EP0045256A2 - Process and apparatus for the production of gas from bio-mass materials - Google Patents

Abstract

Gases which have passed through the materials being treated are extracted (at 13), these gases are recycled and heated to produce hot gases which are injected (at 18) into the treatment chamber (10). Practically all of the materials being treated are traversed by a gas flow in the transverse direction (F) relative to the longitudinal direction (A) of the materials in the chamber (10).

Description

The subject of the present invention is in particular a process for gasifying materials of plant origin in a treatment chamber, a process of the type according to which gases which have passed through materials are being extracted, these gases are recycled and they are reheated to produce hot gases which are injected into the treatment chamber.

Vertical gasifiers have already been known for a long time in which gases are taken up at the top of the column of materials being treated in order to be, after combustion, recycled to a certain level of the gasifier.

With these gasifiers, the complete treatment of materials is very slow, and the injection of gases into the treatment chamber is not carried out uniformly and very efficiently.

In patent application FR 78 31 356, it is proposed to remedy these drawbacks by arranging the chamber there horizontally so as to allow the formation of a natural slope at the front of which the hot gases are injected uniformly over a whole section. transverse of the chamber. Recycling is carried out at high temperature (more than approximately 500 ° C) by establishing forced circulation, which makes it possible to speed up the treatment by passing the materials through a very hot gas flow. In addition, the reduction in the duration of the treatment makes it possible to design gasifiers of smaller size.

The object of the present invention is to further improve the treatment of materials by making them pass optimally through the heated gas flow resulting from recycling, this without necessarily imposing a particular orientation of the treatment chamber.

This object is achieved by the fact that, in accordance with the invention, almost all of the treatment materials arranged in a thin layer are passed through by a ga zeux in direction substantially transverse to the longitudinal direction of progression of the materials being processed in the chamber.

The materials being treated being traversed in their relatively small thickness by the gas flow, this reaches before being too cold all the materials of the layer contained in the treatment chamber.

These materials form a thin layer, that is to say a layer of thickness less than about 10 to 30 times the average size of the particles of material to be treated. This avoids unnecessary pressure drops which would be produced by passing through an additional layer of material within which the chemical reactions would be slow.

Heating of the recycled gases can be carried out by combustion of a part of these combined with combustion air or oxygen or by passage through an electric arc, or by any other suitable means.

According to a particular feature of the process according to the invention, gases from different zones located along the treatment chamber are extracted separately. It is then possible to adjust the flow of extracted gases in the different zones separately. The action of the hot gases can thus be optimized as a function of the flow characteristics of the gases through the layer of material crossed, that is to say in particular as a function of the thickness of this layer and / or of the grain size. subjects.

According to a preferred embodiment of the invention, the materials being processed are advanced in the horizontal direction or slightly inclined relative to the horizontal and the material bed is passed through from its upper surface to its lower surface by hot gas flow.

However, in the case of a horizontal treatment chamber, it is also possible to direct the hot gas flow from the lower surface of the bed of materials to its upper surface, in order to fluidize this bed.

Finally, it is also possible to carry out the process according to the invention with a vertical or practically vertical treatment chamber, that is to say a chamber in which the progression of the materials being treated takes place under the sole effect of gravity.

The object of the present invention is also to provide an installation making it possible to implement the method according to the invention.

This object is achieved by an installation comprising a treatment chamber in which the materials being treated progress longitudinally, an outlet for sampling the gases produced by the installation, extraction means through a wall of the gas chamber having passed through materials being treated, a device for recycling the extracted gases, and means for heating the recycled gases and injecting them into the treatment chamber, installation in which, in accordance with the invention, the treatment chamber present at the at least one longitudinal gas permeable wall which separates the treatment chamber from at least one extraction chamber, and the injection means and the extraction chamber or chambers are located along two opposite longitudinal faces of the treatment in order to make practically all of the materials being treated pass through a gas flow of direction substantially transverse to the direction of progression of the materials to be treated in the treatment chamber.

• - la figure 1 est une vue schématique en élévation et en coupe d'une installation conforme à l'invention,
• - la figure 2 est une vue en coupe suivant la ligne II-II de la figure 1,
• - les figures 3 et 4 sont deux vues schématiques en élévation et en coupe de deux autres modes de réalisation d'une installation conforme à l'invention, et,
• - la figure 5 est une vue en coupe suivant la ligne V-V de la figure 4.

Other particularities and advantages of the method and of the installation in accordance with the invention will emerge on reading the description given below, by way of indication, but not limitation, with reference to the accompanying drawings. on which ones :

• FIG. 1 is a schematic view in elevation and in section of an installation according to the invention,
• FIG. 2 is a sectional view along line II-II of FIG. 1,
• FIGS. 3 and 4 are two schematic views in elevation and in section of two other embodiments of an installation according to the invention, and,
• - Figure 5 is a sectional view along line VV of Figure 4.

Figures 1 and 2 illustrate an installation according to the invention with a treatment chamber 10 of rectangular cross section in which the materials to be treated are introduced at the rear end 10a. The chamber 10 extends longitudinally in the horizontal direction or slightly inclined relative to the horizontal downwards and forwards 10b. The possible inclination of the chamber serves to facilitate the progression of the materials forward, without this progression being possible by the sole effect of gravity. In the example illustrated, the materials to be treated progress in the chamber 10 under the effect of a pusher 11 which is driven back and forth with slow advance and rapid recoil. The loading of the materials to be treated is carried out through a loading opening behind the processing chamber. Other methods could be used to ensure the progression of the materials in the chamber 10, for example a movable grid, scraper bars, vibrating grids, or even fluidization.

The bottom wall 12 of the chamber 10 is permeable to gases from the rear end 10a of the chamber and practically over the entire length of the latter. This wall is for example constituted by a grid 19 which separates the interior of the chamber 10 from several extraction chambers 13. The chambers 13 are arranged side by side substantially along the entire length of the chamber 10 and are separated from each other. other.

As can be seen in Figure 1, the bars of each grid 19 are arranged in longitudinal planes being slightly inclined upwards towards the front of the chamber 10. More precisely, the rear end of each bar is located slightly below the top of the rear wall of the corresponding chamber 13 while the front end of each bar is situated slightly above the front wall of this chamber. Thus, the materials being processed do not encounter obstacles liable to hinder their progress. A recycling duct 14 provided with a suction fan 15 is connected to each chamber 13. At its other end, each recycling duct 14 leads to a particular injector 16 also receiving combustion air or oxygen through a line 17 supplying all the injectors. Each injector 16 opens in a dilution chamber 18 which communicates with the treatment chamber through an opening 18a in the upper wall thereof. It will be noted that the chamber 10 is open practically over its entire upper face, the chambers 18 being arranged side by side along the chamber 10.

One of the chambers 13 constitutes the outlet of the gasometer and is provided with an outlet for the gases produced by the installation. This outlet chamber may possibly not be associated with a recycling conduit.

The chambers 13 are provided, as necessary, with devices for extracting the ashes having passed through the grids 19.

In the example illustrated, each extraction chamber 13 is connected by its particular recycling conduit 14 to a particular injector 16 which occupies, in the row of injectors, the same rank as that occupied by the chamber 13 in the row of chambers extraction.

As a variant, other connection possibilities can be chosen between chambers 13 and injectors 16. It is even conceivable to mix the gases extracted from the different chambers 13 to supply injectors distributed along the chamber 10.

The operation of the installation is as follows. The materials to be gasified are introduced into the chamber. These are materials of plant origin, such as charcoal, wood, coconut shells or other vegetable waste possibly agglomerated. The materials successively undergo drying, pyrolysis and gasification. The gases produced by the installation are collected at the outlet of the chamber 13 provided for this purpose. This is placed downstream of the pyrolysis zone in the direction of progression of the materials to be treated, which makes it possible to collect gases free from the pyrolysis tars and in an area where the carbon layer is homogeneous and sufficient, if the '' we seek to obtain gases with a high lower calorific value. The tars are transported by the recycled gases having passed through the pyrolysis zone and are then removed by cracking or combustion at the outlet of the injectors 16.

When the installation is started, the thermal reaction is initialized by means of burners (not shown) producing the necessary hot gases. After the start-up phase, the burners are shut down and the hot gases are produced by means of the gases which are drawn into the extraction chambers then which are recycled and combined with combustion air or oxygen in the injectors 16. The hot gases are produced in the chambers 18 and attack the upper face of the bed of materials contained in the chamber 10. It will be noted that the chambers 18 as well as the free space between the upper surface of the bed of materials and the upper limit of the room allow dilution of the combustion gases before their penetration into the materials to be treated.

At the front end 10b gas tight of the chamber 10, the part of the ashes and non-combustible bodies is collected constituting the gasification residues which have not fallen through the grids 19.

As illustrated in FIGS. 1 and 2, the hot gas flow (arrows F) generated by the recycling and the exit of the gases passes simultaneously through the entire bed of materials being treated, perpendicular to the direction of advance A of the materials being processed treatment. Thus, the short path of the gas flow allows it to reach with a high temperature all the materials forming the bed throughout its thickness. In this regard, it is desirable that this thickness does not exceed about 10 times for wood and 20 to 30 times for coal the average size of the particles of material to be treated.

It will be noted that the transverse gas flow is established practically over the entire length of the chamber 10, which makes it possible to process the materials quickly and consequently limit the size of the installation.

To optimize the action of the hot gas flow over the entire length of the chamber, it is possible to adjust the gas flow extracted in each chamber 13 as a function of the thickness and / or the particle size characteristics of the materials located in the adjacent zone of chamber 10. This adjustment is made for example by adjusting the speed of each fan 15.

An efficient and rapid treatment is obtained by recycling at a high temperature, that is to say by recycling gases whose temperature is preferably above 500 ° C.

The installation described above with reference to Figures 1 and 2 is of the fixed bed type. It is the preferred embodiment of the invention.

However, the invention can also be applied to installations of the fluidized bed type. For this, it suffices, in the installation illustrated in FIGS. 1 and 2, to reverse the positions of the extraction chambers 13, on the one hand, and of the injectors 16 with the dilution chambers 18, on the other hand go.

The hot gas flow then crosses the bed of materials from bottom to top. It then performs the treatment of the materials and the fluidization of the bed of these materials.

FIGS. 3 to 5 illustrate two other embodiments of the invention using vertical type treatment chambers in which the materials to be treated progress by gravity only.

In the case of the installation illustrated in FIG. 3, we find, as in the installation shown in FIGS. 1 and 2, extraction chambers 33 which are separated from the vertical treatment chamber 30 by a permeable partition 32 gas. One of the chambers 33 is used as an outlet for the gases produced by the installation.

The chamber 30 has a rectangular cross section and its lower end wall is constituted by a grid 39 through which fall the gasification residues.

The chambers 33 are located along one of the two longitudinal walls of the chamber. Along the opposite wall, dilution chambers 38 are arranged which communicate with the interior of the chamber 30 through a gas-permeable wall 31, for example a grid or a perforated sheet, like the wall 32.

Injectors 36 open into the chambers 38. These injectors are connected to the ex chambers traction 33 by recycling conduits (not shown) fitted with ventilator-aspirators establishing forced circulation in these conduits from the chambers 33 to the injectors 36. The gases thus extracted and recycled are partly combined with air or l combustion oxygen supplied via a line 37 to the various injectors 36.

When the installation is in operation, a substantially horizontal hot gas flow is established almost over the entire height of the chamber 30 (arrows F), perpendicular to the direction of advance A of the materials to be treated.

In the case of the installation illustrated in FIGS. 4 and 5, the vertical treatment chamber 40 has a cross section of annular shape delimited laterally by two concentric external 41 and internal 42 walls and lower by a horizontal grid 49.

The inner wall 42 is gas permeable over the entire height of the chamber 40 and delimits a central chamber 48 closed at its upper end by a wall 48a and open at its lower end.

The outer wall 41 is permeable to gases from the upper end of the chamber 40 and over practically the entire height of the latter. This wall 41 separates the interior of the chamber 40 from an extraction chamber 43 which is closed at its upper part by a horizontal annular wall 43a and which extends from the top of the chamber 40 to a lower wall horizontal 43b located below and at a distance from the bottom of the chamber 40.

The outer wall 41 is extended downwards by a solid cylindrical wall to a horizontal end wall 41a provided with an axial opening 41b.

In the space surrounded by the wall 41a, between the wall 41b and the bottom of the chamber 40, there is a fan 45, a nozzle 47a, disposed above the fan 45 and an annular ash boot 50 with inclined bottom 50a arranged immediately below the grid 49.

The nozzle 47a opens axially upwards and is connected by a conduit 47, which passes through the chamber 43 in a sealed manner, to an external supply of air or combustion oxygen.

The ash box 50 is connected to an inclined evacuation passage 51 which passes through the chamber 43 in a leaktight manner and opens to the outside.

The gases extracted in the chamber 43 are sucked by the fan 45 in the recycling duct 44 formed between the walls 43b and 41b and are introduced into the central chamber 48 through the annular space surrounding the nozzle 47a and closing the injector 46 .

The gases heated at the outlet of the injector 46 are distributed in the chamber 48. The suction in the chamber 43 produces a transverse hot gas flow (arrows F) through the entire bed of materials located in the chamber 40. These materials are introduced at the top of the chamber 40 delimited by a solid upper extension of the wall 41, above the upper wall 48a closing the dilution chamber 48.

The gases produced by the installation are sampled in an annular outlet chamber 43 ′ which is adjacent to the wall 41 and which is located inside the extraction chamber 43 while being isolated from it. . The chamber 43 'is located at a level below that of the pyrolysis zone in the chamber 40. A pipe (not shown) communicates the chamber 43' with the outside of the extraction chamber.

In the embodiment which has just been described, a single fan 45 is provided and is arranged below the dilution chamber 48. As a variant, several fans may be arranged at different levels from the dilution chamber, in particular in depending on the height of the installation.

Furthermore, in the installations shown in FIGS. 3 and 4, the gas flow passing through the column of materials is oriented either transversely in one direction (FIG. 3), or radially only from the inside to the outside. It is however possible, in the context of the invention, to pass the column of materials through a gas flow whose direction is always transverse but whose direction may differ in different sections of the column of materials. This can be obtained, in the case for example of FIG. 3, by placing the extraction chambers, as well as the dilution chambers, on each of the opposite sides 31, 32 of the chamber 30 and not on the same side. . Thus, it is possible to make the column of materials pass through the gas flow alternately in one direction and in the other in superimposed sections of said column by arranging, on each side 31, 32, alternately an extraction chamber and a dilution. Other arrangements may be chosen, for example, to circulate the gas flow in one direction for half the height of the column of materials and in the other direction for the other half.

Finally, although it has been envisaged, in all the embodiments described, to reheat the recycled gases by combustion of a fraction of them, other reheating modes could be used as has already been mentioned. However, regardless of the reheating process used, it is important to limit the temperature of the hot gases to a value such that the ash of the materials being treated does not melt. Depending on the nature of these materials, the maximum limit value is from 800 ° C to 1200 ° C or even more in some cases. When the heating of the gases takes place by combustion of a part of them, the temperature limitation is obtained in particular by dilution with the unburned recycled gases.

Claims (18)

1. Process for the gasification of materials of plant origin in a treatment chamber, method according to which gases having passed through materials in the course of treatment and having a temperature preferably above 500 ° C. are extracted, these are recycled gases and they are heated to produce hot combustion gases which are injected into the treatment chamber,
characterized in that practically all of the materials under treatment arranged in a thin layer are passed through by a gas flow in a direction substantially transverse to the longitudinal direction of progression of the materials being treated in the chamber. 2. Method according to claim 1, characterized in that one passes through the gas flow a layer of materials of thickness limited to about 10 to 30 times the average size of the particles of the materials to be treated. 3. Method according to any one of claims 1 and 2, characterized in that the temperature of the hot gases is limited to a value such that the ash of the materials being treated does not melt. 4. Method according to any one of claims 1 to 3, characterized in that the materials being treated are passed through by a gas flow of the same direction and direction throughout all of said materials. 5. Method according to any one of claims 1 to 3, characterized in that the materials being treated are passed through by a gas flow having the same transverse direction but different directions in different slices of the assembly of said materials. 6. Method according to any one of claims 1 to 5, characterized in that gases from different zones located along the treatment chamber and the flow of extracted gases in the different zones is adjusted separately. 7. Method according to any one of claims 1 to 6, during which the treated materials progress in a horizontal direction or slightly inclined relative to the horizontal, characterized in that said gaseous flow crosses the bed of materials of its upper surface towards its lower surface. 8. Method according to any one of claims 1 to 6, during which the treated materials progress in a horizontal direction or slightly inclined with respect to the horizontal, characterized in that said gas flow crosses the bed of materials from its lower surface. towards its upper surface to fluidize the bed of materials. 9. Plant for the gasification of materials of plant origin, comprising a treatment chamber in which the materials being treated progress longitudinally, an outlet for sampling the gases produced by the installation, means of extraction through a wall the gas chamber having passed through materials being treated, a device for recycling the extracted gases, and means for heating the recycled gases and injecting them into the treatment chamber,
characterized in that the treatment chamber has at least one longitudinal gas-permeable wall which separates the treatment chamber from at least one extraction chamber, and the injection means and the extraction chamber or chambers are located on the along two opposite longitudinal faces of the treatment chamber in order to make practically all of the materials being treated pass through a gas flow of direction substantially transverse to the direction of progression of the materials to be treated in the treatment chamber. 10. Installation according to claim 9, characterized in that the extraction means comprise several extraction chambers separated from each other. 11. Installation according to claim 10, characterized in that the extraction chambers are located along the same longitudinal face of the treatment chamber. 12. Installation according to claim 10, characterized in that the extraction chambers are arranged on two opposite sides of the treatment chamber. 13. Installation according to any one of claims 10 to 12, characterized in that particular suction means are associated with each extraction chamber and are individually adjustable. 14. Installation according to any one of claims 9 to 11, in which the treatment chamber is horizontal or slightly inclined relative to the horizontal, characterized in that the extraction means are located on the side of the lower face of bedroom. 15. Installation according to any one of claims 9 to 11, in which the treatment chamber is horizontal or slightly inclined relative to the horizontal, characterized in that the extraction means are situated on the side of the upper face of bedroom. 16. Installation according to any one of claims 9 to 13, wherein the treatment chamber is substantially vertical, characterized in that the 'treatment chamber has a rectangular cross section. 17. Installation according to any one of claims 9 to 13, in which the treatment chamber is substantially vertical, characterized in that the cross section of the treatment chamber has a annular shape. 18. Installation according to claim 17, characterized in that the treatment chamber is surrounded by an annular extraction chamber which contains an outlet chamber for the gases produced by the installation.

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