Method for operating a pulper for producing a suspension, in particular a fibrous suspension

Abstract

The invention relates to a method for operating a screen device (50, 250) for cleaning a fibrous suspension with a rotor (58), arranged in a housing (51, 251) of the screen device (50, 250), and a screen (57), wherein fibrous suspension and rinsing water are fed to the screen device (50), and that proportion of the fibrous suspension which passes through the screen (57) is discharged via an accepted stock discharge (67, 267), wherein an inflow into the screen device (50, 250) and / or a cycle time duration are / is regulated in a manner which is dependent on the power consumption (162) of the rotor drive (59, 259).

Description

[0001] Method for operating a pulper to produce a suspension, in particular a fiber suspension

[0002] The invention relates to a method for operating a screening device for cleaning a fiber suspension according to the preamble of claim 1 and to an arrangement with a screening device for carrying out the method.

[0003] Digitalization enables processes to be controlled and regulated more precisely. This can involve increased computing capacity and AI. Voith already has several specific applications, which are listed below.

[0004] OnEfficiency.BreakProtect uses a unique AI algorithm to automatically detect a wide variety of break causes in paper production. This allows early definition of countermeasures for each specific break type and ensures stable, cost-efficient production.

[0005] OnEfficiency.DIP optimizes an existing DIP line toward consistent DIP quality at minimal cost. Additional actuators are added to the existing flotation system, and new sensors are installed to monitor quality parameters. DIP quality fluctuations caused by incoming raw materials or production changes are reduced through dynamic adjustment of washing / flotation losses and real-time optimization of bleaching chemical dosing.

[0006] The company Valmet has promoted an application for improved refiner quality under the name “Fiber Furnish Control”.

[0007] Pulpers are particularly used in the field of fiber extraction from waste paper. Waste paper and water are fed into a pulper to create a fiber suspension. Waste paper qualities can vary. Patent application DE 10 2021 103 233 describes a method for optically determining waste paper quality. Depending on the recorded properties of the waste paper, control of process parameters such as water addition is provided.

[0008] A discontinuously operated pulper is first filled with water, then the waste paper or pulp is added and pulped there. The pulp suspension is then pumped out and further processed. The pulping time also depends on the quality of the waste paper fed into the pulper.

[0009] There are also continuously operating pulpers, to which waste paper and water are continuously fed. The resulting fiber suspension then passes through a designated screen to an accepts discharge. In such pulpers, impurities are removed from the pulper via a discharge located above the screen plate. The stock consistency of normal pulpers is approximately 3 to 6%.

[0010] Screening devices are used to clean fiber suspensions with a high impurity content. One such screen is known from EP 2104766 A1. This screen has an asymmetrical housing. A screen is arranged in the upper region of the housing. A rotor is assigned to the screen; the rotor keeps the screen free of contaminants. In addition, the fed suspension is set in rotation. Acceptable material is discharged from the top of the housing, relative to the vertical direction, above the suspension feed. In the lower part of the housing there is an outlet opening for impurities leading diagonally downwards. Such screen devices are used in particular to process, for example, the contaminated suspension coming from the pulper.In particular, this screening device is also suitable for a fiber suspension originating from a discontinuously operated pulper without passing through a screen, as described above. The screening device described here operates cyclically. Thus, the throughput cycle, the post-pulping cycle (also known as "slushing"), the rinsing cycle, and the discharge cycle all run cyclically. During the throughput cycle, the fiber suspension is fed into the screening device, and the accepts discharge is open.

[0011] A post-dissolution cycle is a cycle in which no more suspension is added and the rinsing process has not yet begun. The suspension present in the screening device is treated in the screening device.

[0012] During the rinsing cycle, no more fiber suspension is introduced into the screening device, and rinse water is introduced into the screening device. This allows any loosened fibers to be rinsed out of the screening device as acceptable material.

[0013] In the discharge cycle, a contaminant discharge is opened and contaminants are discharged from the screening device as reject.

[0014] Due to fluctuations in the contaminant content in the fiber suspension, high mechanical and / or process-related stresses repeatedly occur. This frequently results in alarms. Due to the frequency of such alarms, such alarms are often acknowledged without any concrete action being taken to intervene in the process and without the cause of the alarm being investigated. Furthermore, intervention is only possible to a limited extent due to the inertia of the system and is difficult due to the multitude of influencing factors.

[0015] The invention is based on the object of improving a method for operating a screening device. In particular, the occurrence of overloads is to be avoided, or at least reduced. In particular, the occurrence of alarm messages is to be reduced without thereby resulting in an overload of the device. This object is achieved by the method having the features of claim 1. The arrangement for achieving this object comprises the features of claim 14. Further advantageous features are recited in the dependent claims.

[0016] To achieve this object, a method for operating a screening device for cleaning a fiber suspension is provided. The screening device has a rotor arranged in a housing of the screening device and a screen arranged in the housing. Fiber suspension and rinse water can be fed to the screening device. The portion of the fiber suspension passing through the screen is discharged via an accepts discharge. Depending on the power consumption of the rotor drive, an inflow into the screening device and / or a cycle time is regulated or controlled. The regulation and control can relate to the power consumption of the rotor in a previous cycle. This allows the inertia of the system to be taken into account on the one hand and continuous regulation or control during operation of the screening device to be ensured on the other.

[0017] In an advantageous embodiment, the cycle duration of at least one cycle of a subsequent cycle sequence is regulated depending on the power consumption of the rotor drive. A cycle sequence comprises at least one pass cycle, a rinsing cycle, and a discharge cycle. Optionally, a post-pulling cycle can be performed between the pass cycle and the rinsing cycle. The provision of a post-pulling cycle can be determined, in particular, depending on the outflow of accepted material during the pass cycle.

[0018] In one embodiment of the method, if the power consumption of the rotor drive exceeds a predetermined limit, the inflow of rinse water is reduced compared to the maximum possible inflow of rinse water, at least at the beginning of a subsequent rinse cycle. This can prevent overloading of the rotor drive. As a result, frequently occurring alarm messages can be prevented. Especially at the beginning of the rinse cycle, the exposure to rinse water can cause a further increase in the power consumption of the rotor of the screening device. It has been shown that a moderate addition of rinse water, particularly at the beginning of the rinse cycle, can significantly influence the maximum power consumption of the rotor in a cycle sequence.

[0019] In one embodiment of the method for operating a screening device, it is provided that, additionally or alternatively, a cycle time of the throughput cycle and / or the rinsing cycle is controlled depending on the flow rate of accept material, and / or an optional post-pulling cycle is provided. The duration of the post-pulling cycle can also be controlled depending on the flow rate of accept material, particularly during the throughput cycle or the post-pulling cycle. Alternatively, if the post-pulling cycle is activated, the post-pulling cycle can be executed for a predetermined duration.

[0020] In one embodiment of the method for operating a screening device, an inlet pressure and / or a differential pressure relative to the pressure of the accepts discharge are taken into account when controlling a subsequent cycle time. This allows conclusions to be drawn about the suspension present in the screening device and its quality. Depending on the suspension quality and quantity present in the screening device, this can be taken into account when controlling the screening device.

[0021] In one embodiment of the method for operating a screening device, plant-specific limit values ​​are read in or manually entered or stored during commissioning. This allows access to these values. For example, it can be provided that this stored data is used in the event of conflicting measured data. When accessing this data, the device is operated in basic mode. This is not dynamically adaptive mode. During application of this basic mode, the stored plant-specific limit values ​​are not adjusted. However, adaptive adjustment of the stored limit values ​​can also be provided during dynamic operation.

[0022] In one embodiment of the method for operating a screening device, a system-specific maximum acceptable material flow is stored. This ensures that malfunctions can be detected and remedied using stored procedures.

[0023] In one embodiment of the method for operating a screening device, a factory setting and / or a default setting are stored in the control system. Operation without adaptive control is possible with the factory setting and the default setting. However, this reduces the efficiency of the device compared to operation with adaptive control.

[0024] In one embodiment of the method for operating a screening device, it is provided that if the power consumption of the rotor drive is outside a stored power range, in particular in the run-through cycle, the operation is continued on the basis of data from a basic setting or factory setting until the recorded operating data are again within the stored standard range.

[0025] In one embodiment of the method for operating a screening device, if an operating parameter falls outside a stored standard range, the method is continued using a predetermined number of cycles, and the operating parameters used are adaptively adjusted for these cycles. This is intended to prevent recourse to basic operation without adaptive control every time a deviation from the standard range occurs. However, if operation within the stored standard ranges cannot be achieved within the predetermined number of cycles, the system switches to basic operation. This can prevent permanent or excessive overloading of the device.In a method for operating a plant with at least a first cyclically operated screening device and a second cyclically operated screening device, a pulper, arranged in parallel, it is provided that the cycles of the at least two screening devices are coordinated with one another in order to utilize peripheral devices, such as a downstream sorting drum, of the plant. Coordination takes place by extending at least one of the rinsing cycles from the currently ongoing sequences and / or shortening at least one of the throughput cycles. This allows optimal utilization of peripheral devices and does not have to be provided separately for each screening device. For example, a pump for supplying fiber suspension can be accessed jointly. It is also possible to supply rinsing water to two screening devices using one pump.

[0026] In one embodiment of the method for operating a plant with a pulper and at least one screening device, fiber suspension is returned to the pulper. The consistency and quantity of the fiber suspension returned to the pulper is taken into account to achieve a constant stock consistency in the pulper. In particular, depending on the consistency and inflow of the fiber suspension returned to the pulper, control of the supply of dilution water can be provided. This makes it possible to minimize fluctuations in the stock consistency of the fiber suspension leaving the pulper. In particular, this makes it possible to maintain a predetermined stock consistency range more precisely, whereby subsequent processing and cleaning of the fiber suspension can be better tailored to the fiber consistency. For example, a predetermined stock consistency consistency of + / - 0.2% absolute percent can be maintained.

[0027] An arrangement comprising a pulper and at least one screening device, wherein a control valve is arranged in the supply of rinse water to the screening device. The control valve is provided for a controlled supply of rinse water to the screening device. This allows the supply of rinse water to be regulated, particularly during the rinse cycle. This controlled supply of rinse water can prevent, or at least reduce, overloading of the rotor drive. The control valve enables a continuous increase in the supplied rinse water.

[0028] During the rinsing cycle and the discharge cycle, the feed of fiber suspension is interrupted. Rinse water is specifically fed to the screening device. The rinse water initially rinses out more fibers. It has been found that this phase in particular is very susceptible to overloading. Not only the drive power required for the fiber suspension enriched with impurities, but also the supplied rinse water inflow affects the rotor. Although the rinse water serves to dilute the fiber suspension present in the screening device, and one might assume that fibers can now flow through the screen more easily, it has been shown that, surprisingly, overload situations occur precisely at these times. By reducing the initial rinse water inflow, an overload situation can be avoided. Additional pressure on the rotor from rinse water can be reduced.Acceptable material can flow through the screen, even if it may be partially covered by impurities. This reduces the peak load on the rotor drive and also reduces the overall load on the drive during the rinsing cycle.

[0029] The duration of the rinse cycle can be adaptively and predictively extended, and the rinse water volume per rinse cycle can still be kept constant throughout the rinse cycle, preferably with a deviation of + / - 10% from a predetermined rinse water volume. This allows a good fiber yield to be achieved by adapting the rinse cycle. Quantities are given in cubic meters. When referring to a flow, such as inflow, flow, or outflow, this refers to volume per unit time, often expressed in liters per minute.

[0030] In a discharge cycle following the rinsing cycle, rinsing water flows in at a predetermined maximum inflow. This removes the suspension remaining in the screening device with concentrated impurities from the

[0031] The screening device is flushed out. The accepts discharge is closed

[0032] One design variant allows the duration of the discharge cycle to be adjusted depending on the rotor's power consumption. This can achieve improved removal of impurities. On the other hand, the discharge cycle should only last as long as a significant amount of impurities is being removed. For example, a rotor power consumption that falls below a predetermined limit can be used as an indication that the screening device has been sufficiently cleaned of impurities.

[0033] In some applications, it has proven advantageous to vary the cycle duration within a predetermined time frame depending on at least the rotor power consumption parameter. This can prevent the cycle from remaining in an operating step when operating data is incorrect.

[0034] The better the removal of impurities, the more efficient the subsequent throughput cycle can be. This allows the rotor's drive power to be reduced because impurities don't remain in the screening device for an unnecessarily long time. Furthermore, there is the positive effect that the impurities are exposed to the rotor for a shorter time, thus preventing, or at least reducing, their abrasion by the rotor.

[0035] It has proven advantageous that the increase in the inflow of rinse water during the rinse cycle adaptively depends on the current load and only occurs as long as the maximum power consumption is below a predetermined maximum upper limit. If this upper limit is exceeded, the rotor drive is overloaded. By preventing the maximum amount of rinse water from being supplied, overload situations in the rotor drive can be prevented, or at least their occurrence can be reduced, and the overload can be mitigated. For example, the inflow of rinse water in the rinse cycle can be reduced from a predetermined limit compared to the maximum inflow of rinse water during the first 5 seconds, or at most during the first 20 seconds. This limit lies below the maximum upper limit. The aim is to prevent the maximum upper limit from being exceeded.

[0036] It has proven advantageous to reduce the rinse water flow to a minimum of 20% of the maximum rinse water flow during the rinse cycle when the inflow is reduced. In an advantageous operating variant, the rinse water volume remains as predefined. This extends the rinse cycle, ensuring a constant amount of rinse water is used to rinse out fibers. This allows fibers to still be rinsed out and prevents overloading of the rotor drive.

[0037] In one embodiment, it can be provided that adaptive, predictive flushing is carried out based on the current impurity load and the rotor drive power until a predetermined lower limit of power consumption is expected to be reached. This ensures that a large portion of the impurities has been flushed out. This creates a good starting point and thus a good filling capacity of the screening device for subsequent cleaning of fiber suspension in the flow cycle and subsequent cycles.

[0038] Adaptive here means adjusting. It is an adjustment based on the detected operating parameters.

[0039] Predictive setpoint adjustment and its control are considered predictive. In particular, the previous cycles 1 to 50 can be used for this purpose. It can be provided that, depending on the power consumption at the end of the discharge cycle above a lower limit, the length of the subsequent or subsequent newly initiated throughput cycle of fiber suspension input is shortened. The drive power of the rotor at the end of the discharge cycle provides an indication of remaining impurities. This impurity can be due to a high impurity load in the fiber suspension fed to the screening device. However, a high impurity load can also have accumulated in the screening device due to a long previous throughput cycle.

[0040] The ability to dynamically respond to the impurity load increases the efficiency of the screening device. If the fiber suspension fed into the throughput cycle contains a low impurity load, the throughput cycles can be extended without risking overloading the rotor drive.

[0041] On the other hand, throughput cycles can be shortened when the impurity load is high. This can be determined by the rapid increase in rotor drive power. Impurities are then removed more frequently and overloading of the rotor drive is counteracted, thus having a positive effect on the service life of the screening device.

[0042] If the accepted material is intended to be returned to the pulper, more frequent removal of impurities in the screening device can also ensure that the impurity load in the pulper is broken down more quickly. This results in less comminution in the pulper. Comminution would result in the crushed impurities becoming apparent as an increased burden in subsequent cleaning process stages and could potentially negatively impact the final accepted material quality.

[0043] One process variant provides for the reduction of the quantity and inflow of fiber suspension fed in at the end of the discharge cycle, depending on the power consumption. This allows the new impurity input per time interval as well as the total quantity of fiber suspension fed in during this cycle and the associated impurity in the screening device at the end of the throughput time to be reduced. This allows overload situations to be counteracted particularly effectively.

[0044] According to the invention, the arrangement with a screening device is characterized in that the arrangement has a controllable valve in the rinse water supply for adjusting the rinse water flow. This makes it possible to dynamically regulate the rinse water flow. The drive power of the rotor drive can be detected by a control system. To prevent overload situations, the control valve can be used to reduce the rinse water flow depending on the rotor drive power. Characteristic curves can be stored or learned in the control system for this purpose.

[0045] In one embodiment, in which a pulper is located upstream of the screening device, the control system is designed to reduce the material feed into the pulper after a predetermined number of cycles with the rotor power consumption of the screening device exceeding a limit value stored in the control system. This counteracts overloading of the fiber processing system. The speed of processing waste paper to accept material can thus be adjusted to the quality of the waste paper fed into the pulper.

[0046] A computer program product allows an existing plant to be retrofitted with a pulper and at least one downstream cyclically operated screening device to carry out the process according to one of the previously described methods according to the invention. This can increase the efficiency of existing plants.

[0047] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. Fig. 1 shows a schematic representation of a system according to the invention.

[0048] Fig. 2 schematic representation of a plant according to the invention with continuously operated pulper

[0049] Fig. 3 schematic representation of a system according to the invention with two screening devices arranged in parallel

[0050] Fig. 4 Schematic representation of a control system Fig. 5 Operational measurement curves in schematic representation a) Drive power pump b) Acceptance discharge c) Drive power rotor of the screening device 50 d) Volume of the supplied dilution wash water

[0051] Figures 1, 2, and 3 show examples of systems for producing a fiber suspension. The challenge in fiber extraction from waste paper is to remove as many contaminants as possible. However, the removal of fibers associated with the removal of contaminants should be kept to a minimum.

[0052] Paper stock, also referred to as waste paper, shown here as waste paper bales 13, is fed to a pulper 20 via a conveyor belt 11. Pulpers 20 are also referred to below as pulpers 20. In the pulper 20, waste paper, for example, is mixed with water as paper stock and converted into a fiber suspension. For this purpose, dilution water is fed to the pulper 20 via a controllable water supply 10 and the feed 15. In addition, a suspension further classified as accepts is fed to the pulper 20 from a screening device 50 and a re-sorting device 70 downstream of the pulper 20. The screening device 50 and the re-sorting device 70 will be discussed in more detail later.

[0053] The pulper 20 is equipped with a screen 29 in its base area, through which a portion of the suspension can pass into the annular space. A rotor 25 is arranged above the screen 29, which on the one hand sets the paper stock-water mixture in rotation and on the other hand keeps the screen 29 clear. The rotor 25 is driven by the drive 27. The fiber suspension that has passed through the screen 25 is discharged via an accepts discharge 21. The portion of the suspension produced in the pulper 20 that is discharged via a contaminant discharge 23 is led into a collection container 30 with a contaminant outlet 31. Coarse heavy dirt contained in the introduced fiber suspension can be separated in the collection container 30. In the collection container 30, the suspension is ideally diluted to 3.5% for more effective heavy particle separation.The coarse, heavy dirt sinks into the collection container 30 and is directly separated through an automatically controlled dirt lock with a contaminant outlet 31. It may be provided that additional dilution water is added to the dirt lock for improved fiber backwashing.

[0054] In the upper area of ​​the collection tank, a discharge 33 for suspension is provided. Fiber suspension is removed from this upper area of ​​the collection tank 30. This fiber suspension is fed by a pump 40 via a line and a feed 52 to the screening device 50 with the housing 51 for further treatment. The pump 40 is a special pump for fiber suspensions containing impurities. This pump 40 can pump the impurity suspension from the pulper into the screening device 50 with a largely blockage-free and reliable approach. This pump 40 is designed with a large nozzle diameter and a free-flow impeller for blockage-free pumping of fiber suspensions with a high impurity content. In particular, the impeller can be optimized for particularly high durability through armor plating. A drive 45 with a frequency converter enables an optimized pump speed for discontinuous pumping operation.As a result, the volume flow delivered by the pump 40, also referred to as flow, can be regulated, preferably continuously.

[0055] The accepted material from the collection container is fed to the downstream screening device 50 for further processing. This is a cyclically operated screening device. A screen 57 is provided in the housing. A rotor 58 is arranged in front of the screen 57. The rotor 58 sets the fiber suspension introduced into the housing 51 of the screening device in rotation in front of the screen 57. The rotor is driven by a drive 59. A portion of the supplied fiber suspension passes through the screen 57 and is discharged from the screening device via an accepted material discharge 67. Figure 5 shows a graphic representation of the outflow of the accepted material discharged from the screening device over time. In addition, Figure 5 shows a graphic representation of the power consumption of the rotor drive 59 over time.

[0056] There is a cycle for feeding fiber suspension, also referred to as a flow cycle. In the flow cycle 117, fiber suspension is fed to the screening device 50. The suspension is set in rotation by the rotor 58. The rotor 58 is arranged in front of a screen 57. Loosened fibers pass through the screen 57. A differential pressure is present, which promotes the outflow of loosened fibers through the screen 57. The accepted material discharge 67 for the outflow of the accepted material with the switching valve 69 (see Figure 4) is open. The impurity discharge 66 with the switching valve 56 (see Figure 4) is closed. As a result, impurities are concentrated in the fiber suspension in the screening device 50 in front of the screen 57.

[0057] For increased processing of this suspension in the screening device 50, the supply of fiber suspension can be interrupted. The switching valve 53 (see Figure 4) is provided for this purpose. The suspension in the screening device 50 is processed by the movement within the screening device 50. The valve 56 of the impurity discharge 66 remains closed, and the accepted material discharge is open. The movement of the suspension can loosen any fiber clumps present in the suspension. The loosened fibers can pass through the screen and flow out via the accepted material discharge 67. This cycle is also referred to as the post-pulling cycle 119.

[0058] The post-pulping cycle 119 or the flow-through cycle 117 is followed by a rinsing cycle 127. In the rinsing cycle 127, a supply of rinsing water is provided. The rinsing water is supplied by the water supply 10. The inflow into the screening device 50 occurs via a control valve 65. The inflow can be regulated by the control valve 65. The inflow 152 of rinsing water can be regulated depending on the power consumption 162 of the rotor. Depending on the drive power of the rotor 58 of the screening device 50, the inflow of rinsing water is initially throttled before the rinsing cycle 127. This prevents or at least reduces overloading of the rotor drive.

[0059] The supplied rinse water flow could also be controlled via a controllable drive of the rinse water supply pump 60. During this cycle, fiber suspension is further rinsed out via an accepts discharge 67.

[0060] The rinsing cycle 127 is followed by a discharge cycle 137. The suspension containing the concentrated impurities is removed from the housing 51 of the screening device 50. For this purpose, the impurity discharge 66, valve 56, is opened. The flow cycle and the rinsing cycle can overlap or be carried out purely serially. A controller 100 can change the length of each cycle and thus adapt it to the respective degree of contamination or the paper quality of the waste paper. The fraction of acceptable material extracted by the screening device 50 is fed back to the pulper 20 via a feed line 17. The fraction of impurities extracted in the screening device 50 is fed to a secondary sorting device 70.

[0061] The re-sorting device 70 provides for further leaching of any fibers still present in the impurities. Here, the re-sorting device 70 comprises a screen drum and a dilution water supply 75. The rotation of the drum causes the introduced fraction to rotate and also move axially. Fibers pass through openings in the drums, together with rinsing water, to an accepts discharge 73 and are fed from the re-sorting device 70 to the pulper 20 via a feed 19. The portion that does not pass the screen is discharged as impurities via a impurity discharge 76. The inflow of rinsing water can also be regulated in the re-sorting device 70. In particular, the amount of rinsing water can be regulated depending on the drive power of the drum in order to avoid overloading the drum drive.

[0062] In the arrangement 1 shown in Figure 2, the fiber suspension produced in the pulper 20 is cyclically fed directly to a downstream screening device 50. The accepts from the screening device 50 are fed to a large collecting container 68, and the impurities separated by the screening device 50 are fed via a pump 40 to a collecting container 30 with an impurity outlet 31. From the collecting container 30, suspension can be continuously fed to a re-sorting device 70 via a feed 71 via an outlet 33. This re-sorting device 70 corresponds to the re-sorting device 70 described with reference to Figure 1. Here, the accepts extracted by the re-sorting device 70 are fed to the pulper 20 via the accepts discharge 73. The portion not remaining as accepts in the re-sorting device 70 is discharged via a impurity discharge 76.

[0063] Figure 3 shows a further variant of a system for fiber processing. This system differs from the system shown in Figure 1 in that two screening devices 50, 250 are arranged parallel to one another. The mode of operation of the screening devices 50, 250 does not differ from the mode of operation of the screening device 50 in Figure 1. The second screening device also has a housing 251, a suspension inlet 252, a drive 259, a rinse water inlet 261, an impurity discharge 266, and an accept discharge 267. For efficient operation, the cycles of the two screening devices are coordinated with one another. Only one pump 40 is provided, through which fiber suspension is supplied to the first screening device 50 or the second screening device 250. A common supply of rinse water is also provided. The impurity from the screening devices is fed to a secondary sorting device 70.Figure 4 shows a more detailed version of a controller 100 for a screening device 50. The controller 100 controls, on the one hand, the motor 45 of the pump 40. A pump controller 140 is provided for this purpose. The pump controller 140 outputs a target value and an actual value for the pump's drive frequency and a drive power 144. The goal is to ensure maximum flow during the flow cycle without overloading the drive, even under changing boundary conditions such as inlet pressure and impurity content. Here, the supply of suspension to the screening device 50 is regulated via the pump 40. A controller 150 for the water pump 60 is provided for the supply of rinse water and the inflow of rinse water. This controller can control the valve 65 provided in the water supply 61. The valve 65 is a controllable valve. The inflow of supplied rinse water can be regulated or controlled by this valve 65.The control 150 of the flushing water pump 60 includes a target value of a flow rate and a base value of the flow rate of the water pump 60. In addition, the current drive power is recorded.

[0064] To control the rinse water pump 60 and to control the rinse water flow and quantity in the respective cycle, particularly during the rinse cycle, values ​​of the drive power 117 of the drive 59 of the rotor 58 of the screening device 50 are included. The control as a function of the drive power of the rotor 58 is described in more detail with reference to Figures 4 and 5.

[0065] The controller 100 can dynamically adjust the duration of individual cycles and adjust the amount of suspension and rinsing water supplied per time.

[0066] The controller 110 records the throughput cycle 117. The throughput cycle is the time period during which fiber suspension is fed to the screening device 50. A base value for a time duration of a throughput cycle is specified, and a target value for a time duration of a throughput cycle is specified adaptively and predictively. An adaptive predictive specification is a predictive presetting that adapts depending on parameters. An adaptive predictive control can be based on stored characteristic curves or it can be provided by an adaptive learning control. If no values ​​or characteristic curves are initially available, an initial learning process is required. Subsequently, a self-learning adjustment of both base values ​​and target values ​​can be provided.

[0067] Different basic values / output values ​​can also be stored in the control system for predetermined grades of waste paper. The duration of the cycles and inflows of rinsing water and suspension are regulated by the control system 100. A determined target value is provided for the individual cycles by the control system. In particular, the power consumption of the rotor drive 58 of the screening device is taken into account. It can be provided that the duration of the throughput cycle is regulated as a function of the minimum power consumption of the rotor in the rinsing cycle. Furthermore, the quality and / or the quantity of accepted material discharged can be taken into account. Adapting a throughput cycle in the range of 15 to 150 s / min, preferably in the range of 60 to 120 s / min, has proven to be a suitable control range. With an identical setup, 50 s / min was specified as the duration for the throughput cycle in static operation.This demonstrates the efficiency improvement achieved through dynamic operation. In case of inconsistent measured values, the values ​​from static operation can be used to continue operation for the time being.

[0068] The control unit 120 is provided for regulating the rinsing cycle 127. In the rinsing cycle 120, rinsing water is fed into the screening device with the aim of rinsing or washing fibers out of the suspension enriched with impurities located in front of the screen. No more fiber suspension is supplied by the pump 40. The switching valve 53 is or will be closed. The valve 69 for discharging the accepted material is still open. The control unit provides for regulating the rinsing cycle 127. An actual rinsing time is specified and a base value for a rinsing time is stored. In addition to the duration of the rinsing cycle, the flow of supplied rinsing water is also regulated depending on the power consumption or detected power consumption of the drive 59 of the rotor 58. The control unit 160 is provided for the rotor drive. The rinsing cycle can also be referred to as a washing cycle.In this cycle, fibers are increasingly washed out of the suspension present in the screening device using the supplied rinse water. No suspension is fed to the screening device 50.

[0069] To regulate the inflow of rinse water, a controller 150 is assigned to the drive of pump 60. A maximum value 154 for the rinse water is provided in the pump controller. The inflow of rinse water can be increased from an initially low value up to the maximum value over the course of a cycle, as shown in Fig. 5. A base value is stored for the duration of rinse cycle 127 and discharge cycle 137. A duration of 15 seconds to 50 seconds has proven to be a suitable dynamic range for rinse cycle 127. In comparison, a duration of 15 seconds is provided for static operation. By extending the duration, a good yield of fibers can be achieved.

[0070] The rinsing cycle is followed by a discharge cycle 137. The discharge cycle 137 is controlled by the control 130 for the discharge cycle. The control valve 65 is open during the discharge cycle 137. The valve 56 for the discharge of impurities is or will be opened and the valve 69 for the accepts removal is closed. The supply of fiber suspension is prevented by the valve 53. In the discharge cycle 137, a maximum inflow of rinsing water is supplied to the screening device in order to achieve thorough rinsing of the suspension enriched with impurities. In dynamic operation, time periods in the range of 15 to 35 seconds are stored in the control system. In static operation, a predetermined constant time of 35 seconds is stored. Since the impurities are conveyed out of the screening device in the discharge cycle 137, this cycle is also frequently referred to as the reject cycle.

[0071] If the drive power of rotor 58 does not fall below a predetermined lower limit value (arrow in Figure 5) in discharge cycle 137 and also in the subsequent throughput cycle 117, the control system then shortens the throughput cycle 117 in the next newly commencing throughput cycle 117. In the next cycle, the subsequent discharge cycle, and thus the time for reject discharge, is extended. Due to the inertia of screening device 50, immediate intervention in an already commenced throughput cycle 17 is not yet possible with currently available screening devices 50. However, if the drive power 162 of rotor 58 exceeds a predetermined limit value, an alarm is issued.

[0072] Figure 5 shows exemplary temporal progressions. The inflow of fiber suspension 112 and the outflow of accept 114, the power consumption 162 of the rotor 58 drive, and the inflow of rinse water 152 are shown in relation to each other and over time. The temporal progression of the rinse water inflow reveals a reduced inflow 158 of rinse water. The maximum inflow of rinse water 154 is supplied in the discharge cycle 137. Cycles such as the throughflow cycle 117, the post-pulping cycle 119, the rinse cycle 127, and the discharge cycle 137 are plotted.

[0073] This process makes it possible to dynamically adjust the fiber yield and the amount of purified suspension to the quality of the supplied suspension. The duration and amount of rinse water supplied to the rinse cycle 127 can be dynamically adjusted.

[0074] List of reference symbols

Claims

Patent claims 1. Method for operating a screening device (50, 250) for cleaning a fiber suspension with a rotor (58) and screen (57) arranged in a housing (51, 251) of the screening device (50, 250), wherein fiber suspension and rinsing water are fed to the screening device (50) and the portion of the fiber suspension passed through the screen (57) is discharged via an accepts discharge (67, 267), characterized in that an inflow into the screening device (50, 250) and / or a cycle time duration is regulated as a function of the power consumption (162) of the rotor drive (59, 259).

2. Method for operating a screening device (50, 250) according to claim 1, characterized in that the cycle time of at least one subsequent cycle such as pass-through cycle (117), post-dissolving cycle (119), rinsing cycle (127) or discharge cycle (137) is regulated as a function of the power consumption (162) of the rotor drive (59, 259).

3. Method for operating a screening device according to claim 1 or 2, characterized in that when the power consumption (162) of the rotor drive (59, 259) exceeds a predetermined limit value, the inflow of rinsing water is reduced at least at the beginning of a subsequent rinsing cycle (127) compared to a maximum possible inflow of rinsing water (154).

4. Method for operating a screening device (50, 250) according to one of the preceding claims, characterized in that additionally or alternatively a cycle time duration of the flow cycle (117) and / or the rinsing cycle (127) is regulated depending on the flow of accepted material. Experienced in operating a screening device (50, 250) according to one of the preceding claims, characterized in that an inlet pressure and / or a differential pressure to the pressure of the accepts discharge is taken into account when controlling a subsequent cycle time. Experienced in operating a screening device (50, 250) according to one of the preceding claims, characterized in that plant-specific limit values ​​are read in or entered manually during commissioning. Experienced in operating a screening device (50, 250) according to claim 6, characterized in that a maximum plant-specific accepts flow is or is stored. Experienced in operating a screening device (50) according to one of claims 6 or 7, characterized in that a factory setting and / or a basic setting is stored in the control system (100), wherein operation without adaptive control is possible with the factory setting and the basic setting.Experienced in operating a screening device (50, 250) according to one of claims 6 to 8, characterized in that when the power consumption of the rotor drive (59, 259) is outside a stored power range, in particular in the run-through cycle (137), the operation is continued on the basis of data from a basic setting or factory setting until the recorded operating data are again within the stored standard range. A method for operating a screening device (50, 250) according to one of claims 6 to 8, characterized in that, if an operating parameter is outside a stored standard range, the method is continued by resorting to a predetermined number of cycles, and an adaptive adjustment of the operating parameters used for the cycles takes place. A method for operating a system with at least one first cyclically operated screening device (50) and a second cyclically operated screening device (250) arranged in parallel, a pulper (20), characterized in that the cycles of the at least two screening devices (50, 250) are coordinated with one another for utilization of peripheral devices (70, 40, 60) of the system (1) by extending at least the rinsing cycle (127) of the currently ongoing sequences and / or shortening at least the throughput cycle (117).Method for operating a plant (1) with a pulper (20) and with at least one screening device (50, 250) according to one of claims 1 to 10, wherein fiber suspension is returned to the pulper (20), characterized in that the consistency and quantity of the fiber suspension returned to the pulper (20) are taken into account for providing a consistency in a predetermined consistency range of the pulper material. Method for operating a plant (1) with a pulper and with at least one screening device (50, 250) according to one of claims 1 to 10, wherein fiber suspension is returned to the pulper (20), characterized in that. that the consistency and quantity of the fiber suspension returned to the pulper (20) is taken into account to ensure consistency in the pulper.

14. Plant (1) with a pulper (20) and at least one screening device (50, 250) and a controller (100) for carrying out the method according to one of the preceding claims, characterized in that a control valve (65) is arranged in the supply of rinsing water to the screening device (50, 250), wherein preferably the control valve (65) is a control valve (65) which can be controlled at least as a function of a detected power consumption (162) of the rotor drive (59, 259).

15. A computer program product for providing a method for fiber processing according to a method operated according to one of claims 1 to 12.

Images