KR20000016015A - Curl control with dryer air caps - Google Patents

Abstract

PURPOSE: A short dryer section is provided to dry both surfaces of a web at the same time and to precisely adjust a paper moisture profile to a machine transverse direction. CONSTITUTION: The dryer section in a papermaking machine has a single tier of all top felted dryer rolls (24) six to nine feet in diameter. Air caps (42) are employed over the dryer rolls (24) to simultaneously dry both sides of the web (28) to prevent curl and to increase drying rates. The air caps (42) employ blown air at a temperature of 250 - 900 degrees Fahrenheit and air speeds of 8000 - 40000 feet per minute. The dryer fabric (32) employed has a permeability of between 300 - 1200 cubic feet per minute per square foot and is designed to withstand peak temperatures of up to 900 degrees Fahrenheit and average temperatures of between 500 - 600 degrees Fahrenheit. A single transfer roll (150), or more advantageously, two grooved vacuum rolls (50) in a vacuum box (54) are disposed between the dryer rolls to maximize the circumferential wrap of the web and, at the same time, support and transport the web between dryer rolls.

Description

Dryer section of paper machine with drier-suppressing dryer air cap

Paper is usually produced by molding a fibrous mat, such as wood fibers, on a movable wire screen. This fiber is diluted in a mixture containing more than 99% water. As the paper web exits the forming screen, it may still contain more than 80% moisture. The paper web exits the forming or wet end of the paper machine and enters a press section, where the web contains 42 to 45 percent fiber content while the web is supported on a dryer fabric. By pressing to have a water content of the paper is reduced. The paper web exiting the press section is dried on numerous steam heated dryer rolls, reducing the moisture content of the paper by about 5 percent.

The dryer section accounts for a significant part of the overall length of the paper machine. When the web moves from the forming end to the take-up roll, its length may extend by about a quarter of a mile. Most of this length will occupy the dryer section. In the paper industry, the running speed of the web is required to have a high speed of about 4,000 to 5,000 feet per minute, so the faster the paper web moves through the dryer, the smaller the drying in each dryer is. The length should be longer.

Dryers of the type known as two-tier dryers comprise steam heated dryers having a diameter of 4 to 7 ft and consisting of two rows. The dryer rolls in the upper row and the dryer rolls in the lower row are staggered from each other. The paper web proceeds from the top row of dryer rolls to the bottom row of dryer rolls and back to the top row of dryer rolls in the form of a winding of the required number of dryer rolls. The upper dryer fabric supports the web when it runs over the dryer rolls in the upper row and separates from the web when it runs over the dryer rolls in the lower row. The upper dryer fabric is run by dryer fabric counter-rotating rolls arranged at a distance between the dryer rolls in the upper row. The web is supported by the lower dryer fabric on the lower row of dryer rolls, which are also rotated between the lower rows of dryer rolls by the lower dryer fabric counterrotating rolls. This structure is advantageous for first drying the first side of the web and then drying the second side of the web, but the paper web is when it passes from the upper row dryer rolls to the lower row dryer rolls and from the lower row dryer rolls to the upper row dryer rolls. It is not supported over some intervals. This unsupported paper web causes problems as the web speed increases. When the speed of the web is high, the paper interacts with the air and starts to flutter. Such flutter causes wrinkles and folds in the paper web, thus significantly reducing the quality of the paper produced. Moreover, such flapping can cause the web to tear or break, leading to a cost increase associated with downtime caused by paper lost during rethreading operations.

The first approach to solve this problem is to use a single dryer fabric or wire that runs with the paper web over the upper and lower rows of dryers so that the paper web is supported as it passes through the open draw. This method can suppress the flutter of the paper in the open draw, but the function of the dryer roll in the lower row is significantly degraded because the dryer fabric is interposed between the paper web to be dried and the dryer rolls in the lower row.

Another solution is to use a row of dryer rolls with the vacuum counter-rotating rolls interposed in between. Vacuum rolls as disclosed in U.S. Patent No. 4,882,854 (Wedel et al.) Use vacuum to secure the paper edges to the reverse rotation roll edges to prevent the edges of the paper from fluttering and to use a dryer fabric with central grooves. Allow the boundary layer to be constrained between and the reverse roll to pass through.

In-line dryer devices can reduce the length of the dryer section of the paper machine and are successful in increasing the drying rate. In order to effectively dry both sides of the web, it is necessary to use both a pedestal in-line dryer and a pedestal in-line dryer. Disadvantages of the dryer with the felt underneath are that it is difficult to remove the fragments of the web from between the dryer fabric and the dryer and this removal is time consuming. On the other hand, in the dryer with the felt installed thereon, the loosening of the dryer fabric allows the fragments of the web to escape relatively easily between the dryer fabric and the dryer roll. Another problem with inline dryers is that one side of the web must first be dried and then the other side sequentially dried. If both sides of the sheet do not dry at the same time, the paper curls because the dimensions of the fibers on one side of the web and the dimensions of the fibers on the other side that are still wet depend on drying. Curls of such sheets cause curling of the paper web in both the machine direction (the longitudinal direction of the web) and the machine transverse direction (the width direction of the web).

The problem of generating curls in the paper web, which occurs when the paper web passes through the dryer section, is another problem because it tends to dry faster at the edge of the web than in the center of the web. In order to solve the problem of changing the moisture profile in the paper web to be dried, conventionally, a method of further drying the center of the web by using an infrared radiator divided by zones has been used. Optionally, water was sprayed onto the edges of the paper to increase the moisture content of the edges to approximate the moisture content in the center of the paper. Another solution is to install a steam box that extends across the width of the paper web, which is connected to a steam source to apply steam to the web, thereby equalizing the properties of the web.

The non-uniform drying of the web along the machine transverse direction by the paper machine results in a non-uniform tension profile as the paper is more heavily deformed at the edge of the dryer, thus providing a cause of curling when the web is molded into the sheet. Coaling of paper has an especially inadequate effect on high-quality paper that will be produced by new printing and copying methods. Laser printers and copiers heat one side of the paper at a very high speed. If the paper is curled due to this heating, the paper fed to the printer or copier may jam.

Accordingly, the problem to be solved by the present invention is to provide a short dryer section that can simultaneously dry both sides of the web and can reliably control the paper moisture profile in the machine transverse direction.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dryer for use in paper machines, and more particularly to a single tier type dryer.

1 is a side view schematically showing a dryer section according to the invention with two counter-rotating rolls,

2 is a side view schematically showing a dryer section according to the present invention having one reverse roll;

3A and 3B schematically illustrate a paper machine equipped with the dryer section of FIG. 1,

4A and 4B are schematic views of another embodiment of a paper machine with a dryer section according to the invention,

FIG. 5 is a perspective view partially cut out of a dryer air cap provided with a plurality of partitions in the machine transverse direction. FIG.

The paper dryer section according to the invention is a lined dryer section with a felt installed on top. The diameter of the dryer rolls is preferably 8 to 12 feet, which is larger than the conventional 6 feet. By arranging the dryers in a row, it is easy to remove the broken webs with a felt on top. An air cap is installed on the dryer rolls to dry both sides of the web simultaneously to prevent curling and increase the drying speed. The temperature of the air blown by this air cap is 200-900 ° F., and the speed is 8,000-40,000 ft per minute. As the dryer fabric, a porous dryer fabric is used which exhibits a permeablity of 400-1,200 cubic feet per square foot and can withstand an average temperature of 500-600 degrees Fahrenheit to a peak temperature of 900 degrees Fahrenheit. One or preferably two vacuum rolls provided in the vacuum box are arranged between the dryer rolls to maximally wind the web in the circumferential direction and at the same time support and transport the web between the dryer rolls.

The dryer section according to another aspect may adopt a configuration consisting of a combination of lined dryer rolls with felt at the top and a lined dryer with felt at the bottom. The air cap may be installed below or above the in-line dryer. The dryer section is additionally provided with an air cap which is optionally divided transversely to the machine. By installing such a split air cap, the machine transverse profile of the amount and temperature of air applied to the web through the dryer fabric allows for a uniform distribution of the moisture content in the machine transverse direction. Beta sensors are used to detect the moisture content of the web when the web leaves the dryer section. The controller will use the moisture profile sensed by the beta sensor to adjust the amount of drying of each web in the machine transverse direction introduced.

It is a feature of the present invention to provide a paper machine capable of increasing the drying rate of a paper web.

Another feature of the present invention is to provide a more compact paper machine.

It is another feature of the present invention to provide a paper machine which prevents curl from occurring in the paper web to be dried.

It is another feature of the present invention to provide a dryer section which can reliably control the moisture content distributed in the machine transverse direction of the paper web.

It is another feature of the present invention to provide a dryer section of a paper machine capable of suppressing curl generation and maximizing the onesideness of the molded paper.

Further features and advantages of the present invention will become more apparent from the following description of various embodiments of the present invention, and from the accompanying drawings.

The same reference numerals shown in Figs. 1 to 5 denote the same components, in particular the papermaking machine 20 is shown in Figs. 3A to 3B. The paper machine is equipped with a dryer section 22. The dryer section consists of steam heated dryer rolls 24 therein, the diameter of which is preferably 8 to 12 feet, which is larger than the conventional 6 feet. The dryer rolls are rotated about an axis 26 lying in a single plane. This arrangement is common in line dryer sections.

As shown in FIGS. 3A and 3B, the paper web 28 has a first dryer fabric 30, a second dryer fabric 32 and a third dryer fabric when it is moved through the dryer section 22. 34 is sequentially wound on the dryer roll (24). Each dryer roll 24 has a dryer surface 36. The dryer surface 36 of the dryer roll is formed into a cylinder so that the cross-sectional area of the roll is circular. The circular cross section has a top or ceiling point 38 and a bottom or ceiling bottom 40 below each dryer roll 24. The dryer fabrics 30, 32, 34 wind the dryer rolls 24 to wrap the ceiling points 38 of the rolls but not the bottom or the bottom 40 of the rolls. This arrangement of the dryer fabric is called the upper felt type.

The upper felt dryer section 22 is advantageous over the felted dryer system in which the bottom of the dryer roll is wrapped around the dryer fabric in that the fragments of the web can be easily removed from the dryer section if the web is torn.

The paper machine 20 as shown in FIGS. 3A-3B is operated at a speed of 6,500 feet per minute. The tearing of paper, which is the most troublesome in paper machines, inevitably occurs, especially when trying to vary the grade of paper or when changing maintenance and dryer fabrics. When a paper tear is detected before the paper machine stops operating, a high amount of paper or debris accumulates in the paper machine due to the high speed operation of the paper machine. As a result, the torn paper webs are often wound around a dryer roll. In the upper felt type, the dry fabric is loosened from the dryer roll 24 so that the laminated paper debris can be easily removed and dropped from the dryer roll. This is due to the fact that the piece of paper between the dryer fabric and the dryer roll must be pulled out and the dryer fabric formed a pocket around the dryer roll that can hold and tear the torn paper and form a felt-lined dryer Is in contrast.

The disadvantage of a lined dryer with felt mounted on top is that typically only one side of both sides of the paper web is dried. When the paper web is dried only in one direction, a dimensional change occurs between the side of the web of the dryer side and the side of the web of the drier fabric, because both sides of the web alternately harden or curl. The dryer section 22 described above solves this problem by using an air cap 42 to dry the side of the dryer fabric side web. This air cap 42 is a hood covering the upper portion 44 of the dryer roll 24, the same speed as the drying rate of the surface of the roll-side paper to be dried by steam heat transferred to the surface 36 of the dryer roll 24 A high speed hot air is blown through the dryer fabric to simultaneously dry the top surfaces of the web.

The dryer fabric must be porous or perforated to allow air to pass through the dryer fabrics 30, 32, 34. Thus, the permeability of the dryer fabric installed in the dryer section 22 is 400 to 1,200 cubic minutes per square foot at a pressure of 0.5 inches of water as measured by a person skilled in the art of designing and manufacturing a paper dryer fabric. Feet. The temperature range of the air supplied by the air cap 42 is 250 to 900 ° F., and the speed is blown at 8,000 to 40,000 ft per minute. The dryer fabric must be able to withstand steady state temperatures in the range of 500 to 600 ° F. and up to 900 ° F. for a short time to be able to operate under these high speed and high temperature air conditions.

Dryer fabrics having these characteristics are high temperature plastics such as metal, polyetheretherketone (PEEK) or polyphenylene sulfide (PPS) under the trade name Ryton 7 fiber manufactured by Philips Petrolium Company, or E.I. at Wilmington Market Street 1007, Delaware, USA. Other high temperature materials such as the tradename Nomex 7 fiber manufactured by DuPont de Nemors Corporation.

As shown in Figs. 3A and 3B, a plurality of dryer fabrics 30, 32, and 34 are installed. In this embodiment, when the paper web 28 is conveyed between the first dryer fabric 30 and the second dryer fabric 32 or between the second dryer fabric 32 and the third dryer fabric 34, A device in the form of a paper web on a dryer roll that is not supported by a dryer fabric over the section 46 is adopted, namely a so-called lick-down web conveying device. Since the air cap 48 adjacent to the rig down conveying device 47 does not blow into the unsupported short section 46, the unsupported web does not scatter from the surface 36 of the dryer roll.

The web 28 is conveyed between the plurality of dryer rolls 24 in a row. Since only one row of dryer rolls 24 are provided in the dryer section 22, the reverse rotation to transfer the paper web 28 from the surface 36 of one dryer roll 24 to another adjacent dryer roll Roll 50 is used. In order to maximize the amount of drying that can be obtained per dryer roll 24, it is desirable that the web be wound as much as possible in the dryer surface 38 of each dryer roll. 1 and 3A-3B, the surface 36 of the roll being wound by the dryer felts 30, 32, 34 and the web by providing two spaced reverse rotating rolls 50 ) Can be maximized. The portion 52 in which the dryer fabric is wound comprises about 80 percent of the dryer roll surface 36, which corresponds to about 290 degrees around the roll surface.

As shown in FIG. 1, when two reverse rotation rolls 50 are installed, the web 28 supports the web as it passes the reverse rotation roll 50 to prevent flapping and further tearing of paper. desirable. The vacuum chamber 54 is formed by a rigid metal structure 58 disposed in the gap 46 between the dryer rolls 24. This vacuum chamber 54 is formed by a metal cover 58 that is sealed against the dryer fabrics 30, 32, 34 that move to generate an internal vacuum where the reduced pressure is drawn. The cover 58 consists of two side plates 60, one of which is shown in FIG. 1. The side plate 60 is connected along the top by the top plate 62. Each side plate 60 is provided with two clearance openings 64 of smaller diameter than the reverse rotation roll 50. It is usually desirable to draw a vacuum into the vacuum box 54, but similar effects can be achieved with a blowing box. However, in the blower box, the decompression obtained by this is limited, so that only a smaller clamping effect is exerted.

The reverse roll 50 has grooves formed along the circumferential direction to easily hold the paper web and the dryer fabric to the reverse roll 50. The reverse rotation roll 50 is rotatably mounted in the vacuum chamber 54. The opening 64 provides a gap for the side wall extension of the shaft (not shown) to which the roll 50 will be mounted. The side plates 60 face each other and are arranged perpendicularly to the central axis of the dryer roll 24. A hole (not shown) drilled through the side plate 60 allows the vacuum of the vacuum chamber 54 to be drawn by an external vacuum means (not shown). Each side plate 60 has an upper segment 66 in which the grooves extend over the shredding rolls 50 and tabs 68 extending downwards for the blocking of air leaving the grooves to the sides of the shredding rolls. The horizontal edge 70 of the lower portion of this tab 68 engages the dryer fabrics 30, 32, 34 passing between two grooved rolls 50. Reinforcing ribs (not shown) protruding inward from the inner circumference of the side plate may be provided to prevent the side plates 60 from being excessively deflected by the application of vacuum. Between the side plates 60 two inclined flanges 72 extend from the top plate 62. Each inclined flange 72 extends upwardly of the top plate 62 and extends inward toward the center of the top plate 62, thereby making an acute angle with respect to the top plate 62. By providing the grooved roll 50 and the vacuum box 54, the web can be constrained and also prevent the tearing that occurs when the supported dryer fabric is transferred from one dryer roll to the next while preventing tearing of the paper. You can do it.

As shown in FIG. 2, the dryer section 122 according to a variant of the present invention uses a dryer roll 124 and an air cap 142. The dryer section 124 is the dryer section 24 shown in FIG. 1 except for using one reverse roll 150 to transfer the web 128 and the dryer fabric 130 between the dryer rolls 124. Similar to). By using one reverse rotating roll, the structure of the dryer section 122 is simplified. However, by using one counter-rotating roll, the percentage of the portion 152 where the fabric is wound over the entire surface area 136 of the roll is to the percentage at which the fabric is wound in the dryer section 22 shown in FIG. Slightly smaller than

The reverse rotation rolls 50 and 150 are preferably placed as close to the dryer roll as possible to minimize the portion of the dryer fabric or web that is not securely anchored to the dryer surface. As the web passes through the dryer section, the quality of the sheet can be improved by pressing the web. Shrinkage in the machine direction can be suppressed by adjusting the dryer speed to exert tension on the web. The machine transverse shrinkage can be suppressed by securing the web to the dryer surface with tension on the dryer fabric, and by holding the web onto the dryer fabric as it moves around the reverse roll under vacuum. Therefore, it is important to constrain the web as much as possible. Using a dryer roll with a diameter of 8 to 12 ft means that the tension of the dryer fabric must be increased if the holding force applied to the surface of the dryer roll is kept constant. Increasing the tension of the dryer fabric increases the load on the dryer roll, the reverse roll, and other rolls on which the dryer fabric is wound, which requires an increase in roll hardness and an increase in roll bearing strength. For example, the tension applied to the dryer fabric is about 10 to 20 pounds per linear inch for a 6ft diameter dryer, which increases in proportion to the dryer diameter up to 20ft diameter.

However, when the paper is torn, the reverse rolls 50,150 cannot be placed too close to the dryer roll because the web is wound around the dryer and then engaged by the adjacent reverse roll. In practice, the minimum spacing between the reversing rolls and the dryer rolls is determined by the thickness of the paper to be manufactured and the speed at which the tearing of the paper is automatically detected and the web is diverging from the dryer section, causing the reversing roll to move away from the dryer roll. It is determined regardless of what is mounted to be pivoted. Thus, the counter-rotating rolls are typically placed on the order of 1 to 5 inches away from the dryer roll for the particular situation as determined by the paper mill operator.

A paper machine 20 according to an embodiment of the invention comprising a dryer section 22 is shown in FIGS. 3A and 3B. The paper machine 20 can be used to produce 28 pounds of newspaper paper using wires 420 inches wide and operating at a speed of 6,500 feet per minute. The paper machine 20 includes a former 88 having a vertically oriented headbox 80, the headbox having a first forming wire 84 and a twin wire former 88. And a slice opening 82 for injecting the pulp stream between the second forming wires 88. Paper web 28 is conveyed to press section 90 where a single expanded nip press 92 will perform a crimping function. The web 28 is then wound on the first dryer fabric 30 and transferred to the dryer section 22. The web after being transferred to the dryer section 22 is calendered using hot soft nip calenders 94 and 95. Following the calendaring, the web is wound on the reel by the winder 96.

The soft nip calendar 94 has an upper hot compress roll 98 and a lower compliant support roll 100. The calendar 94 is of a temperature gradient type, in which the web is deformed when only the surface in contact with the heated roll without being preheated passes through the calendar 94. The second soft nip calender 95 has a lower hot compress roll 102 and an upper support roll 104. The hot press rolls 98 and 102 engage with both sides of the web 28. Accordingly, the surface of the web 28 is changed by changing the temperature of the upper heat pressing roll with respect to the temperature of the lower heat pressing roll, and changing the pressing pressure of the first calender 94 with respect to the pressure of the second calender 95. These may be treated differently to compensate for the twosidedness of the web caused by the dryer section 22.

In an embodiment of the present invention, devices commercially available from Beloit Corporation of Beloit, Wisconsin, USA, are used. The twin wire former may be a Bel-Bai RCB-type closed jet former from Beloit Corporation. The headbox used is also a Concept IV-MH headbox using consistent profiling, a Beloit Corporation product. Press sections, high temperature soft nip calendars and lilos may also be used as Beloit Corporation products.

The paper machine 22 with the dryer section 24 may be a compact structure consisting of a relatively small number of dryer rolls and rolls of any type. Since each roll, as well as their bearings and support devices, are expensive, the example paper machine shown in FIGS. 3A and 3B helps to improve cost, reliability, and operability.

4A and 4B show a variation of paper machine 220 with dryer section 222. This paper machine 220 has a former 224 similar to the former 88 described above. The former 224 includes a headbox 226 with a slice 228 that guides the feed stream between the first wire 230 and the second wire 232. A lumpbreaker press 234 consists of a lower press roll 236 and an upper support roll 238. Lower press roll 236 is embedded in a loop formed by second wire 232.

The upper support roll 238 is embedded in a loop formed by the crimping felt 240. By using the lumpbreaker press 234, the fiber content of the web 242 molded by the former 224 is increased from 16 dry weight percent to 22 dry weight percent. The lumpbreaker press 234 may be placed in front of the crimping felt 240 that engages the second forming wire 232. This arrangement is advantageous in that it can minimize the amount of moisture being pressed into the crimping felt 240. The lower press roll 236 and the upper support roll 238 are preferably provided with an elastic cover to minimize marks remaining on the web formed by the forming wire 224.

A press section 244 having one concave shoe press 246, such as the product name Extended nip7 type press of Beloit Corporation, is subsequently placed in the former 224. The dryer section 248 shown in FIG. 4B is a variant of the dryer section 22. Dryer section 248 uses a tandem dryer. However, the first fabric group 250 does not have an air cap and does not install an air cap from an existing paper machine, i.e., a dryer roll adjacent to the press section. It is a modified form of the dryer section 22 which is made by installing a cap additionally. Moreover, since the first fabric group of dryer roll 250 shown in FIG. 4B includes fewer dryer rolls, the absence of air caps does not have a significant impact on shorter dryer sections. The first fabric group of dryer rolls uses a dryer roll 252 that rotates about an axis 254.

The expression "fabric group" of dryer rolls generally means a group of dryer rolls arranged in a single plane engaged by one dryer fabric. The second fabric group of dryer rolls 256 has an air cap 258 disposed on top of the dryer rolls 260. The reversal rolls 262 between each set of dryer rolls cooperate with the dryer fabric 264 to allow the paper web 242 to be secured by the vacuum drawn through the dryer fabric 264. Each dryer roll 260 has a ceiling point 266 and a ceiling bottom 268. The dryer roll 260 is an upper felt type in which the dryer fabric 264 winds the top of the dryer roll including the ceiling point 266 but not the ceiling bottom 268. Although felt dryer dryer rolls are preferred due to their advantages in handling paper debris, in some situations one or more felt dryer rolls may be provided to enhance dryness on one side of the paper web 242. 270) may also be preferred.

The final dryer roll 272 of the fabric group 256 in front of the dryer roll 270 with the felt installed therein does not have an air cap for space saving, but the S-shaped web feeder 274 shown in FIG. 4B. Will lead to The S-shaped web feeder 274 does not include a web 242 and is provided with a narrow gap between the transfer dryer fabrics for simplicity of the device. The S-shaped web feeder holds the web between the upper dryer felt 264 and the lower dryer felt 276. The S-shaped web feeder provides a means for conveying the web from the first dryer section to the second dryer section, in which the web is felt felt from the top of the dryer fabric group 256 with an upper felt without open draw. Is transferred to the fabric group of the installed dryer rolls 278. Since the S-shaped web feeder forms a joint run of the upper dryer fabric 264 and the lower dryer fabric 276, the web is delivered by the upper dryer fabric in close contact with the lower dryer fabric. The upper dryer fabric then diverges from the web and the web is loaded onto the lower dryer fabric.

Although the air cap 280 is provided in the dryer roll 270 in which the felt is installed in the lower part shown in FIG. 4B, it may not be provided with the air cap depending on the paper to be dried. An advantage of adopting a dryer roll 270 with a felt installed at the bottom thereof is that one side of the web 242 can be dried. In some cases, this advantage is offset by the problems associated with removing web debris from the dryer rolls with the felt underneath. An additional fabric group 282 of felt rolled dryer rolls, followed by a felted fabric group 278 at the bottom, may be used if good drying of the paper web 242 is desired.

A significant problem associated with the drying of paper webs is that the webs tend to dry faster at different locations than at certain locations in the machine transverse direction. As shown in FIG. 5, an air cap 283, divided into baffle compartments 284 by baffles 288, can be used to control the moisture content of the web in the machine transverse direction. As schematically shown in FIG. 4B, a sensor 286 for measuring moisture in the web is mounted to allow the web to be transported in the transverse direction and provides profile data indicative of the moisture contained in the web. Conventional sensors use beta radiation to detect moisture contained in the web.

A computer or controller (not shown) is provided that analyzes the output of the sensor to control the speed of air and / or the temperature of the air introduced into each compartment compartment 284 of the air cap 283. Thus, this controller responds according to the moisture profile in the processed web to adjust the processing of subsequent portions of the web. In practice, a single temperature of air is introduced into each compartment by a series of dampers (not shown) that control the amount of heated air supplied to each compartment compartment 284 under the control of a computer and a controller. The compartment 284 is formed by a baffle 288 that divides the air cap 283 into areas in which air flow can be individually controlled. This baffle 288 extends in the machine direction, and the compartment 284 is aligned in the machine transverse direction. The baffle 288 may be used with any of the air caps 258, 280, 42, 122 shown in FIGS. 1-4B for profiling moisture contained in the web. The air cap 283 is schematically illustrated as disposed above a conventional dryer roll 290. For the sake of simplicity the illustration of additional duckwork and gas firing devices is omitted.

Although the new paper machine can be made by applying the present invention shown in FIGS. 4A and 4B, the existing paper machine can be replaced with the structure according to various embodiments of the present invention. In particular, although the illustrated dryer roll is not provided with an air cap, each dryer roll should be provided with an air cap when it is desired to obtain a maximum drying capacity in a newly produced filing machine. Due to the space constraints associated with the dryer fabric transporter, a partial air cap can be installed if a complete air cap cannot be installed over the dryer roll.

The temperature of the air used in the dryer air cap may vary between the wet and dry ends of the dryer with a higher temperature at the wet end of the dryer.

Typical air speed is 28,000 ft per minute and air temperature can be 750 ° F. In general, the temperature of the air should be at least 250 ° F. when the air velocity is at least 12,000 ft per minute.

The permeability of the dryer fabric, commonly referred to as the specification of a dryer felt or dryer canvas, should be higher than a conventional dryer fabric having a permeability of 90 to 120 cubic feet per minute per square foot at a pressure of 0.5 inches of water column. Preferably, the permeability of the dryer fabric should be higher than 200 to 300 cubic feet per minute per square foot at a pressure of a few 0.5 inches. More preferably, the permeability of the dryer fabric should be higher than 300 to 1,200 cubic feet per minute per square foot at a pressure of a few 0.5 inches.

To make the dryer surface larger for a given flowprint, larger dryer rolls can be used, and the dryer technology used by the Yankee dryer manufacturers allows them to produce dryer rolls as large as 20 feet.

A further advantage of the dryer section 22 according to the invention is that if all the dryer rolls are in line, the dryer section can be mounted directly on the mill floor without the need to install a bottom structure under the dryer. This relatively simple and more robust mounting structure is better.

Although embodiments with three dryer fabrics are shown herein, more or fewer dryer fabrics may be used. Three advantages of using a larger number of dryer fabrics are: First, as the drying process is completed, the length of the paper becomes slightly longer or shorter, which allows the dryer rolls to operate at higher speeds as the paper passes through the dryer section 22. As the number of dryer fabrics increases, the step of increasing the speed of paper further subdivides. Second, more replacement of the dryer fabric can prevent the formation of marks that remain on the surface of the web when using one dryer fabric. Third, as dryer fabrics get shorter, they can be replaced more easily.

While the description and the accompanying drawings disclose preferred embodiments of the invention, those skilled in the art will recognize that many variations and modifications may be made which fall within the spirit and scope of the invention as defined in the appended claims. You will recognize that you can lose.

Claims (24)

At least one group of dryer rolls, each dryer roll having a portion wound by a single porous dryer fabric, each dryer roll of the dryer roll group having a rotation axis, wherein the rotation axes of the plurality of dryer rolls of the group At least one group of dryer rolls arranged in a substantially single plane, each group of dryer rolls having a best ceiling point and a lowest ceiling point; At least one reverse rotation roll disposed between a common dryer roll of the dryer roll group and disposed below a common plane on which the rotation axes of the dryer rolls are placed; A dryer fabric wound around the dryer roll group and the reverse rotation rolls to surround the ceiling point of each dryer roll of the dryer roll group but not to cover the bottom points of all the dryer rolls of the dryer roll group; And And an air cap positioned over almost all of the dryer rolls of the dryer roll group to blow air over the dryer fabric as the dryer fabric wraps around the dryer roll group. The dryer section of claim 1, wherein two counter-rotating rolls are disposed between adjacent dryer rolls. 3. A vacuum box is disposed between the adjacent dryer rolls and the two reverse rotating rolls are disposed between the adjacent dryer rolls to prevent flapping of the paper web as it progresses between adjacent dryer rolls. Dryer section of the paper machine. The dryer section of claim 1, wherein the dryer roll has a diameter of at least 8 feet. The dryer section of claim 1 wherein the diameter of the dryer roll is between 8 and 20 feet. The dryer section of claim 1 wherein the diameter of the dryer roll is between 6 and 20 feet. 3. The dryer section of claim 2, wherein the porous dryer fabric is wound about 290 degrees on each dryer roll. A plurality of first dryer rolls constituting a first dryer section, each first dryer roll forming a rotation axis, the rotation axes of the first dryer roll being arranged in a substantially single plane, each of the first dryer rolls having a ceiling point and A plurality of first dryer rolls having a bottom bottom; At least one first reverse rotation roll having a rotation axis disposed below a common plane on which the rotation axes of the first dryer rolls are placed, and between the adjacent first dryers; At least one first porous dryer fabric wound around each of the ceiling points of the first dryer roll but not around the bottom of any of the first dryer rolls and wound around the plurality of dryer rolls and the reverse rotation rolls; An air cap disposed over at least one of the first dryer rolls to blow heated air to at least a portion of the first dryer fabric when the dryer fabric is wound around the at least one first dryer roll; A plurality of second dryer rolls constituting a second dryer section, each second dryer roll forming an axis of rotation, the axis of rotation of the second dryer roll being arranged in a substantially single plane, each of the second dryer rolls having a ceiling point and A plurality of second dryer rolls having a bottom bottom; At least one second reverse rotation roll having a rotation axis disposed below a common plane on which the rotation axes of the second dryer rolls are placed, and between the adjacent first dryers; At least one second porous dryer fabric wound around each of the ceiling points of the second dryer rolls but not around the bottom points of any of the second dryer rolls and wound around the plurality of dryer rolls and the counter rotating rolls; An air cap disposed over at least one of the second dryer rolls to deliver heated air to at least a portion of the second dryer fabric when the second dryer fabric is wound around the at least one second dryer roll and; Dryer conveying means for conveying a web from a first dryer section to a second dryer section, said dryer conveying means conveying a web without open draw from a first dryer roll to a second dryer roll, said dryer conveying means being a first dryer fabric The web is delivered by the first dryer fabric in close contact with the second dryer fabric because it forms a joint run of the second dryer fabric, and then the first dryer fabric is downstream of the joint run. Dryer section of the paper machine, characterized in that it comprises a dryer conveying means adapted to be supported on the second dryer fabric when diverged from the dryer fabric. 9. The dryer section of claim 8, wherein two counter-rotating rolls are disposed between each pair of adjacent first dryer rolls and each pair of adjacent second dryer rolls. 10. The apparatus of claim 9, wherein a vacuum box is disposed between the adjacent dryer rolls, wherein the two counter-rotating rolls are disposed between the adjacent dryer rolls to prevent flapping of the paper web when the paper web is advanced between adjacent dryer rolls. Dryer section of the paper machine. 9. The dryer section of claim 8, wherein the dryer roll has a diameter of at least 8 ft. 9. The dryer section of claim 8, wherein the diameter of the dryer roll is between 8 and 20 feet. 10. The paper machine of claim 8, wherein the speed of the paper web conveyed to the dryer section increases as the at least three separate dryer fabrics are used and the length thereof increases as the web is moved through the dryer section. Dryer section. 10. The dryer section of claim 9, wherein the porous dryer fabric is wound about 290 degrees on each dryer roll. By drying the paper web in the dryer section of the paper machine, Each dryer roll has a top and a bottom and the web is not wound on any bottom of any roll, and 300 to 1,200 cubic feet per square foot at a pressure of a few inches of pressure around a portion of the plurality of dryer rolls in a nearly single plane. Winding the paper web laid down by the porous dryer fabric with permeability of the pit; And Simultaneously dry both sides of the web by steam heating the dryer roll and blowing air at a temperature higher than 250 ° F. at a rate of 8,000 to 40,000 ft per minute through at least a portion of the porous dryer fabric that places the paper web on the surface of the dryer roll. Drying method of the web, characterized in that it comprises the step of. 16. The method of claim 15, further comprising applying a tension proportional to the dryer diameter up to a 20ft diameter to the porous dryer fabric that is about 10 to 20 pounds per linear inch for a 6ft diameter dryer. As a paper machine for forming a paper web, A line-type dryer roll having felt mounted on at least one upper portion having a first dryer roll rotatable about a first axis and a second dryer roll rotatable about a second axis parallel to the first axis; A first reverse rotation roll disposed between the first dryer roll and the second dryer roll and rotating about an axis parallel to the first and second axes and disposed below the first and second axes; With a dryer fabric extending above the first dryer roll, below the first reverse roll and above the second dryer roll, the web is supported between the dryer fabric and the first dryer roll and the second dryer roll, and the web and the first rotation A dryer fabric disposed on the roll; An air cap located above the first dryer roll and the second dryer roll to release air to a portion of the dryer fabric when at least a portion of the dryer fabric is rolled over the dryer roll, the dryer fabric having an air dryer to allow the web to increase drying. One end of the paper web is exclusively dried on a dryer roll with felt at the top, and the other side is configured to be dried by air from the air cap; A first high temperature soft nip calender in the form in which the web is not preheated and thus the first calender provides temperature-sensitive calendering, the first calender accepting the web for at least one row of dryer rolls, A first high temperature soft nip calender configured to have a first hot press roll in contact with the first surface; And A second high temperature soft nip calender in the form in which the web is not preheated and thus the second calendar provides temperature-sensitive calendering, the second calendar accepting the web relative to the first calendar and And a second hot press roll in contact with the opposite side, the first and second calendars having a first pressure and temperature relative to the pressure and temperature of the second calendar to compensate for the difference in surface characteristics of the web created by driving the web. And a second high temperature soft nip calender configured to form as a means of reducing the double-sidedness of the web by selecting the pressure and temperature of the calender. 18. The paper machine according to claim 17, wherein all of the dryer rolls of the paper machine are provided with felts thereon. 18. The dryer of claim 17, wherein two counter-rotating rolls are disposed between the first dryer roll and the second dryer roll to draw a vacuum on the dryer fabric when transferred from the first dryer roll, the dryer fabric, to the second dryer roll. The paper machine further comprising a vacuum box disposed between the counter-rotating rolls. 20. The vacuum cleaner of claim 19 wherein two counter-rotating rolls are disposed between the first dryer roll and the second dryer roll to draw a vacuum on the dryer fabric when transferred from the first dryer roll, the dryer fabric, to the second dryer roll. The paper machine further comprising a blower box disposed between the counter-rotating rolls. At least one heating dryer roll extending in the machine transverse direction and having a paper drying surface; A paper web that advances to a dryer roll and lies on a portion of the paper dry side; An arrangement arranged to blow the heated air against at least a portion of the drying face of the dryer roll running transverse to the web, the arrangement directing the heated air over the web and extending in the machine transverse direction as the web traverses the dryer roll An air cap divided into a plurality of means provided to form a; Sensor means disposed downstream of the dryer roll to provide a moisture profile of the web in the ging direction of the machine; And a means for adjusting the amount of air reacted according to the moisture profile provided by the sensor means for controlling the moisture profile of the web in the machine transverse direction to direct the heated air directed to the web. section. 22. The apparatus of claim 21, wherein the plurality of dryer rolls comprising a plurality of dryer rolls with felts further included therein, each of the plurality of dryer rolls guiding heated air to the web as the web passes through each dryer roll. A papermaking dryer section comprising an air cap divided by two means. As a method of drying paper webs in paper machines, Shaping the paper web and directing the web to the dryer section; Drying the web on a steam heated dryer roll with the web bound to the dryer roll with a dryer fabric; Measuring the moisture profile of the web in the machine transverse direction after the web leaves the dryer section; Machine crosswise over the dryer roll in response to the measured moisture profile of the web to improve the uniformity of the moisture content distributed across the web in the machine direction, while drying the web by blowing air into the constrained web through the dryer fabric. Drying method of the paper web, characterized in that it comprises the step of adjusting the air blown into. At least one group of dryer rolls, each dryer roll having a portion wound by a single porous dryer fabric, each group of dryer rolls having an axis of rotation, the axes of rotation of the plurality of dryer stones of the group being substantially single A group of at least one dryer roll arranged in a plane, each of said group of dryer rolls having a ceiling point and a ceiling bottom; At least one reverse rotation roll having a rotation axis disposed below a common plane on which the rotation axes of the dryer rolls lie, and between adjacent dryer rolls of the group; A dryer fabric wound around each of the dryer rolls of the group but wound around the dryer roll group and the counter-rotating rolls without winding around the ceiling point of any dryer roll of the group; And A dryer section of the paper machine, comprising an air cap positioned over almost all dryer rolls of the group and arranged to blow air over the dryer fabric when the dryer fabric is wound around a group of dryer rolls. .