CA2740501A1 - Method for the pyrolysis and gasification of biomasses by means of thermochemical conversion - Google Patents

Abstract

The invention relates to a method for extracting carbon dioxide from the atmosphere by thermochemically converting biomasses as a natural intermediate carrier for storing carbon dioxide, a capture of the carbon dioxide being carried out by means of a cycle. thermochemical reactor (3) comprising a combustion reactor (8) and an oxidation chamber (9) interconnected, and in which metal oxides which are alternately oxidized and reduced and which supply oxygen for said combustion, circulate; thermochemical conversion being carried out by means of a pyrolysis reactor (2) and said thermochemical cycle (3). According to the invention, said pyrolysis is preceded by drying (1) of biomasses carried out by fumes in depleted air (13) leaving said oxidation chamber (9) of said thermochemical cycle.

Description

METHOD AND DEVICE FOR EXTRACTING DIOXIDE FROM
CARBON OF THE ATMOSPHERE

The invention relates to a method and a device for extracting carbon dioxide from the atmosphere.
Continuous increase in carbon dioxide (C02) in the atmosphere since 1860, which is now tending to accelerate, emissions from industrial power generation facilities at base of fossil fuels, leads to a global warming of two degrees minimum in 2100 to be limited by dividing C02 emissions by a factor of four to not exceed 550 ppm C02 in the 2100s.
The object of the invention is to extract selectively and economically the C02 of the air of the atmosphere.
Biomass of agricultural and forest origin stores C02 by photosynthesis over periods between one and a hundred years. This biomass being very reactive with more than 70% of dry matter and approximately 50% moisture on crude, the invention proposes to take advantage of these features to convert this biomass into energy and fuels while capturing CO2 emitted with simplified and compact technology.
C02 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 a extraction of CO2 from atmospheric air using an intermediate vector natural storage of CO2 that constitutes biomass.
Patent document WO 01/02513 also describes a method of biomass treatment. Organic substances are first crushed 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 gases of combustion are purified before discharge.

2 According to this known method, no specific capture of CO2 is planned.
US patent document 2003/0029088 discloses a method of conversion of fuel into hydrogen, with capture of carbon dioxide.
According to this method, the capture of carbon dioxide is carried out by a cycle thermochemical comprising a combustion reactor and a chamber interconnected oxidation, and in which metal oxides circulate which are alternately oxidized and reduced and which ensure the supply of oxygen for combustion. A thermochemical conversion is carried out by means of a pyrolysis reactor and this thermochemical cycle.
If it is envisaged to use biomass as a fuel, this document essentially develops the use of coal.
The object of the invention is to adapt such a method to the treatment of non-fossil carbon cycle biomass by an advanced and economical process which can be adapted to any size of installation. In particular, the treatment of biomass, for example agricultural residues, waste forestry and sorted household waste, or biomass grown purposes energy, such as miscanthus or algae, can be very local, close to biomass sources, with amenities small and on a very large scale.
The invention therefore proposes a process for extracting carbon of the atmosphere, by thermochemical conversion of biomass, as a natural intermediate carrier for storing carbon dioxide,, a capture of the carbon dioxide being carried out by a cycle thermochemical comprising a combustion reactor and a chamber interconnected oxidation, and in which metal oxides circulate which are alternately oxidized and reduced and which ensure the supply of oxygen for said combustion, this thermochemical conversion being carried out at means of a pyrolysis reactor and said thermochemical cycle, characterized in that what said pyrolysis is preceded by a drying of the biomasses carried out by

3 fumes in depleted air leaving said oxidation chamber of said cycle thermochemical.
In addition to the advantage of a compact installation, these fumes constitute a inert gas containing less than 5% oxygen which can dry the biomass to a temperature of 750 C without combustion.
Pyrolysis releases the volatile materials contained in the biomass.
This embodiment takes advantage of the high porosity and reactivity of the carbonaceous residue of biomass after the departure of moisture and volatile materials.
According to a preferred embodiment of the invention, this method ensures production of energy and fuels.
Thanks to this process, it is realized a capture of the carbon dioxide with fuel production upstream of the pyrolysis reactor and of electricity upstream of the fluidized bed reactor.
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 residue carbon to be converted may represent only 15% of the fuel fraction entering, the volume of gaseous effluents, excluding pyrolysis gas, is reduced to 15%
fumes from combustion in the air. But it is this flow of gaseous effluents that conditions the equipment size of a thermochemical cycle.
The compactness of this C02 extraction system is therefore extremely high, which reduces investment costs and allows an operator to to dispense with the purchase of C02 allowances, corresponding to the use case of fossil fuels.
The other advantage provided by decomposing this treatment of biomass in three stages, drying, pyrolysis and carbon residue conversion

4 is to minimize the supply of oxygen to bring for the conversion of the residue final carbon solid.
Said production of energy and / or fuels is preferably performed in the form of high-pressure steam and synthesis gas whose composition can be adjusted after reforming to make fuels synthetics of the methanol or di-methyl-ether type.
Preferably, said thermochemical cycle uses air, water vapor and carbon dioxide for oxidizing and reducing said metal oxides.
Said air is advantageously air enriched with oxygen.
The invention also relates to a device for implementing the process specified above, characterized in that said drying is carried out at means of a drying reactor consisting of an aerated mobile bed co-current descending, flared and equipped with devoutors.
The invention is described below in more detail with the aid of FIGS.
representing a preferred embodiment of the invention.
FIG. 1 represents a device for implementing the method according to the invention.
FIG. 2 is a vertical sectional view of a drying device for the implementation of the process according to the invention.
As illustrated in FIG. 1, a device for implementing the method according to the invention comprises three main components interconnected 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 in which circulates metal oxides which are alternately oxidized and reduced.
The treated biomass 4, whose moisture content is 40 to 55%, is finely divided by chip shredding of stationery and sawdust, then introduced into the drying reactor 1, preferably in a moving bed airy with downward current, of flared shape and provided with devoutors, which will be described further. At the outlet of this drying reactor 1, the water vapor and the air depleted 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 about 10 to

15% residual moisture is transferred by screw and gravity drop with sas to a flash pyrolysis reactor 2, carried out at a temperature of between 400 and 800 C, in a fluidized bed fed with hot solids from the thermochemical cycle 3 operating at a temperature of 700 to 1000 C according to the oxides used. The release of volatile materials and the 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 17 to 1200 to 1400 C for convert tars and methane then a step of CO shift for to arrive at a synthetic synthesis loop of synthetic fuels, of the methanol or di-methyl-ether type. The reaction (CO + H20 -> H2 +
C02) represents said CO shift.
The carbon residue remaining after pyrolysis, mixed with the bed material in circulation, is transferred via line 7 to the reactor of combustion 8, supplied with water vapor and CO2 by the pipes 15, 15 'as for a conventional autothermal gasification. The carbon residue is converted progressively in the thermochemical circulating loop 3 until disappearance carbon and residual ash escape by a cyclone and by a bed racking at the bottom of the combustion reactor 8.
The bed material of this combustion reactor 8 is that of the cycle thermochemical 3 in which circulates natural metal oxides or synthetic materials that are alternately oxidized and the intake of oxygen for combustion or gasification, to which 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, plays the

6 role of coolant and contains the carbon residue to be converted. C02 from the conversion of the carbon residue 11 leaves the combustion reactor 8 and undergoes cooling, dedusting, condensation of flue gas and compression for transport. It can then be stored in aquifer. A
part 15 of this CO 2 with water vapor feeds the reactor of combustion 8 and another part 16 with water vapor is injected into the pyrolysis reactor 2, according to the CO / H2 ratio requirements of the step of CO shift, itself dependent on the final synthetic fuel to be produced.
Very fast oxidation of the bed material is ensured by a fluidization with air or air enriched with oxygen 12 in the chamber oxidation 9 arranged in the thermochemical converter 3 having airlock gas. These locks are sealing devices between enclosures containing gases of different composition.
The gas stream 13 discharged from this oxidation chamber 9 is essentially oxygen-depleted air. This gaseous flow of air depleted in oxygen is particularly well suited to highly biomass drying reactive without risk of ignition and is used preferentially for the biomass drying because it accounts for more than 70% of the flue gas installation.
FIG. 2 represents the drying reactor 1 which is preferably a movable bed with downward current provided with theaters. It has a enclosure 1A, of flared shape downwards, its upper part receiving the biomasses from a 1C hopper via a worm input 1B. Its lower part is equipped with 1D output worm.
The fumes in depleted air leaving the oxidation chamber 8 of the thermochemical cycle are injected lE at the top of the enclosure, for carry out the drying and the cooled gases are evacuated 1F in the lower part.

Claims (7)

1. Process for extracting carbon dioxide from the atmosphere, by a thermochemical conversion of biomass as a vector natural intermediate for storing carbon dioxide, a capture of the carbon dioxide being effected by a thermochemical cycle (3) comprising a combustion reactor (8) and an oxidation chamber (9) interconnected, and in which circulate metal oxides which are alternatively oxidized and reduced and which ensure the supply of oxygen for said combustion, this thermochemical conversion being carried out at means of a pyrolysis reactor (2) and said thermochemical cycle (3), characterized in that said pyrolysis is preceded by drying (1) of biomasses carried out by fumes in depleted air (13) leaving said oxidation chamber (9) of said thermochemical cycle. 2. Method according to claim 1, characterized in that it ensures a production of energy and fuels. 3. Method according to one of the preceding claims, characterized in that the hot solids circulating in said thermochemical cycle (3) provide said pyrolysis (2). 4. Method according to the preceding claim, characterized in that the hot solids circulating in said oxidation chamber (9) ensure said pyrolysis (2). 5. 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 synthetic fuels (10). 6. Method according to one of the preceding claims, characterized in that said thermochemical cycle (3) uses air, water vapor and carbon dioxide carbon to oxidize and reduce said metal oxides. 7. Method according to the preceding claim, characterized in that said air is air enriched with oxygen.