METHOD AND SYSTEM FOR PRODUCEING FLAMMABLE MATERIAL FROM ORGANIC WASTE USING A MULTIPLE OF HERBAL PLANTS

Description

[0001] The present invention relates to a method and installation for treating organic waste containing a majority of herbaceous plants, for example animal manure or grass cuttings along transport infrastructure (motorways, roads, railways, canals, rivers, streams), in the context of revalorization by production of combustible material. This organic waste contains, for example, many plants of the Poaceae and grass type.

[0002] This organic waste, which mainly contains herbaceous plants, for example animal manure or grass cuttings along transport infrastructure (motorways, roads, railways, canals, rivers) is currently only recovered through composting or in methanisation facilities.

[0003] Biogas, or fermentation methane, is a way to recycle organic waste containing fibrous, lignin-rich plant material, such as animal manure, particularly horse manure, or grass clippings, for example from clippings along a motorway. Indeed, equestrian centers and farms produce animal manure that can be used to produce biogas, and fibrous plant clippings are also potentially useful for this purpose.

[0004] Manure here means a mixture of animal droppings and organic bedding, such as straw.

[0005] Biogas production is based on the anaerobic digestion of biomass, which makes up most of manure, by microorganisms. These microorganisms are spontaneously present in manure and waste. In particular, they release methane and carbon dioxide from organic molecules.

[0006] Methanization is carried out in methanization facilities, which are generally large. These methanization centers are the places where biogas is generated and used to generate, for example, electrical energy or heat, or to be injected into a gas network. Their location is independent and potentially far from that of the equestrian centers, stud farms and farms where the animals produce manure and the places where shearing and trimming take place and their waste is collected.

[0007] Generally, methanization installations are directly fed by plant waste and introduced into a digester.

[0008] Furthermore, manure and plant waste are continually subject to fermentation by aerobic digestion, and the methane produced during their storage and transport, and therefore before being introduced into the digester, is potentially lost. Furthermore, this lost methane can also pose ecological problems in terms of global warming, given that the greenhouse effect due to methane is four times greater than that of carbon dioxide.

[0009] Furthermore, transporting raw materials is resource-intensive due to the significant weight of manure and waste, particularly due to the large aqueous portion. The water in manure does not contribute to methanization, although it represents a significant weight. Indeed, if animal manure is transported over long distances, it is essentially water. Given the weight of water in animal manure, the number of trucks required to transport the manure is high and also contributes to a negative climate effect.

[0010] The inventors of the present invention were able to observe that this traditional method of recovery can be greatly improved by transforming organic waste containing a majority of herbaceous plants into fuel pellets.

[0011] Currently, there are wood pellets as fuels that are made from wood waste.

[0012] Furthermore, WO2007093143 describes an installation and a method for manufacturing fuel pellets from horse manure which treats the horse manure as a whole.

[0013] There is therefore a need for an improved method of generating a combustible material.

[0014] In order to at least partially overcome the problems mentioned above, the subject of the invention is a method for treating organic waste containing a majority of herbaceous plants, in particular from the grass or poaceae family, preferably at least 60%, such as, for example, animal manure and more specifically horse manure for the production of combustible material, characterized in that it comprises the following steps: a first step of drying the organic matter containing a majority of herbaceous plants by blowing hot air, in particular at a temperature ranging from 60 to 120°C, until a dry mass portion of between 60% and 80% is reached, a separation step in a density separator to extract a dried herbaceous portion from the dried organic matter, a second drying step applied to the dried herbaceous portion until it has a dry mass portion of between 85% and 95%, a step of grinding the dried herbaceous portion from the second drying step in a mechanical grinder into particles smaller than 20mm, preferably between 5 and 15mm, for mechanical bursting of the lignin protection of the cell walls, a step of pressing the dried and ground herbaceous portion into granules in a pellet press.

[0015] The process thus produces a dry raw material that is easy to handle and also has a very low, if not imperceptible, odor. Drying removes the aqueous portion of organic waste, which contains a majority of herbaceous plants, significantly reducing its weight. Drying also interrupts aerobic digestion and the untimely release of methane, thereby retaining the combustible fraction.

[0016] The first drying step before the separation step increases the difference in density between the organic matter and any elements to be removed such as waste, particularly in the case of animal manure, and more specifically horse manure.

[0017] Crushing the dried herbaceous portion after separation mechanically breaks the lignin protection of the cell walls. Since lignin is a hydrophobic protection of the cells, its destruction allows for better dehydration and therefore the production of pellets with a high concentration of easily flammable fuel.

[0018] The material packaged in granules and dried can easily be stored for a long time, and then transported to points of sale or furnaces where it will be burned, for example to heat a building.

[0019] Finally, pellets contain almost only “combustible” material.

[0020] The method may further have one or more of the following features, taken alone or in combination.

[0021] The first and second drying stages are, for example, carried out during the transport of organic matter containing a majority of herbaceous plants to the density separator and to the mechanical grinder respectively.

[0022] The transport and drying of organic matter containing a majority of herbaceous plants are then combined, which allows for almost continuous treatment.

[0023] The drying stages are carried out in particular by a slatted conveyor with a reciprocating movement comprising a transport floor with mobile drive slats equipped with hot air blowing openings for drying the organic matter containing a majority of herbaceous plants during transport.

[0024] The mechanical crusher is notably a hammer crusher, but a blade crusher, a cylinder crusher, a chain crusher, or a scissor crusher are also possible.

[0025] The process may include a final step of heating the granules to a temperature above 100°C for at least 30 minutes for their thermal sterilization.

[0026] More complete sterilization makes it possible to obtain granules that can be handled without anti-pathogenic precautions.

[0027] The invention also relates to an installation for implementing the treatment method as defined above, characterized in that it comprises: a first conveyor-dryer configured to carry out a first step of drying the organic matter containing a majority of herbaceous plants by blowing hot air, in particular at a temperature ranging from 60 to 120°C, until a dry mass portion of between 60% and 80% is reached, a density separator arranged downstream of the first conveyor-dryer and configured to carry out a separation step in order to extract a dried herbaceous portion from the dried organic matter, a second conveyor-dryer arranged downstream of the density separator and configured to carry out a second drying step applied to the dried herbaceous portion until it has a dry mass portion of between 85 and 95%, a mechanical grinder arranged downstream of the second conveyor-dryer and configured to carry out a step of grinding the dried herbaceous portion resulting from the second drying step into particles of a size less than 20 mm,preferably between 5 and 15mm, for mechanical bursting of the lignin protection of the cell walls, a pellet press arranged downstream of the mechanical grinder and configured to carry out a step of pressing the dried and ground herbaceous portion into granules.,

[0028] The first and second conveyor-dryers are, for example, slatted conveyors comprising a transport floor with movable drive slats provided with hot air blowing openings for drying organic matter containing a majority of herbaceous plants during transport.

[0029] The installation may include a heater or oven located downstream of the pellet press and configured to carry out a thermal sterilization step on the pellets from the pellet press.

[0030] The invention also relates to granules obtained by agglomeration of particles of organic matter of size less than 10 mm, the organic matter containing at least 80%, preferably at least 90% of herbaceous plants, in particular of the family of grasses or poaceae and with a dry mass of 85% to 95%.

[0031] The organic matter in these pellets is composed at least partially of mulched manure, and in this case the pellets contain between 0.5 and 3% residual fecal matter forming a binder between the pellet particles.

[0032] The invention may also independently relate to a reciprocating slat conveyor comprising a transport floor with movable slats and provided with hot air blowing openings for drying organic matter containing a majority of herbaceous plants during transport.

[0033] These openings 10 are for example regularly distributed with a spacing of 5 to 15cm, typically 10cm between two openings 10.

[0034] In one aspect, the openings are connected via a pressure relief box arranged under the movable slats to a hot air blower for injecting hot air from below into the organic waste.

[0035] The openings are, for example, made in the form of nozzles, particularly convergent ones, for diffusing hot air.

[0036] Other characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of illustrative and non-limiting example, and the appended drawings among which: [ Fig.1 ] schematically shows a treatment installation for implementing the process, [ Fig.2 ] is a schematic sectional view of a slat of the conveyor of the figure 1 , And [ Fig.3 ] is a linear flowchart of the process associated with the installation of the figure 1 .

[0037] The embodiments described with reference to the figures are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments can also be combined to provide other embodiments.

[0038] By "upstream" or "downstream", we locate the elements / equipment in the direction of transport of the flow of material to be processed. Thus, a first piece of equipment or element is located upstream of a second piece of equipment or element if the material is first processed by the first piece of equipment and then the second piece of equipment.

[0039] Dried herbaceous portion means the part of organic waste free of compacted portions such as animal droppings and other foreign bodies such as metal waste (cans or horseshoes). This is the light dried portion formed by plant particles / strands weighing less than 2g.

[0040] Particle size means the size at its greatest extent, for example the length of a straw.

[0041] There figure 1 is a schematic view of a treatment facility 100 for organic waste containing a majority of herbaceous plants, in particular from the grass or poaceae family, preferably at least 60% such as animal manure and more specifically horse manure for the production of combustible material. It can also be corn stover waste, bagasse and sugar cane stalks or simply downgraded straw or hay.

[0042] These organic wastes are rich in hemicellulose and / or cellulose and poor in lignin, but the lignin polymers make the cell wall rigid and impermeable. These properties make the organic matter unlikely to be completely dried for use as fuel and limit flammability.

[0043] The treatment method 200 implemented in the installation 100 of the figure 1 is represented in figure 3 in the form of a flowchart showing the major steps of said process 200.

[0044] During a preliminary step 201 of the process 200, the organic waste material containing a majority of herbaceous plants is received and placed on a first conveyor-dryer 1A.

[0045] Then, during a first drying step 201, the organic matter containing a majority of herbaceous plants by blowing hot air is heated and dried in particular at a temperature ranging from 60 to 120°C until reaching a dry mass portion of between 60% and 80%.

[0046] This first drying step is carried out by the drying conveyor 1A. Thus, transport to a next processing station and drying can be combined.

[0047] The conveyor-dryer 1A may be a moving slat conveyor, in particular of the KEITH brand (registered trademark), which is suitable for the present invention to allow both conveying and drying.

[0048] The general principle of these slat conveyors is described in patent EP 1 481 925 entitled "high-performance reciprocating slat conveyor" in the name of KEITH INVESTMENTS LLC or in document US5310044. According to the general principle, such a conveyor comprises a floor formed of movable slats 2 driven by a drive mechanism in a reciprocating movement parallel to the transport direction. In operation, the organic waste is discharged at one end onto the movable drive slats 2. According to a transport phase, all the movable drive slats 2 are driven together in the transport direction indicated by a dotted arrow on the figure 1 . During this transport phase, the waste advances by a distance corresponding to the travel of the mobile drive slats 2. Then, during a withdrawal phase, the mobile slats 2 slide in the opposite direction progressively in a time-shifted manner in several groups. For example, first a first third of the slats 2, then a second third and finally a third, each time leaving two slats 2 stationary between two slats 2 which move back until all the mobile drive slats 2 are again in the starting position of the transport phase. Due to the weight of the organic matter and the friction phenomena, during the withdrawal phase, the organic matter remains stationary.

[0049] Unlike the reciprocating slat conveyor described in the prior art, the conveyor-dryer 1A comprises a transport floor with movable slats 2 provided with openings 10 for blowing hot air for drying the organic matter containing a majority of herbaceous plants during transport.

[0050] Thus, the movable slats 2 of the slat conveyor are provided with openings 10, not described in EP 1 481 925, for example in the form of hot air diffusion nozzles. These openings 10 are for example regularly distributed with a spacing of 5 to 15 cm, typically 10 cm between two openings 10.

[0051] As can be seen on the figure 2 which is a sectional view of a slat 2 with a portion of the conveyor 1 in a particular embodiment, the openings 10 are connected via a pressure relief box 21 to a hot air blower 3, producing a flow of air heated to at least 60°C, preferably from 60 to 120°C, here in particular from 60 to 80°C. The air flow is injected through the openings 10 to penetrate the organic waste from below. The organic waste is thus dried during transport. The heated air flow rate and the conveying speed can be adjusted so that the organic material leaving the conveyor-dryer 1 has a dry matter fraction greater than 60 to 80%, in particular 70%.

[0052] According to another embodiment of the conveyor-dryer 1, the openings 10 can be formed by the slots between two adjacent slats 2.

[0053] In the case where the organic waste is animal manure, especially horse manure, the advantage of the reciprocating slat conveyor is that during transport the droppings are dried on the outside without being disintegrated, which facilitates subsequent density separation.

[0054] In a variant not shown, the conveyor-dryer 1A may comprise a rotating drum drying tunnel in which, by means of drive blades, the organic waste material is transported and mixed against a flow of hot air.

[0055] Other types of conveyors can also be used, for example a mobile bin conveyor, a conveyor belt, etc. The drying and transport of organic matter can alternatively be carried out in two separate machines, with a separate oven or dryer and a separate conveyor. The solution proposed in figure 1 however, allows the transport and drying stages to be combined.

[0056] This first drying step 201 prepares the organic waste for density separation. In particular, the herbaceous parts, because they are light, dry more easily and more quickly, so their density decreases more than other fractions, such as dung pellets, which only dry on the surface and retain most of the aqueous part.

[0057] Partial drying is therefore mainly carried out by drying the material forming the light fraction. The remaining moisture will therefore be concentrated mainly in the thicker balls of manure and shavings forming the middle fraction.

[0058] Downstream of the drying conveyor 1A is therefore arranged a density separator 5. The separator 5 is configured to carry out a separation step by density difference 203 in order to extract a dried herbaceous portion from the dried organic matter. When the organic waste is for example animal manure, this dried herbaceous portion essentially comprises strands of straw, fibers and stems, with a large surface / volume ratio. The heavier part is generally formed by horse droppings.

[0059] The density separator 5 therefore makes it possible to divide the dried organic waste into several fractions of different densities, by centrifugation, gravity or air flow entrainment and in particular to separate the portions retaining moisture. The density separator 5 has several outlets 51, 53, 55, for respectively a light fraction (herbaceous portion), medium (for example animal droppings) or dense (for example metal residues) of the organic waste.

[0060] In particular, the density separator 5 separates from the rest of the organic matter a dried herbaceous fraction or portion, containing most of the woody fibers (straw, cut grass, leaves, etc.). The separator 5 also separates the rest of the material into a medium fraction, containing for example partially dried manure and any wood chips, and a dense fraction, then mainly containing metal, plastic or other waste.

[0061] The density separator 5 may further comprise a strip magnet, the organic matter passing close to said strip magnet to extract any remaining metal particles.

[0062] The middle fraction can be burned in a furnace, and the heat released can be used to heat the air in the hot air blower 3. The dense fraction is discarded and sent for household waste treatment or recycling depending on its content.

[0063] The dried herbaceous portion of the organic matter is then sent via the outlet 51 to a second drying conveyor 1B arranged downstream of the density separator 5 and preferably of the same structure as the drying conveyor 1A. The drying conveyor 1B is configured to carry out a second drying step 205 applied to the dried herbaceous portion and only to this until this herbaceous portion has a dry mass portion of between 85 and 95%, typically 90%.

[0064] Drying by blowing hot air also allows for the sanitization of organic matter. Hygienization here means partial pasteurization or sterilization, reducing the pathogen level to acceptable levels. This sanitization, although not eliminating all or almost all pathogens, is sufficient to make the organic matter unlikely to be contaminated by humans during handling.

[0065] Heat treatment by blowing air at 60 to 80°C for several tens of minutes can destroy most parasites such as nematodes, and significantly reduces the number of bacteria present.

[0066] Downstream of the second conveyor-dryer 1B is arranged a mechanical grinder 7 configured to carry out a grinding step 207 of the dried herbaceous portion resulting from the second drying step 205 into particles of a size less than 20 mm, preferably between 5 and 15 mm, for mechanical bursting of the lignin protection of the cell walls.

[0067] The mechanical crusher 7 is in particular a hammer crusher 7, which chops and shears the dried herbaceous portion of the organic matter into pieces and strands.

[0068] Other mechanical crushers can be used: blade crushers, roller crushers, chain crushers, scissor crushers, etc. In particular, depending on the particle size of the organic matter, several different types of crushers can be used successively. Hammer crushers, due to greater compression bursting, produce better quality material than other crushers with the same chip size.

[0069] The lignin in the broken cell walls allows for more efficient and rapid drying. This mechanical breaking of the fibers does not require the addition of substances (acid, enzymes, etc.), and no resting time. Processing the organic matter is therefore rapid and potentially less expensive.

[0070] The entire process takes only a few hours.

[0071] The installation of the figure 1further comprises a pellet press 9 arranged downstream of the mechanical grinder 7. The pellet press 9 presses the dried and ground herbaceous portion into agglomerated pellets, in a manner analogous to the pressing of wood pellets from sawdust during a pressing step 209.

[0072] Such a pellet press 9 comprises, for example, a die such as an endless screw, and a perforated grid. The endless screw guides and compresses the organic matter against the perforated grid, and the compressed organic matter then exits through the perforations of the grid in the form of threads or coils which, after breaking due to their own weight or by cutting, give the pellets.

[0073] The grid, particularly through its perforations, allows the size and shape of the granules to be selected. The granules are typically tubular, with a circular cross-section with a diameter between 4 and 12 mm, generally around 6 to 8 mm. Their average length is then around 5 to 15 mm, with fibers less than 10 mm long.

[0074] Pressing 209 of the dried and ground herbaceous portion into granules makes it possible, on the one hand, to obtain solid, compact and easy-to-handle granules, and on the other hand contributes to the mechanical bursting of the fibers, but to a lesser extent than grinding 207. Pressing 209 also causes a sudden rise in pressure and temperature, contributing to the elimination of potential pathogens (eggs, cysts, spores).

[0075] Optionally, the pellets leaving the pellet press 9 are then heated during a step 211 by a heater or oven 11, to a temperature above 100°C, in particular between 105 and 120°C or more, for 5 to 25 minutes in order to sterilize them by heat treatment. The temperature and duration of sterilization may vary depending on the type of pathogens to be eliminated (viruses, bacteria, amoebas, prions, etc.). Prions, for example, require temperatures of 130 to 140°C for their elimination.

[0076] In particular, there are specific duration and temperature protocols depending on the nature of the pathogens suspected of being present.

[0077] The granules thus obtained can be handled without anti-pathogenic precautions, they have a low odor and their dosage is easy. The granules are also light because they are dried and compact because they are compressed. They can therefore be transported efficiently, and stored for extended periods due to their sterility and / or their dehydrated nature. The simple addition of water, as well as possible ferments, allows for rapid production of significant gas with a high yield.

[0078] Due to the drying, separation and mechanical breaking of the fibers and lignin, the combustible fraction of the organic matter to be treated is concentrated, containing a majority of herbaceous plants.

[0079] The granules obtained by agglomeration of particles of organic matter are less than 10mm in size, and contain at least 80%, preferably at least 90% of herbaceous plants, in particular from the grass or poaceae family and with a dry mass of 85% to 95%.

[0080] When the organic matter is composed at least partially of mulched manure, the pellets contain 0.5 to 3% residual fecal matter. This residual fecal matter forms a binder between the particles during pressing which improves the cohesion of the pellets, while being itself combustible.

[0081] The process 200 can be automated and implemented continuously by connecting the inputs and outputs of the different machines (separator 5, grinder 7, press 9, etc.) in the installation 100 to each other or by means of conveyors.

[0082] Part of the granules obtained can be reused on site, for example to heat the air in the hot air blowers 3 or the sterilization oven 9.

[0083] The process 200 and the associated installation 100 make it possible to obtain, with an energy expenditure of approximately 0.2 MWh per tonne of material, a product making it possible to generate, by combustion, approximately 2 to 3 MWh per tonne of granules, i.e. a factor of at least 10. In addition, the process 200 as a whole can be carried out with a duration of a few hours between the arrival of the organic material and the end of the last sterilization step.

[0084] In summary, the drying and separation steps allow the extraction of a concentrate of combustible organic matter (the dried herbaceous portion) from organic waste containing a majority of herbaceous plants. The grinding step makes the combustible organic matter in the dried herbaceous portion more easily ignitable.

Claims

1. Method for the treatment of waste organic matter containing a predominance of herbaceous plants, notably of the family of the Gramineae or Poaceae, preferably of at least 60%, such as, for example, animal manure and more specifically equine manure, for the production of combustible material, characterized in that it comprises the following stages: - a first stage of drying (201) the organic matter containing a predominance of herbaceous plants by blowing hot air, notably at a temperature ranging from 60°C to 120°C, until a dry weight portion of between 60% and 80% is reached, - a stage of separation (203) in a density separator (5) in order to extract a dried herbaceous portion from the dried organic matter, - a second drying stage (205) applied to the dried herbaceous portion until the latter has a dry weight portion of between 85% and 95%, - a stage of grinding (207) the dried herbaceous portion resulting from the second drying stage in a mechanical grinder (7) to give particles with a size of less than 20 mm, preferably between 5 mm and 15 mm, for mechanical bursting of the lignin protection of the cell walls, - a stage of pressing (209) the dried and ground herbaceous portion to give pellets in a pellet press (9).

2. Method according to Claim 1, characterized in that the first and second drying stages (201, 205) are carried out during the transportation of the organic matter containing a predominance of herbaceous plants respectively to the density separator (5) and to the mechanical grinder (7).

3. Method according to Claim 2, characterized in that the drying stages (201, 205) are carried out by a slat conveyor (1A, 1B) comprising a transportation floor with mobile drive slats (2) provided with openings (10) for hot air blowing for the drying of the organic matter containing a predominance of herbaceous plants during the transportation.

4. Method according to one of the preceding claims, characterized in that the mechanical grinder (7) is a hammer mill.

5. Method according to one of the preceding claims, characterized in that it comprises a final stage of heating the pellets at a temperature of greater than 100°C for at least 30 min for their heat sterilization (211).

6. Installation for the implementation of the treatment method according to at least one of the preceding claims, characterized in that it comprises: - a first conveyor-dryer (1A) configured to carry out a first stage of drying (201) the organic matter containing a predominance of herbaceous plants by blowing hot air, notably at a temperature ranging from 60°C to 120°C, until a dry weight portion of between 60% and 80% is reached, - a density separator (5) arranged downstream of the first conveyor-dryer (1A) and configured to carry out a separation stage (203) in order to extract a dried herbaceous portion from the dried organic matter, - a second conveyor-dryer (1B) arranged downstream of the density separator (5) and configured to carry out a second drying stage (205) applied to the dried herbaceous portion until the latter has a dry weight portion of between 85% and 95%, - a mechanical grinder (7) arranged downstream of the second conveyor-dryer (1B) and configured to carry out a stage of grinding (207) the dried herbaceous portion resulting from the second drying stage to give particles with a size of less than 20 mm, preferably between 5 mm and 15 mm, for mechanical bursting of the lignin protection of the cell walls, - a pellet press (9) arranged downstream of the mechanical grinder (7) and configured to carry out a stage of pressing (209) the dried and ground herbaceous portion to give pellets.

7. Installation according to Claim 6, characterized in that the first and second conveyor-dryers (1A, 1B) are slat conveyors having a to-and-fro movement comprising a transportation floor with mobile drive slats (2) provided with openings (10) for hot air blowing for the drying of the organic matter containing a predominance of herbaceous plants during the transportation.

8. Installation according to either of Claims 6 and 7, characterized in that it comprises heating or an oven (11) arranged downstream of the pellet press (9) and configured to carry out a stage of heat sterilization of the pellets resulting from the pellet press (9).

9. Pellets obtained by agglomeration of particles of organic matter with a size of less than 10 mm by the implementation of the treatment process according to at least one of Claims 1 to 5, the organic matter containing at least 80%, preferably at least 90%, of herbaceous plants, notably of the family of the Gramineae or Poaceae, and with a dry weight of 85% to 95%.

10. Pellets according to Claim 9, characterized in that the organic matter is composed, at least partially, of strawy manure and in that the pellets comprise between 0.5% and 3% of residual faecal matter forming a binder between particles forming the pellets.