Patent Application
20100159352
With today's focus on human-produced CO2 and the effect this substance has on pollution and global heating, it is of great importance to reduce or re-use and recirculate CO2.
It is previously known different materials and methods for methanation and production of hydrogen. Examples of such prior art is represented by the following publications:
Jianjun Guo, Hui Lou, Hong Zhao, Dingfeng Chai and Xiaoming Zheng: “Dry reforming of methane over nickel catalysts supported on magnesium aluminate spines” Applied Catalysis A: General, Volume 273, no. 1-2, 8. October 2004, page 75-82;
M. Wisniewski, A. Boréave and P. Gélin: “Catalytic CO2 reforming of methane over Ir/Ce0.9Gd0.1O2-x” Catalysis Communications, Volume 6, nbo. 9, September 2005, page 596-600;
Masaya Matsouka, Masaaki Kitano, Masato Takeuchi, Koichiro Tsujimaru, Masakazu Anpo and John M. Thomas: “Photocatalysis for new energy production. Recent advances in photo catalytic water splitting reactions for hydrogen production” Catalysis Today, 6. Mar. 2007;
U. (Balu) Balachandran, T. H. Lee and S. E. Dorris: “Hydrogen production by water dissociation using mixed conducting dense ceramic membranes” International Journal of Hydrogen Energy, Volume 32, no. 4, Mar. 2007, page 451-456;
Daniel M. Ginosar, Lucia M. Petkovic, Anne W. Glenn and Kyle C. Burch: “Stability of supported platinum sulfuric acid decomposition catalysts for use in thermo chemical water splitting cycles” International Journal of Hydrogen Energy, Volume 32, no. 4, March 2007, page 482-488;
T. Sano, M. Kojima, N. Hasegawa, M. Tsuji and Y. Tamaura: “Thermo chemical water-splitting by a carbon-bearing Ni(II) ferrite at 300° C.” International Journal of Hydrogen Energy, Volume 21, no. 9, September 1996, page 781-787;
S. K. Mohapatra, M. Misra, V. K. Mahjan and K. S. Raja: “A novel method for the synthesis of titania nano tubes using sono electro chemical method and its application for photo electro chemical splitting of water” Journal of Catalysis, Volume 246, no. 2, 10. March 2007, page 362-369;
S. K. Mohapatra, M. Misra, V. K. Mahajan and K. S. Raja: “A novel method for the synthesis of titania nano tubes using sono electro chemical method and its application for photo electro chemical splitting of water” Journal of Catalysis, Volume 246, no. 2, 10. March 2007, page 362-369;
Meng Ni, Michael K. H. Leung, Dennis Y. C. Leung and K. Sumathy: “A review and recent developments in photo-catalytic water-splitting using TiO2 for hydrogen production”, Renewable and Sustainable Energy Reviews, Volume 11, no. 3, April 2007, page 401-425;
Wenfeng Shangguan: “Hydrogen evolution from water splitting on nano composite photo-catalysts” Science and Technology of Advanced Materials, Volume 8, no. 1-2, January-March 2007, page 76-81, APNF International Symposium on Nanotechnology in Environmental Protection and Pollution (ISNEPP2006);
Seng Sing Tan, Linda Zou and Eric Hu: “Photosynthesis of hydrogen and methane as key components for clean energy system” Science and Technology of Advanced Materials, Volume 8, no. 1-2, January-March 2007, page 89-92, APNF International Symposium on Nanotechnology in Environmental Protection and Pollution (ISNEPP2006);
U.S. Pat. No. 7,087,651 (Lee. Tuffnell et al., 8 Aug. 2006) “Process and apparatus for steam-methane reforming”;
U.S. Pat. No. 6,972,119 (Taguchi et al., Dec. 6, 2005) “Apparatus for forming hydrogen”;
U.S. Pat. No. 6,958,136 (Chandran et al., Oct. 25, 2005) “Process for the treatment of waste streams”;
U.S. Pat. No. 6,838,071 (Olsvik et al., Jan. 4, 2005) “Process for preparing a H2-rich gas and a CO2-rich gas at high pressure”.
The present invention may be summarized as a combined catalytic gas reactor including a catalyzer or process for combustion of fossil fuels/organic material, a catalyzer or process for creating hydrogen and oxygen by splitting of water, and a process with catalyzer or process for creating methane from reactions wherein CO, CO2 and hydrogen participate according to a methanation reaction scheme as follows:
CO+H2O═CO2+H2 1.
CO+3H2═CH4+H2O 2.
CO2+4H2═CH4+2H2O 3.
H2O═H2+½O2 5.
CH4+2O2═CO2+2H2O 6.
The combined complete process described above may be constructed as a Solid Oxide Fuel Cell (SOFC). In the above indicated reactions, the released energy of reactions 3 and 6 will substantially drive the water dissociation reaction according to equation 5.
In the present connection the concept “fossil fuel/organic material” is meant to be any combustible carbon-containing substance, e.g. any hydrocarbon and carbohydrate or derivatives thereof such as CH4, C2H6, C3H8, C2H5OH, C6H12O6, CO(CH3)2, CH3CHO, CnH2n-2 (wherein n is an integer), etc.
The oxidation or combustion of fossil fuels (reaction 6, here symbolized by Methane, CH4), takes place over a catalyst suited for the reaction. This catalyst may consist of:
Supports of metal catalysts may be for example:
Al2O3 (alumina), ZrO2 (zirconia), CeO2—Al2O3 (Al2O3 supported CeO2), CeO2-x—Al2O3 (Al2O3 supported non stoichiometric ceria), La-stabilized Al2O3, Y stabilized ZrO2
The water is split into hydrogen and oxygen according to reaction 5 with thermo chemical membranes/catalysts. Some of these may be:
The membranes may be coated by metals to increase activity in the temperature interval 150 to 600° C., such as;
The methanation reaction may be performed with the catalysts infra with different compositions depending on the condition of the gas that is to be treated, but all methanation catalysts may be used in the temperature interval 150 to 600° C.;
These catalysts are deposited on a support such as for example:
The advantage of the present invention is that CO2 is transformed to methane through the aid of hydrogen and may consequently be used again as a fuel or as a raw material for a number of other processes. Some of these processes may be the production of methane, methanol, ammonia, urea, nitrous acid, ammonium nitrate, NPK, PVC, etc.
The present invention may be used in all forms of exhaust gases wherein fossil or biological fuel is used.
In addition the structure and composition of the reactors and catalyzers according to the present invention solves the problem with emission of VOC (volatile organic compounds), NOx (nitrogen oxides), N2O (laughing gas), NH3 (ammonia) and other greenhouse and in other ways polluting gases.
The present invention produces also energy far more effectively than similar processes today, and has far lower CO2 emission per kWh than contemporary processes with CO2 harvesting. Other advantages of the present process versus others are apparent from table 1 infra.
As a consequence of the development of the present invention, and as a non-separable part thereof, the present invention may be used within the general area of CO2 purification, collection and sequestering.
The present invention is expressed as a reactor concept providing the industrial way of controlling the physical and chemical parameters involved in the following reaction equations:
The present reactions are also disclosed as the application of specific reactor designs providing catalytic and physical characteristics allowing and emphasizing the hydrogenation of CO2 to CH4 (methane).
The present invention may be considered as a tipple process with one part combusting fossil fuel by reaction 6, and with second part producing hydrogen and oxygen according to reaction 5. The total process may take advantage of the produced hydrogen from the first part, but may also individually produce hydrogen from reaction 1. In the third part the produced hydrogen will react with CO and CO2 according to reaction 2 and 3 and produce methane. The produced methane and oxygen may either be re-circulated and combusted in a continuous loop or the methane and oxygen may be separated out and be used as a raw material for producing other chemicals.
Part 1 of the present invention may contain catalysts and other device making it possible to combust the fossil fuel completely (reaction 6).
Part 2 of the present invention may contain catalysts and other devices making it possible to use both the produced hydrogen and the produced oxygen (reaction 5).
Part 3 of the present invention is to contain a catalyst being suited for performing the methanation reaction, reactions 2 and 3, and suppressing the reverse shift reaction, reaction 4.
Part 1, 2 and part 3 may be integrated with each other or may be separate entities.
When all the parts are integrated into a Solid Oxide Fuel Cell (SOFC), the system will have the highest conversion efficiency because the energy in the fuel will be transformed directly into electrical energy rather than first being transformed into vaporization energy, further into mechanical energy thus producing electricity. The electrical efficiency will be higher than 90%.
Part 1 consists in performing the complete oxidation of fuel for thermal energy production. This energy is required for the endothermic section (part 2). A catalyst will be used for this step. The basic principle of catalytic combustion is to permit the combustion reaction to take place on or near the catalyst surface instead of in a flame. The activation energy required is much decreased compared to flame combustion so that combustion can proceed at much lower temperatures than in a flame. The formation of NOx is thus avoided. The emissions of unburnt CO and hydrocarbons is also much reduced. Catalytic combustion is a clean process. Other advantages are the increased stability of the combustion and the ability to combust fuels outside the flammability limits. A wide range of fuel/ratios can be used.
Since high temperatures may be reached during the process, the thermal stability of the catalyst is a major requirement for durability reasons. Basically, two classes of catalysts can be used for catalytic combustion: noble metals (Pd is the most active for CH4 combustion) and metal oxides. The former catalysts are the most active but also the most expensive. In spite of their lower catalytic activity, the latter catalysts offer a good alternative to noble metals due to their much lower price and good thermal stability. Among them, perovskites and substituted hexaaluminates are the most promising ones, since offering a good compromise between activity and thermal stability.
Part 2 is the section wherein the water splitting is performed. This water dissociation needs much energy to happen. This energy may be taken from part 1 and/or part 3 developing large amounts of energy or the energy may be provided from external sources.
Membrane process at 200-900° C. (thermo chemical),
The membranes may be coated by metals to increase activity in the temperature interval 200 to 900° C., such as;
In Part 3 the transforming of CO2 with hydrogen to methane is performed in a reactor with a catalyst. The heat being developed may be used for heating part 1 or in any other way. The shape of the catalyst is not essential and may inter alia comprise coated monoliths, different nano materials and other types and forms of carriers. The carriers may be selected from e.g. TiO2, Al2O3, cordierite, Gd-doped CeO2, perovskites and other types of carrier materials. The catalytic material may also be present in any form as a “pure” catalyst material. The form and composition of the reactor and the catalyst will depend on which emission gas it is wanted to purify. An impure exhaust gas with large amounts of dust (from the combustion of coal) may have a monolithic catalyst carrier whereas a pure exhaust gas (from a natural gas turbine) may have a catalyst in the form of pellets. All types of exhaust gases from all types of combustions of organic material may be treated.
The methanation reaction may be performed with the catalyzers infra with different compositions depending on the condition of the gas that is to be treated, but all methanation catalyzers may be used in the temperature interval 200 to 600° C.:
When re-circulating the methane for further combustion and production of electricity or other forms of energy, the oxygen having been produced at the splitting of water may be used as a source for oxygen for the combustion of methane. Since air is not used as a source for oxygen, nitrogen will not participate as a diluting and reacting gas. Instead of nitrogen as a diluting gas (inert gas), water and CO2 being produced at the combustion may be used. This gas (CO2 and water) will be taken out for recirculation prior to the reactors having been disclosed in the present invention, and thus keeps a combustion temperature being commensurate with the materials that are present today for the construction of such combustion plants.
Nitrogen is the source for NOx at the combustion, and by performing the suggested recirculation the nitrogen will be replaced by CO2 and water thereby avoiding the production of NOx. In avoiding NOx it is also possible to avoid the use of reducing measures creating laughing gas (N2O).
Another theoretical solution for the use of the formed methane may be to produce methanol. This production may conceivably happen according to commercial processes being available today, and the methanol may have several areas of use such as e.g. fuel for transport means.
This process may conceivably be solved in the following way: Fuel is combusted with air in a burner. Electricity, optionally another form of energy, is taken out from the combustion process in the usual way. The CO2 produced is used, as disclosed in the present invention, for producing methane. The methane is separated from the other gases and is used for producing methanol.
The present invention is not limited to these two fields, but may be used in all processes wherein natural gas or other hydrocarbons and organic compounds are one of the raw materials.
The present invention also produces energy far more efficiently than comparable processes today, and has a far lower CO2 emission per kWh than today's processes with capture of CO2. The other advantages of the present process as compared to others are observed in table 1 infra.
A small part of the exhaust gas must be emitted to avoid accumulation of certain trace elements. This exhaust gas contains mainly of CO2 and water. This composition makes it very simple to capture CO2 without using chemicals (e.g. amines and others), since the water may be condensed out while the CO2 still is in a gaseous state. CO2 may then be used for other purposes or may be stored. The cost for capture and optionally storage then become very small.
The disclosed reactions are common reactions (equilibrium reactions) happening in the production of ammonia over different catalytic layers.
The shift reaction happens in the LT or HT shift reactor wherein carbon monoxide reacts to produce carbon dioxide and hydrogen over a iron oxide/chromium oxide respectively a copper oxide/zinc oxide catalyst.
The methanation reaction happens in the methane reactor wherein carbon monoxide and carbon dioxide is reacted into methane and water over a nickel, ruthenium, tungsten or other metal-containing catalyst according to several total reactions (equilibrium reactions), inter alia:
CO+H2O═CO2+H2 1.
CO+3H2═CH4+H2O 2.
CO2+4H2═CH4+2H2O 3.
Since the ammonia process is a process for producing ammonia via hydrogen from methane and nitrogen from air, the reactions 2. and 3. disclosed supra are reactions that are not wanted and which give losses of in the production of ammonia.
In the present invention all of these reactions are wanted since they produce methane being a product or intermediates participating in producing methane, and this effect has not previously been disclosed in the patent literature.
The source of carbon dioxide may be all kinds of combustion of organic materials such as emission gases or combustion gases from power plants, boats, cars, industrial plants that also include other contaminants. These contaminants may be, but are not limited to N2O, NO, NO2, volatile compounds (VOCs), SO2, etc.
Ordinary destruction of these contaminants happens with CO2 present in the combustion gas. An ordinary concentration of CO2 in the combustion gas is about 1-20% by volume. When CO2 is removed prior to the other contaminants the catalyst volume and the addition of chemicals will be reduced dramatically, partly on account of the lowered volume, and partly on account of the inhibitor effect of CO2 if this is present.
Any process solution may be used for removing these contaminants.
The invention may be summarized by the following items:
The present invention may be summarized as a combined catalytic gas reactor including a catalyzer or process for combustion of fossil fuels, a catalyzer or process for creating hydrogen and oxygen by splitting of water and a process with catalyzer or process for creating methane from reactions wherein CO, CO2 and hydrogen participate according to a methanation reaction scheme as follows:
CO+H2O═CO2+H2 1.
CO+3H2═CH4+H2O 2.
CO2═4H2═CH4+2H2O 3.
H2O═H2+½O2 5.
CH4+2O2═CO2+2H2O 6.
The combined complete process described above may be constructed as a Solid Oxide Fuel Cell (SOFC)
The embodiments of the SOFC are directed both towards new uses and reconstruction of existing devices for industrial combustion, and the invention of these rebuilding applications and new installations are claimed.
If there is CO2 in the purge gas (10), it may be compressed and stored in a suitable way.
During normal combustion in a standard type power plant, the electrical efficiency is around 35% because of different mechanical and condensation losses. This mean that the relative carbon-di-oxide emission will be around 2.9 rel/kWh.
The new process will have a much higher electrical efficiency because the chemical energy is directly transformed to electricity. The electrical efficiency may be as high as 95%. This means that the relative carbon-di-oxide emission will be around 1.1 rel/kWh. In all examples air or reintroduced CO2, water and oxygen can be used as a combustion gas.
Aspects of the invention include a process for combustion of organic material/fossil fuel by using oxygen, wherein at least formed carbon monoxide (CO) and carbon dioxide (CO2) and water (H2O) is passed into a three-step catalytic gas reactor wherein said gas reactor in its first step includes a catalyst/membrane for the combustion of organic material/fossil fuel (reaction 6), in its second step a catalyst/membrane forming hydrogen and oxygen by dissociating water (through reaction 5), and in its third step a catalyst forming methane from reactions wherein CO, CO2 and hydrogen participate according to a methanation scheme through reactions 2 and 3 as follows:
CO+H2O═CO2+H2 1.
CO+3H2═CH4+H2O 2.
CO2+4H2═CH4+2H2O 3.
H2O═H2+½O2 5.
CH4+2O2═CO2+2H2 6.
Further aspects of the process according to the invention include that at least parts of the hydrogen being formed at the reaction between carbon monoxide and water is returned to the third step of the reactor for the forming of methane, that the process is performed without any addition of nitrogen-containing gas (such as air) for avoiding the forming of nitrogen oxides, that the process is performed by parts or all of the formed oxygen at the dissociation of water being passed back to the first step for the combustion of the organic material, that the process is performed by parts or all of the formed water and the carbon dioxide is used as inert gas in step 1, that parts or all of the formed methane is used as starting material for other processes, that the formed oxygen is used as a starting material for other processes, that the formed CO2 in the exhaust gas being emitted is caught and stored, that the formed CO2 in the exhaust gas being emitted is caught and used in other connections, and that any step separately or collectively, including the combustion of the organic material, the water-splitting and/or the methanation reaction is/are performed at a temperature in the interval 200-1000° C., more preferred 250-850° C., most preferred 350-650° C.
Furthermore, the present invention includes a solid oxide fuel cell (SOFC) reactor, comprising three steps separately performing the reactions combustion of organic material/fossil fuel by using oxygen, wherein at least formed carbon monoxide (CO) and carbon dioxide (CO2) and water (H2O) is passed into a three-step catalytic gas reactor wherein said gas reactor in its first step includes a catalyst/membrane for the combustion of organic material/fossil fuel (reaction 6), in its second step a catalyst/membrane forming hydrogen and oxygen by dissociating water (through reaction 5), and in its third step a catalyst forming methane from reactions wherein CO, CO2 and hydrogen participate according to a methanation scheme through reactions 2 and 3 as follows:
CO+H2O═CO2+H2 1.
CO+3H2═CH4+H2O 2.
CO2+4H2═CH4+2H2O 3.
H2O═H2+½O2 5.
CH4+2O2═CO2+2H2O 6.
Such a solid oxide fuel cell (SOFC) reactor may in any step of the reactor be operated separately or collectively, including the combustion of the organic material, the water-splitting and/or the methanation reaction, at a temperature in the interval 200-1000° C., more preferred 250-850° C., most preferred 350-650° C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20073080 | Jun 2007 | NO | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NO2008/000222 | 6/18/2008 | WO | 00 | 2/8/2010 |
