device ( 200 ). A conductive level measuring system according to claim 14, wherein the level measuring system ( 107 ) two conductive tubes ( 400 ) corresponding to a contact point ( 401 ) and ( 402 ), wherein the tubes are parallel to and remote from a first plane of symmetry (FIG. 700 ) of the tank ( 100 ) and the contact points ( 401 . 402 ) symmetrically away from a second plane of symmetry ( 800 ) of the tank and symmetrically away from a third plane of symmetry ( 900 ) of the tank are arranged. A conductive level measuring system according to claim 14 or 15, wherein the contact points ( 401 . 402 ) at the ends of the respective tubes ( 400 ) are arranged. A conductive level sensing system according to claim 15, wherein the first plane of symmetry is the horizontal plane of symmetry (Fig. 700 ) in the xy plane, the second plane of symmetry is the vertical plane of symmetry ( 800 ) in the yz plane, and the third plane of symmetry ( 900 ) is the level of the xz plane. A conductive level measuring system according to at least one of the preceding claims 14 to 17, wherein the symmetrical distance of the contact points ( 401 . 402 ) is achieved from the third plane of symmetry by the tubes ( 400 ) are formed with a different length.