Papermaking system

Abstract

A papermaking system consisting of at least three sections wherein a first section forms a sheet of wet paper product and then the sheet of wet paper product is dried in a pre-drying section. The water absorbing strip of the pre-drying section transfers the wet paper product sheet to a heated metal strip that initiates drying the wet paper product sheet by promoting evaporation of water in the wet paper product sheet. The water-absorbing strip is then directed away from the metal strip. The heated metal strip carrying the sheet of wet paper product is then pressed against the same water-absorbing strip that is more dry than before the sheet of wet paper product is transferred to the metal strip. The compaction action further dries the wet paper product by transferring more water into a more dry water absorbing band. The wet paper product sheet is then further dried by an impact dryer and finally collected on a reel.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to Canadian Patent Application No. 3,184,638, filed December 28, 2022, which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to a machine for producing paper products. More particularly, the present disclosure relates to a system for producing tissue paper sheets or paper. Background Art

[0004] The manufacture or production of paper products (such as tissue paper) from a wet stock suspension generally requires a very large and complex system. One such system is the well-known Yankee dryer system. Figure 1 is a schematic diagram of a Yankee dryer system, which is considered the main component of a papermaking machine. The function of the Yankee dryer is to receive a wet paper product formed into an endless sheet and, by applying heat, remove as much water as necessary from the wet paper product so that the resulting dry paper product can be collected on a reel.

[0005] exist Figure 1 In FIG. 1 , a Yankee dryer system 10 includes a clockwise rotating dryer drum (Yankee drum) 12, a wet end hood 14, and a dry end hood 16. Drum 12 is made of steel or cast iron and is configured to receive high-pressure steam internally to heat its outer surface. Both hoods 14 and 16 include a hot air duct 18 and a wet air return duct 20. Both hoods 14 and 16 are configured to surround the approximate circumference of drum 12, with sufficient spacing from the drum surface to allow wet paper products to pass through. Figure 1 Also shown is a felt belt 22 wrapped around a suction roller 24 and a creping blade 26. The suction roller 24 is configured to press the felt belt 22 against the surface of the cylinder 12 and vice versa, as is the edge of the creping blade 26. Although not shown in FIG. Figure 1 1 , but the roll 24 could also be a shoe press with a suction roll positioned downstream of the previous roll 24. Such a shoe press would have a predetermined nip of a width configured to hold the paper product against the surface of the drum 12 to aid in dewatering.

[0006] In an exemplary operation for producing tissue paper, a wet stock suspension is first deposited onto the outer surface of a felt belt 22 (not shown), thereby providing a wet tissue paper sheet. The wet tissue paper sheet undergoes some dewatering (not shown) before being transferred to the surface of a drum 12, where the felt belt 22 contacts the drum 12 surface. Before being transferred to the drum 12 surface by pressing, the tissue paper can have a dryness of approximately 22% in conventional systems, and approximately 45% dryness after pressing, assuming a shoe press is used. The surface of the drum 12 may be sprayed with a special coating to promote adhesion of the wet tissue paper sheet. Because the drum 12 is heated by steam from within, its heated surface begins to dry the wet tissue paper sheet thereon. Simultaneously, as the drum rotates, the wet tissue paper sheet is subjected to high-speed impact from hot air supplied from a hot air duct 18 as it passes within the arc of the wet-end hood 14 and the dry-end hood 16. The moist air is removed via a moist air return duct 20. The creping blade 26 removes the substantially dry tissue paper from the surface of the cylinder 12 while creping the tissue paper. Here, in the system of the known apparatus, the dryness of the tissue paper leaving the Yankee dryer 12 is about 95%.

[0007] An example of a Yankee dryer system using currently known equipment has the following specifications. The drum 12 can have a diameter ranging from 10 to 24 feet and weigh over 100 tons, with the total weight depending on the machine width. Pressurized steam at approximately 160 psi is supplied to the interior of the drum. Fuel-, electricity-, or steam-heated air is driven into the hot air duct 18 by a fan blower, and the moist air from the drying tissue paper is extracted by an exhaust fan. The rollers, belts, and drum 12 are configured to produce tissue paper sheets ranging from 100 to 300 inches wide, and the system operates at speeds ranging from 1,500 to 2,200 meters per minute.

[0008] Yankee dryer systems have several disadvantages. As evidenced by the aforementioned dimensions, these systems are very large, occupying a significant amount of space and increasing the cost of housing the system. Due to their weight, the system includes a substantial base. It should be noted that a network of ducts is used to deliver hot air from the burner or heat exchanger to duct 18 and to deliver humidified air from duct 20 to an area outside the building housing the system. Yankee dryer systems are extremely energy-intensive, as steam must be continuously generated to keep the surface of the drum 12 heated, fuel- or gas-powered burners are required to generate the hot air, and energy is required to power the blower. Most systems are configured to recover heat from the humidified air extracted from duct 20, further increasing the system's complexity, size, and cost.

[0009] Another significant drawback of the Yankee dryer system is its susceptibility to failure due to thermal, mechanical, and pressure stresses, which inevitably lead to safety issues. These failures can include steam leaks in the system that delivers steam to the drum 12. General wear and tear on the components supporting the drum 12 may appear minor, but due to its sheer size and weight, even minor vibrations can lead to catastrophic failures if not addressed immediately. Explosions and ruptures of the drum 12 due to these thermal, mechanical, and pressure stresses have been documented in the past.

[0010] Most Yankee dryer systems use a well-known shoe press to help dewater the tissue paper as it is pressed against and transferred to the cylinder 12. However, there is always a trade-off between the quality of the tissue paper and the energy required to dry it. More specifically, lower nip pressure applied to the tissue paper will result in a sheet with a desired higher volume. However, the sheet will be less dry, requiring more drying energy to complete the drying process. On the other hand, higher nip pressure applied to the tissue paper will result in a sheet with a lower volume but a higher degree of dryness, requiring less energy to complete the drying process.

[0011] Another disadvantage of the Yankee dryer system is that the Yankee dryer is subject to considerable wear due to the permanent contact of the creping blades 26 against the cylinder 12 to crepe the dried paper. To maintain consistent paper quality, the surface of the Yankee dryer 12 must be ground to remove any defects, such as notches and / or grooves. This grinding can only be performed while the cylinder 12 is in the machine and is typically performed every two to five years. This carries significant operational risks and results in approximately two to five days of additional production loss, as the Yankee dryer, and therefore the entire paper machine, is taken out of service for this maintenance.

[0012] It would therefore be desirable to provide a papermaking machine that can dry wet tissue paper, yielding the same performance as a Yankee dryer, but without the disadvantages associated with the operation of a Yankee dryer. Summary of the Invention

[0013] It is an object of the present disclosure to obviate or mitigate at least one disadvantage of previous papermaking systems.

[0014] In a first aspect, the present disclosure provides an apparatus configured to form a paper product from a stock suspension. The apparatus includes a forming section, a pre-drying section, and a drying section. The forming section includes at least one water-permeable belt configured to receive the stock suspension from a headbox and form at least one side of the paper product to provide a wet paper product sheet. The pre-drying section includes a suction belt arranged to continuously move around a first set of rollers configured to receive the wet paper product sheet. The suction belt is configured to initially absorb water from the wet paper product sheet upon contact and is configured to subsequently transfer the wet paper product sheet to a heated metal belt. After the wet paper product sheet is transferred to the metal belt, a first roller in the first set of rollers guides the suction belt away from the metal belt. A dewatering device is included in the section and is configured to dry the suction belt after it is guided away from the metal belt. The pre-drying section also includes a pressing device configured to press the suction belt against the wet paper product sheet carried by the metal belt. The drying section includes a heating element for heating the metal belt before receiving the wet paper product sheet from the absorbent belt, wherein the metal belt is arranged to continuously move around the second set of rollers, wherein the heated metal belt promotes drying of the wet paper product sheet after receiving the wet paper product sheet from the absorbent belt. The drying section also includes a drying device configured to dry the wet paper product sheet carried by the metal belt downstream of the pressurizing device to provide a substantially dry paper product sheet.

[0015] According to an embodiment of the first aspect, the heating element comprises at least one of an induction-based heating element, an infrared-based heating element, and a hot air-based heating element. In this embodiment, the drying section may include a sprayer for spraying adhesive onto the metal belt before the metal belt receives the paper product from the absorbent belt, and a scraper configured to crepe the substantially dried paper product sheet and remove it from the metal belt downstream of the drying device. Alternatively, in this embodiment, the single permeable belt is a metal belt, or the absorbent belt is a felt belt.

[0016] In another embodiment, the drying device includes at least one of an impingement dryer and / or an infrared (IR) dryer. In addition, the drying section may further include an infrared (IR) profiling unit to correct the moisture profile of the wet paper product sheet.

[0017] According to another embodiment of the first aspect, the pressure device is a second roller in the first set of rollers and is configured to press against the absorbent belt when both the absorbent belt and the metal belt surround a portion of the circumference of the second roller. This embodiment further includes at least one pressure roller configured to apply pressure to the metal belt when the metal belt, the wet paper product sheet, and the absorbent belt surround a portion of the circumference of the second roller. The at least one pressure roller can be a small pressure roller, a heavy-duty pressure roller, or a combination of small and heavy-duty pressure rollers. The pressure device can be a shoe press.

[0018] Alternatively, the drying section further comprises another heating element configured to heat the metal belt carrying the wet paper product sheet when the metal belt is in contact with the absorbent belt.

[0019] In another embodiment of the first aspect, a cleaning system is included for cleaning the absorbent belt after the wet paper product is transferred to the metal belt.

[0020] In another embodiment of the first aspect, the forming section includes a single permeable belt arranged to move continuously around a third set of rollers and configured to abut the suction belt as the suction belt orbits a portion of the circumference of the third rollers, wherein the headbox is positioned to inject the stock suspension onto at least one of the single permeable belt and the suction belt before the single permeable belt abuts the suction belt.

[0021] According to one embodiment of the first aspect, the forming section includes a first permeable belt arranged to move continuously around a third set of rollers and configured to cling to a second permeable belt when the second permeable belt surrounds a portion of the circumference of the third rollers, the wet paper product sheet being formed on both sides thereof by the first permeable belt and the second permeable belt, wherein the headbox is positioned to inject the stock suspension onto at least one of the first permeable belt and the second permeable belt before the single permeable belt clings to the second permeable belt, the first permeable belt being configured to transfer the wet paper product sheet to the second permeable belt, and the second permeable belt being configured to transfer the wet paper product sheet to the suction belt.

[0022] For this embodiment, the drying section includes a sprayer for spraying adhesive onto the metal belt before the metal belt receives the wet paper product sheet from the absorbent belt, and a scraper device configured to crepe and remove the substantially dry paper product sheet from the metal belt downstream of the drying device.

[0023] Also for this embodiment, the first water-permeable belt can be a first metal belt, and the second water-permeable belt can be a second metal belt.Alternatively, the water-absorbent belt can be a felt belt.

[0024] According to another embodiment of the first aspect, the forming section includes a single permeable belt arranged to continuously move around a third set of rollers, wherein the headbox is positioned to inject the stock suspension onto the single permeable belt, and the single permeable belt is configured to transfer the paper product to a suction belt. In this embodiment, the drying section may include a sprayer for spraying a silicone-based emulsion onto the metal belt before the metal belt receives the wet paper product sheet from the suction belt. In this embodiment, the forming section may be configured as a Fourdrinier papermaking machine for dewatering the wet paper product sheet before transferring it to the suction belt.

[0025] In another embodiment of the first aspect, the forming section comprises a Fourdrinier papermaking machine configured to form a wet paper product sheet, the predrying section is a second predrying section, and the wet paper product is transferred from the Fourdrinier papermaking machine to the second predrying section after passing through the pre-pressing section and the first predrying section. Here, the drying section may include a third roller as part of a second set of rollers for guiding a metal belt, the third roller and the first roller being configured to press the metal belt against the absorbent belt and transfer the wet paper product sheet onto the metal belt, and the pressing device and the third roller being configured to press the metal belt carrying the wet paper product sheet against the absorbent belt. According to one aspect of this embodiment, a cleaning system may be included for cleaning the absorbent belt after it leaves the first roller and before the second roller presses the belt against the third roller.

[0026] In a second aspect, the present disclosure provides a method for drying a wet paper product sheet in a papermaking system. The method includes heating a metal belt; transferring the wet paper product sheet from a felt belt to the metal belt; drying the felt belt after transferring the wet paper product sheet to the metal belt; after drying the felt belt, placing the felt belt in close contact with the metal belt and the wet paper product sheet; and drying the wet paper product sheet with high-velocity air.

[0027] According to an embodiment of the second aspect, heating the metal belt comprises any one of induction heating, infrared heating and hot air based heating. According to other embodiments of the second aspect, drying the wet paper product sheet comprises any one of impingement drying and infrared (IR) drying.

[0028] In another embodiment of the second aspect, compressing the felt belt includes surrounding a portion of the circumference of a roller with the felt belt and a metal belt carrying the wet tissue paper sheet, wherein the felt belt is positioned between the roller and the metal belt. This embodiment may further include applying pressure to the metal belt while the metal belt, the wet tissue paper sheet, and the absorbent belt surround the portion of the circumference of the roller. Alternatively, compressing the felt belt includes operating a shoe press.

[0029] Other aspects and features of the present disclosure will become apparent to those of ordinary skill in the art by reading the following description of the detailed embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings.

[0031] Figure 1 is a schematic diagram of a Yankee dryer system according to the prior art;

[0032] Figure 2 is a schematic diagram of a papermaking system having a crescent-shaped former configuration according to the present embodiment;

[0033] Figure 3Schematic diagram of a papermaking system according to the present embodiment in a C-wrap former configuration;

[0034] Figure 4 Schematic diagram of a papermaking system in an MG former configuration according to the present embodiment;

[0035] Figure 5 Schematic diagram of a papermaking system having an S-shaped tension former structure according to the present embodiment;

[0036] Figure 6 is a schematic diagram of a papermaking system in a crescent former configuration according to a first alternative embodiment;

[0037] Figure 7 is a schematic diagram of a papermaking system in a crescent former configuration according to a second alternative embodiment;

[0038] Figure 8 is a schematic diagram of a papermaking system in a crescent former configuration according to a third alternative embodiment;

[0039] Figure 9 is a schematic diagram of a papermaking system configured for producing MG paper according to the present embodiment; and

[0040] Figure 10 is a flow chart outlining the operation of the pre-drying section and the drying section of the aforementioned embodiment. DETAILED DESCRIPTION

[0041] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0042] As used herein, the term "about" refers to the typical error margin for a given value given the described technology and context. It should be understood that such variations are always included in any given value provided herein, whether or not specifically mentioned.

[0043] As used herein, the term "plurality" means more than one, eg, two or more, three or more, four or more, etc.

[0044] When used herein in conjunction with the term "comprising," the use of the word "a" may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0045] As used herein, the terms "comprise," "have," "include," and "contain," and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, unenumerated elements and / or method steps. When used in conjunction with an apparatus, system, composition, use, or method herein, the term "consisting essentially of means that there may be additional elements and / or method steps, but these additions will not substantially affect the manner in which the apparatus, system composition, method, or use functions. When used in conjunction with an apparatus, system, composition, use, or method herein, the term "consisting of does not include the presence of additional elements and / or method steps. An apparatus, system composition, use, or method described herein as comprising certain elements and / or steps may also consist essentially of these elements and / or steps in certain embodiments, and consist of these elements and / or steps in other embodiments, regardless of whether these embodiments are specifically mentioned.

[0046] Generally speaking, the present disclosure provides a papermaking system that does not use a Yankee dryer, but instead uses a novel arrangement of heated metal belts and felt belts to dry wet paper product sheets.

[0047] The papermaking system of this embodiment consists of at least three sections. The first section forms a wet paper product sheet, which is then dried in the pre-drying section. A water-absorbing belt in the pre-drying section transfers the wet paper product sheet to a heated metal belt in the drying section, where it is then guided away from the belt. The heated metal belt carrying the wet paper product sheet is then placed against the same absorbent belt, which is drier than before the transfer, to absorb additional water from the wet paper product sheet. The wet paper product sheet then passes through an impingement dryer for further drying and is ultimately collected on a reel.

[0048] According to this embodiment, the first section is a forming section which deposits the wet stock suspension from the headbox onto one or two water-permeable belts to form at least one side of the wet paper product sheet.

[0049] The second section is a pre-drying section having a water-absorbing belt that receives the wet paper product sheet from the water-permeable belt and begins to remove water from the wet paper product sheet.

[0050] The third section is a drying section with a heated metal belt that receives the wet paper product sheet from the absorbent belt in the second section. In this drying section, after releasing the wet paper product sheet onto the metal belt, the absorbent belt is dried to remove water absorbed from the wet paper product sheet. The absorbent belt then wraps around a roller, and the metal belt, carrying the wet paper product sheet, clings to it while both the absorbent belt and the metal belt wrap around a portion of the roller's circumference. The drier absorbent belt absorbs more water from the wet paper product sheet, which is now clinging to it via the metal belt. The now substantially drier paper product sheet is subjected to heated air drying for further drying before being removed from the metal belt by a creping blade.

[0051] Figure 2 is a schematic diagram of a papermaking system according to the present embodiment. More specifically, the presently illustrated papermaking system is shown in a crescent former configuration for producing sheets of wet paper products, such as tissue paper. The crescent former papermaking system 100 is comprised of the three sections generally described above. The components of each section will be discussed first, followed by a description of the operation of these sections in conjunction with one another.

[0052] from Figure 2 Beginning on the left side of the drawing is the forming section, which includes a water-permeable belt (e.g., a metal belt 102), rollers (of which rollers 106 and 108 are labeled) that contact the inner surface of the belt 102, and a headbox 104 that receives the stock suspension and deposits it as a wet tissue paper sheet. In the configuration currently shown, the metal belt 102 moves in a clockwise direction and has an outer surface that receives the wet stock from the headbox 104. The metal belt 102 allows water to drain through it.

[0053] The pre-drying section includes a water-absorbing belt (e.g., felt belt 110) and a set of rollers for guiding the path of the water-absorbing belt, of which rollers 112, 114, and 116 are labeled. Here, the felt belt 110 may be a felt belt that absorbs water. The felt belt 110 moves in a counterclockwise direction. Roller 114 is constructed with an integrated water absorption system to remove as much water as possible from any wet tissue paper sheet on the felt belt 110 and the felt belt 110 itself. Although not described in detail, the rollers 112, 114, and 116 are labeled as shown in FIG. Figure 2 , but the pre-drying section may include at least one additional auxiliary water absorption system that is constructed and positioned to remove water from any wet tissue paper sheet on the felt belt 110 and the felt belt 110 itself. Turning to the left side of the pre-drying section, the metal ribbon 102 is constructed to wrap around and around the felt belt 110 and roller 112, thereby surrounding a portion of the circumference of the roller 112. Figure 2 As shown, the headbox 104 is positioned at an area where the surfaces of the rolls 106 and 112 are adjacent one another to begin to press the belts 102 and 110 against one another.

[0054] The drying section includes a metal belt 118 and rollers in contact with the inner surface of the metal belt 118, with rollers 120, 122, 123 and 124 being labeled. The metal belt 118 can be very thin, for example in the millimeter range. The drying section also includes a heating element 126 for heating the metal belt to a temperature in the range of 105°C-150°C, an impingement dryer 128 for pushing hot air toward the outer surface of the metal belt 118, an infrared (IR) metering unit 129 positioned around a portion of the roller 124, and a corrugating doctor 130 positioned near the roller 120 and having an edge in contact with the metal belt 118. The heating element 126 can be induction-based, infrared-based or hot air-based, but any type of heating element for heating a metal belt can be used. Note that thinner metal belt 118 is heated to the desired temperature more quickly due to its thickness. The impingement dryer can alternatively be an IR dryer or include an IR dryer combined with an air impingement dryer. Although not described in Figure 2 , but the sprayer is positioned to spray an adhesive type liquid onto the surface of the metal belt to promote adhesion to the wet tissue paper sheet.

[0055] In the currently shown Figure 2 In this configuration, the metal belt 118 and the identical felt belt 110 are in close contact with each other at two different locations. The first location where the two belts 110 and 118 are in close contact occurs in the area between rollers 114 and 122. The two belts 110 and 118 then separate, where they again cling to each other around roller 116. Therefore, when roller 116 tensions the metal belt 118, thereby pressing it against the roller with the felt belt 110 and the wet tissue paper sheet positioned therebetween, roller 116 acts as a pressure device. Specifically, the felt belt 110 wraps around the outer surface of roller 116, and the metal belt 118, carrying the wet tissue paper sheet, clings to the felt belt 110, both encircling a portion of the circumference of roller 116. The clamping angle between the belts 110 and 118 can be as low as 30° and as high as 210°. The clamping angle is defined as the angle between the first and last points of contact as the belts travel over the roller.

[0056] Generally, the greater the nip wrap angle, the improved drying performance. Another advantage of the system of the present embodiment described is that every 1% increase in dryness achieved will save approximately 3% to 4% of the energy required by the drying elements (such as the metal belt heating elements 126 and the impingement dryers 128) to dry the finished tissue paper to the desired level.

[0057] Optionally, a small press roller 123 is included that is movable to apply localized pressure to the metal belt 118, the wet tissue paper sheet, the felt belt 110, and the roller 116. The small press roller 123 is positioned to apply this localized pressure to press water from the wet tissue paper sheet into the felt belt 110 before the metal belt 118 and the felt belt 110 separate from each other. Use of the small press roller 123 improves the dryness of the wet tissue paper sheet.

[0058] The operation of a paper machine 100 for producing tissue paper (i.e., a crescent former paper machine 100) will now be described. Such tissue paper may have a viscosity of 10-40 g / m 2 basis weight.

[0059] The process starts from Figure 2 The left side of the slurry begins with the forming section described above. The headbox 104 injects or deposits the wet stock onto at least one of the metal belt 102 and the felt belt 110 so that when the two belts 102 and 110 begin to cling to each other at roller 112, the wet stock is captured between the two belts. The temperature of the wet stock suspension can be maintained between 45°C and 65°C. Roller 106 is positioned so that there is a small gap between it and roller 112 to limit the entry angle of belt 102 as it approaches roller 112. The dryness content of the wet stock can be about 0.2% before dewatering by centrifugal force and compression. During the duration that both belts 102 and 110 are around roller 112, the wet stock is pressed against the felt belt 110 by the metal belt 102, thereby forming a wet paper product sheet, in this embodiment a wet tissue paper sheet. Note that the felt belt 110 immediately begins to absorb water from the wet tissue paper sheet upon contact and allows excess water to drain through it. Some of the excess water in the wet tissue paper sheet is further pressed out because the metal ribbon 102 is pressed against the felt belt 110 and roller 112 under tension. Assume that both the metal ribbon 102 and the felt belt 110 are moving at the same speed.

[0060] Eventually, the metal belt 102 and the felt belt 110 separate, with the wet tissue sheet adhering to the outer surface of the felt belt 110 and effectively exiting the forming section. After dewatering by the compression and centrifugal force of the belts 102 and 110 around roller 112, the wet tissue sheet's dryness content increases, for example, to approximately 12%-14%. The felt belt 110 now conveys the wet tissue sheet from the pre-drying section toward roller 114, which, as previously described, may have an integrated water absorption system. Thus, as the felt belt 110 contacts the surface of roller 114, water is removed from the wet tissue sheet on the felt belt 110 and from the felt belt 110 itself. The dimensions of roller 114, the speed of movement of the felt belt 110, and its water absorption capacity can be configured to further increase the wet tissue sheet's dryness to, for example, between 20%-22% before contact with the metal belt 118. In one example, the roller diameter of roller 114 may be between 800 mm and 1500 mm, and the minimum vacuum level applied may be 0.2 bar, expressed in m 3 The amount of vacuum, expressed in 1000 psi / min, is determined by the open area of the roller 114 and the design of the felt belt 110. Those skilled in the art will appreciate that various combinations of roller diameter, belt tension, and working width may be set to achieve a desired dryness content of the wet tissue paper sheet before it contacts the metal belt 118.

[0061] At roller 114, the felt belt 110 is pressed against the heated metal belt 118, causing the wet tissue paper sheet on the felt belt 110 to be transferred to the heated metal belt 118. The felt belt 110 and the metal belt 118 move at the same rate (speed). The heat of the metal belt 118 immediately begins to promote the drying of the wet tissue paper sheet thereon by evaporating the water therein. Simulations have shown that the drying effect of the heated metal belt can account for at least 50% of the total drying of the wet tissue paper sheet. After the wet tissue paper sheet is transferred to the metal belt 118, the wet tissue paper sheet now enters the drying section and the felt belt 110 moves away from the metal belt 118. It is noted here that after the wet tissue paper sheet is transferred to the metal belt 118, the felt belt 110 is now drier than before the wet tissue paper sheet was transferred to the metal belt 118. After the felt strip 110 leaves the roller 114, the felt strip 110 may optionally be further dried by passing through another water suction device and / or an air impingement dryer, with the goal of drying as much of the felt strip 110 as possible.

[0062] Further downstream, the metal belt 118 carrying the wet tissue sheet and the drier felt belt 110 meet again at roller 116. More specifically, the felt belt wraps around the outer surface of roller 116, and the metal belt is pressed around the felt belt 110, thereby pressing the wet tissue sheet against the drier felt belt 110. This has the effect of removing more water from the wet tissue sheet. This novel technology for drying the wet tissue sheet using the tension of the metal belt 118 around the wet tissue sheet against the felt belt 110 and roller 116 provides low peak pressure, thereby achieving considerable dewatering when using a press nip, while retaining as much volume in the tissue as possible.

[0063] Increasing the tension of the metal belt 118 around the roller 116 increases the dryness of the wet tissue paper sheet, however, this increased tension also reduces the life of the metal belt 118 and the roller. Therefore, some embodiments may use a small pressure roller 123 to remove more water from the wet tissue paper sheet without increasing the tension of the metal belt 118. Because the small pressure roller 123 is movable, different implementations may use different combinations of applied pressure from the small pressure roller 123 and tension in the metal belt 118 to achieve the desired dryness for acceptable reliability of the metal belt 118 and the rollers along which it travels. In some embodiments, the small pressure roller 123 is not included.

[0064] Finally, the felt belt 110 and the metal belt 118 separate after completing their rotation around the roller 116. The metal belt 118 carrying the drier wet tissue paper sheet advances toward roller 124, while the felt belt 110 moves toward roller 112 to repeat the process. Although not shown, before the felt belt 110 arrives at roller 112 to repeat the process, the felt belt 110 is cleaned by a cleaning system (not shown) to wash away residual fibers and any surface dirt. Common cleaning systems in the art include using high-pressure sprayers and vacuum to help dry the felt belt 110. This cleaning system can be located after the felt belt 110 leaves roller 114 but before the felt belt 110 contacts the next roller, otherwise any remaining fibers on the felt belt will be pressed into the felt belt by the next roller, thereby producing undesirable deposits. Alternatively, this cleaning system can be located before the felt belt 110 contacts the metal belt 118 at roller 116.

[0065] At the same time, the metal belt 118 enters a metering unit 129, which senses and corrects the moisture profile of the paper. This unit is configured to individually control the heating of predetermined zones (e.g., a 100 mm width zone along its width) to adjust the dryness profile of the paper. The metal belt with the paper then enters a high-temperature impingement dryer 128 to complete the drying process. The temperature and air flow rate of the impingement dryer 128, combined with the speed of movement of the metal belt 118 and metering unit 129, are configured to ensure that the dryness level of the tissue paper reaches at least 92%. The dried tissue paper is then removed from the metal belt 118 by a creping blade 130 at roller 120 and collected on a reel (not shown).

[0066] In an alternative embodiment, Figure 2 The papermaking machine 100 in the embodiment may be configured as Figure 3 The C-shaped stretch former shown is configured for producing wet paper products such as tissue paper. Figure 3 The C-shaped stretch former papermaking system 200 is composed of the three sections generally described above. The components of each section are discussed first, followed by a description of the operation of these sections when they cooperate with each other.

[0067] exist Figure 3 Starting on the left side of the figure, the forming section comprises a first water-permeable belt (e.g., first metal ribbon 202), a second water-permeable belt (e.g., second metal ribbon 204), rollers for guiding metal ribbons 202 and 204, respectively, and a headbox 206 for receiving and depositing the stock suspension. First metal ribbon 202 is guided by rollers, of which rollers 208 and 209 are labeled. Second metal ribbon 204 is guided by four rollers, of which rollers 210 and 212 are labeled. In the configuration shown, first metal ribbon 202 allows water to drain through it and moves in a counterclockwise direction. Second metal ribbon 204 also allows water to drain through it and moves in a clockwise direction.

[0068] The second metal ribbon 204 is configured to wrap around the outer surface of the roller 210, and the first metal ribbon 202 is configured to wrap around and around the second metal ribbon 204 and the roller 210, thereby surrounding a portion of the circumference of the roller 210. Figure 3 As shown, headbox 206 is positioned at an area where the surfaces of rolls 208 and 210 are adjacent to each other. Roller 208 is positioned so that a small gap exists between it and roll 210 to define the angle of entry of belt 202 as it approaches roll 210.

[0069] The pre-drying section includes a water-absorbing belt (e.g., felt belt 214) and a set of rollers for guiding the path of the felt belt 214, wherein rollers 216, 218, and 220 are labeled. Note that rollers 218 and 220 may be respectively Figure 2Rollers 114 and 116 are identical, with roller 220 acting as a pressure device. The felt belt 214 moves in a counterclockwise direction. Roller 218 is constructed with an integrated water absorption system to remove as much water as possible from any wet paper product on the felt belt 214 and the felt belt 214 itself. Although not shown in FIG. Figure 3 204 to pick up the wet paper product.

[0070] The drying section can be Figure 2 The drying sections shown in the embodiments of FIG. 1 are constructed identically, so the same reference numerals are used and the same corresponding descriptions and operations apply.

[0071] The operation of a papermaking machine 200 for producing tissue paper (ie, a C-type stretch former papermaking machine 200) will now be described.

[0072] The process starts from Figure 3 The left side of the drawing begins with the aforementioned forming section. The headbox 206 injects or deposits wet stock onto at least one of the first and second wires 202, 204, so that as the two wires 202, 204 begin to abut against each other as they wrap around roller 210, the wet stock is trapped between the two wires. The temperature of the wet stock suspension can be maintained between 45°C and 65°C. Prior to compaction, the wet stock can have a dryness of approximately 0.2%. During the duration that both wires 204, 202 wrap around roller 210, the wet stock forms a wet paper product sheet, in this embodiment, a wet tissue paper sheet, by means of the first wire 202 abutting against the second wire 204. Because the first wire 202 is held under tension against the second wire 204 and roller 210, some excess water in the wet tissue paper sheet is pressed out. It is assumed that both the first and second wires 202, 204 move at the same speed. Finally, the first and second metal ribbons 202 and 204 are separated at a point defined by roller 209 after roller 210, wherein the wet tissue paper sheet adheres to the outer surface of the second metal ribbon 204 by means of suction boxes (not shown).

[0073] The wet tissue paper sheet is transported to roller 212 where it is transferred to the outer surface of the felt belt 214 as it abuts the second metal belt 204. The wet tissue paper sheet has now left the forming section. The felt belt 214 and the second metal belt 204 move at the same speed.

[0074] Note that after the compacting action of the belts 202 and 204 around the roller 210 and the conveyance of the wet tissue paper on the second metal belt 204, the dryness content of the wet tissue paper sheet may be, for example, about 12%-16%. The felt belt 214 now conveys the wet tissue paper sheet in the pre-drying section towards the roller 218 which, as previously mentioned, may have an integrated water suction system. Thus, when the felt belt 214 comes into contact with the surface of the roller 218, water is removed from the wet tissue paper sheet on the felt belt 214 and from the felt belt 214 itself. The size of the roller 218, the speed of movement of the felt belt 214 and the water suction capacity may be configured to increase the dryness of the wet tissue paper sheet to, for example, between 20%-22% before the wet tissue paper sheet comes into contact with the metal belt 118. The roller diameter of the roller 218 may be between 800 mm and 1500 mm and the minimum vacuum level applied may be 0.2 bar, expressed in m 3 The amount of vacuum, expressed in 1000 psi / min, is determined by the open area of the roller 218 and the design of the felt belt 214. Those skilled in the art will appreciate that various combinations of roller diameter, belt tension, and working width may be set to achieve a desired dryness content of the wet tissue paper sheet before it contacts the metal belt 118.

[0075] Once the wet tissue paper sheet has been transferred to the metal belt 118 which is moving at the same speed as the felt belt 214, the wet tissue paper sheet follows Figure 2 The same path is used in the implementation of Figure 2 In the embodiment of the present invention, the metal belt 118 interacts with the felt belt 214 in the same manner as the felt belt 110. Finally, the dried tissue paper sheet is removed from the metal belt 118 at roller 120 by a creping blade 130 and collected on a reel (not shown). Ideally, the dryness level of the final tissue paper sheet should be at least 92%.

[0076] Returning to the pre-drying section, after roller 220, the felt belt 214 moves toward roller 216 to repeat the process, and as shown in FIG. Figure 2 Cleaning is performed as described in the foregoing embodiment. Figure 3 In an optional variation of this embodiment, the felt belt 214 may be further dried by any suitable means after being cleaned and before reaching the roller 216. This will allow for greater initial absorption of water from the wet stock deposited by the headbox 206.

[0077] In another alternative embodiment, Figure 2 The papermaking machine 100 in the embodiment may be configured as Figure 4 The MG former configuration shown is used to produce machine-coated paper. Figure 4 The MG former papermaking system 300 is composed of the three sections described generally above. The components of each section are discussed first, followed by a description of the operation of the sections in conjunction with each other.

[0078] from Figure 4 Starting on the left side of the drawing is the forming section, which includes a water-permeable belt (e.g., a wire ribbon 302), rollers (of which rollers 304, 306, and 308 are labeled) for guiding the wire ribbon 302, and a headbox 310 for receiving and depositing the stock suspension. In the configuration currently shown, the wire ribbon 302 allows water to drain through it and moves in a clockwise direction.

[0079] like Figure 4 As shown, a headbox 310 is positioned adjacent to the roller 304 for depositing the stock suspension onto the metal belt 302. The length of the flat portion of the metal belt 302 is predetermined to ensure that water is passively drained by gravity through the open mesh of the metal belt 302, the negative pressure generated by a foil (not shown) located below the belt 302, and finally by a vacuum dewatering box (not shown) also located below the belt 302, so that the wet paper thereon reaches a dryness level of, for example, about 22% when it is transferred to the pre-drying section.

[0080] The pre-drying section includes a water-absorbing belt (e.g., felt belt 312) and a set of rollers for guiding the path of the felt belt 312, wherein rollers 314, 316, and 318 are labeled. Note that rollers 316 and 318 can be respectively Figure 2 The rollers 114 and 116 are identical, with roller 318 acting as a pressure device. The felt belt 312 moves in a counterclockwise direction. Roller 316 is constructed with an integrated water absorption system to remove as much water as possible from any wet paper product on the felt belt 312 and the felt belt 312 itself. Although not shown in FIG. Figure 3 , but the pre-drying section may include at least one additional auxiliary water suction system that is constructed and positioned to remove water from any wet paper product on the felt belt 312 and the felt belt 312 itself. Turning to the left side of the pre-drying section, roller 314 is positioned adjacent to the downwardly inclined section of the wire belt 302 between rollers 306 and 308, so that the felt belt 312 and the wire belt 302 are in close contact with each other. To help pick up the wet paper from the wire belt 302, roller 314 includes a suction element.

[0081] The drying section can be Figure 2 The drying sections shown in the embodiments of FIG. 1 are constructed identically, so the same reference numerals are used and the same corresponding descriptions and operations apply.

[0082] The operation of a paper machine 300 for producing MG paper (i.e., an MG former paper machine 300) will now be described. Such MG paper may have a g / m 2 basis weight.

[0083] The process starts from Figure 4The left side of the 302 begins with the aforementioned forming section. A headbox 310 injects or deposits wet stock onto the wire 302, positioning the wet stock on top of the wire 302 to form a wet sheet of paper as it travels toward roller 306. The temperature of the wet stock suspension can be maintained between 45°C and 65°C. The dryness content of the wet paper begins at approximately 1% immediately after being deposited on the wire 302. Water in the wet paper begins to drain through the wire 302 through gravity, a foil beneath the wire 302, and a vacuum box.

[0084] The wet paper is transported to roller 314 where it is transferred to the outer surface of the felt belt 312 as it abuts the metal belt 302. The wet paper has now left the forming section. The felt belt 312 and the metal belt 302 move at the same speed.

[0085] Note that the dryness content of the wet paper before being transferred to the felt belt 312 can be, for example, about 22%. The felt belt 312 now transports the wet paper in the pre-drying section toward the roller 316, which, as previously described, can have an integrated water absorption system. Thus, when the felt belt 312 comes into contact with the surface of the roller 316, water is removed from the wet paper on the felt belt 312 and the felt belt 312 itself. The size of the roller 316, the moving speed of the felt belt 312, and the water absorption capacity can be configured to increase the dryness content of the wet paper to, for example, about 30% before the wet paper comes into contact with the metal belt 118. The roller diameter of the roller 318 can be between 800 mm and 1500 mm, and the minimum vacuum level applied can be 0.2 bar, expressed in m 3 The vacuum amount in units of 1 / min is determined by the opening area of the roller 318 and the design of the felt belt 312. Similarly, the parameters mentioned in the above embodiments can be set in different combinations to obtain the desired dryness content of the paper.

[0086] Once the wet paper has been transferred to the metal belt 118 which moves at the same speed as the felt belt 312, the wet paper follows the same Figure 2 The same path is used in the implementation of Figure 2 In the embodiment of the present invention, the metal belt 118 interacts with the felt belt 312 in the same manner as the felt belt 110. One difference from the previous embodiment is that instead of spraying an adhesive-type liquid onto the metal belt 118, a type of chemical that allows the wet paper to shrink along its width dimension when applied to the heated metal belt 118 is applied. Since the heated metal belt 118 promotes the evaporation of water, the wet paper shrinks as it dries. An example of such a chemical is a silicone-based emulsion. In this particular embodiment, the heated metal belt not only helps to dry the wet paper, but also provides an ironing effect so that the resulting paper has a desired glossy surface as the wet paper shrinks and slides across the heated metal belt.

[0087] Finally, the dried paper sheet is removed from the metal belt 118 at roller 120 and collected on a reel (not shown). Because the dried paper is harder than the thin paper of the previous embodiment, it is only separated from the metal belt 118 due to the bending of roller 120, without coming into contact with the creping blade 130. In this embodiment, the creping blade 130 functions more like a protective device to prevent any part of the dried paper from adhering to the metal belt 118. Ideally, the final dryness level of the paper should be at least 90%.

[0088] Returning to the pre-drying section, after roller 318, the felt belt 312 moves toward roller 314 to repeat the process. Figure 4 In an optional variation of this embodiment, the felt belt 312 may be further dried by any suitable means after being cleaned and before reaching the roller 314. This will allow for greater initial absorption of water from the wet stock deposited by the headbox 310.

[0089] According to an alternative embodiment, the drying section may be modified to include another heating element positioned proximate to the metal strip 118 as it passes around roller 318 (or rollers 116 and 220 of other embodiments) to apply additional heat to the metal strip to compensate for any heat loss since heat was applied earlier by heating element 126.

[0090] In an alternative embodiment, Figure 2 The papermaking machine 100 in the embodiment may be configured as Figure 5 The S-shaped stretch former shown is configured for producing tissue paper. Figure 5 The S-shaped stretch former papermaking system 400 consists of the three sections generally described above. Figure 3 The main difference of the C-shaped tensioned configuration is the "S" shaped path followed by the two water permeable strips in the forming section. The components of each section are discussed first, followed by a description of the operation of these sections when they cooperate with each other.

[0091] from Figure 5 Starting on the left side of the figure, the forming section comprises a first water-permeable belt (e.g., first metal ribbon 402), a second water-permeable belt (e.g., second metal ribbon 404), rollers for guiding metal ribbons 402 and 404, respectively, and a headbox 406 for receiving and depositing the stock suspension. First metal ribbon 402 is guided by rollers, of which rollers 410 and 408 are labeled. Second metal ribbon 404 is guided by four rollers, of which rollers 412, 414, and 416 are labeled. In the configuration shown, first metal ribbon 402 allows water to drain through it and moves in a counterclockwise direction. Second metal ribbon 404 also allows water to drain through it and moves in a clockwise direction.

[0092] The first metal ribbon 402 is configured to wrap around the outer surfaces of rollers 410 and 412, and also wrap around the metal ribbon 404 at rollers 410 and 412, while the second metal ribbon 404 is configured to wrap around the outer surface of roller 414, and then wrap around and around the first metal ribbon 402 and roller 410 and around roller 412. Therefore, the first metal ribbon 402 and the second metal ribbon 404 both wrap around a portion of the circumference of rollers 410 and 412. Figure 5 As shown, headbox 406 is positioned at an area where the surfaces of rolls 410 and 414 are adjacent to each other. Roller 414 is positioned so that a small gap exists between it and roll 410 to define the angle of entry of belt 402 as it approaches roll 410.

[0093] The pre-drying section includes a water-absorbing belt (e.g., felt belt 418) and a set of rollers for guiding the path of the felt belt 418, wherein rollers 420, 422, and 424 are labeled. Note that rollers 422 and 424 can be respectively Figure 2 The rollers 114 and 116 are identical, with roller 424 acting as a pressure device. The felt belt 418 moves in a counterclockwise direction. Roller 422 is constructed with an integrated water absorption system to remove as much water as possible from any wet paper product on the felt belt 418 and the felt belt 418 itself. Although not shown in FIG. Figure 3 4, but the pre-drying section may include at least one additional auxiliary water suction system that is constructed and positioned to remove water from any wet paper product on the felt belt 418 and the felt belt 418 itself. Turning to the left side of the pre-drying section, a roller 420 with the felt belt 418 is positioned to press slightly into the second wire belt 404 to pick up the wet paper product.

[0094] The drying section can be Figure 2 The drying sections shown in the embodiments of FIG. 1 are constructed identically, so the same reference numerals are used and the same corresponding descriptions and operations apply.

[0095] The operation of the papermaking machine 400 for producing tissue paper (ie, the S-shaped stretch former papermaking machine 400) will now be described.

[0096] The process starts from Figure 5The left side of the drawing begins with the aforementioned forming section. A headbox 406 injects or deposits wet stock onto at least one of the first and second wires 402, 404, so that as the two wires 402 and 404 begin to cling to each other as they wrap around roller 410, the wet stock is trapped between the two wires. The temperature of the wet stock suspension can be maintained between 45°C and 65°C. Prior to compaction, the wet stock can have a dryness of approximately 0.2%. During the duration that both wires 404 and 402 wrap around rollers 410 and 412, the wet stock is pressed against the second wire 404 by the first wire 402, thereby forming a wet paper product sheet, in this embodiment, a wet tissue paper sheet. Because the first wire 402 is pressed against the second wire 404 and rollers 410 and 412 under tension, some excess water in the wet tissue paper sheet is pressed out. It is assumed that both the first and second wires 402 and 404 are controlled to move at the same speed. Finally, the first and second metal ribbons 402 and 404 are separated at a point defined by roller 408 after roller 412, with the wet tissue paper sheet adhering to the outer surface of the second metal ribbon 404 by means of suction boxes (not shown).

[0097] The wet tissue paper sheet is conveyed to roller 416 where it is transferred to the outer surface of the felt belt 418 as it abuts the second metal belt 404 at roller 420. The wet tissue paper sheet has now left the forming section. The felt belt 418 and the second metal belt 404 move at the same speed.

[0098] Note that after the compacting action of the belts 402 and 404 around the roller 210 and the conveyance of the wet tissue paper on the second metal belt 404, the dryness content of the wet tissue paper sheet may be, for example, about 12%-16%. The felt belt 418 now conveys the wet tissue paper sheet in the pre-drying section towards the roller 422 which, as previously described, may have an integrated water absorption system. Thus, when the felt belt 418 comes into contact with the surface of the roller 422, water is removed from the wet tissue paper sheet on the felt belt 418 and from the felt belt 418 itself. The size of the roller 422, the speed of movement of the felt belt 418 and the water absorption capacity may be configured to increase the dryness of the wet tissue paper sheet to, for example, between 20%-22% before the wet tissue paper sheet comes into contact with the metal belt 118. The roller diameter of the roller 422 may be between 800 mm and 1500 mm, the minimum vacuum level applied may be 0.2 bar, and the pressure may be in the range of m 3 The amount of vacuum, expressed in 1000 psi / min, is determined by the open area of the roller 422 and the design of the felt belt 418. Those skilled in the art will appreciate that various combinations of roller diameter, belt tension, and working width may be set to achieve a desired dryness content of the wet tissue paper sheet before it contacts the metal belt 118.

[0099] Once the wet tissue paper sheet has been transferred to the metal belt 118 which is moving at the same speed as the felt belt 418, the wet tissue paper sheet follows the same Figure 2 The same path is used in the implementation of Figure 2 In the embodiment of the present invention, the metal belt 118 interacts with the felt belt 418 in the same manner as the felt belt 110. Finally, the dried tissue paper sheet is removed from the metal belt 118 at roller 120 by a creping blade 130 and collected on a reel (not shown). Ideally, the dryness level of the final tissue paper sheet should be at least 92%.

[0100] Returning to the pre-drying section, after roller 424, the felt belt 418 moves toward roller 420 to repeat the process, and as shown in FIG. Figure 2 Cleaning is performed as described in the foregoing embodiment. Figure 5 In an optional variation of this embodiment, the felt belt 418 may be further dried by any suitable means after being cleaned and before reaching the roller 420. This will allow for greater initial absorption of water from the wet stock deposited by the headbox 406.

[0101] According to an alternative embodiment, the drying section of the aforementioned embodiment may be modified to include another heating element positioned proximate to the metal belt 118 as it wraps around roller 116 (or rollers 220, 318, and 424 of other embodiments) to apply additional heat to the metal belt to compensate for any heat loss since heat was applied earlier by heating element 126.

[0102] Return to Figure 2 In the embodiment of the papermaking system, the drying section is shown to include a small press roller 123, which can be omitted in an alternative embodiment. Figure 2 In another alternative embodiment of the papermaking system, Figure 6 A papermaking system is shown that uses heavy press rolls to improve the drying of wet tissue paper sheets.

[0103] This alternative embodiment Figure 6 The papermaking system 500 has Figure 2 The same forming section and pre-drying section of the papermaking system 100. Figure 6 Used in Figure 2 Like reference numerals denote like elements, so the operation of the forming section and pre-drying section is the same as for the Figure 2 Note that the impingement dryer 128 is shown as Figure 6 There are specific example configurations of hot air ducts and return ducts in the embodiment of FIG.

[0104] Figure 6 The drying section of the papermaking system 500 is Figure 2 The drying section in is basically the same. Figure 6 The same reference numerals are used to denote the same elements. Figure 2 implementation method, Figure 6 The embodiment does not use the small press roller 123, and the heavy press roller 502 replaces the roller 129. The heavy press roller 502 is movable and is controlled to apply localized pressure to the metal belt 118, the wet tissue paper sheet, the felt belt 110, and the roller 116. The heavy press roller 502 has a high linear load, and this final stage of pressing the metal belt 118 against the wet tissue paper sheet and the felt belt 110 has the effect of transferring more water from the wet tissue paper sheet to the felt belt 110, thereby increasing the dryness level of the tissue paper sheet.

[0105] The heavy press roller 502 is positioned to maximize the amount of time the felt belt 110 can absorb water from the wet tissue paper sheet as the wet tissue paper sheet moves around the roller 116. One advantageous result of this configuration is that the removal of water from the wet tissue paper sheet as it travels around the roller 116 results in less volume being lost later due to the heavy press roller 502, thereby improving the quality of the resulting tissue paper.

[0106] Figure 6 An alternative embodiment of the papermaking system is Figure 7 papermaking system. Figure 7 The papermaking system 510 includes Figure 6 The papermaking system 500 includes all the same elements as shown in FIG. 5 , but also includes a small press roller 514. The small press roller 514 is also movable and functions similarly to the Figure 2 The small pressing roller 123 in the embodiment of the present invention. Figure 7 In the embodiment, the small press roller 123 is an additional press to the heavy press roller 502 and can be positioned at any position upstream of the heavy press roller 502 where the metal belt 118 is pressing the wet tissue paper sheet against the felt belt 110 and roller 116. The function of the additional small press roller 514 is to further increase the transfer of water from the wet tissue paper sheet to the felt belt 110.

[0107] exist Figures 2 to 7 In the aforementioned embodiments of the papermaking system shown, the felt belt 110 of the pre-drying section transfers the wet tissue paper sheet it carries to the metal belt 118 and dries as much as possible before coming into contact with the wet tissue paper sheet carried by the metal belt 118 later downstream to help further dry the wet tissue paper sheet by absorbing water from the wet tissue paper sheet. In these embodiments, the wet tissue paper sheet is pressed against the felt belt and roller 116 by the tension of the metal belt 118 to promote water absorption into the felt belt. Adding small pressing rollers and heavy pressing rollers further promotes the drying of the wet tissue paper sheet. Figure 8 This concept is again illustrated in the illustrated alternative embodiment of the papermaking system.

[0108] Figure 8 An alternative embodiment of FIGURE 1 shows an example of this concept, where a felt belt is brought into contact with a heated metal belt on two different occasions to help promote drying of a wet tissue paper sheet. Figure 8 The papermaking system 520 has Figure 2 The forming section and the drying section shown in the embodiment of FIG. 5 are identical forming sections and drying sections, and therefore the same reference numerals are used for the elements shown.

[0109] Figure 2 The implementation method and Figure 8 The difference between the embodiments is the pre-drying section. Figure 8 The pre-drying section is similar to Figure 2 The pre-drying section of FIG. 1 and therefore shares many of the same numbered elements, with the exception of the shoe press 524, which is arranged and positioned to hold the felt belt 110 against the wet tissue paper sheet carried by the metal belt 118 on the roller 124. Again, in Figure 8 In the embodiment shown in FIG. 1 , it can be seen that after the wet tissue paper sheet is transferred to the heated metal belt 118 at roller 114 through the felt belt 110, the felt belt is cleaned and dried as much as possible, and then it passes through the shoe press 524 at roller 124 to cling to the metal belt 118 slightly downstream. The shoe press 524 has a similar effect to the small press roller and heavy press roller shown in the previous embodiment, which is to promote the drying of the wet tissue paper sheet by pressing the water of the wet tissue paper sheet into the felt belt 110.

[0110] The previously described papermaking system embodiments are shown as having at least three sections, with the first section being a forming section, the second section being a predrying section, and the third section being a drying section. In alternative embodiments of each of the previously described papermaking systems, intermediate sections may be inserted between the forming section and the predrying section, and / or an additional finishing section may be added after the drying section before the paper product is collected on a reel. Each section transfers paper to the next section. Thus, after forming a paper or tissue sheet in the forming section, the predrying section ultimately receives the paper or tissue sheet via any number of intermediate sections.

[0111] exist Figure 9 An example of such a system is shown in the alternative embodiment, Figure 9 It is a papermaking system used to produce MG paper. Figure 9 The presently shown embodiment is an alternative configuration to the known configurations for producing MG paper using a Yankee dryer. Prior art configurations include those with Figure 4Similar fourdrinier sections are shown, a pre-press section, a first pre-drying section, a second pre-drying and pressing section, a drying section including a Yankee dryer, and a post-drying section before the finished paper product is finally collected on reels. Figure 9 In this embodiment, the Yankee dryer of the prior art drying section is similar to Figures 2 to 8 The heated metal belt system shown in the previous embodiment is replaced.

[0112] exist Figure 9 In FIG, only a portion of the entire papermaking system 700 is shown. Figure 9 706, and a post-drying section 708. Components of the first pre-drying section 702, the second pre-drying section 704, and a portion of the drying section 706 will now be described in further detail.

[0113] The first pre-drying section 702 has a metal ribbon 710 carrying the paper, which wraps around a felt belt 712 and a portion of a roller 714 of the second pre-drying section 704, clings to the felt belt 712, and wraps around a roller 716. The metal ribbon 710 moves in a clockwise direction.

[0114] The second pre-drying section 704 includes a felt belt 712 guided around a set of rollers, including rollers 714, 718, 720, 722, and 724. Felt belt 712 moves in a counterclockwise direction. Roller 720 presses felt belt 712 against roller 726 of the drying section 706, whereupon it is guided away from roller 726 by roller 722. Although not shown, after leaving roller 720, felt belt 712 is cleaned to remove residual fibers and any surface dirt. This cleaning may also include drying felt belt 712. Felt belt 712 is then compressed between rollers 724 and 726 before being guided away and returned to roller 714. In this embodiment, roller 724 serves as a pressurizing device. Optionally, felt belt 712 undergoes another round of cleaning after leaving roller 724. In a variation of this embodiment, felt belt 712 may be replaced by an impermeable belt. It is worth noting here that the felt belt is pressed against the roller 726 and the metal belt 728 of the drying section 706 at two different times. The relevance of this configuration will be discussed later.

[0115] The drying section 706 includes a metal belt 728 guided around a set of rollers including rollers 726 , 730 , and 732 , an IR meter unit 734 , an impingement dryer 735 , a heating element 736 , and a doctor blade 738 .

[0116] The operation of papermaking system 700 will now be described. It is assumed that the paper has been formed in a forming section (including a Fourdrinier machine), has passed through a pre-pressing section (not shown), and has passed through first pre-drying section 702 while positioned on the upper surface of felt belt 710. When metal belt 710 is pressed against felt belt 712 at roller 714, the paper enters second pre-drying section 704. Prior to entering pre-drying section 704, the paper may have a dryness level of, for example, between 55% and 65%. Both belts 710 and 712 move at the same speed and remain pressed together until they separate at rollers 716 and 718. At this point, the paper is transferred to felt belt 712, where it is compressed between roller 726, heated metal belt 728, felt belt 712, and roller 720. The compression action in this area transfers the paper from felt belt 712 to metal belt 728. Metal belt 728 and felt belt 712 move at the same speed.

[0117] The felt belt 712 is guided away from the metal belt 728 and roller 726, where it is cleaned / dried as described in the previous embodiment, and again compressed between rollers 724 and 726, the metal belt 728, and the paper carried by the metal belt 728. This has the effect of removing some of the moisture from the MG paper, as the cleaned and further dried felt belt 712 contains less moisture than before cleaning. The heated belt 728 carrying the paper, compressed by rollers 720 and 724, provides an ironing effect, giving the paper a glossy finish on one side.

[0118] It can be seen that Figure 9 The papermaking system 700 includes a second pre-drying section with a felt belt 712. This felt belt 712 transfers the wet tissue paper sheet it carries to a metal belt 728 and dries as much of the wet tissue paper sheet as possible before coming into contact with the wet tissue paper sheet carried by the metal belt 728 downstream. This helps further dry the wet tissue paper sheet by absorbing water from the wet tissue paper sheet. This sequence is the same as in the previously described embodiment. Also similar to the previously described embodiment, the wet tissue paper sheet is pressed against the felt belt 712 and roller 724 via the metal belt 728 and roller 726. The roller 726 can be controlled to press against the roller 724, and vice versa, to produce the same effect.

[0119] The metal belt 728 carrying the paper then passes over roller 730, which includes an IR meter 734 that corrects the moisture profile of the paper passing beneath it. The paper is then further dried by an impingement dryer 735 before being removed from the metal belt at roller 732 and fed into the post-drying section 708, where it is subsequently collected on a reel. At this point, the paper 740, due to its rigidity, does not require adjustment from the metal belt 728, so the scraper 738 is present only to prevent any stuck paper from re-entering the drying section 706 by scraping it off the metal belt 728. Returning to the second pre-drying section 704, the felt belt can optionally be cleaned again after leaving roller 724 before returning to roller 714 to repeat the process.

[0120] exist Figures 2 to 9 In all of the embodiments shown, the papermaking system dewaters and dries the paper product without the use of a large Yankee dryer and its required support components, thereby reducing complexity, maintenance costs, and overall costs. Figures 2 to 9 All embodiments can be operated at least at the same speed as current Yankee dryer systems, which is currently around 2000 m / min. By increasing the headbox pressure and a corresponding increase in belt speed, the present embodiments can achieve higher speeds while ensuring that the headbox design avoids any outlet lip deformation. Figures 2 to 5 All previously discussed variations and modifications of the embodiments can be applied to Figures 6 to 9 implementation method.

[0121] exist Figures 2 to 9 In the illustrated embodiment, the width of the wet tissue paper or MG paper is approximately the same as that of the heated metal belt. This ensures that the heat transfer from the metal belt to the applied wet tissue paper sheet is consistent across its width. If the wet tissue paper sheet is too narrow relative to the heated metal belt (referred to herein as constriction), the edges of the wet tissue paper sheet and the uncovered areas of the metal belt may overheat because the exposed metal belt edges are not cooled by the wet paper web after the metal belt is heated by the applied induction and / or impingement drying units. This causes the edges of the wet tissue paper sheet to dry more quickly and potentially separate from the metal belt. Furthermore, the exposed metal belt edges overheat, which negatively impacts the life of the metal belt. Therefore, the design parameters of the papermaking system can be selected to determine the maximum constriction of the wet tissue paper sheet edge relative to the metal belt edge without overdrying or with negligible negative impact on the wet tissue paper sheet edge and / or metal belt life. The width of the wet tissue paper sheet can be set by the forming section of the papermaking system according to embodiments of the present disclosure.

[0122] Alternatively, for Figures 2 to 9 In the embodiment shown, the wet tissue paper sheet can be formed to be wider than the heated metal belt so that the edges of the wet tissue paper sheet overlap relative to the edges of the metal belt. Figure 2 In the papermaking system 100, the wider wet tissue paper sheet disposed through the forming section is ultimately transferred by the belts 102 and 110 toward the roller 114. Because the wet tissue paper sheet is biased to adhere to the smooth surface of the heated metal belt, only the portion of the wet tissue paper sheet that clings to the metal belt 118 at the roller 114 is transferred to the metal belt 118. As a result, the wet tissue paper sheet width is now substantially the same as the metal belt width. The remaining overlapping wet tissue paper sheet edges remain on the felt belt 110. The aforementioned cleaning system of the felt belt 110 after the roller 114 and before the roller 116 can be configured to remove the remaining overlapping wet tissue paper sheet edges from the felt belt 110. Any suitable cleaning technology or system can be used to remove the maximum amount of wet tissue paper sheet fibers from the felt belt before the second contact with the wet tissue paper sheet carried by the metal belt.

[0123] A common feature of the aforementioned papermaking system embodiments is a pre-drying section and a drying section, which operate similarly to one another. Figure 10 The flowchart of FIG. 1 summarizes the common operating steps of the pre-drying section and the drying section of the described papermaking system embodiment.

[0124] Starting from step 800, use any suitable means to heat the metal belt. Next, at step 802, the previously formed wet tissue paper sheet carried by the felt belt is transferred to the heated metal belt, which immediately promotes the drying of the wet tissue paper sheet. After the wet tissue paper sheet is separated from the current wet felt belt, at step 804, any residual paper fibers of the felt belt are removed and the felt belt is dried. The dry felt belt is then pressed against the wet tissue paper sheet carried by the heated metal belt. Because the felt belt has been dried before, it will absorb the water currently in the wet tissue paper sheet. In addition, pressing the felt belt against the metal belt will promote that the drier felt belt absorbs more water. Then, at step 808, the wet tissue paper sheet is subjected to high-speed air drying, and the dry tissue paper sheet is subsequently removed from the metal belt.

[0125] While the previously described embodiments of the papermaking system are examples of tissue and MG paper production, other types of paper can be produced by adjusting the drying curve to accommodate different paper properties and basis weights, taking into account the type of pulp used. The previously disclosed embodiments show example configurations for various sections with a specific number of rollers arranged to guide the belt travel in various directions. It should be understood that variations of these examples can be implemented with different numbers of rollers in different arrangements to achieve the same end result for the sections. Note that the elements shown in the drawings of the disclosed embodiments are not necessarily to scale and are merely illustrative of the manner in which the papermaking system is intended to operate.

[0126] The dryness levels of the tissue or paper indicated at various stages of the above-described papermaking system embodiments are estimates only, and those skilled in the art will understand that adjustments to parameters and variations of the above-described embodiments to include additional elements may result in different dryness levels for the tissue or paper.

[0127] In the preceding description, for purposes of explanation, numerous details were set forth in order to provide a thorough understanding of the embodiments.

[0128] The above embodiments are intended to be illustrative only. Those skilled in the art may make changes, modifications, and variations to the specific embodiments. The scope of the claims should not be limited by the specific embodiments described herein, but should be interpreted in a manner consistent with the specification as a whole.

Claims

1. An apparatus configured to form a paper product from a stock suspension, comprising: A forming section, the forming section comprising: at least one water-permeable belt configured to receive the stock suspension from the headbox and form at least one side of the paper product to provide a wet paper product sheet; A pre-drying section, the pre-drying section comprising: a water-absorbing belt arranged to move continuously around a first set of rollers configured to receive the wet paper product sheet, the water-absorbing belt being configured to initially absorb water from the wet paper product sheet upon contact, and being configured to subsequently transfer the wet paper product sheet to a heated metal belt, a first roller of the first set of rollers that directs the absorbent belt away from the metal belt after the wet paper product sheet is transferred to the metal belt; a water removal device configured to dry the water-absorbing belt after it is directed away from the metal belt; a pressing device configured to press the absorbent belt against the wet paper product sheet carried by the metal belt; The drying section includes: a heating element for heating the metal belt prior to receiving the wet paper product sheet from the absorbent belt; the metal belt being arranged to move continuously around a second set of rollers, wherein the heated metal belt promotes drying of the wet paper product sheet after receiving the wet paper product sheet from the absorbent belt; and A drying device is configured to dry the wet paper product sheet carried by the metal belt downstream of the pressing device to provide a substantially dry paper product sheet. 2 . The apparatus of claim 1 , wherein the heating element comprises at least one of an induction-based heating element, an infrared-based heating element, and a hot air-based heating element.

3. The apparatus of claim 1, wherein the drying device comprises at least one of an impingement dryer and an infrared (IR) dryer.

4. The apparatus according to claim 1, wherein the drying section further comprises an infrared (IR) measurement unit to correct moisture distribution of the wet paper product sheet.

5. The apparatus according to claim 1 , wherein the pressing device is a second roller in the first set of rollers, and the metal belt carrying the wet paper product sheet is configured to cling to the absorbent belt when both the absorbent belt and the metal belt are around a portion of the circumference of the second roller.

6. The apparatus of claim 5, further comprising at least one press roller configured to apply pressure to the metal belt as the metal belt, the wet paper product sheet, and the absorbent belt surround the portion of the circumference of the second roller.

7. The apparatus of claim 6, wherein the at least one press roller is a small press roller.

8. The apparatus of claim 6, wherein the at least one press roller is a heavy duty press roller.

9. The apparatus of claim 6, wherein the at least one press roller comprises a small press roller and a heavy press roller.

10. The apparatus of claim 5, wherein the pressing apparatus is a shoe press.

11. The apparatus of claim 1 , further comprising a cleaning system for cleaning and drying the absorbent belt after the wet paper product is transferred to the metal belt.

12. The apparatus according to claim 1, wherein the drying section further comprises another heating element configured to heat the metal belt carrying the wet paper product sheet when the metal belt is in close contact with the absorbent belt.

13. The apparatus of claim 1 , wherein the forming section comprises: a single water-permeable belt arranged to move continuously around a third set of rollers and configured to cling to the water-permeable belt as it passes around a portion of the circumference of the third rollers, wherein The headbox is positioned to inject the stock suspension onto at least one of the single permeable belt and the suction belt before the single permeable belt abuts the suction belt.

14. The apparatus of claim 2, wherein the drying section comprises: a sprayer for spraying adhesive onto the metal belt before the metal belt receives the paper product from the absorbent belt, and A scraping device is configured to crepe the substantially dry paper product sheet and remove it from the metal belt downstream of the drying device.

15. The apparatus of claim 2, wherein the single water-permeable strip is a metal ribbon.

16. The apparatus of claim 2, wherein the absorbent belt is a felt belt.

17. The apparatus of claim 1 , wherein the forming section comprises: a first water-permeable belt arranged to move continuously around a third set of rollers and configured to abut against the second water-permeable belt as the second water-permeable belt surrounds a portion of the circumference of the third rollers, the wet paper product sheet being formed on both sides thereof by the first water-permeable belt and the second water-permeable belt, wherein The headbox is positioned to inject the stock suspension onto at least one of the first and second water-permeable belts before the single water-permeable belt abuts against the second water-permeable belt, The first water-permeable belt is configured to transfer the wet paper product sheet to the second water-permeable belt, and The second water-permeable belt is configured to transfer the wet paper product sheet to the water-absorbent belt.

18. The apparatus of claim 17, wherein the drying section comprises: a sprayer for spraying adhesive onto the metal belt before the metal belt receives the wet paper product sheet from the absorbent belt, and A scraping device is configured to crepe the substantially dry paper product sheet and remove it from the metal belt downstream of the drying device.

19. The apparatus of claim 17, wherein the first water-permeable belt is a first metal belt and the second water-permeable belt is a second metal belt.

20. The apparatus of claim 17, wherein the absorbent belt is a felt belt.

21. The apparatus of claim 1 , wherein the forming section comprises: A single water-permeable belt arranged to move continuously around a third set of rollers, wherein The headbox is positioned to inject the stock suspension onto the single permeable belt, and the single permeable belt is configured to transfer the paper product to the absorbent belt.

22. The apparatus of claim 21 , wherein the drying section comprises: A sprayer is used to spray a silicon-based type emulsion onto the metal belt before the metal belt receives the wet paper product sheet from the absorbent belt.

23. The apparatus of claim 21, wherein the forming section is configured as a Fourdrinier paper machine for dewatering the wet paper product sheet before transferring the wet paper product sheet to the absorbent belt.

24. The apparatus according to claim 1, wherein the forming section comprises a Fourdrinier papermaking machine configured to form the wet paper product sheet, the predrying section is a second predrying section, and the wet paper product is transferred from the Fourdrinier papermaking machine to the second predrying section after passing through a pre-pressing section and a first predrying section.

25. The apparatus of claim 24, wherein the drying section comprises: a third roller as part of the second set of rollers for guiding the metal belt, the third roller and the first roller being configured to hold the metal belt against the absorbent belt and transfer the wet paper product sheet to the metal belt, and The pressing device and the third roller are configured to press the metal belt carrying the wet paper product sheet against the absorbent belt.

26. The apparatus of claim 25, further comprising a cleaning system for cleaning the absorbent belt after it leaves the first roller and before the second roller presses the absorbent belt against the third roller.

27. A method for drying a wet paper product sheet in a papermaking system, comprising: Heating the metal strip; transferring the wet paper product sheet from the felt belt to the metal belt; drying the felt belt after transferring the wet paper product sheet to the metal belt; After drying the felt belt, placing the felt belt against the metal belt and the wet paper product sheet; as well as The wet paper product sheet is dried with high velocity air.

28. The method of claim 27, wherein heating the metal strip comprises any one of induction heating, infrared heating, and hot air based heating.

29. The method of claim 27, wherein drying the wet paper product sheet comprises any one of impingement drying and infrared (IR) drying.

30. The method of claim 27, wherein compacting the felt belt comprises surrounding a portion of a circumference of a roller with the felt belt and a metal belt carrying the wet tissue paper sheet, the felt belt being located between the roller and the metal belt.

31. The method of claim 30, further comprising applying pressure to the metal belt as the metal belt, the wet paper product sheet, and the absorbent belt surround the portion of the circumference of the roller.

32. The method of claim 27, wherein compacting the felt strip comprises operating a shoe press.

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