Plant for drying biomass and corresponding method of drying biomass

Abstract

A plant for a drying treatment of biomass (100), in particular wood chips and / or calibrated woodchips, comprising a drying room (1) configured to receive at its interior, on a pavement thereof (11), biomass (100) intended for a drying treatment, wherein said drying room (1) comprises at least one roof (10) wholly or partially transparent to incident solar radiation such that said incident solar radiation reaches the interior of said drying room (1), in particular, also one or more side walls (10') comprising one or more portions transparent to incident solar radiation, wherein said pavement (11) supporting said biomass (100) is a heating pavement (11) configured for releasing heat in the drying room (1) to the interior of the drying room (1), in particular to said biomass (100) supported by the pavement (11).

Description

Technical field

[0001] The description refers to a biomass drying plant.

[0002] This drying plant may be used for a drying treatment of biomass of vegetal origin, such as, for example, wood chips and / or calibrated wood chips (small woodchips).Background

[0003] Currently, producing electrical and / or thermal energy from plant-based fuels represents an advantageous choice in terms of raw material availability and reduced carbon dioxide emissions.

[0004] Fuels obtained from biomass of vegetal origin, for example wood chips and / or pellets, may be used as fuel both in small-scale plants (for example, boilers or small plants with a total production of a few kW of power) and in electrical and / or thermal production plants or power stations capable of producing several MW of power.

[0005] Wood chips, in particular, prove to be a particularly advantageous fuel in terms of flexibility of use, energy yield and (relatively low) cost.

[0006] Wood chips and calibrated wood chips (also called "small woodchips", also indicated as A1+ Biomassplus ®< calibrated woodchips) are produced by grinding ("chipping") logs and / or branches into flakes (of variable size from a few millimeters to a few centimeters).

[0007] Before they can be used as fuel, these fuels must be dried in order to reduce their water content (humidity) and consequently increase their calorific value.

[0008] The problem therefore arises of fast and efficient drying treatment of biomass of vegetal origin, such as wood chips and / or small woodchips.Object and summary

[0009] One or more embodiments aim at facilitating the drying treatment of biomass of plant origin.

[0010] According to one or more embodiments, this object is achieved via a drying plant having the characteristics set out in the following claims.

[0011] One or more embodiments relate to a biomass drying method that can be performed using such a drying plant.

[0012] The claims are an integral part of the technical teaching provided with reference to the embodiments.

[0013] In solutions as described herein, the biomass drying treatment takes place in a drying room or greenhouse. The biomass drying treatment is facilitated by a cover of the drying greenhouse that is transparent to solar radiation and by a pavement of the drying greenhouse configured to heat the biomass.

[0014] In solutions such as those described here, the drying greenhouse may be provided with a ventilation system that facilitates the removal of humidity from inside the drying greenhouse.

[0015] In solutions as described herein, a drying plant may comprise a drying greenhouse and a cogeneration system configured to power the drying greenhouse pavement.

[0016] In solutions as described here, the cogeneration system may also be configured to power the ventilation system possibly provided in the drying greenhouse.Brief description of the figures

[0017] One or more embodiments will be now described, purely by way of example, with reference to the attached figures, wherein: Figure 1 is a plan view illustrative of a biomass drying plant according to embodiments of the present description, Figures 2 and 3 (wherein Figure 3 is an enlarged view of the portion of Figure 2 indicated by arrow III) are cross-sectional views illustrative of a biomass drying plant in accordance with embodiments of the present description.

[0018] The corresponding numbers and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.

[0019] The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.

[0020] The edges of the characteristics drawn in the figures do not necessarily indicate the end of the extension of the characteristic.Detailed description

[0021] The following description illustrates one or more specific details in order to provide a thorough understanding of the examples of the embodiments of this description. The embodiments can be obtained without one or more of the specific details, or with other methods, components, materials, etc. In other cases, known structures materials or operations are not illustrated or described in detail so that certain aspects of the embodiments and not rendered unclear.

[0022] The reference to "an embodiment" in the context of the present description indicates that a particular configuration, structure or characteristic described with reference to the embodiment is included in at least one embodiment. Thus, phrases such as "in an embodiment" or the like, which may be present at one or more points in the present description do not necessarily refer to exactly the same embodiment.

[0023] Moreover, particular configurations, structures or characteristics can be combined in any suitable way in one or more embodiments.

[0024] The references used here are provided simply for convenience and therefore do not define the field of protection or scope of the embodiments.

[0025] For simplicity and ease of explanation, throughout this description, and unless the context indicates otherwise, similar parts or elements are indicated in the various figures with similar reference symbols and a corresponding description will not be repeated for each figure.

[0026] The subject of the present description is a plant for drying biomass such as wood chips or calibrated woodchips (also called "small woodchips").

[0027] Figure 1 is a plan view schematically illustrating such a biomass drying plant.

[0028] As schematically illustrated in Figure 1, a plant as described herein comprises (at least) one drying room (or greenhouse) 1 wherein biomass of vegetal origin, such as wood chips and / or wet wood chips, is subjected to a drying treatment so as to make it suitable for use as a fuel in biomass stoves or boilers.

[0029] Still referring to Figure 1, such a biomass drying plant may include a cogeneration system 2, advantageously placed in proximity to the drying room 1, and configured to produce thermal energy that can be used to power the drying greenhouse 1 as described in the following.

[0030] In one or more embodiments, the cogeneration system 2 is also configured to produce electrical energy that may be used to power a ventilation system possibly included in the drying room 1, or fed into the grid.

[0031] Figure 2 is a cross-sectional view illustrative of a drying plant according to embodiments of the present description.

[0032] The drying room 1 substantially comprises an upper wall, or roof, 10, side walls 10' and a pavement 11. In the example, the drying room 1 has a rectangular plan, while the roof 10 has a sloping shape, while in variant forms it may be a flat roof or with another shape.

[0033] As illustrated, the biomass 100 to be dried may be accumulated inside the drying room 1, with a layer of height h on the pavement 11. In a drying room 1 as described herein, maintaining a relatively uniform treatment temperature within the drying room 1 facilitates the simultaneous treatment of a relatively large amount of biomass 100.

[0034] For example, in a drying room with a height of approximately 4 meters, the height h of the biomass 100 accumulated in the drying room 1 may be approximately one meter.

[0035] In embodiments wherein the extension of the drying room 1 has an area of 300 square meters, approximately 300 cubic meters of biomass 100 can be dried simultaneously.

[0036] In a drying room (or greenhouse) 1 as described herein, the drying of biomass 100 is facilitated by reaching and maintaining a desired treatment temperature.

[0037] In one or more embodiments, two aspects of a drying room 1 as described herein contribute to reaching and maintaining the required treatment temperature: comprising at least one roof, or upper wall, 10, wholly or partially transparent to solar radiation, as well as possibly also side walls 10' transparent to solar radiation, and a heated 11 pavement.

[0038] The drying room 1 has a structure substantially similar to the structure of a greenhouse, for example, a greenhouse of the type conventionally used for drying sludge and / or agricultural products.

[0039] The drying room or greenhouse 1 comprises a roof, or upper wall (or cover) 10 which is transparent (wholly or at least partially) to solar rays which are therefore substantially transmitted to the interior of the drying greenhouse 10. The person skilled in the art can appreciate how such a roof 10 may also comprise non-transparent portions, to the extent wherein the solar radiation incident on the upper wall 10 reaches the upper surface of the biomass 100 in sufficient quantity to produce the desired heating for drying. According to the greenhouse principle, the portions that transmit solar radiation are instead configured to reflect or retain the thermal radiation re-emitted by the biomass and the environment.

[0040] As said, the drying greenhouse 1 may also have side walls 10' which are also (at least partially) transparent to solar radiation.

[0041] Suitable materials for the roof and / or side walls 10 of the drying greenhouse 1 comprise, for example, plastic materials (e.g. polyethylene, polyvinyl chloride and ethylene vinyl acetate, or polycarbonate) and / or glass conventionally used in the construction of greenhouses (e.g., greenhouses for agricultural purposes). Transparent to solar radiation means that it transmits a substantial portion, particularly the majority, of solar radiation. For example with transmittances higher than 70%. In variant forms with transmittances greater than 60%. In variant forms with transmittances greater than 50%.

[0042] The drying greenhouse 1 comprising the transparent cover 10 (and, possibly, the side walls) therefore constitutes a sort of "solar plate", configured to let pass (most of) the solar energy incident on the drying greenhouse 1 to pass through.

[0043] As illustrated in Figure 2, the drying greenhouse 1 comprises a heated pavement 11 configured to heat the biomass 100 stored within the drying greenhouse 1.

[0044] In one or more embodiments, the heated pavement 11 substantially comprises a network of pipes / ducts 13 wherein a heating fluid, for example hot water, (for example, water at a temperature of approximately 60°C) supplied at the inlet to the network of pipes is made to flow.

[0045] Such a network of pipes 13 (comprising, for example, a plurality of interconnected coils) is incorporated or "buried" in a support layer of thermally-conductive material 14 so as to facilitate the transfer of heat from the heating fluid flowing inside the pipes towards the inside of the drying greenhouse 1.

[0046] The person skilled in the art can appreciate how the configuration of the piping network may be chosen with different shapes and devices, according to the heating needs of the pavement 11 and its characteristics.

[0047] This heated pavement 11 may comprise, for example, a plurality of so-called radiant panels, of the type currently available on the market and per se known in the art.

[0048] In one or more embodiments, the heated pavement 11 may be such as to provide a thermal power, for example, between 100 W / m 2< and 150 W / m 2< , inside the drying greenhouse 1.

[0049] As mentioned, a drying plant comprising (at least) one drying greenhouse 1 as described in the foregoing, may comprise in addition to this drying greenhouse 1, a cogenerative system (or cogeneration system) 2. In such embodiments, the cogeneration system 2 may be configured to supply the thermal energy (hot water) produced by it entering the heated pavement 11 of the drying greenhouse 1. In other words, the cogeneration system 2 may be configured to supply the heating fluid (at a relatively high temperature) to the heated pavement 11 of the drying greenhouse 1.

[0050] The increase in temperature and the maintenance of the treatment temperature inside the drying greenhouse 1 is, therefore, facilitated by the heated pavement 11 and by the transparent upper (and possibly side) walls 10, which facilitate the heating of the inside of the drying greenhouse 1 by radiation.

[0051] In order to reduce heat loss outside the drying greenhouse 1, its structure may be designed (for example, in the choice of materials) in such a way as to facilitate thermal insulation of the interior of the drying greenhouse 1.

[0052] The (double) heating system of the drying greenhouse 1 facilitates a relatively rapid and efficient drying treatment of the biomass 100 stored inside the drying greenhouse 1. In fact, the double heating system (that is, via solar energy entering through the side and upper walls 10 and via the heated pavement 11) facilitates the maintenance of the desired treatment temperature, uniformly inside the drying greenhouse 1.

[0053] As illustrated in Figure 2, the biomass 100 may be accumulated inside the drying greenhouse 1 in a layer whose height may reach one meter. The biomass 100, although in general it may not have a parallelepiped shape or completely flat surfaces, substantially identifies an upper surface, which receives the incident solar radiation transmitted through, for example, the transparent roof 10, and a lower surface that rests on the pavement 11, and therefore receives the heating heat first. The homogeneous and rapid drying of the biomass 100 facilitated by the double heating system as described above, therefore facilitates the drying of a relatively large quantity of biomass 100 at each treatment cycle.

[0054] In one or more embodiments, the drying greenhouse 1 advantageously comprises a ventilation system 12.

[0055] This ventilation system 12 may comprise, in the simplest embodiments, ventilation openings (e.g. windows) configured to facilitate ventilation of the drying greenhouse 1.

[0056] In one or more embodiments, the ventilation system 12 may comprise a forced ventilation system, this system comprising one or more fans that facilitate the renewal of air inside the drying greenhouse.

[0057] In embodiments wherein the drying plant comprises a cogeneration system 2 configured to produce electrical energy, it is possible to envisage powering the fans of the forced ventilation system 12 with the electrical energy produced by the cogeneration system 3.

[0058] The ventilation of the drying greenhouse 1 facilitates the removal of humidity within the greenhouse that may occur in response to the drying of the treated biomass 100, thus facilitating the reduction of the humidity level within the drying greenhouse 1 and therefore increasing the speed of treatment of the biomass 100.

[0059] As already mentioned, a drying plant as described herein may comprise, in addition to one or more drying greenhouses 1 as described above, a cogeneration system 2.

[0060] As illustrated in Figure 1 or Figure 2, this cogeneration system 2 may be provided in proximity to the drying greenhouse 1.

[0061] The cogeneration system 2 is configured to supply the drying greenhouse 1 with thermal energy (hot water) that facilitates operation thereof.

[0062] As described above, in fact, the drying greenhouse is equipped with a heated pavement 11 configured to receive hot water at its inlet (for example, at a temperature of approximately 60°C) in order to heat the interior of the drying greenhouse 1.

[0063] Furthermore, in the case wherein the drying greenhouse 1 is provided with a forced ventilation system 2 (e.g. electrically-powered fans), the cogeneration system 2 may also be configured to produce electrical energy to be supplied to such ventilation system 12.

[0064] Figure 3 is an enlarged view of the portion of Figure 2 indicated by the arrow III schematically illustrating details of a cogeneration system 2 according to embodiments of the present description.

[0065] As illustrated, this cogeneration system 2 may comprise, housed in a room 20 provided for that purpose, a cogenerative thermal unit 22.

[0066] This cogenerative thermal unit 22 is fueled by biomass (for example, waste biomass such as coarse wood chips); in order to facilitate the feeding of the cogenerative thermal unit, a storage room 21 for feeding the biomass may be provided near the room 20 and configured to feed the cogenerative thermal unit 22 therein.

[0067] As illustrated, the cogeneration system 20 may also comprise, also arranged inside the cogeneration room 20: an inertial tank 24, and a mixing unit 26.

[0068] In more detail, the inertial tank 24 substantially comprises a tank configured to contain and accumulate the heating liquid (e.g., water) produced by the cogenerative thermal unit 22, so as to accumulate the thermal energy and supply it at the outlet when desired.

[0069] As known to those skilled in the art, an inertial tank 24 is characterized by a high insulation capacity, which is advantageous in order to maintain the thermal energy accumulated inside it for as long as possible.

[0070] The cogenerative thermal unit 22 is then configured to produce heating liquid at a desired usage temperature (hot water up to 60°C, for example), which is accumulated in the inertial tank 24.

[0071] As illustrated, in the case - very frequent-wherein water is used as the heating liquid, a duct W may be configured to supply water to the inertial tank 24 also from outside the drying plant, for example, from a water distribution network external to the drying system.

[0072] The tank 24 is associated with a mixing unit 26 configured to receive hot water from the tank 24 and send it, via a pumping system 28 provided for that purpose, towards the heated pavement 11 of the drying greenhouse 1.

[0073] The mixing unit 26 and the pumping system 28 may be configured to modulate / vary the amount of hot water supplied to the heated pavement 12 of the drying greenhouse 1 as a function of, for example, the desired drying temperature inside the drying greenhouse 1.

[0074] These adjustments may be controlled, in a manner known to experts in the field, via an electronic control unit configured for the object. Such an electronic control unit is not visible in the figures for simplicity.

[0075] In the embodiment illustrated in Figure 3, the drying greenhouse 1 is equipped with a forced ventilation system 12, powered by electricity. As previously mentioned, the cogeneration system 2 may be configured, in these cases, to provide electrical energy to operate said forced ventilation system 12.

[0076] The cogenerative thermal unit 22 may, therefore, comprise an electric generation unit (not visible in the Figure for simplicity) configured to generate electrical energy G through combustion of waste biomass.

[0077] The electrical energy G generated by the cogeneration thermal unit 22 may be (at least partially) supplied to the ventilation system 12 of the drying greenhouse. Any excess electricity may be fed into the electricity grid, as per se conventional in the art.

[0078] By way of example, a drying plant as described herein may be considered, comprising a drying greenhouse 1 with an extension in the order of hundreds of square meters. For example, we can consider a drying greenhouse 1 with plan dimensions of 15 m by 20 m, for a total extension of 300 m 2< .

[0079] As already mentioned, the heated pavement 11 according to embodiments of the present description (comprising, for example, a plurality of panels) may provide a thermal output in the range of 100 W / m 2< to 150 W / m 2< . This thermal power (reported here as a mere example and not to be construed in a limiting sense) may be supplied through heated pavements 11 which are currently easy to construct or through radiant panels currently available on the market.

[0080] In embodiments wherein the drying greenhouse area is 300 m 2< and the heated pavement 11 provides a heat output of between 100 W / m 2< and 150 W / m 2< , the total heat output provided by the heated pavement 11 is, therefore, between 30 kW and 45 kW.

[0081] In such embodiments, a cogeneration system 2 suitable for providing, for example, up to a maximum of 90 kW of thermal power can be advantageously installed in a drying plant as described herein. Such a cogeneration system 2 is able to provide a sufficient amount of thermal energy to power the pavement 11 of the drying greenhouse 1.

[0082] In such embodiments, the cogenerative thermal unit 22 may comprise an electric generation unit that may provide an output electric power in the order of 15 / 25 kW, for example. The power generated by the cogenerative thermal unit 22 is sufficient to power a ventilation system 12 (powered by electricity) possibly provided in the drying greenhouse 1.

[0083] Advantageously, the cogeneration system 2 is configured to be fueled by woody biomass. In particular, it may be fed with poor quality woody biomass, for example twigs or tops, obtained in the initial stages of wood processing to obtain wood chips and / or small woodchips.

[0084] In particular, it is advantageous to feed the cogeneration system 2 with waste deriving from the selection of "raw" biomass. In fact, in the case wherein the biomass 100 to be dried comprises wood chips and / or small woodchips, it may be desirable to remove the larger wood chips (for example, larger than 1-2 centimeters), which may be unsuitable for use as fuel in wood chip stoves or boilers currently in use.

[0085] The raw biomass may therefore, depending on its size, be divided into: quality wood chips and / or wood chips 100 to be dried in drying greenhouse 1, and "coarse" wood chips, to be used as fuel in an industrial thermal unit (or even the cogenerative thermal unit 22 described above) and / or for so-called "NO-ENERGY" applications, for example litter or mulching.

[0086] The person skilled in the art may appreciate how providing a cogeneration system 2 fueled by coarse wood chips as described above facilitates the reduction of raw material waste (these coarse wood chips would otherwise be disposed of as waste) and, consequently, facilitates the reduction of the operating costs of the drying plant.

[0087] In summary, a biomass drying treatment plant 100 (for example, wood chips and / or calibrated woodchips) comprises a drying room 1 configured to receive at its interior, on a pavement thereof 11, biomass 100 candidate for a drying treatment.

[0088] Said drying room 1 comprises at least one roof 10, which is wholly or partially transparent to incident solar radiation such that said incident solar radiation reaches the interior of said drying room 1.

[0089] The drying room may also comprise one or more side walls 10' comprising one or more portions transparent to incident solar radiation.

[0090] The pavement 11 supporting said biomass 100 is a heating pavement 11 configured for releasing heat in the drying room 1 to the interior of the drying room 1, in particular to said biomass 100 supported by the pavement 11.

[0091] In one or more embodiments, said heated pavement 11 of the drying room 1 comprises a support layer 14 having a network of pipes 13 embedded therein. The piping network 13 is configured for conveying a heating fluid supplied to said piping network 13. The support layer 14 facilitates the heat exchange between the heating liquid and the interior of the drying room 1.

[0092] Advantageously, said drying room 1 may comprise a forced ventilation system 12 including a set of fans configured for ventilating the interior of the drying room 1 to remove moisture from the interior of the drying room 1, in particular by extracting air from the interior of the drying room 1.

[0093] In one or more embodiments, the system may comprise a cogeneration system 2 configured for powering the heated pavement 11 of the drying room 1.

[0094] For example, the cogeneration system may be configured to supply heating fluid to the piping network 13 of the heated pavement 11.

[0095] In one or more embodiments, the cogeneration system 2 comprises a cogenerative thermal unit 20 configured to be fueled with biomass, in particular to be fueled by waste wood chips.

[0096] In one or more embodiments, the cogeneration system 2 comprises an electrical power generation unit, and the cogeneration system 2 is configured for providing electrical power produced by said electrical power generation unit.

[0097] Part of the electrical energy produced by said generation unit may be supplied to power said forced ventilation system 12 included in the drying room 1.

[0098] Without prejudice to the underlying principles, the details and the embodiments may vary, even appreciably, with respect to what has been described here, purely by way of example, without departing from the embodiments.

[0099] The field of protection is defined by the attached claims.

Claims

1. A plant for a drying treatment of biomass (100), in particular wood chips and / or calibrated wood chips, comprising a drying room (1) configured to receive at its interior, on a pavement thereof (11), biomass (100) candidate for a drying treatment, wherein said drying room (1) comprises at least one roof (10) wholly or partially transparent to incident solar radiation such that said incident solar radiation reaches the interior of said drying room (1), in particular also one or more side walls (10') comprising one or more portions transparent to incident solar radiation, wherein said pavement (11) supporting said biomass (100) is a heating pavement (11) configured for releasing heat in the drying room (1) to the interior of the drying room (1), in particular to said biomass (100) supported by the pavement (11).

2. A plant according to claim 1, wherein said heating pavement (11) of the drying room (1) comprises a support layer (14) having embedded therein a piping network (13), said piping network (13) being configured for conveying a heating fluid supplied to said piping network (13), and wherein said support layer (14) facilitates heat exchange between the heating fluid and said interior of the drying room (1).

3. A plant according to claim 1 or claim 2, wherein said drying room (1) comprises a forced ventilation system (12) including a set of fans configured for ventilating the interior of the drying room (1) to remove moisture from the interior of the drying room (1), in particular by extracting air from the interior of the drying room (1).

4. A plant according to any one of claims 1 to 3, comprising a cogeneration system (2) configured for powering said heating pavement (11) of the drying room (1) .

5. A plant according to claim 4 and claim 2, wherein said cogeneration system (2) is configured for supplying said heating fluid to said piping network (13) of the heating pavement (11).

6. A plant according to claim 4 or claim 5, wherein said cogeneration system (2) comprises a cogeneration thermal unit (20) configured for being supplied with biomass, in particular to be supplied with waste wood chips.

7. A plant according to any one of claims 4 to 6, wherein said cogeneration system (2) comprises an electric power generation unit, and said cogeneration system (2) is configured for providing electrical energy generated by said electric power generation unit.

8. A plant according to claim 3 and claim 7, wherein the cogeneration system (2) is configured for providing at least one portion of the electrical energy produced by said generation unit to supply said forced ventilation system (12) included in the drying room (1) .

9. A method comprising: arranging biomass (100) candidate for a drying treatment in a drying room (1) comprising side and top walls (10) at least partially transparent to solar radiation and a heating pavement (11) configured for heating the interior of the drying room (1), heating the interior of the drying room (1) in response to the solar radiation at least partially transmitted by said side and top walls (10), and heating the interior of the drying room (1) via said heating pavement (11).

10. A method according to claim 9, comprising ventilating the interior of the drying room (1) and removing moisture from the interior of the drying room (1) via a forced ventilation system (12) included in said drying room (1).

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