WO2024141917A1

WO2024141917A1 - Paper producing system

Info

Publication number: WO2024141917A1
Application number: PCT/IB2023/063206
Authority: WO
Inventors: Klaus Gissing; Petr Fisera; Adolf Gogg; Michael Pichler
Original assignee: Paper Excellence Canada Holdings Corporation
Priority date: 2022-12-28
Filing date: 2023-12-22
Publication date: 2024-07-04
Also published as: CA3184638A1

Abstract

A paper producing system consisting of at least three sections, where a first section forms a wet paper product sheet, which is then subjected to drying in a pre- drying section. A water absorbing belt of the pre-drying section transfers the wet paper product sheet to a heated metal belt, which starts drying the wet paper product sheet by promoting evaporation of the water within. The water absorbing belt is then guided away from the metal belt. The heated metal belt carrying the wet paper product sheet is then pressed against the same water absorbing belt, which is dryer than before it transferred the wet paper product sheet to the metal belt. This pressing action further dries the wet paper product by transferring more water into the dryer water absorbing belt. The wet paper product sheet is then further dried by impingement dryers and eventually collected on a reel.

Description

PAPER PRODUCING SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Canada Patent Application No. 3184638 filed on December 28, 2022, which is hereby incorporated by reference.

FIELD

[0002] The present disclosure relates generally to a machine for producing paper products. More specifically, the present disclosure relates to a system for producing tissue or paper sheets.

BACKGROUND

[0003] The manufacturing or production of paper products from a wet stock suspension, such as tissue paper, typically requires a very large and complex system. One such system is the well-known Yankee dryer system. FIG. 1 is a diagram of a Yankee dryer system, considered a primary component of a paper producing machine. The function of a Yankee dryer is to receive a wet paper product formed as an endless sheet, and through the application of heat, removes as much moisture from the wet paper product as needed so that the resulting dried paper product can be collected on a reel.

[0004] In FIG. 1 , the Yankee dryer system 10 includes a dryer cylinder (Yankee cylinder) 12 that rotates in the clockwise direction, a wet end hood 14 and a dry end hood 16. The cylinder 12 is made of steel or cast iron and configured to receive a high-pressure steam inside in order to heat its outer surface. Both hoods 14 and 16 include a hot air duct 18 and a moist air return duct 20, and both hoods 14 and 16 are configured to wrap around a substantial circumference of the cylinder 12 with sufficient spacing from the surface of the cylinder to allow for the passage of the wet paper product. Also shown in FIG. 1 is a felt belt 22 wrapped around a suction press roll 24, and a creping doctor with a crepe blade 26. The suction press roll 24 is configured to press the felt belt 22 against the surface of cylinder 12 and vice versa, as is an edge of the crepe blade 26. While not shown in FIG 1 , roller 24 can also be a shoe press with a suction roll positioned downstream before roller 24. Such a shoe press would have a predefined nip at a width configured to press the paper product against the surface of cylinder 12 to help dewatering.

[0005] In an example operation for producing tissue paper, wet stock suspension is first deposited on the outer surface of the felt belt 22 (not shown), thereby providing a wet sheet of tissue. The wet sheet of tissue is subjected to some dewatering (not shown) and then transferred onto the surface of cylinder 12 where the felt belt 22 and the surface of cylinder 12 make contact. Prior to transfer by pressing onto the surface of cylinder 12, the dryness of the tissue can be about 22% in state of the art systems, and the dryness after the press is about 45%, assuming a shoe press is used to transfer onto the cylinder 12. The surface of cylinder 12 can be sprayed with a special coating to promote adhesion of the wet sheet of tissue to it. Because the cylinder 12 is heated with steam from the inside, its heated surface will begin to dry the wet sheet of tissue up on it. At the same time, as the cylinder rotates the wet sheet of tissue is subjected to high velocity impingement of hot air supplied from the hot air ducts 18 as it passes within the arc of the wet end hood 14 and dry end hood 16. Moist air is removed via the moist air return ducts 20. The crepe blade 26 removes the substantially dried tissue paper from the surface of cylinder 12, while creping the tissue. Here, the tissue has a dryness exiting the Yankee dryer 12 of about 95%, in state of the art systems.

[0006] An example current state-of-the-art Yankee dryer system has the following specifications. The cylinder 12 can be within 10 to 24 feet in diameter and can weigh over 100 tons, where the total weight depends on the machine width. Pressurized steam of about 160 psi is provided to the inside of the cylinder. Fuel, electric or steam heated air is driven into the hot air ducts 18 with fan blowers, and moist air from the drying tissue is extracted by an exhaust fan. The rollers, belts and the cylinder 12 are configured to produce a tissue sheet 100 to 300 inches wide, and the system is operated within a range of 1 ,500 to 2,200 meters/min.

[0007] There are several disadvantages of Yankee dryer systems. These systems are extremely large, as evidenced by the stated dimensions above, thereby occupying significant amounts of space and increasing the cost for housing the system. This includes a massive foundation due to its weight. It should be noted that a network of piping is used to deliver hot air to the ducts 18 from burners or heat exchangers and to deliver the moist air from the ducts 20 to an area outside of the building housing the system. Yankee dryer systems are extremely energy intensive, as steam must be continuously generated to keep the surface of the cylinder 12 heated, a burner consuming fuel or gas is required to generate the hot air, and energy is required to power the blowers. Most systems are configured to reclaim heat from the extracted moist air from ducts 20, thereby further adding complexity, size and cost to the system.

[0008] Another significant disadvantage of Yankee dryer systems is its susceptibility to failures due to thermal, mechanical and pressure stresses, which inevitably lead to safety issues. Such failures can include steam leaks in the system delivering steam to the cylinder 12. General wear and tear of components supporting the cylinder 12 may seem minor, but due to its sheer size and weight, minor vibrations can lead to catastrophic failure if not immediately addressed. Explosions of the cylinder 12 and cracking of the cylinder have been documented in the past due to these thermal, mechanical and pressure stresses.

[0009] Most Yankee dryer systems use a well-known shoe press to help dewater the tissue paper when pressing against and transferring it onto cylinder 12. However there is always a trade-off between the quality of the tissue paper and the amount of energy required to dry it. More specifically, a lower nip pressure that is applied against the tissue paper will result in a sheet with more bulk which is desirable. However the sheet will be less dry thereby requiring more drying energy to complete the drying process. On the other hand a higher nip pressure that is applied against the tissue paper will result in a sheet with less bulk, but with higher dryness thereby requiring less energy to complete the drying process.

[0010] Another disadvantage of a Yankee dryer system is that the Yankee dryer is exposed to certain wear due to the permanent contact of the creping blade 26 which is pressed against the cylinder 12 to crepe the dried paper off. To keep a constant paper quality the Yankee dryer cylinder 12 surface needs to be ground to remove all imperfections, such as notches and/or grooves. This grinding can only be done while the cylinder 12 is in the machine, and is typically performed every 2 to 5 years. This presents a significant operational risk as well as additional production loss of about 2 to 5 days as the Yankee dryer and consequently the whole paper producing machine is taken out of service for this maintenance.

[0011] It is, therefore, desirable to provide a paper producing machine which can dry wet tissue that leads to the same performance of a Yankee dryer, but without the disadvantages that come with operation of a Yankee dryer.

SUMMARY

[0012] It is an object of the present disclosure to obviate or mitigate at least one disadvantage of previous paper producing systems.

[0013] In a first aspect, the present disclosure provides an apparatus configured to form a paper product from stock suspension. The apparatus includes a forming section, a pre-dryer 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-dryer section includes a water absorbing belt arranged to continuously move around a first set of rollers configured to receive the wet paper product sheet, the water absorbing belt configured to start absorbing water of the wet paper product sheet upon contact and configured to subsequently transfer the wet paper product sheet to a heated metal belt, a first roller of the first set of rollers guiding the water absorbing belt away from the metal belt after the wet paper product sheet is transferred to the metal belt. Included in this section is a water removing device configured to dry the water absorbing belt after being guided away from the metal belt. The pre-dryer section further includes a pressing apparatus configured to press the water absorbing belt against the wet paper product sheet carried by the metal belt. The drying section includes heating elements for heating the metal belt before the wet paper product sheet is received from the water absorbing belt, where the metal belt is arranged to continuously move around a second set of rollers, wherein the heated metal belt facilitates drying of the wet paper product sheet after receiving the wet paper product sheet from the water absorbing belt. The drying section further includes a drying device configured to dry the wet paper product sheet carried by the metal belt downstream of the pressing apparatus to provide a substantially dried paper product sheet.

[0014] According to embodiments of the first aspect, the heating elements include at least one of induction based, infrared based and hot air based heating elements. For this embodiment, the drying section can include a sprayer for spraying an adhesive onto the metal belt before the metal belt receives the paper product from the water absorbing belt, and a doctoring device configured to crepe and remove the substantially dried paper product sheet from the metal belt downstream of the drying device. Alternatively for this embodiment, the single water permeable belt is a wire belt or the water absorbing belt is a felt belt.

[0015] In another embodiment, the drying device includes at least one of an impingement dryer and/or an infrared (IR) dryer. Additionally, the drying section can further include an infrared (IR) profiling unit to correct a moisture profile of the wet paper product sheet.

[0016] According to further embodiments of the first aspect, the pressing apparatus is a second roller of the first set of rollers, and is configured to press against the water absorbing belt while both the water absorbing belt and the metal belt encircles the portion of the circumference of the second roller. In this embodiment, at least one press roller is further included and configured to apply pressure against the metal belt while the metal belt, the wet paper product sheet and the water absorbing belt encircles the portion of the circumference of the second roller. The at least one press roller can be a small press roller, a heavy duty press roller, or the combination of a small press roller and a heavy duty press roller. The pressing apparatus can be a shoe press.

[0017] Alternately, the drying section further includes another heating element configured to heat the metal belt carrying the wet paper product sheet as it is pressed against the water absorbing belt.

[0018] In another embodiment of the first aspect, a cleaning system is included for cleaning the water absorbing belt after the wet paper product is transferred to the metal belt.

[0019] In yet a further embodiment of the first aspect, the forming section includes a single water permeable belt arranged to continuously move around a third set of rollers and configured to be pressed against the water absorbing belt while the water absorbing belt encircles a portion of a circumference of a third roller, wherein the headbox is positioned to inject the stock suspension onto at least one of the single water permeable belt and the absorbing belt before the single water permeable belt is pressed against the water absorbing belt.

[0020] According to an embodiment of the first aspect, the forming section includes a first water permeable belt arranged to continuously move around a third set of rollers and configured to be pressed against a second water permeable belt while the second water permeable belt encircles a portion of a circumference of a third roller, 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 water permeable belt and the second water permeable belt before the single water permeable belt is pressed against the second water permeable belt, the first water permeable belt is configured to transfer the wet paper product sheet onto the second water permeable belt, and, the second water permeable belt is configured to transfer the wet paper product sheet onto the water absorbing belt. [0021] For this embodiment, the drying section includes a sprayer for spraying an adhesive onto the metal belt before the metal belt receives the wet paper product sheet from the water absorbing belt, and a doctoring device configured to crepe and remove the substantially dried paper product sheet from the metal belt downstream of the drying device.

[0022] Also for this embodiment, the first water permeable belt can be a first wire belt and the second water permeable belt is a second wire belt. Alternately, the water absorbing belt can be a felt belt.

[0023] According to yet another embodiment of the first aspect, the forming section includes a single water 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 water permeable belt and the single water permeable belt is configured to transfer the paper product onto the water absorbing belt. In this embodiment, the drying section can include a sprayer for spraying a silicon-based type of emulsion onto the metal belt before the metal belt receives the wet paper product sheet from the water absorbing belt. In this embodiment, the forming section can be configured as a Fourdrinier machine for dewatering the wet paper product sheet before transferring the wet paper product sheet onto the water absorbing belt. [0024] In a further embodiment of the first aspect, the forming section includes a Fourdrinier configured to form the wet paper product sheet, the pre-dryer section is a second pre-dryer section, and the wet paper product is transferred from the Fourdrinier to the second pre-dryer section after passing through a pre-press section and a first pre-dryer section. Here the drying section can include 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 press the metal belt against the water absorbing belt and to transfer the wet paper product sheet onto the metal belt, and the pressing apparatus and the third roller are configured to press the metal belt carrying the wet paper product sheet against the water absorbing belt. According to an aspect of the present embodiment, a cleaning system can be included for cleaning the water absorbing belt after the water absorbing belt leaves the first roller and before the water absorbing belt is pressed against the third roller by the second roller.

[0025] In a second aspect, the present disclosure provides a method for drying a wet paper product sheet in a paper producing system. The method includes heating a metal belt; transferring a 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; pressing the felt belt against the metal belt and the wet paper product sheet after drying the felt belt; and, drying the wet paper product sheet with high velocity air.

[0026] According to embodiments of the second aspect, heating the metal belt includes 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 includes any one of impingement drying and an infrared (IR) drying.

[0027] In yet another embodiment of the second aspect, pressing the felt belt includes encircling a portion of a circumference of a roller with the felt belt and metal belt carrying the wet tissue sheet, with the felt belt positioned between the roller and the metal belt. This embodiment can further include applying pressure against the metal belt while the metal belt, the wet paper product sheet and the water absorbing belt encircles the portion of the circumference of the roller. Alternately, pressing the felt belt includes operating a shoe press.

[0028] Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures.

[0030] FIG. 1 is a diagram of a Yankee dryer system, according to the prior art; [0031] FIG. 2 is a diagram of a paper producing system in a crescent former configuration, according to a present embodiment;

[0032] FIG. 3 is a diagram of a paper producing system in a C-wrap former configuration, according to a present embodiment;

[0033] FIG. 4 is a diagram of a paper producing system in a MG former configuration, according to a present embodiment;

[0034] FIG. 5 is a diagram of a paper producing system in an S-wrap former configuration, according to a present embodiment;

[0035] FIG. 6 is a diagram of a paper producing system in a crescent former configuration, according to a first alternate embodiment;

[0036] FIG. 7 is a diagram of a paper producing system in a crescent former configuration, according to a second alternate embodiment;

[0037] FIG. 8 is a diagram of a paper producing system in a crescent former configuration, according to a third alternate embodiment;

[0038] FIG. 9 is a diagram of a paper producing system configured for producing MG paper, according to a present embodiment; and,

[0039] FIG. 10 is a flow chart summarizing the operation of the pre-drying and drying sections of the previously described embodiments.

DETAILED DESCRIPTION

[0040] 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.

[0041] As used herein, the term “about” refers to a typical margin of error for a given value for the described technology and context. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.

[0042] The term “plurality” as used herein means more than one, for example, two or more, three or more, four or more, and the like. [0043] The use of the word “a” or “an” when used herein in conjunction with the term “comprising” may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”.

[0044] As used herein, the terms “comprising”, “having”, “including”, and “containing”, and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, unrecited elements and/or method steps. The term “consisting essentially of” when used herein in connection with an apparatus, system, composition, use or method, denotes that additional elements and/or method steps may be present, but that these additions do not materially affect the manner in which the recited apparatus, system composition, method or use functions. The term “consisting of’ when used herein in connection with an apparatus, system, composition, use or method, excludes 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, in certain embodiments consist essentially of those elements and/or steps, and in other embodiments consist of those elements and/or steps, whether or not these embodiments are specifically referred to.

[0045] Generally, the present disclosure provides a paper producing system which does not use a Yankee dryer, but instead uses a heated metal belt in a novel arrangement with a felt belt to dry a wet paper product sheet.

[0046] The paper producing system of the present embodiments consist of at least three sections, where a first section forms a wet paper product sheet, which is then subjected to drying in a pre-drying section. A water absorbing belt of the predrying section transfers the wet paper product sheet to a heated metal belt of a drying section, and the water absorbing belt is then guided away from the metal belt. The heated metal belt carrying the wet paper product sheet is then pressed against the same water absorbing belt, which is dryer than before it transferred the wet paper product sheet to the metal belt to absorb additional water from the wet paper product sheet. The wet paper product sheet is then further dried by impingement dryers and eventually collected on a reel. [0047] According to a present embodiment, the first section is a forming section that deposits wet stock suspension from a headbox onto one or two water permeable belts to form at least one side of a wet paper product sheet.

[0048] 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 removal of water from the wet paper product sheet.

[0049] The third section is a drying section having a heated metal belt that receives the wet paper product sheet from the water absorbing belt of the second section. In this drying section, the water absorbing belt is subjected to drying after releasing the wet paper product sheet to the metal belt to remove water absorbed from the wet paper product sheet. The water absorbing belt then wraps around a roller, and the metal belt carrying the wet paper product sheet is pressed against the water absorbing belt while both the water absorbing belt and the metal belt encircles a portion of the circumference of the roller. The dryer water absorbing belt receives more water from the wet paper product sheet pressed against it by the metal belt. Now the substantially dryer paper product sheet is subjected to heated air drying to further dry it before it is removed from the metal belt by a crepe blade.

[0050] FIG. 2 is a diagram of a paper producing system, according to a present embodiment. More specifically, the presently shown paper producing system is shown in a crescent former configuration for producing a wet paper product sheet such as tissue paper. The crescent former paper producing system 100 consists of the previously mentioned 3 sections that were generally described. First is a discussion of the components of each section, followed by a description of the operation of the sections as they cooperate with each other.

[0051] Starting at the left side of FIG. 2, is the forming section that includes a water permeable belt such as a wire belt 102, rollers in contact with an inner surface of belt 102 of which rollers 106 and 108 are labelled, and a headbox 104 that receives and deposits stock suspension as a wet tissue sheet. In the presently shown configuration, the wire belt 102 moves in the clockwise direction and has an outer surface that receives the wet stock from the headbox 104. The wire belt 102 enables drainage of water through it.

[0052] The pre-drying section includes a water absorbing belt such as a felt belt 110 and a set of rollers of which rollers 112, 114 and 116 are labelled, for guiding the path of the water absorbing belt. Here the felt belt 110 can be a felt belt that absorbs water. The felt belt 110 moves in the counterclockwise direction. The roller 114 is configured to have an integrated water suctioning system to remove as much water as possible from both any wet tissue sheet on the felt belt 110 and the felt belt 110 itself. While not shown in FIG. 2, the pre-drying section can include at least one further supplemental water suctioning system configured and positioned to remove water from both any wet tissue sheet on the felt belt 110 and the felt belt 110 itself. Turning to the left side of the pre-drying section, the wire belt 102 is configured to wrap over and around felt belt 110 and roller 112, thereby encircling a portion of the circumference of roller 112. As shown in FIG. 2, the headbox 104 is positioned at a region where the surfaces of rollers 106 and 112 are adjacent to each other to begin pressing of the belts 102 and 110 against each other.

[0053] The drying section includes a metal belt 118 and rollers in contact with an inner surface of the metal belt 118, of which rollers 120, 122, 123 and 124 are labelled. The metal belt 118 can be very thin, in the millimeter range by example. The drying section further includes heating elements 126 for heating the metal belt to a temperature in the range of 105°C - 150°C, an impingement dryer 128 to force hot air towards the outer surface of the metal belt 118, an infrared (IR) profiling unit 129 positioned around a portion of roller 124, and a creping doctor 130 positioned proximate to roller 120 and having an edge in contact with the metal belt 118. The heating elements 126 can be induction based, infrared based, or hot air based, but any type of heating element for heating the metal belt can be used. It is noted that a thinner metal belt 118 is more quickly heated through its thickness to the desired temperature. The impingement dryer can alternately be an IR dryer or include an IR dryer in combination with an air impingement dryer. While not shown in FIG. 2, a sprayer is positioned to spray an adhesive type liquid onto the surface of the metal belt to promote adhesion with the wet tissue sheet.

[0054] In the presently shown configuration of FIG. 2, the metal belt 118 and the same felt belt 110 are pressed against each other at two different places. The first place the two belts 110 and 118 are pressed against each other occurs in the region between rollers 114 and 122. Then both belts 110 and 118 are separated from each other, where they are pressed against each other again around roller 116.

Accordingly, roller 116 functions as a pressing apparatus as it tensions the metal belt 118 to thereby press the metal belt against it with the felt belt 110 and wet tissue sheet in between. In particular, the felt belt 110 wraps around an outer surface of roller 116 and the metal belt 118 carrying the wet tissue sheet is pressed against the felt belt 110, both encircling a portion of the circumference of the roller 116. The nip wrapping angle of belts 110 and 118 can be at a minimum 30° and up to a maximum of 210°. The nip wrapping angle is defined as the angle between the first and last contact point of a belt while travelling over a roller.

[0055] Generally, the larger the nip wrapping angle, drying performance is improved. Another advantage of the described system of the present embodiments is that each 1 % increase in dryness that is achieved will save approximately 3% to 4% of energy required by the drying elements, such as the metal belt heating elements 126 and the impingement dryer 128, to dry the finished tissue paper to the desired level.

[0056] There is optionally included a small press roller 123, which is movable to apply localized pressure upon the metal belt 118, the wet tissue sheet, the felt belt 110 and roller 116. The small press roller 123 is positioned to apply this localized pressure to press water from the wet tissue 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 increases the dryness of the wet tissue sheet.

[0057] Now the operation of the paper producing machine 100, namely the crescent former paper producing machine 100, for producing tissue paper is described. Such tissue paper can have a basis weight from 10-40 g/m². [0058] The process starts at the left-hand side of FIG. 2 with the abovedescribed forming section. The headbox 104 injects or deposits the wet stock onto at least one of the wire belt 102 and the felt belt 110, such that the wet stock is trapped between both belts 102 and 110 as both belts begin to be pressed against each other at roller 112. The temperature of wet stock suspension can be maintained between 45 to 65 °C. Roller 106 is positioned such that there is a small gap between it and roller 112, for the purposes of defining an entering angle of belt 102 as it approaches roller 112. Prior to the dewatering by centrifugal force and pressing, the dryness content of the wet stock can be about 0.2%. The wet stock is pressed against the felt belt 110 by the wire belt 102 for the duration of time that both belts 102 and 110 are wrapped around roller 112, thereby forming a wet paper product sheet, in this embodiment being a wet tissue sheet. It is noted that the felt belt 110 immediately begins to absorb water from the wet tissue sheet upon contact and allows discharge of excess water through it. Because the wire belt 102 is pressed with tension against both the felt belt 110 and roller 112, some excess water in the wet tissue sheet is further pressed out. It is assumed that both the wire belt 102 and the felt belt 110 move at the same speed.

[0059] Eventually both the wire 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 leaving the forming section. The dryness content of the wet tissue sheet after the pressing effect and centrifugal force dewatering of belts 102 and 110 around roller 112 is increased, and can be about 12%-14% by example. The felt belt 110 now carries the wet tissue sheet in the pre-drying section towards roller 114, which as previously described can have an integrated water suctioning system. Accordingly, as the felt belt 110 makes contact with a surface of roller 114, water is removed from both the wet tissue sheet on the felt belt 110 and from the felt belt 110 itself. The size of roller 114, the speed of movement of the felt belt 110, and the water suction power can be configured to further increase the dryness content of the wet tissue sheet, by example, to between 20%-22% before the wet tissue sheet makes contact with the metal belt 118. In one example, the roll diameter of roller 114 can be between 800mm to 1500mm, the minimum vacuum level applied can be 0.2 bar, and the amount of vacuum in m³/min is determined by the open area of roller 114 and design of the felt belt 110. Those of skill in the art will understand that various combinations of the roll diameter, belt tension and the working width can be set to achieve a desired dryness content of the wet tissue sheet before it makes contact with the metal belt 118.

[0060] At roller 114, the felt belt 110 is pressed against the heated metal belt 118 resulting in the wet tissue sheet on the felt belt 110 transferring onto 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 drying of the wet tissue sheet upon it, by evaporating the water within. Simulations have shown that the drying effect of the heated metal belt can account for at least 50% of total drying of the wet tissue sheet. After the wet tissue sheet is transferred to the metal belt 118, the wet tissue sheet now enters the drying section and the felt belt 110 is moved away from the metal belt 118. It is noted here that after transferring the wet tissue sheet to the metal belt 118, the felt belt 110 is now dryer than before the wet tissue sheet was transferred to the metal belt 118. The felt belt 110 can be optionally subjected to further drying after it leaves roller 114, either by another water suctioning device and/or an air impingement dryer, with the purpose of drying the felt belt 110 as much as possible.

[0061] Further downstream, the metal belt 118 carrying the wet tissue sheet and the drier felt belt 110 meet up 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 technique for drying the wet tissue sheet using tension of the metal belt 118 around the wet tissue sheet against the felt belt 110 and roller 116 provides low peak pressure resulting in the preservation of as much possible bulk in the tissue while attaining comparable dewatering when using a press nip. [0062] Increased tension of the metal belt 118 around roller 116 increases the dryness of the wet tissue sheet, however increased tension also degrades the lifetime of the metal belt 118 and the rollers. For this reason, certain embodiments can use the small press roller 123 to remove more water from the wet tissue sheet without needing to increase the tension of the metal belt 118. Because the small press roller 123 is movable, different implementations can use different combinations of applied pressure of small press roller 123 and the tension of metal belt 118 to achieve a desired dryness for an acceptable reliability of the metal belt 118 and the rollers it travels upon. In some embodiments, the small press roller 123 is not included.

[0063] Eventually the felt belt 110 and the metal belt 118 separate after completing their rotation around roller 116. The metal belt 118 carrying the dryer wet tissue sheet proceeds towards roller 124 while the felt belt 110 is moved towards roller 112 to repeat the process. While not shown, prior to the felt belt 110 reaching roller 112 to repeat the process, the felt belt 110 is cleaned to wash out residual fibers and any surface dirt by a cleaning system (not shown). Common cleaning systems in the art include the use of high-pressure showers and vacuums to assist drying of the felt belt 110. Such a cleaning system can be located at a position after the felt belt 110 leaves the roller 114, but before the felt belt 110 makes contact with the next roller, otherwise any remaining fibers on the felt belt will get pressed into the felt belt by the next roller thereby creating unwanted deposits. Alternately, such a cleaning system can be located at a position before the felt belt 110 makes contact with the metal belt 118 at roller 116.

[0064] Meanwhile, the metal belt 118 enters the profiling unit 129 which senses and corrects the moisture profile of the paper sheet. It is configured to individually control heating of preset zones, by example 100mm width regions along its width, to adjust the dryness profile of the paper sheet. The metal belt with the paper sheet then enters a high temperature impingement dryer 128 to complete the drying process. The impingement dryer 128 temperature and air flow rate in combination with the movement speed of the metal belt 118 and the profiling unit 129 can be configured to ensure that the dryness level of the tissue sheet reaches at least 92%. The dried tissue sheet is then removed from the metal belt 118 at roller 120 by the creping doctor 130, and collected on a reel (not shown).

[0065] In an alternate embodiment, the paper producing machine 100 in FIG. 2 can be configured in a C-wrap former configuration for producing a wet paper product such as tissue paper as shown in FIG. 3. The C-wrap former paper producing system 200 of FIG. 3 consists of the previously mentioned 3 sections that were generally described. First is a discussion of the components of each section, followed by a description of the operation of the sections as they cooperate with each other.

[0066] Starting at the left side of FIG. 3, is the forming section that includes a first water permeable belt such as a first wire belt 202, a second water permeable belt such as a second wire belt 204, rollers for guiding each of the wire belts 202 and 204, and a headbox 206 that receives and deposits stock suspension. The first wire belt 202 is guided by rollers, of which rollers 208 and 209 are labelled. The second wire belt 204 is guided by four rollers, of which rollers 210 and 212 are labelled. In the presently shown configuration, the first wire belt 202 enables drainage of water through it and moves in the counterclockwise direction. The second wire belt 204 also enables drainage of water through it and moves in the clockwise direction.

[0067] The second wire belt 204 is configured to wrap around the outer surface of roller 210, while the first wire belt 202 is configured to wrap over and around the second wire belt 204 and roller 210, thereby encircling a portion of the circumference of roller 210. As shown in FIG. 3, the headbox 206 is positioned at a region where the surfaces of rollers 208 and 210 are adjacent to each other. Roller 208 is positioned such that there is a small gap between it and roller 210, for the purposes of defining an entering angle of belt 202 as it approaches roller 210.

[0068] The pre-drying section includes a water absorbing belt such as a felt belt 214 and a set of rollers of which rollers 216, 218 and 220 are labelled, for guiding the path of the felt belt 214. It is noted that rollers 218 and 220 can be the same as rollers 114 and 116 respectively from FIG. 2, where roller 220 functions as a pressing apparatus. The felt belt 214 moves in the counterclockwise direction. The roller 218 is configured to have an integrated water suctioning system to remove as much water as possible from both any wet paper product on the felt belt 214 and the felt belt 214 itself. While not shown in FIG. 3, the pre-drying section can include at least one further supplemental water suctioning system configured and positioned to remove water from both any wet paper product on the felt belt 214 and the felt belt 214 itself. Turning to the left side of the pre-drying section, roller 216 with the felt belt 214 is positioned to slightly press into the second wire belt 204 to pick up the wet paper product.

[0069] The drying section can be configured the same as the one shown in the embodiment of FIG. 2, therefore the same reference numbers are used and the same corresponding descriptions and operations thereof apply.

[0070] Now the operation of the paper producing machine 200, namely the C- wrap former paper producing machine 200, for producing tissue paper is described. [0071] The process starts at the left-hand side of FIG. 3 with the abovedescribed forming section. The headbox 206 injects or deposits the wet stock onto at least one of the first wire belt 202 and the second wire belt 204, such that the wet stock is trapped between both belts 202 and 204 as both belts begin to be pressed against each other as they wrap around roller 210. The temperature of wet stock suspension can be maintained between 45 to 65 °C. Prior to the pressing, the dryness content of the wet stock can be about 0.2%. The wet stock is pressed against the second wire belt 204 by the first wire belt 202 for the duration of time that both belts 204 and 202 are wrapped around roller 210, thereby forming a wet paper product sheet, in this embodiment being a wet tissue sheet. Because the first wire belt 202 is pressed with tension against both the second wire belt 204 and roller 210, some excess water in the wet tissue sheet is pressed out. It is assumed that both the first wire belt 202 and the second wire belt 204 move at the same speed. Eventually both the first wire belt 202 and the second wire belt 204 separate after roller 210 at a point defined by roller 209, with the wet tissue sheet adhering to the outer surface of the second wire belt 204 with the aid of a suction box (not shown). [0072] The wet tissue sheet is carried to roller 212, where the wet tissue sheet is transferred to the outer surface of felt belt 214 as the felt belt 214 is pressed against the second wire belt 204. The wet tissue sheet has now left the former section. The felt belt 214 and the second wire belt 204 move at the same speed. [0073] It is noted that the dryness content of the wet tissue sheet after the pressing effect of belts 202 and 204 around roller 210, and transportation of the wet tissue on the second wire belt 204, can be about 12%-16% for example. The felt belt 214 now carries the wet tissue sheet in the pre-drying section towards roller 218, which as previously described can have an integrated water suctioning system. Accordingly, as the felt belt 214 makes contact with a surface of roller 218, water is removed from both the wet tissue sheet on the felt belt 214 and from the felt belt 214 itself. The size of roller 218, the speed of movement of the felt belt 214, and the water suction power can be configured to increase the dryness content of the wet tissue sheet, by example, to between 20%-22% before the wet tissue sheet makes contact with the metal belt 118. The roll diameter of roller 218 can be between 800mm to 1500mm, the minimum vacuum level applied can be 0.2 bar, and the amount of vacuum in m³/min is determined by the open area of roller 218 and design of the felt belt 214. Those of skill in the art will understand that various combinations of the roll diameter, belt tension and the working width can be set to achieve a desired dryness content of the wet tissue sheet before it makes contact with the metal belt 118.

[0074] Once the wet tissue sheet has been transferred to the metal belt 118, which moves at the same speed as felt belt 214, the wet tissue sheet follows the same path as in the embodiment of FIG. 2 and interacts with felt belt 214 in the same way that metal belt 118 interacts with felt belt 110 in the embodiment of FIG. 2. Eventually the dried tissue sheet is removed from the metal belt 118 at roller 120 by the creping doctor 130, and collected on a reel (not shown). Ideally, the dryness level of the final tissue sheet should be at least 92%.

[0075] Returning to the pre-drying section, after roller 220 the felt belt 214 is moved towards roller 216 to repeat the process, and is cleaned as described for the previous embodiment of FIG. 2. In an optional variation of the present embodiment of FIG. 3, the felt belt 214 can be subjected to further drying by any suitable means after being cleaned and before reaching roller 216. This will allow more initial absorption of water from the wet stock deposited by headbox 206.

[0076] In another alternate embodiment, the paper producing machine 100 in FIG. 2 can be configured in a MG former configuration for producing machine glazed paper as shown in FIG. 4. The MG former paper producing system 300 of FIG. 4 consists of the previously mentioned 3 sections that were generally described. First is a discussion of the components of each section, followed by a description of the operation of the sections as they cooperate with each other.

[0077] Starting at the left side of FIG. 4, is the forming section that includes a water permeable belt such as a wire belt 302, rollers for guiding the wire belt 302 of which rollers 304, 306 and 308 are labelled, and a headbox 310 that receives and deposits stock suspension. In the presently shown configuration, the wire belt 302 enables drainage of water through it and moves in the clockwise direction.

[0078] As shown in FIG. 4, the headbox 310 is positioned proximate to roller 304 for depositing the stock suspension onto the wire belt 302. The length of the flat portion of wire belt 302 is preset to ensure that water drains passively by gravity through the open mesh of the wire belt 302, negative pressure created by foils located under belt 302 (not shown), and finally by vacuum dewatering boxes also located below belt 302 (not shown) so that the dryness level of the wet paper sheet upon it reaches, for example, about 22% by the time it is transferred to the pre-drying section.

[0079] The pre-drying section includes a water absorbing belt such as a felt belt 312 and a set of rollers of which rollers 314, 316 and 318 are labelled, for guiding the path of the felt belt 312. It is noted that rollers 316 and 318 can be the same as rollers 114 and 116 respectively from FIG. 2, where roller 318 functions as a pressing apparatus. The felt belt 312 moves in the counterclockwise direction. The roller 316 is configured to have an integrated water suctioning system to remove as much water as possible from both any wet paper product on the felt belt 312 and the felt belt 312 itself. While not shown in FIG. 3, the pre-drying section can include at least one further supplemental water suctioning system configured and positioned to remove water from both 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 placed adjacent to the downward sloping section of the wire belt 302 between rollers 306 and 308, such that the felt belt 312 and the wire belt 302 are pressed against each other. To assist pick up of the wet paper sheet from the wire belt 302, roller 314 includes a suction element.

[0080] The drying section can be configured the same as the one shown in the embodiment of FIG. 2, therefore the same reference numbers are used, and the same corresponding descriptions and operations thereof apply.

[0081] Now the operation of the paper producing machine 300, namely the MG former paper producing machine 300, for producing MG paper is described. Such MG paper can have a basis weight from 20-120 g/m² by example.

[0082] The process starts at the left-hand side of FIG. 4 with the abovedescribed forming section. The headbox 310 injects or deposits the wet stock onto the wire belt 302, such that the wet stock sits atop the wire belt 302, thereby forming a wet paper sheet while travelling towards roller 306. The temperature of wet stock suspension can be maintained between 45 to 65 °C. The dryness content of the wet paper sheet starts at about 1 % just after being deposited on the wire belt 302, and through gravity, foils and vacuum boxes below belt 302 the water in the wet paper sheet will start to drain through the mesh of the wire belt 302.

[0083] The wet paper sheet is carried to roller 314, where the wet paper sheet is transferred to the outer surface of felt belt 312 as the felt belt 312 is pressed against the wire belt 302. The wet paper sheet has now left the former section. The felt belt 312 and the wire belt 302 move at the same speed.

[0084] It is noted that the dryness content of the wet paper sheet prior to transfer onto the felt belt 312 can be for example, about 22%. The felt belt 312 now carries the wet paper sheet in the pre-drying section towards roller 316, which as previously described can have an integrated water suctioning system. Accordingly, as the felt belt 312 makes contact with a surface of roller 316, water is removed from both the wet paper sheet on the felt belt 312 and from the felt belt 312 itself. The size of roller 316, the speed of movement of the felt belt 312, and the water suction power can be configured to increase the dryness content of the wet paper sheet to, by example, about 30% before the wet paper sheet makes contact with the metal belt 118. The roll diameter of roller 318 can be between 800mm to 1500mm, the minimum vacuum level applied can be 0.2 bar, and the amount of vacuum in m³/min is determined by the open area of roller 318 and design of the felt belt 312. Again, the parameters mentioned for the previous embodiments can be set with different combinations to attain the desired dryness content of the paper sheet.

[0085] Once the wet paper sheet has been transferred to the metal belt 118, which moves at the same speed as felt belt 312, the wet paper sheet follows the same path as in the embodiment of FIG. 2 and interacts with felt belt 312 in the same way that metal belt 118 interacts with felt belt 110 in the embodiment of FIG. 2. One difference over the previous embodiment is that instead of spraying an adhesive type of liquid onto the metal belt 118, a type of chemical that allows the wet paper sheet to shrink along its width dimension while on the heated metal belt 118 is applied instead. The shrinking of the wet paper sheet occurs as it dries due to the heated metal belt 118 that promotes evaporation of the water. An example of such a chemical is a silicon-based type of emulsion. In this particular embodiment, the heated metal belt not only helps dry the wet paper sheet, but it also provides an ironing effect as the wet paper sheet shrinks and slides width-wise on the heated metal belt to give the resulting paper sheet its desired glossy surface.

[0086] Eventually 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 sheet is more rigid than tissue paper from the previous embodiments, it simply separates from the metal belt 118 due to the curvature of roller 120 without making contact with creping doctor 130. The creping doctor 130 in this embodiment functions more like a protection device to prevent any part of the dried paper sheet from sticking to the metal belt 118. Ideally, the dryness level of the final paper sheet should be at least 90%. [0087] Returning to the pre-drying section, after roller 318 the felt belt 312 is moved towards roller 314 to repeat the process. In an optional variation of the present embodiment of FIG. 4, the felt belt 312 can be subjected to further drying by any suitable means after being cleaned and before reaching roller 314. This will allow more initial absorption of water from the wet stock deposited by headbox 310.

[0088] According to an alternate embodiment, the drying section can be modified to include another heating element arranged proximate to the metal belt 118 as it encircles roller 318 (or rollers 116 and 220 of the other embodiments), to apply additional heat to the metal belt to compensate for any heat loss since the earlier application of heat by the heating element 126.

[0089] In an alternate embodiment, the paper producing machine 100 in FIG. 2 can be configured in an S-wrap former configuration for producing tissue paper as shown in FIG. 5. The S-wrap former paper producing system 400 of FIG. 5 consists of the previously mentioned 3 sections that were generally described. The main difference over the C-wrap configuration of FIG. 3 is the “S” shaped path followed by both water permeable belts in the forming section. First is a discussion of the components of each section, followed by a description of the operation of the sections as they cooperate with each other.

[0090] Starting at the left side of FIG. 5, is the forming section that includes a first water permeable belt such as a first wire belt 402, a second water permeable belt such as a second wire belt 404, rollers for guiding each of the wire belts 402 and 404, and a headbox 406 that receives and deposits stock suspension. The first wire belt 402 is guided by rollers, of which rollers 410 and 408 are labelled. The second wire belt 404 is guided by four rollers, of which rollers 412, 414 and 416 are labelled. In the presently shown configuration, the first wire belt 402 enables drainage of water through it and moves in the counterclockwise direction. The second wire belt 404 also enables drainage of water through it and moves in the clockwise direction.

[0091] The first wire belt 402 is configured to wrap around the outer surfaces of rollers 410 and 412 at which is also wraps over wire belt 404, while the second wire belt 404 is configured to wrap around the outer surface of roller 414 before wrapping over and around the first wire belt 402 and rollers 410 as well as over roller 412. Therefore both the first wire belt 402 and the second wire belt 404 encircles a portion of the circumference of rollers 410 and 412. As shown in FIG. 5, the headbox 406 is positioned at a region where the surfaces of rollers 410 and 414 are adjacent to each other. Roller 414 is positioned such that there is a small gap between it and roller 410, for the purpose of defining an entering angle of belt 402 as it approaches roller 410.

[0092] The pre-drying section includes a water absorbing belt such as a felt belt 418 and a set of rollers of which rollers 420, 422 and 424 are labelled, for guiding the path of the felt belt 418. It is noted that rollers 422 and 424 can be the same as rollers 114 and 116 respectively from FIG. 2, where roller 424 functions as a pressing apparatus. The felt belt 418 moves in the counterclockwise direction. The roller 422 is configured to have an integrated water suctioning system to remove as much water as possible from both any wet paper product on the felt belt 418 and the felt belt 418 itself. While not shown in FIG. 3, the pre-drying section can include at least one further supplemental water suctioning system configured and positioned to remove water from both 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, roller 420 with the felt belt 418 is positioned to slightly press into the second wire belt 404 to pick up the wet paper product.

[0093] The drying section can be configured the same as the one shown in the embodiment of FIG. 2, therefore the same reference numbers are used, and the same corresponding descriptions and operations thereof apply.

[0094] Now the operation of the paper producing machine 400, namely the S- wrap former paper producing machine 400, for producing tissue paper is described. [0095] The process starts at the left-hand side of FIG. 5 with the abovedescribed forming section. The headbox 406 injects or deposits the wet stock onto at least one of the first wire belt 402 and the second wire belt 404, such that the wet stock is trapped between both belts 402 and 404 as both belts begin to be pressed against each other as they wrap around roller 410. The temperature of wet stock suspension can be maintained between 45 to 65 °C. Prior to the pressing, the dryness content of the wet stock can be about 0.2%. The wet stock is pressed against the second wire belt 404 by the first wire belt 402 for the duration of time that both belts 404 and 402 are wrapped around rollers 410 and 412, thereby forming a wet paper product sheet, in this embodiment being a wet tissue sheet. Because the first wire belt 402 is pressed with tension against both the second wire belt 404 and rollers 410 and 412, some excess water in the wet tissue sheet is pressed out. It is assumed that both the first wire belt 402 and the second wire belt 404 are controlled to move at the same speed. Eventually both the first wire belt 402 and the second wire belt 404 separate after roller 412 at a point defined by roller 408, with the wet tissue sheet adhering to the outer surface of the second wire belt 404 with the aid of a suction box (not shown).

[0096] The wet tissue sheet is carried to roller 416, where the wet tissue sheet is transferred to the outer surface of felt belt 418 as the felt belt 418 is pressed against the second wire belt 404 at roller 420. The wet tissue sheet has now left the former section. The felt belt 418 and the second wire belt 404 move at the same speed.

[0097] It is noted that the dryness content of the wet tissue sheet after the pressing effect of belts 402 and 404 around roller 210, and transportation of the wet tissue on the second wire belt 404, can be about 12%-16% by example. The felt belt 418 now carries the wet tissue sheet in the pre-drying section towards roller 422, which as previously described can have an integrated water suctioning system. Accordingly, as the felt belt 418 makes contact with a surface of roller 422, water is removed from both the wet tissue sheet on the felt belt 418 and from the felt belt 418 itself. The size of roller 422, the speed of movement of the felt belt 418, and the water suction power can be configured to increase the dryness content of the wet tissue sheet to between 20%-22% by example, before the wet tissue sheet makes contact with the metal belt 118. The roll diameter of roller 422 can be between 800mm to 1500mm, the minimum vacuum level applied can be 0.2 bar, and the amount of vacuum in m³/min is determined by the open area of roller 422 and design of the felt belt 418. Those of skill in the art will understand that various combinations of the roll diameter, belt tension and the working width can be set to achieve a desired dryness content of the wet tissue sheet before it makes contact with the metal belt 118.

[0098] Once the wet tissue sheet has been transferred to the metal belt 118, which moves at the same speed as felt belt 418, the wet tissue sheet follows the same path as in the embodiment of FIG. 2 and interacts with felt belt 418 in the same way that metal belt 118 interacts with felt belt 110 in the embodiment of FIG. 2. Eventually the dried tissue sheet is removed from the metal belt 118 at roller 120 by the creping doctor 130, and collected on a reel (not shown). Ideally, the dryness level of the final tissue sheet should be at least 92%.

[0099] Returning to the pre-drying section, after roller 424 the felt belt 418 is moved towards roller 420 to repeat the process, and is cleaned as described for the previous embodiment of FIG. 2. In an optional variation of the present embodiment of FIG. 5, the felt belt 418 can be subjected to further drying by any suitable means after being cleaned and before reaching roller 420. This will allow more initial absorption of water from the wet stock deposited by headbox 406.

[00100] According to an alternate embodiment, the drying section of the previous embodiments can be modified to include another heating element arranged proximate to the metal belt 118 as it encircles roller 116 (or rollers 220, 318 and 424 of the other embodiments), to apply additional heat to the metal belt to compensate for any heat loss since the earlier application of heat by the heating element 126.

[00101] Returning to the paper producing system embodiment of FIG. 2, the drying section is shown to include the small press roller 123, which can be omitted in an alternate embodiment. In a further alternate embodiment to the paper producing system of FIG. 2 that omits the small press roller 123, FIG. 6 shows a paper producing system that uses a heavy-duty press roller to improve drying of the wet tissue sheet.

[00102] The paper producing system 500 of FIG. 6 of the present alternate embodiment has the same forming section and pre-drying section as the paper producing system 100 of FIG. 2. The same reference numerals of FIG. 2 are used here in FIG. 6 to designate the same elements, hence the operation of the forming section and the pre-drying section are the same as described for FIG. 2. It is noted that impingement dryer 128 is illustrated with a specific example configuration of hot air and return ducts in the embodiment of FIG. 6.

[00103] The drying section of paper producing system 500 of FIG. 6 is substantially the same as the one in FIG. 2 with the same reference numerals used here in FIG. 6 to designate the same elements. Relative to the embodiment of FIG. 2, the embodiment of FIG. 6 does not use the small press roller 123, and a heavy-duty press roller 502 replaces the roller 129. The heavy-duty press roller 502 is movable and is controlled to apply localized pressure against the metal belt 118, wet tissue sheet, felt belt 110 and roller 116. The heavy-duty press roller 502 has a high line load, and this final stage of pressing of the metal belt 118 against the wet tissue sheet and felt belt 110 has the effect of transferring more water from the wet tissue sheet to the felt belt 110, thereby increasing the dryness level of the tissue sheet.

[00104] The heavy-duty press roller 502 is positioned to maximize the amount of time the felt belt 110 can absorb water from the wet tissue sheet as it moves around roller 116. One advantageous result of this configuration is that the removal of water from the wet tissue sheet as it travels around roller 116 results in less bulk lost later due to the heavy-duty press roller 502, thereby increasing the quality of the final tissue.

[00105] An alternate embodiment to the paper producing system of FIG. 6 is the paper producing system of FIG. 7. The paper producing system 510 of FIG. 7 includes all the same elements shown in the paper producing system 500 of FIG. 6, but further includes a small press roller 514. This small press roller 514 is also movable and functions similar to the small press roller 123 in the embodiment of FIG. 2. Here in FIG. 7, the small press roller 123 is an additional press to the heavy-duty press roller 502 and can be positioned anywhere upstream of heavy-duty press roller 502 where the metal belt 118 is pressing the wet tissue sheet against the felt belt 110 and roller 116. The effect of the additional small press roller 514 is to further increase the transfer of water from the wet tissue sheet to the felt belt 110. [00106] In the previously described embodiments of the paper producing systems shown in FIGs. 2-7, the felt belt 110 of the pre-drying section transfers the wet tissue sheet it carries to the metal belt 118, and is dried as much as possible before making contact with the wet tissue sheet carried by the metal belt 118 later downstream to help further dry the wet tissue sheet by absorbing its water. In these embodiments, the wet tissue sheet is pressed against the felt belt and the roller 116 by the tension of the metal belt 118, to promote the absorption of water into the felt belt. The addition of small press rollers and heavy-duty press rollers further facilitates the drying of the wet tissue sheet. This concept is illustrated again in the alternate embodiment of a paper producing system shown in FIG. 8.

[00107] The alternate embodiment of FIG. 8 illustrates an example of the concept whereby a felt belt makes contact with a heated metal belt on two different occasions to help facilitate drying of a wet tissue sheet. The paper producing system 520 of FIG. 8 has a forming section and a drying section which are the same as the ones shown in the embodiment of FIG. 2, and therefore the same reference numbers are used for the shown elements.

[00108] The difference between the embodiment of FIG. 2 and the embodiment of FIG. 8 is the pre-drying section. The pre-drying section of FIG. 8 is similar to that of FIG. 2 and therefore shares many of the same numbered elements, except for shoe press 524 which is arranged and positioned to press the felt belt 110 against the wet tissue sheet carried by the metal belt 118 on roller 124. Again, it can be seen in the embodiment of FIG. 8 that after the wet tissue sheet is transferred to the heated metal belt 118 at roller 114 by the felt belt 110, the felt belt is cleaned and dried as much as possible before it is pressed against the metal belt 118 later downstream at roller 124 by the shoe press 524. The shoe press 524 has a similar effect as the small press roller and the heavy-duty press roller shown in the previous embodiments, which is to facilitate drying of the wet tissue sheet by pressing the water of the wet tissue sheet into the felt belt 110.

[00109] The previously described paper producing system embodiments are shown to have at least three sections, where the first section is a forming section, the second section is a pre-drying section, and the third section is a drying section. In alternate embodiments of each of the previously described paper producing systems, intermediate sections can be inserted between the forming section and the pre-drying section, and/or additional finishing sections can be added after the drying section before the paper product is collected on a reel. Each section transfers the paper sheet to the next section. Therefore, after a paper sheet or tissue sheet is formed in the forming section, the same paper or tissue sheet is eventually received by the predrying section via any number of intermediate sections.

[00110] An example of such a system is shown in the alternate embodiment of FIG. 9, which is a paper producing system for producing MG paper. The presently shown embodiment of FIG. 9 is an alternate configuration to a well-known configuration for producing MG paper with a Yankee dryer. The prior art configuration includes a Fourdrinier section, similar to the one shown in FIG. 4, a pre-press section, a first pre-dryer section, a second pre-dryer and press section, a dryer section including the Yankee dryer, and an after dryer section before the finished paper product is finally collected on a reel. According to the present embodiment of FIG. 9 the Yankee dryer of the prior art dryer section is replaced with a heated metal belt system similar to the one shown in the previous embodiments of FIGs. 2- 8.

[00111] In FIG. 9, only a portion of the full paper producing system 700 is shown. Starting on the left side of FIG. 9, the system includes a forming system consisting of a Fourdrinier (not shown), a pre-press section (not shown), a first pre- dryer section 702 (partially shown), a second pre-dryer section 704, a dryer section 706, and an after dryer section 708. The components of a portion of the first pre-dryer section 702, the second pre-dryer section 704 and the dryer section 706 are now described in further detail.

[00112] The first pre-dryer section 702 has a wire belt 710 carrying the paper sheet, which wraps around a felt belt 712 and a portion of roller 714 of the second pre-dryer section 704, presses against felt belt 712 and wraps around roller 716. Wire belt 710 moves in the clockwise direction. [00113] The second pre-dryer section 704 includes the felt belt 712 guided around a set of rollers including rollers 714, 718, 720, 722 and 724. The felt belt 712 moves in the counterclockwise direction. Roller 720 presses the felt belt 712 against roller 726 of the dryer section 706, and the felt belt 712 is then guided away from roller 726 by roller 722. While not shown, the felt belt 712 is cleaned after leaving roller 720 and to wash out residual fibers and any surface dirt. This cleaning can further include drying the felt belt 712. The felt belt 712 is then pressed between rollers 724 and 726, and is then guided away where it returns to roller 714. In this embodiment, roller 724 functions as a pressing apparatus. Optionally, the felt belt 712 is subjected to another round of cleaning after leaving roller 724. The felt belt 712 can be replaced by an impermeable belt in a variation of the present embodiment. It is notable here that the felt belt is pressed against the roller 726 and a metal belt 728 of the dryer section 706 at two different times. The relevance of this configuration is discussed later.

[00114] The dryer section 706 includes the metal belt 728 which is guided around a set of rollers including rollers 726, 730 and 732, an IR profiling unit 734, an impingement dryer 735, heating elements 736, and doctoring blades 738.

[00115] The operation of the paper producing system 700 is now described. It is assumed that a paper sheet has been formed in the former section (including the Fourdrinier), has passed through the pre-press section (not shown), and has passed through the first pre-dryer section 702 with the paper sheet provided on the upper surface of felt belt 710. The paper sheet enters the second pre-dryer section 704 when the wire belt 710 is pressed against felt belt 712 at roller 714. Prior to entering the pre-dryer section 704, the paper sheet can have a dryness level between 55% to 65%, by example. 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 sheet is transferred to felt belt 712, where the paper sheet is pressed between rollers 726, heated metal belt 728, felt belt 712 and roller 720. The pressing action in this area transfers the paper sheet from the felt belt 712 to the metal belt 728. The metal belt 728 and the felt belt 712 move at the same speed. [00116] 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 embodiments, and is again pressed between rollers 724 and 726, metal belt 728, and the paper sheet carried by the metal belt 728. This has the effect of removing some moisture from the MG paper sheet, as the felt belt 712 having been cleaned and further dried will contain less moisture than before it was cleaned. The heated belt 728 carrying the paper sheet being pressed by rollers 720 and 724 provides an ironing effect to give the paper sheet a glossy finish on one side.

[00117] It can be seen that the paper producing system 700 of FIG. 9 has the felt belt 712 of the second pre-drying section transferring the wet tissue sheet it carries to the metal belt 728, and is dried as much as possible before making contact with the wet tissue sheet carried by the metal belt 728 later downstream to help further dry the wet tissue sheet by absorbing its water. This sequence is the same as in the previously described embodiments. Also similar to the previously described embodiments, the wet tissue sheet is pressed against the felt belt 712 and roller 724 by the metal belt 728 and roller 726. Roller 726 can be controlled to press against roller 724, or vice versa, to have the same effect.

[00118] The metal belt 728 carrying the paper sheet then passes over roller 730 which includes the IR profiling unit 734 which corrects the moisture profile of the paper sheet passing underneath. The paper sheet is then further dried by the impingement dryer 735, and is then removed from the metal belt at roller 732 and fed into the after dryer section 708, and subsequently collected on a reel. At this point the paper sheet 740 does not need to be doctored off the metal belt 728 due to its rigidity, therefore the doctor blades 738 are present only to prevent a stuck paper sheet on the metal belt 728 from reentering the dryer section 706 by scraping it off of the metal belt 728. Returning to the second pre-dryer section 704, the felt belt after leaving roller 724 can be optionally cleaned again before it returns to roller 714 to repeat the process.

[00119] In all the embodiments shown in FIGs. 2-9, the paper producing systems dewater and dry paper products without the use of massive Yankee dryers and the supporting components they require, thereby reducing complexity, maintenance and overall costs. All the embodiments of FIGs. 2-9 can be operated at least the same speed as current Yankee dryer systems, which is presently about 2000m/min. Higher speeds can be attained with the present embodiments by increasing the headbox pressure with corresponding belt speed increases, while ensuring that the headbox design avoids any outlet lip deformation. All the previously discussed variations and modifications for the embodiments of FIGs. 2-5 can be applied to the embodiments of FIGs. 6-9.

[00120] In the embodiments shown in FIGs. 2-9, the wet tissue or MG paper sheet is approximately the same width as the heated metal belt. This is to ensure that the heat transfer of the metal belt to the applied wet tissue sheet is consistent across its width. If the wet tissue sheet is overly narrow relative to the heated metal belt, referred here as underlap, then the edges of the wet tissue sheet and the uncovered area of the metal belt may be subjected to overheating because the exposed metal belt edges are not cooled down by the wet paper web after the metal belt was heated by the applied induction and/or impingement drying units. This results in the edges of the wet tissue sheet drying faster and potentially separating from the metal belt. In addition the exposed metal belt edges overheat which has a negative influence on the metal belt lifetime. Accordingly, the design parameters of the paper producing system can be selected such that a maximum underlap of the wet tissue sheet edges relative to the metal belt edges can be determined where the over drying phenomenon does not occur or has a negligible negative effect on the edges of the wet tissue sheet and/or the metal belt lifetime. The width of the wet tissue sheet can be set by the forming section of the paper producing systems of the presently disclosed embodiments.

[00121] Alternately for the embodiments shown in FIGs. 2-9, the wet tissue sheet can be formed to be wider than the heated metal belt, such that there is overlap of the wet tissue sheet edges relative to the metal belt edges. Referring to the paper producing system 100 of FIG. 2 by example, the wider wet tissue sheet set by the forming section is eventually transferred by the belts 102 and 110 towards roller 114. Because the wet tissue sheet is biased to adhere to the smooth surface of the heated metal belt, only the portion of the wet tissue sheet pressed against metal belt 118 at roller 114 is transferred onto the metal belt 118. Therefore the wet tissue sheet width is now substantially the same as the metal belt width. The remaining overlapping wet tissue sheet edges remain on the felt belt 110. The previously described cleaning systems of the felt belt 110 after roller 114 and before roller 116 can be configured to remove this remaining overlapping wet tissue sheet edges from the felt belt 110 Any suitable cleaning technique or system can be used to remove the maximum amount of wet tissue sheet fibers from the felt belt before making second contact with the wet tissue sheet carried by the metal belt.

[00122] A common feature to the previously described paper producing system embodiments is the pre-drying and drying sections, which operate similar to each other. The flowchart of FIG. 10 summarizes the common operational steps of the predrying and drying sections of the described paper producing system embodiments. [00123] Starting at step 800, a metal belt is heated using any suitable means. Following at step 802, a previously formed wet tissue sheet carried by a felt belt is transferred to the heated metal belt, which immediately promotes drying of the wet tissue sheet. After the wet tissue sheet separates from the presently wet felt belt, the felt belt is cleaned of any residual paper fibers and dried at step 804. The dried felt belt is then pressed against the wet tissue sheet which is carried by the heated metal belt. Because the felt belt has been previously dried, it will absorb water presently in the wet tissue sheet. Furthermore, pressing of the felt belt against the metal belt will promote more water absorption by the dryer felt belt. The wet tissue sheet is then subjected to high velocity air drying at step 808, followed by removal of the dried tissue sheet from the metal belt.

[00124] While the previously described embodiments of the paper producing systems are examples of tissue paper and MG paper production, other types of paper can be produced taking into account the type of pulp being used, by adjusting the drying curve to suit different paper properties and basis weight. The previously disclosed embodiments show example configurations of various sections having specific numbers of rollers arranged to guide belts to travel in various directions. It should be understood that variations to these examples can be implemented with different numbers of rollers in different arrangements to achieve the same end result for its section. It is noted that the elements shown in the drawings of the disclosed embodiments are not necessarily shown to scale, and are merely illustrative of how the paper producing systems are intended to operate.

[00125] The dryness levels of the tissue or paper sheet indicated at various stages of the paper producing system embodiments described above are estimates only, and persons of skill in the art will understand that adjustments to parameters and the inclusion of additional elements to variations of the above-described embodiments can result in different dryness levels of the tissue or paper sheet.

[00126] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments.

[00127] The above-described embodiments are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art. The scope of the claims should not be limited by the particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.

Claims

CLAIMS:

1 . An apparatus configured to form a paper product from stock suspension, comprising: a forming section including 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; a pre-dryer section including a water absorbing belt arranged to continuously move around a first set of rollers configured to receive the wet paper product sheet, the water absorbing belt configured to start absorbing water of the wet paper product sheet upon contact and configured to subsequently transfer the wet paper product sheet to a heated metal belt, a first roller of the first set of rollers guiding the water absorbing belt away from the metal belt after the wet paper product sheet is transferred to the metal belt; a water removing device configured to dry the water absorbing belt after being guided away from the metal belt; a pressing apparatus configured to press the water absorbing belt against the wet paper product sheet carried by the metal belt; a drying section including heating elements for heating the metal belt before the wet paper product sheet is received from the water absorbing belt; the metal belt arranged to continuously move around a second set of rollers, wherein the heated metal belt facilitates drying of the wet paper product sheet after receiving the wet paper product sheet from the water absorbing belt; and, a drying device configured to dry the wet paper product sheet carried by the metal belt downstream of the pressing apparatus to provide a substantially dried paper product sheet.

2. The apparatus of claim 1 , wherein the heating elements include at least one of induction based, infrared based and hot air based heating elements.

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

4. The apparatus of claim 1 , wherein the drying section further includes an infrared (IR) profiling unit to correct a moisture profile of the wet paper product sheet.

5. The apparatus of claim 1 , wherein the pressing apparatus is a second roller of the first set of rollers, and the metal belt carrying the wet paper product sheet is configured to press against the water absorbing belt while both the water absorbing belt and the metal belt encircles the portion of the circumference of the second roller.

6. The apparatus of claim 5, further including at least one press roller configured to apply pressure against the metal belt while the metal belt, the wet paper product sheet and the water absorbing belt encircles 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 includes a small press roller and a heavy duty press roller.

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

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

12. The apparatus of claim 1 , wherein the drying section further includes another heating element configured to heat the metal belt carrying the wet paper product sheet as it is pressed against the water absorbing belt.

13. The apparatus of claim 1 , wherein the forming section includes a single water permeable belt arranged to continuously move around a third set of rollers and configured to be pressed against the water absorbing belt while the water absorbing belt encircles a portion of a circumference of a third roller, wherein the headbox is positioned to inject the stock suspension onto at least one of the single water permeable belt and the absorbing belt before the single water permeable belt is pressed against the water absorbing belt.

14. The apparatus of claim 2, wherein the drying section includes a sprayer for spraying an adhesive onto the metal belt before the metal belt receives the paper product from the water absorbing belt, and a doctoring device configured to crepe and remove the substantially dried paper product sheet from the metal belt downstream of the drying device.

15. The apparatus of claim 2, wherein the single water permeable belt is a wire belt.

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

17. The apparatus of claim 1 , wherein the forming section includes a first water permeable belt arranged to continuously move around a third set of rollers and configured to be pressed against a second water permeable belt while the second water permeable belt encircles a portion of a circumference of a third roller, 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 water permeable belt and the second water permeable belt before the single water permeable belt is pressed against the second water permeable belt, the first water permeable belt is configured to transfer the wet paper product sheet onto the second water permeable belt, and, the second water permeable belt is configured to transfer the wet paper product sheet onto the water absorbing belt.

18. The apparatus of claim 17, wherein the drying section includes a sprayer for spraying an adhesive onto the metal belt before the metal belt receives the wet paper product sheet from the water absorbing belt, and a doctoring device configured to crepe and remove the substantially dried paper product sheet from the metal belt downstream of the drying device.

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

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

21. The apparatus of claim 1 , wherein the forming section includes a single water 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 water permeable belt and the single water permeable belt is configured to transfer the paper product onto the water absorbing belt.

22. The apparatus of claim 21 , wherein the drying section includes a sprayer for spraying a silicon-based type of emulsion onto the metal belt before the metal belt receives the wet paper product sheet from the water absorbing belt.

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

24. The apparatus of claim 1 , wherein the forming section includes a Fourdrinier configured to form the wet paper product sheet, the pre-dryer section is a second pre-dryer section, and the wet paper product is transferred from the Fourdrinier to the second pre-dryer section after passing through a pre-press section and a first pre- dryer section.

25. The apparatus of claim 24, wherein the drying section includes 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 press the metal belt against the water absorbing belt and to transfer the wet paper product sheet onto the metal belt, and the pressing apparatus and the third roller are configured to press the metal belt carrying the wet paper product sheet against the water absorbing belt.

26. The apparatus of claim 25, further including a cleaning system for cleaning the water absorbing belt after the water absorbing belt leaves the first roller and before the water absorbing belt is pressed against the third roller by the second roller.

27. A method for drying a wet paper product sheet in a paper producing system, comprising: heating a metal belt; transferring a 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; pressing the felt belt against the metal belt and the wet paper product sheet after drying the felt belt; and, drying the wet paper product sheet with high velocity air.

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

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

30. The method of claim 27, wherein pressing the felt belt includes encircling a portion of a circumference of a roller with the felt belt and metal belt carrying the wet tissue sheet, with the felt belt positioned between the roller and the metal belt.

31. The method of claim 30, further including applying pressure against the metal belt while the metal belt, the wet paper product sheet and the water absorbing belt encircles the portion of the circumference of the roller.

32. The method of claim 27, wherein pressing the felt belt includes operating a shoe press.