RU2224062C2 - Apparatus and method for creating paper pulp turbulence in molding section of elongate reticulate web-type papermaking machine - Google Patents

Abstract

FIELD: pulp-and-paper industry. SUBSTANCE: papermaking machine has water separation chamber adapted for providing of vacuum-controlled drainage and equipped with set of water separation members. Water separation members are designed for generating turbulence in relatively thick paper pulp layer movable at rate equal to or less than 400 rev/min for manufacture of paper product having weight of unit of superficial area of at least 160 g/sq.m. Each set of water separation members comprises inlet member, at least one intermediate member, and lifting member. When molding web moves above intermediate members inclined at an angle of 0-10 deg with respect to plane defined by inlet and lifting member surfaces, upon which molding web rests, its path of advancement declines downward. Vertical displacement arises turbulence in paper pulp and causes mixing process resulting in deflocculation of paper pulp and reduced probability of sheet pressurization. Apparatus may be used in conjunction with known molding and drainage units, which may be arranged downward or upward of process course, when paper pulp has substantial thickness and low movement speed. EFFECT: reduced sheet pressurization owing to creating of sufficient turbulence and deflocculation of paper pulp. 15 cl, 16 dwg

Description

FIELD OF THE INVENTION
The invention relates to a device and method for creating turbulence of paper pulp in the forming section of an open-surface paper machine. In particular, this invention relates to a device and method for generating sufficient turbulence in a paper pulp layer in a forming section with an open surface of a paper machine to provide deflocculation of a relatively thick layer of paper pulp on a relatively slowly moving forming web. Thus, this invention is used in the manufacture of relatively heavy paper, technical pulp and paperboard. In addition, the device can be adjusted so that the amount of turbulence created in the paper pulp layer can be controlled and optimized depending on the class of manufactured products.

State of the art
In a conventional open-surface molding section, aqueous paper pulp containing papermaking fibers and other papermaking solids in an amount of about 0.1% to about 1.5% by weight is fed from the support bar of the paper machine tub to a horizontally moving forming web. In such a molding section, after receiving the pulp from the retaining bar of the vat, the moving molding web is supported by the molding plate, followed by several drainage chambers. Drainage chambers typically comprise water separating devices, such as vanes and films, mounted on the drainage chambers in contact with the machine side of the molding web. Some modern low-speed machines also still use roller tables as water separating devices and devices for creating turbulence. The forming section may also include other devices designed to create at least some turbulence within the pulp, such as molding sprinklers. As the pulp advances on the open surface of the molding web through the molding section, water is removed from the pulp until an initial paper web is formed that contains from about 75% to about 85% water. The remaining water is removed in subsequent parts of the paper machine.

 The thickness of the paper pulp layer applied from the vat retaining bar to the forming sheet depends on the speed of the machine, the water content in the paper pulp supplied from the vat, and on the weight of a unit surface area of the produced paper or paperboard. Heavier grades of products, such as cladding, middle layer of corrugated cardboard, commercial grades of technical pulp and cardboard products require a greater thickness of paper pulp than light grades, such as newsprint.

 To obtain satisfactory quality paper, it is important that the paper-forming solid materials, including paper-forming fibers, are thoroughly mixed and dispersed as evenly as possible in the paper pulp exiting the vat retainer of the paper machine. In practice, this is almost impossible to achieve: part of the paper-forming fibers tends to flocculate in the pulp and is deposited in the form of flakes on the forming web. Flocculation continues in the pulp on the molding web unless measures are taken to generate turbulence within the pulp. If an initial paper web is formed, then it is essentially impossible to disperse the residual flakes. Thus, what happens in the pulp in the forming section when converting a dilute solution of fibers and other solid materials into an initial paper web is critical to paper production.

 Numerous methods have been proposed to randomize the distribution of fibers in the pulp in the forming section. Most of these methods include creating a certain level of turbulence inside the pulp to disperse the flakes. For example, it is known to impart rapid transverse vibrational motion to a molding web adjacent to a tub to create destructive shear forces in the flakes and thereby to redistribute the paper-forming fibers. Molding sprinklers, live rolls, and various jets of air and water located below or above the molding web are also used to create turbulence in the paper pulp layer. The amount of energy needed to create the desired level of turbulence in the pulp generally depends on the thickness of the pulp layer, the speed of the paper machine and the type of milled material present in the pulp.

A common means of creating turbulence inside the pulp on the open surface of a moving molding web is to place the water separating elements (such as films, stirring blades, etc.) in contact with the machine side of the moving molding web. Devices of this type are described in US 2928456 (Wrist), US 3573159 (Sepall), US 3874998 (Johnson), US 4420370 (Saad), US 4687549 and US 4838996 (Kallmes) and US 4789433 (Fuchs). The films have a leading edge that removes liquid from the molding web; the back is inclined downward at an angle of from about 1 ^° to about 8 ^° and serves to create a suction effect that removes liquid from the pulp and causes the web to deviate enough to create at least some turbulence within the pulp.

 The stirring blades are shaped so that they draw a certain amount of water and then again direct it through the molding sheet back into the liquid layer of the paper pulp. To achieve this, a carefully profiled channel is made on the surface of the blades in the transverse direction of the machine; Water that is directed back through the forming sheet creates turbulence in the pulp on the forming sheet, which leads to a deflocculation effect and serves to randomize the distribution of solid materials.

 Another mixing means is disclosed in US 4,140,573 (Johnson). In this device, at least one of the water separating elements in the low vacuum water separating chamber is slightly inclined with respect to the water separating element on the other side, so that when the forming web passes over the sequence of elements, it is slightly deflected by the low vacuum of the water separating chamber and then released, creating some turbulence inside the paper pulp.

 An alternative means for generating paper pulp turbulence is described in US Pat. No. 5,830,322 (Cabrers y Lopez Caram). This device uses a pair of web-supporting elements, namely a primary element with an inclined surface and a rear element with a horizontal surface. The drainage of water from the pulp is controlled by limiting the size of the drainage gap in the transverse direction of the machine between the two elements. The inclined surface of the primary element is designed to create turbulence in the paper pulp above the drainage gap without tilting the molding web down into the drainage gap using blade profiles essentially the same as described in US 4,789,433 (Fuchs) and US 4,838,996 (Kallmes). The device is based on the flow of fluid into and out of the drainage gap and on the shape of the inclined surface of the primary element inside the drainage gap to create turbulence inside the pulp after the liquid has returned through the forming web and the initial paper substrate formed on it in the pulp.

 Other pulp mixing devices are described in US 3922190 (Cowan), US 4999086 (Marx, Jr.), US 5011577 (Hansen et al.), US 5089090 (Hansen) and US 5681430 (Neun).

However, in cases where the paper product being produced requires the molding web to move at a relatively low speed and a relatively thick layer of paper pulp on it, for example, in the manufacture of products with a large surface unit weight, it becomes more difficult to create the desired levels of turbulence within the paper pulp. With a decrease in the speed of the paper machine and an increase in the layer of paper pulp in the manufacture of products with a large weight of a surface unit, it becomes increasingly difficult to create an effective level of turbulence inside the paper pulp, and thereby improve molding. Thus, it was found that for molding sections with an open surface, in which the molding sheet moves at a speed of less than about 400 m / min and carries a layer of paper pulp, the initial thickness of which at the retaining plate of the vat is more than about 2.0 cm, for manufacturing more heavy grade paper products with a weight per unit surface greater than about 160 g / m ^2, a device which is able to create an effective level of turbulence within the stock sufficient to provide at least some deflocculation and within the stock. A significant advantage of this device would be the possibility of simple regulation, so that the level of turbulence can be matched with the requirements of the paper maker.

 An additional problem arises with paper pulp compositions that use milled material having a high content of relatively short fibers or recycled materials. In such a pulp, an almost impermeable substrate may form on the paper side of the surface of the molding web, which effectively seals the molding web and prevents adequate fluid removal from the paper pulp; a phenomenon commonly referred to as "sheet sealing". Therefore, there is a need for a water separating device capable of at least eliminating drainage restrictions caused by this phenomenon.

SUMMARY OF THE INVENTION
The basis of the invention is the creation of a device and method for creating paper pulp turbulence sufficient to provide at least some deflocculation of the pulp and to improve the formation in the section with the open surface of the paper machine, in which the paper pulp layer is relatively thick, and in which the molding web moves at a relatively low speed. Thus, it is an object of the invention to improve the formation of open-surface paper machines that are used to produce products with a relatively large surface unit weight, such as cardboard or the like. The objective of the invention is also to reduce, if not eliminate, the sealing of the sheet by creating sufficient turbulence inside the paper pulp, so as to again distribute the fiber substrate forming a more or less impermeable layer on the paper side of the forming web. Therefore, this invention is particularly suitable when using paper pulp compositions containing a significant amount of relatively short fibers or reusable materials.

 In addition, in a particular embodiment, this invention seeks to provide an adjustable device for creating a controlled level of pulp turbulence sufficient to provide at least some deflocculation and improve the formation of an open surface paper machine in the forming section in which the paper pulp layer is relatively thick and in which the molding web moves at a relatively low speed.

In the context of this invention, the term “relatively low speed” refers to an open-surface molding web that moves through the molding section with a linear velocity of less than about 400 m / min; and the terms “products with a relatively large surface unit weight” and “relatively thick paper pulp layer” refer to a paper machine with an open surface of the forming web, which is used to make products with a final surface unit weight of more than about 160 g / m ² , which is usually requires a paper pulp thickness near the retaining bar of the vat of more than about 2.0 cm. It should also be noted that although this invention focuses on the manufacture of products with a relatively large weight rhnosti, it is not limited to this, and under some conditions, has advantages in the production of lighter products, and at a higher speed of the machine.

According to a first aspect of the present invention, there is provided a device for generating turbulence in paper pulp on a forming sheet in a forming section with an open surface of a paper machine, the forming section including a relatively slow moving forming sheet having a paper side and a machine side, a relatively thick layer of paper pulp on to the side of the paper, a water separating chamber located under the molding web and connected to a controlled source of vacuum, made with possible Stu creating underpressure inside the riser chamber, and a plurality of riser fabric supporting elements mounted on the riser chamber consisting essentially of
(i) an inlet riser having a surface supporting a molding web comprising sequentially
wiping the front edge
essentially horizontal intermediate surface and
inclined back surface;
(ii) a lifting riser having a surface supporting a molding web comprising sequentially
wiping the front edge
inclined surface
exit surface and
a part containing a connection of the inclined and output surfaces; and
(iii) at least one intermediate water separating element located between the inlet water separating element and the lifting element and separated by a gap from each other water separating element, each intermediate element having a surface supporting the molding web comprising
wiping the front edge
inclined surface and
trailing edge;
in which
(a) a portion of the lifting member located on the connection of the inclined surface and the output surface is selected from the group consisting of a vertex in the connection of the inclined surface and the output surface, a short, essentially horizontal surface connecting the inclined surface and the output surface, and a curved surface connecting the inclined surface surface and exit surface;
(b) the intermediate surface of the inlet water separating element and the part of the lifting element containing the connection of the inclined and output surfaces, determine the first plane;
(c) the inclined rear surface of the inlet water separating element and the inclined surface of each intermediate water separating element define a second plane inclined by a predetermined downward rear angle relative to the first plane; and
(d) the cleaning front edge of the lifting element is located above the trailing edge of the adjacent intermediate riser element so that the movement of the forming sheet from the rear edge of the adjacent intermediate water separating element to the cleaning front edge of the lifting element leads to vertical movement of the forming fabric and the initial paper web and paper pulp being moved On him.

 Preferably, at least one intermediate water separating element located between the input water separating element and the lifting element and separated by a gap from each other water separating element is mounted on the water separating chamber with the possibility of regulation, allowing each inclined surface to be arranged in a desired second plane, and allowing movement in another desired second plane. In this embodiment, as detailed below, the angle between the first and second planes is not determined by the angle at which the inclined surface of the intermediate element is cut off, but is determined by installing an adjustable mount to the water separating chamber. In this embodiment, since the input element is not adjustable, it is preferable that its inclined rear surface is arcuate.

In an alternative preferred embodiment, the device further comprises a drainage restricting element that is inserted between the lifting element and the adjacent intermediate element and which has a surface supporting the molding web comprising
wiping the front edge and
upward inclined surface
in which the fastening of the drainage restricting element is made and installed with the possibility of arranging the surface inclined upward at an angle to the second plane with the formation of a shallow V-shaped angle between them, corresponding to the inclined surface of the lifting element. In this embodiment, the attachment of the drainage restricting element to the riser chamber may be selected from the group consisting of a fixed connection, an adjustable connection, and a second adjustable connection included in the first adjustable connection for the intermediate elements.

 All intermediate molding support web members preferably have the same width in the direction of the machine. As an alternative solution, all intermediate elements supporting the molding web have an unequal width in the direction of the machine.

 Each intermediate molding support web member preferably has a substantially flat inclined surface. As an alternative solution, at least one intermediate element has a mixing blade profile.

According to another aspect of the invention, a method is created for creating a desired level of turbulence in a layer of paper pulp located on a molding web in a forming section with an open surface of a paper machine, consisting mainly of moving a molding web carrying a layer of paper pulp over at least one water separating chamber with an installed on it a plurality of elements supporting the molding web under the molding web and in contact with it, and in using a controlled vacuum source for building managed reduced pressure in the riser chamber, the water-separating fabric supporting elements consist essentially of
(i) an inlet riser having a surface supporting a molding web comprising sequentially
wiping the front edge
essentially horizontal intermediate surface and
inclined back surface;
(ii) a lifting riser having a surface supporting a molding web comprising sequentially
wiping the front edge
inclined surface
exit surface and
a part containing a connection of the inclined and output surfaces; and
(iii) at least one intermediate water separating element located between the inlet water separating element and the lifting element and separated by a gap from each other water separating element, each intermediate element having a surface supporting the molding web comprising
wiping the front edge
inclined surface and
trailing edge;
in which
(a) a portion of the lifting member located on the connection of the inclined surface and the output surface is selected from the group consisting of a vertex in the connection of the inclined surface and the output surface, a short, essentially horizontal surface connecting the inclined surface and the output surface, and a curved surface connecting the inclined surface surface and exit surface;
(b) the intermediate surface of the inlet water separating element and the part of the lifting element containing the connection of the inclined and output surfaces, determine the first plane;
(c) the inclined rear surface of the inlet water separating element and the inclined surface of each intermediate water separating element define a second plane inclined by a predetermined downward rear angle relative to the first plane; and
(d) the cleaning front edge of the lifting element is located above the trailing edge of the adjacent intermediate riser element, so that the movement of the forming sheet from the rear edge of the adjacent intermediate water separating element to the cleaning front edge of the lifting element leads to vertical movement of the forming sheet and the initial paper web and paper pulp being moved On him.

 The desired level of turbulence is preferably created and controlled by at least one adjustable intermediate riser element located between the inlet riser element and the lifting element, which is mounted with the possibility of regulation to the riser chamber, allowing each inclined surface to be placed in a second plane; and the level of turbulence is controlled by adjusting the adjustable intermediate supporting element to the desired position of the second plane.

The desired level of turbulence is more preferably created by means of a device further comprising a drainage restricting element which is located between the lifting element and the adjacent intermediate element and which has a surface supporting the molding web comprising
wiping the front edge and
upward inclined surface;
in which the fastening of the drainage restricting element is made and installed with the possibility of arranging the surface inclined upward at an angle to the second plane with the formation of a shallow V-shaped angle between them, corresponding to the inclined surface of the lifting element.

The desired level of turbulence is most preferably created and controlled by
(i) at least one intermediate water separating element located between the input water separating element and the lifting element and mounted on the water separating chamber with the possibility of regulation, allowing to position the inclined surface of each intermediate element in the second plane and
(ii) a drainage restricting member which is located between the lifting member and the adjacent intermediate member and which has a surface supporting the molding web comprising
wiping the front edge and
adjustable upward inclined surface;
in which the level of turbulence is controlled by:
(a) adjusting the adjustable intermediate support member to a desired position of the second plane, or
(b) adjusting the drainage restricting member to a different position, or
(c) adjusting both the adjustable intermediate support member to a desired position of the second plane and adjusting the drainage restricting member to another position.

The angle between the first and second planes is preferably from more than 0 ^o to about 10 ^o .

 An advantage of the device according to the invention is that with a relatively thick layer of paper pulp after creating the desired level of turbulence in the paper pulp, it is possible to more easily maintain the desired level of turbulence when moving further through the forming section. Therefore, although known devices do not always provide a sufficient level of turbulence, they can be used to maintain the level of turbulence after it is created. Thus, this invention can be used to optimize the operation of devices known from the prior art.

With this in mind, the shape of the outlet surface of the lifting blade is determined by what follows the water separating chamber according to the invention in the molding section. For example, if it immediately follows the second set of the same elements, so that the lifting element is both the last element in the first set and the first element in the next set, then the output surface of the lifting blade will have the same shape as the corresponding part of the input element, so that it will have a substantially horizontal intermediate surface, and an inclined rear surface in the same second plane as the subsequent elements. Alternatively, if it is followed by a gap without drainage or a drainage chamber equipped with films, then the output surface of the lifting blade will be made generally as a film blade with a film angle usually from about 0.5 ^° to about 5 ^° .

Brief Description of the Drawings
The following is a description of the invention with reference to the drawings, which depict:
FIG. 1 is a machine-side sectional view of a paper pulp turbulence generating unit according to a first embodiment of the present invention;
figure 2, 3 and 4 is a sectional view of the supporting molding fabric elements used in figure 1;
figure 5 and 6 is an alternative to figure 1 arrangement of elements;
FIG. 7 is a section in the machine direction of the paper pulp turbulence generating unit, which includes two sets of elements supporting the molding web;
Fig. 8 is an intermediate element having a mixing blade profile;
Fig.9 and 10 is a partial section in the machine direction of the block creating turbulence in the paper pulp according to the second embodiment of the present invention;
FIG. 11 and 12 are parts of the rotation and control device used in FIGS. 10 and 11;
Fig.13 is a sectional view of the block according to Fig.9-12;
FIG. 14 is a machine-side sectional view of a paper pulp turbulence generating unit according to a third embodiment of the present invention;
Fig. 15 is a sectional view of the drainage restricting member shown in Fig. 14;
FIG. 16 shows alternative arrangements of intermediate elements applicable to FIG. 1, 7 and 14, including mixing blade profiles for intermediate elements.

Information confirming the possibility of carrying out the invention
In the context of this invention, direction-determining concepts have the following meanings:
“machine direction” is a direction along the machine substantially parallel to the direction of movement of the molding web;
"transverse machine direction" is a direction substantially perpendicular to the machine direction, generally parallel to the plane of the molding web;
"upstream" - the direction closer to the vat from a given point in the machine direction;
"downstream" - the direction further from the vat in the machine direction;
"inlet" is the upstream edge of the element;
"back" - the downstream surface or edge of the element;
“paper side” is the side of the forming web on which the paper pulp is located and the paper web is being formed;
"machine side" is the side of the forming web that is in contact with the elements supporting the forming web, and therefore the side opposite to the side of the paper.

 In all sections of the riser sections schematically shown in the figures, all elements supporting the molding web extend across the machine across the entire width of the molding web. Additionally, all of the angles shown are exaggerated for clarity.

 Figure 1 shows a first embodiment of the invention. Both in this figure and in the following figures, other conventional parts of the molding section are not shown, such as a tub, a retaining rail of the tub, a pre-roll, a molding plate (if any), a molding sprinkler or sprinklers, and other drainage and water separating devices. The device 1 for creating turbulence in the pulp includes a water separation chamber 2, which is equipped with a hydraulically sealed drainage 3 in the lower part, through which water 3A is separated, separated from the pulp. The water separating chamber 2 is connected via a pipe 4 to a vacuum source, which provides a controlled reduced pressure in the range from external pressure to pressure, approximately 7.5 kPa below external pressure.

 The desired level of turbulence in the pulp is created using a set of supporting the forming fabric elements 5, 6, 7 and 8, which are installed on the upper beam of the forming chamber 2 using a conventional T-shaped connection 9A, 9B, 9C. The distance between the T-shaped joints and the width of the elements are determined in combination by the width of the drainage gaps 10, 11 and 12. These gaps are sealed at their lateral edges using end ladle frames (not shown). In the shown embodiment, the gaps 10 and 11 have the same width, and the gap 12 has a large width.

 The factors determining the choice of the width of the gaps are indicated below. Elements 5, 6, 7, and 8 can be made of high density polyethylene with ceramic wear surfaces inserted, or of any other material suitable for the manufacture of surfaces supporting the molding web. In the shown set of elements supporting the molding web, element 5 is an inlet blade, element 8 is a lifting blade, and elements 6 and 7 are intermediate blades.

 The forming web 13 moves in the direction of arrow A, while its machine side is in contact with the supporting members 5-8 of the forming web. Above the gap 12, the forming web 13 rises from the last intermediate element 7 to the lifting member 8. This vertical movement of the forming web and the initial paper web and paper pulp thereon creates turbulence in the adjacent paper pulp and downstream of the outlet surface of the lifting member 8 .

 A cross section of the input element 5 is shown in Fig.2. It includes a wiper leading edge 14, a flat intermediate surface 15 and an inclined rear surface 16. In this embodiment, the rear surface is substantially flat and has an angle of inclination α relative to surface 15. The element is mounted on T-beam 9A so that surface 15 is essentially horizontal. The cleaning front edge 14 removes at least some of the water that passes through the molding web upstream of the inlet member. The cross section of the lifting element 8 is shown in figure 3. It includes a wiper leading edge 17, an inclined surface 17, an output surface 19, and a part 20 comprising a connection between the inclined and the output surfaces. As shown, part 20 is the apex of the connection of two surfaces 18, 19 located on its sides; alternative forms are a short horizontal surface and a curved surface. It is mandatory for the lifting member part 20 to ensure that the support is continuous for the molding sheet moving and bending above it, and that together with the substantially horizontal surface 15 of the input element, it defines the first plane below which the molding sheet deviates while passing over the intermediate elements. The specific shape of the portion 20 is selected depending on the structural material used and the desired length of the inclined surface 18 and the output surface 19. The inclined surface 18 is located at an angle β relative to the first plane defined by surface 15 on the input element and the lifting element part 20. The shape of the exit surface 19 is shown below.

 In FIG. 1 shows two intermediate elements 6 and 7, which are generally the same. Their cross sections are generally the same, and FIG. 4 shows a cross section of an intermediate element 6. It includes a wiping front edge 21, an inclined surface 22 and a trailing edge 23. A set of three elements comprising an input element and two intermediate elements, resting on the T-beams 9C, is spaced so that the surface 16 and the two surfaces 22 are in a common second plane at an angle α relative to the first plane.

 In the device according to the first embodiment of the invention, as shown in FIG. 1, when the molding sheet 13 moves above the water separating chamber 2, the machine side of the sheet 13 first comes into contact with the leading edge 14 of the input element 5, which clears the liquid from the machine side of the sheet 13. Forming the web 13 passes further downstream sequentially over the inclined surface 16, the gap 10, the inclined surface 22 and the trailing edge 23 of the intermediate element 6, the gap 11, the inclined surface 22 and the trailing edge 23 p intermediate element 7, the gap 12, and, finally, the input edge 17 and the surfaces 18, 20 and 19 (in this sequence) of the lifting element 8. The molding sheet is pulled down sequentially on the surface 16 and two surfaces 22 using a controlled low vacuum in the water separator chamber with the formation of a liquid seal on these surfaces. Finally, the molding web rises above the gap 12 and the surfaces of the lifting element 8. This movement up creates turbulence in the paper pulp near the lifting element 8.

In this embodiment, the selected angle α is determined by machine characteristics, which include the total distance between the input and lifting elements, the number of intermediate elements, the speed of the machine, the thickness of the paper pulp layer and the desired level of turbulence in the manufactured products. Therefore, the value of the angle α determines the vertical distance by which the molding web should rise from the point where it loses contact with the last intermediate element, which is located on or near the trailing edge 23 of this element, to the wiping front edge 17 of the lifting element. Typically, the angle α is in the range of about 0.25 ^° to about 10 ^° . It was found that in most cases, the angle α is less than 6 ^o and is often in the range from about 2 ^o to about 4 ^o . The width of the gaps between the elements that make up the kit, in combination with the vacuum used, as well as the properties of the paper pulp and the crushed material in the paper pulp also affect both the amount of drainage that occurs and the level of turbulence created. The level of vacuum used in combination with the width of the gaps must be sufficient to ensure hydraulic contact of the molding web with the surfaces of all elements supporting the molding web. The actual magnitude of the applied vacuum also affects the level of turbulence, since it affects the transition of the molding web from the last intermediate element to the lifting element. At this point, the molding web has a shallow V-shape that is sharper or flatter, depending at least in part on the applied vacuum. The actual values for the angle α and other specified variables are determined by the desired level of turbulence in the paper pulp at this point in the forming section; sometimes it is necessary to conduct experiments to determine the optimal values for a given set of conditions for the manufacture of paper.

The shape of the exit surface 19 of the lifting element 8 depends to a large extent on what follows this element downstream in the molding section, for which there are several possibilities. The lifting element can be followed, for example, by another identical pulp generating unit, an uncontrolled drainage gap, a set of films or an Isoflo ^® drainage block. If the next drainage block is another more or less identical block adjacent to the previous block, or even mounted on the same water separating chamber, then the lifting element becomes common for both blocks. In this case, the output surface of the lifting element has such a profile as if it were an input element, so that it corresponds to the selected angle α for the next block, which may be different from the angle of the previous block. If the lifting element is followed by a gap, or block with films, it is enough to use the output surface, which extends essentially horizontally or tilted down at more or less the same angle that is used for a conventional film blade, i.e. up to about 5 ^o , without intermediate short horizontal surface.

The inclined surface 18 of the lifting member shown in FIG. 3 extends typically with a steeper angle of elevation, since it determines the lifting path of the molding web, as shown in FIG. 3. The angle β shown in FIG. 3 is typically in the range of from about 0 ^° to about 30 ^° . In practice, an angle of from about 10 ^° to about 20 ^{° is} often sufficient. The value of the angle β is determined by the vertical movement of the molding web when it is raised from the inclined surface 22 of the last intermediate element to the surface 20 of the lifting element. The value of β is chosen from the condition of minimum deviation of the molding web at a low level of vacuum. It was found that if during operation the deviation of the molding web is equal to or greater than this minimum deviation, then the molding web still remains in contact and follows the shape of this surface. However, it is necessary to conduct some experiments to determine the optimal angle β for a given set of machine conditions.

 In addition, it was found that after creating the desired level of turbulence in the pulp using the device according to the invention it is easier to create turbulence in the pulp downstream in the molding section, which facilitates the use of downstream subsequent devices to create turbulence. This improves the operation of subsequent conventional deflocculation devices and water separating devices and improves the formation of manufactured products. It was also found that the device according to the invention increases the low level of turbulence created in the paper pulp using an upstream device, such as a molding sprinkler.

Although the embodiment described above can be applied at a molding web speed of 400 m / min or less and with a relatively thick layer of paper pulp, for example 2.0 cm or more, near the vat of the vat, for the manufacture of paper products with a surface unit weight of 160 g / m ² or more, it can be considered that the invention will also provide advantages under other conditions, for example, at higher speeds and / or thinner layers of paper pulp.

 It was unexpectedly found that as soon as the molding sheet 3 moves with machine speed above the water separating chamber 2 with the vacuum applied, it often continues to follow the path defined by the supporting elements 5, 6, 7 and 8, even if the vacuum is reduced. This makes it possible to reduce the amount of drainage above the riser chamber 2. This provides an additional advantage with respect to reducing the tendency to seal the sheet.

 In the embodiment shown in FIG. 1, the turbulence generating unit has two intermediate water separating elements 6 and 7. Other configurations may also be used, depending on the machine characteristics and the manufactured products. Figure 5 shows one water separating element 6 between the input element 5 and the lifting element 8, and figure 6 shows the configuration using five intermediate elements 24, 25, 26, 27 and 28, in which all five intermediate elements are installed in the second plane at a common angle α to the first plane. As shown in Fig.6, the intermediate elements do not have to be all the same width.

This invention can also be used with two water separating units arranged one after another, the lifting element of the first unit also serving as an input element of the second unit. This arrangement is shown in Fig.7. The first set of elements includes an input element 5 and two intermediate elements 29 and 30. The second set of elements again includes two intermediate elements 32 and 33 and a lifting element 8. The central element 31 performs the function of a lifting element for the first set and the function of an input element for second set. Its upstream inclined surface 18 is made corresponding to the lifting element, and its downstream inclined rear surface is made corresponding to the input element. This arrangement can be done in two ways:
(i) you can use one riser 2 with one source 4 of vacuum, as shown in figure 1, or
(ii) a water separation chamber with two hydraulically separated walls 34 can be used with compartments 2A and 2B, each of which has its own vacuum source 4A and 4B, as shown in FIG. 7.

With this last arrangement, the vacuum applied in each compartment does not have to be the same. It is also possible that the angles α ₁ and α ₂ , each of which is measured relative to the first plane, as shown in Fig. 7, may not be the same depending on the desired level of turbulence in each block.

 In the shown embodiment, the intermediate elements have a substantially flat support surface for the molding web. It was found that under certain conditions, depending on machine characteristics, characteristics of paper pulp and manufactured products, it is desirable to create a higher level of turbulence in the paper pulp than it is created by using a flat supporting surface for a molding web on intermediate elements in the second plane. As shown in FIG. 8, an intermediate element with a profile of the so-called mixing blade with one channel 35 can be used to create additional turbulence. Stirring blades having such a profile are described in US 3874998 (Johnson); Other profiles are also known and used. Apparently, the profile of the mixing paddle can enhance the turbulent effects provided by the turbulence generating unit according to this invention.

Similarly, within the framework of the present invention, it is possible to use a common water separating chamber with various water separating devices, such as Isoflo ^® , mixing blades or a set of film blades in the water separating unit.

Experimental test
In an experimental test, the paper pulp turbulence generating unit according to the present invention was installed downstream of the mold sprinkler in the mold section with an open surface of the paper machine. The block shown in FIG. 7 was used, however, without an internal dividing wall 34 and with only one vacuum source. Directly downstream of the unit were two suction chambers equipped with covers, described in US 4140573 (Johnson). The machine speed of the forming section was approximately 320 m / min, and the weight per unit surface of the paperboard was approximately 299 g / m ² . The input element had a width of 38.1 mm with an inclined surface width of 8.5 mm. The two intermediate elements were the same in each pair and had an inclined surface width of 150.9 mm. The width of the drainage gap between each of the elements was 9.5 mm, with the exception of the gap downstream of each last intermediate element, which was 12.7 mm. In both sets of elements, the angle α was 2 ^o . The water separating element, acting as an input element and as a lifting element in the middle of the set, had an inclined surface width of 9.5 mm, and the angle β was 5 ^o . The downstream outlet surface of this common element was substantially flat and tilted downward at an angle of 2 ^° , which corresponds to the angle α. The output surface of the second lifting blade was horizontal. The width of all elements and clearances separating the elements was measured in the machine direction.

 During the test, the level of vacuum created by the suction chambers was varied from external pressure to a pressure of about 5 kPa below external pressure. It was found that when disabling the upstream molding sprinkler installed, the appearance of the paper pulp when passing over the turbulence generating unit did not show increased activity inside the paper pulp. However, it was found that both the drainage of the initial paper web and the quality of the final paper product, manifested in its structure and smoothness, improved compared with the quality before installing the unit. This shows that the unit is effective in creating turbulence inside the pulp and preventing the sheet from sealing, even though the mold sprinkler has been turned off.

 After turning on the molding sprinkler, the appearance of the pulp as it passed over the turbulence generating unit changed dramatically, showing an increased level of activity in the pulp. This shows that the pulp turbulence generating unit is effective both in creating turbulence in the pulp and in improving the formation and preventing sealing of the sheet, and can also improve the effect of other drainage devices and turbulence generating devices.

 In the embodiment described above, the position of the intermediate elements is determined by the fixed structures, and the cross-sectional profile of the intermediate elements determines the angle α. Since the angle α is never too large, the construction requires precise machining and precise installation of the intermediate elements to provide a set of surfaces precisely installed in the second plane.

 In the second embodiment of the present invention, instead of mounting each intermediate element directly on the design of the riser chamber, each intermediate element is mounted with the possibility of regulation on the design of the riser chamber. In this case, it is possible to control the value of the angle α by moving the entire intermediate element to provide an appropriate angle of inclination of the inclined plane by adjusting the adjustable support, instead of performing the element with the required constant angle of inclination. In this configuration, in which more than one intermediate element is used, it is preferable to install all the intermediate elements on one adjustable support in the desired machine direction with their surfaces supporting the molding web in a common plane. In this case, the required angle α is obtained by adjusting the support or supports.

 In addition to greatly simplifying the design of the turbulence generating unit, since all the intermediate elements can be manufactured with substantially the same dimensions, this configuration has the advantage that the angle α can be easily changed to change the level of turbulence created. This may be necessary for various reasons, such as a change of production, a change in the milled material for the same product, as well as less thorough mixing in the vat, leading to problems on the molding web. Thus, in addition to providing means for creating turbulence inside the paper pulp on the forming web, this embodiment of the present invention provides means by which it is possible to control the level of turbulence created and increase or decrease it depending on the requirements of the paper manufacturing conditions.

 This embodiment of the present invention is shown in FIGS. 9-13. In FIG. 9-12, the molding web is not shown for clarity.

 In FIG. 9 and 10 show a partially cutaway isometric view of a block that includes one water separating chamber 2 carrying an input element 5, three intermediate elements 35, 36 and 37, of which the middle element 36 is narrower than the other two elements and the lifting element 8. The input element 5 and the lifting element 8 are based on the T-beams 9A and 9B, each of which rests directly on the frame 38 at the top of the riser chamber 2. Three intermediate elements are supported on the same T-beams 9C, each of which is mounted on the ability to adjust the support frame 40. At the upstream end adjacent to the input element 5, the adjustable frame 40 is supported by the rotary assembly 41. At the downstream end, the adjustable frame 40 is provided with a vertical adjustment unit 42, which in turn is controlled by the adjustment the beam 43, which can be moved in the direction indicated by arrow B, using the handle 44. The adjustment beam 43 is supported by suitable supporting surfaces (not shown) on the cross member 45, resting on the upper beam structure in ootdelyayuschey chamber, designated generally by reference numeral 46.

 The upstream rotary assembly is shown in more detail in FIG. 11. The frame 40 is rotated in a small arc (which provides sufficient angular movement to obtain the desired angle α) around the rod 47, which rests on the wall 50 of the riser chamber 2. The frame 40 is connected to the rod 47 using an adjustable support block 48, mounted on the bracket 49. The support block is held by a locking bolt 51, which passes through the slot 52. This type of connection allows precise control of the surface position of the element 35 relative to the inclined plane of the input element 5. In figure 1 1 shows only one rotary assembly; in practice, there are at least two, and more often more, so that the upstream end of the frame 40 has adequate support over the entire width of the molding section.

 The downstream vertical control unit is shown in more detail in FIG. The control unit 42 is vertically mounted on the downstream side of the frame 40 with bolts 53 and 54 provided with enlarged holes 53A and 54A. The assembly 42 also includes an inclined slot 55 into which the holding pin 56 enters. The outer end of the pin 56 is engaged with the hole 57 in the adjustment beam 43. As a result, the horizontal movement of the beam 43 in the direction of arrow B causes the frame 40 to move vertically in the direction of the arrow C. The enlarged openings 53A, 54A are provided to allow fine adjustment of the assembly 42 relative to the frame 40, so that the same angle α is obtained over the entire width of the molding section. If desired, the beam 43 can be locked in a private position using any suitable locking mechanism. 12 shows only one adjustment unit; in practice, there are at least two, and more often more, so that the downstream end of the frame 40 has adequate support over the entire width of the molding section.

 It is also possible to use other means of vertical regulation: for example, the adjusting beam can be replaced by a screw system, which can be equipped with an electric motor, and it is also possible to replace the adjusting means with a hydraulic or pneumatic system. For the correct operation of the vertical control means, one should choose the place of its installation so as to exclude the possibility of its clogging with solid materials of paper pulp.

 The cross section of the block according to Fig.9-12 is shown schematically in Fig.13. The input element 5 and the lifting element 8 are supported on their T-beams 9A and 9B, mounted directly on the water separating chamber 38. Each of the three intermediate elements 35, 36 and 37 is supported by a corresponding T-beam 9 mounted on the auxiliary frame 40. The auxiliary frame 40 is supported its upstream end to the rod 47, around which it can be rotated to provide a given angle α. At its downstream end, it rests on an adjustment unit 42 controlled by the adjustment beam 43. The actual angle α is determined by the position of the adjustment beam 43 relative to the vertical adjustment unit 42.

 With this arrangement, although the intermediate elements are adjustable to obtain any angle α, the input element is fixed without adjustment so that its inclined rear surface has a constant angle of inclination. It was found that under certain conditions this can lead to a deviation of the molding web over the trailing edge of the input element, which is undesirable for many reasons. Therefore, with this arrangement, it is preferable if the input element has a rounded trailing edge, as indicated by 70 (see also FIG. 10).

 Thus, in this embodiment, instead of adjusting each intermediate element individually to obtain a predetermined angle α, which requires both precise processing and precise installation, or precise individual vertical and angular regulation, the set of intermediate elements is the same and mounted on an auxiliary frame so that all of their surfaces in contact with the molding web are in a common plane, which is usually substantially parallel to the frame itself. After installing the frame and making the necessary adjustments using bolts 51, 53 and 54, the desired angle α is obtained by moving the beam 43 to the desired position, due to which the surfaces of the intermediate elements are inclined to the desired position, thereby determining the second plane.

 In another embodiment, a fourth drainage element is included in the water separating device located in the gap between the lifting element and the intermediate element located directly in front of it upstream. In some configurations, in particular, if the distance between the elements is chosen relatively large or the angle α in combination with the length of the block in the machine direction leads to the formation of a relatively large vertical distance between the last intermediate element and the cleaning front edge of the lifting element, then the molding length is considerable the web may be vacuum-supported drainage between the point at which the machine side of the molding web loses contact with the last intermediate a tape near its trailing edge, and the front wiper edge of the lifting element. This leads to the removal of excess water from the molding web at this point. This can be controlled by inserting a fourth drainage restricting element into this gap, the support surface of which is inclined upwardly in contact with the molding web, so that the supporting surface of the intermediate element and the supporting surface of the drainage restricting element form a shallow letter “V” that supports the machine side of the molding web and limits the area of the machine side of the molding web at this point subjected to vacuum supported by ryazhenu.

There are several options for performing an additional drainage restricting element, for example:
(a) it can be installed without the possibility of regulation, more or less similar to the installation of other elements, or
(b) it may be installed with the possibility of regulation, or
(c) it can be mounted with the possibility of regulation on the auxiliary frame on which the set of intermediate elements is mounted.

 For the same reasons that were given for the intermediate elements, it is preferable to install an additional limiting drainage element with the possibility of regulation. It is more preferable to use for the additional limiting drainage element more or less the same auxiliary frame, which has been described in relation to the intermediate elements.

 In FIG. 14 is a schematic cross-sectional view of an embodiment using a drainage restricting member. The input and lifting elements 5 and 8 are based on their T-beams 9A and 9B. The three intermediate elements 35, 36 and 37 are supported by the corresponding T-beams 9C mounted on the first auxiliary frame 40. The first auxiliary frame 40 is supported by its upstream end on the shaft 47, around which it rotates to provide the required angle α. With its downstream end, it rests on the adjustment unit 42 and the adjustment beam 43. The actual value of the angle α is determined by the position of the beam 43 relative to the vertical regulation unit 42. The drainage restricting member 55 rests on a T-beam 9D mounted on a second auxiliary frame 56, which at the downstream end is rotatably supported on a shaft 57 (similar to the first auxiliary frame 40). The angular position of the drainage restricting element, indicated by the angle γ between the surface 61 and the first plane, is controlled by the upstream support 58, which is vertically adjustable, for the second auxiliary frame 56. It is preferable to use the same device as described for the first auxiliary frame 56. In most cases, the angles β and γ are more or less the same.

 A cross section of a drainage restricting member is shown in FIG. The upstream side 59 includes a front wiper edge 60, followed by an upwardly inclined surface 61, which ends with a trailing edge 62. The element is supported accordingly by the T-beam 9D. The value of the angle δ is chosen so as to obtain the value of the angle γ, which ensures a smooth transition of the moving molding web from the point at which it loses contact with the last intermediate element 37 to the inclined surface of the lifting element 8. Depending on the type of installation of the limiting drainage element, the angle δ may be very small and even be zero, so that the surface inclined upward is essentially perpendicular to the upstream side 59. As indicated above, the point at which the molding web loses contact with element 37 depends, inter alia, on the level of vacuum created in the water separating chamber.

 FIG. 16 schematically shows alternatives to those shown in FIG. 1, 7 and 14, profiles of intermediate elements. On Fig shows a set of seven elements. The first set of elements contains an input element 5 and two intermediate elements 63, 64, each of which has a mixing blade profile. The central element 31 is simultaneously a lifting element for the first set and an input element for the second set. The second set contains two intermediate elements 65, 66, followed by a lifting element 8. Elements 65 and 66 have a substantially flat surface. As shown in FIG. 16, two sets are mounted above a divided riser chamber 2 with separate drainage compartments 2A and 2B in which the same or different vacuum levels can be created. It is also possible that the elements 63 and 64 form the second set, while the elements 65 and 66 form the first set. It follows that combinations of element profiles can be used to create the desired level of turbulence inside the pulp.

 This invention has several advantages over the prior art. A device for creating turbulence in paper pulp can preferably be used to separate water and deflocculate thick and / or heavy paper pulp when using a relatively low vacuum, or, under certain circumstances, a minimum vacuum after the section starts to work. The ability to reduce the used vacuum level significantly reduces the drainage and sealing of the sheet during the passage of the molding web over the block. The turbulence created over the entire thickness of the pulp can also be used to improve the smooth and effective deflocculation of pulp using other mixing devices located both upstream and downstream relative to the block.

Claims (17)

1. Device for creating turbulence in the pulp on the forming sheet in the forming section with the open surface of the paper machine, and the forming section includes a relatively slow-moving forming sheet having a paper side and a machine side, a relatively thick layer of paper pulp on the paper side, separating a chamber located under the molding web and connected to a controlled vacuum source configured to create reduced pressure inside the waterway a chamber, and a plurality of water separating elements supporting the molding web mounted on the water separating chamber, consisting essentially of (i) an inlet water separating element having a surface supporting the molding web, comprising a successively cleaning front edge, a substantially horizontal intermediate surface and an inclined rear surface; (ii) a lifting water separating element having a surface supporting the molding web comprising sequentially cleaning the leading edge, an inclined surface, an output surface and a part comprising a connection of the inclined and output surfaces, and (iii) at least one intermediate water separating element located between the input water separating element and a lifting element and separated from each other water separating element by a gap, and each intermediate element has a supporting ph a ribbed web surface comprising sequentially wiping a leading edge, an inclined surface, and a trailing edge; wherein (a) a portion of the lifting member located at the junction of the inclined surface and the outlet surface is selected from the group consisting of a vertex in the joint of the inclined surface and the output surface, a short, substantially horizontal surface connecting the inclined surface and the output surface, and a curved surface connecting the inclined surface and the output surface; (b) the intermediate surface of the inlet water separating element and the part of the lifting element containing the connection of the inclined and output surfaces, determine the first plane; (c) the inclined rear surface of the inlet riser element and the inclined surface of each intermediate riser element define a second plane inclined downward by a predetermined rear angle relative to the first plane; and (d) the wiper leading edge of the lifting member is located above the trailing edge of the adjacent intermediate riser so that the movement of the molding web from the trailing edge of the adjacent intermediate riser to the wiping leading edge of the lifting member causes vertical movement of the molding web as well as the starting paper web and paper masses moved on it. 2. The device according to claim 1, characterized in that at least one intermediate water separating element located between the input water separating element and the lifting element and separated from each other water separating element by a gap is installed with the possibility of regulation on the water separating chamber, allowing each inclined surface to be placed intermediate elements in the desired second plane and move to another desired second plane. 3. The device according to claim 1 or 2, characterized in that it further comprises a drainage restricting element that is located between the lifting element and the adjacent intermediate element and which has a surface supporting the molding web, comprising a successively cleaning front edge and an upwardly inclined surface in which the connection limiting the drainage element with a riser chamber is made and installed with the possibility of arranging upward inclined surface at an angle to the second plane so that creates Xia shallow V-shaped angle therebetween that corresponds to the inclined surface of the riser element. 4. The device according to any one of claims 1 to 3, characterized in that the connection of the drainage restricting element to the water separating chamber is selected from the group consisting of a fixed connection made with the possibility of regulating the connection, and the second made with the possibility of regulating the connection included in the first made with a possibility of regulation connection for intermediate elements. 5. The device according to any one of claims 1 to 3, characterized in that all intermediate elements supporting the molding web have either the same width or unequal width in the machine direction. 6. Device according to any one of claims 1 to 3, characterized in that each intermediate element supporting the molding web has a substantially flat inclined surface or profile of a mixing blade. 7. The device according to any one of claims 1 to 3, characterized in that the downward rearward angle between the first and second planes is from about 0.25 to about 10 °. 8. The device according to any one of claims 1 to 3, characterized in that it includes sequentially installed first and second devices for creating turbulence, and the output surface of the lifting element of the first device is the rear surface of the input element of the first device and includes one water separating chamber , on which both devices to create turbulence are supported, or includes a water separation chamber with first and second hydraulically isolated compartments, each of which has its own a vacuum gauge, with one device resting on each compartment to create turbulence. 9. The device according to claim 8, characterized in that the angle between the first and second planes in the first device for creating turbulence is equal to or not equal to the angle between the first and second planes in the second device for creating turbulence. 10. The device according to any one of claims 1 to 3, characterized in that the molding sheet moves at a speed of at least less than about 400 m / min. 11. The method of creating the desired level of turbulence in the paper pulp layer located on the molding web in the molding section with the paper machine surface open, which consists mainly in moving the molding web carrying the paper pulp layer over at least one water separating chamber with a plurality of mounted on it elements supporting the molding web under the molding web and in contact with it and in the application of a controlled vacuum source to create a controlled reduced pressure riser chamber, the water-separating fabric supporting elements consist essentially of (i) an input riser element having a fabric supporting surface comprising in sequence a doctoring leading edge, a substantially horizontal intermediate surface and sloped rear surface; (ii) a lifting riser having a surface supporting the molding web comprising sequentially wiping a leading edge, an inclined surface, an output surface, and a part comprising a connection of the inclined and output surfaces; and (iii) at least one intermediate water separating element located between the inlet water separating element and the lifting element and separated by a gap from each other water separating element, each intermediate element having a surface supporting the molding web, comprising a successively cleaning front edge, an inclined surface and a trailing edge ; wherein (a) a portion of the lifting member located at the junction of the inclined surface and the output surface is selected from the group consisting of a vertex at the junction of the inclined surface and the output surface, a short, substantially horizontal surface connecting the inclined surface and the output surface, and curved the surface connecting the inclined surface and the output surface; (b) the intermediate surface of the inlet water separating element and the part of the lifting element containing the connection of the inclined and output surfaces, determine the first plane; (c) the inclined rear surface of the inlet riser element and the inclined surface of each intermediate riser element define a second plane inclined downward by a predetermined rear angle relative to the first plane; and (d) the wiper leading edge of the lifting member is located above the trailing edge of the adjacent intermediate riser so that the movement of the molding web from the trailing edge of the adjacent intermediate riser to the wiping leading edge of the lifting member causes vertical movement of the molding web as well as the starting paper web and paper masses moved on it. 12. The method according to claim 11, characterized in that the desired level of turbulence is created and controlled by means of at least one interchangeably mounted intermediate water separating element, which is located between the input water separating element and the lifting element and is mounted with adjustment possibility on the water separating chamber, allowing to position the inclined surface of each intermediate element in the second plane; and the level of turbulence is controlled by adjusting the intermediate support element that is adjustable to the desired position of the second plane. 13. The method according to claim 11 or 12, characterized in that the device further comprises a drainage restricting element that is located between the lifting element and the adjacent intermediate element and has a surface supporting the molding web, comprising a successively cleaning front edge and an upwardly inclined surface in which the connection limiting the drainage element with a riser chamber is made and installed with the possibility of arranging upward inclined surface at an angle to the second plane so that creates a shallow V-shaped angle between them corresponding to the inclined surface of the lifting element. 14. The method according to any one of paragraphs.11-13, characterized in that the desired level of turbulence is created and controlled using (i) at least one intermediate water separating element located between the input water separating element and the lifting element and mounted on the water separating chamber with the possibility regulation, allowing to position the inclined surface of each intermediate element in the second plane, and (ii) limiting the drainage element, which is located between the lifting element and adjacent intermediate element and having a fabric supporting surface comprising in sequence a doctoring leading edge and an adjustable upwardly inclined surface; wherein the level of turbulence is controlled by (a) adjusting the adjustable intermediate support member to a desired position of the second plane, or (b) adjusting the drainage restricting member to a different position, or (c) adjusting both the adjustable intermediate support member to a desired position of the second plane, and adjusting the drainage restricting member to a different position. 15. The method according to claim 11 or 14, characterized in that the molding web is moved at a speed equal to or less than about 400 m / min. Priority on points: 06/18/1998 according to claims 1, 10, 11. 04/14/1999 according to claims 2-9, 10, 12-15.

Images