Reduced diameter foraminous exhaust cylinder

Abstract

Described herein are devices and methods for the drying of permeable and semi-permeable webs such as paper products in a physical environment with limited space while providing for higher flow rates. The devices and methods of the present invention are for use with rotating, foraminous shelled roll dryers and are implemented by redesigning the aspects of the devices and methods associated with exhausting spent drying gas.

Claims

1. A rotatable, foraminous shelled roll dryer, for drying permeable and semi-permeable webs, with reduced diameter exhaust shell, comprising: a. a first and second spaced apart, circular, parallel end members, each having a diameter and an inner face and an outer face; b. a first foraminous cylinder positioned between and secured to the first and second parallel end members, the first foraminous cylinder having an outer diameter substantially equivalent to the diameter of the parallel end members and having a surface area, the first foraminous cylinder designed for a flow of drying gas into the first foraminous cylinder; and c. a second foraminous cylinder of a smaller diameter than the first foraminous cylinder positioned at the outer face of the first parallel end member and in fluid communication with the first foraminous cylinder, the second foraminous cylinder having a surface area of about 20% to about 75% of the surface area of the first foraminous cylinder, the second foraminous cylinder designed for exhausting drying gas out of the first foraminous cylinder.

2. The foraminous shelled roll dryer of claim 1, wherein the surface area of the second foraminous cylinder is about 30% to about 50% the surface area of the first foraminous cylinder.

3. The foraminous shelled roll dryer of claim 1, wherein the diameter of the second foraminous cylinder is at least 10% less than the diameter of the first foraminous cylinder.

4. The foraminous shelled roll dryer of claim 1, wherein the diameter of the second foraminous cylinder is at least 25% less than the diameter of the first foraminous cylinder.

5. The foraminous shelled roll dryer of claim 1, wherein the diameter of the second foraminous cylinder is at least 10% less but no more than 40% less than the diameter of the first foraminous cylinder.

6. The foraminous shelled roll dryer of claim 1, wherein the second foraminous cylinder has a circular parallel end member positioned at the end of the second foraminous cylinder positioned opposite to the first parallel end member and parallel to the first parallel end member.

7. The foraminous shelled roll dryer of claim 1, further comprising a third foraminous cylinder of a smaller diameter than the first foraminous cylinder positioned at the outer face of the second parallel end member and in fluid communication with the first foraminous cylinder, the second and third foraminous cylinders having a combined surface area of about 20% to about 75% of the surface area of the first foraminous cylinder, the third foraminous cylinder designed for exhausting drying gas out of the first foraminous cylinder.

8. The foraminous shelled roll dryer of claim 7, wherein the combined surface area of the second and third foraminous cylinders is about 30% to about 50% the surface area of the first foraminous cylinder.

9. The foraminous shelled roll dryer of claim 7, wherein the diameter of the third foraminous cylinder is at least 10% less than the diameter of the first foraminous cylinder.

10. The foraminous shelled roll dryer of claim 7, wherein the diameter of the third foraminous cylinder is at least 25% less than the diameter of the first foraminous cylinder.

11. The foraminous shelled roll dryer of claim 7, wherein the third foraminous cylinder has a circular parallel end member positioned at the end of the third foraminous cylinder positioned opposite to the second parallel member and parallel to the second parallel member.

12. The foraminous shelled roll dryer of claim 7, wherein the diameter of the third foraminous cylinder is at least 10% less but no more than 40% less than the diameter of the first foraminous cylinder.

13. The foraminous shelled roll dryer of claim 1, the dryer further comprising an area substantially the length of the first foraminous cylinder designed for the delivery of cooling gas separately from the delivery of the drying gas, the cooling gas at a temperature approximately 4 C. to approximately 32 C., wherein the area designed for the delivery of a cooling gas is located at or proximal to where the web being dried leaves the first foraminous cylinder.

14. The foraminous shelled roll dryer of claim 13, the second foraminous cylinder further comprising an area substantially the length of the second foraminous cylinder designed for the exhausting of cooling gas separately from the exhausting of the drying gas.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a perspective view of the foraminous shelled roll dryer of the present invention with reduced diameter exhaust.

(2) FIG. 2 shows a cross-sectional view of the foraminous shelled roll dryer of the present invention with reduced diameter exhaust. In this embodiment, the openings in the first foraminous cylinder vary in size with the openings having the greatest open area distal to the reduced diameter exhaust.

(3) FIG. 3 shows an embodiment of the foraminous shelled roll dryer of the present invention with flange bearings and mounting blocks providing a rotating distribution means that incorporates a perforated plate that rotates with the shell.

(4) FIG. 4 shows an embodiment of the foraminous shelled roll dryer of the present invention with dual exhaust regions, one on each side of the first foraminous cylinder.

(5) FIG. 5 shows an embodiment of the foraminous shelled roll dryer of the present invention with an extended reduced diameter exhaust.

(6) FIG. 6 shows an embodiment of the foraminous shelled roll dryer of the present invention wherein the air flow is reversed.

(7) FIG. 7 shows an embodiment of the foraminous shelled roll dryer of the present invention with support gussets in the exhaust shell.

(8) FIG. 8 shows an embodiment of the foraminous shelled roll dryer of the present invention with adjustable deckle seals.

(9) FIGS. 9 A & B show an embodiment of the foraminous shelled roll dryer of the present invention wherein the deckle bands are recessed. 9B shows a close-up view of the recessed deckle band.

(10) FIG. 10 shows an embodiment of the foraminous shelled roll dryer of the present invention wherein the deckle bands are exterior to the shell.

(11) FIG. 11 shows an embodiment of the present invention without the use of a centerpipe providing a rotating distribution means that incorporates a perforated plate that rotates with the shell.

(12) FIG. 12 shows three schematic diagrams with three different air handling pathways that are suitable for use with the present invention.

(13) FIGS. 13 A & B show an embodiment of the optional cool zone of the present invention. 13A shows the through air dryer or bonder with cool zone. 13B shows the exhaust cylinder and exhaust duct with a cool zone.

DETAILED DESCRIPTION OF THE INVENTION

(14) The present invention is directed towards apparatuses for and methods of drying permeable and semi-permeable webs such as paper, paper products and other nonwoven fiber products such as, but not limited to, filter media, hygiene products and wipes. U.S. Pat. Nos. 3,259,961, 3,590,453, 4,050,131, 6,314,659 and 8,656,605 describe devices and methods of drying permeable and semi-permeable webs, and are incorporated herein by reference in their entirety. The web may be comprised of woven and/or non-woven fibers. The present invention improves on devices and methods of drying permeable and semi-permeable webs by reconfiguring the device to allow for economical use of space in the drying facility and better control of exhaust gas resulting in greater control of velocity of drying gas across the web, thereby, resulting in greater drying uniformity while lowering energy requirements. Further, the foraminous shelled roll dryer design of the present invention may reduce or eliminate the need for baffles or other partitions in the first foraminous cylinder of the dryer resulting in cost savings in the manufacture of the dryer. In this regard, in an embodiment of the present invention, the device and methods of the present invention relate to the novel and non-obvious design of the exhaust section of the dryer and uses thereof. By reconfiguring the exhaust section of the dryer, the reduced diameter radial exhaust cylinder allows for the adaptation of the apparatus into areas of varying geometries and space constraints, allows for increased heated process gas velocities and allows for decreased energy consumption.

(15) Various embodiments of the invention will now be explained in greater detail. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. Any discussion of certain embodiments or features serves to illustrate certain exemplary aspects of the invention. The invention is not limited to the embodiments specifically discussed herein.

(16) Unless otherwise indicated, all numbers such as those expressing temperatures, weight percent, concentrations, time periods, dimensions, and values for certain parameters used in the specification and claims are to be understood as being modified in all instances by the term about, unless clearly stated otherwise. It should also be understood that the precise numerical values and ranges used in the specification and claims form additional embodiments of the invention.

(17) The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Accordingly, unless explicitly stated otherwise, the descriptions relate to one or more embodiments and should not be construed to limit the embodiments as a whole. This is true regardless of whether or not the disclosure states that a feature is related to a, the, one, one or more, some, or various embodiments. Instead, the proper scope of the embodiments is defined by the appended claims. Further, stating that a feature may exist indicates that the feature may exist in one or more embodiments.

(18) Also, as used in the specification including the appended claims, the singular forms a, an, and the include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from about or approximately one particular value and/or to about or approximately another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value and all values between, regardless as to if they have been explicitly identified. Similarly, when values are expressed as approximations, by use of the antecedent about, it will be understood that the particular value forms another embodiment.

(19) In this disclosure, the terms include, including, comprise, comprising, contain, containing, have, and having when used after a set or a system, mean an open inclusion and do not exclude addition of other, non-enumerated, members to the set or to the system. Further, unless stated otherwise or deducted otherwise from the context, the conjunction or, if used, is not exclusive, but is instead inclusive to mean and/or. Moreover, if these terms are used, a subset of a set may include one or more than one, up to and including all members of the set.

(20) The phrase consisting of excludes any element, step or ingredient not specified in the claim. The phrase consisting essentially of limits the scope of a claim to the specified materials or steps and materials or steps that do not materially affect the basic and novel characteristics of the claimed invention. It is clear from this specification which elements do and do not materially affect the basic and novel characteristics of the claimed invention. Further, any elements recited in a dependent claim, even though further limiting, are not considered to be essential to the elements recited in the identified independent claim. The present disclosure contemplates embodiments of the invention compositions and methods corresponding to the scope of each of these phrases. Thus, a composition or method comprising recited elements or steps contemplates particular embodiments in which the composition or method consists essentially of or consists of those elements or steps.

(21) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods and materials are now described.

(22) Methods of use of the drier/bonder of the present invention are evident from the description herein and are specifically included as part of the disclosed invention.

(23) Dryer Design

(24) The design of the dryer of the present invention, with reduced diameter exhaust cylinders, provides several and varying benefits including better control of drying of the permeable or semi-permeable web owing to better control of air flow characteristics and adaptable physical geometry. The heated drying gas (130 in FIG. 1), after passing through the web and shell and perforated plate of the first foraminous cylinder, is directed axially for a distance to the exhaust head. This design allows for greater control of drying velocity at the edges of the web thereby permitting even drying over the width of the web. The used, moisture laden drying gas exits the exhaust cylinder (170 in FIG. 1).

(25) In this regard, FIGS. 1 and 2 show an embodiment of the present invention 100. The large arrows denote direction of drying gas (i.e., heated process air) flow 130. The foraminous shelled roll dryer comprises a first foraminous cylinder comprising a shell 110, and a perforated plate 112. The web to be dried rotates with the outer shell. The perforated plate is stationary and does not rotate with the shell. The perforated plate and stationary center pipe 120 are connected by the support bars 160 which make up the stationary baffle assembly. The shell is supported by first 142A and second 142B parallel, substantially parallel or essentially parallel end caps or roll heads with optional gusset plates 150. Drying air passes through the web (not shown), the shell and perforated plate. Openings 140 in the perforated plate may be evenly spaced or they may be clustered. The openings may be of the same or similar size. In one embodiment, the sizing and location of the openings aid in the control of air flow through the foraminous shell and the web being dried. Thus, for example, over drying of the edges of a web can be controlled and regulated by the number, size and placement of the openings in foraminous cylinder. See, for example, the sizing difference of the openings 210, 220 in FIG. 2. One of skill in the art, based on the teachings of this specification, will be able to determine opening sizes and locations for the web being dried, without undue experimentation.

(26) The drying gas (e.g., heated process air), after passing over the web and acquiring moisture from the web, exits the first foraminous cylinder axially into the exhaust area comprising a second (FIGS. 2 and 3, 360) and, optionally, a third foraminous cylinder as shown in FIG. 4 (also referred to as the first and second exhaust cylinders), where the moisture laden gas radially exits into duct work (not shown). The exhaust cylinder or cylinders are in fluid communication with the first foraminous cylinder shell. The exhaust cylinder or cylinders have a surface area from about 20% to about 75% of the surface area of the first foraminous cylinder or from about 30% to about 50% of the surface area of the first foraminous cylinder. Each of the one or two exhaust cylinders is at least 10% smaller in diameter than the first foraminous cylinder, at least 25% smaller in diameter than the first foraminous cylinder or at least 40% smaller in diameter than the first foraminous cylinder. The exhaust cylinder or cylinders are designed to handle the volume of drying gas necessary for efficient gas flow through the dryer. In this regard, the size, surface area and porosity of the exhaust cylinder or cylinders is calculated to be able to handle the required maximum volume of drying gas without hindering the drying of the web. The exhaust cylinder (or cylinders) has an end cap 144 that is parallel, substantially parallel or essentially parallel to the first 142A and second 142B end caps. As can be seen in the figures, the end cap between the first foraminous cylinder and second and/or third foraminous cylinders allows for fluid communication between the respective cylinders.

(27) Continuing with the non-limiting embodiment of the present invention represented in FIGS. 2 and 3, the dryer with reduced diameter exhaust comprises a rotatable, first foraminous cylinder with a second foraminous cylinder with reduced diameter or, reduced diameter foraminous exhaust cylinder. The shell and perforated plate rotate about a stationary centerpipe. The dryer comprises a first and second spaced apart, circular, parallel end members, 142A and 142B, each having a diameter and an inner face and an outer face; a first foraminous cylinder 350 positioned between and secured to the first and second parallel end members, said first foraminous cylinder having an outer diameter substantially equivalent to the diameter of the parallel end members and having a surface area, said first foraminous cylinder designed for a flow of drying gas into the first foraminous cylinder. Also shown is the shell 110 of the first foraminous cylinder. A second foraminous cylinder 360 (i.e., the exhaust cylinder) of a smaller diameter than the first foraminous cylinder positioned at the outer face of the first parallel end member 142B and in fluid communication with the first foraminous cylinder, the second foraminous cylinder having an shell 310; the second foraminous cylinder having a surface area of about 20% to about 75% of the surface area of the first foraminous cylinder or having about 40% to about 60% of the surface area of the first foraminous cylinder or having about 30% to about 50% of the surface area of the first foraminous cylinder, said second foraminous cylinder designed for exhausting drying gas out of the first foraminous cylinder. The second foraminous cylinder is at least 10% smaller in diameter than the first foraminous cylinder, at least 25% smaller in diameter than the first foraminous cylinder or at least 40% smaller in diameter than the first foraminous cylinder. Thus, the configuration (i.e., ratio of axial length verses diameter) of the second foraminous cylinder may vary with regard to the spatial and other limitations so long as the surface area and diameter meet the aforementioned criteria. FIG. 3 also shows a pair of flange bearings 370 and mounting blocks 340. The dryer of FIG. 3 shows an embodiment of the foraminous shelled roll dryer of the present invention with flange bearings and mounting blocks that provide a rotating distribution means that incorporates a perforated plate 112 that rotates with the shell 110.

(28) Looking now at FIG. 4, in a non-limiting embodiment of the present invention 400, the foraminous shelled roll dryer may have a third foraminous cylinder 410B of a smaller diameter than the first foraminous cylinder positioned at the outer face of the second parallel end member 420B and in fluid communication with the first foraminous cylinder, in addition to the second foraminous cylinder 410A positioned at the outer face of the first parallel end member 420A. In other words, the dryer may have a foraminous exhaust cylinder at each end of the first foraminous cylinder. In this situation, it is contemplated that each of the exhaust capacity of the two exhaust cylinders combine is substantially equal to the exhaust capacity of a similar or identical dryer with a single exhaust cylinder. In other words, the combined surface area of the second and third foraminous cylinders having a surface area of about 20% to about 75% of the surface area of the first foraminous cylinder or having about 40% to about 60% of the surface area of the first foraminous cylinder or having about 30% to about 50% of the surface area of the first foraminous cylinder. Each of the second foraminous cylinder and the third foraminous cylinder is at least 10% smaller in diameter than the first foraminous cylinder, at least 25% smaller in diameter than the first foraminous cylinder or at least 40% smaller in diameter than the first foraminous cylinder. Thus, the configuration (i.e., ratio of axial length verses diameter) of each of the second and third foraminous cylinders may vary with regard to the spatial and other limitations so long as the surface area and diameter meet the aforementioned criteria. Further, the configuration of the second and third foraminous cylinders may be the same or different as needed.

(29) Looking now at FIG. 5, in a non-limiting embodiment of the present invention 500, the exhaust cylinder (i.e., second foraminous cylinder) 510 of the dryer may be narrower and longer to fit into a required space. Modification of the diameter and length of the exhaust cylinder(s) is contemplated by the present invention so long as the exhaust capacity is sufficient for operation of the dryer as described herein.

(30) Looking now at FIG. 6, in a non-limiting embodiment of the present invention, the gas flow 630 of the device may be reversed such that it enters through the outer shell of the second foraminous cylinder and exits through the outer shell of the first foraminous cylinder 670. Reversing drying gas flow may be required in certain drying situations.

(31) Looking now at FIG. 7, in a non-limiting embodiment of the present invention, the exhaust cylinder has additional support in the form of gussets 710 located, for example, between the exhaust cylinder and the parallel end member of the first foraminous cylinder. Said gussets efficiently reinforce the junction between the exhaust cylinder and foraminous shelled cylinder.

(32) The dryer of the present invention is designed to be flexible with regard to the types, sizes and weights of permeable and semi-permeable webs that can be dried. In this regard, the dryer of the present invention contemplates the incorporation of deckle bands in some embodiments. Deckle bands are known to those of ordinary skill in the art to be bands around the edge of a machine roll or cylinder for drying permeable and semi-permeable webs that determine the active width of the cylinder typically corresponding to the width of the web. Deckle bands are thin, solid strips of material that align along one edge with an end member and wrap around the entire circumference of a cylinder, but extend across only a small portion of the cylinder width. The inboard edge of a deckle band therefore defines the sheet width to be processed by the cylinder. Examples of dryers known in the art are described, for example, by U.S. Pat. Nos. 3,259,961, 3,590,453, and 4,050,131, which are incorporated herein by reference. Deckle bands are also helpful in preventing or limiting over-drying or under-drying of the edges of the web. FIG. 8 shows adjustable deckle shields 810A and 810B that are located in the foraminous shelled cylinder. FIGS. 9A & B show recessed deckle bands 910A and 910B located on the outer edges of the first foraminous shelled cylinder 920. FIG. 10 shows traditional, non-recessed deckle bands 1010A and 1010B.

(33) FIG. 11 shows an embodiment of the present invention with a rotating perforated plate without a center pipe. Mounting blocks are shown at 1110A and 1110B.

(34) FIG. 12 shows three schematics that represent non-limiting embodiments for the flow of drying gas in the device and methods of the present invention. Schematic 1 shows heated drying gas from the air heater being directed through the dryer of the present invention. Exhaust drying gas has, as needed, make-up air added. One or more fans, here represented by the indication of a main fan, move the drying gas through the system. A portion of the spent drying gas is exhausted from the system to regulate the mass balance of the system. The remaining drying gas is directed to the air heater.

(35) Schematic 2 and schematic 3 are further variations on the design show in schematic 1.

(36) With regard to drying webs comprising, for example, of paper and paper by-products, the drying gas (e.g., heated process air) passed through a wet sheet of permeable or semi-permeable web of woven and/or non-woven fibers traveling on the rotating foraminous shell of the first foraminous cylinder with or without a fabric layer there-between. Heated process air may be, for example, about 120 to about 290 degrees Celsius. The heated process air travels through the wet sheet, picks up moisture from the sheet and exits the shell at an exhaust temperature of, for example, about 80 to about 260 degrees Celsius. Through evaporation of the moisture in the wet sheet the heated process air is cooled. It is this cooled process air that exits the exhaust cylinder. Some amount of the cooled process air from 0% and up to 100% is exited from the flow stream. Any remaining cooled process air including makeup air introduced as fresh air, combustion air or parasitic leak is recirculated through the dryer and reheated. The temperature and air flow requirements are determined by the required evaporation from the web being dried and the speed of the rotating first foraminous shelled cylinder. The US Patents referenced herein show that one of ordinary skill in the art can determine the correct process parameters.

(37) It is noted that the foregoing description and examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words, which have been used herein, are words of description and illustration rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims and skill of one of ordinary skill in the art to which the invention pertains.

(38) In some embodiments of the present invention a cool zone is incorporated in the dryer/bonder of the present invention. The cool zone is an area of the shelled foraminous cylinder that runs the length of the cylinder, substantially the length of the cylinder or essentially the length of the cylinder at a position where the web being dried leaves the cylinder or just before the position where the web being dried leaves the cylinder (i.e., proximal to where the web being dried leaves the cylinder). A cool zone is used to lower the temperature of the web prior to leaving the drying cylinder. Cooling the web serves to reduce the likelihood of the web sticking to the wire, cool the product before it is wound on the reel and/or to solidify bond junctions in the web. The cool zone channels drying gas separately from the main drying gas. The cooling gas may be at least 100 C. lower than the temperature of the drying gas. The temperature of the cooling gas is approximately 4 C. to approximately 32 C. but can be cooler or hotter so long as it is effective in cooling the web as it exits the drying cylinder. The temperature of the cooling gas may be ambient temperature. The second and, if present, the third foraminous cylinders may also have a cool zone for the purpose of exhausting the cooling gas from the dryer.

(39) The cool zone works by having cooling gas or cooling air pass through the web. The cooling gas is then exited through the exhaust cylinder(s) of the present invention. FIG. 13 shows an embodiment of the cool zone of the present invention. FIG. 13A shows a cross-section of the through air dryer 1200 with cool zone 1210 with air flow direction 1220 indicated. Also shown are the drying hood 1230 with drying gas flow direction indicated 1240. FIG. 13B shows a cross-section of the through air dryer exhaust 1250, and exhaust duct work 1260 with heated gas exhaust direction indicated 1270. FIG. 13B also shows the cool zone exhaust 1280 with cool zone exhaust direction indicated 1290.