Classifications

• • 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 
  • F23C10/00—Fluidised bed combustion apparatus
  • F23C10/01—Fluidised bed combustion apparatus in a fluidised bed of catalytic particles
• • 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 
  • F23C13/00—Apparatus in which combustion takes place in the presence of catalytic material
• • 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 
  • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
  • F23C2900/99008—Unmixed combustion, i.e. without direct mixing of oxygen gas and fuel, but using the oxygen from a metal oxide, e.g. FeO
• • 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
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2
• • 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
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

• the present invention relates to a process for producing energy by oxidation of a carbonaceous fuel, comprising the capture of the carbon dioxide product, and a device implementing this method.
• Carbon dioxide (CO 2 ) is produced in large quantities by certain human activities, in particular during the industrial production of energy based on the oxidation of carbon compounds, typically the combustion of so-called "fossil” fuels (natural gas, coal, petroleum and their derivatives).
• fluorescence fuels natural gas, coal, petroleum and their derivatives.
• industrialists increasingly want to reduce, or even cancel, the release of CO 2 into the atmosphere, by storing it in appropriate geological layers or by valuing it as a product.
• the CO 2 is found in the fumes, mixed with other products of the reactions involved, and / or compounds which have not or not completely reacted, and / or possibly less reactive or inert compounds, for example nitrogen in the case of a conventional combustion in air.
• to store or recover this CO 2 it is desirable, even necessary, to obtain it in a sufficiently concentrated form.
• some residual compounds may be detrimental to a particular use, such as oxygen or nitrogen oxides in the case of EOR (Enhanced OR Recovery or Enhanced Oil Recovery).
• the first encompasses processes that include extensive post-treatment of fumes or purges related to separations or purifications of CO2. These include the following post-treatments:
• US 4440731 described by For example, the method of absorbing CO2 in combustion fumes in air, by contact with an aqueous solution of alkanolamine. It proposes the use of additives to reduce the degradation of the solution and to reduce the corrosion that this solution causes in metals.
• US 5318758 discloses a device for removing CO2 from the exhaust gas by means of an absorbent containing an aqueous alkanolamine solution; washing with an ammonia solution.
• the second family includes methods for carrying out oxidation of said fuel and heat recovery without introducing undesired compounds found as such in the flue gas or purges, or causing the presence of undesired elements in these fumes or purges.
• oxyfuel combustion or, more generally, processes where the oxidant is a mixture that is more or less enriched in oxygen, up to pure oxygen.
• a fraction of the fumes can be recycled for thermal reasons (ballast effect) and / or reaction (if they contain interesting reagents).
• These methods consume a lot of oxygen, usually from separation of air by cryogenic distillation.
• special materials may be necessary, or special devices, such as burners or heat exchangers.
• US 6955051 discloses a boiler for producing steam by combustion of a fuel with an oxidant whose oxygen concentration is higher than that of air.
• US 6436337 describes an oxygen combustion system comprising an oven with at least one burner, means for providing a flow comprising at least 85% oxygen and a carbonaceous fuel and control devices.
• the Cost and Performance Base report for the Fossil Energy Plants Desk, published by the US Department of Energy (DoE) in May 2007, provides a description of this technology, with detailed energy and mass balances.
• This second category also includes gasification, which consists of a partial oxidation of the fuel, followed by treatments to decarbonize the syngas produced.
• the decarbonized synthesis gas can then be used as fuel in a specific combustion turbine. This process also consumes relatively pure pressurized oxygen.
• the combustion turbine has not yet been developed industrially.
• the Cost and Performance Baseline for Fossil Energy Plants Desk Reference, cited above, also provides a detailed description of this technology.
• thermochemical loop comprising oxidation and reduction chambers, cyclones for separating solid particles from effluent gases, heat exchangers and means of production. of electrical energy from the thermal energy released.
• the application WO2008036902, "Chemical looping combustion” presents an implementation of the chemical loop principle, in particular thanks to a reactor composed of rotary compartments.
• the fumes produced by the reaction generally contain undesired or even toxic compounds, such as CO. For this reason, chemical looping techniques do not allow easy capture of CO2.
• An object of the present invention is to overcome all or part of the disadvantages of the prior art, in particular the consumption of a large amount of an oxidant generally requiring an air separation unit by cryogenic distillation or the systematic recourse to important post-treatments of the fumes or purging of the process.
• the invention firstly relates to a process for producing energy by oxidizing a carbonaceous fuel and capturing the resulting carbon dioxide (CO2), comprising
• a chemical loop step in which said fuel is oxidized by contact with at least one active oxygen-carrying compound, said oxidation producing primary effluents and reducing said active compound, said reduced active compound being then recovered, regenerated by oxidation at contacting a gas comprising oxygen, said regeneration producing regeneration effluents and said regenerated active compound being recovered to oxidize said fuel; b) a step of secondary oxidation of said primary effluents by at least one gas comprising predominantly oxygen, said secondary oxidation producing secondary effluents; c) transfer by heat exchange to at least one thermal fluid of at least a portion of the heat evolved by said chemical loop and secondary oxidation steps; and d) a post-treatment of said secondary effluents comprising one or more of the following: water condensation drying, compression, cooling, passage through adsorbents and / or polymeric and / or ceramic membranes, cryogenic distillation .
• the solution according to the invention mainly combines two oxidation steps a) and b), with a step c) of recovery of the energy released by the oxidation steps and a step d) of treatment and conditioning. effluents.
• steps a) and b) are opposed from the point of view of oxygen consumption, the inventors have established that it is technically and economically advantageous to combine them.
• the chemical looping step a) is known not to require very pure oxygen, therefore a priori no separation of air, while step b) requires an oxidant containing a majority of oxygen, ie at least 50% by volume, which generally requires separation of the air.
• this oxidant does not contain undesired elements (nitrogen, inert, non-completely oxidized compounds, etc.).
• the oxidant used in step b) contains at least 95% oxygen by volume and, even more preferably, at least 99%.
• step b) which uses an oxidant enriched in oxygen with respect to air, the quantities of inert gases other than CO2 and H2O, such as N2 or Ar, are considerably reduced in the effluents. Furthermore, the inventors have determined that the amounts of oxidant required in step b) remain reasonable.
• the combination of the two steps a) and b) makes it possible to generate more energy from the same fuel reference flow rate than if there had been only a chemical loop oxidation.
• step d) a purification of the CO 2 may be useful in some cases, for example if, in step b), an excess of oxygen with respect to the stoichiometry has been used and it is not desired to residual oxygen in the fumes, or even if the CO2 is intended for a particular application requiring a very high purity.
• steps a) and b) make the constraints to satisfy step d) not too severe. This allows savings on the unit process or processes that constitute it.
• the carbonaceous fuel can be solid, liquid or gaseous, or multiphase. It may be a conventional fuel, such as natural gas or naphtha, or a purge from another process, or coal, coke, petroleum coke, biomass or petroleum residues.
• step a it is brought into contact with one or more oxygen-carrying active compounds.
• active compounds may in particular be metals, in a form sometimes oxidized, sometimes reduced.
• the bottom line is that the active compounds can bind the oxygen to a higher oxidation state and release oxygen back to a lower oxidation state.
• the carbonaceous fuel reacts with an oxidized form of the active compounds. This results, on the one hand, the active compound (s) in a reduced form and, on the other hand, effluents which are the products of the oxidation of said fuel.
• the active compounds are recovered, for example by physical separation, and then brought into contact with a gas containing oxygen. Upon contact, the active compounds fix oxygen. This can be done simultaneously or successively and can take several steps. At the end of this regeneration, they are again ready to be used for the oxidation of said fuel.
• the oxidation of the active compounds of the chemical loop is exothermic, whereas their reduction on contact with the fuel is endothermic. It happens nevertheless at high temperature.
• the secondary oxidation in step b) is also exothermic.
• the primary effluents are oxidized by an oxygen-containing gas.
• the inventors have established that it is preferable to perform the oxidation in the presence of one or more catalysts. They may contain in particular one or more of the following chemical elements: Fe, V, Co, Rh.
• the reaction normally takes place at an absolute pressure of less than 50 ⁇ 10 5 Pa (ie 50 bar absolute), at a temperature normally below 1000 ° C. C. It produces hot effluents in which it is arranged that the residual oxygen content is generally less than 5% by volume, preferably less than 2% by volume. In general, it is also arranged so that the residual content of reactive gases (CO, H2, CH4, hydrocarbons) is less than 5% by volume, preferably less than 2% by volume. It is therefore a question of carrying out a chemical reaction with addition of reagents in proportions close to stoichiometry and of obtaining high reaction rates, so as to reduce the presence of excess reagents.
• reactive gases CO, H2, CH4, hydrocarbon
• step c) Part of the heat released by the chemical reactions implemented in steps a) and b) is recovered by heat exchange.
• This is the subject of step c) of the process according to the invention. It is important to note that this step c) may include many heat exchanges so as to recover heat where it is located. This can be recovered in particular in or around the reaction media, or in the primary effluent, secondary, and / or regeneration.
• the heat energy is partly transferred to one or more heat transfer fluids, such as steam or hot oil, according to methods known to those skilled in the art. These fluids, possibly produced at different pressure and / or temperature levels, can be used as they are or to produce mechanical and / or electrical energy.
• the exothermic secondary oxidation step may be performed on a hot effluent at the outlet of the chemical loop, with the advantage of generating, during the secondary oxidation reaction, a heat that will be available at a higher temperature. This allows a higher conversion efficiency in work or electricity.
• the secondary oxidation can also occur on an effluent that has been cooled at the outlet of the chemical loop, which facilitates said secondary oxidation, with less construction constraints or materials. If the mentioned cooling is important, it can lead to the condensation of the water contained in the fumes, with the advantage of reducing the total volume of gas to be treated in b).
• the water contained in the effluents of steps a) and / or b) may optionally be separated from the main flow by cooling resulting in its condensation and / or by an additional drying operation. This may also only occur in step d).
• Secondary effluents are post-treated in step d). This may include one or more operations. Their type and the order in which they are carried out depend on the purpose of the capture of CO2, according to methods conventional for those skilled in the art. In particular, the following operations can be mentioned:
• Flue gas desulphurization according to usual industrial processes, for example by reaction with CaCO3 or Ca (OH) 2, by washing with amino compounds (Cansolv process), or others; - dedusting, for example by filtering (i.e. bag filter, ceramic filter), and / or by electrostatic precipitation (dry or wet); washing, removing certain compounds by contact with aqueous solutions and to cool these fumes; compression, in equipment according to the state of the art, for example by isothermal or adiabatic means, with or without heat exchange with other fluids, with or without recovery of this heat;
• drying and / or adsorption of undesired compounds for example by regenerative processes such as adsorption on alumina, silica gel, zeolite, sieve molecular, activated carbon (alone or in combination) or physical absorption with alcohols;
• traces for example heavy metals (ie Hg, V, Pb), halides (ie Na, K), acids (ie HCl, HF), nitrogen compounds (ie oxides of nitrogen, ammonia), sulfur compounds (ie sulfur oxides, H 2 S), for example by physical or chemical adsorption on doped or non-doped activated carbon beds, or other materials; phase separation, which reduces the content of more volatile compounds (i.e. N2, Ar, O2) in the liquid phase, which will be enriched in CO2; - cryogenic distillation, which makes it possible to deepen the separation of the more volatile compounds, and in particular to reach very low concentrations of oxygen and nitrogen oxides in the main product rich in CO2;
• heavy metals ie Hg, V, Pb
• halides ie Na, K
• acids ie HCl, HF
• nitrogen compounds ie oxides of nitrogen, ammonia
• sulfur compounds ie sulfur oxides, H 2 S
• phase separation which reduces the content of
• step d) can be influenced by the preceding steps. For example, if catalysts sensitive to pollutants present in the effluents to be treated are used in step b), some of the operations mentioned above as being able to be part of step d) are rather carried out before the step b). In particular, if the catalyst contains cobalt (Co) metal, it can be inactivated by the presence of sulfur in the effluent to be oxidized. In this case, it is necessary to include desulfurization and trace purification operations before step b).
• Co cobalt
• the method in question may further include one or more of the following features:
• said active compound used by said chemical loop step is in the form of solid particles; said method comprises transfer by heat exchange to at least one thermal fluid of at least a portion of the heat contained in said solid particles.
• the oxygen-carrying active compound (s) are generally used in the form of solid particles. These particles consist of the active compound or compounds, optionally agglomerated with a binder material according to techniques known to those skilled in the art. It will focus in particular on: to give them a specific capacity (per unit mass) to fix and release the highest possible oxygen, to give them good mechanical resistance, particularly to attrition, to promote the kinetics of reaction between said particles and said carbonaceous fuel and between said particles and the gas comprising oxygen. This feature can be called responsiveness.
• Said particles are generally used in the form of a fluidized bed, for example by injecting steam or CO2-rich gas or fuel gas into a reactor, and injections of air or other gas containing oxygen or steam in another reactor.
• This steam can be produced in the heat exchangers.
• This fluidized bed circulates zones where the reduction of said particles takes place, ie the oxidation of said fuel, towards the zones where the regeneration of said particles takes place, ie the oxidation of the active compounds they contain.
• Said particles are generally separated from the other products of the oxidation of said fuel by physical separation, for example in a cyclone. They are also separated from any other solids arising from the oxidation of the fuel (ash and / or soot and / or unconverted solid fuel). It is the same during the regeneration of said particles.
• Other separating elements may be provided for separating any solids from the reactions of the oxygen-carrying active compound so as to recover the carrier material and to increase the conversion efficiency.
• the method according to the invention may further comprise one or more of the following features:
• said gas for oxidizing said active compound at said chemical loop step is air; the effluents resulting from said regeneration of said active oxygen-carrying compound are used for the preparation of a reduced-oxygen gas. a part of the energy contained in said thermal fluid is converted into mechanical and / or electrical energy.
• the effluents resulting from the regeneration of the active compounds in step a) are depleted of oxygen.
• the invention has the additional advantage of providing a residual gas that can be used in inerting applications.
• Part of the thermal fluids produced by heat exchange can be converted into mechanical energy, for example by steaming. Part of this mechanical energy can then be converted into electricity.
• the invention further relates to a device for producing energy by oxidizing a carbonaceous fuel and capturing the resulting CO2, comprising:
• an installation comprising a chemical loop including at least one reactor for oxidizing said carbonaceous fuel in contact with solid particles incorporating at least one active oxygen-carrying compound, said chemical loop relating to said particles;
• a reactor for oxidizing a gas having at least one inlet for said gas to be oxidized and at least one other inlet connected to a source of gas comprising predominantly oxygen; and at least two heat exchangers for heating at least one thermal fluid, one located in said installation comprising a chemical loop, the other at said oxidation reactor of said gas, said exchangers being able to be within said reactors, or crossed by said effluent and / or said solid particles; characterized in that said gas inlet to be oxidized from said catalytic oxidation reactor is connected to at least one outlet of said oxidation reactor of said fuel so as to receive effluents produced by said oxidation reactor of said fuel.
• Said exchangers can be located within said reactors, or traversed by said effluents and / or said solid particles.
• the device according to the invention may comprise one or more of the following characteristics: it comprises at least one steam turbine connected at the inlet and / or in its intermediate stages to one or more steam pipes coming from said heat exchangers; - Said steam turbine is mechanically coupled to an electricity generator so as to drive said generator.
• the device preferably operates at a pressure greater than that of the surrounding and incorporates means to ensure a good seal of the various components, to avoid possible air inlets which would introduce in particular nitrogen and water. oxygen in the effluents.
• the operating pressure must not be too high either. Indeed, this would induce additional energy expenditure of gas compression and construction constraints.
• the ideal target pressure is between -0.1 barg and 1 barg, preferably between -0.05 barg and 0.3 barg.
• a coal 4 is oxidized in contact with solid ilmenite in reactor 2.
• This oxidation produces primary effluents 5 and ilmenite in reduced form 9.
• This is introduced into reactor 3 where it This reaction produces an oxygen-depleted air 7 that can be used for its inert properties and ilmenite that is sent back into reactor 2 to oxidize the coal 4.
• Tubular heat exchangers 10a, 10b, 10c, 10d are put in place on the output streams of these reactors to produce steam. This steam is introduced into a steam turbine not shown in the figure to produce electricity.
• the primary effluents 11 and pure oxygen 13 are then introduced into the secondary oxidation reactor 12 consisting of a solid vanadium oxide bed and having within it a heat exchanger 10e.
• This reaction produces secondary effluents 14 free of carbon monoxide, hydrocarbons and hydrogen sulfide, the heat of which is recovered by the use of a tubular exchanger 10f.
• the cooled secondary effluents consisting mainly of carbon dioxide are then fed to a post-treatment 16 consisting of adsorption drying and cryogenic distillation.
• This post-treatment produces CO2 17 in supercritical form and a stream 18 containing residual impurities such as nitrogen, oxygen and argon.
• heat is recovered in the exchanger 10g.
• the product 17 is then sent to an appropriate underground storage site.
• a numerical example of a chemical loop is given in the article Design and operation of a 10 kWth chemical-looping combustor for solid fuels - Testing with the South African Coal, of the magazine Fuel n ° 87, 2008, p. 2713-2726.
• the article relates an experiment in which carbon fuel 4 is a South African coal. Its oxidation 2 takes place in a fluidized bed and the active oxygen-carrying compound 8, 9 is ilmenite, a natural oxide of iron and titanium, in the form of granules.
• a regeneration reactor 3 of the active compound is used, with air 6 as oxidant.
• the flow of coal 4 introduced corresponds to a thermal power of 3.3 kW, the temperature being greater than 850 ° C. The tests lasted more than 22 hours.
• the inventors then carried out process calculations corresponding to the combination of the chemical loop 1 carried out in step a) with the secondary oxidation 12 carried out in step b).
• the chemical loop they integrated the average composition estimated from the article. They dimensioned the secondary oxidation reaction 12 on the basis of a flow rate of 329 t / h of effluents 11 from coal oxidation reactor 2, corresponding to an overall plant size capable of producing 450 MW of electricity. .
• the secondary oxidation reaction 12 was calculated under adiabatic conditions (but it could have been in an exchanger reactor), from reagents 11, 13 taken at room temperature.
• the composition of the effluents 14 resulting from the secondary oxidation 12 is much more suitable for the capture of CO2. Indeed, there is almost no CO, H2, CH4. The amount of residual oxygen and argon is minimal. Extremely reduced after-treatment, which is the subject of step d) of the process according to the invention, is then sufficient to condition the CO2 for storage or use as a product.
• the secondary oxidation step makes it possible to release an additional energy of 134 MW thermal, for an injected oxidant flow of the order of 35 to 37 tons / h.
• the main advantages of the invention are to increase the recovered thermal power and to reduce the amount of undesired compounds in the CO2 to be captured, such as oxygen, hydrogen, H2S, NH3, CH4 CO and hydrocarbons, with reasonable consumption of oxidant containing predominantly oxygen.

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• Combustion & Propulsion (AREA)
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• General Engineering & Computer Science (AREA)
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• 2008
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• 2009
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