Device for increasing or decreasing the oxygen content of air, and method of producing and of operating it.

The invention relates to a device for increasing or decreasing the oxygen content of a consumer, in particular a combustion chamber, air to be supplied using a very thin semi-permeable membrane, a first chamber of higher pressure to an input for normal air and an output for O₂-depleted air and a second space of lower pressure to an output 02 for enriched air is separated, and to a method for producing this device and a method for its operation.

In a known device of this kind which is used in particular for the enrichment of breathing air or combustion air with oxygen, an oxygen more than nitrogen-permeable membrane made of silicone rubber is used, which is applied two-dimensionally on a porous support. The case recoverable membrane surfaces are small, with the result that it is also possible only small amounts win ° 2-enriched air. Although the amount can be increased by increasing the differential pressure; such a pressure increase is but for many applications and undesirable for technical reasons anyway possible only to a limited extent.

It is a further dialysis unit for blood purification known, are grouped together in a cylindrical bundle of porous hollow fibers in which in a number of less than 10, 000 and disposed in a cylindrical housing. The fiber ends are sealed through the end walls of the housing. Blood is passed through the hollow interiors of the hollow fibers. The peripheral housing has an input and at the other end an outlet for cleaning fluid which is pumped through the housing space outside the hollow fibers at one end. Here, the toxins do not migrate as a result of a pressure difference but due to a concentration difference of the blood in the cleaning liquid. Thus sufficient time for the passage of toxins into the cleaning liquid remains, the hollow fibers have a length of 220 to 350mm.

The invention has for its object to provide a device of the type described above, which allows to deal with low pressure differences in spatially small dimensions air in larger quantities and / or so that it is particularly suitable for the supply of combustion chambers.

This object is inventively achieved in that hollow fibers having microporous walls which have membrane on a peripheral surface and are arranged in large numbers in parallel in a housing, the opposed end walls are penetrated by the ends of the hollow fibers, said ends being sealed on its outer circumference ,

Since the inner or outer circumferential surfaces of all hollow fibers are provided with a membrane results in an extremely large membrane area. It is therefore possible_Lich, A small amount of O₂-enriched air, _z,_B, for breathing purposes, to produce a very low pressure differentials such as the lung power, or by conventional pressure differentials of about 2 Pa huge amounts 0₂-enriched air, for example, to win the combustion air of a motor vehicle or a furnace. The microporous wall is a sufficiently stable base for an ultra-thin membrane.

Here, the hollow fibers may form a support onto which the membrane is applied. This makes it possible to use a hollow fiber having optimum load properties. The hollow fibers can also be made of the membrane material, so that a one-piece structure obtained with a porous support member and a non-porous membrane. Here, the membrane does not have to be applied subsequently; they may already be produced in the production of the hollow fibers, or by controlled pore formation, either by closing the pores along a peripheral wall. In addition, a particularly good connection between carrier and membrane. Optionally, the hollow fibers may in its wall also comprise reinforcing inserts.

Advantageously, forming the inner cavities of the hollow fibers and the first space of the housing space outside of the hollow fibers the second space. Since the inner cavity of the hollow fibers leads to higher pressure, although a slight elastic expansion of the hollow fibers is possible, but not a compression and an associated reduction of the flow cross-section.

There should be at least 100,000 hollow fibers, preferably more than 0.5 million hollow fibers, can be provided. Devices having more than 5 million hollow fibers are possible without difficulty. In particular, much hollow fibers should be mutually arranged approximately parallel in a hollow fiber battery that a membrane area of ​​15 to 500 m²results.

With particular preference, the hollow fibers are arranged in a housing and it covers at least an output plenum along a parallel to the hollow fibers extending housing sidewall. The 02-enriched air can therefore be sucked substantially transverse to the hollow fibers to the exit plenum through so that the chokes are comparatively small.

In particular, it be ensured that the housing has rectangular end walls with a long and a comparatively short side and that the output plenum extends along a line extending between the long sides of the end walls housing side wall and substantially over its entire surface. Furthermore, a second similar output plenum may extend along the opposite side wall. In this way it is ensured that all the hollow fibers are connected via a short path verhältsnismäßig with an output plenum. Accordingly, the pressure drop between the membrane and exit plenum is correspondingly small. Since the hollow fibers do not absolutely have just remain large enough lanes for the gas even with tightly packed hollow fibers between them. Optionally can be structurally defined by a corresponding arrangement of the hollow fibers or by use of hollow fiber sections of larger diameter such streets but.

Preferably, the hollow fibers have an outer diameter of 100 to 400 microns, preferably 200 microns. Taking into account the achievable wall thicknesses there is a sufficiently large internal cross-section, which opposes the air flowing therethrough is not too large flow resistance.

The hollow fibers do not need greater wall thickness than 20 to have it meet even less than 6 microns. This results in a sufficient stability at the lowest possible resistance to the passing air.

It is advisable_/to hold the hollow fiber length as short as possible, in particular a length of less than 200 mm, preferably 100 mm to be used, so that the diaphragm portion at the rear end of the hollow fibers of the membrane air is available with sufficient oxygen content.

When the pores of the hollow fibers is to be considered that they must both be small enough not to impair the safe support of the membrane, but on the other hand, large enough not to hinder the gas transport to and from the membrane. It is advantageous here if the pore size largely to 1 is in the range 0.1 pm. Preferably, the pore size increases the membrane from back; the small pores for better support of the membrane need be here to extend over only a thin layer so that they do not affect the gas transport noticeably. In particular, the size of the area covered by the membrane pores may be 20 to 50 nm.

In a preferred embodiment it is ensured that the membrane is arranged on the inner circumference of the hollow fibers. This results in a particularly long service life, because the membrane is located well protected and any mechanical stress is avoided, as it may occur in superposed hollow fibers with the outside arranged membrane.

It is also favorable, upstream of the entrance of the first space, an air filter. This ensures that the internal cavities of the hollow fibers do not clog.

When installed in a vehicle, the hollow fibers should extend in the longitudinal direction and one ends be located near the front of the vehicle. In this manner, the running wind can be utilized to drive the air through the hollow fibers, if it is sought to use an oxygen-enriched combustion air in the engine.

To drive the air through the inner cavity of the hollow fibers can be used yet a blower. This can also be additionally incorporated in a motor vehicle.

If the combustion chamber is part of an internal combustion engine or combustion plant, the membrane area should be large enough so that the combustion temperature above 2500 ° C, especially at about 3000 ° C, is. The high combustion temperatures lead to an increase in efficiency and a reduction in fuel consumption. In internal combustion engines, it is also unnecessary that the air-fuel ratio as a function of full load and partial load is changed, thereby Vergaserbau and maintenance are greatly simplified. Since the firing rate is very large, the ignition timing can be placed close to the top dead center. This saves additional fuel and reduces the tendency to self-ignition. The reduced tendency to knock it further allows to increase the compression, whereby the efficiency is further increased. The rapid Zündverlauf also avoids uneven heat transfer to the combustion chamber wall, which leads to a lower cooling water temperature and to a lower fan speed. In addition, the rapid Zündverlauf gives a smooth running at a; Internal combustion engine. The amount of combustion air required for the operation of such a combustion chamber, however, is very large. For example, it is for a 2 liter engine over 100 m³/H. A correspondingly large membrane area can produce but with the help of the hollow fibers without any difficulty.

It is also favorable, if the exhaust gas channel of the combustion chamber is associated to the reduction of the nitrogen oxide content to a device. Hereby the fact is considered that a large amount of nitrogen oxide produced during the desired high combustion temperatures, at 2700 ° C, for example, 5 vol.%. Overall, therefore, results in a device which corresponds to a normal combustion plant (supply of fuel and normal air; removal of an exhaust gas with a low pollutant content), but a significantly improved efficiency with a corresponding fuel saving has.

For example, the exhaust duct having in its first part, a thermal insulation which causes the nitrogen oxide decomposition favoring delay of exhaust gas cooling. Another possibility is to associate the exhaust passage at least a device for reactive free exhaust gas heating.

A method for manufacturing a device, are provided in the hollow fibers of a membrane according to the invention characterized in that the hollow fibers are first prepared and then treated with a coating liquid containing the membrane material, after which the membrane material is cross-linked on the hollow fibers. The coating liquid can be easily applied to the peripheral surfaces of the hollow fibers. Also, the dosage to achieve the desired membrane thickness is possible.

To achieve particularly thin membranes, it is recommended that when the coating liquid is a solvent or; contains dispersing agent for the membrane material, which is then removed. In particular, a solvent or dispersant should be used, which may at least partially escape through the pores of the hollow fibers. The molecules must therefore be smaller than the pores of the hollow fiber. This makes an internal coating possible. At an outside coating, the rate at which the solvent or dispersing agent can be removed is increased.

The removal of the solvent or dispersant can for example take place in that between the inside and outside of the hollow fibers, a pressure differential is applied. Instead, or simultaneously, the solvent or dispersing agent can be removed by evaporation or evaporation. It is often advantageous if the connection is initiated networking of membrane material before the coating treatment. Here, since even larger molecules are formed, it is easier to remove the solvent through the hollow fiber wall without simultaneously diaphragm material is entrained. The coating: liquid may also contain a catalyst. In it can be included a cross-linking component. Another possibility is to let to be provided to be coated hollow fiber surface before with a crosslinker or pass the hollow fibers of a material having active brings about crosslinking groups. If the membrane is provided with a catalyst_; is branwerkstoff good flowability, the possibility exists, contact him directly as a coating liquid to be used.

The application can for example be such that the hollow fibers are moved along a liquid coating position for coating. They may also be dipped in the coating liquid or, preferably, sprayed with the coating liquid.

A particularly advantageous possibility consists in that during the preparation of the hollow fibers for the production of the inner cavity a filler is introduced into the fiber material containing membrane material.

A method for operating the device according to the invention characterized in that a combustion temperature of more than 2500 ° C is achieved by enriching the combustion air with oxygen in the combustion chamber and that the cooling of the combustion chamber exhaust gases leaving over a temperature range of at least 200 ° C is slower than a subsequent temperature range. The sought for a high efficiency combustion temperatures the exhaust gases should be cooled slowly over a considerable temperature range. The lower the cooling rate, the greater the remaining amount of nitrogen oxide. Preferably, the gases remain in the temperature range slow_"Cooling at least 0.3 s.

In particular, the cooling rate should be approximately in the temperature range of the slow cooling temperature-dependent rate of decomposition of nitrous oxide, ie decrease in this temperature range.

It is also favorable if the initial temperature of the slow cooling area is maintained at least 1400 ° C. Therefore, the temperature range, slow cooling is on a relatively high temperature level, can be exploited in the high decay rates.

The invention will be explained with reference to detail in the drawing, exemplary embodiments. Show it:<ul><li>Fig. 1 shows a cross section through a membrane with a plurality of finished hollow fibers,</li><li>Fig. 2 shows a spatial representation of a device according to the invention with a sectional area according to the plane II-II in Fig. 3,</li><li>Fig. 3 shows a horizontal section through the device of Fig. 2,</li><li>Fig. 4 end portions of a modified hollow fiber form in an end wall of the housing,</li><li>Fig. 5 is a section along the line VV in Fig. 4,</li><li>Fig. 6 shows schematically an apparatus for producing hollow fibers,</li><li>Fig. 7 shows a schematic cross section through an embodiment of a hollow fiber with an inner membrane,</li><li>Fig. 8 is a modified embodiment of Fig. 7,</li><li>Fig. 9 schematically illustrates a procedure for generating an inner membrane,</li><li>10 shows a cross-section and</li><li>11 shows a longitudinal section through a device for producing an outer membrane,</li><li>12 shows the state of equilibrium. Air: nitric oxide constituting the nitrogen oxide in an exhaust gas temperature T above the diagram</li><li>Fig. 13 a graph showing the decay half-life t_H of nitric oxide via the exhaust gas temperature T,</li><li>Fig. Schematischcbn 14 in a time chart of the exhaust gas temperature curve during the cooling,</li><li>Fig. 15 schematically illustrates an internal combustion engine with a device for reducing the nitrogen oxide proportion in the exhaust gas,</li><li>Fig. 16 is a cross section through the device along the line VV in Fig. 15,</li><li>Fig. 17 is a schematic cross section through another embodiment of a device for reducing the nitrogen oxide proportion,</li><li>Fig. 18 shows a further embodiment of such a device,</li><li>Fig. 19 shows a fourth embodiment of such a device, and</li><li>Fig. 20 schematically illustrates the installation of the inventive device in a motor vehicle.</li></ul>

In Fig. 1 a plurality of hollow fibers 1 are illustrated in a row above the other, the inside is covered with an ultrathin, semipermeable membrane 2. The hollow fiber has for example an external diameter d of 50 to 400 pm, especially 100 to 200 microns, and a wall thickness s of less than 6 .mu.m to 20 .mu.m, in particular from 5 to 10 microns. The membrane for example has a thickness of 100 nm. The cavities 3 of the hollow fibers form a first space A, the space outside of the hollow fibers constitutes a second space B. If you hold the two spaces at different pressures, so migrates gas from the chamber of higher pressure in the space of lower pressure, the diaphragm 2 is more permeable to oxygen than for nitrogen.

Figs. 2 and 3 show a device in which an extremely large number of hollow fibers as described is used. A battery 4 with the length 1 of 10 cm, the height h of 20 cm and the width b of 60 cm can contain six million and more longitudinally extending parallel to one another hollow fibers 1, having a membrane area of ​​about 180 m² and more yield.

The fiber battery 4 is housed in a casing 5, which has two end walls 6 and 7, in which the ends of the hollow fibers 1 are inserted under sealing at the outer periphery. the end walls are 6 and 7 a1s the peripheries of the fibers together be bonded plastic advantageously. The first space A has therefore before the end wall 6 has an input 8, which may be passed over normal air into the internal cavities of the hollow fibers 3 first Behind the front wall 7 there is an associated output 9, is discharged through the oxygen-depleted air. Before the input 8, an air filter 10 is connected. The whole assembly can be installed for example in a indicated by dashed lines automobile 11 near its front side 12, wherein the hollow fibers 1 extend in the vehicle longitudinal direction, so that the wind for a good air flow ensures through the hollow fibers. Alternatively or additionally, 13 may be provided in the main fan.

Within the fiber battery 4, the hollow fibers 1 are arranged in parallel rows 14, between which streets are 15. These lanes open into output plenums 16 and 17 of the second space B, which is connected via a common output to a suction pump 19 whose delivery side 20 to a consumer, such as an internal combustion engine, performs. The output plenums extending over the entire surface of the upper wall 21 and the lower housing wall 22, so an area 1 x b. In this way, for example, the entire surface of each hollow fiber without disturbing resistances to the output 18 of the second chamber B in communication. The width of the lanes can be relatively small, since the fibers are small and the maximum extension in the vertical direction only h / 2, the embodiment thus 100 mm.

In the embodiment according to FIGS. 4 and 5 are hollow fibers 51, which are covered on the outside with a membrane 52 provided with portions 53 of larger diameter. These can be found here at the ends of the hollow fibers and are eingebetteto sealed in an end wall 6 shown in FIG. 5 can such hollow fibers are arranged side by side in the region of their portions 53, which remain in the remaining course of the hollow fibers lanes 54 which in this case, a waveform have.

Such sections 53 may also be arranged at any point of the hollow fiber length. You also do not need to be, because already 53 at the normal diameter of an adjacent hollow fiber remains through the support of a section sufficient alley in a plane.

The manufacture of such hollow fibers 51 having portions 53 of larger diameter can be followed with the aid of measures he described in conjunction with Fig. 6. Hereinafter, a spray head 55 is provided, the nozzle is a ring for supplying the material 57 for the hollow fiber 51 and a central nozzle 58, via which a gaseous filler at a pressure p is introduced which. This pressure P is temporarily increased, as indicated by pulses 59th In this way, the; enlarged portions 53:

Fig. 7 shows a hollow fiber 1 with inner membrane 2 in cross section. It can be seen that the outer pores 60 are larger than the internal pores 61, which are located immediately below the diaphragm second While the internal pores example, have a size of 15 nm, the pore size increases towards the outside up to about 1 micron. The pores are interconnected.

In FIG. 8, another embodiment is shown, in which a hollow fiber 62 consists of the same material as the diaphragm 63. Again, the pores 64 are smaller from the outside inward. The innermost layer pore is closed, however, so that the desired membrane arises 63rd

The membrane material must be selected with regard to the gas permeability and the O2-N2 separation factor. There are various possibilities. Especially recommended is silicone rubber (dimethyl polysiloxane) or silicone rubber-polycarbonate copolymer of dimethyl polysiloxane and bisphenol A with a high content (over 80%) of the dimethylpolysiloxane. Silicone rubber has; a separation factor between oxygen and nitrogen of 2.2, so that the gas mixture in the space of lower pressure; comprising 35% by volume - an oxygen content of about 30.. It cold vulcanizable membrane materials are expediently used, on fillers, or pigments should be avoided entirely or largely so as not to affect the membrane properties. But there are also hot vulcanizable materials into consideration.

The cross-linking of membrane material is effected with the aid of a crosslinker and a catalyst. As crosslinking the wide variety of known materials may be considered, preferably ortho or polysilicic, trialkoxysilanes or siloxanes with Si-H bonds. Such crosslinking can be added to the vulcanizable membrane material before the Beschichturg, they can be applied to the peripheral wall of the hollow fiber and before coating. If the hollow fiber material active groups such as hydroxyl or alkoxy Gruppeiaufweist can also be dispensed with a crosslinker.

Catalysts which various known materials may be considered. In particular, organic peroxides, amines or carboxylic auere salts such as stannous octoate or dibutyltin dilaurate are suitable, for this purpose.

The membrane material can be mixed with the crosslinker and the catalyst and dissolved by degassing or dispersed. Recommended is a one- to four-percent solution or dispersion. As solvents or dispersion agents aromatic or aliphatic hydrocarbons come (especially petroleum) and chlorinated hydrocarbons.

The hollow fibers should consist of a polyaddition or condensation product. Suitable in particular polyester, polyamide, polysulfone, cellulose, and cellulose acetate. Finest reinforcing inserts made of other materials are possible.

In Fig. 9 schematically shows the process flow when applying a membrane 2 on the inside of a hollow; 1 illustrates fiber. In a first stage 65 of membrane material 67, a catalyst 68 and a cross-linking component 69 are mixed in a container 66th The mixture is then mixed in a step 70 with solvent 71st After a period of inactivity, which already can be held a slight cross-linking, the solution is added 72 in a step 73 in the interior of the hollow fibers. 1 In a step 74, a negative pressure P is generated at room temperature at the outside, whereby the solvent is evaporated and removed through the hollow fiber wall to the outside. The porous wall in this case acts as a filter which allows the solvent to pass, but retaining the membrane material on the inside of the hollow fiber. In a step 75 heat H is supplied at about 50 ° in a heating furnace, whereby the solvent residues are completely removed and the cross-linking is completed faster.

This process is simplified in that the hollow fibers 1 in the already Vorric mounted Pla. For now, the solution can easily be entered through the entrance. 8 The negative pressure generated by the suction pump 19th It gives no difficulties to mount the housing to an elevated temperature. The membranes thus produced are mechanically protected and will not be adversely affected by further processing.

In the embodiment of Figures 10 and 11, two rollers 76 and 77 are provided, each having a circumferential groove 78 or 79th Both circumferential grooves are dimensioned such that they form a passage 80, which is slightly larger than the cross section of a hollow fiber 81 via a hopper 82, a mixture of flowable membrane material, catalyst and crosslinking component is applied to the circumferential direction of the arrow top roller 76th The material arrives on the outside of the hollow fiber 81. The passageway 80 determines the thickness of the applied layer. The rest is stripped and below can be collected again. The hollow fiber may be for the purpose of vulcanization passed through an oven and then wound subsequently. Instead of the hopper 82 and an annular die can be used for applying the membrane vulcanizable material. The material can also be sprayed on or applied by dipping. In this way, also dissolved membrane material can be applied.

Another possibility is the filler be attached to the membrane material in the embodiment of Fig. 6, in gaseous filler in verstäubter form in a liquid filler, for example, in solution.

In the diagram of Fig. 12 of the NO-content is shown in percent by volume about the exhaust gas temperature T. The curve C separates a region 110 is formed in which NO, from an area 111 in which NO decomposes. Links from the dashed line 500 ° limit is an area 112 in which NO is metastable. It can be seen that the NO-content steeply increases with increasing temperature and in exhaust gas at 2700⁰C approximately 5 percent by volume accounts.

In Fig. 13 is on the exhaust gas temperature T with curve D, the decay half-life t_H the NO illustrates. It follows that the NO practically disintegrate immediately at 2700 C, at 2200 ° C in 1/2000 sec, at 1700 ° C in about 0.6 s, at 1200 ° C in several minutes, and at 700^OC in several weeks.

In Fig. 14, the exhaust gas temperature is over the time t ver anschaulicht, wherein the dotted line denotes the outlet of the exhaust gas from the internal combustion engine regardless of the dipstick. In the range below 700 ° C is virtually no NO decay more expected. The curve E shows the known case in which there was a combustion at about 2000 ° to 2200 ° C and the exhaust gas exits at about 1000 ° C from the internal combustion engine. It takes place in the exhaust manifold another sudden cooling, so that the exhaust gas contains a significant proportion of the NO that was present at a higher temperature.

The curve F shows, for the same conditions in the course of cooling an internal combustion engine according to the invention. During a first temperature range 113, which here of about 1000⁰C until something goes under, the cooling is slow. Only in the subsequent temperature range 114 is a sudden cooling. This temperature range is 113 s run through in a time of about 0.5. As in the first temperature range 113 Nitrogen oxides are reduced to a considerable extent, therefore, the nitrogen oxide is smaller before the rapid cooling as in the case of the curve E, you also after cooling a smaller nitrogen oxide in the exhaust gas.

The same applies to the curve G, which denotes the case that the combustion due to a higher oxygen content in the combustion air is performed at about 3000 ° C and the outlet temperature of the exhaust gas is approximately 1700 ° C. Here, the cooling is at a temperature range 115, which extends up to 1300 ° C, carried out slowly, which requires a time of approximately one second is provided. In the subsequent temperature range 116 rapid cooling takes place. In this way, the proportion of nitrogen oxide of the exhaust gas can be reduced down to acceptable low values ​​despite the high output values ​​at the outlet from the internal combustion engine. In practice, the residence can be chosen shorter or longer.

In the embodiment of Fig. 15 of an internal combustion engine 117 is supplied through a conduit 118 combustion air whose oxygen content has been increased in a device 5. The exhaust gas is discharged through a channel 120, which consists of a first tube section 121, a container 122 and a pipe section leading to the silencer 123rd The pipe section 121 and the container 122 are surrounded by a heat insulating 124th In the container, a spiral-shaped wall 125 is provided. Therefore, the supplied exhaust gas in the center passes through a helical channel 126 from the inside to the outside. Due to the delayed heat and relatively long time, in which the exhaust gas is exposed to these conditions, to produce the desired slow cooling than the first temperature range.

In the embodiment of Fig. 17 includes an exhaust channel 127 comprises a first tube section 128, a container 129 and a second tube section 130, all of which are surrounded by a heat insulation 131st In containers are provided on both sides of a central space 132 alternately extending from both sides walls 133 so that two labyrinthine extending exhaust duct sections give 134 and 135th A sufficiently long flow path in the container 129 can be dispensed with the externally applied heat insulation optionally also at the bottom and the side walls, because the exhaust gas flowing through the last channel section 136 in the tank 129 acts as a thermal insulation for the preceding sections.

In the embodiment of Fig. 18, a device 137 is provided having three series-connected containers 138, 139 and 140, which are each connected by throttle portions 141 and 142. In this way, a silencer function. The corresponding heat insulation is not illustrated. is injected via a return line 143 to a compressor 144 by means of an injection device 145 the exhaust gas into the container 139 from the container 140th The compression in the compressor 144 the returned exhaust gas absorbs heat energy. The pressure may be chosen so that this exhaust gas is conducted at very high speed, in particular supersonic speed into the container 139th By the collision of molecules kinetic energy is converted into heat energy, so that the exhaust gas is held for longer in the container 139 at a predetermined temperature level.

In the embodiment of Fig. 19, a first container 146 is connected through a strong channel constriction 147 with a second container 148th The accelerated in the constriction 147 exhaust gas strikes a baffle plate 149, in turn, so the exhaust gas in the vessel 148 is converted into kinetic thermal energy held longer at a certain temperature level.

Fig. Figure 20 shows schematically the arrangement of a housing 5 (Fig. 2 and 3) and a container 120 (FIG. 15) in connection with the internal combustion engine 150 of a motor vehicle 11, via the line 151 becomes 0₂-enriched air the conventional carburetor fed; occur in the exhaust gases 152 from after the combustion of the engine.

Similarly, also a furnace with a correspondingly high efficiency can be operated.