Control of reject

Abstract

The invention relates to a control system (1) for controlling a coarse sorting unit (3) of a fiber processing or papermaking plant, wherein the control system (1) comprises an optical measuring system (4), a control device (19), and a coarse sorting unit (3), wherein the coarse sorting unit (3) is supplied with a stock suspension (12) by a stock dissolver (5), and rejects (13) from the coarse sorting unit (3) are discharged onto a conveyor belt (12), wherein the optical measuring system (4) is configured to measure at least one quality value of the rejects (13) on the conveyor belt (12), and wherein the control device (1) controls at least one component of the coarse sorting unit (3), taking the quality value into account. The invention further relates to stock preparation and a control method.

Description

[0001] The invention relates to a control system for controlling a coarse screening system in a fiber processing or paper production plant. The control system comprises an optical measuring system, a control device, and a coarse screening system. The coarse screening system is supplied with a stock suspension from a pulping system, and broke is discharged from the coarse screening system onto a conveyor belt. Furthermore, the invention relates to a stock processing system comprising a control system and a method for controlling the stock processing system.

[0002] The control system according to the invention, the stock preparation and the method for controlling the stock preparation are advantageously used in the paper industry for preparing the raw materials for paper, board and / or tissue production.

[0003] EP3980598 A1 is known from the prior art. It describes a method in which the raw material is measured in a stock preparation line, and the measured values ​​are used to control subsequent process steps. The products and by-products, especially the rejects, are not considered.

[0004] The object of the invention is to provide an efficient control system for stock preparation. Furthermore, the object of the invention is to provide a method for effectively controlling stock preparation.

[0005] The object is achieved according to the invention by an embodiment according to the independent claim. Further advantageous embodiments of the present invention can be found in the subclaims.

[0006] Furthermore, the object is achieved according to the invention, wherein the optical measuring system is designed to measure at least one quality value of the rejects on the conveyor belt and wherein the control device controls at least one unit of the coarse sorting taking into account the quality value.

[0007] In the coarse screening process, non-soluble parts of the raw material are separated and transported from the stock preparation in solid, or largely solid, form on a conveyor belt. Key components of the broke are plastic components and wet-strength paper. However, through mechanical processing, fibers can still be extracted from the (initially) wet-strength paper, which can be used in paper production. It is therefore advantageous to measure and minimize the proportion of fiber material in the broke.

[0008] An optical measuring system is a sensor or a plurality of sensors designed to measure the surface of the material being measured. The optical measuring system can include camera-based sensors and / or laser measurements. Furthermore, infrared and / or distance measurements can be used. The optical measuring system can further include pattern recognition and / or color recognition to individually record the components of the scrap. The optical measurement can thus capture various quality values; the quality values ​​can include the color values, the proportion of various substances, and the volume of the scrap.

[0009] The controlled units in the coarse screening process can include screening devices such as screen baskets, flat screens, or hydrocyclones. The control can regulate the flow rate, the ratio of acceptable material to rejects, and / or the energy input. In particular, the control of the units can also include a modification of a cascade connection of a plurality of screening devices. Control of the coarse screening process can also be achieved indirectly via valve control.

[0010] A control system is also advantageous, wherein the optical measuring system comprises a camera system designed to measure color values ​​of the rejects.

[0011] The camera system can advantageously measure the color values ​​of the rejects. Image recognition can also be used optionally and advantageously to detect and classify parts with different colors.

[0012] A control system is also advantageous, whereby an image component with a defined color value range is calculated by means of the optical measuring system and is used to determine the quality value.

[0013] For example, image recognition or analysis software can be used to record the number of pixels in a digital image with a specific color value. This makes it possible to identify, for example, brown wet-strength paper on the surface and / or individual plastics with a particular color. By analyzing the image of the scrap captured by a camera, portions of the surface can be assigned different color values. This makes it possible to determine the quality value of the composition of the scrap. The quality value can, in particular, determine the proportion of fiber-containing residues that have a specific color range. The analysis of gloss values ​​and / or reflections can also be used to determine a quality value for the moisture content or the proportion of plastic in the scrap.

[0014] A further advantage is a control system in which the optical measuring system is designed to measure the volume of the rejects on the conveyor belt.

[0015] The volume of the rejects conveyed on the conveyor belt can be measured using optical measurement, particularly an optical distance measurement, if the surface of the rejects is measured in comparison to the surface of the empty conveyor belt. The distance measurement can be recorded using a phase shift in the camera and / or an optical scan of the surface. A laser distance measurement arranged above the conveyor belt can also record a volume flow. Measuring the volume is particularly advantageous for determining the specific proportion of rejects relative to the total volume. For example, quantity shares can be determined as a percentage.

[0016] A control system is also advantageous, wherein the quality value is used for the control of at least one sorting device with a flat screen and / or a sorting basket, wherein the control comprises an adjustment of the drive power and / or the throughput quantities.

[0017] The aim of coarse screening is to separate solid components from the liquid stock suspension. It is therefore an essential component of stock preparation, in which fiber suspension is produced from waste paper, which is then processed into new products in paper, board, or tissue production. Coarse screening typically comprises a plurality of screening devices. These screening devices can comprise flat screens and / or screen baskets, for which the throughput rates and drive power can be controlled. The drives can move the flat screen and / or screen basket themselves, or move a flow device such as a blade or agitator past the screen. The throughput rate can be varied by pumping power and / or valve positions, with the control then having an indirect effect on the throughput rate.

[0018] A control system is also advantageous, whereby the quality value from the optical measuring system is used to control a flow rate and / or an energy input in the material dissolution by means of the control system.

[0019] For example, the drive power of the rotating screen baskets can be controlled, thus advantageously achieving a direct change in the sorting performance. Furthermore, valves can be controlled in such a way that the flow rates, especially the feed, acceptance, and rejection lines, are controlled separately.

[0020] A control system is also advantageous, wherein the quality value from the optical measuring system is used to control a filling and / or a pressure in a sorting device, the coarse sorting, by means of the control system.

[0021] For individual sorting devices, the control of the fill level or filling can also have an impact on the sorting result. Conversely, energy consumption can represent another control objective that is taken into account by the control system.

[0022] Also advantageous is a stock preparation system, a plant for fiber stock preparation and / or paper production comprising a control system, an optical measuring system and a coarse screening system, wherein the coarse screening system is supplied with a stock suspension from a stock dissolving system and broke is carried out on a conveyor belt from the coarse screening system, wherein the stock preparation is designed to be controllable by means of at least one measured value from the optical measuring system, wherein the optical measuring system is designed to measure at least one quality value of the broke on the conveyor belt.

[0023] The purpose of stock preparation is to process waste paper to such an extent that it is available in liquid fiber suspension for downstream paper, board or tissue production. In this process, all residual materials unsuitable for production are sorted out as rejects. The rejects can be fed onto the conveyor belt as solid material using reject processing. Other rejects that come directly from a pulper and / or pulping drum can also be discharged from the stock preparation on the conveyor belt and measured using the optical measuring system. The measured values ​​from the optical measuring system can therefore be used to control a variety of units in stock preparation. This is particularly advantageous when the throughput rate and reject rates of the stock pulping in the pulper and / or pulping drum need to be adjusted.

[0024] Furthermore, a stock preparation is advantageous, wherein the control of the stock preparation is designed to change the flow rates of at least two sorting devices in the coarse sorting.

[0025] A variety of sorting devices and devices for mechanical stock processing are used in stock preparation. These devices are connected by pipes, valves and pumps and connected in cascades. A sorting stage comprises at least one stock inlet, at least one outlet for accept material and at least one outlet for material of lower quality, often called reject. Changing the flow rates can also lead to advantageous changes in the cascading and interconnection. For example, part of the reject from one sorting stage can be fed into the feed line of a downstream sorting stage, and from there part of the accept material can be fed to another sorting stage. Rejects can be further reduced in size by mechanical treatment and thus processed further in suspension as accept material.

[0026] Further advantageous is a material preparation, wherein the quality value is used to control at least one sorting device with a flat screen and / or a sorting basket, wherein the control comprises an adjustment of the drive power and / or the throughput quantities.

[0027] In the coarse screening stage of stock preparation, this also makes it particularly advantageous to control screening devices, especially screening devices with flat screens and / or screening baskets. The quality value, which is determined using an optical measuring system, can advantageously be directly influenced by changing the settings of the screening devices, thus enabling a control loop.

[0028] Furthermore, a control method for controlling a material preparation is advantageous, whereby the following process steps are carried out: Measuring the rejects on the conveyor belt using an optical measuring system Creating a quality value from the measured value of the optical measuring system using a control device Controlling the throughput rates of at least one sorting device in the stock preparation using the quality value

[0029] The process particularly advantageously influences the cascading and / or interconnection of various screening devices to achieve effective and efficient coarse screening. The process allows for targeted intervention in the stock preparation processes using quality values ​​of the broke and to adjust the control to either reduce the broke or reduce the proportion of fibers in the broke, with truly insoluble broke components being preferentially removed from the process.

[0030] A further advantageous control method is one in which, in a further method step, the quality value is used to control at least one sorting device with a flat screen and / or a sorting basket, the control comprising an adjustment of the drive power and / or the throughput quantities.

[0031] If the quality value of the reject shows an increased fiber content, the process can be used to specifically change the energy input or the throughput rate of individual sorting devices and / or material treatment units in order to improve the proportion of recycled fibers.

[0032] The invention is explained below with reference to the figures. The figures show in detail: FIG. 1: Schematic representation of a controllable stock preparation system FIG. 2: Controllable stock preparation system with pulping drum

[0033] Figure 1 (FIG 1) shows a schematic overview of a control device 1 suitable for carrying out a control process 1 in a coarse sorting system 3. The coarse sorting system 3 is arranged downstream of a stock pulping system 5. In the stock pulping system 5, raw material 16, in particular fiber such as waste paper and / or recyclable cardboard, is dissolved with water in a pulper 6 or brought into suspension. In the coarse sorting system 3, solids, portions of the raw material 16 that are not soluble and / or portions of the raw material 16 that are not isolated in suspension in the stock preparation 5 are further processed or sorted out. The coarse sorting system 3 sorts out rejects 13, whereby the rejects 13 essentially comprise solid, insoluble materials such as waste, household waste, plastic parts, metals and the like. However, the rejects 13 can also contain fiber portions that are difficult to dissolve. The rejects 13 are transferred from the rough sorting 3 to a conveyor belt 12.Optionally, a portion of the broke 13 from the pulping 5 can also be transferred directly to a conveyor belt 12 after a broke preparation 8. On the conveyor belt 12, the broke 13 is measured using an optical measuring system 4. The optical measuring system 4 comprises a camera 14 which is configured to transmit measured values, in particular image information, to the control device 1. The optical measuring system 4 further optionally and advantageously comprises an illumination device 15 which enables uniform illumination of the broke 13 on the conveyor belt 12, thus enabling comparability of the measured values ​​or digital images. Furthermore, the optical measuring system 4 optionally and advantageously comprises a shield to shield the optical measuring system 4 from disruptive light influences from the environment, in particular from daylight.

[0034] Figure 2 (FIG 2 )shows a schematic overview of a control device 1 suitable for carrying out a control method 1 in a stock preparation 20. The stock preparation 20 comprises a pulping drum 7 in which the raw material 16 is dissolved and fed to the coarse screening 3 as a fiber suspension 17. The coarse screening 3 comprises a plurality of screening devices 9, 10, 11. Advantageously and optionally, the screening devices 9, 10, 11 are connected in a cascade. The coarse screening advantageously and optionally comprises at least one screening device with a flat screen and screening basket 9, wherein the screening basket and the flat screen can be operated with variable throughput rates and with variable energy input by the drive. Furthermore, the coarse screening 3 advantageously and optionally comprises a screening device with a flat screen 10, here too the energy input can be varied in a controlled manner via the drive, and furthermore the rinsing water and throughput can be varied.For the control, a control device 18 is used which is designed to transmit a control signal 2 to the various units of the coarse sorting 3. The control device 18 uses at least one measured value from the optical measuring system 4 as an input variable. The optical measuring system advantageously comprises a camera 14 and an illumination device 15. Furthermore, the optical measuring system optionally and advantageously comprises a shield in order to minimize the influence of ambient light on the optical measurement. The camera can advantageously and optionally comprise a distance measurement and / or a scanning system which are suitable for recording a volume and / or a volume flow. The optical measuring system is aligned with a conveyor belt 12, wherein rejects from the coarse sorting 3 and / or from a reject processing 8 are transported on the conveyor belt 12. The rejects comprise poorly soluble or solid components which are removed from the raw material 16 orfrom the fiber suspension 17. The broke 13 mainly comprises plastic components, such as films and fiber or paper residues, which are removed in the pulping drum 7 and / or the pulper 6 (see . Figure 1 ) were not resolved. The optical measuring system 4 is designed to perform an analysis of the components of the reject 13. List of reference symbols

[0035] 1Control system, control method 2Control signal 3Coarse screening 4Optical measuring system 5Stock dissolving 6Pulper 7Dissolving drum 8Reject processing 9Sorting device, sorting device with flat screen and sorting basket 10Sorting device, sorting device with flat screen 11Sorting device, sorting device with sorting basket 12Conveyor belt 13Reject 14Camera 15Lighting device 16Raw material 17Fiber suspension 18Control device 20Stock preparation

Claims

1. Control system (1) for controlling a coarse screening system (3) of a plant for fiber processing or paper production, wherein the control system (1) comprises an optical measuring system (4), a control device (19) and a coarse screening system (3), wherein the coarse screening system (3) is supplied with a stock suspension (12) by a stock dissolving system (5) and broke (13) is carried out on a conveyor belt (12) from the coarse screening system (3), characterized in that the optical measuring system (4) is designed to measure at least one quality value of the rejects (13) on the conveyor belt (12), wherein the control device (1) controls at least one unit of the coarse sorting (3) taking into account the quality value.

2. Control system (1) according to claim 1, characterized in that optical measuring system (4) comprises a camera system designed to measure color values ​​of the reject (13).

3. Control system (1) according to claim 1 or 2, characterized in thatthat an image portion with a defined color value range is calculated by means of the optical measuring system (4) and is used to determine the quality value.

4. Control system (1) according to one of the preceding claims, characterized in that the optical measuring system (4) is designed to measure the volume of the rejects (13) on the conveyor belt (12).

5. Control system (1) according to one of the preceding claims, characterized in that the quality value is used for the control of at least one sorting device with a flat sieve (9, 10) and / or a sorting basket (10, 11), wherein the control comprises an adaptation of the drive power and / or the throughput quantities.

6. Control system (1) according to one of the preceding claims, characterized in that that the quality value from the optical measuring system (4) is used to control a flow rate and / or an energy input in the material dissolution (5) by means of the control system (1).

7. Control system (1) according to one of the preceding claims, characterized in that that the quality value from the optical measuring system (4) is used to regulate a filling and / or a pressure in a sorting device (9,10,11), the coarse sorting (3), by means of the control system (1).

8. Stock preparation (20), a plant for fiber preparation and / or paper production comprising a control system (1), an optical measuring system (4) and a coarse screening system (3), wherein the coarse screening system (3) is supplied with a stock suspension (12) from a stock dissolving system (5) and broke (13) is carried out on a conveyor belt (12) from the coarse screening system (3), characterized in that the stock preparation (20) is designed to be controllable by means of at least one measured value from the optical measuring system (4), wherein the optical measuring system (4) is designed to measure at least one quality value of the reject (13) on the conveyor belt (12).

9. Stock preparation (20) according to claim 7, characterized in that the control system (1) of the stock preparation (20) is designed to change the flow rates of at least two sorting devices (9,10,11) in the coarse sorting (3).

10. Stock preparation (20) according to claim 8 or claim 9, characterized in that a flow rate and / or an energy input in the substance dissolution (5) is controlled by means of a control signal (2) from the control system (1), wherein the control system (1) uses a measured value from the optical measuring system (4) for.

11. Stock preparation (20) according to one of claims 8 to 10, characterized in that the quality value is used to control at least one sorting device with a flat screen and / or a sorting basket (9, 10, 11), wherein the control comprises an adjustment of the drive power and / or the throughput quantities.

12. Control method (1) for controlling a material preparation (20) according to one of claims 7 to 10, characterized in thatThe following process steps are carried out: • Measuring the rejects on the conveyor belt using an optical measuring system • Creating a quality value from the measured value of the optical measuring system using a control device • Controlling the throughput rates of at least one sorting device in the material preparation using the quality value 13. Control method (1) according to claim 11, characterized in that in a further method step, the quality value is used to control at least one sorting device with a flat screen and / or a sorting basket, wherein the control comprises an adjustment of the drive power and / or the throughput quantities.

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