JP2007511677A - Fiber web processing method in dryer section of paper machine or paperboard machine with finishing equipment - Google Patents

Abstract

The present invention relates to a dryer section of a paper / board machine and a method for treating a fibrous web which is dried to a specific moisture content in a finishing device (1) following the dryer section (3). The method utilizes water contained within the fibrous web so that the web to be treated is configured to travel between the dryer section and the finishing device under controlled conditions of temperature and moisture. The evaporation of water from the fiber web is adjusted according to the conditions. The fibrous web is dried in the dryer section in such a way that after the dryer section (3) it retains more moisture than usual and final drying is carried out by the finishing device (1).

Description

  The present invention relates to an on-line dryer section of a paper / board production line, a web transfer section located after the dryer section, and an on-line finishing device following the dryer section, such as a calendar or coating device. The present invention relates to a method for treating a fiber web. The calendar may be, for example, a metal belt calender, a long nip calender, a multi-nip calender, a soft calender, or a machine calender.

  In modern paper machine concepts, finishing processes such as dryer section and calendering are separate sub-processes while the paper web is often conveyed as an open draw. As a result of the open draw, a significant amount of moisture evaporates from the web and cools the web, especially when the web is transported to the calendar or to other finishing equipment after drying. Considering the entire process, the evaporation that occurs between the dryer and the calendar is undesirable. This is because the fibrous web should be wet and hot when calendered. As a result of the evaporation, the web cools dramatically, so for example, an on-line calendar must be designed so that its capacity is sufficient to process a partially cooled web. Evaporation is also uneconomical and a burden for air conditioning in the factory building.

  Water application is often used in paper / board production lines to evaporate and re-wet so-called over-dried webs, which is usually placed between the dryer section and the calendering process. The The application method is often fine water mist or steam. Better control of the moisture distribution (moisture profile) of the paper web is aimed at through excessive drying and rewetting as well as a more stable paper structure.

  In current processes where the paper is subjected to excessive drying and then rewet, the extra energy consumption and associated cost per ton of production is greater compared to processes where excessive drying is not performed. One of the most notable energy consumption objectives in paper manufacture is actually drying by evaporation. It is clear that the method in which the web is first dried to about 2-4% moisture in the dryer section and then wetted to about 8-10% and the web is finally dried to about 5% on the calendar is energy efficient. There are disadvantages as a whole from the point of view of consumption.

  Therefore, the present invention has an object to provide a method that can reduce energy consumption of a production line, shorten a dryer assembly, and thereby reduce costs by saving space.

  In order to achieve the object of the object of the present invention, the method according to the present invention is such that the fiber web to be treated travels between the dryer section and the finishing device under controlled conditions with respect to temperature and moisture, and according to said conditions Heat and moisture evaporation from the fiber web is adjusted so that the fiber web maintains a higher moisture content in the dryer section after the dryer section and final drying is performed by the finishing device. In this manner, it is dried.

  In the method according to the invention, the water and heat energy in the fiber web is utilized for the purpose of minimizing or preventing heat and moisture transfer from the web in the section between the dryer section and the calendar. The fiber web to be treated travels between the dryer section and the calendar in a condition that is isolated from the air in the factory building and controlled for temperature and moisture, thereby releasing water and heat from the fiber web. Is controlled. According to the present invention, the fibrous web is evaporated so that a moisture content higher than normal is maintained in the dryer section, and the final drying is carried out by means of a calendar. In the method according to the invention, drying and calendering are integrated in relation to temperature and moisture control, and they work together to ensure that the dryer section dries only the required amount, from the dryer section to the calendar. As the web is transported to the water, the water and heat release is adjusted so that the web is at sufficient moisture and temperature upon arrival at the calendar and a portion of the final drying occurs at the calendar. .

  Hereinafter, the present invention will be described in detail using embodiments with reference to the accompanying drawings.

  FIG. 1 schematically shows a part of an on-line production line, reference number 1 indicates a finishing device realized as a metal belt calender and reference number 3 indicates the end of a dryer section. Reference numeral 2 refers to an enclosed space through which the web can be guided through the enclosed space in a controlled condition with respect to temperature and moisture through the area between the dryer section and the calendar 1. The enclosed space may extend over the entire region between the end of the dryer section and the calendar, or may extend only over a portion of the region.

  The finishing device may be realized, for example, as a long nip type calendar, a multi-nip type calendar, a soft calendar, or a machine calendar. The finishing device may be a coating device such as a dry coating device.

  In the method according to the invention, the water and heat energy contained in the fiber web needs to heat and wet the fiber web as required by the calendar 1 by limiting the release of water and heat in the paper after the dryer section 3. Used in such a manner that the sexuality is reduced. Utilizing this drying process is effective because the paper web will in any case be dried and cooled after or in connection with the calendaring process. As a result, in the method according to the invention, the operation of the dryer section 3, the web transport 2 and the calendar 1 is coordinated in such a way that part of the drying function of the dryer section is assigned to the calendar, The use of heat and water is maximally economical.

  Referring to FIG. 1, the heat and moisture control of the web according to the present invention described above regulates the transfer of water and heat energy between the fiber web and its surroundings between the final drying cylinder 3 and the calendar 1. Can be achieved. According to the present invention, these movement phenomena can be adjusted by configuring the web to run under controlled conditions with respect to temperature and moisture between the dryer section and the calendar. If it is desired to prevent evaporation or cooling, the temperature at or near the outer surface of the web and the ambient moisture (vapor pressure or relative moisture of the air) is an equilibrium state that roughly corresponds to the moisture and temperature of the fiber web. Adjusted to This means that there is no significant temperature or moisture difference between the web and its surroundings, and therefore no moisture or temperature moving flow is formed.

  If desired and convenient, the web's immediate conditions can be adjusted to achieve the desired amount of heat or moisture flow between the web and its immediate surroundings. It is. For example, heat flow in the web direction (additional heating) can be caused by raising the ambient temperature to a level higher than the temperature of the web. It is also possible to cause a flow of moisture (additional wetting) in the direction of the web by raising the ambient humidity to a level higher than the equilibrium moisture content of the web. It is also clearly possible to cause a corresponding reverse movement phenomenon by reversing the corresponding moisture and temperature differences between the web and its surroundings.

  The above-described solution according to the invention for controlling the temperature and moisture of the web may be achieved, for example, by configuring the fiber web to travel through a stationary tunnel (wind tunnel) or hood structure. Good. The walls of the wind tunnel or hood structure define a space inside that has moisture and temperature conditions adjusted to be effective for the process. The wall structure prevents temperature and moisture loss and the space is well sealed and isolated from the air in the factory building.

  Another possibility for realizing the present invention is that the support structure regulates the movement of water and heat to the immediate surroundings in the desired manner and configures the web travel between these moving support structures. is there. The most realistic solution is to support the web travel by a wire or belt loop that rotates on both sides or one side. The wire or belt may be impermeable or permeable to some extent (moisture transfer control) and, if necessary, heated / cooled (heat controlled) if appropriate for the whole. The

  A third theoretical solution for controlling the temperature and moisture of the fibrous web is to control the boundary layer of flow and heat transfer. By replacing the boundary layer air normally mixed by factory air and swirl with controlled moisture and / or temperature-controlled air, the temperature and moisture of the web can be reduced to the web and its immediate surroundings. Will change through the movement phenomenon acting between. For example, to control the moisture of the web, moist air or air saturated with steam is injected into the boundary layer of the moving fibrous web. Air penetration into the boundary layer can be ensured by scraping the previous boundary layer. FIG. 2 schematically shows a solution of this kind, in which the previous boundary layer 7 is removed by the doctor blade 4 and the air forming the new boundary layer 7 is transferred by the jetting means 5 to the surface of the web W. Jetted up.

  In the embodiments described above, moisture and heat transfer between the web and its surroundings may be adjusted both in the machine direction and in particular in the transverse direction, if desired. Furthermore, in addition to the draw between the dryer section and the finisher, moisture and heat transfer can occur between points between different nips of a soft calendar, between different roll stacks of a multi-nip type calendar, or corresponding points. , May be adjusted at points between different parts of the finishing device.

  In one preferred embodiment of the invention, the paper is not dried in the dryer section to a level (about 5%) lower than the water content of the end use of the paper, so that the final drying to that moisture level is Will occur in the calendar.

  The method according to the present invention is applicable to paper and paperboard production lines, where further processing requiring heat or moisture, such as calendering, is placed on the line in an on-line manner. This method is particularly suitable for metal belt calenders and long nip calenders where the calendering action is greater than that of conventional calenders and relies on the softening action of the temperature on the fiber web.

  The present invention is also applicable to processes in which the web is processed in other devices in place of the calendar where control of the web temperature and moisture is important. Such a device may be a coating device, in particular a dry coating device, a fixing press in which a desiccant is contained, ie a sizer press.

  The effect of the method according to the invention over current processes is, among other things, a significant energy saving. Since the method maintains the moisture contained in the web, there is no need for another water / softener application or rewet, which reduces the number of equipment required throughout the line and reduces the second evaporation. It means that production efficiency is improved by eliminating the stage. Since the evaporation of water from the web is significantly reduced, the temperature of the web stays higher, thus eliminating the need to supply as much thermal energy to the web in the calendar.

  A further effect is the fact that the water / softener is better dispersed in the paper structure and it is easier to control the moisture level when evaporation is controlled throughout the transfer. Dispersion with respect to moisture thickness may be affected, for example, by controlling the operation of the drying cylinder or by adjusting the evaporation that occurs during the web transfer itself.

FIG. 2 schematically shows an arrangement for implementing the method according to the invention. FIG. 6 schematically shows another arrangement for implementing the method according to the invention.

Claims (12)

Drying to a specific moisture content by the dryer section (3) of the paper machine or paperboard machine and the web transfer section located after the dryer section and by the on-line finishing device (1) following the dryer section In a method for treating a fibrous web,
The fiber web to be treated travels between the dryer section and the finishing device under conditions (2) controlled with respect to temperature and moisture, and the heat and water evaporation from the fiber web is adjusted by the conditions,
The fibrous web is dried in the dryer section in such a way that after the dryer section it maintains a higher moisture content than usual and final drying is carried out by the finishing device, Method.   The web passes in a closed space formed by the support structure at least in part of the passageway at a point between the dryer section (3) and the finishing device (1) and / or between different parts of the finishing device. The method of claim 1, wherein the running structure is configured in a controlled manner to reduce or prevent water from evaporating from the fibrous web.   The method according to claim 2, wherein the support structure is a belt that runs in a mode in which the web is supported therebetween.   The method according to claim 2, wherein the support structure is a plate-like means that causes the web to travel in a mode in which the web is supported therebetween.   The web is blocked by a wind tunnel structure or a hood structure at least part of the passageway at a point between the dryer section (3) and the finishing device (1) and / or between different parts of the finishing device. The method of claim 1, wherein the method travels in space.   The web has a boundary layer between the dryer section (3) and any part of the finishing device (1) where the temperature or moisture of the boundary layer of the web passes through mechanical guide means or nozzle structure (5). The method according to claim 1, wherein the vehicle travels such that the temperature or moisture led to is controlled by conditioned air.   The method according to claim 1, wherein a metal belt calendar is used as a finishing device.   The method according to claim 1, wherein a long nip type calendar is used as a finishing device.   The method according to claim 1, wherein a multi-nip calender is used as a finishing device.   The method according to claim 1, wherein a soft calendar or a machine calendar is used as a calendar.   The method according to claim 1, wherein the coating apparatus is used as a finishing apparatus.   The method according to claim 1, wherein a dry coating apparatus is used as a finishing apparatus.

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