CA2845883A1 - Gasifier for a solid carbon fuel - Google Patents

Abstract

Carbonaceous solid fuel gasifier comprising at least a first vertical vessel (4) and introduction means (5) for introducing the fuel (2) into an upper part of the first vessel above a pyrolysis zone (10) said pyrolysis zone being an area where the fuel introduced is pyrolyzed to produce pyrolysis gases and carbonized fuel. The gasifier also has a combustion zone (20) for burning said pyrolysis gas, a reduction zone (30) for gasifying the carbonized fuel from the pyrolysis zone (10) to produce synthesis gases and ashes, and an outlet (6) for harvesting said synthesis gases. The first tank (4) comprises a fixed horizontal plate (50) mounted between the introduction means (5) and the pyrolysis zone (10) in order to retain the fuel introduced therein, as well as a movable pusher (51). mounted between the introduction means (5) and the plate (50) for transferring the fuel, retained on the plate, to the pyrolysis zone (10). The plate (50) forms a heat shield at least partially protecting the introduction means (5) and the mobile pusher (51) against the high temperatures prevailing in the first tank (4).

Description

GAS FUEL SOLID CARBON
Field of the invention The invention relates to a gasifier for the gasification of a fuel solid carbon, such as for example solid biomass.
More particularly, the invention relates to such a gasifier, comprising at least a first vertical tank provided with introduction means for introducing the fuel from above and along a first vertical axis in said first tank and having a pyrolysis zone for pyrolyzing the fuel, a zone of combustion to burn pyrolysis gases from the pyrolysis zone, a zone to gasify carbonized fuel from the pyrolysis, and an outlet for harvesting gases produced in the reduction zone, said first further comprising a horizontal tray fixedly mounted between the means of introduction and the pyrolysis zone for receiving and retaining the combustible introduced into the tank.
The invention also relates to a unit for the production and combustion of gas comprising such gasifier to produce said gas.
State of the art Such gasifiers are known and make it possible to produce a fuel gas at go carbonaceous solid fuel, in particular from wood waste, such as from, for example, sawmills or logging operations, or from under agricultural products (straw, etc.), or from recycled wood.
This gas fuel contains in particular carbon monoxide and hydrogen and can then be used for various purposes such as for example to power a turbine to gas or an internal combustion engine or boiler or furnace.

2 In order to supply the first tank with fuel, it is known to provide means of fuel introduction that are gas-tight that will be produced in the tank. This sealing makes it possible to prevent the gases produced in the tank from back fuel storage and supply systems, so that said gases will essentially go to the exit when the gasifier is in operation.
It is known to use for this purpose an airlock mechanism at the entrance of the first tank.
Patent application WO 2007/081296 discloses a gasifier comprising a valve rotative located in the upper part of the reactor. This device presents the advantage to be able to properly measure the fuel supply, but it presents however the disadvantage of not being sufficiently gas-tight and requiring additional sealing mechanism upstream, which increases the cost. Of more, the valve must be able to withstand the high temperatures prevailing in the first tank when the gasifier is in operation, which requires valves particularly expensive.
Other mechanisms use only a two-valve airlock in place and place of the rotary valve of which question above. Besides the fact that this kind of mechanism is less efficient at the level of material dosing (batch dosing), the valve lower must also withstand the said high temperatures and is therefore expensive.
Patent application WO 2001/051591 discloses a gasifier comprising an airlock disposed laterally with respect to the upper part of the reactor, which allows to obtain a good gas-tightness, as well as a lateral pipe provided with of a screw endless link acting as a link between the airlock and the first tank, which allows also to properly dose the material supply. However, such device is expensive and cumbersome. The worm is also likely to get dirty, which requires maintenance, and / or blocking with pieces of fuel.
Moreover, as the end of the screw opens into the tank, it is subject to the high temperatures that prevail when the gasifier is in operation, which requires the use of an expensive screw.

3 Patent application WO 2010/109501 discloses a gasifier in the form of a tank, in the upper part of which the fuel is introduced laterally. The fuel is then retained in a drying area of the tank by means of a horizontal wall pierced with an orifice at its center. Through this hole is placed vertically a worm which allows to transfer the fuel from the zone of drying to a pyrolysis zone just below the wall horizontal. This worm opens into the pyrolysis zone and must be able to withstand tall temperatures that prevail when the gasifier is in operation, which requires particularly strong and expensive screws. The worm is also likely to get dirty, which requires maintenance, and / or block by pieces of fuel.
Summary of the invention An object of the invention is to at least partially solve the problems of gasifiers mentioned above.
For this purpose, the gasifier according to the invention is characterized in that first tank comprises a movable pusher mounted between the introduction means and the tray horizontal, said movable pusher being adapted to push the fuel retained on the horizontal tray to the pyrolysis zone and being positioned or positionable at above the horizontal board.
With such a configuration, the horizontal tray will form a screen thermal that will protect both the fuel introduction means and the pusher against the high temperatures that prevail in the first tank (against the radiation and the flames in particular). This makes it possible to use transfer mechanisms of material (means of introduction, push) cheaper and / or increase their durability and / or their reliability.

4 Such a mobile pusher also takes up less height and is simpler and more reliable than the vertical auger (12) proposed in the WO-Patent 2010/109501.
Preferably, the movable pusher has at least one branch extending horizontally above the plateau and rotatably mounted around a second axis vertical. A rotary pusher makes it possible to better distribute the fuel on the bed of fuel in the pyrolysis zone which improves the quality of the reaction of pyrolysis. In particular, this reduces the tar content of the gas product.
Different mechanisms have been devised in the past for better divide the fuel on the fuel bed after its introduction into the first tank.
US Pat. No. 5,755,837 (see FIGS. 4 and 5) proposes, for example, to provide the part top of the first tank of an inclined weir. These measures cause nevertheless a greater accumulation of material at the place of their points of fall on the fuel bed. In particular, the fuel level will be more important on the peripheral part of the first tank that in its part Central.
Patent GB 696682 proposes for its part to provide the upper part of the first bowl of a mechanism with two rotating plates pierced with orifices. Here too, the combustible will pose preferentially to the right of orifices. Moreover, this mechanism is likely to get dirty and / or blocked by pieces of combustible.
In order to address these problems, the gasifier according to the invention comprises preference leveling means capable of leveling at least partially a surface higher solid fuel bed in the pyrolysis zone. The inventors so planned a mechanism acting directly on the fuel bed rather than acting on the fuel spill on the bed, reducing or eliminating the cons known mechanisms. The means of leveling allow even better divide the fuel on the fuel bed in the pyrolysis zone, which improves quality of the pyrolysis reaction.

According to a preferred embodiment, the leveling means comprise at least one minus one arm extending horizontally at the level of the upper surface of the bed of solid fuel in the pyrolysis zone, said at least one arm being rotatably mounted around a third vertical axis C. This constitutes a simple means, reliable and

5 effective to spread the solid matter more evenly over the bed of matter in the pyrolysis zone.
Brief description of the figures These aspects as well as other aspects of the invention will be clarified in the description of particular embodiments of the invention, reference being made to drawings of the figures, in which:
Fig.1 shows schematically a frontal section of a gasifier according to the invention;
Fig.2 schematically shows a frontal cut of a mode of production preferred embodiment of a gasifier according to the invention;
Fig. 3 schematically shows a cross section of the gasifier of Fig.2;
Fig.4 schematically shows a frontal cut of a mode of achievement more preferred embodiment of a gasifier according to the invention;
Fig.5 schematically shows a frontal cut of a mode of production still more preferred of a gasifier according to the invention;
Fig.6 schematically shows a cross-section of the gasifier of Fig.5;
Figs.7a and 7b show schematically, respectively a frontal section and cross-section of an even more preferred embodiment of a gasifier according to the invention;
Figs.8a and 8b respectively show a frontal section and a section transversal of a preferred embodiment of a gasifier according to the invention.
The drawings of the figures are not to scale. Generally, elements similar are denoted by similar references in the figures.

6 Detailed description of particular embodiments The examples of embodiment described below relate to a gasifier with running, in bed fixed, and formed by a single vessel comprising both the pyrolysis zone, the zone of combustion and the reduction zone. It will be obvious that the invention is not limited to this type of gasifier but concerns all the gasifiers with features of the preamble of the first claim, such as example of countercurrent gasifiers, or gasifiers with several tanks put next to each other, the first tank being the one where take place the reactions pyrolysis of the fuel.
Similarly, the embodiments described below use biomass solid in as an exemplary fuel, but it will be obvious that any other type of carbonaceous solid fuel will also be suitable.
Fig.1 shows schematically a frontal section of a gasifier (1) according to the invention. In this example, it is a gasifier co-current and bed fixed. This gasifier is essentially formed by a reactor having the shape of a tank vertical (4) comprising successively and from top to bottom:
an inlet lock (5) for introducing biomass (2) into the tank according to a first vertical axis (A), a pyrolysis zone (10) for pyrolyzing the biomass introduced into the tank, a combustion zone (20) for combusting pyrolysis gases originating from the pyrolysis zone, a reduction zone (30) for gasifying carbonized biomass from of the pyrolysis zone, an outlet (6) for collecting gases from the reduction zone, and an area (40) for collecting and discharging ashes.

7 It should be noted that the airlock can take various forms, such as example a rotary valve and / or a two-valve lock and / or any other means known introduction of the skilled person.
The biomass (2), for example wood chips, is introduced into the tank (4) by the up via the airlock (5) and then arrives - via the device intermediate (50, 51) described in more detail below - in the pyrolysis zone (10) where it is breaks down, under the effect of heat in volatile matter and in a rich solid residue in carbon usually called char or coke. This reaction occurs typically in a temperature range between 300 C and 700 C.
In order to reach these temperatures, the tank generally comprises first means for admitting a pyrolysis agent (11) - for example one or more nozzle (s) opening laterally into the tank at the level of the zone of pyrolysis ¨ and which allows to introduce a gas that will bring directly or indirectly the energy necessary for the decomposition of biomass into volatile matter and in tank . Said pyrolysis agent may for example be a reactive gas containing of oxygen which, by burning a fraction of the biomass or products of the decomposition of the biomass, will release the energy necessary for pyrolysis. he can also an inert gas (such as carbon dioxide, nitrogen, water vapor) which, preheated, will provide the necessary energy for pyrolysis. It can also be a combination of these two types of gas.
The tank> is then transferred to the reduction zone (30) by means goods known, for example those described in patent application EP11171156.
Volatiles (also called pyrolysis gases) entering the zone of combustion (20) are burned partially or totally. In order to favor this combustion, the vessel preferably comprises second intake means of a gasifying agent (21). These second admission means may for example include a several nozzle (s) opening laterally into the tank at the level of the zone of WO 2013/03460

8 PCT / EP2012 / 067349 combustion. By gasifying agent, it is necessary to understand a gas capable of reacting with the carbon and / or with the hydrogen contained in the solid fuel. Said agent gasifier can therefore for example be ambient air, a stronger gas concentration oxygen, water vapor, carbon dioxide or a mixture of these gas. This combustion produces mainly carbon dioxide (CO2), the water (H20), and of course heat. Typically, temperatures greater than 1100 C are attainable in the combustion zone.
The tank that has been transferred to the reduction zone will react with the products of combustion to form in particular carbon monoxide (CO) and hydrogen (H2).
In the case, for example, of an autothermic reaction of cellulose - such as wood - and the use of ambient air at room temperature as As a gassing agent, this reaction typically occurs in a range of temperature between 300 C and 800 C. This temperature may nevertheless to be higher and reach or even exceed 1300 C in the case of using a higher carbon fuel and / or reagents preheated. Gas produced by this reaction will be collected at the outlet (6) of the reactor is located in the bottom of the tank (4). At exit (6) there is thus a fuel gas comprising typically about 15% to 30% CO, 10% to 25% H2, 0.5 to 3% CH4, 5%
15% of CO2 and 49% N2 when using ambient air as a gasifier.
The ashes can be collected in the bottom (40) of the tank.
Such gasifiers are known and therefore will not be entered in more detail in their design or their operation.
Attention will now be focused on the device (50, 51) just below the airlock (5).
This device comprises firstly a horizontal plate (50) mounted so fixed between the airlock (5) and the pyrolysis zone (10). Said plate (50) is positioned and

9 sized to receive and at least partially retain the fuel (2) introduced into the tank (4) via the airlock (5).
Preferably, the tray is positioned and dimensioned so that it retain the fuel completely and that the fuel can only flow towards the zone of pyrolysis under an external action, as under the action of the pusher described below.
To this end, the position and size of the tray will be adapted to properties flow of the fuel used, in particular its angle of repose (ex.
for some copaux de bois, the slope angle is of the order of 600).
The device further comprises a movable pusher (51) mounted between the airlock input (5) and the horizontal tray (50). Said pusher (51) is positioned at above the board horizontally (50), so that the horizontal tray forms a screen thermal protecting the pusher from the heat prevailing below the tray when the gasifier is in operation. As illustrated in the figure, it can be by example of a cylinder horizontal and at the end of which is mounted a vertical plate serving as button.
When the cylinder is actuated, the fuel retained on the plate will be pushed by the plate and will fall by gravity into the pyrolysis zone (10). The dosage of combustible can be achieved by controlling the movement of the cylinder.
Fig.2 shows schematically a frontal section of an embodiment prefer a gasifier according to the invention. According to this preferred mode, the mobile pusher (51) has at least one limb (52) extending horizontally over the tray horizontal (10) and rotatably mounted about a second vertical axis (B).
This branch can for example consist of a vertical plate.
One end of the branch is here connected to a shaft of an engine (M) for allow the rotation of the branch. The movable pusher (51, 52) is thus positionable at top of the horizontal tray (50), which allows the tray to fill its screen role when the pusher is actually positioned above the tray. We understand that the pusher may temporarily overflow the tray when the motor (M) is rotated, but it is important for the pusher to be able to moment or another being positioned above the board.

Preferably, the motor (M) is provided with a speed reducer so to increase the torque and the precision of the movement transmitted to the first branch. Of preferably, the motor (M) is mounted above the tray so that the tray also forms a heat shield vis-à-vis the engine. More preferably, the motor (M) is 5 mounted outside the tank, in which case his shaft will pass through the part top of the tank via a seal or a sealed bearing to be connected then to the first branch (case not shown).
Preferably, the second axis (B) is offset with respect to the first axis (A).
Fig.3 schematically shows a cross section of the gasifier of the Fig.2. We see an example of the shape that can have the horizontal tray (50) and the branch (52) of the pusher and how these two elements can be arranged one by report to the other.
Preferably, the gasifier comprises a motor (M) for driving the at least one a branch (52) of the pusher rotating about the second axis (B) and first control means (60) able to control the motor (M) to give a movement at least one arm (52) about said second axis (B).
For this can be used for example a motor whose direction of rotation can to be reversed, such as for example a DC motor.
This allows the biomass to be overflowed by a first end (56) of the tray when the engine rotates in a first direction of rotation and to make overflow the biomass by a second end (57) of the plate, opposite to the first side, when the engine rotates in a second direction of rotation opposite the first meaning of rotation. This provides a more even distribution of the fuel on the bed in the pyrolysis zone.
Preferably, the first control means (60) are able to regulate a starting angular position (P1) and an amplitude (A1) of the movement of pendulum, which makes it possible to regulate even more precisely the transfer of biomass of plateau towards the pyrolysis zone. For this purpose, for example, one can appeal has a stepper motor provided with an encoder wheel of the angular position of the tree of engine as well as a suitable controller, this type of assembly being largely known in as such.
Fig.4 shows schematically a frontal section of an embodiment more preferred embodiment of a gasifier according to the invention.
Here, the first tank (4) further comprises leveling means (70) suitable to level at least partially an upper surface (80) of the biomass bed in the zone of pyrolysis (10). As illustrated in the figure, these leveling means include by example a horizontal cylinder whose end is provided with a scraper. said scraper is located at the upper surface (80) of the biomass bed in the area Pyrolysis

(10). Preferably, the scraper is in the form of a rake whose teeth are oriented towards the bottom. The actuation of the jack will thus level the said surface superior (80) biomass bed.
Fig.5 shows schematically a frontal section of an embodiment again most preferred of a gasifier according to the invention. According to this version more favorite, leveling means (70) comprise at least one leveling arm (71) extending horizontally at the top surface (80) of the fuel bed solid in the pyrolysis zone (10), said at least one leveling arm (71) being mounted rotating around a third vertical axis (C). The leveling arm can example to be consisting of a vertical plate or a rake whose teeth are oriented to the low.
One end of the leveling arm (71) is here connected to a shaft of an engine (M) for allow the rotation of said arm (71). Preferably, this motor (M) is provided speed reducer to increase the torque and accuracy of the movement transmitted to the arm (71). Actuation of the motor will allow to level the area higher (80) of the biomass bed when the gasifier is in operation.
Fig.6 schematically shows a cross-section of the gasifier of the Fig.5. We sees better the leveling arm (71) and its rotary movement.

Preferably, the leveling means comprise six arms mounted radially all 60 degrees around a C-axis rotary shaft.
Preferably, the axis B and the axis C are merged. More preferably, the at least a branch (52) of the pusher and the at least one arm (71) of the leveling means are mounted on the same rotary shaft (75). An example of realization is provided in Figs. 7a and 7b.
Here, a single motor (M3) drives both the branch (52) of the pusher and the arm of leveling (71) via a common rotary shaft (75), which simplifies assembly and makes it therefore less expensive, less bulky and more reliable.
In such a configuration, the branch (52) of the pusher and the arm of leveling (71) are preferably mounted in opposition, that is to say angularly offset from 180 degrees, as best seen in FIG. 7b. When the common motor (M3) is piloted for print a pendulum movement to the limb (52) and to the arm (71), this allows ensure that, with each movement to and fro, the arm (71) will move above biomass previously discharged onto the bed (80) of biomass by the branch (52) pusher. This gives a very good equalization of the surface of the bed of biomass in the pyrolysis zone, which improves the pyrolysis reaction.
Figs.8a and 8b respectively show a frontal section and a section cross-section of a preferred embodiment of a gasifier according to the invention. Here, the plate is formed by a fixed plate (50) which extends substantially over all the cross section of the tank (4). The plate (50) is also provided at least one opening (58) through which the pusher (52) can push the fuel (2) retained by the plate so that it falls by gravity into the pyrolysis zone (10).
The opening (58) is offset relative to the intake means (5) so that the fuel can not fall directly into the pyrolysis zone. For the rest, this gasifier is similar to those described above.

As can be seen in Fig. 8a, the motor (M3) will preferably be deported out of the tank (4) in order to access it more easily and so that it is not subject to conditions prevailing inside the tank (temperature, presence of gas, etc ...).
Many other forms of tray and pusher can be envisaged, from moment that the tray is able to retain the fuel from the means introductory (5) and that the pusher (52) is able to push and to fall by gravity the fuel retained, to the pyrolysis zone (10).
The invention also relates to a production and combustion unit of gas comprising a gasifier according to any one of the preceding claims for produce said gas. It can act for example of a set comprising a gasifier as described above and an internal combustion engine, the outlet (6) of the gasifier being connected to an engine fuel injection system internal.
The present invention has been described in relation to embodiments specific, which have a purely illustrative value and need not be considered as limiting. In general, it will be obvious to the man of career that the present invention is not limited to the illustrated examples and / or described above.
The invention comprises each of the novel features as well as all their combinations.
The presence of reference numbers in the drawings can not be considered as limiting, including when these numbers are indicated in the claims.
The use of verbs include, include, include, or any other variant, as well as their conjugations, can in no way exclude the presence items other than those mentioned.
The use of the indefinite article one, one, or the definite article the, where, to introduce an element does not exclude the presence of a plurality of these elements.

In summary, the invention can also be described as follows: a gasifier of carbonaceous solid fuel (2) having at least one first vertical vessel (4) and introduction means (5) for introducing the fuel (2) into a part top of the first tank above a pyrolysis zone (10), said zone of pyrolysis being an area where the fuel introduced is pyrolyzed to produce gases pyrolysis and carbonized fuel. The gasifier also has a zone of combustion (20) for burning said pyrolysis gases, a reduction zone (30) for gasifying the carbonized fuel from the pyrolysis zone (10) to of produce syngas and ash, and an outlet (6) for harvesting said gases of synthesis. The first vat (4) has a fixed horizontal tray (50) mounted between the introduction means (5) and the pyrolysis zone (10) in order to retain the combustible introduced, and a movable pusher (51) mounted between the means of introduction (5) and the tray (50) to transfer the fuel retained on the tray to the zone of pyrolysis (10). The tray (50) forms a heat shield protecting at least partially the introduction means (5) and the movable pusher (51) against the high temperatures prevailing in the first tank (4) when it is in operation.

Claims (11)

1. Gasifier (1) for the gasification of carbonaceous solid fuel (2), having at least one first vertical vessel (4) provided with means (5) for introducing the fuel (2) from the top and according to a first vertical axis (A) in said first tank (4) and having a zone of pyrolysis (10) for pyrolyzing the fuel, a combustion zone (20) for to burn pyrolysis gases from the pyrolysis zone (10), a zone of reduction (30) for gasifying carbonized fuel from the pyrolysis (10), and an outlet (6) for harvesting gases produced in the zone of reduction, said first tank (4) comprises a horizontal plate (50) mounted of fixed way between the introduction means (5) and the pyrolysis zone (10) for receiving and retaining the fuel (2) introduced into the tank (4), characterized in that the first tank (4) comprises a movable pusher (51) mounted between the introduction means (5) and the horizontal plate (50), said movable pusher (51) being adapted to push the retained fuel onto the horizontal tray to the pyrolysis zone and being positioned or positionable at above the horizontal platter (50); 2. Gasifier according to claim 1, characterized in that the pusher mobile (51) has at least one limb (52) extending horizontally over the tray (10) and rotatably mounted about a second vertical axis (B); 3. Gasifier according to claim 2, characterized in that the second axis (B) is offset from the first axis (A); 4. Gasifier according to claim 2 or 3, characterized in that has a motor (M) for driving the at least one leg (52) of the rotary pusher around the second axis (B) and the first control means (60) suitable for control the motor (M) to give a pendulum movement to the said at least one limb (52) about said second axis (B); 5. Gasifier according to claim 4, characterized in that the first means of control (60) are able to set a starting angular position (P1) as well as a amplitude (A1) of the pendulum movement; 6. Gasifier according to any one of the preceding claims, characterized in the first tank (4) comprises leveling means (70) suitable for level at least partially an upper surface (80) of the fuel bed solid in the pyrolysis zone (10); Gasifier according to Claim 6, characterized in that the means for leveling (70) have at least one leveling arm (71) extending horizontally at level of the upper surface (80) of the solid fuel bed in the zone of pyrolysis (10), said at least one arm (71) being rotatably mounted around a third vertical axis (C); 8. Gasifier according to claim 7, characterized in that the means of leveling have six arms mounted radially every 60 degrees around a tree rotary C axis; 9. Gasifier according to claim 7 or 8, characterized in that the axis B
and the C axis are confused; 10. Gasifier according to claim 9, characterized in that the at least one a branch (52) of the pusher and the at least one arm (71) of the leveling means are mounted on the same rotary shaft (75); 11. Gas production and combustion unit comprising a gasifier according to one any of the preceding claims for producing said gas.