FR2937333A1 - METHOD AND DEVICE FOR EXTRACTING CARBON DIOXIDE FROM THE ATMOSPHERE - Google Patents

Abstract

The invention relates to a process for extracting carbon dioxide from the atmosphere by thermochemically converting biomasses as a natural intermediary carrier for storing carbon dioxide, with production of energy and fuels, this thermochemical conversion. being carried out by means of a pyrolysis reactor (2) and a fluidized bed combustion reactor (8). According to the invention, a capture of the carbon dioxide is carried out by a thermochemical cycle (3) comprising said interconnected combustion reactor (8) and an oxidation chamber (9), and in which metal oxides which are alternately oxidized circulate. and reduced and which ensure the supply of oxygen for said combustion.

Description

METHOD AND DEVICE FOR EXTRACTING CARBON DIOXIDE FROM THE ATMOSPHERE

The invention relates to a method and a device for extracting carbon dioxide from the atmosphere. The steady increase in carbon dioxide (CO2) levels in the atmosphere since 1860, which is now accelerating, as a result of emissions from industrial fossil fuel global warming of at least two degrees in 2100, which must be limited by dividing CO2 emissions by a factor of four so as not to exceed 550 ppm of CO2 in the years 2100. The aim of the invention is to extract selectively and economically the CO2 of the air from the atmosphere.

Biomass of agricultural and forest origin stores CO2 by photosynthesis over periods of between one and a hundred years. Since this biomass is very reactive with more than 70% dry matter and about 50% moisture on crude, the invention proposes to take advantage of these characteristics to convert this biomass into energy and fuels while capturing the CO2 emitted with a simplified and compact technology. CO2 that is captured can be stored for several hundred years in the basement, for example in submarine aquifers. Thanks to the invention, this new approach achieves CO2 extraction from atmospheric air by using a natural intermediate CO2 storage vector constituted by biomass. Patent document WO 01/02513 also describes a method for treating biomass. The organic substances are first milled and / or dried and then introduced into a pyrolysis reactor in which they are brought into contact with the material of an associated fluidized bed whose combustion gases are purified before being discharged.

According to this known method, no specific capture of CO2 is expected. The invention solves this problem by an economical process that can be adapted to any size of installation. In particular, the treatment of biomass, for example agricultural residues, forest waste and sorted household waste, can be carried out very locally, close to biomass sources, with small and very large scale installations. The invention therefore proposes a process for extracting carbon dioxide from the atmosphere, by thermochemical conversion of biomasses, as a natural intermediary carrier for storing carbon dioxide, with production of energy and fuels, this conversion thermochemical being produced by means of a pyrolysis reactor and a fluidized bed combustion reactor, characterized in that a capture of the carbon dioxide is carried out by a thermochemical cycle comprising said combustion reactor and an oxidation chamber interconnected, and in which circulate metal oxides which are alternately oxidized and reduced and which provide the supply of oxygen for said combustion. With this process, a carbon dioxide capture with fuel production is performed upstream of the pyrolysis and electricity reactor upstream of the fluidized bed reactor. Pyrolysis releases the volatile matter contained in the biomass. This embodiment takes advantage of the high porosity and reactivity of the carbonaceous residue of biomass after starting moisture and volatile materials. According to a preferred embodiment, said pyrolysis is preferably preceded by a drying of the biomasses using the residual heat available on some of the resulting gaseous effluents.

Preferably, the drying is carried out by fumes in depleted air leaving said oxidation chamber of said thermochemical cycle. The hot solids circulating in said thermochemical cycle preferably provide said pyrolysis.

Advantageously, the hot solids circulating in said oxidation chamber provide said pyrolysis. The system is as compact as possible. Knowing that the carbon residue to be converted can represent only 15% of the incoming fuel fraction, the volume of gaseous effluents, excluding pyrolysis gas, is reduced to 15% of the fumes of an air combustion. It is this flow of gaseous effluents that determines the equipment size of a thermochemical cycle. The compactness of this CO2 extraction system is therefore extremely high, which reduces the investment costs and allows an operator to dispense with the purchase of CO2 allowances, corresponding to the case of use of fossil fuels. The other advantage provided by decomposing, this three-step biomass treatment, drying, pyrolysis and conversion of the carbonaceous residue is to minimize the supply of oxygen to be provided for the conversion of the final carbonaceous solid residue.

Said production of energy and / or fuels is preferably carried out in the form of high pressure steam and synthesis gas whose composition can be adjusted after reforming to manufacture synthetic fuels of the methanol or di-methyl-ether type. Preferably, said thermochemical cycle uses air, water vapor and carbon dioxide to oxidize and reduce said metal oxides. Said air is advantageously air enriched with oxygen. The invention also relates to a device for implementing the method specified above, characterized in that said drying is carried out by means of a drying reactor consisting of an aerated mobile bed downward co-current, shaped flared and equipped with devasters.

The invention is described below in more detail with the aid of figures representing only a preferred embodiment of the invention. FIG. 1 represents a device for implementing the method according to the invention.

Figure 2 is a vertical sectional view of a drying device for carrying out the method according to the invention. As illustrated in FIG. 1, a device for carrying out the process according to the invention comprises three main interconnected components, a drying reactor 1, a flash pyrolysis reactor 2 and a thermochemical converter 3, constituting a thermochemical cycle comprising a combustion reactor 8 and an oxidation chamber 9 interconnected and wherein circulates metal oxides which are alternately oxidized and reduced. The treated biomass 4, the moisture content of which is 40 to 55%, is finely divided by shredding into papermaking chips and sawdust, and then introduced into the drying reactor 1, preferably into a downflow aerated moving bed, flared shape and equipped with devactors, which will be described later. At the outlet of this drying reactor 1, the water vapor and the depleted air 14 are released into the atmosphere.

The gases admitted to this drying reactor 1 are at a temperature of 400 to 600 ° C. The biomass once dried at approximately 10 to 15% residual moisture is transferred by screw and gravity drop with airlock to a flash pyrolysis reactor 2, carried out at a temperature of between 400 and 800 ° C., in a fluidized bed fed with solids. from the thermochemical cycle 3 operating at a temperature of 700 to 1000 ° C depending on the oxides used. The release of volatile matter and residual moisture contained in the introduced biomass is immediate and constitutes the outlet 6 of pyrolysis gas of the process. This gaseous composition can be adjusted by oxygen reforming at 1200 to 1400 ° C. to convert the tars and methane and then a CO shift step to arrive at a synthesis loop for the production of synthetic fuels, of the methanol type. or di-methyl-ether. The reaction (CO + H2O -> H2 + CO2) represents said CO shift. The carbon residue remaining after pyrolysis, mixed with the bed material in circulation, is transferred via a pipe 7 to the combustion reactor 8, supplied with steam and CO2 by the pipes 15, 15 'as for a conventional autothermal gasification. The carbonaceous residue is progressively converted in the thermochemical circulating loop 3 until the carbon disappears and the residual ash escapes by a cyclone and by a bed withdrawal at the bottom of the combustion reactor 8. The bed material of this reactor combustion 8 is that of the thermochemical cycle 3 in which circulates natural or synthetic metal oxides which are alternately oxidized and reduced and which provide the supply of oxygen for combustion or gasification, which is superimposed the bed material containing the carbonaceous residue. This circulating bed material which consists of fine particles of mixed oxides of iron, titanium and / or manganese type is oxidized, reduced, acts as a coolant and contains the carbon residue to be converted. The CO2 resulting from the conversion of the carbonaceous residue 11 leaves the combustion reactor 8 and undergoes cooling, dedusting, condensation of the flue gas and compression for transport. It can then be stored in aquifer. Part of this CO 2 with water vapor feeds the combustion reactor 8 and another part 16 with steam is injected into the pyrolysis reactor 2, according to the CO / ratio requirements. H2 of the CO shift stage, itself dependent on the final synthetic fuel to be produced. Very rapid oxidation of the bed material is provided by fluidization with air or air enriched with oxygen 12 in the oxidation chamber 9 provided in the thermochemical converter 3 comprising gas locks. These locks are sealing devices between enclosures containing gases of different composition.

The gas stream 13 discharged from this oxidation chamber 9 is essentially air depleted of oxygen. This gaseous stream of oxygen-depleted air is particularly well suited to the drying of highly reactive biomass without the risk of ignition and is used preferentially for the drying of biomass, since it represents more than 70% of the flue gas flow of the installation. . Fig. 2 shows the drying reactor 1 which is preferably a downflow moving bed provided with coasters. It comprises a chamber 1A, of flared shape downwards, its upper part receiving the biomasses from a hopper 1C via an input worm 1B. Its lower part is equipped with worm output ID. The fumes in depleted air coming out of the oxidation chamber 8 of the thermochemical cycle are injected 1E in the upper part of the chamber, to carry out the drying and the cooled gases are discharged 1F in the lower part.

Claims (9)

REVENDICATIONS1. A process for extracting carbon dioxide from the atmosphere by thermochemically converting biomasses as a natural carbon dioxide intermediate carrier with production of energy and fuels, said thermochemical conversion being carried out by means of a pyrolysis reactor (2) and a fluidized bed combustion reactor (8), characterized in that carbon dioxide is captured by a thermochemical cycle (3) comprising said combustion reactor (8) and an oxidation chamber (9) interconnected, and in which metal oxides are circulated which are alternately oxidized and reduced and which supply oxygen for said combustion. 2. Method according to the preceding claim, characterized in that said pyrolysis is preceded by a drying (1) biomasses using available residual heat on some of the resulting gaseous effluents. 3. Method according to claim 2, characterized in that said drying (1) is performed by fumes depleted air (13) exiting said oxidation chamber (9) of said thermochemical cycle. 4. Method according to one of the preceding claims, characterized in that the hot solids circulating in said thermochemical cycle (3) provide said pyrolysis (2). 5. Method according to the preceding claim, characterized in that the hot solids circulating in said oxidation chamber (9) provide said pyrolysis (2). 6. Method according to one of the preceding claims, characterized in that said production of energy and / or fuels is carried out in the form of high pressure steam and synthesis gas whose composition can be adjusted after reforming to produce fuels. synthetic (10). 7. Method according to one of the preceding claims, characterized in that said thermochemical cycle (3) uses air, water vapor and carbon dioxide to oxidize and reduce said metal oxides. 8. Method according to the preceding claim, characterized in that said air is air enriched with oxygen. 9. Device for carrying out the method according to one of claims 6 to 8, characterized in that said drying is carried out by means of a drying reactor (1 ') consisting of a co-current moving bed descending, flared shape.