US3791049A

US3791049A - Drying methods with moisture profile control

Info

Publication number: US3791049A
Application number: US00186372A
Authority: US
Inventors: H Smith
Original assignee: SMITHERM INDUSTRIES
Current assignee: SMITHERM IND INC US; SMITHERM INDUSTRIES
Priority date: 1971-10-04
Filing date: 1971-10-04
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12

Abstract

Methods of and apparatus for drying material in web, sheet, and similar forms by a combination of radiant and convective heating in which provision is made for controlling the moisture or other volatiles profile across the width of the material being dried.

Description

iJnited States Patent- 1191 Smith, Jr. Feb. 12, 1974 1 DRYING METHODS WITH MOISTURE 3,479,746 11/1969 Bahmsen 34 17 PROFILE CONTROL 3,099,541 7/1963 Hildebrand 34/18 2,101,301 12/1937 Wellmar 34/18 Inventor: Home SmIth, J Richm 2,101,335 12/1937 Jennings et a1. 34/18 Va. 3,403,454 10/1968 Smith, Jr 34/155 x 3,214,845 11/1965 Huffman 34 48 [73] Ass'gneel lndllsmes 3,293,770 12/1966 Rausko1b.... 34/48 Richmond 2,874,482 2 1959 l-laltmeier 34/48 x 3,358,378 12/1967 Downs v 34/48 [22] 1971 3,625,812 12/1971 Gudaz 34/54 x App]. No.: 186,372

Related US. Application Data Continuation of Ser. No. 46,704, June 16, 1970, abandoned.

US. Cl 34/16, 34/18, 34/48, 34/54 int. Cl. F26b 7/00 Field of Search 34/16, 18, 17, 46, 48, 54

References Cited UNITED STATES PATENTS 12/1964 Gschwind et a1. 34/114 X Primary Examiner-William F. ODea Assistant Examiner-Wi11iam C. Anderson Attorney, Agent, or FirmStrauch, Nolan, Neale, Nies & Kurz [5 7] ABSTRACT Methods of and apparatus for drying material in web, sheet, and similar forms by a combination of radiant and convective heating in which provision is made for controlling the moisture or other volatiles profile across the width of the material being dried.

7 Claims, 10 Drawing Figures Patented Feb. 12, 1974 3,791,049

6 Sheets-Sheet 1 Patented Feb. 12, 1974 6 Sheets-Sheet 2 Patented Feb. 12, 1974 3,791,049

6 Sheet -s 4 Patented Feb. 12, 1974 6 Sheets-Sheet 6 I DRYING METHODS WITH MOISTURE PROFILE CONTROL The present application is a continuation of application No. 46,704 filed June 16, 1970, which has been abandoned.

This invention relates to drying and, more particularly, to the drying of materials in sheet, web, and similar configurations.

Paper, fiberboard, and other cellulosic products as well as other materials in web, sheet, and similar forms have, except in the immediate past, been dried almost exclusively on drum type dryers. In this method the material to be dried is successively moved over a large number of steam-heated, rotating rolls or cylinders arranged in one or more decks. The rolls transfer heat to the material being dried by conduction, causing evaporation of moisture or other volatiles from the web.

Such dryers have a number of disadvantages. One of these is that the surface temperature profiles of the rolls or cylinders are not uniform throughout their length but typically vary up to some 30 to 40 Fahrenheit. Also, the concentration of evolved volatiles adjacent the surfaces of the rolls will vary considerably throughout their length. As a result, there is uneven drying across the width of the material; and material dried on this conventional equipment therefore typically has a highly irregular moisture or volatiles profile. This is, of course, undesirable because of the resultant lack of uniformity in the dried product.

Another problem with an irregular volatiles profile is that this makes the material subject to breakage when it is in web form. When the web breaks, the system must be shut down and the broke removed from the dryer section. This downtime is enormously expensive in the case of modern, high speed equipment in which the web may commonly be 30 feet wide.

In my previous U.S..Pat. Nos. 3,403,454 issued Oct. 1, 1968, for HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL and 3,403,456 issued Oct. 1, 1968, for IMPINGEMENT TYPE DRYING APPARATUS, I disclose a novel drying technique in which uniform evolution of volatiles across the width of the material being dried is obtained by a combination of radiant heating and impinging air. Consequently, this novel drying technique eliminates one of the major causes of irregular volatiles profiles.

However, other major sources of an irregular profile in the dried product are not compensated for by the technique just discussed. These are attributable to factors such as an uneven concentration of pulp in papermaking and similar machines, unevenness of press rolls, and the like. (1. See in this regard, US. Pat. No. 3,089,252 issued May 14, 1963, to Daane for WEB MOISTURE PROFILE CONTROL FOR PAPER MA- CHINE.) The drying technique described in my issued patents does not satisfactorily eliminate such irregularities since it is designed to produce a fixed heat distribution pattern, and the profile irregularities attributable to the factors just discussed can vary considerably over a period of time as the product is formed.

I have now discovered that irregularities originating before the material to be dried enters the dryer or drying section can be corrected by adding to the dryer one or more radiant heating-fluid impingement units in which the distribution of radiant energy and/or impinging air in each of several narrow regions spanning the material being dried can be individually regulated.

Consequently, the rate of evaporation in each of these regions can be matched to the concentration of volatiles in the material, resulting in a dried sheet, web, etc. with a substantially uniform volatiles profile. I

The novel volatiles profile correcting units of the present invention may be located at either the wet or the dry end of the dryer section although the former location will in most cases be preferred. Also, in some applications, profile correction can be advantageously employed at both the wet and dry ends of the dryer section.

My novel volatiles profile correcting units can also be employed to advantage in conjunction with dryers other than those discussed above. Accordingly, in another aspect, the present invention provides novel, improved volatiles profile correcting unitswhich can be employed to advantage with various types of dryers, either as add-on units or as integral dryer units.

Moisture profile control units have heretofore been proposed, those disclosed in the following US. Pats. being typical: No. 2,269,236 issued Jan. 6, 1942, to WELLMAR for METHOD AND DEVICE FOR CON- TROLLING THE HEAT SUPPLY IN CELLULOSIC DRYERS; No. 2,837,830 issued June 10, 1958, to FRY for METHOD 'AND APPARATUS FOR DRYING FLEXIBLE SHEET MATERIAL: No. $052,991 issued Sept. 1 1, 1962, to GOLDNER for APPARATUS FOR UNIFORM ACCELERATED DRYING OF WEB MATERIAL, No. 3,161,482 issued Dec. 15, 1964, to GSCHWIND for FLUID DISTRIBUTING APPARA- TUS FOR MATERIAL TREATING; No. 3,167,408 issued Jan. 26, 1965 to JUSTUS for DRYER HOOD CONSTRUCTION FOR WEB MATERIAL; 3,214,845 issued Nov. 2, 1965, to HUFFMAN for MOISTURE MEASURING AND SELECTIVE DRYER CON- TROL SYSTEM; No. 3,284,920 issued Nov. 15, 1966, to HAYRINEN for APPARATUS FOR DRYING WEB MATERIAL; 3,292,274 issued Dec. 20, 1966, to SETH for ARRANGEMENT IN A DRYER or A SIMILAR TREATMENT PLANT; and No. 3,293,770 issued Dec. 27, 1966 to RAUSKALB for WEB DRYING PERMITTING WIDTHWISE MOISTURE CON TROL.

However, these previously proposed moisture profile controls differ considerably from the profile correcting units Ihave invented, both in structure and in mode of operation. Furthermore, they do not possess the versatility or efficacy of the novel units described herein.

From the foregoing it willbe apparent that the primary object of thepresent invention is the provision of novel, improved methods of and apparatus for drying material in sheet, web, and similar configurations.

Another important and related object of the invention resides in the provision of novel, improved drying methods and apparatus in which provision is made for controlling the concentrationof volatiles in the material being dried across its entire width.

Additional objects, other important features, and further advantages of the present invention will become apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing, in which:

FIG. 1 is a generally diagrammatic plan view of drying apparatus incorporating the principles of the present' invention;

FIG. 2 is a section through the apparatus of FIG. 1, taken substantially along line 2--2 of the latter Figure;

FIG. 3 is a fragment of FIG. 1 to an enlarged scale;

FIG. 4 is a fragmentary longitudinal section through a radiant heating-fluid impingement unit which may be employed in the drying system of FIG. 1;

FIG. 5 is a fragmentary longitudinal section through second form of radiant heating-fluid impingement unit which may be employed in the drying system of FIG. 1;

FIG. 6 is a view similar to FIG. 1 of a second form of drying apparatus embodying the principles of the present invention;

FIG. 7 is a fragment of FIG. 6 to an enlarged scale;

FIG. 8 is a longitudinal section through a volatiles profile correcting unit employed in the drying system of FIG. 6;

FIG. 9 is a view similar to FIG. 1 of a third form of drying apparatus embodying the principles of the present invention; and

FIG. 10 is a partial plan view of yet another volatiles profile correcting unit embodying the principles of the present invention.

Referring now to the drawing, FIGS. l-3 depict a single pass dryer having fluid impingement and radiant heating units 22 for drying the product to be treated and a novel unit 24 for correcting the volatiles profile across the width of the product, which is constructed in accord with the principles of the present invention. Dryer 20 also includes a series of parallel, spaced apart, rotatably mounted rolls 26 establishing a path 28 for the product or material being dried which is in the form of a web 30. (2. Dryer 20 will typically also include endless, open mesh belts or felts for confining and preventing warpage of web 30 together with idler and drive rolls for supporting and effecting movement of the felts. For convenience and clarity, these components have not been shown.) Except as discussed below the dryer components are of conventional construction and will not be described further herein.

As shown in FIG. 2, units 22 are located between adjacent rolls 26 and on both sides of path 28 to dry web 30 by simultaneously applying radiant heat to both sides of the web to evolve volatiles from it. Units 22 also direct air or other treating fluid at high velocity into contact with the upper and lower surfaces of the web to assist in evolving the volatiles and to scour evolved volatiles from adjacent its surfaces. The high velocity fluid thus prevents a retardtion of the drying process by eliminating the formation of a stagnant layer adjacent the web and, in addition, causes evaporative cooling adjacent the surfaces of the material being treated and thereby prevents it from being overheated. It is preferred that the treating fluid also be heated since a hot, high velocity fluid such as air is a highly effective drying agent.

Referring now to FIGS. 1-5, each of the radiant heating-fluid impingement units 22 incorporated in dryer 20 includes a casing 32 having an open side which faces downwardly in the case of the units above path 28 and upwardly in the case of those below the path. The open side of each casing 32 is closed by the radiant energy emitting plate 36 of a radiant heater 37 incorporated in each unit 22. Plates 36 are fabricated of a material which is a good thermal conductor and has a relatively high coefficient of emission. One satisfactory material of this sort is sheet steel.

Sealed to the rear or inner side of each radiant energy emitting plate 36'as by welding are members 38 providing interconnected fluid flow channels 40 disposed in parallel, spaced relationship and extending at right angles to the path 28 of web 30 through the drying apparatus. (3. As an alternate, properly configured tubing may be fixed to the inner sides of plates 36 to provide the flow channels as disclosed in my U.S. Pat. No. 3,403,454, for example.) A heat transfer liquid is circulated through channels 40 as will be described hereinafter in more detail. This fluid heats plates 36, causing them to radiate energy in the infrared portion of the electromagnetic spectrum. (4. To increase the emissivity of plates 36, the surfaces of the plates facing the path 28 of web 30 may be coated with a material having a high coeffectient of emission. A number coatings suitable for this purpose are described in my U.S. Pat. No. 3,262,494 issued July 26, 1966, for HEAT EXCHANGERS.) As best shown in FIGS. 4 and 5, channels 40 are covered with insulation 41 to prevent the dissipation of sensible heat.

Disposed between each of the channels 40 are fluid flow nozzles 42, which communicate at their inlet ends with the interior of casing 32. The outlets of nozzles 42 extend through radiant plates 36 and are flush with the surfaces of the latter facing web 30.

Referring now to FIGS. 3-5, there will typically be two rows of nozzles 42 between the channels 40 of the radiant heater in each of the radiant heating-fluid impingement units 22. However, the number of nozzles in each row and the number of rows are not critical and will vary for different applications of the invention.

Nozzles 42 may be oriented normally to the path 28 of web 30 as shown in FIG. 4. However, it is preferred that they be inclined at an angle to the web as shown in FIG. 5 in which the radiant heating-fluid impingement unit is identified by reference character 22a. This gives the air or other gas flowing through the nozzles a velocity and pressure distribution pattern which results in minimization of flutter of the web as it moves at high speed through the radiant heating-fluid impingement unit. Also, the inclined nozzle arrangement virtually eliminates areas in which the flow velocities are too low to produce the desired scouring effect. (5. To further promote the scouring effect of the air or other fluid flowing through nozzles 42, the nozzles in one of the two rows between adjacent radiant heater flow channels may be inclined in the direction of movement of web 30 and those in the other row inclined in the opposite direction.) This is important since it produces uniformity of treatment.

Referring next to FIG. I, the treating fluid is supplied to units 22 by a blower 52 connected through a duct 54 to a fluid heater 56. As it flows through the fluid heater, the treating fluid is heated by a heat exchanger 58. From heater 56, the fluid flows through main supply duct 60 and branch supply ducts 62 to plenum chambers 63 in the casings of units 22.

From plenum chambers 63 the fluid flows through nozzles 42 and impinges on web 30 to assist in evolving volatiles and to scour them away from the surfaces of the web as described above. The spent fluid, together with its burden of evolved volatiles, flows from adjacent web 30 into an exhaust plenum 66 (6. Because a volatiles profile correcting unit is employed in dryer 20, the relatively sophisticated arrangement of exhaust plenums and ducts employed in the dryers described in my patents nos. 3,403,454, and 3,403,456 to promote uniform dyring across the width of the material is not necessary. Accordingly, the provision of a profile correcting unit makes it possible to simplify the exhaust system and thereby reduces the cost of the dryer or drying section.) extending along one side of dryer and then through return duct 68 to blower 52. A valve or damper 69 in duct 68 may be adjusted to control the rate of flow of fluid through the closed circulation system just described.

In many applications of the present invention the percentage of moisture or other volatiles in the treating fluid must be closely controlled to produce the desired characteristics in the treated product. To permit such control return duct 68 is provided with a make-up duct 70; and a vent duct 71 branches from the duct 54 between blower 52 and fluid heater 56.

Valves

72 and 73 control the flow through make-up and vent

ducts

70 and 71, respectively. By adjusting

valves

72 and 73, recirculated fluid can be discharged from the system and replaced with fluid having a lower content of volatiles to maintain the concentration of volatiles in the fluid delivered to units 22 at the desired level.

Valves

72 and 73 may be adjusted manually or, if desired, may be automatically adjusted by controllers of any suitable type or by a system of the type described in my U.S. Pat. No. 3,208,158 issued Sept. 28, 1965, for DRYERS.

An economizer 76 of conventional construction may be connected between the vent and make-up ducts to extract sensible heat from the vented fluid and add it to the make-up fluid. This recovers otherwise wasted heat, increasing the efficiency of the drying system.

Referring still to FIG. 1, the heat exchanger 58 in fluid heating unit 56 as well as the radiant heaters 37 in radiant heating-fluid impingement units 22 are of the type through which a heated fluid heat transfer medium is circulated to elevate them to the desired temperature. The preferred heat transfer mediums are high boiling point organic liquids and eutectic mixtures of inorganic salts, which can be circulated at extremely high temperatures in liquid form. Suitable media of this type are discussed in detail in my U.S. Pat. No. 3,262,494.

The system illustrated in FIG. 1 for heating and circulatingthe liquid heat transfer medium. includes a storage tank (not shown) from which the liquid can be pumped to the main circulation system. This includes main supply and return

conduits

78 and 80 and is a closed loop through which the liquid is circulated by a pump 82.

From main return conduit 80 the heat transfer liquid flows into a liquid heating unit 84 where it is heated to the desired temperature. This unit may be of any desired construction and preferably includes a temperature responsive controller 86 which so regulates the flow of fuel to the burner or burners in the heating unit through valve 88 and conduit 90 as to maintain the temperature of the heated liquid flowing into main supply conduit 78 substantially constant.

From main supply conduit 78, part of the heated liquid flows through branch supply conduit 92 to the heat exchanger 58 in fluid heater 56. The volume of flow through conduit 92 is controlled by temperature responsive controller 94, which is connected to a valve 96 in conduit 92, and has a sensor (not shown) in supply duct 60. Controller 94 regulates valve 96 so as to maintain the temperature of the treating fluid flowing into the supply trunk substantially constant.

From fluid heating unit 56, the heat transfer liquid flows through return conduit 98 back into the main return conduit 80.

Another portion of the heat transfer liquid flowing through main supply conduit 78 is diverted through supply conduits 104 to the radiant heaters 37 in radiant heating-fluid impingement units 22 of dryer 20. From heaters 37 the heat transfer liquid flows through conduits 106 and return conduits 98 and back to heating unit 84.

The heat transfer liquid circulation system also includes an expansion tank 108 connected by branch conduit 110 to main return conduit 98 and a bypass conduit 112 connected between supply conduit 78 and return conduit 80. A pressure relief valve 114 in bypass conduit 112 insures continued flow through heating unit 84 under abnormal conditions such as conduit blockage and therefore prevents such abnormal conditions from causing damage to the system.

Further details and the advantages of the foregoing heating and circulating system are described in my U.S. Pat. No. 3,236,292 issued Feb. 22, 1966, for DRYERS, for example.

Drying apparatus of the type described above is very efficient and is highly effective in providing uniformity of drying. However, as discussed above, I have now discovered that even greater uniformity in the dried product can be accomplished by incorporating in the drying section an additional unit capable of correcting the vol atiles profile across the width of the material being dried.

Referring now to FIGS. 1 and 3, the novel units 24 incorporated in dryer 20 to correct the volatiles profile of web 30 are disposed both above and below the path 28 of web 30 in series with radiant heating-fluid impingement units 22 as best shown in FIG. 2. Each of the units 24 includes a casing 116 defining a plenum cham ber 117, which is connected by a branch supply duct 118 to the main impingement fluid supply duct 60. Spent fluid is returned through exhaust plenum 66 to main fluid return duct 68. The sides of casings 1 16 facing web 30 are closed by a radiant heater 122 including a radiant energy emitting plate 124 spanning the open side of the casing and a plurality of channel defining members 126 sealed as by welding to the interior or back sideof the radiant energy emitting plate. As best shown in FIG. 3, members 126 provide a plurality of parallel, spaced apart flow channels 127 extending in the same direction as path 28 of web 30. At one end, the flow channels are connected in parallel to an inlet header 128 by conduits 129. At the opposite ends, the flow channels are connected by conduits 130, in which flow control valves 132 are interposed, to an outlet header 134. The radiant heater is preferably insulated in the same manner as the radiant heaters 37 in radiant heating-fluid impingement units 22.

Referring now specifically to FIG. 1, inlet header 128 is connected to the liquid heat transfer medium supply line 78. The outlet header is connected by conduit 138 to branch return conduit 98.

As in the case of the radiant heating units 37 incorporated in radiant heating-fluid impingement units 22, the radiant energy emitting plates 124 may be covered with a high emissivity coating to increase the absorption of energy from liquid flowing through channels 127 and to increase the emissivity of the plates.

Also included in the volatiles profile correcting units 24 are nozzles 140, a row of such nozzles being disposed between each of the flow channel defining members 126. These nozzles may be of the type described above in conjunction with units 22.

It will be apparent from the foregoing that unit 24 also contributes to the-.evolution of volatiles from web 30 by a combination of radiant energy and impinging gaseous fluid, the flow of the latter being controlled by a valve or damper 142 in supply duct 118. The rate of evolution of volatiles from different lateral regions of web 30 can be made different and proportioned to the concentration of the volatiles in the different regions of the material by independently adjusting the valves 132, which control the flow of heat transfer liquid through the different flow channels 127.

As the rate-of-flow of the heat transfer liquid through a channel is decreased, the temperature of that portion of the radiant energy emitting plate 124 contacted by the fluid and the adjacent portions drops, decreasing the amount of energy emitted from such portion of the plate and impinging on the part of web 30 thereopposite. Therefore, by reducing the flow of heat transfer liquid through the channels opposite the drier parts of the web, the rate of evolution of volatiles from such parts of the web may be decreased without lowering the rate of evolution of volatiles from those parts of the web having a higher concentration of volatiles. By thus varying the rate of drying across the width of the material, it can be so dried that it will have a uniform moisture or other volatiles profile across its width.

The regulation of valves 132 may be accomplished manually or automatically, if desired. One suitable automatic control system, shown schematically in FIGS. 1 and 3, includes a moisture or other volatiles sensor 144 for each of the flow control valves 132. One example of a suitable sensing arrangement is described in TAPPI 52, Feb. 1969, pages 276-278. Another suitable system is described in PLYWOOD AND PANEL, March 1969, page ll. Volatiles sensors 144 are connected to a conventional programmed controller 146, which in turn is connected to valves 132 to adjust the valves so as to proportion the flow rate through the associated channel to the volatiles concentration in the region of the web opposite the conduit.

A number of variations may be made in the arrangement of the volatiles profile correcting unit without departing from the scope of the present invention. For example, the profile may be corrected by varying the distribution of the impinging fluid across the width of the material being dried rather than controlling the lateral distribution of the radiant energy as in the embodiment of the invention just described. Or, if desired, the lateral distribution of both the impinging fluid and radiant energy may be proportioned to the volatiles concentration in the material. An arrangement for controlling the lateral distribution of the impinging fluid or radiant energy or both is illustrated in FIGS. 6-8. (7. To the extent that the dryer 150 illustrated in FIGS. 6-8 and dryer 20 are the same, their components are identified by identical reference characters.)

Referring now to the Figures just mentioned, the drying section 150 illustrated in FIG. 6 is identical to the drying section 20 described previously except for the details of the profile correcting arrangement 152 employed in the latter. This unit differs from the unit 24 discussed above primarily by inclusion of an arrangement for independently regulating the flow of the impinging fluid through a number of channels or ducts disposed in side-by-side relationship in the unit. More particularly, in profile correcting unit 152 vertical, longitudinally extending partitions 154 divide the interior of casing 156 into a plurality of side-by-side channels 158 extending in the same direction as web path 28. The inlet ends 160 of channels 158 communicate with a plenum 162 at the inlet end of casing 156. Plenum 162 is supplied with impinging fluid through supply duct 118.

As best shown in FIG. 8, a flow controlling valve or damper 166 is rotatably supported in the inlet end of each channel 158 by a vertical pivot member 168 which extends through the wall 170 of casing 156 furtherest from web 30. Dampers 166 are adjusted by motors 172 having piston rods 173 pivotally connected to cranks 174. These cranks are fixed to the shafts 168 on which the dampers are mounted. Motors 172 are actuated to adjust the positions of dampers 166 by a control system which may be substantially identical to that described above in conjunction with the embodiment of FIGS. 1-5.

Profile correcting unit 152 also differs from the unit 24 described above in that the outer casing wall 170 is inclined from the horizontal so that the flow channels 158 for the impinging fluid are tapered, decreasing in depth from their inlet to their outlet ends. This arrangement provides a uniform longitudinal pressure distribution profile in the flow channels.

As indicated above, the lateral distribution of radiant energy or impinging fluid or both can be regulated in unit 152 to correct the moisture or other volatiles profile of web 30. The lateral distribution of radiant energy is regulated by adjusting valves 132 to control the flow of heat transfer liquid through channels 127 as described above. The lateral distribution of impinging fluid is regulated by the adjustment of dampers 166. Either valves 132 or dampers 166 or both may be employed, depending upon the application of the dryer section. Typically, one controller will be used to adjust both valves 132 and dampers 166. However, if desired, two controllers may be used so that the valves and dampers can be separately or independently regulated.

Another variation which may be made within the scope of the present invention is the location of the profile correcting unit. As discussed above, in many applications of the present invention, variations in the volatiles profile across the width of the material being dried will occur in the wet end of the machine as opposed to the dryer section. In such applications, it may prove advantageous to locate the profile correcting unit at the wet end rather than the dry end of the dryer section. Also, in some applications, it may prove advantageous to locate one profile correcting unit at the wet end of the dryer section and a similar unit at the dry end to provide a final correction in the profile of the material being dried. An arrangement of the latter type is shown in FIG. 9 in which the reference characters employed are the same as those utilized earlier except to the extent that the components of the several embodiments of the invention are different.

Referring now to the Figures just mentioned, the dryer section 180 illustrated in FIG. 9 includes a first profile correcting unit 182 located at the wet end of the section ahead of radiant heating-fluid impingement units 22 and a second profile correcting unit 184 located at the dry end of the section after units 22. These units may be of the type shown in FIG. 1, in which only the distribution of radiant energy laterally of the material being dried is controlled or of the type shown in FIG. 6 in which the distribution of radiant energy or of impinging fluid or both may be controlled. Unit 182 is connected to fluid supply duct 60 by branch supply duct 186. Unit 184 is similarly connected to the main supply duct by branch supply duct 190. The radiant heating units of the two profile correcting units are connected to heat transfer liquid supply conduit 78 by branch conduits 194 and 196 and to return conduit 98 by

branch conduits

198 and 200. In this arrangement either

unit

182 or 184 or both of these units may be employed, as appropriate, to provide a uniform volatiles profile across the width of the material being dried.

FIG. 10 shows yet another form of volatiles profile correcting unit 210 constructed 'in accord with the principles of the present invention. This unit is similar to that illustrated in FIG. 6 and discussed above, differing only in that the channels 212 for the heat transfer liquid in radiant heating unit 214 extend laterally across the width of the material being dried, and no provision is made for individually regulating the flow of heat transfer liquid through these channels. That is, in unit 210 volatiles profile correction is obtained solely by varying the lateral distribution of the impinging fluid across the width of the material being dried. This unit has the advantage of extreme simplicity. Also, the back-and-forth, serpentine arrangement of the channels in radiant heater 214 provides a uniform average temperature across the web, and, at the same time, a high temperature gradient from the inlet to the outlet of the channel system. Thus, this particular arrangement provides both uniform drying across the web and efficient utilization of the sensible heat in the heat transfer liquid.

Units of the type illustrated in FIG. 10 may be located at either the wet endor the dry end of a dryer or dryer section. Alternatively, such units may be employed at both ends of the dryer or dryer section as shown in FIG. 9 or may be employed at one such end with one of the types of profile correcting units described earlier being employed at the other end.

Still other modifications may be made in the structure discussed above without exceeding the scope of the present invention. For example, the temperature of the impinging fluid or heat transfer liquid supplied to the profile correcting unit may be varied rather than the volume rate-of-flow. Such variations are of course intended to be covered by the appended claims to the extent they are not expressly excluded therefrom.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range'of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A method of drying materials of sheet, web, and similar forms comprising the steps of moving the material to be dried through at least one drying zone; directing radiant energy against the material as it is moved through said drying zone to evolve volatiles therefrom; directing a flow of heated fluid against the material as it moves through the drying zone to assist in evolving volatiles from the materials being dried and to scour evolved volatiles away from the surface of the material; and correcting the volatiles profile of the material being dried across the width of the material so that the volatiles content of the dried product will be substantially uniform across its width, the correction of the volatiles profile being effected by moving the material through a zone distinct from the aforesaid drying zone; directing radiant energy against the material as it moves through said distinct zone; directing a flow of heated fluid against said material as it moves through said distinct zone; and proportioning the intensity of the radiant energy and the volume of fluid directed against successive lateral regions of the material being dried to the volatiles content of the material in each of such regions.

2. A method of drying materials of sheet, web, and similar forms comprising the steps of moving the material to be dried through at least one drying zone; directing radiant energy against the material as it is moved through said drying zone to evolve volatiles therefrom; directing a flow of heated fluid against the material as it moves through the drying zone to assist in evolving volatiles from the material being dried and to scour evolved volatiles away from the surface of the material; and correcting the volatiles profile of the material being dried across the width of the material so that the volatiles content of the dried product will be substantially uniform across its width, the correction of the volatiles profile being effected by moving the material through a zone distinct from the aforesaid drying zone; directing radiant energy against the material as it moves through said distinct zone; directing a flow of heated fluid against said material as it moves through said distinct zone; and proportioning the volume of fluid directed against successive lateral regions of the material being dried to the volatiles content of the material in each of such regions.

3. The method of claim 2, wherein, in the volatiles profile correcting step, the heated fluid is directed against an area of the material which is substantially coincident with the area against which the radiant energy is' directed.

4. A method of drying materials of sheet, web, and similar forms comprising the steps of moving the material to be dried through at least one drying zone; directing radiant energy against the material as it is moved through said drying zone to evolve volatiles therefrom; directing a flow of heated fluid against the material as it moves through the drying zone to assist in evolving volatiles from the material being dried and to scour evolved volatiles away from the surface of the material; and correcting the volatiles profile of the material being dried across the width of the material so that the volatiles content of the dried product will be substantially uniform across its width, the correction of the volatiles profile being effected by moving the material through a zone distinct from the aforesaid drying zone;

directing radiant energy against the material as it moves through said distinct zone; directing a flow of heated fluid against said material as it moves through said distinct zone; and proportioning the intensity of the radiant energy directed against successive lateral regions of the material being dried to the volatiles content of the material in each of such regions.

5. The method of claim 4, wherein, in the volatiles profile correcting step, the heated fluid is directed against an area of the material which is substantially coincident with the area against which the radiant energy is directed.

6. A method of drying materials of sheet, web, and similar forms comprising the steps of moving the material to be dried through at least one drying zone; directing radiant energy against the material as it is moved through said drying zone to evolve volatiles therefrom; directing a flow of heated fluid in impinging relationship against the material as it moves through the drying zone over an area generally coincident with that against which the radiant energy is directed to assist in evolving volatiles from the material being dried and to scour evolved volatiles away from the surface of the material; and correcting the volatiles profile of the material being dried across the width of the material in a zone distinct from the drying zone so that the volatiles content of the dried product will be substantially uniform across its width, the volatiles profile of the material being dried being corrected by directing radiant energy and a flow of heated fluid against said material in said distinct zone and by proportioning the intensity of the radiant energy and the volume of fluid directed against successive lateral regions of the material being dried to the volatiles content of the material in each of such regions.

7. A method of drying materials of sheet, web, and similar forms comprising the steps of correcting the volatiles profile of the material being dried across the width of the material in a first zone so that the volatiles content across its width will be substantially unform; thereafter moving the material to be dried through at least one drying zone distinct from said first zone; directing radiant energy against the material as it is moved through said drying zone to evolve volatiles therefrom; directing a flow of heated fluid against the material as it moves through the drying zone to assist in evolving volatiles from the material being dried and to scour evolved volatiles away from the surface of the material; and subsequently again correcting the volatiles profile of the material as aforesaid in a second zone distinct from said first zone and said drying zone to minimize variations in the volatiles content of the material across its width, the volatiles profile of the material being dried being corrected in said volatiles profile correcting steps by directing radiant energy against the material being dried as it moves through each of said first and second zones; directing a flow of heated fluid against said material as it moves through said first and second zones; and, in each of said first and second zones, proportioning the intensity of the radiant energy directed against successive lateral regions of the material being dried to the volatiles content of the material in each of said lateral regions.

Claims

3. The method of claim 2, wherein, in the volatiles profile correcting step, the heated fluid is directed against an area of the material which is substantially coincident with the area against which the radiant energy is directed.

4. A method of drying materials of sheet, web, and similar forms comprising the steps of moving the material to be dried through at least one drying zone; directing radiant energy against the material as it is moved through said drying zone to evolve volatiles therefrom; directing a flow of heated fluid against the material as it moves through the drying zone to assist in evolving volatiles from the material being dried and to scour evolved volatiles away from the surface of the material; and correcting the volatiles profile of the material being dried across the width of the material so that the volatiles content of the dried product will be substantially uniform across its width, the correction of the volatiles profile being effected by moving the material through a zone distinct from the aforesaid drying zone; directing radiant energy against the material as it moves through said distinct zone; directing a flow of heated fluid against said material as it moves through said distinct zone; and proportioning the intEnsity of the radiant energy directed against successive lateral regions of the material being dried to the volatiles content of the material in each of such regions.