US20170089569A1 - Method For The Combustion Of An Alloy Of An Electropositive Metal - Google Patents

Method For The Combustion Of An Alloy Of An Electropositive Metal Download PDF

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US20170089569A1
US20170089569A1 US15/311,229 US201515311229A US2017089569A1 US 20170089569 A1 US20170089569 A1 US 20170089569A1 US 201515311229 A US201515311229 A US 201515311229A US 2017089569 A1 US2017089569 A1 US 2017089569A1
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Prior art keywords
alloy
combustion
fuel gas
electropositive metal
electropositive
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Helmut Eckert
Renate Elena Kellermann
Guenter Schmid
Dan Taroata
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Siemens AG
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Siemens AG
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Assigned to SIEMENS AKTIENGESELLSCHAFT reassignment SIEMENS AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KELLERMANN, RENATE ELENA, ECKERT, HELMUT, SCHMID, GUENTER, TAROATA, DAN
Publication of US20170089569A1 publication Critical patent/US20170089569A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
    • F23B90/00—Combustion methods not related to a particular type of apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C99/00—Subject-matter not provided for in other groups of this subclass
    • F23C99/006—Flameless combustion stabilised within a bed of porous heat-resistant material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23B—METHODS OR APPARATUS FOR COMBUSTION USING ONLY SOLID FUEL
    • F23B2900/00—Special features of, or arrangements for combustion apparatus using solid fuels; Combustion processes therefor
    • F23B2900/00003—Combustion devices specially adapted for burning metal fuels, e.g. Al or Mg
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel

Definitions

  • the present invention relates to a process for combusting an alloy of an electropositive metal, wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, with a fuel gas, wherein the alloy of the electropositive metal comprises at least two electropositive metals, in which the alloy of the electropositive metal is combusted with the fuel gas, and to an apparatus for conducting the process.
  • the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, with a fuel gas
  • the alloy of the electropositive metal comprises at least two electropositive metals, in which the alloy of the electropositive metal is combusted with the fuel gas, and to an apparatus for conducting the process.
  • Fossil fuels deliver tens of thousands of terawatt hours of electrical, thermal and mechanical energy per year.
  • carbon dioxide (CO 2 ) is increasingly becoming an environmental and climatic problem.
  • the solid final end product of the reaction of lithium in each case, optionally after hydrolysis, as in the case of nitride, is the oxide or carbonate, which can then be reduced again by means of electrolysis to lithium metal.
  • This establishes a circuit in which, by means of wind power, photovoltaics or other renewable energy sources, surplus power can be produced, stored and converted back to power at the desired time, or else chemical commodity materials can be obtained.
  • Substantially complete separation of liquid and solid combustion residues from the offgas stream is important in order not to generate any surface deposits or blockages in the downstream apparatuses. More particularly, it is very demanding to guide the offgas stream directly to a gas turbine, since it has to be ensured in that case that all particles have been completely removed from the offgas stream. Such particles cause long-term damage to the gas turbine blades and lead to failure of the plant.
  • DE 10 2014 203039.0 describes the use of alkali metals as energy storage means and utilization thereof in power plant operation
  • DE 10 2014 203039.0 a construction—cyclone burner—for combustion of lithium in CO 2 - or N 2 -containing atmospheres and simultaneous separation of the solid and gaseous reaction products by means of the cyclone.
  • a problem here is the high temperatures in the combustion of the electropositive metal and the exothermicity of the reaction, which lead to high demands on the combustion apparatus and the control of the reaction.
  • One embodiment provides a process for combusting an alloy of an electropositive metal, wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, with a fuel gas, wherein the alloy of the electropositive metal comprises at least two electropositive metals, in which the alloy of the electropositive metal is combusted with the fuel gas.
  • the alloy of the electropositive metal is combusted in liquid form.
  • the combustion takes place at a temperature above the melting point of the salts formed in the reaction of the alloy of the electropositive metal and the fuel gas.
  • the alloy of the electropositive metal is guided in liquid form into a pore burner and combusted with the aid of the pore burner, wherein the fuel gas is optionally guided to the outer surfaces of the pore burner and combusted with the alloy of the electropositive metal.
  • the alloy of the electropositive metal preferably in liquid form, is atomized and combusted with the fuel gas.
  • reaction products are separated after the combustion, preferably with the aid of a cyclone.
  • reaction products of the combustion are used to generate energy, preferably using at least one expander turbine and/or at least one steam turbine and/or at least one heat exchanger and/or at least one boiler.
  • Another embodiment provides an apparatus for combustion of an alloy of an electropositive metal, wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, and the alloy of the electropositive metal includes at least two electropositive metals, comprising a pore burner or a unit for atomizing the alloy of the electropositive metal, a feed unit for the alloy of the electropositive metal, preferably in liquid form, to the interior of the pore burner or the unit for atomizing the alloy, which is designed to supply the pore burner or the unit for atomizing the alloy with the alloy of the electropositive metal, preferably in liquid form, a feed unit for a fuel gas, which is designed to supply fuel gas, and optionally a heating apparatus for providing the alloy of the electropositive metal in liquid form, which is designed to liquefy the alloy of the electropositive metal.
  • the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof
  • the alloy of the electropositive metal includes at least two
  • the apparatus comprises a pore burner, comprising a pore burner, wherein the feed unit for the fuel gas is arranged such that it guides the fuel gas at least partly to the surface of the pore burner.
  • the pore burner is arranged such that reaction products that form from the combustion and optionally the electropositive metal can be separated by gravity from the surface of the pore burner.
  • the pore burner or the unit for atomizing the alloy of the electropositive metal consists of a material selected from the group consisting of iron, chromium, nickel, niobium, tantalum, molybdenum, tungsten, zircalloy and alloys of these metals, and also steels such as stainless steel and chromium-nickel steel.
  • the apparatus comprises a separating unit for the products of the combustion of the electropositive metal, preferably a cyclone, wherein the cyclone may further preferably have a perforated plate.
  • the apparatus further comprises at least one expander turbine and/or at least one steam turbine and/or at least one heat exchanger and/or at least one boiler.
  • FIG. 1 shows, in schematic form, an illustrative arrangement for an apparatus of the invention.
  • FIG. 2 shows, in schematic form, a detail view in a further illustrative arrangement for an apparatus of the invention.
  • FIG. 3 shows, in schematic form, a further detail view in an additional illustrative arrangement for an apparatus of the invention.
  • FIG. 4 illustrates, in schematic form, an illustrative cross section through an illustrative apparatus of the invention in the region of the feed unit of the carrier gas to the reactor.
  • FIG. 5 shows, in schematic form, a further possible arrangement for an apparatus of the invention.
  • FIG. 6 illustrates, in schematic form, another possible arrangement for an apparatus of the invention.
  • FIG. 7 shows a scheme for an illustrative reaction of an alloy of an electropositive metal according to the invention and carbon dioxide to give carbonate, which can be conducted by the process according to the invention.
  • FIG. 8 shows a scheme for a further illustrative reaction of an alloy of an electropositive metal according to the invention and nitrogen to give nitride and further conversion products, which can be conducted by the process according to the invention.
  • Some embodiments of the present invention provide a process and an apparatus in which combustion of electropositive metals can be conducted at lower temperatures. Some embodiments provide a process in which effective combustion of electropositive metals can be conducted with avoidance of excessive cooling for protection of the plant and hence with reduction of heat losses. Some embodiments provide a process in which the starting materials from the combustion of the electropositive metals can be obtained in a simple and energetically improved manner. Some embodiments provide a process in which the energy required for activation of the combustion reaction can be lowered. Some embodiments provide a process in which liquid transport of combustion products away from the combustion can take place at minimum temperature, since the longer these remain liquid, the lower the temperature can be in the combustion, which also protects the plant.
  • alloys of electropositive metals wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, and wherein the alloy of the electropositive metal comprises at least two electropositive metals, enables lowering of the reaction temperature in the combustion, and better controllability of the exothermic combustion reaction and more effective control of the plant.
  • the separation of the gases formed in the reaction for example CO in the case of combustion in CO 2
  • the salt mixture for example carbonates in the case of combustion in CO 2
  • the alloys can usually be provided more easily than the pure electropositive metals, since the electrolysis of salt mixtures of various electropositive metals can also be conducted more easily and less energy-intensively than the electrolysis of salts of just one electropositive metal.
  • Embodiments of the present invention thus relate to a process and a construction for combustion, optionally under pressure, of alloys comprising alkali metals and/or alkaline earth metals, aluminum and/or zinc, in different reaction gas atmospheres such as carbon dioxide, nitrogen, steam, oxygen, air, etc.
  • Some embodiments provide a process for combusting an alloy of an electropositive metal, wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, with a fuel gas, wherein the alloy of the electropositive metal comprises at least two electropositive metals, in which the alloy of the electropositive metal is combusted with the fuel gas.
  • an apparatus for combustion of an alloy of an electropositive metal wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, and the alloy of the electropositive metal includes at least two electropositive metals, comprising a pore burner or a unit for atomizing the alloy of the electropositive metal, a feed unit for the alloy of the electropositive metal, preferably in liquid form, to the interior of the pore burner or the unit for atomizing the alloy, which is designed to supply the pore burner or the unit for atomizing the alloy with the alloy of the electropositive metal, preferably in liquid form, a feed unit for a fuel gas which is designed to supply fuel gas, and optionally a heating apparatus for providing the alloy of the electropositive metal in liquid form, which is designed to liquefy the alloy of the electropositive metal.
  • the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof
  • the alloy of the electropositive metal includes at least two electropositive metals,
  • One embodiment provides a process for combusting an alloy of an electropositive metal, wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures of such alloys, with a fuel gas, wherein the alloy of the electropositive metal comprises at least two electropositive metals, in which the alloy of the electropositive metal is combusted with the fuel gas.
  • the electropositive metal in the alloy L is selected from alkali metals,
  • the electropositive metal in the alloy is selected from Li, Na, K, Mg, Ca, Al and Zn, and the alloy further preferably comprises at least two electropositive metals selected from Li, Na, K, Ca and Mg, where the alloy in particular embodiments more preferably comprises at least lithium or magnesium.
  • the alloy is additionally not particularly restricted and may, for example, be in solid or liquid form.
  • the alloy in the combustion is liquid, since simple transport of the alloy can take place in this way.
  • Useful fuel gases are those which can react with the alloy L mentioned in an exothermic reaction, although these are not particularly restricted.
  • the fuel gas may comprise air, oxygen, carbon dioxide, hydrogen, water vapor, nitrogen oxides NO x such as dinitrogen monoxide, nitrogen, sulfur dioxide, or mixtures thereof.
  • the process can thus also be used for desulfurization or NOx removal.
  • the fuel gas it is possible here to obtain various products with the various alloys L, which may be in solid, liquid or else gaseous form.
  • a reaction of an alloy L, for example an alloy of lithium and magnesium, with nitrogen can give rise, inter alia, to metal nitride, such as a mixture of lithium nitride and magnesium nitride, which can then be allowed to react further at a later stage to give ammonia
  • a reaction of alloy L, for example lithium and sodium, with carbon dioxide can give rise, for example, to metal carbonate, for example a mixture of lithium carbonate and sodium carbonate, carbon monoxide, metal oxide, for example lithium oxide and sodium oxide, or else metal carbide, for example lithium carbide and sodium carbide, or else mixtures thereof, it being possible to use the carbon monoxide to obtain higher-value products, for example including longer-chain hydrocarbonaceous products such as methane, ethane, etc., up to and including benzine, diesel, but also methanol etc., for example in a Fischer-Tropsch process, whereas it is possible to use metal carbide, for example lithium carbide and sodium carbide, to obtain
  • metal nitride for example.
  • an alloy of lithium and potassium, on combustion gives rise, for example, to a salt mixture of the corresponding lithium and potassium salts
  • an alloy of sodium and potassium, on combustion gives rise, for example, to a salt mixture of the corresponding sodium and potassium salts.
  • Corresponding reactions can also be conducted with alloys comprising 3 or more metals, for example lithium, sodium and potassium.
  • alloys for example, composed of magnesium and calcium or magnesium and zinc, or composed of magnesium and aluminum, etc.
  • nitride For a conversion to nitride, preference is given, for example, to Li/Mg or any mixture of the alkaline earth metals, especially Mg/Ca, although Be, for example, does not work as well.
  • Suitable alloys for combustion with CO 2 are, for example, Na/K, Na/Li/K, Li/K, Li/Na, Li/Mg, the above alloys. Alloys with barium, for example, can also be obtained and used in a simple manner, since barytes are very common in nature.
  • alloys by virtue of the lower melting temperature of the salt mixture compared to the melting temperature of the individual alkali metal and alkaline earth metal carbonates, can enable flexible adjustment of flame temperature, with simultaneous assurance of removal of the salt mixture in liquid form.
  • the adiabatic flame temperature of the stoichiometric combustion reaction in the case of combustion of lithium in carbon dioxide or nitrogen atmosphere is in the region of >2000 K.
  • the exothermic reaction releases heat, at a comparable thermal level to that in the combustion of carbon-based energy carriers under air. For these reasons, simpler control of the combustion reaction is advantageous.
  • further components are present in the alloy L, for example further metals.
  • Such further components are present in a total amount of less than 50% by weight, preferably less than 25% by weight, further preferably less than 10% by weight and even further preferably less than 5% by weight, based on the alloy.
  • the alloy contains only metals selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, but unavoidable impurities may likewise be present, for example in an amount of less than 1% by weight, based on the alloy.
  • the alloy constituents are adjusted so as to give rise to approximately a minimum of the melting point for the alloy—i.e. a eutectic mixture of the metals—and/or a minimum of the melting point of the corresponding salts, with possible temperature deviations in the melting point of the alloy or the salt mixture of not more than +200° C. in relation to the temperature minimum.
  • a minimum of the melting point for the alloy i.e. a eutectic mixture of the metals
  • the salt mixture i.e. a eutectic mixture of the metals
  • there is a minimum of the melting point of the corresponding salts eutectic mixture/eutectic
  • the corresponding melting points of the alloys or the salts formed in the combustion can be found in a suitable manner from known phase diagrams or calculated in a simple manner.
  • the salts obtained are sodium carbonate and potassium carbonate, for which a melting point minimum of 709° C. is found at a molar ratio of sodium salt to mixture of 0.59.
  • a value of 498° C. is found at a molar ratio of sodium salt to mixture of 0.49.
  • lithium and potassium, for the carbonates there are actually two melting point minima of 503° C.
  • the proportion of the electropositive metals and further components in the alloy is chosen so as to give a melting point of the salts formed which is lower than the lowest melting point of each of the individual salts; in other words, for example, that for the lithium carbonate/sodium carbonate system is lower than the melting point of lithium carbonate, since potassium carbonate has a higher melting point.
  • the alloy of the electropositive metal is combusted in liquid form.
  • the combustion additionally takes place at a temperature above the melting point of the salts formed in the reaction of the alloy of the electropositive metal and the fuel gas.
  • This configuration gives rise, on combustion of the alloy, to liquid reaction products which, in contrast to reaction products in the form of dusts or powder, can be separated relatively easily from the gaseous reaction products which form.
  • the salts are in liquid form and, just like the further gaseous and any liquid reaction products or unconsumed reactants, for example liquid alloy L or liquid metal, can be removed easily from the reaction site. This is advantageous especially where the combustion takes place at the exit site of the alloy from a feed unit, for example in the case of atomization or combustion using a pore burner.
  • Atomization of the alloy can be effected here in a suitable manner and is not particularly restricted.
  • the type of nozzle is likewise not particularly restricted and may include one-phase and two-phase nozzles.
  • the alloy L of the electropositive metal is atomized, preferably in liquid form, and combusted with the fuel gas.
  • An alternative possibility is atomization of alloy particles.
  • more efficient atomization can be achieved by using the alloy L in liquid form, in which case self-ignition of the combustion reaction may also be possible as a result of the temperature, such that no ignition source is required.
  • the alloy of the electropositive metal is guided in liquid form into a pore burner and combusted with the aid of the pore burner, wherein the fuel gas is optionally guided to the outer surfaces of the pore burner and combusted with the alloy of the electropositive metal.
  • the pore burner is thus a pore burner without internal mixing.
  • the pores serve solely to increase the surface area of the alloy L.
  • a reaction with the fuel gas can take place at the exit of the pores close to the surface of the pore burner, provided that it can be ensured that reaction products that form are conveyed out of the pore burner by further delivery of alloy L.
  • the combustion reaction takes place outside the pores of the pore burner, for example at the surface of the pore burner or even after exit of the alloy L from the pore burner, i.e. only at the surface of the exiting alloy L.
  • a reactor/combustion space in which the combustion of the alloy L with the fuel gas can take place, for example in the case of atomization or combustion with the aid of a pore burner.
  • the reactor/combustion space is not particularly restricted, provided that the combustion can take place therein.
  • the combustion can be localized in the pore burner, in which case the combustion products are also obtained in or close to the pore burner.
  • the combustion products are obtained throughout the reactor and solid and liquid reaction products have to be separated again in a complex manner from gaseous reaction products
  • in the case of combustion with a pore burner there is localization of solid and liquid reaction products in particular close to the pore burner, which facilitates separation thereof from gaseous combustion products.
  • the entire combustion apparatus can also be made more compact and the combustion can be configured so as to be gentler in respect of the apparatus through localization of the combustion process.
  • the pore burner is not particularly restricted in terms of its form and, in particular embodiments, comprises a porous tube as burner.
  • the pore burner comprises a porous tube which can be supplied with the alloy L at at least one orifice.
  • the alloy L is supplied only through one orifice of the tube and the other end of the tube is closed or likewise consists of the material of the porous tube.
  • the porous tube here may, for example, be a porous metal tube, for example made of iron, chromium, nickel, niobium, tantalum, molybdenum, tungsten, zircalloy and alloys of these metals, and also steels such as stainless steel and chromium-nickel steel.
  • the pore burner preferably consists of a material selected from the group consisting of iron,
  • steels such as stainless steel and chromium-nickel steel.
  • austenitic chromium-nickel steels which are very resistant, for example, to erosion by sodium at high temperature, but materials having 32% nickel and 20% chromium, such as AC 66, Incoloy 800 or Pyrotherm G 20132 Nb also exhibit relatively favorable corrosion characteristics.
  • the further constituents of the pore burner are not subject to any further restriction and may comprise the feed unit for the metal M and optionally an ignition source, etc.
  • the pore burner is supplied with the alloy L in liquid form in the interior of the pore burner. This leads to better distribution of the alloy L in the pore burner and more homogeneous exit of the alloy from the pores of the porous tube, such that a more homogeneous reaction can take place between alloy L and fuel gas.
  • the combustion of alloy L and fuel gas can be suitably controlled for example, via the pore size of the pores of the tube, the alloy L used, the density thereof—which can be correlated to the temperature of the alloy L, the pressure with which the alloy L is introduced into the pore burner, the pressure or the application/feed rate of the fuel gas, etc.; the alloy L, for example comprising lithium and sodium, in particular embodiments, is accordingly used in liquid form, i.e., for example, above the melting point of the alloy.
  • the liquid alloy L can be injected here into the porous tube, for example also with the aid of a further gas under pressure, which is not restricted, provided that it does not react with the alloy L, for example an inert gas.
  • the liquid alloy L then passes through the pores of the tube to the surface and burns with the gas to give the respective reaction product(s).
  • the fuel gas is guided to the outer surfaces of the pore burner and combusted with the alloy L. This can reduce or prevent blockage of the pores of the porous tube, such that cleaning of the pore burner is prevented or else wear can be reduced.
  • the combustion of the alloy L at the surface of the porous tube reduces the tendency for passage of small particles into the gas space/reaction space, such that, at best, relatively large droplets of reaction products arise, but these can be easily separated from gaseous reaction products, for example be deposited onto the reactor wall by means of a cyclone.
  • the main portion of the combustion products can be separated out, for example, in liquid form.
  • the reactor wall can be cooled, for example with heat exchangers, in which case these may also be connected to turbines and generators.
  • the combustion is effected at a temperature above the melting point of the salts formed in the reaction of alloy L and fuel gas.
  • the salts formed in the combustion of alloy L and fuel gas may have a melting point here above the melting point of the alloy L, such that supply of liquid alloy L at elevated temperature may be required.
  • the combustion at a temperature above the melting point of the salts formed can additionally avoid contamination or coverage of the pore burner or a nozzle by the salts formed, such that the pore burner or the nozzle can be better protected against contamination, for example of the pores as well. This enables better operation and reduced cleaning of the apparatus, and also longer use times without cleaning. It is also possible for liquid reaction products to simply drip off the burner.
  • preferred materials for the burner and the nozzle are those that can withstand the temperatures, for example iron, chromium, nickel, niobium, tantalum, molybdenum, tungsten, zircalloy and alloys of these metals, and also steels such as stainless steel and chromium-nickel steel.
  • the combustion temperature is thus preferably higher than the melting point of the respective reaction product(s), in order that the pores of the pore burner or the nozzle are not blocked and the reaction products can be transported away.
  • a certain degree of mixing between the liquid alloy L and the reaction product can also take place, such that the combustion can take place not only locally at the pore opening or the nozzle exit, but distributed over the entire surface of the tube or the nozzle. This can be controlled, for example, via the feed rate of the alloy L.
  • the alloy L as an alloy of at least two electropositive metals, it is possible to achieve melting point depression of the alloy compared to the respective metals and of the metal salts formed, such that the process can be conducted at lower temperatures and hence in a gentler manner in respect of the apparatus, and the use of highly refractory materials in the apparatus can be reduced or avoided.
  • the gaseous products formed in the reaction can be separated from the solid and liquid combustion products and utilized further.
  • the salts formed in the exothermic reaction can be drawn off in liquid form and the offgas (composed of gaseous reaction products and any reaction gas introduced in excess) can be conducted under pressure through an expander turbine free of solid particles.
  • the combustion can be effected with a certain excess of fuel gas, for example in a molar ratio of fuel gas to metal M of 1.01:1 or more, preferably 1.05:1 or more, further preferably 5:1 or more, even further preferably 10:1 or more, for example even 100:1 or more, in order to stabilize the offgas temperature within a particular temperature range.
  • the fuel gas can also serve here for removal of heat in the expander portion of a turbine etc.
  • a separation of offgas from solid and/or liquid reaction products can additionally be effected in the case of combustion of the alloy L with a fuel gas, in which case, in particular embodiments, in a reaction step, the fuel gas is combusted with the alloy L and offgas and further solid and/or liquid reaction products are formed, and, in a separation step, the offgas is separated from the solid and/or liquid reaction products.
  • a carrier gas can additionally be added and the carrier gas can be removed as a mixture with the offgas.
  • the carrier gas here may also correspond to the offgas, such that, for example, the combustion gives rise to an offgas corresponding to the carrier gas supplied, or else may correspond to the fuel gas. In the process of the invention, it is thus possible, in particular embodiments, to separate the reaction products after the combustion.
  • the carrier gas is not particularly restricted, and may correspond to the fuel gas, but may also be different therefrom.
  • Carrier gases employed may, for example, be air, carbon monoxide, carbon dioxide, oxygen, methane, hydrogen, water vapor, nitrogen, dinitrogen monoxide, mixtures of two or more of these gases, etc. It is possible here for various gases, for example methane, to serve for heat transport and remove the heat of reaction of the reaction of metal M with the fuel gas from the reactor.
  • the various carrier gases can, for example, be suitably matched to the reaction of the fuel gas with the alloy L, in order possibly to achieve synergistic effects here.
  • the gas which is optionally used in the supply of the alloy L may likewise correspond to the carrier gas.
  • the carrier gas used may, for example, be carbon monoxide and may optionally be circulated, i.e. at least partly recycled again as carrier gas after removal.
  • the carrier gas is matched to the offgas, such that a portion of the carrier gas can optionally be withdrawn as product of value, for example for a subsequent Fischer-Tropsch synthesis, while it is regenerated by the combustion of carbon dioxide with alloy L, such that there is at least partial conversion of carbon dioxide to carbon monoxide overall, preferably to an extent of 90% by volume or more, further preferably 95% by volume or more, even further preferably 99% by volume or more and especially preferably to an extent of 100% by volume, based on the carbon dioxide used, and is withdrawn as product of value.
  • the more carbon monoxide is generated the cleaner the carbon monoxide removed.
  • the carrier gas used may, for example, be nitrogen, such that unreacted nitrogen in the offgas from the combustion may be present as “offgas” alongside the nitrogen carrier gas, as a result of which a separation of gas, if desired, can be conducted in a simpler manner and, in particular embodiments, in the case of appropriate, preferably quantitative, combustion of alloy L and nitrogen using suitable, easily determinable parameters, may even not be required. It is possible, for example, to easily remove ammonia from the nitride formed by scrubbing or cooling.
  • the offgas may correspond to the carrier gas.
  • the offgas may correspond to the carrier gas to an extent of at least 10% by volume, preferably 50% by volume or more, further preferably 60% by volume or more, even further preferably 70% by volume or more, and even more preferably 80% by volume or more, based on the total volume of the offgas.
  • the fuel gas may correspond to the carrier gas to an extent of 90% by volume or more, based on the total volume of the offgas, and may in some cases even correspond to the carrier gas to an extent of 100% by volume.
  • the mixture of offgas and carrier gas can be supplied at least partly back to the separation step as carrier gas and/or to the combustion step as fuel gas. Recycling of the mixture of offgas and carrier gas can be effected, for example, to an extent of 10% by volume or more, preferably 50% by volume or more, further preferably 60% by volume or more, even further preferably 70% by volume or more, and even more preferably 80% by volume or more, based on the total volume of carrier gas and offgas. In particular embodiments, recycling of the mixture of offgas and carrier gas can be effected to an extent of 90% by volume or more, based on the total volume of carrier gas and offgas. In embodiments that are preferred in accordance with the invention, a reaction between fuel gas and alloy can be effected in such a way that the offgas formed is the carrier gas, for example with carbon dioxide as fuel gas and carbon monoxide as carrier gas, such that the mixture of
  • carrier gas and offgas then consists essentially of the carrier gas, preferably to an extent of 90% by volume or more, further preferably to an extent of 95% by volume or more, even further preferably to an extent of 99% by volume or more and more preferably to an extent of 100% by volume, based on the mixture of offgas and carrier gas.
  • the carrier gas can then be continuously circulated and withdrawn in such an amount as it is reformed by the combustion of alloy L and fuel gas.
  • a separation of carrier gas and offgas is optionally effected, it is possible here, for example, to obtain a product of value, for example carbon monoxide, which can be withdrawn continuously.
  • the separation step in a process of the invention is effected in a cyclone or a cyclone reactor.
  • the cyclone reactor here is not particularly restricted in terms of its setup and may, for example, have a form as possessed by standard cyclone reactors.
  • a cyclone reactor may comprise a reaction region to which there may be connected feed units for the fuel gas, alloy L and the carrier gas (which may optionally also be combined and then supplied together to the reaction region), for example in the form of a rotationally symmetric upper section, a separation region which has a conical configuration, for example, and an expansion chamber to which there may be connected a removal apparatus for solid and/or liquid reaction products from the combustion of metal M with the fuel gas, for example in the form of a star feeder, and a removal unit for the mixture of offgas and carrier gas, which arises after the mixing of the two gases after the combustion of the metal M in the fuel gas.
  • Such apparatus components are, for example, typically present in cyclone separators.
  • a cyclone reactor used in accordance with the invention may alternatively have a different construction and may optionally also comprise further regions.
  • individual regions e.g. reaction region, separation region, expansion chamber
  • carrier gas also to be added in a region in which the reaction of the alloy L and the fuel gas is advanced or even already complete.
  • the cyclone keeps the reaction products largely in the center of the reactor, for example of a furnace space.
  • One advantage of the use of a pore burner is that the combustion at the surface of the porous tube does not give rise to any small particles as in the case of atomization, such that the offgas is free of solid or liquid particles, such that it is also possible to connect a gas turbine or expanded turbine downstream in a simple manner within the offgas stream.
  • suitable supply of carrier gas it is also possible to achieve an efficient separation of offgas from solid and liquid reaction products in the case of atomization of the alloy L. Under these circumstances, it is possible with this combustion concept to introduce the offgas stream directly into a gas turbine after the combustion of the alloy L and the separation of the reaction products.
  • the offgas temperature, in particular embodiments, in the different combustion processes, can be controlled via the excess of gas, such that it is higher than the melting temperature of the reaction products or mixture thereof.
  • the cyclone reactor additionally comprises a grid, by means of which the solid and/or liquid reaction products can be removed in the combustion of the alloy L with the fuel gas.
  • a grid can additionally
  • the reaction products of the combustion can be used to generate energy, preferably using at least one expander turbine and/or at least one gas turbine, for example a steam turbine, and/or at least one heat exchanger and/or at least one boiler, for which it is possible here, in particular embodiments, to use either the solid and/or liquid reaction products formed, for example with use of a heat exchanger in the reactor, or else the gaseous reaction products.
  • the thermal energy released in the combustion can thus be converted (for example via an expander turbine and/or steam turbine) to electrical energy.
  • the thermal energy released can, for example, be converted back to power by means of a heat exchanger and downstream steam turbine.
  • Higher efficiencies are achievable, for example, via the use of gas turbines in combination with steam turbines. For this purpose, in particular embodiments, it has to be ensured that the offgas is free of particles after the metal combustion, since these particles can otherwise cause long-term damage to the turbine.
  • the mixture of offgas and carrier gas in particular embodiments, for example in the reactor and/or in the case of and/or after removal from the reactor, can be used for heating of a boiler or for heat transfer in a heat exchanger or a turbine, for example a gas turbine or an expander turbine.
  • the mixture of the carrier gas and the offgas in particular embodiments, may be under elevated pressure after the combustion, for example more than 1 bar, at least 2 bar, at least 5 bar or at least 20 bar.
  • an apparatus for combustion of an alloy L of an electropositive metal wherein the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof, and the alloy L of the electropositive metal includes at least two electropositive metals, comprising a pore burner or a unit for atomizing the alloy L of the electropositive metal, a feed unit for the alloy L of the electropositive metal, preferably in liquid form, to the interior of the pore burner or the unit for atomizing the alloy L, which is designed to supply the pore burner or the unit for atomizing the alloy L with the alloy L of the electropositive metal, preferably in liquid form, a feed unit for a fuel gas, which is designed to supply fuel gas, and optionally a heating apparatus for providing the alloy L of the electropositive metal in liquid form, which is designed to liquefy the alloy L of the electropositive metal.
  • the electropositive metal is selected from alkali metals, alkaline earth metals, aluminum and zinc, and mixtures thereof
  • the unit for atomization of the alloy L is not particularly restricted here and may comprise, for example, a one-phase nozzle or a two-phase nozzle.
  • the pore burner may be configured as described above.
  • the feed unit used for alloy L may, for example, be tubes or hoses, or else conveyor belts, which may be heated, which can be suitably determined, for example, on the basis of the state of matter of the alloy L.
  • the feed unit for the alloy L may also be connected to a further feed unit for a gas, optionally with a control unit such as a valve, with which the supply of the alloy L can be regulated.
  • the feed unit for the fuel gas may be configured as a tube or hose, etc., which may optionally be heated, in which case the feed unit can be
  • the feed unit for the fuel gas is arranged such that it guides the fuel gas, at least partly and preferably completely, to the surface of the pore burner or to the exit of the nozzle. This achieves an improved reaction between alloy L and fuel gas.
  • the pore burner in preferred embodiments, is arranged such that reaction products formed in the combustion and optionally the unreacted alloy L can be removed from the surface of the pore burner by gravity, for example by virtue of the pore burner being mounted vertically in the reactor, pointing toward the surface of the earth.
  • the liquid reaction product formed can run out of the tube and then drip downward into the furnace bottom.
  • the possibly dissolved alloy L for example composed of lithium and sodium, which has not reacted in the pore burner beforehand is also combusted, and the heat of reaction is released to the fuel gas and carrier gas flowing past.
  • the pore burner or the nozzle consists of a material selected from the group consisting of iron, chromium, nickel, niobium, tantalum, molybdenum, tungsten, zircalloy and alloys of these metals, and also steels such as stainless steel and chromium-nickel steel.
  • steels such as stainless steel and chromium-nickel steel.
  • austenitic chromium-nickel steels which are very resistant, for example, to erosion by sodium at high temperature, but materials having 32% nickel and 20% chromium, such as AC 66, Incoloy 800 or Pyrotherm G 20132 Nb also exhibit relatively favorable corrosion characteristics. These materials are preferred for use at relatively high temperatures, where the reaction with liquid
  • the apparatus of the invention may further include a separation unit for the products of the combustion of the alloy L, which is designed to separate the combustion products of the alloy L and of the fuel gas, the separation unit preferably being a cyclone reactor.
  • the separation unit may serve here for separation of offgas in the combustion of the alloy L with a fuel gas, and may comprise:
  • the feed unit for carrier gas is likewise not particularly restricted and comprises, for example, tubes, hoses, etc., it being possible to suitably determine the feed unit for carrier gas on the basis of the state of the carrier gas, which may optionally also be under pressure.
  • the reactor is likewise not particularly restricted, provided that the combustion of the fuel gas with the alloy L can take place therein.
  • the reactor may be a cyclone reactor as shown by way of example in FIG. 1 and in detail in a further embodiment in FIG. 2 .
  • the cyclone reactor may, in particular embodiments, comprise a reaction region to which there may be connected the feed units for the fuel gas, alloy L and the carrier gas and the pore burner, for example in the form of a rotationally symmetric upper section, a separation region which has a conical configuration, for example, and an expansion chamber to which there may be connected a removal apparatus for solid and/or liquid reaction products from the combustion of alloy L with the fuel gas, for example in the form of a star feeder, and a removal unit for the mixture of offgas and carrier gas, which arises after the mixing of the two gases after the combustion of the alloy L in the fuel gas.
  • Such apparatus components are, for example, typically present in cyclone separators.
  • a cyclone reactor used in accordance with the invention may alternatively have a different construction and may optionally also comprise further regions.
  • individual regions e.g. reaction region, separation region, expansion chamber
  • FIG. 1 An illustrative cyclone reactor is shown in FIG. 1 .
  • the cyclone reactor 6 shown in FIG. 1 comprises a reaction region 20 a, a separation region 20 b which is both together with the reaction region 20 a in the upper component 6 a and together with the expansion chamber 20 c in the lower component 6 b, and an expansion chamber 20 c.
  • a feed unit 1 Connected to the cyclone reactor in the upper section are a feed unit 1
  • the alloy L is fed in with the aid of a gas in a feed unit 2 ′ for gas, for example a tube or hose, the feed of which can be controlled with a valve 2 ′′.
  • the alloy L and the fuel gas are fed to the reaction region 20 a.
  • the carrier gas is supplied to a region 4 ′ for gas distribution, from which the carrier gas is then supplied to the separation region 20 b via nozzles 5 with which a cyclone can be formed.
  • a detail of such a feed unit 4 having a region 4 ′ for gas distribution and a nozzle 5 is specified in cross section, by way of example, in FIG. 4 (illustration without pore burner 3 ), but it is also possible for more nozzles 5 to be present, for example at a suitable distance in a ring around the inner wall of the region 4 ′, in order to generate a suitable cyclone.
  • Solid and/or liquid reaction products are removed from the lower component 6 b comprising the expansion chamber 20 c via the removal unit 7 for solid and/or liquid reaction products of the combustion of alloy L with the fuel gas, while the mixture of offgas and carrier gas is removed via the removal unit 8 for the mixture of offgas and carrier gas.
  • an ignition apparatus for example an electrical ignition apparatus or a plasma arc
  • an ignition apparatus may be required, which may depend on the nature and state of the alloy L, for example the temperature and/or state of matter thereof, the characteristics of the fuel gas, for example the pressure and/or temperature thereof, and the arrangement of components in the apparatus, for example the nature and characteristics of the feed units.
  • the internal reactor material may consist of alloys of high heat resistance, for example the abovementioned alloys and, in the extreme case, even of the material Haynes 214.
  • this material which is merely supposed to withstand the high temperature, it is then possible to arrange a thermal insulation which allows a sufficiently small amount of heat through, such that a steel wall on the outside, which may additionally also be air- or water-cooled, absorbs the compressive stress.
  • the offgas can then be supplied to the further process step with the elevated or high operating pressure.
  • the reactor for example a cyclone reactor, may also comprise heating and/or cooling apparatuses which may be present in the reaction region, the separation region and/or the expansion chamber, and also in the various feed and/or removal apparatuses, optionally the burner, and/or optionally the ignition apparatus.
  • further components such as pumps for generation of a pressure or a vacuum, etc. may be present in an apparatus of the invention.
  • the cyclone reactor may comprise a grid which is designed such that the solid and/or liquid reaction products can be removed through the grid on combustion of the alloy L with the fuel gas.
  • a grid may alternatively also be present in other reactors which may be provided in the apparatus of the invention.
  • the use of the grid in the reactor or cyclone reactor can achieve better separation of the solid and/or liquid reaction products in the combustion of the alloy L with the fuel gas from the mixture of offgas and carrier gas.
  • Such a grid is shown by way of example in FIG. 2 , in which the grid
  • the geometry of the feed units for the carrier gas is not particularly restricted, provided that the carrier gas can be mixed with the offgas from the combustion of alloy L and fuel gas.
  • a cyclone preferably forms here, for example with the apparatus shown in FIG. 1 .
  • a cyclone can alternatively be generated by other arrangements of the feed units with respect to one another.
  • the feed unit for the carrier gas is also present at the top of the reactor close to the feed units for alloy L and fuel.
  • suitable geometries for the injection can easily be determined in a suitable manner, for example on the basis of flow simulations.
  • removal units particularly restricted, it being possible, for example, for the removal unit for the mixture of offgas and carrier gas to be configured as a tube, while the removal unit for the solid and/or liquid reaction products of the combustion of metal M with the fuel gas may be configured, for example, as a star feeder and/or as a tube with a siphon. It is also possible here for various valves, such as pressure valves, and/or further regulators to be provided.
  • An illustrative removal unit 7 shown in FIG. 3 for example of the cyclone reactor 6 shown in FIG. 1 , may, in this context, comprise a siphon 9 , a valve 10 for degassing and a pressure regulator 11 , but is not restricted to such a removal unit.
  • reaction products of the combustion of alloy L with the fuel gas may be used, for example, in order to enable an elevated or high operating pressure.
  • the removal unit for the mixture of offgas and carrier gas may, in particular embodiments, also comprise a separation apparatus for the offgas and carrier gas and/or individual components of the offgas.
  • the removal unit for a mixture of offgas and carrier gas may be connected to the feed unit for carrier gas and/or the feed unit for fuel gas in such a way that the mixture of offgas and carrier gas is fed at least partly to the reactor as carrier gas and/or to the burner as fuel gas.
  • the proportion of recycled gas here may be 10% by volume or more, preferably 50% by volume or more, further preferably 60% by volume or more, even further preferably 70% by volume or more, and even more preferably 80% by volume or more, based on the total volume of carrier gas and offgas.
  • recycling of the mixture of offgas and carrier gas can be effected to an extent of 90% by volume or more, based on the total volume of carrier gas and offgas.
  • an apparatus of the invention may additionally further comprise at least one boiler and/or at least one heat exchanger and/or at least one gas turbine and/or at least one expander turbine present in the reactor and/or the removal unit for the mixture of offgas and carrier gas. It is thus possible, for example, in the apparatus of FIG. 1 comprising a cyclone reactor 6 , for one or more heat exchangers and/or boilers and/or gas turbines and/or expander turbines, which are not shown, to be provided in the reactor 6 , in the removal unit 8 and/or in a unit connected to the removal unit 8 .
  • heat exchange it is also possible for heat exchange to take place in the cyclone reactor 6 itself, for example at the outer walls in the reaction region 20 a and/or the separation region 20 b, or else optionally in the region of the expansion chamber 20 c, in which case the corresponding heat exchangers can also be connected to turbines for power generation in generators.
  • the offgases can thus, as a mixture with carrier gas, be sent to a further use, for example heating of a boiler for steam raising, release of heat in a heat exchanger, operation of a turbine, etc.
  • liquid reaction products for example liquid Li 2 CO 3 and Na 2 CO 3
  • the reactor wall it is possible, for example, for the reactor wall to function as heat exchanger, whereas, in the case of solid reaction products that form, special heat exchangers may be required.
  • direct guiding of the mixture of offgas and carrier gas to a turbine may also be possible, such that it may then be the case here too that no heat exchangers and/or boilers are required in the offgas stream.
  • an apparatus of the invention may comprise a withdrawal apparatus in the removal unit for the mixture of offgas and carrier gas, which is designed to remove a portion of the mixture of offgas and carrier gas in the case of recycling of the mixture of offgas and carrier gas to the feed unit for carrier gas and/or the feed unit for fuel gas through connection of the removal unit for the mixture of offgas and carrier gas to the feed unit for carrier gas and/or the feed unit for fuel gas.
  • a portion may, for example, be more than 1% by volume, preferably 5% by volume or more and further preferably 10% by volume or more, based on the total volume of the mixture of offgas and carrier gas.
  • not more than 50% by volume preferably 40% by volume or less, further preferably 30% by volume or less, more preferably 20% by volume or less, based on the total volume of the mixture of offgas and carrier gas, may be removed from the recycled mixture of offgas and carrier gas.
  • the gas withdrawn may then be available, for example, as product of value for further reactions, for example when carbon monoxide is discharged and then converted in a Fischer-Tropsch process to higher-value hydrocarbons.
  • metal nitride prepared from combustion with nitrogen can be converted by hydrolysis with water to ammonia and alkali, in which case the alkali formed can also serve as scavenger for carbon dioxide and/or sulfur dioxide.
  • the alloy L for example composed of lithium and sodium
  • the alloy L is used in liquid form, i.e. above the melting point of the alloy.
  • the liquid alloy L for example composed of lithium and sodium
  • the liquid alloy L can be introduced into a pore burner and then reacts directly, optionally after ignition to start the reaction, with the particular fuel gas, for example air, oxygen, carbon dioxide, sulfur dioxide, hydrogen, water vapor, nitrogen oxides NO x such as dinitrogen monoxide, or nitrogen.
  • the combustion of the alloy L can be effected in the apparatus shown in FIG. 1 , for example with more than the stoichiometric amount of the fuel gas, in order not to generate excessively high offgas temperatures.
  • the fuel gas can be added in a stoichiometric or substoichiometric amount compared to the metal M.
  • a carrier gas for example nitrogen, air, carbon monoxide, carbon dioxide and ammonia
  • the hot offgas stream can then be used to heat a boiler or for heat transfer in a heat exchanger or the like.
  • the fuel gas used may be carbon dioxide and the carrier gas used may be carbon monoxide in the apparatus shown in FIG. 1 .
  • the alloy L used is, for example, one of lithium and sodium, for example in liquid form.
  • the liquid alloy is introduced into the pore burner 3 and then reacts directly with the fuel gas. It may be the case that electrical ignition or an additional ignition burner are required.
  • a reaction can also be effected with an alloy of sodium and potassium according to this example, in which case the alloy of sodium and potassium may be in liquid form at room temperature.
  • the combustion of the alloy L is effected in the pore burner 3 , preferably with the amount of carbon dioxide required in stoichiometric terms, although it is also possible to choose a slightly super- or substoichiometric ratio (e.g. 0.95:1 to 1:0.95 for the ratio of CO 2 :alloy L).
  • a slightly super- or substoichiometric ratio e.g. 0.95:1 to 1:0.95 for the ratio of CO 2 :alloy L.
  • carbide it is possible, for example, for carbide to form as the salt, from which acetylene can then be obtained.
  • the combustion products are mixed with the carbon monoxide carrier gas which is blown into the reactor 6 by nozzles 5 .
  • an excess of carrier gas is used in order to ensure that the heat that arises through the combustion is transported away sufficiently. As a result, it is possible to suitably adjust the temperature in the reactor 6 .
  • the lithium carbonate-sodium carbonate mixture formed in the case of a eutectic mixture, has a melting point of 498° C. If the
  • combustion temperature of the reaction products is kept above at least 498° C. by mixing in carrier gas and/or fuel gas through the feed units 1 , 5 , liquid reaction products can be expected for the combustion.
  • the feed units can be used here for cooling in the strongly exothermic reaction, in order that the plant does not heat up too much, and the lower temperature limit may be the melting point of the salt mixture formed.
  • the cyclone is additionally operated with gases other than carbon dioxide, for example air or further gases, it is also possible, for example, for the oxides of lithium and sodium to form as a mixture in the reaction products.
  • the mixture of offgas and carrier gas is guided, for example, into a boiler and utilized for evaporation of water, in order then to drive a steam turbine with downstream generator or to operate other technical apparatuses (for example heat exchangers).
  • the mixture of offgas and carrier gas cooled down by this process can then, for example, be utilized again as carrier gas for heating of the cyclone in the furnace.
  • the residual heat from the offgas after the evaporation process is utilized in the boiler, and only the amount of carbon dioxide needed in stoichiometric terms for the combustion with Li/Na has to be obtained by offgas cleaning, for example in coal-fired power plants.
  • the combustion can be effected with a certain excess of fuel gas, for example in a molar ratio of fuel gas to alloy L of more than 1.01:1, preferably more than 1.05:1, further preferably 5:1 or more, even further preferably 10:1 or more, for example even 100:1 or more, in order to stabilize the offgas temperature within a particular temperature range, and it is possible to add further fuel gas or carrier gas for absorption of heat by means of a cyclone as well as the addition of fuel gas and the inflow of the alloy L in an arrangement of nozzles, as shown in FIG. 1 and FIG. 4 .
  • the offgas temperature in particular embodiments, in the different combustion processes, can be controlled via the excess of gas, such that it may be higher than the melting temperature of the reaction products or mixture thereof.
  • the product gas consists mainly of CO and only of small impurities of CO 2 .
  • the majority of the CO is circulated and the amount of CO removed from the circuit is just as much as is reformed by the reaction of CO 2 and Li/Na—and also generally with electropositive metal alloy.
  • such a circuit may arise when CO is used as carrier gas in a ratio of 90% by volume or more, based on the mixture of offgas and carrier gas.
  • a suitable amount of carbon dioxide can thus be supplied constantly to the combustion process, whereas a corresponding amount of carbon monoxide can be withdrawn constantly from the circuit as product of value.
  • a corresponding reaction regime is also shown by way of example in FIG. 5 .
  • Carbon dioxide is separated from an offgas 100 , for example from a combustion power plant such as a coal-fired power plant, in a CO 2 removal 101 , and then it is combusted with the alloy in step 102 , using CO as carrier gas.
  • This forms the carbonate salt mixture 103 , and a mixture of offgas and carrier gas comprising CO 2 and CO, optionally after a separation 104 , can be passed through a boiler 105 , with the aid of which a steam turbine 106 and hence a generator 107 are operated.
  • the fuel gas and carrier gas used may be nitrogen in the apparatus shown in FIG. 1 .
  • the alloy L used is, for example, one of lithium and magnesium, for example in liquid form.
  • the alloy L is fed to the pore burner 3 and then reacts directly with the fuel gas. It may be the case that electrical ignition or an additional ignition burner are required.
  • the combustion of the alloy L is effected in the pore burner 3 with the amount of nitrogen required in stoichiometric terms, although it is also possible to choose a slightly super- or substoichiometric ratio (e.g. 0.95:1 to 1:0.95 for the ratio of N 2 :alloy L).
  • the combustion products are mixed with the carrier gas, for example nitrogen, which is blown into the reactor 6 through the nozzles 5 .
  • the carrier gas for example nitrogen
  • the lower temperature limit may be the melting point of the salt mixture formed.
  • the cyclone is operated with gases other than nitrogen, for example air or carbon dioxide or further gases, it is also possible for oxide or carbonate to form in the reaction products.
  • the offgas is guided, for example, into a boiler and utilized for evaporation of water, in order then to drive a turbine with downstream generator or to operate other technical apparatuses (for example heat exchangers).
  • the offgas cooled after this process can then, for example, be utilized again to generate the cyclone in the reactor 6 .
  • the residual heat from the offgas after the evaporation process is utilized in the boiler, and only the amount of nitrogen needed in stoichiometric terms for the combustion has to be obtained, for example by fractionation of air.
  • the combustion can be effected with a certain excess of fuel gas, for example in a molar ratio of fuel gas to alloy L of more than 1.01:1, preferably more than 1.05:1, further preferably 5:1 or more, even further preferably 10:1 or more, for example even 100:1 or more, in order to stabilize the offgas temperature within a particular temperature range, and it is possible to add further fuel gas or carrier gas for absorption of heat by means of a cyclone as well as the addition of fuel gas and the inflow of the alloy L in an arrangement of nozzles, as shown in FIG. 1 and FIG. 4 .
  • a corresponding reaction regime is also shown by way of example in FIG. 6 .
  • Nitrogen is separated from the air 200 in an air fractionation 201 and then combusted with the alloy L in step 202 , using nitrogen, for example likewise from the air fractionation 201 , as carrier gas.
  • nitrogen for example likewise from the air fractionation 201 , as carrier gas.
  • This forms a nitride salt mixture of lithium nitride and magnesium nitride 203 , and the mixture of offgas and carrier gas
  • N 2 204 can be guided through a boiler 205 , with the aid of which a steam turbine 206 and hence a generator 207 are operated. There is recycling of offgas 208 as carrier gas.
  • Ammonia 210 can be obtained from the nitride salt mixture 203 by hydrolysis 209 , forming hydroxide 211 which can be reacted with carbon dioxide to give carbonate 212 .
  • a fourth illustrative embodiment it may also be possible, for example in the case of use of air as fuel gas, to use two reactors, for example two cyclone reactors, connected in series, in which case, in the first cyclone reactor, the alloy and the oxygen from the air can be used to produce a metal oxide mixture and the offgas contains primarily nitrogen, and this offgas can then react in a second cyclone reactor as fuel gas with alloy L to give metal nitride.
  • nitrogen can function as carrier gas, which can also be obtained from the first offgas, or the first offgas itself if it is being circulated, for example.
  • FIG. 5 A fifth illustrative embodiment is shown in FIG. 5 , in which the reactor is similar to the reactor shown in FIG. 1 .
  • the alloy L for example Na/K
  • the alloy L is fed to the cyclone reactor 6 ( 6 a, 6 b ) via the pore burner 3 , optionally in liquid form at room temperature, and the fuel gas, for example carbon dioxide, via the feed unit 1 .
  • a particularly advantageous feature is the injection of the fuel in the cyclone reactor ( 6 a, 6 b ) at points with high gas velocity, in order that the liquid metal droplets can be easily torn away from the pore burner 3 .
  • reaction products are separated by the cyclone and the salt products of the alloy L, for
  • the offgas In the case of an excess of CO 2 in the reaction gas, the offgas, after exit from the expander turbine 16 , can be recycled to the cyclone reactor 6 as reaction gas and hence the CO concentration in the offgas can be increased. Recycling of offgas thus takes place via a recycling unit 18 , and the offgas can in turn be used as carrier gas in the cyclone reactor 6 ( 6 a, 6 b ). In addition, offgas can be withdrawn via a withdrawal port and fed to an offgas separation 17 , for example in the case of use of CO 2 as fuel gas and CO as carrier gas and product of the combustion.
  • FIG. 6 A sixth illustrative embodiment is shown in FIG. 6 , wherein, instead of a pore burner 3 , atomization of the alloy L takes place at the end of the feed unit 2 and, in the reaction space 30 , the reaction then takes place with the fuel gas from the feed units 1 . Thereafter, the reaction products formed are transferred into the cyclone reactor 6 ( 6 a, 6 b ). Even though the reaction space 30 is connected laterally in FIG. 6 , it may also be connected to the cyclone reactor in other ways, for example at the top, provided that the reaction products are subjected to the cyclone separation.
  • the invention describes the suitable use of alloys of electropositive metals as physical energy storage means, which can be produced electrochemically with utilization of renewable electrical energy (overproduction,
  • the discharge of the energy storage means can be achieved in the form of a combustion process in carbon dioxide, nitrogen, oxygen, air, atmosphere, etc.
  • the present invention in particular embodiments, can ensure the separation of the gaseous reaction products from the salts formed in the reaction by the use of a cyclone and the liquid removal of the salt mixture.
  • alloys L of electropositive metals and the lower melting temperature of the salt mixtures formed in the case of combustion compared to the individual metal compounds, to establish the combustion reaction at lower temperatures as well and hence avoid the use of costly materials for the combustion space, with simultaneous assurance of liquid removal of the salt mixture.
  • Reconversion of the thermal energy released in the combustion to power can be effected, for example, either through the use of an expander turbine for the gases which may be removed under pressure and at high temperature or by heat exchangers at the reactor wall and subsequently a steam turbine.
  • the apparatus of the invention Through the construction of the apparatus of the invention, especially through the use of porous combustion tubes, it is possible to separate the solid or liquid reaction products or mixtures thereof in a simple manner from the offgases formed, and hence to send the offgases to a use in, for example, a gas turbine or expander turbine, a heat exchanger, or a boiler.
  • the entire combustion apparatus can also be made more compact and the combustion can be configured so as to be gentler in respect of the apparatus through localization of the combustion process.
  • the apparatus for example a reactor such as a furnace, can be run at elevated operating pressure, and thus the combustion and deposition process can be matched to the respective conditions of the downstream step.

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EP3146265A1 (fr) 2017-03-29
KR20180095137A (ko) 2018-08-24
KR20170007453A (ko) 2017-01-18
CN107046808A (zh) 2017-08-15
WO2015176944A1 (fr) 2015-11-26
RU2656217C1 (ru) 2018-06-01

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