CA1142100A - Endothermal water decomposition unit for producing hydrogen and oxygen - Google Patents
Endothermal water decomposition unit for producing hydrogen and oxygenInfo
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- CA1142100A CA1142100A CA000353647A CA353647A CA1142100A CA 1142100 A CA1142100 A CA 1142100A CA 000353647 A CA000353647 A CA 000353647A CA 353647 A CA353647 A CA 353647A CA 1142100 A CA1142100 A CA 1142100A
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- permeable membrane
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Abstract
ABSTRACT OF THE DISCLOSURE
The manufacture of hydrogen and oxygen by the dissociation of water vapor at elevated temperatures followed by separation of hydrogen from the water vapor and the oxygen produced using a hydrogen permeable membrane is improved by increasing the surface area of the membrane exposed to the dissociation gas mixture. One way of increasing the surface area of contact, according to an embodiment of the present invention, is to form a hydrogen permeable membrane coated on one side of a porous refractory wafer with an inlet hole through the wafer connecting the beginning of a grooved maze and an outlet at the end of the maze facing the opposite direction from the inlet. A number of these wafers are then stacked or replicated front-to-back, with each outlet regis-tering with the inlet of the next wafer to give a compact and efficient hydrogen diffusion separator.
The manufacture of hydrogen and oxygen by the dissociation of water vapor at elevated temperatures followed by separation of hydrogen from the water vapor and the oxygen produced using a hydrogen permeable membrane is improved by increasing the surface area of the membrane exposed to the dissociation gas mixture. One way of increasing the surface area of contact, according to an embodiment of the present invention, is to form a hydrogen permeable membrane coated on one side of a porous refractory wafer with an inlet hole through the wafer connecting the beginning of a grooved maze and an outlet at the end of the maze facing the opposite direction from the inlet. A number of these wafers are then stacked or replicated front-to-back, with each outlet regis-tering with the inlet of the next wafer to give a compact and efficient hydrogen diffusion separator.
Description
11~2100 This invention relates to apparatus for separating hydrogen from a hydrogen-containing gas mixture. The field of the invention is gas separation by a barrier for selective diffusion of gases.
The state of the art of dissociation of water vapor by thermal energy into hydrogen and oxygen followed by the separation of the hydrogen with a hydrogen permeable membrane is disclosed in U.S. Patents 4,003,725;
4,019,868; and 4,053,576. Technical Support Package TSP 75-10314 for NASA TECH BRIEF 75-10314 (MSC-12600) entitled "Using Permeable Membranes to Produce Hydrogen and Oxygen from Water".
Solar heat is one of the ways thermally to dissociate water vapor and this is disclosed in previously mentioned U.S. Patents 4,019,868 and 4,053,576 and U.S. Patent 4,030,890. Other heat sources, e.g. nuclear energy and electrical resistance furnaces, are suitable for bringing water vapor to a dissociation temperature. TSP 75-10314 and U.S. Patent 4,003,725 show resistance furnaces:suitable for the use with aspects of the present invention.
That platinum, palladium and palladium alloy metal films are permeable to hydrogen and have been used as barriers for selective dif-fusion of hydrogen has been known, as disclosed by Kirk-Othmer "Encyclo-pedia of Chemical Technology", 2nd - -- 1 -- ,.,,5,si '3 edition, vol. 15 (196B) under the section Platinum Group Metals, pages 832-860, particularly page 832 where the melting point of palladium is given as 1552C, pages 853 and 854 wher~ the use of palladium and a 75% Pd - 25~ Ag alloy is disclosed for the separation of pure hydrogen from mixed gases by dif-fusion at a temperature of 350C in tubes of the alloy with a wall thickness of 0.003 inches and page 855 where electrodeposition of palladium is disclosed TSP 75-10314 discloses, among other things, the separation of hydrogen from oxygen and water vapor at temperatures of 600C to 950~C and pressures from 5 mm ~g (0.1 psia) to 760 mm Hg (14.7 psia) using tubes of 0.1 mm (0.004 inches) wall thickness as the diffusion membrane.
This diffusion membrane was made from pure platinum, pure palladium, 75% palladium - 25~ silver and 90% palladium - 10% silver with 90% palladium - 10 silver giving preferred results.
One of the many problems experienced by the pricr art was to increase the surface area of CQn-tact at elevated temperatures between the platinum and palladium diffusion membranes and the aissoci-ating water vapor or other hydrogen containing mixtures.
All prior art methods of proaucing hydrogen by aissociation of water vapor or from gaseous : -2-mixtures containing hydrogen have been limited by inability to separate large quantities of hydrogen from a mixture of hydrogen containing gas mixtures in a small sapce at elevated temperatures and at elevated pres-sures.
Having in mind the limitations of the prior art, it i9 an object of a main aspect of the present invention to provide a gaseous diffusion separator for hydrogen which provides a large diffusion area in a given ~pace for separating pure hydrogen from a mixture of gases containing hy-drogen.
An object of the present invention includes the improvements an improvement in the process of producing hydrogen from water by solar energy using the diffusion separator of aspects of the present invention.
Another aspect of the present invention includes the improvements in processes for separating hydrogen from a mixture of gases produced by the thermal dissociation of water vapor using surplus heat sources.
An object of still another aspect of the present invention is the recovery of the oxygen separated from the hydrogen by the selective dif-fusion.
By one broad aspect of this invention, a coated article is pro-vided comprising a porous refractory base material with a hydrogen permea-ble membrane coated on portions thereof, the base material having at least first and second flat surfaces, such base material having a top and bottom, a hole extending through the base material at the top thereof, a grooved maze in at least one of such flat surfaces extending from the hole at the top to the bottom and such grcoved maze being coated with the hydrogen permeable membrane.
By a variant of such coated article, the base material is selec-ted from the group consisting of'aluminum oxide, beryllium oxide, calcium oxide, magnesium oxide, thorium oxide, titanium oxide, uranium oxide, .
11~2100 spinel, iridium, rhodium, chromium and platinum.
By a further variant of such coated article, the hydrogen per-meable membxane is selected from the group consisting of platinum, palla-dium and alloys of silver and palladium.
By another variant of such coated article, circular portions at the centers of flat surfaces are uncoated and the remainder of such flat surfaces and the edges of the base material are coated with the hydrogen permeable membrane.
By yet another variant of such coated article, a circular por-tion at the center of the second flat suxface having such a maze is un-coated and the xemainder of the flat surfaces and the edges of such base material are coated with the hydrogen permeable membrane.
By still another variant of such coated article, the coated gr~oved ma~e is in the second flat surface and the first flat surface is coated with the hydrogen permeable membrane.
By a further variant of such coated article, circular portions at the centers of the first and second flat surfaces are uncoated and the remainder of the first and second flat surfaces and the edges of the base material are coated with the hydrogen permeable membrane, and the hydrogen permeable membrane has a thickness of 0.0012 - 0.012 cm.
By another variant of such coated article the hydrogen permeable membrane has a thickness of 0.0025 - 0.0075 cm.
By another aspect of this invention, an apparatus is provided for separating hydrogen from a hydrogen-containing gas mixture, the appara-tus comprising a plurality of wafers stacked back-to-front, each of the wafers comprising a porous refractory base material with a hydrogen per-meable membrane coated on portions thereof, such base material having at least first and second flat surfaces, the base material having a top and bottom, a hole extending through the base material at the top thereof, and . ~ - 4 -11~2100 defining an inle~, a grooved maze in the second flat surface extending from the hole at the top to the bottom and defining an outlet at the ter-mination thereof such grooved maze and the first flat surface being coated with the hydrogen permeable membrane and the outlets of successive wafers registered with the inlets of successive wafers in such plurality.
By a variant of such apparatus a circle of uncoated base material is located on the first and second flat surfaces at the center thereof and the remainder of the flat surfaces and the edges of the base material are coatea with the hydrogen permeable membrane.
By another variant of such apparatus, a circle of uncoated base material is located on the second flat surface at the center thereof, and the remainder of the flat surfaces and the edge of the base material are coated with the hydrogen permeable membrane.
By another aspect of this invention, an apparatus is provided for separating hydrogen and oxygen from thermally dissociating water vapor, the apparatus comprising:-(a) a closed furnace chamber; ~b) means for heating the chamber; (c) means for introducing water vapor into the cham-ber; (d) means for removing hydrogen from the chamber; (e) means for re-moving oxygen from the chamber; and (f) means for separating hydrogen and oxygen from thermally dissociating water vapor comprising a plurality of wafers stacked back-to-front, each of the wafers comprising a porous re-fractory base material with a hydrogen permeable membrane coated on por-tions thereof, the base material having at least first and second flat sur-faces, such base material having a top and bottom, a hole extending through the base material at the top thereof and defining an inlet, a grooved maze in the second flat surface extending from the hole at the top to the bottom and defining an ou'let at the termination thereof, the grooved maze and the first flat surface beinq coated with the hydrogen permeable membrane and ~14Z100 the outlets of successive wafers registered with the inlets of successive wafers in plurality, the first of the inlets connecting with the means for introducing water vapor and the last of the outlets connected to the means for removing oxygen from the chamber.
By a variant of such apparatus a circle of uncoated base material is located on the first and second surfaces at the center thereof and the remainder of the flat surfaces and the edges of the base material are coated with the hydrogen permeable membrane, the circles connected with the means for removing hydrogen from the chamber.
According to a main embodiment of the present invention, a mix-ture of gases containing hydrogen are prepared by the dissociation of water vaEor at temperatures between 350~C and 1250C, with a range of 550C to 950C preferred. This gaseous mixture is then passed through a maze which has a hydrogen permeable platinum~ group metal membrane, pre-ferably an alloy of 90% palladium - 10% silver, and hydrogen is separated to leave an oxygen enriched gas.
';
~421VO
One embodiment of the gaseous diffusion maze is a plurality of wafers made from porous refractory materials, each of which has an inlet on one side connected with the beginning of the maze traced on the surface of the wafer and an outlet at the end of the maze on the opposite side of the wafer from the inlet. The porous refractory materials are coated with a film of the hydrogen permeable membrane (90% Pd - 10% Ag) lo so that the maze for the transport of the dis-sociating water vapor is surrounded by the hydro-gen permeable membrane.
A plurality of these wafers is stacked back-to-front with the respective outlet to inlet indexed so that a continuous path is created from wafer to wafer.
Hydrogen separated through the membrane is passed through the porosity of the refractory and can be directed to a particular section of the wafers for transport and collection. In one 11~2~00 embodiment, the whole wafer is coated with 90% Pd - 10% Ag except for a circle at the center of the wafer to which hydrogen is directed. In another embodiment the edges are left uncoated and hydrogen passes through these edges as water vapor is introduced at the beginning of the maze and oxygen is separated and collected at the end of the maze.
The various elements of aspects of this invention cooperating to-wards the purpose by the dissociation of water vapor at elevated tempera-tures as well as conventional means and methods not claimed per se but de-sirable in the implementation of aspects of this invention are discussed in detail below in relation to the drawings and examples. For the sake of overview, a complete qualitative discussion of aspects of the invention relating the drawings is provided first, followed by spècific examples at the end.
In the accompanying drawings, Figure 1 is a front elevation view of one embodiment of an in-dividual integral wafer of an aspect of the present invention having a gas diffusion maze therein;
Figure 2 is a side view along the line II-II of Figure l;
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Figure 3 is a rear elevation view of the wafer of Figure 1 showing the inlet hole and hydrogen passage therein;
Figure 4 is an exploded, partial side view showing in cross sectiDn one embodiment of a wafer combination of an aspect of the present invention in assembly with the outlet wafer on the left, the inlet wafer on the right, and one example of the plurality of intermediate wafers of Figures 1-3 therebetween;
Figure 5 is another emboaiment of the assem-bly of Figure 4 which takes advantage of counter-current circulation of the hydrogen produced;
Figure 6 is a perspective view of an assembly of wafers from Figure 4;
Figure 7 shows the assembly of wafers of Figure 6 mounted in an electric resistance furnace;
Figure 8 shows another embodiment of an assembly of wafers mounted in an electric resis-tance furnace where the porous edges of the wafers are uncoated with the hydrogen permeable membrane and hydrogen being produced from the porous edges;
and Figure 9 is a detailed showing in cross section of the end wafer of Figure 4 with a stain-less steel or palladium outlet circuit mounted therein for the hydrogen and oxygen.
';':' With particular reference to Figures 1-3, the integral porous refractory wafer 2 is shown having an inlet hole 4 through the wafer from bac~-to-front. A maze 6 is acid etched, molded, pressed, sintered or gouged across at least one flat surface 8 of the wafer. The maze has a plurality of turns or corners 10 ending at outlet 12 which faces out in Figure 1.
The front, back and edge of the wafer are coated with a hydrogen permeable membrane 14, e. g.
10~ Ag - 90~ Pd, wi~. the exception of concentric circles 16 and 18, where the porous refractory material, e.g. A12O3, shows through.
The wafer 2 of Figures 1-3 is shown in the partial exploded view of Figure 4 as the second wafer from the right. Wafers 20 and 22, which are the first and last wafers in an assembly, differ from the plurality of wafers 2 making up the com-posite assembly. In the embodiment of Figure 4, the first wafer 20 has no hole 18 on the outside wall and the last wafer 22 need not have a maze on either flat surface. Wafer 20 has water vapor inlet 3 and wafer 22 has oxygen outlet 5.
Figure 5 is another embodiment of Figure 4 wherein first wafer 24 has a circle 18 with the porous refractory material showing through the outside wall. Last wafer 26 has no circle in the outside wall as does wafer 22 of Figure`4.
Figure 6 i8 a perspective showing of an assembly of Figure 4 defining the endothermal water decompo-sition unit 38 of an aspect of the present invention having a plurality of wafers 2 sandwiched between first and last wafers 20 and 22.
Figure 7 shows the assembly of Figure 4 mounted in an electric resistance furnace 28 having stain-less steel walls 30 and a plurality of heating ele-ments 32. A water vapor inlet 34 of stainless steel tubing enters on the left and the water vapor is passed through 10~ Ag - 90~ Pd tubing 36 into the assembly 38. The 10% Ag - 90% Pd collared tubing 40 connects with the 2 outlet of wafer 22 for distribution to stainless steel outlet 42 con-taining 2 10% Ag - 90% Pd collared tubing 44 conducts H2 from circle 16 on wafer 22 through the wall of the furnace to H2 collecting tube 46.
In the embodiment of Figure 8, the wafers have edges which are porous and uncoated so that hydrogen produced in the endothermal water decom-position unit 60 can diffuse to the outside of the unit and be picked up by an inert carrier gas such as nitrogen which enters through stainless steel conduit ~B. The hydrogen produced is swept out of th~ furnace ~y the inert carrier for collection through stainless steel conduit 52.
Figure 9 shows one way of mounting conduits 44 and 40 in the hydrogen and oxygen outlets of the last wafer 22' of the assembly. The wafer 22' has 11~2100 holes 58 and 60 with respective recesses 62 and 64 molded therein in the green state for holding the collared conduits 44 and 40. Of course, a collared conduit 36 can be mounted in the same way in the first wafer 20.
The best mode of carrying out a preferred aspect of the present invention is disclosed with particular reference to Figures 4, 5, 7 and 8.
Water vapor is introduced into the furnace of Figure 7 by way of stainless steel conduit 34 and conduit 36 or inlet 3 into the endothermal water decomposition unit 38. Inside the furnace the temperature is conveniently maintained between 350C and 1250~C and pressures of from 5 mm Hg to superatmospheric can be maintained.
Even though the platinum group metal membrane is applied in a thickness of 0.0012 - 0.012 cm, 0.0025 - 0.0075 cm, a considerable pres-sure, superatmospheric, can be applied inside the endothermal water decompositior. unit because the porous refractory wafer backing of the membrane is strong in compressive load. Of course, it is possible to do away with the 90% Pd - 10% Ag con-duits 34, 42 and 46 under compressive load from the walls of the furnace.
As shown in Figure 4, the water vapor enters at inlet 3, travels through the platlnum or pal-ladium metal coated maze of wafer 20 and ~2 is diffused through the membrane in the grooves of 11~21~0 the ma~e into the porosity of the refractory of water 20. H2 diffuses simultaneously through the membrane on the right of wafer 2 opposite the maze and grooves of wafer 20. H2 moves through the porosity of wafer 20 to the uncoated center hole 16 where it is channelled from wafer through the centers thereof.
After passing to the outlet 12 of wafer 20, the oxygen enriched water vapor now passes through inlet 4 of wafer 2 and proceeds through the maze of wafer 2 where the water vapor becomes more enriched with oxygen.
Hydrogen passes through the membrane into the porosity of the wafer and proceeds to the collection area in the centers of the wafers. ~he same mechanism of integral wafer 2 takes place through the stack of wafers un-til the last wafer 22 is reached and oxygen exits from outlet 5 and hydro-gen exits from outlet 16.
Figure 5 shows an aspect of the invention operated with counter-current flow of the hydrogen. This is accomplished by having a circle of uncoated refractory 18 on the first wafer 24.
The process in the Figure 8 embodiment is carried out by leaving the porous edges of the wafers uncoated so that hydrogen is passed directly into the body of the furnace. At elevated pressures, there is no need for an inert carrier gas, but when the separation is carried out at less than atmospheric pressure, it is necessary to pass an inert carrier gas, e.g.
nitrogen or argon therethrough.
"~
1~2100 The wafers of aspects of the present invention may be made from refractory materials or from refractory metals. Kirk-Othmer, ibid., discloses, in Vol. 17 (1968), suitable refractories, with the exception of silica refractories which poison the platinum group membranes, on pages 227-267, particularly page 24~ w~ich discloses aluminum oxide, beryllium oxide, calcium oxide, magnesium oxide, thorium oxide, titanium oxide, uranium oxide, and sp~nel. The refractory metals are disclosed on pages 267,284, particularly page 267 which discloses that iridium, rhodium, chromium and platinum are resistant to air at 1400C.
me refractory materials can be processed into the wafers of aspects of the present invention using the techniques disclosed in Kirk-Othmer, ibid, Supplement Volume (1971), p. 15Q, where the cold pressing and isotactic pressing of aluminum oxide ceramics is disclosed.
~1421~0 The refractory metals can be processed into porous wafers using the techniques of powder metallurgy as disclosed in Rirk-Othmer, ibid., vol. 16 (1968), pages 401-435, particularly page 415 where sintering is disclosed and page 425 where the preparation of porous sintered materials is disclosed.
The porosity in the manufacture of the porous refractory wafers of aspects of the present invention can be controlled by using the tech-niques disclosed for the manufacture of aluminum oxide abrasive grinding wheels as disclosed in Rrik-Othmer, ibid., vol. 1 ~1963), page 32, where a chart of the grain sizes used is given, pages 34 and 35, where the con-trol of open structu~e is disclosed and pages 35 and 36 where the methods of manufacture are given.
In addition to the above procedures for fabricating the wafers of aspects of the present invention, it is also possible to use the ~ , ~.
" ll~Z100 techni~ues disclosed in ~.S. Patents 3,344,586 and 3,499,265, but with the addition of the step of molding a maze into at least one side of the wafer when the ceramic or refractory material is in the green state.
Having all the above in mind, a porous refractory wafer can be produced for aspects of the present invention as follows:
A dry mixture of 25% Georgia kaolin, 15% Tennessee ball clay, 55%
nepheline syenite, and 5% silica is made by tumbling these ingredients in a bottle for several hours after which 200 mesh carbon black is added and thoroughly mixed in by further tunbling for 8 hours. The porosity of the finished piece is largely determined by the amount of carbon black used and for a porosity of 40-50%, which is preferred in accordance with aspects of the invention; the proportion of carbon black to the other ingredient is 20-4G%.
ll~Z100 When the dry mixing is complete, the mixture is dampened with a fluid which serves as a binder and lubricant. The moisture content i8 preferably 25 - 30% which supplies the moisture necessary to be able to press the mass into the desired disk shape satisfactorily. The fluid is suitably 3 - 10 glycerine as the binder and the remainder water as the lubricant.
The fluid is mixed in to dampen the mixture lo thoroughly.
Then the mixture is molded in a round mold having a plunger design which produces the maze as shown in Figure 1 of an aspect of the present invention. Al-though wafers of 7.75 cm diameter and 0.3 cm thick are ~roduced, any suitable size can be made.
These wafers are then air dried overnight and fired in a periodic furnace which is raised to a tempera-ture of 100C progressively over a period of 24 hours.
The porous ceramic wafers are first coated on the maze side with palladium by brushing on a solu-tion of palladium resinate aissolved in oil of peppermint and chloroform and containing 3.5% Pd by weight. ~welve coats are applied with each fired ~21~)0 at about 350C in air to thermally decompose the resinate to metal. After 12 coats, a palladium film about 1.2 microns thick is on the substrate. This film is then fired to 1000C in air with a one hour soak to compact the film and bond it to the substrate.
The uncoated circle indicated at 16 in Figure 1 is maintained by placing a cardboard circle there-over and then removing it after all layers have been applied.
A silver naphthenate solution having a vis-cosity suitable for application by brushing was made as follows:
Grams Silver naphthenate ~32~ Ag) 3.35 Toluene 11.13 14.48 The silver naphthenate was dissolved to a stiff gel by stirring mechanically for 2 hours at room tem-perature. 0.52 Grams of t-octyl amine were then added and, with stirring continued for a few more minutesO The solution became fluid. The amber brushing solution then contained 7.15~ Ag by weight or approximately 0.01 mole of silver naphthenate and 0.004 mole of amine.
The silver naphthenate solution is then ap~
plied by brushing over the palladium in several coats with each fired at about 200C in air. When a silver weight equal to 1/3 of the palladium weight has been 1.~42100 added, the coated ceramic is heated for 4 hours at 600C in hydrogen to form a 75:25 Pd:Ag alloy in situ.
The other side of the wafer and the edges are then coated as above to produce a wafer coated except for bare circles 16 and 18 on the front and back as shown-in Figures 1-3.
The method of Example 1 is carried out for molaing and preparing wafers prior to coating. In this example, only the maze 6 of Figure 1 is coated and the back of the wafer is coated following the techniques of Example 1. Such wafers are useful in the apparatus shown in Figure 8.
' The method of Example 1 is modifiea slightly to prepare the wafer 20 of Figure 4. No circle of cardboard îs used in the coating of the right siae of wafer 20 to prevent a coating.
One wafer from Example 3 and a plurality of wafers from Example 1 are secured together to make an assembly by brushing powdered qlaze ma-terial, e.g. that known by the Trade Mark PEMCO FRIT P-1701 on a small portion of adjacent ~2~00 flat sides taking care not to coat the maze. The glaze is fired to fuse the wafers together.
The state of the art of dissociation of water vapor by thermal energy into hydrogen and oxygen followed by the separation of the hydrogen with a hydrogen permeable membrane is disclosed in U.S. Patents 4,003,725;
4,019,868; and 4,053,576. Technical Support Package TSP 75-10314 for NASA TECH BRIEF 75-10314 (MSC-12600) entitled "Using Permeable Membranes to Produce Hydrogen and Oxygen from Water".
Solar heat is one of the ways thermally to dissociate water vapor and this is disclosed in previously mentioned U.S. Patents 4,019,868 and 4,053,576 and U.S. Patent 4,030,890. Other heat sources, e.g. nuclear energy and electrical resistance furnaces, are suitable for bringing water vapor to a dissociation temperature. TSP 75-10314 and U.S. Patent 4,003,725 show resistance furnaces:suitable for the use with aspects of the present invention.
That platinum, palladium and palladium alloy metal films are permeable to hydrogen and have been used as barriers for selective dif-fusion of hydrogen has been known, as disclosed by Kirk-Othmer "Encyclo-pedia of Chemical Technology", 2nd - -- 1 -- ,.,,5,si '3 edition, vol. 15 (196B) under the section Platinum Group Metals, pages 832-860, particularly page 832 where the melting point of palladium is given as 1552C, pages 853 and 854 wher~ the use of palladium and a 75% Pd - 25~ Ag alloy is disclosed for the separation of pure hydrogen from mixed gases by dif-fusion at a temperature of 350C in tubes of the alloy with a wall thickness of 0.003 inches and page 855 where electrodeposition of palladium is disclosed TSP 75-10314 discloses, among other things, the separation of hydrogen from oxygen and water vapor at temperatures of 600C to 950~C and pressures from 5 mm ~g (0.1 psia) to 760 mm Hg (14.7 psia) using tubes of 0.1 mm (0.004 inches) wall thickness as the diffusion membrane.
This diffusion membrane was made from pure platinum, pure palladium, 75% palladium - 25~ silver and 90% palladium - 10% silver with 90% palladium - 10 silver giving preferred results.
One of the many problems experienced by the pricr art was to increase the surface area of CQn-tact at elevated temperatures between the platinum and palladium diffusion membranes and the aissoci-ating water vapor or other hydrogen containing mixtures.
All prior art methods of proaucing hydrogen by aissociation of water vapor or from gaseous : -2-mixtures containing hydrogen have been limited by inability to separate large quantities of hydrogen from a mixture of hydrogen containing gas mixtures in a small sapce at elevated temperatures and at elevated pres-sures.
Having in mind the limitations of the prior art, it i9 an object of a main aspect of the present invention to provide a gaseous diffusion separator for hydrogen which provides a large diffusion area in a given ~pace for separating pure hydrogen from a mixture of gases containing hy-drogen.
An object of the present invention includes the improvements an improvement in the process of producing hydrogen from water by solar energy using the diffusion separator of aspects of the present invention.
Another aspect of the present invention includes the improvements in processes for separating hydrogen from a mixture of gases produced by the thermal dissociation of water vapor using surplus heat sources.
An object of still another aspect of the present invention is the recovery of the oxygen separated from the hydrogen by the selective dif-fusion.
By one broad aspect of this invention, a coated article is pro-vided comprising a porous refractory base material with a hydrogen permea-ble membrane coated on portions thereof, the base material having at least first and second flat surfaces, such base material having a top and bottom, a hole extending through the base material at the top thereof, a grooved maze in at least one of such flat surfaces extending from the hole at the top to the bottom and such grcoved maze being coated with the hydrogen permeable membrane.
By a variant of such coated article, the base material is selec-ted from the group consisting of'aluminum oxide, beryllium oxide, calcium oxide, magnesium oxide, thorium oxide, titanium oxide, uranium oxide, .
11~2100 spinel, iridium, rhodium, chromium and platinum.
By a further variant of such coated article, the hydrogen per-meable membxane is selected from the group consisting of platinum, palla-dium and alloys of silver and palladium.
By another variant of such coated article, circular portions at the centers of flat surfaces are uncoated and the remainder of such flat surfaces and the edges of the base material are coated with the hydrogen permeable membrane.
By yet another variant of such coated article, a circular por-tion at the center of the second flat suxface having such a maze is un-coated and the xemainder of the flat surfaces and the edges of such base material are coated with the hydrogen permeable membrane.
By still another variant of such coated article, the coated gr~oved ma~e is in the second flat surface and the first flat surface is coated with the hydrogen permeable membrane.
By a further variant of such coated article, circular portions at the centers of the first and second flat surfaces are uncoated and the remainder of the first and second flat surfaces and the edges of the base material are coated with the hydrogen permeable membrane, and the hydrogen permeable membrane has a thickness of 0.0012 - 0.012 cm.
By another variant of such coated article the hydrogen permeable membrane has a thickness of 0.0025 - 0.0075 cm.
By another aspect of this invention, an apparatus is provided for separating hydrogen from a hydrogen-containing gas mixture, the appara-tus comprising a plurality of wafers stacked back-to-front, each of the wafers comprising a porous refractory base material with a hydrogen per-meable membrane coated on portions thereof, such base material having at least first and second flat surfaces, the base material having a top and bottom, a hole extending through the base material at the top thereof, and . ~ - 4 -11~2100 defining an inle~, a grooved maze in the second flat surface extending from the hole at the top to the bottom and defining an outlet at the ter-mination thereof such grooved maze and the first flat surface being coated with the hydrogen permeable membrane and the outlets of successive wafers registered with the inlets of successive wafers in such plurality.
By a variant of such apparatus a circle of uncoated base material is located on the first and second flat surfaces at the center thereof and the remainder of the flat surfaces and the edges of the base material are coatea with the hydrogen permeable membrane.
By another variant of such apparatus, a circle of uncoated base material is located on the second flat surface at the center thereof, and the remainder of the flat surfaces and the edge of the base material are coated with the hydrogen permeable membrane.
By another aspect of this invention, an apparatus is provided for separating hydrogen and oxygen from thermally dissociating water vapor, the apparatus comprising:-(a) a closed furnace chamber; ~b) means for heating the chamber; (c) means for introducing water vapor into the cham-ber; (d) means for removing hydrogen from the chamber; (e) means for re-moving oxygen from the chamber; and (f) means for separating hydrogen and oxygen from thermally dissociating water vapor comprising a plurality of wafers stacked back-to-front, each of the wafers comprising a porous re-fractory base material with a hydrogen permeable membrane coated on por-tions thereof, the base material having at least first and second flat sur-faces, such base material having a top and bottom, a hole extending through the base material at the top thereof and defining an inlet, a grooved maze in the second flat surface extending from the hole at the top to the bottom and defining an ou'let at the termination thereof, the grooved maze and the first flat surface beinq coated with the hydrogen permeable membrane and ~14Z100 the outlets of successive wafers registered with the inlets of successive wafers in plurality, the first of the inlets connecting with the means for introducing water vapor and the last of the outlets connected to the means for removing oxygen from the chamber.
By a variant of such apparatus a circle of uncoated base material is located on the first and second surfaces at the center thereof and the remainder of the flat surfaces and the edges of the base material are coated with the hydrogen permeable membrane, the circles connected with the means for removing hydrogen from the chamber.
According to a main embodiment of the present invention, a mix-ture of gases containing hydrogen are prepared by the dissociation of water vaEor at temperatures between 350~C and 1250C, with a range of 550C to 950C preferred. This gaseous mixture is then passed through a maze which has a hydrogen permeable platinum~ group metal membrane, pre-ferably an alloy of 90% palladium - 10% silver, and hydrogen is separated to leave an oxygen enriched gas.
';
~421VO
One embodiment of the gaseous diffusion maze is a plurality of wafers made from porous refractory materials, each of which has an inlet on one side connected with the beginning of the maze traced on the surface of the wafer and an outlet at the end of the maze on the opposite side of the wafer from the inlet. The porous refractory materials are coated with a film of the hydrogen permeable membrane (90% Pd - 10% Ag) lo so that the maze for the transport of the dis-sociating water vapor is surrounded by the hydro-gen permeable membrane.
A plurality of these wafers is stacked back-to-front with the respective outlet to inlet indexed so that a continuous path is created from wafer to wafer.
Hydrogen separated through the membrane is passed through the porosity of the refractory and can be directed to a particular section of the wafers for transport and collection. In one 11~2~00 embodiment, the whole wafer is coated with 90% Pd - 10% Ag except for a circle at the center of the wafer to which hydrogen is directed. In another embodiment the edges are left uncoated and hydrogen passes through these edges as water vapor is introduced at the beginning of the maze and oxygen is separated and collected at the end of the maze.
The various elements of aspects of this invention cooperating to-wards the purpose by the dissociation of water vapor at elevated tempera-tures as well as conventional means and methods not claimed per se but de-sirable in the implementation of aspects of this invention are discussed in detail below in relation to the drawings and examples. For the sake of overview, a complete qualitative discussion of aspects of the invention relating the drawings is provided first, followed by spècific examples at the end.
In the accompanying drawings, Figure 1 is a front elevation view of one embodiment of an in-dividual integral wafer of an aspect of the present invention having a gas diffusion maze therein;
Figure 2 is a side view along the line II-II of Figure l;
:
' ~';
c~
ll~lZl~)O
Figure 3 is a rear elevation view of the wafer of Figure 1 showing the inlet hole and hydrogen passage therein;
Figure 4 is an exploded, partial side view showing in cross sectiDn one embodiment of a wafer combination of an aspect of the present invention in assembly with the outlet wafer on the left, the inlet wafer on the right, and one example of the plurality of intermediate wafers of Figures 1-3 therebetween;
Figure 5 is another emboaiment of the assem-bly of Figure 4 which takes advantage of counter-current circulation of the hydrogen produced;
Figure 6 is a perspective view of an assembly of wafers from Figure 4;
Figure 7 shows the assembly of wafers of Figure 6 mounted in an electric resistance furnace;
Figure 8 shows another embodiment of an assembly of wafers mounted in an electric resis-tance furnace where the porous edges of the wafers are uncoated with the hydrogen permeable membrane and hydrogen being produced from the porous edges;
and Figure 9 is a detailed showing in cross section of the end wafer of Figure 4 with a stain-less steel or palladium outlet circuit mounted therein for the hydrogen and oxygen.
';':' With particular reference to Figures 1-3, the integral porous refractory wafer 2 is shown having an inlet hole 4 through the wafer from bac~-to-front. A maze 6 is acid etched, molded, pressed, sintered or gouged across at least one flat surface 8 of the wafer. The maze has a plurality of turns or corners 10 ending at outlet 12 which faces out in Figure 1.
The front, back and edge of the wafer are coated with a hydrogen permeable membrane 14, e. g.
10~ Ag - 90~ Pd, wi~. the exception of concentric circles 16 and 18, where the porous refractory material, e.g. A12O3, shows through.
The wafer 2 of Figures 1-3 is shown in the partial exploded view of Figure 4 as the second wafer from the right. Wafers 20 and 22, which are the first and last wafers in an assembly, differ from the plurality of wafers 2 making up the com-posite assembly. In the embodiment of Figure 4, the first wafer 20 has no hole 18 on the outside wall and the last wafer 22 need not have a maze on either flat surface. Wafer 20 has water vapor inlet 3 and wafer 22 has oxygen outlet 5.
Figure 5 is another embodiment of Figure 4 wherein first wafer 24 has a circle 18 with the porous refractory material showing through the outside wall. Last wafer 26 has no circle in the outside wall as does wafer 22 of Figure`4.
Figure 6 i8 a perspective showing of an assembly of Figure 4 defining the endothermal water decompo-sition unit 38 of an aspect of the present invention having a plurality of wafers 2 sandwiched between first and last wafers 20 and 22.
Figure 7 shows the assembly of Figure 4 mounted in an electric resistance furnace 28 having stain-less steel walls 30 and a plurality of heating ele-ments 32. A water vapor inlet 34 of stainless steel tubing enters on the left and the water vapor is passed through 10~ Ag - 90~ Pd tubing 36 into the assembly 38. The 10% Ag - 90% Pd collared tubing 40 connects with the 2 outlet of wafer 22 for distribution to stainless steel outlet 42 con-taining 2 10% Ag - 90% Pd collared tubing 44 conducts H2 from circle 16 on wafer 22 through the wall of the furnace to H2 collecting tube 46.
In the embodiment of Figure 8, the wafers have edges which are porous and uncoated so that hydrogen produced in the endothermal water decom-position unit 60 can diffuse to the outside of the unit and be picked up by an inert carrier gas such as nitrogen which enters through stainless steel conduit ~B. The hydrogen produced is swept out of th~ furnace ~y the inert carrier for collection through stainless steel conduit 52.
Figure 9 shows one way of mounting conduits 44 and 40 in the hydrogen and oxygen outlets of the last wafer 22' of the assembly. The wafer 22' has 11~2100 holes 58 and 60 with respective recesses 62 and 64 molded therein in the green state for holding the collared conduits 44 and 40. Of course, a collared conduit 36 can be mounted in the same way in the first wafer 20.
The best mode of carrying out a preferred aspect of the present invention is disclosed with particular reference to Figures 4, 5, 7 and 8.
Water vapor is introduced into the furnace of Figure 7 by way of stainless steel conduit 34 and conduit 36 or inlet 3 into the endothermal water decomposition unit 38. Inside the furnace the temperature is conveniently maintained between 350C and 1250~C and pressures of from 5 mm Hg to superatmospheric can be maintained.
Even though the platinum group metal membrane is applied in a thickness of 0.0012 - 0.012 cm, 0.0025 - 0.0075 cm, a considerable pres-sure, superatmospheric, can be applied inside the endothermal water decompositior. unit because the porous refractory wafer backing of the membrane is strong in compressive load. Of course, it is possible to do away with the 90% Pd - 10% Ag con-duits 34, 42 and 46 under compressive load from the walls of the furnace.
As shown in Figure 4, the water vapor enters at inlet 3, travels through the platlnum or pal-ladium metal coated maze of wafer 20 and ~2 is diffused through the membrane in the grooves of 11~21~0 the ma~e into the porosity of the refractory of water 20. H2 diffuses simultaneously through the membrane on the right of wafer 2 opposite the maze and grooves of wafer 20. H2 moves through the porosity of wafer 20 to the uncoated center hole 16 where it is channelled from wafer through the centers thereof.
After passing to the outlet 12 of wafer 20, the oxygen enriched water vapor now passes through inlet 4 of wafer 2 and proceeds through the maze of wafer 2 where the water vapor becomes more enriched with oxygen.
Hydrogen passes through the membrane into the porosity of the wafer and proceeds to the collection area in the centers of the wafers. ~he same mechanism of integral wafer 2 takes place through the stack of wafers un-til the last wafer 22 is reached and oxygen exits from outlet 5 and hydro-gen exits from outlet 16.
Figure 5 shows an aspect of the invention operated with counter-current flow of the hydrogen. This is accomplished by having a circle of uncoated refractory 18 on the first wafer 24.
The process in the Figure 8 embodiment is carried out by leaving the porous edges of the wafers uncoated so that hydrogen is passed directly into the body of the furnace. At elevated pressures, there is no need for an inert carrier gas, but when the separation is carried out at less than atmospheric pressure, it is necessary to pass an inert carrier gas, e.g.
nitrogen or argon therethrough.
"~
1~2100 The wafers of aspects of the present invention may be made from refractory materials or from refractory metals. Kirk-Othmer, ibid., discloses, in Vol. 17 (1968), suitable refractories, with the exception of silica refractories which poison the platinum group membranes, on pages 227-267, particularly page 24~ w~ich discloses aluminum oxide, beryllium oxide, calcium oxide, magnesium oxide, thorium oxide, titanium oxide, uranium oxide, and sp~nel. The refractory metals are disclosed on pages 267,284, particularly page 267 which discloses that iridium, rhodium, chromium and platinum are resistant to air at 1400C.
me refractory materials can be processed into the wafers of aspects of the present invention using the techniques disclosed in Kirk-Othmer, ibid, Supplement Volume (1971), p. 15Q, where the cold pressing and isotactic pressing of aluminum oxide ceramics is disclosed.
~1421~0 The refractory metals can be processed into porous wafers using the techniques of powder metallurgy as disclosed in Rirk-Othmer, ibid., vol. 16 (1968), pages 401-435, particularly page 415 where sintering is disclosed and page 425 where the preparation of porous sintered materials is disclosed.
The porosity in the manufacture of the porous refractory wafers of aspects of the present invention can be controlled by using the tech-niques disclosed for the manufacture of aluminum oxide abrasive grinding wheels as disclosed in Rrik-Othmer, ibid., vol. 1 ~1963), page 32, where a chart of the grain sizes used is given, pages 34 and 35, where the con-trol of open structu~e is disclosed and pages 35 and 36 where the methods of manufacture are given.
In addition to the above procedures for fabricating the wafers of aspects of the present invention, it is also possible to use the ~ , ~.
" ll~Z100 techni~ues disclosed in ~.S. Patents 3,344,586 and 3,499,265, but with the addition of the step of molding a maze into at least one side of the wafer when the ceramic or refractory material is in the green state.
Having all the above in mind, a porous refractory wafer can be produced for aspects of the present invention as follows:
A dry mixture of 25% Georgia kaolin, 15% Tennessee ball clay, 55%
nepheline syenite, and 5% silica is made by tumbling these ingredients in a bottle for several hours after which 200 mesh carbon black is added and thoroughly mixed in by further tunbling for 8 hours. The porosity of the finished piece is largely determined by the amount of carbon black used and for a porosity of 40-50%, which is preferred in accordance with aspects of the invention; the proportion of carbon black to the other ingredient is 20-4G%.
ll~Z100 When the dry mixing is complete, the mixture is dampened with a fluid which serves as a binder and lubricant. The moisture content i8 preferably 25 - 30% which supplies the moisture necessary to be able to press the mass into the desired disk shape satisfactorily. The fluid is suitably 3 - 10 glycerine as the binder and the remainder water as the lubricant.
The fluid is mixed in to dampen the mixture lo thoroughly.
Then the mixture is molded in a round mold having a plunger design which produces the maze as shown in Figure 1 of an aspect of the present invention. Al-though wafers of 7.75 cm diameter and 0.3 cm thick are ~roduced, any suitable size can be made.
These wafers are then air dried overnight and fired in a periodic furnace which is raised to a tempera-ture of 100C progressively over a period of 24 hours.
The porous ceramic wafers are first coated on the maze side with palladium by brushing on a solu-tion of palladium resinate aissolved in oil of peppermint and chloroform and containing 3.5% Pd by weight. ~welve coats are applied with each fired ~21~)0 at about 350C in air to thermally decompose the resinate to metal. After 12 coats, a palladium film about 1.2 microns thick is on the substrate. This film is then fired to 1000C in air with a one hour soak to compact the film and bond it to the substrate.
The uncoated circle indicated at 16 in Figure 1 is maintained by placing a cardboard circle there-over and then removing it after all layers have been applied.
A silver naphthenate solution having a vis-cosity suitable for application by brushing was made as follows:
Grams Silver naphthenate ~32~ Ag) 3.35 Toluene 11.13 14.48 The silver naphthenate was dissolved to a stiff gel by stirring mechanically for 2 hours at room tem-perature. 0.52 Grams of t-octyl amine were then added and, with stirring continued for a few more minutesO The solution became fluid. The amber brushing solution then contained 7.15~ Ag by weight or approximately 0.01 mole of silver naphthenate and 0.004 mole of amine.
The silver naphthenate solution is then ap~
plied by brushing over the palladium in several coats with each fired at about 200C in air. When a silver weight equal to 1/3 of the palladium weight has been 1.~42100 added, the coated ceramic is heated for 4 hours at 600C in hydrogen to form a 75:25 Pd:Ag alloy in situ.
The other side of the wafer and the edges are then coated as above to produce a wafer coated except for bare circles 16 and 18 on the front and back as shown-in Figures 1-3.
The method of Example 1 is carried out for molaing and preparing wafers prior to coating. In this example, only the maze 6 of Figure 1 is coated and the back of the wafer is coated following the techniques of Example 1. Such wafers are useful in the apparatus shown in Figure 8.
' The method of Example 1 is modifiea slightly to prepare the wafer 20 of Figure 4. No circle of cardboard îs used in the coating of the right siae of wafer 20 to prevent a coating.
One wafer from Example 3 and a plurality of wafers from Example 1 are secured together to make an assembly by brushing powdered qlaze ma-terial, e.g. that known by the Trade Mark PEMCO FRIT P-1701 on a small portion of adjacent ~2~00 flat sides taking care not to coat the maze. The glaze is fired to fuse the wafers together.
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A coated article comprising a porous refractory base material with a hydrogen permeable membrane coated on portions thereof, said base material having at least first and second flat surfaces, said base material having a top and a bottom, a hole extending through said base material at the top thereof, a grooved maze in at least one of said flat surfaces ex-tending from said hole at the top to the bottom and said grooved maze coated with said hydrogen permeable membrane.
2. The coated article of Claim 1, wherein said base material is selected from the group consisting of aluminum oxide, beryllium oxide, calcium oxide, magnesium oxide, thorium oxide, titanium oxide, uranium oxide, spinel, iridium, rhodium, chromium and platinum.
3. The coated article of Claim 1, wherein said hydrogen permeable membrane is selected from the group consisting of platinum, palladium and alloys of silver and palladium.
4. The coated article of Claim 1, wherein circular portions at the centers of said flat surfaces are uncoated and the remainder of said flat surfaces and the edges of said base material are coated with said hydrogen permeable membrane.
5. The coated article of Claim 1, wherein a circular portion at the center of said second flat surface having said maze is uncoated and the remainder of said flat surfaces and the edges of said base material are coated with said hydrogen permeable membrane.
6. The coated article of Claim 1, wherein said coated grooved maze is in said second flat surface and said first flat surface is coated with said hydrogen permeable membrane.
7. The coated article of Claim 4, wherein said hydrogen permeable membrane has a thickness of 0.0012-0.012 cm.
8. The coated article of Claim 7, wherein said hydrogen permeable membrane has a thickness of 0.0025-0.0075 cm.
9. An apparatus for separating hydrogen from a hydrogen contain-ing gas mixture comprising a plurality of wafers stacked back-to-front, each of said wafers comprising a porous refractory base material with a hydrogen permeable membrane coated on portions thereof, said base material having at least first and second flat surfaces, said base material having a top and a bottom, a hole extending through said base material at the top thereof and defining an inlet, a grooved maze in said second flat surface extending from said hole at the top to the said bottom and defining an outlet at the ter-mination thereof, said grooved maze and said first flat surface coated with said hydrogen permeable membrane and said outlets of successive wafers registered with said inlets of successive wafers in said plurality.
10. The apparatus of Claim 9, wherein a circle of uncoated base material is located on said first and second flat surfaces at the center thereof and the remainder of the said flat surfaces and the edges of said base material are coated with said hydrogen per-meable membrane.
11. The apparatus of Claim 9, wherein a circle of uncoated base material is located on said second flat surface at the center thereof and the remainder of said flat surfaces and the edges of said base material are coated with said hydrogen permeable membrane.
12. An apparatus for separating hydrogen and oxygen from thermally dissociating water vapor comprising:
(a) a closed furnace chamber;
(b) means for heating said chamber;
(c) means for introducing water vapor into said chamber;
(d) means for removing hydrogen from said chamber;
(e) means for removing oxygen from said chamber;
(f) means for separating hydrogen and oxygen from thermally dissociating water vapor comprising a plurality of wafers stacked back-to-front, each of said wafers comprising a porous refractory base material with a hydrogen permeable membrane coated on portions thereof, said base material having at least first and second flat surfaces, said base material having a top and a bottom, a hole extending through said base material at the top thereof and defining an inlet, a grooved maze in said second flat surface extending from said hole at the top to said bottom and defining an outlet at the termination thereof, said grooved maze and said first flat sur-face coated with said hydrogen permeable membrane and said outlets of successive wafers registered with said inlets of successive wafers in said plurality, the first of said inlets connected with said means for introducing water vapor and the last of said outlets connected to said means for removing oxygen from said chamber.
(a) a closed furnace chamber;
(b) means for heating said chamber;
(c) means for introducing water vapor into said chamber;
(d) means for removing hydrogen from said chamber;
(e) means for removing oxygen from said chamber;
(f) means for separating hydrogen and oxygen from thermally dissociating water vapor comprising a plurality of wafers stacked back-to-front, each of said wafers comprising a porous refractory base material with a hydrogen permeable membrane coated on portions thereof, said base material having at least first and second flat surfaces, said base material having a top and a bottom, a hole extending through said base material at the top thereof and defining an inlet, a grooved maze in said second flat surface extending from said hole at the top to said bottom and defining an outlet at the termination thereof, said grooved maze and said first flat sur-face coated with said hydrogen permeable membrane and said outlets of successive wafers registered with said inlets of successive wafers in said plurality, the first of said inlets connected with said means for introducing water vapor and the last of said outlets connected to said means for removing oxygen from said chamber.
13. The apparatus of Claim 12, wherein a circle of uncoated base material is located on said first and second surfaces at the center thereof and the remainder of said flat surfaces and the edges of said base material are coated with said hydrogen permeable membrane, said circles connected with said means for removing hydrogen from said chamber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000353647A CA1142100A (en) | 1980-06-06 | 1980-06-06 | Endothermal water decomposition unit for producing hydrogen and oxygen |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000353647A CA1142100A (en) | 1980-06-06 | 1980-06-06 | Endothermal water decomposition unit for producing hydrogen and oxygen |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142100A true CA1142100A (en) | 1983-03-01 |
Family
ID=4117146
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000353647A Expired CA1142100A (en) | 1980-06-06 | 1980-06-06 | Endothermal water decomposition unit for producing hydrogen and oxygen |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1142100A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111591957A (en) * | 2020-05-25 | 2020-08-28 | 中国矿业大学(北京) | Coal bed gas combined cycle power generation and CO2Trapping system and method |
-
1980
- 1980-06-06 CA CA000353647A patent/CA1142100A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111591957A (en) * | 2020-05-25 | 2020-08-28 | 中国矿业大学(北京) | Coal bed gas combined cycle power generation and CO2Trapping system and method |
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