WO2021123497A1

WO2021123497A1 - A drying unit, a web production system, and a method for drying a tissue or non-woven web

Info

Publication number: WO2021123497A1
Application number: PCT/FI2020/050826
Authority: WO
Inventors: Riku Pihko; Timo Rantanen
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2019-12-19
Filing date: 2020-12-10
Publication date: 2021-06-24
Also published as: FI20196106A1

Abstract

According to an example aspect of the present invention, there is provided a drying unit for a web, particularly a tissue or non-woven web, comprising: an entry for transferring the web to the drying unit, an exit for transferring the web from the drying unit, a belt configured to move between the entry and the exit for supporting and moving of the web, and a drying device configured between the entry and the exit to heat the belt and web for drying of the web. The entry is free of a nip and the drying unit is configured to dry the web to include a dry bulk of over 5 cm3/g.

Description

A DRYING UNIT, A WEB PRODUCTION SYSTEM, AND A METHOD FOR DRYING

A TISSUE OR NON- WO YEN WEB

FIELD [0001] The invention relates to a production of a tissue and non- woven paper, and in particular to drying of a tissue and non- woven web.

BACKGROUND

[0002] Generally a Yankee drying cylinder is used in the production of tissue and non- woven paper for removing excess moisture from a web. The Yankee comprises a doctor blade for detaching the web from a surface of the Yankee and for achieving a creped structure of the tissue and non-woven paper.

[0003] The Yankee drying cylinder is traditionally made of cast iron and has diameters up to 6 m. Therefore, the Yankees are very heavy and difficult and expensive to cast. In addition, the Yankee has a limited drying length due to a practically limited diameter. The Yankee requires a relatively dry web achieved with pressing. Thus, before the web is entering to the Yankee, the web is pressed between a suction press roll and the Yankee for removing water with a felt from the web. Moreover, the Yankee drying cylinder has poor energy efficiency because it consumes a lot of energy to maintain high pressure in vapor inside of the cylinder. [0004] On top of this, the Yankee made of cast iron is brittle and very sensitive to temperature differences, which makes it dangerous to use. For example, when the Yankee is receiving steam while it is not rotating, or direct jets of cold water to the surface of the hot Yankee in a case of a fire may damage it by the temperature difference and cause an explosion of the Yankee. [0005] It is therefore an aim to provide a more energy efficient, simple and safe solution for drying a web.

SUMMARY OF THE INVENTION

[0006] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims. [0007] According to a first aspect of the present invention, there is provided a drying unit for a web, particularly a tissue or non-woven web, comprising an entry for transferring the web to the drying unit, an exit for transferring the web from the drying unit, a belt configured to move between the entry and the exit for supporting and moving of the web, and a drying device configured between the entry and the exit to heat the belt and web for drying of the web. The entry is free of a nip and the drying unit is configured to dry the web to include a dry bulk of over 5 cm³/g.

[0008] According to a second aspect of the present invention, there is provided a web production system comprising a former for forming a web, particularly a tissue or non-woven web, and a drying unit provided after the former for drying the web.

[0009] According to a third aspect of the present invention, there is provided a method for drying a tissue or non-woven web comprising: transferring the web to a drying unit via an entry, supporting and moving of the web by a belt configured to move between the entry and an exit of the drying unit, drying the web in a drying device configured between the entry and the exit of the drying unit, and transferring of the web out from the drying unit via the exit. The entry is free of a nip and the drying unit is configured to dry the web to include a dry bulk of over 5 cm³/g.

[0010] According to an embodiment, the drying device is configured to apply steam vapor or air to the belt and the web for heating the belt and the web.

[0011] According to an embodiment, the web production system further comprises a transition conveyor for drawing and/or supporting the web by a fabric, vacuum or air blow before accessing the web to the drying unit.

[0012] The present invention provides several advantages. It provides an inexpensive, simple and energy efficient way to dry a web. There is no need for a nip, a process zone or a pressure roll like in traditional web production systems. Then, the web may be transferred on and off a belt by a speed difference between a current and a next stage. Moreover, there is no need to remove excessive water by pressing before a drying unit because the drying unit may be used to dry webs which have lower dryness than webs which are dried by the Yankee. In addition, higher bulk may be achieved when no nip, process zone or pressure roll is used. A length of the belt is flexibly adjustable and the belt can be tilted up to take an advantage of a height of a facility. In addition, there is no need for complex belt systems due to the simple solitary belt. Importantly, the drying unit is safe to use because there is no risk of explosion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIGURE 1 illustrates a web producing system in accordance with at least some embodiments of the present invention, and

[0014] FIGURE 2 illustrates a method for drying a web in accordance with at least some embodiments of the present invention.

EMBODIMENTS

[0015] In the present context, the term “tissue” comprises tissue paper, which can be made from virgin or recycled paper pulp. Tissue paper may be for example, hygienic tissue paper, facial tissue paper, paper towel, wrapping tissue, toilet tissue or table napkin.

[0016] In the present context, the term “non-woven” comprises fabric-like material made from fibres bonded together by chemical, mechanical, heat or solvent treatment.

[0017] In the present context, the term “web” comprises a fibrous web, particularly a tissue and non-woven web.

[0018] In the present context, the term “machine direction” refers to a moving direction of a web in a web production process.

[0019] In the present context, the term “cross direction” refers to a direction, which is perpendicular to a moving direction of a web in a web production process. [0020] In the present context, the term “dryness” may be understood as the dry content of the web or solids content or dry matter content (DMC).

[0021] A Yankee drying cylinder is difficult and expensive to cast and it has a limited drying length. The Yankee consumes a lot of energy to maintain high pressure in vapor inside of the cylinder. Moreover, drying a web with the Yankee may be even dangerous due to brittleness and sensitivity of the Yankee to temperature differences, which may even cause explosion of the Yankee. The present embodiments provide a solution to at least some of above mentioned problems. [0022] FIGURE 1 illustrates a web production system 100 in accordance with at least some embodiments of the present invention. The web production system 100 comprises a former 10 for forming a web 20, particularly a tissue or non- woven web, and a drying unit 40 provided after the former 10 for drying the web 20. It should be appreciated that FIGURE 1 illustrates only one example of the web production system and the web production system may comprise further production units and some of the illustrated units may be even omitted.

[0023] The former 10 may comprise a headbox or a feeding unit 11, a plurality of rolls 12, 13, a fabric or felt 14, 15. The fabric or felt 14, 15 may form a loop around the rolls and may have a different length depending on a forming section configuration. A stock is provided to the headbox or the feeding unit 11 from which it is sprayed into the production system and distributed evenly on the fabric or felt 14, 15. The stock forming a web 20 attaches to the fabric 14 and/or fabric or felt 15 and follows it on the production system.

[0024] According to some embodiments, the web producing system 100 further comprises a transition conveyor 30 for drawing and/or supporting the web 20 before accessing the web 20 to the drying unit 40. The transition conveyor 30 enables transferring of the web from the former 10 to the drying unit 40. The transition conveyor may transfer the web with a different speed than the belt. Thus, the web can be transferred to the drying unit 40 with a speed difference.

[0025] Alternatively, a separate transition conveyor 30 may not be used and the web 20 is transferred directly from the fabric or felt 15 to the drying unit 40. Instead, it is possible to use a long version of the fabric or felt 15 to carry the web from forming to the drying unit 40. A long version of the fabric or felt 15 reaches the vicinity of the entry 41 so as to bring the web 20 from the feeding unit 11 to the drying unit 40. FIGURE 1 shows the alternative felt configuration in a dashed line. In other words, the fabric or felt 15 may be integrated to that of the transition conveyor 30.

[0026] According to some embodiments, the transition conveyor 30 may be configured to draw and/or support the web 20 by a fabric or felt 15, vacuum and/or air blow before accessing the web 20 to the drying unit 40. The transition conveyor may comprise a plurality of rolls for supporting and guiding the fabric. A vacuum and an air blow transition conveyor enables safe, delicate, clean and efficient transfer of the web. [0027] According to some embodiments, the entry 41 may be free of a nip. Thus, the web 20 may entry to the drying 40 unit without a nip, a process zone or a pressure roll. There is no need to remove excessive water by pressing before the drying unit because the drying unit may be used to dry webs which have lower dryness than webs which are dried by the Yankee. In addition, higher bulk may be achieved when no nip, process zone or pressure roll is used.

[0028] The web 20 may be transferred on and/or off the belt 33 by different embodiments or by combination of these embodiments as described in more detail below.

[0029] According to some embodiments, the web 20 may be transferred on and off the belt 33 by the speed difference between a current and a next stage. For example, the transition conveyor 30 may transfer the web 20 with a different speed than the belt 33.

[0030] According to some embodiments, a surface or a roll may be configured to transfer the web 20 on the belt 33 by forming a long over 10 mm wrap against a first steel belt loop roll 81. This ensures a good contact between the web and the belt 33 and a high heat transfer from the belt to the web prior to the entry 41.

[0031] According to some embodiments, a transition conveyor 30 or fabric 15 may be configured to transfer the web 20 on the belt 33 by forming a long over 10 mm wrap against the first steel belt loop roll 81. This ensures a good contact between the web and the belt 33 and a high heat transfer from the belt to the web prior to the entry 41.

[0032] According to some embodiments, a vacuum or air blow nozzle component 91 may be configured to transfer the web 20 on the belt 33 by removing air between the web 20 and the belt 33. The vacuum or air blow nozzle component 91 may be applied prior to the web and the belt contact point. A vacuum or air blow nozzle component ensures a good contact between the web and the belt and a high heat transfer from the belt to the web prior to the entry 41.

[0033] According to some embodiments, a water or additive spray 72 is configured to improve contact between the web 20 and the belt 33. In addition to spraying, unit 72 may comprise a doctor or air blow to ensure the correct layer amount of water or additive between the web and the belt. A water or additive spray may be applied prior to web and the belt contact point to improve contact between the web 20 and the belt 33. The water or additive spray ensures a high heat transfer from the belt to the web prior to the entry 41. [0034] All of the abovementioned embodiments can be applied separately or together to ensure a good contact between the belt 33 and the web 20. They improve heat transfer from belt to web, increase web drying rate, produce higher web smoothening effect, improve process runnability, i.e. web stays with even contact and positioning during the drying.

[0035] According to some embodiments, the drying unit 40 for a web 20 comprises an entry 41 for transferring the web 20 to the drying unit 40, an exit 42 for transferring the web 20 from the drying unit 40, a belt 33 configured to move between the entry 41 and the exit 42 for supporting and moving of the web 20, and a drying device 44 configured between the entry 41 and the exit 42 to heat the belt 33 for drying of the web 20. This provides an inexpensive, simple, energy efficient and safe way to dry the web. It is noteworthy that, preferably, the entry 41 does not comprise a nip. Indeed, it is preferable that the web does not experience processing under elevated pressure, such as processing with a pressure roll, during drying. Accordingly, the web will enter the drying unit 40 uncompressed.

[0036] This can be further defined that according to some embodiments a fabric 14, a fabric or a felt 15 or water removal vacuum components may exert a pressure level of 1 to 100 kPa, particularly less than 70 kPa, to the web 20 prior to the entry 41.

[0037] According to some embodiments, a fabric 14, a fabric or felt 15 or water removal vacuum or drying components may exert a pressure of 0.01 to 10 kPa, particularly less than 10 kPa, on the web between the entry 41 and the exit 42.

[0038] It is to be noted that the abovementioned pressure levels are significantly lower than the pressure levels web experiences in a pressing or process zone nips, which are typically 1 to 10 MPa. Therefore a significantly higher bulk can be achieved by applying present embodiments.

[0039] A length of the drying unit 40 may be configured according to preferred dryness and other properties of an end product. The length of the drying unit defined as a contact length between the belt 33 and the web 20 may be for example, 2 to 100 m. The length of the drying unit is more flexibly adjustable than with the traditional Yankee drying cylinder which has a limited drying length due to a practically limited diameter. That’s why a longer drying length may be achieved with the drying unit 40. [0040] The drying unit 40 can be tilted up to take advantage of a height of a facility. The drying unit belt 33 tilt defined as part of the belt length in running direction may be tilted up for example, 0 to 90 degrees upwardly inclined with respect to the horizontal direction. Then, the drying unit requires less space in the horizontal direction and factory facilities can be used more effectively.

[0041] The drying unit 40 may comprise side covers, a cover hood or an enclosure. These prevent the drying unit against dirt and dust and improve safety of users of the drying unit.

[0042] The enclosure of the drying unit 40 may be insulated. Insulation prevents heat from escaping from the drying unit which increases energy efficiency. Moreover, lower heating temperatures may be used due to insulation.

[0043] The drying device 44 may comprise at least one heating unit. The heating unit(s) may be configured under and/or above the belt 33. The heating unit may apply steam, hot air blow or vacuum to dry the web and heating power of each heating unit may be controlled separately in machine and cross direction to achieve an efficient and even drying. When the heating unit is arranged under the belt, heat can be guided directly to a heating of the belt. This enables fast and energy efficient heating of the belt. When the heating unit is arranged above the belt, air surrounding the belt in the heating unit can be also heated. This may provide faster and even more efficient heating.

[0044] According to some embodiments, the drying device 44 is configured to heat the belt 33 to a temperature of 70 to 200 °C, especially 80 to 130 °C, for drying the web 20. Then, the web configured on the belt is heated and dried efficiently.

[0045] According to some embodiments, the drying device 44 is configured to apply steam vapor or air to the belt 33 and the web 20 for heating the belt and the web 20. Alternatively, other suitable methods, such as electrical induction, infrared radiation or direct electric heating, may be used for heating the belt and the web. Moreover, different types of drying devices may be combined.

[0046] A temperature of steam vapor or air may be for example, 80 to 400 °C. Steam vapor or air enables fast, even, and energy efficient heating of the belt and stable web runnability. In addition, they enable even web product drying, better dimension stability and quality of the web. [0047] The drying device 44 may comprise nozzles, such as slots or holes, for directing air or vapor with a predetermined velocity to the belt 33. Air and steam vapor may be directed to the belt perpendicularly to the belt. This enables faster heating of the belt and higher evaporation rate of the moisture of the web.

[0048] According to some embodiments, the drying unit 40 may be configured to dry the web 20 which has a dryness of 4-70 %, preferably 17-35 %. Thus, relatively wet webs can be dried with the drying unit.

[0049] The dryness of the web can be relatively high, such as 4-70 %, by providing for example, a flow-through drying unit or a vacuum dewatering unit before the drying unit 40. Then, the drying unit 40 may be configured to dry the web 20 which has a dryness of up to 70 %.

[0050] According to some embodiments, the drying unit 40 may be configured to dry the web 20 to include a dryness of 70-98 %. Therefore, a high dryness may be achieved with the drying unit. Moreover, there is no need for following drying stages, especially with light basis weight webs.

[0051] According to some embodiments, the drying unit 40 may be configured to dry the web 20 to include a dry bulk of 60-100 % of the dry bulk of the web before the drying unit. The dry bulk of the web is defined by measuring an uncreped dry web product thickness without compressing the product during the measurement and by measuring dry web basis weight under laboratory conditions (e.g. T = 23 ± 2 °C, RH = 50% ± 10%).

[0052] According to some embodiments, the drying unit 40 may be configured to dry the web 20 to include a dry bulk over 5 cm³/g. Therefore, a high bulk web (i.e. web dry bulk is over 5 cm³/g) may be achieved with the drying unit 40. A high dry bulk is a significant measure related to many web products since it enables e.g. good absorption, softness and insulation properties. A high web bulk enables also raw material and energy savings since with high bulk less material is needed to produce good quality webs.

[0053] According to some embodiments, the drying unit 40 may be configured to heat the web 20 to a temperature of at least 70 °C, preferably 70 to 200 °C, particularly between 70 and 90 °C. This enables high evaporation rate of the moisture of the web. The temperature of the web in the drying unit may be configured according to preferred end product properties, such as the dryness of the web. The highest web temperatures are applied when activation or vulcanization of web additives is needed.

[0054] The belt 33 is configured to support and move the web in a machine direction. Therefore, the belt can be easily configured after the former 10 and before further production stages, such as creping or reeling, in the web production system 100.

[0055] A speed of the belt may be for example, 1 to 2500 m/min. The speed of the belt may be configured according to other process parameters, such as the heating temperature of the belt, and preferred end product properties, such as the end dryness or moisture of the web. For example, the speed of the web may be increased when the temperature of the belt is increased.

[0056] The belt 33 may be a solitary belt. Thus, the drying unit may comprise only one belt which forms an endless closed loop. The belt may comprise a plurality of guiding rolls. Therefore, there is no need for built and maintain complex belt systems, which makes the web production system simpler and more inexpensive.

[0057] The belt 33 may be configured to move at least between the entry 41 and the exit 42 of the drying unit. The belt may be also configured to move around a drying section comprising also for example, a doctor blade 51 , such as a creping doctor blade, a cleaning unit with doctor(s) and shower(s) 61, 62 and/or a chemical treatment or addition unit 71, as illustrated in FIGURE 1.

[0058] According to some embodiments, the belt 33 is an uncoated or coated metal belt, for example a steel belt. Metal provides a good thermal conductivity and resistivity to high temperatures and is durable.

[0059] A coating of the belt 33 may comprise for example, polymer, such as polyurethane, neoprene, silicone, rubber or polytetrafluoroethylene. The coating of the belt increases or decreases friction and anti- stick properties of the belt. Moreover, the coating may prevent the belt from corrosion and increase service life of the belt.

[0060] Alternatively or in addition, a coating of the belt 33 may comprise a coating mixture. The coating mixture may comprise for example, polymers, such as polyamide, as adhesives and different oils, such as mineral or vegetable oils, as release agents. The coating may be modified for example, depending on the web grade to adjust adhesion between the belt and the web to a correct level. The coating mixture may be mixed in water before applying on the belt. The coating mixture may be applied on the belt before and/or during the web production process.

[0061] The belt 33 or the fabric 14, 30 that is in contact with the belt may be patterned to produce a patterned web 20. The surface of the belt or the coating of the belt or the fabric in contact with the belt may be embossed. The patterned belt creates a textured design pattern, such as dots, swirls or lines, onto the web.

[0062] In addition or alternatively, a surface of the belt 33 may be at least partially treated, such as roughened or smoothed. The roughening of the surface of the belt enables better adhesion of the web 20 to the belt. The smoothing of the surface of the belt ensures that the web is not adhered too tightly to the web and is detached more easily from the belt.

[0063] Alternatively, the fabric 14 may be patterned to a produce a patterned product.

[0064] According to some embodiments, the web production system 100 may further comprise at least one doctor blade 51 for detaching the web 20 from the belt 33. The doctor blade 51 may be configured in a cross direction of the web. The doctor blade may extend a whole width of the web. The doctor blade may be connected to a doctor blade holder to place the doctor blade against the belt. A support roll may be applied at the backside of the belt to support the belt against the doctor.

[0065] In addition, the web production system may further comprise at least one doctor blade for creping the web. Then, folds and micro-folds are introduced into the web in the cross direction of the web, which means the sheet decreases in length by for example, 10 to 25 %. Creping gives the paper higher bulk and improves softness, absorbency, and stretch. It also reduces the tensile strength.

[0066] The doctor blade 51 may comprise for example, steel, ceramic, carbon fibre or fiberglass, which are durable, lightweight and corrosion-resistant materials. Thus, they may reduce a need to change the blade and may give a finer crepe.

[0067] The web production system 100 may further comprise a reel (not illustrated) for rolling up the web 20. Then, the web is ready for shipping to customer or processing in other machines, in order to be made into a final product. [0068] The web producing system 100 may further comprise a cleaning unit 61, 62 for cleaning the belt 33. The cleaning unit may use a doctor blade, an abrasive, an emery cloth or a washing solution for cleaning the belt. For example, the washing solution may be sprayed to the belt. The cleaning unit may remove fibres and excessive coating from the belt. This enhances a surface quality and cleanliness of the web. In addition, each roll in the web production system 100 that is in contact with the belt, fabric, felt or web may be cleaned continuously to ensure stable and good quality web production.

[0069] The web producing system 100 may further comprise a chemical treatment unit 71 for chemically treating and/or coating the belt 33 in order to control web adhesion to belt and web drying and release properties. An applied coating may comprise the coating mixture comprising for example, polymers and different oils. The coating can be applied on the belt for example, by spraying and/or doctoring.

[0070] FIGURE 2 illustrates a method 200 according to some embodiments. The method for drying a web 20 comprises transferring 201 the web 20 to a drying unit 40 via an entry 41, supporting and moving 202 of the web 20 by a belt 33 configured to move between the entry 41 and an exit 42 of the drying unit 40, drying 203 the web 20 in a drying device 44 configured between the entry 41 and the exit 42 of the drying unit 40, and transferring 204 of the web 20 out from the drying unit 40 via the exit 42. The method enables energy efficient and safe way to produce the web 20, particularly a tissue or non- woven web.

[0071] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0072] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0073] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0074] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0075] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0076] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality. LIST OF REFERENCE NUMERALS

Claims

CLAIMS:

1. A drying unit (40) for a web, particularly a tissue or non-woven web (20), comprising:

- an entry (41) for transferring the web (20) to the drying unit (40),

- an exit (42) for transferring the web (20) from the drying unit (40),

- a belt (33) configured to move between the entry (41) and the exit (42) for supporting and moving of the web (20), and

- a drying device (44) configured between the entry (41) and the exit (42) to heat the belt (33) and web (20) for drying of the web (20), characterized in that the entry (41) is free of a nip and the drying unit (40) is configured to dry the web (20) to include a dry bulk of over 5 cm³/g.

2. The drying unit of claim 1, wherein the drying device (44) is configured to heat the belt (33) to a temperature of 70 to 200 °C for drying the web (20).

3. The drying unit of claim 1 or 2, wherein the drying device (44) is configured to apply steam vapor or air to the belt (33) and the web (20) for heating the belt (33) and the web (20).

4. The drying unit of any one of the preceding claims, wherein the belt (33) is uncoated or coated metal belt, particularly steel belt.

5. The drying unit of any one of the preceding claims, wherein the drying unit (40) is configured to dry the web (20) which has a dryness of 4-70 %, such as 17-35 %.

6. The drying unit of any one of the preceding claims, wherein the drying unit (40) is configured to dry the web (20) to include a dryness of 70-98 %.

7. The drying unit of any one of the preceding claims, wherein the drying unit (40) is configured to dry the web (20) to include a dry bulk of 60-100 % of the dry bulk of the web (20) before the drying unit (40).

8. The drying unit of any one of the preceding claims, wherein the drying unit (40) is configured to heat the web (20) to a temperature of at least 70 °C, preferably 70 to 200 °C, particularly between 70 and 90 °C.

9. The drying unit of any one of the preceding claims, wherein a fabric (14), a fabric or a felt (15) or water removal vacuum components exert a pressure on the web (20) of less than 70 kPa prior to the entry (41).

10. A web production system (100) comprising:

- a former (10) for forming a web (20), particularly a tissue or non- woven web, and

- a drying unit (40) of any one of the preceding claims 1-9 provided after the former (10) for drying the web (20).

11. The web production system of claim 10, wherein the web production system (100) further comprises a transition conveyor (30) for drawing and/or supporting the web (20) by a fabric, vacuum or air blow before accessing the web (20) to the drying unit (40).

12. The web production system of claim 10 to 11, wherein a surface or a roll is configured to transfer the web (20) on the belt (33) by forming a long over 10 mm wrap against a first steel belt loop roll (81).

13. The web production system of claim 10 to 12, wherein a transition conveyor (30) or fabric (15) is configured to transfer the web (20) on the belt (33) by forming a long over 10 mm wrap against the first steel belt loop roll (81).

14. The web production system of claim 10 to 13, wherein a vacuum or air blow nozzle component (91) is configured to transfer the web (20) on the belt (33) by removing air between the web (20) and the belt (33).

15. The web production system of claim 10 to 14, wherein a water or additive spray (72) is configured to improve contact between the web (20) and the belt (33).

16. The web production system of claims 10 or 15, wherein the web producing system (100) further comprises at least one doctor blade (51), particularly a creping doctor blade, for detaching the web (20) from a belt (33) and/or creping the web (20).

17. The web production system of any one of claims 10 to 16, wherein the web drying unit (40) further comprises a cleaning unit (61) for cleaning the belt (33).

18. The web production system of any one of claims 10 to 17, wherein the web drying unit (40) further comprises a chemical treatment unit (71) for chemically treating and/or coating the belt (33).

19. The web production system of claims 10 to 18, wherein the web production system further comprise a device prior to the entry (41), which device is configured to decrease the amount of air between the web (20) and belt (33) or to push the web (20) against the belt (33).

20. The web production system of claims 10 to 19, wherein a fabric (14), a fabric or felt (15) or water removal vacuum or drying components exert a pressure on the web (20) of less than 10 kPa between the entry (41) and the exit (42).

21. A method (200) for drying a tissue or non- woven web (20) comprising:

- transferring (201) the web (20) to a drying unit (40) via an entry (41),

- supporting and moving (202) of the web (20) by a belt (33) configured to move between the entry (41) and an exit (42) of the drying unit (40),

- drying (203) the web (20) in a drying device (44) configured between the entry (41) and the exit (42) of the drying unit (40), and

- transferring (204) of the web (20) out from the drying unit (40) via the exit (42), characterized in that the entry (41) is free of a nip and the drying unit (40) is configured to dry the web (20) to include a dry bulk of over 5 cm³/g.

22. The method of claim 21, wherein the drying device (44) is configured to apply vapor or air to the belt (33) and the web (20) for heating the belt (33).

23. The method of claim 21 or 22, wherein the method comprises:

- detaching the web (20) from the belt (33) or

- creping the web (20) or

- both detaching and creping the web (20) after drying with a doctor blade (51), particularly a creping doctor blade.

24. The method of any of the preceding claims 21 to 23, wherein the drying unit (40) is that defined in any of the preceding claims 1 to 9.

25. The method of any one of the preceding claims 21 to 24, wherein the method (200) of drying a web (20) is performed in the web production system (100) according to any one of the preceding claims 10 to 20.