Patent Application
20140182490
This disclosure relates generally to gasifiers and, more specifically to a gasifier for gasification of a solid carbon fuel, such as, for example, solid biomass.
Known gasifiers make it possible to produce a fuel gas starting from a solid carbon fuel, in particular starting from wood waste, such as that obtained, for example, from sawmills or from logging operations, or starting from agricultural byproducts (straw, etc.), or also from recycled wood. This fuel gas contains carbon monoxide and hydrogen and can subsequently be used for various purposes such as, for example, feed for a gas turbine or an internal-combustion engine, a boiler, or a furnace.
To feed a vessel with fuel, it is known to provide fuel feeding means that are impervious to the gases that will be produced in the vessel. This hermeticity prevents the gases produced in the vessel from entering the systems for fuel storage and feed, so that said gases will travel toward the outlet when the gasifier is in operation.
Use of a lock mechanism at the inlet of the first vessel for this purpose is known.
Patent application WO 2007/081296 mentions a gasifier that includes a rotary valve located in the upper part of the reactor. This device offers proper metering of fuel feed, but it does have the drawback that it is not sufficiently impervious to the gases and requires an additional sealing mechanism upstream, which increases its cost. Moreover, the valve must be able to withstand the high temperatures prevailing in the first vessel when the gasifier is in operation, which requires valves that are particularly expensive.
Other mechanisms only employ a double flap sluice in place of the rotary valve discussed above. Besides the fact that this type of mechanism is less efficient with respect to the metering of material (batch metering), the bottom flap must also withstand said high temperatures and is therefore expensive.
Patent application WO 2001/051591 mentions a gasifier that includes a lock arranged laterally relative to the upper part of the reactor, which can provide good hermeticity against the gases. This patent application also mentions a lateral conduit equipped with an endless screw providing the connection between the lock and the first vessel, which also provides proper metering of the feed of material. However, such a device is expensive and unwieldy. The endless screw is also liable to become fouled, which requires maintenance, and/or to become blocked with pieces of fuel. Moreover, as the end of the screw opens into the vessel, it is subjected to the high temperatures prevailing there when the gasifier is in operation, which makes it necessary to use an expensive screw.
Patent application WO 2010/109501 mentions a gasifier in the form of a vessel, in the upper part of which the fuel is introduced laterally. The fuel is then retained in a drying zone of the vessel by means of a horizontal partition with a central hole. An endless screw is mounted vertically through this hole for transferring the fuel from the drying zone to a pyrolysis zone located directly underneath the horizontal partition. This endless screw opens into the pyrolysis zone and must be able to withstand the high temperatures prevailing there when the gasifier is in operation, which requires screws that are particularly resistant and expensive. The endless screw is also liable to become fouled, which requires maintenance, and/or to become blocked with pieces of fuel.
One aim of the teachings of the present disclosure is to solve, at least partially, the problems with the gasifiers mentioned above.
For this purpose, an example gasifier according to the teachings of this disclosure includes a first vessel that includes a movable pusher mounted between feeding means and a horizontal plate. In this example, the movable pusher is designed for pushing the fuel retained on the horizontal plate into a pyrolysis zone and is positioned or positionable above the horizontal plate.
With this configuration, the horizontal plate forms a thermal screen that protects both the fuel feeding means and the pusher against the high temperatures prevailing in the first vessel (such as, for example, against the radiation and the flames in particular). This makes it possible to use material transfer mechanisms (e.g., the feeding means and/or the pusher) that are less expensive and/or increase their durability and/or their reliability.
A movable pusher of this example also takes up less space vertically and is simpler and more reliable than the vertical endless screw (12) proposed in patent application WO-2010/109501.
In some examples, the movable pusher includes at least one arm extending horizontally above the plate and mounted rotatably about a second vertical axis. A rotary pusher allows better distribution of the fuel on the fuel bed in the pyrolysis zone, which improves the quality of the pyrolysis reaction. This can reduce the tar content of the gas produced.
Some mechanisms were devised in the past for distribution of the fuel on the fuel bed after the fuel is fed into the first vessel.
For example, U.S. Pat. No. 5,755,837 proposes equipping an upper part of a vessel with an inclined channel. However, this device will cause greater accumulation of material at the points where it falls onto the fuel bed. In particular, the level of fuel will be greater at the periphery of the first vessel than in its central part.
Also, British Patent GB 696682, proposes equipping an upper part of a vessel with a mechanism with two perforated rotating plates. Here once again, the fuel will be placed opposite the holes. Moreover, this mechanism is liable to become fouled and/or to become blocked with pieces of fuel.
The example gasifier according to the teachings of this disclosure has advantages over these known devices. For example, the example gasifier disclosed herein includes levelling means that are adapted to at least partially level a top surface of a bed of solid fuel in the pyrolysis zone. The examples disclosed herein include a mechanism acting directly on the fuel bed rather than acting on the pouring of fuel onto the bed, thus reducing or eliminating the drawbacks of the known mechanisms. The levelling means can give even better distribution of the fuel on the fuel bed in the pyrolysis zone, which improves the quality of the pyrolysis reaction.
According to an example disclosed herein, the levelling means includes at least one arm extending horizontally at a level of a top surface of the bed of solid fuel in the pyrolysis zone. In this example, the at least one arm is mounted rotatably about a third vertical axis C. This constitutes a simple, reliable and effective means for distributing the solid material more uniformly on the bed of material in the pyrolysis zone.
These aspects as well as other aspects of the disclosure will be clarified in the detailed description of particular examples disclosed herein, reference being made to the drawings in the figures, where:
a and 7b show schematically a front section and cross section, respectively, of another example a gasifier according to the teachings of this disclosure;
a and 8b show respectively a front section and a cross section of another example gasifier according to the teachings of this disclosure.
The drawings in the figures are not to scale. Generally, similar elements are denoted by similar references in the figures.
Disclosed herein are example gasifiers that include at least one first vertical vessel equipped with feeding means for introducing fuel at a top and along a first vertical axis in the first vessel. The example vessel includes a pyrolysis zone wherein the fuel undergoes pyrolysis, a combustion zone for burning pyrolysis gases from the pyrolysis zone, a reduction zone for gasifying the carbonized fuel from the pyrolysis zone, and an outlet for collecting gases produced in the reduction zone. The example first vessel further comprising a horizontal plate mounted fixedly between the feeding means and the pyrolysis zone for receiving and retaining the fuel fed into the vessel.
Also disclosed herein are example units for production and combustion of gas that include the example gasifiers disclosed herein for producing the gas.
The examples disclosed herein relate to a co-current fixed-bed gasifier, formed by a single vessel simultaneously including the pyrolysis zone, the combustion zone and the reduction zone. The teachings of this disclosure, however, are not limited to this type of gasifier but relates to all gasifiers having features of the claims, such as for example counter-current gasifiers, and/or gasifiers that include several vessels in succession, the first vessel being the one where the reactions of pyrolysis of the fuel take place.
The examples disclosed herein use solid biomass as an example of fuel, in some examples, any other type of solid carbon fuel will also be suitable.
In some examples, the inlet lock (5) has multiple other forms, for example a rotary valve and/or a double flap sluice and/or any other suitable introducing means.
The biomass (2), for example wood chips, is introduced into the vessel (4) at the top via the inlet lock (5). The biomass (2) arrives - via the intermediate device (50, 51) described in more detail below - in the pyrolysis zone (10), where the biomass (2) decomposes, under the effect of the heat, into volatile matter and into a carbon-rich solid residue generally called “char” or “coke”. This reaction typically takes place in a temperature range between 300° C. and 700° C.
In order to reach these temperatures, the vessel includes first means for admission of a pyrolysis agent (11)—for example one or more nozzle(s) opening laterally in the vessel at the level of the pyrolysis zone—and which make it possible to introduce a gas there which will supply, directly or indirectly, the energy required for decomposition of the biomass into volatile matter and “char”. The pyrolysis agent can be, for example, a reactive gas containing oxygen which, by burning a fraction of the biomass or of the products of decomposition of the biomass, will release the energy to implement, effect or perform pyrolysis. The pyrolysis agent may also be an inert gas (such as carbon dioxide, nitrogen, steam) which, when preheated, will supply the energy to implement, effect or perform pyrolysis. It can also be a combination of these two types of gases.
The “char” is then transferred to the reduction zone (30) by means that are well known, for example those described in European Patent Application EP11171156.
The volatile matter (also called “pyrolysis gases”) entering the combustion zone (20) is burned there partially or completely. To promote this combustion, the example vessel includes second means for admission of a gasifying agent (21). These second means of admission can include, for example, one or more nozzle(s) opening laterally in the vessel at the level of the combustion zone. “Gasifying agent” is to be understood as a gas capable of reacting with the carbon and/or with the hydrogen contained in the solid fuel. Therefore the gasifying agent can be, for example, the ambient air, a gas with higher oxygen concentration, steam, carbon dioxide or else a mixture of these gases. This combustion produces carbon dioxide (CO2), water (H2O), and heat. Typically, temperatures above 1100° C. can be reached in the combustion zone.
The “char” that was transferred into the reduction zone will react with the combustion products to form carbon monoxide (CO) and hydrogen (H2).
In the case, for example, of an autothermal reaction of lignocellulosic materials—such as wood—and the use of ambient air at ambient temperature as gasifying agent, this reaction typically takes place in a temperature range between 300° C. and 800° C. However, it will be possible for this temperature to be higher and reach or even exceed 1300° C. in the case when a fuel richer in carbon is used and/or when preheated reagents are used. The gases produced by this reaction will be collected at the outlet (6) of the reactor, which is located at the bottom of the vessel (4). At the outlet (6), there is a combustible gas including about 15% to about 30% of CO, about 10% to about 25% of Hz, about 0.5 to about 3% of CH4, about 5% to about 15% of CO2 and about 49% of N2 when ambient air is used as gasifying agent.
The ash can be collected at the bottom (40) of the vessel.
Turning to the example device (50, 51) that is located just below the inlet lock (5), this device includes a horizontal plate (50) mounted fixedly between the inlet lock (5) and the pyrolysis zone (10). The example plate (50) is positioned and dimensioned to receive and retain, at least partially, the fuel (2) introduced into the vessel (4) via the inlet lock (5).
In some examples, the plate is positioned and dimensioned so that the plate retains the fuel completely and so that the latter can only flow to the pyrolysis zone under an external action, such as under the action of the pusher described below.
For this purpose, the position and size of the plate will be adapted to the flow properties of the fuel used, in particular its slope angle (e.g. for wood chips, the slope angle is of the order of 60°).
The example device further includes a movable pusher (51) mounted between the inlet lock (5) and the horizontal plate (50). The pusher (51) is positioned above the horizontal plate (50), so that the horizontal plate forms a thermal screen protecting the pusher from the heat prevailing underneath the plate when the gasifier is operating. As shown in the
Here, one end of the example arm is connected to a shaft of a motor (M) for rotating the arm. The movable pusher (51, 52) is positionable above the horizontal plate (50), which allows the plate to perform its role of thermal screen when the pusher is effectively positioned above the plate. In this example, the pusher can temporarily project beyond the plate when the motor (M) is started, and the pusher can at some point in time be positioned above the plate.
In some examples, the motor (M) is equipped with reduction gearing in order to increase the torque and the precision of the movement transmitted to the first arm. In some examples, the motor (M) is mounted above the plate so that the plate also forms a thermal screen with respect to the motor. Also, in some examples, the motor (M) is mounted outside the vessel, in which case the motor shaft passes through the upper part of the vessel via a seal or a sealed bearing and is connected to the first arm (case not shown).
In some examples, the second axis (B) is offset relative to the first axis (A).
In some examples, the gasifier includes a motor (M) for driving the at least one arm (52) of the pusher in rotation about the second axis (B) and first controlling means (60) suitable for controlling the motor (M) to give a rocking, oscillation or rotating motion to the at least one arm (52) about the second axis (B). For this, it is possible for example to use a motor with reversible rotational directions such as, for example, a direct-current motor.
This makes it possible to cause the biomass to overflow from a first end (56) of the plate when the motor rotates in a first direction of rotation and to cause the biomass to overflow from a second end (57) of the plate, opposite the first side, when the motor rotates in a second direction of rotation opposite to the first direction of rotation. This makes it possible to obtain a more uniform distribution of the fuel on the bed in the pyrolysis zone.
In some examples, the first controlling means (60) are able to set an initial angular position (P1) as well as an amplitude (A1) of the rocking, oscillation or rotating motion, which allows even more precise control of the transfer of biomass from the plate to the pyrolysis zone. For this purpose, it is possible for example to employ a stepping motor equipped with an encoder wheel for the angular position of the motor shaft as well as a suitable controller.
Here, the example first vessel (4) further includes levelling means (70) suitable for at least partially levelling a top surface (80) of the bed of biomass in the pyrolysis zone (10). As shown in the figure, these levelling means includes for example a horizontal jack whose end is equipped with a scraper. The example scraper is located at the level of the top surface (80) of the bed of biomass in the pyrolysis zone (10). In some examples, the scraper is in the form of a rake that has teeth directed downwards. Actuation of the jack makes it possible to level the top surface (80) of the bed of biomass.
Here, one end of the levelling arm (71) is connected to a shaft of a motor (M) for rotating the arm (71). In some example, the motor (M) is equipped with reduction gearing in order to increase the torque and the precision of the movement transmitted to the arm (71). Operation of the motor makes it possible to level the top surface (80) of the bed of biomass when the example gasifier is in operation.
In some examples, the levelling means includes six arms mounted radially at intervals of 60 degrees around a rotating shaft with axis C.
In some examples, axis B and axis C coincide. Also, in some examples, the at least one arm (52) of the pusher and the at least one arm (71) of the levelling means are mounted on one and the same rotating shaft (75). One such example is presented in
As shown in
In such a configuration, the arm (52) of the pusher and the levelling arm (71) are, in some examples, mounted in opposition, i.e. with angular offset of 180 degrees, as can be seen more clearly in
a and 8b show a front section and a cross section, respectively, of another example gasifier according to the teachings of this disclosure. Here, the example plate is formed by a fixed plate (50) which extends substantially over the whole cross section of the vessel (4). The plate (50) is equipped with at least one opening (58) through which the pusher (52) can push the fuel (2) retained by the plate so that the fuel (2) falls by gravity into the pyrolysis zone (10). The opening (58) is offset relative to the means of admission (5) so that the fuel cannot fall directly into the pyrolysis zone. Otherwise this gasifier is similar to those disclosed above.
As shown in
Many other forms of example plate and of the example pusher can be envisaged, provided that the plate is able to retain the fuel delivered by the feeding means (5) and that the pusher (52) is able to push the retained fuel and cause the fuel to fall by gravity onto the pyrolysis zone (10).
The teachings of this disclosure also relate to a unit for production and combustion of gas, comprising a gasifier as disclosed and/or claimed in the present application. The example unit may be, for example, an assembly that includes a gasifier as disclosed above and an internal-combustion engine, the outlet (6) of the gasifier being connected to a fuel admission system of the internal-combustion engine.
The present disclosure has been described in relation to specific example that are given purely for purposes of illustration and must not be regarded as limiting. Generally a person skilled in the art would understand that the present disclosure is not limited to the examples illustrated and/or described and disclosed above.
The presence of reference numbers to the drawings cannot be regarded as limiting, including when these numbers are stated in the claims.
The use of the verbs “comprise”, “include”, “contain”, or any other variant, as well as their conjugations, does not in any way exclude the presence of elements other than those mentioned.
The use of the indefinite article “a”, or the definite article “the”, for introducing an element does not exclude the presence of a plurality of these elements.
The present disclosure can also be described as follows: a gasifier of solid carbon fuel (2) comprising at least one first vertical vessel (4) and feeding means (5) for introducing the fuel (2) into an upper part of the first vessel above a pyrolysis zone (10), the pyrolysis zone being a zone where the fuel introduced undergoes pyrolysis to produce pyrolysis gases and carbonized fuel. The gasifier also comprises a combustion zone (20) for burning the pyrolysis gases, a reduction zone (30) for gasifying the carbonized fuel from the pyrolysis zone (10) in order to produce synthesis gases and ash, and an outlet (6) for collecting the synthesis gases. The first vessel (4) comprises a fixed horizontal plate (50) mounted between the feeding means (5) and the pyrolysis zone (10) so that the fuel introduced is retained there, as well as a movable pusher (51) mounted between the feeding means (5) and the plate (50) for transferring the fuel retained on the plate to the pyrolysis zone (10). The plate (50) forms a thermal screen at least partially protecting the feeding means (5) and the movable pusher (51) against the high temperatures prevailing in the first vessel (4) when the latter is in operation.
Although certain example methods and apparatus have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11180062.9 | Sep 2011 | EP | regional |
This patent is a continuation of International Patent Application Serial No. PCT/EP2012/067349, filed on Sep. 5, 2012, which claims priority to European Patent Application 11180062.9, filed on Sep. 5, 2011, both of which are hereby incorporated herein by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2012/067349 | Sep 2012 | US |
| Child | 14196534 | US |
