EP3099764A1

EP3099764A1 - Device for unloading bulk material and facility comprising a container provided with such an unloading device

Info

Publication number: EP3099764A1
Application number: EP15701045.5A
Authority: EP
Inventors: José Barros; Luiz CARVALHO
Original assignee: Lmk Energy
Current assignee: Lmk Energy
Priority date: 2014-01-27
Filing date: 2015-01-27
Publication date: 2016-12-07
Also published as: FR3016867A1; FR3016867B1; WO2015110662A1

Abstract

The invention relates to a device for unloading bulk material, which comprises a plurality of elongate retaining elements (12, 14) extending parallel to one another in a longitudinal direction (X), forming a support surface (16) for the material, intended for being in contact with the material, in which the retaining elements (12, 14) are arranged next to one another in a transverse direction (Y) perpendicular to the longitudinal direction (X) while also defining interstices therebetween, intended for allowing the flow by gravity of at least one portion of the material, in which at least two retaining elements (12, 14) are translatably movable relative to one another in the longitudinal direction (X). The invention can be used in a storage silo or in a biomass roasting column.

Description

Device for unloading bulk material and installation comprising a container provided with such an unloading device

The present invention relates to the field of unloading bulk material, in particular at the outlet of a container, for example a bulk material storage container such as a storage silo or a biomass roasting container.

It is possible to roast lignocellulosic biomass for drying and extract some of the volatile organic compounds while retaining the most energetic compounds, so as to make a fuel. Biomass is roasted for example by a gravity flow of biomass in a roasting container in which hot gases circulate against the flow of biomass.

The characteristics of the roasted biomass depend in particular on the time of exposure to the hot gases in the container. It is therefore desirable to have a container unloading device for ensuring a controlled flow of biomass at the outlet of the container.

DE 26 42 002 and WO 201 1/076444 A1 disclose unloading devices of a container comprising bulk material support assemblies formed of parallel rollers retaining the material while permitting the passage of material in interstices provided between the rollers , the rollers being rotatable about their respective axes to control the flow of the material.

To ensure satisfactory roasting of the biomass, it is desirable to ensure a uniform flow of biomass, avoiding areas of stagnation or areas of compression of the biomass.

One of the aims of the invention is to propose a device for unloading bulk material which is reliable and economical and which makes it possible to ensure a uniform flow of the material.

For this purpose, the invention proposes a device for unloading bulk material, comprising a plurality of elongate retaining elements extending in parallel in a longitudinal direction by forming a support surface for the material intended to be in contact with the material. material, wherein the retaining elements are arranged side by side in a transverse direction perpendicular to the longitudinal direction by defining between them interstices for allowing the gravity flow of at least a portion of the material, wherein at least two elements retainers are movable in translation relative to each other in the longitudinal direction.

The relative movement of the retaining members in the longitudinal direction causes disintegration of bulk material particles permitting passage of particles between the retaining members and / or movement of particles to an edge of the support surface where the particles can fall. The displacement characteristics of the retaining elements (amplitude, speed, frequency, etc.) make it possible to easily control the flow of the material.

According to particular embodiments, the unloading device comprises one or more of the following characteristics, taken separately or in any technically possible combination:

- At least two retaining elements are movable in translation in the longitudinal direction in opposite directions;

- At least one retaining element is movable in continuous translation in the longitudinal direction;

- It comprises retaining elements movable in translation in the longitudinal direction in a first direction alternating in the transverse direction with retaining elements movable in translation in the transverse direction in a second direction opposite to the first direction;

each movable retaining element is movable in continuous translation in the longitudinal direction;

each movable retaining element is a retaining strand of a flexible endless member;

- It comprises first endless members and second endless members driven so that the retaining strands of the first endless bodies move in translation in the longitudinal direction relative to the retaining strands of the second endless members;

the first endless members and the second endless members are driven in such a way that the retaining strands of the first endless members move in translation in the longitudinal direction in the opposite direction of the retaining strands of the second endless members;

- The retaining strands of the first endless members are alternated in the transverse direction with the retaining strands of the second endless members;

the first members and the second endless members are wound on a first shaft and a second shaft which are mutually parallel and counter-rotating, each first endless member cooperating with a fixed wheel of the first shaft and a idler wheel of the second shaft, and each second endless member cooperating with a idler wheel of the first shaft and a fixed wheel of the second shaft;

- The first endless members are wound on a first drive shaft and a first countershaft, and wherein the second endless members are wound on a second drive shaft and a second countershaft; each endless member has a retaining strand defining a retaining member and a return strand along a path away from the retaining surface;

each endless organ is an endless chain.

The invention also relates to an installation comprising a container for receiving bulk material, the container being provided with an outlet, and an unloading device disposed across the outlet so that bulk material is retained by the surface of the material. support of the unloading device.

In one embodiment, the installation comprises a container in the form of a column and a gas circuit for injecting hot gases at the bottom of the container and recovering hot gases at the top of the container.

In one embodiment, the gas circuit is connected to the closed loop gas circulation container, the gas circuit comprising at least one heat exchanger for heating the gases flowing in the gas circuit by heat exchange with a source. external heat.

The invention and its advantages will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which:

- Figure 1 is a side view of an unloading device;

- Figure 2 is a top view of the unloading device;

- Figure 3 is a top view of an unloading device according to a variant;

- Figure 4 is a schematic view of a roasting facility comprising an unloading device; and

- Figure 5 is a schematic view of another roasting facility comprising an unloading device.

The unloading device 2 of FIGS. 1 to 3 is disposed at an outlet opening 4 of a container 6 for controlling the gravity flow of a material 8 in bulk contained in the container 6 through the outlet opening 4 .

The unloading device 2 comprises a perforated extraction system 10 adapted to retain at least a portion of the material 8 in the container 6 while allowing gravity flow of at least a portion of the material 8 through the extraction system 10, in a controlled manner, in a vertical direction Z.

The extraction system 10 can also allow the flow of a gaseous flow through the extraction system 10, for example countercurrent to the gravitational flow of the material 8. The extraction system 10 extends across the outlet opening 4 by closing it. The material 8 contained in the container 6 is supported and retained by the extraction system 10. The extraction system 10 prevents the free flow of the material through the outlet opening 4.

The extraction system 10 comprises a plurality of elongate retaining elements 12, 14 extending parallel to each other in a longitudinal direction X. The longitudinal direction X is perpendicular to the vertical direction Z. The retaining elements 12, 14 form together a perforated support surface 16 intended to be in contact with the material 8. The material 8 rests on the support surface 16. The support surface 16 forms a bottom of the container 6.

The retaining elements 12, 14 are coplanar. The support surface 16 extends in a horizontal plane. The plane of extension of the support surface 16 is perpendicular to the vertical direction Z. The outlet opening 4 extends in a substantially horizontal plane.

The retaining elements 12, 14 are arranged side by side in a transverse direction Y perpendicular to the longitudinal direction X. The transverse direction Y is perpendicular to the vertical direction Z. The retaining elements 12, 14 are spaced from each other according to the transverse direction Y. The retaining elements 12, 14 delimit transversely between them interstices 17. Each gap 17 is delimited between two adjacent retaining elements 12, 14.

The interstices 17 allow the passage of at least a portion of the material 8 through the support surface 16.

The size of the interstices 17 is a function of the size or the granulometry of the bulk material to be extracted. By way of example, in the case of extraction of roasted wood, the gap 17 which is delimited between two adjacent retaining elements 12, 14 is defined according to the particle size standards defined in the standards of G100, G50, G30 or G20. from the AWWA (American Water Waste Association).

The extraction system 10 has retaining elements 12, 14 movable in translation along the longitudinal direction X with respect to each other.

More specifically, the extraction system 10 has here retaining elements 12, 14 movable in translation in the longitudinal direction X in opposite directions.

The extraction system 10 has retaining elements 12 moving in translation along the longitudinal direction X in a first direction (to the right in FIG. 3) and retaining elements 14 moving in translation in the direction longitudinal X in a second direction (to the left in Figure 3) opposite the first direction.

The retaining elements 12 moving in the first direction are alternated in the transverse direction Y with the retaining elements 14 moving in the second direction.

Each retaining element 12, 14 moves in the opposite direction of the or each adjacent retaining element 12, 14.

The retaining elements 12 moving in the first direction and the retaining elements 14 moving in the second direction preferably move at the same speed.

In the illustrated example, each movable retainer 12, 14 is a strand of an endless member 18, 20 flexible.

The endless members 18, 20 flexible here are endless chains. Endless chains are suitable for lignocellulosic biomass, especially wood or bagasse.

Alternatively, the flexible endless members are endless belts. Endless belts are suitable for biomass with high flowability, for example seeds or cereals.

Each endless member 18, 20 comprises at least one retaining strand 12, 14 defining a retaining element, and at least one return strand 22, 24 traveling in a return path away from the support surface 16 formed by the retaining strands 12, 14.

Each retaining element is here a strand of an endless member 18, 20 respectively. Each endless member 18, 20 here comprises exactly one retaining strand 12, 14.

The retaining strand 12, 14 and the return strand 22, 24 of each endless member 18,

20 are here parallel to each other. The retaining strands 12, 14 are coplanar. The return strands 22, 24 are coplanar. The retaining strands 14, 12 extend in an upper horizontal plane and the return strands 22, 24 extend in a lower horizontal plane.

The retaining strand 12, 14 of each endless member 18, 20 is aligned vertically with the return strand 22, 24 of this endless member 18, 20 being located above the return strand 22, 24.

The endless members 18, 20 extend parallel to each other in the longitudinal direction X. During the displacement of the endless members 18, 20, their retaining strands 12, 14 move in translation in the longitudinal direction X. The unloading device 2 comprises a set of first endless members 18 and a set of second endless members 20 whose retaining strands 12, 14 respectively, move in translation in the longitudinal direction X in opposite directions.

As shown in FIG. 2, the retaining strands 12 of the first endless members 18 move in a first direction (to the right in FIG. 2), while the retaining strands 14 of the second endless members 20 move in a second (to the left in Figure 2) opposite the first direction.

The retaining strands 12 of the first endless members 18 and the retaining strands 14 of the second endless members 20 are alternated in the transverse direction Y.

As seen in Figure 2, the extraction system 10 comprises a first drive shaft 26 and a second drive shaft 28 parallel to each other, extending in the transverse direction Y and spaced in the longitudinal direction X. The first drive shaft 26 and the second drive shaft 28 are each provided with wheels respectively distributed along the shaft, each of the first shaft 26 and the second shaft 28 being provided with fixed drive wheels 30, ie integral in rotation of the drive shaft and return wheels 32 idle, ie freely rotatably mounted on the drive shaft. The drive and return wheels 32 of each of the first drive shaft 26 and the second drive shaft 28 are alternately disposed along the drive shaft. Each drive wheel 30 of one of the first drive shaft 26 and the second drive shaft 28 is aligned in the longitudinal direction X with a drive wheel 32 of the other drive shaft of the first drive shaft 28. drive shaft 26 and the second drive shaft 28. For purposes of illustration, the drive wheels 30 are greyed out, while the return wheels 32 are white.

The first drive shaft 26 and the second drive shaft 28 are counter-rotating - they rotate about their respective axes in opposite directions. The first drive shaft 26 and the second drive shaft 28 are here each coupled to a respective drive motor, namely a first drive motor 34 coupled to the first drive shaft 26 and a second drive motor. drive 36 coupled to the second drive shaft 28.

Each first endless member 18 cooperates with a drive wheel 30 of the first shaft 26 and a return wheel 32 of the second drive shaft 28, and each second endless member 20 cooperates with a return wheel 32 of the first shaft 26 and a drive wheel 30 of the second drive shaft 28. Thus, the first drive shaft 26 drives the first endless members 18 and returns the second endless members 20, and the second drive shaft 28 returns the first endless members 18 and drives the second endless members 20.

Each retaining strand 12, 14 extends between a deflection wheel 32 and a drive wheel 30. Each retaining strand 12, 14 is preferably moved from the deflection wheel 32 to the drive wheel 30. The drive wheel 30 is rotated so as to pull the retaining strand 12, 14.

The first drive shaft 26 and the second drive shaft 28 being counter-rotating, the retaining strands 12 of the first endless members 18 and the retaining strands 14 of the second endless members 20 move in translation in the longitudinal direction X in opposite directions.

Each drive wheel 30 is formed of a single piece of material with the corresponding drive shaft or attached thereto being rotatably connected thereto, for example by means of a key.

Each return wheel 32 is attached to the corresponding drive shaft with the interposition of a bearing, for example a sliding bearing or a rolling element bearing, such as a ball bearing, a rolling bearing or a bearing. needles.

The drive wheels 30 and the return wheels 32 are here toothed wheels - or pinions - meshing with the endless members 18, 20 provided in the form of chains. Alternatively, the wheels are for example pulleys, especially if the endless members are provided in the form of belts.

The unloading device 2 comprises a perforated support apron 37 arranged under the retaining elements 12, 14 formed by the retaining strands to support the retaining elements and prevent their excessive bending under the weight of the material 8.

The openwork support apron 37 comprises openings 37A for the flow of at least a portion of the material through the support apron 37.

The support apron 37 is here arranged below the retaining strands 12, 14. The support apron 37 is in contact with the retaining strands 12, 14. The retaining strands 12, 14 bear against the support strut. support 37 under the effect of the weight of the bulk material 8 supported by the extraction system 10.

In operation, the material 8 rests on the support surface 16 with which it is in contact. The retaining elements 12, 14 move in translation relative to each other.

Preferably, the retaining elements 12, 14 move in continuous translation in the longitudinal direction X, the first retaining elements 12 are moving in the opposite direction of the second retaining elements 14, preferably at the same linear speed.

Bulk material 8 is of a particulate nature. The perforated extraction system prevents the particles from flowing freely, so that the extraction system 10 retains at least a portion of the material 8 and allows the flow of at least a portion of the material 8.

The relative translational movement of the retaining elements 12, 14 (formed here by the retaining strands) in translation along the longitudinal direction X of their elongation causes a reorientation of the particles and / or a disintegration of the particles in contact with the support surface 16. This allows the passage of sufficiently fine particles between the retaining members 12, 14, and here through the openings 37A of the support deck 37 (Arrow F1).

The retaining elements 12, 14 formed by endless body retaining strands 18, 20 allow a continuous translation movement of the retaining elements 12, 14 in the longitudinal direction X of their elongation. This makes it possible to convey the larger particles towards the edges of the extraction system 10 (arrows F2). This also allows reliable operation.

The retaining elements 12, 14 movable in translation in the longitudinal direction X of their elongation in opposite directions urge the column of material 8 resting on the support surface 16 with a substantially zero overall result in the longitudinal direction X. This allows a uniform flow of the material and avoids the appearance of stagnation zones or compression zones in the material.

The relative displacement characteristics of the retaining elements 12, 14 (amplitude, speed, etc.) makes it possible to easily control the flow of the material 8 through the unloading device 2. The displacement characteristics are chosen in particular as a function of the material in question. bulk and dimensions of the outlet opening 4 of the container 6. The displacement characteristics can be determined experimentally from tests.

The choice of the supporting apron 37, and in particular the dimensions of its openings 37A, makes it possible to easily adjust the flow of the material, for example as a function of the particle size of the material 8. The openings have smaller dimensions, the more the flow of the material 8 is thwarted.

The translational movement of the retaining elements 12, 14 is preferably continuous. In a variant, the translational movement of the retaining elements 12, 14 is an alternating translational movement. This is easily achieved in the illustrated example simply by controlling the motors 34, 36 for alternating rotation.

In the case of an alternative translation movement, it is possible to replace the flexible endless members simply by flexible members having two free ends.

In a possible variant, the retaining elements are formed by rigid parallel bars forming a grid, each retaining element being formed by a respective bar, the bars being movable in translation translation with respect to each other.

The number of retaining elements 12, 14 and their length depend on the area and the shape of the outlet of the container closed by the unloading device 2.

The extraction system 10 here comprises sixteen retaining elements. For a container receiving biomass and having a circular outlet having a diameter of 2.5 m, the extraction system 10 comprises for example thirty-two retaining elements (sixteen moving in one direction and sixteen in the other direction). ), preferably in the form of chain retaining strands.

In general, the extraction system 10 preferably comprises at least eight retaining elements, in particular at least sixteen retaining elements.

The extraction system 10 of Figure 3 differs from that of Figures 1 and 2 in that the return wheels 32 are carried by deflection shafts 38, 40 separate from the drive shafts.

A respective return shaft 38, 40 is associated with each drive shaft 26, 28. Each deflection shaft 38, 40 is parallel to the associated drive shaft 26, 28. Each drive shaft 26, 28 carries driving wheels 30, the deflection shaft 38, 40 carrying return wheels 32. Each drive shaft 26, 28 is motorized.

A first countershaft 38 is associated with the first drive shaft 26. The first drive shaft 26 and the first countershaft 38 are mutually parallel and extend in the transverse direction Y. The first endless members 18 are wound around the drive wheels 30 of the first drive shaft 26 and the deflection wheels 32 of the first countershaft 38.

A second countershaft 40 is associated with the second drive shaft 28. The second drive shaft 28 and the second countershaft 40 are mutually parallel and extend in the transverse direction Y. The second endless members 20 are wound around the drive wheels 30 of the second drive shaft 28 and the deflection wheels 32 of the second drive shaft 40. The first drive shaft 26, the first drive shaft 38, the second drive shaft 28 and the second drive shaft 40 are distinct from each other.

The first drive shaft 26 and the second drive shaft 28 are counter-rotating. Thus, the retaining strands 12 of the first endless members 18 and the retaining strands 14 of the second endless members 20 move in opposite directions along the longitudinal direction X.

The first drive shaft 26 and the second drive shaft 28 are each coupled to a respective drive motor, namely the first drive motor 34 and the second drive motor 36.

The first countershaft 38 and the second countershaft 40 are each freely rotatably mounted about their respective axes, the return wheels 32 being fixedly mounted on the first countershaft 38 and the second countershaft 40. Alternatively, the first countershaft 38 and the second countershaft 40 are each rotatably mounted about their respective axes, the return wheels 32 being mounted idle on the first countershaft 38 and the second countershaft 40.

The first endless members 18, the first drive shaft 26 and the first countershaft 38 form a first extraction assembly, and the second endless members 20, the second drive shaft 28 and the second countershaft 40 form a second separate extraction assembly of the first extraction assembly. The first extraction set and the second extraction set are identical. They are nested so that the retaining strands 12 of the first endless members 18 and the retaining strands 14 of the second endless members 20 are arranged side by side in the transverse direction Y so as to form the support surface 16, and move in the opposite direction in the longitudinal direction X. The first extraction assembly and the second extraction assembly are arranged head to tail in plan view (Figure 3).

As illustrated in Figure 4, a roasting facility 42 is provided for the roasting of biomass, in particular lignocellulosic biomass. Lignocellulosic biomass is for example made of wood, hulls of nuts, bagasse, straws (rice straw, wheat, ...), bark, or residues of use of the oil palm fruit. (called EFB acronym for "Empty Fruit Branch").

The roasting plant 42 comprises a container in the form of a roasting column 44 for gravity flow of biomass from top to bottom in the column 44, against the flow of hot gases flowing from bottom to top in column 44. The column 44 is tubular and extends vertically. The column 44 advantageously has a frustoconical shape widening downwards.

The roasting system 42 comprises a feed system 46 for introducing the biomass BB at the top of the column 44. The feed system 46 is sealed to prevent the exit of hot gases from the column 44. For this purpose, the feeding system 46 comprises for example an airlock 47 and preferably a honeycomb valve

The roasting installation 42 comprises an extraction system 48 for extracting the roasted biomass BT at the bottom of the column 44.

The extraction system 48 comprises an unloading device 2 arranged at the bottom of the column 44 to control the gravity flow of the biomass in the column 44. The unloading device 2 is arranged so that it closes the lower end. of the column 44 forming the outlet of the column 44.

The extraction system 48 here comprises an unloading box 49 disposed at the bottom of the column 44, the unloading device 2 being disposed in the gas box 49 by closing the bottom of the column 44.

The unloading box 49 includes a gas inlet 49A for the injection of the hot gases. The hot gases injected into the unloading box 49 enter the column through the unloading device 2.

The material discharged by the unloading device 2 flows gravitarily towards the bottom of the unloading box 49. The extraction system 48 is sealed to prevent the exit of hot gases from the column 44. Extraction 48 comprises, for example, at the bottom of the unloading box 49, an airlock 50 and preferably a cellular valve.

In operation, the biomass introduced in bulk at the top of the column 44 forms a stack resting at the bottom of the column 44, more specifically on the unloading device 2. The unloading of the biomass roasted from the bottom of the stack and the introduction Biomass from the top of the stack provides biomass flow from the top of column 44 down column 44. Biomass unloading at the bottom of the stack causes the gravity flow of the rest of the biomass downwards. of the column. Feeding from above compensates for biomass extracted from the bottom.

The roasting installation 42 comprises a transport and cooling device 51 for cooling the roasted biomass extracted by the extraction system 48.

The roasting installation 42 comprises a gas circuit 52 for recovering the gases at the top of the column 44 and reinjecting the recovered gases at the bottom of the column 44. gas circuit 52 provides a closed loop gas flow in column 44 and gas circuit 52.

In operation, the gases flow from bottom to top in the column 44 in contact with the biomass being treated, then are recovered at the top of the column 44 by the gas circuit 52, and reinjected by the gas circuit 52 at the bottom The gases pass through the stack of bulk biomass packed in column 44.

The gas circuit 52 comprises a heating device 54 for indirectly heating the gases before reinjecting them down the column 44. The heating device 54 is configured for heating the gases without gas injection in the gas circuit 52.

The heating device 54 comprises a heat exchanger 56 for heating the gases flowing in the gas circuit 52 by a heat exchange between the gases flowing in the gas circuit 52 and a heat source, without adding any material in the circulating gas. in the gas circuit 52.

The heat exchanger 56 maintains a physical separation between the gases flowing in the gas circuit 52 and the heat source. The supply of heat to the gas flowing in the gas circuit 52 is performed solely by heat exchange in the heat exchanger 56, without exchange of material between the gas flowing in the gas circuit 52 and the heat source.

In one mode of implementation, the heat source is formed of combustion gases supplied by a combustion system 58 burning a fuel, the combustion gases generated by the combustion system 58 supplying heat to the gases flowing in the circuit of gas 52 in the heat exchanger 56, without mixing between the gases flowing in the gas circuit 52 and the combustion gases supplied by the combustion system 58. The heat exchanger 56 is then for example a gas-gas heat exchanger .

The gas circuit 52 comprises a gas purification system located in the gas circuit 52 between the top of the column 44 and the heat exchanger 56 of the heating device 54, to purify the gases leaving the column 44 before they pass. in the heat exchanger 56.The gas circuit 52 comprises a condenser 60 for condensing compounds present in the gas leaving the top of the column 44. The condenser 60 is disposed in the gas circuit between the top of the column 44 and the heating device 54. The condensate 61 formed in the condenser 60 is removed from the gas circuit.

The gas circuit 52 comprises a filtering device disposed between the top of the column 44 and the heat exchanger 56 of the heating device 54 to remove fine solid particles present gases recovered at the top of the column. The filtering device is here a cyclone separator 62. The separator 62 is disposed in the gas circuit 52 upstream of the heating device 54. It is here disposed downstream of the condenser 60.

Advantageously, the condenser 60 and the filtering device are integrated in the same unit 59 as shown in dashed lines in FIG. 5.

Optionally, the gas circuit 52 comprises, upstream of the condenser 60, an upstream filtering system 63, for example a cyclone separator and in particular a multi-cyclone separator, whose function is to filter the larger solid particles. present in the recovered gases at the top of the column. This improves the operation of the condenser 60 and the downstream filter device (separator 62) which is then responsible for filtering only the finest particles.

The condenser 60, the downstream filtering device 62 and the upstream filtering device 63 form the purification system. In a variant, the purification system comprises a single filtering device arranged upstream or downstream of the condenser 60.

The roasting installation 42 comprises a pressure regulating device for regulating the pressure of the gases flowing in the column 44 and the gas circuit 52.

The pressure regulating device is formed by a discharge branch 61 feeding into the gas circuit 52, provided with a regulating valve 64, and opening into a discharge chimney 65. The pressure regulating device is located upstream of the heat exchanger 56 of the heating device 54. The exhaust branch 61 is fed here upstream of the heating device 14 and downstream of the separator 62.

The opening of the control valve 64 makes it possible to evacuate towards the exhaust stack 65 an excess of gas, to limit the pressure inside the column 44 and the gas circuit 52. The control valve 64 enables regulating the flow of gas extracted from the gas circuit 52 and the column 44.

The roasting plant 42 comprises a source of inert gas 66 for the injection of an inert gas into the column 44 and the gas circuit 52.

The inert gas source 66 is connected to the gas circuit 52 at one or more injection points for injection of the inert gas into the gas circuit 52.

The source of inert gas 66 is for example connected to the gas circuit 52 at an injection point situated upstream of the bottom of the column 44 and downstream of the heating device 54 and / or at an injection point downstream of the top of the column 44 and upstream of the heater 54. The source of inert gas 66 is here connected to the gas circuit 52 at two injection points: an injection point upstream of the bottom of the column 44 and downstream of the heating device 54, and an injection point in downstream of the top of the column 44 and upstream of the heating device.

Preferably one or both of the two injection points will be used selectively to introduce the inert gas into the gas circuit 52. In a particular embodiment, the two injection points are used alternately.

Inert gas is a non-combustible gas. The inert gas is, for example, dinitrogen (N ₂ ).

The gas circuit 52 comprises a carbon monoxide sensor 68 for measuring the carbon monoxide (CO) content of the gases flowing in the column 44 and the gas circuit 52. The carbon monoxide sensor 68 is here located on the gas circuit 52 downstream of the heater 54.

The gas circuit 52 comprises an oxygen sensor 69 for measuring the oxygen content (02) of the gases flowing in the column 44 and the gas circuit 52. The oxygen sensor 69 is here located on the gas circuit 52 downstream of the heating device 54. Its role is to control the oxygen content present in the installation during purging operations during the preparation and start-up phases of the installation, and also to detect any accidental presence of oxygen in the plant. mode of production and thus control the injection of inert gas. Its installation between the heating device 14 and the bottom of the column 44 where the gases are reinjected into the column makes it possible to control the oxygen level of the gases at the inlet of the column 44 to avoid any risk of combustion of the biomass in the column 44 and explosion with carbon monoxide present in the gas circuti 12, in case of oxygen level too high.

The oxygen content of the flow of hot gases injected at the bottom of the column 44, controlled by the oxygen sensor, is less than 2%.

In operation, the torrefaction installation 42 makes it possible to implement a roasting process comprising a preparation phase, a start-up phase and then a continuous production phase.

Column 44 is initially filled with biomass. The bulk biomass forms a stack in the column 44, based on the unloading device 2.

Then, in a preparation phase, the roasting process comprises sweeping the column 44 and the gas circuit 52 with neutral gas, so as to evacuate the gases initially present in the column 44 and the gas circuit 52 and to fill the column 44 and the gas circuit 52 with inert gas. The gas circuit 52 is thus free of oxygen (O ₂ ). The inert gas is injected using the gas source inert 66. The column 44 and the gas circuit 52 are filled with inert gas until a starting pressure equal to or less than 0.5 bar at any point of the circuit.

Then, in a start-up phase, the gases present in the column 44 and the gas circuit 52 are circulated in a closed loop and heated with the aid of the heating device 54. The biomass exposed to the hot gases first starts to evacuate. water vapor. In the start-up phase, the gases flowing in the column 44 and the gas circuit 52 essentially contain inert gas and water.

Then, in a continuous production phase, when the closed-loop gases reach a sufficient temperature down the column 44 (about 200 ° C), the roasting of the biomass begins.

Due to roasting, organic compounds of the biomass are evaporated. The organic compounds and their respective proportions depend on the biomass used. In general, the organic compounds are mainly carbon dioxide (CO 2), carbon monoxide (CO), methanol (CH ₃ OH), acetic acid (CH ₃ COOH), formic or acidic acid methanoecious (HCOOCH) and furfural (C ₅ H4O ₂ ). Other organic compounds appear as traces.

The gases leaving the top of column 44 pass into condenser 60. The less volatile compounds are condensed. Most of the methanol, acetic acid, formic acid, furfural and other organic compounds resulting from the roasting is condensed in the condenser 60 and recovered in liquid form. These organic compounds remain in the form of traces downstream of the condenser 60.

Downstream of the condenser 60, the gases mainly contain water vapor, nitrogen, carbon dioxide and carbon monoxide. There are traces of organic compounds and oxygen.

The gases leaving the top of the column 44 are purified by removal of the solid particles, here by passing through the cyclone separator 62. This makes it possible to remove fine particles of biomass carried by the gas flow as it passes through the column 44. Such particles could eventually clog the gas circuit.

Because of the roasting, even if most of the organic compounds are recovered in liquid form in the condenser 60, the amount of gas flowing in the column 44 and the gas circuit 52 tends to increase, which tends to increase the pressure. The pressure control valve 64 maintains the pressure in the column and the gas circuit 52 within a determined pressure range (<0.5 bar).

In the continuous production phase, the gases flowing in the column 44 and the gas circuit 52 reach an equilibrium in their composition. Carbon monoxide is a combustible gas. An excessive presence of carbon monoxide is likely to lead to a combustion of the biomass present in column 44. However, this risk of combustion is only real if the CO level reaches its flammability threshold, if it is simultaneously worn. at a sufficient temperature and if further it is brought into contact with an oxidizer.

The roasting process comprises measuring the carbon monoxide content in the gases flowing in the column 44 and the gas circuit 52. The measurement is made here using the carbon monoxide sensor 68.

The roasting process comprises injecting inert gas into the gases flowing in the column 44 and the gas circuit 52 to limit the carbon monoxide content during roasting. The injection is carried out using the source of inert gas 66.

In one embodiment, the roasting process comprises the injection of neutral gas when the content of carbon monoxide in the gases flowing in the column 44 and the gas circuit 52 exceeds a predetermined threshold.

During the continuous production phase, the bulk biomass forms a compact stack in the column 44, based on the extraction device 2. The treated biomass is extracted as the bottom of the column 44, and the new biomass is extracted. biomass is fed progressively from the top of column 44. A flow of biomass flows in column 44 from top to bottom.

During the continuous production phase, the gases are introduced at the bottom of the column 44 at a first temperature T1 and emerge at the top of the column 44 at a second temperature T2 lower than the first temperature T1.

The gases flow from the bottom of the column 44 to the top of the column 44 through the biomass stack present in the column 44. The gases arrive hot down the column 44 and cool progressively flowing up the column 44 and working the biomass pile. Thus, a decreasing temperature gradient from the bottom of column 44 to column 44 is established in column 44. The biomass is exposed to a progressively increasing temperature from the top of column 44 to the bottom of the column. 44.

The first temperature T1 is between 200 ° C and 350 ° C, preferably between 240 ° C and 280 ° C. The second temperature T2 is preferably equal to or less than 80 ° C. The second temperature T2 is for example between 60 ° C and 80 ° C.

Between the top of the column 44 and the bottom of the column 44, the gases are reheated in the gas circuit 52, from the second temperature T2 to the first temperature T1, by passing through the heat exchanger 56. The heating is carried out in the heat exchanger 56, without injecting gas into the gases flowing in the column 44 and the gas circuit 52. The heating is carried out by heat exchange between the gases and a heat source through a wall of the heat exchanger 56.

Thus, the heating of the gases flowing in the column 44 and the gas circuit 52 does not change their composition. In particular, the heating of the gases flowing in the column 44 and the gas circuit 52 with the aid of a heat exchanger is not likely to introduce oxygen into the gases.

The heating of the gases in a heat exchanger 56 makes it possible to use different heat sources to heat the gases. The source of heat is, for example, biomass, a solid or gaseous fossil source, fatal heat or a source of geothermal heat. The term "lethal heat" refers to heat produced by an industrial installation, not valorised on site in this industrial facility generating this heat and sent to another industrial facility that uses heat. The heat transport vector is, for example, water vapor or fumes.

All the recycled gases passing through the heat exchanger 56 are injected at the bottom of the column 44. The gases possibly discharged by the pressure regulating device are taken from the circuit 52 upstream of the heat exchanger 56.

During the continuous production phase, only the gases generated by the roasting are added to the gases circulating in a closed loop in the column 44 and the gas circuit 52. This limits the thermal losses, and improves the overall energy efficiency of the installation. The only gas that may be added is additional inert gas to limit the carbon monoxide content. The roasting is carried out in the absence of oxygen, which limits any risk of combustion.

It is possible to fill the column 44 with 80% biomass by volume while having satisfactory thermal exchanges between the hot gases and the biomass. The roasting in a column 44 thus makes it possible to treat a large amount of biomass while maintaining a compact and inexpensive roasting facility 42.

The roasting process enables efficient roasting at a temperature between 240 ° C and 280 ° C, which limits the energy cost of the implementation of roasting by limiting the temperature of the gas, while obtaining a satisfactory performance .

The installation of FIG. 5 differs from that of FIG. 4 in that the gas circuit 52 for a closed loop gas flow is not configured with a heat exchanger but with a burner 72 integrated into the gas circuit 52 feeding the column 44 with hot gases, the burner 72 burning the roasting gases through the addition of an additional fuel in the presence of air used as an oxidizer.

The burner 72 has a controlled air inlet 72A and an additional fuel inlet 72B for obtaining a hot combustion gas stream having a controlled oxygen level at the outlet of the burner 72, so that this hot combustion gas stream contains less than 2% oxygen. The oxygen sensor 69 is disposed in the gas circuit 52 upstream of the bottom of the column 44.

The hot combustion gases having a controlled rate of less than 2% oxygen at the outlet of the burner 72 are injected into the bottom of the column 44 at the unloading box 49. The unloading box 49 comprises an inlet of 49A gas for the injection of hot gases. The gas circuit 52 comprises, downstream of the burner 72 and upstream of the column, an oxygen sensor making it possible to control that the stream of hot gases has an oxygen content of less than 2%.

The hot gases injected into the unloading box 49 enter the column through the unloading device 2.

The gas circuit 52 comprises, for example, at least one condenser 60, at least one separator 62 for filtering the solid particles contained in the roasting gases leaving the top of the column 44

The supply of heat in the gas circuit 52 is therefore here by a supply of material in the form of hot combustion gases.

The installation of FIG. 5 is equipped with a pressure regulating device whose exhaust branch 61 is fed into the gas circuit 52 downstream of the burner 72.

The invention is not limited to an unloading device at the outlet of a biomass roasting column. In general, the unloading device may be disposed at the outlet of a storage or reaction container. A storage container is for example a storage silo.

Claims

1. - Bulk material unloading device, comprising a plurality of elongate retaining members (12, 14) extending in parallel in a longitudinal direction (X) forming a support surface (16) for the material to be contact with the material, in which the retaining elements (12, 14) are arranged side by side in a transverse direction (Y) perpendicular to the longitudinal direction (X), defining between them interstices intended to allow the gravitational flow of at least a part of the material, wherein at least two retaining elements (12, 14) are translatable relative to each other in the longitudinal direction (X).

2. - Unloading device according to claim 1, wherein at least two retaining elements (12, 14) are movable in translation in the longitudinal direction (X) in opposite directions.

3. - Unloading device according to claim 1 or 2, wherein at least one retaining element (12, 14) is movable in continuous translation in the longitudinal direction (X).

4. - Unloading device according to any one of the preceding claims, wherein at least one retaining element (12, 14) is movable in alternative translation in the longitudinal direction (X).

5. Unloading device according to any one of the preceding claims, comprising retaining elements (12) movable in translation in the longitudinal direction (X) in a first direction, alternated in the transverse direction with retaining elements (14). ) movable in translation in the transverse direction (X) in a second direction opposite to the first direction.

6. Unloading device according to any one of the preceding claims, wherein each movable retaining element (12, 14) is movable in continuous translation in the longitudinal direction (X).

7. - Unloading device according to any one of the preceding claims, wherein each movable retaining element is a retaining strand (12, 14) of a flexible member, in particular a flexible endless member.

8. - Unloading device according to claim 7, comprising first endless members (18, 20) and second endless members driven so that the retaining strands (12) of the first endless members (18) move in translation along the longitudinal direction relative to the retaining strands (14) of the second endless members (20).

9. - Unloading device according to claim 8, wherein the first endless members (18) and the second endless members (20) are driven so that the retaining strands of the first endless bodies move in translation according to the longitudinal direction in opposite directions of the retaining strands of the second endless members.

10. - Unloading device according to claim 8 or 9, wherein the retaining strands (12) of the first endless members (18) are alternated in the transverse direction with the retaining strands (14) of the second endless members ( 20).

1 1. - Unloading device according to any one of claims 8 to 10, wherein the first members (18) and the second endless members (20) are wound on a first shaft (26) and a second shaft (28) parallel between they and counter-rotating, each first endless member (18) cooperating with a fixed wheel (30) of the first shaft and a idler wheel (32) of the second shaft, and each second endless member (20) cooperating with a idler wheel (32). ) of the first shaft and a fixed wheel (30) of the second shaft.

12. - Unloading device according to any one of claims 8 to 10, wherein the first endless members (18) are wound on a first drive shaft (26) and a first return shaft (38), and wherein the second endless members (20) are wound on a second drive shaft (28) and a second drive shaft (40).

An unloading device according to any one of claims 7 to 12, wherein each endless member (18, 20) has a retaining strand (12, 14) defining a retaining member and a return strand (22). , 24) along a path away from the retaining surface (16).

14.- Unloading device according to any one of claims 7 to 13, wherein each endless member is an endless chain.

15. - Installation comprising a container (6) for receiving bulk material, the container being provided with an outlet, and an unloading device (2) according to any one of the preceding claims, arranged across the outlet ( 4) so that bulk material is retained by the support surface (16) of the unloading device.

16. - Plant according to claim 15, for the roasting of biomass, comprising a container (44) in the form of a column and a gas circuit (52) for the injection of hot gases at the bottom of the container and the recovery hot gases at the top of the container.

17.- Installation according to claim 16, wherein the gas circuit is connected to the container for the circulation of closed loop gas, the gas circuit comprising at least one heat exchanger (56) for heating the gas flowing in the circuit. gas by heat exchange with an external heat source.