Slurry mixing method and slurry mixing system

Abstract

The invention relates to a slurry mixing method in which a slurry (S) is mixed by dilution water (DW) and at least two slurry components (SC1, SC2, SC3, SCN-1, SCN), and the slurry mixing method is carried out in a slurry mixing system (100). In the method, slurry components (SC1, SC2, SC3, SCN-1, SCN) are mixed in an assembly of a mixing manifold (10) and a static mixer (40), which assembly is part of a slurry mixing system (100). The slurry components (SC1, SC2, SC3, SCN-1, SCN) are fed into a mixing manifold (10), the dilution water (DW) is fed into the mixing manifold (10) as a last but one additive at the latest, and at least one slurry component (SCN) is fed into a slurry mixture of the slurry components (SC1, SC2, SC3, SCN-1) in the mixing manifold (10) as a last additive. The invention also relates to a slurry mixing system (100).

Description

Technical Field

[0001] The present invention relates to stock mixing, especially in connection with pulp, textile and fiber web production. More particularly, the present invention relates to a stock mixing method and a stock mixing system. Background Art

[0002] It is known from the prior art that in fiber web production lines, especially paper and board production lines, fiber webs are produced and processed in an assembly formed by a plurality of devices arranged in succession on a process line. A typical production and processing line comprises a forming section (including a headbox and a forming unit), a press section and a subsequent drying section and a reel. A fiber web production line may also comprise further equipment and sections for finishing the fiber web, such as a size press section, a calender, a coating section and usually at least one slitter-winder for forming customer rolls and a roll packaging device.

[0003] The slurry formed by the fiber suspension including the fibers is processed before the headbox to be fed into the headbox and used to produce the fiber web on the fiber web production line. Therefore, the system for preparing the fiber suspension (called slurry) is before the fiber web production line. In this system (slurry preparation system), various slurry components, for example, virgin pulp and / or recycled pulp and / or damaged pulp are mixed with dilution water, fillers and other required additives are mixed with the slurry, and if necessary, the slurry or one or more of its components are degassed. The slurry is fed into the fiber web production line via one / multiple mixing tanks and one / multiple machine tanks. The various component slurries included in the slurry (i.e., component slurries containing different types of fibers) constitute the first raw material of the slurry (i.e., the fiber raw material of the slurry). In addition, different fillers, additives or chemicals are added to the slurry or slurry components to improve the quality and printability of the finished paper or the operability of the manufacturing process. Usually, the component slurries, fillers, additives and chemicals are stored in large tanks. The composition of the stock components delivered to the fiber web production line is adjusted in a dosing system at the stock preparation, where the different stock components included in the stock are blended with each other in pipes leading to a mixing tank and in the mixing tank itself, from which it is delivered to a machine tank and from which it is delivered to the fiber web production line. The concentration of the stock delivered to the paper machine is adjusted by changing the amount of dilution water fed to the stock, i.e., the adjustment of the stock concentration is related to the dilution water added to the stock in an appropriate proportion according to the amount and concentration of the stock.

[0004] It is known from the prior art that in slurry preparation systems, different types of slurry mixing systems are used to mix different slurry components and dilution water. The mixing system includes separate mixing tanks and machine tanks to provide a slurry of uniform and consistent concentration. Typically, the mixing system includes two tanks, two pumps, two mixers, and a piping system between the tanks. This makes the system quite complex and bulky, and consumes space and energy. In addition, the system also emits a large amount of carbon dioxide.

[0005] Patent application publication DE102008000256A1 discloses a system for diluting a fiber suspension in a dilution device and adding several fluids to the fiber suspension flow via at least one feed device, wherein at least one feed device is arranged before a mixing device, at least one feed device is arranged after the mixing device, and the dilution device is arranged before the first feed device.

[0006] Patent application publication US2005269051A1 discloses a device for merging various liquid flows in a papermaking machine, the device comprising a mixing tube into which the various liquid flows are discharged and a degassing rotor located in the mixing tube, wherein at least three feed pipes convey three respective liquid flows into the mixing tube, and one of the feed pipes discharges dilution water into the mixing tube, and at least two feed pipes discharge two respective pulp components into the mixing tube.

[0007] Utility model patent publication CN206661107U discloses a slurry mixing system, which includes a distribution port, a static mixer, a dynamic mixer and a slurry tank, wherein the slurry is conveyed to a channel, which passes through the static mixer and the dynamic mixer in sequence, and successively, the static mixer and the dynamic mixer mix the slurries conveyed from multiple slurry distribution ports to complete the mixed slurry entering the slurry tank.

[0008] Patent application publication EP2690216A1 discloses a system for producing cellulose web or cellulose sheet from an aqueous suspension of cellulose fibers, the system comprising a mixing section and a dilution section for cellulose fiber pulp, wherein the cellulose fiber pulp from the mixing section is diluted with water from a paper machine to form an aqueous suspension of cellulose fibers, wherein the mixing section for the cellulose fiber pulp comprises a mixer with a vertically extending tubular body, which is fluidically connected to the lower part of a machine tank equipped with a machine mixer; and the machine tank is fluidically connected to the dilution section, there is no other intermediate tank between the machine tank and the dilution section, and the mixer is connected to the lower part of the machine tank through a curved connecting pipe.

[0009] The object of the present invention is to create a slurry mixing method and system in which the disadvantages and problems of the prior art are eliminated or at least reduced.

[0010] In particular, the object of the present invention is to create an improved slurry mixing method and system, in particular with regard to space and energy requirements. Summary of the invention

[0011] In order to achieve the above-mentioned objects and the objects that will be revealed later, the main features of the slurry mixing method according to the present invention are as follows. Accordingly, the main features of the slurry mixing system according to the present invention are also as follows. The advantages and features of the present invention are as follows.

[0012] According to the present invention, in a slurry mixing method, a slurry is mixed by dilution water and at least two slurry components, and the slurry mixing method is performed in a slurry mixing system, wherein, in the method, the slurry components are mixed in an assembly of a mixing manifold and a static mixer for premixing the slurry components, which assembly is part of the slurry mixing system, the slurry components are fed into the mixing manifold, and the dilution water is fed into the mixing manifold at the latest as the second to last addition, and at least one slurry component is fed into the slurry mixture of the slurry components in the mixing manifold as the last addition.

[0013] According to the present invention, in the method, after premixing the slurry components with the dilution water in the mixing manifold, the slurry mixture of the slurry components and the dilution water is mixed in the static mixer.

[0014] According to an advantageous feature of the invention, in the method, the ingredients include pulp ingredients, wherein the pulp ingredients SC1, SC2, SC3, SCN can be non-synthetic and / or synthetic fiber based pulps. The concentration and content of the pulp ingredients can vary. The pulp ingredients can include water and / or chemicals and / or natural fibers and / or synthetic fibers and / or fillers.

[0015] According to an advantageous feature of the invention, the slurry constituents are added in a concentration not exceeding 5%.

[0016] According to the invention, the slurry mixing system comprises at least one pipeline for dilution water and at least two pipelines for slurry components to be mixed, wherein the slurry mixing system comprises an assembly of a mixing manifold and a static mixer for mixing the dilution water and the slurry components, and only one tank for the slurry in which the dilution water is mixed with the slurry components, which tank is located after the static mixer in the flow direction, wherein the pipelines for the dilution water and the slurry components are connected to the feed branches of the mixing manifold, and in the flow direction, at least one feed branch for at least one of the slurry components is located after the feed branch for the dilution water. Advantageously, the only one tank is a mixing tank or a machine tank.

[0017] According to an advantageous characteristic of the invention, the static mixer is connected to the machine tank by at least one straight or curved outlet pipe.

[0018] According to an advantageous feature of the invention, the curved outlet pipe has a curvature of 0-180 degrees, advantageously 0-90 degrees.

[0019] According to an advantageous feature of the invention, the mixing manifold has a substantially conical shape.By the shape of the mixing manifold, the flow dynamics in the mixing manifold are optimized so that preferably an accelerated flow is provided.

[0020] According to an advantageous feature of the invention, the mixing manifold comprises a tube part and at least one conical tube part.

[0021] According to an advantageous feature of the invention, the diameter of the tube elements increases in the flow direction of the mixing manifold, so that the tube elements upstream in the flow direction of the mixing manifold have a smaller diameter than the diameter of the tube elements downstream in the flow direction of the mixing manifold. This provides that the flow velocity is maintained at a desired level during the passage of the stream or slurry through the mixing manifold.

[0022] According to an advantageous feature of the invention, the cone angle of the conical tube part is constant in the flow direction of the mixing manifold and the length of the conical tube part varies in the flow direction of the mixing manifold.

[0023] According to an advantageous feature of the invention, the cone angle of the conical tube part increases in the flow direction of the mixing manifold, the length of the conical tube part being constant in the flow direction of the mixing manifold.

[0024] According to an advantageous feature of the invention, the static mixer comprises a streamlined wedge attached to the inner surface of the static mixer.

[0025] According to an advantageous aspect of the invention, the mixing system comprises an assembly of a mixing manifold and a static mixer. The mixing system comprises only one tank. Advantageously, the tank is a mixing tank or a machine tank. Thus, improved space and energy requirements are achieved compared to prior art systems, since multiple tanks are no longer required. In addition, a homogeneous consistency of the slurry is achieved by premixing the slurry components in the mixing manifold and subsequently performing the mixing process in the static mixer. This also provides a suitable slurry for concentration measurement, since the slurry is very homogeneous and no significant concentration changes occur after the slurry components pass through the assembly of the mixing manifold and the static mixer.

[0026] According to an advantageous technical aspect of the invention, the mixing manifold is sized to provide a velocity ratio exceeding 1 after addition of the slurry components.

[0027] According to an advantageous technical aspect of the invention, the dimensions of the mixing manifold are configured to provide a flow velocity in the range of 0.5-4 m / s so that the turbulence of the slurry flow is at a desired level under concentration measurement requirements.

[0028] In addition to the slurry mixing methods and systems associated with fiber web production, such as paper and board webs, the systems and methods of the present invention are also applicable to the mixing of textile fiber slurries.

[0029] By means of the present invention and its advantageous features, several advantages are achieved: Compared to slurry mixing systems known in the prior art for providing slurries with corresponding properties, the mixing system according to the present invention requires fewer tanks, fewer pumps and related equipment, fewer pipes and related instruments, and therefore, requires less space and less energy, as well as reduced carbon dioxide emissions. In addition, the slurry components and the dilution water are mixed into a consistent, homogeneous and uniform slurry. Since the assembly of the mixing manifold and the static mixer provides a good turbulence of the slurry, the present invention also provides reliable concentration measurement of the slurry flow at a desired position in relation to the mixing tank or machine tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Aspects of the present invention together with additional objects and advantages thereof will be best understood from the following description of certain exemplary embodiments when read in conjunction with the accompanying drawings, and the invention is described in more detail below with reference to the accompanying drawings, in which:

[0031] exist Figure 1 An advantageous example of a slurry mixing system according to the invention is schematically shown in FIG.

[0032] exist Figure 2 An advantageous example of an assembly of a slurry mixing manifold and a static mixer according to the invention is schematically shown in FIG.

[0033] exist Figure 3 Another advantageous example of a slurry of an assembly of a mixing manifold and a static mixer according to the invention is schematically shown in FIG.

[0034] exist Figure 4A-4B An advantageous example of a static mixer is schematically shown in .

[0035] Reference numerals:

[0036] 10 Mixing manifold

[0037] 11, 12, 13, 14, 15, 16, 17, 18 Feed branches

[0038] 21, 22, 23, 24 pipe parts

[0039] 31, 32 cone tube parts

[0040] 40 static mixer

[0041] 41, 42 flange connection

[0042] 43, 44 outlet pipe

[0043] 45 Streamlined Wedge

[0044] 50 Mixing tank or machine tank

[0045] 100 Mixing System

[0046] C Center

[0047] DW dilution water

[0048] FFlow direction

[0049] LD, L1, L2, L3, LN, L40, L50 pipelines

[0050] S slurry

[0051] SC1, SC2, SC3, SCN-1, SCN slurry composition DETAILED DESCRIPTION

[0052] In the course of this specification, the same numerals and symbols will be used to identify the same elements according to the different views illustrating the present invention. For the sake of clarity, some repeated reference numerals may be omitted in the figures.

[0053] exist Figure 1 An example of a slurry mixing system 100 is schematically shown in FIG. The mixing system 100 comprises pipelines LD, L1, L2, L3, LN: more than one pipeline L1, L2, L3, LN for conducting slurry components SC1, SC2, SC3, SCN for mixing; and at least one pipeline LD for conducting dilution water DW for adjusting the concentration of the slurry S formed by mixing the slurry components SC1, SC2, SC3, SCN and the dilution water DW. The mixing system 100 comprises a mixing manifold 10 to which the dilution water DW via the pipeline LD and the slurry components SC1, SC2, SC3, SCN via the pipelines L1, L2, L3, LN are conducted for premixing and for adjusting the concentration of the slurry S. The dilution water DW is supplied to the mixing manifold 10 by the pipeline LD before at least one location where the slurry component SCN is supplied. Therefore, the last component supplied to the mixing manifold is not the dilution water DW, but the slurry component SCN. The mixing manifold 10 forms an assembly with a static mixer for mixing the slurry S. The mixed slurry S is led via line L40 to a mixing tank or machine tank 50 for shaping and storing the slurry S for further processing of the slurry via a further system via line L50 to a headbox of a fiber web production line for producing a fiber web. The mixing system 100 comprises only one mixing tank or machine tank 50. The flow directions of the lines LD, L1, L2, L3, LN, L40, L50 are indicated by arrow symbols associated with the lines LD, L1, L2, L3, LN, L40, L50.

[0054] In the slurry mixing method, slurry components SC1, SC2, SC3, SCN for slurry S are selected and added to the mixing manifold 10 for premixing. In the method, a certain amount of dilution water DW is added to the mixing manifold. The slurry components SC1, SC2, SC3, SCN can be non-synthetic and / or synthetic fiber-based slurries. The concentration and content of the slurry components SC1, SC2, SC3, SCN can vary. The slurry components may include water and / or chemicals and / or natural fibers and / or synthetic fibers and / or fillers. Advantageously, the slurry components are added in a concentration of not more than 5%. The concentration of the slurry component mixture is adjusted by adding dilution water DW. In the slurry mixing method, the dilution water DW is added to the slurry component mixture in the mixing manifold 10 as the second to last addition at the latest, so that the slurry components are added to the mixing manifold 10 last. The slurry components SC1, SC2, SC3, SCN are premixed in the mixing manifold 10 and subsequently fed into the static mixer 40 for mixing and then advantageously the concentration of the slurry component mixture is determined by measurement.

[0055] exist Figure 2 An example of a slurry mixing manifold 10 and a static mixer 40 assembly of a mixing system 100 is schematically shown in FIG. In this example, the mixing manifold 10 is connectable to eight pipelines for providing slurry components SC1, SC2, SC3, SCN-1, SCN and dilution water DW to form a slurry S. The mixing manifold 10 comprises feed branches 11, 12, 13, 14, 15, 16, 17, 18 connectable to pipelines for providing slurry components SC1, SC2, SC3, SCN-1, SCN and dilution water DW. The dilution water DW is provided to the mixing manifold 10 by a pipeline before at least one of the positions where the slurry components SCN-1, SCN are provided, i.e., advantageously via the second to last or third to last feed branches 16, 17. Therefore, the last component provided to the mixing manifold is not the dilution water DW, but the slurry component SCN provided via the last feed branch 18. The feed branches 11, 12, 13, 14, 15, 16, 17, 18 can be located around the main circumference of the mixing manifold 10 at desired angular positions, i.e. not only as Figure 2The examples shown are mainly of the same angular position. At least two of the feed branches 11, 12, 13, 14, 15, 16, 17, 18 can also be located at positions of the same length but at different angles. The mixing manifold 10 comprises tube parts 21, 22, 23, 24 and conical tube parts 31, 32. The tube parts 21, 22, 23, 24 are essentially cylindrical, i.e., have the same diameter along the length of the tube parts. The conical tube parts 31, 32 are conical in the flow direction F of the slurry components in the mixing manifold, i.e., have an increasing diameter along the length of the conical tube parts. The mixing manifold 10 can be composed of releasable tube parts and / or conical tube parts that are connected to each other. The mixing manifold 10 has an increasing diameter in the flow direction F of the slurry components in the mixing manifold 10 to control the flow velocity of the slurry components in the mixing manifold 10. The diameters of the tube parts 21, 22, 23, 24 and the taper of the conical tube parts 31, 32 are selected so that the flow velocity in the mixing manifold 10 is in the range of 0.5-4 m / s. To form an assembly of the mixing manifold 10 and the static mixer 40, the static mixer 40 is connected to the mixing manifold 10 with a flange connection 41. The static mixer 40 is also connected to an outlet pipe 43 with another flange connection 42, which leads the slurry to the outlet end of the mixing manifold 10, to the mixing tank 10 or the machine tank 50 ( Figure 1 ).

[0056] exist Figure 3 Another example of a slurry mixing manifold 10 and a static mixer 40 assembly of a mixing system 100 is schematically shown in FIG. In this example, the mixing manifold 10 is connectable to eight pipelines for providing slurry components SC1, SC2, SC3, SCN and dilution water DW to form a slurry S. The mixing manifold 10 comprises feed branches 11, 12, 13, 14, 15, 16, 17 connectable to pipelines for providing slurry components SC1, SC2, SC3, SCN and dilution water DW. The dilution water DW is provided to the mixing manifold 10 by a pipeline at least one position before the position where the slurry component SCN is provided, i.e. advantageously via the penultimate feed branch 16. Therefore, the last component provided to the mixing manifold is not the dilution water DW, but the slurry component SCN provided via the last feed branch 17. The feed branches 11, 12, 13, 14, 15, 16, 17 can be located around the main circumference of the mixing manifold 10 at desired angular positions, not just as shown in FIG. Figure 2The examples shown are mainly of the same angular position. At least two of the feed branches 11, 12, 13, 14, 15, 16, 17 can also be located at the same length but at different angular positions. The mixing manifold 10 comprises tube parts 21, 22, 23, 24 and conical tube parts 31, 32. The tube parts 21, 22, 23, 24 are essentially cylindrical, i.e., the diameter is the same along the length of the tube parts. The conical tube parts 31, 32 are conical in the flow direction F of the slurry components in the mixing manifold, i.e., have an increasing diameter along the length of the conical tube parts. The mixing manifold 10 can be composed of releasable tube parts and / or conical tube parts that are connected to each other. The mixing manifold 10 has an increasing diameter in the flow direction F of the slurry components in the mixing manifold 10 to control the flow velocity of the slurry components in the mixing manifold 10. The diameters of the tube parts 21, 22, 23, 24 and the taper of the conical tube parts 31, 32 are selected so that the flow velocity in the mixing manifold 10 is 0.5-4 m / s. To form an assembly of the mixing manifold 10 and the static mixer 40, the static mixer 40 is connected to the mixing manifold 10 with a flange connection 41. The static mixer 40 is also connected to a curved outlet pipe 44 with another flange connection 42 to improve the homogeneity of the slurry S. The curved outlet pipe 44 is attached to an outlet pipe 43, which leads the slurry to the outlet end of the mixing manifold 10, leading to a mixing tank or machine tank 50 ( Figure 1 ). The pipe parts 21, 22, 23, 24 and the conical pipe parts 31, 32 may have the same or different imaginary central axes. The curved form of the curved outlet pipe 44 further improves the mixing of the slurry S.

[0057] The configuration of the components of the mixing manifold 10 and the static mixer 40 provides turbulence of the slurry components SC1, SC2, SC3, SCN-1, SCN and the dilution water DW in the mixing manifold 10, improves the uniformity and homogeneity of the slurry mixture of the slurry components SC1, SC2, SC3, SCN-1, SCN and the dilution water DW, and the subsequent mixing process in the static mixer 40 further improves the uniformity and homogeneity of the slurry S. Thereby, a very good slurry S is obtained for further processing, and it is particularly suitable with respect to the concentration measurement characteristics of the slurry S.

[0058] Advantageously, the mixing manifold 10 is substantially conical in form.

[0059] Figure 4A-4BAn example of a static mixer 40 is schematically shown, which is provided with flange connections 41, 42 for attaching the static mixer 40 to an inlet pipe and an outlet pipe. The static mixer 40 comprises a streamlined wedge 45 of the static mixer, which is attached to the inner surface of the static mixer 40 and is axially located at least partially over the length of the static mixer 40. The static mixer 40 comprises at least three wedges, advantageously at least six wedges. The streamlined wedge 45 is substantially triangular, with the apex of the triangle pointing to the center C of the static mixer 40. The flow direction F in the static mixer 40 is determined by Figure 4A The arrow in indicates.

[0060] In the above description, although some functions have been described with reference to some features, these functions may also be performed by other features whether described or not. Although features have been described with reference to certain embodiments or examples, these features may also exist in other embodiments or examples whether described or not. The above description of the invention refers only to some advantageous examples, and the invention is not limited to these examples. Many modifications and changes may be made within the scope of the invention as defined by the following claims.

Claims

1. A slurry mixing method, in which a slurry (S) is mixed with dilution water (DW) and at least two slurry components (SC1, SC2, SC3, SCN-1, SCN), and the slurry mixing method is performed in a slurry mixing system (100), in which the slurry components (SC1, SC2, SC3, SCN-1, SCN) are mixed in an assembly of a mixing manifold (10) and a static mixer (40), the assembly being part of the slurry mixing system (100), the slurry components (SC1, SC2, SC3, SCN-1, SCN) being fed into the mixing manifold (10), the dilution water (DW) being fed into the mixing manifold (10) at the latest as the second to last addition, and at least one slurry component (SCN) being fed as the last addition into the slurry mixture of the slurry components (SC1, SC2, SC3, SCN-1) in the mixing manifold (10), characterized in that In the method, after premixing the slurry components (SC1, SC2, SC3, SCN-1, SCN) and the dilution water (DW) in the mixing manifold (10), the slurry mixture of the slurry components (SC1, SC2, SC3, SCN-1, SCN) and the dilution water (DW) is mixed in the static mixer (40).

2. The slurry mixing method according to claim 1, characterized in that: In said method, the ingredients (SC1, SC2, SC3, SCN-1, SCN) include pulp ingredients of non-synthetic and / or synthetic fiber based pulp.

3. The slurry mixing method according to claim 1 or 2, characterized in that: The slurry ingredients are added at a concentration not exceeding 5%.

4. A slurry mixing system (100) comprising at least one line (LD) for dilution water (DW) and at least two lines (L1, L2, L3, LN) for slurry components to be mixed (SC1, SC2, SC3, SCN-1, SCN), the slurry mixing system (100) comprising a mixing manifold (10), characterized in that The slurry mixing system (100) comprises: an assembly formed by the mixing manifold (10) and the static mixer (40) for mixing the dilution water (DW) and the slurry components (SC1, SC2, SC3, SCN-1, SCN); and only one tank (50) for mixing the slurry of the dilution water (DW) and the slurry components (SC1, SC2, SC3, SCN-1, SCN), the tank (50) being located after the static mixer (40) in the flow direction and for mixing the dilution water (DW) and the slurry components (SC1, SC2, SC3, SCN-1, SCN). The pipelines (LD, L1, L2, L3, LN) of the slurry components (SC1, SC2, SC3, SCN-1, SCN) are connected to the feed branches (11, 12, 13, 14, 15, 16, 17, 18) of the mixing manifold (10), and, in the flow direction (F), at least one feed branch (18) for at least one slurry component (SCN) among the slurry components (SC1, SC2, SC3, SCN-1, SCN) is located after the feed branches (16, 17) for the dilution water (DW).

5. The slurry mixing system according to claim 4, characterized in that: The static mixer (40) is connected to the machine tank (50) via at least one straight or curved outlet pipe (44).

6. The slurry mixing system according to claim 5, characterized in that: The curvature of the curved outlet pipe (44) is 0-180 degrees, advantageously 0-90 degrees.

7. The slurry mixing system according to any one of claims 4 to 6, characterized in that: The mixing manifold (10) has a substantially conical shape.

8. The slurry mixing system according to any one of claims 4 to 7, characterized in that: The mixing manifold (10) comprises tube components (21, 22, 23, 24) and at least one conical tube component (31, 32).

9. The slurry mixing system according to claim 8, characterized in that: The diameters of the tube components (21, 22, 23, 24) increase in the flow direction (F) of the mixing manifold (10), so that the tube components upstream in the flow direction (F) of the mixing manifold (10) have a smaller diameter than the diameters of the tube components downstream in the flow direction (F) of the mixing manifold (10).

10. The slurry mixing system according to any one of claims 4 to 9, characterized in that: The static mixer (40) includes a streamlined wedge (45) attached to an inner surface of the static mixer (40).

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