A system and method for controlling a particle size of a pulverized base material

Abstract

The present invention relates to a system (1) for controlling a particle size of a pulverized base material. The system comprises a pulverizing device (10) comprising a housing (3) having an interior space (5). The pulverizing device (10) further comprises at least one pulverizing unit (14) disposed in the interior space (5) and arranged rotatable with respect to the housing (3) about a rotational axis (R). The pulverizing device (10) further comprises an inlet opening (19) for feeding base material to the interior space (5) and an outlet opening (21) for dispatching the pulverized material from the interior space. The system (1) further comprises a chamber (30) arranged at the outlet opening (21) for receiving the pulverized material from the pulverizing device (10). The system (1) further comprises a pressure sensor (32) configured to measure the pressure at the outlet opening (21). The system (1) further comprises a transportation arrangement (34) configured to transport the pulverized material from the chamber (30), wherein the transport arrangement (34) is adapted to create an under pressure in the chamber (30). The system further comprises a pressure controlling device (36) configured to regulate the pressure in the chamber (30) based on the measured pressure and a set value for the pressure at the outlet opening (21), wherein the set value is selected in dependence on a desired particle size.

Description

[0001] A system and method for controlling a particle size of a pulverized base material

[0002] Technical field

[0003] The present invention relates to a system for pulverizing a base material. In particular, the present invention relates to a system and method for controlling a particle size of a pulverized base material.

[0004] When pulverizing a base material such as wool, pellets coal, vagaries, etc the output will be in different size. This can be achieved in different ways with different types of mills, for instance a hammer mill, sawmill or a ball mill. The output can graphically be described in a powder distribution chart. Earlier, a desired particle size could be achieved through a sifting process with feedback and re pulverizing of the undesired powder size. This is energy consuming and would require a sifting devise to achieve the desired output.

[0005] In many applications, the size of the particles in the pulverized material is important. For example, finely pulverized wood powder burns better and dries faster than wood powder including larger particles. Thus, it is desired to control the size of the pulverized material.

[0006] Summary

[0007] An object of the present invention is to provide an improved system for controlling a particle size when pulverizing a base material.

[0008] According to an aspect of the invention, the object is achieved by a system for controlling a particle size of a pulverized base material as defined in claim 1.

[0009] The system comprises a pulverizing device. The pulverizing device comprises a housing having an interior space and at least one pulverizing unit disposed in the interior space and arranged rotatable with respect to the housing about a rotational axis. The pulverizing device further comprises an inlet opening for feeding base material to the interior space and an outlet opening for dispatching the pulverized material, e.g. powder, from the interior space.

[0010] The system further comprises a chamber arranged at the outlet opening of the pulverizing device for receiving the pulverized material from the pulverizing device. The at least one pulverizing unit 14 may be rotating with a high speed so that an overpressure is created at the outlet opening 21 and the pulverized material is dispatched from the pulverizing device to the chamber 30 by means of the centrifugal force.

[0011] The system further comprises a transportation arrangement configured to transport the pulverized material from the chamber, wherein the transport arrangement is adapted to create an under pressure in the chamber. The under pressure is created in the chamber to try to cancel out the over pressure from the outlet opening. The aim is to provide a pressure as close to zero as possible so that the pulverized material falls down due to gravity. Pulverized material having a larger particle size than the desired particle size will not fall down. The pulverized material may be transported to a pulverized material receiver, e.g. a burner, arranged to receive the pulverized material from the transportation arrangement. The pulverized material may be transported via a transportation pipe.

[0012] The system further comprises a pressure sensor configured to measure the pressure at the outlet opening. The pressure sensor may also be configured to measure the pressure in the chamber.

[0013] The system further comprises a pressure controlling device configured to regulate the pressure in the chamber based on the measured pressure and a set value for the pressure at the outlet opening, wherein the set value is selected in dependence on a desired particle size.

[0014] Such a system according to the invention allows controlling the particle size of the pulverized base material by regulating the pressure in the chamber arranged at the outlet opening of the pulverizing device. The system makes it possible to pulverize base material into particles of a desired size which in turn allows producing a desired amount and / or size of pulverized material. Further, the system according to the invention reduces the need of a silo for storing the pulverized material and consequently also the need for transporting the pulverized material from the silo. This in turn will reduce the costs for storing and manufacturing the pulverized material. And without a silo there will be no problems with arch formation.

[0015] According to an embodiment of the invention, a higher set value for the pressure results in a coarser particle size, and wherein a lower set value for the pressure results in a finer particle size. Thus, by regulating the pressure the desired particle size can be achieved.

[0016] According to an embodiment of the invention, the chamber has an outlet for the pulverized material and the transportation arrangement comprises an ejector arranged to suck out the pulverized material from the outlet of the chamber. The ejector thus enables that the under pressure is created in the chamber.

[0017] According to an embodiment of the invention, the transportation arrangement comprises a blowing unit arranged to transport, e.g. forward, the pulverized material to the ejector. The ejector then transports the pulverized material to a pulverized material receiver. The blowing unit may comprise a compressor or a fan with a variable speed.

[0018] According to an embodiment of the invention, the transportation arrangement further comprises a blow through rotary valve disposed in the chamber. The blowing unit is arranged to blow the pulverized material through the rotary valve. The blow through rotary valve is arranged to portion the pulverized material that has fallen down and forward it to the ejector.

[0019] According to an embodiment of the invention, the pressure controlling device comprises a controllable valve that is opened or closed to regulate the pressure in the chamber and a pressure regulator unit configured to control the controllable valve based on the measured pressure. The pressure regulator may comprise a first control unit such as a Programmable Logic Controller (PLC) a microcomputer or other or other digital hardware configured to control the controllable valve.

[0020] According to an embodiment of the invention, the system further comprises a material dosing unit connected to the pulverizing device. The material dosing unit may comprise a dosing screw unit arranged to dose the feed of the base material to the interior space of the pulverizing device.

[0021] According to an embodiment of the invention, the system further comprises a pulverized material receiver arranged to receive the pulverized material from the transportation arrangement and to provide a feedback signal to the material dosing unit to inform the material dosing unit about the current need of pulverized material, and wherein the material dosing unit is configured to receive the feedback signal and to dose the feed of the base material to the interior space of the pulverizing device based on the feedback signal. The material dosing unit and the pulverized material receiver may comprise a second control unit and third control unit, respectively, configured to communicate with each other. The second and third control units may e.g. be a controller such as a microcontroller, a microprocessor, a data logger unit, a PLC, or other digital hardware, configured to processes data coming from input devices and control outputs.

[0022] According to an embodiment of the invention, the at least one pulverizing unit is rotating with a high speed so that an overpressure is created at the outlet opening and the pulverized material is dispatched from to the chamber by means of the centrifugal force. According to an embodiment of the invention, the at least one pulverizing unit may comprise a plurality of saw blades, wherein each of the sawblades is disc-shaped and has a periphery provided with a plurality of cutting teeth for cutting the material and a plurality of collecting notches for collecting the cut material.

[0023] The system is particularly useful for controlling particle sizes from wood powder. However, the system according to the invention is useful also for controlling the particle sizes of many different types of pulverizing material, such as plastic particles, metal particles, food, dust or seed. According to another aspect of the invention, the above object is achieved by a method for controlling a particle size of a pulverized base material using a system as defined in claim 10.

[0024] The system comprises a pulverizing device comprising a housing having an interior space, and at least one pulverizing unit disposed in the interior space and arranged rotatable with respect to the housing about a rotational axis, and an inlet opening for feeding base material to the interior space, and an outlet opening for dispatching the pulverized material from the interior space. The system further comprises a chamber arranged at the outlet opening for receiving the pulverized material from the pulverizing device. The system further comprises a pressure sensor configured to measure the pressure at the outlet opening of the pulverizing device. The system further comprises a transportation arrangement configured to transport the pulverized material from the chamber, wherein the transport arrangement is adapted to create an under pressure in the chamber.

[0025] The method comprises repeatedly:

[0026] - receiving pressure measurements from the pressure sensor;

[0027] - comparing the pressure measurements with a set value for the pressure at the outlet opening of the pulverizing device, wherein the set value is determined in dependence on a desired particle size;

[0028] - increasing the pressure in the chamber when the pressure measurement is lower than the set value; and

[0029] - decreasing the pressure in the chamber when the pressure measurement is higher than the set value.

[0030] According to an embodiment, a higher set value for the pressure results in a coarser particle size, and a lower set value for the pressure results in a finer particle size. For example, the set value may be a value between 0 and 100000 Pascal.

[0031] According to an embodiment of the invention, increasing the pressure in the chamber comprises opening the controllable valve and decreasing the pressure in the chamber comprises closing the controllable valve. The opening and closing of the controllable valve may be controlled by the pressure regulator unit, e.g. a PLC or a microcomputer, based on the measured pressure.

[0032] The method according to the invention allows controlling the particle size of the pulverized base material by regulating the pressure in the chamber arranged at the outlet opening of the pulverizing device.

[0033] Brief description of the drawings The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

[0034] Fig. la shows a schematic overview of an example of a system according to the invention. Fig. lb shows a schematic overview of an example of a system according to the invention.

[0035] Fig. lc shows a schematic overview of an example of a system for controlling a particle size of a pulverized base material, according to the invention.

[0036] Fig. 2 shows an example of a pulverizing device for pulverizing a material.

[0037] Fig. 3 shows the pulverizing device of figure 2 in a perspective view.

[0038] Fig. 4 shows a flowchart of an example of a method for controlling a particle size of a pulverized base material according to the invention.

[0039] It should be noted that the drawings have not necessarily been drawn to scale and that the dimensions of certain features may have been exaggerated for the sake of clarity.

[0040] Any feature of any embodiment of the device or method depicted or described in any part of this document may be combined with any one or more features of any other embodiment, unless such a combination is explicitly excluded herein.

[0041] Detailed description

[0042] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The system can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0043] Figure la shows a schematic overview of an example of a system 1. The system 1 comprises a pulverizing device 10. The pulverizing device 10 can be used for pulverizing various types of material, such as wood or plastic. The pulverizing device 10 comprises a housing 3, e.g. a stationary housing, having an interior space 5 and at least one interior wall 7 facing the interior space 5, as shown in figure 3. The pulverizing device 10 further comprises at least one pulverizing unit 14 disposed in the interior space 5 and arranged rotatable with respect to the housing 3 about a rotational axis R. The at least one pulverizing unit 14 may be rotating with a high speed so that an overpressure is created at the outlet opening 21 and the pulverized material is dispatched from the pulverizing device to the chamber 30 by means of the centrifugal force. The shape of the interior space 5 may be substantially cylindrical and have a central axis that coincides with the rotational axis R. The pulverizing device 10 further comprises an inlet opening 19 arranged for feeding base material to the interior space 5, and an outlet opening 21 for dispatching the pulverized material from the interior space 5. The system 1 further comprises a chamber 30 arranged at the outlet opening 21 for receiving the pulverized material from the pulverizing device 10. The chamber 30 may have an outlet for the pulverized material.

[0044] The system 1 further comprises a pressure sensor 32 configured to measure the pressure at the outlet opening 21. The pressure sensor 32 may be arranged in the chamber 30 and / or in the outlet opening 21 and the pressure sensor 32 may be configured to measure the pressure in the chamber 30.

[0045] The system 1 further comprises a transportation arrangement 34 configured to transport the pulverized material from the chamber 30. The transport arrangement 34 is adapted to create an under pressure in the chamber 30. The transportation arrangement 34 may comprise an ejector 38 arranged to suck out the pulverized material from the outlet of the chamber 30. Thereby an under pressure is created in the chamber 30 which counteracts the over pressure at the outlet opening 21. The transportation arrangement 34 may further comprise a blowing unit 40 arranged to transport the pulverized material to the ejector 38. The blowing unit 40 may comprise a compressor or a fan with a variable speed. The transportation arrangement 34 may further comprise a blow through rotary valve 42 disposed in the chamber 30 and the blowing unit 40 is arranged to blow the pulverized material through the rotary valve 42.

[0046] The system 1 further comprises a pressure controlling device 36 configured to regulate the pressure in the chamber 30 based on the measured pressure and a set value for the pressure at the outlet opening, wherein the set value is selected in dependence on a desired particle size. A higher set value for the pressure may result in a coarser particle size and a lower set value for the pressure may result in a finer particle size. The pressure controlling device 36 may comprise a controllable valve that is opened or closed to regulate the pressure in the chamber 40 and a pressure regulator unit, e.g. a first control unit such as a PLC or a microcomputer, configured to control the controllable valve based on the measured pressure.

[0047] The system 1 may further comprise a material dosing unit 44 connected to the pulverizing device 10. The material dosing unit 44 may comprise a dosing screw unit 46 arranged to dose the feed of the base material to the interior space 5 of the pulverizing device 10.

[0048] The system 1 may further comprise a pulverized material receiver 48, e.g. a burner or a device that receives material, arranged to receive the pulverized material from the transportation arrangement 34, e.g. via a transportation pipe. The pulverized material receiver 48 is also arranged to provide a feedback signal to the material dosing unit 44 to inform the material dosing unit 44 about the current need of pulverized material. The material dosing unit 44 is configured to receive the feedback signal and to dose the feed of the base material to the interior space 5 of the pulverizing device 10 based on the feedback signal. Figure lb shows a schematic overview of an example of the system 1. In this example, the transportation arrangement 34 comprises the blowing unit 40 and the ejector 38.

[0049] Figure 1c shows a schematic overview of an example of the system 1 for controlling a particle size of a pulverized base material, according to the invention. The pulverizing device 10 comprises the housing 3 having the interior space 5, and at least one pulverizing unit 14 disposed in the interior space 5 and arranged rotatable with respect to the housing 3 about the rotational axis R, and the inlet opening 19 for feeding base material to the interior space 5, and the outlet opening 21 for dispatching the pulverized material from the interior space 5, The system 1 further comprises the chamber 30 arranged at the outlet opening 21 for receiving the pulverized material from the pulverizing device 10, the pressure sensor 32 configured to measure the pressure at the outlet opening 21, the transportation arrangement 34 configured to transport the pulverized material from the chamber 30, wherein the transport arrangement 34 is adapted to create an under pressure in the chamber 30, and the pressure controlling device 36 configured to regulate the pressure in the chamber 30 based on the measured pressure and the set value for the pressure at the outlet opening 21, wherein the set value is selected in dependence on the desired particle size. The transport arrangement 34 may comprise the blowing unit 40 and the ejector 38, or the transport arrangement 34 may comprise the blowing unit 40, the ejector 38 and the blow through rotary valve 42, as illustrated in figure la. The blow through rotary valve may be disposed in the chamber 30 or outside the chamber 30. The ejector 38 may be arranged to suck out the pulverized material from the outlet of the chamber 30. When the transport arrangement 34 comprises a blow through rotary valve 42, the blowing unit 40 may be arranged to blow the pulverized material through the rotary valve 42 to the ejector 38, otherwise the blowing unit 40 may be arranged to blow the pulverized material directly to the ejector 38.

[0050] Figure 2 shows an example of the pulverizing device 10 for pulverizing a material in a crosssection perpendicular to a rotational axis R. Figure 3 shows the pulverizing device 10 in a perspective view. The at least one pulverizing unit 14 may comprise one or more sawblades 9 disposed in the interior space 5 and arranged rotatable with respect to the housing 3 about the rotational axis R. The one or more sawblades 9 may be disc-shaped and have a substantially circular periphery. Preferably, the pulverizing device 10 comprises two or more sawblades 9. The number of sawblades 9 needed depends on the width of the base material to be pulverized. The rotational axis R of the one or more sawblades 9 coincides with the central axis of the interior space 5. The rotational direction D of the one or more sawblades 9 is illustrated by an arrow in the figure 2. The periphery 12 of sawblade 9 may be provided with a plurality of cutting teeth 15 for cutting the material and a plurality of collecting notches 17 for collecting the cut material. The cutting teeth 15 may have cutting edges for cutting the material. The shape of the collecting notches 17 may vary. In this example, the collecting notches 17 are U-shaped. Alternatively, the collecting notches 17 can be V-shaped. The collecting notches 17 are disposed in front of the cutting teeth 15 with respect to the rotational direction R so that the material cut by the teeth can be collected. The cutting teeth 15 may be disposed at rear ends of the collecting notches 17. When one or more of the teeth 15 has cut the material, the cut material is collected in the collecting notch 17.

[0051] The interior space 5 is designed for housing the one or more sawblades 9. The at least one sawblade 9 may be disposed in the interior space 5 at a distance from the interior wall 7 of the housing 3 so that a gap 18 is formed between the periphery 12 of the sawblade 9 and the interior wall 7 of the housing 3 for housing a flow of cut material, as shown in figure 3. The width of the gap 18 varies depending on the position of the sawblade 9 with respect to the interior wall 7 of the housing 3. Preferably, the gap is larger than 0.2 mm. The pulverizing device 10 may further comprise an inlet 19 having an opening for feeding material to be pulverized to the interior space 5, and an outlet 21 having an opening for dispatching the pulverized material from the interior space 5.

[0052] The interior wall 7 is provided with a plurality of recesses 23 facing the periphery 12 of the sawblade 9, and accordingly facing the cutting teeth 15 and the collecting notches 17. The recesses 23 are designed so that they encourage a flow of cut material in the rotational direction of the cutting plates. The recesses 23 are arranged to receive cut material from the collecting notches 17 of the sawblade 9, and to revert the cut material to the periphery 12 of the sawblade 9 so that the material will be cut multiple times before it is dispatched from the pulverizing device 10. The number of recesses 23 may vary. Preferably, the number of recesses 23 is more than three. The number of times the material is cut depends on the number of cutting teeth 15 and the number of recesses 23. Thus, number of recesses 23 is selected in dependence on the desired particle size. The recesses 23 are elongated in a tangential direction with respect to the periphery 12 of the sawblade 9, as shown in figure 2.

[0053] The recesses 23 have a first end 24 and a second end 25, as shown in figure 2. The length L of the recesses 23, in a cross-section perpendicular to the rotational axis R, may be larger than the length L2 of the collecting notches 17. Preferably, the length L of the recesses 23 may be at least two times larger than the length L2 of the collecting notches 17 in a cross-section perpendicular to the rotational axis R, and more preferably, the length L of the recesses 23 may be at least three times larger than the length L2 of the collecting notches 17. The shape of the recesses 23 may vary. In one aspect, the shape of the recesses 23, in a cross-section perpendicular to the rotational axis, may be tapering in a direction reverse the rotational direction D of the at least one sawblade 9. The second end 25 of the recess may have a guiding surface 27 designed to guide the flow of cut material in the recess towards the periphery 12 of the at least one sawblade 9. The design of the guiding surface 27 may vary as long as it directs the flow of cut material towards the periphery 12 of the sawblade 9. In this example, the guiding surface 27 is concave. However, the guiding surface 27 can also be straight and extend in a radial direction of the sawblade 9. The recesses 23 may be elongated in a direction parallel to the rotational axis R. In this example, the recesses 23 extend in parallel with the rotational axis R. Alternatively, the recesses 23 may extend at an angle with respect to the rotational axis R.

[0054] The housing 3 may comprise a plurality of plate-shaped pieces 28 having two parallel main sides 29, as shown in figure 3. The plate-shaped pieces 28 are attached to each other with the main sides 29 facing each other so that that the pieces 28 together form the housing 3 with the interior space 5.

[0055] An example of a method comprising actions for controlling a particle size of a pulverized base material using the system 1 by regulating the pressure in the chamber 40, will now be described with reference to a flowchart depicted in Figure 4. The actions do not have to be taken in the order stated below but may be taken in any suitable order. As described above, the system 1 comprises the a pulverizing device 10 comprising the housing 3 having the interior space 5, and the at least one pulverizing unit 14 disposed in the interior space 5 and arranged rotatable with respect to the housing 3 about the rotational axis R, and the inlet opening 19 for feeding base material to the interior space 5, and the outlet opening 21 for dispatching the pulverized material from the interior space 5. The system further comprises the chamber 30 arranged at the outlet opening 21 for receiving the pulverized material from the pulverizing device 10, the pressure sensor 32 configured to measure the pressure at the outlet opening 21, the transportation arrangement 34 configured to transport the pulverized material from the chamber 30, wherein the transport arrangement 34 is adapted to create an under pressure in the chamber 30, and the pressure controlling device 36 configured to regulate the pressure in the chamber 30 based on the measured pressure and a set value for the pressure at the outlet opening 21, wherein the set value is selected in dependence on a desired particle size.

[0056] Action 401

[0057] The pressure controlling device 36 may comprise a controllable valve that is opened or closed to regulate the pressure in the chamber 30 and a pressure regulator unit configured to control the controllable valve based on the measured pressure. The pressure controlling device 36 first receives pressure measurements from the pressure sensor 32.

[0058] Action 402

[0059] The pressure controlling device 36 then compares the pressure measurements with a set value for the pressure at the outlet opening 21 of the pulverizing device 10, wherein the set value is determined in dependence on a desired particle size.

[0060] Action 403

[0061] When the measurements have been compared with the set value the pressure controlling device 36 increases the pressure in the chamber 30 when the pressure measurement is lower than the set value. Action 404

[0062] The pressure controlling device 36 decreases the pressure in the chamber 30 when the pressure measurement is higher than the set value. A higher set value for the pressure may result in a coarser particle size, and a lower set value for the pressure may result in a finer particle size. According to one embodiment, increasing the pressure in the chamber comprises opening the controllable valve and wherein decreasing the pressure in the chamber comprises closing the controllable valve and wherein the opening and closing of the controllable valve is controlled by the pressure regulator unit, based on the measured pressure.

[0063] It will be appreciated that the foregoing description and the accompanying drawings represent non-limiting examples of the method and system taught herein. As such, the system and techniques taught herein are not limited by the foregoing description and accompanying drawings. Thus, the present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims. For example, the shapes of the recesses, the collecting notches, the chamber, the pressure sensor, the transportation arrangement, the pressure controlling device, the ejector, the blow through rotary valve, the material dosing unit, the dosing screw unit, and the pulverized material receiver may vary.

[0064] Reference list

[0065] 1 System

[0066] 3 Housing

[0067] 5 Interior space

[0068] 7 Interior wall

[0069] 9 Sawblade

[0070] 10 Pulverizing device

[0071] 12 Periphery of the sawblade

[0072] 14 Pulverizing unit

[0073] 15 Teeth

[0074] 17 Collecting notches

[0075] 18 Gap

[0076] 19 Inlet opening

[0077] 21 Outlet opening

[0078] 23 Recesses

[0079] 24 First end of the recess

[0080] 25 Second end of the recess

[0081] 27 Guiding surface

[0082] 28 Plate-shaped pieces

[0083] 29 Main sides

[0084] 30 Chamber

[0085] 32 Pressure sensor

[0086] 34 Transportation arrangement

[0087] 36 Pressure controlling device

[0088] 38 Ejector

[0089] 40 Blowing unit

[0090] 42 Blow through rotary valve

[0091] 44 Material dosing unit

[0092] 46 Dosing screw unit

[0093] 48 Pulverized material receiver

[0094] R Rotational axis

[0095] D rotational direction

[0096] L Length of recesses

[0097] L2 Length of notches

Claims

Claims1. A system (1) for controlling a particle size of a pulverized base material, comprising:- a pulverizing device (10) comprising a housing (3) having an interior space (5), and at least one pulverizing unit (14) disposed in the interior space (5) and arranged rotatable with respect to the housing (3) about a rotational axis (R), and an inlet opening (19) for feeding base material to the interior space (5), and an outlet opening (21) for dispatching the pulverized material from the interior space (5), characterized in that the system (1) further comprises:- a chamber (30) arranged at the outlet opening (21) for receiving the pulverized material from the pulverizing device (10),- a pressure sensor (32) configured to measure the pressure at the outlet opening (21),- a transportation arrangement (34) configured to transport the pulverized material from the chamber (30), wherein the transport arrangement (34) is adapted to create an under pressure in the chamber (30), and- a pressure controlling device (36) configured to regulate the pressure in the chamber (30) based on the measured pressure and a set value for the pressure at the outlet opening (21), wherein the set value is selected in dependence on a desired particle size.

2. The system (1) according to claim 1, wherein a higher set value for the pressure results in a coarser particle size, and wherein a lower set value for the pressure results in a finer particle size.

3. The system (1) according to claim 1 or 2, wherein the chamber (30) has an outlet for the pulverized material, and the transportation arrangement (34) comprises an ejector (38) arranged to suck out the pulverized material from the outlet of the chamber (30).

4. The system (1) according to any of the preceding claims, wherein the transportation arrangement (34) comprises a blowing unit (40) arranged to transport the pulverized material to the ejector (38).

5. The system (1) according to claim 4, wherein the transportation arrangement (34) further comprises a blow through rotary valve (42) disposed in the chamber (30) and the blowing unit (40) is arranged to blow the pulverized material through the rotary valve (42).

6. The system (1) according to any of the preceding claims, wherein the pressure controlling device (36) comprises a controllable valve that is opened or closed to regulate the pressure in the chamber (30) and a pressure regulator unit configured to control the controllable valve based on the measured pressure.

7. The system (1) according to any of the preceding claims, further comprising a material dosing unit (44) connected to the pulverizing device (10), wherein the material dosing unit (44) comprises a dosing screw unit (46) arranged to dose the feed of the base material to the interior space (5) of the pulverizing device (10).

8. The system (1) according to any of the preceding claims, further comprising a pulverized material receiver (48) arranged to receive the pulverized material from the transportation arrangement (34) and to provide a feedback signal to the material dosing unit (44) to inform the material dosing unit (44) about the current need of pulverized material, and wherein the material dosing unit (44) is configured to receive the feedback signal and to dose the feed of the base material to the interior space (5) of the pulverizing device (10) based on the feedback signal.

9. The system (1) according to any of the preceding claims, wherein the at least one pulverizing unit (14) is rotating with a high speed so that an overpressure is created at the outlet opening (21) and the pulverized material is dispatched from the pulverizing device (10) to the chamber (30) by means of the centrifugal force.

10. A method for controlling a particle size of a pulverized base material using a system (1) comprising:- a pulverizing device (10) comprising a housing (3) having an interior space, and at least one pulverizing unit (14) disposed in the interior space (5) and arranged rotatable with respect to the housing (3) about a rotational axis (R), and an inlet opening (19) for feeding base material to the interior space (5), and an outlet opening (21) for dispatching the pulverized material from the interior space (5),- a chamber (30) arranged at the outlet opening for receiving the pulverized material from the pulverizing device (10),- a pressure sensor (32) configured to measure the pressure at the outlet opening (21) of the pulverizing device,- a transportation arrangement (26) configured to transport the pulverized material from the chamber (30), wherein the transport arrangement is adapted to create an under pressure in the chamber,- a pressure controlling device (36) configured to regulate the pressure in the chamber (40) based on the measured pressure and a set value for the pressure at the outlet opening (21), wherein the set value is selected in dependence on a desired particle size, wherein the method comprises repeatedly: receiving (401) pressure measurements from the pressure sensor, comparing (402) the pressure measurements with a set value for the pressure at the outlet opening (21) of the pulverizing device (10), wherein the set value is determined in dependence on a desired particle size,increasing (403) the pressure in the chamber (30) when the pressure measurementhan the set value, and decreasing (404) the pressure in the chamber (30) when the pressure measurement than the set value.

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