Paper drier

Application filed March 17,

This invention relates to a paper machine and more particularly to a paper machine wherein both the wet and dry ends of the machine are totally enclosed within a subβ stantially air-tight housing or casing to permit the substantial exclusion of air from within the casing and permit the effecting of a considerable economy of heat in the drying operation.

The art of drying paper as heretofore practiced may logically be divided into three classifications; (1) drying under purely atmospheric conditions without the application of artificial heat; (2) drying paper in an 15 open type drier by contact between the wet web of paper and traveling heated surfaces, such as drier drums, and (3) drying paper in a totally enclosed drier unit under vacuum.

The purely atmospheric type of drier 80 wherein no artificial heat is employed would obviously require a tremendous amount of space in which to Complete the drying of the paper, or if unheated rolls were employed for supporting the paper web during the air ⁸⁶ drying operation, a very large number of such rolls would be necessary to take care' of the output of an ordinary present day paper machine.

The use of the steam heated, unenclosed 30 drier, as compared with the purely atmospheric type of drier, would permit a considerable diminution in the number of drier drums required but the fuel efficiency of the open type of steam drier drum drier unit is 35 relativelv low owing to the fact that heat is expended not only in evaporating moisture from the paper web but also in heating the surrounding air. Thus in this type of drier, the size of drier unit is reduced at the' ex¹⁰ pense of fuel cost.

In the third type of drier, wherein the. drying operation is carried out in an enclosed chamber under vacuum, a reduction both in the size of the drier unit, i. e. in the area of ¹⁵ drying surface, and in the fuel cost is effected, the. latter because of the fact that the heat supplied is utilized entirely in the evaporation of the moisture in the paper and there is no loss because of unnecessary heat^,0 ing of air. However, the construction cost

DRIER

1930. Serial No. 436,307.

of this type of drier is relatively high due to the necessity of an air-tight casing and seals, vacuum pumps and the like. Furthermore, although a considerable saving in fuel is effected using this vacuum type of drier, 5« as compared with the steam heated, unenclosed type, it is nevertheless evident that, since all of the water in the paper is evaporated entirely by means of applied heat, the fuel, economy is not great as should be the- 60 oretically possible, as will later be evident from a consideration of my invention as hereinafter described.

While the development of the paper drier through these three classes or stages repre- W sents a very marked progress in the art of drying paper, it is nevertheless pointed out that such progress has been undertaken with reduction in the size of equipment as its main aim and with, fuel economy as a sec- 70 ondary gain and without a full recognition of the further possibility for substantial additional savino· in fuel both for heating and power purposes, provided the desideratum of size' and first cost of construction be 75 abandoned.

In other words, reviewing past progress in paper drying through thethree steps just outlined, in passing from the first to the second step, the speed of the drying operation 80 was greatly increased with a reduction in the size of drier.equipment but this was done at the cost of increasing fuel consumption from nothing at all to a third or so more than that required theoretically to evaporate ⁸⁵the moisture in the paper. In passing from the second stage to the third, the gain has again been primarily in smaller size of drier equipment with an incidental reduction of fuel .consumption back to about 1.00% of ⁰⁰that.theoretically required for directlv evaporating the moisture in the paper.

The present invention contemplates sacrificing. somewhat- initi al cost of construction and size of paper machine in order to obtain ⁸⁵greater fuel efficiency. In order to do this I make use of the.principle of multiple effect evaporation, a principle which to the best of my knowledge has never heretofore been applied to the drying of paper. I furthermore ¹⁰⁰

1,854,956 utilize the cooler atmosphere at the wet end of the paper machine, the showers, and the like, for condensing a portion of the steam generated from the moisture in the paper 5 web during the drying operation, at the same time effecting a heat interchange between such steam or water vapor and the paper stock on the forming part of the machine. To best accomplish these ends, I provide a 10 paper machine that is wholly enclosed within a casing divided into compartments. In these compartments, contrasted degrees of pressures may be obtained with substantial exclusion of air or air may be admitted to one or 15 more compartments with the provision of a heat interchanging air regenerator for utilizing the heat of the air within the casing to preheat the air admitted to the casing.

It is accordingly an object of the present 20 invention to provide a paper machine that is entirely enclosed and that is divided into different sections or compartments which may be operated under contrasted conditions of presslire to obtain the advantages of mul25 tiple effect evaporation.

It is a further important object of this invention to provide an enclosed sectional drier from which air is substantially excluded and in -which steam generated from the moisture ³⁰ contained in the paper web in one section is utilized in the drying or heating element of another section, whereby a great economy in heat consumption for effecting the drying of the paper may be realized.

³⁵ It is a further important object of this invention to provide as one section of the enclosed drier unit, high pressure steam coils in place of the usual drier drums. .

It is a further important object of this invention to provide a paper machine and housing therefor enclosing the entire machine and means for drawing steam generated from the moisture in the paper as it traverses a portion of the driers towards the extreme ⁴⁵ wet end of the machine to effect a substantial condensation thereof and the heat interchange between such steam and the paper stock on the forming portion of the machine.

It is a further object of this invention to ⁵⁰ save fuel by enclosing all or a part of the drier drums in a substantially air-tight casing, not subjected to vacuum, through which air is circulated, the heat abstracted there₅₃ from being utilized to preheat the incoming air, instead of to evaporate moisture in drier compartments of lower pressure.

Other and further important objects of this invention will be apparent from the dis60 closures in the specification and the accompanying drawings.

This invention (in a preferred form) is illustrated in the drawings and hereinafter more fully described.

®δ On the drawings:

The drawings as a whole represent diagrammatically an entire paper machine embodying the various features of my invention.

Figure 1 is a side elevational view, with 70 the side of the casing removed, of a fourdrinier forming part of a paper machine embodying my invention.

Figure 2 is a continuation of Figure 1 showing the presses, the details of which form 7fi no part of my invention but this figure is included to show a continuous machine.

Figures 3 and 4 are similar continuations of Figures 1 and 2 showing intermediate drier sections. ⁸⁽¹

Figure 5 is a side elevational view of a drier section containing high pressure steam coils.

Figure 6 is a continuation of Figure 5 showing the end of the drier unit and calender 8£ stack.

Figure 7 is a side elevational view of a modified form of the drier compartment shown in Figure 6.

As shown on the drawings: ^9t

The reference numeral 1 indicates as a whole a Fourdrinier paper making machine which is, in accordance with my invention, entirely enclosed within a housing or casing 2. The paper machine 1 comprises the usual 9£ main sections of a machine of this type, viz., a fourdrinier 3, presses 4 and a drier 5. All of these sections are included within the main casing 2, which is itself preferably divided into separate sections or compartments: compartment A including the forming part 3, the press part 4 and a portion of the drier drums of the drier part 5; a compartment B constituting the middle drier section; compartment C housing high pres- J< sure steam coils 6: and compartment D constituting an equalizing chamber from which the paper passes off of the paper machine to a calender stack 7. It will be understood that the division of the paper machine housing L into compartments is a more or less arbitrary one and that fewer or more compartments may be provided.

The forming portion of the paper machine, which is supported from a flooring 9, may ¹be of a conventional type, including a head box 10, a Fourdrinier table structure 11, flat stationary suction boxes 12 and a suction couch roll 13. A forming wire 14 is trained in the usual manner around a breast roll 15( ^1!over table rolls 16, the flat boxes 12 and around the suction couch roll 13, the under or lower run of the wire being supported by various idler and tension rolls 17.

In accordance with my invention, stock is - admitted into the head box 10 of the paper machine through a piping 18, in which is provided a valve 19 and a loop or sinuous bend 20, both of which serve to control and throttle down the flow of stock to the head box 10. ¹

1.864.066 3

The entire compartment A in which, is housed the forming part 1, press part 4 and portion 5 of the drum driers, is maintained under a suitable vacuum, preferably as high as can 5 be practically maintained. It is for this reason that the valve 19 and serpentine pipe 20 are provided, in order that: the stock flowing to the machine may be throttled sufficiently to maintain fair constancy of flow in the face 10 of possible variations in the vacuum within the compartment A. The serpentine pipe 20 is preferably arranged horizontally, but is shown here as vertically arranged for convenience in, .depiction. .From the head box 15 10, the stock-flows over a suitable apron 21 onto the forming wire 14 and in passing over the table rolls 16 and suction boxes 12 and suction couch roll 13, water is extracted from the stock to form the moist web of paper, 20 indicated by the reference numeral 22. The white water collecting under the table rolls 16 in a save-all 23 is discharged through a pipe 24 leading into a white water pump (not shown), positioned in the basement.

Vacuum is maintained within the casing A by means of one or more suction pumps 100 having a branched intake 101 connected to the flat boxes by means of pipes 27 and 28 and to the suction chamber of the couch roll ³⁰ 13 by a pipe 29. Said intake of the pump 100 is likewise connected by a pipe 30 through an automatic reducing valve 31 to the upper extreme end of the casing 2. The reducing valve 31 in the pipe 30 is set to impose a small ³⁵ difference in pressure between the interior of the suction boxes 12 and of the suction chamber within the couch roll 13, on the one hand, and the interior of the compartment A. Because of this difference being but slight, the ⁴⁰ suction boxes may be given a larger area than usual. The vacuum pump 100 connected to ·. the pipes 27, 28, 29 and 30 may be regarded as the equivalent of the vacuum pump forming a part of all Fourdrinier machines, being ⁴⁵ merely somewhat larger for the attainment of a higher vacuum, but not absorbing necessarily much more power.

Inasmuch as compartment A includes a number of steam heated drier drums 33, there ⁰⁰ is, of course, a considerable amount of steam or water vapor· formed within this compartment from the moisture in the heated web of paper and as all of this water vapor is drawn to the wet end of the compartment A by 55 virtue of the suction created within the pipes 27, 28, 29 and 30, a considerable amount of condensation takes place as the steam or water vapor passes into the cooler portion of the compartment A and contacts the stock and ³⁰ various showers in the press part 4 and forming part 1. To aid in removing the condensed water and to further insure condensation of the water vapor from the air removed from compartment A, a partition or baffle 34 is pro^c3 vided above the head box 10 extending the width of the casing and a plurality of conduits 103 are arranged to pass through the head box 10 to connect the underneath portion of the Fourdrinier section with the part of the compartment immediately adjacent the jq pipe 30. In this way, all of the moisture laden air must pass through or around the various sprays on the paper machine before, finding an exit through the pipe 30, with the result that substantially all of the moisture is 75 condensed out and removed. Any moisture condensing in the conduits 103 drains by gravity into the save-all 23.

The paper web 22 passes from the couch roll 13 onto the first press felt 35, through go the first set of presses 36 and thence to the second press felt 37. After passing through the second set of presses 38, the direction of the web 14 is reversed and the web passed through the third set of presses 39, from 85 which it passes in a relatively dry state into the nip between the first bottom drier drum 40 and the lower drier felt 41 (Figure 3). The paper web 22 passes around the lower drier drum 40 and between the upper drier so felt 42 and first upper drum 43 and thence around the remaining upper and lower drum in the usual maner until it reaches the end of compartment A. Compartment A is divided from compartment B by means of 95 upper and lower partitions, 44 and 45 respectively, and seals 46 and 47 joined thereto. Said seals 46 and 47 may suitably comprise flexible metal plates 48 having rounded edges 49 and pivoted to a supporting plate 100 from the partitions 44 and 45 as at 50 and 51, respectively. The particular form and construction of the seals 46 and 47 form no part of the present invention.

The paper web 22 passes in a similar man- 105 ner over and around the drier drums contained in compartment B and through a similar sealing mechanism, designated as a whole by the reference numeral 52 into compartment C. no

Compartment C houses, in place of the usual drier drums, a system of high pressure steam coils 6 arranged in horizontal tiers. In order to support the paper web in spaced relation to the steam pipes or coils 6, plates 115 53 are supported above each tier of coils to extend between rolls 54 and 55, and similar pairs of rolls, positioned at the respective ends of the compartment C. The paper web may suitably be supported upon these horizontal 120 or slightly inclined plates 53 in their circuitous travel around the various rolls, such as the rolls 54 and 55, in their passage through compartment C. Each of the plates 53 may be formed of wire reinforced glass or any other 125 suitable translucent material which will serve to transmit radiant heat.

From compartment C, the web is led through a seal, designated as a whole by the reference numeral 57, into a relatively small 130

1,864,966 compartment D in which are housed a plurality of steam drier drums 58. From the compartment D, the paper web passes out through a sealing mechanism 59 to the calender stack 7.

* Compartment D may be operated as an outlying portion of section B or may be operated at its own peculiar pressure with its drums supplied with exhaust steam from any incidental source.

The arrangement of the drier sections will now be explained. High pressure steam is admitted to the pipes or coils 6 in compartment c through a pipe 60 and after travers16 *ⁿS the various coils of the system, the condensate is discharged through a bottom pipe 61, which may suitably lead to a trap (not shown) for the removal of condensate, and whatever steam may inadvertently escape is ₂q to be led by suitable connections (not shown) into pipe 62, thence to the driers 58 in the compartment D. In operation, the steam admitted to the coils 6 in the drying system of compartment C may be superneat26 ed and at a relatively high pressure, say 150 to 200 lbs. per sq. in. Heat radiated from the steam pipes 6 causes the evaporation of the , mositure contained in the paper web, but at this heat is largely radiant heat, the paper 30 web is not necessarily raised to any high temperature corresponding with that of the steam in the coils and naturally this is so, as long as the paper web contains any moisture in it at all.

Under these conditions, the temperature of the paper web must remain at about the temperature of saturated steam corresponding with the pressure within the chamber C, although the web may. be receiving radiant 40 heat at short range having a temperature 100° or more higher than the aforesaid temperature. Under such conditions, the web is in danger of being overheated only should it come into contact with the high pressure 45 steam coils, but this is precluded by the provision of translucent plates between the steam coils and the traveling web of paper being dried.

There is thus produced an atmosphere of so dry steam within the casing C, which steam may or may not be superheated but is preferably kept under a super atmospheric pressure, the pressure being as high as it is practical to build the casing to withstand. The 53 steam thus generated from the mositure contained in the paper web is conducted from the upper portion of the compartment 5 through a conduit 62 to the drier drums in compartment B.

co The conduit 62 may serve as a header to which the drier drums in section B are connected by means of individual pipes 63, or a part of the drier drums in said compartment B may be connected in series to the 65 conduit 62.

Steam generated from the web of paper as it passes through compartment B is conducted from said compartment by means of a pipe or conduit 64 and branch pipes 65 to the drier drums in compartment A. It is ⁷⁰therefore necessary that compartment B be maintained under less pressure than compartment C and under greater pressure than compartment A. For instance, if compartment C is maintained under 30 lbs. gage pres- ⁷⁵sure, compartment B might be maintained under a pressure varying from atmospheric to a few inches of vacuum and compartment A might be maintained under the highest vacuum practicable. By this arrangement, ⁸⁰there is obtained in substance a multiple effect evaporation of the moisture or water contained in the paper web. Such construction with the accompanying multiple effect mode of operation develops fuel efficiency to ⁸⁵the maximum.

Compartment D constitutes a kind of equalizing chamber or lock between the high pressure compartment C and the atmosphere. A pressure relief valve 67 maintains a pres- ⁹⁰sure within compartment D only slightly above atmospheric and from it steam generated from the paper web within said compartment may be conducted through a. pipe 68 into the conduit 62 or into the conduit 64. ⁹⁵Valves 69 and 70 are provided for controlling the disposition of the steam passing through the relief valve 67. Any other supplies of steam necessary to the operation of the driers may be conducted to the suitable compart- ¹⁰⁰ment through these same valves.

It should be noted that the arrangement of graduated pressures in the various compartments ana of seals separating the compartments is conducive to a relaxation of the ¹⁰⁵efficiency of the seals, such as is required in the types of vacuum drier now in use. The primary seal between the highest vacuum, viz. that in compartment A, and the atmosphere, is maintained by the valve 17 and the ¹¹⁰seal provided by the solid column of water dr stock ahead of said valve 17. The seal 59, which is the only seal of appreciable dimension which connects the interior of the housing with the atmosphere, is subject to in- ¹¹⁵ternal steam pressure from within the compartment D, so that whatever leakage may occur here flows outwardly constituting merely a loss of so much steam. Leakage through the seals between the various compartments ¹²⁰cannot vitiate the maintenance of air-free vapor in casing C. Nor can leakage through the seals 46 and 47 into section A vitiate the vacuum therein, although such leakage may impose an extra load upon the vacuum pump ¹²⁵100.

The seals 46, 47, 52 and 57 merely seal vapor against vapor. If they leak, neither steam heat nor vacuum is lost thereby but merely a fractional availability of the steam 120

1,854,056 s

with resultant loss of slight fuel efficiency. The steam leakage past the seal 59 may take the place, in part, of the usual sweat rolls, which serve to recondition the paper after ⁵ being dried.

Such a construction as above described would develop fuel efficiency to the maximum, consuming theoretically only about one-third of the steam consumed by known ¹⁰ types of vacuum driers now in use, or about one-quarter of the. steam consumption of the usual type of open driers. Furthermore, the incidental operative cost, as for vacuum pump, power, and the like, would be not more ¹⁵ and probably less than the corresponding cost in the operation of the present type of vacuum driers. The size and initial cost of a machine of my invention, however, would be relatively large as compared with the present type of vacuum drier, owing to the necessity for using more drier drums and the enclosing of the entire paper machine rather than the drier unit only.

As shown in Figure 7, one or more of the compartments of the drier unit, such as the compartment D, may be provided with means for circulating air through the drier compartment and with means for reutilizing the heat of the exit air and gases, which otherwise would be lost, in the preheating of the air admitted to the compartment.

For this purpose, a fan or blower 105, having an intake pipe 106, is connected by means of a discharge pipe 107 through a heat interchanging air regenerating device .108 to the compartment D, preferably to the lower portion of said compartment as at 109. Another pipe 110 leading from near the top of the compartment D, conducts the exit air and gases from said compartment through the heat interchanging device 108 where a portion or all of the heat of the exit gases is given up to the incoming air. The gases are finally discharged from the heat interchanging device 108 through a discharge pipe 111.

It will be understood that any conventional type of heat interchanging device may be used for effecting the utilization of a portion of the heat contained in the exit gases from the compartment D for preheating the incoming air. By this arrangement, effective air circulation can be maintained within the compartment D without resulting in a loss of heat values such as normally occurs in the open or unenclosed type of steam paper drier units. The compartment D will, of course, be maintained under substantially atmospheric pressure so that there will be no necessity for expensive sealing mechanism or air-tight casing construction.

While the provision of air circulating and heat interchanging means has been shown only in connection with a single compartment, it will be understood that other (compartments may be similarly arranged¹. If this same principle be applied to the entire machine and the machine enclosed but not provided with evacuating devices, with the air circulated through the casing in the manner described, then it is evident that such a drier unit combines the features of the type of drier previously discussed wherein no fuel is wasted in heating air and also the advantage of economy in area of drier surface offered by the type of drier wherein the drier unit is composed of steam heated drums not enclosed within a casing. This modified form of drier of my invention eliminates the waste of heat of the open type of drier unit and also the necessity of expensive apparatus as required in the vacuum, enclosed type of drier unit.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art. ;