Screening process and screening system

Abstract

The invention relates to a screening process, which is a part of a fiber web production process, in which process a treatment substance used in the fiber web production process is screened in at least one screen (11, 15, 16) of a screening system (10), in which process the treatment substance flows in flow lines (L1-L8) of the screening system (10). In the screening process, the at least one screen (11, 15, 16) is disconnected from the screening process for a period of time and at least partially emptied while disconnected; in order to connect the at least one screen (11, 15, 16) back to the screening process, the at least one screen (11, 15, 16) is filled by a filling flow line, which is connected to one of the flow lines (L1-L8) in which the treatment substance flows, and the filling flow line of the screen (11, 15, 16) is an independent flow line in relation to the supply flow line of the screen (11, 15, 16).

Description

Technical Field

[0001] This invention relates to a screening process and screening system for fiber web making machines, used in the production process of fiber webs. Background Technology

[0002] As is known from existing technology in the fields of fiber web machines, particularly paper and paperboard machines, fiber webs are produced and processed in an assembly consisting of multiple devices arranged sequentially in a process line. A typical production and processing line includes a forming section, a press section, and subsequent drying and winding machines. The forming section includes a headbox and a forming unit with a wet-end chemical treatment system. The production and processing line may also include other devices and sections for finishing the fiber webs, such as sizing machines, calenders, and coating sections. The production and processing line typically also includes at least one rewinder for forming customer rolls, and roll packaging equipment.

[0003] The sieve is used in conjunction with a wet-end chemical treatment system, which is used to feed chemicals into the pulp mass before the headbox in the wet end, or onto the fiber web after the headbox, for example, connected to a forming device. Common wet-end chemicals processed in the wet-end chemical treatment system include fillers, pigments, sizing agents such as starch, latex, or binding chemicals.

[0004] The sieve is also used in conjunction with the application device of the fiber web production line to screen the treatment materials related to the application of the treatment material. The treatment material is typically a mixture of colorant paste, coating pigment, sizing agent, starch, etc., used to treat the fiber web, for example, by coating or sizing. The mixture has different components and contains different types of dry matter (i.e., solids) and liquids (e.g., water), and is usually formulated for specific applications. To obtain high-quality fiber webs, these mixtures need to be screened. Typically, the mixture is initially screened during formulation, and sieves are also arranged at processing stations associated with the mixture feed cycle. The purpose of screening is to separate dry matter aggregates, detached fibers, and other foreign matter from the treatment material mixture that could cause problems in the treatment material application process and / or defects in the treatment material applied to the fiber web.

[0005] As is known from the prior art, screening generates a reject, which is a mixture of materials in the process with impurities such as fibers, sand, plastics, gel particles, agglomerates, and aggregated particles, which needs to be removed from the sieve. As mentioned above, the sieve is typically positioned in relation to the sizing or coating section, or to the machine cycle.

[0006] In existing technology layouts, screening processes and systems typically use more than one screen. To facilitate, for example, waste removal, one screen is disconnected from the process or system, while another screen is connected to continue screening. Typically, in existing layouts, screens are changed during operation using several control valves. When a screen needs to be connected, the corresponding control valve is slowly opened to fill the screen from the feed flow line before it is put into use. However, in some cases, this method can cause slight but significant pressure drops or variations that impact the process. Even when the control valves are controlled to open only slightly, large line diameters can cause pressure fluctuations. In many cases, this prevents automatic screen changing during production, requiring manual operation. Even with careful manual operation, problematic pressure fluctuations, and / or pressure spikes / drops and shocks often occur, which can lead to problems with the treatment material application process and / or defects in the treatment material applied to the fiber web. This can result in decreased product quality, even production interruptions, leading to high costs. Summary of the Invention

[0007] The purpose of this invention is to provide a screening process and screening system that can eliminate or at least minimize the defects and problems of screening processes and screening systems known in the prior art.

[0008] In particular, the present invention aims to provide an improved screening process and an improved screening system, especially capable of preventing pressure fluctuations, pressure peaks, pressure drops and pressure shocks.

[0009] To achieve the above objectives and other objectives that will become apparent below, the main features of the screening process and screening system are described below.

[0010] According to the present invention, the screening process used in the screening system is part of a fiber web production process, in which a processing material for the fiber web production process is screened in at least one sieve of the screening system, the processing material flows in a flow line of the screening system, wherein, in the screening process, at least one sieve is disconnected from the screening process for a period of time and is at least partially emptied during disconnection; in order to reconnect the at least one sieve back to the screening process, the at least one sieve is filled by a filling flow line connected to a flow line in which the processing material flows, and the filling flow line of the sieve is an independent flow line relative to the supply flow line of the sieve.

[0011] According to the present invention, a screening system is part of a fiber web production line, the screening system comprising at least one sieve for screening processing material of the fiber web production line, and a flow line in which the processing material is configured to flow, wherein the at least one sieve is configured to be disconnected from operation of the screening system for a period of time and is at least partially emptied upon disconnection; the screening system includes a filling flow line configured to be connected to the at least one sieve in a flow connection and to fill the at least one sieve to connect the at least one sieve back to operation of the screening system; the filling flow line is connected in a flow connection with a flow line in which the processing material is configured to flow in the screening system, and the filling flow line of the sieve is an independent flow line relative to the supply flow line of the sieve.

[0012] Surprisingly, it was discovered that in the screening process and sieve system, a pressurized flow of treatment material with substantially the same treatment material from the process / system flow can be used as a filling flow to fill disconnected sieves, thereby reconnecting the sieves to the process / system without interfering with the applied flow in the supply flow.

[0013] In this specification and claims, the term "treatment substance" refers to a substance used throughout the process, although its composition may vary slightly throughout the process due to different processing steps, but its composition remains substantially the same. The treatment substance is a substance used in wet-end chemical treatment systems, such as fillers, pigments, sizing agents like starch, latex, or adhesive chemicals; or a substance used in treatment substance application processes (e.g., in sizing or coating). Therefore, the treatment substance may be a mixture of pigment paste, coating pigment, sizing agent, or starch. In screening processes, the treatment substance is at least screened, and other process treatments that do not significantly alter the composition of the treatment substance may be performed, such as removing air from the suspension or mixture, or temperature control of the suspension or mixture.

[0014] In this specification and claims, the term "pressurized flow" refers to the flow of processed material in the process flow line, the pressure of which is substantially the same as the pressure on the accept side of the sieve (approximately ±3 bar).

[0015] According to an advantageous aspect of the invention, in the screening process and screening system, the filling stream for the filling flow is typically taken from a pressurized stream within a process / system stream for the processed material, said process / system stream including possible pressurized side circulation streams of process / system streams for substantially the same processed material. Advantageously, the filling flow for the filling stream is selected from: 1. The screening process and screening system, including the feed flow line between the storage tank and the supply tank, and its possible side circulation flow line; 2. The feed flow line of the screening process and screening system located after the feed pump that feeds the material into the screen; 3. Screening process and screening system sieves or other process / system devices for good slurry flow lines or waste residue flow lines; 4. The lower flow line or return circulation flow line of the screening process and screening system; 5. Bypass flow lines for sieves or other process / system devices in screening processes and systems; 6. Screening process and pressurized return flow line of the screening system to the return tank; 7. Circulation flow lines for screening processes and systems, such as temperature-controlled circulation flow lines or screening circulation flow lines; or 8. Air removal flow line of the sieve in the screening process and screening system.

[0016] According to an advantageous aspect of the invention, in the screening process and screening system, a disconnected sieve can be reconnected to the system by filling it with a return flow from a return flow line or a bypass flow from a bypass flow line without interfering with the applied flow. The flow in the return flow line is under gravity pressure, so it does not affect the applied flow in the supply flow line in any way. The bypass flow in the bypass flow line is separated from the applied flow in the supply flow line by a valve (e.g., an on / off valve or a control valve), and its pressure level is the same as the return flow in the return flow line, so it does not affect the pressure of the applied flow in the supply flow line in any way.

[0017] According to an advantageous aspect of the invention, an on / off valve is used instead of a control valve in the screening process and screening system.

[0018] According to an advantageous aspect of the invention, in the screening process and screening system, air is removed from the sieve via a de-aeration flow line.

[0019] According to an advantageous aspect of the invention, in the screening process and screening system, the sieve is filled by a filling flow line independent of the supply flow line used for applying the flow. Advantageously, the diameter of the independent filling flow line is small, ranging from DN5 to DN150 (ISO 6708).

[0020] According to an advantageous aspect of the invention, in the screening process and screening system, the independent filling flow line includes a small-diameter on / off valve or control valve, advantageously a small-diameter on / off valve, to guide the filling flow in the filling flow line. The diameter range of the small-diameter on / off valve or control valve is defined according to the corresponding filling flow line.

[0021] According to an advantageous aspect of the invention, in the screening process and screening system, the filling flow in the filling flow line is defined according to the corresponding filling flow line.

[0022] This invention and its advantageous features enable several benefits: during the production operation of the screening process and screening system, the sieve can be subjected to slag discharge, cleaning, reverse cleaning, maintenance, repair, or overhaul operations without interfering with the pressure or flow of the applied stream. During the production operation of the screening process and screening system, the sieve can be bypassed and / or reconnected without interfering with the pressure or flow of the applied stream. During the production operation of the screening process and screening system, the sieve can be replaced without interfering with the pressure or flow of the applied stream. Attached Figure Description

[0023] However, the various aspects of the present invention, as well as its additional objects and advantages, will be best understood by reading the following description of several exemplary embodiments in conjunction with the accompanying drawings, in which: Figure 1 An advantageous example of a screening process and screening system according to the present invention is illustrated schematically.

[0024] Figure 2 and Figure 3 Partial process views are schematically shown for some other advantageous examples of screening processes and screening systems according to the present invention.

[0025] List of reference numerals

[0026] 10-sieve system

[0027] 11 sieves

[0028] 12 Material Feeding Section

[0029] 13 Material Feeding Section

[0030] 14 Machine Tanks

[0031] 15 sieves

[0032] 16 sieves

[0033] 17. Air removal device

[0034] 18 sieves

[0035] 19 sieves

[0036] 21. Processing material feeding section

[0037] 22 Processing material application and return section

[0038] 23 Return Tank

[0039] L1 is the feed flow line located between the storage tank and the supply tank.

[0040] L2 is located in the feed flow line after the feed pump that feeds the material to the screen.

[0041] L3 sieve or other process / system equipment for good slurry flow line or waste sludge flow line

[0042] L4 lower streamline or return circulation streamline

[0043] L5 bypass flow line for sieves or other process / system devices

[0044] L6 pressurized return flow line leading to the return tank

[0045] L7 Circulating Streamline

[0046] L8 sieve air removal streamline

[0047] FF and FA fill streamlines

[0048] VL2 On / off valve or control valve for the feed flow line

[0049] VL3 is the on / off valve or control valve for the good pulp flow line.

[0050] VFF, VFA, VL2 flow-through valves or control valves

[0051] VR degassing valve Detailed Implementation

[0052] Throughout this specification, the same reference numerals and symbols are used to identify the same elements in different views of the invention. For clarity, some repeated reference numerals may be omitted from the drawings.

[0053] Figure 1 An example of a sieve system 10 for a screening process is schematically shown. The sieve system 10 includes at least one sieve 11, 15, 16, 18, 19. Figure 1 In the example, the screening system 10 has three sieves 11, 15, and 16 on the inlet side and two sieves 18 and 19 on the return side. The processing material is fed into the screening system 10 from the processing material feed sections 12 and 13. First, the processing material flows from the processing material feed sections 12 and 13 to the machine tank 14 (i.e., the supply tank 14) via the feed flow line L1. The machine tank 14 is also flow-connected via a screening process and a screening system circulation flow line L7, for example, a temperature control circulation flow line L7 for controlling the temperature of the processing material, and a screening circulation flow line L7 with sieves 11 for screening the processing material in the machine tank 14. The processing material flows from the machine tank 14 to the sieves 15 and 16 via the supply flow line L2, which screens 15 and 16 for screening the processing material before it flows to the processing material application feed section 21 via the good slurry flow line L3. The good slurry flow line L3 is connected to the return circulation flow line L4. Figure 1 In the example, the sieving system 10 further includes an air removal device 17 for removing air from the processed material before it flows to and is applied via the processed material application feed section 21. The sieving system may also include sieves 18, 19 connected on the return side via a bypass flow line L5. The sieving system may also include other process / system devices. Figure 1 In one example, the sieving system 10 further includes a processing material application return section 22 for recovering processing material not used at the application point. The processing material application return section 22 is flow-connected to a return tank 23 via a return flow line L6, the return tank 23 being used to collect the returned processing material.

[0054] In the screening process and sieve system 10, a pressurized flow of material substantially the same as the processing material from flow lines L1-L8 of the process / system 10 is used as a filling flow line to fill disconnected sieves 11, 15, 16, 18, and 19, thereby reconnecting sieves 11, 15, 16, 18, and 19 back to the process / system without interfering with the application flow in the supply flow line 21 (i.e., the processing material application feed section 21). In the screening process and sieve system 10, the filling flow line for the filling flow can be taken from the pressurized flow within the process / system flow lines of substantially the same processing material, including possible pressurized side circulation flow lines of process / system flow lines of substantially the same processing material.

[0055] When replacing sieves, the filling flow used to fill the disconnected sieves 11, 15, 16, 18, and 19 before connecting sieves 11, 15, 16, 18, and 19 is selected from: Flow line L1: The feed flow line and its possible side circulation flow line located between the storage tank and the supply tank 14 in the screening process and screening system; Streamline L2: The feed flow line (supply flow line) of the screening process and screening system located after the feed pumps that feed into sieves 11, 15, 16, 18, and 19. Streamline L3: Good slurry or waste residue flow line of sieves 11, 15, 16, 18, 19 or other process / system devices in screening processes and systems; Streamline L4: The lower streamline or return circulation streamline of the screening process and screening system; Streamline L5: Bypass flowline for inlet-side screens 11, 15, 16 or return-side screens 18, 19 or other process / system devices in the screening process and screening system; Streamline L6: Pressurized return streamline leading to return tank 23 for the screening process and screening system; Streamline L7: Circulation flow line for screening processes and systems, such as temperature control circulation flow line or screening circulation flow line; or Streamline L8: Air removal streamline for sieves 11, 15, 16, 18, and 19 in the screening process and screening system.

[0056] In the screening system 10, on-off valves or control valves are used in the flow lines L1-L8 to guide the flow. Advantageously, the filling flow lines include small-diameter on-off valves or control valves to guide the filling flow in the filling flow lines.

[0057] The filling streamlines of sieves 11, 15, 16, 18, and 19 are independent streamlines relative to the streamlines of sieves 11, 15, 16, 18, and 19 used for processing material flows. Advantageously, the independent filling streamlines have smaller diameters.

[0058] Figure 2 An example of a portion of a screening system 10 used in a screening process is shown schematically. Figure 2 In the example, the screening system 10 includes two sieves 15 and 16. The material to be processed is fed to the sieves 15 and 16 via a feed (supply) flow line L2 for screening before flowing to the material application feed section via a good slurry flow line L3. The feed flow line L2 includes an on / off valve or control valve VL2 to guide the flow. The good slurry flow line L3 includes an on / off valve or control valve VL3 to guide the flow. Figure 2 In this example, the filling flow line FF for filling is taken from the pressurized feed flow line L2. Advantageously, in the screening process and sieve system, on-off valves are used instead of control valves. Therefore, in this example, when changing sieves, the filling flow of the filling flow line FF, used to fill the disconnected sieves 15 and 16 before connecting sieves 15 and 16, is taken from the feed flow line L2 via the filling flow connection line FF, which is located after the feed pump that feeds the sieves 15 and 16 to the screening process. The filling flow line FF includes an on-off valve or control valve VFF, advantageously a small-diameter on-off valve or control valve, more advantageously a small-diameter on-off valve, for guiding the filling flow in the filling flow line FF. The filling flow line FF for sieves 15 and 16 is a separate flow line relative to the supply (feed) flow line for processing the material flow of sieves 15 and 16. Advantageously, the separate filling flow line FF has a smaller diameter.

[0059] When sieves 15 and 16, which have been disconnected from screening system 10, need to be reconnected to screening system 10, a flow connection from feed flow line L2 is first established by opening the corresponding on / off valve or control valve VFF to guide the flow of processed material in the filling flow line FF of sieves 15 and 16. During the filling process, air in sieves 15 and 16 is removed by degassing valve VR. Filling and feeding continue until sieves 15 and 16 are filled to the point where they return to operation (i.e., screening of the processed material).

[0060] Figure 3An example of a portion of a screening system 10 used in a screening process is shown schematically. Figure 3 In the example, the screening system 10 includes two sieves 15 and 16. The material to be processed is fed to the sieves 15 and 16 via a feed (supply) flow line L2 for screening before flowing to the material application feed section via a good slurry flow line L3. The feed flow line L2 includes an on / off valve or control valve VL2 to guide the flow. The good slurry flow line L3 includes an on / off valve or control valve VL3 to guide the flow. Figure 3 In this example, the filling flow line FA for filling is taken from the main good pulp flow line L3 via the filling flow connection line FA. Advantageously, in the screening process and screening system, on-off valves are used instead of control valves. Therefore, in this example, when changing screens, the filling flow of the filling flow line FA for filling the disconnected screens 15 and 16 before connecting screens 15 and 16 is taken from the main good pulp flow line L3 of the screening process screens 15 and 16 via the filling flow line FA. The filling flow line FA includes on-off valves or control valves VFA and VL2, advantageously small-diameter on-off valves or control valves, more advantageously small-diameter on-off valves, for guiding the filling flow in the filling flow line FA. The filling flow line FA of screens 15 and 16 is an independent flow line relative to the supply (feed) flow line and the good pulp flow line L3 of screens 15 and 16 for processing material flow. Advantageously, the independent filling flow line FA has a smaller diameter.

[0061] When sieves 15 and 16, which have been disconnected from screening system 10, need to be reconnected to screening system 10, a flow connection from the good slurry flow line L3 is first established by opening the corresponding on / off valves or control valves VFA and VL2 to guide the flow of processed material in the filling flow line FA of sieves 15 and 16. During the filling process, air in sieves 15 and 16 is removed by degassing valve VR. Filling and feeding continue until sieves 15 and 16 are filled to the point of return operation (i.e., screening of the processed material).

[0062] In the foregoing description, although certain functions have been described with reference to specific features, those functions may also be performed by other features, regardless of whether those other features have been described. Although features have been described with reference to specific embodiments or examples, those features may also exist in other embodiments or examples, regardless of whether those other embodiments or examples have been described. The invention has been described above with reference only to several advantageous examples, and the invention is not narrowly limited to those examples. Various modifications and variations are possible within the scope of the invention as defined in the following claims.

Claims

1. A screening process in a screening system (10), The screening process is part of the fiber web production process. In the screening process, the processing material for the fiber web production process is screened in at least one sieve (11, 15, 16) of the screening system (10). In the screening process, the material to be processed flows in the streamlines (L1-L8) of the screening system (10). Its features are, In the screening process, at least one sieve (11, 15, 16) is disconnected from the screening process for a period of time and is at least partially emptied during the disconnection. To reconnect the at least one sieve (11, 15, 16) to the screening process, the at least one sieve (11, 15, 16) is filled via a filling flow line connected to one of the flow lines (L1-L8) in which the processed material flows, and The filling flow lines of the sieves (11, 15, 16) are independent flow lines relative to the supply flow lines of the sieves (11, 15, 16).

2. The screening process according to claim 1, characterized in that, One of the streamlines (L1-L8) connected to the filling streamlines used to fill the disconnected sieves (11, 15, 16) is selected from: Streamline (L1): It is the feed flowline and its possible side circulation flowline of the screening process and the screening system (10) located between the storage tank and the supply tank; Streamline (L2): It is the feed flowline of the screening process and the sieve system (10) located after the feed pump that feeds the sieves (11, 15, 16); Streamline (L3): It is the good slurry streamline or waste sludge streamline of the sieves (11, 15, 16) or other process / system devices (17) of the screening process and the sieve system (10); Streamline (L4): It is the lower streamline or return circulation streamline of the screening process and the screening system (10); Streamline (L5): It is the bypass flowline of the sieves (11, 15, 16; 18; 19) or other process / system devices of the screening process and the screening system (10); Streamline (L6): It is the pressurized return streamline of the screening process and the screening system (10) leading to the return tank (23); Streamline (L7): This is the circulation flow line of the screening process and the screening system (10); or Streamline (L8): It is the air removal streamline of the sieves (11, 15, 16) of the screening process and the sieve system (10).

3. The screening process according to claim 1 or 2, characterized in that, The flow in a flow line (L1-L8) connected to the filling flow line of the sieves (11, 15, 16) is guided by an on / off valve.

4. The screening process according to any one of claims 1 to 3, characterized in that, The flow in the filling stream is guided by an on / off valve.

5. The screening process according to any one of the preceding claims, characterized in that, The diameter of the filler streamline is small, and the diameter range of the filler streamline is advantageously DN5 to DN150 (ISO 6708).

6. The screening process according to any one of the preceding claims, characterized in that, The flow in the filling streamline is guided by a small-diameter on / off valve, and the diameter of the small-diameter on / off valve is defined according to the corresponding filling streamline.

7. A screening system, The screening system (10) is part of the fiber web production line. The screening system (10) includes at least one sieve (11, 15, 16) for screening the processing materials of the fiber web production line. The sieving system (10) includes streamlines (L1-L8) in which the processed material is configured to flow. Its features are, The at least one sieve (11, 15, 16) is configured to be disconnected from the operation of the sieve system (10) for a period of time and to be at least partially emptied during disconnection. The sieving system (10) includes a filling flow line configured to connect to form a flow connection with the at least one sieve (11, 15, 16) and to fill the at least one sieve (11, 15, 16) to connect the at least one sieve (11, 15, 16) back to the sieving system (10). The filling streamlines are connected to flow through one of the streamlines (L1-L8), and the processed material is configured to flow in that streamline within the sieve system (10). The filling flow lines of the sieves (11, 15, 16) are independent flow lines relative to the supply flow lines of the sieves (11, 15, 16).

8. The sieving system according to claim 7, characterized in that, The flow line (L1-L8) connected to the filling flow line of the sieves (11, 15, 16) for filling the disconnected sieves (11, 15, 16) is selected from: Streamline (L1): It is the feed flowline and its possible side circulation flowline of the screening process and the screening system (10) located between the storage tank and the supply tank; Streamline (L2): It is the feed flowline of the screening process and the sieve system (10) located after the feed pump that feeds the sieves (11, 15, 16); Streamline (L3): It is the good slurry streamline or waste sludge streamline of the sieves (11, 15, 16) or other process / system devices (17) of the screening process and the sieve system (10); Streamline (L4): It is the lower streamline or return circulation streamline of the screening process and the screening system (10); Streamline (L5): It is the bypass flowline of the sieves (11, 15, 16; 18; 19) or other process / system devices of the screening process and the screening system (10); Streamline (L6): It is the pressurized return streamline of the screening process and the screening system (10) leading to the return tank (23); Streamline (L7): This is the circulation flow line of the screening process and the screening system (10); or Streamline (L8): It is the air removal streamline of the sieves (11, 15, 16) of the screening process and the sieve system (10).

9. The sieving system according to claim 7 or 8, characterized in that, A flow line (L1-L8) connected to the filling flow line of the sieves (11, 15, 16) includes at least one on / off valve.

10. The sieving system according to any one of claims 7 to 9, characterized in that, The filling flow line includes at least one on / off valve.

11. The sieving system according to any one of claims 7 to 10, characterized in that, The diameter of the filler streamline is small, and the diameter range of the filler streamline is advantageously DN5 to DN150 (ISO 6708).

12. The sieving system according to any one of claims 7 to 11, characterized in that, The filling flow line includes at least one small-diameter on / off valve, and the diameter of the small-diameter on / off valve is defined according to the corresponding filling flow line.

Images