Patent Application
20090193679
The present invention relates to a method and a system for roasting a load of plant biomass and more particularly a load of wood.
The field of the invention is the field of roasting a load of plant biomass and in particular a load of wood.
Plant biomass is a renewable raw material whose energy potential, released on combustion, is very similar to that of coal. Depending on its manner of thermal upgrading, plant biomass can have an energy efficiency from 35% to 100%. This is due to the “hydrophilicity” of the plant fibres, which soak up water, removal of which consumes energy. The average lower heating value (LHV) of dry plant biomass is about 18 100 kJ/kg.
By applying certain methodologies for thermal upgrading to plant biomass, the final product can be brought up to the theoretical value of its higher heating value (HHV), i.e. 32 750 kJ/kg. This increase in energy potential is peculiar to plant biomass and more particularly to its chemical characteristics. This increase in HHV per kilogram of final product is originating by degradation of the starting biomass, at the expense of its original intrinsic energy value. Thus, it is found that the HHV of the combustible components of 1 kg of anhydrous biomass can reach an average value of 23 600 kJ/kg. The same dried biomass, in the current process conditions, has a usual average HHV of 19 100 kJ/kg.
One of the principles of optimization is to reduce the amount of oxygen contained in the anhydrous matter, so as to increase the percentage by weight of carbon. Roasting is one of the methods currently used for achieving this result.
For roasting, a load of biomass must be heated to temperatures between 280 and 320° C. These are high temperatures, and the energy consumed in heating a load of wood to these temperatures is considerable and puts a strain on the overall efficiency of the methods of roasting used at present.
One of the objectives of the invention is to propose a method and a system for roasting a load of plant biomass offering better yield than the methods and systems currently in use.
Another objective of the invention is to propose a method and system for roasting a load of plant biomass which requires less external energy supply for roasting a load of biomass than the existing methods and systems.
Another objective of the invention is to propose a method and a system for roasting that displays optimum environmental performance, better than with the existing roasting systems.
The invention proposes overcoming the aforementioned problems by a method for roasting a load of plant biomass, comprising the following stages:
The method according to the invention employs a thermal base composed essentially of a bed of material at high temperature. This layer of material at high temperature is then used for recycling the treatment gas stream laden with gaseous components and in particular water steam. The recycling of the treatment gas stream makes it possible to recover some of the energy contained in the laden gas stream by passing the laden gas stream through the thermal base. Such a recycling can provide better roasting efficiency/yield, a decrease in energy of the external energy supply required for roasting, and less pollution in comparison with the existing roasting methods and systems.
In a particular embodiment of the method according to the invention, the thermal base is composed essentially of an optimized load of plant biomass, combustion of which is carried out under optimum conditions, allowing high temperatures to be obtained. This layer of material at high temperature is then used for recycling the gas stream used in the treatment method according to the invention. This stream is laden with gaseous components after treatment of the biomass that is to be roasted, in particular with water steam, contained in the raw material, and organic compounds, gasified in the course of roasting. By recycling the treatment gas stream it is possible to recover some of the energy contained in the water steam, extracted from the starting biomass. Passage of the gas stream, laden with pyrolysis gases containing volatile organic compounds (VOC), through the thermal base permits their combustion at high temperature and utilization of the energy released. This recycling optimizes the efficiency of roasting of the plant biomass and protects the environment:
Advantageously the treatment gas stream is essentially composed of CO2.
Moreover, the thermal base generated in the method according to the invention is essentially composed of carbon-containing constituents at high temperature.
The generation of the thermal base can comprise combustion of roasted biomass under O2, said combustion producing carbon-containing constituents at high temperature. The biomass used as fuel can be of vegetable or animal type or of any other type.
The reactive thermal base according to the invention can be burning at a temperature that is controlled by injection of oxygen in the centre of said thermal base. This injection of oxygen can serve for controlling the temperature and the production of energy within the thermal base.
The method according to the invention can comprise co-generation of electricity from the water steam originating from a cooling circuit or from any other circuit that can be employed in the method according to the invention. The methods of co-generation of electricity from water steam are well known to a person skilled in the art.
The method according to the invention can in addition comprise combustion, during passage of the laden gas stream through the thermal base, of organic gaseous components originating from the load of biomass and present in the laden gas stream, this combustion producing thermal energy that can be used directly in the method and/or electric power by means of dedicated systems. The thermal energy produced can be used for roasting a new load of wood.
Advantageously, the method according to the invention can comprise recycling of the laden gas stream to recover gas that is suitable for use in the treatment gas stream. The recovered gas can be heat-transfer CO2.
This recycling can comprise filtering of the laden gas stream, after passage of the stream through the thermal base. This filtering can have the purpose of removing unburnt compounds during passage of the laden gas stream through the thermal base.
In a particular version of the invention, generation of the gas stream for roasting can comprise combustion of roasted biomass under O2, this combustion producing a combustion gas essentially comprising CO2. The roasted biomass can be plant biomass. In a particular version of the method according to the invention, the roasted biomass used for generating the gas stream and/or for generating the thermal base can be roasted plant biomass obtained by roasting plant biomass by the method according to the invention.
After a combustion gas has been obtained, the method according to the invention can comprise a preliminary phase of condensation of elements contained in the combustion gas, for recovery of a residual gas comprising carbon dioxide, this condensation in particular having the purpose of removing the water steam contained in the combustion gas.
The method according to the invention can in particular comprise compression of the residual gas, for condensing and recovering the carbon dioxide in liquid phase.
The residual gas can also travel through at least one heat exchanger so that it is raised to the treatment temperature, and can then returned to the treatment cycle, to be used in the treatment of the load of biomass to be roasted.
The thermal energy required to heat the residual gas to the treatment temperature can be obtained by combustion of roasted biomass, in particular of roasted biomass obtained by the method according to the invention, and by the combustion of the volatile organic compounds.
In a particularly advantageous version of the invention, the treatment gas stream can be generated by combustion of a solid fuel, said combustion also generating at least a portion of the thermal base.
According to another aspect of the invention, a system for roasting a load of plant biomass is proposed, comprising:
The generating means comprise a device for combustion of a solid fuel provided for generating the treatment gas stream by combustion of said fuel.
The generating means also comprise a device for combustion of a solid fuel, arranged in such a way that the combustion of said solid fuel forms at least a portion of the thermal base.
In a particularly advantageous variant of the invention, the generating means comprise a thermal generator provided for generating at least a portion of the treatment gas stream, said generator also being provided for generating at least a portion of the thermal base.
The thermal generator can comprise a thermal reactor or a solid-fuel furnace or a hybrid device, allowing the combustion of a solid fuel, in particular of roasted plant biomass, this combustion producing, on the one hand, a combustion gas stream of which at least a part can be used as treatment gas stream, and on the other hand, carbon-containing constituents at high temperature, at least a portion of which can be used for producing the bed of material at high temperature called the thermal base.
Advantageously, the thermal generator can be equipped with a system for cooling by circulation of a heat-transfer fluid. The generator can comprise double walls, between which the heat-transfer liquid, for example water under pressure, can circulate. The heat-transfer liquid can also be sprayed onto the walls of the thermal generator.
In a particular variant of the invention, the thermal generator can comprise a grate-type furnace intended to receive the thermal base and arranged for effecting transfer of the laden gases originating from the treatment unit.
The grate-type furnace can advantageously be equipped with a system for cooling by circulation of a heat-transfer fluid in the furnace grate.
The thermal generator can also comprise means for injecting oxygen. The injection of oxygen can, on the one hand, provide combustion of a solid fuel intended for the generation of the treatment gas stream and/or of the thermal base, and on the other hand for regulating the temperature in the thermal base.
The thermal generator can in particular comprise a chamber for post-combustion of pyrolysis gases generated by the roasting of the load of biomass and/or by the incomplete combustion of a solid fuel. This post-combustion chamber is employed in particular for combustion of the volatile organic compounds and the pyrolysis gases.
Advantageously, the thermal generator can comprise at least one heat exchanger, said heat exchanger being provided for effecting heat exchange between either a combustion gas and the treatment gas stream, or a fluid composed essentially of saturated water steam and superheated water and the treatment gas stream, this fluid being essentially composed of water steam that comes either from roasting of the load of biomass, or from a circuit for cooling a part of the system.
The treatment furnace according to the invention can be a cylindrical assembly comprising an inner cylinder housed in an outer cylinder defining a space for treatment of the load of biomass, said inner cylinder receiving the load of plant biomass that is to be roasted.
The inner cylinder can in particular be provided with freedom to rotate about a longitudinal axis relative to the outer cylinder.
The wall forming the inner cylinder can advantageously be perforated, in such a way that, on the one hand, the treatment gas can be fed into this cylinder and come in contact with the load of biomass to be treated, and on the other hand, the laden gas can leave this cylinder after treatment of the load of biomass.
Moreover, the inner cylinder can comprise at least one protuberance on its inside wall, over almost the entire length of the inside wall, said protuberance ensuring the entrainment and mixing of the load of biomass during the treatment. Contact of the treatment gas with the load of biomass is thus facilitated and treatment of the load of biomass is improved. After treatment, mixing of the treated load of wood facilitates the release of the laden treatment gas.
In an advantageous version of the system according to the invention, the outer cylinder can comprise a heat-insulated shell limiting the heat losses and increasing system security.
The outer cylinder can moreover comprise a solid inside wall enveloping the inner cylinder and delimiting the space for treatment of the load of biomass. This inside wall defines the treatment space that is in contact with the various gas streams.
Advantageously, the treatment furnace can comprise a deflector on almost the entire length of the cylinder, intended for directing the treatment gas stream towards the lower portion of the treatment space so as to distribute said stream onto all of the biomass load.
The treatment furnace can comprise at least two brushes mounted in contact, on the one hand, with the inside wall of the outer cylinder, and on the other hand, between the outside wall of the inner cylinder in order to delimit a zone for feed of the treatment gas stream into the treatment furnace and a zone for withdrawal of the gas stream after treatment of the load of biomass.
These brushes can advantageously be arranged for brushing the outside wall of the inner cylinder so as to dislodge particles of the load of biomass retained on the inner cylinder.
The treatment furnace additionally comprises a pipe for feed of the treatment gas stream into the treatment space. This pipe for feed of the gas stream can be heat-insulated by the methods and systems known by a person skilled in the art.
The treatment furnace also comprises a pipe for withdrawal of the treatment gas stream. This pipe for withdrawal of the treatment gas stream can be heat-insulated.
The treatment furnace can advantageously comprise a pipe for injecting liquid CO2 into the treatment zone. This pipe for injecting CO2 is provided for safety reasons and for regulating the temperature within the space for treatment of the load of plant biomass.
In a particular embodiment the treatment unit can comprise driving means arranged for providing rotation of the inner cylinder about a longitudinal axis. These rotating means, by effecting rotation of the inner cylinder, provide mixing of the load of biomass present in the inner cylinder.
According to a particular embodiment of the system according to the invention, one end of the inner cylinder and of the outer cylinder is provided with an opening for feeding the load of biomass into the inner cylinder before treatment and for extracting the load of biomass after the treatment, the other end being closed.
During treatment of the load of biomass, this opening is tightly closed by piston-actuated sealing means.
The treatment unit can moreover comprise means for horizontal positioning of the treatment furnace. These positioning means allow the treatment unit to move to a horizontal position, said position being maintained during treatment of the load of wood.
The treatment unit can moreover comprise means arranged for rotation of the cylindrical assembly about a horizontal axis. These rotating means are arranged for positioning the treatment unit in particular positions for charging and discharging of the load of biomass.
The treatment unit can advantageously comprise means for receiving the load of biomass after treatment. These receiving means can comprise a receiving tank or a receiving wagon.
In one position, called the charging position, the cylindrical assembly is positioned vertically, the end having an opening in the inner and outer cylinders being at the top, in such a way that the load of biomass to be treated can be fed into the inner cylinder. This position can be used advantageously for dismounting the cylindrical assembly, or one of the cylinders of the treatment unit, for maintenance operations. This position permits very practical and very ergonomic charging of the wood load directly into the inner cylinder.
In one position, called the discharging position, the cylindrical assembly is positioned vertically, the end having an opening in the inner and outer cylinders being placed near the bottom, in such a way that the treated biomass load is collected in receiving means. This discharging position permits practical and simple discharging of the load of biomass into means for receiving the load of biomass.
In another position, called the processing position, the cylindrical assembly is positioned horizontally, the opening in the inner and outer cylinders being tightly closed by the sealing means.
The system according to the invention can moreover comprise means for extracting the gas mixture from the treatment space for keeping said treatment space permanently at low pressure. These extracting means can comprise means allowing aspiration of the treatment gas stream and can be positioned downstream of the treatment space and connected to the pipe for withdrawing the laden gas stream.
The system according to the invention can further comprise a water steam generating device, utilizing the thermal energy from any element of the system.
Advantageously, the system according to the invention can comprise means for co-generation or for tri-generation of energy from the recovered thermal energy.
The system according to the invention can in addition comprise means for storage and/or distribution of O2 and means for storage and/or liquefaction and/or distribution of CO2.
Other advantages and characteristics of the invention will become apparent on examination of the detailed description of an embodiment which is in no way limitative, and the attached drawings in which:
The example discussed below is a particular, non-limitative example of the present invention. It relates to a system for roasting a load of plant biomass and more particularly a load of wood.
The system described in the present example comprises a treatment unit 1 as shown in
The outer cylinder 11 has a solid inner wall, which envelops the perforated inner cylinder 12 for roasting, and it is in the zone delimited by this cylinder 11 that the stream of heat-transfer gas (composed essentially of CO2) is introduced and withdrawn. This zone is called the treatment space.
The treatment space is separated into two parts, 13 and 14, by special high-temperature brushes 18. This space is thus divided into two zones, namely:
The inlet zone 13 of the treatment gas stream also corresponds to a zone for expansion and distribution of the hot, dry heat-transfer CO2, the gas being distributed over the entire outside surface of the rotating perforated inner cylinder 12 corresponding to the surface occupied by the load of wood to be roasted.
The outlet zone 14 corresponds to the treatment space not occupied by the wood load to be roasted downstream of the industrial brushes 18. The hot, dry heat-transfer CO2 that is fed into zone 13 passes through the wood to be roasted, in which it will transfer its thermal energy to the wood load B by the three known methods of heat transfer:
But also by a fourth heat transfer method: that of osmosis of the CO2 with the moisture contained in the biomass that is to be roasted. After passing through the wood, the heat-transfer gas stream entrains:
The laden gas stream is then drawn through the perforations of the inner cylinder 12 and is extracted via the outlet pipe 16.
The brushes 18 are arranged over the entire length of the cylinder of the inside wall of the outer cylinder 11 at the junctions of the inlet zone 13 and outlet zone 14. These industrial brushes 18 are detachable so that they can be replaced if they are worn; their role is to separate the treatment space into two zones and to provide constant brushing of the outside wall of the inner cylinder 12 to dislodge particles of wood that could be retained by the perforations present on said cylinder 12.
The treatment furnace 10 also comprises a heat-insulated outer shell, which corresponds to the outside wall 111 of the outer cylinder 11. The furnace 10 can also have a buffer zone 112, and this too can be heat-insulated.
The treatment furnace 10 also comprises an inlet pipe 15 of the high-temperature heat-transfer gas stream, this pipe 15 and the opposite outlet pipe 16 for the laden gas stream are integral with the outer cylinder 11. They swivel in the supports 191 when the roaster is tilted for charging with wet wood B1 or for discharge of roasted wood B2. The roasted wood B2 is received at the end of treatment in the detachable tank 17.
The outlet pipe for the laden gas stream (i.e. the treatment gas stream and, depending on the phase of the treatment, the moisture from the wood or the pyrolysis gases) can be supplemented with an electric extractor (not shown) which maintains a constant low pressure in the roaster.
The pipes 15 and 16 are heat-insulated. They are connected to fixed pipelines (not shown), for feed of the heat-transfer gas stream and for extraction of the treatment gas, from the recycling loop leaving the heat exchangers and returning to the thermal generator.
The treatment furnace 10 also comprises at least one deflector 132 which directs the heat-transfer gas stream to the bottom portion of the inner cylinder 12 containing the wood load B to provide distribution throughout the mass of wood to be roasted.
The treatment furnace 10 further comprises a pipe 131 for injection of liquid CO2, the purpose of said pipe being:
The pipe 131 for injection of liquid CO2 is connected to a system for distribution of liquid CO2 under pressure, shown diagrammatically in
The treatment unit 1 comprises fixed supports 19 for the roasting furnace 10 which receive the means 191 and 192 that enable the furnace 10 to swivel about the axis A2. The height of said supports 19 permits tilting of the roasting furnace 10, above the receiving tank 17 for the roasted wood during its rotation in the vertical positions for charging and discharging of the roasted wood load.
The swivelling of furnace 10 about the axis A2 is provided by the rotating means 191 and 192 which can comprise a chain-driven electric mechanism or any other known means, positioned on one of the supports. The pipes 15 and 16 are the shafts for support and swivelling/rotation of the roasting furnace.
The supports 19, as shown in
The sealing means comprise a piston 24 which pushes a plug/a door 23 against the open ends of cylinders 11 and 12 of the roasting furnace 10 to close them tightly during treatment of a wood load B.
The means for horizontal positioning of the roasting furnace comprise:
The rotation of cylinder 12 within the treatment furnace 10 about axis A1 is provided by a mechanism with an electric motor 25.
An example of a system for roasting a load of wood according to the invention and its principle of operation are shown in
The roasting system as shown in
The system also comprises a gas/gas heat exchanger E3 (whose purpose is to cool the combustible gases) in which the laden gas stream exchanges the residual thermal capacity (that it acquired on passing through the thermal reactor R and the residual heat from the treatment furnace 10) with the cold, dry heat-transfer CO2 arriving from the dehydrator D. At least a portion of the water steam (extracted from the load of wood to be roasted) is condensed in this exchanger E3, its latent heat of condensation thus being recovered.
In
Also in
The roasting system advantageously comprises an O2 system for storage and distribution of the oxygen for supporting combustion. The consumption of oxygen, as supporter of combustion of the “thermal base”, is related to the power used.
Finally the system can comprise a water steam generating device VAP. The production of water steam has several possible functions:
The generator G and more particularly the reactor R, comprises a grate-type furnace, which can be cooled conventionally by circulation of water or by any hydraulic heat-transfer means. The walls of the generator are also under thermal control, cooled by the same method, or configured so as to optimize heat exchange to the heat-transfer gas stream. The grate of the furnace receives the fuel in a bed of solid fuel. This bed is preferably composed of roasted plant biomass, densified or not, but can be pre-dried, anhydrous plant biomass, or a compacted form of plant biomass. Combustion is preferably effected with oxygen injected into the furnace, at the reactive centre of the biomass.
The generator can also comprise a chamber for post-combustion of the pyrolysis gases generated by the roasting and combustion of the biomass on the grate of the furnace. The system is then dedicated purely to the optimum thermal upgrading of the roasting process.
Combustion of the bed of combustible biomass can take place under O2 as the supporter of combustion or under air as the supporter of combustion, said reactions are then carried out “ALTERNATELY and SEPARATELY”, to produce a bed of embers and thus form the “thermal base”, through which the gases extracted from the roasting furnace 10 pass, and are purified there. The gas mixture, combustion gas in below-stoichiometric conditions and pyrolysis gases, is thus brought to the ad hoc temperature for stoichiometric post-combustion.
The bed of solid fuel, called the thermal base, is composed of anhydrous biomass, preferably roasted and therefore with higher concentration of vegetable carbon. Combustion of the thermal base under O2 as supporter of combustion permits fine control of combustion. This bed of roasted biomass burns at high temperature.
The first objective of the generator G is to produce, for the roasting system:
Combustion of the roasted biomass under O2 is complete and only produces CO2. The CO2 introduces a process of heat transfer supplementary to the known processes of heat transfer. This process of heat transfer is specific to the raw material, composed of plant biomass, and is osmosis of the CO2 with the moisture contained in the biomass.
This osmosis is made possible by the phytobiological symbiosis of the CO2 and the “biomass” material:
The second purpose of said generator G is to carry out complete combustion of the combustible constituents generated by the process, for upgrading its thermal potential, in order to:
The CO2 produced by combustion of plant biomass is considered to be neutral since the biomass is renewable and the same amount of atmospheric CO2 will be used for growth of the same amount of biomass. Combustion of the biomass must therefore be complete so that the discarded CO2 does not contribute to the greenhouse gases.
The CO2 resulting from combustion of the biomass under O2 passes through the primary pipes of the heat exchangers where it will transmit its heat to the heat-transfer components of the system:
Once cooled to a temperature below the temperature of condensation of the water steam contained in the gas<70° C., the dewatered CO2 is filtered (to trap the carbon particles that could have been entrained in the stream). It is then in the required conditions for utilization as heat-transfer means for roasting the wood load B.
This gas is then transferred to the heat exchanger to be brought to the temperature required for the roasting treatment. The heat-transfer CO2 is then fed into the roasting furnace 10, where it transmits its heat capacity to the wood B to be roasted. Heat transfer to the wood, according to the four processes of heat transmission defined above, raises its temperature and enables the moisture contained in the wood B to be evaporated.
The laden gas mixture (heat-transfer CO2+water steam and then heat-transfer CO2+VOC, extracted from the wood to be roasted) is then withdrawn from the roasting furnace 10 and transferred to the thermal generator to be:
Everything takes place with continuous recycling, up to the end of roasting.
The roasting cycle of this design is carried out in conditions of total self-production of energy; only the purchase of oxygen as supporter of combustion and of the electricity used by the system (unless it is self-produced) have to be taken into account in this part of the direct operating costs.
In another operational configuration, the heat-transfer gas circuit is arranged as a closed loop, which contains the volume of heat-transfer CO2 used for the heat exchanges in the process. The heat-transfer gas stream travelling in this circuit no longer passes through the “thermal base” reactor of the generator during the dehydration phase, but only through the exchangers where:
When the wood is dried, the laden gas mixture extracted from the wood to be roasted, heat-transfer CO2+volatile organic compounds (VOC), then travels through the thermal reactor of the generator, for stoichiometric combustion of the VOC under O2 as supporter of combustion. The combustion gases are composed essentially of CO2. If they are at the right temperature for roasting, then they are fed directly into the roasting furnace 10, without any other form of treatment. If their heat capacity is excessive, then they are discharged in a heat exchanger to the benefit of a heat-transfer component dedicated to another application and/or for buffer thermal storage.
In this case combustion of the VOC can take place under atmospheric (air) supporter of combustion, this solution only being envisaged if the combustion gases are not used in the roasting process: too much heat-transfer CO2, too much thermal energy, etc. The excess thermal energy is removed from the combustion gases in the exchanger, and they are cooled to the temperature required for discharge to atmosphere.
The condensation of H2O simplifies the recycling and recovery of the CO2, as the latter can be reused immediately in the process. Its purity makes it a strategic product, by substituting industrial CO2 which is generated by chemical reactions on fossil materials and thus decreasing the impact of greenhouse gases, etc.
A portion of the CO2 will be stored in a buffer tank, under pressure, to maintain the capacity used in process start-up. A portion can also be condensed by known systems, such as freezing-out and/or compression:
The CO2 cycle can be described as follows:
Once the total CO2 capacity is reached, combustion within the thermal generator can be carried out under atmosphere. This situation does not prevail if the excess combustion gas is not utilized in a total system with energy self-sufficiency or in ancillary applications.
In an existing conventional method, with the starting wood at 45% moisture (with lower heating value (LHV) of 7900 kJ/kg) it is necessary to supply 3690 kJ per kilogram (kg) of raw material for roasting it (latent heat of dehydration+sensible heat of roasting). The 0.44 kg of roasted product originating will have an LHV of 10 331 kJ (or an LHV/kg of 23 480 kJ/kg), which gives an overall energy efficiency (except combustion efficiency linked to the performance of the generator) of 10 331 kJ minus the 3690 kJ consumed=6641 kJ per kg of wet raw material (B1).
In the method according to the invention, the water steam extracted from the starting wood at 45% moisture is partly reduced on passing through the “thermal base” of the generator. The resultant gas mixture is thermally reactive: it holds, in its formulation, the “exhaustive” principles of restitution of the energy employed in the process. The combustion of these components can thus be optimized in the post-combustion chamber, where heat exchange with the heat-transfer gas stream is at its optimum:
It can therefore be stated that with starting wood at 45% moisture, we no longer consider the lower heating value of 7900 kJ/kg, as is the case in the conventional methods, but the HHV of the components contained in the anhydrous wood, i.e. 23 600 kJ/kg since:
Finally, a roasted product will be obtained, per kg of raw material employed for roasting, LHV of which will also be 10 331 kJ, but as there is an excess in the energy balance of the process (combustion of the VOC and direct utilization of the energy generated) the process is considered not to have consumed anything for the reaction.
One kilogram of raw material (starting wood) is therefore upgraded from 7900 kJ to 10 331 kJ, or a gain of 30.77%.
Relative to the “conventional” methods of roasting (for which the LHV of the amount of material roasted is disconnected from the energy employed for the process, i.e. a final LHV of 6641 kJ), the gain is 55.58%.
Relative to forestry chips, supplied wet for feed to installations for energy production using plant biomass, the environmental benefits associated with the life cycle of the roasted wood used as energy-producing wood, are:
This system for roasting plant biomass can be arranged in a battery of cylindrical assemblies, to satisfy the continually varying demand for roasted wood.
The advantage of this system is that the cylindrical roasting assemblies can be dimensioned for a standardized unit capacity. Arranged in a battery, they will be supplied and controlled by a single system for thermal generation/utilization of the pyrolysis gases and one and the same system for management of the CO2 produced.
The invention is not limited to the example that has just been described, but can be applied to the roasting of all plant biomasses.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0605840 | Jun 2006 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2007/001086 | 6/28/2007 | WO | 00 | 12/29/2008 |
