Patent Application
20250059708
Not applicable.
The invention relates to processing equipment for processing fibrous material. Especially the invention relates to adjusting of a size of a blade gap between substantially oppositely positioned processing elements in the processing equipment for processing fibrous material.
A refiner, such as a refiner for refining lignocellulose-containing wood-based fibrous material, plant-based fibrous material, or recycled textile material, provides a kind of processing equipment for processing fibrous material. The refiner comprises typically two oppositely positioned refining elements, one of them typically being a stationary refining element and the other one a rotatable refining element that is arranged to be rotated relative to the stationary refining element. Between the opposing refining elements there is a free distance, i.e., a blade gap or a refining chamber, into which the fibrous material to be refined is supplied. In the blade gap the fibrous material is subjected to the refining effect determined by properties of refining surfaces in the refining elements and operational characteristics of the refiner, such as a rotational speed of the rotatable refining element and/or a pressure prevailing in the blade gap.
A prior art arrangement for adjusting a size of a blade gap in a conical refiner comprises a loading device coupled to the rotatable refining element for moving the rotatable refining element in respect of the stationary refining element in an axial direction of the refiner. In this arrangement the loading device comprises a gearing coupled to a shaft of the rotatable refining element and a motor coupled to the gearing to operate the gearing, whereby the gearing and the motor coupled to the gearing together provide a gearmotor for moving the rotatable refining element in respect of the stationary refining element. The actual blade gap adjustment is, however, based on a power control of a main motor of the refiner, i.e., on the control of the power of the motor intended to rotate the rotatable refining element. The power required by the main motor to rotate the rotatable refining element provides an indication about a position of the rotatable refining element relative to the stationary refining element so that the closer the rotatable refining element is to the stationary refining element, the higher the power needed by the main motor to rotate the rotatable refining element because of a pressure increase in the blade gap. In this solution, to prevent the rotatable refining element to be moved too close to the stationary refining element, the loading device is equipped with a mechanical friction coupling that provides a mechanical overload protection for the loading device so that the mechanical friction coupling is arranged to slip in case of force used to move the rotatable refining element towards the stationary refining element rises too high. The mechanical friction coupling thereby limits the force to be applied to move the rotatable refining element towards the stationary refining element. Additionally, this prior art arrangement may comprise a sensor arranged in the refiner to measure the position of the rotatable refining element in the refiner, whereby measurement information provided by this sensor may be applied to prevent the movement of the rotatable refining element too close to the stationary refining element so that they would clash with each other.
Despite of some disadvantages, such as a very high gear ratio of the gearmotor, that being typically over 1000:1, which makes the implementation of the gearing substantially complicated, or of the substantially complicated and expensive implementation of the mechanical friction coupling that also requires regular maintenance, the prior art arrangement for adjusting the size of the blade gap in the conical refiner is very applicable in typical refining applications, wherein only properties of the fibers are intended to be affected without substantially affecting fiber length of the fibrous material, i.e., without substantially cutting the fibers shorter. However, the power control of the main motor of the refiner is not a very applicable way to adjust the size of the blade gap in refining applications wherein especially the fiber length of the fibrous material is intended to be affected, i.e., wherein the fibers are intended to be cut to have a shorter length, such as in manufacturing of microfibrillar cellulose (MFC) or nanofibrillar cellulose (NFC) wherein a very accurate constant blade gap is essential.
An object of the present invention is to provide a novel loading device, and an arrangement and method for adjusting a blade gap in processing equipment for processing fibrous material.
The invention is based on the idea of combining the frequency converter, the cage induction motor and the position sensor measuring the rotational position of the shaft of the cage induction motor arranged to operate the gearing of the loading device to move the at least one processing element in respect of the at least one another processing element for adjusting the size of the blade gap between the processing elements.
An advantage of the invention is that it provides an accurate and simple closed-loop position control application for adjusting the size of the blade gap. The combination of the frequency converter and the cage induction motor allows a substantially low gear ratio, for example between 100:1 and 150:1, which, in turn, simplifies the implementation of the gearing.
In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings.
For the sake of clarity, the figures show some embodiments of the invention in a simplified manner. Like reference numerals identify like elements in the figures.
The refiner 1 has an axial direction as shown schematically with an arrow indicated with the reference sign A and a radial direction as shown schematically with an arrow indicated with the reference sign R. In the axial direction A the conical refiner 1 has a first end E1 of smaller diameter and a second end E2 of larger diameter.
The refiner 1 comprises a frame 2, at least one supply connection 3 for supplying or feeding at least one flow of the fibrous material to be refined into the refiner 1, as shown schematically with an arrow indicated with the reference sign S, as well as at least one discharge connection 4 for discharging out of the refiner 1 at least one flow of the fibrous material already refined in the refiner 1, as shown schematically with an arrow indicated with the reference sign D.
The refiner 1 comprises a stationary refining element 5, i.e., a stator 5, having a first end of smaller diameter facing towards the first end E1 of the refiner 1 and a second end of larger diameter facing towards the second end E2 of the refiner 1. Therefore, for the sake of clarity, the reference sign E1 is also used to denote the first end of the stator 5 and the reference sign E2 is also used to denote the second end of the stator 5. The stator 5 is supported to a frame structure 2 of the refiner 1. The stator 5 thus forms a stationary processing element of the refiner 1.
The refiner 1 further comprises a rotatable refining element 6, i.e., a rotor 6, having a first end of smaller diameter facing towards the first end E1 of the refiner 1 and a second end of larger diameter facing towards the second end E2 of the refiner 1. Therefore, for the sake of clarity, the reference sign E1 is also used to denote the first end of the rotor 6 and the reference sign E2 is also used to denote the second end of the rotor 6. The rotor 6 is connected to a shaft 7 that extends substantially in the axial direction A of the refiner 1. The shaft 7 is connected to a main motor 8 of the refiner 1. The main motor 8 is arranged to rotate the shaft 7 and, by the shaft 7, the rotor 6 for example in a rotation direction indicated with an arrow RD in
The stator 5 comprises a refining surface 5a facing the rotor 6. The rotor 6 has a refining surface 6a facing the stator 5. The refining surfaces 5a, 6a have typically blade bars and blade grooves therebetween, in a manner known by a person skilled in the art. Therefore, for the sake of clarity, the refining surfaces 5a, 6a are not shown in detail in
In the conical refiner 1 the rotor 6 is arranged substantially within the stator 5 so that the stator 5 and the rotor 6 are positioned substantially oppositely relative to each other so that there is a blade gap 9 between the substantially oppositely positioned refining surfaces 5a, 6a of the stator 5 and the rotor 6. The blade gap 9, i.e., a refining chamber 9, forms a volume wherein the fibrous material is refined. A free distance D between the opposing stator 5 and the rotor 6 indicates a size of the blade gap 9. The size of the blade gap 9 relative to the other components of the refiner 1 is highly exaggerated in
The operation of the refiner 1 of
A flow of the fibrous material is supplied into the refiner 1 through the supply connection 3 at the first end E1 of the refiner 1, as shown schematically with the arrow indicated with the reference sign S, wherein the fibrous material to be refined flows into the blade gap 9 at the first end E1 of the stator 5 and the rotor 6. When the rotor 6 is rotated, the fibrous material flows forward in the blade gap 9 from the first end E1 of the refiner 1 towards the second end E2 of the refiner 1 and is subjected to a refining effect by the opposite refining surfaces 5a, 6a of the stator 5 and the rotor 6 until the fibrous material flows out of the blade gap 9 at the second end E2 of the refiner 1. The flow of the fibrous material in the blade gap 9 is shown schematically with arrows denoted with the reference sign F. The fibrous material refined in the blade gap 9 is discharged out of the refiner 1 for further processing through the discharge connection 4 at the second end E2 of the refiner 1. The refining effect to which the fibrous material in the blade gap 9 is subjected may be adjusted, for example, by adjusting a rotational speed of the rotor 6 and/or by adjusting the distance D between the stator 5 and the rotor 6, i.e., by adjusting the size of the blade gap 9.
Further,
The loading device 10 of
The loading device 10 of
The loading device 10 of
The loading device 10 of
The position control module PCM of the frequency converter 17 is further configured to receive as an input a set value SET-D for the distance D between the rotor 6 and the stator 5 of the refiner 1, i.e., the set value for the size of the blade gap 9, to be applied in the refining under operation. Based on the measured rotational position M-RP of the shaft 15 of the cage induction motor 14 and the set value SET-D for the size of the blade gap 9, the position control module PCM is further configured to determine a control signal RP-CO to control the operation of the cage induction motor 14 for controlling the operation of the gearing 12 to move the rotor 6 in respect of the stator 5 in the event the current size of the blade gap 9 differs from the set value SET-D for the size of the blade gap 9.
In the event of the current size of the blade gap 9 being larger than the set value SET-D for the size of the blade gap 9, the frequency converter 17 is configured to control the cage induction motor 14 to cause the rotor 6 to move towards the stator 5 according to the control signal RP-CO provided by the frequency controller 17.
In the event of the current size of the blade gap 9 being smaller than the set value SET-D for the size of the blade gap 9, the frequency converter 17 is configured to control the cage induction motor 14 to cause the rotor 6 to move away from the stator 5 according to the control signal RP-CO provided by the frequency controller 17. Alternatively, in the event of the current size of the blade gap 9 being smaller than the set value SET-D for the size of the blade gap 9, the frequency converter 17 may be configured to not provide any control signal that would cause the cage induction motor 14 to move the rotor 6 relative to the stator 5 if it is expected that for example because of wear of the refining surfaces 5a, 6a of the stator 5 and the rotor 6 the size of the blade gap 9, i.e., the distance D between the rotor 6 and the stator 5, will soon be according to the set value SET-D.
In the event of the current size of the blade gap 9 being substantially the same as the set value SET-D for the size of the blade gap 9, any control action to move the rotor 6 relative to the stator 5 is not necessary.
The combination of the cage induction motor 14, the position sensor 16 and the frequency converter 17 provides a closed-loop position control application for controlling the position of the rotor 6 of the refiner 1 relative to the stator 5 of the refiner 1 for adjusting the size of the blade gap 9 in the refiner 1. This closed-loop position control application provides an accurate way to determine and control the current size of the blade gap 9 in a simple way, whereby a sensor possibly arranged in the refiner to measure the position of the rotor 6 in the refiner 1 may be omitted.
The combination of the frequency converter 17 and the cage induction motor 14 provides an accurate control, whereby the gear ratio of the gearing 12 may be selected to be substantially low, for example between 100:1 and 150:1. This, in turn, simplifies the implementation of the gearing 12, leading to cost savings in the implementation of the loading device 10.
The accurate adjustment of the size of the blade gap 9 is especially important in manufacturing of microfibrillar cellulose (MFC) or nanofibrillar cellulose (NFC). The term “nanofibrillar cellulose” refers herein to a collection of separate cellulose microfibrils or microfibril bundles derived from plant-based, and especially wood-based fibrous material. Synonyms for the nanofibrillar cellulose (NFC) are for example nanofibrillated cellulose, nanocellulose, microfibrillar cellulose, cellulose nanofiber, nano-scale cellulose, microfibrillated cellulose (MFC) or cellulose microfibrils. Depending on the degree of grinding a particle size of the separate cellulose microfibrils or microfibril bundles is of some nanometers (nm) or micrometers (μm). A mean length of the separate cellulose microfibrils or microfibril bundles may for example be 0.2-200 μm and a mean diameter may for example be 2-1000 nm.
According to an embodiment, the frequency converter 17 is configured to determine a torque TQ of the cage induction motor 14 applied to move the rotor 6 relative to the stator 5 during adjusting the size of the blade gap 9 according to the position control signal RP-CO. The torque TQ may be determined based on the power and frequency used to operate the cage induction motor 14 by the frequency converter 17. The determined torque TQ may be compared with a maximum torque limit value TQMAX whereby in the event of the comparison of the determined torque TQ with the maximum torque limit value TQMAX indicating that the determined torque TQ is equal to or exceeds the maximum torque limit value TQMAX, the frequency converter 17 is configured to cause the cage induction motor 14 to stop, thus causing to interrupt the movement of the rotor 6 relative to the stator 5. The determination of the torque TQ and the comparison thereof to the maximum torque limit value TQMAX provides an electrically implemented overload protection for the cage induction motor 14, whereby the mechanical friction coupling applied in the prior art may be omitted. This further provides cost savings in the implementation of the loading device 10.
According to an embodiment, the frequency converter 17 comprises a torque control module TCM that is configured to determine the torque TQ of the cage induction motor 14 applied to move the rotor 6 relative to the stator 5, as well as to compare the determined torque with the maximum torque limit value TQMAX. In response to the comparison of the determined torque TQ with the maximum torque limit value TQMAX indicating that the determined torque TQ is equal to or exceeds the maximum torque limit value TQMAX, the frequency converter 17 is configured to cause the cage induction motor 14 to stop with a specific torque control signal TQ-CO, or by interrupting the power supply to the cage induction motor 14. The torque control module TCM may be implemented by hardware or software or by a combination thereof.
According to an embodiment, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 is applied during the operation of the refiner 1, for example to prevent an application of excessive load to the fibrous material to be refined and/or to prevent the opposite refining elements 5, 6 to clash with each other. In practice, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 may be utilized at least at the instants when the rotor 6 is moved towards the stator 5 for reducing the size of the blade gap 9. However, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 may also be utilized when the rotor 6 is moved away from the stator 5 for increasing the size of the blade gap 9, whereby a possible malfunction in an internal operation of the loading device 10 or its coupling to the rotor 6 may be observed based on the rise of the torque TQ needed by the cage induction motor 14 to move the rotor 6.
According to an embodiment, the determination of the torque TQ applied in the adjustment of the size of the blade gap 9 is utilized for a calibration of the loading device 10 which takes place in an unoperated state of the refiner 1. During the calibration of the loading device 10 the rotor 6 is moved towards the stator 5 until the rotor 6 comes into contact with, i.e., meets, the stator 5, which may be observed based on the determined torque TQ being equal to or exceeding a corresponding torque limit value TQLIMIT, which may be the same limit value as the maximum torque limit value TQMAX above or a specific limit value applied during the calibration of the loading device 10. This kind of calibration operation is also called a zero-point calibration. At the point when the rotor 6 meets the stator 5, the rotational position of the shaft 15 of the cage induction motor 14 may be stored into the position control module PCM, for example, and applied later when adjusting the size of the blade gap 9.
According to an embodiment, the loading device 10 comprises a blade gap control module BGCM configured to control the operation of the frequency converter 17 for controlling the adjustment of the size of the blade gap 9. The blade gap control module BGCM may for example be configured to determine the set value SET-D for the size of the blade gap 9 and/or to determine the maximum torque limit value TQMAX for the torque applied in the adjustment of the size of the blade gap 9 during the operation of the refiner 1 and/or the torque limit value TQLIMIT applied during the calibration of the loading device 10. The measured rotational position M-RP of the shaft 15 of the cage induction motor 14 and the determined torque TQ may be input as measuring values into the blade gap control module BGCM and utilized therein for the control of the loading device 10, for example for the determination of the set value SET-D for the size of the blade gap 9. The blade gap control module BGCM may be implemented by hardware or software or by a combination thereof.
In the embodiment of
The process control system PCS may comprise or receive information related for example to the fiber pulp to be produced, such as a quality or other desired characteristic of the fiber pulp to be produced, a quality or other characteristic of the fibrous raw material to be used as well as additives to be mixed into the fiber pulp to be produced and characteristics thereof. Based on the information received from the process control system PCS, the blade gap control module BGCM may determine setting parameters for the operation of the frequency converter 17, such as the set value SET-D for the size of the blade gap 9 and/or the maximum torque limit value TQMAX to be applied in the adjustment of the size of the blade gap 9 so that the desired refining effect is subjected to the fibrous material to be refined.
According to an embodiment, the blade gap control module BGCM is configured to estimate wear of the opposing refining surfaces 5a, 6a during the refining based on for example characteristics of the refining surfaces 5a, 6a, characteristics of the fibrous material to be refined and possibly other characteristics relating to the refining, and to determine the set value SET-D for the size of the blade gap 9 by taking into account also the estimated wear of the refining surfaces 5a, 6a.
According to an embodiment, the loading device 10 comprises a vibration sensor 18 to be arranged to measure a vibration of the refiner 1 during the operation thereof. In the embodiment of
In the examples above the rotor 6 is arranged to be moved relative to the stator 5 when adjusting the size of the blade gap 9 but alternatively, the stator 5 may be arranged to be moved relative to the rotor 6 for adjusting the size of the blade gap 9.
Furthermore, in the examples above the disclosed solution for adjusting the size of the blade gap 9 is applied in a conical refiner 1, but the disclosed solution is correspondingly applicable for adjusting the size of the blade gap 9 also in disc refiners comprising disc-like stationary and rotatable refining elements, whereby a change in the size of the blade gap takes place in an axial direction of the refiner.
Furthermore, in the examples above, the disclosed solution for adjusting the size of the blade gap 9 is applied in a refiner comprising a stator and a rotor opposite to the stator, but the disclosed solution is correspondingly applicable for adjusting the size of the blade gap 9 also in refiners wherein both opposite refining elements are rotors.
The disclosed loading device 10, as well as its different embodiments above, may alternatively be applied in a disperser which is also a kind of processing equipment for processing fibrous material. The disperser is thus a dispersing device that is intended to disperse the fibrous material in a blade gap between oppositely positioned dispersing elements. The fibrous material to be dispersed may for example be lignocellulose-containing wood-based fibrous material, or plant-based fibrous material, or a fibrous material originating from recycled textile material. The fibrous material to be dispersed is in a form of pulp, i.e., a mixture of water and fibrous material and possibly some additives. A fiber consistency of the fibrous material to be dispersed may vary depending for example on the raw material of the fibrous material, the fiber consistency being typically between 3-40%.
In the disperser the dispersing elements are the processing elements that provide the processing effect, i.e., a dispersion effect, subjected to the fibrous material in the blade gap, and the blade gap forms a dispersing chamber or volume wherein this dispersion effect is subjected to the fibrous material to be processed. The basic construction and operation of dispersers are substantially similar to that of the refiners, despite some characteristics in dispersing surfaces of the dispersing elements if compared to characteristics in the refining surfaces of the refining elements. Thereby the loading device 10 and different embodiments thereof as disclosed above in connection with the refiner 1 are as well applicable when the loading device 10 is applied in connection with dispersers for adjusting the size of the blade gap in the dispersers.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20225018 | Jan 2022 | FI | national |
This application is a US national stage application of PCT/FI2023/050014, filed Jan. 5, 2023, and claims priority on Finnish Application No. FI 20225018, filed Jan. 11, 2022, the disclosures of which are incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FI2023/050014 | 1/5/2023 | WO |
