Device for crushing and torrefying biomass and waste fuels

Abstract

Torrefaction device for producing a fine-grained fuel from energy raw materials, in particular comprising biomass and / or alternative fuels from waste, with a reactor (2) for comminution and torrefaction of the raw material. A hot gas supply device (4) and a separation device (6) are provided below a grinding mill (35) in a working chamber (22). The grinding mill is a vertical roller mill (3), with the raw material supply device (4) being located in the lower part of the reactor (2) such that it opens into the lower part of the working chamber (22). Since the hot gas is also supplied there, torrefaction begins even before the raw material reaches the grinding media, utilizing the high temperature of the hot gas at the inlet. Thus, pre-embrittlement of the raw material is achieved on the short path from the feed point to the initial contact with the grinding media. It is therefore comminuted more effectively by the grinding media.Initially, improved comminution and torrefaction are achieved. This combination increases efficiency.

Description

[0001] The invention relates to a torrefaction device for producing a fine-grained fuel from energy feedstocks, in particular comprising biomass and / or refuse-derived fuels from waste (also known as Refuse Derived Fuel (RDF), or its higher-grade form Solid Recovered Fuel (SRF)). The torrefaction device comprises a vertical roller mill with grinding elements moving relative to one another in a working chamber, wherein the rolling elements roll along a grinding track actuated by a grinding drive. Hot gas and the feedstock are supplied to the working chamber via feed devices. A material outlet with a separation device is provided in the upper region.

[0002] Torrefaction is a mild thermal treatment of solid fuels without exposure to air (oxygen content preferably below 4 wt%), resulting in pyrolytic decomposition and drying. It typically takes place at temperatures of 200 to 320 °C. Torrefaction is a well-known process familiar to those skilled in the art, so a more detailed description is unnecessary.

[0003] To obtain sustainable fuels from biomass and other waste, gasification is necessary to produce gaseous and / or liquid fuels in subsequent steps. A common process is torrefaction, in which fresh biomass or waste is dried and torrefied. This process removes volatile components and moisture, thus reducing the mass, while retaining a large portion of the energy content. Torrefaction increases the energy content relative to the mass. The resulting product can be easily pressed or further shredded, facilitating transport and subsequent use, particularly through gasification.

[0004] Another advantage of torrefaction is that the cell structures of the biomass are weakened as a result of the thermal treatment under mild pyrolysis conditions, so that the mechanical effort required for subsequent comminution is greatly reduced.

[0005] A device capable of both crushing and torrefying raw material is known from WO 2011 / 057822 A1. It comprises a reactor with a working chamber containing a rotor and impact elements as a grinding unit. Hot torrefaction gas is supplied via a feed device in the lower part of the working chamber, and a feed device for the raw material is located in the top part of the reactor. A gas stream containing the crushed and torrefied particles is discharged by a vent, also located in the top part, and separated in a downstream separation device.

[0006] The purpose of the invention is to create an improved device that can increase the efficiency of torrefaction and comminution.

[0007] The solution according to the invention lies in the features of the independent claim. Advantageous further developments are the subject of the dependent claims.

[0008] In a torrefaction device for producing a fine-grained fuel from energy raw materials as feedstock, in particular comprising biomass and / or alternative fuels from waste (also known as Refuse Derived Fuel (RDF), respectively).of which higher-grade form Solid Recovered Fuel (SRF)), with a reactor designed for comminution and torrefaction of the raw material in a working chamber, comprising a grinding unit, at least one hot gas supply device for supplying hot gas into the working chamber below the grinding unit, at least one raw material supply device for supplying the raw material into the working chamber, and a separation device in the upper region of the working chamber cooperating with a material outlet, is provided according to the invention that the reactor in the working chamber has a vertical roller mill, the grinding unit of which rotates about a vertical axis and comprises as grinding elements a grinding track and rolling elements which roll relative to each other when actuated by a grinding drive, wherein the raw material supply device is provided in the lower region of the reactor such that its opening into the working chamber is arranged in the lower region of the working chamber up to a maximum height of the grinding elements.

[0009] The following explains some of the terms used: Refuse-derived fuel (RDF) is a form of municipal solid waste (MSW) that has undergone treatment to make it more combustible. Solid recovered fuel (SRF) is fuel recovered from waste that meets a higher quality specification than RDF.

[0010] This does not include organic waste such as food waste like fruit, vegetables, dough and baked goods, dairy products and classic food waste.

[0011] A material outlet is understood to be an outlet for the material (supplied as raw material) after torrefaction and comminution. This occurs in particle form, with the particles typically having dimensions of < 1 mm, preferably < 500 µm (based on at least 95%, preferably at least 98% of the particles).

[0012] The terms "below" and "above" refer to the torrefaction device and its reactor in the assembled, operational state. "Below" here refers specifically to the direction in which matter can move under the influence of gravity (vertically downwards or obliquely downwards).

[0013] Hot gas refers to gas with a temperature elevated enough to cause torrefaction. In practice, this means temperatures of at least 200 °C and typically a maximum of 450 °C.

[0014] In the course of process intensification, the raw material is heated to the temperature according to the invention within a few seconds.

[0015] Hot gas is defined as gas with a reduced oxygen content, in particular below 10 vol% oxygen, preferably below 4 vol% oxygen. This is particularly advantageous with regard to preventing dust explosions.

[0016] The lower part of the reactor comprises the area below the grinding media, bounded at the top by the grinding media themselves. This boundary is no higher than the grinding media, preferably no higher than approximately half the height of the grinding media.

[0017] The invention is based on the concept of providing a vertical roller mill for comminution in the working chamber, in which the raw material is fed from below, specifically in the area below the grinding elements up to a maximum height of the grinding elements. The invention further recognizes that for effective comminution in the vertical roller mill, it is crucial that the raw material is at least initially torrefied before first contact with the grinding elements, so that it breaks at least partially under the pressure in the roller mill. This avoids a typical problem in the processing of particularly fresh biomass (e.g., green wood) and / or fresh waste, namely that they are not brittle and therefore cannot be comminuted by pressure alone (they cannot be ground; their so-called Hardgrove index is zero).

[0018] This bottom-feeding system feeds the material to the same point where the hot gas supply enters the reactor's working chamber. This allows torrefaction to begin even before the material reaches the grinding media, utilizing the hot gas in its hottest phase as it enters the working chamber. As the invention surprisingly demonstrates, this enables pre-embrittlement of the raw material even on its way from the feed point to initial contact with the grinding media. The raw material is thus "toasted" and becomes brittle—at least to some extent—before it even comes into contact with the grinding media. This allows it to be at least partially comminuted under pressure from the grinding media. Since all of this occurs in the feed area, where the hot gas reaches its highest temperature, not only is improved comminution achieved initially, but also initial torrefaction.This increases the effectiveness of grinding torrefaction (simultaneous grinding and torrefaction), and vertical roller mills can be used with good success.

[0019] Following this initial torrefaction and comminution, the now partially torrefied raw material undergoes the main torrefaction process in the vertical roller mill. The still coarse raw material migrates against the centrifugal force to the lower section of the grinding media, where it is captured and at least partially comminuted. This still coarse raw material is neither completely torrefied nor ideally comminuted, but at least some areas, especially already torrefied corners and edges, will break off. This material will then follow the centrifugal force and migrate further outwards, where it is captured by the hot gas stream and continues torrefy as circulating material. All of this takes place preferentially in a vortex zone between the grinding media and the outer wall of the working chamber.

[0020] The upward flow caused by the hot gas supplied from below causes the circulating material, especially its coarser components, to fly upwards through a gap between the grinding media and the outer shell of the working chamber. Here, the particles separate into two fractions: a coarser and a finer one. The particles belonging to the coarser fraction precipitate and preferentially return to the center of the grinding media, where they are ground again, transported outwards once more by centrifugal force, and further filtered in the rising hot gas stream, particularly in the vortex zone. The particles belonging to the finer fraction continue to rise to the top of the mill, where the separation device is located. There, those particles that have been sufficiently filtered and exhibit a predetermined required fineness (for example, less than 500 µm) are separated and discharged via the material outlet.The other particles, which still need to be further crushed and torrefied, slide back down towards the center of the mill, where they reach the grinding media again and are crushed, transported outwards by centrifugal force and further torrefied in the rising hot gas stream, especially in the vortex zone, as described above.

[0021] The invention further utilizes the fact that in vertical roller mills with hot gas supplied from below, a vortex zone forms in the area around the grinding media. The raw material supplied from below thus enters into intensive heat exchange with the hot gas at an early stage, so that torrefaction begins quickly. A high heat transfer coefficient is achieved in this vortex zone, which promotes rapid torrefaction. This allows the residence time of the particles in the working chamber to be reduced without having to increase the torrefaction temperature. Overall, this can result in a faster torrefaction process.

[0022] The raw material to be torrefied must pass through two points on its way to the reactor working chamber where at least partial or partial torrefaction takes place: the nozzle ring and the vortex zone above the nozzle ring. In this process, it is torrefied, i.e., embrittled, to such an extent that it fractures at least partially under pressure.

[0023] This is combined with the further advantage of the vertical roller mill that, due to the relative rolling motion of its grinding media, the resulting milled grains (particles) have an almost cubic shape, rather than the shape of needles or flakes. This cubic shape of the milled and torrefied particles offers the advantage of being particularly well-suited for utilization in a downstream thermal processing stage. In particular, this cubic shape is suitable for feeding gasifiers (e.g., entrained-flow gasifiers) to utilize the torrefied raw material as fuel. Specifically, this enables a higher loading rate in the form of pneumatic dense-phase conveying (potentially achieving values ​​of up to or even over 100 kg of solids per kg of conveying gas).

[0024] Overall, this results in significantly more favorable conditions for torrefaction, leading to faster and more complete torrefaction and comminution compared to conventional systems. This means that the material separated from the reactor is highly torrefied upon exiting and exhibits such a high particle fineness that it can be directly fed into a gasification process. Downstream comminution plants, which are often required in the prior art to obtain the necessary fineness for gasifiers, particularly entrained-flow gasifiers, are thus rendered unnecessary and can be omitted in the device according to the invention.

[0025] Thanks to the initial and more intensive torrefaction process according to the invention, milder conditions are sufficient for torrefaction, for example, with lower temperatures. This not only improves product quality in terms of a more homogeneous end product, but also results in fewer undesirable byproducts, such as less under-torrefied fresh biomass and less undesirable over-torrefied mass (such as charcoal). Overall, this leads to an increase in product quality as well as a reduction in energy losses.

[0026] Advantageously, the raw material feed device and the hot gas feed device are combined to feed the raw material together with at least a portion of the hot gas, preferably with all of the hot gas supplied externally. It is understood that the feed of raw material and hot gas then takes place in the lower section of the reactor, as described above. In this way, the raw material to be treated comes into contact with the hot gas directly in the feed device, so that mixing of the hot gas and the raw material to be treated occurs there. Heat transfer can then begin in the combined feed. This establishes close contact between the hot gas on the one hand and the raw material to be torrefied on the other right from the start.It is advantageous for a lock to be connected to the hot gas supply, through which the raw material to be treated is fed into the hot gas supply and subsequently, together with the hot gas, into the working chamber of the reactor. It is not absolutely necessary for all of the supplied hot gas to be combined with the raw material supply at this point.

[0027] Optionally, a portion of the hot gas can be diverted to an additional supply point located elsewhere in the working chamber, preferably above the mill. This additional hot gas supply creates a second zone within the working chamber, further promoting and accelerating the torrefaction process. Advantageously, the temperature of the hot gas at the additional supply point is adjustable independently of the temperature of the hot gas at the supply point for combination with the raw material. This allows for finer control of the torrefaction process. Preferably, the respective flow rates for the hot gas supply points can also be adjusted accordingly.

[0028] Preferably, the raw material feed device is designed to supply the raw material via several outlets distributed circumferentially, which are located particularly at the lower end of the working chamber. This results in a distributed introduction of the raw material into the working chamber, thus preventing clumping of the raw material, which is unfavorable for torrefaction. On the contrary, this achieves a favorable, even distribution of the raw material, fanning it out in a manner advantageous for rapid torrefaction. This is particularly beneficial when these distributed outlets are located at the lower end of the working chamber. This results in a favorable, even distribution of the raw material in the area below the grinding media and subsequently throughout the entire vortex zone of the vertical roller mill, with correspondingly positive effects on the speed and efficiency of the torrefaction process.The following paragraph also refers to the aspect of the vortex zone.

[0029] A further improvement can be achieved by providing a nozzle ring in the lower part of the working chamber, at or below the level of the grinding media. Hot gas is introduced through this nozzle ring into the working chamber to create a vortex zone around the grinding media, and the raw material is also introduced into this vortex zone. Advantageously, the nozzle ring is designed to encircle the grinding mechanism. The nozzle ring ensures a fine distribution of the supplied hot gas, enabling good and uniform exposure of the raw material to the hot gas. Introducing the hot gas via the nozzle ring promotes the formation of a vortex zone around the grinding mechanism. In this zone, as described above, a high gas velocity can be achieved in the area of ​​the grinding media. Thanks to the turbulence, a high heat transfer coefficient to the raw material and its particles, and thus efficient torrefaction, can be achieved.

[0030] It is particularly preferred if flow disruptors, preferably rod-shaped, are provided at the vortex zone of the mill and / or in the combined feed device, projecting into the hot gas and raw material stream. Such flow disruptors can be provided individually or in groups. They can be arranged in or near the vortex zone; both are encompassed by the term. With such flow disruptors, targeted air turbulences similar to a vortex finger can be generated, which locally cause a significant increase in the heat transfer coefficient through the turbulence. In this way, the heat transfer from the hot gas to the raw material to be torrefied can be increased, thereby reducing the required residence time and increasing the temperature gradient with respect to the heating of the raw material.Such flow disruptors thus act as amplifiers for increased heat transfer and therefore more efficient and faster torrefaction of the raw material. They can be designed in virtually any way, but are preferably finger-like or rod-like. The latter offers the advantage of simple installation and rod repositioning. These movable disruptors allow for rapid and excellent control of the heat transfer coefficient, which is otherwise difficult to regulate.

[0031] Advantageously, the flow disturbance elements are adjustable between a disturbance position and a rest position, in which the flow disturbance they cause is reduced. This allows control over the vortex formation caused by the flow disturbance elements and thus the increase in the heat transfer coefficient. If greater heat transfer is desired, the flow disturbance elements are moved into their disturbance position; for example, rods are inserted deeper. Conversely, if less heat transfer is desired, the flow disturbance elements are moved into their rest position; for example, rods are partially or completely removed. In this way, the heat transfer and thus the heat transfer coefficient can be controlled as needed by moving the flow disturbance elements back and forth. This enables fast, efficient, and precise control of the heat transfer coefficient.

[0032] Advantageously, the raw material feed device is connected to a recirculation line that forms part of the hot gas supply system. It is often beneficial for the hot gas to be at least partially recirculated. In this way, the hot gas extracted at the separator can be reused, thereby reducing the need for freshly heated hot gas and thus lowering energy consumption. The raw material feed device can also be advantageously connected to this recirculation line, enabling a convenient and efficient introduction of the raw material to be torrefied into the incoming hot gas.

[0033] The raw material feed system is advantageously equipped with a pre-embrittlement device. This device is designed for pre-torrefaction of the raw material before it enters the working chamber. This provides a special feature that allows the raw material to be at least partially pre-torrefied before it enters the working chamber of the vertical roller mill. As a result, the raw material enters the vertical roller mill in a partially pre-torrefied state, allowing the subsequent torrefaction process to proceed more quickly and efficiently. A particular advantage of the pre-embrittlement device is that the treated raw material is already significantly pre-torrefied upon entering the working chamber, making it brittle and enabling efficient grinding by the milling media upon initial contact. This noticeably accelerates the entire subsequent torrefaction process within the working chamber.

[0034] Pre-torfaction refers to the torfaction of the raw material before it enters the work area.

[0035] The pre-embrittlement device does not necessarily need to be of a complex design. It can suffice to have a common pre-flow section located upstream of the gas and raw material feed opening into the working chamber, in which the raw material is guided together with the hot gas. In this way, an initial, incomplete torrefaction of the raw material can be achieved even before it enters the working chamber. Even if only the corners or edges of the raw material particles are torrefied, the desired effect is achieved: the raw material particles are reduced much more effectively upon entering the working chamber and impacting the grinding media than particles that are still completely untorrefied. This can be further improved if the pre-embrittlement device includes a mixing unit, such as a mixing drum.Mixing hot gas with the raw material can achieve better pre-gate refraction, and the more intensive the mixing, the greater the improvement.

[0036] This means that the raw material to be torrefied has to pass not just two, but three points on its way to the reactor's working chamber where at least partial or partial torrefaction takes place: namely, the common feed section, the nozzle ring, and the vortex zone above the nozzle ring. Even difficult-to-treat raw materials, such as green wood, are torrefied—that is, made brittle—to such an extent that they break, at least partially, under pressure.

[0037] It is particularly advantageous if the pre-embrittlement device includes a labyrinth element. Such a labyrinth element allows for a significant lengthening of the pre-flow path without requiring much installation space. The labyrinth element is characterized by multiple deflections, meaning the gas path is deflected several times by at least 90°. This can be achieved with angular or curved sections. As a result, there is no direct, straight path between the inlet and outlet. This lengthens the flow path and thus increases the residence time. Furthermore, the labyrinth element offers the advantage that its compact design minimizes heat loss from the supplied hot gas, ensuring a high temperature within the labyrinth element and thus enabling efficient pre-refluxing.The labyrinth element preferably comprises several chambers arranged above or next to each other, or a combination of both, with these chambers potentially connected in a meandering pattern. This results in a particularly long common feed path, even in limited installation space, offering corresponding advantages in terms of the achieved pre-torrefaction. The labyrinth element can also be designed as a spiral chamber. This results in a concentric flow of the hot gas and the raw material to be torrefied over several cycles, combining a high pre-torrefaction effect with low flow resistance. Furthermore, the spiral chamber design also allows for a central feed of hot gas and raw material with external outlets, optimally designed for distributed distribution across the lower area of ​​the working chamber.In this way, pre-torrefaction can be combined with good distribution of the raw material upon entry into the working chamber. This positively influences the torrefaction quality. Furthermore, the residence time in the pre-embrittlement unit can be adjusted by the design of the labyrinth element and, in particular, its length.

[0038] The grinding mechanism can be designed in various ways. It is always a grinding mechanism with rolling elements, preferably designed as a ball ring grinder, a conical roller grinder, a drum grinder, or a pendulum roller grinder. These designs offer advantages in terms of good grinding results, compact installation space, effective comminution, and the application of hot gas to the material being ground for efficient torrefaction.

[0039] Preferably, an internal circulation system is formed within the reactor's working chamber, whereby partially torrefied raw material and larger particles are returned downwards from the separation device into the working chamber, preferably to the area of ​​a hot vortex zone near the grinding media, particularly above the nozzle ring. Thanks to this internal circulation system, the particles are circulated within the working chamber, repeatedly passing through the hot vortex zone near the grinding media above the nozzle ring and undergoing further torrefaction until they are sufficiently small and torrefied to exit the working chamber and the reactor via the separation device. This ensures continuous and reliable torrefaction of the particles. Partially torrefied raw material is defined as material that is not yet fully torrefied.

[0040] Larger particles are defined as those exceeding an adjustable particle size. The separation device is designed to operate at this adjustable particle size threshold. Particles larger than this threshold are recirculated, while particles smaller than the threshold are separated and discharged. Thus, particles larger than the threshold of the separation device are recirculated. These particles can collectively be referred to as the "heavy fraction." The remaining particles discharged by the separation device can be described as the "fine fraction."

[0041] This ensures that partially and / or insufficiently torrefied particles cannot yet leave the working chamber, but are continuously circulated until they are fully torrefied. The difference between fully torrefied and fully torrefied is defined by the achieved grindability, for which a measure of grindability is specific to the industry. One such measure is the Hardgrove grindability index (HGI). Values ​​below 30 HGI are insufficient; values ​​of at least 50 HGI for the removed torrefied particles are targeted.

[0042] The separation unit functions as a classifier, designed to separate smaller (finer) particles from larger ones. It can be designed as a static classifier. Static classifiers have the advantage of being simple in design and very robust. This makes them reliable and able to withstand high temperatures without the need for complex measures to protect sensitive components such as bearings. The static classifier preferably has adjustable flaps, allowing the threshold for particle size to be set. Thus, the classification of a static classifier can be easily adjusted by changing the flaps, making it simple to adapt the separation unit to changing conditions.This flap adjustment can be remotely adjustable, thus enabling automated control.

[0043] It is particularly advantageous if the separation system includes a dynamic classifier, where the fineness of the separated particles can be adjusted by changing the classifier speed. With a dynamic classifier, the classification system can thus be adjusted very easily by changing the speed, allowing the separation system to be readily adapted to changing conditions. In this way, it is possible to easily change the fineness of the separated particles as needed, especially within the framework of a control system. It is advantageous to set the system so that particles <= 500 µm are separated, which means that the separated particles already have a sufficiently fineness for combustion in a carburetor, especially a variegated carburetor. This offers significant advantages with regard to subsequent processing.

[0044] Advantageously, a pre-compression stage is installed upstream of the torrefaction device. This stage is expediently designed as a hammer mill or cutting mill. In this way, the raw material can be reduced to a particle size favorable for torrefaction in the vertical roller mill according to the invention before it is fed into the device. Particle sizes of no more than 4 mm at the outlet of the hammer mill or cutting mill are advantageous. Such a pre-compression stage can, for example, be designed as a hammer mill or a cutting mill. These are robust and ensure efficient pre-compression.

[0045] Advantageously, a control device is provided that is designed to achieve a preset degree of torrefaction by changing the torrefaction temperature, residence time, and / or heat transfer coefficient. The degree of torrefaction can conveniently be determined by the embrittlement achieved. In this sense, embrittlement is a measure of torrefaction; thus, sufficient embrittlement is synonymous with sufficient torrefaction. On the other hand, excessive torrefaction must be avoided. Put simply, with organic raw materials such as wood, both insufficiently torrefied material ("fresh wood") and excessively torrefied material ("charcoal") must be avoided. Embrittlement, and thus achieving sufficient embrittlement, is only possible if the raw material has been sufficiently reduced to fine, and in particular nearly cubic, particles.

[0046] One way to determine the degree of torrefaction is, for example, to directly measure particle shape or size via inline analysis and use this as the basis for control, so that the control system regulates the parameters important for torrefaction, especially temperature, residence time, and heat transfer coefficient, to achieve a predetermined particle shape. An alternative way to determine the degree of torrefaction is to do so indirectly and use the pressure drop across the reactor (the difference between the gas pressure before and after the reactor) as a measure of sufficient embrittlement or sufficient torrefaction (and thus also as an indirect measure of an approximately cubic particle shape). This is based on the understanding that insufficiently embrittled material is difficult to comminute, which results in a high pressure drop across the reactor.On the other hand, excessively brittle material is often difficult to comminute, which can also manifest itself in a high reactor pressure drop. The invention recognizes that a minimum pressure drop can characterize optimal embrittlement. However, it may also suffice to maintain a predetermined pressure drop range (pressure drop window), as determined, for example, through preliminary tests. If the control device is designed to regulate to this reactor pressure drop, optimal embrittlement can be achieved. Preferably, pressure sensors for the reactor inlet and outlet pressure are provided for this indirect determination of the degree of torrefaction. The pressure drop determined on this basis then serves as a measure of the aforementioned degree of torrefaction.

[0047] The control device is preferably designed so that the torrefaction temperature is controlled by a measured temperature upstream of the reactor and a temperature downstream of the reactor. In particular, the hot gas temperature in the hot gas duct before the feed of the raw material can be measured "upstream of the reactor." In particular, the exhaust gas temperature downstream of the separator device in the pipe to the filter can be measured "downstream of the reactor." Further temperature measuring points, e.g., at a selectable distance above the nozzle ring, are not excluded and can also be included in the control concept.

[0048] If the temperature after the reactor is too low, the temperature before the reactor is increased accordingly by supplying more or hotter hot gas, and vice versa. In this way, maintaining the desired torrefaction temperature can be ensured.

[0049] The control unit is preferably further designed to control the residence time of the raw material in the reactor by adjusting the volumetric flow rate of the hot gas supply. The residence time control advantageously works in conjunction with the torrefaction temperature control, such that a slightly lower torrefaction temperature is set for longer residence times, thereby achieving milder torrefaction conditions overall. This can lead to greater homogeneity of the torrefied product, i.e., a lower proportion of insufficiently torrefied ("fresh wood") or excessively torrefied material ("charcoal"). This not only means an increase in product quality but also lower energy losses.

[0050] Furthermore, the control device can be configured to control the heat transfer coefficient by means of the aforementioned flow disturbance elements. The heat transfer coefficient can be used, in particular, to control the rate of torrefaction, thus allowing, for example, a reduction in residence time. On the other hand, it should be noted that shorter residence times result in a less gentle torrefaction process. However, this is offset by the advantage that the throughput of the torrefaction device can be increased.

[0051] The control device can also be designed to be set to a particle size distribution of the material exiting the reactor of 0 to 500 pm, preferably for raw material with a particle size of 0 to 4 mm. To achieve this particle size, a hammer mill or a cutting mill is preferably installed upstream of the raw material feed device. In this way, the torrefaction device can be operated to produce torrefied material directly from the raw material, ready for gasification. This is particularly suitable for the technically and economically important gasification process in entrained-flow gasifiers. Furthermore, torrefied material of this fineness is well suited for compaction, especially by pelletizing, for subsequent transport. The compacted material, especially the pellets, then only needs to be deagglomerated at the destination and, thanks to its fineness of max.500 µm directly for thermal utilization in (flow-flow) carburetors.

[0052] Advantageously, a hot gas generator is connected to the hot gas supply device and / or a raw material feed is connected to the raw material feed device. The raw material feed can be designed, in particular, as a rotary valve, preferably a rotary valve. This allows the torrefaction device to be fed with material in an efficient manner.

[0053] The invention is explained in more detail below with reference to the accompanying drawing and exemplary embodiments. The drawing shows: Fig. 1 a schematic cross-sectional view of a torrefaction device according to a first embodiment of the invention; Fig. 2 an enlarged view of the lower region of a reactor with a grinder, grinding drive, and feed devices for hot gas and raw material; Fig. 3 a schematic overview of a torrefaction plant; Fig. 4 a detailed view of the feed of hot gas and raw material below a nozzle ring; Fig. 5 a schematic cross-sectional view of a torrefaction device with a static classifier according to a second embodiment; Fig. 6A, B top view and cross-sectional view of a flow disturbance element; Fig. 7 cross-sectional view of a labyrinth element for pre-embrittlement; Fig. 8A, B cross-sectional view of an alternative labyrinth element for pre-embrittlement; and Fig. 9A-C various variants of grinders.

[0054] First, let's focus on Fig. 3 Reference is made to the figure. It shows the integration of the torrefaction device according to the invention, which in its entirety is designated by the reference numeral 1, into a torrefaction system and also serves to clarify the entire process flow.

[0055] Raw material 9, for example fresh wood or other biomass, is introduced at a feed point 54. It can first pass through a hammer mill or cutting mill 16 to perform pre-shredding, preferably reducing the raw material 9 to coarse particles 91 with maximum dimensions of 4 mm. This is then fed as a raw material stream 50 via a sluice gate 55, preferably a rotary valve, to a raw material feed device 5 and into the torrefaction device 1. Hot gas generated by a hot gas source 41, for example a gas burner, is supplied as a hot gas stream 40 to a hot gas feed device 4. Raw material stream 50 and hot gas stream 40 are then fed via a common feed 45 to a reactor 2 of the torrefaction device 1, specifically at the lower part of reactor 2. The hot gas stream 40 also serves as the transport gas for the raw material of raw material stream 50.Reactor 2 has an internal working chamber 22 containing a vertical roller mill 3, which serves to grind and torrefy the raw material. The resulting torrefied particles are discharged at a head 21 of reactor 2 to a separation device (e.g., filter or cyclone) 17, which is designed to remove the particles from the gas stream drawn from reactor 2. The particles are transported by a solids conveying device 18 to a storage silo 19. The separated gas can be partially recirculated back to the hot gas or raw material feed device via a recirculation line 15.

[0056] For a more detailed explanation of the structure and operation of reactor 2 of the torrefaction device 1, please refer to the following. Fig. 1 und 2 Reference is made to the reactor 2. The reactor 2 has a housing 20 in which a working chamber 22 and the vertical roller mill 3 are arranged. A grinding mechanism 35 rotates within this mill about a vertical axis 30, which typically also forms a central axis of the working chamber 22. The grinding mechanism 35 in the Fig.1 The illustrated embodiment is designed as a ball ring grinder and comprises grinding elements 36. These include a circular grinding track 37 and grinding balls 38 that roll on it. A pressure ring 34 applies additional pressure to the grinding balls 38. The grinder 35 is actuated by a grinding drive 39, which rotates the grinding track 37. The grinding balls 38 roll on the rotating grinding track 37 and crush the material lying on the grinding track 37 due to their own weight and the pressure of the pressure ring 34 pressing down on them from above. For this to be successful, the material to be ground must be brittle. Pre-embrittlement of the material to be ground and torrefied to this extent before initial contact with the grinding elements 36 is a key aspect of the invention.

[0057] A cone 28 is arranged in the upper part of the working chamber 22. A separation device 6 is arranged in the head 21 of the reactor 2 above the cone 28. It comprises, in the case of the Fig. 1 The illustrated embodiment features a rotating dynamic classifier 65, driven by a speed-adjustable drive 66. It is designed to classify larger and heavier particles on the one hand and smaller and lighter particles on the other. The separation device 6, with its classifier 65, separates an incoming particle stream, containing particles of different sizes and masses, into two groups. Particles 94 of one group are already sufficiently small and light (the so-called fine fraction) and are discharged via an outlet 27 of the reactor 2. Particles 93 of the other group, which are still too large and heavy (the so-called heavy fraction), are, however, discharged via the cone 28 and returned to the vertical mill 3 by gravity. This creates an internal circulation 24 within the working chamber 22.

[0058] The threshold of the classifier 65 for distinguishing between the heavy and fine fractions is adjustable via the rotational speed of its drive 66. By changing the setting of the drive 66, the rotational speed of the dynamic classifier 65 can be altered, thereby adjusting the classifier's threshold at which coarse particles 93 are rejected and fine particles 92 are separated. In this way, the fineness of the torrefied product obtained at the outlet 27 of reactor 2, or of the fine particles 94 discharged there, can be easily adjusted.

[0059] In the lower area 23 of the working space 22, a nozzle ring 25 surrounds the grinding media 36 in their lower area (see Fig. 2 The nozzle ring 25 is arranged between the grinding media 36 and a housing wall 20 surrounding the working chamber 22. The supply devices for the hot gas stream 40 and the raw material stream 50 are connected below the nozzle ring 25. During operation, a vortex zone 26 forms above the nozzle ring 25. An additional gas supply 44 can be provided in the central area of ​​the working chamber 22, by means of which a partial stream of the hot gas is introduced directly into the working chamber 22.

[0060] Raw material 9 is, as in Fig. 2 The schematic representation shows the feed for pre-crushing in an optional hammer mill or cutting mill 16. This causes pre-crushing into coarse particles, the maximum dimensions of which are preferably 4 mm. The hammer mill or cutting mill 16 is not required if the raw material is already particulate with corresponding maximum dimensions of preferably no more than 4 mm. The coarse particles 91 of the raw material 9 are introduced into the raw material feed device 5 by means of the rotary valve 55. Hot gas stream 40 generated by the hot gas generator 41 is introduced via the hot gas feed device. In the illustrated embodiment, these are combined by means of a T-piece, so that the supply of hot gas and raw material to the reactor 2 occurs together via a common feed 45, which forms a section 45 of the gas feed 4.Through this joint feed 45 in this section, a pre-embrittlement of the coarse particles 91 of the raw material 9 already takes place using the hot gas 40 in its hottest phase, namely shortly after the hot gas source 41 and before entering the working chamber 22.

[0061] At an opening 51, the particles 92, which have already been partially torrefied by the common feed 45, enter the reactor 2 together with the hot gas stream 40, specifically in a lower region 23 of the working chamber 22. This lower region 23 extends to a maximum of approximately half the height of the grinding media 36 and is bounded at the top by the nozzle ring 25. The feed of the hot gas stream 40 with the particles into the reactor 2, as well as the spatial position of the nozzle ring 25 and the vortex zone 26 through which the gas flows, are shown in detail in enlarged form in the following figure. Fig. 4 . Subsequently, the hot gas stream 40, together with the particles 91, enters the actual working chamber 22 via the nozzle ring 25.

[0062] During this passage through the nozzle ring 25, the particles are in extremely close contact with the hot gas and the resulting high heat transfer coefficient, and an even greater heat transfer occurs for the particles in the vortex zone 26. At these two points 25 and 26, they are already so thoroughly antorrefied (so to speak, "roasted") that upon their first contact with the grinding media, they are at least brittle at their corners and edges, causing these to break and the comminution of the particles by the grinding media 36 of the grinding mechanism 35 to begin.

[0063] Following this initial torrefaction and comminution, the particles now participate in the actual torrefaction process in the working chamber 22 of reactor 2. The hot gas 40, supplied from below, creates an upward flow, causing the now partially torrefied particles 92 to fly upwards through the vortex zone and the gap between the grinding media 36 in the wall of the housing 20 of the working chamber 22. Very large and very heavy particles cannot follow this upward movement and fall back down into the grinding mechanism 35, where centrifugal force carries them outwards to the grinding media 36 and back into the vortex zone 26 for further comminution and torrefaction. Smaller and lighter particles can continue to rise until they reach the classifier 65 of the separation unit 6. This separates the very small and fine particles 94, which are then drawn off via the outlet 27.Larger and heavier particles 93 are rejected by the classifier 65 and enter the cone 28, which functions as part of an inner circulation system 24. This system transports the rejected particles 93 back down, where they enter the central grinding unit 35. From there, centrifugal force propels them to the grinding media 36 for comminution and into the vortex zone 26 for further torrefaction. The larger and heavier particles 93 undergo this cycle several times until they are sufficiently small and fine to be drawn off by the classifier 65.

[0064] A second embodiment is shown in Fig. 5 It is essentially identical to the one in Fig. 1 The second embodiment is described in the illustration, where the same reference numerals are chosen for similar components. The main difference lies in the fact that in the second embodiment, the separation device 6 is designed with a static classifier 62. The threshold value of the classifier 62, at which the coarse particles 93 are rejected and the fine particles 94 are separated, can be adjusted, for example, by means of pivotable flaps 63 on the static classifier 62. In this way, the fineness of the torrefied product obtained at the outlet of the reactor 2 or of the fine particles 94 discharged there can be adjusted.

[0065] To improve the heat transfer between the hot gas and the particles, which is crucial for torrefaction, baffles 46 are provided. These can be located, in particular, in the hot gas supply unit 40, specifically in the section of the combined feed 45, but also in the vortex zone 26 and elsewhere in the working chamber 22. These baffles 46 are, for example, rod-shaped and project transversely into the gas flow. They thus form flow obstructions, behind which (viewed in the direction of flow) a flow disturbance in the form of vortices 49 is created (so-called vortex fingers). These vortices 49 increase the heat transfer from the hot gas to the particles of the material to be torrefied, thereby reducing the required residence time. These baffles 46 thus make a significant contribution to increasing the efficiency of reactor 2.They are movable between a disturbance position 47, in which they are fully inserted into the gas flow and generate maximum vortices 49 or vortex fingers, as in . Fig. 6A und Fig. 6B depicted, and a resting position in which they are extended out of the gas stream and generate little or no turbulence. This mobility is shown in Fig. 6A This is visualized by a double arrow 48. This allows for rapid and excellent controllability of the otherwise difficult-to-control heat transfer coefficient.

[0066] A cross-sectional view of a labyrinth element 71 for the pre-embrittlement device 7 is shown in Fig. 7 The labyrinth element 71 is arranged axially below the reactor 2. It has upwardly directed outlets that introduce the hot gas stream 40 containing the particles 91 to be torrefied directly into the annular area below the nozzle ring 25. The labyrinth element 71 is designed as a meandering chamber 74. It has a central inlet 72 at its lower end and the outlets 73 at its upper end. Between these, a multitude of chambers are arranged in a meandering pattern one after the other in the direction of flow, thereby significantly lengthening the flow path. This correspondingly increases the transit time for the hot gas, thus providing more time for the embrittlement of the particles 91 to be torrefied that are carried along. In this way, effective pre-embrittlement can be achieved.It can be increased by also providing the above-described disruptive elements 46 in the labyrinth element 71.

[0067] An alternative labyrinth element 71' is shown in Fig. 8A, 8B This labyrinth element is designed with a spiral chamber 76. A horizontal cross-section through the spiral chamber 76 is shown in Fig. 8A As shown, in particular, from the radial cross-sectional representation in Fig. 8B As can be clearly seen, the inlet 72 is located on the lower side close to the center and the outlets are distributed in a ring shape along the outermost spiral path, resulting in a large-area and particularly uniform transition to reactor 2 in the area below nozzle ring 25.

[0068] The labyrinth elements 71, 71` can also be combined with each other, especially in the form of a multi-level labyrinth element, resulting in an enormous increase in the common approach path and thus in the achieved degree of an-torrefaction.

[0069] A control unit 8 is provided for monitoring operation and setting parameters. Pressure and temperature sensors 11, 12, located in the area of ​​the common feed 45 and measuring the pressure and temperature upstream of the reactor 22, are connected to this control unit. A further set of pressure and temperature sensors 13, 14, located at the outlet 27 of the reactor 2, measuring the pressure and temperature downstream of the reactor 22, is also connected. The control unit 8 is designed to determine and set the torrefaction temperature in the reactor 2 via the temperature downstream of the reactor 22 and the temperature upstream of the reactor 22, as measured by sensors 14 and 12, respectively. The residence time of the particles in the reactor 2 is preferably set by the control unit 8 via the volumetric flow rate of the gas feed unit 40.The fineness of the torrefied particles 94 at the reactor outlet 27 can be controlled, in particular, via the separation device 6, preferably via the rotational speed set on the drive 66 of the dynamic classifier 65. The heat transfer coefficient, and thus the rate of torrefaction in the various areas, especially the pre-embrittlement device 7, the nozzle ring 25, the vortex zone 26, and the working chamber 22 itself, can be effectively controlled in this way. In particular, the required temperature and residence time can also be influenced in this manner.

[0070] To monitor and control the torrefaction result, particularly the degree of sufficient embrittlement or torrefaction, the pressure drop across reactor 22 can be determined. This pressure drop serves both as a measure of sufficient embrittlement or torrefaction and, as explained in the introduction, as an indirect indicator of an approximately cubic particle shape. In this way, complex and versatile control of the torrefaction process can be achieved with relatively simple means.

[0071] The grinding mechanism 35 does not necessarily have to be a ball-ring grinding mechanism, as in Fig. 1 and Fig. 5 As shown. Alternative versions of the grinder 35 are possible. Examples are shown in the Fig. 9A bis 9C depicted. Fig. 9A Figure 35 shows a conical roller mill 35'. It comprises a rotating grinding plate 37' on which at least two, usually opposing, conical rollers 38' run. The conical rollers 38' are arranged at one end of their respective axles 31', and a pressure device (e.g., a compression spring) is arranged at the other end, with a pivot bearing in between. Under the pressure of the pressure device, the conical rollers 38' are pressed onto the grinding plate 37'. The force can be increased by lever action depending on the position of the pivot bearing. The resulting independent spring mounting of the conical rollers 38' also makes this design less sensitive to unevenly distributed material on the grinding plate 37'.

[0072] Another alternative embodiment is a roller mill 35", as in Fig. 9B As shown, at least two opposing rollers 38" run along a flat, annular grinding track 37". They are each arranged at one end of a common axis 33", the axis 33" being driven by a drive such that it rotates about its vertical orthonormal. The rollers 38" roll in a circle on the annular grinding track 37".

[0073] Another alternative embodiment is described in Fig. 9CThe device is depicted as a pendulum roller mill 35"'. At least two rollers 38"' are suspended by pendulums on horizontally arranged, rotating arms. The rollers 38"' have a vertical axis of rotation and can pivot inwards or outwards. The rollers 38"' run on their far side along a path that encircles the entire arrangement of rollers 38"', describing a circular shell 37"'. Due to the pendulum mounting, the contact force of the rollers 38"' against the inside of the circular shell 37"' can be changed by altering the drive speed of the rotating arms. As the rotational speed increases, the greater centrifugal force presses them more strongly against the inside of the circular shell 37"'.

[0074] The specific selection of the grinding mechanism 35 is left to the person skilled in the art. The effects and advantages achieved according to the invention, as described above, apply to all grinding mechanisms. Furthermore, the different grinding mechanisms each offer individual advantages, which the person skilled in the art considers when making their selection, depending on the raw material to be processed and other circumstances.

Claims

1. Torrefaction device for producing a fine-grained fuel from energy raw materials as feedstock, in particular comprising biomass and / or alternative fuels from waste, with a reactor (2) designed for comminution and torrefaction of the feedstock in a working chamber (22), comprising a grinding mill (35), at least one hot gas supply device (4) for supplying hot gas into the working chamber below the grinding mill (35), at least one feedstock feed device (5) for supplying the feedstock into the working chamber (22), and a separation device (6) in the upper area of ​​the working chamber (22) cooperating with a material outlet (27), characterized by the fact thatThe reactor (2) in the working chamber (22) has a vertical roller mill (3) whose grinding mechanism rotates about a vertical axis (30) and comprises a grinding track (37) and rolling elements (38) as grinding bodies (36), which roll relative to each other when actuated by a grinding drive (39), wherein the raw material feed device (4) is provided in the lower area of ​​the reactor (2) such that its opening (51) into the working chamber (22) is arranged in the lower area of ​​the working chamber (22) up to a maximum height of the grinding bodies (36).

2. Torrefication device according to claim 1, characterized by the fact that the raw material feed device (4) and the hot gas feed device (5) are designed to supply the raw material together with at least a part of the hot gas, preferably with all of the supplied hot gas.

3. Torrefaction device according to claim 1 or 2, characterized by the fact thatthe raw material feed device (4) is designed to feed the raw material via several outlets arranged in the circumferential direction, which are arranged in particular at the lower end of the working space (22).

4. Torrefaction device according to claim 2 or 3, characterized by the fact that in the lower part of the working space (22) at the level of the grinding media (36) or below, a nozzle ring (25) is provided, through which the hot gas is guided into the working space (22) to form a vortex zone in the area of ​​the grinding media (36), and the raw material is guided into this vortex zone (26).

5. Torrefaction device according to one of claims 2 to 4, characterized by the fact that Flow disturbance elements (46) are provided at the vortex zone (26) at the mill and / or in the combined feed device in the hot gas and raw material flow, which are preferably rod-shaped.

6. Torrefication device according to the preceding claim, characterized by the fact thatthe flow disturbance elements (46) are adjustable between a disturbance position (47) and a rest position in which a flow disturbance caused by them is reduced, preferably by extending or retracting the flow disturbance elements (46) to different depths.

7. Torrefaction device according to any one of claims 2 to 6, characterized by the fact that the raw material supply device is connected to a recirculation line (15) which forms part of the hot gas supply device (4).

8. Torrefication device according to one of the preceding claims, characterized by the fact that the raw material feed device (5) is equipped with a pre-embrittlement device (7) which is designed for pre-gate refraction before feeding into the working space (22).

9. Torrefication device according to the preceding claim, characterized by the fact thatthe pre-embrittlement device (7) comprises a labyrinth element (71) which has several chambers arranged one above the other and / or next to each other, which are connected in a meandering (74) shape, and / or is designed as a spiral chamber (75).

10. Torrefication device according to one of the preceding claims, characterized by the fact that in the working chamber (22) an inner circulation (24) is formed, whereby partially torrefied raw material and larger particles are returned downwards from the separation device (6) into the working chamber up to the area of ​​a hot vortex zone (26) at the grinding media (36), in particular above the nozzle ring (25).

11. Torrefication device according to the preceding claim, characterized by the fact thatthe separation device (6) comprises a dynamic classifier (65) wherein the fineness of separated raw material can be adjusted by adjusting the classifier speed, or a static classifier (62), preferably with adjustable flaps (63).

12. Torrefication device according to one of the preceding claims, characterized by the fact that it is provided with a pre-comminuted stage for pre-comminuted grinding, which is preferably designed as a hammer or cutting mill (16).

13. Torrefication device according to one of the preceding claims, characterized by the fact that an additional gas supply (44) for hot gas into the working chamber (22) is provided, which preferably opens above the grinding mechanism (35).

14. Torrefication device according to one of the preceding claims, characterized by the fact thata control device (8) is provided which is designed to achieve a preset degree of torrefaction by changing the torrefaction temperature, residence time and / or heat transfer coefficient.

15. Torrefication device according to the preceding claim, characterized by the fact that the control device (8) is designed such that the torrefaction temperature is controlled by a measured temperature before the reactor (2) and temperature after the reactor (2), and / or that the residence time is controlled by setting a volume flow rate of the hot gas supply (4), and / or that the heat transfer coefficient is controlled by means of flow disturbance elements (46).

16. Torrefaction device according to one of claims 14 or 15, characterized by the fact thatby means of pressure sensors (11, 12) an inlet and outlet pressure of the reactor (2) is determined and serves as a measure of the degree of torrefaction, and / or that the control device (8) is set to a particle size distribution of the material exiting the reactor (2) of 0 to 500 µm, preferably with raw material supplied with a particle size of 0 to 4 mm.

17. Torrefication device according to one of the preceding claims, characterized by the fact that a hot gas generator (41) and / or a raw material feed (54) are connected to the hot gas supply device (4).

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